/*
 * Copyright (c) 2022, Circle Internet Financial Limited.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
pragma solidity 0.7.6;

/*
The MIT License (MIT)

Copyright (c) 2016 Smart Contract Solutions, Inc.

Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:

The above copyright notice and this permission notice shall be included
in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/

/**
 * @title SafeMath
 * @dev Math operations with safety checks that throw on error
 */
library SafeMathTMV {
    /**
     * @dev Multiplies two numbers, throws on overflow.
     */
    function mul(uint256 _a, uint256 _b) internal pure returns (uint256 c) {
        // Gas optimization: this is cheaper than asserting 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522
        if (_a == 0) {
            return 0;
        }

        c = _a * _b;
        require(c / _a == _b, "Overflow during multiplication.");
        return c;
    }

    /**
     * @dev Integer division of two numbers, truncating the quotient.
     */
    function div(uint256 _a, uint256 _b) internal pure returns (uint256) {
        // assert(_b > 0); // Solidity automatically throws when dividing by 0
        // uint256 c = _a / _b;
        // assert(_a == _b * c + _a % _b); // There is no case in which this doesn't hold
        return _a / _b;
    }

    /**
     * @dev Subtracts two numbers, throws on overflow (i.e. if subtrahend is greater than minuend).
     */
    function sub(uint256 _a, uint256 _b) internal pure returns (uint256) {
        require(_b <= _a, "Underflow during subtraction.");
        return _a - _b;
    }

    /**
     * @dev Adds two numbers, throws on overflow.
     */
    function add(uint256 _a, uint256 _b) internal pure returns (uint256 c) {
        c = _a + _b;
        require(c >= _a, "Overflow during addition.");
        return c;
    }
}

library TypedMemView {
    using SafeMathTMV for uint256;

    // Why does this exist?
    // the solidity `bytes memory` type has a few weaknesses.
    // 1. You can't index ranges effectively
    // 2. You can't slice without copying
    // 3. The underlying data may represent any type
    // 4. Solidity never deallocates memory, and memory costs grow
    //    superlinearly

    // By using a memory view instead of a `bytes memory` we get the following
    // advantages:
    // 1. Slices are done on the stack, by manipulating the pointer
    // 2. We can index arbitrary ranges and quickly convert them to stack types
    // 3. We can insert type info into the pointer, and typecheck at runtime

    // This makes `TypedMemView` a useful tool for efficient zero-copy
    // algorithms.

    // Why bytes29?
    // We want to avoid confusion between views, digests, and other common
    // types so we chose a large and uncommonly used odd number of bytes
    //
    // Note that while bytes are left-aligned in a word, integers and addresses
    // are right-aligned. This means when working in assembly we have to
    // account for the 3 unused bytes on the righthand side
    //
    // First 5 bytes are a type flag.
    // - ff_ffff_fffe is reserved for unknown type.
    // - ff_ffff_ffff is reserved for invalid types/errors.
    // next 12 are memory address
    // next 12 are len
    // bottom 3 bytes are empty

    // Assumptions:
    // - non-modification of memory.
    // - No Solidity updates
    // - - wrt free mem point
    // - - wrt bytes representation in memory
    // - - wrt memory addressing in general

    // Usage:
    // - create type constants
    // - use `assertType` for runtime type assertions
    // - - unfortunately we can't do this at compile time yet :(
    // - recommended: implement modifiers that perform type checking
    // - - e.g.
    // - - `uint40 constant MY_TYPE = 3;`
    // - - ` modifer onlyMyType(bytes29 myView) { myView.assertType(MY_TYPE); }`
    // - instantiate a typed view from a bytearray using `ref`
    // - use `index` to inspect the contents of the view
    // - use `slice` to create smaller views into the same memory
    // - - `slice` can increase the offset
    // - - `slice can decrease the length`
    // - - must specify the output type of `slice`
    // - - `slice` will return a null view if you try to overrun
    // - - make sure to explicitly check for this with `notNull` or `assertType`
    // - use `equal` for typed comparisons.

    // The null view
    bytes29 public constant NULL =
        hex"ffffffffffffffffffffffffffffffffffffffffffffffffffffffffff";
    uint256 constant LOW_12_MASK = 0xffffffffffffffffffffffff;
    uint8 constant TWELVE_BYTES = 96;

    /**
     * @notice      Returns the encoded hex character that represents the lower 4 bits of the argument.
     * @param _b    The byte
     * @return      char - The encoded hex character
     */
    function nibbleHex(uint8 _b) internal pure returns (uint8 char) {
        // This can probably be done more efficiently, but it's only in error
        // paths, so we don't really care :)
        uint8 _nibble = _b | 0xf0; // set top 4, keep bottom 4
        if (_nibble == 0xf0) {
            return 0x30;
        } // 0
        if (_nibble == 0xf1) {
            return 0x31;
        } // 1
        if (_nibble == 0xf2) {
            return 0x32;
        } // 2
        if (_nibble == 0xf3) {
            return 0x33;
        } // 3
        if (_nibble == 0xf4) {
            return 0x34;
        } // 4
        if (_nibble == 0xf5) {
            return 0x35;
        } // 5
        if (_nibble == 0xf6) {
            return 0x36;
        } // 6
        if (_nibble == 0xf7) {
            return 0x37;
        } // 7
        if (_nibble == 0xf8) {
            return 0x38;
        } // 8
        if (_nibble == 0xf9) {
            return 0x39;
        } // 9
        if (_nibble == 0xfa) {
            return 0x61;
        } // a
        if (_nibble == 0xfb) {
            return 0x62;
        } // b
        if (_nibble == 0xfc) {
            return 0x63;
        } // c
        if (_nibble == 0xfd) {
            return 0x64;
        } // d
        if (_nibble == 0xfe) {
            return 0x65;
        } // e
        if (_nibble == 0xff) {
            return 0x66;
        } // f
    }

    /**
     * @notice      Returns a uint16 containing the hex-encoded byte.
     * @param _b    The byte
     * @return      encoded - The hex-encoded byte
     */
    function byteHex(uint8 _b) internal pure returns (uint16 encoded) {
        encoded |= nibbleHex(_b >> 4); // top 4 bits
        encoded <<= 8;
        encoded |= nibbleHex(_b); // lower 4 bits
    }

    /**
     * @notice      Encodes the uint256 to hex. `first` contains the encoded top 16 bytes.
     *              `second` contains the encoded lower 16 bytes.
     *
     * @param _b    The 32 bytes as uint256
     * @return      first - The top 16 bytes
     * @return      second - The bottom 16 bytes
     */
    function encodeHex(uint256 _b)
        internal
        pure
        returns (uint256 first, uint256 second)
    {
        for (uint8 i = 31; i > 15; i -= 1) {
            uint8 _byte = uint8(_b >> (i * 8));
            first |= byteHex(_byte);
            if (i != 16) {
                first <<= 16;
            }
        }

        // abusing underflow here =_=
        for (uint8 i = 15; i < 255; i -= 1) {
            uint8 _byte = uint8(_b >> (i * 8));
            second |= byteHex(_byte);
            if (i != 0) {
                second <<= 16;
            }
        }
    }

    /**
     * @notice          Changes the endianness of a uint256.
     * @dev             https://graphics.stanford.edu/~seander/bithacks.html#ReverseParallel
     * @param _b        The unsigned integer to reverse
     * @return          v - The reversed value
     */
    function reverseUint256(uint256 _b) internal pure returns (uint256 v) {
        v = _b;

        // swap bytes
        v =
            ((v >> 8) &
                0x00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF) |
            ((v &
                0x00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF) <<
                8);
        // swap 2-byte long pairs
        v =
            ((v >> 16) &
                0x0000FFFF0000FFFF0000FFFF0000FFFF0000FFFF0000FFFF0000FFFF0000FFFF) |
            ((v &
                0x0000FFFF0000FFFF0000FFFF0000FFFF0000FFFF0000FFFF0000FFFF0000FFFF) <<
                16);
        // swap 4-byte long pairs
        v =
            ((v >> 32) &
                0x00000000FFFFFFFF00000000FFFFFFFF00000000FFFFFFFF00000000FFFFFFFF) |
            ((v &
                0x00000000FFFFFFFF00000000FFFFFFFF00000000FFFFFFFF00000000FFFFFFFF) <<
                32);
        // swap 8-byte long pairs
        v =
            ((v >> 64) &
                0x0000000000000000FFFFFFFFFFFFFFFF0000000000000000FFFFFFFFFFFFFFFF) |
            ((v &
                0x0000000000000000FFFFFFFFFFFFFFFF0000000000000000FFFFFFFFFFFFFFFF) <<
                64);
        // swap 16-byte long pairs
        v = (v >> 128) | (v << 128);
    }

    /**
     * @notice      Create a mask with the highest `_len` bits set.
     * @param _len  The length
     * @return      mask - The mask
     */
    function leftMask(uint8 _len) private pure returns (uint256 mask) {
        // ugly. redo without assembly?
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            mask := sar(
                sub(_len, 1),
                0x8000000000000000000000000000000000000000000000000000000000000000
            )
        }
    }

    /**
     * @notice      Return the null view.
     * @return      bytes29 - The null view
     */
    function nullView() internal pure returns (bytes29) {
        return NULL;
    }

    /**
     * @notice      Check if the view is null.
     * @return      bool - True if the view is null
     */
    function isNull(bytes29 memView) internal pure returns (bool) {
        return memView == NULL;
    }

    /**
     * @notice      Check if the view is not null.
     * @return      bool - True if the view is not null
     */
    function notNull(bytes29 memView) internal pure returns (bool) {
        return !isNull(memView);
    }

    /**
     * @notice          Check if the view is of a valid type and points to a valid location
     *                  in memory.
     * @dev             We perform this check by examining solidity's unallocated memory
     *                  pointer and ensuring that the view's upper bound is less than that.
     * @param memView   The view
     * @return          ret - True if the view is valid
     */
    function isValid(bytes29 memView) internal pure returns (bool ret) {
        if (typeOf(memView) == 0xffffffffff) {
            return false;
        }
        uint256 _end = end(memView);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            ret := not(gt(_end, mload(0x40)))
        }
    }

    /**
     * @notice          Require that a typed memory view be valid.
     * @dev             Returns the view for easy chaining.
     * @param memView   The view
     * @return          bytes29 - The validated view
     */
    function assertValid(bytes29 memView) internal pure returns (bytes29) {
        require(isValid(memView), "Validity assertion failed");
        return memView;
    }

    /**
     * @notice          Return true if the memview is of the expected type. Otherwise false.
     * @param memView   The view
     * @param _expected The expected type
     * @return          bool - True if the memview is of the expected type
     */
    function isType(bytes29 memView, uint40 _expected)
        internal
        pure
        returns (bool)
    {
        return typeOf(memView) == _expected;
    }

    /**
     * @notice          Require that a typed memory view has a specific type.
     * @dev             Returns the view for easy chaining.
     * @param memView   The view
     * @param _expected The expected type
     * @return          bytes29 - The view with validated type
     */
    function assertType(bytes29 memView, uint40 _expected)
        internal
        pure
        returns (bytes29)
    {
        if (!isType(memView, _expected)) {
            (, uint256 g) = encodeHex(uint256(typeOf(memView)));
            (, uint256 e) = encodeHex(uint256(_expected));
            string memory err = string(
                abi.encodePacked(
                    "Type assertion failed. Got 0x",
                    uint80(g),
                    ". Expected 0x",
                    uint80(e)
                )
            );
            revert(err);
        }
        return memView;
    }

    /**
     * @notice          Return an identical view with a different type.
     * @param memView   The view
     * @param _newType  The new type
     * @return          newView - The new view with the specified type
     */
    function castTo(bytes29 memView, uint40 _newType)
        internal
        pure
        returns (bytes29 newView)
    {
        // then | in the new type
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            // shift off the top 5 bytes
            newView := or(newView, shr(40, shl(40, memView)))
            newView := or(newView, shl(216, _newType))
        }
    }

    /**
     * @notice          Unsafe raw pointer construction. This should generally not be called
     *                  directly. Prefer `ref` wherever possible.
     * @dev             Unsafe raw pointer construction. This should generally not be called
     *                  directly. Prefer `ref` wherever possible.
     * @param _type     The type
     * @param _loc      The memory address
     * @param _len      The length
     * @return          newView - The new view with the specified type, location and length
     */
    function unsafeBuildUnchecked(
        uint256 _type,
        uint256 _loc,
        uint256 _len
    ) private pure returns (bytes29 newView) {
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            newView := shl(96, or(newView, _type)) // insert type
            newView := shl(96, or(newView, _loc)) // insert loc
            newView := shl(24, or(newView, _len)) // empty bottom 3 bytes
        }
    }

    /**
     * @notice          Instantiate a new memory view. This should generally not be called
     *                  directly. Prefer `ref` wherever possible.
     * @dev             Instantiate a new memory view. This should generally not be called
     *                  directly. Prefer `ref` wherever possible.
     * @param _type     The type
     * @param _loc      The memory address
     * @param _len      The length
     * @return          newView - The new view with the specified type, location and length
     */
    function build(
        uint256 _type,
        uint256 _loc,
        uint256 _len
    ) internal pure returns (bytes29 newView) {
        uint256 _end = _loc.add(_len);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            if gt(_end, mload(0x40)) {
                _end := 0
            }
        }
        if (_end == 0) {
            return NULL;
        }
        newView = unsafeBuildUnchecked(_type, _loc, _len);
    }

    /**
     * @notice          Instantiate a memory view from a byte array.
     * @dev             Note that due to Solidity memory representation, it is not possible to
     *                  implement a deref, as the `bytes` type stores its len in memory.
     * @param arr       The byte array
     * @param newType   The type
     * @return          bytes29 - The memory view
     */
    function ref(bytes memory arr, uint40 newType)
        internal
        pure
        returns (bytes29)
    {
        uint256 _len = arr.length;

        uint256 _loc;
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            _loc := add(arr, 0x20) // our view is of the data, not the struct
        }

        return build(newType, _loc, _len);
    }

    /**
     * @notice          Return the associated type information.
     * @param memView   The memory view
     * @return          _type - The type associated with the view
     */
    function typeOf(bytes29 memView) internal pure returns (uint40 _type) {
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            // 216 == 256 - 40
            _type := shr(216, memView) // shift out lower 24 bytes
        }
    }

    /**
     * @notice          Optimized type comparison. Checks that the 5-byte type flag is equal.
     * @param left      The first view
     * @param right     The second view
     * @return          bool - True if the 5-byte type flag is equal
     */
    function sameType(bytes29 left, bytes29 right)
        internal
        pure
        returns (bool)
    {
        return (left ^ right) >> (2 * TWELVE_BYTES) == 0;
    }

    /**
     * @notice          Return the memory address of the underlying bytes.
     * @param memView   The view
     * @return          _loc - The memory address
     */
    function loc(bytes29 memView) internal pure returns (uint96 _loc) {
        uint256 _mask = LOW_12_MASK; // assembly can't use globals
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            // 120 bits = 12 bytes (the encoded loc) + 3 bytes (empty low space)
            _loc := and(shr(120, memView), _mask)
        }
    }

    /**
     * @notice          The number of memory words this memory view occupies, rounded up.
     * @param memView   The view
     * @return          uint256 - The number of memory words
     */
    function words(bytes29 memView) internal pure returns (uint256) {
        return uint256(len(memView)).add(32) / 32;
    }

    /**
     * @notice          The in-memory footprint of a fresh copy of the view.
     * @param memView   The view
     * @return          uint256 - The in-memory footprint of a fresh copy of the view.
     */
    function footprint(bytes29 memView) internal pure returns (uint256) {
        return words(memView) * 32;
    }

    /**
     * @notice          The number of bytes of the view.
     * @param memView   The view
     * @return          _len - The length of the view
     */
    function len(bytes29 memView) internal pure returns (uint96 _len) {
        uint256 _mask = LOW_12_MASK; // assembly can't use globals
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            _len := and(shr(24, memView), _mask)
        }
    }

    /**
     * @notice          Returns the endpoint of `memView`.
     * @param memView   The view
     * @return          uint256 - The endpoint of `memView`
     */
    function end(bytes29 memView) internal pure returns (uint256) {
        return loc(memView) + len(memView);
    }

    /**
     * @notice          Safe slicing without memory modification.
     * @param memView   The view
     * @param _index    The start index
     * @param _len      The length
     * @param newType   The new type
     * @return          bytes29 - The new view
     */
    function slice(
        bytes29 memView,
        uint256 _index,
        uint256 _len,
        uint40 newType
    ) internal pure returns (bytes29) {
        uint256 _loc = loc(memView);

        // Ensure it doesn't overrun the view
        if (_loc.add(_index).add(_len) > end(memView)) {
            return NULL;
        }

        _loc = _loc.add(_index);
        return build(newType, _loc, _len);
    }

    /**
     * @notice          Shortcut to `slice`. Gets a view representing the first `_len` bytes.
     * @param memView   The view
     * @param _len      The length
     * @param newType   The new type
     * @return          bytes29 - The new view
     */
    function prefix(
        bytes29 memView,
        uint256 _len,
        uint40 newType
    ) internal pure returns (bytes29) {
        return slice(memView, 0, _len, newType);
    }

    /**
     * @notice          Shortcut to `slice`. Gets a view representing the last `_len` byte.
     * @param memView   The view
     * @param _len      The length
     * @param newType   The new type
     * @return          bytes29 - The new view
     */
    function postfix(
        bytes29 memView,
        uint256 _len,
        uint40 newType
    ) internal pure returns (bytes29) {
        return slice(memView, uint256(len(memView)).sub(_len), _len, newType);
    }

    /**
     * @notice          Construct an error message for an indexing overrun.
     * @param _loc      The memory address
     * @param _len      The length
     * @param _index    The index
     * @param _slice    The slice where the overrun occurred
     * @return          err - The err
     */
    function indexErrOverrun(
        uint256 _loc,
        uint256 _len,
        uint256 _index,
        uint256 _slice
    ) internal pure returns (string memory err) {
        (, uint256 a) = encodeHex(_loc);
        (, uint256 b) = encodeHex(_len);
        (, uint256 c) = encodeHex(_index);
        (, uint256 d) = encodeHex(_slice);
        err = string(
            abi.encodePacked(
                "TypedMemView/index - Overran the view. Slice is at 0x",
                uint48(a),
                " with length 0x",
                uint48(b),
                ". Attempted to index at offset 0x",
                uint48(c),
                " with length 0x",
                uint48(d),
                "."
            )
        );
    }

    /**
     * @notice          Load up to 32 bytes from the view onto the stack.
     * @dev             Returns a bytes32 with only the `_bytes` highest bytes set.
     *                  This can be immediately cast to a smaller fixed-length byte array.
     *                  To automatically cast to an integer, use `indexUint`.
     * @param memView   The view
     * @param _index    The index
     * @param _bytes    The bytes
     * @return          result - The 32 byte result
     */
    function index(
        bytes29 memView,
        uint256 _index,
        uint8 _bytes
    ) internal pure returns (bytes32 result) {
        if (_bytes == 0) {
            return bytes32(0);
        }
        if (_index.add(_bytes) > len(memView)) {
            revert(
                indexErrOverrun(
                    loc(memView),
                    len(memView),
                    _index,
                    uint256(_bytes)
                )
            );
        }
        require(
            _bytes <= 32,
            "TypedMemView/index - Attempted to index more than 32 bytes"
        );

        uint8 bitLength = _bytes * 8;
        uint256 _loc = loc(memView);
        uint256 _mask = leftMask(bitLength);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            result := and(mload(add(_loc, _index)), _mask)
        }
    }

    /**
     * @notice          Parse an unsigned integer from the view at `_index`.
     * @dev             Requires that the view have >= `_bytes` bytes following that index.
     * @param memView   The view
     * @param _index    The index
     * @param _bytes    The bytes
     * @return          result - The unsigned integer
     */
    function indexUint(
        bytes29 memView,
        uint256 _index,
        uint8 _bytes
    ) internal pure returns (uint256 result) {
        return uint256(index(memView, _index, _bytes)) >> ((32 - _bytes) * 8);
    }

    /**
     * @notice          Parse an unsigned integer from LE bytes.
     * @param memView   The view
     * @param _index    The index
     * @param _bytes    The bytes
     * @return          result - The unsigned integer
     */
    function indexLEUint(
        bytes29 memView,
        uint256 _index,
        uint8 _bytes
    ) internal pure returns (uint256 result) {
        return reverseUint256(uint256(index(memView, _index, _bytes)));
    }

    /**
     * @notice          Parse an address from the view at `_index`. Requires that the view have >= 20 bytes
     *                  following that index.
     * @param memView   The view
     * @param _index    The index
     * @return          address - The address
     */
    function indexAddress(bytes29 memView, uint256 _index)
        internal
        pure
        returns (address)
    {
        return address(uint160(indexUint(memView, _index, 20)));
    }

    /**
     * @notice          Return the keccak256 hash of the underlying memory
     * @param memView   The view
     * @return          digest - The keccak256 hash of the underlying memory
     */
    function keccak(bytes29 memView) internal pure returns (bytes32 digest) {
        uint256 _loc = loc(memView);
        uint256 _len = len(memView);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            digest := keccak256(_loc, _len)
        }
    }

    /**
     * @notice          Return the sha2 digest of the underlying memory.
     * @dev             We explicitly deallocate memory afterwards.
     * @param memView   The view
     * @return          digest - The sha2 hash of the underlying memory
     */
    function sha2(bytes29 memView) internal view returns (bytes32 digest) {
        uint256 _loc = loc(memView);
        uint256 _len = len(memView);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            let ptr := mload(0x40)
            pop(staticcall(gas(), 2, _loc, _len, ptr, 0x20)) // sha2 #1
            digest := mload(ptr)
        }
    }

    /**
     * @notice          Implements bitcoin's hash160 (rmd160(sha2()))
     * @param memView   The pre-image
     * @return          digest - the Digest
     */
    function hash160(bytes29 memView) internal view returns (bytes20 digest) {
        uint256 _loc = loc(memView);
        uint256 _len = len(memView);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            let ptr := mload(0x40)
            pop(staticcall(gas(), 2, _loc, _len, ptr, 0x20)) // sha2
            pop(staticcall(gas(), 3, ptr, 0x20, ptr, 0x20)) // rmd160
            digest := mload(add(ptr, 0xc)) // return value is 0-prefixed.
        }
    }

    /**
     * @notice          Implements bitcoin's hash256 (double sha2)
     * @param memView   A view of the preimage
     * @return          digest - the Digest
     */
    function hash256(bytes29 memView) internal view returns (bytes32 digest) {
        uint256 _loc = loc(memView);
        uint256 _len = len(memView);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            let ptr := mload(0x40)
            pop(staticcall(gas(), 2, _loc, _len, ptr, 0x20)) // sha2 #1
            pop(staticcall(gas(), 2, ptr, 0x20, ptr, 0x20)) // sha2 #2
            digest := mload(ptr)
        }
    }

    /**
     * @notice          Return true if the underlying memory is equal. Else false.
     * @param left      The first view
     * @param right     The second view
     * @return          bool - True if the underlying memory is equal
     */
    function untypedEqual(bytes29 left, bytes29 right)
        internal
        pure
        returns (bool)
    {
        return
            (loc(left) == loc(right) && len(left) == len(right)) ||
            keccak(left) == keccak(right);
    }

    /**
     * @notice          Return false if the underlying memory is equal. Else true.
     * @param left      The first view
     * @param right     The second view
     * @return          bool - False if the underlying memory is equal
     */
    function untypedNotEqual(bytes29 left, bytes29 right)
        internal
        pure
        returns (bool)
    {
        return !untypedEqual(left, right);
    }

    /**
     * @notice          Compares type equality.
     * @dev             Shortcuts if the pointers are identical, otherwise compares type and digest.
     * @param left      The first view
     * @param right     The second view
     * @return          bool - True if the types are the same
     */
    function equal(bytes29 left, bytes29 right) internal pure returns (bool) {
        return
            left == right ||
            (typeOf(left) == typeOf(right) && keccak(left) == keccak(right));
    }

    /**
     * @notice          Compares type inequality.
     * @dev             Shortcuts if the pointers are identical, otherwise compares type and digest.
     * @param left      The first view
     * @param right     The second view
     * @return          bool - True if the types are not the same
     */
    function notEqual(bytes29 left, bytes29 right)
        internal
        pure
        returns (bool)
    {
        return !equal(left, right);
    }

    /**
     * @notice          Copy the view to a location, return an unsafe memory reference
     * @dev             Super Dangerous direct memory access.
     *
     *                  This reference can be overwritten if anything else modifies memory (!!!).
     *                  As such it MUST be consumed IMMEDIATELY.
     *                  This function is private to prevent unsafe usage by callers.
     * @param memView   The view
     * @param _newLoc   The new location
     * @return          written - the unsafe memory reference
     */
    function unsafeCopyTo(bytes29 memView, uint256 _newLoc)
        private
        view
        returns (bytes29 written)
    {
        require(notNull(memView), "TypedMemView/copyTo - Null pointer deref");
        require(
            isValid(memView),
            "TypedMemView/copyTo - Invalid pointer deref"
        );
        uint256 _len = len(memView);
        uint256 _oldLoc = loc(memView);

        uint256 ptr;
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            ptr := mload(0x40)
            // revert if we're writing in occupied memory
            if gt(ptr, _newLoc) {
                revert(0x60, 0x20) // empty revert message
            }

            // use the identity precompile to copy
            // guaranteed not to fail, so pop the success
            pop(staticcall(gas(), 4, _oldLoc, _len, _newLoc, _len))
        }

        written = unsafeBuildUnchecked(typeOf(memView), _newLoc, _len);
    }

    /**
     * @notice          Copies the referenced memory to a new loc in memory, returning a `bytes` pointing to
     *                  the new memory
     * @dev             Shortcuts if the pointers are identical, otherwise compares type and digest.
     * @param memView   The view
     * @return          ret - The view pointing to the new memory
     */
    function clone(bytes29 memView) internal view returns (bytes memory ret) {
        uint256 ptr;
        uint256 _len = len(memView);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            ptr := mload(0x40) // load unused memory pointer
            ret := ptr
        }
        unsafeCopyTo(memView, ptr + 0x20);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            mstore(0x40, add(add(ptr, _len), 0x20)) // write new unused pointer
            mstore(ptr, _len) // write len of new array (in bytes)
        }
    }

    /**
     * @notice          Join the views in memory, return an unsafe reference to the memory.
     * @dev             Super Dangerous direct memory access.
     *
     *                  This reference can be overwritten if anything else modifies memory (!!!).
     *                  As such it MUST be consumed IMMEDIATELY.
     *                  This function is private to prevent unsafe usage by callers.
     * @param memViews  The views
     * @return          unsafeView - The conjoined view pointing to the new memory
     */
    function unsafeJoin(bytes29[] memory memViews, uint256 _location)
        private
        view
        returns (bytes29 unsafeView)
    {
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            let ptr := mload(0x40)
            // revert if we're writing in occupied memory
            if gt(ptr, _location) {
                revert(0x60, 0x20) // empty revert message
            }
        }

        uint256 _offset = 0;
        for (uint256 i = 0; i < memViews.length; i++) {
            bytes29 memView = memViews[i];
            unsafeCopyTo(memView, _location + _offset);
            _offset += len(memView);
        }
        unsafeView = unsafeBuildUnchecked(0, _location, _offset);
    }

    /**
     * @notice          Produce the keccak256 digest of the concatenated contents of multiple views.
     * @param memViews  The views
     * @return          bytes32 - The keccak256 digest
     */
    function joinKeccak(bytes29[] memory memViews)
        internal
        view
        returns (bytes32)
    {
        uint256 ptr;
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            ptr := mload(0x40) // load unused memory pointer
        }
        return keccak(unsafeJoin(memViews, ptr));
    }

    /**
     * @notice          Produce the sha256 digest of the concatenated contents of multiple views.
     * @param memViews  The views
     * @return          bytes32 - The sha256 digest
     */
    function joinSha2(bytes29[] memory memViews)
        internal
        view
        returns (bytes32)
    {
        uint256 ptr;
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            ptr := mload(0x40) // load unused memory pointer
        }
        return sha2(unsafeJoin(memViews, ptr));
    }

    /**
     * @notice          copies all views, joins them into a new bytearray.
     * @param memViews  The views
     * @return          ret - The new byte array
     */
    function join(bytes29[] memory memViews)
        internal
        view
        returns (bytes memory ret)
    {
        uint256 ptr;
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            ptr := mload(0x40) // load unused memory pointer
        }

        bytes29 _newView = unsafeJoin(memViews, ptr + 0x20);
        uint256 _written = len(_newView);
        uint256 _footprint = footprint(_newView);

        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            // store the legnth
            mstore(ptr, _written)
            // new pointer is old + 0x20 + the footprint of the body
            mstore(0x40, add(add(ptr, _footprint), 0x20))
            ret := ptr
        }
    }
}

/*
 * Copyright (c) 2022, Circle Internet Financial Limited.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * Copyright (c) 2022, Circle Internet Financial Limited.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @title IRelayer
 * @notice Sends messages from source domain to destination domain
 */
interface IRelayer {
    /**
     * @notice Sends an outgoing message from the source domain.
     * @dev Increment nonce, format the message, and emit `MessageSent` event with message information.
     * @param destinationDomain Domain of destination chain
     * @param recipient Address of message recipient on destination domain as bytes32
     * @param messageBody Raw bytes content of message
     * @return nonce reserved by message
     */
    function sendMessage(
        uint32 destinationDomain,
        bytes32 recipient,
        bytes calldata messageBody
    ) external returns (uint64);

    /**
     * @notice Sends an outgoing message from the source domain, with a specified caller on the
     * destination domain.
     * @dev Increment nonce, format the message, and emit `MessageSent` event with message information.
     * WARNING: if the `destinationCaller` does not represent a valid address as bytes32, then it will not be possible
     * to broadcast the message on the destination domain. This is an advanced feature, and the standard
     * sendMessage() should be preferred for use cases where a specific destination caller is not required.
     * @param destinationDomain Domain of destination chain
     * @param recipient Address of message recipient on destination domain as bytes32
     * @param destinationCaller caller on the destination domain, as bytes32
     * @param messageBody Raw bytes content of message
     * @return nonce reserved by message
     */
    function sendMessageWithCaller(
        uint32 destinationDomain,
        bytes32 recipient,
        bytes32 destinationCaller,
        bytes calldata messageBody
    ) external returns (uint64);

    /**
     * @notice Replace a message with a new message body and/or destination caller.
     * @dev The `originalAttestation` must be a valid attestation of `originalMessage`.
     * @param originalMessage original message to replace
     * @param originalAttestation attestation of `originalMessage`
     * @param newMessageBody new message body of replaced message
     * @param newDestinationCaller the new destination caller
     */
    function replaceMessage(
        bytes calldata originalMessage,
        bytes calldata originalAttestation,
        bytes calldata newMessageBody,
        bytes32 newDestinationCaller
    ) external;
}

/*
 * Copyright (c) 2022, Circle Internet Financial Limited.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @title IReceiver
 * @notice Receives messages on destination chain and forwards them to IMessageDestinationHandler
 */
interface IReceiver {
    /**
     * @notice Receives an incoming message, validating the header and passing
     * the body to application-specific handler.
     * @param message The message raw bytes
     * @param signature The message signature
     * @return success bool, true if successful
     */
    function receiveMessage(bytes calldata message, bytes calldata signature)
        external
        returns (bool success);
}

/**
 * @title IMessageTransmitter
 * @notice Interface for message transmitters, which both relay and receive messages.
 */
interface IMessageTransmitter is IRelayer, IReceiver {

}

/*
 * Copyright (c) 2022, Circle Internet Financial Limited.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @title IMessageHandler
 * @notice Handles messages on destination domain forwarded from
 * an IReceiver
 */
interface IMessageHandler {
    /**
     * @notice handles an incoming message from a Receiver
     * @param sourceDomain the source domain of the message
     * @param sender the sender of the message
     * @param messageBody The message raw bytes
     * @return success bool, true if successful
     */
    function handleReceiveMessage(
        uint32 sourceDomain,
        bytes32 sender,
        bytes calldata messageBody
    ) external returns (bool);
}

/*
 * Copyright (c) 2022, Circle Internet Financial Limited.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @title Message Library
 * @notice Library for formatted messages used by Relayer and Receiver.
 *
 * @dev The message body is dynamically-sized to support custom message body
 * formats. Other fields must be fixed-size to avoid hash collisions.
 * Each other input value has an explicit type to guarantee fixed-size.
 * Padding: uintNN fields are left-padded, and bytesNN fields are right-padded.
 *
 * Field                 Bytes      Type       Index
 * version               4          uint32     0
 * sourceDomain          4          uint32     4
 * destinationDomain     4          uint32     8
 * nonce                 8          uint64     12
 * sender                32         bytes32    20
 * recipient             32         bytes32    52
 * destinationCaller     32         bytes32    84
 * messageBody           dynamic    bytes      116
 *
 **/
library Message {
    using TypedMemView for bytes;
    using TypedMemView for bytes29;

    // Indices of each field in message
    uint8 private constant VERSION_INDEX = 0;
    uint8 private constant SOURCE_DOMAIN_INDEX = 4;
    uint8 private constant DESTINATION_DOMAIN_INDEX = 8;
    uint8 private constant NONCE_INDEX = 12;
    uint8 private constant SENDER_INDEX = 20;
    uint8 private constant RECIPIENT_INDEX = 52;
    uint8 private constant DESTINATION_CALLER_INDEX = 84;
    uint8 private constant MESSAGE_BODY_INDEX = 116;

    /**
     * @notice Returns formatted (packed) message with provided fields
     * @param _msgVersion the version of the message format
     * @param _msgSourceDomain Domain of home chain
     * @param _msgDestinationDomain Domain of destination chain
     * @param _msgNonce Destination-specific nonce
     * @param _msgSender Address of sender on source chain as bytes32
     * @param _msgRecipient Address of recipient on destination chain as bytes32
     * @param _msgDestinationCaller Address of caller on destination chain as bytes32
     * @param _msgRawBody Raw bytes of message body
     * @return Formatted message
     **/
    function _formatMessage(
        uint32 _msgVersion,
        uint32 _msgSourceDomain,
        uint32 _msgDestinationDomain,
        uint64 _msgNonce,
        bytes32 _msgSender,
        bytes32 _msgRecipient,
        bytes32 _msgDestinationCaller,
        bytes memory _msgRawBody
    ) internal pure returns (bytes memory) {
        return
            abi.encodePacked(
                _msgVersion,
                _msgSourceDomain,
                _msgDestinationDomain,
                _msgNonce,
                _msgSender,
                _msgRecipient,
                _msgDestinationCaller,
                _msgRawBody
            );
    }

    // @notice Returns _message's version field
    function _version(bytes29 _message) internal pure returns (uint32) {
        return uint32(_message.indexUint(VERSION_INDEX, 4));
    }

    // @notice Returns _message's sourceDomain field
    function _sourceDomain(bytes29 _message) internal pure returns (uint32) {
        return uint32(_message.indexUint(SOURCE_DOMAIN_INDEX, 4));
    }

    // @notice Returns _message's destinationDomain field
    function _destinationDomain(bytes29 _message)
        internal
        pure
        returns (uint32)
    {
        return uint32(_message.indexUint(DESTINATION_DOMAIN_INDEX, 4));
    }

    // @notice Returns _message's nonce field
    function _nonce(bytes29 _message) internal pure returns (uint64) {
        return uint64(_message.indexUint(NONCE_INDEX, 8));
    }

    // @notice Returns _message's sender field
    function _sender(bytes29 _message) internal pure returns (bytes32) {
        return _message.index(SENDER_INDEX, 32);
    }

    // @notice Returns _message's recipient field
    function _recipient(bytes29 _message) internal pure returns (bytes32) {
        return _message.index(RECIPIENT_INDEX, 32);
    }

    // @notice Returns _message's destinationCaller field
    function _destinationCaller(bytes29 _message)
        internal
        pure
        returns (bytes32)
    {
        return _message.index(DESTINATION_CALLER_INDEX, 32);
    }

    // @notice Returns _message's messageBody field
    function _messageBody(bytes29 _message) internal pure returns (bytes29) {
        return
            _message.slice(
                MESSAGE_BODY_INDEX,
                _message.len() - MESSAGE_BODY_INDEX,
                0
            );
    }

    /**
     * @notice converts address to bytes32 (alignment preserving cast.)
     * @param addr the address to convert to bytes32
     */
    function addressToBytes32(address addr) external pure returns (bytes32) {
        return bytes32(uint256(uint160(addr)));
    }

    /**
     * @notice converts bytes32 to address (alignment preserving cast.)
     * @dev Warning: it is possible to have different input values _buf map to the same address.
     * For use cases where this is not acceptable, validate that the first 12 bytes of _buf are zero-padding.
     * @param _buf the bytes32 to convert to address
     */
    function bytes32ToAddress(bytes32 _buf) public pure returns (address) {
        return address(uint160(uint256(_buf)));
    }

    /**
     * @notice Reverts if message is malformed or incorrect length
     * @param _message The message as bytes29
     */
    function _validateMessageFormat(bytes29 _message) internal pure {
        require(_message.isValid(), "Malformed message");
        require(
            _message.len() >= MESSAGE_BODY_INDEX,
            "Invalid message: too short"
        );
    }
}

/*
 * Copyright (c) 2022, Circle Internet Financial Limited.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * Copyright (c) 2022, Circle Internet Financial Limited.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * Copyright (c) 2022, Circle Internet Financial Limited.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with GSN meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address payable) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

/**
 * @dev forked from https://github.com/OpenZeppelin/openzeppelin-contracts/blob/7c5f6bc2c8743d83443fa46395d75f2f3f99054a/contracts/access/Ownable.sol
 * Modifications:
 * 1. Update Solidity version from 0.8.0 to 0.7.6 (11/9/2022). (v8 was used
 * as base because it includes internal _transferOwnership method.)
 * 2. Remove renounceOwnership function
 *
 * Description
 * Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(
        address indexed previousOwner,
        address indexed newOwner
    );

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() {
        _transferOwnership(_msgSender());
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        _checkOwner();
        _;
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if the sender is not the owner.
     */
    function _checkOwner() internal view virtual {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(
            newOwner != address(0),
            "Ownable: new owner is the zero address"
        );
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

/**
 * @dev forked from https://github.com/OpenZeppelin/openzeppelin-contracts/blob/7c5f6bc2c8743d83443fa46395d75f2f3f99054a/contracts/access/Ownable2Step.sol
 * Modifications:
 * 1. Update Solidity version from 0.8.0 to 0.7.6. Version 0.8.0 was used
 * as base because this contract was added to OZ repo after version 0.8.0.
 *
 * Contract module which provides access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership} and {acceptOwnership}.
 *
 * This module is used through inheritance. It will make available all functions
 * from parent (Ownable).
 */
abstract contract Ownable2Step is Ownable {
    address private _pendingOwner;

    event OwnershipTransferStarted(
        address indexed previousOwner,
        address indexed newOwner
    );

    /**
     * @dev Returns the address of the pending owner.
     */
    function pendingOwner() public view virtual returns (address) {
        return _pendingOwner;
    }

    /**
     * @dev Starts the ownership transfer of the contract to a new account. Replaces the pending transfer if there is one.
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner)
        public
        virtual
        override
        onlyOwner
    {
        _pendingOwner = newOwner;
        emit OwnershipTransferStarted(owner(), newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`) and deletes any pending owner.
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual override {
        delete _pendingOwner;
        super._transferOwnership(newOwner);
    }

    /**
     * @dev The new owner accepts the ownership transfer.
     */
    function acceptOwnership() external {
        address sender = _msgSender();
        require(
            pendingOwner() == sender,
            "Ownable2Step: caller is not the new owner"
        );
        _transferOwnership(sender);
    }
}

/**
 * @notice Base contract which allows children to implement an emergency stop
 * mechanism
 * @dev Forked from https://github.com/centrehq/centre-tokens/blob/0d3cab14ebd133a83fc834dbd48d0468bdf0b391/contracts/v1/Pausable.sol
 * Modifications:
 * 1. Update Solidity version from 0.6.12 to 0.7.6 (8/23/2022)
 * 2. Change pauser visibility to private, declare external getter (11/19/22)
 */
contract Pausable is Ownable2Step {
    event Pause();
    event Unpause();
    event PauserChanged(address indexed newAddress);

    address private _pauser;
    bool public paused = false;

    /**
     * @dev Modifier to make a function callable only when the contract is not paused.
     */
    modifier whenNotPaused() {
        require(!paused, "Pausable: paused");
        _;
    }

    /**
     * @dev throws if called by any account other than the pauser
     */
    modifier onlyPauser() {
        require(msg.sender == _pauser, "Pausable: caller is not the pauser");
        _;
    }

    /**
     * @notice Returns current pauser
     * @return Pauser's address
     */
    function pauser() external view returns (address) {
        return _pauser;
    }

    /**
     * @dev called by the owner to pause, triggers stopped state
     */
    function pause() external onlyPauser {
        paused = true;
        emit Pause();
    }

    /**
     * @dev called by the owner to unpause, returns to normal state
     */
    function unpause() external onlyPauser {
        paused = false;
        emit Unpause();
    }

    /**
     * @dev update the pauser role
     */
    function updatePauser(address _newPauser) external onlyOwner {
        require(
            _newPauser != address(0),
            "Pausable: new pauser is the zero address"
        );
        _pauser = _newPauser;
        emit PauserChanged(_pauser);
    }
}

