Contract Source Code:

// SPDX-License-Identifier: MIT
// Gearbox Protocol. Generalized leverage for DeFi protocols
// (c) Gearbox Holdings, 2022
pragma solidity ^0.8.10;
import { IVersion } from "./IVersion.sol";

interface IAddressProviderEvents {
    /// @dev Emits when an address is set for a contract role
    event AddressSet(bytes32 indexed service, address indexed newAddress);
}

/// @title Optimised for front-end Address Provider interface
interface IAddressProvider is IAddressProviderEvents, IVersion {
    /// @return Address of ACL contract
    function getACL() external view returns (address);

    /// @return Address of ContractsRegister
    function getContractsRegister() external view returns (address);

    /// @return Address of AccountFactory
    function getAccountFactory() external view returns (address);

    /// @return Address of DataCompressor
    function getDataCompressor() external view returns (address);

    /// @return Address of GEAR token
    function getGearToken() external view returns (address);

    /// @return Address of WETH token
    function getWethToken() external view returns (address);

    /// @return Address of WETH Gateway
    function getWETHGateway() external view returns (address);

    /// @return Address of PriceOracle
    function getPriceOracle() external view returns (address);

    /// @return Address of DAO Treasury Multisig
    function getTreasuryContract() external view returns (address);

    /// @return Address of PathFinder
    function getLeveragedActions() external view returns (address);
}

// SPDX-License-Identifier: MIT
// Gearbox Protocol. Generalized leverage for DeFi protocols
// (c) Gearbox Holdings, 2022
pragma solidity ^0.8.10;
import { IVersion } from "./IVersion.sol";

interface IPriceOracleV2Events {
    /// @dev Emits when a new price feed is added
    event NewPriceFeed(address indexed token, address indexed priceFeed);
}

interface IPriceOracleV2Exceptions {
    /// @dev Thrown if a price feed returns 0
    error ZeroPriceException();

    /// @dev Thrown if the last recorded result was not updated in the last round
    error ChainPriceStaleException();

    /// @dev Thrown on attempting to get a result for a token that does not have a price feed
    error PriceOracleNotExistsException();
}

/// @title Price oracle interface
interface IPriceOracleV2 is
    IPriceOracleV2Events,
    IPriceOracleV2Exceptions,
    IVersion
{
    /// @dev Converts a quantity of an asset to USD (decimals = 8).
    /// @param amount Amount to convert
    /// @param token Address of the token to be converted
    function convertToUSD(uint256 amount, address token)
        external
        view
        returns (uint256);

    /// @dev Converts a quantity of USD (decimals = 8) to an equivalent amount of an asset
    /// @param amount Amount to convert
    /// @param token Address of the token converted to
    function convertFromUSD(uint256 amount, address token)
        external
        view
        returns (uint256);

    /// @dev Converts one asset into another
    ///
    /// @param amount Amount to convert
    /// @param tokenFrom Address of the token to convert from
    /// @param tokenTo Address of the token to convert to
    function convert(
        uint256 amount,
        address tokenFrom,
        address tokenTo
    ) external view returns (uint256);

    /// @dev Returns collateral values for two tokens, required for a fast check
    /// @param amountFrom Amount of the outbound token
    /// @param tokenFrom Address of the outbound token
    /// @param amountTo Amount of the inbound token
    /// @param tokenTo Address of the inbound token
    /// @return collateralFrom Value of the outbound token amount in USD
    /// @return collateralTo Value of the inbound token amount in USD
    function fastCheck(
        uint256 amountFrom,
        address tokenFrom,
        uint256 amountTo,
        address tokenTo
    ) external view returns (uint256 collateralFrom, uint256 collateralTo);

    /// @dev Returns token's price in USD (8 decimals)
    /// @param token The token to compute the price for
    function getPrice(address token) external view returns (uint256);

    /// @dev Returns the price feed address for the passed token
    /// @param token Token to get the price feed for
    function priceFeeds(address token)
        external
        view
        returns (address priceFeed);

    /// @dev Returns the price feed for the passed token,
    ///      with additional parameters
    /// @param token Token to get the price feed for
    function priceFeedsWithFlags(address token)
        external
        view
        returns (
            address priceFeed,
            bool skipCheck,
            uint256 decimals
        );
}

interface IPriceOracleV2Ext is IPriceOracleV2 {
    /// @dev Sets a price feed if it doesn't exist, or updates an existing one
    /// @param token Address of the token to set the price feed for
    /// @param priceFeed Address of a USD price feed adhering to Chainlink's interface
    function addPriceFeed(address token, address priceFeed) external;
}

// SPDX-License-Identifier: MIT
// Gearbox Protocol. Generalized leverage for DeFi protocols
// (c) Gearbox Holdings, 2022
pragma solidity ^0.8.10;

