// SPDX-License-Identifier: MIT
/*
                    ████████╗██╗  ██╗███████╗
                    ╚══██╔══╝██║  ██║██╔════╝
                       ██║   ███████║█████╗
                       ██║   ██╔══██║██╔══╝
                       ██║   ██║  ██║███████╗
                       ╚═╝   ╚═╝  ╚═╝╚══════╝
██╗  ██╗██╗   ██╗███╗   ███╗ █████╗ ███╗   ██╗ ██████╗ ██╗██████╗ ███████╗
██║  ██║██║   ██║████╗ ████║██╔══██╗████╗  ██║██╔═══██╗██║██╔══██╗██╔════╝
███████║██║   ██║██╔████╔██║███████║██╔██╗ ██║██║   ██║██║██║  ██║███████╗
██╔══██║██║   ██║██║╚██╔╝██║██╔══██║██║╚██╗██║██║   ██║██║██║  ██║╚════██║
██║  ██║╚██████╔╝██║ ╚═╝ ██║██║  ██║██║ ╚████║╚██████╔╝██║██████╔╝███████║
╚═╝  ╚═╝ ╚═════╝ ╚═╝     ╚═╝╚═╝  ╚═╝╚═╝  ╚═══╝ ╚═════╝ ╚═╝╚═════╝ ╚══════╝
The Humanoids Staking Contract
*/
pragma solidity =0.8.11;
import "@openzeppelin/contracts/token/ERC721/IERC721.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "./IStakingReward.sol";
contract TheHumanoidsStaking is Ownable {
    bool public canStake;
    address public stakingRewardContract;
    IERC721 private constant _NFT_CONTRACT = IERC721(0x3a5051566b2241285BE871f650C445A88A970edd);
    struct Token {
        address owner;
        uint64 timestamp;
        uint16 index;
    }
    mapping(uint256 => Token) private _tokens;
    mapping(address => uint16[]) private _stakedTokens;
    constructor() {}
    function setStaking(bool _canStake) external onlyOwner {
        canStake = _canStake;
    }
    function setStakingRewardContract(address newStakingRewardContract) external onlyOwner {
        address oldStakingRewardContract = stakingRewardContract;
        require(newStakingRewardContract != oldStakingRewardContract, "New staking reward contract is same as old contract");
        if (oldStakingRewardContract != address(0)) {
            IStakingReward(oldStakingRewardContract).willBeReplacedByContract(newStakingRewardContract);
        }
        stakingRewardContract = newStakingRewardContract;
        if (newStakingRewardContract != address(0)) {
            IStakingReward(newStakingRewardContract).didReplaceContract(oldStakingRewardContract);
        }
    }
    function stakedTokensBalanceOf(address account) external view returns (uint256) {
        return _stakedTokens[account].length;
    }
    function stakedTokensOf(address account) external view returns (uint16[] memory) {
        return _stakedTokens[account];
    }
    function ownerOf(uint256 tokenId) external view returns (address) {
        address owner = _tokens[tokenId].owner;
        require(owner != address(0), "Token not staked");
        return owner;
    }
    function timestampOf(uint256 tokenId) external view returns (uint256) {
        uint256 timestamp = uint256(_tokens[tokenId].timestamp);
        require(timestamp != 0, "Token not staked");
        return timestamp;
    }
    function stake(uint16[] calldata tokenIds) external {
        require(canStake, "Staking not enabled");
        uint length = tokenIds.length;
        require(length > 0, "tokenIds array is empty");
        if (stakingRewardContract != address(0)) {
            IStakingReward(stakingRewardContract).willStakeTokens(msg.sender, tokenIds);
        }
        uint64 timestamp = uint64(block.timestamp);
        uint16[] storage stakedTokens = _stakedTokens[msg.sender];
        uint16 index = uint16(stakedTokens.length);
        unchecked {
            for (uint i=0; i<length; i++) {
                uint16 tokenId = tokenIds[i];
                _NFT_CONTRACT.transferFrom(msg.sender, address(this), tokenId);
                Token storage token = _tokens[tokenId];
                token.owner = msg.sender;
                token.timestamp = timestamp;
                token.index = index;
                index++;
                stakedTokens.push(tokenId);
            }
        }
    }
    function unstake(uint16[] calldata tokenIds) external {
        uint length = tokenIds.length;
        require(length > 0, "tokenIds array is empty");
        if (stakingRewardContract != address(0)) {
            IStakingReward(stakingRewardContract).willUnstakeTokens(msg.sender, tokenIds);
        }
        unchecked {
            uint16[] storage stakedTokens = _stakedTokens[msg.sender];
            for (uint i=0; i<length; i++) {
                uint256 tokenId = tokenIds[i];
                require(_tokens[tokenId].owner == msg.sender, "Token not staked or not owned");
                uint index = _tokens[tokenId].index;
                uint lastIndex = stakedTokens.length-1;
                if (index != lastIndex) {
                    uint16 lastTokenId = stakedTokens[lastIndex];
                    stakedTokens[index] = lastTokenId;
                    _tokens[lastTokenId].index = uint16(index);
                }
                stakedTokens.pop();
                delete _tokens[tokenId];
                _NFT_CONTRACT.transferFrom(address(this), msg.sender, tokenId);
            }
        }
    }
    function unstakeAll() external {
        uint16[] storage stakedTokens = _stakedTokens[msg.sender];
        uint length = stakedTokens.length;
        require(length > 0, "Nothing staked");
        if (stakingRewardContract != address(0)) {
            IStakingReward(stakingRewardContract).willUnstakeTokens(msg.sender, stakedTokens);
        }
        unchecked {
            for (uint i=0; i<length; i++) {
                uint256 tokenId = stakedTokens[i];
                delete _tokens[tokenId];
                _NFT_CONTRACT.transferFrom(address(this), msg.sender, tokenId);
            }
        }
        delete _stakedTokens[msg.sender];
    }
}
// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC721/IERC721.sol)
pragma solidity ^0.8.0;
import "../../utils/introspection/IERC165.sol";
/**
 * @dev Required interface of an ERC721 compliant contract.
 */
interface IERC721 is IERC165 {
    /**
     * @dev Emitted when `tokenId` token is transferred from `from` to `to`.
     */
    event Transfer(address indexed from, address indexed to, uint256 indexed tokenId);
    /**
     * @dev Emitted when `owner` enables `approved` to manage the `tokenId` token.
     */
    event Approval(address indexed owner, address indexed approved, uint256 indexed tokenId);
    /**
     * @dev Emitted when `owner` enables or disables (`approved`) `operator` to manage all of its assets.
     */
    event ApprovalForAll(address indexed owner, address indexed operator, bool approved);
    /**
     * @dev Returns the number of tokens in ``owner``'s account.
     */
    function balanceOf(address owner) external view returns (uint256 balance);
    /**
     * @dev Returns the owner of the `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function ownerOf(uint256 tokenId) external view returns (address owner);
    /**
     * @dev Safely transfers `tokenId` token from `from` to `to`, checking first that contract recipients
     * are aware of the ERC721 protocol to prevent tokens from being forever locked.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If the caller is not `from`, it must be have been allowed to move this token by either {approve} or {setApprovalForAll}.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId
    ) external;
    /**
     * @dev Transfers `tokenId` token from `from` to `to`.
     *
     * WARNING: Usage of this method is discouraged, use {safeTransferFrom} whenever possible.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must be owned by `from`.
     * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(
        address from,
        address to,
        uint256 tokenId
    ) external;
    /**
     * @dev Gives permission to `to` to transfer `tokenId` token to another account.
     * The approval is cleared when the token is transferred.
     *
     * Only a single account can be approved at a time, so approving the zero address clears previous approvals.
     *
     * Requirements:
     *
     * - The caller must own the token or be an approved operator.
     * - `tokenId` must exist.
     *
     * Emits an {Approval} event.
     */
    function approve(address to, uint256 tokenId) external;
    /**
     * @dev Returns the account approved for `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function getApproved(uint256 tokenId) external view returns (address operator);
    /**
     * @dev Approve or remove `operator` as an operator for the caller.
     * Operators can call {transferFrom} or {safeTransferFrom} for any token owned by the caller.
     *
     * Requirements:
     *
     * - The `operator` cannot be the caller.
     *
     * Emits an {ApprovalForAll} event.
     */
    function setApprovalForAll(address operator, bool _approved) external;
    /**
     * @dev Returns if the `operator` is allowed to manage all of the assets of `owner`.
     *
     * See {setApprovalForAll}
     */
    function isApprovedForAll(address owner, address operator) external view returns (bool);
    /**
     * @dev Safely transfers `tokenId` token from `from` to `to`.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId,
        bytes calldata data
    ) external;
}
// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (access/Ownable.sol)
pragma solidity ^0.8.0;
import "../utils/Context.sol";
/**
 * @dev 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 Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }
    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
        _;
    }
    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        _transferOwnership(address(0));
    }
    /**
     * @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);
    }
}
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
interface IStakingReward {
    function willStakeTokens(address account, uint16[] calldata tokenIds) external;
    function willUnstakeTokens(address account, uint16[] calldata tokenIds) external;
    function willBeReplacedByContract(address stakingRewardContract) external;
    function didReplaceContract(address stakingRewardContract) external;
}
// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/introspection/IERC165.sol)
pragma solidity ^0.8.0;
/**
 * @dev Interface of the ERC165 standard, as defined in the
 * https://eips.ethereum.org/EIPS/eip-165[EIP].
 *
 * Implementers can declare support of contract interfaces, which can then be
 * queried by others ({ERC165Checker}).
 *
 * For an implementation, see {ERC165}.
 */
interface IERC165 {
    /**
     * @dev Returns true if this contract implements the interface defined by
     * `interfaceId`. See the corresponding
     * https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified[EIP section]
     * to learn more about how these ids are created.
     *
     * This function call must use less than 30 000 gas.
     */
    function supportsInterface(bytes4 interfaceId) external view returns (bool);
}
// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/Context.sol)
pragma solidity ^0.8.0;
/**
 * @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 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) {
        return msg.sender;
    }
    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}