/*
 * Copyright (c) 2022, Circle Internet Financial Limited.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount)
        external
        returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender)
        external
        view
        returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(
        address indexed owner,
        address indexed spender,
        uint256 value
    );
}

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b)
        internal
        pure
        returns (bool, uint256)
    {
        uint256 c = a + b;
        if (c < a) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b)
        internal
        pure
        returns (bool, uint256)
    {
        if (b > a) return (false, 0);
        return (true, a - b);
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b)
        internal
        pure
        returns (bool, uint256)
    {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) return (true, 0);
        uint256 c = a * b;
        if (c / a != b) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b)
        internal
        pure
        returns (bool, uint256)
    {
        if (b == 0) return (false, 0);
        return (true, a / b);
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b)
        internal
        pure
        returns (bool, uint256)
    {
        if (b == 0) return (false, 0);
        return (true, a % b);
    }

    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");
        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a, "SafeMath: subtraction overflow");
        return a - b;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a == 0) return 0;
        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");
        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: division by zero");
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: modulo by zero");
        return a % b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        return a - b;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryDiv}.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a % b;
    }
}

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly {
            size := extcodesize(account)
        }
        return size > 0;
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(
            address(this).balance >= amount,
            "Address: insufficient balance"
        );

        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (bool success, ) = recipient.call{value: amount}("");
        require(
            success,
            "Address: unable to send value, recipient may have reverted"
        );
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain`call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data)
        internal
        returns (bytes memory)
    {
        return functionCall(target, data, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value
    ) internal returns (bytes memory) {
        return
            functionCallWithValue(
                target,
                data,
                value,
                "Address: low-level call with value failed"
            );
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(
            address(this).balance >= value,
            "Address: insufficient balance for call"
        );
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{value: value}(
            data
        );
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data)
        internal
        view
        returns (bytes memory)
    {
        return
            functionStaticCall(
                target,
                data,
                "Address: low-level static call failed"
            );
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.staticcall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data)
        internal
        returns (bytes memory)
    {
        return
            functionDelegateCall(
                target,
                data,
                "Address: low-level delegate call failed"
            );
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    function _verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) private pure returns (bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    using SafeMath for uint256;
    using Address for address;

    function safeTransfer(
        IERC20 token,
        address to,
        uint256 value
    ) internal {
        _callOptionalReturn(
            token,
            abi.encodeWithSelector(token.transfer.selector, to, value)
        );
    }

    function safeTransferFrom(
        IERC20 token,
        address from,
        address to,
        uint256 value
    ) internal {
        _callOptionalReturn(
            token,
            abi.encodeWithSelector(token.transferFrom.selector, from, to, value)
        );
    }

    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    function safeApprove(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        // solhint-disable-next-line max-line-length
        require(
            (value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        _callOptionalReturn(
            token,
            abi.encodeWithSelector(token.approve.selector, spender, value)
        );
    }

    function safeIncreaseAllowance(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        uint256 newAllowance = token.allowance(address(this), spender).add(
            value
        );
        _callOptionalReturn(
            token,
            abi.encodeWithSelector(
                token.approve.selector,
                spender,
                newAllowance
            )
        );
    }

    function safeDecreaseAllowance(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        uint256 newAllowance = token.allowance(address(this), spender).sub(
            value,
            "SafeERC20: decreased allowance below zero"
        );
        _callOptionalReturn(
            token,
            abi.encodeWithSelector(
                token.approve.selector,
                spender,
                newAllowance
            )
        );
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function _callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

        bytes memory returndata = address(token).functionCall(
            data,
            "SafeERC20: low-level call failed"
        );
        if (returndata.length > 0) {
            // Return data is optional
            // solhint-disable-next-line max-line-length
            require(
                abi.decode(returndata, (bool)),
                "SafeERC20: ERC20 operation did not succeed"
            );
        }
    }
}

/**
 * @notice Base contract which allows children to rescue ERC20 locked in their contract.
 * @dev Forked from https://github.com/centrehq/centre-tokens/blob/0d3cab14ebd133a83fc834dbd48d0468bdf0b391/contracts/v1.1/Rescuable.sol
 * Modifications:
 * 1. Update Solidity version from 0.6.12 to 0.7.6 (8/23/2022)
 */
contract Rescuable is Ownable2Step {
    using SafeERC20 for IERC20;

    address private _rescuer;

    event RescuerChanged(address indexed newRescuer);

    /**
     * @notice Returns current rescuer
     * @return Rescuer's address
     */
    function rescuer() external view returns (address) {
        return _rescuer;
    }

    /**
     * @notice Revert if called by any account other than the rescuer.
     */
    modifier onlyRescuer() {
        require(msg.sender == _rescuer, "Rescuable: caller is not the rescuer");
        _;
    }

    /**
     * @notice Rescue ERC20 tokens locked up in this contract.
     * @param tokenContract ERC20 token contract address
     * @param to        Recipient address
     * @param amount    Amount to withdraw
     */
    function rescueERC20(
        IERC20 tokenContract,
        address to,
        uint256 amount
    ) external onlyRescuer {
        tokenContract.safeTransfer(to, amount);
    }

    /**
     * @notice Assign the rescuer role to a given address.
     * @param newRescuer New rescuer's address
     */
    function updateRescuer(address newRescuer) external onlyOwner {
        require(
            newRescuer != address(0),
            "Rescuable: new rescuer is the zero address"
        );
        _rescuer = newRescuer;
        emit RescuerChanged(newRescuer);
    }
}

/*
 * Copyright (c) 2022, Circle Internet Financial Limited.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @dev Library for managing
 * https://en.wikipedia.org/wiki/Set_(abstract_data_type)[sets] of primitive
 * types.
 *
 * Sets have the following properties:
 *
 * - Elements are added, removed, and checked for existence in constant time
 * (O(1)).
 * - Elements are enumerated in O(n). No guarantees are made on the ordering.
 *
 * ```
 * contract Example {
 *     // Add the library methods
 *     using EnumerableSet for EnumerableSet.AddressSet;
 *
 *     // Declare a set state variable
 *     EnumerableSet.AddressSet private mySet;
 * }
 * ```
 *
 * As of v3.3.0, sets of type `bytes32` (`Bytes32Set`), `address` (`AddressSet`)
 * and `uint256` (`UintSet`) are supported.
 */
library EnumerableSet {
    // To implement this library for multiple types with as little code
    // repetition as possible, we write it in terms of a generic Set type with
    // bytes32 values.
    // The Set implementation uses private functions, and user-facing
    // implementations (such as AddressSet) are just wrappers around the
    // underlying Set.
    // This means that we can only create new EnumerableSets for types that fit
    // in bytes32.

    struct Set {
        // Storage of set values
        bytes32[] _values;
        // Position of the value in the `values` array, plus 1 because index 0
        // means a value is not in the set.
        mapping(bytes32 => uint256) _indexes;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function _add(Set storage set, bytes32 value) private returns (bool) {
        if (!_contains(set, value)) {
            set._values.push(value);
            // The value is stored at length-1, but we add 1 to all indexes
            // and use 0 as a sentinel value
            set._indexes[value] = set._values.length;
            return true;
        } else {
            return false;
        }
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function _remove(Set storage set, bytes32 value) private returns (bool) {
        // We read and store the value's index to prevent multiple reads from the same storage slot
        uint256 valueIndex = set._indexes[value];

        if (valueIndex != 0) {
            // Equivalent to contains(set, value)
            // To delete an element from the _values array in O(1), we swap the element to delete with the last one in
            // the array, and then remove the last element (sometimes called as 'swap and pop').
            // This modifies the order of the array, as noted in {at}.

            uint256 toDeleteIndex = valueIndex - 1;
            uint256 lastIndex = set._values.length - 1;

            // When the value to delete is the last one, the swap operation is unnecessary. However, since this occurs
            // so rarely, we still do the swap anyway to avoid the gas cost of adding an 'if' statement.

            bytes32 lastvalue = set._values[lastIndex];

            // Move the last value to the index where the value to delete is
            set._values[toDeleteIndex] = lastvalue;
            // Update the index for the moved value
            set._indexes[lastvalue] = toDeleteIndex + 1; // All indexes are 1-based

            // Delete the slot where the moved value was stored
            set._values.pop();

            // Delete the index for the deleted slot
            delete set._indexes[value];

            return true;
        } else {
            return false;
        }
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function _contains(Set storage set, bytes32 value)
        private
        view
        returns (bool)
    {
        return set._indexes[value] != 0;
    }

    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function _length(Set storage set) private view returns (uint256) {
        return set._values.length;
    }

    /**
     * @dev Returns the value stored at position `index` in the set. O(1).
     *
     * Note that there are no guarantees on the ordering of values inside the
     * array, and it may change when more values are added or removed.
     *
     * Requirements:
     *
     * - `index` must be strictly less than {length}.
     */
    function _at(Set storage set, uint256 index)
        private
        view
        returns (bytes32)
    {
        require(
            set._values.length > index,
            "EnumerableSet: index out of bounds"
        );
        return set._values[index];
    }

    // Bytes32Set

    struct Bytes32Set {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(Bytes32Set storage set, bytes32 value)
        internal
        returns (bool)
    {
        return _add(set._inner, value);
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(Bytes32Set storage set, bytes32 value)
        internal
        returns (bool)
    {
        return _remove(set._inner, value);
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(Bytes32Set storage set, bytes32 value)
        internal
        view
        returns (bool)
    {
        return _contains(set._inner, value);
    }

    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(Bytes32Set storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

    /**
     * @dev Returns the value stored at position `index` in the set. O(1).
     *
     * Note that there are no guarantees on the ordering of values inside the
     * array, and it may change when more values are added or removed.
     *
     * Requirements:
     *
     * - `index` must be strictly less than {length}.
     */
    function at(Bytes32Set storage set, uint256 index)
        internal
        view
        returns (bytes32)
    {
        return _at(set._inner, index);
    }

    // AddressSet

    struct AddressSet {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(AddressSet storage set, address value)
        internal
        returns (bool)
    {
        return _add(set._inner, bytes32(uint256(uint160(value))));
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(AddressSet storage set, address value)
        internal
        returns (bool)
    {
        return _remove(set._inner, bytes32(uint256(uint160(value))));
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(AddressSet storage set, address value)
        internal
        view
        returns (bool)
    {
        return _contains(set._inner, bytes32(uint256(uint160(value))));
    }

    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(AddressSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

    /**
     * @dev Returns the value stored at position `index` in the set. O(1).
     *
     * Note that there are no guarantees on the ordering of values inside the
     * array, and it may change when more values are added or removed.
     *
     * Requirements:
     *
     * - `index` must be strictly less than {length}.
     */
    function at(AddressSet storage set, uint256 index)
        internal
        view
        returns (address)
    {
        return address(uint160(uint256(_at(set._inner, index))));
    }

    // UintSet

    struct UintSet {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(UintSet storage set, uint256 value) internal returns (bool) {
        return _add(set._inner, bytes32(value));
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(UintSet storage set, uint256 value)
        internal
        returns (bool)
    {
        return _remove(set._inner, bytes32(value));
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(UintSet storage set, uint256 value)
        internal
        view
        returns (bool)
    {
        return _contains(set._inner, bytes32(value));
    }

    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function length(UintSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

    /**
     * @dev Returns the value stored at position `index` in the set. O(1).
     *
     * Note that there are no guarantees on the ordering of values inside the
     * array, and it may change when more values are added or removed.
     *
     * Requirements:
     *
     * - `index` must be strictly less than {length}.
     */
    function at(UintSet storage set, uint256 index)
        internal
        view
        returns (uint256)
    {
        return uint256(_at(set._inner, index));
    }
}

/**
 * @dev Elliptic Curve Digital Signature Algorithm (ECDSA) operations.
 *
 * These functions can be used to verify that a message was signed by the holder
 * of the private keys of a given address.
 */
library ECDSA {
    /**
     * @dev Returns the address that signed a hashed message (`hash`) with
     * `signature`. This address can then be used for verification purposes.
     *
     * The `ecrecover` EVM opcode allows for malleable (non-unique) signatures:
     * this function rejects them by requiring the `s` value to be in the lower
     * half order, and the `v` value to be either 27 or 28.
     *
     * IMPORTANT: `hash` _must_ be the result of a hash operation for the
     * verification to be secure: it is possible to craft signatures that
     * recover to arbitrary addresses for non-hashed data. A safe way to ensure
     * this is by receiving a hash of the original message (which may otherwise
     * be too long), and then calling {toEthSignedMessageHash} on it.
     */
    function recover(bytes32 hash, bytes memory signature)
        internal
        pure
        returns (address)
    {
        // Check the signature length
        if (signature.length != 65) {
            revert("ECDSA: invalid signature length");
        }

        // Divide the signature in r, s and v variables
        bytes32 r;
        bytes32 s;
        uint8 v;

        // ecrecover takes the signature parameters, and the only way to get them
        // currently is to use assembly.
        // solhint-disable-next-line no-inline-assembly
        assembly {
            r := mload(add(signature, 0x20))
            s := mload(add(signature, 0x40))
            v := byte(0, mload(add(signature, 0x60)))
        }

        return recover(hash, v, r, s);
    }

    /**
     * @dev Overload of {ECDSA-recover-bytes32-bytes-} that receives the `v`,
     * `r` and `s` signature fields separately.
     */
    function recover(
        bytes32 hash,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) internal pure returns (address) {
        // EIP-2 still allows signature malleability for ecrecover(). Remove this possibility and make the signature
        // unique. Appendix F in the Ethereum Yellow paper (https://ethereum.github.io/yellowpaper/paper.pdf), defines
        // the valid range for s in (281): 0 < s < secp256k1n ÷ 2 + 1, and for v in (282): v ∈ {27, 28}. Most
        // signatures from current libraries generate a unique signature with an s-value in the lower half order.
        //
        // If your library generates malleable signatures, such as s-values in the upper range, calculate a new s-value
        // with 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141 - s1 and flip v from 27 to 28 or
        // vice versa. If your library also generates signatures with 0/1 for v instead 27/28, add 27 to v to accept
        // these malleable signatures as well.
        require(
            uint256(s) <=
                0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0,
            "ECDSA: invalid signature 's' value"
        );
        require(v == 27 || v == 28, "ECDSA: invalid signature 'v' value");

        // If the signature is valid (and not malleable), return the signer address
        address signer = ecrecover(hash, v, r, s);
        require(signer != address(0), "ECDSA: invalid signature");

        return signer;
    }

    /**
     * @dev Returns an Ethereum Signed Message, created from a `hash`. This
     * replicates the behavior of the
     * https://github.com/ethereum/wiki/wiki/JSON-RPC#eth_sign[`eth_sign`]
     * JSON-RPC method.
     *
     * See {recover}.
     */
    function toEthSignedMessageHash(bytes32 hash)
        internal
        pure
        returns (bytes32)
    {
        // 32 is the length in bytes of hash,
        // enforced by the type signature above
        return
            keccak256(
                abi.encodePacked("\x19Ethereum Signed Message:\n32", hash)
            );
    }
}

contract Attestable is Ownable2Step {
    // ============ Events ============
    /**
     * @notice Emitted when an attester is enabled
     * @param attester newly enabled attester
     */
    event AttesterEnabled(address indexed attester);

    /**
     * @notice Emitted when an attester is disabled
     * @param attester newly disabled attester
     */
    event AttesterDisabled(address indexed attester);

    /**
     * @notice Emitted when threshold number of attestations (m in m/n multisig) is updated
     * @param oldSignatureThreshold old signature threshold
     * @param newSignatureThreshold new signature threshold
     */
    event SignatureThresholdUpdated(
        uint256 oldSignatureThreshold,
        uint256 newSignatureThreshold
    );

    /**
     * @dev Emitted when attester manager address is updated
     * @param previousAttesterManager representing the address of the previous attester manager
     * @param newAttesterManager representing the address of the new attester manager
     */
    event AttesterManagerUpdated(
        address indexed previousAttesterManager,
        address indexed newAttesterManager
    );

    // ============ Libraries ============
    using EnumerableSet for EnumerableSet.AddressSet;

    // ============ State Variables ============
    // number of signatures from distinct attesters required for a message to be received (m in m/n multisig)
    uint256 public signatureThreshold;

    // 65-byte ECDSA signature: v (32) + r (32) + s (1)
    uint256 internal constant signatureLength = 65;

    // enabled attesters (message signers)
    // (length of enabledAttesters is n in m/n multisig of message signers)
    EnumerableSet.AddressSet private enabledAttesters;

    // Attester Manager of the contract
    address private _attesterManager;

    // ============ Modifiers ============
    /**
     * @dev Throws if called by any account other than the attester manager.
     */
    modifier onlyAttesterManager() {
        require(msg.sender == _attesterManager, "Caller not attester manager");
        _;
    }

    // ============ Constructor ============
    /**
     * @dev The constructor sets the original attester manager of the contract to the sender account.
     * @param attester attester to initialize
     */
    constructor(address attester) {
        _setAttesterManager(msg.sender);
        // Initially 1 signature is required. Threshold can be increased by attesterManager.
        signatureThreshold = 1;
        enableAttester(attester);
    }

    // ============ Public/External Functions  ============
    /**
     * @notice Enables an attester
     * @dev Only callable by attesterManager. New attester must be nonzero, and currently disabled.
     * @param newAttester attester to enable
     */
    function enableAttester(address newAttester) public onlyAttesterManager {
        require(newAttester != address(0), "New attester must be nonzero");
        require(enabledAttesters.add(newAttester), "Attester already enabled");
        emit AttesterEnabled(newAttester);
    }

    /**
     * @notice returns true if given `attester` is enabled, else false
     * @param attester attester to check enabled status of
     * @return true if given `attester` is enabled, else false
     */
    function isEnabledAttester(address attester) public view returns (bool) {
        return enabledAttesters.contains(attester);
    }

    /**
     * @notice returns the number of enabled attesters
     * @return number of enabled attesters
     */
    function getNumEnabledAttesters() public view returns (uint256) {
        return enabledAttesters.length();
    }

    /**
     * @dev Allows the current attester manager to transfer control of the contract to a newAttesterManager.
     * @param newAttesterManager The address to update attester manager to.
     */
    function updateAttesterManager(address newAttesterManager)
        external
        onlyOwner
    {
        require(
            newAttesterManager != address(0),
            "Invalid attester manager address"
        );
        address _oldAttesterManager = _attesterManager;
        _setAttesterManager(newAttesterManager);
        emit AttesterManagerUpdated(_oldAttesterManager, newAttesterManager);
    }

    /**
     * @notice Disables an attester
     * @dev Only callable by attesterManager. Disabling the attester is not allowed if there is only one attester
     * enabled, or if it would cause the number of enabled attesters to become less than signatureThreshold.
     * (Attester must be currently enabled.)
     * @param attester attester to disable
     */
    function disableAttester(address attester) external onlyAttesterManager {
        // Disallow disabling attester if there is only 1 active attester
        uint256 _numEnabledAttesters = getNumEnabledAttesters();

        require(_numEnabledAttesters > 1, "Too few enabled attesters");

        // Disallow disabling an attester if it would cause the n in m/n multisig to fall below m (threshold # of signers).
        require(
            _numEnabledAttesters > signatureThreshold,
            "Signature threshold is too low"
        );

        require(enabledAttesters.remove(attester), "Attester already disabled");
        emit AttesterDisabled(attester);
    }

    /**
     * @notice Sets the threshold of signatures required to attest to a message.
     * (This is the m in m/n multisig.)
     * @dev new signature threshold must be nonzero, and must not exceed number
     * of enabled attesters.
     * @param newSignatureThreshold new signature threshold
     */
    function setSignatureThreshold(uint256 newSignatureThreshold)
        external
        onlyAttesterManager
    {
        require(newSignatureThreshold != 0, "Invalid signature threshold");

        // New signature threshold cannot exceed the number of enabled attesters
        require(
            newSignatureThreshold <= enabledAttesters.length(),
            "New signature threshold too high"
        );

        require(
            newSignatureThreshold != signatureThreshold,
            "Signature threshold already set"
        );

        uint256 _oldSignatureThreshold = signatureThreshold;
        signatureThreshold = newSignatureThreshold;
        emit SignatureThresholdUpdated(
            _oldSignatureThreshold,
            signatureThreshold
        );
    }

    /**
     * @dev Returns the address of the attester manager
     * @return address of the attester manager
     */
    function attesterManager() external view returns (address) {
        return _attesterManager;
    }

    /**
     * @notice gets enabled attester at given `index`
     * @param index index of attester to check
     * @return enabled attester at given `index`
     */
    function getEnabledAttester(uint256 index) external view returns (address) {
        return enabledAttesters.at(index);
    }

    // ============ Internal Utils ============
    /**
     * @dev Sets a new attester manager address
     * @param _newAttesterManager attester manager address to set
     */
    function _setAttesterManager(address _newAttesterManager) internal {
        _attesterManager = _newAttesterManager;
    }

    /**
     * @notice reverts if the attestation, which is comprised of one or more concatenated 65-byte signatures, is invalid.
     * @dev Rules for valid attestation:
     * 1. length of `_attestation` == 65 (signature length) * signatureThreshold
     * 2. addresses recovered from attestation must be in increasing order.
     * For example, if signature A is signed by address 0x1..., and signature B
     * is signed by address 0x2..., attestation must be passed as AB.
     * 3. no duplicate signers
     * 4. all signers must be enabled attesters
     *
     * Based on Christian Lundkvist's Simple Multisig
     * (https://github.com/christianlundkvist/simple-multisig/tree/560c463c8651e0a4da331bd8f245ccd2a48ab63d)
     * @param _message message to verify attestation of
     * @param _attestation attestation of `_message`
     */
    function _verifyAttestationSignatures(
        bytes calldata _message,
        bytes calldata _attestation
    ) internal view {
        require(
            _attestation.length == signatureLength * signatureThreshold,
            "Invalid attestation length"
        );

        // (Attesters cannot be address(0))
        address _latestAttesterAddress = address(0);
        // Address recovered from signatures must be in increasing order, to prevent duplicates

        bytes32 _digest = keccak256(_message);

        for (uint256 i; i < signatureThreshold; ++i) {
            bytes memory _signature = _attestation[i * signatureLength:i *
                signatureLength +
                signatureLength];

            address _recoveredAttester = _recoverAttesterSignature(
                _digest,
                _signature
            );

            // Signatures must be in increasing order of address, and may not duplicate signatures from same address
            require(
                _recoveredAttester > _latestAttesterAddress,
                "Invalid signature order or dupe"
            );
            require(
                isEnabledAttester(_recoveredAttester),
                "Invalid signature: not attester"
            );
            _latestAttesterAddress = _recoveredAttester;
        }
    }

    /**
     * @notice Checks that signature was signed by attester
     * @param _digest message hash
     * @param _signature message signature
     * @return address of recovered signer
     **/
    function _recoverAttesterSignature(bytes32 _digest, bytes memory _signature)
        internal
        pure
        returns (address)
    {
        return (ECDSA.recover(_digest, _signature));
    }
}

/**
 * @title MessageTransmitter
 * @notice Contract responsible for sending and receiving messages across chains.
 */
contract MessageTransmitter is
    IMessageTransmitter,
    Pausable,
    Rescuable,
    Attestable
{
    // ============ Events ============
    /**
     * @notice Emitted when a new message is dispatched
     * @param message Raw bytes of message
     */
    event MessageSent(bytes message);

    /**
     * @notice Emitted when a new message is received
     * @param caller Caller (msg.sender) on destination domain
     * @param sourceDomain The source domain this message originated from
     * @param nonce The nonce unique to this message
     * @param sender The sender of this message
     * @param messageBody message body bytes
     */
    event MessageReceived(
        address indexed caller,
        uint32 sourceDomain,
        uint64 indexed nonce,
        bytes32 sender,
        bytes messageBody
    );

    /**
     * @notice Emitted when max message body size is updated
     * @param newMaxMessageBodySize new maximum message body size, in bytes
     */
    event MaxMessageBodySizeUpdated(uint256 newMaxMessageBodySize);

    // ============ Libraries ============
    using TypedMemView for bytes;
    using TypedMemView for bytes29;
    using Message for bytes29;

    // ============ State Variables ============
    // Domain of chain on which the contract is deployed
    uint32 public immutable localDomain;

    // Message Format version
    uint32 public immutable version;

    // Maximum size of message body, in bytes.
    // This value is set by owner.
    uint256 public maxMessageBodySize;

    // Next available nonce from this source domain
    uint64 public nextAvailableNonce;

    // Maps a bytes32 hash of (sourceDomain, nonce) -> uint256 (0 if unused, 1 if used)
    mapping(bytes32 => uint256) public usedNonces;

    // ============ Constructor ============
    constructor(
        uint32 _localDomain,
        address _attester,
        uint32 _maxMessageBodySize,
        uint32 _version
    ) Attestable(_attester) {
        localDomain = _localDomain;
        maxMessageBodySize = _maxMessageBodySize;
        version = _version;
    }

    // ============ External Functions  ============
    /**
     * @notice Send the message to the destination domain and recipient
     * @dev Increment nonce, format the message, and emit `MessageSent` event with message information.
     * @param destinationDomain Domain of destination chain
     * @param recipient Address of message recipient on destination chain as bytes32
     * @param messageBody Raw bytes content of message
     * @return nonce reserved by message
     */
    function sendMessage(
        uint32 destinationDomain,
        bytes32 recipient,
        bytes calldata messageBody
    ) external override whenNotPaused returns (uint64) {
        bytes32 _emptyDestinationCaller = bytes32(0);
        uint64 _nonce = _reserveAndIncrementNonce();
        bytes32 _messageSender = Message.addressToBytes32(msg.sender);

        _sendMessage(
            destinationDomain,
            recipient,
            _emptyDestinationCaller,
            _messageSender,
            _nonce,
            messageBody
        );

        return _nonce;
    }

    /**
     * @notice Replace a message with a new message body and/or destination caller.
     * @dev The `originalAttestation` must be a valid attestation of `originalMessage`.
     * Reverts if msg.sender does not match sender of original message, or if the source domain of the original message
     * does not match this MessageTransmitter's local domain.
     * @param originalMessage original message to replace
     * @param originalAttestation attestation of `originalMessage`
     * @param newMessageBody new message body of replaced message
     * @param newDestinationCaller the new destination caller, which may be the
     * same as the original destination caller, a new destination caller, or an empty
     * destination caller (bytes32(0), indicating that any destination caller is valid.)
     */
    function replaceMessage(
        bytes calldata originalMessage,
        bytes calldata originalAttestation,
        bytes calldata newMessageBody,
        bytes32 newDestinationCaller
    ) external override whenNotPaused {
        // Validate each signature in the attestation
        _verifyAttestationSignatures(originalMessage, originalAttestation);

        bytes29 _originalMsg = originalMessage.ref(0);

        // Validate message format
        _originalMsg._validateMessageFormat();

        // Validate message sender
        bytes32 _sender = _originalMsg._sender();
        require(
            msg.sender == Message.bytes32ToAddress(_sender),
            "Sender not permitted to use nonce"
        );

        // Validate source domain
        uint32 _sourceDomain = _originalMsg._sourceDomain();
        require(
            _sourceDomain == localDomain,
            "Message not originally sent from this domain"
        );

        uint32 _destinationDomain = _originalMsg._destinationDomain();
        bytes32 _recipient = _originalMsg._recipient();
        uint64 _nonce = _originalMsg._nonce();

        _sendMessage(
            _destinationDomain,
            _recipient,
            newDestinationCaller,
            _sender,
            _nonce,
            newMessageBody
        );
    }

    /**
     * @notice Send the message to the destination domain and recipient, for a specified `destinationCaller` on the
     * destination domain.
     * @dev Increment nonce, format the message, and emit `MessageSent` event with message information.
     * WARNING: if the `destinationCaller` does not represent a valid address, then it will not be possible
     * to broadcast the message on the destination domain. This is an advanced feature, and the standard
     * sendMessage() should be preferred for use cases where a specific destination caller is not required.
     * @param destinationDomain Domain of destination chain
     * @param recipient Address of message recipient on destination domain as bytes32
     * @param destinationCaller caller on the destination domain, as bytes32
     * @param messageBody Raw bytes content of message
     * @return nonce reserved by message
     */
    function sendMessageWithCaller(
        uint32 destinationDomain,
        bytes32 recipient,
        bytes32 destinationCaller,
        bytes calldata messageBody
    ) external override whenNotPaused returns (uint64) {
        require(
            destinationCaller != bytes32(0),
            "Destination caller must be nonzero"
        );

        uint64 _nonce = _reserveAndIncrementNonce();
        bytes32 _messageSender = Message.addressToBytes32(msg.sender);

        _sendMessage(
            destinationDomain,
            recipient,
            destinationCaller,
            _messageSender,
            _nonce,
            messageBody
        );

        return _nonce;
    }

    /**
     * @notice Receive a message. Messages with a given nonce
     * can only be broadcast once for a (sourceDomain, destinationDomain)
     * pair. The message body of a valid message is passed to the
     * specified recipient for further processing.
     *
     * @dev Attestation format:
     * A valid attestation is the concatenated 65-byte signature(s) of exactly
     * `thresholdSignature` signatures, in increasing order of attester address.
     * ***If the attester addresses recovered from signatures are not in
     * increasing order, signature verification will fail.***
     * If incorrect number of signatures or duplicate signatures are supplied,
     * signature verification will fail.
     *
     * Message format:
     * Field                 Bytes      Type       Index
     * version               4          uint32     0
     * sourceDomain          4          uint32     4
     * destinationDomain     4          uint32     8
     * nonce                 8          uint64     12
     * sender                32         bytes32    20
     * recipient             32         bytes32    52
     * messageBody           dynamic    bytes      84
     * @param message Message bytes
     * @param attestation Concatenated 65-byte signature(s) of `message`, in increasing order
     * of the attester address recovered from signatures.
     * @return success bool, true if successful
     */
    function receiveMessage(bytes calldata message, bytes calldata attestation)
        external
        override
        whenNotPaused
        returns (bool success)
    {
        // Validate each signature in the attestation
        _verifyAttestationSignatures(message, attestation);

        bytes29 _msg = message.ref(0);

        // Validate message format
        _msg._validateMessageFormat();

        // Validate domain
        require(
            _msg._destinationDomain() == localDomain,
            "Invalid destination domain"
        );

        // Validate destination caller
        if (_msg._destinationCaller() != bytes32(0)) {
            require(
                _msg._destinationCaller() ==
                    Message.addressToBytes32(msg.sender),
                "Invalid caller for message"
            );
        }

        // Validate version
        require(_msg._version() == version, "Invalid message version");

        // Validate nonce is available
        uint32 _sourceDomain = _msg._sourceDomain();
        uint64 _nonce = _msg._nonce();
        bytes32 _sourceAndNonce = _hashSourceAndNonce(_sourceDomain, _nonce);
        require(usedNonces[_sourceAndNonce] == 0, "Nonce already used");
        // Mark nonce used
        usedNonces[_sourceAndNonce] = 1;

        // Handle receive message
        bytes32 _sender = _msg._sender();
        bytes memory _messageBody = _msg._messageBody().clone();
        require(
            IMessageHandler(Message.bytes32ToAddress(_msg._recipient()))
                .handleReceiveMessage(_sourceDomain, _sender, _messageBody),
            "handleReceiveMessage() failed"
        );

        // Emit MessageReceived event
        emit MessageReceived(
            msg.sender,
            _sourceDomain,
            _nonce,
            _sender,
            _messageBody
        );
        return true;
    }

    /**
     * @notice Sets the max message body size
     * @dev This value should not be reduced without good reason,
     * to avoid impacting users who rely on large messages.
     * @param newMaxMessageBodySize new max message body size, in bytes
     */
    function setMaxMessageBodySize(uint256 newMaxMessageBodySize)
        external
        onlyOwner
    {
        maxMessageBodySize = newMaxMessageBodySize;
        emit MaxMessageBodySizeUpdated(maxMessageBodySize);
    }

    // ============ Internal Utils ============
    /**
     * @notice Send the message to the destination domain and recipient. If `_destinationCaller` is not equal to bytes32(0),
     * the message can only be received on the destination chain when called by `_destinationCaller`.
     * @dev Format the message and emit `MessageSent` event with message information.
     * @param _destinationDomain Domain of destination chain
     * @param _recipient Address of message recipient on destination domain as bytes32
     * @param _destinationCaller caller on the destination domain, as bytes32
     * @param _sender message sender, as bytes32
     * @param _nonce nonce reserved for message
     * @param _messageBody Raw bytes content of message
     */
    function _sendMessage(
        uint32 _destinationDomain,
        bytes32 _recipient,
        bytes32 _destinationCaller,
        bytes32 _sender,
        uint64 _nonce,
        bytes calldata _messageBody
    ) internal {
        // Validate message body length
        require(
            _messageBody.length <= maxMessageBodySize,
            "Message body exceeds max size"
        );

        require(_recipient != bytes32(0), "Recipient must be nonzero");

        // serialize message
        bytes memory _message = Message._formatMessage(
            version,
            localDomain,
            _destinationDomain,
            _nonce,
            _sender,
            _recipient,
            _destinationCaller,
            _messageBody
        );

        // Emit MessageSent event
        emit MessageSent(_message);
    }

    /**
     * @notice hashes `_source` and `_nonce`.
     * @param _source Domain of chain where the transfer originated
     * @param _nonce The unique identifier for the message from source to
              destination
     * @return hash of source and nonce
     */
    function _hashSourceAndNonce(uint32 _source, uint64 _nonce)
        internal
        pure
        returns (bytes32)
    {
        return keccak256(abi.encodePacked(_source, _nonce));
    }

    /**
     * Reserve and increment next available nonce
     * @return nonce reserved
     */
    function _reserveAndIncrementNonce() internal returns (uint64) {
        uint64 _nonceReserved = nextAvailableNonce;
        nextAvailableNonce = nextAvailableNonce + 1;
        return _nonceReserved;
    }
}

pragma solidity ^0.4.24;

// File: zos-lib/contracts/upgradeability/Proxy.sol

/**
 * @title Proxy
 * @dev Implements delegation of calls to other contracts, with proper
 * forwarding of return values and bubbling of failures.
 * It defines a fallback function that delegates all calls to the address
 * returned by the abstract _implementation() internal function.
 */
contract Proxy {
  /**
   * @dev Fallback function.
   * Implemented entirely in `_fallback`.
   */
  function () payable external {
    _fallback();
  }

  /**
   * @return The Address of the implementation.
   */
  function _implementation() internal view returns (address);

  /**
   * @dev Delegates execution to an implementation contract.
   * This is a low level function that doesn't return to its internal call site.
   * It will return to the external caller whatever the implementation returns.
   * @param implementation Address to delegate.
   */
  function _delegate(address implementation) internal {
    assembly {
      // Copy msg.data. We take full control of memory in this inline assembly
      // block because it will not return to Solidity code. We overwrite the
      // Solidity scratch pad at memory position 0.
      calldatacopy(0, 0, calldatasize)

      // Call the implementation.
      // out and outsize are 0 because we don't know the size yet.
      let result := delegatecall(gas, implementation, 0, calldatasize, 0, 0)

      // Copy the returned data.
      returndatacopy(0, 0, returndatasize)

      switch result
      // delegatecall returns 0 on error.
      case 0 { revert(0, returndatasize) }
      default { return(0, returndatasize) }
    }
  }

  /**
   * @dev Function that is run as the first thing in the fallback function.
   * Can be redefined in derived contracts to add functionality.
   * Redefinitions must call super._willFallback().
   */
  function _willFallback() internal {
  }

  /**
   * @dev fallback implementation.
   * Extracted to enable manual triggering.
   */
  function _fallback() internal {
    _willFallback();
    _delegate(_implementation());
  }
}

// File: openzeppelin-solidity/contracts/AddressUtils.sol

/**
 * Utility library of inline functions on addresses
 */
library AddressUtils {

  /**
   * Returns whether the target address is a contract
   * @dev This function will return false if invoked during the constructor of a contract,
   * as the code is not actually created until after the constructor finishes.
   * @param addr address to check
   * @return whether the target address is a contract
   */
  function isContract(address addr) internal view returns (bool) {
    uint256 size;
    // XXX Currently there is no better way to check if there is a contract in an address
    // than to check the size of the code at that address.
    // See https://ethereum.stackexchange.com/a/14016/36603
    // for more details about how this works.
    // TODO Check this again before the Serenity release, because all addresses will be
    // contracts then.
    // solium-disable-next-line security/no-inline-assembly
    assembly { size := extcodesize(addr) }
    return size > 0;
  }

}

// File: zos-lib/contracts/upgradeability/UpgradeabilityProxy.sol

/**
 * @title UpgradeabilityProxy
 * @dev This contract implements a proxy that allows to change the
 * implementation address to which it will delegate.
 * Such a change is called an implementation upgrade.
 */
contract UpgradeabilityProxy is Proxy {
  /**
   * @dev Emitted when the implementation is upgraded.
   * @param implementation Address of the new implementation.
   */
  event Upgraded(address implementation);

  /**
   * @dev Storage slot with the address of the current implementation.
   * This is the keccak-256 hash of "org.zeppelinos.proxy.implementation", and is
   * validated in the constructor.
   */
  bytes32 private constant IMPLEMENTATION_SLOT = 0x7050c9e0f4ca769c69bd3a8ef740bc37934f8e2c036e5a723fd8ee048ed3f8c3;

  /**
   * @dev Contract constructor.
   * @param _implementation Address of the initial implementation.
   */
  constructor(address _implementation) public {
    assert(IMPLEMENTATION_SLOT == keccak256("org.zeppelinos.proxy.implementation"));

    _setImplementation(_implementation);
  }

  /**
   * @dev Returns the current implementation.
   * @return Address of the current implementation
   */
  function _implementation() internal view returns (address impl) {
    bytes32 slot = IMPLEMENTATION_SLOT;
    assembly {
      impl := sload(slot)
    }
  }

  /**
   * @dev Upgrades the proxy to a new implementation.
   * @param newImplementation Address of the new implementation.
   */
  function _upgradeTo(address newImplementation) internal {
    _setImplementation(newImplementation);
    emit Upgraded(newImplementation);
  }

  /**
   * @dev Sets the implementation address of the proxy.
   * @param newImplementation Address of the new implementation.
   */
  function _setImplementation(address newImplementation) private {
    require(AddressUtils.isContract(newImplementation), "Cannot set a proxy implementation to a non-contract address");

    bytes32 slot = IMPLEMENTATION_SLOT;

    assembly {
      sstore(slot, newImplementation)
    }
  }
}

// File: zos-lib/contracts/upgradeability/AdminUpgradeabilityProxy.sol

/**
 * @title AdminUpgradeabilityProxy
 * @dev This contract combines an upgradeability proxy with an authorization
 * mechanism for administrative tasks.
 * All external functions in this contract must be guarded by the
 * `ifAdmin` modifier. See ethereum/solidity#3864 for a Solidity
 * feature proposal that would enable this to be done automatically.
 */
contract AdminUpgradeabilityProxy is UpgradeabilityProxy {
  /**
   * @dev Emitted when the administration has been transferred.
   * @param previousAdmin Address of the previous admin.
   * @param newAdmin Address of the new admin.
   */
  event AdminChanged(address previousAdmin, address newAdmin);

  /**
   * @dev Storage slot with the admin of the contract.
   * This is the keccak-256 hash of "org.zeppelinos.proxy.admin", and is
   * validated in the constructor.
   */
  bytes32 private constant ADMIN_SLOT = 0x10d6a54a4754c8869d6886b5f5d7fbfa5b4522237ea5c60d11bc4e7a1ff9390b;

  /**
   * @dev Modifier to check whether the `msg.sender` is the admin.
   * If it is, it will run the function. Otherwise, it will delegate the call
   * to the implementation.
   */
  modifier ifAdmin() {
    if (msg.sender == _admin()) {
      _;
    } else {
      _fallback();
    }
  }

  /**
   * Contract constructor.
   * It sets the `msg.sender` as the proxy administrator.
   * @param _implementation address of the initial implementation.
   */
  constructor(address _implementation) UpgradeabilityProxy(_implementation) public {
    assert(ADMIN_SLOT == keccak256("org.zeppelinos.proxy.admin"));

    _setAdmin(msg.sender);
  }

  /**
   * @return The address of the proxy admin.
   */
  function admin() external view ifAdmin returns (address) {
    return _admin();
  }

  /**
   * @return The address of the implementation.
   */
  function implementation() external view ifAdmin returns (address) {
    return _implementation();
  }

  /**
   * @dev Changes the admin of the proxy.
   * Only the current admin can call this function.
   * @param newAdmin Address to transfer proxy administration to.
   */
  function changeAdmin(address newAdmin) external ifAdmin {
    require(newAdmin != address(0), "Cannot change the admin of a proxy to the zero address");
    emit AdminChanged(_admin(), newAdmin);
    _setAdmin(newAdmin);
  }

  /**
   * @dev Upgrade the backing implementation of the proxy.
   * Only the admin can call this function.
   * @param newImplementation Address of the new implementation.
   */
  function upgradeTo(address newImplementation) external ifAdmin {
    _upgradeTo(newImplementation);
  }

  /**
   * @dev Upgrade the backing implementation of the proxy and call a function
   * on the new implementation.
   * This is useful to initialize the proxied contract.
   * @param newImplementation Address of the new implementation.
   * @param data Data to send as msg.data in the low level call.
   * It should include the signature and the parameters of the function to be
   * called, as described in
   * https://solidity.readthedocs.io/en/develop/abi-spec.html#function-selector-and-argument-encoding.
   */
  function upgradeToAndCall(address newImplementation, bytes data) payable external ifAdmin {
    _upgradeTo(newImplementation);
    require(address(this).call.value(msg.value)(data));
  }

