Contract Source Code:

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (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;

import "./token/ERC20/IERC20.sol";
import "./token/Address.sol";
import "./token/ERC20/SafeER20.sol";
import "./interface/bebop_aggregation_contract.sol";
import "@openzeppelin/contracts/interfaces/IERC1271.sol";

contract BebopAggregationContract is IBebopAggregationContract {

    bytes4 constant internal EIP1271_MAGICVALUE = bytes4(keccak256("isValidSignature(bytes32,bytes)"));

    using SafeERC20 for IERC20;

    function getChainID() private view returns (uint256) {
        uint256 id;
        assembly {
            id := chainid()
        }
        return id;
    }

    uint256 chainId = getChainID();
    address verifyingContract = address(this);
    string private constant EIP712_DOMAIN =
        "EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)";

    bytes32 public constant EIP712_DOMAIN_TYPEHASH =
        keccak256(abi.encodePacked(EIP712_DOMAIN));

    string constant AGGREGATED_ORDER_TYPE =
        "AggregateOrder(uint256 expiry,address taker_address,address[] maker_addresses,uint256[] maker_nonces,address[][] taker_tokens,address[][] maker_tokens,uint256[][] taker_amounts,uint256[][] maker_amounts,address receiver)";
    bytes32 constant AGGREGATED_ORDER_TYPE_HASH = keccak256(abi.encodePacked(AGGREGATED_ORDER_TYPE));

    string constant PARTIAL_AGGREGATED_ORDER_TYPE =
        "PartialOrder(uint256 expiry,address taker_address,address maker_address,uint256 maker_nonce,address[] taker_tokens,address[] maker_tokens,uint256[] taker_amounts,uint256[] maker_amounts,address receiver)";
    bytes32 constant PARTIAL_AGGREGATED_ORDER_TYPE_HASH = keccak256(abi.encodePacked(PARTIAL_AGGREGATED_ORDER_TYPE));

    bytes32 private DOMAIN_SEPARATOR;

    uint256 private constant ETH_SIGN_HASH_PREFIX = 0x19457468657265756d205369676e6564204d6573736167653a0a333200000000;

    mapping(address => mapping(uint256 => uint256)) private maker_validator;
    mapping(address => mapping(address => bool)) orderSignerRegistry;

    constructor() {
        DOMAIN_SEPARATOR = keccak256(
            abi.encode(
                EIP712_DOMAIN_TYPEHASH,
                keccak256("BebopAggregationContract"),
                keccak256("1"),
                chainId,
                verifyingContract
            )
        );
    }

    function getRsv(bytes memory sig) internal pure returns (bytes32, bytes32, uint8)
    {
        require(sig.length == 65, "Invalid signature length");
        bytes32 r;
        bytes32 s;
        uint8 v;
        assembly {
            r := mload(add(sig, 32))
            s := mload(add(sig, 64))
            v := and(mload(add(sig, 65)), 255)
        }
        require(uint256(s) <= 0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0, "Invalid sig value S");
        require(v == 27 || v == 28, "Invalid sig value V");
        return (r, s, v);
    }

    function encodeTightlyPackedNestedInt(uint256[][] memory _nested_array) internal pure returns(bytes memory encoded) {
        uint nested_array_length = _nested_array.length;
        for (uint i = 0; i < nested_array_length; i++) {
            encoded = abi.encodePacked(
                encoded,
                keccak256(abi.encodePacked(_nested_array[i]))
            );
        }
        return encoded;
    }

    function encodeTightlyPackedNested(address[][] memory _nested_array) internal pure returns(bytes memory encoded) {
        uint nested_array_length = _nested_array.length;
        for (uint i = 0; i < nested_array_length; i++) {
            encoded = abi.encodePacked(
                encoded,
                keccak256(abi.encodePacked(_nested_array[i]))
            );
        }
        return encoded;
    }

    function registerAllowedOrderSigner(address signer, bool allowed) external override {
        orderSignerRegistry[msg.sender][signer] = allowed;
        emit OrderSignerRegistered(msg.sender, signer, allowed);
    }