// File: @openzeppelin/contracts/utils/cryptography/ECDSA.sol



pragma solidity ^0.8.0;

/**
 * @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 {
    enum RecoverError {
        NoError,
        InvalidSignature,
        InvalidSignatureLength,
        InvalidSignatureS,
        InvalidSignatureV
    }

    function _throwError(RecoverError error) private pure {
        if (error == RecoverError.NoError) {
            return; // no error: do nothing
        } else if (error == RecoverError.InvalidSignature) {
            revert("ECDSA: invalid signature");
        } else if (error == RecoverError.InvalidSignatureLength) {
            revert("ECDSA: invalid signature length");
        } else if (error == RecoverError.InvalidSignatureS) {
            revert("ECDSA: invalid signature 's' value");
        } else if (error == RecoverError.InvalidSignatureV) {
            revert("ECDSA: invalid signature 'v' value");
        }
    }

    /**
     * @dev Returns the address that signed a hashed message (`hash`) with
     * `signature` or error string. 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.
     *
     * Documentation for signature generation:
     * - with https://web3js.readthedocs.io/en/v1.3.4/web3-eth-accounts.html#sign[Web3.js]
     * - with https://docs.ethers.io/v5/api/signer/#Signer-signMessage[ethers]
     *
     * _Available since v4.3._
     */
    function tryRecover(bytes32 hash, bytes memory signature) internal pure returns (address, RecoverError) {
        // Check the signature length
        // - case 65: r,s,v signature (standard)
        // - case 64: r,vs signature (cf https://eips.ethereum.org/EIPS/eip-2098) _Available since v4.1._
        if (signature.length == 65) {
            bytes32 r;
            bytes32 s;
            uint8 v;
            // ecrecover takes the signature parameters, and the only way to get them
            // currently is to use assembly.
            assembly {
                r := mload(add(signature, 0x20))
                s := mload(add(signature, 0x40))
                v := byte(0, mload(add(signature, 0x60)))
            }
            return tryRecover(hash, v, r, s);
        } else if (signature.length == 64) {
            bytes32 r;
            bytes32 vs;
            // ecrecover takes the signature parameters, and the only way to get them
            // currently is to use assembly.
            assembly {
                r := mload(add(signature, 0x20))
                vs := mload(add(signature, 0x40))
            }
            return tryRecover(hash, r, vs);
        } else {
            return (address(0), RecoverError.InvalidSignatureLength);
        }
    }

    /**
     * @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) {
        (address recovered, RecoverError error) = tryRecover(hash, signature);
        _throwError(error);
        return recovered;
    }

    /**
     * @dev Overload of {ECDSA-tryRecover} that receives the `r` and `vs` short-signature fields separately.
     *
     * See https://eips.ethereum.org/EIPS/eip-2098[EIP-2098 short signatures]
     *
     * _Available since v4.3._
     */
    function tryRecover(
        bytes32 hash,
        bytes32 r,
        bytes32 vs
    ) internal pure returns (address, RecoverError) {
        bytes32 s;
        uint8 v;
        assembly {
            s := and(vs, 0x7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff)
            v := add(shr(255, vs), 27)
        }
        return tryRecover(hash, v, r, s);
    }

    /**
     * @dev Overload of {ECDSA-recover} that receives the `r and `vs` short-signature fields separately.
     *
     * _Available since v4.2._
     */
    function recover(
        bytes32 hash,
        bytes32 r,
        bytes32 vs
    ) internal pure returns (address) {
        (address recovered, RecoverError error) = tryRecover(hash, r, vs);
        _throwError(error);
        return recovered;
    }

