ETH Price: $2,676.69 (+7.20%)

Transaction Decoder

Block:
21693260 at Jan-24-2025 08:47:23 AM +UTC
Transaction Fee:
0.00097817008460145 ETH $2.62
Gas Used:
233,350 Gas / 4.191858087 Gwei

Emitted Events:

303 TWCloneFactory.ProxyDeployed( implementation=AirdropERC20Claimable, proxy=AirdropERC20Claimable, deployer=[Sender] 0x17b7f3251e5e97bdbd2e76be4ff9208da4af1c92 )
304 AirdropERC20Claimable.Initialized( version=1 )

Account State Difference:

  Address   Before After State Difference Code
0x17B7f325...dA4AF1c92
0.006581730486344197 Eth
Nonce: 5
0.005603560401742747 Eth
Nonce: 6
0.00097817008460145
0x76F948E5...Bf524805E
(beaverbuild)
16.523676178542846057 Eth16.523677119550056057 Eth0.00000094100721
0x9Dd69572...E243a5554
0 Eth
Nonce: 0
0 Eth
Nonce: 1
From: 0 To: 497590261154554171967156193956062121012234710125214252792683648403149628927925113351317266922110277111340019

Execution Trace

TWCloneFactory.deployProxyByImplementation( _implementation=0x0f2f02D8fE02E9C14A65A5A33073bD1ADD9aa53B, _data=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salt=00000000000000000000000000000000000000000000000000000000014B0348 ) => ( deployedProxy=0x9Dd6957298Eeef89511c3e356921e4EE243a5554 )
  • AirdropERC20Claimable.3d602d80( )
  • AirdropERC20Claimable.initialize( _trustedForwarders=[], _tokenOwner=0x40D9Ce00E43890C3358406D843e520D269844D5f, _airdropTokenAddress=0xd328a1C97e9b6b3Afd42eAf535bcB55A85cDcA7B, _airdropAmount=901374355000001400, _expirationTimestamp=1740441599, _openClaimLimitPerWallet=0, _merkleRoot=28810B19562CA91B39D207674B32585F93054D773D34BEF5362006FA960A04D7 )
    • AirdropERC20Claimable.initialize( _trustedForwarders=[], _tokenOwner=0x40D9Ce00E43890C3358406D843e520D269844D5f, _airdropTokenAddress=0xd328a1C97e9b6b3Afd42eAf535bcB55A85cDcA7B, _airdropAmount=901374355000001400, _expirationTimestamp=1740441599, _openClaimLimitPerWallet=0, _merkleRoot=28810B19562CA91B39D207674B32585F93054D773D34BEF5362006FA960A04D7 )
      File 1 of 3: TWCloneFactory
      // SPDX-License-Identifier: Apache-2.0
      pragma solidity ^0.8.11;
      /// @author thirdweb
      //   $$\\     $$\\       $$\\                 $$\\                         $$\\
      //   $$ |    $$ |      \\__|                $$ |                        $$ |
      // $$$$$$\\   $$$$$$$\\  $$\\  $$$$$$\\   $$$$$$$ |$$\\  $$\\  $$\\  $$$$$$\\  $$$$$$$\\
      // \\_$$  _|  $$  __$$\\ $$ |$$  __$$\\ $$  __$$ |$$ | $$ | $$ |$$  __$$\\ $$  __$$\\
      //   $$ |    $$ |  $$ |$$ |$$ |  \\__|$$ /  $$ |$$ | $$ | $$ |$$$$$$$$ |$$ |  $$ |
      //   $$ |$$\\ $$ |  $$ |$$ |$$ |      $$ |  $$ |$$ | $$ | $$ |$$   ____|$$ |  $$ |
      //   \\$$$$  |$$ |  $$ |$$ |$$ |      \\$$$$$$$ |\\$$$$$\\$$$$  |\\$$$$$$$\\ $$$$$$$  |
      //    \\____/ \\__|  \\__|\\__|\\__|       \\_______| \\_____\\____/  \\_______|\\_______/
      import "./extension/interface/IContractFactory.sol";
      import "@openzeppelin/contracts/metatx/ERC2771Context.sol";
      import "@openzeppelin/contracts/utils/Multicall.sol";
      import "@openzeppelin/contracts/proxy/Clones.sol";
      contract TWCloneFactory is Multicall, ERC2771Context, IContractFactory {
          /// @dev Emitted when a proxy is deployed.
          event ProxyDeployed(address indexed implementation, address proxy, address indexed deployer);
          constructor(address _trustedForwarder) ERC2771Context(_trustedForwarder) {}
          /// @dev Deploys a proxy that points to the given implementation.
          function deployProxyByImplementation(
              address _implementation,
              bytes memory _data,
              bytes32 _salt
          ) public override returns (address deployedProxy) {
              bytes32 salthash = keccak256(abi.encodePacked(_msgSender(), _salt));
              deployedProxy = Clones.cloneDeterministic(_implementation, salthash);
              emit ProxyDeployed(_implementation, deployedProxy, _msgSender());
              if (_data.length > 0) {
                  // slither-disable-next-line unused-return
                  Address.functionCall(deployedProxy, _data);
              }
          }
          function _msgSender() internal view virtual override returns (address sender) {
              return ERC2771Context._msgSender();
          }
          function _msgData() internal view virtual override returns (bytes calldata) {
              return ERC2771Context._msgData();
          }
      }
      // SPDX-License-Identifier: Apache-2.0
      pragma solidity ^0.8.0;
      /// @author thirdweb
      interface IContractFactory {
          /**
           *  @notice Deploys a proxy that points to that points to the given implementation.
           *
           *  @param implementation           Address of the implementation to point to.
           *
           *  @param data                     Additional data to pass to the proxy constructor or any other data useful during deployement.
           *  @param salt                     Salt to use for the deterministic address generation.
           */
          function deployProxyByImplementation(
              address implementation,
              bytes memory data,
              bytes32 salt
          ) external returns (address);
      }
      // SPDX-License-Identifier: MIT
      // OpenZeppelin Contracts (last updated v4.7.0) (metatx/ERC2771Context.sol)
      pragma solidity ^0.8.9;
      import "../utils/Context.sol";
      /**
       * @dev Context variant with ERC2771 support.
       */
      abstract contract ERC2771Context is Context {
          /// @custom:oz-upgrades-unsafe-allow state-variable-immutable
          address private immutable _trustedForwarder;
          /// @custom:oz-upgrades-unsafe-allow constructor
          constructor(address trustedForwarder) {
              _trustedForwarder = trustedForwarder;
          }
          function isTrustedForwarder(address forwarder) public view virtual returns (bool) {
              return forwarder == _trustedForwarder;
          }
          function _msgSender() internal view virtual override returns (address sender) {
              if (isTrustedForwarder(msg.sender)) {
                  // The assembly code is more direct than the Solidity version using `abi.decode`.
                  /// @solidity memory-safe-assembly
                  assembly {
                      sender := shr(96, calldataload(sub(calldatasize(), 20)))
                  }
              } else {
                  return super._msgSender();
              }
          }
          function _msgData() internal view virtual override returns (bytes calldata) {
              if (isTrustedForwarder(msg.sender)) {
                  return msg.data[:msg.data.length - 20];
              } else {
                  return super._msgData();
              }
          }
      }
      // SPDX-License-Identifier: MIT
      // OpenZeppelin Contracts (last updated v4.7.0) (proxy/Clones.sol)
      pragma solidity ^0.8.0;
      /**
       * @dev https://eips.ethereum.org/EIPS/eip-1167[EIP 1167] is a standard for
       * deploying minimal proxy contracts, also known as "clones".
       *
       * > To simply and cheaply clone contract functionality in an immutable way, this standard specifies
       * > a minimal bytecode implementation that delegates all calls to a known, fixed address.
       *
       * The library includes functions to deploy a proxy using either `create` (traditional deployment) or `create2`
       * (salted deterministic deployment). It also includes functions to predict the addresses of clones deployed using the
       * deterministic method.
       *
       * _Available since v3.4._
       */
      library Clones {
          /**
           * @dev Deploys and returns the address of a clone that mimics the behaviour of `implementation`.
           *
           * This function uses the create opcode, which should never revert.
           */
          function clone(address implementation) internal returns (address instance) {
              /// @solidity memory-safe-assembly
              assembly {
                  let ptr := mload(0x40)
                  mstore(ptr, 0x3d602d80600a3d3981f3363d3d373d3d3d363d73000000000000000000000000)
                  mstore(add(ptr, 0x14), shl(0x60, implementation))
                  mstore(add(ptr, 0x28), 0x5af43d82803e903d91602b57fd5bf30000000000000000000000000000000000)
                  instance := create(0, ptr, 0x37)
              }
              require(instance != address(0), "ERC1167: create failed");
          }
          /**
           * @dev Deploys and returns the address of a clone that mimics the behaviour of `implementation`.
