Contract Diff Checker

Contract Name:
LimitOrderProtocol

Contract Source Code:

// SPDX-License-Identifier: MIT

pragma solidity 0.8.10;

import "@openzeppelin/contracts/utils/cryptography/draft-EIP712.sol";
import "./OrderMixin.sol";
import "./OrderRFQMixin.sol";

/// @title 1inch Limit Order Protocol v2
contract LimitOrderProtocol is
    EIP712("1inch Limit Order Protocol", "2"),
    OrderMixin,
    OrderRFQMixin
{
    // solhint-disable-next-line func-name-mixedcase
    function DOMAIN_SEPARATOR() external view returns(bytes32) {
        return _domainSeparatorV4();
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.0 (utils/cryptography/draft-EIP712.sol)

pragma solidity ^0.8.0;

import "./ECDSA.sol";

/**
 * @dev https://eips.ethereum.org/EIPS/eip-712[EIP 712] is a standard for hashing and signing of typed structured data.
 *
 * The encoding specified in the EIP is very generic, and such a generic implementation in Solidity is not feasible,
 * thus this contract does not implement the encoding itself. Protocols need to implement the type-specific encoding
 * they need in their contracts using a combination of `abi.encode` and `keccak256`.
 *
 * This contract implements the EIP 712 domain separator ({_domainSeparatorV4}) that is used as part of the encoding
 * scheme, and the final step of the encoding to obtain the message digest that is then signed via ECDSA
 * ({_hashTypedDataV4}).
 *
 * The implementation of the domain separator was designed to be as efficient as possible while still properly updating
 * the chain id to protect against replay attacks on an eventual fork of the chain.
 *
 * NOTE: This contract implements the version of the encoding known as "v4", as implemented by the JSON RPC method
 * https://docs.metamask.io/guide/signing-data.html[`eth_signTypedDataV4` in MetaMask].
 *
 * _Available since v3.4._
 */
abstract contract EIP712 {
    /* solhint-disable var-name-mixedcase */
    // Cache the domain separator as an immutable value, but also store the chain id that it corresponds to, in order to
    // invalidate the cached domain separator if the chain id changes.
    bytes32 private immutable _CACHED_DOMAIN_SEPARATOR;
    uint256 private immutable _CACHED_CHAIN_ID;
    address private immutable _CACHED_THIS;

    bytes32 private immutable _HASHED_NAME;
    bytes32 private immutable _HASHED_VERSION;
    bytes32 private immutable _TYPE_HASH;

    /* solhint-enable var-name-mixedcase */

    /**
     * @dev Initializes the domain separator and parameter caches.
     *
     * The meaning of `name` and `version` is specified in
     * https://eips.ethereum.org/EIPS/eip-712#definition-of-domainseparator[EIP 712]:
     *
     * - `name`: the user readable name of the signing domain, i.e. the name of the DApp or the protocol.
     * - `version`: the current major version of the signing domain.
     *
     * NOTE: These parameters cannot be changed except through a xref:learn::upgrading-smart-contracts.adoc[smart
     * contract upgrade].
     */
    constructor(string memory name, string memory version) {
        bytes32 hashedName = keccak256(bytes(name));
        bytes32 hashedVersion = keccak256(bytes(version));
        bytes32 typeHash = keccak256(
            "EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)"
        );
        _HASHED_NAME = hashedName;
        _HASHED_VERSION = hashedVersion;
        _CACHED_CHAIN_ID = block.chainid;
        _CACHED_DOMAIN_SEPARATOR = _buildDomainSeparator(typeHash, hashedName, hashedVersion);
        _CACHED_THIS = address(this);
        _TYPE_HASH = typeHash;
    }

    /**
     * @dev Returns the domain separator for the current chain.
     */
    function _domainSeparatorV4() internal view returns (bytes32) {
        if (address(this) == _CACHED_THIS && block.chainid == _CACHED_CHAIN_ID) {
            return _CACHED_DOMAIN_SEPARATOR;
        } else {
            return _buildDomainSeparator(_TYPE_HASH, _HASHED_NAME, _HASHED_VERSION);
        }
    }

    function _buildDomainSeparator(
        bytes32 typeHash,
        bytes32 nameHash,
        bytes32 versionHash
    ) private view returns (bytes32) {
        return keccak256(abi.encode(typeHash, nameHash, versionHash, block.chainid, address(this)));
    }

    /**
     * @dev Given an already https://eips.ethereum.org/EIPS/eip-712#definition-of-hashstruct[hashed struct], this
     * function returns the hash of the fully encoded EIP712 message for this domain.
     *
     * This hash can be used together with {ECDSA-recover} to obtain the signer of a message. For example:
     *
     * ```solidity
     * bytes32 digest = _hashTypedDataV4(keccak256(abi.encode(
     *     keccak256("Mail(address to,string contents)"),
     *     mailTo,
     *     keccak256(bytes(mailContents))
     * )));
     * address signer = ECDSA.recover(digest, signature);
     * ```
     */
    function _hashTypedDataV4(bytes32 structHash) internal view virtual returns (bytes32) {
        return ECDSA.toTypedDataHash(_domainSeparatorV4(), structHash);
    }
}

// SPDX-License-Identifier: MIT

pragma solidity 0.8.10;

import "@openzeppelin/contracts/utils/Address.sol";
import "@openzeppelin/contracts/utils/cryptography/draft-EIP712.sol";
import "@openzeppelin/contracts/utils/cryptography/SignatureChecker.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";

import "./helpers/AmountCalculator.sol";
import "./helpers/ChainlinkCalculator.sol";
import "./helpers/NonceManager.sol";
import "./helpers/PredicateHelper.sol";
import "./interfaces/InteractiveNotificationReceiver.sol";
import "./libraries/ArgumentsDecoder.sol";
import "./libraries/Permitable.sol";

/// @title Regular Limit Order mixin
abstract contract OrderMixin is
    EIP712,
    AmountCalculator,
    ChainlinkCalculator,
    NonceManager,
    PredicateHelper,
    Permitable
{
    using Address for address;
    using ArgumentsDecoder for bytes;

    /// @notice Emitted every time order gets filled, including partial fills
    event OrderFilled(
        address indexed maker,
        bytes32 orderHash,
        uint256 remaining
    );

    /// @notice Emitted when order gets cancelled
    event OrderCanceled(
        address indexed maker,
        bytes32 orderHash,
        uint256 remainingRaw
    );

    // Fixed-size order part with core information
    struct StaticOrder {
        uint256 salt;
        address makerAsset;
        address takerAsset;
        address maker;
        address receiver;
        address allowedSender;  // equals to Zero address on public orders
        uint256 makingAmount;
        uint256 takingAmount;
    }