  /**
   * @return The admin slot.
   */
  function _admin() internal view returns (address adm) {
    bytes32 slot = ADMIN_SLOT;
    assembly {
      adm := sload(slot)
    }
  }

  /**
   * @dev Sets the address of the proxy admin.
   * @param newAdmin Address of the new proxy admin.
   */
  function _setAdmin(address newAdmin) internal {
    bytes32 slot = ADMIN_SLOT;

    assembly {
      sstore(slot, newAdmin)
    }
  }

  /**
   * @dev Only fall back when the sender is not the admin.
   */
  function _willFallback() internal {
    require(msg.sender != _admin(), "Cannot call fallback function from the proxy admin");
    super._willFallback();
  }
}

// File: contracts/FiatTokenProxy.sol

/**
* Copyright CENTRE SECZ 2018
*
* Permission is hereby granted, free of charge, to any person obtaining a copy 
* of this software and associated documentation files (the "Software"), to deal 
* in the Software without restriction, including without limitation the rights 
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 
* copies of the Software, and to permit persons to whom the Software is furnished to 
* do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all 
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN 
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/

pragma solidity ^0.4.24;


/**
 * @title FiatTokenProxy
 * @dev This contract proxies FiatToken calls and enables FiatToken upgrades
*/ 
contract FiatTokenProxy is AdminUpgradeabilityProxy {
    constructor(address _implementation) public AdminUpgradeabilityProxy(_implementation) {
    }
}

/*
 * Copyright (c) 2022, Circle Internet Financial Limited.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
pragma solidity 0.7.6;

/*
 * Copyright (c) 2022, Circle Internet Financial Limited.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @title IMessageHandler
 * @notice Handles messages on destination domain forwarded from
 * an IReceiver
 */
interface IMessageHandler {
    /**
     * @notice handles an incoming message from a Receiver
     * @param sourceDomain the source domain of the message
     * @param sender the sender of the message
     * @param messageBody The message raw bytes
     * @return success bool, true if successful
     */
    function handleReceiveMessage(
        uint32 sourceDomain,
        bytes32 sender,
        bytes calldata messageBody
    ) external returns (bool);
}

/*
 * Copyright (c) 2022, Circle Internet Financial Limited.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @title ITokenMinter
 * @notice interface for minter of tokens that are mintable, burnable, and interchangeable
 * across domains.
 */
interface ITokenMinter {
    /**
     * @notice Mints `amount` of local tokens corresponding to the
     * given (`sourceDomain`, `burnToken`) pair, to `to` address.
     * @dev reverts if the (`sourceDomain`, `burnToken`) pair does not
     * map to a nonzero local token address. This mapping can be queried using
     * getLocalToken().
     * @param sourceDomain Source domain where `burnToken` was burned.
     * @param burnToken Burned token address as bytes32.
     * @param to Address to receive minted tokens, corresponding to `burnToken`,
     * on this domain.
     * @param amount Amount of tokens to mint. Must be less than or equal
     * to the minterAllowance of this TokenMinter for given `_mintToken`.
     * @return mintToken token minted.
     */
    function mint(
        uint32 sourceDomain,
        bytes32 burnToken,
        address to,
        uint256 amount
    ) external returns (address mintToken);

    /**
     * @notice Burn tokens owned by this ITokenMinter.
     * @param burnToken burnable token.
     * @param amount amount of tokens to burn. Must be less than or equal to this ITokenMinter's
     * account balance of the given `_burnToken`.
     */
    function burn(address burnToken, uint256 amount) external;

    /**
     * @notice Get the local token associated with the given remote domain and token.
     * @param remoteDomain Remote domain
     * @param remoteToken Remote token
     * @return local token address
     */
    function getLocalToken(uint32 remoteDomain, bytes32 remoteToken)
        external
        view
        returns (address);

    /**
     * @notice Set the token controller of this ITokenMinter. Token controller
     * is responsible for mapping local tokens to remote tokens, and managing
     * token-specific limits
     * @param newTokenController new token controller address
     */
    function setTokenController(address newTokenController) external;
}

/*
 * Copyright (c) 2022, Circle Internet Financial Limited.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount)
        external
        returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender)
        external
        view
        returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(
        address indexed owner,
        address indexed spender,
        uint256 value
    );
}

/**
 * @title IMintBurnToken
 * @notice interface for mintable and burnable ERC20 token
 */
interface IMintBurnToken is IERC20 {
    /**
     * @dev Function to mint tokens
     * @param to The address that will receive the minted tokens.
     * @param amount The amount of tokens to mint. Must be less than or equal
     * to the minterAllowance of the caller.
     * @return A boolean that indicates if the operation was successful.
     */
    function mint(address to, uint256 amount) external returns (bool);

    /**
     * @dev allows a minter to burn some of its own tokens
     * Validates that caller is a minter and that sender is not blacklisted
     * amount is less than or equal to the minter's account balance
     * @param amount uint256 the amount of tokens to be burned
     */
    function burn(uint256 amount) external;
}

/*
 * Copyright (c) 2022, Circle Internet Financial Limited.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @title IRelayer
 * @notice Sends messages from source domain to destination domain
 */
interface IRelayer {
    /**
     * @notice Sends an outgoing message from the source domain.
     * @dev Increment nonce, format the message, and emit `MessageSent` event with message information.
     * @param destinationDomain Domain of destination chain
     * @param recipient Address of message recipient on destination domain as bytes32
     * @param messageBody Raw bytes content of message
     * @return nonce reserved by message
     */
    function sendMessage(
        uint32 destinationDomain,
        bytes32 recipient,
        bytes calldata messageBody
    ) external returns (uint64);

    /**
     * @notice Sends an outgoing message from the source domain, with a specified caller on the
     * destination domain.
     * @dev Increment nonce, format the message, and emit `MessageSent` event with message information.
     * WARNING: if the `destinationCaller` does not represent a valid address as bytes32, then it will not be possible
     * to broadcast the message on the destination domain. This is an advanced feature, and the standard
     * sendMessage() should be preferred for use cases where a specific destination caller is not required.
     * @param destinationDomain Domain of destination chain
     * @param recipient Address of message recipient on destination domain as bytes32
     * @param destinationCaller caller on the destination domain, as bytes32
     * @param messageBody Raw bytes content of message
     * @return nonce reserved by message
     */
    function sendMessageWithCaller(
        uint32 destinationDomain,
        bytes32 recipient,
        bytes32 destinationCaller,
        bytes calldata messageBody
    ) external returns (uint64);

    /**
     * @notice Replace a message with a new message body and/or destination caller.
     * @dev The `originalAttestation` must be a valid attestation of `originalMessage`.
     * @param originalMessage original message to replace
     * @param originalAttestation attestation of `originalMessage`
     * @param newMessageBody new message body of replaced message
     * @param newDestinationCaller the new destination caller
     */
    function replaceMessage(
        bytes calldata originalMessage,
        bytes calldata originalAttestation,
        bytes calldata newMessageBody,
        bytes32 newDestinationCaller
    ) external;
}

/*
 * Copyright (c) 2022, Circle Internet Financial Limited.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @title IReceiver
 * @notice Receives messages on destination chain and forwards them to IMessageDestinationHandler
 */
interface IReceiver {
    /**
     * @notice Receives an incoming message, validating the header and passing
     * the body to application-specific handler.
     * @param message The message raw bytes
     * @param signature The message signature
     * @return success bool, true if successful
     */
    function receiveMessage(bytes calldata message, bytes calldata signature)
        external
        returns (bool success);
}

/**
 * @title IMessageTransmitter
 * @notice Interface for message transmitters, which both relay and receive messages.
 */
interface IMessageTransmitter is IRelayer, IReceiver {

}

/*
 * Copyright (c) 2022, Circle Internet Financial Limited.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
The MIT License (MIT)

Copyright (c) 2016 Smart Contract Solutions, Inc.

Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:

The above copyright notice and this permission notice shall be included
in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/

/**
 * @title SafeMath_TMV
 * @dev Math operations with safety checks that throw on error
 * @notice SafeMath_TMV is the version of SafeMath used by TypedMemView
 */
library SafeMath_TMV {
    /**
     * @dev Multiplies two numbers, throws on overflow.
     */
    function mul(uint256 _a, uint256 _b) internal pure returns (uint256 c) {
        // Gas optimization: this is cheaper than asserting 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522
        if (_a == 0) {
            return 0;
        }

        c = _a * _b;
        require(c / _a == _b, "Overflow during multiplication.");
        return c;
    }

    /**
     * @dev Integer division of two numbers, truncating the quotient.
     */
    function div(uint256 _a, uint256 _b) internal pure returns (uint256) {
        // assert(_b > 0); // Solidity automatically throws when dividing by 0
        // uint256 c = _a / _b;
        // assert(_a == _b * c + _a % _b); // There is no case in which this doesn't hold
        return _a / _b;
    }

    /**
     * @dev Subtracts two numbers, throws on overflow (i.e. if subtrahend is greater than minuend).
     */
    function sub(uint256 _a, uint256 _b) internal pure returns (uint256) {
        require(_b <= _a, "Underflow during subtraction.");
        return _a - _b;
    }

    /**
     * @dev Adds two numbers, throws on overflow.
     */
    function add(uint256 _a, uint256 _b) internal pure returns (uint256 c) {
        c = _a + _b;
        require(c >= _a, "Overflow during addition.");
        return c;
    }
}

library TypedMemView {
    using SafeMath_TMV for uint256;

    // Why does this exist?
    // the solidity `bytes memory` type has a few weaknesses.
    // 1. You can't index ranges effectively
    // 2. You can't slice without copying
    // 3. The underlying data may represent any type
    // 4. Solidity never deallocates memory, and memory costs grow
    //    superlinearly

    // By using a memory view instead of a `bytes memory` we get the following
    // advantages:
    // 1. Slices are done on the stack, by manipulating the pointer
    // 2. We can index arbitrary ranges and quickly convert them to stack types
    // 3. We can insert type info into the pointer, and typecheck at runtime

    // This makes `TypedMemView` a useful tool for efficient zero-copy
    // algorithms.

    // Why bytes29?
    // We want to avoid confusion between views, digests, and other common
    // types so we chose a large and uncommonly used odd number of bytes
    //
    // Note that while bytes are left-aligned in a word, integers and addresses
    // are right-aligned. This means when working in assembly we have to
    // account for the 3 unused bytes on the righthand side
    //
    // First 5 bytes are a type flag.
    // - ff_ffff_fffe is reserved for unknown type.
    // - ff_ffff_ffff is reserved for invalid types/errors.
    // next 12 are memory address
    // next 12 are len
    // bottom 3 bytes are empty

    // Assumptions:
    // - non-modification of memory.
    // - No Solidity updates
    // - - wrt free mem point
    // - - wrt bytes representation in memory
    // - - wrt memory addressing in general

    // Usage:
    // - create type constants
    // - use `assertType` for runtime type assertions
    // - - unfortunately we can't do this at compile time yet :(
    // - recommended: implement modifiers that perform type checking
    // - - e.g.
    // - - `uint40 constant MY_TYPE = 3;`
    // - - ` modifer onlyMyType(bytes29 myView) { myView.assertType(MY_TYPE); }`
    // - instantiate a typed view from a bytearray using `ref`
    // - use `index` to inspect the contents of the view
    // - use `slice` to create smaller views into the same memory
    // - - `slice` can increase the offset
    // - - `slice can decrease the length`
    // - - must specify the output type of `slice`
    // - - `slice` will return a null view if you try to overrun
    // - - make sure to explicitly check for this with `notNull` or `assertType`
    // - use `equal` for typed comparisons.

    // The null view
    bytes29 public constant NULL =
        hex"ffffffffffffffffffffffffffffffffffffffffffffffffffffffffff";
    uint256 constant LOW_12_MASK = 0xffffffffffffffffffffffff;
    uint8 constant TWELVE_BYTES = 96;

    /**
     * @notice      Returns the encoded hex character that represents the lower 4 bits of the argument.
     * @param _b    The byte
     * @return      char - The encoded hex character
     */
    function nibbleHex(uint8 _b) internal pure returns (uint8 char) {
        // This can probably be done more efficiently, but it's only in error
        // paths, so we don't really care :)
        uint8 _nibble = _b | 0xf0; // set top 4, keep bottom 4
        if (_nibble == 0xf0) {
            return 0x30;
        } // 0
        if (_nibble == 0xf1) {
            return 0x31;
        } // 1
        if (_nibble == 0xf2) {
            return 0x32;
        } // 2
        if (_nibble == 0xf3) {
            return 0x33;
        } // 3
        if (_nibble == 0xf4) {
            return 0x34;
        } // 4
        if (_nibble == 0xf5) {
            return 0x35;
        } // 5
        if (_nibble == 0xf6) {
            return 0x36;
        } // 6
        if (_nibble == 0xf7) {
            return 0x37;
        } // 7
        if (_nibble == 0xf8) {
            return 0x38;
        } // 8
        if (_nibble == 0xf9) {
            return 0x39;
        } // 9
        if (_nibble == 0xfa) {
            return 0x61;
        } // a
        if (_nibble == 0xfb) {
            return 0x62;
        } // b
        if (_nibble == 0xfc) {
            return 0x63;
        } // c
        if (_nibble == 0xfd) {
            return 0x64;
        } // d
        if (_nibble == 0xfe) {
            return 0x65;
        } // e
        if (_nibble == 0xff) {
            return 0x66;
        } // f
    }

    /**
     * @notice      Returns a uint16 containing the hex-encoded byte.
     * @param _b    The byte
     * @return      encoded - The hex-encoded byte
     */
    function byteHex(uint8 _b) internal pure returns (uint16 encoded) {
        encoded |= nibbleHex(_b >> 4); // top 4 bits
        encoded <<= 8;
        encoded |= nibbleHex(_b); // lower 4 bits
    }

    /**
     * @notice      Encodes the uint256 to hex. `first` contains the encoded top 16 bytes.
     *              `second` contains the encoded lower 16 bytes.
     *
     * @param _b    The 32 bytes as uint256
     * @return      first - The top 16 bytes
     * @return      second - The bottom 16 bytes
     */
    function encodeHex(uint256 _b)
        internal
        pure
        returns (uint256 first, uint256 second)
    {
        for (uint8 i = 31; i > 15; i -= 1) {
            uint8 _byte = uint8(_b >> (i * 8));
            first |= byteHex(_byte);
            if (i != 16) {
                first <<= 16;
            }
        }

        // abusing underflow here =_=
        for (uint8 i = 15; i < 255; i -= 1) {
            uint8 _byte = uint8(_b >> (i * 8));
            second |= byteHex(_byte);
            if (i != 0) {
                second <<= 16;
            }
        }
    }

    /**
     * @notice          Changes the endianness of a uint256.
     * @dev             https://graphics.stanford.edu/~seander/bithacks.html#ReverseParallel
     * @param _b        The unsigned integer to reverse
     * @return          v - The reversed value
     */
    function reverseUint256(uint256 _b) internal pure returns (uint256 v) {
        v = _b;

        // swap bytes
        v =
            ((v >> 8) &
                0x00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF) |
            ((v &
                0x00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF) <<
                8);
        // swap 2-byte long pairs
        v =
            ((v >> 16) &
                0x0000FFFF0000FFFF0000FFFF0000FFFF0000FFFF0000FFFF0000FFFF0000FFFF) |
            ((v &
                0x0000FFFF0000FFFF0000FFFF0000FFFF0000FFFF0000FFFF0000FFFF0000FFFF) <<
                16);
        // swap 4-byte long pairs
        v =
            ((v >> 32) &
                0x00000000FFFFFFFF00000000FFFFFFFF00000000FFFFFFFF00000000FFFFFFFF) |
            ((v &
                0x00000000FFFFFFFF00000000FFFFFFFF00000000FFFFFFFF00000000FFFFFFFF) <<
                32);
        // swap 8-byte long pairs
        v =
            ((v >> 64) &
                0x0000000000000000FFFFFFFFFFFFFFFF0000000000000000FFFFFFFFFFFFFFFF) |
            ((v &
                0x0000000000000000FFFFFFFFFFFFFFFF0000000000000000FFFFFFFFFFFFFFFF) <<
                64);
        // swap 16-byte long pairs
        v = (v >> 128) | (v << 128);
    }

    /**
     * @notice      Create a mask with the highest `_len` bits set.
     * @param _len  The length
     * @return      mask - The mask
     */
    function leftMask(uint8 _len) private pure returns (uint256 mask) {
        // ugly. redo without assembly?
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            mask := sar(
                sub(_len, 1),
                0x8000000000000000000000000000000000000000000000000000000000000000
            )
        }
    }

    /**
     * @notice      Return the null view.
     * @return      bytes29 - The null view
     */
    function nullView() internal pure returns (bytes29) {
        return NULL;
    }

    /**
     * @notice      Check if the view is null.
     * @return      bool - True if the view is null
     */
    function isNull(bytes29 memView) internal pure returns (bool) {
        return memView == NULL;
    }

    /**
     * @notice      Check if the view is not null.
     * @return      bool - True if the view is not null
     */
    function notNull(bytes29 memView) internal pure returns (bool) {
        return !isNull(memView);
    }

    /**
     * @notice          Check if the view is of a valid type and points to a valid location
     *                  in memory.
     * @dev             We perform this check by examining solidity's unallocated memory
     *                  pointer and ensuring that the view's upper bound is less than that.
     * @param memView   The view
     * @return          ret - True if the view is valid
     */
    function isValid(bytes29 memView) internal pure returns (bool ret) {
        if (typeOf(memView) == 0xffffffffff) {
            return false;
        }
        uint256 _end = end(memView);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            ret := not(gt(_end, mload(0x40)))
        }
    }

    /**
     * @notice          Require that a typed memory view be valid.
     * @dev             Returns the view for easy chaining.
     * @param memView   The view
     * @return          bytes29 - The validated view
     */
    function assertValid(bytes29 memView) internal pure returns (bytes29) {
        require(isValid(memView), "Validity assertion failed");
        return memView;
    }

    /**
     * @notice          Return true if the memview is of the expected type. Otherwise false.
     * @param memView   The view
     * @param _expected The expected type
     * @return          bool - True if the memview is of the expected type
     */
    function isType(bytes29 memView, uint40 _expected)
        internal
        pure
        returns (bool)
    {
        return typeOf(memView) == _expected;
    }

    /**
     * @notice          Require that a typed memory view has a specific type.
     * @dev             Returns the view for easy chaining.
     * @param memView   The view
     * @param _expected The expected type
     * @return          bytes29 - The view with validated type
     */
    function assertType(bytes29 memView, uint40 _expected)
        internal
        pure
        returns (bytes29)
    {
        if (!isType(memView, _expected)) {
            (, uint256 g) = encodeHex(uint256(typeOf(memView)));
            (, uint256 e) = encodeHex(uint256(_expected));
            string memory err = string(
                abi.encodePacked(
                    "Type assertion failed. Got 0x",
                    uint80(g),
                    ". Expected 0x",
                    uint80(e)
                )
            );
            revert(err);
        }
        return memView;
    }

    /**
     * @notice          Return an identical view with a different type.
     * @param memView   The view
     * @param _newType  The new type
     * @return          newView - The new view with the specified type
     */
    function castTo(bytes29 memView, uint40 _newType)
        internal
        pure
        returns (bytes29 newView)
    {
        // then | in the new type
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            // shift off the top 5 bytes
            newView := or(newView, shr(40, shl(40, memView)))
            newView := or(newView, shl(216, _newType))
        }
    }

    /**
     * @notice          Unsafe raw pointer construction. This should generally not be called
     *                  directly. Prefer `ref` wherever possible.
     * @dev             Unsafe raw pointer construction. This should generally not be called
     *                  directly. Prefer `ref` wherever possible.
     * @param _type     The type
     * @param _loc      The memory address
     * @param _len      The length
     * @return          newView - The new view with the specified type, location and length
     */
    function unsafeBuildUnchecked(
        uint256 _type,
        uint256 _loc,
        uint256 _len
    ) private pure returns (bytes29 newView) {
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            newView := shl(96, or(newView, _type)) // insert type
            newView := shl(96, or(newView, _loc)) // insert loc
            newView := shl(24, or(newView, _len)) // empty bottom 3 bytes
        }
    }

    /**
     * @notice          Instantiate a new memory view. This should generally not be called
     *                  directly. Prefer `ref` wherever possible.
     * @dev             Instantiate a new memory view. This should generally not be called
     *                  directly. Prefer `ref` wherever possible.
     * @param _type     The type
     * @param _loc      The memory address
     * @param _len      The length
     * @return          newView - The new view with the specified type, location and length
     */
    function build(
        uint256 _type,
        uint256 _loc,
        uint256 _len
    ) internal pure returns (bytes29 newView) {
        uint256 _end = _loc.add(_len);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            if gt(_end, mload(0x40)) {
                _end := 0
            }
        }
        if (_end == 0) {
            return NULL;
        }
        newView = unsafeBuildUnchecked(_type, _loc, _len);
    }

    /**
     * @notice          Instantiate a memory view from a byte array.
     * @dev             Note that due to Solidity memory representation, it is not possible to
     *                  implement a deref, as the `bytes` type stores its len in memory.
     * @param arr       The byte array
     * @param newType   The type
     * @return          bytes29 - The memory view
     */
    function ref(bytes memory arr, uint40 newType)
        internal
        pure
        returns (bytes29)
    {
        uint256 _len = arr.length;

        uint256 _loc;
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            _loc := add(arr, 0x20) // our view is of the data, not the struct
        }

        return build(newType, _loc, _len);
    }

    /**
     * @notice          Return the associated type information.
     * @param memView   The memory view
     * @return          _type - The type associated with the view
     */
    function typeOf(bytes29 memView) internal pure returns (uint40 _type) {
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            // 216 == 256 - 40
            _type := shr(216, memView) // shift out lower 24 bytes
        }
    }

    /**
     * @notice          Optimized type comparison. Checks that the 5-byte type flag is equal.
     * @param left      The first view
     * @param right     The second view
     * @return          bool - True if the 5-byte type flag is equal
     */
    function sameType(bytes29 left, bytes29 right)
        internal
        pure
        returns (bool)
    {
        return (left ^ right) >> (2 * TWELVE_BYTES) == 0;
    }

    /**
     * @notice          Return the memory address of the underlying bytes.
     * @param memView   The view
     * @return          _loc - The memory address
     */
    function loc(bytes29 memView) internal pure returns (uint96 _loc) {
        uint256 _mask = LOW_12_MASK; // assembly can't use globals
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            // 120 bits = 12 bytes (the encoded loc) + 3 bytes (empty low space)
            _loc := and(shr(120, memView), _mask)
        }
    }

    /**
     * @notice          The number of memory words this memory view occupies, rounded up.
     * @param memView   The view
     * @return          uint256 - The number of memory words
     */
    function words(bytes29 memView) internal pure returns (uint256) {
        return uint256(len(memView)).add(32) / 32;
    }

    /**
     * @notice          The in-memory footprint of a fresh copy of the view.
     * @param memView   The view
     * @return          uint256 - The in-memory footprint of a fresh copy of the view.
     */
    function footprint(bytes29 memView) internal pure returns (uint256) {
        return words(memView) * 32;
    }

    /**
     * @notice          The number of bytes of the view.
     * @param memView   The view
     * @return          _len - The length of the view
     */
    function len(bytes29 memView) internal pure returns (uint96 _len) {
        uint256 _mask = LOW_12_MASK; // assembly can't use globals
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            _len := and(shr(24, memView), _mask)
        }
    }

    /**
     * @notice          Returns the endpoint of `memView`.
     * @param memView   The view
     * @return          uint256 - The endpoint of `memView`
     */
    function end(bytes29 memView) internal pure returns (uint256) {
        return loc(memView) + len(memView);
    }

    /**
     * @notice          Safe slicing without memory modification.
     * @param memView   The view
     * @param _index    The start index
     * @param _len      The length
     * @param newType   The new type
     * @return          bytes29 - The new view
     */
    function slice(
        bytes29 memView,
        uint256 _index,
        uint256 _len,
        uint40 newType
    ) internal pure returns (bytes29) {
        uint256 _loc = loc(memView);

        // Ensure it doesn't overrun the view
        if (_loc.add(_index).add(_len) > end(memView)) {
            return NULL;
        }

        _loc = _loc.add(_index);
        return build(newType, _loc, _len);
    }

    /**
     * @notice          Shortcut to `slice`. Gets a view representing the first `_len` bytes.
     * @param memView   The view
     * @param _len      The length
     * @param newType   The new type
     * @return          bytes29 - The new view
     */
    function prefix(
        bytes29 memView,
        uint256 _len,
        uint40 newType
    ) internal pure returns (bytes29) {
        return slice(memView, 0, _len, newType);
    }

    /**
     * @notice          Shortcut to `slice`. Gets a view representing the last `_len` byte.
     * @param memView   The view
     * @param _len      The length
     * @param newType   The new type
     * @return          bytes29 - The new view
     */
    function postfix(
        bytes29 memView,
        uint256 _len,
        uint40 newType
    ) internal pure returns (bytes29) {
        return slice(memView, uint256(len(memView)).sub(_len), _len, newType);
    }

    /**
     * @notice          Construct an error message for an indexing overrun.
     * @param _loc      The memory address
     * @param _len      The length
     * @param _index    The index
     * @param _slice    The slice where the overrun occurred
     * @return          err - The err
     */
    function indexErrOverrun(
        uint256 _loc,
        uint256 _len,
        uint256 _index,
        uint256 _slice
    ) internal pure returns (string memory err) {
        (, uint256 a) = encodeHex(_loc);
        (, uint256 b) = encodeHex(_len);
        (, uint256 c) = encodeHex(_index);
        (, uint256 d) = encodeHex(_slice);
        err = string(
            abi.encodePacked(
                "TypedMemView/index - Overran the view. Slice is at 0x",
                uint48(a),
                " with length 0x",
                uint48(b),
                ". Attempted to index at offset 0x",
                uint48(c),
                " with length 0x",
                uint48(d),
                "."
            )
        );
    }

    /**
     * @notice          Load up to 32 bytes from the view onto the stack.
     * @dev             Returns a bytes32 with only the `_bytes` highest bytes set.
     *                  This can be immediately cast to a smaller fixed-length byte array.
     *                  To automatically cast to an integer, use `indexUint`.
     * @param memView   The view
     * @param _index    The index
     * @param _bytes    The bytes
     * @return          result - The 32 byte result
     */
    function index(
        bytes29 memView,
        uint256 _index,
        uint8 _bytes
    ) internal pure returns (bytes32 result) {
        if (_bytes == 0) {
            return bytes32(0);
        }
        if (_index.add(_bytes) > len(memView)) {
            revert(
                indexErrOverrun(
                    loc(memView),
                    len(memView),
                    _index,
                    uint256(_bytes)
                )
            );
        }
        require(
            _bytes <= 32,
            "TypedMemView/index - Attempted to index more than 32 bytes"
        );

        uint8 bitLength = _bytes * 8;
        uint256 _loc = loc(memView);
        uint256 _mask = leftMask(bitLength);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            result := and(mload(add(_loc, _index)), _mask)
        }
    }

    /**
     * @notice          Parse an unsigned integer from the view at `_index`.
     * @dev             Requires that the view have >= `_bytes` bytes following that index.
     * @param memView   The view
     * @param _index    The index
     * @param _bytes    The bytes
     * @return          result - The unsigned integer
     */
    function indexUint(
        bytes29 memView,
        uint256 _index,
        uint8 _bytes
    ) internal pure returns (uint256 result) {
        return uint256(index(memView, _index, _bytes)) >> ((32 - _bytes) * 8);
    }

    /**
     * @notice          Parse an unsigned integer from LE bytes.
     * @param memView   The view
     * @param _index    The index
     * @param _bytes    The bytes
     * @return          result - The unsigned integer
     */
    function indexLEUint(
        bytes29 memView,
        uint256 _index,
        uint8 _bytes
    ) internal pure returns (uint256 result) {
        return reverseUint256(uint256(index(memView, _index, _bytes)));
    }

    /**
     * @notice          Parse an address from the view at `_index`. Requires that the view have >= 20 bytes
     *                  following that index.
     * @param memView   The view
     * @param _index    The index
     * @return          address - The address
     */
    function indexAddress(bytes29 memView, uint256 _index)
        internal
        pure
        returns (address)
    {
        return address(uint160(indexUint(memView, _index, 20)));
    }

    /**
     * @notice          Return the keccak256 hash of the underlying memory
     * @param memView   The view
     * @return          digest - The keccak256 hash of the underlying memory
     */
    function keccak(bytes29 memView) internal pure returns (bytes32 digest) {
        uint256 _loc = loc(memView);
        uint256 _len = len(memView);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            digest := keccak256(_loc, _len)
        }
    }

    /**
     * @notice          Return the sha2 digest of the underlying memory.
     * @dev             We explicitly deallocate memory afterwards.
     * @param memView   The view
     * @return          digest - The sha2 hash of the underlying memory
     */
    function sha2(bytes29 memView) internal view returns (bytes32 digest) {
        uint256 _loc = loc(memView);
        uint256 _len = len(memView);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            let ptr := mload(0x40)
            pop(staticcall(gas(), 2, _loc, _len, ptr, 0x20)) // sha2 #1
            digest := mload(ptr)
        }
    }

    /**
     * @notice          Implements bitcoin's hash160 (rmd160(sha2()))
     * @param memView   The pre-image
     * @return          digest - the Digest
     */
    function hash160(bytes29 memView) internal view returns (bytes20 digest) {
        uint256 _loc = loc(memView);
        uint256 _len = len(memView);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            let ptr := mload(0x40)
            pop(staticcall(gas(), 2, _loc, _len, ptr, 0x20)) // sha2
            pop(staticcall(gas(), 3, ptr, 0x20, ptr, 0x20)) // rmd160
            digest := mload(add(ptr, 0xc)) // return value is 0-prefixed.
        }
    }

    /**
     * @notice          Implements bitcoin's hash256 (double sha2)
     * @param memView   A view of the preimage
     * @return          digest - the Digest
     */
    function hash256(bytes29 memView) internal view returns (bytes32 digest) {
        uint256 _loc = loc(memView);
        uint256 _len = len(memView);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            let ptr := mload(0x40)
            pop(staticcall(gas(), 2, _loc, _len, ptr, 0x20)) // sha2 #1
            pop(staticcall(gas(), 2, ptr, 0x20, ptr, 0x20)) // sha2 #2
            digest := mload(ptr)
        }
    }

    /**
     * @notice          Return true if the underlying memory is equal. Else false.
     * @param left      The first view
     * @param right     The second view
     * @return          bool - True if the underlying memory is equal
     */
    function untypedEqual(bytes29 left, bytes29 right)
        internal
        pure
        returns (bool)
    {
        return
            (loc(left) == loc(right) && len(left) == len(right)) ||
            keccak(left) == keccak(right);
    }

    /**
     * @notice          Return false if the underlying memory is equal. Else true.
     * @param left      The first view
     * @param right     The second view
     * @return          bool - False if the underlying memory is equal
     */
    function untypedNotEqual(bytes29 left, bytes29 right)
        internal
        pure
        returns (bool)
    {
        return !untypedEqual(left, right);
    }

    /**
     * @notice          Compares type equality.
     * @dev             Shortcuts if the pointers are identical, otherwise compares type and digest.
     * @param left      The first view
     * @param right     The second view
     * @return          bool - True if the types are the same
     */
    function equal(bytes29 left, bytes29 right) internal pure returns (bool) {
        return
            left == right ||
            (typeOf(left) == typeOf(right) && keccak(left) == keccak(right));
    }

    /**
     * @notice          Compares type inequality.
     * @dev             Shortcuts if the pointers are identical, otherwise compares type and digest.
     * @param left      The first view
     * @param right     The second view
     * @return          bool - True if the types are not the same
     */
    function notEqual(bytes29 left, bytes29 right)
        internal
        pure
        returns (bool)
    {
        return !equal(left, right);
    }

    /**
     * @notice          Copy the view to a location, return an unsafe memory reference
     * @dev             Super Dangerous direct memory access.
     *
     *                  This reference can be overwritten if anything else modifies memory (!!!).
     *                  As such it MUST be consumed IMMEDIATELY.
     *                  This function is private to prevent unsafe usage by callers.
     * @param memView   The view
     * @param _newLoc   The new location
     * @return          written - the unsafe memory reference
     */
    function unsafeCopyTo(bytes29 memView, uint256 _newLoc)
        private
        view
        returns (bytes29 written)
    {
        require(notNull(memView), "TypedMemView/copyTo - Null pointer deref");
        require(
            isValid(memView),
            "TypedMemView/copyTo - Invalid pointer deref"
        );
        uint256 _len = len(memView);
        uint256 _oldLoc = loc(memView);

        uint256 ptr;
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            ptr := mload(0x40)
            // revert if we're writing in occupied memory
            if gt(ptr, _newLoc) {
                revert(0x60, 0x20) // empty revert message
            }

            // use the identity precompile to copy
            // guaranteed not to fail, so pop the success
            pop(staticcall(gas(), 4, _oldLoc, _len, _newLoc, _len))
        }

        written = unsafeBuildUnchecked(typeOf(memView), _newLoc, _len);
    }

    /**
     * @notice          Copies the referenced memory to a new loc in memory, returning a `bytes` pointing to
     *                  the new memory
     * @dev             Shortcuts if the pointers are identical, otherwise compares type and digest.
     * @param memView   The view
     * @return          ret - The view pointing to the new memory
     */
    function clone(bytes29 memView) internal view returns (bytes memory ret) {
        uint256 ptr;
        uint256 _len = len(memView);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            ptr := mload(0x40) // load unused memory pointer
            ret := ptr
        }
        unsafeCopyTo(memView, ptr + 0x20);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            mstore(0x40, add(add(ptr, _len), 0x20)) // write new unused pointer
            mstore(ptr, _len) // write len of new array (in bytes)
        }
    }

    /**
     * @notice          Join the views in memory, return an unsafe reference to the memory.
     * @dev             Super Dangerous direct memory access.
     *
     *                  This reference can be overwritten if anything else modifies memory (!!!).
     *                  As such it MUST be consumed IMMEDIATELY.
     *                  This function is private to prevent unsafe usage by callers.
     * @param memViews  The views
     * @return          unsafeView - The conjoined view pointing to the new memory
     */
    function unsafeJoin(bytes29[] memory memViews, uint256 _location)
        private
        view
        returns (bytes29 unsafeView)
    {
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            let ptr := mload(0x40)
            // revert if we're writing in occupied memory
            if gt(ptr, _location) {
                revert(0x60, 0x20) // empty revert message
            }
        }

        uint256 _offset = 0;
        for (uint256 i = 0; i < memViews.length; i++) {
            bytes29 memView = memViews[i];
            unsafeCopyTo(memView, _location + _offset);
            _offset += len(memView);
        }
        unsafeView = unsafeBuildUnchecked(0, _location, _offset);
    }

    /**
     * @notice          Produce the keccak256 digest of the concatenated contents of multiple views.
     * @param memViews  The views
     * @return          bytes32 - The keccak256 digest
     */
    function joinKeccak(bytes29[] memory memViews)
        internal
        view
        returns (bytes32)
    {
        uint256 ptr;
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            ptr := mload(0x40) // load unused memory pointer
        }
        return keccak(unsafeJoin(memViews, ptr));
    }

    /**
     * @notice          Produce the sha256 digest of the concatenated contents of multiple views.
     * @param memViews  The views
     * @return          bytes32 - The sha256 digest
     */
    function joinSha2(bytes29[] memory memViews)
        internal
        view
        returns (bytes32)
    {
        uint256 ptr;
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            ptr := mload(0x40) // load unused memory pointer
        }
        return sha2(unsafeJoin(memViews, ptr));
    }

    /**
     * @notice          copies all views, joins them into a new bytearray.
     * @param memViews  The views
     * @return          ret - The new byte array
     */
    function join(bytes29[] memory memViews)
        internal
        view
        returns (bytes memory ret)
    {
        uint256 ptr;
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            ptr := mload(0x40) // load unused memory pointer
        }

        bytes29 _newView = unsafeJoin(memViews, ptr + 0x20);
        uint256 _written = len(_newView);
        uint256 _footprint = footprint(_newView);

        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            // store the legnth
            mstore(ptr, _written)
            // new pointer is old + 0x20 + the footprint of the body
            mstore(0x40, add(add(ptr, _footprint), 0x20))
            ret := ptr
        }
    }
}

/**
 * @title BurnMessage Library
 * @notice Library for formatted BurnMessages used by TokenMessenger.
 * @dev BurnMessage format:
 * Field                 Bytes      Type       Index
 * version               4          uint32     0
 * burnToken             32         bytes32    4
 * mintRecipient         32         bytes32    36
 * amount                32         uint256    68
 * messageSender         32         bytes32    100
 **/
library BurnMessage {
    using TypedMemView for bytes;
    using TypedMemView for bytes29;

    uint8 private constant VERSION_INDEX = 0;
    uint8 private constant VERSION_LEN = 4;
    uint8 private constant BURN_TOKEN_INDEX = 4;
    uint8 private constant BURN_TOKEN_LEN = 32;
    uint8 private constant MINT_RECIPIENT_INDEX = 36;
    uint8 private constant MINT_RECIPIENT_LEN = 32;
    uint8 private constant AMOUNT_INDEX = 68;
    uint8 private constant AMOUNT_LEN = 32;
    uint8 private constant MSG_SENDER_INDEX = 100;
    uint8 private constant MSG_SENDER_LEN = 32;
    // 4 byte version + 32 bytes burnToken + 32 bytes mintRecipient + 32 bytes amount + 32 bytes messageSender
    uint8 private constant BURN_MESSAGE_LEN = 132;

    /**
     * @notice Formats Burn message
     * @param _version The message body version
     * @param _burnToken The burn token address on source domain as bytes32
     * @param _mintRecipient The mint recipient address as bytes32
     * @param _amount The burn amount
     * @param _messageSender The message sender
     * @return Burn formatted message.
     */
    function _formatMessage(
        uint32 _version,
        bytes32 _burnToken,
        bytes32 _mintRecipient,
        uint256 _amount,
        bytes32 _messageSender
    ) internal pure returns (bytes memory) {
        return
            abi.encodePacked(
                _version,
                _burnToken,
                _mintRecipient,
                _amount,
                _messageSender
            );
    }

    /**
     * @notice Retrieves the burnToken from a DepositForBurn BurnMessage
     * @param _message The message
     * @return sourceToken address as bytes32
     */
    function _getMessageSender(bytes29 _message)
        internal
        pure
        returns (bytes32)
    {
        return _message.index(MSG_SENDER_INDEX, MSG_SENDER_LEN);
    }

    /**
     * @notice Retrieves the burnToken from a DepositForBurn BurnMessage
     * @param _message The message
     * @return sourceToken address as bytes32
     */
    function _getBurnToken(bytes29 _message) internal pure returns (bytes32) {
        return _message.index(BURN_TOKEN_INDEX, BURN_TOKEN_LEN);
    }

    /**
     * @notice Retrieves the mintRecipient from a BurnMessage
     * @param _message The message
     * @return mintRecipient
     */
    function _getMintRecipient(bytes29 _message)
        internal
        pure
        returns (bytes32)
    {
        return _message.index(MINT_RECIPIENT_INDEX, MINT_RECIPIENT_LEN);
    }

    /**
     * @notice Retrieves the amount from a BurnMessage
     * @param _message The message
     * @return amount
     */
    function _getAmount(bytes29 _message) internal pure returns (uint256) {
        return _message.indexUint(AMOUNT_INDEX, AMOUNT_LEN);
    }

    /**
     * @notice Retrieves the version from a Burn message
     * @param _message The message
     * @return version
     */
    function _getVersion(bytes29 _message) internal pure returns (uint32) {
        return uint32(_message.indexUint(VERSION_INDEX, VERSION_LEN));
    }

    /**
     * @notice Reverts if burn message is malformed or invalid length
     * @param _message The burn message as bytes29
     */
    function _validateBurnMessageFormat(bytes29 _message) internal pure {
        require(_message.isValid(), "Malformed message");
        require(_message.len() == BURN_MESSAGE_LEN, "Invalid message length");
    }
}

/*
 * Copyright (c) 2022, Circle Internet Financial Limited.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @title Message Library
 * @notice Library for formatted messages used by Relayer and Receiver.
 *
 * @dev The message body is dynamically-sized to support custom message body
 * formats. Other fields must be fixed-size to avoid hash collisions.
 * Each other input value has an explicit type to guarantee fixed-size.
 * Padding: uintNN fields are left-padded, and bytesNN fields are right-padded.
 *
 * Field                 Bytes      Type       Index
 * version               4          uint32     0
 * sourceDomain          4          uint32     4
 * destinationDomain     4          uint32     8
 * nonce                 8          uint64     12
 * sender                32         bytes32    20
 * recipient             32         bytes32    52
 * destinationCaller     32         bytes32    84
 * messageBody           dynamic    bytes      116
 *
 **/
library Message {
    using TypedMemView for bytes;
    using TypedMemView for bytes29;