           *
           * This function uses the create2 opcode and a `salt` to deterministically deploy
           * the clone. Using the same `implementation` and `salt` multiple time will revert, since
           * the clones cannot be deployed twice at the same address.
           */
          function cloneDeterministic(address implementation, bytes32 salt) internal returns (address instance) {
              /// @solidity memory-safe-assembly
              assembly {
                  let ptr := mload(0x40)
                  mstore(ptr, 0x3d602d80600a3d3981f3363d3d373d3d3d363d73000000000000000000000000)
                  mstore(add(ptr, 0x14), shl(0x60, implementation))
                  mstore(add(ptr, 0x28), 0x5af43d82803e903d91602b57fd5bf30000000000000000000000000000000000)
                  instance := create2(0, ptr, 0x37, salt)
              }
              require(instance != address(0), "ERC1167: create2 failed");
          }
          /**
           * @dev Computes the address of a clone deployed using {Clones-cloneDeterministic}.
           */
          function predictDeterministicAddress(
              address implementation,
              bytes32 salt,
              address deployer
          ) internal pure returns (address predicted) {
              /// @solidity memory-safe-assembly
              assembly {
                  let ptr := mload(0x40)
                  mstore(ptr, 0x3d602d80600a3d3981f3363d3d373d3d3d363d73000000000000000000000000)
                  mstore(add(ptr, 0x14), shl(0x60, implementation))
                  mstore(add(ptr, 0x28), 0x5af43d82803e903d91602b57fd5bf3ff00000000000000000000000000000000)
                  mstore(add(ptr, 0x38), shl(0x60, deployer))
                  mstore(add(ptr, 0x4c), salt)
                  mstore(add(ptr, 0x6c), keccak256(ptr, 0x37))
                  predicted := keccak256(add(ptr, 0x37), 0x55)
              }
          }
          /**
           * @dev Computes the address of a clone deployed using {Clones-cloneDeterministic}.
           */
          function predictDeterministicAddress(address implementation, bytes32 salt)
              internal
              view
              returns (address predicted)
          {
              return predictDeterministicAddress(implementation, salt, address(this));
          }
      }
      // SPDX-License-Identifier: MIT
      // OpenZeppelin Contracts (last updated v4.7.0) (utils/Address.sol)
      pragma solidity ^0.8.1;
      /**
       * @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
           * ====
           *
           * [IMPORTANT]
           * ====
           * You shouldn't rely on `isContract` to protect against flash loan attacks!
           *
           * Preventing calls from contracts is highly discouraged. It breaks composability, breaks support for smart wallets
           * like Gnosis Safe, and does not provide security since it can be circumvented by calling from a contract
           * constructor.
           * ====
           */
          function isContract(address account) internal view returns (bool) {
              // This method relies on extcodesize/address.code.length, which returns 0
              // for contracts in construction, since the code is only stored at the end
              // of the constructor execution.
              return account.code.length > 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
                      /// @solidity memory-safe-assembly
                      assembly {
                          let returndata_size := mload(returndata)
                          revert(add(32, returndata), returndata_size)
                      }
                  } else {
                      revert(errorMessage);
                  }
              }
          }
      }
      // 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 (last updated v4.5.0) (utils/Multicall.sol)
      pragma solidity ^0.8.0;
      import "./Address.sol";
      /**
       * @dev Provides a function to batch together multiple calls in a single external call.
       *
       * _Available since v4.1._
       */
      abstract contract Multicall {
          /**
           * @dev Receives and executes a batch of function calls on this contract.
           */
          function multicall(bytes[] calldata data) external virtual returns (bytes[] memory results) {
              results = new bytes[](data.length);
              for (uint256 i = 0; i < data.length; i++) {
                  results[i] = Address.functionDelegateCall(address(this), data[i]);
              }
              return results;
          }
      }
      

      File 2 of 3: AirdropERC20Claimable
      // SPDX-License-Identifier: Apache 2.0
      pragma solidity ^0.8.0;
      /// @author thirdweb
      import "../lib/Address.sol";
      import "./interface/IMulticall.sol";
      /**
       * @dev Provides a function to batch together multiple calls in a single external call.
       *
       * _Available since v4.1._
       */
      contract Multicall is IMulticall {
          /**
           *  @notice Receives and executes a batch of function calls on this contract.
           *  @dev Receives and executes a batch of function calls on this contract.
           *
           *  @param data The bytes data that makes up the batch of function calls to execute.
           *  @return results The bytes data that makes up the result of the batch of function calls executed.
           */
          function multicall(bytes[] calldata data) external returns (bytes[] memory results) {
              results = new bytes[](data.length);
              address sender = _msgSender();
              bool isForwarder = msg.sender != sender;
              for (uint256 i = 0; i < data.length; i++) {
                  if (isForwarder) {
                      results[i] = Address.functionDelegateCall(address(this), abi.encodePacked(data[i], sender));
                  } else {
                      results[i] = Address.functionDelegateCall(address(this), data[i]);
                  }
              }
              return results;
          }
          /// @notice Returns the sender in the given execution context.
          function _msgSender() internal view virtual returns (address) {
              return msg.sender;
          }
      }
      // SPDX-License-Identifier: MIT
      pragma solidity ^0.8.0;
      /// @author thirdweb
      /**
       * @dev Provides a function to batch together multiple calls in a single external call.
       *
       * _Available since v4.1._
       */
      interface IMulticall {
          /**
           * @dev Receives and executes a batch of function calls on this contract.
           */
          function multicall(bytes[] calldata data) external returns (bytes[] memory results);
      }
      // SPDX-License-Identifier: MIT
      // OpenZeppelin Contracts v4.4.0 (metatx/ERC2771Context.sol)
      pragma solidity ^0.8.11;
      import "@openzeppelin/contracts-upgradeable/utils/ContextUpgradeable.sol";
      import "@openzeppelin/contracts-upgradeable/proxy/utils/Initializable.sol";
      /**
       * @dev Context variant with ERC2771 support.
       */
      abstract contract ERC2771ContextUpgradeable is Initializable, ContextUpgradeable {
          mapping(address => bool) private _trustedForwarder;
          function __ERC2771Context_init(address[] memory trustedForwarder) internal onlyInitializing {
              __Context_init_unchained();
              __ERC2771Context_init_unchained(trustedForwarder);
          }
          function __ERC2771Context_init_unchained(address[] memory trustedForwarder) internal onlyInitializing {
              for (uint256 i = 0; i < trustedForwarder.length; i++) {
                  _trustedForwarder[trustedForwarder[i]] = true;
              }
          }
          function isTrustedForwarder(address forwarder) public view virtual returns (bool) {
              return _trustedForwarder[forwarder];
          }
          function _msgSender() internal view virtual override returns (address sender) {
              if (isTrustedForwarder(msg.sender)) {
                  // The assembly code is more direct than the Solidity version using `abi.decode`.
                  assembly {
                      sender := shr(96, calldataload(sub(calldatasize(), 20)))
                  }
              } else {
                  return super._msgSender();
              }
          }
          function _msgData() internal view virtual override returns (bytes calldata) {
              if (isTrustedForwarder(msg.sender)) {
                  return msg.data[:msg.data.length - 20];
              } else {
                  return super._msgData();
              }
          }
          uint256[49] private __gap;
      }
      // SPDX-License-Identifier: Apache-2.0
      pragma solidity ^0.8.1;
      /// @author thirdweb, OpenZeppelin Contracts (v4.9.0)
      /**
       * @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
           *
           * Furthermore, `isContract` will also return true if the target contract within
           * the same transaction is already scheduled for destruction by `SELFDESTRUCT`,
           * which only has an effect at the end of a transaction.
           * ====
           *
           * [IMPORTANT]
           * ====
           * You shouldn't rely on `isContract` to protect against flash loan attacks!
           *
           * Preventing calls from contracts is highly discouraged. It breaks composability, breaks support for smart wallets
           * like Gnosis Safe, and does not provide security since it can be circumvented by calling from a contract
           * constructor.
           * ====
           */
          function isContract(address account) internal view returns (bool) {
              // This method relies on extcodesize/address.code.length, which returns 0
              // for contracts in construction, since the code is only stored at the end
              // of the constructor execution.
              return account.code.length > 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://consensys.net/diligence/blog/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/v0.8.0/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 functionCallWithValue(target, data, 0, "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");
              (bool success, bytes memory returndata) = target.call{ value: value }(data);
              return verifyCallResultFromTarget(target, 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) {
              (bool success, bytes memory returndata) = target.staticcall(data);
              return verifyCallResultFromTarget(target, 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) {
              (bool success, bytes memory returndata) = target.delegatecall(data);
              return verifyCallResultFromTarget(target, success, returndata, errorMessage);
          }
          /**
           * @dev Tool to verify that a low level call to smart-contract was successful, and revert (either by bubbling
           * the revert reason or using the provided one) in case of unsuccessful call or if target was not a contract.