    // `StaticOrder` extension including variable-sized additional order meta information
    struct Order {
        uint256 salt;
        address makerAsset;
        address takerAsset;
        address maker;
        address receiver;
        address allowedSender;  // equals to Zero address on public orders
        uint256 makingAmount;
        uint256 takingAmount;
        bytes makerAssetData;
        bytes takerAssetData;
        bytes getMakerAmount; // this.staticcall(abi.encodePacked(bytes, swapTakerAmount)) => (swapMakerAmount)
        bytes getTakerAmount; // this.staticcall(abi.encodePacked(bytes, swapMakerAmount)) => (swapTakerAmount)
        bytes predicate;      // this.staticcall(bytes) => (bool)
        bytes permit;         // On first fill: permit.1.call(abi.encodePacked(permit.selector, permit.2))
        bytes interaction;
    }

    bytes32 constant public LIMIT_ORDER_TYPEHASH = keccak256(
        "Order(uint256 salt,address makerAsset,address takerAsset,address maker,address receiver,address allowedSender,uint256 makingAmount,uint256 takingAmount,bytes makerAssetData,bytes takerAssetData,bytes getMakerAmount,bytes getTakerAmount,bytes predicate,bytes permit,bytes interaction)"
    );
    uint256 constant private _ORDER_DOES_NOT_EXIST = 0;
    uint256 constant private _ORDER_FILLED = 1;

    /// @notice Stores unfilled amounts for each order plus one.
    /// Therefore 0 means order doesn't exist and 1 means order was filled
    mapping(bytes32 => uint256) private _remaining;

    /// @notice Returns unfilled amount for order. Throws if order does not exist
    function remaining(bytes32 orderHash) external view returns(uint256) {
        uint256 amount = _remaining[orderHash];
        require(amount != _ORDER_DOES_NOT_EXIST, "LOP: Unknown order");
        unchecked { amount -= 1; }
        return amount;
    }

    /// @notice Returns unfilled amount for order
    /// @return Result Unfilled amount of order plus one if order exists. Otherwise 0
    function remainingRaw(bytes32 orderHash) external view returns(uint256) {
        return _remaining[orderHash];
    }

    /// @notice Same as `remainingRaw` but for multiple orders
    function remainingsRaw(bytes32[] memory orderHashes) external view returns(uint256[] memory) {
        uint256[] memory results = new uint256[](orderHashes.length);
        for (uint256 i = 0; i < orderHashes.length; i++) {
            results[i] = _remaining[orderHashes[i]];
        }
        return results;
    }

    /**
     * @notice Calls every target with corresponding data. Then reverts with CALL_RESULTS_0101011 where zeroes and ones
     * denote failure or success of the corresponding call
     * @param targets Array of addresses that will be called
     * @param data Array of data that will be passed to each call
     */
    function simulateCalls(address[] calldata targets, bytes[] calldata data) external {
        require(targets.length == data.length, "LOP: array size mismatch");
        bytes memory reason = new bytes(targets.length);
        for (uint256 i = 0; i < targets.length; i++) {
            // solhint-disable-next-line avoid-low-level-calls
            (bool success, bytes memory result) = targets[i].call(data[i]);
            if (success && result.length > 0) {
                success = result.length == 32 && result.decodeBool();
            }
            reason[i] = success ? bytes1("1") : bytes1("0");
        }

        // Always revert and provide per call results
        revert(string(abi.encodePacked("CALL_RESULTS_", reason)));
    }

    /// @notice Cancels order by setting remaining amount to zero
    function cancelOrder(Order memory order) external {
        require(order.maker == msg.sender, "LOP: Access denied");

        bytes32 orderHash = hashOrder(order);
        uint256 orderRemaining = _remaining[orderHash];
        require(orderRemaining != _ORDER_FILLED, "LOP: already filled");
        emit OrderCanceled(msg.sender, orderHash, orderRemaining);
        _remaining[orderHash] = _ORDER_FILLED;
    }

    /// @notice Fills an order. If one doesn't exist (first fill) it will be created using order.makerAssetData
    /// @param order Order quote to fill
    /// @param signature Signature to confirm quote ownership
    /// @param makingAmount Making amount
    /// @param takingAmount Taking amount
    /// @param thresholdAmount Specifies maximum allowed takingAmount when takingAmount is zero, otherwise specifies minimum allowed makingAmount
    function fillOrder(
        Order memory order,
        bytes calldata signature,
        uint256 makingAmount,
        uint256 takingAmount,
        uint256 thresholdAmount
    ) external returns(uint256 /* actualMakingAmount */, uint256 /* actualTakingAmount */) {
        return fillOrderTo(order, signature, makingAmount, takingAmount, thresholdAmount, msg.sender);
    }

    /// @notice Same as `fillOrder` but calls permit first,
    /// allowing to approve token spending and make a swap in one transaction.
    /// Also allows to specify funds destination instead of `msg.sender`
    /// @param order Order quote to fill
    /// @param signature Signature to confirm quote ownership
    /// @param makingAmount Making amount
    /// @param takingAmount Taking amount
    /// @param thresholdAmount Specifies maximum allowed takingAmount when takingAmount is zero, otherwise specifies minimum allowed makingAmount
    /// @param target Address that will receive swap funds
    /// @param permit Should consist of abiencoded token address and encoded `IERC20Permit.permit` call.
    /// @dev See tests for examples
    function fillOrderToWithPermit(
        Order memory order,
        bytes calldata signature,
        uint256 makingAmount,
        uint256 takingAmount,
        uint256 thresholdAmount,
        address target,
        bytes calldata permit
    ) external returns(uint256 /* actualMakingAmount */, uint256 /* actualTakingAmount */) {
        require(permit.length >= 20, "LOP: permit length too low");
        (address token, bytes calldata permitData) = permit.decodeTargetAndData();
        _permit(token, permitData);
        return fillOrderTo(order, signature, makingAmount, takingAmount, thresholdAmount, target);
    }

    /// @notice Same as `fillOrder` but allows to specify funds destination instead of `msg.sender`
    /// @param order Order quote to fill
    /// @param signature Signature to confirm quote ownership
    /// @param makingAmount Making amount
    /// @param takingAmount Taking amount
    /// @param thresholdAmount Specifies maximum allowed takingAmount when takingAmount is zero, otherwise specifies minimum allowed makingAmount
    /// @param target Address that will receive swap funds
    function fillOrderTo(
        Order memory order,
        bytes calldata signature,
        uint256 makingAmount,
        uint256 takingAmount,
        uint256 thresholdAmount,
        address target
    ) public returns(uint256 /* actualMakingAmount */, uint256 /* actualTakingAmount */) {
        require(target != address(0), "LOP: zero target is forbidden");
        bytes32 orderHash = hashOrder(order);

        {  // Stack too deep
            uint256 remainingMakerAmount = _remaining[orderHash];
            require(remainingMakerAmount != _ORDER_FILLED, "LOP: remaining amount is 0");
            require(order.allowedSender == address(0) || order.allowedSender == msg.sender, "LOP: private order");
            if (remainingMakerAmount == _ORDER_DOES_NOT_EXIST) {
                // First fill: validate order and permit maker asset
                require(SignatureChecker.isValidSignatureNow(order.maker, orderHash, signature), "LOP: bad signature");
                remainingMakerAmount = order.makingAmount;
                if (order.permit.length >= 20) {
                    // proceed only if permit length is enough to store address
                    (address token, bytes memory permit) = order.permit.decodeTargetAndCalldata();
                    _permitMemory(token, permit);
                    require(_remaining[orderHash] == _ORDER_DOES_NOT_EXIST, "LOP: reentrancy detected");
                }
            } else {
                unchecked { remainingMakerAmount -= 1; }
            }

            // Check if order is valid
            if (order.predicate.length > 0) {
                require(checkPredicate(order), "LOP: predicate returned false");
            }