    /**
     * @dev Overload of {ECDSA-tryRecover} that receives the `v`,
     * `r` and `s` signature fields separately.
     *
     * _Available since v4.3._
     */
    function tryRecover(
        bytes32 hash,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) internal pure returns (address, RecoverError) {
        // 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 (301): 0 < s < secp256k1n ÷ 2 + 1, and for v in (302): 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) {
            return (address(0), RecoverError.InvalidSignatureS);
        }
        if (v != 27 && v != 28) {
            return (address(0), RecoverError.InvalidSignatureV);
        }

        // If the signature is valid (and not malleable), return the signer address
        address signer = ecrecover(hash, v, r, s);
        if (signer == address(0)) {
            return (address(0), RecoverError.InvalidSignature);
        }

        return (signer, RecoverError.NoError);
    }

    /**
     * @dev Overload of {ECDSA-recover} that receives the `v`,
     * `r` and `s` signature fields separately.
     */
    function recover(
        bytes32 hash,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) internal pure returns (address) {
        (address recovered, RecoverError error) = tryRecover(hash, v, r, s);
        _throwError(error);
        return recovered;
    }

    /**
     * @dev Returns an Ethereum Signed Message, created from a `hash`. This
     * produces hash corresponding to the one signed with the
     * https://eth.wiki/json-rpc/API#eth_sign[`eth_sign`]
     * JSON-RPC method as part of EIP-191.
     *
     * 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));
    }

    /**
     * @dev Returns an Ethereum Signed Typed Data, created from a
     * `domainSeparator` and a `structHash`. This produces hash corresponding
     * to the one signed with the
     * https://eips.ethereum.org/EIPS/eip-712[`eth_signTypedData`]
     * JSON-RPC method as part of EIP-712.
     *
     * See {recover}.
     */
    function toTypedDataHash(bytes32 domainSeparator, bytes32 structHash) internal pure returns (bytes32) {
        return keccak256(abi.encodePacked("\x19\x01", domainSeparator, structHash));
    }
}

// File: @openzeppelin/contracts/utils/Counters.sol



pragma solidity ^0.8.0;

/**
 * @title Counters
 * @author Matt Condon (@shrugs)
 * @dev Provides counters that can only be incremented, decremented or reset. This can be used e.g. to track the number
 * of elements in a mapping, issuing ERC721 ids, or counting request ids.
 *
 * Include with `using Counters for Counters.Counter;`
 */
library Counters {
    struct Counter {
        // This variable should never be directly accessed by users of the library: interactions must be restricted to
        // the library's function. As of Solidity v0.5.2, this cannot be enforced, though there is a proposal to add
        // this feature: see https://github.com/ethereum/solidity/issues/4637
        uint256 _value; // default: 0
    }

    function current(Counter storage counter) internal view returns (uint256) {
        return counter._value;
    }

    function increment(Counter storage counter) internal {
        unchecked {
            counter._value += 1;
        }
    }

    function decrement(Counter storage counter) internal {
        uint256 value = counter._value;
        require(value > 0, "Counter: decrement overflow");
        unchecked {
            counter._value = value - 1;
        }
    }

    function reset(Counter storage counter) internal {
        counter._value = 0;
    }
}




// File: @openzeppelin/contracts/utils/Strings.sol



pragma solidity ^0.8.0;

/**
 * @dev String operations.
 */
library Strings {
    bytes16 private constant _HEX_SYMBOLS = "0123456789abcdef";

    /**
     * @dev Converts a `uint256` to its ASCII `string` decimal representation.
     */
    function toString(uint256 value) internal pure returns (string memory) {
        // Inspired by OraclizeAPI's implementation - MIT licence
        // https://github.com/oraclize/ethereum-api/blob/b42146b063c7d6ee1358846c198246239e9360e8/oraclizeAPI_0.4.25.sol

        if (value == 0) {
            return "0";
        }
        uint256 temp = value;
        uint256 digits;
        while (temp != 0) {
            digits++;
            temp /= 10;
        }
        bytes memory buffer = new bytes(digits);
        while (value != 0) {
            digits -= 1;
            buffer[digits] = bytes1(uint8(48 + uint256(value % 10)));
            value /= 10;
        }
        return string(buffer);
    }

    /**
     * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation.
     */
    function toHexString(uint256 value) internal pure returns (string memory) {
        if (value == 0) {
            return "0x00";
        }
        uint256 temp = value;
        uint256 length = 0;
        while (temp != 0) {
            length++;
            temp >>= 8;
        }
        return toHexString(value, length);
    }

    /**
     * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation with fixed length.
     */
    function toHexString(uint256 value, uint256 length) internal pure returns (string memory) {
        bytes memory buffer = new bytes(2 * length + 2);
        buffer[0] = "0";
        buffer[1] = "x";
        for (uint256 i = 2 * length + 1; i > 1; --i) {
            buffer[i] = _HEX_SYMBOLS[value & 0xf];
            value >>= 4;
        }
        require(value == 0, "Strings: hex length insufficient");
        return string(buffer);
    }
}

// File: @openzeppelin/contracts/utils/Context.sol



pragma solidity ^0.8.0;

/**
 * @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 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) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}

// File: @openzeppelin/contracts/access/Ownable.sol



pragma solidity ^0.8.0;


/**
 * @dev 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() {
        _setOwner(_msgSender());
    }

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

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
        _;
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        _setOwner(address(0));
    }

    /**
     * @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");
        _setOwner(newOwner);
    }

    function _setOwner(address newOwner) private {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

// File: @openzeppelin/contracts/utils/Address.sol



pragma solidity ^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;
        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");

        (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");

        (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");

        (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");

        (bool success, bytes memory returndata) = target.delegatecall(data);
        return verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Tool to verifies that a low level call was successful, and revert if it wasn't, either by bubbling the
     * revert reason using the provided one.
     *
     * _Available since v4.3._
     */
    function verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal 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

                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}



// File: @openzeppelin/contracts/token/ERC721/IERC721Receiver.sol



pragma solidity ^0.8.0;

/**
 * @title ERC721 token receiver interface
 * @dev Interface for any contract that wants to support safeTransfers
 * from ERC721 asset contracts.
 */
interface IERC721Receiver {
    /**
     * @dev Whenever an {IERC721} `tokenId` token is transferred to this contract via {IERC721-safeTransferFrom}
     * by `operator` from `from`, this function is called.
     *
     * It must return its Solidity selector to confirm the token transfer.
     * If any other value is returned or the interface is not implemented by the recipient, the transfer will be reverted.
     *
     * The selector can be obtained in Solidity with `IERC721.onERC721Received.selector`.
     */
    function onERC721Received(
        address operator,
        address from,
        uint256 tokenId,
        bytes calldata data
    ) external returns (bytes4);
}