    // Indices of each field in message
    uint8 private constant VERSION_INDEX = 0;
    uint8 private constant SOURCE_DOMAIN_INDEX = 4;
    uint8 private constant DESTINATION_DOMAIN_INDEX = 8;
    uint8 private constant NONCE_INDEX = 12;
    uint8 private constant SENDER_INDEX = 20;
    uint8 private constant RECIPIENT_INDEX = 52;
    uint8 private constant DESTINATION_CALLER_INDEX = 84;
    uint8 private constant MESSAGE_BODY_INDEX = 116;

    /**
     * @notice Returns formatted (packed) message with provided fields
     * @param _msgVersion the version of the message format
     * @param _msgSourceDomain Domain of home chain
     * @param _msgDestinationDomain Domain of destination chain
     * @param _msgNonce Destination-specific nonce
     * @param _msgSender Address of sender on source chain as bytes32
     * @param _msgRecipient Address of recipient on destination chain as bytes32
     * @param _msgDestinationCaller Address of caller on destination chain as bytes32
     * @param _msgRawBody Raw bytes of message body
     * @return Formatted message
     **/
    function _formatMessage(
        uint32 _msgVersion,
        uint32 _msgSourceDomain,
        uint32 _msgDestinationDomain,
        uint64 _msgNonce,
        bytes32 _msgSender,
        bytes32 _msgRecipient,
        bytes32 _msgDestinationCaller,
        bytes memory _msgRawBody
    ) internal pure returns (bytes memory) {
        return
            abi.encodePacked(
                _msgVersion,
                _msgSourceDomain,
                _msgDestinationDomain,
                _msgNonce,
                _msgSender,
                _msgRecipient,
                _msgDestinationCaller,
                _msgRawBody
            );
    }

    // @notice Returns _message's version field
    function _version(bytes29 _message) internal pure returns (uint32) {
        return uint32(_message.indexUint(VERSION_INDEX, 4));
    }

    // @notice Returns _message's sourceDomain field
    function _sourceDomain(bytes29 _message) internal pure returns (uint32) {
        return uint32(_message.indexUint(SOURCE_DOMAIN_INDEX, 4));
    }

    // @notice Returns _message's destinationDomain field
    function _destinationDomain(bytes29 _message)
        internal
        pure
        returns (uint32)
    {
        return uint32(_message.indexUint(DESTINATION_DOMAIN_INDEX, 4));
    }

    // @notice Returns _message's nonce field
    function _nonce(bytes29 _message) internal pure returns (uint64) {
        return uint64(_message.indexUint(NONCE_INDEX, 8));
    }

    // @notice Returns _message's sender field
    function _sender(bytes29 _message) internal pure returns (bytes32) {
        return _message.index(SENDER_INDEX, 32);
    }

    // @notice Returns _message's recipient field
    function _recipient(bytes29 _message) internal pure returns (bytes32) {
        return _message.index(RECIPIENT_INDEX, 32);
    }

    // @notice Returns _message's destinationCaller field
    function _destinationCaller(bytes29 _message)
        internal
        pure
        returns (bytes32)
    {
        return _message.index(DESTINATION_CALLER_INDEX, 32);
    }

    // @notice Returns _message's messageBody field
    function _messageBody(bytes29 _message) internal pure returns (bytes29) {
        return
            _message.slice(
                MESSAGE_BODY_INDEX,
                _message.len() - MESSAGE_BODY_INDEX,
                0
            );
    }

    /**
     * @notice converts address to bytes32 (alignment preserving cast.)
     * @param addr the address to convert to bytes32
     */
    function addressToBytes32(address addr) external pure returns (bytes32) {
        return bytes32(uint256(uint160(addr)));
    }

    /**
     * @notice converts bytes32 to address (alignment preserving cast.)
     * @dev Warning: it is possible to have different input values _buf map to the same address.
     * For use cases where this is not acceptable, validate that the first 12 bytes of _buf are zero-padding.
     * @param _buf the bytes32 to convert to address
     */
    function bytes32ToAddress(bytes32 _buf) public pure returns (address) {
        return address(uint160(uint256(_buf)));
    }

    /**
     * @notice Reverts if message is malformed or incorrect length
     * @param _message The message as bytes29
     */
    function _validateMessageFormat(bytes29 _message) internal pure {
        require(_message.isValid(), "Malformed message");
        require(
            _message.len() >= MESSAGE_BODY_INDEX,
            "Invalid message: too short"
        );
    }
}

/*
 * Copyright (c) 2022, Circle Internet Financial Limited.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with GSN meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address payable) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

/**
 * @dev forked from https://github.com/OpenZeppelin/openzeppelin-contracts/blob/7c5f6bc2c8743d83443fa46395d75f2f3f99054a/contracts/access/Ownable.sol
 * Modifications:
 * 1. Update Solidity version from 0.8.0 to 0.7.6 (11/9/2022). (v8 was used
 * as base because it includes internal _transferOwnership method.)
 * 2. Remove renounceOwnership function
 *
 * Description
 * Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(
        address indexed previousOwner,
        address indexed newOwner
    );

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() {
        _transferOwnership(_msgSender());
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        _checkOwner();
        _;
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if the sender is not the owner.
     */
    function _checkOwner() internal view virtual {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(
            newOwner != address(0),
            "Ownable: new owner is the zero address"
        );
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

/**
 * @dev forked from https://github.com/OpenZeppelin/openzeppelin-contracts/blob/7c5f6bc2c8743d83443fa46395d75f2f3f99054a/contracts/access/Ownable2Step.sol
 * Modifications:
 * 1. Update Solidity version from 0.8.0 to 0.7.6. Version 0.8.0 was used
 * as base because this contract was added to OZ repo after version 0.8.0.
 *
 * Contract module which provides access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership} and {acceptOwnership}.
 *
 * This module is used through inheritance. It will make available all functions
 * from parent (Ownable).
 */
abstract contract Ownable2Step is Ownable {
    address private _pendingOwner;

    event OwnershipTransferStarted(
        address indexed previousOwner,
        address indexed newOwner
    );

    /**
     * @dev Returns the address of the pending owner.
     */
    function pendingOwner() public view virtual returns (address) {
        return _pendingOwner;
    }

    /**
     * @dev Starts the ownership transfer of the contract to a new account. Replaces the pending transfer if there is one.
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner)
        public
        virtual
        override
        onlyOwner
    {
        _pendingOwner = newOwner;
        emit OwnershipTransferStarted(owner(), newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`) and deletes any pending owner.
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual override {
        delete _pendingOwner;
        super._transferOwnership(newOwner);
    }

    /**
     * @dev The new owner accepts the ownership transfer.
     */
    function acceptOwnership() external {
        address sender = _msgSender();
        require(
            pendingOwner() == sender,
            "Ownable2Step: caller is not the new owner"
        );
        _transferOwnership(sender);
    }
}

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b)
        internal
        pure
        returns (bool, uint256)
    {
        uint256 c = a + b;
        if (c < a) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b)
        internal
        pure
        returns (bool, uint256)
    {
        if (b > a) return (false, 0);
        return (true, a - b);
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b)
        internal
        pure
        returns (bool, uint256)
    {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) return (true, 0);
        uint256 c = a * b;
        if (c / a != b) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b)
        internal
        pure
        returns (bool, uint256)
    {
        if (b == 0) return (false, 0);
        return (true, a / b);
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b)
        internal
        pure
        returns (bool, uint256)
    {
        if (b == 0) return (false, 0);
        return (true, a % b);
    }

    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");
        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a, "SafeMath: subtraction overflow");
        return a - b;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a == 0) return 0;
        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");
        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: division by zero");
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: modulo by zero");
        return a % b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        return a - b;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryDiv}.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a % b;
    }
}

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly {
            size := extcodesize(account)
        }
        return size > 0;
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(
            address(this).balance >= amount,
            "Address: insufficient balance"
        );

        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (bool success, ) = recipient.call{value: amount}("");
        require(
            success,
            "Address: unable to send value, recipient may have reverted"
        );
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain`call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data)
        internal
        returns (bytes memory)
    {
        return functionCall(target, data, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value
    ) internal returns (bytes memory) {
        return
            functionCallWithValue(
                target,
                data,
                value,
                "Address: low-level call with value failed"
            );
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(
            address(this).balance >= value,
            "Address: insufficient balance for call"
        );
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{value: value}(
            data
        );
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data)
        internal
        view
        returns (bytes memory)
    {
        return
            functionStaticCall(
                target,
                data,
                "Address: low-level static call failed"
            );
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.staticcall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data)
        internal
        returns (bytes memory)
    {
        return
            functionDelegateCall(
                target,
                data,
                "Address: low-level delegate call failed"
            );
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    function _verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) private pure returns (bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    using SafeMath for uint256;
    using Address for address;

    function safeTransfer(
        IERC20 token,
        address to,
        uint256 value
    ) internal {
        _callOptionalReturn(
            token,
            abi.encodeWithSelector(token.transfer.selector, to, value)
        );
    }

    function safeTransferFrom(
        IERC20 token,
        address from,
        address to,
        uint256 value
    ) internal {
        _callOptionalReturn(
            token,
            abi.encodeWithSelector(token.transferFrom.selector, from, to, value)
        );
    }

    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    function safeApprove(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        // solhint-disable-next-line max-line-length
        require(
            (value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        _callOptionalReturn(
            token,
            abi.encodeWithSelector(token.approve.selector, spender, value)
        );
    }

    function safeIncreaseAllowance(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        uint256 newAllowance = token.allowance(address(this), spender).add(
            value
        );
        _callOptionalReturn(
            token,
            abi.encodeWithSelector(
                token.approve.selector,
                spender,
                newAllowance
            )
        );
    }

    function safeDecreaseAllowance(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        uint256 newAllowance = token.allowance(address(this), spender).sub(
            value,
            "SafeERC20: decreased allowance below zero"
        );
        _callOptionalReturn(
            token,
            abi.encodeWithSelector(
                token.approve.selector,
                spender,
                newAllowance
            )
        );
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function _callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

        bytes memory returndata = address(token).functionCall(
            data,
            "SafeERC20: low-level call failed"
        );
        if (returndata.length > 0) {
            // Return data is optional
            // solhint-disable-next-line max-line-length
            require(
                abi.decode(returndata, (bool)),
                "SafeERC20: ERC20 operation did not succeed"
            );
        }
    }
}

/**
 * @notice Base contract which allows children to rescue ERC20 locked in their contract.
 * @dev Forked from https://github.com/centrehq/centre-tokens/blob/0d3cab14ebd133a83fc834dbd48d0468bdf0b391/contracts/v1.1/Rescuable.sol
 * Modifications:
 * 1. Update Solidity version from 0.6.12 to 0.7.6 (8/23/2022)
 */
contract Rescuable is Ownable2Step {
    using SafeERC20 for IERC20;

    address private _rescuer;

    event RescuerChanged(address indexed newRescuer);

    /**
     * @notice Returns current rescuer
     * @return Rescuer's address
     */
    function rescuer() external view returns (address) {
        return _rescuer;
    }

    /**
     * @notice Revert if called by any account other than the rescuer.
     */
    modifier onlyRescuer() {
        require(msg.sender == _rescuer, "Rescuable: caller is not the rescuer");
        _;
    }

    /**
     * @notice Rescue ERC20 tokens locked up in this contract.
     * @param tokenContract ERC20 token contract address
     * @param to        Recipient address
     * @param amount    Amount to withdraw
     */
    function rescueERC20(
        IERC20 tokenContract,
        address to,
        uint256 amount
    ) external onlyRescuer {
        tokenContract.safeTransfer(to, amount);
    }

    /**
     * @notice Assign the rescuer role to a given address.
     * @param newRescuer New rescuer's address
     */
    function updateRescuer(address newRescuer) external onlyOwner {
        require(
            newRescuer != address(0),
            "Rescuable: new rescuer is the zero address"
        );
        _rescuer = newRescuer;
        emit RescuerChanged(newRescuer);
    }
}

/**
 * @title TokenMessenger
 * @notice Sends messages and receives messages to/from MessageTransmitters
 * and to/from TokenMinters
 */
contract TokenMessenger is IMessageHandler, Rescuable {
    // ============ Events ============
    /**
     * @notice Emitted when a DepositForBurn message is sent
     * @param nonce unique nonce reserved by message
     * @param burnToken address of token burnt on source domain
     * @param amount deposit amount
     * @param depositor address where deposit is transferred from
     * @param mintRecipient address receiving minted tokens on destination domain as bytes32
     * @param destinationDomain destination domain
     * @param destinationTokenMessenger address of TokenMessenger on destination domain as bytes32
     * @param destinationCaller authorized caller as bytes32 of receiveMessage() on destination domain, if not equal to bytes32(0).
     * If equal to bytes32(0), any address can call receiveMessage().
     */
    event DepositForBurn(
        uint64 indexed nonce,
        address indexed burnToken,
        uint256 amount,
        address indexed depositor,
        bytes32 mintRecipient,
        uint32 destinationDomain,
        bytes32 destinationTokenMessenger,
        bytes32 destinationCaller
    );

    /**
     * @notice Emitted when tokens are minted
     * @param mintRecipient recipient address of minted tokens
     * @param amount amount of minted tokens
     * @param mintToken contract address of minted token
     */
    event MintAndWithdraw(
        address indexed mintRecipient,
        uint256 amount,
        address indexed mintToken
    );

    /**
     * @notice Emitted when a remote TokenMessenger is added
     * @param domain remote domain
     * @param tokenMessenger TokenMessenger on remote domain
     */
    event RemoteTokenMessengerAdded(uint32 domain, bytes32 tokenMessenger);

    /**
     * @notice Emitted when a remote TokenMessenger is removed
     * @param domain remote domain
     * @param tokenMessenger TokenMessenger on remote domain
     */
    event RemoteTokenMessengerRemoved(uint32 domain, bytes32 tokenMessenger);

    /**
     * @notice Emitted when the local minter is added
     * @param localMinter address of local minter
     * @notice Emitted when the local minter is added
     */
    event LocalMinterAdded(address localMinter);

    /**
     * @notice Emitted when the local minter is removed
     * @param localMinter address of local minter
     * @notice Emitted when the local minter is removed
     */
    event LocalMinterRemoved(address localMinter);

    // ============ Libraries ============
    using TypedMemView for bytes;
    using TypedMemView for bytes29;
    using BurnMessage for bytes29;
    using Message for bytes29;

    // ============ State Variables ============
    // Local Message Transmitter responsible for sending and receiving messages to/from remote domains
    IMessageTransmitter public immutable localMessageTransmitter;

    // Version of message body format
    uint32 public immutable messageBodyVersion;

    // Minter responsible for minting and burning tokens on the local domain
    ITokenMinter public localMinter;

    // Valid TokenMessengers on remote domains
    mapping(uint32 => bytes32) public remoteTokenMessengers;

    // ============ Modifiers ============
    /**
     * @notice Only accept messages from a registered TokenMessenger contract on given remote domain
     * @param domain The remote domain
     * @param tokenMessenger The address of the TokenMessenger contract for the given remote domain
     */
    modifier onlyRemoteTokenMessenger(uint32 domain, bytes32 tokenMessenger) {
        require(
            _isRemoteTokenMessenger(domain, tokenMessenger),
            "Remote TokenMessenger unsupported"
        );
        _;
    }

    /**
     * @notice Only accept messages from the registered message transmitter on local domain
     */
    modifier onlyLocalMessageTransmitter() {
        // Caller must be the registered message transmitter for this domain
        require(_isLocalMessageTransmitter(), "Invalid message transmitter");
        _;
    }

    // ============ Constructor ============
    /**
     * @param _messageTransmitter Message transmitter address
     * @param _messageBodyVersion Message body version
     */
    constructor(address _messageTransmitter, uint32 _messageBodyVersion) {
        require(
            _messageTransmitter != address(0),
            "MessageTransmitter not set"
        );
        localMessageTransmitter = IMessageTransmitter(_messageTransmitter);
        messageBodyVersion = _messageBodyVersion;
    }

    // ============ External Functions  ============
    /**
     * @notice Deposits and burns tokens from sender to be minted on destination domain.
     * Emits a `DepositForBurn` event.
     * @dev reverts if:
     * - given burnToken is not supported
     * - given destinationDomain has no TokenMessenger registered
     * - transferFrom() reverts. For example, if sender's burnToken balance or approved allowance
     * to this contract is less than `amount`.
     * - burn() reverts. For example, if `amount` is 0.
     * - MessageTransmitter returns false or reverts.
     * @param amount amount of tokens to burn
     * @param destinationDomain destination domain
     * @param mintRecipient address of mint recipient on destination domain
     * @param burnToken address of contract to burn deposited tokens, on local domain
     * @return _nonce unique nonce reserved by message
     */
    function depositForBurn(
        uint256 amount,
        uint32 destinationDomain,
        bytes32 mintRecipient,
        address burnToken
    ) external returns (uint64 _nonce) {
        return
            _depositForBurn(
                amount,
                destinationDomain,
                mintRecipient,
                burnToken,
                // (bytes32(0) here indicates that any address can call receiveMessage()
                // on the destination domain, triggering mint to specified `mintRecipient`)
                bytes32(0)
            );
    }

    /**
     * @notice Deposits and burns tokens from sender to be minted on destination domain. The mint
     * on the destination domain must be called by `destinationCaller`.
     * WARNING: if the `destinationCaller` does not represent a valid address as bytes32, then it will not be possible
     * to broadcast the message on the destination domain. This is an advanced feature, and the standard
     * depositForBurn() should be preferred for use cases where a specific destination caller is not required.
     * Emits a `DepositForBurn` event.
     * @dev reverts if:
     * - given destinationCaller is zero address
     * - given burnToken is not supported
     * - given destinationDomain has no TokenMessenger registered
     * - transferFrom() reverts. For example, if sender's burnToken balance or approved allowance
     * to this contract is less than `amount`.
     * - burn() reverts. For example, if `amount` is 0.
     * - MessageTransmitter returns false or reverts.
     * @param amount amount of tokens to burn
     * @param destinationDomain destination domain
     * @param mintRecipient address of mint recipient on destination domain
     * @param burnToken address of contract to burn deposited tokens, on local domain
     * @param destinationCaller caller on the destination domain, as bytes32
     * @return nonce unique nonce reserved by message
     */
    function depositForBurnWithCaller(
        uint256 amount,
        uint32 destinationDomain,
        bytes32 mintRecipient,
        address burnToken,
        bytes32 destinationCaller
    ) external returns (uint64 nonce) {
        // Destination caller must be nonzero. To allow any destination caller, use depositForBurn().
        require(destinationCaller != bytes32(0), "Invalid destination caller");

        return
            _depositForBurn(
                amount,
                destinationDomain,
                mintRecipient,
                burnToken,
                destinationCaller
            );
    }

    /**
     * @notice Replace a BurnMessage to change the mint recipient and/or
     * destination caller. Allows the sender of a previous BurnMessage
     * (created by depositForBurn or depositForBurnWithCaller)
     * to send a new BurnMessage to replace the original.
     * The new BurnMessage will reuse the amount and burn token of the original,
     * without requiring a new deposit.
     * @dev The new message will reuse the original message's nonce. For a
     * given nonce, all replacement message(s) and the original message are
     * valid to broadcast on the destination domain, until the first message
     * at the nonce confirms, at which point all others are invalidated.
     * Note: The msg.sender of the replaced message must be the same as the
     * msg.sender of the original message.
     * @param originalMessage original message bytes (to replace)
     * @param originalAttestation original attestation bytes
     * @param newDestinationCaller the new destination caller, which may be the
     * same as the original destination caller, a new destination caller, or an empty
     * destination caller (bytes32(0), indicating that any destination caller is valid.)
     * @param newMintRecipient the new mint recipient, which may be the same as the
     * original mint recipient, or different.
     */
    function replaceDepositForBurn(
        bytes calldata originalMessage,
        bytes calldata originalAttestation,
        bytes32 newDestinationCaller,
        bytes32 newMintRecipient
    ) external {
        bytes29 _originalMsg = originalMessage.ref(0);
        _originalMsg._validateMessageFormat();
        bytes29 _originalMsgBody = _originalMsg._messageBody();
        _originalMsgBody._validateBurnMessageFormat();

        bytes32 _originalMsgSender = _originalMsgBody._getMessageSender();
        // _originalMsgSender must match msg.sender of original message
        require(
            msg.sender == Message.bytes32ToAddress(_originalMsgSender),
            "Invalid sender for message"
        );
        require(
            newMintRecipient != bytes32(0),
            "Mint recipient must be nonzero"
        );

        bytes32 _burnToken = _originalMsgBody._getBurnToken();
        uint256 _amount = _originalMsgBody._getAmount();

        bytes memory _newMessageBody = BurnMessage._formatMessage(
            messageBodyVersion,
            _burnToken,
            newMintRecipient,
            _amount,
            _originalMsgSender
        );

        localMessageTransmitter.replaceMessage(
            originalMessage,
            originalAttestation,
            _newMessageBody,
            newDestinationCaller
        );

        emit DepositForBurn(
            _originalMsg._nonce(),
            Message.bytes32ToAddress(_burnToken),
            _amount,
            msg.sender,
            newMintRecipient,
            _originalMsg._destinationDomain(),
            _originalMsg._recipient(),
            newDestinationCaller
        );
    }

    /**
     * @notice Handles an incoming message received by the local MessageTransmitter,
     * and takes the appropriate action. For a burn message, mints the
     * associated token to the requested recipient on the local domain.
     * @dev Validates the local sender is the local MessageTransmitter, and the
     * remote sender is a registered remote TokenMessenger for `remoteDomain`.
     * @param remoteDomain The domain where the message originated from.
     * @param sender The sender of the message (remote TokenMessenger).
     * @param messageBody The message body bytes.
     * @return success Bool, true if successful.
     */
    function handleReceiveMessage(
        uint32 remoteDomain,
        bytes32 sender,
        bytes calldata messageBody
    )
        external
        override
        onlyLocalMessageTransmitter
        onlyRemoteTokenMessenger(remoteDomain, sender)
        returns (bool)
    {
        bytes29 _msg = messageBody.ref(0);
        _msg._validateBurnMessageFormat();
        require(
            _msg._getVersion() == messageBodyVersion,
            "Invalid message body version"
        );

        bytes32 _mintRecipient = _msg._getMintRecipient();
        bytes32 _burnToken = _msg._getBurnToken();
        uint256 _amount = _msg._getAmount();

        ITokenMinter _localMinter = _getLocalMinter();

        _mintAndWithdraw(
            address(_localMinter),
            remoteDomain,
            _burnToken,
            Message.bytes32ToAddress(_mintRecipient),
            _amount
        );

        return true;
    }

    /**
     * @notice Add the TokenMessenger for a remote domain.
     * @dev Reverts if there is already a TokenMessenger set for domain.
     * @param domain Domain of remote TokenMessenger.
     * @param tokenMessenger Address of remote TokenMessenger as bytes32.
     */
    function addRemoteTokenMessenger(uint32 domain, bytes32 tokenMessenger)
        external
        onlyOwner
    {
        require(tokenMessenger != bytes32(0), "bytes32(0) not allowed");

        require(
            remoteTokenMessengers[domain] == bytes32(0),
            "TokenMessenger already set"
        );

        remoteTokenMessengers[domain] = tokenMessenger;
        emit RemoteTokenMessengerAdded(domain, tokenMessenger);
    }

    /**
     * @notice Remove the TokenMessenger for a remote domain.
     * @dev Reverts if there is no TokenMessenger set for `domain`.
     * @param domain Domain of remote TokenMessenger
     */
    function removeRemoteTokenMessenger(uint32 domain) external onlyOwner {
        // No TokenMessenger set for given remote domain.
        require(
            remoteTokenMessengers[domain] != bytes32(0),
            "No TokenMessenger set"
        );

        bytes32 _removedTokenMessenger = remoteTokenMessengers[domain];
        delete remoteTokenMessengers[domain];
        emit RemoteTokenMessengerRemoved(domain, _removedTokenMessenger);
    }

    /**
     * @notice Add minter for the local domain.
     * @dev Reverts if a minter is already set for the local domain.
     * @param newLocalMinter The address of the minter on the local domain.
     */
    function addLocalMinter(address newLocalMinter) external onlyOwner {
        require(newLocalMinter != address(0), "Zero address not allowed");

        require(
            address(localMinter) == address(0),
            "Local minter is already set."
        );

        localMinter = ITokenMinter(newLocalMinter);

        emit LocalMinterAdded(newLocalMinter);
    }

    /**
     * @notice Remove the minter for the local domain.
     * @dev Reverts if the minter of the local domain is not set.
     */
    function removeLocalMinter() external onlyOwner {
        address _localMinterAddress = address(localMinter);
        require(_localMinterAddress != address(0), "No local minter is set.");

        delete localMinter;
        emit LocalMinterRemoved(_localMinterAddress);
    }

    // ============ Internal Utils ============
    /**
     * @notice Deposits and burns tokens from sender to be minted on destination domain.
     * Emits a `DepositForBurn` event.
     * @param _amount amount of tokens to burn (must be non-zero)
     * @param _destinationDomain destination domain
     * @param _mintRecipient address of mint recipient on destination domain
     * @param _burnToken address of contract to burn deposited tokens, on local domain
     * @param _destinationCaller caller on the destination domain, as bytes32
     * @return nonce unique nonce reserved by message
     */
    function _depositForBurn(
        uint256 _amount,
        uint32 _destinationDomain,
        bytes32 _mintRecipient,
        address _burnToken,
        bytes32 _destinationCaller
    ) internal returns (uint64 nonce) {
        require(_amount > 0, "Amount must be nonzero");
        require(_mintRecipient != bytes32(0), "Mint recipient must be nonzero");

        bytes32 _destinationTokenMessenger = _getRemoteTokenMessenger(
            _destinationDomain
        );

        ITokenMinter _localMinter = _getLocalMinter();
        IMintBurnToken _mintBurnToken = IMintBurnToken(_burnToken);
        require(
            _mintBurnToken.transferFrom(
                msg.sender,
                address(_localMinter),
                _amount
            ),
            "Transfer operation failed"
        );
        _localMinter.burn(_burnToken, _amount);

        // Format message body
        bytes memory _burnMessage = BurnMessage._formatMessage(
            messageBodyVersion,
            Message.addressToBytes32(_burnToken),
            _mintRecipient,
            _amount,
            Message.addressToBytes32(msg.sender)
        );

        uint64 _nonceReserved = _sendDepositForBurnMessage(
            _destinationDomain,
            _destinationTokenMessenger,
            _destinationCaller,
            _burnMessage
        );

        emit DepositForBurn(
            _nonceReserved,
            _burnToken,
            _amount,
            msg.sender,
            _mintRecipient,
            _destinationDomain,
            _destinationTokenMessenger,
            _destinationCaller
        );

        return _nonceReserved;
    }

    /**
     * @notice Sends a BurnMessage through the local message transmitter
     * @dev calls local message transmitter's sendMessage() function if `_destinationCaller` == bytes32(0),
     * or else calls sendMessageWithCaller().
     * @param _destinationDomain destination domain
     * @param _destinationTokenMessenger address of registered TokenMessenger contract on destination domain, as bytes32
     * @param _destinationCaller caller on the destination domain, as bytes32. If `_destinationCaller` == bytes32(0),
     * any address can call receiveMessage() on destination domain.
     * @param _burnMessage formatted BurnMessage bytes (message body)
     * @return nonce unique nonce reserved by message
     */
    function _sendDepositForBurnMessage(
        uint32 _destinationDomain,
        bytes32 _destinationTokenMessenger,
        bytes32 _destinationCaller,
        bytes memory _burnMessage
    ) internal returns (uint64 nonce) {
        if (_destinationCaller == bytes32(0)) {
            return
                localMessageTransmitter.sendMessage(
                    _destinationDomain,
                    _destinationTokenMessenger,
                    _burnMessage
                );
        } else {
            return
                localMessageTransmitter.sendMessageWithCaller(
                    _destinationDomain,
                    _destinationTokenMessenger,
                    _destinationCaller,
                    _burnMessage
                );
        }
    }

    /**
     * @notice Mints tokens to a recipient
     * @param _tokenMinter address of TokenMinter contract
     * @param _remoteDomain domain where burned tokens originate from
     * @param _burnToken address of token burned
     * @param _mintRecipient recipient address of minted tokens
     * @param _amount amount of minted tokens
     */
    function _mintAndWithdraw(
        address _tokenMinter,
        uint32 _remoteDomain,
        bytes32 _burnToken,
        address _mintRecipient,
        uint256 _amount
    ) internal {
        ITokenMinter _minter = ITokenMinter(_tokenMinter);
        address _mintToken = _minter.mint(
            _remoteDomain,
            _burnToken,
            _mintRecipient,
            _amount
        );

        emit MintAndWithdraw(_mintRecipient, _amount, _mintToken);
    }

    /**
     * @notice return the remote TokenMessenger for the given `_domain` if one exists, else revert.
     * @param _domain The domain for which to get the remote TokenMessenger
     * @return _tokenMessenger The address of the TokenMessenger on `_domain` as bytes32
     */
    function _getRemoteTokenMessenger(uint32 _domain)
        internal
        view
        returns (bytes32)
    {
        bytes32 _tokenMessenger = remoteTokenMessengers[_domain];
        require(_tokenMessenger != bytes32(0), "No TokenMessenger for domain");
        return _tokenMessenger;
    }

    /**
     * @notice return the local minter address if it is set, else revert.
     * @return local minter as ITokenMinter.
     */
    function _getLocalMinter() internal view returns (ITokenMinter) {
        require(address(localMinter) != address(0), "Local minter is not set");
        return localMinter;
    }

    /**
     * @notice Return true if the given remote domain and TokenMessenger is registered
     * on this TokenMessenger.
     * @param _domain The remote domain of the message.
     * @param _tokenMessenger The address of the TokenMessenger on remote domain.
     * @return true if a remote TokenMessenger is registered for `_domain` and `_tokenMessenger`,
     * on this TokenMessenger.
     */
    function _isRemoteTokenMessenger(uint32 _domain, bytes32 _tokenMessenger)
        internal
        view
        returns (bool)
    {
        return
            _tokenMessenger != bytes32(0) &&
            remoteTokenMessengers[_domain] == _tokenMessenger;
    }

    /**
     * @notice Returns true if the message sender is the local registered MessageTransmitter
     * @return true if message sender is the registered local message transmitter
     */
    function _isLocalMessageTransmitter() internal view returns (bool) {
        return
            address(localMessageTransmitter) != address(0) &&
            msg.sender == address(localMessageTransmitter);
    }
}

/*
 * Copyright (c) 2022, Circle Internet Financial Limited.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
pragma solidity 0.7.6;

/*
The MIT License (MIT)

Copyright (c) 2016 Smart Contract Solutions, Inc.

Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:

The above copyright notice and this permission notice shall be included
in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/

/**
 * @title SafeMath
 * @dev Math operations with safety checks that throw on error
 */
library SafeMath {

    /**
     * @dev Multiplies two numbers, throws on overflow.
     */
    function mul(uint256 _a, uint256 _b) internal pure returns (uint256 c) {
        // Gas optimization: this is cheaper than asserting 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522
        if (_a == 0) {
            return 0;
        }

        c = _a * _b;
        require(c / _a == _b, "Overflow during multiplication.");
        return c;
    }

    /**
     * @dev Integer division of two numbers, truncating the quotient.
     */
    function div(uint256 _a, uint256 _b) internal pure returns (uint256) {
        // assert(_b > 0); // Solidity automatically throws when dividing by 0
        // uint256 c = _a / _b;
        // assert(_a == _b * c + _a % _b); // There is no case in which this doesn't hold
        return _a / _b;
    }

    /**
     * @dev Subtracts two numbers, throws on overflow (i.e. if subtrahend is greater than minuend).
     */
    function sub(uint256 _a, uint256 _b) internal pure returns (uint256) {
        require(_b <= _a, "Underflow during subtraction.");
        return _a - _b;
    }

    /**
     * @dev Adds two numbers, throws on overflow.
     */
    function add(uint256 _a, uint256 _b) internal pure returns (uint256 c) {
        c = _a + _b;
        require(c >= _a, "Overflow during addition.");
        return c;
    }
}

library TypedMemView {
    using SafeMath for uint256;

    // Why does this exist?
    // the solidity `bytes memory` type has a few weaknesses.
    // 1. You can't index ranges effectively
    // 2. You can't slice without copying
    // 3. The underlying data may represent any type
    // 4. Solidity never deallocates memory, and memory costs grow
    //    superlinearly

    // By using a memory view instead of a `bytes memory` we get the following
    // advantages:
    // 1. Slices are done on the stack, by manipulating the pointer
    // 2. We can index arbitrary ranges and quickly convert them to stack types
    // 3. We can insert type info into the pointer, and typecheck at runtime

    // This makes `TypedMemView` a useful tool for efficient zero-copy
    // algorithms.

    // Why bytes29?
    // We want to avoid confusion between views, digests, and other common
    // types so we chose a large and uncommonly used odd number of bytes
    //
    // Note that while bytes are left-aligned in a word, integers and addresses
    // are right-aligned. This means when working in assembly we have to
    // account for the 3 unused bytes on the righthand side
    //
    // First 5 bytes are a type flag.
    // - ff_ffff_fffe is reserved for unknown type.
    // - ff_ffff_ffff is reserved for invalid types/errors.
    // next 12 are memory address
    // next 12 are len
    // bottom 3 bytes are empty

    // Assumptions:
    // - non-modification of memory.
    // - No Solidity updates
    // - - wrt free mem point
    // - - wrt bytes representation in memory
    // - - wrt memory addressing in general

    // Usage:
    // - create type constants
    // - use `assertType` for runtime type assertions
    // - - unfortunately we can't do this at compile time yet :(
    // - recommended: implement modifiers that perform type checking
    // - - e.g.
    // - - `uint40 constant MY_TYPE = 3;`
    // - - ` modifer onlyMyType(bytes29 myView) { myView.assertType(MY_TYPE); }`
    // - instantiate a typed view from a bytearray using `ref`
    // - use `index` to inspect the contents of the view
    // - use `slice` to create smaller views into the same memory
    // - - `slice` can increase the offset
    // - - `slice can decrease the length`
    // - - must specify the output type of `slice`
    // - - `slice` will return a null view if you try to overrun
    // - - make sure to explicitly check for this with `notNull` or `assertType`
    // - use `equal` for typed comparisons.

    // The null view
    bytes29 public constant NULL = hex"ffffffffffffffffffffffffffffffffffffffffffffffffffffffffff";
    uint256 constant LOW_12_MASK = 0xffffffffffffffffffffffff;
    uint8 constant TWELVE_BYTES = 96;

    /**
     * @notice      Returns the encoded hex character that represents the lower 4 bits of the argument.
     * @param _b    The byte
     * @return      char - The encoded hex character
     */
    function nibbleHex(uint8 _b) internal pure returns (uint8 char) {
        // This can probably be done more efficiently, but it's only in error
        // paths, so we don't really care :)
        uint8 _nibble = _b | 0xf0; // set top 4, keep bottom 4
        if (_nibble == 0xf0) {return 0x30;} // 0
        if (_nibble == 0xf1) {return 0x31;} // 1
        if (_nibble == 0xf2) {return 0x32;} // 2
        if (_nibble == 0xf3) {return 0x33;} // 3
        if (_nibble == 0xf4) {return 0x34;} // 4
        if (_nibble == 0xf5) {return 0x35;} // 5
        if (_nibble == 0xf6) {return 0x36;} // 6
        if (_nibble == 0xf7) {return 0x37;} // 7
        if (_nibble == 0xf8) {return 0x38;} // 8
        if (_nibble == 0xf9) {return 0x39;} // 9
        if (_nibble == 0xfa) {return 0x61;} // a
        if (_nibble == 0xfb) {return 0x62;} // b
        if (_nibble == 0xfc) {return 0x63;} // c
        if (_nibble == 0xfd) {return 0x64;} // d
        if (_nibble == 0xfe) {return 0x65;} // e
        if (_nibble == 0xff) {return 0x66;} // f
    }

    /**
     * @notice      Returns a uint16 containing the hex-encoded byte.
     * @param _b    The byte
     * @return      encoded - The hex-encoded byte
     */
    function byteHex(uint8 _b) internal pure returns (uint16 encoded) {
        encoded |= nibbleHex(_b >> 4); // top 4 bits
        encoded <<= 8;
        encoded |= nibbleHex(_b); // lower 4 bits
    }

    /**
     * @notice      Encodes the uint256 to hex. `first` contains the encoded top 16 bytes.
     *              `second` contains the encoded lower 16 bytes.
     *
     * @param _b    The 32 bytes as uint256
     * @return      first - The top 16 bytes
     * @return      second - The bottom 16 bytes
     */
    function encodeHex(uint256 _b) internal pure returns (uint256 first, uint256 second) {
        for (uint8 i = 31; i > 15; i -= 1) {
            uint8 _byte = uint8(_b >> (i * 8));
            first |= byteHex(_byte);
            if (i != 16) {
                first <<= 16;
            }
        }

        // abusing underflow here =_=
        for (uint8 i = 15; i < 255 ; i -= 1) {
            uint8 _byte = uint8(_b >> (i * 8));
            second |= byteHex(_byte);
            if (i != 0) {
                second <<= 16;
            }
        }
    }

    /**
     * @notice          Changes the endianness of a uint256.
     * @dev             https://graphics.stanford.edu/~seander/bithacks.html#ReverseParallel
     * @param _b        The unsigned integer to reverse
     * @return          v - The reversed value
     */
    function reverseUint256(uint256 _b) internal pure returns (uint256 v) {
        v = _b;

        // swap bytes
        v = ((v >> 8) & 0x00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF) |
            ((v & 0x00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF) << 8);
        // swap 2-byte long pairs
        v = ((v >> 16) & 0x0000FFFF0000FFFF0000FFFF0000FFFF0000FFFF0000FFFF0000FFFF0000FFFF) |
            ((v & 0x0000FFFF0000FFFF0000FFFF0000FFFF0000FFFF0000FFFF0000FFFF0000FFFF) << 16);
        // swap 4-byte long pairs
        v = ((v >> 32) & 0x00000000FFFFFFFF00000000FFFFFFFF00000000FFFFFFFF00000000FFFFFFFF) |
            ((v & 0x00000000FFFFFFFF00000000FFFFFFFF00000000FFFFFFFF00000000FFFFFFFF) << 32);
        // swap 8-byte long pairs
        v = ((v >> 64) & 0x0000000000000000FFFFFFFFFFFFFFFF0000000000000000FFFFFFFFFFFFFFFF) |
            ((v & 0x0000000000000000FFFFFFFFFFFFFFFF0000000000000000FFFFFFFFFFFFFFFF) << 64);
        // swap 16-byte long pairs
        v = (v >> 128) | (v << 128);
    }

    /**
     * @notice      Create a mask with the highest `_len` bits set.
     * @param _len  The length
     * @return      mask - The mask
     */
    function leftMask(uint8 _len) private pure returns (uint256 mask) {
        // ugly. redo without assembly?
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            mask := sar(
                sub(_len, 1),
                0x8000000000000000000000000000000000000000000000000000000000000000
            )
        }
    }

    /**
     * @notice      Return the null view.
     * @return      bytes29 - The null view
     */
    function nullView() internal pure returns (bytes29) {
        return NULL;
    }

    /**
     * @notice      Check if the view is null.
     * @return      bool - True if the view is null
     */
    function isNull(bytes29 memView) internal pure returns (bool) {
        return memView == NULL;
    }

    /**
     * @notice      Check if the view is not null.
     * @return      bool - True if the view is not null
     */
    function notNull(bytes29 memView) internal pure returns (bool) {
        return !isNull(memView);
    }

    /**
     * @notice          Check if the view is of a valid type and points to a valid location
     *                  in memory.
     * @dev             We perform this check by examining solidity's unallocated memory
     *                  pointer and ensuring that the view's upper bound is less than that.
     * @param memView   The view
     * @return          ret - True if the view is valid
     */
    function isValid(bytes29 memView) internal pure returns (bool ret) {
        if (typeOf(memView) == 0xffffffffff) {return false;}
        uint256 _end = end(memView);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            ret := not(gt(_end, mload(0x40)))
        }
    }

    /**
     * @notice          Require that a typed memory view be valid.
     * @dev             Returns the view for easy chaining.
     * @param memView   The view
     * @return          bytes29 - The validated view
     */
    function assertValid(bytes29 memView) internal pure returns (bytes29) {
        require(isValid(memView), "Validity assertion failed");
        return memView;
    }

    /**
     * @notice          Return true if the memview is of the expected type. Otherwise false.
     * @param memView   The view
     * @param _expected The expected type
     * @return          bool - True if the memview is of the expected type
     */
    function isType(bytes29 memView, uint40 _expected) internal pure returns (bool) {
        return typeOf(memView) == _expected;
    }

    /**
     * @notice          Require that a typed memory view has a specific type.
     * @dev             Returns the view for easy chaining.
     * @param memView   The view
     * @param _expected The expected type
     * @return          bytes29 - The view with validated type
     */
    function assertType(bytes29 memView, uint40 _expected) internal pure returns (bytes29) {
        if (!isType(memView, _expected)) {
            (, uint256 g) = encodeHex(uint256(typeOf(memView)));
            (, uint256 e) = encodeHex(uint256(_expected));
            string memory err = string(
                abi.encodePacked(
                    "Type assertion failed. Got 0x",
                    uint80(g),
                    ". Expected 0x",
                    uint80(e)
                )
            );
            revert(err);
        }
        return memView;
    }

    /**
     * @notice          Return an identical view with a different type.
     * @param memView   The view
     * @param _newType  The new type
     * @return          newView - The new view with the specified type
     */
    function castTo(bytes29 memView, uint40 _newType) internal pure returns (bytes29 newView) {
        // then | in the new type
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            // shift off the top 5 bytes
            newView := or(newView, shr(40, shl(40, memView)))
            newView := or(newView, shl(216, _newType))
        }
    }

