/**
 *Submitted for verification at Etherscan.io on 2021-12-21
*/

// SPDX-License-Identifier: AGPL-3.0

pragma solidity 0.6.12;
pragma experimental ABIEncoderV2;

// Global Enums and Structs



struct StrategyParams {
    uint256 performanceFee;
    uint256 activation;
    uint256 debtRatio;
    uint256 minDebtPerHarvest;
    uint256 maxDebtPerHarvest;
    uint256 lastReport;
    uint256 totalDebt;
    uint256 totalGain;
    uint256 totalLoss;
}

// Part: IBaseFee

interface IBaseFee {
    function isCurrentBaseFeeAcceptable() external view returns (bool);
}

// Part: IConvexDeposit

interface IConvexDeposit {
    // deposit into convex, receive a tokenized deposit.  parameter to stake immediately (we always do this).
    function deposit(
        uint256 _pid,
        uint256 _amount,
        bool _stake
    ) external returns (bool);

    // burn a tokenized deposit (Convex deposit tokens) to receive curve lp tokens back
    function withdraw(uint256 _pid, uint256 _amount) external returns (bool);

    // give us info about a pool based on its pid
    function poolInfo(uint256)
        external
        view
        returns (
            address,
            address,
            address,
            address,
            address,
            bool
        );
}

// Part: IConvexRewards

interface IConvexRewards {
    // strategy's staked balance in the synthetix staking contract
    function balanceOf(address account) external view returns (uint256);

    // read how much claimable CRV a strategy has
    function earned(address account) external view returns (uint256);

    // stake a convex tokenized deposit
    function stake(uint256 _amount) external returns (bool);

    // withdraw to a convex tokenized deposit, probably never need to use this
    function withdraw(uint256 _amount, bool _claim) external returns (bool);

    // withdraw directly to curve LP token, this is what we primarily use
    function withdrawAndUnwrap(uint256 _amount, bool _claim)
        external
        returns (bool);

    // claim rewards, with an option to claim extra rewards or not
    function getReward(address _account, bool _claimExtras)
        external
        returns (bool);

    // check if we have rewards on a pool
    function extraRewardsLength() external view returns (uint256);

    // if we have rewards, see what the address is
    function extraRewards(uint256 _reward) external view returns (address);

    // read our rewards token
    function rewardToken() external view returns (address);

    // check our reward period finish
    function periodFinish() external view returns (uint256);
}

// Part: ICurveFi

interface ICurveFi {
    function get_virtual_price() external view returns (uint256);

    function add_liquidity(
        // EURt
        uint256[2] calldata amounts,
        uint256 min_mint_amount
    ) external payable;

    function add_liquidity(
        // Compound, sAave
        uint256[2] calldata amounts,
        uint256 min_mint_amount,
        bool _use_underlying
    ) external payable returns (uint256);

    function add_liquidity(
        // Iron Bank, Aave
        uint256[3] calldata amounts,
        uint256 min_mint_amount,
        bool _use_underlying
    ) external payable returns (uint256);

    function add_liquidity(
        // 3Crv Metapools
        address pool,
        uint256[4] calldata amounts,
        uint256 min_mint_amount
    ) external;

    function add_liquidity(
        // Y and yBUSD
        uint256[4] calldata amounts,
        uint256 min_mint_amount,
        bool _use_underlying
    ) external payable returns (uint256);

    function add_liquidity(
        // 3pool
        uint256[3] calldata amounts,
        uint256 min_mint_amount
    ) external payable;

    function add_liquidity(
        // sUSD
        uint256[4] calldata amounts,
        uint256 min_mint_amount
    ) external payable;

    function remove_liquidity_imbalance(
        uint256[2] calldata amounts,
        uint256 max_burn_amount
    ) external;

    function remove_liquidity(uint256 _amount, uint256[2] calldata amounts)
        external;

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

    function exchange(
        int128 from,
        int128 to,
        uint256 _from_amount,
        uint256 _min_to_amount
    ) external;

    function exchange(
        uint256 from,
        uint256 to,
        uint256 _from_amount,
        uint256 _min_to_amount,
        bool use_eth
    ) external;

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

    function get_dy(
        int128 from,
        int128 to,
        uint256 _from_amount
    ) external view returns (uint256);

    // EURt
    function calc_token_amount(uint256[2] calldata _amounts, bool _is_deposit)
        external
        view
        returns (uint256);

    // 3Crv Metapools
    function calc_token_amount(
        address _pool,
        uint256[4] calldata _amounts,
        bool _is_deposit
    ) external view returns (uint256);

    // sUSD, Y pool, etc
    function calc_token_amount(uint256[4] calldata _amounts, bool _is_deposit)
        external
        view
        returns (uint256);

    // 3pool, Iron Bank, etc
    function calc_token_amount(uint256[3] calldata _amounts, bool _is_deposit)
        external
        view
        returns (uint256);

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

// Part: IUniV3

interface IUniV3 {
    struct ExactInputParams {
        bytes path;
        address recipient;
        uint256 deadline;
        uint256 amountIn;
        uint256 amountOutMinimum;
    }

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

// Part: IUniswapV2Router01

interface IUniswapV2Router01 {
    function factory() external pure returns (address);

    function WETH() external pure returns (address);

    function addLiquidity(
        address tokenA,
        address tokenB,
        uint256 amountADesired,
        uint256 amountBDesired,
        uint256 amountAMin,
        uint256 amountBMin,
        address to,
        uint256 deadline
    )
        external
        returns (
            uint256 amountA,
            uint256 amountB,
            uint256 liquidity
        );

    function addLiquidityETH(
        address token,
        uint256 amountTokenDesired,
        uint256 amountTokenMin,
        uint256 amountETHMin,
        address to,
        uint256 deadline
    )
        external
        payable
        returns (
            uint256 amountToken,
            uint256 amountETH,
            uint256 liquidity
        );

    function removeLiquidity(
        address tokenA,
        address tokenB,
        uint256 liquidity,
        uint256 amountAMin,
        uint256 amountBMin,
        address to,
        uint256 deadline
    ) external returns (uint256 amountA, uint256 amountB);

    function removeLiquidityETH(
        address token,
        uint256 liquidity,
        uint256 amountTokenMin,
        uint256 amountETHMin,
        address to,
        uint256 deadline
    ) external returns (uint256 amountToken, uint256 amountETH);

    function removeLiquidityWithPermit(
        address tokenA,
        address tokenB,
        uint256 liquidity,
        uint256 amountAMin,
        uint256 amountBMin,
        address to,
        uint256 deadline,
        bool approveMax,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external returns (uint256 amountA, uint256 amountB);

    function removeLiquidityETHWithPermit(
        address token,
        uint256 liquidity,
        uint256 amountTokenMin,
        uint256 amountETHMin,
        address to,
        uint256 deadline,
        bool approveMax,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external returns (uint256 amountToken, uint256 amountETH);

