// File: @yield-protocol/vault-v2/contracts/other/tether/TetherJoin.sol



// SPDX-License-Identifier: BUSL-1.1
// Audit as of 2023-02-03, commit 99464fe, https://hackmd.io/AY6oeTvVSCyLdCh1MEG7yQ
pragma solidity >=0.8.13;

import "./IUSDT.sol";
import "../../FlashJoin.sol";
import "@yield-protocol/utils-v2/contracts/token/IERC20.sol";
import "@yield-protocol/utils-v2/contracts/access/AccessControl.sol";
import "@yield-protocol/utils-v2/contracts/token/TransferHelper.sol";
import "@yield-protocol/utils-v2/contracts/math/WDiv.sol";

/// @dev Tether includes code in its contract to apply a fee to transfers. In developing this contract,
/// we took a selfish approach. The TetherJoin will only care about the amount that USDT that it receives,
/// and about the amount of USDT that it sends. If fees are enabled, the TetherJoin will expect to have 
/// the amount specified in the join function arguments, and if pulling from the user, it will pull the
/// amount that it expects to receive, plus the fee. Likewise, if sending to the user, it will send the
/// amount specified as an argument, and it is responsibility of the receiver to deal with any shortage
/// on receival due to fees. This aproach extends to flash loans.
contract TetherJoin is FlashJoin {
    using TransferHelper for IERC20;
    using WDiv for uint256;

    constructor(address asset_) FlashJoin(asset_) {}

    /// @dev Calculate the minimum of two uint256s.
    function _min(uint256 a, uint256 b) internal pure returns (uint256) {
        return a < b ? a : b;
    }

    /// @dev Calculate the amount of `asset` that needs to be sent to receive `amount` of USDT.
    function _reverseFee(uint256 amount) internal view returns (uint256) {
        return _min(amount.wdiv(1e18 - IUSDT(asset).basisPointsRate() * 1e14), amount + IUSDT(asset).maximumFee());
    }

    /// @dev Take `asset` from `user` using `transferFrom`, minus any unaccounted `asset` in this contract, so that `amount` of USDT is received.
    function _join(address user, uint128 amount) internal override returns (uint128) {
        IERC20 token = IERC20(asset);
        uint256 _storedBalance = storedBalance;
        uint256 available = token.balanceOf(address(this)) - _storedBalance; // Fine to panic if this underflows
        unchecked {
            if (available == 0) {
                token.safeTransferFrom(user, address(this), _reverseFee(amount));
                amount = uint128(token.balanceOf(address(this)) - _storedBalance);
            } else if (available < amount) {
                token.safeTransferFrom(user, address(this), _reverseFee(amount - available));
                amount = uint128(token.balanceOf(address(this)) - _storedBalance);
            }
            storedBalance = _storedBalance + amount; // Unlikely that a uint128 added to the stored balance will make it overflow
        }
        return amount;
    }
}
// File: @yield-protocol/vault-v2/contracts/FlashJoin.sol



// SPDX-License-Identifier: BUSL-1.1
pragma solidity >=0.8.13;

import "erc3156/contracts/interfaces/IERC3156FlashBorrower.sol";
import "erc3156/contracts/interfaces/IERC3156FlashLender.sol";
import "@yield-protocol/utils-v2/contracts/token/TransferHelper.sol";
import "@yield-protocol/utils-v2/contracts/math/WMul.sol";
import "@yield-protocol/utils-v2/contracts/cast/CastU256U128.sol";
import "./Join.sol";

contract FlashJoin is Join, IERC3156FlashLender {
    using WMul for uint256;
    using CastU256U128 for uint256;
    event FlashFeeFactorSet(uint256 indexed fee);

    bytes32 internal constant FLASH_LOAN_RETURN = keccak256("ERC3156FlashBorrower.onFlashLoan");
    uint256 public constant FLASH_LOANS_DISABLED = type(uint256).max;

    uint256 public flashFeeFactor = FLASH_LOANS_DISABLED; // Fee on flash loans, as a percentage in fixed point with 18 decimals. Flash loans disabled by default.

    constructor(address asset_) Join(asset_) {}

    /// @dev Set the flash loan fee factor
    function setFlashFeeFactor(uint256 flashFeeFactor_) external auth {
        flashFeeFactor = flashFeeFactor_;
        emit FlashFeeFactorSet(flashFeeFactor_);
    }

