// SPDX-License-Identifier: MIT

pragma solidity 0.8.9;



// Part: ICurveV2Pool

interface ICurveV2Pool {
    function get_dy(
        uint256 i,
        uint256 j,
        uint256 dx
    ) external view returns (uint256);

    function calc_token_amount(uint256[2] calldata amounts)
        external
        view
        returns (uint256);

    function exchange_underlying(
        uint256 i,
        uint256 j,
        uint256 dx,
        uint256 min_dy
    ) external payable returns (uint256);

    function add_liquidity(uint256[2] calldata amounts, uint256 min_mint_amount)
        external
        returns (uint256);

    function lp_price() external view returns (uint256);

    function price_oracle() external view returns (uint256);

    function remove_liquidity_one_coin(
        uint256 token_amount,
        uint256 i,
        uint256 min_amount,
        bool use_eth,
        address receiver
    ) external returns (uint256);
}

// Part: IUniV2Router

interface IUniV2Router {
    function swapExactTokensForETH(
        uint256 amountIn,
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external payable returns (uint256[] memory amounts);

    function swapExactETHForTokens(
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external payable returns (uint256[] memory amounts);

    function swapExactTokensForTokens(
        uint256 amountIn,
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external returns (uint256[] memory amounts);

    function getAmountsOut(uint256 amountIn, address[] memory path)
        external
        view
        returns (uint256[] memory amounts);
}

// Part: IUniV3Router

interface IUniV3Router {
    struct ExactInputSingleParams {
        address tokenIn;
        address tokenOut;
        uint24 fee;
        address recipient;
        uint256 deadline;
        uint256 amountIn;
        uint256 amountOutMinimum;
        uint160 sqrtPriceLimitX96;
    }

    function exactInputSingle(ExactInputSingleParams calldata params)
        external
        payable
        returns (uint256 amountOut);

    struct ExactInputParams {
        bytes path;
        address recipient;
        uint256 deadline;
        uint256 amountIn;
        uint256 amountOutMinimum;
    }

    function exactInput(ExactInputParams calldata params)
        external
        payable
        returns (uint256 amountOut);
}

// Part: IWETH

interface IWETH {
    function deposit() external payable;

    function transfer(address to, uint256 value) external returns (bool);

    function withdraw(uint256) external;
}

// Part: OpenZeppelin/openzeppelin-contracts@4.1.0/Address

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

        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly { size := extcodesize(account) }
        return size > 0;
    }

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

        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (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");

        // solhint-disable-next-line avoid-low-level-calls
        (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");

        // solhint-disable-next-line avoid-low-level-calls
        (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");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage) private 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

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// Part: OpenZeppelin/openzeppelin-contracts@4.1.0/Context

/*
 * @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) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

// Part: OpenZeppelin/openzeppelin-contracts@4.1.0/IERC20

/**
 * @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);
}

// Part: OpenZeppelin/openzeppelin-contracts@4.1.0/Ownable

/**
 * @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 () {
        address msgSender = _msgSender();
        _owner = msgSender;
        emit OwnershipTransferred(address(0), msgSender);
    }

    /**
     * @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() == _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 {
        emit OwnershipTransferred(_owner, address(0));
        _owner = 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");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}

// Part: OpenZeppelin/openzeppelin-contracts@4.1.0/SafeERC20

/**
 * @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'
        // solhint-disable-next-line max-line-length
        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
            // solhint-disable-next-line max-line-length
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

// File: FXSSwapper.sol

contract FXSSwapper is Ownable {
    using SafeERC20 for IERC20;

    address public constant CURVE_FXS_ETH_POOL =
        0x941Eb6F616114e4Ecaa85377945EA306002612FE;
    address public constant FXS_TOKEN =
        0x3432B6A60D23Ca0dFCa7761B7ab56459D9C964D0;
    address public constant UNISWAP_ROUTER =
        0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D;
    address public constant UNIV3_ROUTER =
        0xE592427A0AEce92De3Edee1F18E0157C05861564;
    address public constant WETH_TOKEN =
        0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2;
    address public constant USDT_TOKEN =
        0xdAC17F958D2ee523a2206206994597C13D831ec7;
    address public constant USDC_TOKEN =
        0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48;
    address public constant FRAX_TOKEN =
        0x853d955aCEf822Db058eb8505911ED77F175b99e;
    address public depositor;