            // Compute maker and taker assets amount
            if ((takingAmount == 0) == (makingAmount == 0)) {
                revert("LOP: only one amount should be 0");
            } else if (takingAmount == 0) {
                uint256 requestedMakingAmount = makingAmount;
                if (makingAmount > remainingMakerAmount) {
                    makingAmount = remainingMakerAmount;
                }
                takingAmount = _callGetter(order.getTakerAmount, order.makingAmount, makingAmount, order.takingAmount);
                // check that actual rate is not worse than what was expected
                // takingAmount / makingAmount <= thresholdAmount / requestedMakingAmount
                require(takingAmount * requestedMakingAmount <= thresholdAmount * makingAmount, "LOP: taking amount too high");
            } else {
                uint256 requestedTakingAmount = takingAmount;
                makingAmount = _callGetter(order.getMakerAmount, order.takingAmount, takingAmount, order.makingAmount);
                if (makingAmount > remainingMakerAmount) {
                    makingAmount = remainingMakerAmount;
                    takingAmount = _callGetter(order.getTakerAmount, order.makingAmount, makingAmount, order.takingAmount);
                }
                // check that actual rate is not worse than what was expected
                // makingAmount / takingAmount >= thresholdAmount / requestedTakingAmount
                require(makingAmount * requestedTakingAmount >= thresholdAmount * takingAmount, "LOP: making amount too low");
            }

            require(makingAmount > 0 && takingAmount > 0, "LOP: can't swap 0 amount");

            // Update remaining amount in storage
            unchecked {
                remainingMakerAmount = remainingMakerAmount - makingAmount;
                _remaining[orderHash] = remainingMakerAmount + 1;
            }
            emit OrderFilled(msg.sender, orderHash, remainingMakerAmount);
        }

        // Taker => Maker
        _makeCall(
            order.takerAsset,
            abi.encodePacked(
                IERC20.transferFrom.selector,
                uint256(uint160(msg.sender)),
                uint256(uint160(order.receiver == address(0) ? order.maker : order.receiver)),
                takingAmount,
                order.takerAssetData
            )
        );

        // Maker can handle funds interactively
        if (order.interaction.length >= 20) {
            // proceed only if interaction length is enough to store address
            (address interactionTarget, bytes memory interactionData) = order.interaction.decodeTargetAndCalldata();
            InteractiveNotificationReceiver(interactionTarget).notifyFillOrder(
                msg.sender, order.makerAsset, order.takerAsset, makingAmount, takingAmount, interactionData
            );
        }

        // Maker => Taker
        _makeCall(
            order.makerAsset,
            abi.encodePacked(
                IERC20.transferFrom.selector,
                uint256(uint160(order.maker)),
                uint256(uint160(target)),
                makingAmount,
                order.makerAssetData
            )
        );

        return (makingAmount, takingAmount);
    }

    /// @notice Checks order predicate
    function checkPredicate(Order memory order) public view returns(bool) {
        bytes memory result = address(this).functionStaticCall(order.predicate, "LOP: predicate call failed");
        require(result.length == 32, "LOP: invalid predicate return");
        return result.decodeBool();
    }

    function hashOrder(Order memory order) public view returns(bytes32) {
        StaticOrder memory staticOrder;
        assembly {  // solhint-disable-line no-inline-assembly
            staticOrder := order
        }
        return _hashTypedDataV4(
            keccak256(
                abi.encode(
                    LIMIT_ORDER_TYPEHASH,
                    staticOrder,
                    keccak256(order.makerAssetData),
                    keccak256(order.takerAssetData),
                    keccak256(order.getMakerAmount),
                    keccak256(order.getTakerAmount),
                    keccak256(order.predicate),
                    keccak256(order.permit),
                    keccak256(order.interaction)
                )
            )
        );
    }

    function _makeCall(address asset, bytes memory assetData) private {
        bytes memory result = asset.functionCall(assetData, "LOP: asset.call failed");
        if (result.length > 0) {
            require(result.length == 32 && result.decodeBool(), "LOP: asset.call bad result");
        }
    }

    function _callGetter(bytes memory getter, uint256 orderExpectedAmount, uint256 amount, uint256 orderResultAmount) private view returns(uint256) {
        if (getter.length == 0) {
            // On empty getter calldata only exact amount is allowed
            require(amount == orderExpectedAmount, "LOP: wrong amount");
            return orderResultAmount;
        } else {
            bytes memory result = address(this).functionStaticCall(abi.encodePacked(getter, amount), "LOP: getAmount call failed");
            require(result.length == 32, "LOP: invalid getAmount return");
            return result.decodeUint256();
        }
    }
}

// SPDX-License-Identifier: MIT

pragma solidity 0.8.10;

import "@openzeppelin/contracts/utils/cryptography/draft-EIP712.sol";
import "@openzeppelin/contracts/utils/cryptography/SignatureChecker.sol";
import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";

import "./helpers/AmountCalculator.sol";
import "./libraries/Permitable.sol";

/// @title RFQ Limit Order mixin
abstract contract OrderRFQMixin is EIP712, AmountCalculator, Permitable {
    using SafeERC20 for IERC20;

    /// @notice Emitted when RFQ gets filled
    event OrderFilledRFQ(
        bytes32 orderHash,
        uint256 makingAmount
    );

    struct OrderRFQ {
        uint256 info;  // lowest 64 bits is the order id, next 64 bits is the expiration timestamp
        IERC20 makerAsset;
        IERC20 takerAsset;
        address maker;
        address allowedSender;  // equals to Zero address on public orders
        uint256 makingAmount;
        uint256 takingAmount;
    }

    bytes32 constant public LIMIT_ORDER_RFQ_TYPEHASH = keccak256(
        "OrderRFQ(uint256 info,address makerAsset,address takerAsset,address maker,address allowedSender,uint256 makingAmount,uint256 takingAmount)"
    );

    mapping(address => mapping(uint256 => uint256)) private _invalidator;

    /// @notice Returns bitmask for double-spend invalidators based on lowest byte of order.info and filled quotes
    /// @return Result Each bit represents whether corresponding was already invalidated
    function invalidatorForOrderRFQ(address maker, uint256 slot) external view returns(uint256) {
        return _invalidator[maker][slot];
    }

    /// @notice Cancels order's quote
    function cancelOrderRFQ(uint256 orderInfo) external {
        _invalidateOrder(msg.sender, orderInfo);
    }

    /// @notice Fills order's quote, fully or partially (whichever is possible)
    /// @param order Order quote to fill
    /// @param signature Signature to confirm quote ownership
    /// @param makingAmount Making amount
    /// @param takingAmount Taking amount
    function fillOrderRFQ(
        OrderRFQ memory order,
        bytes calldata signature,
        uint256 makingAmount,
        uint256 takingAmount
    ) external returns(uint256, uint256) {
        return fillOrderRFQTo(order, signature, makingAmount, takingAmount, msg.sender);
    }