    /**
     * @dev From ERC-3156. The amount of currency available to be lended.
     * @param token The loan currency. It must be a FYDai contract.
     * @return The amount of `token` that can be borrowed.
     */
    function maxFlashLoan(address token) external view override returns (uint256) {
        return token == asset ? storedBalance : 0;
    }

    /**
     * @dev From ERC-3156. The fee to be charged for a given loan.
     * @param token The loan currency. It must be the asset.
     * @param amount The amount of tokens lent.
     * @return The amount of `token` to be charged for the loan, on top of the returned principal.
     */
    function flashFee(address token, uint256 amount) external view override returns (uint256) {
        require(token == asset, "Unsupported currency");
        return _flashFee(amount);
    }

    /**
     * @dev The fee to be charged for a given loan.
     * @param amount The amount of tokens lent.
     * @return The amount of `token` to be charged for the loan, on top of the returned principal.
     */
    function _flashFee(uint256 amount) internal view returns (uint256) {
        return amount.wmul(flashFeeFactor);
    }

    /**
     * @dev From ERC-3156. Loan `amount` `asset` to `receiver`, which needs to return them plus fee to this contract within the same transaction.
     * If the principal + fee are transferred to this contract, they won't be pulled from the receiver.
     * @param receiver The contract receiving the tokens, needs to implement the `onFlashLoan(address user, uint256 amount, uint256 fee, bytes calldata)` interface.
     * @param token The loan currency. Must be a fyDai contract.
     * @param amount The amount of tokens lent.
     * @param data A data parameter to be passed on to the `receiver` for any custom use.
     */
    function flashLoan(
        IERC3156FlashBorrower receiver,
        address token,
        uint256 amount,
        bytes memory data
    ) external override returns (bool) {
        require(token == asset, "Unsupported currency");
        uint128 _amount = amount.u128();
        uint128 _fee = _flashFee(amount).u128();
        _exit(address(receiver), _amount);

        require(
            receiver.onFlashLoan(msg.sender, token, _amount, _fee, data) == FLASH_LOAN_RETURN,
            "Non-compliant borrower"
        );

        _join(address(receiver), _amount + _fee);
        return true;
    }
}

// File: @yield-protocol/utils-v2/contracts/access/AccessControl.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

/**
 * @dev Contract module that allows children to implement role-based access
 * control mechanisms.
 *
 * Roles are referred to by their `bytes4` identifier. These are expected to be the 
 * signatures for all the functions in the contract. Special roles should be exposed
 * in the external API and be unique:
 *
 * ```
 * bytes4 public constant ROOT = 0x00000000;
 * ```
 *
 * Roles represent restricted access to a function call. For that purpose, use {auth}:
 *
 * ```
 * function foo() public auth {
 *     ...
 * }
 * ```
 *
 * Roles can be granted and revoked dynamically via the {grantRole} and
 * {revokeRole} functions. Each role has an associated admin role, and only
 * accounts that have a role's admin role can call {grantRole} and {revokeRole}.
 *
 * By default, the admin role for all roles is `ROOT`, which means
 * that only accounts with this role will be able to grant or revoke other
 * roles. More complex role relationships can be created by using
 * {setRoleAdmin}.
 *
 * WARNING: The `ROOT` is also its own admin: it has permission to
 * grant and revoke this role. Extra precautions should be taken to secure
 * accounts that have been granted it.
 */
contract AccessControl {
    struct RoleData {
        mapping (address => bool) members;
        bytes4 adminRole;
    }

    mapping (bytes4 => RoleData) private _roles;

    bytes4 public constant ROOT = 0x00000000;
    bytes4 public constant ROOT4146650865 = 0x00000000; // Collision protection for ROOT, test with ROOT12007226833()
    bytes4 public constant LOCK = 0xFFFFFFFF;           // Used to disable further permissioning of a function
    bytes4 public constant LOCK8605463013 = 0xFFFFFFFF; // Collision protection for LOCK, test with LOCK10462387368()

    /**
     * @dev Emitted when `newAdminRole` is set as ``role``'s admin role
     *
     * `ROOT` is the starting admin for all roles, despite
     * {RoleAdminChanged} not being emitted signaling this.
     *
     * _Available since v3.1._
     */
    event RoleAdminChanged(bytes4 indexed role, bytes4 indexed newAdminRole);