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

    function swapTokensForExactTokens(
        uint256 amountOut,
        uint256 amountInMax,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external returns (uint256[] memory amounts);

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

    function swapTokensForExactETH(
        uint256 amountOut,
        uint256 amountInMax,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external returns (uint256[] memory amounts);

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

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

    function quote(
        uint256 amountA,
        uint256 reserveA,
        uint256 reserveB
    ) external pure returns (uint256 amountB);

    function getAmountOut(
        uint256 amountIn,
        uint256 reserveIn,
        uint256 reserveOut
    ) external pure returns (uint256 amountOut);

    function getAmountIn(
        uint256 amountOut,
        uint256 reserveIn,
        uint256 reserveOut
    ) external pure returns (uint256 amountIn);

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

    function getAmountsIn(uint256 amountOut, address[] calldata path)
        external
        view
        returns (uint256[] memory amounts);
}

// Part: OpenZeppelin/[email protected]/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) {
        // According to EIP-1052, 0x0 is the value returned for not-yet created accounts
        // and 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470 is returned
        // for accounts without code, i.e. `keccak256('')`
        bytes32 codehash;
        bytes32 accountHash = 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470;
        // solhint-disable-next-line no-inline-assembly
        assembly { codehash := extcodehash(account) }
        return (codehash != accountHash && codehash != 0x0);
    }

    /**
     * @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");
        return _functionCallWithValue(target, data, value, errorMessage);
    }

    function _functionCallWithValue(address target, bytes memory data, uint256 weiValue, string memory errorMessage) private returns (bytes memory) {
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: weiValue }(data);
        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/[email protected]/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/[email protected]/Math

/**
 * @dev Standard math utilities missing in the Solidity language.
 */
library Math {
    /**
     * @dev Returns the largest of two numbers.
     */
    function max(uint256 a, uint256 b) internal pure returns (uint256) {
        return a >= b ? a : b;
    }

    /**
     * @dev Returns the smallest of two numbers.
     */
    function min(uint256 a, uint256 b) internal pure returns (uint256) {
        return a < b ? a : b;
    }

    /**
     * @dev Returns the average of two numbers. The result is rounded towards
     * zero.
     */
    function average(uint256 a, uint256 b) internal pure returns (uint256) {
        // (a + b) / 2 can overflow, so we distribute
        return (a / 2) + (b / 2) + ((a % 2 + b % 2) / 2);
    }
}

// Part: OpenZeppelin/[email protected]/SafeMath

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts with custom message when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

// Part: yearn/[email protected]/HealthCheck

interface HealthCheck {
    function check(
        uint256 profit,
        uint256 loss,
        uint256 debtPayment,
        uint256 debtOutstanding,
        uint256 totalDebt
    ) external view returns (bool);
}

// Part: IUniswapV2Router02

interface IUniswapV2Router02 is IUniswapV2Router01 {
    function removeLiquidityETHSupportingFeeOnTransferTokens(
        address token,
        uint256 liquidity,
        uint256 amountTokenMin,
        uint256 amountETHMin,
        address to,
        uint256 deadline
    ) external returns (uint256 amountETH);

    function removeLiquidityETHWithPermitSupportingFeeOnTransferTokens(
        address token,
        uint256 liquidity,
        uint256 amountTokenMin,
        uint256 amountETHMin,
        address to,
        uint256 deadline,
        bool approveMax,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external returns (uint256 amountETH);

    function swapExactTokensForTokensSupportingFeeOnTransferTokens(
        uint256 amountIn,
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external;

    function swapExactETHForTokensSupportingFeeOnTransferTokens(
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external payable;

    function swapExactTokensForETHSupportingFeeOnTransferTokens(
        uint256 amountIn,
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external;
}

// Part: OpenZeppelin/[email protected]/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 SafeMath for uint256;
    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).add(value);
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).sub(value, "SafeERC20: decreased allowance below zero");
        _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");
        }
    }
}

// Part: yearn/[email protected]/VaultAPI

interface VaultAPI is IERC20 {
    function apiVersion() external pure returns (string memory);

    function withdraw(uint256 shares, address recipient) external returns (uint256);

    function token() external view returns (address);

    function strategies(address _strategy) external view returns (StrategyParams memory);

    /**
     * View how much the Vault would increase this Strategy's borrow limit,
     * based on its present performance (since its last report). Can be used to
     * determine expectedReturn in your Strategy.
     */
    function creditAvailable() external view returns (uint256);

    /**
     * View how much the Vault would like to pull back from the Strategy,
     * based on its present performance (since its last report). Can be used to
     * determine expectedReturn in your Strategy.
     */
    function debtOutstanding() external view returns (uint256);

    /**
     * View how much the Vault expect this Strategy to return at the current
     * block, based on its present performance (since its last report). Can be
     * used to determine expectedReturn in your Strategy.
     */
    function expectedReturn() external view returns (uint256);

    /**
     * This is the main contact point where the Strategy interacts with the
     * Vault. It is critical that this call is handled as intended by the
     * Strategy. Therefore, this function will be called by BaseStrategy to
     * make sure the integration is correct.
     */
    function report(
        uint256 _gain,
        uint256 _loss,
        uint256 _debtPayment
    ) external returns (uint256);

    /**
     * This function should only be used in the scenario where the Strategy is
     * being retired but no migration of the positions are possible, or in the
     * extreme scenario that the Strategy needs to be put into "Emergency Exit"
     * mode in order for it to exit as quickly as possible. The latter scenario
     * could be for any reason that is considered "critical" that the Strategy
     * exits its position as fast as possible, such as a sudden change in
     * market conditions leading to losses, or an imminent failure in an
     * external dependency.
     */
    function revokeStrategy() external;

    /**
     * View the governance address of the Vault to assert privileged functions
     * can only be called by governance. The Strategy serves the Vault, so it
     * is subject to governance defined by the Vault.
     */
    function governance() external view returns (address);

