// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

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

        uint256 size;
        assembly {
            size := extcodesize(account)
        }
        return size > 0;
    }

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

        (bool success, ) = recipient.call{value: amount}("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

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

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

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

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

        (bool success, bytes memory returndata) = target.call{value: value}(data);
        return verifyCallResult(success, returndata, errorMessage);
    }

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

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

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

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

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

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

    /**
     * @dev Tool to verifies that a low level call was successful, and revert if it wasn't, either by bubbling the
     * revert reason using the provided one.
     *
     * _Available since v4.3._
     */
    function verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal pure returns (bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

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

// SPDX-License-Identifier: UNLICENSED
pragma solidity 0.8.13;

import { LibAsset } from "../Libraries/LibAsset.sol";

/// @title Fee Collector
/// @author LI.FI (https://li.fi)
/// @notice Provides functionality for collecting integrator fees
contract FeeCollector {
    /// State ///

    // Integrator -> TokenAddress -> Balance
    mapping(address => mapping(address => uint256)) private _balances;
    // TokenAddress -> Balance
    mapping(address => uint256) private _lifiBalances;
    address public owner;
    address public pendingOwner;

    /// Errors ///
    error Unauthorized(address);
    error NoNullOwner();
    error NewOwnerMustNotBeSelf();
    error NoPendingOwnershipTransfer();
    error NotPendingOwner();
    error TransferFailure();

    /// Events ///
    event FeesCollected(address indexed _token, address indexed _integrator, uint256 _integratorFee, uint256 _lifiFee);
    event FeesWithdrawn(address indexed _token, address indexed _to, uint256 _amount);
    event LiFiFeesWithdrawn(address indexed _token, address indexed _to, uint256 _amount);
    event OwnershipTransferRequested(address indexed _from, address indexed _to);
    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /// Constructor ///

    constructor(address _owner) {
        owner = _owner;
    }

    /// External Methods ///

    /// @notice Collects fees for the integrator
    /// @param tokenAddress address of the token to collect fees for
    /// @param integratorFee amount of fees to collect going to the integrator
    /// @param lifiFee amount of fees to collect going to lifi
    /// @param integratorAddress address of the integrator
    function collectTokenFees(
        address tokenAddress,
        uint256 integratorFee,
        uint256 lifiFee,
        address integratorAddress
    ) external {
        LibAsset.depositAsset(tokenAddress, integratorFee + lifiFee);
        _balances[integratorAddress][tokenAddress] += integratorFee;
        _lifiBalances[tokenAddress] += lifiFee;
        emit FeesCollected(tokenAddress, integratorAddress, integratorFee, lifiFee);
    }

    /// @notice Collects fees for the integrator in native token
    /// @param integratorFee amount of fees to collect going to the integrator
    /// @param lifiFee amount of fees to collect going to lifi
    /// @param integratorAddress address of the integrator
    function collectNativeFees(
        uint256 integratorFee,
        uint256 lifiFee,
        address integratorAddress
    ) external payable {
        _balances[integratorAddress][LibAsset.NULL_ADDRESS] += integratorFee;
        _lifiBalances[LibAsset.NULL_ADDRESS] += lifiFee;
        uint256 remaining = msg.value - (integratorFee + lifiFee);
        // Prevent extra native token from being locked in the contract
        if (remaining > 0) {
            (bool success, ) = msg.sender.call{ value: remaining }("");
            if (!success) {
                revert TransferFailure();
            }
        }
        emit FeesCollected(LibAsset.NULL_ADDRESS, integratorAddress, integratorFee, lifiFee);
    }

    /// @notice Withdraw fees and sends to the integrator
    /// @param tokenAddress address of the token to withdraw fees for
    function withdrawIntegratorFees(address tokenAddress) external {
        uint256 balance = _balances[msg.sender][tokenAddress];
        if (balance == 0) {
            return;
        }
        _balances[msg.sender][tokenAddress] = 0;
        LibAsset.transferAsset(tokenAddress, payable(msg.sender), balance);
        emit FeesWithdrawn(tokenAddress, msg.sender, balance);
    }

    /// @notice Batch withdraw fees and sends to the integrator
    /// @param tokenAddresses addresses of the tokens to withdraw fees for
    function batchWithdrawIntegratorFees(address[] memory tokenAddresses) external {
        uint256 length = tokenAddresses.length;
        uint256 balance;
        for (uint256 i = 0; i < length; i++) {
            balance = _balances[msg.sender][tokenAddresses[i]];
            if (balance == 0) {
                continue;
            }
            _balances[msg.sender][tokenAddresses[i]] = 0;
            LibAsset.transferAsset(tokenAddresses[i], payable(msg.sender), balance);
            emit FeesWithdrawn(tokenAddresses[i], msg.sender, balance);
        }
    }