           *
           * _Available since v4.8._
           */
          function verifyCallResultFromTarget(
              address target,
              bool success,
              bytes memory returndata,
              string memory errorMessage
          ) internal view returns (bytes memory) {
              if (success) {
                  if (returndata.length == 0) {
                      // only check isContract if the call was successful and the return data is empty
                      // otherwise we already know that it was a contract
                      require(isContract(target), "Address: call to non-contract");
                  }
                  return returndata;
              } else {
                  _revert(returndata, errorMessage);
              }
          }
          /**
           * @dev Tool to verify that a low level call was successful, and revert if it wasn't, either by bubbling the
           * revert reason or 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 {
                  _revert(returndata, errorMessage);
              }
          }
          function _revert(bytes memory returndata, string memory errorMessage) private pure {
              // 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
                  /// @solidity memory-safe-assembly
                  assembly {
                      let returndata_size := mload(returndata)
                      revert(add(32, returndata), returndata_size)
                  }
              } else {
                  revert(errorMessage);
              }
          }
      }
      // SPDX-License-Identifier: Apache 2.0
      pragma solidity ^0.8.0;
      /// @author thirdweb
      library MerkleProof {
          function verify(bytes32[] memory proof, bytes32 root, bytes32 leaf) internal pure returns (bool, uint256) {
              bytes32 computedHash = leaf;
              uint256 index = 0;
              for (uint256 i = 0; i < proof.length; i++) {
                  index *= 2;
                  bytes32 proofElement = proof[i];
                  if (computedHash <= proofElement) {
                      // Hash(current computed hash + current element of the proof)
                      computedHash = keccak256(abi.encodePacked(computedHash, proofElement));
                  } else {
                      // Hash(current element of the proof + current computed hash)
                      computedHash = keccak256(abi.encodePacked(proofElement, computedHash));
                      index += 1;
                  }
              }
              // Check if the computed hash (root) is equal to the provided root
              return (computedHash == root, index);
          }
      }
      // SPDX-License-Identifier: Apache-2.0
      pragma solidity ^0.8.11;
      /**
       *  Thirdweb's `Airdrop` contracts provide a lightweight and easy to use mechanism
       *  to drop tokens.
       *
       *  `AirdropERC20Claimable` contract is an airdrop contract for ERC20 tokens. It follows a
       *  pull mechanism for transfer of tokens, where allowlisted recipients can claim tokens from
       *  the contract.
       */
      interface IAirdropERC20Claimable {
          /// @dev Emitted when tokens are claimed.
          event TokensClaimed(address indexed claimer, address indexed receiver, uint256 quantityClaimed);
          /**
           *  @notice Lets an account claim a given quantity of NFTs.
           *
           *  @param receiver                       The receiver of the NFTs to claim.
           *  @param quantity                       The quantity of NFTs to claim.
           *  @param proofs                         The proof of the claimer's inclusion in the merkle root allowlist
           *                                        of the claim conditions that apply.
           *  @param proofMaxQuantityForWallet      The maximum number of NFTs an address included in an
           *                                        allowlist can claim.
           */
          function claim(
              address receiver,
              uint256 quantity,
              bytes32[] calldata proofs,
              uint256 proofMaxQuantityForWallet
          ) external;
      }
      // SPDX-License-Identifier: Apache-2.0
      pragma solidity ^0.8.11;
      /// @author thirdweb
      //   $$\\     $$\\       $$\\                 $$\\                         $$\\
      //   $$ |    $$ |      \\__|                $$ |                        $$ |
      // $$$$$$\\   $$$$$$$\\  $$\\  $$$$$$\\   $$$$$$$ |$$\\  $$\\  $$\\  $$$$$$\\  $$$$$$$\\
      // \\_$$  _|  $$  __$$\\ $$ |$$  __$$\\ $$  __$$ |$$ | $$ | $$ |$$  __$$\\ $$  __$$\\
      //   $$ |    $$ |  $$ |$$ |$$ |  \\__|$$ /  $$ |$$ | $$ | $$ |$$$$$$$$ |$$ |  $$ |
      //   $$ |$$\\ $$ |  $$ |$$ |$$ |      $$ |  $$ |$$ | $$ | $$ |$$   ____|$$ |  $$ |
      //   \\$$$$  |$$ |  $$ |$$ |$$ |      \\$$$$$$$ |\\$$$$$\\$$$$  |\\$$$$$$$\\ $$$$$$$  |
      //    \\____/ \\__|  \\__|\\__|\\__|       \\_______| \\_____\\____/  \\_______|\\_______/
      //  ==========  External imports    ==========
      import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
      import "@openzeppelin/contracts-upgradeable/security/ReentrancyGuardUpgradeable.sol";
      import "../../../extension/Multicall.sol";
      //  ==========  Internal imports    ==========
      import "../../interface/airdrop/IAirdropERC20Claimable.sol";
      //  ==========  Features    ==========
      import "../../../external-deps/openzeppelin/metatx/ERC2771ContextUpgradeable.sol";
      import "../../../lib/MerkleProof.sol";
      contract AirdropERC20Claimable is
          Initializable,
          ReentrancyGuardUpgradeable,
          ERC2771ContextUpgradeable,
          Multicall,
          IAirdropERC20Claimable
      {
          /*///////////////////////////////////////////////////////////////
                                  State variables
          //////////////////////////////////////////////////////////////*/
          /// @dev address of token being airdropped.
          address public airdropTokenAddress;
          /// @dev address of owner of tokens being airdropped.
          address public tokenOwner;
          /// @dev number tokens available to claim.
          uint256 public availableAmount;
          /// @dev airdrop expiration timestamp.
          uint256 public expirationTimestamp;
          /// @dev claim limit for open/public claiming without allowlist.
          uint256 public openClaimLimitPerWallet;
          /// @dev merkle root of the allowlist of addresses eligible to claim.
          bytes32 public merkleRoot;
          /*///////////////////////////////////////////////////////////////
                                      Mappings
          //////////////////////////////////////////////////////////////*/
          /// @dev Mapping from address => total number of tokens a wallet has claimed.
          mapping(address => uint256) public supplyClaimedByWallet;
          /*///////////////////////////////////////////////////////////////
                          Constructor + initializer logic
          //////////////////////////////////////////////////////////////*/
          constructor() {
              _disableInitializers();
          }
          /// @dev Initializes the contract, like a constructor.
          function initialize(
              address[] memory _trustedForwarders,
              address _tokenOwner,
              address _airdropTokenAddress,
              uint256 _airdropAmount,
              uint256 _expirationTimestamp,
              uint256 _openClaimLimitPerWallet,
              bytes32 _merkleRoot
          ) external initializer {
              __ReentrancyGuard_init();
              __ERC2771Context_init(_trustedForwarders);
              tokenOwner = _tokenOwner;
              airdropTokenAddress = _airdropTokenAddress;
              availableAmount = _airdropAmount;
              expirationTimestamp = _expirationTimestamp;
              openClaimLimitPerWallet = _openClaimLimitPerWallet;
              merkleRoot = _merkleRoot;
          }
          /*///////////////////////////////////////////////////////////////
                                  Claim logic
          //////////////////////////////////////////////////////////////*/
          /**
           *  @notice Lets an account claim a given quantity of NFTs.
           *
           *  @param _receiver                       The receiver of the NFTs to claim.
           *  @param _quantity                       The quantity of NFTs to claim.
           *  @param _proofs                         The proof of the claimer's inclusion in the merkle root allowlist
           *                                        of the claim conditions that apply.
           *  @param _proofMaxQuantityForWallet      The maximum number of NFTs an address included in an
           *                                        allowlist can claim.
           */
          function claim(
              address _receiver,
              uint256 _quantity,
              bytes32[] calldata _proofs,
              uint256 _proofMaxQuantityForWallet
          ) external nonReentrant {
              address claimer = _msgSender();
              verifyClaim(claimer, _quantity, _proofs, _proofMaxQuantityForWallet);
              _transferClaimedTokens(_receiver, _quantity);
              emit TokensClaimed(_msgSender(), _receiver, _quantity);
          }
          /// @dev Checks a request to claim tokens against the active claim condition's criteria.
          function verifyClaim(
              address _claimer,
              uint256 _quantity,
              bytes32[] calldata _proofs,
              uint256 _proofMaxQuantityForWallet
          ) public view {
              bool isOverride;
              /*
               * Here `isOverride` implies that if the merkle proof verification fails,
               * the claimer would claim through open claim limit instead of allowlisted limit.
