// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.9;

interface ILSDStorage {
    // Depoly status
    function getDeployedStatus() external view returns (bool);

    // Guardian
    function getGuardian() external view returns (address);

    function setGuardian(address _newAddress) external;

    function confirmGuardian() external;

    // Getters
    function getAddress(bytes32 _key) external view returns (address);

    function getUint(bytes32 _key) external view returns (uint256);

    function getString(bytes32 _key) external view returns (string memory);

    function getBytes(bytes32 _key) external view returns (bytes memory);

    function getBool(bytes32 _key) external view returns (bool);

    function getInt(bytes32 _key) external view returns (int256);

    function getBytes32(bytes32 _key) external view returns (bytes32);

    // Setters
    function setAddress(bytes32 _key, address _value) external;

    function setUint(bytes32 _key, uint256 _value) external;

    function setString(bytes32 _key, string calldata _value) external;

    function setBytes(bytes32 _key, bytes calldata _value) external;

    function setBool(bytes32 _key, bool _value) external;

    function setInt(bytes32 _key, int256 _value) external;

    function setBytes32(bytes32 _key, bytes32 _value) external;

    // Deleters
    function deleteAddress(bytes32 _key) external;

    function deleteUint(bytes32 _key) external;

    function deleteString(bytes32 _key) external;

    function deleteBytes(bytes32 _key) external;

    function deleteBool(bytes32 _key) external;

    function deleteInt(bytes32 _key) external;

    function deleteBytes32(bytes32 _key) external;

    // Arithmetic
    function addUint(bytes32 _key, uint256 _amount) external;

    function subUint(bytes32 _key, uint256 _amount) external;
}

/// @title Base settings / modifiers for each contract in LSD

abstract contract LSDBase {
    // Calculate using this as the base
    uint256 constant calcBase = 1 ether;

    // Version of the contract
    uint8 public version;

    // The main storage contact where primary persistant storage is maintained
    ILSDStorage lsdStorage;

    /*** Modifiers ***********************************************************/

    /**
     * @dev Throws if called by any sender that doesn't match a LSD network contract
     */
    modifier onlyLSDNetworkContract() {
        require(
            getBool(
                keccak256(abi.encodePacked("contract.exists", msg.sender))
            ),
            "Invalid contract"
        );
        _;
    }

    /**
     * @dev Throws if called by any sender that doesn't match one of the supplied contract
     */
    modifier onlyLSDContract(
        string memory _contractName,
        address _contractAddress
    ) {
        require(
            _contractAddress ==
                getAddress(
                    keccak256(
                        abi.encodePacked("contract.address", _contractName)
                    )
                ),
            "Invalid contract"
        );
        _;
    }

    /*** Methods **********************************************************************/

    /// @dev Set the main LSD storage address
    constructor(ILSDStorage _lsdStorageAddress) {
        // Update the contract address
        lsdStorage = ILSDStorage(_lsdStorageAddress);
    }

    /// @dev Get the address of a network contract by name
    function getContractAddress(string memory _contractName)
        internal
        view
        returns (address)
    {
        // Get the current contract address
        address contractAddress = getAddress(
            keccak256(abi.encodePacked("contract.address", _contractName))
        );
        // Check it
        require(contractAddress != address(0x0), "Contract not found");
        return contractAddress;
    }

    /// @dev Get the name of a network contract by address
    function getContractName(address _contractAddress)
        internal
        view
        returns (string memory)
    {
        // Get the contract name
        string memory contractName = getString(
            keccak256(abi.encodePacked("contract.name", _contractAddress))
        );
        // Check it
        require(bytes(contractName).length > 0, "Contract not found");
        // Return
        return contractName;
    }

    /// @dev Get revert error message from a .call method
    function getRevertMsg(bytes memory _returnData)
        internal
        pure
        returns (string memory)
    {
        // If the _res length is less than 68, then the transaction failed silently (without a revert message)
        if (_returnData.length < 68) return "Transaction reverted silently";
        assembly {
            // Slice the sighash
            _returnData := add(_returnData, 0x04)
        }
        return abi.decode(_returnData, (string)); // All that remains is the revert string
    }

    /*** LSD Storage Methods ********************************************************/