// File: @openzeppelin/contracts/utils/introspection/IERC165.sol



pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC165 standard, as defined in the
 * https://eips.ethereum.org/EIPS/eip-165[EIP].
 *
 * Implementers can declare support of contract interfaces, which can then be
 * queried by others ({ERC165Checker}).
 *
 * For an implementation, see {ERC165}.
 */
interface IERC165 {
    /**
     * @dev Returns true if this contract implements the interface defined by
     * `interfaceId`. See the corresponding
     * https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified[EIP section]
     * to learn more about how these ids are created.
     *
     * This function call must use less than 30 000 gas.
     */
    function supportsInterface(bytes4 interfaceId) external view returns (bool);
}

// File: @openzeppelin/contracts/utils/introspection/ERC165.sol



pragma solidity ^0.8.0;


/**
 * @dev Implementation of the {IERC165} interface.
 *
 * Contracts that want to implement ERC165 should inherit from this contract and override {supportsInterface} to check
 * for the additional interface id that will be supported. For example:
 *
 * ```solidity
 * function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
 *     return interfaceId == type(MyInterface).interfaceId || super.supportsInterface(interfaceId);
 * }
 * ```
 *
 * Alternatively, {ERC165Storage} provides an easier to use but more expensive implementation.
 */
abstract contract ERC165 is IERC165 {
    /**
     * @dev See {IERC165-supportsInterface}.
     */
    function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
        return interfaceId == type(IERC165).interfaceId;
    }
}


// File: @openzeppelin/contracts/token/ERC721/IERC721.sol



pragma solidity ^0.8.0;


/**
 * @dev Required interface of an ERC721 compliant contract.
 */
interface IERC721 is IERC165 {
    /**
     * @dev Emitted when `tokenId` token is transferred from `from` to `to`.
     */
    event Transfer(address indexed from, address indexed to, uint256 indexed tokenId);

    /**
     * @dev Emitted when `owner` enables `approved` to manage the `tokenId` token.
     */
    event Approval(address indexed owner, address indexed approved, uint256 indexed tokenId);

    /**
     * @dev Emitted when `owner` enables or disables (`approved`) `operator` to manage all of its assets.
     */
    event ApprovalForAll(address indexed owner, address indexed operator, bool approved);

    /**
     * @dev Returns the number of tokens in ``owner``'s account.
     */
    function balanceOf(address owner) external view returns (uint256 balance);

    /**
     * @dev Returns the owner of the `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function ownerOf(uint256 tokenId) external view returns (address owner);

    /**
     * @dev Safely transfers `tokenId` token from `from` to `to`, checking first that contract recipients
     * are aware of the ERC721 protocol to prevent tokens from being forever locked.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If the caller is not `from`, it must be have been allowed to move this token by either {approve} or {setApprovalForAll}.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId
    ) external;

    /**
     * @dev Transfers `tokenId` token from `from` to `to`.
     *
     * WARNING: Usage of this method is discouraged, use {safeTransferFrom} whenever possible.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must be owned by `from`.
     * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(
        address from,
        address to,
        uint256 tokenId
    ) external;

    /**
     * @dev Gives permission to `to` to transfer `tokenId` token to another account.
     * The approval is cleared when the token is transferred.
     *
     * Only a single account can be approved at a time, so approving the zero address clears previous approvals.
     *
     * Requirements:
     *
     * - The caller must own the token or be an approved operator.
     * - `tokenId` must exist.
     *
     * Emits an {Approval} event.
     */
    function approve(address to, uint256 tokenId) external;

    /**
     * @dev Returns the account approved for `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function getApproved(uint256 tokenId) external view returns (address operator);

    /**
     * @dev Approve or remove `operator` as an operator for the caller.
     * Operators can call {transferFrom} or {safeTransferFrom} for any token owned by the caller.
     *
     * Requirements:
     *
     * - The `operator` cannot be the caller.
     *
     * Emits an {ApprovalForAll} event.
     */
    function setApprovalForAll(address operator, bool _approved) external;

    /**
     * @dev Returns if the `operator` is allowed to manage all of the assets of `owner`.
     *
     * See {setApprovalForAll}
     */
    function isApprovedForAll(address owner, address operator) external view returns (bool);

    /**
     * @dev Safely transfers `tokenId` token from `from` to `to`.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId,
        bytes calldata data
    ) external;
}


// File: @openzeppelin/contracts/token/ERC721/extensions/IERC721Metadata.sol



pragma solidity ^0.8.0;


/**
 * @title ERC-721 Non-Fungible Token Standard, optional metadata extension
 * @dev See https://eips.ethereum.org/EIPS/eip-721
 */
interface IERC721Metadata is IERC721 {
    /**
     * @dev Returns the token collection name.
     */
    function name() external view returns (string memory);

    /**
     * @dev Returns the token collection symbol.
     */
    function symbol() external view returns (string memory);

    /**
     * @dev Returns the Uniform Resource Identifier (URI) for `tokenId` token.
     */
    function tokenURI(uint256 tokenId) external view returns (string memory);
}

// File: @openzeppelin/contracts/token/ERC721/ERC721.sol



pragma solidity ^0.8.0;



/**
 * @dev Implementation of https://eips.ethereum.org/EIPS/eip-721[ERC721] Non-Fungible Token Standard, including
 * the Metadata extension, but not including the Enumerable extension, which is available separately as
 * {ERC721Enumerable}.
 */
contract ERC721 is Context, ERC165, IERC721, IERC721Metadata {
    using Address for address;
    using Strings for uint256;

    // Token name
    string private _name;

    // Token symbol
    string private _symbol;

    // Mapping from token ID to owner address
    mapping(uint256 => address) private _owners;

    // Mapping owner address to token count
    mapping(address => uint256) private _balances;

    // Mapping from token ID to approved address
    mapping(uint256 => address) private _tokenApprovals;

    // Mapping from owner to operator approvals
    mapping(address => mapping(address => bool)) private _operatorApprovals;

    /**
     * @dev Initializes the contract by setting a `name` and a `symbol` to the token collection.
     */
    constructor(string memory name_, string memory symbol_) {
        _name = name_;
        _symbol = symbol_;
    }

    /**
     * @dev See {IERC165-supportsInterface}.
     */
    function supportsInterface(bytes4 interfaceId) public view virtual override(ERC165, IERC165) returns (bool) {
        return
            interfaceId == type(IERC721).interfaceId ||
            interfaceId == type(IERC721Metadata).interfaceId ||
            super.supportsInterface(interfaceId);
    }

    /**
     * @dev See {IERC721-balanceOf}.
     */
    function balanceOf(address owner) public view virtual override returns (uint256) {
        require(owner != address(0), "ERC721: balance query for the zero address");
        return _balances[owner];
    }

    /**
     * @dev See {IERC721-ownerOf}.
     */
    function ownerOf(uint256 tokenId) public view virtual override returns (address) {
        address owner = _owners[tokenId];
        require(owner != address(0), "ERC721: owner query for nonexistent token");
        return owner;
    }

