Contract Source Code:

// SPDX-License-Identifier: GPL-3.0-only

pragma solidity ^0.8.17;

import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
import "./FeeOperator.sol";
import "../interfaces/ICircleBridge.sol";
import "../safeguard/Governor.sol";
import "../safeguard/Pauser.sol";

contract CircleBridgeProxy is FeeOperator, Governor, Pauser, ReentrancyGuard {
    using SafeERC20 for IERC20;

    address public immutable circleBridge;

    uint32 public feePercGlobal; //in 1e6
    // chainId => feePercOverride, support override fee perc by dst chain
    mapping(uint64 => uint32) public feePercOverride;
    /// per dest chain id executor fee in this chain's USDC token
    mapping(uint64 => uint256) public dstTxFee;
    
    // 0 is regarded as not registered. Set to a negative value if target domain is actually 0.
    mapping(uint64 => int32) public chidToDomain;

    event FeePercUpdated(uint64[] chainIds, uint32[] feePercs);
    event TxFeeUpdated(uint64[] chainIds, uint256[] fees);
    event ChidToDomainUpdated(uint64[] chainIds, int32[] domains);
    event Deposited(address sender, bytes32 recipient, uint64 dstChid, uint256 amount, uint256 txFee, uint256 percFee, uint64 nonce);

    constructor(
        address _circleBridge,
        address _feeCollector
    ) FeeOperator(_feeCollector) {
        circleBridge = _circleBridge;
    }

    function depositForBurn(
        uint256 _amount,
        uint64 _dstChid,
        bytes32 _mintRecipient,
        address _burnToken
    ) external nonReentrant whenNotPaused returns (uint64 _nonce) {
        int32 dstDomain = chidToDomain[_dstChid];
        require (dstDomain != 0, "dst domain not registered");
        if (dstDomain < 0) {
            dstDomain = 0; // a negative value indicates the target domain is 0 actually.
        }
        (uint256 fee, uint256 txFee, uint256 percFee) = totalFee(_amount, _dstChid);
        require (_amount > fee, "fee not covered");

        IERC20(_burnToken).safeTransferFrom(msg.sender, address(this), _amount);
        uint256 bridgeAmt = _amount - fee;
        IERC20(_burnToken).safeIncreaseAllowance(circleBridge, bridgeAmt);
        _nonce = ICircleBridge(circleBridge).depositForBurn(bridgeAmt, uint32(dstDomain), _mintRecipient, _burnToken);
        IERC20(_burnToken).safeApprove(circleBridge, 0);
        emit Deposited(msg.sender, _mintRecipient, _dstChid, _amount, txFee, percFee, _nonce);
    }

    function totalFee(
        uint256 _amount,
        uint64 _dstChid
    ) public view returns (uint256 _fee, uint256 _txFee, uint256 _percFee) {
        uint32 feePerc = feePercOverride[_dstChid];
        if (feePerc == 0) {
            feePerc = feePercGlobal;
        }
        _txFee = dstTxFee[_dstChid];
        _percFee = (_amount * feePerc) / 1e6;
        _fee = _txFee + _percFee;
    }

    function setFeePerc(uint64[] calldata _chainIds, uint32[] calldata _feePercs) external onlyGovernor {
        require(_chainIds.length == _feePercs.length, "length mismatch");
        for (uint256 i = 0; i < _chainIds.length; i++) {
            require(_feePercs[i] < 1e6, "fee percentage too large");
            if (_chainIds[i] == 0) {
                feePercGlobal = _feePercs[i];
            } else {
                feePercOverride[_chainIds[i]] = _feePercs[i];
            }
        }
        emit FeePercUpdated(_chainIds, _feePercs);
    }

    function setTxFee(uint64[] calldata _chainIds, uint256[] calldata _fees) external onlyGovernor {
        require(_chainIds.length == _fees.length, "length mismatch");
        for (uint256 i = 0; i < _chainIds.length; i++) {
            dstTxFee[_chainIds[i]] = _fees[i];
        }
        emit TxFeeUpdated(_chainIds, _fees);
    }

    function setChidToDomain(uint64[] calldata _chainIds, int32[] calldata _domains) external onlyGovernor {
        require(_chainIds.length == _domains.length, "length mismatch");
        for (uint256 i = 0; i < _chainIds.length; i++) {
            chidToDomain[_chainIds[i]] = _domains[i];
        }
        emit ChidToDomainUpdated(_chainIds, _domains);
    }
}