    /// @notice Withdraws fees and sends to lifi
    /// @param tokenAddress address of the token to withdraw fees for
    function withdrawLifiFees(address tokenAddress) external {
        _enforceIsContractOwner();

        uint256 balance = _lifiBalances[tokenAddress];
        if (balance == 0) {
            return;
        }
        _lifiBalances[tokenAddress] = 0;
        LibAsset.transferAsset(tokenAddress, payable(owner), balance);
        emit LiFiFeesWithdrawn(tokenAddress, msg.sender, balance);
    }

    /// @notice Batch withdraws fees and sends to lifi
    /// @param tokenAddresses addresses of the tokens to withdraw fees for
    function batchWithdrawLifiFees(address[] memory tokenAddresses) external {
        _enforceIsContractOwner();

        uint256 length = tokenAddresses.length;
        uint256 balance;
        for (uint256 i = 0; i < length; i++) {
            balance = _lifiBalances[tokenAddresses[i]];
            if (balance == 0) {
                continue;
            }
            _lifiBalances[tokenAddresses[i]] = 0;
            LibAsset.transferAsset(tokenAddresses[i], payable(owner), balance);
            emit LiFiFeesWithdrawn(tokenAddresses[i], msg.sender, balance);
        }
    }

    /// @notice Returns the balance of the integrator
    /// @param integratorAddress address of the integrator
    /// @param tokenAddress address of the token to get the balance of
    function getTokenBalance(address integratorAddress, address tokenAddress) external view returns (uint256) {
        return _balances[integratorAddress][tokenAddress];
    }

    /// @notice Returns the balance of lifi
    /// @param tokenAddress address of the token to get the balance of
    function getLifiTokenBalance(address tokenAddress) external view returns (uint256) {
        return _lifiBalances[tokenAddress];
    }

    /// @notice Intitiates transfer of ownership to a new address
    /// @param _newOwner the address to transfer ownership to
    function transferOwnership(address _newOwner) external {
        _enforceIsContractOwner();

        if (_newOwner == LibAsset.NULL_ADDRESS) revert NoNullOwner();

        if (_newOwner == owner) revert NewOwnerMustNotBeSelf();

        pendingOwner = _newOwner;
        emit OwnershipTransferRequested(msg.sender, pendingOwner);
    }

    /// @notice Cancel transfer of ownership
    function cancelOnwershipTransfer() external {
        _enforceIsContractOwner();

        if (pendingOwner == LibAsset.NULL_ADDRESS) revert NoPendingOwnershipTransfer();
        pendingOwner = LibAsset.NULL_ADDRESS;
    }

    /// @notice Confirms transfer of ownership to the calling address (msg.sender)
    function confirmOwnershipTransfer() external {
        if (msg.sender != pendingOwner) revert NotPendingOwner();
        owner = pendingOwner;
        pendingOwner = LibAsset.NULL_ADDRESS;
        emit OwnershipTransferred(owner, pendingOwner);
    }

    /// Private Methods ///

    /// @notice Ensures that the calling address is the owner of the contract
    function _enforceIsContractOwner() private view {
        if (msg.sender != owner) {
            revert Unauthorized(msg.sender);
        }
    }
}

// SPDX-License-Identifier: MIT
pragma solidity 0.8.13;

error InvalidAmount();
error TokenAddressIsZero();
error CannotBridgeToSameNetwork();
error ZeroPostSwapBalance();
error InvalidBridgeConfigLength();
error NoSwapDataProvided();
error NativeValueWithERC();
error ContractCallNotAllowed();
error NullAddrIsNotAValidSpender();
error NullAddrIsNotAnERC20Token();
error NoTransferToNullAddress();
error NativeAssetTransferFailed();
error InvalidContract();
error InvalidConfig();

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

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

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

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

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

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

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

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

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

// SPDX-License-Identifier: UNLICENSED
pragma solidity 0.8.13;
import { NullAddrIsNotAnERC20Token, NullAddrIsNotAValidSpender, NoTransferToNullAddress, InvalidAmount, NativeValueWithERC, NativeAssetTransferFailed } from "../Errors/GenericErrors.sol";
import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";

/// @title LibAsset
/// @author Connext <support@connext.network>
/// @notice This library contains helpers for dealing with onchain transfers
///         of assets, including accounting for the native asset `assetId`
///         conventions and any noncompliant ERC20 transfers
library LibAsset {
    uint256 private constant MAX_INT = type(uint256).max;

    address internal constant NULL_ADDRESS = 0x0000000000000000000000000000000000000000; //address(0)

    /// @dev All native assets use the empty address for their asset id
    ///      by convention

    address internal constant NATIVE_ASSETID = NULL_ADDRESS; //address(0)