    /**
     * View the management address of the Vault to assert privileged functions
     * can only be called by management. The Strategy serves the Vault, so it
     * is subject to management defined by the Vault.
     */
    function management() external view returns (address);

    /**
     * View the guardian address of the Vault to assert privileged functions
     * can only be called by guardian. The Strategy serves the Vault, so it
     * is subject to guardian defined by the Vault.
     */
    function guardian() external view returns (address);
}

// Part: yearn/[email protected]/BaseStrategy

/**
 * @title Yearn Base Strategy
 * @author yearn.finance
 * @notice
 *  BaseStrategy implements all of the required functionality to interoperate
 *  closely with the Vault contract. This contract should be inherited and the
 *  abstract methods implemented to adapt the Strategy to the particular needs
 *  it has to create a return.
 *
 *  Of special interest is the relationship between `harvest()` and
 *  `vault.report()'. `harvest()` may be called simply because enough time has
 *  elapsed since the last report, and not because any funds need to be moved
 *  or positions adjusted. This is critical so that the Vault may maintain an
 *  accurate picture of the Strategy's performance. See  `vault.report()`,
 *  `harvest()`, and `harvestTrigger()` for further details.
 */
abstract contract BaseStrategy {
    using SafeMath for uint256;
    using SafeERC20 for IERC20;
    string public metadataURI;

    // health checks
    bool public doHealthCheck;
    address public healthCheck;

    /**
     * @notice
     *  Used to track which version of `StrategyAPI` this Strategy
     *  implements.
     * @dev The Strategy's version must match the Vault's `API_VERSION`.
     * @return A string which holds the current API version of this contract.
     */
    function apiVersion() public pure returns (string memory) {
        return "0.3.2";
    }

    /**
     * @notice This Strategy's name.
     * @dev
     *  You can use this field to manage the "version" of this Strategy, e.g.
     *  `StrategySomethingOrOtherV1`. However, "API Version" is managed by
     *  `apiVersion()` function above.
     * @return This Strategy's name.
     */
    function name() external virtual view returns (string memory);

    /**
     * @notice
     *  The amount (priced in want) of the total assets managed by this strategy should not count
     *  towards Yearn's TVL calculations.
     * @dev
     *  You can override this field to set it to a non-zero value if some of the assets of this
     *  Strategy is somehow delegated inside another part of of Yearn's ecosystem e.g. another Vault.
     *  Note that this value must be strictly less than or equal to the amount provided by
     *  `estimatedTotalAssets()` below, as the TVL calc will be total assets minus delegated assets.
     * @return
     *  The amount of assets this strategy manages that should not be included in Yearn's Total Value
     *  Locked (TVL) calculation across it's ecosystem.
     */
    function delegatedAssets() external virtual view returns (uint256) {
        return 0;
    }

    VaultAPI public vault;
    address public strategist;
    address public rewards;
    address public keeper;

    IERC20 public want;

    // So indexers can keep track of this
    event Harvested(uint256 profit, uint256 loss, uint256 debtPayment, uint256 debtOutstanding);

    event UpdatedStrategist(address newStrategist);

    event UpdatedKeeper(address newKeeper);

    event UpdatedRewards(address rewards);

    event UpdatedMinReportDelay(uint256 delay);

    event UpdatedMaxReportDelay(uint256 delay);

    event UpdatedProfitFactor(uint256 profitFactor);

    event UpdatedDebtThreshold(uint256 debtThreshold);

    event EmergencyExitEnabled();

    event UpdatedMetadataURI(string metadataURI);

    // The minimum number of seconds between harvest calls. See
    // `setMinReportDelay()` for more details.
    uint256 public minReportDelay = 0;

    // The maximum number of seconds between harvest calls. See
    // `setMaxReportDelay()` for more details.
    uint256 public maxReportDelay = 86400; // ~ once a day

    // The minimum multiple that `callCost` must be above the credit/profit to
    // be "justifiable". See `setProfitFactor()` for more details.
    uint256 public profitFactor = 100;

    // Use this to adjust the threshold at which running a debt causes a
    // harvest trigger. See `setDebtThreshold()` for more details.
    uint256 public debtThreshold = 0;

    // See note on `setEmergencyExit()`.
    bool public emergencyExit;

    // modifiers
    modifier onlyAuthorized() {
        require(msg.sender == strategist || msg.sender == governance(), "!authorized");
        _;
    }

    modifier onlyStrategist() {
        require(msg.sender == strategist, "!strategist");
        _;
    }

    modifier onlyGovernance() {
        require(msg.sender == governance(), "!authorized");
        _;
    }

    modifier onlyKeepers() {
        require(
            msg.sender == keeper ||
                msg.sender == strategist ||
                msg.sender == governance() ||
                msg.sender == vault.guardian() ||
                msg.sender == vault.management(),
            "!authorized"
        );
        _;
    }

    modifier onlyVaultManagers() {
        require(
            msg.sender == vault.management() || msg.sender == governance(),
            "!authorized"
        );
        _;
    }


    constructor(address _vault) public {
        _initialize(_vault, msg.sender, msg.sender, msg.sender);
    }

    /**
     * @notice
     *  Initializes the Strategy, this is called only once, when the
     *  contract is deployed.
     * @dev `_vault` should implement `VaultAPI`.
     * @param _vault The address of the Vault responsible for this Strategy.
     */
    function _initialize(
        address _vault,
        address _strategist,
        address _rewards,
        address _keeper
    ) internal {
        require(address(want) == address(0), "Strategy already initialized");

        vault = VaultAPI(_vault);
        want = IERC20(vault.token());
        want.safeApprove(_vault, uint256(-1)); // Give Vault unlimited access (might save gas)
        strategist = _strategist;
        rewards = _rewards;
        keeper = _keeper;
        vault.approve(rewards, uint256(-1)); // Allow rewards to be pulled
    }

    function setHealthCheck(address _healthCheck) external onlyVaultManagers {
        healthCheck = _healthCheck;
    }

    function setDoHealthCheck(bool _doHealthCheck) external onlyVaultManagers {
        doHealthCheck = _doHealthCheck;
    }

    /**
     * @notice
     *  Used to change `strategist`.
     *
     *  This may only be called by governance or the existing strategist.
     * @param _strategist The new address to assign as `strategist`.
     */
    function setStrategist(address _strategist) external onlyAuthorized {
        require(_strategist != address(0));
        strategist = _strategist;
        emit UpdatedStrategist(_strategist);
    }