// SPDX-License-Identifier: GPL-3.0-only

pragma solidity ^0.8.17;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
import "../safeguard/Ownable.sol";

abstract contract FeeOperator is Ownable {
    using SafeERC20 for IERC20;

    address public feeCollector;

    event FeeCollectorUpdated(address from, address to);

    modifier onlyFeeCollector() {
        require(msg.sender == feeCollector, "not fee collector");
        _;
    }

    constructor(address _feeCollector) {
        feeCollector = _feeCollector;
    }

    function collectFee(address[] calldata _tokens, address _to) external onlyFeeCollector {
        for (uint256 i = 0; i < _tokens.length; i++) {
            // use zero address to denote native token
            if (_tokens[i] == address(0)) {
                uint256 bal = address(this).balance;
                (bool sent, ) = _to.call{value: bal, gas: 50000}("");
                require(sent, "send native failed");
            } else {
                uint256 balance = IERC20(_tokens[i]).balanceOf(address(this));
                IERC20(_tokens[i]).safeTransfer(_to, balance);
            }
        }
    }

    function setFeeCollector(address _feeCollector) external onlyOwner {
        address oldFeeCollector = feeCollector;
        feeCollector = _feeCollector;
        emit FeeCollectorUpdated(oldFeeCollector, _feeCollector);
    }
}

// SPDX-License-Identifier: GPL-3.0-only

pragma solidity ^0.8.0;

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 *
 * This adds a normal func that setOwner if _owner is address(0). So we can't allow
 * renounceOwnership. So we can support Proxy based upgradable contract
 */
abstract contract Ownable {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() {
        _setOwner(msg.sender);
    }

    /**
     * @dev Only to be called by inherit contracts, in their init func called by Proxy
     * we require _owner == address(0), which is only possible when it's a delegateCall
     * because constructor sets _owner in contract state.
     */
    function initOwner() internal {
        require(_owner == address(0), "owner already set");
        _setOwner(msg.sender);
    }

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

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

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        _setOwner(newOwner);
    }

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

// SPDX-License-Identifier: GPL-3.0-only

pragma solidity >=0.8.0;

interface ICircleBridge {
    /**
    * @notice Deposits and burns tokens from sender to be minted on destination domain.
    * Emits a `DepositForBurn` event.
    * @dev reverts if:
    * - given burnToken is not supported
    * - given destinationDomain has no CircleBridge registered
    * - transferFrom() reverts. For example, if sender's burnToken balance or approved allowance
    * to this contract is less than `amount`.
    * - burn() reverts. For example, if `amount` is 0.
    * - MessageTransmitter returns false or reverts.
    * @param _amount amount of tokens to burn
    * @param _destinationDomain destination domain (ETH = 0, AVAX = 1)
    * @param _mintRecipient address of mint recipient on destination domain
    * @param _burnToken address of contract to burn deposited tokens, on local domain
    * @return _nonce unique nonce reserved by message
    */
    function depositForBurn(
        uint256 _amount,
        uint32 _destinationDomain,
        bytes32 _mintRecipient,
        address _burnToken
    ) external returns (uint64 _nonce);
}

// SPDX-License-Identifier: GPL-3.0-only

pragma solidity 0.8.17;

import "./Ownable.sol";

abstract contract Governor is Ownable {
    mapping(address => bool) public governors;

    event GovernorAdded(address account);
    event GovernorRemoved(address account);

    modifier onlyGovernor() {
        require(isGovernor(msg.sender), "Caller is not governor");
        _;
    }

    constructor() {
        _addGovernor(msg.sender);
    }

    function isGovernor(address _account) public view returns (bool) {
        return governors[_account];
    }

    function addGovernor(address _account) public onlyOwner {
        _addGovernor(_account);
    }

    function removeGovernor(address _account) public onlyOwner {
        _removeGovernor(_account);
    }

    function renounceGovernor() public {
        _removeGovernor(msg.sender);
    }

    function _addGovernor(address _account) private {
        require(!isGovernor(_account), "Account is already governor");
        governors[_account] = true;
        emit GovernorAdded(_account);
    }

    function _removeGovernor(address _account) private {
        require(isGovernor(_account), "Account is not governor");
        governors[_account] = false;
        emit GovernorRemoved(_account);
    }
}