               */
              if (merkleRoot != bytes32(0)) {
                  (isOverride, ) = MerkleProof.verify(
                      _proofs,
                      merkleRoot,
                      keccak256(abi.encodePacked(_claimer, _proofMaxQuantityForWallet))
                  );
              }
              uint256 supplyClaimedAlready = supplyClaimedByWallet[_claimer];
              require(_quantity > 0, "Claiming zero tokens");
              require(_quantity <= availableAmount, "exceeds available tokens.");
              uint256 expTimestamp = expirationTimestamp;
              require(expTimestamp == 0 || block.timestamp < expTimestamp, "airdrop expired.");
              uint256 claimLimitForWallet = isOverride ? _proofMaxQuantityForWallet : openClaimLimitPerWallet;
              require(_quantity + supplyClaimedAlready <= claimLimitForWallet, "invalid quantity.");
          }
          /// @dev Transfers the tokens being claimed.
          function _transferClaimedTokens(address _to, uint256 _quantityBeingClaimed) internal {
              // if transfer claimed tokens is called when `to != msg.sender`, it'd use msg.sender's limits.
              // behavior would be similar to `msg.sender` mint for itself, then transfer to `_to`.
              supplyClaimedByWallet[_msgSender()] += _quantityBeingClaimed;
              availableAmount -= _quantityBeingClaimed;
              require(IERC20(airdropTokenAddress).transferFrom(tokenOwner, _to, _quantityBeingClaimed), "transfer failed");
          }
          /*///////////////////////////////////////////////////////////////
                              Miscellaneous
          //////////////////////////////////////////////////////////////*/
          function _msgSender()
              internal
              view
              virtual
              override(ERC2771ContextUpgradeable, Multicall)
              returns (address sender)
          {
              return ERC2771ContextUpgradeable._msgSender();
          }
      }
      // SPDX-License-Identifier: MIT
      // OpenZeppelin Contracts (last updated v4.9.0) (proxy/utils/Initializable.sol)
      pragma solidity ^0.8.2;
      import "../../utils/AddressUpgradeable.sol";
      /**
       * @dev This is a base contract to aid in writing upgradeable contracts, or any kind of contract that will be deployed
       * behind a proxy. Since proxied contracts do not make use of a constructor, it's common to move constructor logic to an
       * external initializer function, usually called `initialize`. It then becomes necessary to protect this initializer
       * function so it can only be called once. The {initializer} modifier provided by this contract will have this effect.
       *
       * The initialization functions use a version number. Once a version number is used, it is consumed and cannot be
       * reused. This mechanism prevents re-execution of each "step" but allows the creation of new initialization steps in
       * case an upgrade adds a module that needs to be initialized.
       *
       * For example:
       *
       * [.hljs-theme-light.nopadding]
       * ```solidity
       * contract MyToken is ERC20Upgradeable {
       *     function initialize() initializer public {
       *         __ERC20_init("MyToken", "MTK");
       *     }
       * }
       *
       * contract MyTokenV2 is MyToken, ERC20PermitUpgradeable {
       *     function initializeV2() reinitializer(2) public {
       *         __ERC20Permit_init("MyToken");
       *     }
       * }
       * ```
       *
       * TIP: To avoid leaving the proxy in an uninitialized state, the initializer function should be called as early as
       * possible by providing the encoded function call as the `_data` argument to {ERC1967Proxy-constructor}.
       *
       * CAUTION: When used with inheritance, manual care must be taken to not invoke a parent initializer twice, or to ensure
       * that all initializers are idempotent. This is not verified automatically as constructors are by Solidity.
       *
       * [CAUTION]
       * ====
       * Avoid leaving a contract uninitialized.
       *
       * An uninitialized contract can be taken over by an attacker. This applies to both a proxy and its implementation
       * contract, which may impact the proxy. To prevent the implementation contract from being used, you should invoke
       * the {_disableInitializers} function in the constructor to automatically lock it when it is deployed:
       *
       * [.hljs-theme-light.nopadding]
       * ```
       * /// @custom:oz-upgrades-unsafe-allow constructor
       * constructor() {
       *     _disableInitializers();
       * }
       * ```
       * ====
       */
      abstract contract Initializable {
          /**
           * @dev Indicates that the contract has been initialized.
           * @custom:oz-retyped-from bool
           */
          uint8 private _initialized;
          /**
           * @dev Indicates that the contract is in the process of being initialized.
           */
          bool private _initializing;
          /**
           * @dev Triggered when the contract has been initialized or reinitialized.
           */
          event Initialized(uint8 version);
          /**
           * @dev A modifier that defines a protected initializer function that can be invoked at most once. In its scope,
           * `onlyInitializing` functions can be used to initialize parent contracts.
           *
           * Similar to `reinitializer(1)`, except that functions marked with `initializer` can be nested in the context of a
           * constructor.
           *
           * Emits an {Initialized} event.
           */
          modifier initializer() {
              bool isTopLevelCall = !_initializing;
              require(
                  (isTopLevelCall && _initialized < 1) || (!AddressUpgradeable.isContract(address(this)) && _initialized == 1),
                  "Initializable: contract is already initialized"
              );
              _initialized = 1;
              if (isTopLevelCall) {
                  _initializing = true;
              }
              _;
              if (isTopLevelCall) {
                  _initializing = false;
                  emit Initialized(1);
              }
          }
          /**
           * @dev A modifier that defines a protected reinitializer function that can be invoked at most once, and only if the
           * contract hasn't been initialized to a greater version before. In its scope, `onlyInitializing` functions can be
           * used to initialize parent contracts.
           *
           * A reinitializer may be used after the original initialization step. This is essential to configure modules that
           * are added through upgrades and that require initialization.
           *
           * When `version` is 1, this modifier is similar to `initializer`, except that functions marked with `reinitializer`
           * cannot be nested. If one is invoked in the context of another, execution will revert.
           *
           * Note that versions can jump in increments greater than 1; this implies that if multiple reinitializers coexist in
           * a contract, executing them in the right order is up to the developer or operator.
           *
           * WARNING: setting the version to 255 will prevent any future reinitialization.
           *
           * Emits an {Initialized} event.
           */
          modifier reinitializer(uint8 version) {
              require(!_initializing && _initialized < version, "Initializable: contract is already initialized");
              _initialized = version;
              _initializing = true;
              _;
              _initializing = false;
              emit Initialized(version);
          }
          /**
           * @dev Modifier to protect an initialization function so that it can only be invoked by functions with the
           * {initializer} and {reinitializer} modifiers, directly or indirectly.
           */
          modifier onlyInitializing() {
              require(_initializing, "Initializable: contract is not initializing");
              _;
          }
          /**
           * @dev Locks the contract, preventing any future reinitialization. This cannot be part of an initializer call.
           * Calling this in the constructor of a contract will prevent that contract from being initialized or reinitialized
           * to any version. It is recommended to use this to lock implementation contracts that are designed to be called
           * through proxies.
           *
           * Emits an {Initialized} event the first time it is successfully executed.
           */
          function _disableInitializers() internal virtual {
              require(!_initializing, "Initializable: contract is initializing");
              if (_initialized != type(uint8).max) {
                  _initialized = type(uint8).max;
                  emit Initialized(type(uint8).max);
              }
          }
          /**
           * @dev Returns the highest version that has been initialized. See {reinitializer}.
           */
          function _getInitializedVersion() internal view returns (uint8) {
              return _initialized;
          }
          /**
           * @dev Returns `true` if the contract is currently initializing. See {onlyInitializing}.
           */
          function _isInitializing() internal view returns (bool) {
              return _initializing;
          }
      }
      // SPDX-License-Identifier: MIT
      // OpenZeppelin Contracts (last updated v4.9.0) (security/ReentrancyGuard.sol)
      pragma solidity ^0.8.0;
      import "../proxy/utils/Initializable.sol";
      /**
       * @dev Contract module that helps prevent reentrant calls to a function.
       *
       * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
       * available, which can be applied to functions to make sure there are no nested
       * (reentrant) calls to them.
       *
       * Note that because there is a single `nonReentrant` guard, functions marked as
       * `nonReentrant` may not call one another. This can be worked around by making
       * those functions `private`, and then adding `external` `nonReentrant` entry
       * points to them.
       *
       * TIP: If you would like to learn more about reentrancy and alternative ways
       * to protect against it, check out our blog post
       * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
       */
      abstract contract ReentrancyGuardUpgradeable is Initializable {
          // Booleans are more expensive than uint256 or any type that takes up a full
          // word because each write operation emits an extra SLOAD to first read the
          // slot's contents, replace the bits taken up by the boolean, and then write
          // back. This is the compiler's defense against contract upgrades and
          // pointer aliasing, and it cannot be disabled.