    function hashAggregateOrder(AggregateOrder memory order) public view override returns (bytes32) {
        return
        keccak256(
            abi.encodePacked(
                "\x19\x01",
                DOMAIN_SEPARATOR,
                keccak256(
                    abi.encode(
                        AGGREGATED_ORDER_TYPE_HASH,
                        order.expiry,
                        order.taker_address,
                        keccak256(abi.encodePacked(order.maker_addresses)),
                        keccak256(abi.encodePacked(order.maker_nonces)),
                        keccak256(encodeTightlyPackedNested(order.taker_tokens)),
                        keccak256(encodeTightlyPackedNested(order.maker_tokens)),
                        keccak256(encodeTightlyPackedNestedInt(order.taker_amounts)),
                        keccak256(encodeTightlyPackedNestedInt(order.maker_amounts)),
                        order.receiver
                    )
                )
            )
        );
    }

    function hashPartialOrder(PartialOrder memory order) public view override returns (bytes32) {
        return
            keccak256(
                abi.encodePacked(
                    "\x19\x01",
                    DOMAIN_SEPARATOR,
                    keccak256(
                        abi.encode(
                            PARTIAL_AGGREGATED_ORDER_TYPE_HASH,
                            order.expiry,
                            order.taker_address,
                            order.maker_address,
                            order.maker_nonce,
                            keccak256(abi.encodePacked(order.taker_tokens)),
                            keccak256(abi.encodePacked(order.maker_tokens)),
                            keccak256(abi.encodePacked(order.taker_amounts)),
                            keccak256(abi.encodePacked(order.maker_amounts)),
                            order.receiver
                        )
                    )
                )
            );
    }

    function invalidateOrder(address maker, uint256 nonce) private {
        require(nonce != 0, "Nonce must be non-zero");
        uint256 invalidatorSlot = uint64(nonce) >> 8;
        uint256 invalidatorBit = 1 << uint8(nonce);
        mapping(uint256 => uint256) storage invalidatorStorage = maker_validator[maker];
        uint256 invalidator = invalidatorStorage[invalidatorSlot];
        require(invalidator & invalidatorBit == 0, "Invalid maker order (nonce)");
        invalidatorStorage[invalidatorSlot] = invalidator | invalidatorBit;
    }

    function validateMakerSignature(
        address maker_address,
        bytes32 hash,
        Signature memory signature
    ) public view override {
        if (signature.signatureType == SignatureType.EIP712) {
            // Signed using EIP712
            (bytes32 r, bytes32 s, uint8 v) = getRsv(signature.signatureBytes);
            address signer = ecrecover(hash, v, r, s);
            require(signer != address(0), "Invalid signer");
            if (signer != maker_address && !orderSignerRegistry[maker_address][signer]) {
                revert("Invalid maker signature");
            }
        } else if (signature.signatureType == SignatureType.EIP1271) {
            require(IERC1271(maker_address).isValidSignature(hash, signature.signatureBytes) == EIP1271_MAGICVALUE, "Invalid Maker EIP 1271 Signature");
        } else if (signature.signatureType == SignatureType.ETHSIGN) {
            bytes32 ethSignHash;
            assembly {
                mstore(0, ETH_SIGN_HASH_PREFIX) // length of 28 bytes
                mstore(28, hash) // length of 32 bytes
                ethSignHash := keccak256(0, 60)
            }
            (bytes32 r, bytes32 s, uint8 v) = getRsv(signature.signatureBytes);
            address signer = ecrecover(ethSignHash, v, r, s);
            require(signer != address(0), "Invalid signer");
            if (signer != maker_address && !orderSignerRegistry[maker_address][signer]) {
                revert("Invalid maker signature");
            }
        } else {
            revert("Invalid Signature Type");
        }
    }

