// File: contracts/ReimbursementPool.sol



// SPDX-License-Identifier: GPL-3.0-only
//
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//
//                           Trust math, not hardware.

pragma solidity 0.8.17;

import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";

contract ReimbursementPool is Ownable, ReentrancyGuard {
    /// @notice Authorized contracts that can interact with the reimbursment pool.
    ///         Authorization can be granted and removed by the owner.
    mapping(address => bool) public isAuthorized;

    /// @notice Static gas includes:
    ///         - cost of the refund function
    ///         - base transaction cost
    uint256 public staticGas;

    /// @notice Max gas price used to reimburse a transaction submitter. Protects
    ///         against malicious operator-miners.
    uint256 public maxGasPrice;

    event StaticGasUpdated(uint256 newStaticGas);

    event MaxGasPriceUpdated(uint256 newMaxGasPrice);

    event SendingEtherFailed(uint256 refundAmount, address receiver);

    event AuthorizedContract(address thirdPartyContract);

    event UnauthorizedContract(address thirdPartyContract);

    event FundsWithdrawn(uint256 withdrawnAmount, address receiver);

    constructor(uint256 _staticGas, uint256 _maxGasPrice) {
        staticGas = _staticGas;
        maxGasPrice = _maxGasPrice;
    }

    /// @notice Receive ETH
    receive() external payable {}

    /// @notice Refunds ETH to a spender for executing specific transactions.
    /// @dev Ignoring the result of sending ETH to a receiver is made on purpose.
    ///      For EOA receiving ETH should always work. If a receiver is a smart
    ///      contract, then we do not want to fail a transaction, because in some
    ///      cases the refund is done at the very end of multiple calls where all
    ///      the previous calls were already paid off. It is a receiver's smart
    ///      contract resposibility to make sure it can receive ETH.
    /// @dev Only authorized contracts are allowed calling this function.
    /// @param gasSpent Gas spent on a transaction that needs to be reimbursed.
    /// @param receiver Address where the reimbursment is sent.
    function refund(uint256 gasSpent, address receiver) external nonReentrant {
        require(
            isAuthorized[msg.sender],
            "Contract is not authorized for a refund"
        );
        require(receiver != address(0), "Receiver's address cannot be zero");

        uint256 gasPrice = tx.gasprice < maxGasPrice
            ? tx.gasprice
            : maxGasPrice;

        uint256 refundAmount = (gasSpent + staticGas) * gasPrice;

        /* solhint-disable avoid-low-level-calls */
        // slither-disable-next-line low-level-calls,unchecked-lowlevel
        (bool sent, ) = receiver.call{value: refundAmount}("");
        /* solhint-enable avoid-low-level-calls */
        if (!sent) {
            // slither-disable-next-line reentrancy-events
            emit SendingEtherFailed(refundAmount, receiver);
        }
    }

    /// @notice Authorize a contract that can interact with this reimbursment pool.
    ///         Can be authorized by the owner only.
    /// @param _contract Authorized contract.
    function authorize(address _contract) external onlyOwner {
        isAuthorized[_contract] = true;

        emit AuthorizedContract(_contract);
    }

    /// @notice Unauthorize a contract that was previously authorized to interact
    ///         with this reimbursment pool. Can be unauthorized by the
    ///         owner only.
    /// @param _contract Authorized contract.
    function unauthorize(address _contract) external onlyOwner {
        delete isAuthorized[_contract];

        emit UnauthorizedContract(_contract);
    }

    /// @notice Setting a static gas cost for executing a transaction. Can be set
    ///         by the owner only.
    /// @param _staticGas Static gas cost.
    function setStaticGas(uint256 _staticGas) external onlyOwner {
        staticGas = _staticGas;

        emit StaticGasUpdated(_staticGas);
    }

    /// @notice Setting a max gas price for transactions. Can be set by the
    ///         owner only.
    /// @param _maxGasPrice Max gas price used to reimburse tx submitters.
    function setMaxGasPrice(uint256 _maxGasPrice) external onlyOwner {
        maxGasPrice = _maxGasPrice;

        emit MaxGasPriceUpdated(_maxGasPrice);
    }

    /// @notice Withdraws all ETH from this pool which are sent to a given
    ///         address. Can be set by the owner only.
    /// @param receiver An address where ETH is sent.
    function withdrawAll(address receiver) external onlyOwner {
        withdraw(address(this).balance, receiver);
    }

    /// @notice Withdraws ETH amount from this pool which are sent to a given
    ///         address. Can be set by the owner only.
    /// @param amount Amount to withdraw from the pool.
    /// @param receiver An address where ETH is sent.
    function withdraw(uint256 amount, address receiver) public onlyOwner {
        require(
            address(this).balance >= amount,
            "Insufficient contract balance"
        );
        require(receiver != address(0), "Receiver's address cannot be zero");

        emit FundsWithdrawn(amount, receiver);

        /* solhint-disable avoid-low-level-calls */
        // slither-disable-next-line low-level-calls,arbitrary-send
        (bool sent, ) = receiver.call{value: amount}("");
        /* solhint-enable avoid-low-level-calls */
        require(sent, "Failed to send Ether");
    }
}

// File: @openzeppelin/contracts/access/Ownable.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (access/Ownable.sol)

pragma solidity ^0.8.0;

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

/**
 * @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.
 */
abstract contract Ownable is Context {
    address private _owner;

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

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() {
        _transferOwnership(_msgSender());
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        _checkOwner();
        _;
    }

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

    /**
     * @dev Throws if the sender is not the owner.
     */
    function _checkOwner() internal view virtual {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        _transferOwnership(address(0));
    }

    /**
     * @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");
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

// File: @openzeppelin/contracts/security/ReentrancyGuard.sol



// 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;
    }
}

// File: @openzeppelin/contracts/utils/Context.sol



// 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;
    }
}