    /**
     * @notice
     *  Used to change `keeper`.
     *
     *  `keeper` is the only address that may call `tend()` or `harvest()`,
     *  other than `governance()` or `strategist`. However, unlike
     *  `governance()` or `strategist`, `keeper` may *only* call `tend()`
     *  and `harvest()`, and no other authorized functions, following the
     *  principle of least privilege.
     *
     *  This may only be called by governance or the strategist.
     * @param _keeper The new address to assign as `keeper`.
     */
    function setKeeper(address _keeper) external onlyAuthorized {
        require(_keeper != address(0));
        keeper = _keeper;
        emit UpdatedKeeper(_keeper);
    }

    /**
     * @notice
     *  Used to change `rewards`. EOA or smart contract which has the permission
     *  to pull rewards from the vault.
     *
     *  This may only be called by the strategist.
     * @param _rewards The address to use for pulling rewards.
     */
    function setRewards(address _rewards) external onlyStrategist {
        require(_rewards != address(0));
        vault.approve(rewards, 0);
        rewards = _rewards;
        vault.approve(rewards, uint256(-1));
        emit UpdatedRewards(_rewards);
    }

    /**
     * @notice
     *  Used to change `minReportDelay`. `minReportDelay` is the minimum number
     *  of blocks that should pass for `harvest()` to be called.
     *
     *  For external keepers (such as the Keep3r network), this is the minimum
     *  time between jobs to wait. (see `harvestTrigger()`
     *  for more details.)
     *
     *  This may only be called by governance or the strategist.
     * @param _delay The minimum number of seconds to wait between harvests.
     */
    function setMinReportDelay(uint256 _delay) external onlyAuthorized {
        minReportDelay = _delay;
        emit UpdatedMinReportDelay(_delay);
    }

    /**
     * @notice
     *  Used to change `maxReportDelay`. `maxReportDelay` is the maximum number
     *  of blocks that should pass for `harvest()` to be called.
     *
     *  For external keepers (such as the Keep3r network), this is the maximum
     *  time between jobs to wait. (see `harvestTrigger()`
     *  for more details.)
     *
     *  This may only be called by governance or the strategist.
     * @param _delay The maximum number of seconds to wait between harvests.
     */
    function setMaxReportDelay(uint256 _delay) external onlyAuthorized {
        maxReportDelay = _delay;
        emit UpdatedMaxReportDelay(_delay);
    }

    /**
     * @notice
     *  Used to change `profitFactor`. `profitFactor` is used to determine
     *  if it's worthwhile to harvest, given gas costs. (See `harvestTrigger()`
     *  for more details.)
     *
     *  This may only be called by governance or the strategist.
     * @param _profitFactor A ratio to multiply anticipated
     * `harvest()` gas cost against.
     */
    function setProfitFactor(uint256 _profitFactor) external onlyAuthorized {
        profitFactor = _profitFactor;
        emit UpdatedProfitFactor(_profitFactor);
    }

    /**
     * @notice
     *  Sets how far the Strategy can go into loss without a harvest and report
     *  being required.
     *
     *  By default this is 0, meaning any losses would cause a harvest which
     *  will subsequently report the loss to the Vault for tracking. (See
     *  `harvestTrigger()` for more details.)
     *
     *  This may only be called by governance or the strategist.
     * @param _debtThreshold How big of a loss this Strategy may carry without
     * being required to report to the Vault.
     */
    function setDebtThreshold(uint256 _debtThreshold) external onlyAuthorized {
        debtThreshold = _debtThreshold;
        emit UpdatedDebtThreshold(_debtThreshold);
    }

    /**
     * @notice
     *  Used to change `metadataURI`. `metadataURI` is used to store the URI
     * of the file describing the strategy.
     *
     *  This may only be called by governance or the strategist.
     * @param _metadataURI The URI that describe the strategy.
     */
    function setMetadataURI(string calldata _metadataURI) external onlyAuthorized {
        metadataURI = _metadataURI;
        emit UpdatedMetadataURI(_metadataURI);
    }

    /**
     * Resolve governance address from Vault contract, used to make assertions
     * on protected functions in the Strategy.
     */
    function governance() internal view returns (address) {
        return vault.governance();
    }

    /**
     * @notice
     *  Provide an accurate estimate for the total amount of assets
     *  (principle + return) that this Strategy is currently managing,
     *  denominated in terms of `want` tokens.
     *
     *  This total should be "realizable" e.g. the total value that could
     *  *actually* be obtained from this Strategy if it were to divest its
     *  entire position based on current on-chain conditions.
     * @dev
     *  Care must be taken in using this function, since it relies on external
     *  systems, which could be manipulated by the attacker to give an inflated
     *  (or reduced) value produced by this function, based on current on-chain
     *  conditions (e.g. this function is possible to influence through
     *  flashloan attacks, oracle manipulations, or other DeFi attack
     *  mechanisms).
     *
     *  It is up to governance to use this function to correctly order this
     *  Strategy relative to its peers in the withdrawal queue to minimize
     *  losses for the Vault based on sudden withdrawals. This value should be
     *  higher than the total debt of the Strategy and higher than its expected
     *  value to be "safe".
     * @return The estimated total assets in this Strategy.
     */
    function estimatedTotalAssets() public virtual view returns (uint256);

    /*
     * @notice
     *  Provide an indication of whether this strategy is currently "active"
     *  in that it is managing an active position, or will manage a position in
     *  the future. This should correlate to `harvest()` activity, so that Harvest
     *  events can be tracked externally by indexing agents.
     * @return True if the strategy is actively managing a position.
     */
    function isActive() public view returns (bool) {
        return vault.strategies(address(this)).debtRatio > 0 || estimatedTotalAssets() > 0;
    }