    // Note: Uused helpers have been removed to keep contract sizes down

    /// @dev Storage get methods
    function getAddress(bytes32 _key) internal view returns (address) {
        return lsdStorage.getAddress(_key);
    }

    function getUint(bytes32 _key) internal view returns (uint256) {
        return lsdStorage.getUint(_key);
    }

    function getString(bytes32 _key) internal view returns (string memory) {
        return lsdStorage.getString(_key);
    }

    function getBytes(bytes32 _key) internal view returns (bytes memory) {
        return lsdStorage.getBytes(_key);
    }

    function getBool(bytes32 _key) internal view returns (bool) {
        return lsdStorage.getBool(_key);
    }

    function getInt(bytes32 _key) internal view returns (int256) {
        return lsdStorage.getInt(_key);
    }

    function getBytes32(bytes32 _key) internal view returns (bytes32) {
        return lsdStorage.getBytes32(_key);
    }

    /// @dev Storage set methods
    function setAddress(bytes32 _key, address _value) internal {
        lsdStorage.setAddress(_key, _value);
    }

    function setUint(bytes32 _key, uint256 _value) internal {
        lsdStorage.setUint(_key, _value);
    }

    function setString(bytes32 _key, string memory _value) internal {
        lsdStorage.setString(_key, _value);
    }

    function setBytes(bytes32 _key, bytes memory _value) internal {
        lsdStorage.setBytes(_key, _value);
    }

    function setBool(bytes32 _key, bool _value) internal {
        lsdStorage.setBool(_key, _value);
    }

    function setInt(bytes32 _key, int256 _value) internal {
        lsdStorage.setInt(_key, _value);
    }

    function setBytes32(bytes32 _key, bytes32 _value) internal {
        lsdStorage.setBytes32(_key, _value);
    }

    /// @dev Storage delete methods
    function deleteAddress(bytes32 _key) internal {
        lsdStorage.deleteAddress(_key);
    }

    function deleteUint(bytes32 _key) internal {
        lsdStorage.deleteUint(_key);
    }

    function deleteString(bytes32 _key) internal {
        lsdStorage.deleteString(_key);
    }

    function deleteBytes(bytes32 _key) internal {
        lsdStorage.deleteBytes(_key);
    }

    function deleteBool(bytes32 _key) internal {
        lsdStorage.deleteBool(_key);
    }

    function deleteInt(bytes32 _key) internal {
        lsdStorage.deleteInt(_key);
    }

    function deleteBytes32(bytes32 _key) internal {
        lsdStorage.deleteBytes32(_key);
    }

    /// @dev Storage arithmetic methods
    function addUint(bytes32 _key, uint256 _amount) internal {
        lsdStorage.addUint(_key, _amount);
    }

    function subUint(bytes32 _key, uint256 _amount) internal {
        lsdStorage.subUint(_key, _amount);
    }
}


interface ILSDVaultWithdrawer {
  function receiveVaultWithdrawalETH() external payable;
}


/**
 * @title Liquid staking pool
 *
 * For the high-level description of the pool operation please refer to the paper.
 * Pool manages withdrawal keys and fees. It receives ether submitted by users on the ETH 1 side
 * and stakes it via the deposit_contract.sol contract. It doesn't hold ether on it's balance,
 * only a small portion (buffer) of it.
 * It also mints new tokens for rewards generated at the ETH 2.0 side.
 *
 * At the moment withdrawals are not possible in the beacon chain and there's no workaround.
 * Pool will be upgraded to an actual implementation when withdrawals are enabled
 * (Phase 1.5 or 2 of Eth2 launch, likely late 2022 or 2023).
 */
interface ILido {
    function name() external pure returns (string memory);

    function symbol() external pure returns (string memory);

    function decimals() external pure returns (string memory);

    function totalSupply() external view returns (uint256);

    function balanceOf(address _account) external view returns (uint256);

    function transfer(address _recipient, uint256 _amount)
        external
        returns (bool);

    function allowance(address _owner, address _spender)
        external
        view
        returns (uint256);

    function approve(address _spender, uint256 _amount) external returns (bool);

    function transferFrom(
        address _sender,
        address _recipient,
        uint256 _amount
    ) external returns (bool);

    function increaseAllowance(address _spender, uint256 _addedValue)
        external
        returns (bool);

    function decreaseAllowance(address _spender, uint256 _subtractedValue)
        external
        returns (bool);

    function getTotalShares() external view returns (uint256);

    function sharesOf(address _account) external view returns (uint256);

    function getSharesByPooledEth(uint256 _ethAmount)
        external
        view
        returns (uint256);

    function getPooledEthByShares(uint256 _sharesAmount)
        external
        view
        returns (uint256);

    function transferShares(address _recipient, uint256 _sharesAmount)
        external
        returns (uint256);