// SPDX-License-Identifier: GPL-3.0-only

pragma solidity 0.8.17;

import "@openzeppelin/contracts/security/Pausable.sol";
import "./Ownable.sol";

abstract contract Pauser is Ownable, Pausable {
    mapping(address => bool) public pausers;

    event PauserAdded(address account);
    event PauserRemoved(address account);

    constructor() {
        _addPauser(msg.sender);
    }

    modifier onlyPauser() {
        require(isPauser(msg.sender), "Caller is not pauser");
        _;
    }

    function pause() public onlyPauser {
        _pause();
    }

    function unpause() public onlyPauser {
        _unpause();
    }

    function isPauser(address account) public view returns (bool) {
        return pausers[account];
    }

    function addPauser(address account) public onlyOwner {
        _addPauser(account);
    }

    function removePauser(address account) public onlyOwner {
        _removePauser(account);
    }

    function renouncePauser() public {
        _removePauser(msg.sender);
    }

    function _addPauser(address account) private {
        require(!isPauser(account), "Account is already pauser");
        pausers[account] = true;
        emit PauserAdded(account);
    }

    function _removePauser(address account) private {
        require(isPauser(account), "Account is not pauser");
        pausers[account] = false;
        emit PauserRemoved(account);
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (security/ReentrancyGuard.sol)

pragma solidity ^0.8.0;

/**
 * @dev Contract module that helps prevent reentrant calls to a function.
 *
 * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
 * available, which can be applied to functions to make sure there are no nested
 * (reentrant) calls to them.
 *
 * Note that because there is a single `nonReentrant` guard, functions marked as
 * `nonReentrant` may not call one another. This can be worked around by making
 * those functions `private`, and then adding `external` `nonReentrant` entry
 * points to them.
 *
 * TIP: If you would like to learn more about reentrancy and alternative ways
 * to protect against it, check out our blog post
 * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
 */
abstract contract ReentrancyGuard {
    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.

    // The values being non-zero value makes deployment a bit more expensive,
    // but in exchange the refund on every call to nonReentrant will be lower in
    // amount. Since refunds are capped to a percentage of the total
    // transaction's gas, it is best to keep them low in cases like this one, to
    // increase the likelihood of the full refund coming into effect.
    uint256 private constant _NOT_ENTERED = 1;
    uint256 private constant _ENTERED = 2;

    uint256 private _status;

    constructor() {
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and making it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        // On the first call to nonReentrant, _notEntered will be true
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

        // Any calls to nonReentrant after this point will fail
        _status = _ENTERED;

        _;

        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        _status = _NOT_ENTERED;
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (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 `to`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address to, uint256 amount) external returns (bool);

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

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

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

    /**
     * @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
// OpenZeppelin Contracts v4.4.1 (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");
        }
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (utils/Address.sol)

pragma solidity ^0.8.1;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     *
     * [IMPORTANT]
     * ====
     * You shouldn't rely on `isContract` to protect against flash loan attacks!
     *
     * Preventing calls from contracts is highly discouraged. It breaks composability, breaks support for smart wallets
     * like Gnosis Safe, and does not provide security since it can be circumvented by calling from a contract
     * constructor.
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize/address.code.length, which returns 0
        // for contracts in construction, since the code is only stored at the end
        // of the constructor execution.

        return account.code.length > 0;
    }

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (security/Pausable.sol)

pragma solidity ^0.8.0;

import "../utils/Context.sol";

/**
 * @dev Contract module which allows children to implement an emergency stop
 * mechanism that can be triggered by an authorized account.
 *
 * This module is used through inheritance. It will make available the
 * modifiers `whenNotPaused` and `whenPaused`, which can be applied to
 * the functions of your contract. Note that they will not be pausable by
 * simply including this module, only once the modifiers are put in place.
 */
abstract contract Pausable is Context {
    /**
     * @dev Emitted when the pause is triggered by `account`.
     */
    event Paused(address account);

    /**
     * @dev Emitted when the pause is lifted by `account`.
     */
    event Unpaused(address account);

    bool private _paused;

    /**
     * @dev Initializes the contract in unpaused state.
     */
    constructor() {
        _paused = false;
    }

    /**
     * @dev Returns true if the contract is paused, and false otherwise.
     */
    function paused() public view virtual returns (bool) {
        return _paused;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is not paused.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    modifier whenNotPaused() {
        require(!paused(), "Pausable: paused");
        _;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is paused.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    modifier whenPaused() {
        require(paused(), "Pausable: not paused");
        _;
    }

    /**
     * @dev Triggers stopped state.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    function _pause() internal virtual whenNotPaused {
        _paused = true;
        emit Paused(_msgSender());
    }

    /**
     * @dev Returns to normal state.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    function _unpause() internal virtual whenPaused {
        _paused = false;
        emit Unpaused(_msgSender());
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/Context.sol)

pragma solidity ^0.8.0;

/**
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

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