    /**
     * @dev Emitted when `account` is granted `role`.
     *
     * `sender` is the account that originated the contract call.
     */
    event RoleGranted(bytes4 indexed role, address indexed account, address indexed sender);

    /**
     * @dev Emitted when `account` is revoked `role`.
     *
     * `sender` is the account that originated the contract call:
     *   - if using `revokeRole`, it is the admin role bearer
     *   - if using `renounceRole`, it is the role bearer (i.e. `account`)
     */
    event RoleRevoked(bytes4 indexed role, address indexed account, address indexed sender);

    /**
     * @dev Give msg.sender the ROOT role and create a LOCK role with itself as the admin role and no members. 
     * Calling setRoleAdmin(msg.sig, LOCK) means no one can grant that msg.sig role anymore.
     */
    constructor () {
        _grantRole(ROOT, msg.sender);   // Grant ROOT to msg.sender
        _setRoleAdmin(LOCK, LOCK);      // Create the LOCK role by setting itself as its own admin, creating an independent role tree
    }

    /**
     * @dev Each function in the contract has its own role, identified by their msg.sig signature.
     * ROOT can give and remove access to each function, lock any further access being granted to
     * a specific action, or even create other roles to delegate admin control over a function.
     */
    modifier auth() {
        require (_hasRole(msg.sig, msg.sender), "Access denied");
        _;
    }

    /**
     * @dev Allow only if the caller has been granted the admin role of `role`.
     */
    modifier admin(bytes4 role) {
        require (_hasRole(_getRoleAdmin(role), msg.sender), "Only admin");
        _;
    }

    /**
     * @dev Returns `true` if `account` has been granted `role`.
     */
    function hasRole(bytes4 role, address account) external view returns (bool) {
        return _hasRole(role, account);
    }

    /**
     * @dev Returns the admin role that controls `role`. See {grantRole} and
     * {revokeRole}.
     *
     * To change a role's admin, use {_setRoleAdmin}.
     */
    function getRoleAdmin(bytes4 role) external view returns (bytes4) {
        return _getRoleAdmin(role);
    }

    /**
     * @dev Sets `adminRole` as ``role``'s admin role.

     * If ``role``'s admin role is not `adminRole` emits a {RoleAdminChanged} event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     */
    function setRoleAdmin(bytes4 role, bytes4 adminRole) external virtual admin(role) {
        _setRoleAdmin(role, adminRole);
    }

    /**
     * @dev Grants `role` to `account`.
     *
     * If `account` had not been already granted `role`, emits a {RoleGranted}
     * event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     */
    function grantRole(bytes4 role, address account) external virtual admin(role) {
        _grantRole(role, account);
    }

    
    /**
     * @dev Grants all of `role` in `roles` to `account`.
     *
     * If `account` had not been already granted `role`, emits a {RoleGranted}
     * event.
     *
     * Requirements:
     *
     * - For each `role` in `roles`, the caller must have ``role``'s admin role.
     */
    function grantRoles(bytes4[] memory roles, address account) external virtual {
        for (uint256 i = 0; i < roles.length; i++) {
            require (_hasRole(_getRoleAdmin(roles[i]), msg.sender), "Only admin");
            _grantRole(roles[i], account);
        }
    }

    /**
     * @dev Sets LOCK as ``role``'s admin role. LOCK has no members, so this disables admin management of ``role``.

     * Emits a {RoleAdminChanged} event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     */
    function lockRole(bytes4 role) external virtual admin(role) {
        _setRoleAdmin(role, LOCK);
    }

    /**
     * @dev Revokes `role` from `account`.
     *
     * If `account` had been granted `role`, emits a {RoleRevoked} event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     */
    function revokeRole(bytes4 role, address account) external virtual admin(role) {
        _revokeRole(role, account);
    }

    /**
     * @dev Revokes all of `role` in `roles` from `account`.
     *
     * If `account` had been granted `role`, emits a {RoleRevoked} event.
     *
     * Requirements:
     *
     * - For each `role` in `roles`, the caller must have ``role``'s admin role.
     */
    function revokeRoles(bytes4[] memory roles, address account) external virtual {
        for (uint256 i = 0; i < roles.length; i++) {
            require (_hasRole(_getRoleAdmin(roles[i]), msg.sender), "Only admin");
            _revokeRole(roles[i], account);
        }
    }