    /**
     * Perform any Strategy unwinding or other calls necessary to capture the
     * "free return" this Strategy has generated since the last time its core
     * position(s) were adjusted. Examples include unwrapping extra rewards.
     * This call is only used during "normal operation" of a Strategy, and
     * should be optimized to minimize losses as much as possible.
     *
     * This method returns any realized profits and/or realized losses
     * incurred, and should return the total amounts of profits/losses/debt
     * payments (in `want` tokens) for the Vault's accounting (e.g.
     * `want.balanceOf(this) >= _debtPayment + _profit - _loss`).
     *
     * `_debtOutstanding` will be 0 if the Strategy is not past the configured
     * debt limit, otherwise its value will be how far past the debt limit
     * the Strategy is. The Strategy's debt limit is configured in the Vault.
     *
     * NOTE: `_debtPayment` should be less than or equal to `_debtOutstanding`.
     *       It is okay for it to be less than `_debtOutstanding`, as that
     *       should only used as a guide for how much is left to pay back.
     *       Payments should be made to minimize loss from slippage, debt,
     *       withdrawal fees, etc.
     *
     * See `vault.debtOutstanding()`.
     */
    function prepareReturn(uint256 _debtOutstanding)
        internal
        virtual
        returns (
            uint256 _profit,
            uint256 _loss,
            uint256 _debtPayment
        );

    /**
     * Perform any adjustments to the core position(s) of this Strategy given
     * what change the Vault made in the "investable capital" available to the
     * Strategy. Note that all "free capital" in the Strategy after the report
     * was made is available for reinvestment. Also note that this number
     * could be 0, and you should handle that scenario accordingly.
     *
     * See comments regarding `_debtOutstanding` on `prepareReturn()`.
     */
    function adjustPosition(uint256 _debtOutstanding) internal virtual;

    /**
     * Liquidate up to `_amountNeeded` of `want` of this strategy's positions,
     * irregardless of slippage. Any excess will be re-invested with `adjustPosition()`.
     * This function should return the amount of `want` tokens made available by the
     * liquidation. If there is a difference between them, `_loss` indicates whether the
     * difference is due to a realized loss, or if there is some other sitution at play
     * (e.g. locked funds) where the amount made available is less than what is needed.
     * This function is used during emergency exit instead of `prepareReturn()` to
     * liquidate all of the Strategy's positions back to the Vault.
     *
     * NOTE: The invariant `_liquidatedAmount + _loss <= _amountNeeded` should always be maintained
     */
    function liquidatePosition(uint256 _amountNeeded) internal virtual returns (uint256 _liquidatedAmount, uint256 _loss);

    /**
     * @notice
     *  Provide a signal to the keeper that `tend()` should be called. The
     *  keeper will provide the estimated gas cost that they would pay to call
     *  `tend()`, and this function should use that estimate to make a
     *  determination if calling it is "worth it" for the keeper. This is not
     *  the only consideration into issuing this trigger, for example if the
     *  position would be negatively affected if `tend()` is not called
     *  shortly, then this can return `true` even if the keeper might be
     *  "at a loss" (keepers are always reimbursed by Yearn).
     * @dev
     *  `callCost` must be priced in terms of `want`.
     *
     *  This call and `harvestTrigger()` should never return `true` at the same
     *  time.
     * @param callCost The keeper's estimated cast cost to call `tend()`.
     * @return `true` if `tend()` should be called, `false` otherwise.
     */
    function tendTrigger(uint256 callCost) public virtual view returns (bool) {
        // We usually don't need tend, but if there are positions that need
        // active maintainence, overriding this function is how you would
        // signal for that.
        return false;
    }

    /**
     * @notice
     *  Adjust the Strategy's position. The purpose of tending isn't to
     *  realize gains, but to maximize yield by reinvesting any returns.
     *
     *  See comments on `adjustPosition()`.
     *
     *  This may only be called by governance, the strategist, or the keeper.
     */
    function tend() external onlyKeepers {
        // Don't take profits with this call, but adjust for better gains
        adjustPosition(vault.debtOutstanding());
    }

    /**
     * @notice
     *  Provide a signal to the keeper that `harvest()` should be called. The
     *  keeper will provide the estimated gas cost that they would pay to call
     *  `harvest()`, and this function should use that estimate to make a
     *  determination if calling it is "worth it" for the keeper. This is not
     *  the only consideration into issuing this trigger, for example if the
     *  position would be negatively affected if `harvest()` is not called
     *  shortly, then this can return `true` even if the keeper might be "at a
     *  loss" (keepers are always reimbursed by Yearn).
     * @dev
     *  `callCost` must be priced in terms of `want`.
     *
     *  This call and `tendTrigger` should never return `true` at the
     *  same time.
     *
     *  See `min/maxReportDelay`, `profitFactor`, `debtThreshold` to adjust the
     *  strategist-controlled parameters that will influence whether this call
     *  returns `true` or not. These parameters will be used in conjunction
     *  with the parameters reported to the Vault (see `params`) to determine
     *  if calling `harvest()` is merited.
     *
     *  It is expected that an external system will check `harvestTrigger()`.
     *  This could be a script run off a desktop or cloud bot (e.g.
     *  https://github.com/iearn-finance/yearn-vaults/blob/master/scripts/keep.py),
     *  or via an integration with the Keep3r network (e.g.
     *  https://github.com/Macarse/GenericKeep3rV2/blob/master/contracts/keep3r/GenericKeep3rV2.sol).
     * @param callCost The keeper's estimated cast cost to call `harvest()`.
     * @return `true` if `harvest()` should be called, `false` otherwise.
     */
    function harvestTrigger(uint256 callCost) public virtual view returns (bool) {
        StrategyParams memory params = vault.strategies(address(this));

        // Should not trigger if Strategy is not activated
        if (params.activation == 0) return false;

        // Should not trigger if we haven't waited long enough since previous harvest
        if (block.timestamp.sub(params.lastReport) < minReportDelay) return false;

        // Should trigger if hasn't been called in a while
        if (block.timestamp.sub(params.lastReport) >= maxReportDelay) return true;

        // If some amount is owed, pay it back
        // NOTE: Since debt is based on deposits, it makes sense to guard against large
        //       changes to the value from triggering a harvest directly through user
        //       behavior. This should ensure reasonable resistance to manipulation
        //       from user-initiated withdrawals as the outstanding debt fluctuates.
        uint256 outstanding = vault.debtOutstanding();
        if (outstanding > debtThreshold) return true;

        // Check for profits and losses
        uint256 total = estimatedTotalAssets();
        // Trigger if we have a loss to report
        if (total.add(debtThreshold) < params.totalDebt) return true;

        uint256 profit = 0;
        if (total > params.totalDebt) profit = total.sub(params.totalDebt); // We've earned a profit!

