Contract Source Code:

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.0.0) (access/Ownable.sol)

pragma solidity ^0.8.20;

import {Context} from "../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.
 *
 * The initial owner is set to the address provided by the deployer. 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;

    /**
     * @dev The caller account is not authorized to perform an operation.
     */
    error OwnableUnauthorizedAccount(address account);

    /**
     * @dev The owner is not a valid owner account. (eg. `address(0)`)
     */
    error OwnableInvalidOwner(address owner);

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

    /**
     * @dev Initializes the contract setting the address provided by the deployer as the initial owner.
     */
    constructor(address initialOwner) {
        if (initialOwner == address(0)) {
            revert OwnableInvalidOwner(address(0));
        }
        _transferOwnership(initialOwner);
    }

    /**
     * @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 {
        if (owner() != _msgSender()) {
            revert OwnableUnauthorizedAccount(_msgSender());
        }
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby disabling 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 {
        if (newOwner == address(0)) {
            revert OwnableInvalidOwner(address(0));
        }
        _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);
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.1.0) (token/ERC20/IERC20.sol)

pragma solidity ^0.8.20;

/**
 * @dev Interface of the ERC-20 standard as defined in the ERC.
 */
interface IERC20 {
    /**
     * @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);

    /**
     * @dev Returns the value of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

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

    /**
     * @dev Moves a `value` amount of 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 value) 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 a `value` amount of tokens 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 value) external returns (bool);

    /**
     * @dev Moves a `value` amount of tokens from `from` to `to` using the
     * allowance mechanism. `value` 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 value) external returns (bool);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.0.1) (utils/Context.sol)

pragma solidity ^0.8.20;

/**
 * @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;
    }

    function _contextSuffixLength() internal view virtual returns (uint256) {
        return 0;
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.1.0) (utils/ReentrancyGuard.sol)

pragma solidity ^0.8.20;

/**
 * @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 EIP-1153 (transient storage) is available on the chain you're deploying at,
 * consider using {ReentrancyGuardTransient} instead.
 *
 * 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;

    /**
     * @dev Unauthorized reentrant call.
     */
    error ReentrancyGuardReentrantCall();

    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() {
        _nonReentrantBefore();
        _;
        _nonReentrantAfter();
    }

    function _nonReentrantBefore() private {
        // On the first call to nonReentrant, _status will be NOT_ENTERED
        if (_status == ENTERED) {
            revert ReentrancyGuardReentrantCall();
        }

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

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

    /**
     * @dev Returns true if the reentrancy guard is currently set to "entered", which indicates there is a
     * `nonReentrant` function in the call stack.
     */
    function _reentrancyGuardEntered() internal view returns (bool) {
        return _status == ENTERED;
    }
}

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

import "@openzeppelin/contracts/utils/ReentrancyGuard.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/access/Ownable.sol";

/**
 * @title SwapWithEthFee
 * @notice A contract that wraps a 1inch swap and takes a fee in ETH
 * @dev Collects a platform fee in ETH before forwarding the swap call to 1inch router
 */
contract SwapWithEthFee is ReentrancyGuard, Ownable {
    // The address that will receive the ETH fee
    address public immutable feeReceiver;
    
    // 1inch Router address (mainnet)
    address public immutable oneInchRouter;
    
    // Maximum fee percentage (5%)
    uint256 public constant MAX_FEE_PERCENT = 5;
    
    // Events
    event SwapExecuted(address indexed sender, uint256 feeAmount, uint256 swapAmount);
    event FeeReceiverUpdated(address indexed oldReceiver, address indexed newReceiver);
    event TokensRescued(address indexed token, address indexed recipient, uint256 amount);
    event EthRescued(address indexed recipient, uint256 amount);
    
    /**
     * @dev Constructor sets the fee receiver address and router address
     * @param _feeReceiver Address that will receive the ETH fee
     * @param _oneInchRouter Address of the 1inch router (default: 0x1111111254EEB25477B68fb85Ed929f73A960582)
     */
    constructor(
        address _feeReceiver, 
        address _oneInchRouter
    ) Ownable(msg.sender) {
        require(_feeReceiver != address(0), "Fee receiver cannot be zero address");
        require(_oneInchRouter != address(0), "Router cannot be zero address");
        
        feeReceiver = _feeReceiver;
        oneInchRouter = _oneInchRouter;
    }
    
    /**
     * @dev Main function to perform a swap with 1inch while taking a fee
     * @param feeAmount Amount of ETH to take as a fee
     * @param swapData The calldata to forward to the 1inch router
     */
    function swapAndTakeFee(uint256 feeAmount, bytes calldata swapData) external payable nonReentrant {
        require(msg.value > feeAmount, "Not enough ETH sent for fee and swap");
        require(feeAmount <= msg.value * MAX_FEE_PERCENT / 100, "Fee exceeds maximum allowed (5%)");
        
        // Transfer fee to the fee receiver
        (bool feeSuccess, ) = feeReceiver.call{value: feeAmount}("");
        require(feeSuccess, "Fee transfer failed");
        
        // Calculate remaining ETH for the swap
        uint256 swapAmount = msg.value - feeAmount;
        
        // Expected balance should be 0 after we send ETH to the router
        // Record balance before sending ETH to router
        uint256 preSwapBalance = address(this).balance;
        
        // Forward remaining ETH and calldata to 1inch router
        (bool swapSuccess, ) = oneInchRouter.call{value: swapAmount}(swapData);
        require(swapSuccess, "Swap execution failed");
        
        // Calculate expected post-swap balance (should be 0 if no other ETH was in contract)
        uint256 expectedBalance = preSwapBalance - swapAmount;
        
        // After swap, check if we received any ETH back from the router
        uint256 currentBalance = address(this).balance;
        
        if (currentBalance > expectedBalance) {
            // Calculate refund amount (only the excess from this transaction)
            uint256 refundAmount = currentBalance - expectedBalance;
            
            // Send refund back to the sender
            (bool refundSuccess, ) = msg.sender.call{value: refundAmount}("");
            require(refundSuccess, "Refund transfer failed");
        }
        
        emit SwapExecuted(msg.sender, feeAmount, swapAmount);
    }
    
    /**
     * @dev Function to rescue ERC20 tokens that are accidentally sent to the contract
     * @param token Address of the token to rescue
     * @param recipient Address to send the tokens to
     * @param amount Amount of tokens to rescue
     */
    function rescueTokens(IERC20 token, address recipient, uint256 amount) external onlyOwner {
        require(recipient != address(0), "Cannot rescue to zero address");
        require(amount > 0, "Amount must be greater than zero");
        
        bool success = token.transfer(recipient, amount);
        require(success, "Token rescue failed");
        
        emit TokensRescued(address(token), recipient, amount);
    }
    
    /**
     * @dev Function to rescue ETH that might be stuck in the contract
     * @param recipient Address to send the ETH to
     * @param amount Amount of ETH to rescue
     */
    function rescueETH(address payable recipient, uint256 amount) external onlyOwner {
        require(recipient != address(0), "Cannot rescue to zero address");
        require(amount > 0 && amount <= address(this).balance, "Invalid amount");
        
        (bool success, ) = recipient.call{value: amount}("");
        require(success, "ETH rescue failed");
        
        emit EthRescued(recipient, amount);
    }
    
    /**
     * @dev Function to verify if the contract is still receiving funds after swap
     * @notice This is a fallback function to handle any unexpected ETH that might be sent back
     */
    receive() external payable {
        // Accept ETH transfers (e.g., refunds or partial fills from swaps)
    }
}