    /**
     * @notice          Unsafe raw pointer construction. This should generally not be called
     *                  directly. Prefer `ref` wherever possible.
     * @dev             Unsafe raw pointer construction. This should generally not be called
     *                  directly. Prefer `ref` wherever possible.
     * @param _type     The type
     * @param _loc      The memory address
     * @param _len      The length
     * @return          newView - The new view with the specified type, location and length
     */
    function unsafeBuildUnchecked(uint256 _type, uint256 _loc, uint256 _len) private pure returns (bytes29 newView) {
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            newView := shl(96, or(newView, _type)) // insert type
            newView := shl(96, or(newView, _loc))  // insert loc
            newView := shl(24, or(newView, _len))  // empty bottom 3 bytes
        }
    }

    /**
     * @notice          Instantiate a new memory view. This should generally not be called
     *                  directly. Prefer `ref` wherever possible.
     * @dev             Instantiate a new memory view. This should generally not be called
     *                  directly. Prefer `ref` wherever possible.
     * @param _type     The type
     * @param _loc      The memory address
     * @param _len      The length
     * @return          newView - The new view with the specified type, location and length
     */
    function build(uint256 _type, uint256 _loc, uint256 _len) internal pure returns (bytes29 newView) {
        uint256 _end = _loc.add(_len);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            if gt(_end, mload(0x40)) {
                _end := 0
            }
        }
        if (_end == 0) {
            return NULL;
        }
        newView = unsafeBuildUnchecked(_type, _loc, _len);
    }

    /**
     * @notice          Instantiate a memory view from a byte array.
     * @dev             Note that due to Solidity memory representation, it is not possible to
     *                  implement a deref, as the `bytes` type stores its len in memory.
     * @param arr       The byte array
     * @param newType   The type
     * @return          bytes29 - The memory view
     */
    function ref(bytes memory arr, uint40 newType) internal pure returns (bytes29) {
        uint256 _len = arr.length;

        uint256 _loc;
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            _loc := add(arr, 0x20)  // our view is of the data, not the struct
        }

        return build(newType, _loc, _len);
    }

    /**
     * @notice          Return the associated type information.
     * @param memView   The memory view
     * @return          _type - The type associated with the view
     */
    function typeOf(bytes29 memView) internal pure returns (uint40 _type) {
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            // 216 == 256 - 40
            _type := shr(216, memView) // shift out lower 24 bytes
        }
    }

    /**
     * @notice          Optimized type comparison. Checks that the 5-byte type flag is equal.
     * @param left      The first view
     * @param right     The second view
     * @return          bool - True if the 5-byte type flag is equal
     */
    function sameType(bytes29 left, bytes29 right) internal pure returns (bool) {
        return (left ^ right) >> (2 * TWELVE_BYTES) == 0;
    }

    /**
     * @notice          Return the memory address of the underlying bytes.
     * @param memView   The view
     * @return          _loc - The memory address
     */
    function loc(bytes29 memView) internal pure returns (uint96 _loc) {
        uint256 _mask = LOW_12_MASK;  // assembly can't use globals
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            // 120 bits = 12 bytes (the encoded loc) + 3 bytes (empty low space)
            _loc := and(shr(120, memView), _mask)
        }
    }

    /**
     * @notice          The number of memory words this memory view occupies, rounded up.
     * @param memView   The view
     * @return          uint256 - The number of memory words
     */
    function words(bytes29 memView) internal pure returns (uint256) {
        return uint256(len(memView)).add(32) / 32;
    }

    /**
     * @notice          The in-memory footprint of a fresh copy of the view.
     * @param memView   The view
     * @return          uint256 - The in-memory footprint of a fresh copy of the view.
     */
    function footprint(bytes29 memView) internal pure returns (uint256) {
        return words(memView) * 32;
    }

    /**
     * @notice          The number of bytes of the view.
     * @param memView   The view
     * @return          _len - The length of the view
     */
    function len(bytes29 memView) internal pure returns (uint96 _len) {
        uint256 _mask = LOW_12_MASK;  // assembly can't use globals
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            _len := and(shr(24, memView), _mask)
        }
    }

    /**
     * @notice          Returns the endpoint of `memView`.
     * @param memView   The view
     * @return          uint256 - The endpoint of `memView`
     */
    function end(bytes29 memView) internal pure returns (uint256) {
        return loc(memView) + len(memView);
    }

    /**
     * @notice          Safe slicing without memory modification.
     * @param memView   The view
     * @param _index    The start index
     * @param _len      The length
     * @param newType   The new type
     * @return          bytes29 - The new view
     */
    function slice(bytes29 memView, uint256 _index, uint256 _len, uint40 newType) internal pure returns (bytes29) {
        uint256 _loc = loc(memView);

        // Ensure it doesn't overrun the view
        if (_loc.add(_index).add(_len) > end(memView)) {
            return NULL;
        }

        _loc = _loc.add(_index);
        return build(newType, _loc, _len);
    }

    /**
     * @notice          Shortcut to `slice`. Gets a view representing the first `_len` bytes.
     * @param memView   The view
     * @param _len      The length
     * @param newType   The new type
     * @return          bytes29 - The new view
     */
    function prefix(bytes29 memView, uint256 _len, uint40 newType) internal pure returns (bytes29) {
        return slice(memView, 0, _len, newType);
    }

    /**
     * @notice          Shortcut to `slice`. Gets a view representing the last `_len` byte.
     * @param memView   The view
     * @param _len      The length
     * @param newType   The new type
     * @return          bytes29 - The new view
     */
    function postfix(bytes29 memView, uint256 _len, uint40 newType) internal pure returns (bytes29) {
        return slice(memView, uint256(len(memView)).sub(_len), _len, newType);
    }

    /**
     * @notice          Construct an error message for an indexing overrun.
     * @param _loc      The memory address
     * @param _len      The length
     * @param _index    The index
     * @param _slice    The slice where the overrun occurred
     * @return          err - The err
     */
    function indexErrOverrun(
        uint256 _loc,
        uint256 _len,
        uint256 _index,
        uint256 _slice
    ) internal pure returns (string memory err) {
        (, uint256 a) = encodeHex(_loc);
        (, uint256 b) = encodeHex(_len);
        (, uint256 c) = encodeHex(_index);
        (, uint256 d) = encodeHex(_slice);
        err = string(
            abi.encodePacked(
                "TypedMemView/index - Overran the view. Slice is at 0x",
                uint48(a),
                " with length 0x",
                uint48(b),
                ". Attempted to index at offset 0x",
                uint48(c),
                " with length 0x",
                uint48(d),
                "."
            )
        );
    }

    /**
     * @notice          Load up to 32 bytes from the view onto the stack.
     * @dev             Returns a bytes32 with only the `_bytes` highest bytes set.
     *                  This can be immediately cast to a smaller fixed-length byte array.
     *                  To automatically cast to an integer, use `indexUint`.
     * @param memView   The view
     * @param _index    The index
     * @param _bytes    The bytes
     * @return          result - The 32 byte result
     */
    function index(bytes29 memView, uint256 _index, uint8 _bytes) internal pure returns (bytes32 result) {
        if (_bytes == 0) {return bytes32(0);}
        if (_index.add(_bytes) > len(memView)) {
            revert(indexErrOverrun(loc(memView), len(memView), _index, uint256(_bytes)));
        }
        require(_bytes <= 32, "TypedMemView/index - Attempted to index more than 32 bytes");

        uint8 bitLength = _bytes * 8;
        uint256 _loc = loc(memView);
        uint256 _mask = leftMask(bitLength);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            result := and(mload(add(_loc, _index)), _mask)
        }
    }

    /**
     * @notice          Parse an unsigned integer from the view at `_index`.
     * @dev             Requires that the view have >= `_bytes` bytes following that index.
     * @param memView   The view
     * @param _index    The index
     * @param _bytes    The bytes
     * @return          result - The unsigned integer
     */
    function indexUint(bytes29 memView, uint256 _index, uint8 _bytes) internal pure returns (uint256 result) {
        return uint256(index(memView, _index, _bytes)) >> ((32 - _bytes) * 8);
    }

    /**
     * @notice          Parse an unsigned integer from LE bytes.
     * @param memView   The view
     * @param _index    The index
     * @param _bytes    The bytes
     * @return          result - The unsigned integer
     */
    function indexLEUint(bytes29 memView, uint256 _index, uint8 _bytes) internal pure returns (uint256 result) {
        return reverseUint256(uint256(index(memView, _index, _bytes)));
    }

    /**
     * @notice          Parse an address from the view at `_index`. Requires that the view have >= 20 bytes
     *                  following that index.
     * @param memView   The view
     * @param _index    The index
     * @return          address - The address
     */
    function indexAddress(bytes29 memView, uint256 _index) internal pure returns (address) {
        return address(uint160(indexUint(memView, _index, 20)));
    }

    /**
     * @notice          Return the keccak256 hash of the underlying memory
     * @param memView   The view
     * @return          digest - The keccak256 hash of the underlying memory
     */
    function keccak(bytes29 memView) internal pure returns (bytes32 digest) {
        uint256 _loc = loc(memView);
        uint256 _len = len(memView);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            digest := keccak256(_loc, _len)
        }
    }

    /**
     * @notice          Return the sha2 digest of the underlying memory.
     * @dev             We explicitly deallocate memory afterwards.
     * @param memView   The view
     * @return          digest - The sha2 hash of the underlying memory
     */
    function sha2(bytes29 memView) internal view returns (bytes32 digest) {
        uint256 _loc = loc(memView);
        uint256 _len = len(memView);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            let ptr := mload(0x40)
            pop(staticcall(gas(), 2, _loc, _len, ptr, 0x20)) // sha2 #1
            digest := mload(ptr)
        }
    }

    /**
     * @notice          Implements bitcoin's hash160 (rmd160(sha2()))
     * @param memView   The pre-image
     * @return          digest - the Digest
     */
    function hash160(bytes29 memView) internal view returns (bytes20 digest) {
        uint256 _loc = loc(memView);
        uint256 _len = len(memView);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            let ptr := mload(0x40)
            pop(staticcall(gas(), 2, _loc, _len, ptr, 0x20)) // sha2
            pop(staticcall(gas(), 3, ptr, 0x20, ptr, 0x20)) // rmd160
            digest := mload(add(ptr, 0xc)) // return value is 0-prefixed.
        }
    }

    /**
     * @notice          Implements bitcoin's hash256 (double sha2)
     * @param memView   A view of the preimage
     * @return          digest - the Digest
     */
    function hash256(bytes29 memView) internal view returns (bytes32 digest) {
        uint256 _loc = loc(memView);
        uint256 _len = len(memView);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            let ptr := mload(0x40)
            pop(staticcall(gas(), 2, _loc, _len, ptr, 0x20)) // sha2 #1
            pop(staticcall(gas(), 2, ptr, 0x20, ptr, 0x20)) // sha2 #2
            digest := mload(ptr)
        }
    }

    /**
     * @notice          Return true if the underlying memory is equal. Else false.
     * @param left      The first view
     * @param right     The second view
     * @return          bool - True if the underlying memory is equal
     */
    function untypedEqual(bytes29 left, bytes29 right) internal pure returns (bool) {
        return (loc(left) == loc(right) && len(left) == len(right)) || keccak(left) == keccak(right);
    }

    /**
     * @notice          Return false if the underlying memory is equal. Else true.
     * @param left      The first view
     * @param right     The second view
     * @return          bool - False if the underlying memory is equal
     */
    function untypedNotEqual(bytes29 left, bytes29 right) internal pure returns (bool) {
        return !untypedEqual(left, right);
    }

    /**
     * @notice          Compares type equality.
     * @dev             Shortcuts if the pointers are identical, otherwise compares type and digest.
     * @param left      The first view
     * @param right     The second view
     * @return          bool - True if the types are the same
     */
    function equal(bytes29 left, bytes29 right) internal pure returns (bool) {
        return left == right || (typeOf(left) == typeOf(right) && keccak(left) == keccak(right));
    }

    /**
     * @notice          Compares type inequality.
     * @dev             Shortcuts if the pointers are identical, otherwise compares type and digest.
     * @param left      The first view
     * @param right     The second view
     * @return          bool - True if the types are not the same
     */
    function notEqual(bytes29 left, bytes29 right) internal pure returns (bool) {
        return !equal(left, right);
    }

    /**
     * @notice          Copy the view to a location, return an unsafe memory reference
     * @dev             Super Dangerous direct memory access.
     *
     *                  This reference can be overwritten if anything else modifies memory (!!!).
     *                  As such it MUST be consumed IMMEDIATELY.
     *                  This function is private to prevent unsafe usage by callers.
     * @param memView   The view
     * @param _newLoc   The new location
     * @return          written - the unsafe memory reference
     */
    function unsafeCopyTo(bytes29 memView, uint256 _newLoc) private view returns (bytes29 written) {
        require(notNull(memView), "TypedMemView/copyTo - Null pointer deref");
        require(isValid(memView), "TypedMemView/copyTo - Invalid pointer deref");
        uint256 _len = len(memView);
        uint256 _oldLoc = loc(memView);

        uint256 ptr;
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            ptr := mload(0x40)
            // revert if we're writing in occupied memory
            if gt(ptr, _newLoc) {
                revert(0x60, 0x20) // empty revert message
            }

            // use the identity precompile to copy
            // guaranteed not to fail, so pop the success
            pop(staticcall(gas(), 4, _oldLoc, _len, _newLoc, _len))
        }

        written = unsafeBuildUnchecked(typeOf(memView), _newLoc, _len);
    }

    /**
     * @notice          Copies the referenced memory to a new loc in memory, returning a `bytes` pointing to
     *                  the new memory
     * @dev             Shortcuts if the pointers are identical, otherwise compares type and digest.
     * @param memView   The view
     * @return          ret - The view pointing to the new memory
     */
    function clone(bytes29 memView) internal view returns (bytes memory ret) {
        uint256 ptr;
        uint256 _len = len(memView);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            ptr := mload(0x40) // load unused memory pointer
            ret := ptr
        }
        unsafeCopyTo(memView, ptr + 0x20);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            mstore(0x40, add(add(ptr, _len), 0x20)) // write new unused pointer
            mstore(ptr, _len) // write len of new array (in bytes)
        }
    }

    /**
     * @notice          Join the views in memory, return an unsafe reference to the memory.
     * @dev             Super Dangerous direct memory access.
     *
     *                  This reference can be overwritten if anything else modifies memory (!!!).
     *                  As such it MUST be consumed IMMEDIATELY.
     *                  This function is private to prevent unsafe usage by callers.
     * @param memViews  The views
     * @return          unsafeView - The conjoined view pointing to the new memory
     */
    function unsafeJoin(bytes29[] memory memViews, uint256 _location) private view returns (bytes29 unsafeView) {
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            let ptr := mload(0x40)
            // revert if we're writing in occupied memory
            if gt(ptr, _location) {
                revert(0x60, 0x20) // empty revert message
            }
        }

        uint256 _offset = 0;
        for (uint256 i = 0; i < memViews.length; i ++) {
            bytes29 memView = memViews[i];
            unsafeCopyTo(memView, _location + _offset);
            _offset += len(memView);
        }
        unsafeView = unsafeBuildUnchecked(0, _location, _offset);
    }

    /**
     * @notice          Produce the keccak256 digest of the concatenated contents of multiple views.
     * @param memViews  The views
     * @return          bytes32 - The keccak256 digest
     */
    function joinKeccak(bytes29[] memory memViews) internal view returns (bytes32) {
        uint256 ptr;
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            ptr := mload(0x40) // load unused memory pointer
        }
        return keccak(unsafeJoin(memViews, ptr));
    }

    /**
     * @notice          Produce the sha256 digest of the concatenated contents of multiple views.
     * @param memViews  The views
     * @return          bytes32 - The sha256 digest
     */
    function joinSha2(bytes29[] memory memViews) internal view returns (bytes32) {
        uint256 ptr;
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            ptr := mload(0x40) // load unused memory pointer
        }
        return sha2(unsafeJoin(memViews, ptr));
    }

    /**
     * @notice          copies all views, joins them into a new bytearray.
     * @param memViews  The views
     * @return          ret - The new byte array
     */
    function join(bytes29[] memory memViews) internal view returns (bytes memory ret) {
        uint256 ptr;
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            ptr := mload(0x40) // load unused memory pointer
        }

        bytes29 _newView = unsafeJoin(memViews, ptr + 0x20);
        uint256 _written = len(_newView);
        uint256 _footprint = footprint(_newView);

        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            // store the legnth
            mstore(ptr, _written)
            // new pointer is old + 0x20 + the footprint of the body
            mstore(0x40, add(add(ptr, _footprint), 0x20))
            ret := ptr
        }
    }
}

/**
 * @title Message Library
 * @notice Library for formatted messages used by Relayer and Receiver.
 *
 * @dev The message body is dynamically-sized to support custom message body
 * formats. Other fields must be fixed-size to avoid hash collisions.
 * Each other input value has an explicit type to guarantee fixed-size.
 * Padding: uintNN fields are left-padded, and bytesNN fields are right-padded.
 *
 * Field                 Bytes      Type       Index
 * version               4          uint32     0
 * sourceDomain          4          uint32     4
 * destinationDomain     4          uint32     8
 * nonce                 8          uint64     12
 * sender                32         bytes32    20
 * recipient             32         bytes32    52
 * destinationCaller     32         bytes32    84
 * messageBody           dynamic    bytes      116
 *
 **/
library Message {
    using TypedMemView for bytes;
    using TypedMemView for bytes29;

    // Indices of each field in message
    uint8 private constant VERSION_INDEX = 0;
    uint8 private constant SOURCE_DOMAIN_INDEX = 4;
    uint8 private constant DESTINATION_DOMAIN_INDEX = 8;
    uint8 private constant NONCE_INDEX = 12;
    uint8 private constant SENDER_INDEX = 20;
    uint8 private constant RECIPIENT_INDEX = 52;
    uint8 private constant DESTINATION_CALLER_INDEX = 84;
    uint8 private constant MESSAGE_BODY_INDEX = 116;

    /**
     * @notice Returns formatted (packed) message with provided fields
     * @param _msgVersion the version of the message format
     * @param _msgSourceDomain Domain of home chain
     * @param _msgDestinationDomain Domain of destination chain
     * @param _msgNonce Destination-specific nonce
     * @param _msgSender Address of sender on source chain as bytes32
     * @param _msgRecipient Address of recipient on destination chain as bytes32
     * @param _msgDestinationCaller Address of caller on destination chain as bytes32
     * @param _msgRawBody Raw bytes of message body
     * @return Formatted message
     **/
    function _formatMessage(
        uint32 _msgVersion,
        uint32 _msgSourceDomain,
        uint32 _msgDestinationDomain,
        uint64 _msgNonce,
        bytes32 _msgSender,
        bytes32 _msgRecipient,
        bytes32 _msgDestinationCaller,
        bytes memory _msgRawBody
    ) internal pure returns (bytes memory) {
        return
            abi.encodePacked(
                _msgVersion,
                _msgSourceDomain,
                _msgDestinationDomain,
                _msgNonce,
                _msgSender,
                _msgRecipient,
                _msgDestinationCaller,
                _msgRawBody
            );
    }

    // @notice Returns _message's version field
    function _version(bytes29 _message) internal pure returns (uint32) {
        return uint32(_message.indexUint(VERSION_INDEX, 4));
    }

    // @notice Returns _message's sourceDomain field
    function _sourceDomain(bytes29 _message) internal pure returns (uint32) {
        return uint32(_message.indexUint(SOURCE_DOMAIN_INDEX, 4));
    }

    // @notice Returns _message's destinationDomain field
    function _destinationDomain(bytes29 _message)
        internal
        pure
        returns (uint32)
    {
        return uint32(_message.indexUint(DESTINATION_DOMAIN_INDEX, 4));
    }

    // @notice Returns _message's nonce field
    function _nonce(bytes29 _message) internal pure returns (uint64) {
        return uint64(_message.indexUint(NONCE_INDEX, 8));
    }

    // @notice Returns _message's sender field
    function _sender(bytes29 _message) internal pure returns (bytes32) {
        return _message.index(SENDER_INDEX, 32);
    }

    // @notice Returns _message's recipient field
    function _recipient(bytes29 _message) internal pure returns (bytes32) {
        return _message.index(RECIPIENT_INDEX, 32);
    }

    // @notice Returns _message's destinationCaller field
    function _destinationCaller(bytes29 _message)
        internal
        pure
        returns (bytes32)
    {
        return _message.index(DESTINATION_CALLER_INDEX, 32);
    }

    // @notice Returns _message's messageBody field
    function _messageBody(bytes29 _message) internal pure returns (bytes29) {
        return
            _message.slice(
                MESSAGE_BODY_INDEX,
                _message.len() - MESSAGE_BODY_INDEX,
                0
            );
    }

    /**
     * @notice converts address to bytes32 (alignment preserving cast.)
     * @param addr the address to convert to bytes32
     */
    function addressToBytes32(address addr) external pure returns (bytes32) {
        return bytes32(uint256(uint160(addr)));
    }

    /**
     * @notice converts bytes32 to address (alignment preserving cast.)
     * @dev Warning: it is possible to have different input values _buf map to the same address.
     * For use cases where this is not acceptable, validate that the first 12 bytes of _buf are zero-padding.
     * @param _buf the bytes32 to convert to address
     */
    function bytes32ToAddress(bytes32 _buf) public pure returns (address) {
        return address(uint160(uint256(_buf)));
    }

    /**
     * @notice Reverts if message is malformed or incorrect length
     * @param _message The message as bytes29
     */
    function _validateMessageFormat(bytes29 _message) internal pure {
        require(_message.isValid(), "Malformed message");
        require(
            _message.len() >= MESSAGE_BODY_INDEX,
            "Invalid message: too short"
        );
    }
}

/*
 * Copyright (c) 2022, Circle Internet Financial Limited.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
pragma solidity 0.7.6;

/*
 * Copyright (c) 2022, Circle Internet Financial Limited.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @title ITokenMinter
 * @notice interface for minter of tokens that are mintable, burnable, and interchangeable
 * across domains.
 */
interface ITokenMinter {
    /**
     * @notice Mints `amount` of local tokens corresponding to the
     * given (`sourceDomain`, `burnToken`) pair, to `to` address.
     * @dev reverts if the (`sourceDomain`, `burnToken`) pair does not
     * map to a nonzero local token address. This mapping can be queried using
     * getLocalToken().
     * @param sourceDomain Source domain where `burnToken` was burned.
     * @param burnToken Burned token address as bytes32.
     * @param to Address to receive minted tokens, corresponding to `burnToken`,
     * on this domain.
     * @param amount Amount of tokens to mint. Must be less than or equal
     * to the minterAllowance of this TokenMinter for given `_mintToken`.
     * @return mintToken token minted.
     */
    function mint(
        uint32 sourceDomain,
        bytes32 burnToken,
        address to,
        uint256 amount
    ) external returns (address mintToken);

    /**
     * @notice Burn tokens owned by this ITokenMinter.
     * @param burnToken burnable token.
     * @param amount amount of tokens to burn. Must be less than or equal to this ITokenMinter's
     * account balance of the given `_burnToken`.
     */
    function burn(address burnToken, uint256 amount) external;

    /**
     * @notice Get the local token associated with the given remote domain and token.
     * @param remoteDomain Remote domain
     * @param remoteToken Remote token
     * @return local token address
     */
    function getLocalToken(uint32 remoteDomain, bytes32 remoteToken)
        external
        view
        returns (address);

    /**
     * @notice Set the token controller of this ITokenMinter. Token controller
     * is responsible for mapping local tokens to remote tokens, and managing
     * token-specific limits
     * @param newTokenController new token controller address
     */
    function setTokenController(address newTokenController) external;
}

/*
 * Copyright (c) 2022, Circle Internet Financial Limited.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount)
        external
        returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender)
        external
        view
        returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(
        address indexed owner,
        address indexed spender,
        uint256 value
    );
}

/**
 * @title IMintBurnToken
 * @notice interface for mintable and burnable ERC20 token
 */
interface IMintBurnToken is IERC20 {
    /**
     * @dev Function to mint tokens
     * @param to The address that will receive the minted tokens.
     * @param amount The amount of tokens to mint. Must be less than or equal
     * to the minterAllowance of the caller.
     * @return A boolean that indicates if the operation was successful.
     */
    function mint(address to, uint256 amount) external returns (bool);

    /**
     * @dev allows a minter to burn some of its own tokens
     * Validates that caller is a minter and that sender is not blacklisted
     * amount is less than or equal to the minter's account balance
     * @param amount uint256 the amount of tokens to be burned
     */
    function burn(uint256 amount) external;
}

/*
 * Copyright (c) 2022, Circle Internet Financial Limited.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with GSN meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address payable) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

/**
 * @dev forked from https://github.com/OpenZeppelin/openzeppelin-contracts/blob/7c5f6bc2c8743d83443fa46395d75f2f3f99054a/contracts/access/Ownable.sol
 * Modifications:
 * 1. Update Solidity version from 0.8.0 to 0.7.6 (11/9/2022). (v8 was used
 * as base because it includes internal _transferOwnership method.)
 * 2. Remove renounceOwnership function
 *
 * Description
 * Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(
        address indexed previousOwner,
        address indexed newOwner
    );

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() {
        _transferOwnership(_msgSender());
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        _checkOwner();
        _;
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if the sender is not the owner.
     */
    function _checkOwner() internal view virtual {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(
            newOwner != address(0),
            "Ownable: new owner is the zero address"
        );
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

/**
 * @dev forked from https://github.com/OpenZeppelin/openzeppelin-contracts/blob/7c5f6bc2c8743d83443fa46395d75f2f3f99054a/contracts/access/Ownable2Step.sol
 * Modifications:
 * 1. Update Solidity version from 0.8.0 to 0.7.6. Version 0.8.0 was used
 * as base because this contract was added to OZ repo after version 0.8.0.
 *
 * Contract module which provides access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership} and {acceptOwnership}.
 *
 * This module is used through inheritance. It will make available all functions
 * from parent (Ownable).
 */
abstract contract Ownable2Step is Ownable {
    address private _pendingOwner;

    event OwnershipTransferStarted(
        address indexed previousOwner,
        address indexed newOwner
    );

    /**
     * @dev Returns the address of the pending owner.
     */
    function pendingOwner() public view virtual returns (address) {
        return _pendingOwner;
    }

    /**
     * @dev Starts the ownership transfer of the contract to a new account. Replaces the pending transfer if there is one.
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner)
        public
        virtual
        override
        onlyOwner
    {
        _pendingOwner = newOwner;
        emit OwnershipTransferStarted(owner(), newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`) and deletes any pending owner.
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual override {
        delete _pendingOwner;
        super._transferOwnership(newOwner);
    }

    /**
     * @dev The new owner accepts the ownership transfer.
     */
    function acceptOwnership() external {
        address sender = _msgSender();
        require(
            pendingOwner() == sender,
            "Ownable2Step: caller is not the new owner"
        );
        _transferOwnership(sender);
    }
}

/**
 * @notice Base contract which allows children to implement an emergency stop
 * mechanism
 * @dev Forked from https://github.com/centrehq/centre-tokens/blob/0d3cab14ebd133a83fc834dbd48d0468bdf0b391/contracts/v1/Pausable.sol
 * Modifications:
 * 1. Update Solidity version from 0.6.12 to 0.7.6 (8/23/2022)
 * 2. Change pauser visibility to private, declare external getter (11/19/22)
 */
contract Pausable is Ownable2Step {
    event Pause();
    event Unpause();
    event PauserChanged(address indexed newAddress);

    address private _pauser;
    bool public paused = false;

    /**
     * @dev Modifier to make a function callable only when the contract is not paused.
     */
    modifier whenNotPaused() {
        require(!paused, "Pausable: paused");
        _;
    }

    /**
     * @dev throws if called by any account other than the pauser
     */
    modifier onlyPauser() {
        require(msg.sender == _pauser, "Pausable: caller is not the pauser");
        _;
    }

    /**
     * @notice Returns current pauser
     * @return Pauser's address
     */
    function pauser() external view returns (address) {
        return _pauser;
    }

    /**
     * @dev called by the owner to pause, triggers stopped state
     */
    function pause() external onlyPauser {
        paused = true;
        emit Pause();
    }

    /**
     * @dev called by the owner to unpause, returns to normal state
     */
    function unpause() external onlyPauser {
        paused = false;
        emit Unpause();
    }

    /**
     * @dev update the pauser role
     */
    function updatePauser(address _newPauser) external onlyOwner {
        require(
            _newPauser != address(0),
            "Pausable: new pauser is the zero address"
        );
        _pauser = _newPauser;
        emit PauserChanged(_pauser);
    }
}

/*
 * Copyright (c) 2022, Circle Internet Financial Limited.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b)
        internal
        pure
        returns (bool, uint256)
    {
        uint256 c = a + b;
        if (c < a) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b)
        internal
        pure
        returns (bool, uint256)
    {
        if (b > a) return (false, 0);
        return (true, a - b);
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b)
        internal
        pure
        returns (bool, uint256)
    {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) return (true, 0);
        uint256 c = a * b;
        if (c / a != b) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b)
        internal
        pure
        returns (bool, uint256)
    {
        if (b == 0) return (false, 0);
        return (true, a / b);
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b)
        internal
        pure
        returns (bool, uint256)
    {
        if (b == 0) return (false, 0);
        return (true, a % b);
    }

    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");
        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a, "SafeMath: subtraction overflow");
        return a - b;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a == 0) return 0;
        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");
        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: division by zero");
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: modulo by zero");
        return a % b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        return a - b;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryDiv}.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a % b;
    }
}

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly {
            size := extcodesize(account)
        }
        return size > 0;
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(
            address(this).balance >= amount,
            "Address: insufficient balance"
        );

        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (bool success, ) = recipient.call{value: amount}("");
        require(
            success,
            "Address: unable to send value, recipient may have reverted"
        );
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain`call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data)
        internal
        returns (bytes memory)
    {
        return functionCall(target, data, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value
    ) internal returns (bytes memory) {
        return
            functionCallWithValue(
                target,
                data,
                value,
                "Address: low-level call with value failed"
            );
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(
            address(this).balance >= value,
            "Address: insufficient balance for call"
        );
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{value: value}(
            data
        );
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data)
        internal
        view
        returns (bytes memory)
    {
        return
            functionStaticCall(
                target,
                data,
                "Address: low-level static call failed"
            );
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.staticcall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data)
        internal
        returns (bytes memory)
    {
        return
            functionDelegateCall(
                target,
                data,
                "Address: low-level delegate call failed"
            );
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    function _verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) private pure returns (bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    using SafeMath for uint256;
    using Address for address;

    function safeTransfer(
        IERC20 token,
        address to,
        uint256 value
    ) internal {
        _callOptionalReturn(
            token,
            abi.encodeWithSelector(token.transfer.selector, to, value)
        );
    }

    function safeTransferFrom(
        IERC20 token,
        address from,
        address to,
        uint256 value
    ) internal {
        _callOptionalReturn(
            token,
            abi.encodeWithSelector(token.transferFrom.selector, from, to, value)
        );
    }

    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    function safeApprove(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        // solhint-disable-next-line max-line-length
        require(
            (value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        _callOptionalReturn(
            token,
            abi.encodeWithSelector(token.approve.selector, spender, value)
        );
    }

    function safeIncreaseAllowance(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        uint256 newAllowance = token.allowance(address(this), spender).add(
            value
        );
        _callOptionalReturn(
            token,
            abi.encodeWithSelector(
                token.approve.selector,
                spender,
                newAllowance
            )
        );
    }

    function safeDecreaseAllowance(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        uint256 newAllowance = token.allowance(address(this), spender).sub(
            value,
            "SafeERC20: decreased allowance below zero"
        );
        _callOptionalReturn(
            token,
            abi.encodeWithSelector(
                token.approve.selector,
                spender,
                newAllowance
            )
        );
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function _callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

        bytes memory returndata = address(token).functionCall(
            data,
            "SafeERC20: low-level call failed"
        );
        if (returndata.length > 0) {
            // Return data is optional
            // solhint-disable-next-line max-line-length
            require(
                abi.decode(returndata, (bool)),
                "SafeERC20: ERC20 operation did not succeed"
            );
        }
    }
}

/**
 * @notice Base contract which allows children to rescue ERC20 locked in their contract.
 * @dev Forked from https://github.com/centrehq/centre-tokens/blob/0d3cab14ebd133a83fc834dbd48d0468bdf0b391/contracts/v1.1/Rescuable.sol
 * Modifications:
 * 1. Update Solidity version from 0.6.12 to 0.7.6 (8/23/2022)
 */
contract Rescuable is Ownable2Step {
    using SafeERC20 for IERC20;

    address private _rescuer;

    event RescuerChanged(address indexed newRescuer);

    /**
     * @notice Returns current rescuer
     * @return Rescuer's address
     */
    function rescuer() external view returns (address) {
        return _rescuer;
    }

    /**
     * @notice Revert if called by any account other than the rescuer.
     */
    modifier onlyRescuer() {
        require(msg.sender == _rescuer, "Rescuable: caller is not the rescuer");
        _;
    }

    /**
     * @notice Rescue ERC20 tokens locked up in this contract.
     * @param tokenContract ERC20 token contract address
     * @param to        Recipient address
     * @param amount    Amount to withdraw
     */
    function rescueERC20(
        IERC20 tokenContract,
        address to,
        uint256 amount
    ) external onlyRescuer {
        tokenContract.safeTransfer(to, amount);
    }

    /**
     * @notice Assign the rescuer role to a given address.
     * @param newRescuer New rescuer's address
     */
    function updateRescuer(address newRescuer) external onlyOwner {
        require(
            newRescuer != address(0),
            "Rescuable: new rescuer is the zero address"
        );
        _rescuer = newRescuer;
        emit RescuerChanged(newRescuer);
    }
}

/*
 * Copyright (c) 2022, Circle Internet Financial Limited.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @title TokenController
 * @notice Base contract which allows children to control tokens, including mapping
 * address of local tokens to addresses of corresponding tokens on remote domains,
 * and limiting the amount of each token that can be burned per message.
 */
abstract contract TokenController {
    // ============ Events ============
    /**
     * @notice Emitted when a token pair is linked
     * @param localToken local token to support
     * @param remoteDomain remote domain
     * @param remoteToken token on `remoteDomain` corresponding to `localToken`
     */
    event TokenPairLinked(
        address localToken,
        uint32 remoteDomain,
        bytes32 remoteToken
    );

    /**
     * @notice Emitted when a token pair is unlinked
     * @param localToken local token address
     * @param remoteDomain remote domain
     * @param remoteToken token on `remoteDomain` unlinked from `localToken`
     */
    event TokenPairUnlinked(
        address localToken,
        uint32 remoteDomain,
        bytes32 remoteToken
    );

    /**
     * @notice Emitted when a burn limit per message is set for a particular token
     * @param token local token address
     * @param burnLimitPerMessage burn limit per message for `token`
     */
    event SetBurnLimitPerMessage(
        address indexed token,
        uint256 burnLimitPerMessage
    );

    /**
     * @notice Emitted when token controller is set
     * @param tokenController token controller address set
     */
    event SetTokenController(address tokenController);

    // ============ State Variables ============
    // Supported burnable tokens on the local domain
    // local token (address) => maximum burn amounts per message
    mapping(address => uint256) public burnLimitsPerMessage;

    // Supported mintable tokens on remote domains, mapped to their corresponding local token
    // hash(remote domain & remote token bytes32 address) => local token (address)
    mapping(bytes32 => address) public remoteTokensToLocalTokens;

    // Role with permission to manage token address mapping across domains, and per-message burn limits
    address private _tokenController;

    // ============ Modifiers ============
    /**
     * @dev Throws if called by any account other than the tokenController.
     */
    modifier onlyTokenController() {
        require(
            msg.sender == _tokenController,
            "Caller is not tokenController"
        );
        _;
    }

    /**
     * @notice ensures that attempted burn does not exceed
     * burn limit per-message for given `burnToken`.
     * @dev reverts if allowed burn amount is 0, or burnAmount exceeds
     * allowed burn amount.
     * @param token address of token to burn
     * @param amount amount of `token` to burn
     */
    modifier onlyWithinBurnLimit(address token, uint256 amount) {
        uint256 _allowedBurnAmount = burnLimitsPerMessage[token];
        require(_allowedBurnAmount > 0, "Burn token not supported");
        require(
            amount <= _allowedBurnAmount,
            "Burn amount exceeds per tx limit"
        );
        _;
    }

    // ============ Public/External Functions  ============
    /**
     * @dev Returns the address of the tokenController
     * @return address of the tokenController
     */
    function tokenController() external view returns (address) {
        return _tokenController;
    }

    /**
     * @notice Links a pair of local and remote tokens to be supported by this TokenMinter.
     * @dev Associates a (`remoteToken`, `localToken`) pair by updating remoteTokensToLocalTokens mapping.
     * Reverts if the remote token (for the given `remoteDomain`) already maps to a nonzero local token.
     * Note:
     * - A remote token (on a certain remote domain) can only map to one local token, but many remote tokens
     * can map to the same local token.
     * - Setting a token pair does not enable the `localToken` (that requires calling setLocalTokenEnabledStatus.)
     */
    function linkTokenPair(
        address localToken,
        uint32 remoteDomain,
        bytes32 remoteToken
    ) external onlyTokenController {
        bytes32 _remoteTokensKey = _hashRemoteDomainAndToken(
            remoteDomain,
            remoteToken
        );

        // remote token must not be already linked to a local token
        require(
            remoteTokensToLocalTokens[_remoteTokensKey] == address(0),
            "Unable to link token pair"
        );

        remoteTokensToLocalTokens[_remoteTokensKey] = localToken;

        emit TokenPairLinked(localToken, remoteDomain, remoteToken);
    }

    /**
     * @notice Unlinks a pair of local and remote tokens for this TokenMinter.
     * @dev Removes link from `remoteToken`, to `localToken` for given `remoteDomain`
     * by updating remoteTokensToLocalTokens mapping.
     * Reverts if the remote token (for the given `remoteDomain`) already maps to the zero address.
     * Note:
     * - A remote token (on a certain remote domain) can only map to one local token, but many remote tokens
     * can map to the same local token.
     * - Unlinking a token pair does not disable burning the `localToken` (that requires calling setMaxBurnAmountPerMessage.)
     */
    function unlinkTokenPair(
        address localToken,
        uint32 remoteDomain,
        bytes32 remoteToken
    ) external onlyTokenController {
        bytes32 _remoteTokensKey = _hashRemoteDomainAndToken(
            remoteDomain,
            remoteToken
        );

        // remote token must be linked to a local token before unlink
        require(
            remoteTokensToLocalTokens[_remoteTokensKey] != address(0),
            "Unable to unlink token pair"
        );

        delete remoteTokensToLocalTokens[_remoteTokensKey];

        emit TokenPairUnlinked(localToken, remoteDomain, remoteToken);
    }

    /**
     * @notice Sets the maximum burn amount per message for a given `localToken`.
     * @dev Burns with amounts exceeding `burnLimitPerMessage` will revert. Mints do not
     * respect this value, so if this limit is reduced, previously burned tokens will still
     * be mintable.
     * @param localToken Local token to set the maximum burn amount per message of.
     * @param burnLimitPerMessage Maximum burn amount per message to set.
     */
    function setMaxBurnAmountPerMessage(
        address localToken,
        uint256 burnLimitPerMessage
    ) external onlyTokenController {
        burnLimitsPerMessage[localToken] = burnLimitPerMessage;

        emit SetBurnLimitPerMessage(localToken, burnLimitPerMessage);
    }

    // ============ Internal Utils ============
    /**
     * @notice Set tokenController to `newTokenController`, and
     * emit `SetTokenController` event.
     * @dev newTokenController must be nonzero.
     * @param newTokenController address of new token controller
     */
    function _setTokenController(address newTokenController) internal {
        require(
            newTokenController != address(0),
            "Invalid token controller address"
        );
        _tokenController = newTokenController;
        emit SetTokenController(newTokenController);
    }

    /**
     * @notice Get the enabled local token associated with the given remote domain and token.
     * @param remoteDomain Remote domain
     * @param remoteToken Remote token
     * @return Local token address
     */
    function _getLocalToken(uint32 remoteDomain, bytes32 remoteToken)
        internal
        view
        returns (address)
    {
        bytes32 _remoteTokensKey = _hashRemoteDomainAndToken(
            remoteDomain,
            remoteToken
        );

        return remoteTokensToLocalTokens[_remoteTokensKey];
    }

    /**
     * @notice hashes packed `_remoteDomain` and `_remoteToken`.
     * @param remoteDomain Domain where message originated from
     * @param remoteToken Address of remote token as bytes32
     * @return keccak hash of packed remote domain and token
     */
    function _hashRemoteDomainAndToken(uint32 remoteDomain, bytes32 remoteToken)
        internal
        pure
        returns (bytes32)
    {
        return keccak256(abi.encodePacked(remoteDomain, remoteToken));
    }
}

/*
 * Copyright (c) 2022, Circle Internet Financial Limited.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @title IMessageHandler
 * @notice Handles messages on destination domain forwarded from
 * an IReceiver
 */
interface IMessageHandler {
    /**
     * @notice handles an incoming message from a Receiver
     * @param sourceDomain the source domain of the message
     * @param sender the sender of the message
     * @param messageBody The message raw bytes
     * @return success bool, true if successful
     */
    function handleReceiveMessage(
        uint32 sourceDomain,
        bytes32 sender,
        bytes calldata messageBody
    ) external returns (bool);
}

/*
 * Copyright (c) 2022, Circle Internet Financial Limited.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @title IRelayer
 * @notice Sends messages from source domain to destination domain
 */
interface IRelayer {
    /**
     * @notice Sends an outgoing message from the source domain.
     * @dev Increment nonce, format the message, and emit `MessageSent` event with message information.
     * @param destinationDomain Domain of destination chain
     * @param recipient Address of message recipient on destination domain as bytes32
     * @param messageBody Raw bytes content of message
     * @return nonce reserved by message
     */
    function sendMessage(
        uint32 destinationDomain,
        bytes32 recipient,
        bytes calldata messageBody
    ) external returns (uint64);

    /**
     * @notice Sends an outgoing message from the source domain, with a specified caller on the
     * destination domain.
     * @dev Increment nonce, format the message, and emit `MessageSent` event with message information.
     * WARNING: if the `destinationCaller` does not represent a valid address as bytes32, then it will not be possible
     * to broadcast the message on the destination domain. This is an advanced feature, and the standard
     * sendMessage() should be preferred for use cases where a specific destination caller is not required.
     * @param destinationDomain Domain of destination chain
     * @param recipient Address of message recipient on destination domain as bytes32
     * @param destinationCaller caller on the destination domain, as bytes32
     * @param messageBody Raw bytes content of message
     * @return nonce reserved by message
     */
    function sendMessageWithCaller(
        uint32 destinationDomain,
        bytes32 recipient,
        bytes32 destinationCaller,
        bytes calldata messageBody
    ) external returns (uint64);

    /**
     * @notice Replace a message with a new message body and/or destination caller.
     * @dev The `originalAttestation` must be a valid attestation of `originalMessage`.
     * @param originalMessage original message to replace
     * @param originalAttestation attestation of `originalMessage`
     * @param newMessageBody new message body of replaced message
     * @param newDestinationCaller the new destination caller
     */
    function replaceMessage(
        bytes calldata originalMessage,
        bytes calldata originalAttestation,
        bytes calldata newMessageBody,
        bytes32 newDestinationCaller
    ) external;
}

/*
 * Copyright (c) 2022, Circle Internet Financial Limited.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @title IReceiver
 * @notice Receives messages on destination chain and forwards them to IMessageDestinationHandler
 */
interface IReceiver {
    /**
     * @notice Receives an incoming message, validating the header and passing
     * the body to application-specific handler.
     * @param message The message raw bytes
     * @param signature The message signature
     * @return success bool, true if successful
     */
    function receiveMessage(bytes calldata message, bytes calldata signature)
        external
        returns (bool success);
}

/**
 * @title IMessageTransmitter
 * @notice Interface for message transmitters, which both relay and receive messages.
 */
interface IMessageTransmitter is IRelayer, IReceiver {

}

/*
 * Copyright (c) 2022, Circle Internet Financial Limited.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

library TypedMemView {
    using SafeMath for uint256;

    // Why does this exist?
    // the solidity `bytes memory` type has a few weaknesses.
    // 1. You can't index ranges effectively
    // 2. You can't slice without copying
    // 3. The underlying data may represent any type
    // 4. Solidity never deallocates memory, and memory costs grow
    //    superlinearly

    // By using a memory view instead of a `bytes memory` we get the following
    // advantages:
    // 1. Slices are done on the stack, by manipulating the pointer
    // 2. We can index arbitrary ranges and quickly convert them to stack types
    // 3. We can insert type info into the pointer, and typecheck at runtime

    // This makes `TypedMemView` a useful tool for efficient zero-copy
    // algorithms.