        // Otherwise, only trigger if it "makes sense" economically (gas cost
        // is <N% of value moved)
        uint256 credit = vault.creditAvailable();
        return (profitFactor.mul(callCost) < credit.add(profit));
    }

    /**
     * @notice
     *  Harvests the Strategy, recognizing any profits or losses and adjusting
     *  the Strategy's position.
     *
     *  In the rare case the Strategy is in emergency shutdown, this will exit
     *  the Strategy's position.
     *
     *  This may only be called by governance, the strategist, or the keeper.
     * @dev
     *  When `harvest()` is called, the Strategy reports to the Vault (via
     *  `vault.report()`), so in some cases `harvest()` must be called in order
     *  to take in profits, to borrow newly available funds from the Vault, or
     *  otherwise adjust its position. In other cases `harvest()` must be
     *  called to report to the Vault on the Strategy's position, especially if
     *  any losses have occurred.
     */
    function harvest() external onlyKeepers {
        uint256 profit = 0;
        uint256 loss = 0;
        uint256 debtOutstanding = vault.debtOutstanding();
        uint256 debtPayment = 0;
        if (emergencyExit) {
            // Free up as much capital as possible
            uint256 totalAssets = estimatedTotalAssets();
            // NOTE: use the larger of total assets or debt outstanding to book losses properly
            (debtPayment, loss) = liquidatePosition(totalAssets > debtOutstanding ? totalAssets : debtOutstanding);
            // NOTE: take up any remainder here as profit
            if (debtPayment > debtOutstanding) {
                profit = debtPayment.sub(debtOutstanding);
                debtPayment = debtOutstanding;
            }
        } else {
            // Free up returns for Vault to pull
            (profit, loss, debtPayment) = prepareReturn(debtOutstanding);
        }

        // Allow Vault to take up to the "harvested" balance of this contract,
        // which is the amount it has earned since the last time it reported to
        // the Vault.
        uint256 totalDebt = vault.strategies(address(this)).totalDebt;
        debtOutstanding = vault.report(profit, loss, debtPayment);

        // Check if free returns are left, and re-invest them
        adjustPosition(debtOutstanding);

        // call healthCheck contract
        if (doHealthCheck && healthCheck != address(0)) {
            require(
                HealthCheck(healthCheck).check(
                    profit,
                    loss,
                    debtPayment,
                    debtOutstanding,
                    totalDebt
                ),
                "!healthcheck"
            );
        } else {
            doHealthCheck = true;
        }

        emit Harvested(profit, loss, debtPayment, debtOutstanding);
    }

    /**
     * @notice
     *  Withdraws `_amountNeeded` to `vault`.
     *
     *  This may only be called by the Vault.
     * @param _amountNeeded How much `want` to withdraw.
     * @return _loss Any realized losses
     */
    function withdraw(uint256 _amountNeeded) external returns (uint256 _loss) {
        require(msg.sender == address(vault), "!vault");
        // Liquidate as much as possible to `want`, up to `_amountNeeded`
        uint256 amountFreed;
        (amountFreed, _loss) = liquidatePosition(_amountNeeded);
        // sanity check
        require(_amountNeeded == amountFreed.add(_loss), "!withdraw");
        // Send it directly back (NOTE: Using `msg.sender` saves some gas here)
        want.safeTransfer(msg.sender, amountFreed);
        // NOTE: Reinvest anything leftover on next `tend`/`harvest`
    }

    /**
     * Do anything necessary to prepare this Strategy for migration, such as
     * transferring any reserve or LP tokens, CDPs, or other tokens or stores of
     * value.
     */
    function prepareMigration(address _newStrategy) internal virtual;

    /**
     * @notice
     *  Transfers all `want` from this Strategy to `_newStrategy`.
     *
     *  This may only be called by governance or the Vault.
     * @dev
     *  The new Strategy's Vault must be the same as this Strategy's Vault.
     * @param _newStrategy The Strategy to migrate to.
     */
    function migrate(address _newStrategy) external {
        require(msg.sender == address(vault) || msg.sender == governance());
        require(BaseStrategy(_newStrategy).vault() == vault);
        prepareMigration(_newStrategy);
        want.safeTransfer(_newStrategy, want.balanceOf(address(this)));
    }

    /**
     * @notice
     *  Activates emergency exit. Once activated, the Strategy will exit its
     *  position upon the next harvest, depositing all funds into the Vault as
     *  quickly as is reasonable given on-chain conditions.
     *
     *  This may only be called by governance or the strategist.
     * @dev
     *  See `vault.setEmergencyShutdown()` and `harvest()` for further details.
     */
    function setEmergencyExit() external onlyAuthorized {
        emergencyExit = true;
        vault.revokeStrategy();

        emit EmergencyExitEnabled();
    }

    /**
     * Override this to add all tokens/tokenized positions this contract
     * manages on a *persistent* basis (e.g. not just for swapping back to
     * want ephemerally).
     *
     * NOTE: Do *not* include `want`, already included in `sweep` below.
     *
     * Example:
     *
     *    function protectedTokens() internal override view returns (address[] memory) {
     *      address[] memory protected = new address[](3);
     *      protected[0] = tokenA;
     *      protected[1] = tokenB;
     *      protected[2] = tokenC;
     *      return protected;
     *    }
     */
    function protectedTokens() internal virtual view returns (address[] memory);

    /**
     * @notice
     *  Removes tokens from this Strategy that are not the type of tokens
     *  managed by this Strategy. This may be used in case of accidentally
     *  sending the wrong kind of token to this Strategy.
     *
     *  Tokens will be sent to `governance()`.
     *
     *  This will fail if an attempt is made to sweep `want`, or any tokens
     *  that are protected by this Strategy.
     *
     *  This may only be called by governance.
     * @dev
     *  Implement `protectedTokens()` to specify any additional tokens that
     *  should be protected from sweeping in addition to `want`.
     * @param _token The token to transfer out of this vault.
     */
    function sweep(address _token) external onlyGovernance {
        require(_token != address(want), "!want");
        require(_token != address(vault), "!shares");

        address[] memory _protectedTokens = protectedTokens();
        for (uint256 i; i < _protectedTokens.length; i++) require(_token != _protectedTokens[i], "!protected");

        IERC20(_token).safeTransfer(governance(), IERC20(_token).balanceOf(address(this)));
    }
}

// Part: StrategyConvexBase

abstract contract StrategyConvexBase is BaseStrategy {
    using SafeERC20 for IERC20;
    using Address for address;
    using SafeMath for uint256;

    /* ========== STATE VARIABLES ========== */
    // these should stay the same across different wants.