    /**
     * @dev Revokes `role` from the calling account.
     *
     * Roles are often managed via {grantRole} and {revokeRole}: this function's
     * purpose is to provide a mechanism for accounts to lose their privileges
     * if they are compromised (such as when a trusted device is misplaced).
     *
     * If the calling account had been granted `role`, emits a {RoleRevoked}
     * event.
     *
     * Requirements:
     *
     * - the caller must be `account`.
     */
    function renounceRole(bytes4 role, address account) external virtual {
        require(account == msg.sender, "Renounce only for self");

        _revokeRole(role, account);
    }

    function _hasRole(bytes4 role, address account) internal view returns (bool) {
        return _roles[role].members[account];
    }

    function _getRoleAdmin(bytes4 role) internal view returns (bytes4) {
        return _roles[role].adminRole;
    }

    function _setRoleAdmin(bytes4 role, bytes4 adminRole) internal virtual {
        if (_getRoleAdmin(role) != adminRole) {
            _roles[role].adminRole = adminRole;
            emit RoleAdminChanged(role, adminRole);
        }
    }

    function _grantRole(bytes4 role, address account) internal {
        if (!_hasRole(role, account)) {
            _roles[role].members[account] = true;
            emit RoleGranted(role, account, msg.sender);
        }
    }

    function _revokeRole(bytes4 role, address account) internal {
        if (_hasRole(role, account)) {
            _roles[role].members[account] = false;
            emit RoleRevoked(role, account, msg.sender);
        }
    }
}
// File: @yield-protocol/utils-v2/contracts/token/TransferHelper.sol



// SPDX-License-Identifier: MIT
// Taken from https://github.com/Uniswap/uniswap-lib/blob/master/contracts/libraries/TransferHelper.sol
pragma solidity ^0.8.0;

import "./IERC20.sol";
import "../utils/RevertMsgExtractor.sol";

// helper methods for interacting with ERC20 tokens and sending ETH that do not consistently return true/false
// USDT is a well known token that returns nothing for its transfer, transferFrom, and approve functions
// and part of the reason this library exists
library TransferHelper {
    /// @notice Transfers tokens from msg.sender to a recipient
    /// @dev Errors with the underlying revert message if transfer fails
    /// @param token The contract address of the token which will be transferred
    /// @param to The recipient of the transfer
    /// @param value The value of the transfer
    function safeTransfer(
        IERC20 token,
        address to,
        uint256 value
    ) internal {
        (bool success, bytes memory data) = address(token).call(abi.encodeWithSelector(IERC20.transfer.selector, to, value));
        if (!(success && _returnTrueOrNothing(data))) revert(RevertMsgExtractor.getRevertMsg(data));
    }

    /// @notice Approves a spender to transfer tokens from msg.sender
    /// @dev Errors with the underlying revert message if transfer fails
    /// @param token The contract address of the token which will be approved
    /// @param spender The approved spender
    /// @param value The value of the allowance
    function safeApprove(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        (bool success, bytes memory data) = address(token).call(abi.encodeWithSelector(IERC20.approve.selector, spender, value));
        if (!(success && _returnTrueOrNothing(data))) revert(RevertMsgExtractor.getRevertMsg(data));
    }

    /// @notice Transfers tokens from the targeted address to the given destination
    /// @dev Errors with the underlying revert message if transfer fails
    /// @param token The contract address of the token to be transferred
    /// @param from The originating address from which the tokens will be transferred
    /// @param to The destination address of the transfer
    /// @param value The amount to be transferred
    function safeTransferFrom(
        IERC20 token,
        address from,
        address to,
        uint256 value
    ) internal {
        (bool success, bytes memory data) = address(token).call(abi.encodeWithSelector(IERC20.transferFrom.selector, from, to, value));
        if (!(success && _returnTrueOrNothing(data))) revert(RevertMsgExtractor.getRevertMsg(data));
    }

    /// @notice Transfers ETH to the recipient address
    /// @dev Errors with the underlying revert message if transfer fails
    /// @param to The destination of the transfer
    /// @param value The value to be transferred
    function safeTransferETH(address payable to, uint256 value) internal {
        (bool success, bytes memory data) = to.call{value: value}(new bytes(0));
        if (!success) revert(RevertMsgExtractor.getRevertMsg(data));
    }

    function _returnTrueOrNothing(bytes memory data) internal pure returns(bool) {
        return (data.length == 0 || abi.decode(data, (bool)));
    }
}