    /// @notice Fills Same as `fillOrderRFQ` but calls permit first,
    /// allowing to approve token spending and make a swap in one transaction.
    /// Also allows to specify funds destination instead of `msg.sender`
    /// @param order Order quote to fill
    /// @param signature Signature to confirm quote ownership
    /// @param makingAmount Making amount
    /// @param takingAmount Taking amount
    /// @param target Address that will receive swap funds
    /// @param permit Should consist of abiencoded token address and encoded `IERC20Permit.permit` call.
    /// @dev See tests for examples
    function fillOrderRFQToWithPermit(
        OrderRFQ memory order,
        bytes calldata signature,
        uint256 makingAmount,
        uint256 takingAmount,
        address target,
        bytes calldata permit
    ) external returns(uint256, uint256) {
        _permit(address(order.takerAsset), permit);
        return fillOrderRFQTo(order, signature, makingAmount, takingAmount, target);
    }

    /// @notice Same as `fillOrderRFQ` but allows to specify funds destination instead of `msg.sender`
    /// @param order Order quote to fill
    /// @param signature Signature to confirm quote ownership
    /// @param makingAmount Making amount
    /// @param takingAmount Taking amount
    /// @param target Address that will receive swap funds
    function fillOrderRFQTo(
        OrderRFQ memory order,
        bytes calldata signature,
        uint256 makingAmount,
        uint256 takingAmount,
        address target
    ) public returns(uint256, uint256) {
        require(target != address(0), "LOP: zero target is forbidden");

        address maker = order.maker;

        // Validate order
        require(order.allowedSender == address(0) || order.allowedSender == msg.sender, "LOP: private order");
        bytes32 orderHash = _hashTypedDataV4(keccak256(abi.encode(LIMIT_ORDER_RFQ_TYPEHASH, order)));
        require(SignatureChecker.isValidSignatureNow(maker, orderHash, signature), "LOP: bad signature");

        {  // Stack too deep
            uint256 info = order.info;
            // Check time expiration
            uint256 expiration = uint128(info) >> 64;
            require(expiration == 0 || block.timestamp <= expiration, "LOP: order expired");  // solhint-disable-line not-rely-on-time
            _invalidateOrder(maker, info);
        }

        {  // stack too deep
            uint256 orderMakingAmount = order.makingAmount;
            uint256 orderTakingAmount = order.takingAmount;
            // Compute partial fill if needed
            if (takingAmount == 0 && makingAmount == 0) {
                // Two zeros means whole order
                makingAmount = orderMakingAmount;
                takingAmount = orderTakingAmount;
            }
            else if (takingAmount == 0) {
                require(makingAmount <= orderMakingAmount, "LOP: making amount exceeded");
                takingAmount = getTakerAmount(orderMakingAmount, orderTakingAmount, makingAmount);
            }
            else if (makingAmount == 0) {
                require(takingAmount <= orderTakingAmount, "LOP: taking amount exceeded");
                makingAmount = getMakerAmount(orderMakingAmount, orderTakingAmount, takingAmount);
            }
            else {
                revert("LOP: both amounts are non-zero");
            }
        }

        require(makingAmount > 0 && takingAmount > 0, "LOP: can't swap 0 amount");

        // Maker => Taker, Taker => Maker
        order.makerAsset.safeTransferFrom(maker, target, makingAmount);
        order.takerAsset.safeTransferFrom(msg.sender, maker, takingAmount);

        emit OrderFilledRFQ(orderHash, makingAmount);
        return (makingAmount, takingAmount);
    }

    function _invalidateOrder(address maker, uint256 orderInfo) private {
        uint256 invalidatorSlot = uint64(orderInfo) >> 8;
        uint256 invalidatorBit = 1 << uint8(orderInfo);
        mapping(uint256 => uint256) storage invalidatorStorage = _invalidator[maker];
        uint256 invalidator = invalidatorStorage[invalidatorSlot];
        require(invalidator & invalidatorBit == 0, "LOP: invalidated order");
        invalidatorStorage[invalidatorSlot] = invalidator | invalidatorBit;
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.0 (utils/cryptography/ECDSA.sol)

pragma solidity ^0.8.0;

import "../Strings.sol";

/**
 * @dev Elliptic Curve Digital Signature Algorithm (ECDSA) operations.
 *
 * These functions can be used to verify that a message was signed by the holder
 * of the private keys of a given address.
 */
library ECDSA {
    enum RecoverError {
        NoError,
        InvalidSignature,
        InvalidSignatureLength,
        InvalidSignatureS,
        InvalidSignatureV
    }

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

    /**
     * @dev Returns the address that signed a hashed message (`hash`) with
     * `signature` or error string. This address can then be used for verification purposes.
     *
     * The `ecrecover` EVM opcode allows for malleable (non-unique) signatures:
     * this function rejects them by requiring the `s` value to be in the lower
     * half order, and the `v` value to be either 27 or 28.
     *
     * IMPORTANT: `hash` _must_ be the result of a hash operation for the
     * verification to be secure: it is possible to craft signatures that
     * recover to arbitrary addresses for non-hashed data. A safe way to ensure
     * this is by receiving a hash of the original message (which may otherwise
     * be too long), and then calling {toEthSignedMessageHash} on it.
     *
     * Documentation for signature generation:
     * - with https://web3js.readthedocs.io/en/v1.3.4/web3-eth-accounts.html#sign[Web3.js]
     * - with https://docs.ethers.io/v5/api/signer/#Signer-signMessage[ethers]
     *
     * _Available since v4.3._
     */
    function tryRecover(bytes32 hash, bytes memory signature) internal pure returns (address, RecoverError) {
        // Check the signature length
        // - case 65: r,s,v signature (standard)
        // - case 64: r,vs signature (cf https://eips.ethereum.org/EIPS/eip-2098) _Available since v4.1._
        if (signature.length == 65) {
            bytes32 r;
            bytes32 s;
            uint8 v;
            // ecrecover takes the signature parameters, and the only way to get them
            // currently is to use assembly.
            assembly {
                r := mload(add(signature, 0x20))
                s := mload(add(signature, 0x40))
                v := byte(0, mload(add(signature, 0x60)))
            }
            return tryRecover(hash, v, r, s);
        } else if (signature.length == 64) {
            bytes32 r;
            bytes32 vs;
            // ecrecover takes the signature parameters, and the only way to get them
            // currently is to use assembly.
            assembly {
                r := mload(add(signature, 0x20))
                vs := mload(add(signature, 0x40))
            }
            return tryRecover(hash, r, vs);
        } else {
            return (address(0), RecoverError.InvalidSignatureLength);
        }
    }

    /**
     * @dev Returns the address that signed a hashed message (`hash`) with
     * `signature`. This address can then be used for verification purposes.
     *
     * The `ecrecover` EVM opcode allows for malleable (non-unique) signatures:
     * this function rejects them by requiring the `s` value to be in the lower
     * half order, and the `v` value to be either 27 or 28.
     *
     * IMPORTANT: `hash` _must_ be the result of a hash operation for the
     * verification to be secure: it is possible to craft signatures that
     * recover to arbitrary addresses for non-hashed data. A safe way to ensure
     * this is by receiving a hash of the original message (which may otherwise
     * be too long), and then calling {toEthSignedMessageHash} on it.
     */
    function recover(bytes32 hash, bytes memory signature) internal pure returns (address) {
        (address recovered, RecoverError error) = tryRecover(hash, signature);
        _throwError(error);
        return recovered;
    }