    /**
     * @dev See {IERC721Metadata-name}.
     */
    function name() public view virtual override returns (string memory) {
        return _name;
    }

    /**
     * @dev See {IERC721Metadata-symbol}.
     */
    function symbol() public view virtual override returns (string memory) {
        return _symbol;
    }

    /**
     * @dev See {IERC721Metadata-tokenURI}.
     */
    function tokenURI(uint256 tokenId) public view virtual override returns (string memory) {
        require(_exists(tokenId), "ERC721Metadata: URI query for nonexistent token");

        string memory baseURI = _baseURI();
        return bytes(baseURI).length > 0 ? string(abi.encodePacked(baseURI, tokenId.toString())) : "";
    }

    /**
     * @dev Base URI for computing {tokenURI}. If set, the resulting URI for each
     * token will be the concatenation of the `baseURI` and the `tokenId`. Empty
     * by default, can be overriden in child contracts.
     */
    function _baseURI() internal view virtual returns (string memory) {
        return "";
    }

    /**
     * @dev See {IERC721-approve}.
     */
    function approve(address to, uint256 tokenId) public virtual override {
        address owner = ERC721.ownerOf(tokenId);
        require(to != owner, "ERC721: approval to current owner");

        require(
            _msgSender() == owner || isApprovedForAll(owner, _msgSender()),
            "ERC721: approve caller is not owner nor approved for all"
        );

        _approve(to, tokenId);
    }

    /**
     * @dev See {IERC721-getApproved}.
     */
    function getApproved(uint256 tokenId) public view virtual override returns (address) {
        require(_exists(tokenId), "ERC721: approved query for nonexistent token");

        return _tokenApprovals[tokenId];
    }

    /**
     * @dev See {IERC721-setApprovalForAll}.
     */
    function setApprovalForAll(address operator, bool approved) public virtual override {
        require(operator != _msgSender(), "ERC721: approve to caller");

        _operatorApprovals[_msgSender()][operator] = approved;
        emit ApprovalForAll(_msgSender(), operator, approved);
    }

    /**
     * @dev See {IERC721-isApprovedForAll}.
     */
    function isApprovedForAll(address owner, address operator) public view virtual override returns (bool) {
        return _operatorApprovals[owner][operator];
    }

    /**
     * @dev See {IERC721-transferFrom}.
     */
    function transferFrom(
        address from,
        address to,
        uint256 tokenId
    ) public virtual override {
        //solhint-disable-next-line max-line-length
        require(_isApprovedOrOwner(_msgSender(), tokenId), "ERC721: transfer caller is not owner nor approved");

        _transfer(from, to, tokenId);
    }

    /**
     * @dev See {IERC721-safeTransferFrom}.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId
    ) public virtual override {
        safeTransferFrom(from, to, tokenId, "");
    }

    /**
     * @dev See {IERC721-safeTransferFrom}.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId,
        bytes memory _data
    ) public virtual override {
        require(_isApprovedOrOwner(_msgSender(), tokenId), "ERC721: transfer caller is not owner nor approved");
        _safeTransfer(from, to, tokenId, _data);
    }

    /**
     * @dev Safely transfers `tokenId` token from `from` to `to`, checking first that contract recipients
     * are aware of the ERC721 protocol to prevent tokens from being forever locked.
     *
     * `_data` is additional data, it has no specified format and it is sent in call to `to`.
     *
     * This internal function is equivalent to {safeTransferFrom}, and can be used to e.g.
     * implement alternative mechanisms to perform token transfer, such as signature-based.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function _safeTransfer(
        address from,
        address to,
        uint256 tokenId,
        bytes memory _data
    ) internal virtual {
        _transfer(from, to, tokenId);
        require(_checkOnERC721Received(from, to, tokenId, _data), "ERC721: transfer to non ERC721Receiver implementer");
    }

    /**
     * @dev Returns whether `tokenId` exists.
     *
     * Tokens can be managed by their owner or approved accounts via {approve} or {setApprovalForAll}.
     *
     * Tokens start existing when they are minted (`_mint`),
     * and stop existing when they are burned (`_burn`).
     */
    function _exists(uint256 tokenId) internal view virtual returns (bool) {
        return _owners[tokenId] != address(0);
    }

    /**
     * @dev Returns whether `spender` is allowed to manage `tokenId`.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function _isApprovedOrOwner(address spender, uint256 tokenId) internal view virtual returns (bool) {
        require(_exists(tokenId), "ERC721: operator query for nonexistent token");
        address owner = ERC721.ownerOf(tokenId);
        return (spender == owner || getApproved(tokenId) == spender || isApprovedForAll(owner, spender));
    }

    /**
     * @dev Safely mints `tokenId` and transfers it to `to`.
     *
     * Requirements:
     *
     * - `tokenId` must not exist.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function _safeMint(address to, uint256 tokenId) internal virtual {
        _safeMint(to, tokenId, "");
    }

    /**
     * @dev Same as {xref-ERC721-_safeMint-address-uint256-}[`_safeMint`], with an additional `data` parameter which is
     * forwarded in {IERC721Receiver-onERC721Received} to contract recipients.
     */
    function _safeMint(
        address to,
        uint256 tokenId,
        bytes memory _data
    ) internal virtual {
        _mint(to, tokenId);
        require(
            _checkOnERC721Received(address(0), to, tokenId, _data),
            "ERC721: transfer to non ERC721Receiver implementer"
        );
    }

    /**
     * @dev Mints `tokenId` and transfers it to `to`.
     *
     * WARNING: Usage of this method is discouraged, use {_safeMint} whenever possible
     *
     * Requirements:
     *
     * - `tokenId` must not exist.
     * - `to` cannot be the zero address.
     *
     * Emits a {Transfer} event.
     */
    function _mint(address to, uint256 tokenId) internal virtual {
        require(to != address(0), "ERC721: mint to the zero address");
        require(!_exists(tokenId), "ERC721: token already minted");

        _beforeTokenTransfer(address(0), to, tokenId);

        _balances[to] += 1;
        _owners[tokenId] = to;

        emit Transfer(address(0), to, tokenId);
    }

    /**
     * @dev Destroys `tokenId`.
     * The approval is cleared when the token is burned.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     *
     * Emits a {Transfer} event.
     */
    function _burn(uint256 tokenId) internal virtual {
        address owner = ERC721.ownerOf(tokenId);

        _beforeTokenTransfer(owner, address(0), tokenId);

        // Clear approvals
        _approve(address(0), tokenId);