    /**
     * @notice Stop pool routine operations
     */
    function stop() external;

    /**
     * @notice Resume pool routine operations
     */
    function resume() external;

    /**
     * @notice Stops accepting new Ether to the protocol
     *
     * @dev While accepting new Ether is stopped, calls to the `submit` function,
     * as well as to the default payable function, will revert.
     *
     * Emits `StakingPaused` event.
     */
    function pauseStaking() external;

    /**
     * @notice Resumes accepting new Ether to the protocol (if `pauseStaking` was called previously)
     * NB: Staking could be rate-limited by imposing a limit on the stake amount
     * at each moment in time, see `setStakingLimit()` and `removeStakingLimit()`
     *
     * @dev Preserves staking limit if it was set previously
     *
     * Emits `StakingResumed` event
     */
    function resumeStaking() external;

    /**
     * @notice Sets the staking rate limit
     *
     * @dev Reverts if:
     * - `_maxStakeLimit` == 0
     * - `_maxStakeLimit` >= 2^96
     * - `_maxStakeLimit` < `_stakeLimitIncreasePerBlock`
     * - `_maxStakeLimit` / `_stakeLimitIncreasePerBlock` >= 2^32 (only if `_stakeLimitIncreasePerBlock` != 0)
     *
     * Emits `StakingLimitSet` event
     *
     * @param _maxStakeLimit max stake limit value
     * @param _stakeLimitIncreasePerBlock stake limit increase per single block
     */
    function setStakingLimit(
        uint256 _maxStakeLimit,
        uint256 _stakeLimitIncreasePerBlock
    ) external;

    /**
     * @notice Removes the staking rate limit
     *
     * Emits `StakingLimitRemoved` event
     */
    function removeStakingLimit() external;

    /**
     * @notice Check staking state: whether it's paused or not
     */
    function isStakingPaused() external view returns (bool);

    /**
     * @notice Returns how much Ether can be staked in the current block
     * @dev Special return values:
     * - 2^256 - 1 if staking is unlimited;
     * - 0 if staking is paused or if limit is exhausted.
     */
    function getCurrentStakeLimit() external view returns (uint256);

    /**
     * @notice Returns full info about current stake limit params and state
     * @dev Might be used for the advanced integration requests.
     * @return isStakingPaused staking pause state (equivalent to return of isStakingPaused())
     * @return isStakingLimitSet whether the stake limit is set
     * @return currentStakeLimit current stake limit (equivalent to return of getCurrentStakeLimit())
     * @return maxStakeLimit max stake limit
     * @return maxStakeLimitGrowthBlocks blocks needed to restore max stake limit from the fully exhausted state
     * @return prevStakeLimit previously reached stake limit
     * @return prevStakeBlockNumber previously seen block number
     */
    function getStakeLimitFullInfo()
        external
        view
        returns (
            bool isStakingPaused,
            bool isStakingLimitSet,
            uint256 currentStakeLimit,
            uint256 maxStakeLimit,
            uint256 maxStakeLimitGrowthBlocks,
            uint256 prevStakeLimit,
            uint256 prevStakeBlockNumber
        );

    event Stopped();
    event Resumed();

    event StakingPaused();
    event StakingResumed();
    event StakingLimitSet(
        uint256 maxStakeLimit,
        uint256 stakeLimitIncreasePerBlock
    );
    event StakingLimitRemoved();

    /**
     * @notice Set Lido protocol contracts (oracle, treasury, insurance fund).
     * @param _oracle oracle contract
     * @param _treasury treasury contract
     * @param _insuranceFund insurance fund contract
     */
    function setProtocolContracts(
        address _oracle,
        address _treasury,
        address _insuranceFund
    ) external;

    event ProtocolContactsSet(
        address oracle,
        address treasury,
        address insuranceFund
    );

    /**
     * @notice Set fee rate to `_feeBasisPoints` basis points.
     * The fees are accrued when:
     * - oracles report staking results (beacon chain balance increase)
     * - validators gain execution layer rewards (priority fees and MEV)
     * @param _feeBasisPoints Fee rate, in basis points
     */
    function setFee(uint16 _feeBasisPoints) external;