    // Why bytes29?
    // We want to avoid confusion between views, digests, and other common
    // types so we chose a large and uncommonly used odd number of bytes
    //
    // Note that while bytes are left-aligned in a word, integers and addresses
    // are right-aligned. This means when working in assembly we have to
    // account for the 3 unused bytes on the righthand side
    //
    // First 5 bytes are a type flag.
    // - ff_ffff_fffe is reserved for unknown type.
    // - ff_ffff_ffff is reserved for invalid types/errors.
    // next 12 are memory address
    // next 12 are len
    // bottom 3 bytes are empty

    // Assumptions:
    // - non-modification of memory.
    // - No Solidity updates
    // - - wrt free mem point
    // - - wrt bytes representation in memory
    // - - wrt memory addressing in general

    // Usage:
    // - create type constants
    // - use `assertType` for runtime type assertions
    // - - unfortunately we can't do this at compile time yet :(
    // - recommended: implement modifiers that perform type checking
    // - - e.g.
    // - - `uint40 constant MY_TYPE = 3;`
    // - - ` modifer onlyMyType(bytes29 myView) { myView.assertType(MY_TYPE); }`
    // - instantiate a typed view from a bytearray using `ref`
    // - use `index` to inspect the contents of the view
    // - use `slice` to create smaller views into the same memory
    // - - `slice` can increase the offset
    // - - `slice can decrease the length`
    // - - must specify the output type of `slice`
    // - - `slice` will return a null view if you try to overrun
    // - - make sure to explicitly check for this with `notNull` or `assertType`
    // - use `equal` for typed comparisons.

    // The null view
    bytes29 public constant NULL =
        hex"ffffffffffffffffffffffffffffffffffffffffffffffffffffffffff";
    uint256 constant LOW_12_MASK = 0xffffffffffffffffffffffff;
    uint8 constant TWELVE_BYTES = 96;

    /**
     * @notice      Returns the encoded hex character that represents the lower 4 bits of the argument.
     * @param _b    The byte
     * @return      char - The encoded hex character
     */
    function nibbleHex(uint8 _b) internal pure returns (uint8 char) {
        // This can probably be done more efficiently, but it's only in error
        // paths, so we don't really care :)
        uint8 _nibble = _b | 0xf0; // set top 4, keep bottom 4
        if (_nibble == 0xf0) {
            return 0x30;
        } // 0
        if (_nibble == 0xf1) {
            return 0x31;
        } // 1
        if (_nibble == 0xf2) {
            return 0x32;
        } // 2
        if (_nibble == 0xf3) {
            return 0x33;
        } // 3
        if (_nibble == 0xf4) {
            return 0x34;
        } // 4
        if (_nibble == 0xf5) {
            return 0x35;
        } // 5
        if (_nibble == 0xf6) {
            return 0x36;
        } // 6
        if (_nibble == 0xf7) {
            return 0x37;
        } // 7
        if (_nibble == 0xf8) {
            return 0x38;
        } // 8
        if (_nibble == 0xf9) {
            return 0x39;
        } // 9
        if (_nibble == 0xfa) {
            return 0x61;
        } // a
        if (_nibble == 0xfb) {
            return 0x62;
        } // b
        if (_nibble == 0xfc) {
            return 0x63;
        } // c
        if (_nibble == 0xfd) {
            return 0x64;
        } // d
        if (_nibble == 0xfe) {
            return 0x65;
        } // e
        if (_nibble == 0xff) {
            return 0x66;
        } // f
    }

    /**
     * @notice      Returns a uint16 containing the hex-encoded byte.
     * @param _b    The byte
     * @return      encoded - The hex-encoded byte
     */
    function byteHex(uint8 _b) internal pure returns (uint16 encoded) {
        encoded |= nibbleHex(_b >> 4); // top 4 bits
        encoded <<= 8;
        encoded |= nibbleHex(_b); // lower 4 bits
    }

    /**
     * @notice      Encodes the uint256 to hex. `first` contains the encoded top 16 bytes.
     *              `second` contains the encoded lower 16 bytes.
     *
     * @param _b    The 32 bytes as uint256
     * @return      first - The top 16 bytes
     * @return      second - The bottom 16 bytes
     */
    function encodeHex(uint256 _b)
        internal
        pure
        returns (uint256 first, uint256 second)
    {
        for (uint8 i = 31; i > 15; i -= 1) {
            uint8 _byte = uint8(_b >> (i * 8));
            first |= byteHex(_byte);
            if (i != 16) {
                first <<= 16;
            }
        }

        // abusing underflow here =_=
        for (uint8 i = 15; i < 255; i -= 1) {
            uint8 _byte = uint8(_b >> (i * 8));
            second |= byteHex(_byte);
            if (i != 0) {
                second <<= 16;
            }
        }
    }

    /**
     * @notice          Changes the endianness of a uint256.
     * @dev             https://graphics.stanford.edu/~seander/bithacks.html#ReverseParallel
     * @param _b        The unsigned integer to reverse
     * @return          v - The reversed value
     */
    function reverseUint256(uint256 _b) internal pure returns (uint256 v) {
        v = _b;

        // swap bytes
        v =
            ((v >> 8) &
                0x00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF) |
            ((v &
                0x00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF00FF) <<
                8);
        // swap 2-byte long pairs
        v =
            ((v >> 16) &
                0x0000FFFF0000FFFF0000FFFF0000FFFF0000FFFF0000FFFF0000FFFF0000FFFF) |
            ((v &
                0x0000FFFF0000FFFF0000FFFF0000FFFF0000FFFF0000FFFF0000FFFF0000FFFF) <<
                16);
        // swap 4-byte long pairs
        v =
            ((v >> 32) &
                0x00000000FFFFFFFF00000000FFFFFFFF00000000FFFFFFFF00000000FFFFFFFF) |
            ((v &
                0x00000000FFFFFFFF00000000FFFFFFFF00000000FFFFFFFF00000000FFFFFFFF) <<
                32);
        // swap 8-byte long pairs
        v =
            ((v >> 64) &
                0x0000000000000000FFFFFFFFFFFFFFFF0000000000000000FFFFFFFFFFFFFFFF) |
            ((v &
                0x0000000000000000FFFFFFFFFFFFFFFF0000000000000000FFFFFFFFFFFFFFFF) <<
                64);
        // swap 16-byte long pairs
        v = (v >> 128) | (v << 128);
    }

    /**
     * @notice      Create a mask with the highest `_len` bits set.
     * @param _len  The length
     * @return      mask - The mask
     */
    function leftMask(uint8 _len) private pure returns (uint256 mask) {
        // ugly. redo without assembly?
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            mask := sar(
                sub(_len, 1),
                0x8000000000000000000000000000000000000000000000000000000000000000
            )
        }
    }

    /**
     * @notice      Return the null view.
     * @return      bytes29 - The null view
     */
    function nullView() internal pure returns (bytes29) {
        return NULL;
    }

    /**
     * @notice      Check if the view is null.
     * @return      bool - True if the view is null
     */
    function isNull(bytes29 memView) internal pure returns (bool) {
        return memView == NULL;
    }

    /**
     * @notice      Check if the view is not null.
     * @return      bool - True if the view is not null
     */
    function notNull(bytes29 memView) internal pure returns (bool) {
        return !isNull(memView);
    }

    /**
     * @notice          Check if the view is of a valid type and points to a valid location
     *                  in memory.
     * @dev             We perform this check by examining solidity's unallocated memory
     *                  pointer and ensuring that the view's upper bound is less than that.
     * @param memView   The view
     * @return          ret - True if the view is valid
     */
    function isValid(bytes29 memView) internal pure returns (bool ret) {
        if (typeOf(memView) == 0xffffffffff) {
            return false;
        }
        uint256 _end = end(memView);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            ret := not(gt(_end, mload(0x40)))
        }
    }

    /**
     * @notice          Require that a typed memory view be valid.
     * @dev             Returns the view for easy chaining.
     * @param memView   The view
     * @return          bytes29 - The validated view
     */
    function assertValid(bytes29 memView) internal pure returns (bytes29) {
        require(isValid(memView), "Validity assertion failed");
        return memView;
    }

    /**
     * @notice          Return true if the memview is of the expected type. Otherwise false.
     * @param memView   The view
     * @param _expected The expected type
     * @return          bool - True if the memview is of the expected type
     */
    function isType(bytes29 memView, uint40 _expected)
        internal
        pure
        returns (bool)
    {
        return typeOf(memView) == _expected;
    }

    /**
     * @notice          Require that a typed memory view has a specific type.
     * @dev             Returns the view for easy chaining.
     * @param memView   The view
     * @param _expected The expected type
     * @return          bytes29 - The view with validated type
     */
    function assertType(bytes29 memView, uint40 _expected)
        internal
        pure
        returns (bytes29)
    {
        if (!isType(memView, _expected)) {
            (, uint256 g) = encodeHex(uint256(typeOf(memView)));
            (, uint256 e) = encodeHex(uint256(_expected));
            string memory err = string(
                abi.encodePacked(
                    "Type assertion failed. Got 0x",
                    uint80(g),
                    ". Expected 0x",
                    uint80(e)
                )
            );
            revert(err);
        }
        return memView;
    }

    /**
     * @notice          Return an identical view with a different type.
     * @param memView   The view
     * @param _newType  The new type
     * @return          newView - The new view with the specified type
     */
    function castTo(bytes29 memView, uint40 _newType)
        internal
        pure
        returns (bytes29 newView)
    {
        // then | in the new type
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            // shift off the top 5 bytes
            newView := or(newView, shr(40, shl(40, memView)))
            newView := or(newView, shl(216, _newType))
        }
    }

    /**
     * @notice          Unsafe raw pointer construction. This should generally not be called
     *                  directly. Prefer `ref` wherever possible.
     * @dev             Unsafe raw pointer construction. This should generally not be called
     *                  directly. Prefer `ref` wherever possible.
     * @param _type     The type
     * @param _loc      The memory address
     * @param _len      The length
     * @return          newView - The new view with the specified type, location and length
     */
    function unsafeBuildUnchecked(
        uint256 _type,
        uint256 _loc,
        uint256 _len
    ) private pure returns (bytes29 newView) {
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            newView := shl(96, or(newView, _type)) // insert type
            newView := shl(96, or(newView, _loc)) // insert loc
            newView := shl(24, or(newView, _len)) // empty bottom 3 bytes
        }
    }

    /**
     * @notice          Instantiate a new memory view. This should generally not be called
     *                  directly. Prefer `ref` wherever possible.
     * @dev             Instantiate a new memory view. This should generally not be called
     *                  directly. Prefer `ref` wherever possible.
     * @param _type     The type
     * @param _loc      The memory address
     * @param _len      The length
     * @return          newView - The new view with the specified type, location and length
     */
    function build(
        uint256 _type,
        uint256 _loc,
        uint256 _len
    ) internal pure returns (bytes29 newView) {
        uint256 _end = _loc.add(_len);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            if gt(_end, mload(0x40)) {
                _end := 0
            }
        }
        if (_end == 0) {
            return NULL;
        }
        newView = unsafeBuildUnchecked(_type, _loc, _len);
    }

    /**
     * @notice          Instantiate a memory view from a byte array.
     * @dev             Note that due to Solidity memory representation, it is not possible to
     *                  implement a deref, as the `bytes` type stores its len in memory.
     * @param arr       The byte array
     * @param newType   The type
     * @return          bytes29 - The memory view
     */
    function ref(bytes memory arr, uint40 newType)
        internal
        pure
        returns (bytes29)
    {
        uint256 _len = arr.length;

        uint256 _loc;
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            _loc := add(arr, 0x20) // our view is of the data, not the struct
        }

        return build(newType, _loc, _len);
    }

    /**
     * @notice          Return the associated type information.
     * @param memView   The memory view
     * @return          _type - The type associated with the view
     */
    function typeOf(bytes29 memView) internal pure returns (uint40 _type) {
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            // 216 == 256 - 40
            _type := shr(216, memView) // shift out lower 24 bytes
        }
    }

    /**
     * @notice          Optimized type comparison. Checks that the 5-byte type flag is equal.
     * @param left      The first view
     * @param right     The second view
     * @return          bool - True if the 5-byte type flag is equal
     */
    function sameType(bytes29 left, bytes29 right)
        internal
        pure
        returns (bool)
    {
        return (left ^ right) >> (2 * TWELVE_BYTES) == 0;
    }

    /**
     * @notice          Return the memory address of the underlying bytes.
     * @param memView   The view
     * @return          _loc - The memory address
     */
    function loc(bytes29 memView) internal pure returns (uint96 _loc) {
        uint256 _mask = LOW_12_MASK; // assembly can't use globals
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            // 120 bits = 12 bytes (the encoded loc) + 3 bytes (empty low space)
            _loc := and(shr(120, memView), _mask)
        }
    }

    /**
     * @notice          The number of memory words this memory view occupies, rounded up.
     * @param memView   The view
     * @return          uint256 - The number of memory words
     */
    function words(bytes29 memView) internal pure returns (uint256) {
        return uint256(len(memView)).add(32) / 32;
    }

    /**
     * @notice          The in-memory footprint of a fresh copy of the view.
     * @param memView   The view
     * @return          uint256 - The in-memory footprint of a fresh copy of the view.
     */
    function footprint(bytes29 memView) internal pure returns (uint256) {
        return words(memView) * 32;
    }

    /**
     * @notice          The number of bytes of the view.
     * @param memView   The view
     * @return          _len - The length of the view
     */
    function len(bytes29 memView) internal pure returns (uint96 _len) {
        uint256 _mask = LOW_12_MASK; // assembly can't use globals
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            _len := and(shr(24, memView), _mask)
        }
    }

    /**
     * @notice          Returns the endpoint of `memView`.
     * @param memView   The view
     * @return          uint256 - The endpoint of `memView`
     */
    function end(bytes29 memView) internal pure returns (uint256) {
        return loc(memView) + len(memView);
    }

    /**
     * @notice          Safe slicing without memory modification.
     * @param memView   The view
     * @param _index    The start index
     * @param _len      The length
     * @param newType   The new type
     * @return          bytes29 - The new view
     */
    function slice(
        bytes29 memView,
        uint256 _index,
        uint256 _len,
        uint40 newType
    ) internal pure returns (bytes29) {
        uint256 _loc = loc(memView);

        // Ensure it doesn't overrun the view
        if (_loc.add(_index).add(_len) > end(memView)) {
            return NULL;
        }

        _loc = _loc.add(_index);
        return build(newType, _loc, _len);
    }

    /**
     * @notice          Shortcut to `slice`. Gets a view representing the first `_len` bytes.
     * @param memView   The view
     * @param _len      The length
     * @param newType   The new type
     * @return          bytes29 - The new view
     */
    function prefix(
        bytes29 memView,
        uint256 _len,
        uint40 newType
    ) internal pure returns (bytes29) {
        return slice(memView, 0, _len, newType);
    }

    /**
     * @notice          Shortcut to `slice`. Gets a view representing the last `_len` byte.
     * @param memView   The view
     * @param _len      The length
     * @param newType   The new type
     * @return          bytes29 - The new view
     */
    function postfix(
        bytes29 memView,
        uint256 _len,
        uint40 newType
    ) internal pure returns (bytes29) {
        return slice(memView, uint256(len(memView)).sub(_len), _len, newType);
    }

    /**
     * @notice          Construct an error message for an indexing overrun.
     * @param _loc      The memory address
     * @param _len      The length
     * @param _index    The index
     * @param _slice    The slice where the overrun occurred
     * @return          err - The err
     */
    function indexErrOverrun(
        uint256 _loc,
        uint256 _len,
        uint256 _index,
        uint256 _slice
    ) internal pure returns (string memory err) {
        (, uint256 a) = encodeHex(_loc);
        (, uint256 b) = encodeHex(_len);
        (, uint256 c) = encodeHex(_index);
        (, uint256 d) = encodeHex(_slice);
        err = string(
            abi.encodePacked(
                "TypedMemView/index - Overran the view. Slice is at 0x",
                uint48(a),
                " with length 0x",
                uint48(b),
                ". Attempted to index at offset 0x",
                uint48(c),
                " with length 0x",
                uint48(d),
                "."
            )
        );
    }

    /**
     * @notice          Load up to 32 bytes from the view onto the stack.
     * @dev             Returns a bytes32 with only the `_bytes` highest bytes set.
     *                  This can be immediately cast to a smaller fixed-length byte array.
     *                  To automatically cast to an integer, use `indexUint`.
     * @param memView   The view
     * @param _index    The index
     * @param _bytes    The bytes
     * @return          result - The 32 byte result
     */
    function index(
        bytes29 memView,
        uint256 _index,
        uint8 _bytes
    ) internal pure returns (bytes32 result) {
        if (_bytes == 0) {
            return bytes32(0);
        }
        if (_index.add(_bytes) > len(memView)) {
            revert(
                indexErrOverrun(
                    loc(memView),
                    len(memView),
                    _index,
                    uint256(_bytes)
                )
            );
        }
        require(
            _bytes <= 32,
            "TypedMemView/index - Attempted to index more than 32 bytes"
        );

        uint8 bitLength = _bytes * 8;
        uint256 _loc = loc(memView);
        uint256 _mask = leftMask(bitLength);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            result := and(mload(add(_loc, _index)), _mask)
        }
    }

    /**
     * @notice          Parse an unsigned integer from the view at `_index`.
     * @dev             Requires that the view have >= `_bytes` bytes following that index.
     * @param memView   The view
     * @param _index    The index
     * @param _bytes    The bytes
     * @return          result - The unsigned integer
     */
    function indexUint(
        bytes29 memView,
        uint256 _index,
        uint8 _bytes
    ) internal pure returns (uint256 result) {
        return uint256(index(memView, _index, _bytes)) >> ((32 - _bytes) * 8);
    }

    /**
     * @notice          Parse an unsigned integer from LE bytes.
     * @param memView   The view
     * @param _index    The index
     * @param _bytes    The bytes
     * @return          result - The unsigned integer
     */
    function indexLEUint(
        bytes29 memView,
        uint256 _index,
        uint8 _bytes
    ) internal pure returns (uint256 result) {
        return reverseUint256(uint256(index(memView, _index, _bytes)));
    }

    /**
     * @notice          Parse an address from the view at `_index`. Requires that the view have >= 20 bytes
     *                  following that index.
     * @param memView   The view
     * @param _index    The index
     * @return          address - The address
     */
    function indexAddress(bytes29 memView, uint256 _index)
        internal
        pure
        returns (address)
    {
        return address(uint160(indexUint(memView, _index, 20)));
    }

    /**
     * @notice          Return the keccak256 hash of the underlying memory
     * @param memView   The view
     * @return          digest - The keccak256 hash of the underlying memory
     */
    function keccak(bytes29 memView) internal pure returns (bytes32 digest) {
        uint256 _loc = loc(memView);
        uint256 _len = len(memView);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            digest := keccak256(_loc, _len)
        }
    }

    /**
     * @notice          Return the sha2 digest of the underlying memory.
     * @dev             We explicitly deallocate memory afterwards.
     * @param memView   The view
     * @return          digest - The sha2 hash of the underlying memory
     */
    function sha2(bytes29 memView) internal view returns (bytes32 digest) {
        uint256 _loc = loc(memView);
        uint256 _len = len(memView);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            let ptr := mload(0x40)
            pop(staticcall(gas(), 2, _loc, _len, ptr, 0x20)) // sha2 #1
            digest := mload(ptr)
        }
    }

    /**
     * @notice          Implements bitcoin's hash160 (rmd160(sha2()))
     * @param memView   The pre-image
     * @return          digest - the Digest
     */
    function hash160(bytes29 memView) internal view returns (bytes20 digest) {
        uint256 _loc = loc(memView);
        uint256 _len = len(memView);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            let ptr := mload(0x40)
            pop(staticcall(gas(), 2, _loc, _len, ptr, 0x20)) // sha2
            pop(staticcall(gas(), 3, ptr, 0x20, ptr, 0x20)) // rmd160
            digest := mload(add(ptr, 0xc)) // return value is 0-prefixed.
        }
    }

    /**
     * @notice          Implements bitcoin's hash256 (double sha2)
     * @param memView   A view of the preimage
     * @return          digest - the Digest
     */
    function hash256(bytes29 memView) internal view returns (bytes32 digest) {
        uint256 _loc = loc(memView);
        uint256 _len = len(memView);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            let ptr := mload(0x40)
            pop(staticcall(gas(), 2, _loc, _len, ptr, 0x20)) // sha2 #1
            pop(staticcall(gas(), 2, ptr, 0x20, ptr, 0x20)) // sha2 #2
            digest := mload(ptr)
        }
    }

    /**
     * @notice          Return true if the underlying memory is equal. Else false.
     * @param left      The first view
     * @param right     The second view
     * @return          bool - True if the underlying memory is equal
     */
    function untypedEqual(bytes29 left, bytes29 right)
        internal
        pure
        returns (bool)
    {
        return
            (loc(left) == loc(right) && len(left) == len(right)) ||
            keccak(left) == keccak(right);
    }

    /**
     * @notice          Return false if the underlying memory is equal. Else true.
     * @param left      The first view
     * @param right     The second view
     * @return          bool - False if the underlying memory is equal
     */
    function untypedNotEqual(bytes29 left, bytes29 right)
        internal
        pure
        returns (bool)
    {
        return !untypedEqual(left, right);
    }

    /**
     * @notice          Compares type equality.
     * @dev             Shortcuts if the pointers are identical, otherwise compares type and digest.
     * @param left      The first view
     * @param right     The second view
     * @return          bool - True if the types are the same
     */
    function equal(bytes29 left, bytes29 right) internal pure returns (bool) {
        return
            left == right ||
            (typeOf(left) == typeOf(right) && keccak(left) == keccak(right));
    }

    /**
     * @notice          Compares type inequality.
     * @dev             Shortcuts if the pointers are identical, otherwise compares type and digest.
     * @param left      The first view
     * @param right     The second view
     * @return          bool - True if the types are not the same
     */
    function notEqual(bytes29 left, bytes29 right)
        internal
        pure
        returns (bool)
    {
        return !equal(left, right);
    }

    /**
     * @notice          Copy the view to a location, return an unsafe memory reference
     * @dev             Super Dangerous direct memory access.
     *
     *                  This reference can be overwritten if anything else modifies memory (!!!).
     *                  As such it MUST be consumed IMMEDIATELY.
     *                  This function is private to prevent unsafe usage by callers.
     * @param memView   The view
     * @param _newLoc   The new location
     * @return          written - the unsafe memory reference
     */
    function unsafeCopyTo(bytes29 memView, uint256 _newLoc)
        private
        view
        returns (bytes29 written)
    {
        require(notNull(memView), "TypedMemView/copyTo - Null pointer deref");
        require(
            isValid(memView),
            "TypedMemView/copyTo - Invalid pointer deref"
        );
        uint256 _len = len(memView);
        uint256 _oldLoc = loc(memView);

        uint256 ptr;
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            ptr := mload(0x40)
            // revert if we're writing in occupied memory
            if gt(ptr, _newLoc) {
                revert(0x60, 0x20) // empty revert message
            }

            // use the identity precompile to copy
            // guaranteed not to fail, so pop the success
            pop(staticcall(gas(), 4, _oldLoc, _len, _newLoc, _len))
        }

        written = unsafeBuildUnchecked(typeOf(memView), _newLoc, _len);
    }

    /**
     * @notice          Copies the referenced memory to a new loc in memory, returning a `bytes` pointing to
     *                  the new memory
     * @dev             Shortcuts if the pointers are identical, otherwise compares type and digest.
     * @param memView   The view
     * @return          ret - The view pointing to the new memory
     */
    function clone(bytes29 memView) internal view returns (bytes memory ret) {
        uint256 ptr;
        uint256 _len = len(memView);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            ptr := mload(0x40) // load unused memory pointer
            ret := ptr
        }
        unsafeCopyTo(memView, ptr + 0x20);
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            mstore(0x40, add(add(ptr, _len), 0x20)) // write new unused pointer
            mstore(ptr, _len) // write len of new array (in bytes)
        }
    }

    /**
     * @notice          Join the views in memory, return an unsafe reference to the memory.
     * @dev             Super Dangerous direct memory access.
     *
     *                  This reference can be overwritten if anything else modifies memory (!!!).
     *                  As such it MUST be consumed IMMEDIATELY.
     *                  This function is private to prevent unsafe usage by callers.
     * @param memViews  The views
     * @return          unsafeView - The conjoined view pointing to the new memory
     */
    function unsafeJoin(bytes29[] memory memViews, uint256 _location)
        private
        view
        returns (bytes29 unsafeView)
    {
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            let ptr := mload(0x40)
            // revert if we're writing in occupied memory
            if gt(ptr, _location) {
                revert(0x60, 0x20) // empty revert message
            }
        }

        uint256 _offset = 0;
        for (uint256 i = 0; i < memViews.length; i++) {
            bytes29 memView = memViews[i];
            unsafeCopyTo(memView, _location + _offset);
            _offset += len(memView);
        }
        unsafeView = unsafeBuildUnchecked(0, _location, _offset);
    }

    /**
     * @notice          Produce the keccak256 digest of the concatenated contents of multiple views.
     * @param memViews  The views
     * @return          bytes32 - The keccak256 digest
     */
    function joinKeccak(bytes29[] memory memViews)
        internal
        view
        returns (bytes32)
    {
        uint256 ptr;
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            ptr := mload(0x40) // load unused memory pointer
        }
        return keccak(unsafeJoin(memViews, ptr));
    }

    /**
     * @notice          Produce the sha256 digest of the concatenated contents of multiple views.
     * @param memViews  The views
     * @return          bytes32 - The sha256 digest
     */
    function joinSha2(bytes29[] memory memViews)
        internal
        view
        returns (bytes32)
    {
        uint256 ptr;
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            ptr := mload(0x40) // load unused memory pointer
        }
        return sha2(unsafeJoin(memViews, ptr));
    }

    /**
     * @notice          copies all views, joins them into a new bytearray.
     * @param memViews  The views
     * @return          ret - The new byte array
     */
    function join(bytes29[] memory memViews)
        internal
        view
        returns (bytes memory ret)
    {
        uint256 ptr;
        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            ptr := mload(0x40) // load unused memory pointer
        }

        bytes29 _newView = unsafeJoin(memViews, ptr + 0x20);
        uint256 _written = len(_newView);
        uint256 _footprint = footprint(_newView);

        assembly {
            // solium-disable-previous-line security/no-inline-assembly
            // store the legnth
            mstore(ptr, _written)
            // new pointer is old + 0x20 + the footprint of the body
            mstore(0x40, add(add(ptr, _footprint), 0x20))
            ret := ptr
        }
    }
}

/**
 * @title BurnMessage Library
 * @notice Library for formatted BurnMessages used by TokenMessenger.
 * @dev BurnMessage format:
 * Field                 Bytes      Type       Index
 * version               4          uint32     0
 * burnToken             32         bytes32    4
 * mintRecipient         32         bytes32    36
 * amount                32         uint256    68
 * messageSender         32         bytes32    100
 **/
library BurnMessage {
    using TypedMemView for bytes;
    using TypedMemView for bytes29;

    uint8 private constant VERSION_INDEX = 0;
    uint8 private constant VERSION_LEN = 4;
    uint8 private constant BURN_TOKEN_INDEX = 4;
    uint8 private constant BURN_TOKEN_LEN = 32;
    uint8 private constant MINT_RECIPIENT_INDEX = 36;
    uint8 private constant MINT_RECIPIENT_LEN = 32;
    uint8 private constant AMOUNT_INDEX = 68;
    uint8 private constant AMOUNT_LEN = 32;
    uint8 private constant MSG_SENDER_INDEX = 100;
    uint8 private constant MSG_SENDER_LEN = 32;
    // 4 byte version + 32 bytes burnToken + 32 bytes mintRecipient + 32 bytes amount + 32 bytes messageSender
    uint8 private constant BURN_MESSAGE_LEN = 132;

    /**
     * @notice Formats Burn message
     * @param _version The message body version
     * @param _burnToken The burn token address on source domain as bytes32
     * @param _mintRecipient The mint recipient address as bytes32
     * @param _amount The burn amount
     * @param _messageSender The message sender
     * @return Burn formatted message.
     */
    function _formatMessage(
        uint32 _version,
        bytes32 _burnToken,
        bytes32 _mintRecipient,
        uint256 _amount,
        bytes32 _messageSender
    ) internal pure returns (bytes memory) {
        return
            abi.encodePacked(
                _version,
                _burnToken,
                _mintRecipient,
                _amount,
                _messageSender
            );
    }

    /**
     * @notice Retrieves the burnToken from a DepositForBurn BurnMessage
     * @param _message The message
     * @return sourceToken address as bytes32
     */
    function _getMessageSender(bytes29 _message)
        internal
        pure
        returns (bytes32)
    {
        return _message.index(MSG_SENDER_INDEX, MSG_SENDER_LEN);
    }

    /**
     * @notice Retrieves the burnToken from a DepositForBurn BurnMessage
     * @param _message The message
     * @return sourceToken address as bytes32
     */
    function _getBurnToken(bytes29 _message) internal pure returns (bytes32) {
        return _message.index(BURN_TOKEN_INDEX, BURN_TOKEN_LEN);
    }

    /**
     * @notice Retrieves the mintRecipient from a BurnMessage
     * @param _message The message
     * @return mintRecipient
     */
    function _getMintRecipient(bytes29 _message)
        internal
        pure
        returns (bytes32)
    {
        return _message.index(MINT_RECIPIENT_INDEX, MINT_RECIPIENT_LEN);
    }

    /**
     * @notice Retrieves the amount from a BurnMessage
     * @param _message The message
     * @return amount
     */
    function _getAmount(bytes29 _message) internal pure returns (uint256) {
        return _message.indexUint(AMOUNT_INDEX, AMOUNT_LEN);
    }

    /**
     * @notice Retrieves the version from a Burn message
     * @param _message The message
     * @return version
     */
    function _getVersion(bytes29 _message) internal pure returns (uint32) {
        return uint32(_message.indexUint(VERSION_INDEX, VERSION_LEN));
    }

    /**
     * @notice Reverts if burn message is malformed or invalid length
     * @param _message The burn message as bytes29
     */
    function _validateBurnMessageFormat(bytes29 _message) internal pure {
        require(_message.isValid(), "Malformed message");
        require(_message.len() == BURN_MESSAGE_LEN, "Invalid message length");
    }
}

/*
 * Copyright (c) 2022, Circle Internet Financial Limited.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @title Message Library
 * @notice Library for formatted messages used by Relayer and Receiver.
 *
 * @dev The message body is dynamically-sized to support custom message body
 * formats. Other fields must be fixed-size to avoid hash collisions.
 * Each other input value has an explicit type to guarantee fixed-size.
 * Padding: uintNN fields are left-padded, and bytesNN fields are right-padded.
 *
 * Field                 Bytes      Type       Index
 * version               4          uint32     0
 * sourceDomain          4          uint32     4
 * destinationDomain     4          uint32     8
 * nonce                 8          uint64     12
 * sender                32         bytes32    20
 * recipient             32         bytes32    52
 * destinationCaller     32         bytes32    84
 * messageBody           dynamic    bytes      116
 *
 **/
library Message {
    using TypedMemView for bytes;
    using TypedMemView for bytes29;

    // Indices of each field in message
    uint8 private constant VERSION_INDEX = 0;
    uint8 private constant SOURCE_DOMAIN_INDEX = 4;
    uint8 private constant DESTINATION_DOMAIN_INDEX = 8;
    uint8 private constant NONCE_INDEX = 12;
    uint8 private constant SENDER_INDEX = 20;
    uint8 private constant RECIPIENT_INDEX = 52;
    uint8 private constant DESTINATION_CALLER_INDEX = 84;
    uint8 private constant MESSAGE_BODY_INDEX = 116;

    /**
     * @notice Returns formatted (packed) message with provided fields
     * @param _msgVersion the version of the message format
     * @param _msgSourceDomain Domain of home chain
     * @param _msgDestinationDomain Domain of destination chain
     * @param _msgNonce Destination-specific nonce
     * @param _msgSender Address of sender on source chain as bytes32
     * @param _msgRecipient Address of recipient on destination chain as bytes32
     * @param _msgDestinationCaller Address of caller on destination chain as bytes32
     * @param _msgRawBody Raw bytes of message body
     * @return Formatted message
     **/
    function _formatMessage(
        uint32 _msgVersion,
        uint32 _msgSourceDomain,
        uint32 _msgDestinationDomain,
        uint64 _msgNonce,
        bytes32 _msgSender,
        bytes32 _msgRecipient,
        bytes32 _msgDestinationCaller,
        bytes memory _msgRawBody
    ) internal pure returns (bytes memory) {
        return
            abi.encodePacked(
                _msgVersion,
                _msgSourceDomain,
                _msgDestinationDomain,
                _msgNonce,
                _msgSender,
                _msgRecipient,
                _msgDestinationCaller,
                _msgRawBody
            );
    }

    // @notice Returns _message's version field
    function _version(bytes29 _message) internal pure returns (uint32) {
        return uint32(_message.indexUint(VERSION_INDEX, 4));
    }

    // @notice Returns _message's sourceDomain field
    function _sourceDomain(bytes29 _message) internal pure returns (uint32) {
        return uint32(_message.indexUint(SOURCE_DOMAIN_INDEX, 4));
    }

    // @notice Returns _message's destinationDomain field
    function _destinationDomain(bytes29 _message)
        internal
        pure
        returns (uint32)
    {
        return uint32(_message.indexUint(DESTINATION_DOMAIN_INDEX, 4));
    }

    // @notice Returns _message's nonce field
    function _nonce(bytes29 _message) internal pure returns (uint64) {
        return uint64(_message.indexUint(NONCE_INDEX, 8));
    }

    // @notice Returns _message's sender field
    function _sender(bytes29 _message) internal pure returns (bytes32) {
        return _message.index(SENDER_INDEX, 32);
    }

    // @notice Returns _message's recipient field
    function _recipient(bytes29 _message) internal pure returns (bytes32) {
        return _message.index(RECIPIENT_INDEX, 32);
    }

    // @notice Returns _message's destinationCaller field
    function _destinationCaller(bytes29 _message)
        internal
        pure
        returns (bytes32)
    {
        return _message.index(DESTINATION_CALLER_INDEX, 32);
    }

    // @notice Returns _message's messageBody field
    function _messageBody(bytes29 _message) internal pure returns (bytes29) {
        return
            _message.slice(
                MESSAGE_BODY_INDEX,
                _message.len() - MESSAGE_BODY_INDEX,
                0
            );
    }

    /**
     * @notice converts address to bytes32 (alignment preserving cast.)
     * @param addr the address to convert to bytes32
     */
    function addressToBytes32(address addr) external pure returns (bytes32) {
        return bytes32(uint256(uint160(addr)));
    }

    /**
     * @notice converts bytes32 to address (alignment preserving cast.)
     * @dev Warning: it is possible to have different input values _buf map to the same address.
     * For use cases where this is not acceptable, validate that the first 12 bytes of _buf are zero-padding.
     * @param _buf the bytes32 to convert to address
     */
    function bytes32ToAddress(bytes32 _buf) public pure returns (address) {
        return address(uint160(uint256(_buf)));
    }

    /**
     * @notice Reverts if message is malformed or incorrect length
     * @param _message The message as bytes29
     */
    function _validateMessageFormat(bytes29 _message) internal pure {
        require(_message.isValid(), "Malformed message");
        require(
            _message.len() >= MESSAGE_BODY_INDEX,
            "Invalid message: too short"
        );
    }
}

/**
 * @title TokenMessenger
 * @notice Sends messages and receives messages to/from MessageTransmitters
 * and to/from TokenMinters
 */
contract TokenMessenger is IMessageHandler, Rescuable {
    // ============ Events ============
    /**
     * @notice Emitted when a DepositForBurn message is sent
     * @param nonce unique nonce reserved by message
     * @param burnToken address of token burnt on source domain
     * @param amount deposit amount
     * @param depositor address where deposit is transferred from
     * @param mintRecipient address receiving minted tokens on destination domain as bytes32
     * @param destinationDomain destination domain
     * @param destinationTokenMessenger address of TokenMessenger on destination domain as bytes32
     * @param destinationCaller authorized caller as bytes32 of receiveMessage() on destination domain, if not equal to bytes32(0).
     * If equal to bytes32(0), any address can call receiveMessage().
     */
    event DepositForBurn(
        uint64 indexed nonce,
        address indexed burnToken,
        uint256 amount,
        address indexed depositor,
        bytes32 mintRecipient,
        uint32 destinationDomain,
        bytes32 destinationTokenMessenger,
        bytes32 destinationCaller
    );

    /**
     * @notice Emitted when tokens are minted
     * @param mintRecipient recipient address of minted tokens
     * @param amount amount of minted tokens
     * @param mintToken contract address of minted token
     */
    event MintAndWithdraw(
        address indexed mintRecipient,
        uint256 amount,
        address indexed mintToken
    );

    /**
     * @notice Emitted when a remote TokenMessenger is added
     * @param domain remote domain
     * @param tokenMessenger TokenMessenger on remote domain
     */
    event RemoteTokenMessengerAdded(uint32 domain, bytes32 tokenMessenger);

    /**
     * @notice Emitted when a remote TokenMessenger is removed
     * @param domain remote domain
     * @param tokenMessenger TokenMessenger on remote domain
     */
    event RemoteTokenMessengerRemoved(uint32 domain, bytes32 tokenMessenger);

    /**
     * @notice Emitted when the local minter is added
     * @param localMinter address of local minter
     * @notice Emitted when the local minter is added
     */
    event LocalMinterAdded(address localMinter);

    /**
     * @notice Emitted when the local minter is removed
     * @param localMinter address of local minter
     * @notice Emitted when the local minter is removed
     */
    event LocalMinterRemoved(address localMinter);