    function assertAndInvalidateMakerOrders(
        AggregateOrder memory order,
        Signature[] memory makerSigs
    ) private {
        // number of columns = number of sigs otherwise unwarranted columns can be injected by sender.
        require(order.taker_tokens.length == makerSigs.length, "Taker tokens length mismatch");
        require(order.maker_tokens.length == makerSigs.length, "Maker tokens length mismatch");
        require(order.taker_amounts.length == makerSigs.length, "Taker amounts length mismatch");
        require(order.maker_amounts.length == makerSigs.length, "Maker amounts length mismatch");
        require(order.maker_nonces.length == makerSigs.length, "Maker nonces length mismatch");
        require(order.maker_addresses.length == makerSigs.length, "Maker addresses length mismatch");
        uint numMakerSigs = makerSigs.length;
        for (uint256 i = 0; i < numMakerSigs; i++) {
            // validate the partially signed orders.
            address maker_address = order.maker_addresses[i];
            require(order.maker_tokens[i].length == order.maker_amounts[i].length, "Maker tokens and amounts length mismatch");
            require(order.taker_tokens[i].length == order.taker_amounts[i].length, "Taker tokens and amounts length mismatch");
            PartialOrder memory partial_order = PartialOrder(
                 order.expiry,
                 order.taker_address,
                 maker_address,
                 order.maker_nonces[i],
                 order.taker_tokens[i],
                 order.maker_tokens[i],
                 order.taker_amounts[i],
                 order.maker_amounts[i],
                 order.receiver
            );
            bytes32 partial_hash = hashPartialOrder(partial_order);
            Signature memory makerSig = makerSigs[i];
            validateMakerSignature(maker_address, partial_hash, makerSig);
            invalidateOrder(maker_address, order.maker_nonces[i]);
        }
    }

    // Construct partial orders from aggregated orders
    function assertAndInvalidateAggregateOrder(
        AggregateOrder memory order,
        bytes memory takerSig,
        Signature[] memory makerSigs
    ) internal returns (bytes32) {
        bytes32 h = hashAggregateOrder(order);
        (bytes32 R, bytes32 S, uint8 V) = getRsv(takerSig);
        address taker = ecrecover(h, V, R, S);
        require(taker == order.taker_address, "Invalid taker signature");

        // construct and validate maker partial orders
        assertAndInvalidateMakerOrders(order, makerSigs);

        require(order.expiry > block.timestamp, "Signature expired");
        return h;
    }

    function makerTransferFunds(
        address from,
        address to,
        uint256 quantity,
        address token
    ) private returns (bool) {
        IERC20(token).safeTransferFrom(from, to, quantity);
        return true;
    }

    function SettleAggregateOrder(
        AggregateOrder memory order,
        bytes memory takerSig,
        Signature[] memory makerSigs
    ) public payable override returns (bool) {
        bytes32 h = assertAndInvalidateAggregateOrder(
            order,
            takerSig,
            makerSigs
        );

        // for each distinct maker
        uint numMakerSigs = makerSigs.length;
        for (uint256 i = 0; i < numMakerSigs; i++) {
            // for each of that maker's tokens
            uint makerTokensLength = order.maker_tokens[i].length;
            uint takerTokensLength = order.taker_tokens[i].length;
            for (uint256 j = 0; j < makerTokensLength; j++) {
                require(
                    // transfer those tokens to the receiver
                    makerTransferFunds(
                        order.maker_addresses[i],
                        order.receiver,
                        order.maker_amounts[i][j],
                        order.maker_tokens[i][j]
                    )
                );
            }