    // convex stuff
    address internal constant depositContract =
        0xF403C135812408BFbE8713b5A23a04b3D48AAE31; // this is the deposit contract that all pools use, aka booster
    IConvexRewards public rewardsContract; // This is unique to each curve pool
    uint256 public pid; // this is unique to each pool

    // keepCRV stuff
    uint256 public keepCRV; // the percentage of CRV we re-lock for boost (in basis points)
    address public constant voter = 0xF147b8125d2ef93FB6965Db97D6746952a133934; // Yearn's veCRV voter, we send some extra CRV here
    uint256 internal constant FEE_DENOMINATOR = 10000; // this means all of our fee values are in basis points

    // Swap stuff
    address internal constant sushiswap =
        0xd9e1cE17f2641f24aE83637ab66a2cca9C378B9F; // default to sushiswap, more CRV and CVX liquidity there

    IERC20 internal constant crv =
        IERC20(0xD533a949740bb3306d119CC777fa900bA034cd52);
    IERC20 internal constant convexToken =
        IERC20(0x4e3FBD56CD56c3e72c1403e103b45Db9da5B9D2B);
    IERC20 internal constant weth =
        IERC20(0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2);

    // keeper stuff
    uint256 public harvestProfitMin; // minimum size in USDT that we want to harvest
    uint256 public harvestProfitMax; // maximum size in USDT that we want to harvest
    bool internal forceHarvestTriggerOnce; // only set this to true when we want to trigger our keepers to harvest for us

    string internal stratName; // we use this to be able to adjust our strategy's name

    // convex-specific variables
    bool public claimRewards; // boolean if we should always claim rewards when withdrawing, usually withdrawAndUnwrap (generally this should be false)

    /* ========== CONSTRUCTOR ========== */

    constructor(address _vault) public BaseStrategy(_vault) {}

    /* ========== VIEWS ========== */

    function name() external view override returns (string memory) {
        return stratName;
    }

    function stakedBalance() public view returns (uint256) {
        // how much want we have staked in Convex
        return rewardsContract.balanceOf(address(this));
    }

    function balanceOfWant() public view returns (uint256) {
        // balance of want sitting in our strategy
        return want.balanceOf(address(this));
    }

    function claimableBalance() public view returns (uint256) {
        // how much CRV we can claim from the staking contract
        return rewardsContract.earned(address(this));
    }

    function estimatedTotalAssets() public view override returns (uint256) {
        return balanceOfWant().add(stakedBalance());
    }

    /* ========== CONSTANT FUNCTIONS ========== */
    // these should stay the same across different wants.

    function adjustPosition(uint256 _debtOutstanding) internal override {
        if (emergencyExit) {
            return;
        }
        // Send all of our Curve pool tokens to be deposited
        uint256 _toInvest = balanceOfWant();
        // deposit into convex and stake immediately but only if we have something to invest
        if (_toInvest > 0) {
            IConvexDeposit(depositContract).deposit(pid, _toInvest, true);
        }
    }

    function liquidatePosition(uint256 _amountNeeded)
        internal
        override
        returns (uint256 _liquidatedAmount, uint256 _loss)
    {
        uint256 _wantBal = balanceOfWant();
        if (_amountNeeded > _wantBal) {
            uint256 _stakedBal = stakedBalance();
            if (_stakedBal > 0) {
                rewardsContract.withdrawAndUnwrap(
                    Math.min(_stakedBal, _amountNeeded.sub(_wantBal)),
                    claimRewards
                );
            }
            uint256 _withdrawnBal = balanceOfWant();
            _liquidatedAmount = Math.min(_amountNeeded, _withdrawnBal);
            _loss = _amountNeeded.sub(_liquidatedAmount);
        } else {
            // we have enough balance to cover the liquidation available
            return (_amountNeeded, 0);
        }
    }

    // in case we need to exit into the convex deposit token, this will allow us to do that
    // make sure to check claimRewards before this step if needed
    // plan to have gov sweep convex deposit tokens from strategy after this
    function withdrawToConvexDepositTokens() external onlyAuthorized {
        uint256 _stakedBal = stakedBalance();
        if (_stakedBal > 0) {
            rewardsContract.withdraw(_stakedBal, claimRewards);
        }
    }

    // we don't want for these tokens to be swept out. We allow gov to sweep out cvx vault tokens; we would only be holding these if things were really, really rekt.
    function protectedTokens()
        internal
        view
        override
        returns (address[] memory)
    {}

    /* ========== SETTERS ========== */

    // These functions are useful for setting parameters of the strategy that may need to be adjusted.

    // Set the amount of CRV to be locked in Yearn's veCRV voter from each harvest. Default is 10%.
    function setKeepCRV(uint256 _keepCRV) external onlyAuthorized {
        require(_keepCRV <= 10_000);
        keepCRV = _keepCRV;
    }

    // We usually don't need to claim rewards on withdrawals, but might change our mind for migrations etc
    function setClaimRewards(bool _claimRewards) external onlyAuthorized {
        claimRewards = _claimRewards;
    }

    // This determines when we tell our keepers to start allowing harvests based on profit, and when to sell no matter what. this is how much in USDT we need to make. remember, 6 decimals!
    function setHarvestProfitNeeded(
        uint256 _harvestProfitMin,
        uint256 _harvestProfitMax
    ) external onlyAuthorized {
        harvestProfitMin = _harvestProfitMin;
        harvestProfitMax = _harvestProfitMax;
    }

    // This allows us to manually harvest with our keeper as needed
    function setForceHarvestTriggerOnce(bool _forceHarvestTriggerOnce)
        external
        onlyAuthorized
    {
        forceHarvestTriggerOnce = _forceHarvestTriggerOnce;
    }
}

// File: StrategyConvexIronBank.sol

contract StrategyConvexIronBank is StrategyConvexBase {
    /* ========== STATE VARIABLES ========== */
    // these will likely change across different wants.