    // ============ Libraries ============
    using TypedMemView for bytes;
    using TypedMemView for bytes29;
    using BurnMessage for bytes29;
    using Message for bytes29;

    // ============ State Variables ============
    // Local Message Transmitter responsible for sending and receiving messages to/from remote domains
    IMessageTransmitter public immutable localMessageTransmitter;

    // Version of message body format
    uint32 public immutable messageBodyVersion;

    // Minter responsible for minting and burning tokens on the local domain
    ITokenMinter public localMinter;

    // Valid TokenMessengers on remote domains
    mapping(uint32 => bytes32) public remoteTokenMessengers;

    // ============ Modifiers ============
    /**
     * @notice Only accept messages from a registered TokenMessenger contract on given remote domain
     * @param domain The remote domain
     * @param tokenMessenger The address of the TokenMessenger contract for the given remote domain
     */
    modifier onlyRemoteTokenMessenger(uint32 domain, bytes32 tokenMessenger) {
        require(
            _isRemoteTokenMessenger(domain, tokenMessenger),
            "Remote TokenMessenger unsupported"
        );
        _;
    }

    /**
     * @notice Only accept messages from the registered message transmitter on local domain
     */
    modifier onlyLocalMessageTransmitter() {
        // Caller must be the registered message transmitter for this domain
        require(_isLocalMessageTransmitter(), "Invalid message transmitter");
        _;
    }

    // ============ Constructor ============
    /**
     * @param _messageTransmitter Message transmitter address
     * @param _messageBodyVersion Message body version
     */
    constructor(address _messageTransmitter, uint32 _messageBodyVersion) {
        require(
            _messageTransmitter != address(0),
            "MessageTransmitter not set"
        );
        localMessageTransmitter = IMessageTransmitter(_messageTransmitter);
        messageBodyVersion = _messageBodyVersion;
    }

    // ============ External Functions  ============
    /**
     * @notice Deposits and burns tokens from sender to be minted on destination domain.
     * Emits a `DepositForBurn` event.
     * @dev reverts if:
     * - given burnToken is not supported
     * - given destinationDomain has no TokenMessenger registered
     * - transferFrom() reverts. For example, if sender's burnToken balance or approved allowance
     * to this contract is less than `amount`.
     * - burn() reverts. For example, if `amount` is 0.
     * - MessageTransmitter returns false or reverts.
     * @param amount amount of tokens to burn
     * @param destinationDomain destination domain
     * @param mintRecipient address of mint recipient on destination domain
     * @param burnToken address of contract to burn deposited tokens, on local domain
     * @return _nonce unique nonce reserved by message
     */
    function depositForBurn(
        uint256 amount,
        uint32 destinationDomain,
        bytes32 mintRecipient,
        address burnToken
    ) external returns (uint64 _nonce) {
        return
            _depositForBurn(
                amount,
                destinationDomain,
                mintRecipient,
                burnToken,
                // (bytes32(0) here indicates that any address can call receiveMessage()
                // on the destination domain, triggering mint to specified `mintRecipient`)
                bytes32(0)
            );
    }

    /**
     * @notice Deposits and burns tokens from sender to be minted on destination domain. The mint
     * on the destination domain must be called by `destinationCaller`.
     * WARNING: if the `destinationCaller` does not represent a valid address as bytes32, then it will not be possible
     * to broadcast the message on the destination domain. This is an advanced feature, and the standard
     * depositForBurn() should be preferred for use cases where a specific destination caller is not required.
     * Emits a `DepositForBurn` event.
     * @dev reverts if:
     * - given destinationCaller is zero address
     * - given burnToken is not supported
     * - given destinationDomain has no TokenMessenger registered
     * - transferFrom() reverts. For example, if sender's burnToken balance or approved allowance
     * to this contract is less than `amount`.
     * - burn() reverts. For example, if `amount` is 0.
     * - MessageTransmitter returns false or reverts.
     * @param amount amount of tokens to burn
     * @param destinationDomain destination domain
     * @param mintRecipient address of mint recipient on destination domain
     * @param burnToken address of contract to burn deposited tokens, on local domain
     * @param destinationCaller caller on the destination domain, as bytes32
     * @return nonce unique nonce reserved by message
     */
    function depositForBurnWithCaller(
        uint256 amount,
        uint32 destinationDomain,
        bytes32 mintRecipient,
        address burnToken,
        bytes32 destinationCaller
    ) external returns (uint64 nonce) {
        // Destination caller must be nonzero. To allow any destination caller, use depositForBurn().
        require(destinationCaller != bytes32(0), "Invalid destination caller");

        return
            _depositForBurn(
                amount,
                destinationDomain,
                mintRecipient,
                burnToken,
                destinationCaller
            );
    }

    /**
     * @notice Replace a BurnMessage to change the mint recipient and/or
     * destination caller. Allows the sender of a previous BurnMessage
     * (created by depositForBurn or depositForBurnWithCaller)
     * to send a new BurnMessage to replace the original.
     * The new BurnMessage will reuse the amount and burn token of the original,
     * without requiring a new deposit.
     * @dev The new message will reuse the original message's nonce. For a
     * given nonce, all replacement message(s) and the original message are
     * valid to broadcast on the destination domain, until the first message
     * at the nonce confirms, at which point all others are invalidated.
     * Note: The msg.sender of the replaced message must be the same as the
     * msg.sender of the original message.
     * @param originalMessage original message bytes (to replace)
     * @param originalAttestation original attestation bytes
     * @param newDestinationCaller the new destination caller, which may be the
     * same as the original destination caller, a new destination caller, or an empty
     * destination caller (bytes32(0), indicating that any destination caller is valid.)
     * @param newMintRecipient the new mint recipient, which may be the same as the
     * original mint recipient, or different.
     */
    function replaceDepositForBurn(
        bytes calldata originalMessage,
        bytes calldata originalAttestation,
        bytes32 newDestinationCaller,
        bytes32 newMintRecipient
    ) external {
        bytes29 _originalMsg = originalMessage.ref(0);
        _originalMsg._validateMessageFormat();
        bytes29 _originalMsgBody = _originalMsg._messageBody();
        _originalMsgBody._validateBurnMessageFormat();

        bytes32 _originalMsgSender = _originalMsgBody._getMessageSender();
        // _originalMsgSender must match msg.sender of original message
        require(
            msg.sender == Message.bytes32ToAddress(_originalMsgSender),
            "Invalid sender for message"
        );
        require(
            newMintRecipient != bytes32(0),
            "Mint recipient must be nonzero"
        );

        bytes32 _burnToken = _originalMsgBody._getBurnToken();
        uint256 _amount = _originalMsgBody._getAmount();

        bytes memory _newMessageBody = BurnMessage._formatMessage(
            messageBodyVersion,
            _burnToken,
            newMintRecipient,
            _amount,
            _originalMsgSender
        );

        localMessageTransmitter.replaceMessage(
            originalMessage,
            originalAttestation,
            _newMessageBody,
            newDestinationCaller
        );

        emit DepositForBurn(
            _originalMsg._nonce(),
            Message.bytes32ToAddress(_burnToken),
            _amount,
            msg.sender,
            newMintRecipient,
            _originalMsg._destinationDomain(),
            _originalMsg._recipient(),
            newDestinationCaller
        );
    }

    /**
     * @notice Handles an incoming message received by the local MessageTransmitter,
     * and takes the appropriate action. For a burn message, mints the
     * associated token to the requested recipient on the local domain.
     * @dev Validates the local sender is the local MessageTransmitter, and the
     * remote sender is a registered remote TokenMessenger for `remoteDomain`.
     * @param remoteDomain The domain where the message originated from.
     * @param sender The sender of the message (remote TokenMessenger).
     * @param messageBody The message body bytes.
     * @return success Bool, true if successful.
     */
    function handleReceiveMessage(
        uint32 remoteDomain,
        bytes32 sender,
        bytes calldata messageBody
    )
        external
        override
        onlyLocalMessageTransmitter
        onlyRemoteTokenMessenger(remoteDomain, sender)
        returns (bool)
    {
        bytes29 _msg = messageBody.ref(0);
        _msg._validateBurnMessageFormat();
        require(
            _msg._getVersion() == messageBodyVersion,
            "Invalid message body version"
        );

        bytes32 _mintRecipient = _msg._getMintRecipient();
        bytes32 _burnToken = _msg._getBurnToken();
        uint256 _amount = _msg._getAmount();

        ITokenMinter _localMinter = _getLocalMinter();

        _mintAndWithdraw(
            address(_localMinter),
            remoteDomain,
            _burnToken,
            Message.bytes32ToAddress(_mintRecipient),
            _amount
        );

        return true;
    }

    /**
     * @notice Add the TokenMessenger for a remote domain.
     * @dev Reverts if there is already a TokenMessenger set for domain.
     * @param domain Domain of remote TokenMessenger.
     * @param tokenMessenger Address of remote TokenMessenger as bytes32.
     */
    function addRemoteTokenMessenger(uint32 domain, bytes32 tokenMessenger)
        external
        onlyOwner
    {
        require(tokenMessenger != bytes32(0), "bytes32(0) not allowed");

        require(
            remoteTokenMessengers[domain] == bytes32(0),
            "TokenMessenger already set"
        );

        remoteTokenMessengers[domain] = tokenMessenger;
        emit RemoteTokenMessengerAdded(domain, tokenMessenger);
    }

    /**
     * @notice Remove the TokenMessenger for a remote domain.
     * @dev Reverts if there is no TokenMessenger set for `domain`.
     * @param domain Domain of remote TokenMessenger
     */
    function removeRemoteTokenMessenger(uint32 domain) external onlyOwner {
        // No TokenMessenger set for given remote domain.
        require(
            remoteTokenMessengers[domain] != bytes32(0),
            "No TokenMessenger set"
        );

        bytes32 _removedTokenMessenger = remoteTokenMessengers[domain];
        delete remoteTokenMessengers[domain];
        emit RemoteTokenMessengerRemoved(domain, _removedTokenMessenger);
    }

    /**
     * @notice Add minter for the local domain.
     * @dev Reverts if a minter is already set for the local domain.
     * @param newLocalMinter The address of the minter on the local domain.
     */
    function addLocalMinter(address newLocalMinter) external onlyOwner {
        require(newLocalMinter != address(0), "Zero address not allowed");

        require(
            address(localMinter) == address(0),
            "Local minter is already set."
        );

        localMinter = ITokenMinter(newLocalMinter);

        emit LocalMinterAdded(newLocalMinter);
    }

    /**
     * @notice Remove the minter for the local domain.
     * @dev Reverts if the minter of the local domain is not set.
     */
    function removeLocalMinter() external onlyOwner {
        address _localMinterAddress = address(localMinter);
        require(_localMinterAddress != address(0), "No local minter is set.");

        delete localMinter;
        emit LocalMinterRemoved(_localMinterAddress);
    }

    // ============ Internal Utils ============
    /**
     * @notice Deposits and burns tokens from sender to be minted on destination domain.
     * Emits a `DepositForBurn` event.
     * @param _amount amount of tokens to burn (must be non-zero)
     * @param _destinationDomain destination domain
     * @param _mintRecipient address of mint recipient on destination domain
     * @param _burnToken address of contract to burn deposited tokens, on local domain
     * @param _destinationCaller caller on the destination domain, as bytes32
     * @return nonce unique nonce reserved by message
     */
    function _depositForBurn(
        uint256 _amount,
        uint32 _destinationDomain,
        bytes32 _mintRecipient,
        address _burnToken,
        bytes32 _destinationCaller
    ) internal returns (uint64 nonce) {
        require(_amount > 0, "Amount must be nonzero");
        require(_mintRecipient != bytes32(0), "Mint recipient must be nonzero");

        bytes32 _destinationTokenMessenger = _getRemoteTokenMessenger(
            _destinationDomain
        );

        ITokenMinter _localMinter = _getLocalMinter();
        IMintBurnToken _mintBurnToken = IMintBurnToken(_burnToken);
        require(
            _mintBurnToken.transferFrom(
                msg.sender,
                address(_localMinter),
                _amount
            ),
            "Transfer operation failed"
        );
        _localMinter.burn(_burnToken, _amount);

        // Format message body
        bytes memory _burnMessage = BurnMessage._formatMessage(
            messageBodyVersion,
            Message.addressToBytes32(_burnToken),
            _mintRecipient,
            _amount,
            Message.addressToBytes32(msg.sender)
        );

        uint64 _nonceReserved = _sendDepositForBurnMessage(
            _destinationDomain,
            _destinationTokenMessenger,
            _destinationCaller,
            _burnMessage
        );

        emit DepositForBurn(
            _nonceReserved,
            _burnToken,
            _amount,
            msg.sender,
            _mintRecipient,
            _destinationDomain,
            _destinationTokenMessenger,
            _destinationCaller
        );

        return _nonceReserved;
    }

    /**
     * @notice Sends a BurnMessage through the local message transmitter
     * @dev calls local message transmitter's sendMessage() function if `_destinationCaller` == bytes32(0),
     * or else calls sendMessageWithCaller().
     * @param _destinationDomain destination domain
     * @param _destinationTokenMessenger address of registered TokenMessenger contract on destination domain, as bytes32
     * @param _destinationCaller caller on the destination domain, as bytes32. If `_destinationCaller` == bytes32(0),
     * any address can call receiveMessage() on destination domain.
     * @param _burnMessage formatted BurnMessage bytes (message body)
     * @return nonce unique nonce reserved by message
     */
    function _sendDepositForBurnMessage(
        uint32 _destinationDomain,
        bytes32 _destinationTokenMessenger,
        bytes32 _destinationCaller,
        bytes memory _burnMessage
    ) internal returns (uint64 nonce) {
        if (_destinationCaller == bytes32(0)) {
            return
                localMessageTransmitter.sendMessage(
                    _destinationDomain,
                    _destinationTokenMessenger,
                    _burnMessage
                );
        } else {
            return
                localMessageTransmitter.sendMessageWithCaller(
                    _destinationDomain,
                    _destinationTokenMessenger,
                    _destinationCaller,
                    _burnMessage
                );
        }
    }

    /**
     * @notice Mints tokens to a recipient
     * @param _tokenMinter address of TokenMinter contract
     * @param _remoteDomain domain where burned tokens originate from
     * @param _burnToken address of token burned
     * @param _mintRecipient recipient address of minted tokens
     * @param _amount amount of minted tokens
     */
    function _mintAndWithdraw(
        address _tokenMinter,
        uint32 _remoteDomain,
        bytes32 _burnToken,
        address _mintRecipient,
        uint256 _amount
    ) internal {
        ITokenMinter _minter = ITokenMinter(_tokenMinter);
        address _mintToken = _minter.mint(
            _remoteDomain,
            _burnToken,
            _mintRecipient,
            _amount
        );

        emit MintAndWithdraw(_mintRecipient, _amount, _mintToken);
    }

    /**
     * @notice return the remote TokenMessenger for the given `_domain` if one exists, else revert.
     * @param _domain The domain for which to get the remote TokenMessenger
     * @return _tokenMessenger The address of the TokenMessenger on `_domain` as bytes32
     */
    function _getRemoteTokenMessenger(uint32 _domain)
        internal
        view
        returns (bytes32)
    {
        bytes32 _tokenMessenger = remoteTokenMessengers[_domain];
        require(_tokenMessenger != bytes32(0), "No TokenMessenger for domain");
        return _tokenMessenger;
    }

    /**
     * @notice return the local minter address if it is set, else revert.
     * @return local minter as ITokenMinter.
     */
    function _getLocalMinter() internal view returns (ITokenMinter) {
        require(address(localMinter) != address(0), "Local minter is not set");
        return localMinter;
    }

    /**
     * @notice Return true if the given remote domain and TokenMessenger is registered
     * on this TokenMessenger.
     * @param _domain The remote domain of the message.
     * @param _tokenMessenger The address of the TokenMessenger on remote domain.
     * @return true if a remote TokenMessenger is registered for `_domain` and `_tokenMessenger`,
     * on this TokenMessenger.
     */
    function _isRemoteTokenMessenger(uint32 _domain, bytes32 _tokenMessenger)
        internal
        view
        returns (bool)
    {
        return
            _tokenMessenger != bytes32(0) &&
            remoteTokenMessengers[_domain] == _tokenMessenger;
    }

    /**
     * @notice Returns true if the message sender is the local registered MessageTransmitter
     * @return true if message sender is the registered local message transmitter
     */
    function _isLocalMessageTransmitter() internal view returns (bool) {
        return
            address(localMessageTransmitter) != address(0) &&
            msg.sender == address(localMessageTransmitter);
    }
}

/**
 * @title TokenMinter
 * @notice Token Minter and Burner
 * @dev Maintains registry of local mintable tokens and corresponding tokens on remote domains.
 * This registry can be used by caller to determine which token on local domain to mint for a
 * burned token on a remote domain, and vice versa.
 * It is assumed that local and remote tokens are fungible at a constant 1:1 exchange rate.
 */
contract TokenMinter is ITokenMinter, TokenController, Pausable, Rescuable {
    // ============ Events ============
    /**
     * @notice Emitted when a local TokenMessenger is added
     * @param localTokenMessenger address of local TokenMessenger
     * @notice Emitted when a local TokenMessenger is added
     */
    event LocalTokenMessengerAdded(address localTokenMessenger);

    /**
     * @notice Emitted when a local TokenMessenger is removed
     * @param localTokenMessenger address of local TokenMessenger
     * @notice Emitted when a local TokenMessenger is removed
     */
    event LocalTokenMessengerRemoved(address localTokenMessenger);

    // ============ State Variables ============
    // Local TokenMessenger with permission to call mint and burn on this TokenMinter
    address public localTokenMessenger;

    // ============ Modifiers ============
    /**
     * @notice Only accept messages from the registered message transmitter on local domain
     */
    modifier onlyLocalTokenMessenger() {
        require(_isLocalTokenMessenger(), "Caller not local TokenMessenger");
        _;
    }

    // ============ Constructor ============
    /**
     * @param _tokenController Token controller address
     */
    constructor(address _tokenController) {
        _setTokenController(_tokenController);
    }

    // ============ External Functions  ============
    /**
     * @notice Mints `amount` of local tokens corresponding to the
     * given (`sourceDomain`, `burnToken`) pair, to `to` address.
     * @dev reverts if the (`sourceDomain`, `burnToken`) pair does not
     * map to a nonzero local token address. This mapping can be queried using
     * getLocalToken().
     * @param sourceDomain Source domain where `burnToken` was burned.
     * @param burnToken Burned token address as bytes32.
     * @param to Address to receive minted tokens, corresponding to `burnToken`,
     * on this domain.
     * @param amount Amount of tokens to mint. Must be less than or equal
     * to the minterAllowance of this TokenMinter for given `_mintToken`.
     * @return mintToken token minted.
     */
    function mint(
        uint32 sourceDomain,
        bytes32 burnToken,
        address to,
        uint256 amount
    )
        external
        override
        whenNotPaused
        onlyLocalTokenMessenger
        returns (address mintToken)
    {
        address _mintToken = _getLocalToken(sourceDomain, burnToken);
        require(_mintToken != address(0), "Mint token not supported");
        IMintBurnToken _token = IMintBurnToken(_mintToken);

        require(_token.mint(to, amount), "Mint operation failed");
        return _mintToken;
    }

    /**
     * @notice Burn tokens owned by this TokenMinter.
     * @param burnToken burnable token address.
     * @param burnAmount amount of tokens to burn. Must be
     * > 0, and <= maximum burn amount per message.
     */
    function burn(address burnToken, uint256 burnAmount)
        external
        override
        whenNotPaused
        onlyLocalTokenMessenger
        onlyWithinBurnLimit(burnToken, burnAmount)
    {
        IMintBurnToken _token = IMintBurnToken(burnToken);
        _token.burn(burnAmount);
    }

    /**
     * @notice Add TokenMessenger for the local domain. Only this TokenMessenger
     * has permission to call mint() and burn() on this TokenMinter.
     * @dev Reverts if a TokenMessenger is already set for the local domain.
     * @param newLocalTokenMessenger The address of the new TokenMessenger on the local domain.
     */
    function addLocalTokenMessenger(address newLocalTokenMessenger)
        external
        onlyOwner
    {
        require(
            newLocalTokenMessenger != address(0),
            "Invalid TokenMessenger address"
        );

        require(
            localTokenMessenger == address(0),
            "Local TokenMessenger already set"
        );

        localTokenMessenger = newLocalTokenMessenger;

        emit LocalTokenMessengerAdded(localTokenMessenger);
    }

    /**
     * @notice Remove the TokenMessenger for the local domain.
     * @dev Reverts if the TokenMessenger of the local domain is not set.
     */
    function removeLocalTokenMessenger() external onlyOwner {
        address _localTokenMessengerBeforeRemoval = localTokenMessenger;
        require(
            _localTokenMessengerBeforeRemoval != address(0),
            "No local TokenMessenger is set"
        );

        delete localTokenMessenger;
        emit LocalTokenMessengerRemoved(_localTokenMessengerBeforeRemoval);
    }

    /**
     * @notice Set tokenController to `newTokenController`, and
     * emit `SetTokenController` event.
     * @dev newTokenController must be nonzero.
     * @param newTokenController address of new token controller
     */
    function setTokenController(address newTokenController)
        external
        override
        onlyOwner
    {
        _setTokenController(newTokenController);
    }

    /**
     * @notice Get the local token address associated with the given
     * remote domain and token.
     * @param remoteDomain Remote domain
     * @param remoteToken Remote token
     * @return local token address
     */
    function getLocalToken(uint32 remoteDomain, bytes32 remoteToken)
        external
        view
        override
        returns (address)
    {
        return _getLocalToken(remoteDomain, remoteToken);
    }

    // ============ Internal Utils ============
    /**
     * @notice Returns true if the message sender is the registered local TokenMessenger
     * @return True if the message sender is the registered local TokenMessenger
     */
    function _isLocalTokenMessenger() internal view returns (bool) {
        return
            address(localTokenMessenger) != address(0) &&
            msg.sender == address(localTokenMessenger);
    }
}