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

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

    /**
     * @dev Overload of {ECDSA-tryRecover} that receives the `v`,
     * `r` and `s` signature fields separately.
     *
     * _Available since v4.3._
     */
    function tryRecover(
        bytes32 hash,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) internal pure returns (address, RecoverError) {
        // EIP-2 still allows signature malleability for ecrecover(). Remove this possibility and make the signature
        // unique. Appendix F in the Ethereum Yellow paper (https://ethereum.github.io/yellowpaper/paper.pdf), defines
        // the valid range for s in (301): 0 < s < secp256k1n ÷ 2 + 1, and for v in (302): v ∈ {27, 28}. Most
        // signatures from current libraries generate a unique signature with an s-value in the lower half order.
        //
        // If your library generates malleable signatures, such as s-values in the upper range, calculate a new s-value
        // with 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141 - s1 and flip v from 27 to 28 or
        // vice versa. If your library also generates signatures with 0/1 for v instead 27/28, add 27 to v to accept
        // these malleable signatures as well.
        if (uint256(s) > 0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0) {
            return (address(0), RecoverError.InvalidSignatureS);
        }
        if (v != 27 && v != 28) {
            return (address(0), RecoverError.InvalidSignatureV);
        }

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

        return (signer, RecoverError.NoError);
    }

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

    /**
     * @dev Returns an Ethereum Signed Message, created from a `hash`. This
     * produces hash corresponding to the one signed with the
     * https://eth.wiki/json-rpc/API#eth_sign[`eth_sign`]
     * JSON-RPC method as part of EIP-191.
     *
     * See {recover}.
     */
    function toEthSignedMessageHash(bytes32 hash) internal pure returns (bytes32) {
        // 32 is the length in bytes of hash,
        // enforced by the type signature above
        return keccak256(abi.encodePacked("\x19Ethereum Signed Message:\n32", hash));
    }

    /**
     * @dev Returns an Ethereum Signed Message, created from `s`. This
     * produces hash corresponding to the one signed with the
     * https://eth.wiki/json-rpc/API#eth_sign[`eth_sign`]
     * JSON-RPC method as part of EIP-191.
     *
     * See {recover}.
     */
    function toEthSignedMessageHash(bytes memory s) internal pure returns (bytes32) {
        return keccak256(abi.encodePacked("\x19Ethereum Signed Message:\n", Strings.toString(s.length), s));
    }

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

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.0 (utils/Strings.sol)

pragma solidity ^0.8.0;

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

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

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

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

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

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.0 (utils/Address.sol)

pragma solidity ^0.8.0;

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.0 (utils/cryptography/SignatureChecker.sol)

pragma solidity ^0.8.0;

import "./ECDSA.sol";
import "../Address.sol";
import "../../interfaces/IERC1271.sol";

/**
 * @dev Signature verification helper: Provide a single mechanism to verify both private-key (EOA) ECDSA signature and
 * ERC1271 contract signatures. Using this instead of ECDSA.recover in your contract will make them compatible with
 * smart contract wallets such as Argent and Gnosis.
 *
 * Note: unlike ECDSA signatures, contract signature's are revocable, and the outcome of this function can thus change
 * through time. It could return true at block N and false at block N+1 (or the opposite).
 *
 * _Available since v4.1._
 */
library SignatureChecker {
    function isValidSignatureNow(
        address signer,
        bytes32 hash,
        bytes memory signature
    ) internal view returns (bool) {
        (address recovered, ECDSA.RecoverError error) = ECDSA.tryRecover(hash, signature);
        if (error == ECDSA.RecoverError.NoError && recovered == signer) {
            return true;
        }

        (bool success, bytes memory result) = signer.staticcall(
            abi.encodeWithSelector(IERC1271.isValidSignature.selector, hash, signature)
        );
        return (success && result.length == 32 && abi.decode(result, (bytes4)) == IERC1271.isValidSignature.selector);
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.0 (token/ERC20/IERC20.sol)

pragma solidity ^0.8.0;

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

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

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

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

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

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

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

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

// SPDX-License-Identifier: MIT

pragma solidity 0.8.10;
pragma abicoder v1;

import "@openzeppelin/contracts/utils/Address.sol";

/// @title A helper contract for calculations related to order amounts
contract AmountCalculator {
    using Address for address;

    /// @notice Calculates maker amount
    /// @return Result Floored maker amount
    function getMakerAmount(uint256 orderMakerAmount, uint256 orderTakerAmount, uint256 swapTakerAmount) public pure returns(uint256) {
        return swapTakerAmount * orderMakerAmount / orderTakerAmount;
    }

    /// @notice Calculates taker amount
    /// @return Result Ceiled taker amount
    function getTakerAmount(uint256 orderMakerAmount, uint256 orderTakerAmount, uint256 swapMakerAmount) public pure returns(uint256) {
        return (swapMakerAmount * orderTakerAmount + orderMakerAmount - 1) / orderMakerAmount;
    }

    /// @notice Performs an arbitrary call to target with data
    /// @return Result Bytes transmuted to uint256
    function arbitraryStaticCall(address target, bytes memory data) external view returns(uint256) {
        (bytes memory result) = target.functionStaticCall(data, "AC: arbitraryStaticCall");
        return abi.decode(result, (uint256));
    }
}

// SPDX-License-Identifier: MIT

pragma solidity 0.8.10;
pragma abicoder v1;

import "@chainlink/contracts/src/v0.8/interfaces/AggregatorV3Interface.sol";
import "@openzeppelin/contracts/utils/math/SafeCast.sol";


/// @title A helper contract for interactions with https://docs.chain.link
contract ChainlinkCalculator {
    using SafeCast for int256;

    uint256 private constant _SPREAD_DENOMINATOR = 1e9;
    uint256 private constant _ORACLE_EXPIRATION_TIME = 30 minutes;
    uint256 private constant _INVERSE_MASK = 1 << 255;

    /// @notice Calculates price of token relative to oracle unit (ETH or USD)
    /// @param inverseAndSpread concatenated inverse flag and spread.
    /// Lowest 254 bits specify spread amount. Spread is scaled by 1e9, i.e. 101% = 1.01e9, 99% = 0.99e9.
    /// Highest bit is set when oracle price should be inverted,
    /// e.g. for DAI-ETH oracle, inverse=false means that we request DAI price in ETH
    /// and inverse=true means that we request ETH price in DAI
    /// @return Amount * spread * oracle price
    function singlePrice(AggregatorV3Interface oracle, uint256 inverseAndSpread, uint256 amount) external view returns(uint256) {
        (, int256 latestAnswer,, uint256 latestTimestamp,) = oracle.latestRoundData();
        // solhint-disable-next-line not-rely-on-time
        require(latestTimestamp + _ORACLE_EXPIRATION_TIME > block.timestamp, "CC: stale data");
        bool inverse = inverseAndSpread & _INVERSE_MASK > 0;
        uint256 spread = inverseAndSpread & (~_INVERSE_MASK);
        if (inverse) {
            return amount * spread * (10 ** oracle.decimals()) / latestAnswer.toUint256() / _SPREAD_DENOMINATOR;
        } else {
            return amount * spread * latestAnswer.toUint256() / (10 ** oracle.decimals()) / _SPREAD_DENOMINATOR;
        }
    }

    /// @notice Calculates price of token A relative to token B. Note that order is important
    /// @return Result Token A relative price times amount
    function doublePrice(AggregatorV3Interface oracle1, AggregatorV3Interface oracle2, uint256 spread, uint256 amount) external view returns(uint256) {
        require(oracle1.decimals() == oracle2.decimals(), "CC: oracle decimals don't match");