    ICurveV2Pool fxsEthSwap = ICurveV2Pool(CURVE_FXS_ETH_POOL);
    // The swap strategy to use when going eth -> fxs
    enum SwapOption {
        Curve,
        Uniswap,
        Unistables
    }
    SwapOption public swapOption = SwapOption.Unistables;

    constructor(address _depositor) {
        require(_depositor != address(0));
        depositor = _depositor;
    }

    /// @notice Set approvals for the contracts used when swapping & staking
    function setApprovals() external {
        IERC20(FXS_TOKEN).safeApprove(CURVE_FXS_ETH_POOL, 0);
        IERC20(FXS_TOKEN).safeApprove(CURVE_FXS_ETH_POOL, type(uint256).max);

        IERC20(FXS_TOKEN).safeApprove(UNISWAP_ROUTER, 0);
        IERC20(FXS_TOKEN).safeApprove(UNISWAP_ROUTER, type(uint256).max);

        IERC20(FXS_TOKEN).safeApprove(UNIV3_ROUTER, 0);
        IERC20(FXS_TOKEN).safeApprove(UNIV3_ROUTER, type(uint256).max);

        IERC20(FRAX_TOKEN).safeApprove(UNISWAP_ROUTER, 0);
        IERC20(FRAX_TOKEN).safeApprove(UNISWAP_ROUTER, type(uint256).max);
    }

    /// @notice Change the contract authorized to call buy and sell functions
    /// @param _depositor - address of the new depositor
    function updateDepositor(address _depositor) external onlyOwner {
        require(_depositor != address(0));
        depositor = _depositor;
    }

    /// @notice Change the swap option for FXS/ETH
    /// @param _option - the new swap option
    function updateOption(SwapOption _option) external onlyOwner {
        swapOption = _option;
    }

    /// @notice Buy FXS with ETH
    /// @param amount - amount of ETH to buy with
    /// @return amount of FXS bought
    /// @dev ETH must have been sent to the contract prior
    function buy(uint256 amount) external onlyDepositor returns (uint256) {
        uint256 _received = _swapEthForFxs(amount, swapOption);
        IERC20(FXS_TOKEN).safeTransfer(depositor, _received);
        return _received;
    }

    /// @notice Sell FXS for ETH
    /// @param amount - amount of FXS to sell
    /// @return amount of ETH bought
    /// @dev FXS must have been sent to the contract prior
    function sell(uint256 amount) external onlyDepositor returns (uint256) {
        uint256 _received = _swapFxsForEth(amount, swapOption);
        (bool success, ) = depositor.call{value: _received}("");
        require(success, "ETH transfer failed");
        return _received;
    }

    /// @notice Swap native ETH for FXS via different routes
    /// @param _ethAmount - amount to swap
    /// @param _option - the option to use when swapping
    /// @return amount of FXS obtained after the swap
    function _swapEthForFxs(uint256 _ethAmount, SwapOption _option)
        internal
        returns (uint256)
    {
        return _swapEthFxs(_ethAmount, _option, true);
    }

    /// @notice Swap FXS for native ETH via different routes
    /// @param _fxsAmount - amount to swap
    /// @param _option - the option to use when swapping
    /// @return amount of ETH obtained after the swap
    function _swapFxsForEth(uint256 _fxsAmount, SwapOption _option)
        internal
        returns (uint256)
    {
        return _swapEthFxs(_fxsAmount, _option, false);
    }

    /// @notice Swap ETH<->FXS on Curve
    /// @param _amount - amount to swap
    /// @param _ethToFxs - whether to swap from eth to fxs or the inverse
    /// @return amount of token obtained after the swap
    function _curveEthFxsSwap(uint256 _amount, bool _ethToFxs)
        internal
        returns (uint256)
    {
        return
            fxsEthSwap.exchange_underlying{value: _ethToFxs ? _amount : 0}(
                _ethToFxs ? 0 : 1,
                _ethToFxs ? 1 : 0,
                _amount,
                0
            );
    }