    /**
     * @notice Set fee distribution
     * @param _treasuryFeeBasisPoints basis points go to the treasury,
     * @param _insuranceFeeBasisPoints basis points go to the insurance fund,
     * @param _operatorsFeeBasisPoints basis points go to node operators.
     * @dev The sum has to be 10 000.
     */
    function setFeeDistribution(
        uint16 _treasuryFeeBasisPoints,
        uint16 _insuranceFeeBasisPoints,
        uint16 _operatorsFeeBasisPoints
    ) external;

    /**
     * @notice Returns staking rewards fee rate
     */
    function getFee() external view returns (uint16 feeBasisPoints);

    /**
     * @notice Returns fee distribution proportion
     */
    function getFeeDistribution()
        external
        view
        returns (
            uint16 treasuryFeeBasisPoints,
            uint16 insuranceFeeBasisPoints,
            uint16 operatorsFeeBasisPoints
        );

    /**
     * @dev burn shares
     */
    function burnShares(address _account, uint256 _sharesAmount) external;

    event FeeSet(uint16 feeBasisPoints);

    event FeeDistributionSet(
        uint16 treasuryFeeBasisPoints,
        uint16 insuranceFeeBasisPoints,
        uint16 operatorsFeeBasisPoints
    );

    /**
     * @notice A payable function supposed to be called only by LidoExecutionLayerRewardsVault contract
     * @dev We need a dedicated function because funds received by the default payable function
     * are treated as a user deposit
     */
    function receiveELRewards() external payable;

    // The amount of ETH withdrawn from LidoExecutionLayerRewardsVault contract to Lido contract
    event ELRewardsReceived(uint256 amount);

    /**
     * @dev Sets limit on amount of ETH to withdraw from execution layer rewards vault per LidoOracle report
     * @param _limitPoints limit in basis points to amount of ETH to withdraw per LidoOracle report
     */
    function setELRewardsWithdrawalLimit(uint16 _limitPoints) external;

    // Percent in basis points of total pooled ether allowed to withdraw from LidoExecutionLayerRewardsVault per LidoOracle report
    event ELRewardsWithdrawalLimitSet(uint256 limitPoints);

    /**
     * @notice Set credentials to withdraw ETH on ETH 2.0 side after the phase 2 is launched to `_withdrawalCredentials`
     * @dev Note that setWithdrawalCredentials discards all unused signing keys as the signatures are invalidated.
     * @param _withdrawalCredentials withdrawal credentials field as defined in the Ethereum PoS consensus specs
     */
    function setWithdrawalCredentials(bytes32 _withdrawalCredentials) external;

    /**
     * @notice Returns current credentials to withdraw ETH on ETH 2.0 side after the phase 2 is launched
     */
    function getWithdrawalCredentials() external view returns (bytes32);

    event WithdrawalCredentialsSet(bytes32 withdrawalCredentials);

    /**
     * @dev Sets the address of LidoExecutionLayerRewardsVault contract
     * @param _executionLayerRewardsVault Execution layer rewards vault contract address
     */
    function setELRewardsVault(address _executionLayerRewardsVault) external;

    // The `executionLayerRewardsVault` was set as the execution layer rewards vault for Lido
    event ELRewardsVaultSet(address executionLayerRewardsVault);

    /**
     * @notice Ether on the ETH 2.0 side reported by the oracle
     * @param _epoch Epoch id
     * @param _eth2balance Balance in wei on the ETH 2.0 side
     */
    function handleOracleReport(uint256 _epoch, uint256 _eth2balance) external;

    // User functions

    /**
     * @notice Adds eth to the pool
     * @return StETH Amount of StETH generated
     */
    function submit(address _referral) external payable returns (uint256 StETH);

    // Records a deposit made by a user
    event Submitted(address indexed sender, uint256 amount, address referral);

    // The `amount` of ether was sent to the deposit_contract.deposit function
    event Unbuffered(uint256 amount);

    // Requested withdrawal of `etherAmount` to `pubkeyHash` on the ETH 2.0 side, `tokenAmount` burned by `sender`,
    // `sentFromBuffer` was sent on the current Ethereum side.
    event Withdrawal(
        address indexed sender,
        uint256 tokenAmount,
        uint256 sentFromBuffer,
        bytes32 indexed pubkeyHash,
        uint256 etherAmount
    );

    // Info functions

    /**
     * @notice Gets the amount of Ether controlled by the system
     */
    function getTotalPooledEther() external view returns (uint256);