        (, int256 latestAnswer1,, uint256 latestTimestamp1,) = oracle1.latestRoundData();
        (, int256 latestAnswer2,, uint256 latestTimestamp2,) = oracle2.latestRoundData();
        // solhint-disable-next-line not-rely-on-time
        require(latestTimestamp1 + _ORACLE_EXPIRATION_TIME > block.timestamp, "CC: stale data O1");
        // solhint-disable-next-line not-rely-on-time
        require(latestTimestamp2 + _ORACLE_EXPIRATION_TIME > block.timestamp, "CC: stale data O2");

        return amount * spread * latestAnswer1.toUint256() / latestAnswer2.toUint256() / _SPREAD_DENOMINATOR;
    }
}

// SPDX-License-Identifier: MIT

pragma solidity 0.8.10;
pragma abicoder v1;

/// @title A helper contract for managing nonce of tx sender
contract NonceManager {
    event NonceIncreased(address indexed maker, uint256 newNonce);

    mapping(address => uint256) public nonce;

    /// @notice Advances nonce by one
    function increaseNonce() external {
        advanceNonce(1);
    }

    /// @notice Advances nonce by specified amount
    function advanceNonce(uint8 amount) public {
        uint256 newNonce = nonce[msg.sender] + amount;
        nonce[msg.sender] = newNonce;
        emit NonceIncreased(msg.sender, newNonce);
    }

    /// @notice Checks if `makerAddress` has specified `makerNonce`
    /// @return Result True if `makerAddress` has specified nonce. Otherwise, false
    function nonceEquals(address makerAddress, uint256 makerNonce) external view returns(bool) {
        return nonce[makerAddress] == makerNonce;
    }
}

// SPDX-License-Identifier: MIT

pragma solidity 0.8.10;

import "@openzeppelin/contracts/utils/Address.sol";


/// @title A helper contract for executing boolean functions on arbitrary target call results
contract PredicateHelper {
    using Address for address;

    /// @notice Calls every target with corresponding data
    /// @return Result True if call to any target returned True. Otherwise, false
    function or(address[] calldata targets, bytes[] calldata data) external view returns(bool) {
        require(targets.length == data.length, "PH: input array size mismatch");
        for (uint256 i = 0; i < targets.length; i++) {
            bytes memory result = targets[i].functionStaticCall(data[i], "PH: 'or' subcall failed");
            require(result.length == 32, "PH: invalid call result");
            if (abi.decode(result, (bool))) {
                return true;
            }
        }
        return false;
    }

    /// @notice Calls every target with corresponding data
    /// @return Result True if calls to all targets returned True. Otherwise, false
    function and(address[] calldata targets, bytes[] calldata data) external view returns(bool) {
        require(targets.length == data.length, "PH: input array size mismatch");
        for (uint256 i = 0; i < targets.length; i++) {
            bytes memory result = targets[i].functionStaticCall(data[i], "PH: 'and' subcall failed");
            require(result.length == 32, "PH: invalid call result");
            if (!abi.decode(result, (bool))) {
                return false;
            }
        }
        return true;
    }

    /// @notice Calls target with specified data and tests if it's equal to the value
    /// @param value Value to test
    /// @return Result True if call to target returns the same value as `value`. Otherwise, false
    function eq(uint256 value, address target, bytes memory data) external view returns(bool) {
        bytes memory result = target.functionStaticCall(data, "PH: eq");
        require(result.length == 32, "PH: invalid call result");
        return abi.decode(result, (uint256)) == value;
    }

    /// @notice Calls target with specified data and tests if it's lower than value
    /// @param value Value to test
    /// @return Result True if call to target returns value which is lower than `value`. Otherwise, false
    function lt(uint256 value, address target, bytes memory data) external view returns(bool) {
        bytes memory result = target.functionStaticCall(data, "PH: lt");
        require(result.length == 32, "PH: invalid call result");
        return abi.decode(result, (uint256)) < value;
    }

    /// @notice Calls target with specified data and tests if it's bigger than value
    /// @param value Value to test
    /// @return Result True if call to target returns value which is bigger than `value`. Otherwise, false
    function gt(uint256 value, address target, bytes memory data) external view returns(bool) {
        bytes memory result = target.functionStaticCall(data, "PH: gt");
        require(result.length == 32, "PH: invalid call result");
        return abi.decode(result, (uint256)) > value;
    }

    /// @notice Checks passed time against block timestamp
    /// @return Result True if current block timestamp is lower than `time`. Otherwise, false
    function timestampBelow(uint256 time) external view returns(bool) {
        return block.timestamp < time;  // solhint-disable-line not-rely-on-time
    }
}

// SPDX-License-Identifier: MIT

pragma solidity 0.8.10;
pragma abicoder v1;

/// @title Interface for interactor which acts between `maker => taker` and `taker => maker` transfers.
interface InteractiveNotificationReceiver {
    /// @notice Callback method that gets called after taker transferred funds to maker but before
    /// the opposite transfer happened
    function notifyFillOrder(
        address taker,
        address makerAsset,
        address takerAsset,
        uint256 makingAmount,
        uint256 takingAmount,
        bytes memory interactiveData
    ) external;
}

// SPDX-License-Identifier: MIT

pragma solidity 0.8.10;
pragma abicoder v1;

/// @title Library with gas efficient alternatives to `abi.decode`
library ArgumentsDecoder {
    function decodeUint256(bytes memory data) internal pure returns(uint256) {
        uint256 value;
        assembly { // solhint-disable-line no-inline-assembly
            value := mload(add(data, 0x20))
        }
        return value;
    }

    function decodeBool(bytes memory data) internal pure returns(bool) {
        bool value;
        assembly { // solhint-disable-line no-inline-assembly
            value := eq(mload(add(data, 0x20)), 1)
        }
        return value;
    }

    function decodeTargetAndCalldata(bytes memory data) internal pure returns(address, bytes memory) {
        address target;
        bytes memory args;
        assembly {  // solhint-disable-line no-inline-assembly
            target := mload(add(data, 0x14))
            args := add(data, 0x14)
            mstore(args, sub(mload(data), 0x14))
        }
        return (target, args);
    }

    function decodeTargetAndData(bytes calldata data) internal pure returns(address, bytes calldata) {
        address target;
        bytes calldata args;
        assembly {  // solhint-disable-line no-inline-assembly
            target := shr(96, calldataload(data.offset))
        }
        args = data[20:];
        return (target, args);
    }
}

// SPDX-License-Identifier: MIT

pragma solidity 0.8.10;
pragma abicoder v1;

import "@openzeppelin/contracts/token/ERC20/extensions/draft-IERC20Permit.sol";
import "./RevertReasonParser.sol";
import "../interfaces/IDaiLikePermit.sol";