// File: @yield-protocol/utils-v2/contracts/token/IERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

/**
 * @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);
}
// File: @yield-protocol/utils-v2/contracts/math/WDiv.sol



// SPDX-License-Identifier: BUSL-1.1
pragma solidity ^0.8.0;


library WDiv { // Fixed point arithmetic in 18 decimal units
    // Taken from https://github.com/usmfum/USM/blob/master/contracts/WadMath.sol
    /// @dev Divide an amount by a fixed point factor with 18 decimals
    function wdiv(uint256 x, uint256 y) internal pure returns (uint256 z) {
        z = (x * 1e18) / y;
    }
}
// File: @yield-protocol/vault-v2/contracts/other/tether/IUSDT.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.13;

/**
 * @dev Interface for the optional metadata functions from the ERC20 standard.
 */
interface IUSDT {
    function name() external view returns (string memory);

    function decimals() external view returns (uint8);

    function totalSupply() external returns (uint);

    function balances(address) external returns (uint);

    function balanceOf(address _owner) external returns (uint balance);

    function allowance(address owner, address spender) external returns (uint);

    function allowed(address, address) external returns (uint);

    function approve(address spender, uint value) external;

    function basisPointsRate() external view returns (uint256);

    function maximumFee() external view returns (uint256);

    function transfer(address to, uint value) external;

    function transferFrom(address from, address to, uint value) external;

    function setParams(uint newBasisPoints, uint newMaxFee) external;
}
// File: erc3156/contracts/interfaces/IERC3156FlashBorrower.sol



// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.9.0;


interface IERC3156FlashBorrower {

    /**
     * @dev Receive a flash loan.
     * @param initiator The initiator of the loan.
     * @param token The loan currency.
     * @param amount The amount of tokens lent.
     * @param fee The additional amount of tokens to repay.
     * @param data Arbitrary data structure, intended to contain user-defined parameters.
     * @return The keccak256 hash of "ERC3156FlashBorrower.onFlashLoan"
     */
    function onFlashLoan(
        address initiator,
        address token,
        uint256 amount,
        uint256 fee,
        bytes calldata data
    ) external returns (bytes32);
}

// File: erc3156/contracts/interfaces/IERC3156FlashLender.sol



// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.9.0;
import "./IERC3156FlashBorrower.sol";


interface IERC3156FlashLender {

    /**
     * @dev The amount of currency available to be lended.
     * @param token The loan currency.
     * @return The amount of `token` that can be borrowed.
     */
    function maxFlashLoan(
        address token
    ) external view returns (uint256);

    /**
     * @dev The fee to be charged for a given loan.
     * @param token The loan currency.
     * @param amount The amount of tokens lent.
     * @return The amount of `token` to be charged for the loan, on top of the returned principal.
     */
    function flashFee(
        address token,
        uint256 amount
    ) external view returns (uint256);

    /**
     * @dev Initiate a flash loan.
     * @param receiver The receiver of the tokens in the loan, and the receiver of the callback.
     * @param token The loan currency.
     * @param amount The amount of tokens lent.
     * @param data Arbitrary data structure, intended to contain user-defined parameters.
     */
    function flashLoan(
        IERC3156FlashBorrower receiver,
        address token,
        uint256 amount,
        bytes calldata data
    ) external returns (bool);
}
// File: @yield-protocol/utils-v2/contracts/math/WMul.sol



// SPDX-License-Identifier: BUSL-1.1
pragma solidity ^0.8.0;


library WMul {
    // Taken from https://github.com/usmfum/USM/blob/master/contracts/WadMath.sol
    /// @dev Multiply an amount by a fixed point factor with 18 decimals, rounds down.
    function wmul(uint256 x, uint256 y) internal pure returns (uint256 z) {
        z = x * y;
        unchecked { z /= 1e18; }
    }
}
// File: @yield-protocol/utils-v2/contracts/cast/CastU256U128.sol