          // The values being non-zero value makes deployment a bit more expensive,
          // but in exchange the refund on every call to nonReentrant will be lower in
          // amount. Since refunds are capped to a percentage of the total
          // transaction's gas, it is best to keep them low in cases like this one, to
          // increase the likelihood of the full refund coming into effect.
          uint256 private constant _NOT_ENTERED = 1;
          uint256 private constant _ENTERED = 2;
          uint256 private _status;
          function __ReentrancyGuard_init() internal onlyInitializing {
              __ReentrancyGuard_init_unchained();
          }
          function __ReentrancyGuard_init_unchained() internal onlyInitializing {
              _status = _NOT_ENTERED;
          }
          /**
           * @dev Prevents a contract from calling itself, directly or indirectly.
           * Calling a `nonReentrant` function from another `nonReentrant`
           * function is not supported. It is possible to prevent this from happening
           * by making the `nonReentrant` function external, and making it call a
           * `private` function that does the actual work.
           */
          modifier nonReentrant() {
              _nonReentrantBefore();
              _;
              _nonReentrantAfter();
          }
          function _nonReentrantBefore() private {
              // On the first call to nonReentrant, _status will be _NOT_ENTERED
              require(_status != _ENTERED, "ReentrancyGuard: reentrant call");
              // Any calls to nonReentrant after this point will fail
              _status = _ENTERED;
          }
          function _nonReentrantAfter() private {
              // By storing the original value once again, a refund is triggered (see
              // https://eips.ethereum.org/EIPS/eip-2200)
              _status = _NOT_ENTERED;
          }
          /**
           * @dev Returns true if the reentrancy guard is currently set to "entered", which indicates there is a
           * `nonReentrant` function in the call stack.
           */
          function _reentrancyGuardEntered() internal view returns (bool) {
              return _status == _ENTERED;
          }
          /**
           * @dev This empty reserved space is put in place to allow future versions to add new
           * variables without shifting down storage in the inheritance chain.
           * See https://docs.openzeppelin.com/contracts/4.x/upgradeable#storage_gaps
           */
          uint256[49] private __gap;
      }
      // SPDX-License-Identifier: MIT
      // OpenZeppelin Contracts (last updated v4.9.0) (utils/Address.sol)
      pragma solidity ^0.8.1;
      /**
       * @dev Collection of functions related to the address type
       */
      library AddressUpgradeable {
          /**
           * @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
           *
           * Furthermore, `isContract` will also return true if the target contract within
           * the same transaction is already scheduled for destruction by `SELFDESTRUCT`,
           * which only has an effect at the end of a transaction.
           * ====
           *
           * [IMPORTANT]
           * ====
           * You shouldn't rely on `isContract` to protect against flash loan attacks!
           *
           * Preventing calls from contracts is highly discouraged. It breaks composability, breaks support for smart wallets
           * like Gnosis Safe, and does not provide security since it can be circumvented by calling from a contract
           * constructor.
           * ====
           */
          function isContract(address account) internal view returns (bool) {
              // This method relies on extcodesize/address.code.length, which returns 0
              // for contracts in construction, since the code is only stored at the end
              // of the constructor execution.
              return account.code.length > 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://consensys.net/diligence/blog/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/v0.8.0/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 functionCallWithValue(target, data, 0, "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");
              (bool success, bytes memory returndata) = target.call{value: value}(data);
              return verifyCallResultFromTarget(target, 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) {
              (bool success, bytes memory returndata) = target.staticcall(data);
              return verifyCallResultFromTarget(target, 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) {
              (bool success, bytes memory returndata) = target.delegatecall(data);
              return verifyCallResultFromTarget(target, success, returndata, errorMessage);
          }
          /**
           * @dev Tool to verify that a low level call to smart-contract was successful, and revert (either by bubbling
           * the revert reason or using the provided one) in case of unsuccessful call or if target was not a contract.
           *
           * _Available since v4.8._
           */
          function verifyCallResultFromTarget(
              address target,
              bool success,
              bytes memory returndata,
              string memory errorMessage
          ) internal view returns (bytes memory) {
              if (success) {
                  if (returndata.length == 0) {
                      // only check isContract if the call was successful and the return data is empty
                      // otherwise we already know that it was a contract
                      require(isContract(target), "Address: call to non-contract");
                  }
                  return returndata;
              } else {
                  _revert(returndata, errorMessage);
              }
          }
          /**
           * @dev Tool to verify that a low level call was successful, and revert if it wasn't, either by bubbling the
           * revert reason or 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 {
                  _revert(returndata, errorMessage);
              }
          }
          function _revert(bytes memory returndata, string memory errorMessage) private pure {
              // 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
                  /// @solidity memory-safe-assembly
                  assembly {
                      let returndata_size := mload(returndata)
                      revert(add(32, returndata), returndata_size)
                  }
              } else {
                  revert(errorMessage);
              }
          }
      }
      // SPDX-License-Identifier: MIT
      // OpenZeppelin Contracts v4.4.1 (utils/Context.sol)
      pragma solidity ^0.8.0;
      import "../proxy/utils/Initializable.sol";
      /**
       * @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 ContextUpgradeable is Initializable {
          function __Context_init() internal onlyInitializing {
          }
          function __Context_init_unchained() internal onlyInitializing {
          }
          function _msgSender() internal view virtual returns (address) {
              return msg.sender;
          }
          function _msgData() internal view virtual returns (bytes calldata) {
              return msg.data;
          }
          /**
           * @dev This empty reserved space is put in place to allow future versions to add new
           * variables without shifting down storage in the inheritance chain.
           * See https://docs.openzeppelin.com/contracts/4.x/upgradeable#storage_gaps
           */
          uint256[50] private __gap;
      }
      // SPDX-License-Identifier: MIT
      // OpenZeppelin Contracts (last updated v4.9.0) (token/ERC20/IERC20.sol)
      pragma solidity ^0.8.0;
      /**
       * @dev Interface of the ERC20 standard as defined in the EIP.
       */
      interface IERC20 {
          /**
           * @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 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 `to`.
           *
           * Returns a boolean value indicating whether the operation succeeded.
           *
           * Emits a {Transfer} event.
           */
          function transfer(address to, 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 `from` to `to` 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 from, address to, uint256 amount) external returns (bool);
      }
      

      File 3 of 3: AirdropERC20Claimable
      // SPDX-License-Identifier: Apache 2.0
      pragma solidity ^0.8.0;
      /// @author thirdweb
      import "../lib/Address.sol";
      import "./interface/IMulticall.sol";
      /**
       * @dev Provides a function to batch together multiple calls in a single external call.
       *
       * _Available since v4.1._
       */
      contract Multicall is IMulticall {
          /**
           *  @notice Receives and executes a batch of function calls on this contract.
           *  @dev Receives and executes a batch of function calls on this contract.
           *
           *  @param data The bytes data that makes up the batch of function calls to execute.
           *  @return results The bytes data that makes up the result of the batch of function calls executed.
           */
          function multicall(bytes[] calldata data) external returns (bytes[] memory results) {
              results = new bytes[](data.length);
              address sender = _msgSender();
              bool isForwarder = msg.sender != sender;
              for (uint256 i = 0; i < data.length; i++) {
                  if (isForwarder) {
                      results[i] = Address.functionDelegateCall(address(this), abi.encodePacked(data[i], sender));
                  } else {
                      results[i] = Address.functionDelegateCall(address(this), data[i]);
                  }
              }
              return results;
          }
          /// @notice Returns the sender in the given execution context.
          function _msgSender() internal view virtual returns (address) {
              return msg.sender;
          }
      }
      // SPDX-License-Identifier: MIT
      pragma solidity ^0.8.0;
      /// @author thirdweb
      /**
       * @dev Provides a function to batch together multiple calls in a single external call.
       *
       * _Available since v4.1._
       */
      interface IMulticall {
          /**
           * @dev Receives and executes a batch of function calls on this contract.
           */
          function multicall(bytes[] calldata data) external returns (bytes[] memory results);
      }
      // SPDX-License-Identifier: MIT
      // OpenZeppelin Contracts v4.4.0 (metatx/ERC2771Context.sol)
      pragma solidity ^0.8.11;
      import "@openzeppelin/contracts-upgradeable/utils/ContextUpgradeable.sol";
      import "@openzeppelin/contracts-upgradeable/proxy/utils/Initializable.sol";
      /**
       * @dev Context variant with ERC2771 support.