        _balances[owner] -= 1;
        delete _owners[tokenId];

        emit Transfer(owner, address(0), tokenId);
    }

    /**
     * @dev Transfers `tokenId` from `from` to `to`.
     *  As opposed to {transferFrom}, this imposes no restrictions on msg.sender.
     *
     * Requirements:
     *
     * - `to` cannot be the zero address.
     * - `tokenId` token must be owned by `from`.
     *
     * Emits a {Transfer} event.
     */
    function _transfer(
        address from,
        address to,
        uint256 tokenId
    ) internal virtual {
        require(ERC721.ownerOf(tokenId) == from, "ERC721: transfer of token that is not own");
        require(to != address(0), "ERC721: transfer to the zero address");

        _beforeTokenTransfer(from, to, tokenId);

        // Clear approvals from the previous owner
        _approve(address(0), tokenId);

        _balances[from] -= 1;
        _balances[to] += 1;
        _owners[tokenId] = to;

        emit Transfer(from, to, tokenId);
    }

    /**
     * @dev Approve `to` to operate on `tokenId`
     *
     * Emits a {Approval} event.
     */
    function _approve(address to, uint256 tokenId) internal virtual {
        _tokenApprovals[tokenId] = to;
        emit Approval(ERC721.ownerOf(tokenId), to, tokenId);
    }

    /**
     * @dev Internal function to invoke {IERC721Receiver-onERC721Received} on a target address.
     * The call is not executed if the target address is not a contract.
     *
     * @param from address representing the previous owner of the given token ID
     * @param to target address that will receive the tokens
     * @param tokenId uint256 ID of the token to be transferred
     * @param _data bytes optional data to send along with the call
     * @return bool whether the call correctly returned the expected magic value
     */
    function _checkOnERC721Received(
        address from,
        address to,
        uint256 tokenId,
        bytes memory _data
    ) private returns (bool) {
        if (to.isContract()) {
            try IERC721Receiver(to).onERC721Received(_msgSender(), from, tokenId, _data) returns (bytes4 retval) {
                return retval == IERC721Receiver.onERC721Received.selector;
            } catch (bytes memory reason) {
                if (reason.length == 0) {
                    revert("ERC721: transfer to non ERC721Receiver implementer");
                } else {
                    assembly {
                        revert(add(32, reason), mload(reason))
                    }
                }
            }
        } else {
            return true;
        }
    }

    /**
     * @dev Hook that is called before any token transfer. This includes minting
     * and burning.
     *
     * Calling conditions:
     *
     * - When `from` and `to` are both non-zero, ``from``'s `tokenId` will be
     * transferred to `to`.
     * - When `from` is zero, `tokenId` will be minted for `to`.
     * - When `to` is zero, ``from``'s `tokenId` will be burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 tokenId
    ) internal virtual {}
}



// File: contracts/thehumanoids.sol


pragma solidity 0.8.0;






contract TheHumanoids is ERC721, Ownable {
    using Address for address;
    using Counters for Counters.Counter;

    Counters.Counter private _tokenCount; 

    string public baseURI;
    uint256 public constant price = 80000000000000000; // 0.08 ETH
    uint256 public constant maxTokens = 10000;
    uint256 public maxWallet = 10;
    bool public saleIsActive = false;
    bool public presaleIsActive = false;
    bool public hasReserved = false;

    mapping(address => uint256) public minted; // To check how many tokens an address has minted
    address private _signerAddress = 0xe6317C8292182bd4edd882946D54D51E970d10fb; 

    constructor() ERC721("The Humanoids ", "HMNDS") {
    }

    // reserve (60 tokens)
    function reserve() external onlyOwner {
        require(!hasReserved, "Tokens have already been reserved.");

        for (uint i; i < 60; i++) {
            _tokenCount.increment();
            _safeMint(msg.sender, _tokenCount.current());
        }
        hasReserved = true;
    }

    function mint(uint256 _amount) external payable {
        require(saleIsActive, "Sale must be active");
        require(!Address.isContract(msg.sender), "Contracts are not allowed to mint");
        require(minted[msg.sender] + _amount <= maxWallet, "Purchase would exceed max tokens per wallet");
        require(_tokenCount.current() + _amount <= maxTokens, "Purchase would exceed max supply of tokens");
        require(msg.value >= price * _amount, "Ether value sent is not correct");


        for(uint i; i < _amount; i++) {
            _tokenCount.increment();
            _safeMint(msg.sender, _tokenCount.current());
        }

        minted[msg.sender] += _amount;
    }

    function mintPresale(uint256 _amount, uint256 _maxTotal, uint8 _signatureV, bytes32 _signatureR, bytes32 _signatureS) external payable {
        require(presaleIsActive,"Presale must be active");
        require(_tokenCount.current() + _amount <= maxTokens, "Purchase would exceed max supply of Tokens");
        require(msg.value >= price * _amount, "Ether value sent is not correct");
        require(minted[msg.sender] + _amount <= _maxTotal, "Purchase would exceed max tokens for presale");

        bytes32 hash = keccak256(abi.encode(msg.sender, _maxTotal));
        address signer = ECDSA.recover(hash, _signatureV,  _signatureR,  _signatureS);
        require(signer == _signerAddress, "Invalid signature");
        
        for(uint i; i < _amount; i++){
            _tokenCount.increment();
            _safeMint(msg.sender, _tokenCount.current());
        }

        minted[msg.sender] += _amount;
    }

    function totalSupply() public view returns (uint256) { 
        return _tokenCount.current(); 
    }

    function setBaseURI(string memory __baseURI) external onlyOwner {
        baseURI = __baseURI;
    }
    
    function _baseURI() internal view override returns (string memory) {
        return baseURI;
    }

    function flipSaleState() public onlyOwner {
        saleIsActive = !saleIsActive;
    }

    function flipPresaleState() public onlyOwner {
        presaleIsActive = !presaleIsActive;
    }

    function setMaxWallet(uint _newMaxWallet) external onlyOwner {
        maxWallet = _newMaxWallet;
    }

    function withdrawAll() external onlyOwner {
        uint balance = address(this).balance;
        payable(msg.sender).transfer(balance);
    }