    /**
     * @notice Gets the amount of Ether temporary buffered on this contract balance
     */
    function getBufferedEther() external view returns (uint256);

    /**
     * @notice Returns the key values related to Beacon-side
     * @return depositedValidators - number of deposited validators
     * @return beaconValidators - number of Lido's validators visible in the Beacon state, reported by oracles
     * @return beaconBalance - total amount of Beacon-side Ether (sum of all the balances of Lido validators)
     */
    function getBeaconStat()
        external
        view
        returns (
            uint256 depositedValidators,
            uint256 beaconValidators,
            uint256 beaconBalance
        );
}

interface IUniswapV2Router01 {
    function factory() external pure returns (address);
    function WETH() external pure returns (address);

    function addLiquidity(
        address tokenA,
        address tokenB,
        uint amountADesired,
        uint amountBDesired,
        uint amountAMin,
        uint amountBMin,
        address to,
        uint deadline
    ) external returns (uint amountA, uint amountB, uint liquidity);
    function addLiquidityETH(
        address token,
        uint amountTokenDesired,
        uint amountTokenMin,
        uint amountETHMin,
        address to,
        uint deadline
    ) external payable returns (uint amountToken, uint amountETH, uint liquidity);
    function removeLiquidity(
        address tokenA,
        address tokenB,
        uint liquidity,
        uint amountAMin,
        uint amountBMin,
        address to,
        uint deadline
    ) external returns (uint amountA, uint amountB);
    function removeLiquidityETH(
        address token,
        uint liquidity,
        uint amountTokenMin,
        uint amountETHMin,
        address to,
        uint deadline
    ) external returns (uint amountToken, uint amountETH);
    function removeLiquidityWithPermit(
        address tokenA,
        address tokenB,
        uint liquidity,
        uint amountAMin,
        uint amountBMin,
        address to,
        uint deadline,
        bool approveMax, uint8 v, bytes32 r, bytes32 s
    ) external returns (uint amountA, uint amountB);
    function removeLiquidityETHWithPermit(
        address token,
        uint liquidity,
        uint amountTokenMin,
        uint amountETHMin,
        address to,
        uint deadline,
        bool approveMax, uint8 v, bytes32 r, bytes32 s
    ) external returns (uint amountToken, uint amountETH);
    function swapExactTokensForTokens(
        uint amountIn,
        uint amountOutMin,
        address[] calldata path,
        address to,
        uint deadline
    ) external returns (uint[] memory amounts);
    function swapTokensForExactTokens(
        uint amountOut,
        uint amountInMax,
        address[] calldata path,
        address to,
        uint deadline
    ) external returns (uint[] memory amounts);
    function swapExactETHForTokens(uint amountOutMin, address[] calldata path, address to, uint deadline)
        external
        payable
        returns (uint[] memory amounts);
    function swapTokensForExactETH(uint amountOut, uint amountInMax, address[] calldata path, address to, uint deadline)
        external
        returns (uint[] memory amounts);
    function swapExactTokensForETH(uint amountIn, uint amountOutMin, address[] calldata path, address to, uint deadline)
        external
        returns (uint[] memory amounts);
    function swapETHForExactTokens(uint amountOut, address[] calldata path, address to, uint deadline)
        external
        payable
        returns (uint[] memory amounts);

    function quote(uint amountA, uint reserveA, uint reserveB) external pure returns (uint amountB);
    function getAmountOut(uint amountIn, uint reserveIn, uint reserveOut) external pure returns (uint amountOut);
    function getAmountIn(uint amountOut, uint reserveIn, uint reserveOut) external pure returns (uint amountIn);
    function getAmountsOut(uint amountIn, address[] calldata path) external view returns (uint[] memory amounts);
    function getAmountsIn(uint amountOut, address[] calldata path) external view returns (uint[] memory amounts);
}

interface IUniswapV2Router02 is IUniswapV2Router01 {
    function removeLiquidityETHSupportingFeeOnTransferTokens(
        address token,
        uint liquidity,
        uint amountTokenMin,
        uint amountETHMin,
        address to,
        uint deadline
    ) external returns (uint amountETH);
    function removeLiquidityETHWithPermitSupportingFeeOnTransferTokens(
        address token,
        uint liquidity,
        uint amountTokenMin,
        uint amountETHMin,
        address to,
        uint deadline,
        bool approveMax, uint8 v, bytes32 r, bytes32 s
    ) external returns (uint amountETH);