       */
      abstract contract ERC2771ContextUpgradeable is Initializable, ContextUpgradeable {
          mapping(address => bool) private _trustedForwarder;
          function __ERC2771Context_init(address[] memory trustedForwarder) internal onlyInitializing {
              __Context_init_unchained();
              __ERC2771Context_init_unchained(trustedForwarder);
          }
          function __ERC2771Context_init_unchained(address[] memory trustedForwarder) internal onlyInitializing {
              for (uint256 i = 0; i < trustedForwarder.length; i++) {
                  _trustedForwarder[trustedForwarder[i]] = true;
              }
          }
          function isTrustedForwarder(address forwarder) public view virtual returns (bool) {
              return _trustedForwarder[forwarder];
          }
          function _msgSender() internal view virtual override returns (address sender) {
              if (isTrustedForwarder(msg.sender)) {
                  // The assembly code is more direct than the Solidity version using `abi.decode`.
                  assembly {
                      sender := shr(96, calldataload(sub(calldatasize(), 20)))
                  }
              } else {
                  return super._msgSender();
              }
          }
          function _msgData() internal view virtual override returns (bytes calldata) {
              if (isTrustedForwarder(msg.sender)) {
                  return msg.data[:msg.data.length - 20];
              } else {
                  return super._msgData();
              }
          }
          uint256[49] private __gap;
      }
      // SPDX-License-Identifier: Apache-2.0
      pragma solidity ^0.8.1;
      /// @author thirdweb, OpenZeppelin Contracts (v4.9.0)
      /**
       * @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
           *
           * Furthermore, `isContract` will also return true if the target contract within
           * the same transaction is already scheduled for destruction by `SELFDESTRUCT`,
           * which only has an effect at the end of a transaction.
           * ====
           *
           * [IMPORTANT]
           * ====
           * You shouldn't rely on `isContract` to protect against flash loan attacks!
           *
           * Preventing calls from contracts is highly discouraged. It breaks composability, breaks support for smart wallets
           * like Gnosis Safe, and does not provide security since it can be circumvented by calling from a contract
           * constructor.
           * ====
           */
          function isContract(address account) internal view returns (bool) {
              // This method relies on extcodesize/address.code.length, which returns 0
              // for contracts in construction, since the code is only stored at the end
              // of the constructor execution.
              return account.code.length > 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://consensys.net/diligence/blog/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/v0.8.0/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 functionCallWithValue(target, data, 0, "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");
              (bool success, bytes memory returndata) = target.call{ value: value }(data);
              return verifyCallResultFromTarget(target, 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) {
              (bool success, bytes memory returndata) = target.staticcall(data);
              return verifyCallResultFromTarget(target, 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) {
              (bool success, bytes memory returndata) = target.delegatecall(data);
              return verifyCallResultFromTarget(target, success, returndata, errorMessage);
          }
          /**
           * @dev Tool to verify that a low level call to smart-contract was successful, and revert (either by bubbling
           * the revert reason or using the provided one) in case of unsuccessful call or if target was not a contract.
           *
           * _Available since v4.8._
           */
          function verifyCallResultFromTarget(
              address target,
              bool success,
              bytes memory returndata,
              string memory errorMessage
          ) internal view returns (bytes memory) {
              if (success) {
                  if (returndata.length == 0) {
                      // only check isContract if the call was successful and the return data is empty
                      // otherwise we already know that it was a contract
                      require(isContract(target), "Address: call to non-contract");
                  }
                  return returndata;
              } else {
                  _revert(returndata, errorMessage);
              }
          }
          /**
           * @dev Tool to verify that a low level call was successful, and revert if it wasn't, either by bubbling the
           * revert reason or 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 {
                  _revert(returndata, errorMessage);
              }
          }
          function _revert(bytes memory returndata, string memory errorMessage) private pure {
              // 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
                  /// @solidity memory-safe-assembly
                  assembly {
                      let returndata_size := mload(returndata)
                      revert(add(32, returndata), returndata_size)
                  }
              } else {
                  revert(errorMessage);
              }
          }
      }
      // SPDX-License-Identifier: Apache 2.0
      pragma solidity ^0.8.0;
      /// @author thirdweb
      library MerkleProof {
          function verify(bytes32[] memory proof, bytes32 root, bytes32 leaf) internal pure returns (bool, uint256) {
              bytes32 computedHash = leaf;
              uint256 index = 0;
              for (uint256 i = 0; i < proof.length; i++) {
                  index *= 2;
                  bytes32 proofElement = proof[i];
                  if (computedHash <= proofElement) {
                      // Hash(current computed hash + current element of the proof)
                      computedHash = keccak256(abi.encodePacked(computedHash, proofElement));
                  } else {
                      // Hash(current element of the proof + current computed hash)
                      computedHash = keccak256(abi.encodePacked(proofElement, computedHash));
                      index += 1;
                  }
              }
              // Check if the computed hash (root) is equal to the provided root
              return (computedHash == root, index);
          }
      }
      // SPDX-License-Identifier: Apache-2.0
      pragma solidity ^0.8.11;
      /**
       *  Thirdweb's `Airdrop` contracts provide a lightweight and easy to use mechanism
       *  to drop tokens.
       *
       *  `AirdropERC20Claimable` contract is an airdrop contract for ERC20 tokens. It follows a
       *  pull mechanism for transfer of tokens, where allowlisted recipients can claim tokens from
       *  the contract.
       */
      interface IAirdropERC20Claimable {
          /// @dev Emitted when tokens are claimed.
          event TokensClaimed(address indexed claimer, address indexed receiver, uint256 quantityClaimed);
          /**
           *  @notice Lets an account claim a given quantity of NFTs.
           *
           *  @param receiver                       The receiver of the NFTs to claim.
           *  @param quantity                       The quantity of NFTs to claim.
           *  @param proofs                         The proof of the claimer's inclusion in the merkle root allowlist
           *                                        of the claim conditions that apply.
           *  @param proofMaxQuantityForWallet      The maximum number of NFTs an address included in an
           *                                        allowlist can claim.
           */
          function claim(
              address receiver,
              uint256 quantity,
              bytes32[] calldata proofs,
              uint256 proofMaxQuantityForWallet
          ) external;
      }
      // SPDX-License-Identifier: Apache-2.0
      pragma solidity ^0.8.11;
      /// @author thirdweb
      //   $$\\     $$\\       $$\\                 $$\\                         $$\\
      //   $$ |    $$ |      \\__|                $$ |                        $$ |
      // $$$$$$\\   $$$$$$$\\  $$\\  $$$$$$\\   $$$$$$$ |$$\\  $$\\  $$\\  $$$$$$\\  $$$$$$$\\
      // \\_$$  _|  $$  __$$\\ $$ |$$  __$$\\ $$  __$$ |$$ | $$ | $$ |$$  __$$\\ $$  __$$\\
      //   $$ |    $$ |  $$ |$$ |$$ |  \\__|$$ /  $$ |$$ | $$ | $$ |$$$$$$$$ |$$ |  $$ |
      //   $$ |$$\\ $$ |  $$ |$$ |$$ |      $$ |  $$ |$$ | $$ | $$ |$$   ____|$$ |  $$ |
      //   \\$$$$  |$$ |  $$ |$$ |$$ |      \\$$$$$$$ |\\$$$$$\\$$$$  |\\$$$$$$$\\ $$$$$$$  |
      //    \\____/ \\__|  \\__|\\__|\\__|       \\_______| \\_____\\____/  \\_______|\\_______/
      //  ==========  External imports    ==========
      import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
      import "@openzeppelin/contracts-upgradeable/security/ReentrancyGuardUpgradeable.sol";
      import "../../../extension/Multicall.sol";
      //  ==========  Internal imports    ==========
      import "../../interface/airdrop/IAirdropERC20Claimable.sol";
      //  ==========  Features    ==========
      import "../../../external-deps/openzeppelin/metatx/ERC2771ContextUpgradeable.sol";
      import "../../../lib/MerkleProof.sol";
      contract AirdropERC20Claimable is
          Initializable,
          ReentrancyGuardUpgradeable,
          ERC2771ContextUpgradeable,
          Multicall,
          IAirdropERC20Claimable
      {
          /*///////////////////////////////////////////////////////////////
                                  State variables
          //////////////////////////////////////////////////////////////*/
          /// @dev address of token being airdropped.
          address public airdropTokenAddress;
          /// @dev address of owner of tokens being airdropped.
          address public tokenOwner;
          /// @dev number tokens available to claim.
          uint256 public availableAmount;
          /// @dev airdrop expiration timestamp.
          uint256 public expirationTimestamp;
          /// @dev claim limit for open/public claiming without allowlist.
          uint256 public openClaimLimitPerWallet;
          /// @dev merkle root of the allowlist of addresses eligible to claim.
          bytes32 public merkleRoot;
          /*///////////////////////////////////////////////////////////////
                                      Mappings
          //////////////////////////////////////////////////////////////*/
          /// @dev Mapping from address => total number of tokens a wallet has claimed.
          mapping(address => uint256) public supplyClaimedByWallet;
          /*///////////////////////////////////////////////////////////////
                          Constructor + initializer logic
          //////////////////////////////////////////////////////////////*/
          constructor() {
              _disableInitializers();
          }
          /// @dev Initializes the contract, like a constructor.
          function initialize(
              address[] memory _trustedForwarders,
              address _tokenOwner,
              address _airdropTokenAddress,
              uint256 _airdropAmount,
              uint256 _expirationTimestamp,
              uint256 _openClaimLimitPerWallet,
              bytes32 _merkleRoot
          ) external initializer {
              __ReentrancyGuard_init();
              __ERC2771Context_init(_trustedForwarders);
              tokenOwner = _tokenOwner;
              airdropTokenAddress = _airdropTokenAddress;
              availableAmount = _airdropAmount;
              expirationTimestamp = _expirationTimestamp;
              openClaimLimitPerWallet = _openClaimLimitPerWallet;
              merkleRoot = _merkleRoot;
          }
          /*///////////////////////////////////////////////////////////////
                                  Claim logic
          //////////////////////////////////////////////////////////////*/
          /**
           *  @notice Lets an account claim a given quantity of NFTs.