}

// SPDX-License-Identifier: MIT
/*
                    ████████╗██╗  ██╗███████╗
                    ╚══██╔══╝██║  ██║██╔════╝
                       ██║   ███████║█████╗
                       ██║   ██╔══██║██╔══╝
                       ██║   ██║  ██║███████╗
                       ╚═╝   ╚═╝  ╚═╝╚══════╝
██╗  ██╗██╗   ██╗███╗   ███╗ █████╗ ███╗   ██╗ ██████╗ ██╗██████╗ ███████╗
██║  ██║██║   ██║████╗ ████║██╔══██╗████╗  ██║██╔═══██╗██║██╔══██╗██╔════╝
███████║██║   ██║██╔████╔██║███████║██╔██╗ ██║██║   ██║██║██║  ██║███████╗
██╔══██║██║   ██║██║╚██╔╝██║██╔══██║██║╚██╗██║██║   ██║██║██║  ██║╚════██║
██║  ██║╚██████╔╝██║ ╚═╝ ██║██║  ██║██║ ╚████║╚██████╔╝██║██████╔╝███████║
╚═╝  ╚═╝ ╚═════╝ ╚═╝     ╚═╝╚═╝  ╚═╝╚═╝  ╚═══╝ ╚═════╝ ╚═╝╚═════╝ ╚══════╝
The Humanoids Staking Reward Contract, earning $10 ION per day
*/
pragma solidity =0.8.11;
import "./OwnableTokenAccessControl.sol";
import "./IStakingReward.sol";
import "./IERC20Mint.sol";
contract TheHumanoidsStakingReward is OwnableTokenAccessControl, IStakingReward {
    uint256 public constant REWARD_RATE_PER_DAY = 10 ether;
    uint256 public stakingRewardEndTimestamp = 1736152962;
    mapping(address => uint256) private _stakeData; // packed bits balance:208 timestamp:34 stakedCount:14
    address private constant STAKING_ADDRESS = address(0x3d6a1F739e471c61328Eb8a8D8d998E591C0FD42);
    address private constant TOKEN_ADDRESS = address(0x831dAA3B72576867cD66319259bf022AFB1D9211);
    /// @dev Emitted when `account` claims `amount` of reward.
    event Claim(address indexed account, uint256 amount);
    function setStakingRewardEndTimestamp(uint256 timestamp) external onlyOwner {
        require(stakingRewardEndTimestamp > block.timestamp, "Staking has already ended");
        require(timestamp > block.timestamp, "Must be a time in the future");
        stakingRewardEndTimestamp = timestamp;
    }
    modifier onlyStaking() {
        require(STAKING_ADDRESS == _msgSender(), "Not allowed");
        _;
    }
    function _reward(uint256 timestampFrom, uint256 timestampTo) internal pure returns (uint256) {
        unchecked {
            return ((timestampTo - timestampFrom) * REWARD_RATE_PER_DAY) / 1 days;
        }
    }
    function reward(uint256 timestampFrom, uint256 timestampTo) external view returns (uint256) {
        if (timestampTo > stakingRewardEndTimestamp) {
            timestampTo = stakingRewardEndTimestamp;
        }
        if (timestampFrom < timestampTo) {
            return _reward(timestampFrom, timestampTo);
        }
        return 0;
    }
    function timestampUntilRewardAmount(uint256 targetRewardAmount, uint256 stakedCount, uint256 timestampFrom) public view returns (uint256) {
        require(stakedCount > 0, "stakedCount cannot be zero");
        uint256 div = REWARD_RATE_PER_DAY * stakedCount;
        uint256 duration = ((targetRewardAmount * 1 days) + div - 1) / div; // ceil
        uint256 timestampTo = timestampFrom + duration;
        require(timestampTo <= stakingRewardEndTimestamp, "Cannot get reward amount before staking ends");
        return timestampTo;
    }
    function stakedTokensBalanceOf(address account) external view returns (uint256 stakedCount) {
        stakedCount = _stakeData[account] & 0x3fff;
    }
    function lastClaimTimestampOf(address account) external view returns (uint256 lastClaimTimestamp) {
        lastClaimTimestamp = (_stakeData[account] >> 14) & 0x3ffffffff;
    }
    function rawStakeDataOf(address account) external view returns (uint256 stakeData) {
        stakeData = _stakeData[account];
    }
    function _calculateRewards(uint256 stakeData, uint256 unclaimedBalance) internal view returns (uint256, uint256, uint256) {
        uint256 timestamp = 0;
        uint256 stakedCount = stakeData & 0x3fff;
        if (stakedCount > 0) {
            timestamp = block.timestamp;
            if (timestamp > stakingRewardEndTimestamp) {
                timestamp = stakingRewardEndTimestamp;
            }
            uint256 lastClaimTimestamp = (stakeData >> 14) & 0x3ffffffff;
            if (lastClaimTimestamp < timestamp) {
                unchecked {
                    unclaimedBalance += _reward(lastClaimTimestamp, timestamp) * stakedCount;
                }
            }
        }
        return (unclaimedBalance, timestamp, stakedCount);
    }
    function willStakeTokens(address account, uint16[] calldata tokenIds) external override onlyStaking {
        uint256 stakeData = _stakeData[account];
        (uint256 unclaimedBalance, , uint256 stakedCount) = _calculateRewards(stakeData, stakeData >> 48);
        unchecked {
            _stakeData[account] = (unclaimedBalance << 48) | (block.timestamp << 14) | (stakedCount + tokenIds.length);
        }
    }
    function willUnstakeTokens(address account, uint16[] calldata tokenIds) external override onlyStaking {
        uint256 stakeData = _stakeData[account];
        (uint256 unclaimedBalance, uint256 timestamp, uint256 stakedCount) = _calculateRewards(stakeData, stakeData >> 48);
        uint256 unstakeCount = tokenIds.length;
        if (unstakeCount < stakedCount) {
            unchecked {
                stakedCount -= unstakeCount;
            }
        }
        else {
            stakedCount = 0;
            if (unclaimedBalance == 0) {
                timestamp = 0;
            }
        }
        _stakeData[account] = (unclaimedBalance << 48) | (timestamp << 14) | stakedCount;
    }
    function willBeReplacedByContract(address /*stakingRewardContract*/) external override onlyStaking {
        uint256 timestamp = block.timestamp;
        if (stakingRewardEndTimestamp > timestamp) {
            stakingRewardEndTimestamp = timestamp;
        }
    }
    function didReplaceContract(address /*stakingRewardContract*/) external override onlyStaking {
    }
    function stakeDataOf(address account) external view returns (uint256) {
        uint256 stakeData = _stakeData[account];
        if (stakeData != 0) {
            (uint256 unclaimedBalance, uint256 timestamp, uint256 stakedCount) = _calculateRewards(stakeData, stakeData >> 48);
            stakeData = (unclaimedBalance << 48) | (timestamp << 14) | (stakedCount);
        }
        return stakeData;
    }
    function claimStakeDataFor(address account) external returns (uint256) {
        uint256 stakeData = _stakeData[account];
        if (stakeData != 0) {
            require(_hasAccess(Access.Claim, _msgSender()), "Not allowed to claim");
            (uint256 unclaimedBalance, uint256 timestamp, uint256 stakedCount) = _calculateRewards(stakeData, stakeData >> 48);
            stakeData = (unclaimedBalance << 48) | (timestamp << 14) | (stakedCount);
            delete _stakeData[account];
        }
        return stakeData;
    }
    function _claim(address account, uint256 amount) private {
        if (amount == 0) {
            return;
        }
        uint256 stakeData = _stakeData[account];
        uint256 balance = stakeData >> 48;
        if (balance > amount) {
            unchecked {
                _stakeData[account] = ((balance - amount) << 48) | (stakeData & 0xffffffffffff);
            }
            emit Claim(account, amount);
            return;
        }
        (uint256 unclaimedBalance, uint256 timestamp, uint256 stakedCount) = _calculateRewards(stakeData, balance);
        require(unclaimedBalance >= amount, "Not enough rewards to claim");
        unchecked {