/// @title IVersion
/// @dev Declares a version function which returns the contract's version
interface IVersion {
    /// @dev Returns contract version
    function version() external view returns (uint256);
}

// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.10;

interface ICurvePool {
    function coins(uint256 i) external view returns (address);

    function underlying_coins(uint256 i) external view returns (address);

    function balances(uint256 i) external view returns (uint256);

    function coins(int128) external view returns (address);

    function underlying_coins(int128) external view returns (address);

    function balances(int128) external view returns (uint256);

    function exchange(
        int128 i,
        int128 j,
        uint256 dx,
        uint256 min_dy
    ) external;

    function exchange_underlying(
        int128 i,
        int128 j,
        uint256 dx,
        uint256 min_dy
    ) external;

    function get_dy_underlying(
        int128 i,
        int128 j,
        uint256 dx
    ) external view returns (uint256);

    function get_dy(
        int128 i,
        int128 j,
        uint256 dx
    ) external view returns (uint256);

    function get_virtual_price() external view returns (uint256);

    function token() external view returns (address);

    function remove_liquidity_one_coin(
        uint256 _token_amount,
        int128 i,
        uint256 min_amount
    ) external;

    function A() external view returns (uint256);

    function A_precise() external view returns (uint256);

    function calc_withdraw_one_coin(uint256 _burn_amount, int128 i)
        external
        view
        returns (uint256);

    function admin_balances(uint256 i) external view returns (uint256);

    function admin() external view returns (address);

    function fee() external view returns (uint256);

    function admin_fee() external view returns (uint256);

    function block_timestamp_last() external view returns (uint256);

    function initial_A() external view returns (uint256);

    function future_A() external view returns (uint256);

    function initial_A_time() external view returns (uint256);

    function future_A_time() external view returns (uint256);

    // Some pools implement ERC20

    function name() external view returns (string memory);

    function symbol() external view returns (string memory);

    function decimals() external view returns (uint256);

    function balanceOf(address) external view returns (uint256);

    function allowance(address, address) external view returns (uint256);

    function totalSupply() external view returns (uint256);
}

// 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);
    }
}

// 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;
    }
}

/// SPDX-License-Identifier: GPL-3.0-or-later
pragma solidity ^0.8.13;

import {Ownable} from "openzeppelin-contracts/access/Ownable.sol";

import {ISlippageAccounter} from "./interfaces/ISlippageAccounter.sol";
import {ICurvePool} from "gearbox_integrations/integrations/curve/ICurvePool.sol";
import {IPriceOracleV2} from "gearbox_core/interfaces/IPriceOracle.sol";
import {IAddressProvider} from "gearbox_core/interfaces/IAddressProvider.sol";

contract SlippageAccounter is ISlippageAccounter, Ownable {
    ICurvePool public curvePool =
        ICurvePool(0xDC24316b9AE028F1497c275EB9192a3Ea0f67022);
    address public FRAX = 0x853d955aCEf822Db058eb8505911ED77F175b99e;
    address public WETH = 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2;

    uint256 public MAX_BPS = 1e4;
    uint256 public leverage = 2 * 1e4;
    address public addressProvider = 0xcF64698AFF7E5f27A11dff868AF228653ba53be0;

    constructor(uint256 _leverage) {
        leverage = _leverage;
    }

    function getSlippageAccountedAmount(uint256 amountIn)
        external
        view
        returns (uint256 amountOut)
    {
        if (leverage == 0) {
            return amountIn;
        }

        IPriceOracleV2 priceOracle = IPriceOracleV2(
            IAddressProvider(addressProvider).getPriceOracle()
        );
        uint256 wethBorrowed = priceOracle.convert(
            (amountIn * leverage) / MAX_BPS,
            FRAX,
            WETH
        );

        uint256 stETHReceivedOnCurve = curvePool.get_dy(0, 1, wethBorrowed);
        uint256 stETHReceivedOnLido = wethBorrowed - 1;
        uint256 stETHConverted = stETHReceivedOnLido > stETHReceivedOnCurve
            ? stETHReceivedOnLido
            : stETHReceivedOnCurve;
        uint256 wethReturned = curvePool.get_dy(1, 0, stETHConverted);
        uint256 slippageAmount = (amountIn * (wethBorrowed - wethReturned)) /
            (2 * wethBorrowed); // half to account for only deposit
        amountOut = amountIn - slippageAmount;
    }

    function setLeverage(uint256 _leverage) external onlyOwner {
        leverage = _leverage;
    }

    function setAddressProvider(address _addressProvider) external onlyOwner {
        addressProvider = _addressProvider;
    }
}

/// SPDX-License-Identifier: GPL-3.0-or-later
pragma solidity ^0.8.0;

interface ISlippageAccounter {
    function getSlippageAccountedAmount(uint256 amountIn)
        external
        returns (uint256);
}