           *
           *  @param _receiver                       The receiver of the NFTs to claim.
           *  @param _quantity                       The quantity of NFTs to claim.
           *  @param _proofs                         The proof of the claimer's inclusion in the merkle root allowlist
           *                                        of the claim conditions that apply.
           *  @param _proofMaxQuantityForWallet      The maximum number of NFTs an address included in an
           *                                        allowlist can claim.
           */
          function claim(
              address _receiver,
              uint256 _quantity,
              bytes32[] calldata _proofs,
              uint256 _proofMaxQuantityForWallet
          ) external nonReentrant {
              address claimer = _msgSender();
              verifyClaim(claimer, _quantity, _proofs, _proofMaxQuantityForWallet);
              _transferClaimedTokens(_receiver, _quantity);
              emit TokensClaimed(_msgSender(), _receiver, _quantity);
          }
          /// @dev Checks a request to claim tokens against the active claim condition's criteria.
          function verifyClaim(
              address _claimer,
              uint256 _quantity,
              bytes32[] calldata _proofs,
              uint256 _proofMaxQuantityForWallet
          ) public view {
              bool isOverride;
              /*
               * Here `isOverride` implies that if the merkle proof verification fails,
               * the claimer would claim through open claim limit instead of allowlisted limit.
               */
              if (merkleRoot != bytes32(0)) {
                  (isOverride, ) = MerkleProof.verify(
                      _proofs,
                      merkleRoot,
                      keccak256(abi.encodePacked(_claimer, _proofMaxQuantityForWallet))
                  );
              }
              uint256 supplyClaimedAlready = supplyClaimedByWallet[_claimer];
              require(_quantity > 0, "Claiming zero tokens");
              require(_quantity <= availableAmount, "exceeds available tokens.");
              uint256 expTimestamp = expirationTimestamp;
              require(expTimestamp == 0 || block.timestamp < expTimestamp, "airdrop expired.");
              uint256 claimLimitForWallet = isOverride ? _proofMaxQuantityForWallet : openClaimLimitPerWallet;
              require(_quantity + supplyClaimedAlready <= claimLimitForWallet, "invalid quantity.");
          }
          /// @dev Transfers the tokens being claimed.
          function _transferClaimedTokens(address _to, uint256 _quantityBeingClaimed) internal {
              // if transfer claimed tokens is called when `to != msg.sender`, it'd use msg.sender's limits.
              // behavior would be similar to `msg.sender` mint for itself, then transfer to `_to`.
              supplyClaimedByWallet[_msgSender()] += _quantityBeingClaimed;
              availableAmount -= _quantityBeingClaimed;
              require(IERC20(airdropTokenAddress).transferFrom(tokenOwner, _to, _quantityBeingClaimed), "transfer failed");
          }
          /*///////////////////////////////////////////////////////////////
                              Miscellaneous
          //////////////////////////////////////////////////////////////*/
          function _msgSender()
              internal
              view
              virtual
              override(ERC2771ContextUpgradeable, Multicall)
              returns (address sender)
          {
              return ERC2771ContextUpgradeable._msgSender();
          }
      }
      // SPDX-License-Identifier: MIT
      // OpenZeppelin Contracts (last updated v4.9.0) (proxy/utils/Initializable.sol)
      pragma solidity ^0.8.2;
      import "../../utils/AddressUpgradeable.sol";
      /**
       * @dev This is a base contract to aid in writing upgradeable contracts, or any kind of contract that will be deployed
       * behind a proxy. Since proxied contracts do not make use of a constructor, it's common to move constructor logic to an
       * external initializer function, usually called `initialize`. It then becomes necessary to protect this initializer
       * function so it can only be called once. The {initializer} modifier provided by this contract will have this effect.
       *
       * The initialization functions use a version number. Once a version number is used, it is consumed and cannot be
       * reused. This mechanism prevents re-execution of each "step" but allows the creation of new initialization steps in
       * case an upgrade adds a module that needs to be initialized.
       *
       * For example:
       *
       * [.hljs-theme-light.nopadding]
       * ```solidity
       * contract MyToken is ERC20Upgradeable {
       *     function initialize() initializer public {
       *         __ERC20_init("MyToken", "MTK");
       *     }
       * }
       *
       * contract MyTokenV2 is MyToken, ERC20PermitUpgradeable {
       *     function initializeV2() reinitializer(2) public {
       *         __ERC20Permit_init("MyToken");
       *     }
       * }
       * ```
       *
       * TIP: To avoid leaving the proxy in an uninitialized state, the initializer function should be called as early as
       * possible by providing the encoded function call as the `_data` argument to {ERC1967Proxy-constructor}.
       *
       * CAUTION: When used with inheritance, manual care must be taken to not invoke a parent initializer twice, or to ensure
       * that all initializers are idempotent. This is not verified automatically as constructors are by Solidity.
       *
       * [CAUTION]
       * ====
       * Avoid leaving a contract uninitialized.
       *
       * An uninitialized contract can be taken over by an attacker. This applies to both a proxy and its implementation
       * contract, which may impact the proxy. To prevent the implementation contract from being used, you should invoke
       * the {_disableInitializers} function in the constructor to automatically lock it when it is deployed:
       *
       * [.hljs-theme-light.nopadding]
       * ```
       * /// @custom:oz-upgrades-unsafe-allow constructor
       * constructor() {
       *     _disableInitializers();
       * }
       * ```
       * ====
       */
      abstract contract Initializable {
          /**
           * @dev Indicates that the contract has been initialized.
           * @custom:oz-retyped-from bool
           */
          uint8 private _initialized;
          /**
           * @dev Indicates that the contract is in the process of being initialized.
           */
          bool private _initializing;
          /**
           * @dev Triggered when the contract has been initialized or reinitialized.
           */
          event Initialized(uint8 version);
          /**
           * @dev A modifier that defines a protected initializer function that can be invoked at most once. In its scope,
           * `onlyInitializing` functions can be used to initialize parent contracts.
           *
           * Similar to `reinitializer(1)`, except that functions marked with `initializer` can be nested in the context of a
           * constructor.
           *
           * Emits an {Initialized} event.
           */
          modifier initializer() {
              bool isTopLevelCall = !_initializing;
              require(
                  (isTopLevelCall && _initialized < 1) || (!AddressUpgradeable.isContract(address(this)) && _initialized == 1),
                  "Initializable: contract is already initialized"
              );
              _initialized = 1;
              if (isTopLevelCall) {
                  _initializing = true;
              }
              _;
              if (isTopLevelCall) {
                  _initializing = false;
                  emit Initialized(1);
              }
          }
          /**
           * @dev A modifier that defines a protected reinitializer function that can be invoked at most once, and only if the
           * contract hasn't been initialized to a greater version before. In its scope, `onlyInitializing` functions can be
           * used to initialize parent contracts.
           *
           * A reinitializer may be used after the original initialization step. This is essential to configure modules that
           * are added through upgrades and that require initialization.
           *
           * When `version` is 1, this modifier is similar to `initializer`, except that functions marked with `reinitializer`
           * cannot be nested. If one is invoked in the context of another, execution will revert.
           *
           * Note that versions can jump in increments greater than 1; this implies that if multiple reinitializers coexist in
           * a contract, executing them in the right order is up to the developer or operator.
           *
           * WARNING: setting the version to 255 will prevent any future reinitialization.
           *
           * Emits an {Initialized} event.