            // for each of the takers tokens (corresponding to each maker)
            for (uint k = 0; k < takerTokensLength; k++){
                // transfer each of those tokens to the corresponding maker
                IERC20(address(order.taker_tokens[i][k])).safeTransferFrom(
                    order.taker_address,
                    order.maker_addresses[i],
                    order.taker_amounts[i][k]
                );
            }
        }

        emit AggregateOrderExecuted(
            h
        );

        return true;
    }
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

enum SignatureType {
    EIP712,  //0
    EIP1271, //1
    ETHSIGN  //2
}

struct Signature {
    SignatureType signatureType;
    bytes signatureBytes;
}

struct AggregateOrder {
    uint256 expiry;
    address taker_address;
    address[] maker_addresses;
    uint256[] maker_nonces;
    address[][] taker_tokens;
    address[][] maker_tokens;
    uint256[][] taker_amounts;
    uint256[][] maker_amounts;
    address receiver;
}

struct PartialOrder {
    uint256 expiry;
    address taker_address;
    address maker_address;
    uint256 maker_nonce;
    address[] taker_tokens;
    address[] maker_tokens;
    uint256[] taker_amounts;
    uint256[] maker_amounts;
    address receiver;
}

interface IBebopAggregationContract {
    event AggregateOrderExecuted(
        bytes32 order_hash
    );

    event OrderSignerRegistered(address maker, address signer, bool allowed);

    function hashAggregateOrder(AggregateOrder memory order) external view returns (bytes32);
    function hashPartialOrder(PartialOrder memory order) external view returns (bytes32);
    function registerAllowedOrderSigner(address signer, bool allowed) external;

    function validateMakerSignature(
        address maker_address,
        bytes32 hash,
        Signature memory signature
    ) external view;

    function SettleAggregateOrder(
        AggregateOrder memory order,
        bytes memory takerSig,
        Signature[] memory makerSigs
    ) external payable returns (bool);

}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (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
     * ====
     *
     * [IMPORTANT]
     * ====
     * You shouldn't rely on `isContract` to protect against flash loan attacks!
     *
     * Preventing calls from contracts is highly discouraged. It breaks composability, breaks support for smart wallets
     * like Gnosis Safe, and does not provide security since it can be circumvented by calling from a contract
     * constructor.
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize/address.code.length, which returns 0
        // for contracts in construction, since the code is only stored at the end
        // of the constructor execution.

        return account.code.length > 0;
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://consensys.net/diligence/blog/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/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 functionCallWithValue(target, data, 0, "Address: low-level call failed");
    }

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

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

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

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

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal view returns (bytes memory) {
        (bool success, bytes memory returndata) = target.staticcall(data);
        return verifyCallResultFromTarget(target, success, returndata, errorMessage);
    }

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

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return verifyCallResultFromTarget(target, success, returndata, errorMessage);
    }

    /**
     * @dev Tool to verify that a low level call to smart-contract was successful, and revert (either by bubbling
     * the revert reason or using the provided one) in case of unsuccessful call or if target was not a contract.
     *
     * _Available since v4.8._
     */
    function verifyCallResultFromTarget(
        address target,
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal view returns (bytes memory) {
        if (success) {
            if (returndata.length == 0) {
                // only check isContract if the call was successful and the return data is empty
                // otherwise we already know that it was a contract
                require(isContract(target), "Address: call to non-contract");
            }
            return returndata;
        } else {
            _revert(returndata, errorMessage);
        }
    }

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

    function _revert(bytes memory returndata, string memory errorMessage) private pure {
        // Look for revert reason and bubble it up if present
        if (returndata.length > 0) {
            // The easiest way to bubble the revert reason is using memory via assembly
            /// @solidity memory-safe-assembly
            assembly {
                let returndata_size := mload(returndata)
                revert(add(32, returndata), returndata_size)
            }
        } else {
            revert(errorMessage);
        }
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (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 ^0.8.0;

/**
 * @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);
}

pragma solidity ^0.8.0;

import "../Address.sol";
import "./IERC20.sol";
import "./draft-IERC20Permit.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));
    }
    }

    function safePermit(
        IERC20Permit token,
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) internal {
        uint256 nonceBefore = token.nonces(owner);
        token.permit(owner, spender, value, deadline, v, r, s);
        uint256 nonceAfter = token.nonces(owner);
        require(nonceAfter == nonceBefore + 1, "SafeERC20: permit did not succeed");
    }

    /**
     * @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");
        }
    }
}