/// @title Base contract with common permit handling logics
abstract contract Permitable {
    function _permit(address token, bytes calldata permit) internal {
        if (permit.length > 0) {
            bool success;
            bytes memory result;
            if (permit.length == 32 * 7) {
                // solhint-disable-next-line avoid-low-level-calls
                (success, result) = token.call(abi.encodePacked(IERC20Permit.permit.selector, permit));
            } else if (permit.length == 32 * 8) {
                // solhint-disable-next-line avoid-low-level-calls
                (success, result) = token.call(abi.encodePacked(IDaiLikePermit.permit.selector, permit));
            } else {
                revert("Wrong permit length");
            }
            if (!success) {
                revert(RevertReasonParser.parse(result, "Permit failed: "));
            }
        }
    }

    function _permitMemory(address token, bytes memory permit) internal {
        if (permit.length > 0) {
            bool success;
            bytes memory result;
            if (permit.length == 32 * 7) {
                // solhint-disable-next-line avoid-low-level-calls
                (success, result) = token.call(abi.encodePacked(IERC20Permit.permit.selector, permit));
            } else if (permit.length == 32 * 8) {
                // solhint-disable-next-line avoid-low-level-calls
                (success, result) = token.call(abi.encodePacked(IDaiLikePermit.permit.selector, permit));
            } else {
                revert("Wrong permit length");
            }
            if (!success) {
                revert(RevertReasonParser.parse(result, "Permit failed: "));
            }
        }
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.0 (interfaces/IERC1271.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC1271 standard signature validation method for
 * contracts as defined in https://eips.ethereum.org/EIPS/eip-1271[ERC-1271].
 *
 * _Available since v4.1._
 */
interface IERC1271 {
    /**
     * @dev Should return whether the signature provided is valid for the provided data
     * @param hash      Hash of the data to be signed
     * @param signature Signature byte array associated with _data
     */
    function isValidSignature(bytes32 hash, bytes memory signature) external view returns (bytes4 magicValue);
}

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

interface AggregatorV3Interface {

  function decimals()
    external
    view
    returns (
      uint8
    );

  function description()
    external
    view
    returns (
      string memory
    );

  function version()
    external
    view
    returns (
      uint256
    );

  // getRoundData and latestRoundData should both raise "No data present"
  // if they do not have data to report, instead of returning unset values
  // which could be misinterpreted as actual reported values.
  function getRoundData(
    uint80 _roundId
  )
    external
    view
    returns (
      uint80 roundId,
      int256 answer,
      uint256 startedAt,
      uint256 updatedAt,
      uint80 answeredInRound
    );

  function latestRoundData()
    external
    view
    returns (
      uint80 roundId,
      int256 answer,
      uint256 startedAt,
      uint256 updatedAt,
      uint80 answeredInRound
    );

}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.0 (utils/math/SafeCast.sol)

pragma solidity ^0.8.0;

/**
 * @dev Wrappers over Solidity's uintXX/intXX casting operators with added overflow
 * checks.
 *
 * Downcasting from uint256/int256 in Solidity does not revert on overflow. This can
 * easily result in undesired exploitation or bugs, since developers usually
 * assume that overflows raise errors. `SafeCast` restores this intuition by
 * reverting the transaction when such an operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 *
 * Can be combined with {SafeMath} and {SignedSafeMath} to extend it to smaller types, by performing
 * all math on `uint256` and `int256` and then downcasting.
 */
library SafeCast {
    /**
     * @dev Returns the downcasted uint224 from uint256, reverting on
     * overflow (when the input is greater than largest uint224).
     *
     * Counterpart to Solidity's `uint224` operator.
     *
     * Requirements:
     *
     * - input must fit into 224 bits
     */
    function toUint224(uint256 value) internal pure returns (uint224) {
        require(value <= type(uint224).max, "SafeCast: value doesn't fit in 224 bits");
        return uint224(value);
    }

    /**
     * @dev Returns the downcasted uint128 from uint256, reverting on
     * overflow (when the input is greater than largest uint128).
     *
     * Counterpart to Solidity's `uint128` operator.
     *
     * Requirements:
     *
     * - input must fit into 128 bits
     */
    function toUint128(uint256 value) internal pure returns (uint128) {
        require(value <= type(uint128).max, "SafeCast: value doesn't fit in 128 bits");
        return uint128(value);
    }

    /**
     * @dev Returns the downcasted uint96 from uint256, reverting on
     * overflow (when the input is greater than largest uint96).
     *
     * Counterpart to Solidity's `uint96` operator.
     *
     * Requirements:
     *
     * - input must fit into 96 bits
     */
    function toUint96(uint256 value) internal pure returns (uint96) {
        require(value <= type(uint96).max, "SafeCast: value doesn't fit in 96 bits");
        return uint96(value);
    }

    /**
     * @dev Returns the downcasted uint64 from uint256, reverting on
     * overflow (when the input is greater than largest uint64).
     *
     * Counterpart to Solidity's `uint64` operator.
     *
     * Requirements:
     *
     * - input must fit into 64 bits
     */
    function toUint64(uint256 value) internal pure returns (uint64) {
        require(value <= type(uint64).max, "SafeCast: value doesn't fit in 64 bits");
        return uint64(value);
    }

    /**
     * @dev Returns the downcasted uint32 from uint256, reverting on
     * overflow (when the input is greater than largest uint32).
     *
     * Counterpart to Solidity's `uint32` operator.
     *
     * Requirements:
     *
     * - input must fit into 32 bits
     */
    function toUint32(uint256 value) internal pure returns (uint32) {
        require(value <= type(uint32).max, "SafeCast: value doesn't fit in 32 bits");
        return uint32(value);
    }

    /**
     * @dev Returns the downcasted uint16 from uint256, reverting on
     * overflow (when the input is greater than largest uint16).
     *
     * Counterpart to Solidity's `uint16` operator.
     *
     * Requirements:
     *
     * - input must fit into 16 bits
     */
    function toUint16(uint256 value) internal pure returns (uint16) {
        require(value <= type(uint16).max, "SafeCast: value doesn't fit in 16 bits");
        return uint16(value);
    }

    /**
     * @dev Returns the downcasted uint8 from uint256, reverting on
     * overflow (when the input is greater than largest uint8).
     *
     * Counterpart to Solidity's `uint8` operator.
     *
     * Requirements:
     *
     * - input must fit into 8 bits.
     */
    function toUint8(uint256 value) internal pure returns (uint8) {
        require(value <= type(uint8).max, "SafeCast: value doesn't fit in 8 bits");
        return uint8(value);
    }

    /**
     * @dev Converts a signed int256 into an unsigned uint256.
     *
     * Requirements:
     *
     * - input must be greater than or equal to 0.
     */
    function toUint256(int256 value) internal pure returns (uint256) {
        require(value >= 0, "SafeCast: value must be positive");
        return uint256(value);
    }

    /**
     * @dev Returns the downcasted int128 from int256, reverting on
     * overflow (when the input is less than smallest int128 or
     * greater than largest int128).
     *
     * Counterpart to Solidity's `int128` operator.
     *
     * Requirements:
     *
     * - input must fit into 128 bits
     *
     * _Available since v3.1._
     */
    function toInt128(int256 value) internal pure returns (int128) {
        require(value >= type(int128).min && value <= type(int128).max, "SafeCast: value doesn't fit in 128 bits");
        return int128(value);
    }

    /**
     * @dev Returns the downcasted int64 from int256, reverting on
     * overflow (when the input is less than smallest int64 or
     * greater than largest int64).
     *
     * Counterpart to Solidity's `int64` operator.
     *
     * Requirements:
     *
     * - input must fit into 64 bits
     *
     * _Available since v3.1._
     */
    function toInt64(int256 value) internal pure returns (int64) {
        require(value >= type(int64).min && value <= type(int64).max, "SafeCast: value doesn't fit in 64 bits");
        return int64(value);
    }