    /// @notice Gets the balance of the inheriting contract for the given asset
    /// @param assetId The asset identifier to get the balance of
    /// @return Balance held by contracts using this library
    function getOwnBalance(address assetId) internal view returns (uint256) {
        return assetId == NATIVE_ASSETID ? address(this).balance : IERC20(assetId).balanceOf(address(this));
    }

    /// @notice Transfers ether from the inheriting contract to a given
    ///         recipient
    /// @param recipient Address to send ether to
    /// @param amount Amount to send to given recipient
    function transferNativeAsset(address payable recipient, uint256 amount) private {
        if (recipient == NULL_ADDRESS) revert NoTransferToNullAddress();
        // solhint-disable-next-line avoid-low-level-calls
        (bool success, ) = recipient.call{ value: amount }("");
        if (!success) revert NativeAssetTransferFailed();
    }

    /// @notice Gives MAX approval for another address to spend tokens
    /// @param assetId Token address to transfer
    /// @param spender Address to give spend approval to
    /// @param amount Amount to approve for spending
    function maxApproveERC20(
        IERC20 assetId,
        address spender,
        uint256 amount
    ) internal {
        if (address(assetId) == NATIVE_ASSETID) return;
        if (spender == NULL_ADDRESS) revert NullAddrIsNotAValidSpender();
        uint256 allowance = assetId.allowance(address(this), spender);
        if (allowance < amount) SafeERC20.safeApprove(IERC20(assetId), spender, MAX_INT);
    }

    /// @notice Transfers tokens from the inheriting contract to a given
    ///         recipient
    /// @param assetId Token address to transfer
    /// @param recipient Address to send token to
    /// @param amount Amount to send to given recipient
    function transferERC20(
        address assetId,
        address recipient,
        uint256 amount
    ) private {
        if (isNativeAsset(assetId)) revert NullAddrIsNotAnERC20Token();
        SafeERC20.safeTransfer(IERC20(assetId), recipient, amount);
    }

    /// @notice Transfers tokens from a sender to a given recipient
    /// @param assetId Token address to transfer
    /// @param from Address of sender/owner
    /// @param to Address of recipient/spender
    /// @param amount Amount to transfer from owner to spender
    function transferFromERC20(
        address assetId,
        address from,
        address to,
        uint256 amount
    ) internal {
        if (assetId == NATIVE_ASSETID) revert NullAddrIsNotAnERC20Token();
        if (to == NULL_ADDRESS) revert NoTransferToNullAddress();
        SafeERC20.safeTransferFrom(IERC20(assetId), from, to, amount);
    }

    /// @notice Deposits an asset into the contract and performs checks to avoid NativeValueWithERC
    /// @param tokenId Token to deposit
    /// @param amount Amount to deposit
    /// @param isNative Wether the token is native or ERC20
    function depositAsset(
        address tokenId,
        uint256 amount,
        bool isNative
    ) internal {
        if (amount == 0) revert InvalidAmount();
        if (isNative) {
            if (msg.value != amount) revert InvalidAmount();
        } else {
            if (msg.value != 0) revert NativeValueWithERC();
            uint256 _fromTokenBalance = LibAsset.getOwnBalance(tokenId);
            LibAsset.transferFromERC20(tokenId, msg.sender, address(this), amount);
            if (LibAsset.getOwnBalance(tokenId) - _fromTokenBalance != amount) revert InvalidAmount();
        }
    }

    /// @notice Overload for depositAsset(address tokenId, uint256 amount, bool isNative)
    /// @param tokenId Token to deposit
    /// @param amount Amount to deposit
    function depositAsset(address tokenId, uint256 amount) internal {
        return depositAsset(tokenId, amount, tokenId == NATIVE_ASSETID);
    }

    /// @notice Determines whether the given assetId is the native asset
    /// @param assetId The asset identifier to evaluate
    /// @return Boolean indicating if the asset is the native asset
    function isNativeAsset(address assetId) internal pure returns (bool) {
        return assetId == NATIVE_ASSETID;
    }

    /// @notice Wrapper function to transfer a given asset (native or erc20) to
    ///         some recipient. Should handle all non-compliant return value
    ///         tokens as well by using the SafeERC20 contract by open zeppelin.
    /// @param assetId Asset id for transfer (address(0) for native asset,
    ///                token address for erc20s)
    /// @param recipient Address to send asset to
    /// @param amount Amount to send to given recipient
    function transferAsset(
        address assetId,
        address payable recipient,
        uint256 amount
    ) internal {
        (assetId == NATIVE_ASSETID)
            ? transferNativeAsset(recipient, amount)
            : transferERC20(assetId, recipient, amount);
    }

    /// @dev Checks whether the given address is a contract and contains code
    function isContract(address _contractAddr) internal view returns (bool) {
        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly {
            size := extcodesize(_contractAddr)
        }
        return size > 0;
    }
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "../IERC20.sol";
import "../../../utils/Address.sol";

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

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

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

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

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

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

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

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

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