            _stakeData[account] = ((unclaimedBalance - amount) << 48) | (timestamp << 14) | stakedCount;
        }
        emit Claim(account, amount);
    }
    function _transfer(address account, address to, uint256 amount) internal {
        _claim(account, amount);
        IERC20Mint(TOKEN_ADDRESS).mint(to, amount);
    }
    function claimRewardsAmount(uint256 amount) external {
        address account = _msgSender();
        _transfer(account, account, amount);
    }
    function claimRewards() external {
        address account = _msgSender();
        uint256 stakeData = _stakeData[account];
        (uint256 unclaimedBalance, uint256 timestamp, uint256 stakedCount) = _calculateRewards(stakeData, stakeData >> 48);
        require(unclaimedBalance > 0, "Nothing to claim");
        _stakeData[account] = (timestamp << 14) | stakedCount;
        emit Claim(account, unclaimedBalance);
        IERC20Mint(TOKEN_ADDRESS).mint(account, unclaimedBalance);
    }
    // ERC20 compatible functions
    function balanceOf(address account) external view returns (uint256) {
        uint256 stakeData = _stakeData[account];
        (uint256 unclaimedBalance, , ) = _calculateRewards(stakeData, stakeData >> 48);
        return unclaimedBalance;
    }
    function transfer(address to, uint256 amount) external returns (bool) {
        _transfer(_msgSender(), to, amount);
        return true;
    }
    function transferFrom(address account, address to, uint256 amount) external returns (bool) {
        require(_hasAccess(Access.Transfer, _msgSender()), "Not allowed to transfer");
        _transfer(account, to, amount);
        return true;
    }
    function burn(uint256 amount) external {
        _claim(_msgSender(), amount);
    }
    function burnFrom(address account, uint256 amount) external {
        require(_hasAccess(Access.Burn, _msgSender()), "Not allowed to burn");
        _claim(account, amount);
    }
}
// SPDX-License-Identifier: MIT
pragma solidity =0.8.11;
import "@openzeppelin/contracts/access/Ownable.sol";
/// @title OwnableTokenAccessControl
/// @notice Basic access control for utility tokens 
/// @author ponky
contract OwnableTokenAccessControl is Ownable {
    /// @dev Keeps track of how many accounts have been granted each type of access
    uint96 private _accessCounts;
    mapping (address => uint256) private _accessFlags;
    /// @dev Access types
    enum Access { Mint, Burn, Transfer, Claim }
    /// @dev Emitted when `account` is granted `access`.
    event AccessGranted(bytes32 indexed access, address indexed account);
    /// @dev Emitted when `account` is revoked `access`.
    event AccessRevoked(bytes32 indexed access, address indexed account);
    /// @dev Helper constants for fitting each access index into _accessCounts
    uint constant private _AC_BASE          = 4;
    uint constant private _AC_MASK_BITSIZE  = 1 << _AC_BASE;
    uint constant private _AC_DISABLED      = (1 << (_AC_MASK_BITSIZE - 1));
    uint constant private _AC_MASK_COUNT    = _AC_DISABLED - 1;
    /// @dev Convert the string `access` to an uint
    function _accessToIndex(bytes32 access) internal pure virtual returns (uint index) {
        if (access == 'MINT')       {return uint(Access.Mint);}
        if (access == 'BURN')       {return uint(Access.Burn);}
        if (access == 'TRANSFER')   {return uint(Access.Transfer);}
        if (access == 'CLAIM')      {return uint(Access.Claim);}
        revert("Access type does not exist");
    }
    function _hasAccess(Access access, address account) internal view returns (bool) {
        return (_accessFlags[account] & (1 << uint(access))) != 0;
    }
    function hasAccess(bytes32 access, address account) public view returns (bool) {
        uint256 flag = 1 << _accessToIndex(access);        
        return (_accessFlags[account] & flag) != 0;
    }
    function grantAccess(bytes32 access, address account) external onlyOwner {
        require(account.code.length > 0, "Can only grant access to a contract");
        uint index = _accessToIndex(access);
        uint256 flags = _accessFlags[account];
        uint256 newFlags = flags | (1 << index);
        require(flags != newFlags, "Account already has access");
        _accessFlags[account] = newFlags;
        uint shift = index << _AC_BASE;
        uint256 accessCount = _accessCounts >> shift;
        require((accessCount & _AC_DISABLED) == 0, "Granting this access is permanently disabled");
        require((accessCount & _AC_MASK_COUNT) < _AC_MASK_COUNT, "Access limit reached");
        unchecked {
            _accessCounts += uint96(1 << shift);
        }
        emit AccessGranted(access, account);
    }
    function revokeAccess(bytes32 access, address account) external onlyOwner {
        uint index = _accessToIndex(access);
        uint256 flags = _accessFlags[account];
        uint256 newFlags = flags & ~(1 << index);
        require(flags != newFlags, "Account does not have access");
        _accessFlags[account] = newFlags;
        uint shift = index << _AC_BASE;
        unchecked {
            _accessCounts -= uint96(1 << shift);
        }
        emit AccessRevoked(access, account);
    }
    /// @dev Returns the number of contracts that have `access`.
    function countOfAccess(bytes32 access) external view returns (uint256 accessCount) {
        uint index = _accessToIndex(access);
        uint shift = index << _AC_BASE;
        accessCount = (_accessCounts >> shift) & _AC_MASK_COUNT;
    }
    /// @dev `access` can still be revoked but not granted
    function permanentlyDisableGrantingAccess(bytes32 access) external onlyOwner {
        uint index = _accessToIndex(access);
        
        uint shift = index << _AC_BASE;
        uint256 flag = _AC_DISABLED << shift;
        uint256 accessCounts = _accessCounts;
        require((accessCounts & flag) == 0, "Granting this access is already disabled");
        _accessCounts = uint96(accessCounts | flag);
    }
}
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
interface IStakingReward {
    function willStakeTokens(address account, uint16[] calldata tokenIds) external;
    function willUnstakeTokens(address account, uint16[] calldata tokenIds) external;
    function willBeReplacedByContract(address stakingRewardContract) external;
    function didReplaceContract(address stakingRewardContract) external;
}
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
interface IERC20Mint is IERC20 {
    function mint(address to, uint256 amount) external;
}
// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (access/Ownable.sol)
pragma solidity ^0.8.0;
import "../utils/Context.sol";
/**
 * @dev 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 Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }
    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
        _;
    }
    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        _transferOwnership(address(0));
    }
    /**
     * @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);
    }
}
// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/Context.sol)
pragma solidity ^0.8.0;
/**
 * @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 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) {
        return msg.sender;
    }
    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}
// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/IERC20.sol)
pragma solidity ^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);
}