/**
 * SPDX-License-Identifier: Apache-2.0
 *
 * Copyright (c) 2023, Circle Internet Financial, LLC.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
pragma solidity 0.6.12;
import { EIP712Domain } from "./EIP712Domain.sol"; // solhint-disable-line no-unused-import
import { Blacklistable } from "../v1/Blacklistable.sol"; // solhint-disable-line no-unused-import
import { FiatTokenV1 } from "../v1/FiatTokenV1.sol"; // solhint-disable-line no-unused-import
import { FiatTokenV2 } from "./FiatTokenV2.sol"; // solhint-disable-line no-unused-import
import { FiatTokenV2_1 } from "./FiatTokenV2_1.sol";
import { EIP712 } from "../util/EIP712.sol";
// solhint-disable func-name-mixedcase
/**
 * @title FiatToken V2.2
 * @notice ERC20 Token backed by fiat reserves, version 2.2
 */
contract FiatTokenV2_2 is FiatTokenV2_1 {
    /**
     * @notice Initialize v2.2
     * @param accountsToBlacklist   A list of accounts to migrate from the old blacklist
     * @param newSymbol             New token symbol
     * data structure to the new blacklist data structure.
     */
    function initializeV2_2(
        address[] calldata accountsToBlacklist,
        string calldata newSymbol
    ) external {
        // solhint-disable-next-line reason-string
        require(_initializedVersion == 2);
        // Update fiat token symbol
        symbol = newSymbol;
        // Add previously blacklisted accounts to the new blacklist data structure
        // and remove them from the old blacklist data structure.
        for (uint256 i = 0; i < accountsToBlacklist.length; i++) {
            require(
                _deprecatedBlacklisted[accountsToBlacklist[i]],
                "FiatTokenV2_2: Blacklisting previously unblacklisted account!"
            );
            _blacklist(accountsToBlacklist[i]);
            delete _deprecatedBlacklisted[accountsToBlacklist[i]];
        }
        _blacklist(address(this));
        delete _deprecatedBlacklisted[address(this)];
        _initializedVersion = 3;
    }
    /**
     * @dev Internal function to get the current chain id.
     * @return The current chain id.
     */
    function _chainId() internal virtual view returns (uint256) {
        uint256 chainId;
        assembly {
            chainId := chainid()
        }
        return chainId;
    }
    /**
     * @inheritdoc EIP712Domain
     */
    function _domainSeparator() internal override view returns (bytes32) {
        return EIP712.makeDomainSeparator(name, "2", _chainId());
    }
    /**
     * @notice Update allowance with a signed permit
     * @dev EOA wallet signatures should be packed in the order of r, s, v.
     * @param owner       Token owner's address (Authorizer)
     * @param spender     Spender's address
     * @param value       Amount of allowance
     * @param deadline    The time at which the signature expires (unix time), or max uint256 value to signal no expiration
     * @param signature   Signature bytes signed by an EOA wallet or a contract wallet
     */
    function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        bytes memory signature
    ) external whenNotPaused {
        _permit(owner, spender, value, deadline, signature);
    }
    /**
     * @notice Execute a transfer with a signed authorization
     * @dev EOA wallet signatures should be packed in the order of r, s, v.
     * @param from          Payer's address (Authorizer)
     * @param to            Payee's address
     * @param value         Amount to be transferred
     * @param validAfter    The time after which this is valid (unix time)
     * @param validBefore   The time before which this is valid (unix time)
     * @param nonce         Unique nonce
     * @param signature     Signature bytes signed by an EOA wallet or a contract wallet
     */
    function transferWithAuthorization(
        address from,
        address to,
        uint256 value,
        uint256 validAfter,
        uint256 validBefore,
        bytes32 nonce,
        bytes memory signature
    ) external whenNotPaused notBlacklisted(from) notBlacklisted(to) {
        _transferWithAuthorization(
            from,
            to,
            value,
            validAfter,
            validBefore,
            nonce,
            signature
        );
    }
    /**
     * @notice Receive a transfer with a signed authorization from the payer
     * @dev This has an additional check to ensure that the payee's address
     * matches the caller of this function to prevent front-running attacks.
     * EOA wallet signatures should be packed in the order of r, s, v.
     * @param from          Payer's address (Authorizer)
     * @param to            Payee's address
     * @param value         Amount to be transferred
     * @param validAfter    The time after which this is valid (unix time)
     * @param validBefore   The time before which this is valid (unix time)
     * @param nonce         Unique nonce
     * @param signature     Signature bytes signed by an EOA wallet or a contract wallet
     */
    function receiveWithAuthorization(
        address from,
        address to,
        uint256 value,
        uint256 validAfter,
        uint256 validBefore,
        bytes32 nonce,
        bytes memory signature
    ) external whenNotPaused notBlacklisted(from) notBlacklisted(to) {
        _receiveWithAuthorization(
            from,
            to,
            value,
            validAfter,
            validBefore,
            nonce,
            signature
        );
    }
    /**
     * @notice Attempt to cancel an authorization
     * @dev Works only if the authorization is not yet used.
     * EOA wallet signatures should be packed in the order of r, s, v.
     * @param authorizer    Authorizer's address
     * @param nonce         Nonce of the authorization
     * @param signature     Signature bytes signed by an EOA wallet or a contract wallet
     */
    function cancelAuthorization(
        address authorizer,
        bytes32 nonce,
        bytes memory signature
    ) external whenNotPaused {
        _cancelAuthorization(authorizer, nonce, signature);
    }
    /**
     * @dev Helper method that sets the blacklist state of an account on balanceAndBlacklistStates.
     * If _shouldBlacklist is true, we apply a (1 << 255) bitmask with an OR operation on the
     * account's balanceAndBlacklistState. This flips the high bit for the account to 1,
     * indicating that the account is blacklisted.
     *
     * If _shouldBlacklist if false, we reset the account's balanceAndBlacklistStates to their
     * balances. This clears the high bit for the account, indicating that the account is unblacklisted.
     * @param _account         The address of the account.
     * @param _shouldBlacklist True if the account should be blacklisted, false if the account should be unblacklisted.
     */
    function _setBlacklistState(address _account, bool _shouldBlacklist)
        internal
        override
    {
        balanceAndBlacklistStates[_account] = _shouldBlacklist
            ? balanceAndBlacklistStates[_account] | (1 << 255)
            : _balanceOf(_account);
    }
    /**
     * @dev Helper method that sets the balance of an account on balanceAndBlacklistStates.
     * Since balances are stored in the last 255 bits of the balanceAndBlacklistStates value,
     * we need to ensure that the updated balance does not exceed (2^255 - 1).
     * Since blacklisted accounts' balances cannot be updated, the method will also
     * revert if the account is blacklisted
     * @param _account The address of the account.
     * @param _balance The new fiat token balance of the account (max: (2^255 - 1)).
     */
    function _setBalance(address _account, uint256 _balance) internal override {
        require(
            _balance <= ((1 << 255) - 1),
            "FiatTokenV2_2: Balance exceeds (2^255 - 1)"
        );
        require(
            !_isBlacklisted(_account),
            "FiatTokenV2_2: Account is blacklisted"
        );
        balanceAndBlacklistStates[_account] = _balance;
    }
    /**
     * @inheritdoc Blacklistable
     */
    function _isBlacklisted(address _account)
        internal
        override
        view
        returns (bool)
    {
        return balanceAndBlacklistStates[_account] >> 255 == 1;
    }
    /**
     * @dev Helper method to obtain the balance of an account. Since balances
     * are stored in the last 255 bits of the balanceAndBlacklistStates value,
     * we apply a ((1 << 255) - 1) bit bitmask with an AND operation on the
     * balanceAndBlacklistState to obtain the balance.
     * @param _account  The address of the account.
     * @return          The fiat token balance of the account.
     */
    function _balanceOf(address _account)
        internal
        override
        view
        returns (uint256)
    {
        return balanceAndBlacklistStates[_account] & ((1 << 255) - 1);
    }
    /**
     * @inheritdoc FiatTokenV1
     */
    function approve(address spender, uint256 value)
        external
        override
        whenNotPaused
        returns (bool)
    {
        _approve(msg.sender, spender, value);
        return true;
    }
    /**
     * @inheritdoc FiatTokenV2
     */
    function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external override whenNotPaused {
        _permit(owner, spender, value, deadline, v, r, s);
    }
    /**
     * @inheritdoc FiatTokenV2
     */
    function increaseAllowance(address spender, uint256 increment)
        external
        override
        whenNotPaused
        returns (bool)
    {
        _increaseAllowance(msg.sender, spender, increment);
        return true;
    }
    /**
     * @inheritdoc FiatTokenV2
     */
    function decreaseAllowance(address spender, uint256 decrement)
        external
        override
        whenNotPaused
        returns (bool)
    {
        _decreaseAllowance(msg.sender, spender, decrement);
        return true;
    }
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.2 <0.8.0;
/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.
        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly { size := extcodesize(account) }
        return size > 0;
    }
    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");
        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (bool success, ) = recipient.call{ value: amount }("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }
    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain`call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
      return functionCall(target, data, "Address: low-level call failed");
    }
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }
    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        require(isContract(target), "Address: call to non-contract");
        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: value }(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data, string memory errorMessage) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");
        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.staticcall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");
        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }
    function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage) private pure returns(bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly
                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;
import "./IERC20.sol";
import "../../math/SafeMath.sol";
import "../../utils/Address.sol";
/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    using SafeMath for uint256;
    using Address for address;
    function safeTransfer(IERC20 token, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }
    function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }
    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    function safeApprove(IERC20 token, address spender, uint256 value) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        // solhint-disable-next-line max-line-length
        require((value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }
    function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).add(value);
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }
    function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).sub(value, "SafeERC20: decreased allowance below zero");
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }
    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function _callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.
        bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
        if (returndata.length > 0) { // Return data is optional
            // solhint-disable-next-line max-line-length
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;
/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);
    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);
    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);
    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);
    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);
    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);
    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);
    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;
/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        uint256 c = a + b;
        if (c < a) return (false, 0);
        return (true, c);
    }
    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b > a) return (false, 0);
        return (true, a - b);
    }
    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) return (true, 0);
        uint256 c = a * b;
        if (c / a != b) return (false, 0);
        return (true, c);
    }
    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a / b);
    }
    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a % b);
    }
    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");
        return c;
    }
    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a, "SafeMath: subtraction overflow");
        return a - b;
    }
    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a == 0) return 0;
        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");
        return c;
    }
    /**
     * @dev Returns the integer division of two unsigned integers, reverting on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: division by zero");
        return a / b;
    }
    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: modulo by zero");
        return a % b;
    }
    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        return a - b;
    }
    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryDiv}.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a / b;
    }
    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a % b;
    }
}
/**
 * SPDX-License-Identifier: Apache-2.0
 *
 * Copyright (c) 2023, Circle Internet Financial, LLC.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
pragma solidity 0.6.12;
import { FiatTokenV2 } from "./FiatTokenV2.sol";
// solhint-disable func-name-mixedcase
/**
 * @title FiatToken V2.1
 * @notice ERC20 Token backed by fiat reserves, version 2.1
 */
contract FiatTokenV2_1 is FiatTokenV2 {
    /**
     * @notice Initialize v2.1
     * @param lostAndFound  The address to which the locked funds are sent
     */
    function initializeV2_1(address lostAndFound) external {
        // solhint-disable-next-line reason-string
        require(_initializedVersion == 1);
        uint256 lockedAmount = _balanceOf(address(this));
        if (lockedAmount > 0) {
            _transfer(address(this), lostAndFound, lockedAmount);
        }
        _blacklist(address(this));
        _initializedVersion = 2;
    }
    /**
     * @notice Version string for the EIP712 domain separator
     * @return Version string
     */
    function version() external pure returns (string memory) {
        return "2";
    }
}
/**
 * SPDX-License-Identifier: Apache-2.0
 *
 * Copyright (c) 2023, Circle Internet Financial, LLC.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
pragma solidity 0.6.12;
import { FiatTokenV1_1 } from "../v1.1/FiatTokenV1_1.sol";
import { EIP712 } from "../util/EIP712.sol";
import { EIP3009 } from "./EIP3009.sol";
import { EIP2612 } from "./EIP2612.sol";
/**
 * @title FiatToken V2
 * @notice ERC20 Token backed by fiat reserves, version 2
 */
contract FiatTokenV2 is FiatTokenV1_1, EIP3009, EIP2612 {
    uint8 internal _initializedVersion;
    /**
     * @notice Initialize v2
     * @param newName   New token name
     */
    function initializeV2(string calldata newName) external {
        // solhint-disable-next-line reason-string
        require(initialized && _initializedVersion == 0);
        name = newName;
        _DEPRECATED_CACHED_DOMAIN_SEPARATOR = EIP712.makeDomainSeparator(
            newName,
            "2"
        );
        _initializedVersion = 1;
    }
    /**
     * @notice Increase the allowance by a given increment
     * @param spender   Spender's address
     * @param increment Amount of increase in allowance
     * @return True if successful
     */
    function increaseAllowance(address spender, uint256 increment)
        external
        virtual
        whenNotPaused
        notBlacklisted(msg.sender)
        notBlacklisted(spender)
        returns (bool)
    {
        _increaseAllowance(msg.sender, spender, increment);
        return true;
    }
    /**
     * @notice Decrease the allowance by a given decrement
     * @param spender   Spender's address
     * @param decrement Amount of decrease in allowance
     * @return True if successful
     */
    function decreaseAllowance(address spender, uint256 decrement)
        external
        virtual
        whenNotPaused
        notBlacklisted(msg.sender)
        notBlacklisted(spender)
        returns (bool)
    {
        _decreaseAllowance(msg.sender, spender, decrement);
        return true;
    }
    /**
     * @notice Execute a transfer with a signed authorization
     * @param from          Payer's address (Authorizer)
     * @param to            Payee's address
     * @param value         Amount to be transferred
     * @param validAfter    The time after which this is valid (unix time)
     * @param validBefore   The time before which this is valid (unix time)
     * @param nonce         Unique nonce
     * @param v             v of the signature
     * @param r             r of the signature
     * @param s             s of the signature
     */
    function transferWithAuthorization(
        address from,
        address to,
        uint256 value,
        uint256 validAfter,
        uint256 validBefore,
        bytes32 nonce,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external whenNotPaused notBlacklisted(from) notBlacklisted(to) {
        _transferWithAuthorization(
            from,
            to,
            value,
            validAfter,
            validBefore,
            nonce,
            v,
            r,
            s
        );
    }
    /**
     * @notice Receive a transfer with a signed authorization from the payer
     * @dev This has an additional check to ensure that the payee's address
     * matches the caller of this function to prevent front-running attacks.
     * @param from          Payer's address (Authorizer)
     * @param to            Payee's address
     * @param value         Amount to be transferred
     * @param validAfter    The time after which this is valid (unix time)
     * @param validBefore   The time before which this is valid (unix time)
     * @param nonce         Unique nonce
     * @param v             v of the signature
     * @param r             r of the signature
     * @param s             s of the signature
     */
    function receiveWithAuthorization(
        address from,
        address to,
        uint256 value,
        uint256 validAfter,
        uint256 validBefore,
        bytes32 nonce,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external whenNotPaused notBlacklisted(from) notBlacklisted(to) {
        _receiveWithAuthorization(
            from,
            to,
            value,
            validAfter,
            validBefore,
            nonce,
            v,
            r,
            s
        );
    }
    /**
     * @notice Attempt to cancel an authorization
     * @dev Works only if the authorization is not yet used.
     * @param authorizer    Authorizer's address
     * @param nonce         Nonce of the authorization
     * @param v             v of the signature
     * @param r             r of the signature
     * @param s             s of the signature
     */
    function cancelAuthorization(
        address authorizer,
        bytes32 nonce,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external whenNotPaused {
        _cancelAuthorization(authorizer, nonce, v, r, s);
    }
    /**
     * @notice Update allowance with a signed permit
     * @param owner       Token owner's address (Authorizer)
     * @param spender     Spender's address
     * @param value       Amount of allowance
     * @param deadline    The time at which the signature expires (unix time), or max uint256 value to signal no expiration
     * @param v           v of the signature
     * @param r           r of the signature
     * @param s           s of the signature
     */
    function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    )
        external
        virtual
        whenNotPaused
        notBlacklisted(owner)
        notBlacklisted(spender)
    {
        _permit(owner, spender, value, deadline, v, r, s);
    }
    /**
     * @dev Internal function to increase the allowance by a given increment
     * @param owner     Token owner's address
     * @param spender   Spender's address
     * @param increment Amount of increase
     */
    function _increaseAllowance(
        address owner,
        address spender,
        uint256 increment
    ) internal override {
        _approve(owner, spender, allowed[owner][spender].add(increment));
    }
    /**
     * @dev Internal function to decrease the allowance by a given decrement
     * @param owner     Token owner's address
     * @param spender   Spender's address
     * @param decrement Amount of decrease
     */
    function _decreaseAllowance(
        address owner,
        address spender,
        uint256 decrement
    ) internal override {
        _approve(
            owner,
            spender,
            allowed[owner][spender].sub(
                decrement,
                "ERC20: decreased allowance below zero"
            )
        );
    }
}
/**
 * SPDX-License-Identifier: Apache-2.0
 *
 * Copyright (c) 2023, Circle Internet Financial, LLC.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
pragma solidity 0.6.12;
// solhint-disable func-name-mixedcase
/**
 * @title EIP712 Domain
 */
contract EIP712Domain {
    // was originally DOMAIN_SEPARATOR
    // but that has been moved to a method so we can override it in V2_2+
    bytes32 internal _DEPRECATED_CACHED_DOMAIN_SEPARATOR;
    /**
     * @notice Get the EIP712 Domain Separator.
     * @return The bytes32 EIP712 domain separator.
     */
    function DOMAIN_SEPARATOR() external view returns (bytes32) {
        return _domainSeparator();
    }
    /**
     * @dev Internal method to get the EIP712 Domain Separator.
     * @return The bytes32 EIP712 domain separator.
     */
    function _domainSeparator() internal virtual view returns (bytes32) {
        return _DEPRECATED_CACHED_DOMAIN_SEPARATOR;
    }
}
/**
 * SPDX-License-Identifier: Apache-2.0
 *
 * Copyright (c) 2023, Circle Internet Financial, LLC.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
pragma solidity 0.6.12;
import { AbstractFiatTokenV2 } from "./AbstractFiatTokenV2.sol";
import { EIP712Domain } from "./EIP712Domain.sol";
import { SignatureChecker } from "../util/SignatureChecker.sol";
import { MessageHashUtils } from "../util/MessageHashUtils.sol";
/**
 * @title EIP-3009
 * @notice Provide internal implementation for gas-abstracted transfers
 * @dev Contracts that inherit from this must wrap these with publicly
 * accessible functions, optionally adding modifiers where necessary
 */
abstract contract EIP3009 is AbstractFiatTokenV2, EIP712Domain {
    // keccak256("TransferWithAuthorization(address from,address to,uint256 value,uint256 validAfter,uint256 validBefore,bytes32 nonce)")
    bytes32
        public constant TRANSFER_WITH_AUTHORIZATION_TYPEHASH = 0x7c7c6cdb67a18743f49ec6fa9b35f50d52ed05cbed4cc592e13b44501c1a2267;
    // keccak256("ReceiveWithAuthorization(address from,address to,uint256 value,uint256 validAfter,uint256 validBefore,bytes32 nonce)")
    bytes32
        public constant RECEIVE_WITH_AUTHORIZATION_TYPEHASH = 0xd099cc98ef71107a616c4f0f941f04c322d8e254fe26b3c6668db87aae413de8;
    // keccak256("CancelAuthorization(address authorizer,bytes32 nonce)")
    bytes32
        public constant CANCEL_AUTHORIZATION_TYPEHASH = 0x158b0a9edf7a828aad02f63cd515c68ef2f50ba807396f6d12842833a1597429;
    /**
     * @dev authorizer address => nonce => bool (true if nonce is used)
     */
    mapping(address => mapping(bytes32 => bool)) private _authorizationStates;
    event AuthorizationUsed(address indexed authorizer, bytes32 indexed nonce);
    event AuthorizationCanceled(
        address indexed authorizer,
        bytes32 indexed nonce
    );
    /**
     * @notice Returns the state of an authorization
     * @dev Nonces are randomly generated 32-byte data unique to the
     * authorizer's address
     * @param authorizer    Authorizer's address
     * @param nonce         Nonce of the authorization
     * @return True if the nonce is used
     */
    function authorizationState(address authorizer, bytes32 nonce)
        external
        view
        returns (bool)
    {
        return _authorizationStates[authorizer][nonce];
    }
    /**
     * @notice Execute a transfer with a signed authorization
     * @param from          Payer's address (Authorizer)
     * @param to            Payee's address
     * @param value         Amount to be transferred
     * @param validAfter    The time after which this is valid (unix time)
     * @param validBefore   The time before which this is valid (unix time)
     * @param nonce         Unique nonce
     * @param v             v of the signature
     * @param r             r of the signature
     * @param s             s of the signature
     */
    function _transferWithAuthorization(
        address from,
        address to,
        uint256 value,
        uint256 validAfter,
        uint256 validBefore,
        bytes32 nonce,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) internal {
        _transferWithAuthorization(
            from,
            to,
            value,
            validAfter,
            validBefore,
            nonce,
            abi.encodePacked(r, s, v)
        );
    }
    /**
     * @notice Execute a transfer with a signed authorization
     * @dev EOA wallet signatures should be packed in the order of r, s, v.
     * @param from          Payer's address (Authorizer)
     * @param to            Payee's address
     * @param value         Amount to be transferred
     * @param validAfter    The time after which this is valid (unix time)
     * @param validBefore   The time before which this is valid (unix time)
     * @param nonce         Unique nonce
     * @param signature     Signature byte array produced by an EOA wallet or a contract wallet
     */
    function _transferWithAuthorization(
        address from,
        address to,
        uint256 value,
        uint256 validAfter,
        uint256 validBefore,
        bytes32 nonce,
        bytes memory signature
    ) internal {
        _requireValidAuthorization(from, nonce, validAfter, validBefore);
        _requireValidSignature(
            from,
            keccak256(
                abi.encode(
                    TRANSFER_WITH_AUTHORIZATION_TYPEHASH,
                    from,
                    to,
                    value,
                    validAfter,
                    validBefore,
                    nonce
                )
            ),
            signature
        );
        _markAuthorizationAsUsed(from, nonce);
        _transfer(from, to, value);
    }
    /**
     * @notice Receive a transfer with a signed authorization from the payer
     * @dev This has an additional check to ensure that the payee's address
     * matches the caller of this function to prevent front-running attacks.
     * @param from          Payer's address (Authorizer)
     * @param to            Payee's address
     * @param value         Amount to be transferred
     * @param validAfter    The time after which this is valid (unix time)
     * @param validBefore   The time before which this is valid (unix time)
     * @param nonce         Unique nonce
     * @param v             v of the signature
     * @param r             r of the signature
     * @param s             s of the signature
     */
    function _receiveWithAuthorization(
        address from,
        address to,
        uint256 value,
        uint256 validAfter,
        uint256 validBefore,
        bytes32 nonce,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) internal {
        _receiveWithAuthorization(
            from,
            to,
            value,
            validAfter,
            validBefore,
            nonce,
            abi.encodePacked(r, s, v)
        );
    }
    /**
     * @notice Receive a transfer with a signed authorization from the payer
     * @dev This has an additional check to ensure that the payee's address
     * matches the caller of this function to prevent front-running attacks.
     * EOA wallet signatures should be packed in the order of r, s, v.
     * @param from          Payer's address (Authorizer)
     * @param to            Payee's address
     * @param value         Amount to be transferred
     * @param validAfter    The time after which this is valid (unix time)
     * @param validBefore   The time before which this is valid (unix time)
     * @param nonce         Unique nonce
     * @param signature     Signature byte array produced by an EOA wallet or a contract wallet
     */
    function _receiveWithAuthorization(
        address from,
        address to,
        uint256 value,
        uint256 validAfter,
        uint256 validBefore,
        bytes32 nonce,
        bytes memory signature
    ) internal {
        require(to == msg.sender, "FiatTokenV2: caller must be the payee");
        _requireValidAuthorization(from, nonce, validAfter, validBefore);
        _requireValidSignature(
            from,
            keccak256(
                abi.encode(
                    RECEIVE_WITH_AUTHORIZATION_TYPEHASH,
                    from,
                    to,
                    value,
                    validAfter,
                    validBefore,
                    nonce
                )
            ),
            signature
        );
        _markAuthorizationAsUsed(from, nonce);
        _transfer(from, to, value);
    }
    /**
     * @notice Attempt to cancel an authorization
     * @param authorizer    Authorizer's address
     * @param nonce         Nonce of the authorization
     * @param v             v of the signature
     * @param r             r of the signature
     * @param s             s of the signature
     */
    function _cancelAuthorization(
        address authorizer,
        bytes32 nonce,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) internal {
        _cancelAuthorization(authorizer, nonce, abi.encodePacked(r, s, v));
    }
    /**
     * @notice Attempt to cancel an authorization
     * @dev EOA wallet signatures should be packed in the order of r, s, v.
     * @param authorizer    Authorizer's address
     * @param nonce         Nonce of the authorization
     * @param signature     Signature byte array produced by an EOA wallet or a contract wallet
     */
    function _cancelAuthorization(
        address authorizer,
        bytes32 nonce,
        bytes memory signature
    ) internal {
        _requireUnusedAuthorization(authorizer, nonce);
        _requireValidSignature(
            authorizer,
            keccak256(
                abi.encode(CANCEL_AUTHORIZATION_TYPEHASH, authorizer, nonce)
            ),
            signature
        );
        _authorizationStates[authorizer][nonce] = true;
        emit AuthorizationCanceled(authorizer, nonce);
    }
    /**
     * @notice Validates that signature against input data struct
     * @param signer        Signer's address
     * @param dataHash      Hash of encoded data struct
     * @param signature     Signature byte array produced by an EOA wallet or a contract wallet
     */
    function _requireValidSignature(
        address signer,
        bytes32 dataHash,
        bytes memory signature
    ) private view {
        require(
            SignatureChecker.isValidSignatureNow(
                signer,
                MessageHashUtils.toTypedDataHash(_domainSeparator(), dataHash),
                signature
            ),
            "FiatTokenV2: invalid signature"
        );
    }
    /**
     * @notice Check that an authorization is unused
     * @param authorizer    Authorizer's address
     * @param nonce         Nonce of the authorization
     */
    function _requireUnusedAuthorization(address authorizer, bytes32 nonce)
        private
        view
    {
        require(
            !_authorizationStates[authorizer][nonce],
            "FiatTokenV2: authorization is used or canceled"
        );
    }
    /**
     * @notice Check that authorization is valid
     * @param authorizer    Authorizer's address
     * @param nonce         Nonce of the authorization
     * @param validAfter    The time after which this is valid (unix time)
     * @param validBefore   The time before which this is valid (unix time)
     */
    function _requireValidAuthorization(
        address authorizer,
        bytes32 nonce,
        uint256 validAfter,
        uint256 validBefore
    ) private view {
        require(
            now > validAfter,
            "FiatTokenV2: authorization is not yet valid"
        );
        require(now < validBefore, "FiatTokenV2: authorization is expired");
        _requireUnusedAuthorization(authorizer, nonce);
    }
    /**
     * @notice Mark an authorization as used
     * @param authorizer    Authorizer's address
     * @param nonce         Nonce of the authorization
     */
    function _markAuthorizationAsUsed(address authorizer, bytes32 nonce)
        private
    {
        _authorizationStates[authorizer][nonce] = true;
        emit AuthorizationUsed(authorizer, nonce);
    }
}
/**
 * SPDX-License-Identifier: Apache-2.0
 *
 * Copyright (c) 2023, Circle Internet Financial, LLC.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
pragma solidity 0.6.12;
import { AbstractFiatTokenV2 } from "./AbstractFiatTokenV2.sol";
import { EIP712Domain } from "./EIP712Domain.sol";
import { MessageHashUtils } from "../util/MessageHashUtils.sol";
import { SignatureChecker } from "../util/SignatureChecker.sol";
/**
 * @title EIP-2612
 * @notice Provide internal implementation for gas-abstracted approvals
 */
abstract contract EIP2612 is AbstractFiatTokenV2, EIP712Domain {
    // keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)")
    bytes32
        public constant PERMIT_TYPEHASH = 0x6e71edae12b1b97f4d1f60370fef10105fa2faae0126114a169c64845d6126c9;
    mapping(address => uint256) private _permitNonces;
    /**
     * @notice Nonces for permit
     * @param owner Token owner's address (Authorizer)
     * @return Next nonce
     */
    function nonces(address owner) external view returns (uint256) {
        return _permitNonces[owner];
    }
    /**
     * @notice Verify a signed approval permit and execute if valid
     * @param owner     Token owner's address (Authorizer)
     * @param spender   Spender's address
     * @param value     Amount of allowance
     * @param deadline  The time at which the signature expires (unix time), or max uint256 value to signal no expiration
     * @param v         v of the signature
     * @param r         r of the signature
     * @param s         s of the signature
     */
    function _permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) internal {
        _permit(owner, spender, value, deadline, abi.encodePacked(r, s, v));
    }
    /**
     * @notice Verify a signed approval permit and execute if valid
     * @dev EOA wallet signatures should be packed in the order of r, s, v.
     * @param owner      Token owner's address (Authorizer)
     * @param spender    Spender's address
     * @param value      Amount of allowance
     * @param deadline   The time at which the signature expires (unix time), or max uint256 value to signal no expiration
     * @param signature  Signature byte array signed by an EOA wallet or a contract wallet
     */
    function _permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        bytes memory signature
    ) internal {
        require(
            deadline == type(uint256).max || deadline >= now,
            "FiatTokenV2: permit is expired"
        );
        bytes32 typedDataHash = MessageHashUtils.toTypedDataHash(
            _domainSeparator(),
            keccak256(
                abi.encode(
                    PERMIT_TYPEHASH,
                    owner,
                    spender,
                    value,
                    _permitNonces[owner]++,
                    deadline
                )
            )
        );
        require(
            SignatureChecker.isValidSignatureNow(
                owner,
                typedDataHash,
                signature
            ),
            "EIP2612: invalid signature"
        );
        _approve(owner, spender, value);
    }
}
/**
 * SPDX-License-Identifier: Apache-2.0
 *
 * Copyright (c) 2023, Circle Internet Financial, LLC.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
pragma solidity 0.6.12;
import { AbstractFiatTokenV1 } from "../v1/AbstractFiatTokenV1.sol";
abstract contract AbstractFiatTokenV2 is AbstractFiatTokenV1 {
    function _increaseAllowance(
        address owner,
        address spender,
        uint256 increment
    ) internal virtual;
    function _decreaseAllowance(
        address owner,
        address spender,
        uint256 decrement
    ) internal virtual;
}
/**
 * SPDX-License-Identifier: MIT
 *
 * Copyright (c) 2016 Smart Contract Solutions, Inc.
 * Copyright (c) 2018-2020 CENTRE SECZ
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
pragma solidity 0.6.12;
import { Ownable } from "./Ownable.sol";
/**
 * @notice Base contract which allows children to implement an emergency stop
 * mechanism
 * @dev Forked from https://github.com/OpenZeppelin/openzeppelin-contracts/blob/feb665136c0dae9912e08397c1a21c4af3651ef3/contracts/lifecycle/Pausable.sol
 * Modifications:
 * 1. Added pauser role, switched pause/unpause to be onlyPauser (6/14/2018)
 * 2. Removed whenNotPause/whenPaused from pause/unpause (6/14/2018)
 * 3. Removed whenPaused (6/14/2018)
 * 4. Switches ownable library to use ZeppelinOS (7/12/18)
 * 5. Remove constructor (7/13/18)
 * 6. Reformat, conform to Solidity 0.6 syntax and add error messages (5/13/20)
 * 7. Make public functions external (5/27/20)
 */
contract Pausable is Ownable {
    event Pause();
    event Unpause();
    event PauserChanged(address indexed newAddress);
    address public pauser;
    bool public paused = false;
    /**
     * @dev Modifier to make a function callable only when the contract is not paused.
     */
    modifier whenNotPaused() {
        require(!paused, "Pausable: paused");
        _;
    }
    /**
     * @dev throws if called by any account other than the pauser
     */
    modifier onlyPauser() {
        require(msg.sender == pauser, "Pausable: caller is not the pauser");
        _;
    }
    /**
     * @dev called by the owner to pause, triggers stopped state
     */
    function pause() external onlyPauser {
        paused = true;
        emit Pause();
    }
    /**
     * @dev called by the owner to unpause, returns to normal state
     */
    function unpause() external onlyPauser {
        paused = false;
        emit Unpause();
    }
    /**
     * @notice Updates the pauser address.
     * @param _newPauser The address of the new pauser.
     */
    function updatePauser(address _newPauser) external onlyOwner {
        require(
            _newPauser != address(0),
            "Pausable: new pauser is the zero address"
        );
        pauser = _newPauser;
        emit PauserChanged(pauser);
    }
}
/**
 * SPDX-License-Identifier: MIT
 *
 * Copyright (c) 2018 zOS Global Limited.
 * Copyright (c) 2018-2020 CENTRE SECZ
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
pragma solidity 0.6.12;
/**
 * @notice The Ownable contract has an owner address, and provides basic
 * authorization control functions
 * @dev Forked from https://github.com/OpenZeppelin/openzeppelin-labs/blob/3887ab77b8adafba4a26ace002f3a684c1a3388b/upgradeability_ownership/contracts/ownership/Ownable.sol
 * Modifications:
 * 1. Consolidate OwnableStorage into this contract (7/13/18)
 * 2. Reformat, conform to Solidity 0.6 syntax, and add error messages (5/13/20)
 * 3. Make public functions external (5/27/20)
 */
contract Ownable {
    // Owner of the contract
    address private _owner;
    /**
     * @dev Event to show ownership has been transferred
     * @param previousOwner representing the address of the previous owner
     * @param newOwner representing the address of the new owner
     */
    event OwnershipTransferred(address previousOwner, address newOwner);
    /**
     * @dev The constructor sets the original owner of the contract to the sender account.
     */
    constructor() public {
        setOwner(msg.sender);
    }
    /**
     * @dev Tells the address of the owner
     * @return the address of the owner
     */
    function owner() external view returns (address) {
        return _owner;
    }
    /**
     * @dev Sets a new owner address
     */
    function setOwner(address newOwner) internal {
        _owner = newOwner;
    }
    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(msg.sender == _owner, "Ownable: caller is not the owner");
        _;
    }
    /**
     * @dev Allows the current owner to transfer control of the contract to a newOwner.
     * @param newOwner The address to transfer ownership to.
     */
    function transferOwnership(address newOwner) external onlyOwner {
        require(
            newOwner != address(0),
            "Ownable: new owner is the zero address"
        );
        emit OwnershipTransferred(_owner, newOwner);
        setOwner(newOwner);
    }
}
/**
 * SPDX-License-Identifier: Apache-2.0
 *
 * Copyright (c) 2023, Circle Internet Financial, LLC.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
pragma solidity 0.6.12;
import { SafeMath } from "@openzeppelin/contracts/math/SafeMath.sol";
import { AbstractFiatTokenV1 } from "./AbstractFiatTokenV1.sol";
import { Ownable } from "./Ownable.sol";
import { Pausable } from "./Pausable.sol";
import { Blacklistable } from "./Blacklistable.sol";
/**
 * @title FiatToken
 * @dev ERC20 Token backed by fiat reserves
 */
contract FiatTokenV1 is AbstractFiatTokenV1, Ownable, Pausable, Blacklistable {
    using SafeMath for uint256;
    string public name;
    string public symbol;
    uint8 public decimals;
    string public currency;
    address public masterMinter;
    bool internal initialized;
    /// @dev A mapping that stores the balance and blacklist states for a given address.
    /// The first bit defines whether the address is blacklisted (1 if blacklisted, 0 otherwise).
    /// The last 255 bits define the balance for the address.
    mapping(address => uint256) internal balanceAndBlacklistStates;
    mapping(address => mapping(address => uint256)) internal allowed;
    uint256 internal totalSupply_ = 0;
    mapping(address => bool) internal minters;
    mapping(address => uint256) internal minterAllowed;
    event Mint(address indexed minter, address indexed to, uint256 amount);
    event Burn(address indexed burner, uint256 amount);
    event MinterConfigured(address indexed minter, uint256 minterAllowedAmount);
    event MinterRemoved(address indexed oldMinter);
    event MasterMinterChanged(address indexed newMasterMinter);
    /**
     * @notice Initializes the fiat token contract.
     * @param tokenName       The name of the fiat token.
     * @param tokenSymbol     The symbol of the fiat token.
     * @param tokenCurrency   The fiat currency that the token represents.
     * @param tokenDecimals   The number of decimals that the token uses.
     * @param newMasterMinter The masterMinter address for the fiat token.
     * @param newPauser       The pauser address for the fiat token.
     * @param newBlacklister  The blacklister address for the fiat token.
     * @param newOwner        The owner of the fiat token.
     */
    function initialize(
        string memory tokenName,
        string memory tokenSymbol,
        string memory tokenCurrency,
        uint8 tokenDecimals,
        address newMasterMinter,
        address newPauser,
        address newBlacklister,
        address newOwner
    ) public {
        require(!initialized, "FiatToken: contract is already initialized");
        require(
            newMasterMinter != address(0),
            "FiatToken: new masterMinter is the zero address"
        );
        require(
            newPauser != address(0),
            "FiatToken: new pauser is the zero address"
        );
        require(
            newBlacklister != address(0),
            "FiatToken: new blacklister is the zero address"
        );
        require(
            newOwner != address(0),
            "FiatToken: new owner is the zero address"
        );
        name = tokenName;
        symbol = tokenSymbol;
        currency = tokenCurrency;
        decimals = tokenDecimals;
        masterMinter = newMasterMinter;
        pauser = newPauser;
        blacklister = newBlacklister;
        setOwner(newOwner);
        initialized = true;
    }
    /**
     * @dev Throws if called by any account other than a minter.
     */
    modifier onlyMinters() {
        require(minters[msg.sender], "FiatToken: caller is not a minter");
        _;
    }
    /**
     * @notice Mints fiat tokens to an address.
     * @param _to The address that will receive the minted tokens.
     * @param _amount The amount of tokens to mint. Must be less than or equal
     * to the minterAllowance of the caller.
     * @return True if the operation was successful.
     */
    function mint(address _to, uint256 _amount)
        external
        whenNotPaused
        onlyMinters
        notBlacklisted(msg.sender)
        notBlacklisted(_to)
        returns (bool)
    {
        require(_to != address(0), "FiatToken: mint to the zero address");
        require(_amount > 0, "FiatToken: mint amount not greater than 0");
        uint256 mintingAllowedAmount = minterAllowed[msg.sender];
        require(
            _amount <= mintingAllowedAmount,
            "FiatToken: mint amount exceeds minterAllowance"
        );
        totalSupply_ = totalSupply_.add(_amount);
        _setBalance(_to, _balanceOf(_to).add(_amount));
        minterAllowed[msg.sender] = mintingAllowedAmount.sub(_amount);
        emit Mint(msg.sender, _to, _amount);
        emit Transfer(address(0), _to, _amount);
        return true;
    }
    /**
     * @dev Throws if called by any account other than the masterMinter
     */
    modifier onlyMasterMinter() {
        require(
            msg.sender == masterMinter,
            "FiatToken: caller is not the masterMinter"
        );
        _;
    }
    /**
     * @notice Gets the minter allowance for an account.
     * @param minter The address to check.
     * @return The remaining minter allowance for the account.
     */
    function minterAllowance(address minter) external view returns (uint256) {
        return minterAllowed[minter];
    }
    /**
     * @notice Checks if an account is a minter.
     * @param account The address to check.
     * @return True if the account is a minter, false if the account is not a minter.
     */
    function isMinter(address account) external view returns (bool) {
        return minters[account];
    }
    /**
     * @notice Gets the remaining amount of fiat tokens a spender is allowed to transfer on
     * behalf of the token owner.
     * @param owner   The token owner's address.
     * @param spender The spender's address.
     * @return The remaining allowance.
     */
    function allowance(address owner, address spender)
        external
        override
        view
        returns (uint256)
    {
        return allowed[owner][spender];
    }
    /**
     * @notice Gets the totalSupply of the fiat token.
     * @return The totalSupply of the fiat token.
     */
    function totalSupply() external override view returns (uint256) {
        return totalSupply_;
    }
    /**
     * @notice Gets the fiat token balance of an account.
     * @param account  The address to check.
     * @return balance The fiat token balance of the account.
     */
    function balanceOf(address account)
        external
        override
        view
        returns (uint256)
    {
        return _balanceOf(account);
    }
    /**
     * @notice Sets a fiat token allowance for a spender to spend on behalf of the caller.
     * @param spender The spender's address.
     * @param value   The allowance amount.
     * @return True if the operation was successful.
     */
    function approve(address spender, uint256 value)
        external
        virtual
        override
        whenNotPaused
        notBlacklisted(msg.sender)
        notBlacklisted(spender)
        returns (bool)
    {
        _approve(msg.sender, spender, value);
        return true;
    }
    /**
     * @dev Internal function to set allowance.
     * @param owner     Token owner's address.
     * @param spender   Spender's address.
     * @param value     Allowance amount.
     */
    function _approve(
        address owner,
        address spender,
        uint256 value
    ) internal override {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");
        allowed[owner][spender] = value;
        emit Approval(owner, spender, value);
    }
    /**
     * @notice Transfers tokens from an address to another by spending the caller's allowance.
     * @dev The caller must have some fiat token allowance on the payer's tokens.
     * @param from  Payer's address.
     * @param to    Payee's address.
     * @param value Transfer amount.
     * @return True if the operation was successful.
     */
    function transferFrom(
        address from,
        address to,
        uint256 value
    )
        external
        override
        whenNotPaused
        notBlacklisted(msg.sender)
        notBlacklisted(from)
        notBlacklisted(to)
        returns (bool)
    {
        require(
            value <= allowed[from][msg.sender],
            "ERC20: transfer amount exceeds allowance"
        );
        _transfer(from, to, value);
        allowed[from][msg.sender] = allowed[from][msg.sender].sub(value);
        return true;
    }
    /**
     * @notice Transfers tokens from the caller.
     * @param to    Payee's address.
     * @param value Transfer amount.
     * @return True if the operation was successful.
     */
    function transfer(address to, uint256 value)
        external
        override
        whenNotPaused
        notBlacklisted(msg.sender)
        notBlacklisted(to)
        returns (bool)
    {
        _transfer(msg.sender, to, value);
        return true;
    }
    /**
     * @dev Internal function to process transfers.
     * @param from  Payer's address.
     * @param to    Payee's address.
     * @param value Transfer amount.
     */
    function _transfer(
        address from,
        address to,
        uint256 value
    ) internal override {
        require(from != address(0), "ERC20: transfer from the zero address");
        require(to != address(0), "ERC20: transfer to the zero address");
        require(
            value <= _balanceOf(from),
            "ERC20: transfer amount exceeds balance"
        );
        _setBalance(from, _balanceOf(from).sub(value));
        _setBalance(to, _balanceOf(to).add(value));
        emit Transfer(from, to, value);
    }
    /**
     * @notice Adds or updates a new minter with a mint allowance.
     * @param minter The address of the minter.
     * @param minterAllowedAmount The minting amount allowed for the minter.
     * @return True if the operation was successful.
     */
    function configureMinter(address minter, uint256 minterAllowedAmount)
        external
        whenNotPaused
        onlyMasterMinter
        returns (bool)
    {
        minters[minter] = true;
        minterAllowed[minter] = minterAllowedAmount;
        emit MinterConfigured(minter, minterAllowedAmount);
        return true;
    }
    /**
     * @notice Removes a minter.
     * @param minter The address of the minter to remove.
     * @return True if the operation was successful.
     */
    function removeMinter(address minter)
        external
        onlyMasterMinter
        returns (bool)
    {
        minters[minter] = false;
        minterAllowed[minter] = 0;
        emit MinterRemoved(minter);
        return true;
    }
    /**
     * @notice Allows a minter to burn some of its own tokens.
     * @dev The caller must be a minter, must not be blacklisted, and the amount to burn
     * should be less than or equal to the account's balance.
     * @param _amount the amount of tokens to be burned.
     */
    function burn(uint256 _amount)
        external
        whenNotPaused
        onlyMinters
        notBlacklisted(msg.sender)
    {
        uint256 balance = _balanceOf(msg.sender);
        require(_amount > 0, "FiatToken: burn amount not greater than 0");
        require(balance >= _amount, "FiatToken: burn amount exceeds balance");
        totalSupply_ = totalSupply_.sub(_amount);
        _setBalance(msg.sender, balance.sub(_amount));
        emit Burn(msg.sender, _amount);
        emit Transfer(msg.sender, address(0), _amount);
    }
    /**
     * @notice Updates the master minter address.
     * @param _newMasterMinter The address of the new master minter.
     */
    function updateMasterMinter(address _newMasterMinter) external onlyOwner {
        require(
            _newMasterMinter != address(0),
            "FiatToken: new masterMinter is the zero address"
        );
        masterMinter = _newMasterMinter;
        emit MasterMinterChanged(masterMinter);
    }
    /**
     * @inheritdoc Blacklistable
     */
    function _blacklist(address _account) internal override {
        _setBlacklistState(_account, true);
    }
    /**
     * @inheritdoc Blacklistable
     */
    function _unBlacklist(address _account) internal override {
        _setBlacklistState(_account, false);
    }
    /**
     * @dev Helper method that sets the blacklist state of an account.
     * @param _account         The address of the account.
     * @param _shouldBlacklist True if the account should be blacklisted, false if the account should be unblacklisted.
     */
    function _setBlacklistState(address _account, bool _shouldBlacklist)
        internal
        virtual
    {
        _deprecatedBlacklisted[_account] = _shouldBlacklist;
    }
    /**
     * @dev Helper method that sets the balance of an account.
     * @param _account The address of the account.
     * @param _balance The new fiat token balance of the account.
     */
    function _setBalance(address _account, uint256 _balance) internal virtual {
        balanceAndBlacklistStates[_account] = _balance;
    }
    /**
     * @inheritdoc Blacklistable
     */
    function _isBlacklisted(address _account)
        internal
        virtual
        override
        view
        returns (bool)
    {
        return _deprecatedBlacklisted[_account];
    }
    /**
     * @dev Helper method to obtain the balance of an account.
     * @param _account  The address of the account.
     * @return          The fiat token balance of the account.
     */
    function _balanceOf(address _account)
        internal
        virtual
        view
        returns (uint256)
    {
        return balanceAndBlacklistStates[_account];
    }
}
/**
 * SPDX-License-Identifier: Apache-2.0
 *
 * Copyright (c) 2023, Circle Internet Financial, LLC.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
pragma solidity 0.6.12;
import { Ownable } from "./Ownable.sol";
/**
 * @title Blacklistable Token
 * @dev Allows accounts to be blacklisted by a "blacklister" role
 */
abstract contract Blacklistable is Ownable {
    address public blacklister;
    mapping(address => bool) internal _deprecatedBlacklisted;
    event Blacklisted(address indexed _account);
    event UnBlacklisted(address indexed _account);
    event BlacklisterChanged(address indexed newBlacklister);
    /**
     * @dev Throws if called by any account other than the blacklister.
     */
    modifier onlyBlacklister() {
        require(
            msg.sender == blacklister,
            "Blacklistable: caller is not the blacklister"
        );
        _;
    }
    /**
     * @dev Throws if argument account is blacklisted.
     * @param _account The address to check.
     */
    modifier notBlacklisted(address _account) {
        require(
            !_isBlacklisted(_account),
            "Blacklistable: account is blacklisted"
        );
        _;
    }
    /**
     * @notice Checks if account is blacklisted.
     * @param _account The address to check.
     * @return True if the account is blacklisted, false if the account is not blacklisted.
     */
    function isBlacklisted(address _account) external view returns (bool) {
        return _isBlacklisted(_account);
    }
    /**
     * @notice Adds account to blacklist.
     * @param _account The address to blacklist.
     */
    function blacklist(address _account) external onlyBlacklister {
        _blacklist(_account);
        emit Blacklisted(_account);
    }
    /**
     * @notice Removes account from blacklist.
     * @param _account The address to remove from the blacklist.
     */
    function unBlacklist(address _account) external onlyBlacklister {
        _unBlacklist(_account);
        emit UnBlacklisted(_account);
    }
    /**
     * @notice Updates the blacklister address.
     * @param _newBlacklister The address of the new blacklister.
     */
    function updateBlacklister(address _newBlacklister) external onlyOwner {
        require(
            _newBlacklister != address(0),
            "Blacklistable: new blacklister is the zero address"
        );
        blacklister = _newBlacklister;
        emit BlacklisterChanged(blacklister);
    }
    /**
     * @dev Checks if account is blacklisted.
     * @param _account The address to check.
     * @return true if the account is blacklisted, false otherwise.
     */
    function _isBlacklisted(address _account)
        internal
        virtual
        view
        returns (bool);
    /**
     * @dev Helper method that blacklists an account.
     * @param _account The address to blacklist.
     */
    function _blacklist(address _account) internal virtual;
    /**
     * @dev Helper method that unblacklists an account.
     * @param _account The address to unblacklist.
     */
    function _unBlacklist(address _account) internal virtual;
}
/**
 * SPDX-License-Identifier: Apache-2.0
 *
 * Copyright (c) 2023, Circle Internet Financial, LLC.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
pragma solidity 0.6.12;
import { IERC20 } from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
abstract contract AbstractFiatTokenV1 is IERC20 {
    function _approve(
        address owner,
        address spender,
        uint256 value
    ) internal virtual;
    function _transfer(
        address from,
        address to,
        uint256 value
    ) internal virtual;
}
/**
 * SPDX-License-Identifier: Apache-2.0
 *
 * Copyright (c) 2023, Circle Internet Financial, LLC.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
pragma solidity 0.6.12;
import { Ownable } from "../v1/Ownable.sol";
import { IERC20 } from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import { SafeERC20 } from "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";
contract Rescuable is Ownable {
    using SafeERC20 for IERC20;
    address private _rescuer;
    event RescuerChanged(address indexed newRescuer);
    /**
     * @notice Returns current rescuer
     * @return Rescuer's address
     */
    function rescuer() external view returns (address) {
        return _rescuer;
    }
    /**
     * @notice Revert if called by any account other than the rescuer.
     */
    modifier onlyRescuer() {
        require(msg.sender == _rescuer, "Rescuable: caller is not the rescuer");
        _;
    }
    /**
     * @notice Rescue ERC20 tokens locked up in this contract.
     * @param tokenContract ERC20 token contract address
     * @param to        Recipient address
     * @param amount    Amount to withdraw
     */
    function rescueERC20(
        IERC20 tokenContract,
        address to,
        uint256 amount
    ) external onlyRescuer {
        tokenContract.safeTransfer(to, amount);
    }
    /**
     * @notice Updates the rescuer address.
     * @param newRescuer The address of the new rescuer.
     */
    function updateRescuer(address newRescuer) external onlyOwner {
        require(
            newRescuer != address(0),
            "Rescuable: new rescuer is the zero address"
        );
        _rescuer = newRescuer;
        emit RescuerChanged(newRescuer);
    }
}
/**
 * SPDX-License-Identifier: Apache-2.0
 *
 * Copyright (c) 2023, Circle Internet Financial, LLC.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
pragma solidity 0.6.12;
import { FiatTokenV1 } from "../v1/FiatTokenV1.sol";
import { Rescuable } from "./Rescuable.sol";
/**
 * @title FiatTokenV1_1
 * @dev ERC20 Token backed by fiat reserves
 */
contract FiatTokenV1_1 is FiatTokenV1, Rescuable {
}
/**
 * SPDX-License-Identifier: Apache-2.0
 *
 * Copyright (c) 2023, Circle Internet Financial, LLC.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
pragma solidity 0.6.12;
import { ECRecover } from "./ECRecover.sol";
import { IERC1271 } from "../interface/IERC1271.sol";
/**
 * @dev Signature verification helper that can be used instead of `ECRecover.recover` to seamlessly support both ECDSA
 * signatures from externally owned accounts (EOAs) as well as ERC1271 signatures from smart contract wallets.
 *
 * Adapted from https://github.com/OpenZeppelin/openzeppelin-contracts/blob/21bb89ef5bfc789b9333eb05e3ba2b7b284ac77c/contracts/utils/cryptography/SignatureChecker.sol
 */
library SignatureChecker {
    /**
     * @dev Checks if a signature is valid for a given signer and data hash. If the signer is a smart contract, the
     * signature is validated against that smart contract using ERC1271, otherwise it's validated using `ECRecover.recover`.
     * @param signer        Address of the claimed signer
     * @param digest        Keccak-256 hash digest of the signed message
     * @param signature     Signature byte array associated with hash
     */
    function isValidSignatureNow(
        address signer,
        bytes32 digest,
        bytes memory signature
    ) external view returns (bool) {
        if (!isContract(signer)) {
            return ECRecover.recover(digest, signature) == signer;
        }
        return isValidERC1271SignatureNow(signer, digest, signature);
    }
    /**
     * @dev Checks if a signature is valid for a given signer and data hash. The signature is validated
     * against the signer smart contract using ERC1271.
     * @param signer        Address of the claimed signer
     * @param digest        Keccak-256 hash digest of the signed message
     * @param signature     Signature byte array associated with hash
     *
     * NOTE: Unlike ECDSA signatures, contract signatures are revocable, and the outcome of this function can thus
     * change through time. It could return true at block N and false at block N+1 (or the opposite).
     */
    function isValidERC1271SignatureNow(
        address signer,
        bytes32 digest,
        bytes memory signature
    ) internal view returns (bool) {
        (bool success, bytes memory result) = signer.staticcall(
            abi.encodeWithSelector(
                IERC1271.isValidSignature.selector,
                digest,
                signature
            )
        );
        return (success &&
            result.length >= 32 &&
            abi.decode(result, (bytes32)) ==
            bytes32(IERC1271.isValidSignature.selector));
    }
    /**
     * @dev Checks if the input address is a smart contract.
     */
    function isContract(address addr) internal view returns (bool) {
        uint256 size;
        assembly {
            size := extcodesize(addr)
        }
        return size > 0;
    }
}
/**
 * SPDX-License-Identifier: Apache-2.0
 *
 * Copyright (c) 2023, Circle Internet Financial, LLC.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
pragma solidity 0.6.12;
/**
 * @dev Signature message hash utilities for producing digests to be consumed by {ECDSA} recovery or signing.
 *
 * The library provides methods for generating a hash of a message that conforms to the
 * https://eips.ethereum.org/EIPS/eip-191[EIP 191] and https://eips.ethereum.org/EIPS/eip-712[EIP 712]
 * specifications.
 */
library MessageHashUtils {
    /**
     * @dev Returns the keccak256 digest of an EIP-712 typed data (EIP-191 version `0x01`).
     * Adapted from https://github.com/OpenZeppelin/openzeppelin-contracts/blob/21bb89ef5bfc789b9333eb05e3ba2b7b284ac77c/contracts/utils/cryptography/MessageHashUtils.sol
     *
     * The digest is calculated from a `domainSeparator` and a `structHash`, by prefixing them with
     * `\\x19\\x01` and hashing the result. It corresponds to the hash signed by the
     * https://eips.ethereum.org/EIPS/eip-712[`eth_signTypedData`] JSON-RPC method as part of EIP-712.
     *
     * @param domainSeparator    Domain separator
     * @param structHash         Hashed EIP-712 data struct
     * @return digest            The keccak256 digest of an EIP-712 typed data
     */
    function toTypedDataHash(bytes32 domainSeparator, bytes32 structHash)
        internal
        pure
        returns (bytes32 digest)
    {
        assembly {
            let ptr := mload(0x40)
            mstore(ptr, "\\x19\\x01")
            mstore(add(ptr, 0x02), domainSeparator)
            mstore(add(ptr, 0x22), structHash)
            digest := keccak256(ptr, 0x42)
        }
    }
}
/**
 * SPDX-License-Identifier: Apache-2.0
 *
 * Copyright (c) 2023, Circle Internet Financial, LLC.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
pragma solidity 0.6.12;
/**
 * @title EIP712
 * @notice A library that provides EIP712 helper functions
 */
library EIP712 {
    /**
     * @notice Make EIP712 domain separator
     * @param name      Contract name
     * @param version   Contract version
     * @param chainId   Blockchain ID
     * @return Domain separator
     */
    function makeDomainSeparator(
        string memory name,
        string memory version,
        uint256 chainId
    ) internal view returns (bytes32) {
        return
            keccak256(
                abi.encode(
                    // keccak256("EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)")
                    0x8b73c3c69bb8fe3d512ecc4cf759cc79239f7b179b0ffacaa9a75d522b39400f,
                    keccak256(bytes(name)),
                    keccak256(bytes(version)),
                    chainId,
                    address(this)
                )
            );
    }
    /**
     * @notice Make EIP712 domain separator
     * @param name      Contract name
     * @param version   Contract version
     * @return Domain separator
     */
    function makeDomainSeparator(string memory name, string memory version)
        internal
        view
        returns (bytes32)
    {
        uint256 chainId;
        assembly {
            chainId := chainid()
        }
        return makeDomainSeparator(name, version, chainId);
    }
}
/**
 * SPDX-License-Identifier: Apache-2.0
 *
 * Copyright (c) 2023, Circle Internet Financial, LLC.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
pragma solidity 0.6.12;
/**
 * @title ECRecover
 * @notice A library that provides a safe ECDSA recovery function
 */
library ECRecover {
    /**
     * @notice Recover signer's address from a signed message
     * @dev Adapted from: https://github.com/OpenZeppelin/openzeppelin-contracts/blob/65e4ffde586ec89af3b7e9140bdc9235d1254853/contracts/cryptography/ECDSA.sol
     * Modifications: Accept v, r, and s as separate arguments
     * @param digest    Keccak-256 hash digest of the signed message
     * @param v         v of the signature
     * @param r         r of the signature
     * @param s         s of the signature
     * @return Signer address
     */
    function recover(
        bytes32 digest,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) internal pure returns (address) {
        // EIP-2 still allows signature malleability for ecrecover(). Remove this possibility and make the signature
        // unique. Appendix F in the Ethereum Yellow paper (https://ethereum.github.io/yellowpaper/paper.pdf), defines
        // the valid range for s in (281): 0 < s < secp256k1n ÷ 2 + 1, and for v in (282): v ∈ {27, 28}. Most
        // signatures from current libraries generate a unique signature with an s-value in the lower half order.
        //
        // If your library generates malleable signatures, such as s-values in the upper range, calculate a new s-value
        // with 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141 - s1 and flip v from 27 to 28 or
        // vice versa. If your library also generates signatures with 0/1 for v instead 27/28, add 27 to v to accept
        // these malleable signatures as well.
        if (
            uint256(s) >
            0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0
        ) {
            revert("ECRecover: invalid signature 's' value");
        }
        if (v != 27 && v != 28) {
            revert("ECRecover: invalid signature 'v' value");
        }
        // If the signature is valid (and not malleable), return the signer address
        address signer = ecrecover(digest, v, r, s);
        require(signer != address(0), "ECRecover: invalid signature");
        return signer;
    }
    /**
     * @notice Recover signer's address from a signed message
     * @dev Adapted from: https://github.com/OpenZeppelin/openzeppelin-contracts/blob/0053ee040a7ff1dbc39691c9e67a69f564930a88/contracts/utils/cryptography/ECDSA.sol
     * @param digest    Keccak-256 hash digest of the signed message
     * @param signature Signature byte array associated with hash
     * @return Signer address
     */
    function recover(bytes32 digest, bytes memory signature)
        internal
        pure
        returns (address)
    {
        require(signature.length == 65, "ECRecover: invalid signature length");
        bytes32 r;
        bytes32 s;
        uint8 v;
        // ecrecover takes the signature parameters, and the only way to get them
        // currently is to use assembly.
        /// @solidity memory-safe-assembly
        assembly {
            r := mload(add(signature, 0x20))
            s := mload(add(signature, 0x40))
            v := byte(0, mload(add(signature, 0x60)))
        }
        return recover(digest, v, r, s);
    }
}
/**
 * SPDX-License-Identifier: Apache-2.0
 *
 * Copyright (c) 2023, Circle Internet Financial, LLC.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
pragma solidity 0.6.12;
/**
 * @dev Interface of the ERC1271 standard signature validation method for
 * contracts as defined in https://eips.ethereum.org/EIPS/eip-1271[ERC-1271].
 */
interface IERC1271 {
    /**
     * @dev Should return whether the signature provided is valid for the provided data
     * @param hash          Hash of the data to be signed
     * @param signature     Signature byte array associated with the provided data hash
     * @return magicValue   bytes4 magic value 0x1626ba7e when function passes
     */
    function isValidSignature(bytes32 hash, bytes memory signature)
        external
        view
        returns (bytes4 magicValue);
}