SwapStables

{{
  "language": "Solidity",
  "sources": {
    "contracts/SwapStables.sol": {
      "content": "//SPDX-License-Identifier: MIT
pragma solidity >=0.8.11 <0.9.0;

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

interface IUniswapV2Router02 {
    function WETH() external pure returns (address);
    function getAmountsOut(uint256 amountIn, address[] calldata path)
        external
        view
        returns (uint256[] memory amounts);
    function swapExactTokensForETH(
        uint256 amountIn,
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external returns (uint256[] memory amounts);

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

contract SwapStables is Ownable, ReentrancyGuard {
    // Custom errors
    error SwapStables__TransferFromFailed();
    error SwapStables__InvalidRouter();
    error SwapStables__RouterNotConfigured();
    error SwapStables__NoPaths();
    error SwapStables__NoValidPath();
    error SwapStables__ZeroAmountIn();
    error SwapStables__EthSendFailed();
    error SwapStables__DeadlineExpired();
    error SwapStables__ApproveFailed();

    IUniswapV2Router02 public immutable uniV2; // On mainnet addr = "0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D"

    event SwapExecuted(address indexed sender, address indexed tokenIn, uint256 amountIn, uint256 amountOut);

    // Router is provided at construction and is immutable
    constructor(address _uniV2) Ownable(msg.sender) {
        if (_uniV2 == address(0)) revert SwapStables__InvalidRouter();
        uniV2 = IUniswapV2Router02(_uniV2);
    }

    /**
     * @notice Estimate best amount out among candidate paths
     * @param amountIn amount of input token
     * @param paths array of candidate paths (each is an array of addresses)
     */
    function estimateBestOut(uint256 amountIn, address[][] memory paths)
        internal
        view
        returns (uint256 bestOut, uint256 bestIndex)
    {
        if (address(uniV2) == address(0)) revert SwapStables__RouterNotConfigured();
        if (paths.length == 0) revert SwapStables__NoPaths();

        bestOut = 0;
        bestIndex = 0;

        for (uint256 i = 0; i < paths.length; i++) {
            address[] memory p = paths[i];
            // skip invalid small paths
            if (p.length < 2) continue;
            try uniV2.getAmountsOut(amountIn, p) returns (uint256[] memory amounts) {
                uint256 out = amounts[amounts.length - 1];
                if (out > bestOut) {
                    bestOut = out;
                    bestIndex = i;
                }
            } catch {
                // ignore failing path, reverts by bestOut remaining 0
                continue;
            }
        }
        if (bestOut == 0) revert SwapStables__NoValidPath();
    }

    /**
     * @notice Swap an ERC20 stable token for ETH using Uniswap V2, choosing the most profitable path
     * @param tokenIn input ERC20 token
     * @param amountIn amount of token to swap (caller must approve this contract)
     * @param paths candidate paths where each path is an array of token addresses (last should be WETH)
     * @param amountOutMin minimum acceptable ETH out (slippage protection)
     * @param deadline unix timestamp after which the swap will fail
     */
    function swapStableToETHBest(
        address tokenIn,
        uint256 amountIn,
        address[][] calldata paths,
        uint256 amountOutMin,
        uint256 deadline
    ) external nonReentrant returns (uint256 amountOut) {
        if (amountIn == 0) revert SwapStables__ZeroAmountIn();
        if (paths.length == 0) revert SwapStables__NoPaths();
        if (address(uniV2) == address(0)) revert SwapStables__RouterNotConfigured();

        // deadline check: enforcing deadline locally in case of router failure
        if (deadline < block.timestamp) revert SwapStables__DeadlineExpired();

        // pull tokens from caller
        (bool success) = IERC20(tokenIn).transferFrom(msg.sender, address(this), amountIn);
        if (!success) revert SwapStables__TransferFromFailed();

        // approve router (reset then set). Check return values for non-standard tokens that return false
        bool approved;
        approved = IERC20(tokenIn).approve(address(uniV2), 0);
        if (!approved) revert SwapStables__ApproveFailed();
        approved = IERC20(tokenIn).approve(address(uniV2), amountIn);
        if (!approved) revert SwapStables__ApproveFailed();

        // find best path
        (, uint256 bestIndex) = estimateBestOut(amountIn, paths);

        address[] memory bestPath = paths[bestIndex];

        // execute swap: expect last token to be ETH
        // the router will return ETH to this contract for swapExactTokensForETH
        uint256[] memory amounts =
            uniV2.swapExactTokensForETH(amountIn, amountOutMin, bestPath, address(this), deadline);

        amountOut = amounts[amounts.length - 1];

        // forward ETH to sender
        (bool sent,) = payable(msg.sender).call{ value: amountOut }(" ");
        if (!sent) revert SwapStables__EthSendFailed();

        emit SwapExecuted(msg.sender, tokenIn, amountIn, amountOut);
    }

    // receive ETH from router when swapping
    receive() external payable { }
}
"
    },
    "lib/openzeppelin-contracts/contracts/access/Ownable.sol": {
      "content": "// 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);
    }
}
"
    },
    "lib/openzeppelin-contracts/contracts/utils/ReentrancyGuard.sol": {
      "content": "// 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;
    }
}
"
    },
    "lib/openzeppelin-contracts/contracts/token/ERC20/IERC20.sol": {
      "content": "// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.4.0) (token/ERC20/IERC20.sol)

pragma solidity >=0.4.16;

/**
 * @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);
}
"
    },
    "lib/openzeppelin-contracts/contracts/utils/Context.sol": {
      "content": "// 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;
    }
}
"
    }
  },
  "settings": {
    "remappings": [
      "@openzeppelin/contracts/=lib/openzeppelin-contracts/contracts/",
      "ds-test/=lib/solidity-bytes-utils/lib/forge-std/lib/ds-test/src/",
      "erc4626-tests/=lib/openzeppelin-contracts/lib/erc4626-tests/",
      "forge-std/=lib/forge-std/src/",
      "halmos-cheatcodes/=lib/openzeppelin-contracts/lib/halmos-cheatcodes/src/",
      "openzeppelin-contracts/=lib/openzeppelin-contracts/",
      "solidity-bytes-utils/=lib/solidity-bytes-utils/contracts/"
    ],
    "optimizer": {
      "enabled": false,
      "runs": 200
    },
    "metadata": {
      "useLiteralContent": false,
      "bytecodeHash": "ipfs",
      "appendCBOR": true
    },
    "outputSelection": {
      "*": {
        "*": [
          "evm.bytecode",
          "evm.deployedBytecode",
          "devdoc",
          "userdoc",
          "metadata",
          "abi"
        ]
      }
    },
    "evmVersion": "cancun",
    "viaIR": false
  }
}}