    /**
     * @dev Returns the downcasted int32 from int256, reverting on
     * overflow (when the input is less than smallest int32 or
     * greater than largest int32).
     *
     * Counterpart to Solidity's `int32` operator.
     *
     * Requirements:
     *
     * - input must fit into 32 bits
     *
     * _Available since v3.1._
     */
    function toInt32(int256 value) internal pure returns (int32) {
        require(value >= type(int32).min && value <= type(int32).max, "SafeCast: value doesn't fit in 32 bits");
        return int32(value);
    }

    /**
     * @dev Returns the downcasted int16 from int256, reverting on
     * overflow (when the input is less than smallest int16 or
     * greater than largest int16).
     *
     * Counterpart to Solidity's `int16` operator.
     *
     * Requirements:
     *
     * - input must fit into 16 bits
     *
     * _Available since v3.1._
     */
    function toInt16(int256 value) internal pure returns (int16) {
        require(value >= type(int16).min && value <= type(int16).max, "SafeCast: value doesn't fit in 16 bits");
        return int16(value);
    }

    /**
     * @dev Returns the downcasted int8 from int256, reverting on
     * overflow (when the input is less than smallest int8 or
     * greater than largest int8).
     *
     * Counterpart to Solidity's `int8` operator.
     *
     * Requirements:
     *
     * - input must fit into 8 bits.
     *
     * _Available since v3.1._
     */
    function toInt8(int256 value) internal pure returns (int8) {
        require(value >= type(int8).min && value <= type(int8).max, "SafeCast: value doesn't fit in 8 bits");
        return int8(value);
    }

    /**
     * @dev Converts an unsigned uint256 into a signed int256.
     *
     * Requirements:
     *
     * - input must be less than or equal to maxInt256.
     */
    function toInt256(uint256 value) internal pure returns (int256) {
        // Note: Unsafe cast below is okay because `type(int256).max` is guaranteed to be positive
        require(value <= uint256(type(int256).max), "SafeCast: value doesn't fit in an int256");
        return int256(value);
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.0 (token/ERC20/extensions/draft-IERC20Permit.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 Permit extension allowing approvals to be made via signatures, as defined in
 * https://eips.ethereum.org/EIPS/eip-2612[EIP-2612].
 *
 * Adds the {permit} method, which can be used to change an account's ERC20 allowance (see {IERC20-allowance}) by
 * presenting a message signed by the account. By not relying on {IERC20-approve}, the token holder account doesn't
 * need to send a transaction, and thus is not required to hold Ether at all.
 */
interface IERC20Permit {
    /**
     * @dev Sets `value` as the allowance of `spender` over ``owner``'s tokens,
     * given ``owner``'s signed approval.
     *
     * IMPORTANT: The same issues {IERC20-approve} has related to transaction
     * ordering also apply here.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `deadline` must be a timestamp in the future.
     * - `v`, `r` and `s` must be a valid `secp256k1` signature from `owner`
     * over the EIP712-formatted function arguments.
     * - the signature must use ``owner``'s current nonce (see {nonces}).
     *
     * For more information on the signature format, see the
     * https://eips.ethereum.org/EIPS/eip-2612#specification[relevant EIP
     * section].
     */
    function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external;

    /**
     * @dev Returns the current nonce for `owner`. This value must be
     * included whenever a signature is generated for {permit}.
     *
     * Every successful call to {permit} increases ``owner``'s nonce by one. This
     * prevents a signature from being used multiple times.
     */
    function nonces(address owner) external view returns (uint256);

    /**
     * @dev Returns the domain separator used in the encoding of the signature for {permit}, as defined by {EIP712}.
     */
    // solhint-disable-next-line func-name-mixedcase
    function DOMAIN_SEPARATOR() external view returns (bytes32);
}

// SPDX-License-Identifier: MIT

pragma solidity 0.8.10;
pragma abicoder v1;


/// @title Library that allows to parse unsuccessful arbitrary calls revert reasons.
/// See https://solidity.readthedocs.io/en/latest/control-structures.html#revert for details.
/// Note that we assume revert reason being abi-encoded as Error(string) so it may fail to parse reason
/// if structured reverts appear in the future.
///
/// All unsuccessful parsings get encoded as Unknown(data) string
library RevertReasonParser {
    bytes4 constant private _PANIC_SELECTOR = bytes4(keccak256("Panic(uint256)"));
    bytes4 constant private _ERROR_SELECTOR = bytes4(keccak256("Error(string)"));

    function parse(bytes memory data, string memory prefix) internal pure returns (string memory) {
        if (data.length >= 4) {
            bytes4 selector;

            assembly {  // solhint-disable-line no-inline-assembly
                selector := mload(add(data, 0x20))
            }

            // 68 = 4-byte selector + 32 bytes offset + 32 bytes length
            if (selector == _ERROR_SELECTOR && data.length >= 68) {
                uint256 offset;
                bytes memory reason;
                assembly {  // solhint-disable-line no-inline-assembly
                    // 36 = 32 bytes data length + 4-byte selector
                    offset := mload(add(data, 36))
                    reason := add(data, add(36, offset))
                }
                /*
                    revert reason is padded up to 32 bytes with ABI encoder: Error(string)
                    also sometimes there is extra 32 bytes of zeros padded in the end:
                    https://github.com/ethereum/solidity/issues/10170
                    because of that we can't check for equality and instead check
                    that offset + string length + extra 36 bytes is less than overall data length
                */
                require(data.length >= 36 + offset + reason.length, "Invalid revert reason");
                return string(abi.encodePacked(prefix, "Error(", reason, ")"));
            }
            // 36 = 4-byte selector + 32 bytes integer
            else if (selector == _PANIC_SELECTOR && data.length == 36) {
                uint256 code;
                assembly {  // solhint-disable-line no-inline-assembly
                    // 36 = 32 bytes data length + 4-byte selector
                    code := mload(add(data, 36))
                }
                return string(abi.encodePacked(prefix, "Panic(", _toHex(code), ")"));
            }
        }

        return string(abi.encodePacked(prefix, "Unknown(", _toHex(data), ")"));
    }

    function _toHex(uint256 value) private pure returns(string memory) {
        return _toHex(abi.encodePacked(value));
    }

    function _toHex(bytes memory data) private pure returns(string memory) {
        bytes16 alphabet = 0x30313233343536373839616263646566;
        bytes memory str = new bytes(2 + data.length * 2);
        str[0] = "0";
        str[1] = "x";
        for (uint256 i = 0; i < data.length; i++) {
            str[2 * i + 2] = alphabet[uint8(data[i] >> 4)];
            str[2 * i + 3] = alphabet[uint8(data[i] & 0x0f)];
        }
        return string(str);
    }
}

// SPDX-License-Identifier: MIT

pragma solidity 0.8.10;
pragma abicoder v1;

/// @title Interface for DAI-style permits
interface IDaiLikePermit {
    function permit(address holder, address spender, uint256 nonce, uint256 expiry, bool allowed, uint8 v, bytes32 r, bytes32 s) external;
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.0 (token/ERC20/utils/SafeERC20.sol)

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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