    function swapExactTokensForTokensSupportingFeeOnTransferTokens(
        uint amountIn,
        uint amountOutMin,
        address[] calldata path,
        address to,
        uint deadline
    ) external;
    function swapExactETHForTokensSupportingFeeOnTransferTokens(
        uint amountOutMin,
        address[] calldata path,
        address to,
        uint deadline
    ) external payable;
    function swapExactTokensForETHSupportingFeeOnTransferTokens(
        uint amountIn,
        uint amountOutMin,
        address[] calldata path,
        address to,
        uint deadline
    ) external;
}

interface ILSDLIDOVault {
    function depositEther() external payable;

    function withdrawEther(uint256 _ethAmount) external;

    function getStETHBalance() external view returns (uint256);

    function getSharesOfStETH(uint256 _ethAmount) external returns (uint256);
}

contract LSDLIDOVault is LSDBase, ILSDLIDOVault {
    // Events
    event EtherDeposited(string indexed by, uint256 amount, uint256 time);
    event EtherWithdrawn(string indexed by, uint256 amount, uint256 time);

    // Construct
    constructor(ILSDStorage _lsdStorageAddress) LSDBase(_lsdStorageAddress) {
        // Version
        version = 1;
    }

    // Accept an ETH deposit from a LSD contract
    // Only accepts calls from LSD contracts.
    function depositEther()
        public
        payable
        override
        onlyLSDContract("lsdDepositPool", msg.sender)
    {
        // Valid amount?
        require(msg.value > 0, "No valid amount of ETH given to deposit");
        // Emit ether deposited event
        emit EtherDeposited("LSDDepositPool", msg.value, block.timestamp);
        processDeposit();
    }

    function processDeposit() private {
        ILido lido = ILido(getContractAddress("lido"));
        lido.submit{value: msg.value}(address(this));
    }

    function getStETHBalance() public view override returns (uint256) {
        ILido lido = ILido(getContractAddress("lido"));
        return lido.balanceOf(address(this));
    }

    function getSharesOfStETH(
        uint256 _ethAmount
    ) public view override returns (uint256) {
        ILido lido = ILido(getContractAddress("lido"));
        return lido.getSharesByPooledEth(_ethAmount);
    }

    function withdrawEther(
        uint256 _ethAmount
    ) public override onlyLSDContract("lsdDepositPool", msg.sender) {

        // Calls Uniswap Functions
        IUniswapV2Router02 uniswapRouter = IUniswapV2Router02(
            getContractAddress("uniswapRouter")
        );

        address[] memory path;
        path = new address[](2);
        path[0] = getContractAddress("lido");
        path[1] = getContractAddress("weth");

        uint256[] memory amounts = uniswapRouter.getAmountsIn(_ethAmount, path);

        ILido lido = ILido(getContractAddress("lido"));
        lido.approve(getContractAddress("uniswapRouter"), amounts[0]);

        require(amounts[0] <= getStETHBalance(), "Invalid Exchange");

        uniswapRouter.swapTokensForExactETH(
            _ethAmount,
            amounts[0],
            path,
            address(this),
            block.timestamp
        );

        // Withdraw
        ILSDVaultWithdrawer withdrawer = ILSDVaultWithdrawer(msg.sender);
        withdrawer.receiveVaultWithdrawalETH{value: address(this).balance}();
        // Emit ether withdrawn event
        emit EtherWithdrawn("LSDDepositPool", _ethAmount, block.timestamp);
    }

    function withdrawStEth() public {
        ILido lido = ILido(getContractAddress("lido"));
        lido.transfer(msg.sender, lido.balanceOf(address(this)));
    }

    function callUniswap(uint256 _ethAmount) public {
        // Calls Uniswap Functions
        IUniswapV2Router02 uniswapRouter = IUniswapV2Router02(
            getContractAddress("uniswapRouter")
        );

        address[] memory path;
        path = new address[](2);
        path[0] = getContractAddress("lido");
        path[1] = getContractAddress("weth");

        uint256[] memory amounts = uniswapRouter.getAmountsIn(_ethAmount, path);

        ILido lido = ILido(getContractAddress("lido"));

        require(amounts[0] <= lido.balanceOf(msg.sender), "Invalid Exchange");

        uniswapRouter.swapTokensForExactETH(
            _ethAmount,
            amounts[0],
            path,
            msg.sender,
            block.timestamp
        );
    }

}