    /// @notice Swap ETH<->FXS on UniV3 FXSETH pool
    /// @param _amount - amount to swap
    /// @param _ethToFxs - whether to swap from eth to fxs or the inverse
    /// @return amount of token obtained after the swap
    function _uniV3EthFxsSwap(uint256 _amount, bool _ethToFxs)
        internal
        returns (uint256)
    {
        IUniV3Router.ExactInputSingleParams memory _params = IUniV3Router
            .ExactInputSingleParams(
                _ethToFxs ? WETH_TOKEN : FXS_TOKEN,
                _ethToFxs ? FXS_TOKEN : WETH_TOKEN,
                10000,
                address(this),
                block.timestamp + 1,
                _amount,
                1,
                0
            );

        uint256 _receivedAmount = IUniV3Router(UNIV3_ROUTER).exactInputSingle{
            value: _ethToFxs ? _amount : 0
        }(_params);
        if (!_ethToFxs) {
            IWETH(WETH_TOKEN).withdraw(_receivedAmount);
        }
        return _receivedAmount;
    }

    /// @notice Swap ETH->FXS on UniV3 via stable pair
    /// @param _amount - amount to swap
    /// @return amount of token obtained after the swap
    function _uniStableEthToFxsSwap(uint256 _amount)
        internal
        returns (uint256)
    {
        uint24 fee = 500;
        IUniV3Router.ExactInputParams memory _params = IUniV3Router
            .ExactInputParams(
                abi.encodePacked(WETH_TOKEN, fee, USDC_TOKEN, fee, FRAX_TOKEN),
                address(this),
                block.timestamp + 1,
                _amount,
                0
            );

        uint256 _fraxAmount = IUniV3Router(UNIV3_ROUTER).exactInput{
            value: _amount
        }(_params);
        address[] memory _path = new address[](2);
        _path[0] = FRAX_TOKEN;
        _path[1] = FXS_TOKEN;
        uint256[] memory amounts = IUniV2Router(UNISWAP_ROUTER)
            .swapExactTokensForTokens(
                _fraxAmount,
                1,
                _path,
                address(this),
                block.timestamp + 1
            );
        return amounts[1];
    }

    /// @notice Swap FXS->ETH on UniV3 via stable pair
    /// @param _amount - amount to swap
    /// @return amount of token obtained after the swap
    function _uniStableFxsToEthSwap(uint256 _amount)
        internal
        returns (uint256)
    {
        address[] memory _path = new address[](2);
        _path[0] = FXS_TOKEN;
        _path[1] = FRAX_TOKEN;
        uint256[] memory amounts = IUniV2Router(UNISWAP_ROUTER)
            .swapExactTokensForTokens(
                _amount,
                1,
                _path,
                address(this),
                block.timestamp + 1
            );

        uint256 _fraxAmount = amounts[1];
        uint24 fee = 500;

        IUniV3Router.ExactInputParams memory _params = IUniV3Router
            .ExactInputParams(
                abi.encodePacked(FRAX_TOKEN, fee, USDC_TOKEN, fee, WETH_TOKEN),
                address(this),
                block.timestamp + 1,
                _fraxAmount,
                0
            );

        uint256 _ethAmount = IUniV3Router(UNIV3_ROUTER).exactInput{value: 0}(
            _params
        );
        IWETH(WETH_TOKEN).withdraw(_ethAmount);
        return _ethAmount;
    }

    /// @notice Swap native ETH for FXS via different routes
    /// @param _amount - amount to swap
    /// @param _option - the option to use when swapping
    /// @param _ethToFxs - whether to swap from eth to fxs or the inverse
    /// @return amount of token obtained after the swap
    function _swapEthFxs(
        uint256 _amount,
        SwapOption _option,
        bool _ethToFxs
    ) internal returns (uint256) {
        if (_option == SwapOption.Curve) {
            return _curveEthFxsSwap(_amount, _ethToFxs);
        } else if (_option == SwapOption.Uniswap) {
            return _uniV3EthFxsSwap(_amount, _ethToFxs);
        } else {
            return
                _ethToFxs
                    ? _uniStableEthToFxsSwap(_amount)
                    : _uniStableFxsToEthSwap(_amount);
        }
    }

    receive() external payable {}

    modifier onlyDepositor() {
        require(msg.sender == depositor, "Depositor only");
        _;
    }
}