           */
          modifier reinitializer(uint8 version) {
              require(!_initializing && _initialized < version, "Initializable: contract is already initialized");
              _initialized = version;
              _initializing = true;
              _;
              _initializing = false;
              emit Initialized(version);
          }
          /**
           * @dev Modifier to protect an initialization function so that it can only be invoked by functions with the
           * {initializer} and {reinitializer} modifiers, directly or indirectly.
           */
          modifier onlyInitializing() {
              require(_initializing, "Initializable: contract is not initializing");
              _;
          }
          /**
           * @dev Locks the contract, preventing any future reinitialization. This cannot be part of an initializer call.
           * Calling this in the constructor of a contract will prevent that contract from being initialized or reinitialized
           * to any version. It is recommended to use this to lock implementation contracts that are designed to be called
           * through proxies.
           *
           * Emits an {Initialized} event the first time it is successfully executed.
           */
          function _disableInitializers() internal virtual {
              require(!_initializing, "Initializable: contract is initializing");
              if (_initialized != type(uint8).max) {
                  _initialized = type(uint8).max;
                  emit Initialized(type(uint8).max);
              }
          }
          /**
           * @dev Returns the highest version that has been initialized. See {reinitializer}.
           */
          function _getInitializedVersion() internal view returns (uint8) {
              return _initialized;
          }
          /**
           * @dev Returns `true` if the contract is currently initializing. See {onlyInitializing}.
           */
          function _isInitializing() internal view returns (bool) {
              return _initializing;
          }
      }
      // SPDX-License-Identifier: MIT
      // OpenZeppelin Contracts (last updated v4.9.0) (security/ReentrancyGuard.sol)
      pragma solidity ^0.8.0;
      import "../proxy/utils/Initializable.sol";
      /**
       * @dev Contract module that helps prevent reentrant calls to a function.
       *
       * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
       * available, which can be applied to functions to make sure there are no nested
       * (reentrant) calls to them.
       *
       * Note that because there is a single `nonReentrant` guard, functions marked as
       * `nonReentrant` may not call one another. This can be worked around by making
       * those functions `private`, and then adding `external` `nonReentrant` entry
       * points to them.
       *
       * TIP: If you would like to learn more about reentrancy and alternative ways
       * to protect against it, check out our blog post
       * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
       */
      abstract contract ReentrancyGuardUpgradeable is Initializable {
          // Booleans are more expensive than uint256 or any type that takes up a full
          // word because each write operation emits an extra SLOAD to first read the
          // slot's contents, replace the bits taken up by the boolean, and then write
          // back. This is the compiler's defense against contract upgrades and
          // pointer aliasing, and it cannot be disabled.
          // The values being non-zero value makes deployment a bit more expensive,
          // but in exchange the refund on every call to nonReentrant will be lower in
          // amount. Since refunds are capped to a percentage of the total
          // transaction's gas, it is best to keep them low in cases like this one, to
          // increase the likelihood of the full refund coming into effect.
          uint256 private constant _NOT_ENTERED = 1;
          uint256 private constant _ENTERED = 2;
          uint256 private _status;
          function __ReentrancyGuard_init() internal onlyInitializing {
              __ReentrancyGuard_init_unchained();
          }
          function __ReentrancyGuard_init_unchained() internal onlyInitializing {
              _status = _NOT_ENTERED;
          }
          /**
           * @dev Prevents a contract from calling itself, directly or indirectly.
           * Calling a `nonReentrant` function from another `nonReentrant`
           * function is not supported. It is possible to prevent this from happening
           * by making the `nonReentrant` function external, and making it call a
           * `private` function that does the actual work.
           */
          modifier nonReentrant() {
              _nonReentrantBefore();
              _;
              _nonReentrantAfter();
          }
          function _nonReentrantBefore() private {
              // On the first call to nonReentrant, _status will be _NOT_ENTERED
              require(_status != _ENTERED, "ReentrancyGuard: reentrant call");
              // Any calls to nonReentrant after this point will fail
              _status = _ENTERED;
          }
          function _nonReentrantAfter() private {
              // By storing the original value once again, a refund is triggered (see
              // https://eips.ethereum.org/EIPS/eip-2200)
              _status = _NOT_ENTERED;
          }
          /**
           * @dev Returns true if the reentrancy guard is currently set to "entered", which indicates there is a
           * `nonReentrant` function in the call stack.
           */
          function _reentrancyGuardEntered() internal view returns (bool) {
              return _status == _ENTERED;
          }
          /**
           * @dev This empty reserved space is put in place to allow future versions to add new
           * variables without shifting down storage in the inheritance chain.
           * See https://docs.openzeppelin.com/contracts/4.x/upgradeable#storage_gaps
           */
          uint256[49] private __gap;
      }
      // SPDX-License-Identifier: MIT
      // OpenZeppelin Contracts (last updated v4.9.0) (utils/Address.sol)
      pragma solidity ^0.8.1;
      /**
       * @dev Collection of functions related to the address type
       */
      library AddressUpgradeable {
          /**
           * @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
           *
           * Furthermore, `isContract` will also return true if the target contract within
           * the same transaction is already scheduled for destruction by `SELFDESTRUCT`,
           * which only has an effect at the end of a transaction.
           * ====
           *
           * [IMPORTANT]
           * ====
           * You shouldn't rely on `isContract` to protect against flash loan attacks!
           *
           * Preventing calls from contracts is highly discouraged. It breaks composability, breaks support for smart wallets
           * like Gnosis Safe, and does not provide security since it can be circumvented by calling from a contract
           * constructor.
           * ====
           */
          function isContract(address account) internal view returns (bool) {
              // This method relies on extcodesize/address.code.length, which returns 0
              // for contracts in construction, since the code is only stored at the end
              // of the constructor execution.
              return account.code.length > 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://consensys.net/diligence/blog/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/v0.8.0/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 functionCallWithValue(target, data, 0, "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");
              (bool success, bytes memory returndata) = target.call{value: value}(data);
              return verifyCallResultFromTarget(target, 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) {
              (bool success, bytes memory returndata) = target.staticcall(data);
              return verifyCallResultFromTarget(target, 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) {
              (bool success, bytes memory returndata) = target.delegatecall(data);
              return verifyCallResultFromTarget(target, success, returndata, errorMessage);
          }
          /**
           * @dev Tool to verify that a low level call to smart-contract was successful, and revert (either by bubbling
           * the revert reason or using the provided one) in case of unsuccessful call or if target was not a contract.
           *
           * _Available since v4.8._
           */
          function verifyCallResultFromTarget(
              address target,
              bool success,
              bytes memory returndata,
              string memory errorMessage
          ) internal view returns (bytes memory) {
              if (success) {
                  if (returndata.length == 0) {
                      // only check isContract if the call was successful and the return data is empty
                      // otherwise we already know that it was a contract
                      require(isContract(target), "Address: call to non-contract");
                  }
                  return returndata;
              } else {
                  _revert(returndata, errorMessage);
              }
          }
          /**
           * @dev Tool to verify that a low level call was successful, and revert if it wasn't, either by bubbling the
           * revert reason or 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 {
                  _revert(returndata, errorMessage);
              }
          }
          function _revert(bytes memory returndata, string memory errorMessage) private pure {
              // 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
                  /// @solidity memory-safe-assembly
                  assembly {
                      let returndata_size := mload(returndata)
                      revert(add(32, returndata), returndata_size)
                  }
              } else {
                  revert(errorMessage);
              }
          }
      }
      // SPDX-License-Identifier: MIT
      // OpenZeppelin Contracts v4.4.1 (utils/Context.sol)
      pragma solidity ^0.8.0;
      import "../proxy/utils/Initializable.sol";
      /**
       * @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 ContextUpgradeable is Initializable {
          function __Context_init() internal onlyInitializing {
          }
          function __Context_init_unchained() internal onlyInitializing {
          }
          function _msgSender() internal view virtual returns (address) {
              return msg.sender;
          }
          function _msgData() internal view virtual returns (bytes calldata) {
              return msg.data;
          }
          /**
           * @dev This empty reserved space is put in place to allow future versions to add new
           * variables without shifting down storage in the inheritance chain.
           * See https://docs.openzeppelin.com/contracts/4.x/upgradeable#storage_gaps
           */
          uint256[50] private __gap;
      }
      // SPDX-License-Identifier: MIT
      // OpenZeppelin Contracts (last updated v4.9.0) (token/ERC20/IERC20.sol)
      pragma solidity ^0.8.0;
      /**
       * @dev Interface of the ERC20 standard as defined in the EIP.
       */
      interface IERC20 {
          /**
           * @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 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 `to`.
           *
           * Returns a boolean value indicating whether the operation succeeded.
           *
           * Emits a {Transfer} event.
           */
          function transfer(address to, 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 `from` to `to` 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 from, address to, uint256 amount) external returns (bool);
      }