// SPDX-License-Identifier: BUSL-1.1
pragma solidity ^0.8.0;


library CastU256U128 {
    /// @dev Safely cast an uint256 to an uint128
    function u128(uint256 x) internal pure returns (uint128 y) {
        require (x <= type(uint128).max, "Cast overflow");
        y = uint128(x);
    }
}
// File: @yield-protocol/vault-v2/contracts/Join.sol



// SPDX-License-Identifier: BUSL-1.1
pragma solidity >=0.8.13;

import "erc3156/contracts/interfaces/IERC3156FlashBorrower.sol";
import "erc3156/contracts/interfaces/IERC3156FlashLender.sol";
import "./interfaces/IJoin.sol";
import "./interfaces/IJoinFactory.sol";
import "@yield-protocol/utils-v2/contracts/token/IERC20.sol";
import "@yield-protocol/utils-v2/contracts/access/AccessControl.sol";
import "@yield-protocol/utils-v2/contracts/token/TransferHelper.sol";
import "@yield-protocol/utils-v2/contracts/math/WMul.sol";
import "@yield-protocol/utils-v2/contracts/cast/CastU256U128.sol";

contract Join is IJoin, AccessControl {
    using TransferHelper for IERC20;
    using WMul for uint256;
    using CastU256U128 for uint256;

    address public immutable override asset;
    uint256 public override storedBalance;

    constructor(address asset_) {
        asset = asset_;
    }

    /// @dev Take `amount` `asset` from `user` using `transferFrom`, minus any unaccounted `asset` in this contract.
    function join(address user, uint128 amount) external virtual override auth returns (uint128) {
        return _join(user, amount);
    }

    /// @dev Take `amount` `asset` from `user` using `transferFrom`, minus any unaccounted `asset` in this contract.
    function _join(address user, uint128 amount) internal virtual returns (uint128) {
        IERC20 token = IERC20(asset);
        uint256 _storedBalance = storedBalance;
        uint256 available = token.balanceOf(address(this)) - _storedBalance; // Fine to panic if this underflows
        unchecked {
            storedBalance = _storedBalance + amount; // Unlikely that a uint128 added to the stored balance will make it overflow
            if (available < amount) token.safeTransferFrom(user, address(this), amount - available);
        }
        return amount;
    }

    /// @dev Transfer `amount` `asset` to `user`
    function exit(address user, uint128 amount) external virtual override auth returns (uint128) {
        return _exit(user, amount);
    }

    /// @dev Transfer `amount` `asset` to `user`
    function _exit(address user, uint128 amount) internal virtual returns (uint128) {
        IERC20 token = IERC20(asset);
        storedBalance -= amount;
        token.safeTransfer(user, amount);
        return amount;
    }

    /// @dev Retrieve any tokens other than the `asset`. Useful for airdropped tokens.
    function retrieve(IERC20 token, address to) external virtual override auth {
        require(address(token) != address(asset), "Use exit for asset");
        token.safeTransfer(to, token.balanceOf(address(this)));
    }
}

// File: @yield-protocol/utils-v2/contracts/utils/RevertMsgExtractor.sol



// SPDX-License-Identifier: MIT
// Taken from https://github.com/sushiswap/BoringSolidity/blob/441e51c0544cf2451e6116fe00515e71d7c42e2c/contracts/BoringBatchable.sol

pragma solidity >=0.6.0;


library RevertMsgExtractor {
    /// @dev Helper function to extract a useful revert message from a failed call.
    /// If the returned data is malformed or not correctly abi encoded then this call can fail itself.
    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
    }
}
// File: @yield-protocol/vault-v2/contracts/interfaces/IJoinFactory.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

interface IJoinFactory {
    event JoinCreated(address indexed asset, address pool);

    function createJoin(address asset) external returns (address);
}

// File: @yield-protocol/vault-v2/contracts/interfaces/IJoin.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
import "@yield-protocol/utils-v2/contracts/token/IERC20.sol";

interface IJoin {
    /// @dev asset managed by this contract
    function asset() external view returns (address);

    /// @dev amount of assets held by this contract
    function storedBalance() external view returns (uint256);

    /// @dev Add tokens to this contract.
    function join(address user, uint128 wad) external returns (uint128);

    /// @dev Remove tokens to this contract.
    function exit(address user, uint128 wad) external returns (uint128);

    /// @dev Retrieve any tokens other than the `asset`. Useful for airdropped tokens.
    function retrieve(IERC20 token, address to) external;
}