    // Curve stuff
    ICurveFi public curve =
        ICurveFi(0x2dded6Da1BF5DBdF597C45fcFaa3194e53EcfeAF); // Curve Pool, this is our pool specific to this vault

    bool public checkEarmark; // this determines if we should check if we need to earmark rewards before harvesting

    // we use these to deposit to our curve pool
    address public targetStable;
    address internal constant uniswapv3 =
        0xE592427A0AEce92De3Edee1F18E0157C05861564;
    ICurveFi internal constant crveth =
        ICurveFi(0x8301AE4fc9c624d1D396cbDAa1ed877821D7C511); // use curve's new CRV-ETH crypto pool to sell our CRV
    IERC20 internal constant usdt =
        IERC20(0xdAC17F958D2ee523a2206206994597C13D831ec7);
    IERC20 internal constant usdc =
        IERC20(0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48);
    IERC20 internal constant dai =
        IERC20(0x6B175474E89094C44Da98b954EedeAC495271d0F);
    uint24 public uniStableFee; // this is equal to 0.05%, can change this later if a different path becomes more optimal

    /* ========== CONSTRUCTOR ========== */

    constructor(
        address _vault,
        uint256 _pid,
        string memory _name
    ) public StrategyConvexBase(_vault) {
        // want = Curve LP
        want.approve(address(depositContract), type(uint256).max);
        convexToken.approve(sushiswap, type(uint256).max);
        crv.approve(address(crveth), type(uint256).max);
        weth.approve(uniswapv3, type(uint256).max);

        // setup our rewards contract
        pid = _pid; // this is the pool ID on convex, we use this to determine what the reweardsContract address is
        (address lptoken, , , address _rewardsContract, , ) =
            IConvexDeposit(depositContract).poolInfo(_pid);

        // set up our rewardsContract
        rewardsContract = IConvexRewards(_rewardsContract);

        // check that our LP token based on our pid matches our want
        require(address(lptoken) == address(want));

        // set our strategy's name
        stratName = _name;

        // these are our approvals and path specific to this contract
        dai.approve(address(curve), type(uint256).max);
        usdt.safeApprove(address(curve), type(uint256).max); // USDT requires safeApprove(), funky token
        usdc.approve(address(curve), type(uint256).max);

        // start with usdt
        targetStable = address(usdt);

        // set our uniswap pool fees
        uniStableFee = 500;
    }

    /* ========== VARIABLE FUNCTIONS ========== */
    // these will likely change across different wants.

    function prepareReturn(uint256 _debtOutstanding)
        internal
        override
        returns (
            uint256 _profit,
            uint256 _loss,
            uint256 _debtPayment
        )
    {
        // this claims our CRV, CVX, and any extra tokens like SNX or ANKR. no harm leaving this true even if no extra rewards currently.
        rewardsContract.getReward(address(this), true);

        uint256 crvBalance = crv.balanceOf(address(this));
        uint256 convexBalance = convexToken.balanceOf(address(this));

        uint256 _sendToVoter = crvBalance.mul(keepCRV).div(FEE_DENOMINATOR);
        if (_sendToVoter > 0) {
            crv.safeTransfer(voter, _sendToVoter);
        }

        // check our balance again after transferring some crv to our voter
        crvBalance = crv.balanceOf(address(this));

        if (crvBalance > 0 || convexBalance > 0) {
            _sellCrvAndCvx(crvBalance, convexBalance);
        }

        // check for balances of tokens to deposit
        uint256 _daiBalance = dai.balanceOf(address(this));
        uint256 _usdcBalance = usdc.balanceOf(address(this));
        uint256 _usdtBalance = usdt.balanceOf(address(this));

        // deposit our balance to Curve if we have any
        if (_daiBalance > 0 || _usdcBalance > 0 || _usdtBalance > 0) {
            curve.add_liquidity(
                [_daiBalance, _usdcBalance, _usdtBalance],
                0,
                true
            );
        }

        // debtOustanding will only be > 0 in the event of revoking or if we need to rebalance from a withdrawal or lowering the debtRatio
        if (_debtOutstanding > 0) {
            uint256 _stakedBal = stakedBalance();
            if (_stakedBal > 0) {
                rewardsContract.withdrawAndUnwrap(
                    Math.min(_stakedBal, _debtOutstanding),
                    claimRewards
                );
            }
            uint256 _withdrawnBal = balanceOfWant();
            _debtPayment = Math.min(_debtOutstanding, _withdrawnBal);
        }

        // serious loss should never happen, but if it does (for instance, if Curve is hacked), let's record it accurately
        uint256 assets = estimatedTotalAssets();
        uint256 debt = vault.strategies(address(this)).totalDebt;

        // if assets are greater than debt, things are working great!
        if (assets > debt) {
            _profit = assets.sub(debt);
            uint256 _wantBal = balanceOfWant();
            if (_profit.add(_debtPayment) > _wantBal) {
                // this should only be hit following donations to strategy
                liquidatePosition(assets);
            }
        }
        // if assets are less than debt, we are in trouble
        else {
            _loss = debt.sub(assets);
        }

        // we're done harvesting, so reset our trigger if we used it
        forceHarvestTriggerOnce = false;
    }

    // migrate our want token to a new strategy if needed, make sure to check claimRewards first
    // also send over any CRV or CVX that is claimed; for migrations we definitely want to claim
    function prepareMigration(address _newStrategy) internal override {
        uint256 _stakedBal = stakedBalance();
        if (_stakedBal > 0) {
            rewardsContract.withdrawAndUnwrap(_stakedBal, claimRewards);
        }
    }

    // Sells our CRV -> WETH on UniV3 and CVX -> WETH on Sushi, then WETH -> stables together on UniV3
    function _sellCrvAndCvx(uint256 _crvAmount, uint256 _convexAmount)
        internal
    {
        address[] memory convexTokenPath = new address[](2);
        convexTokenPath[0] = address(convexToken);
        convexTokenPath[1] = address(weth);

        if (_convexAmount > 0) {
            IUniswapV2Router02(sushiswap).swapExactTokensForTokens(
                _convexAmount,
                uint256(0),
                convexTokenPath,
                address(this),
                block.timestamp
            );
        }

        if (_crvAmount > 0) {
            crveth.exchange(1, 0, _crvAmount, 0, false);
        }

        uint256 _wethBalance = weth.balanceOf(address(this));
        IUniV3(uniswapv3).exactInput(
            IUniV3.ExactInputParams(
                abi.encodePacked(
                    address(weth),
                    uint24(uniStableFee),
                    address(targetStable)
                ),
                address(this),
                block.timestamp,
                _wethBalance,
                uint256(1)
            )
        );
    }

    /* ========== KEEP3RS ========== */
    // use this to determine when to harvest
    function harvestTrigger(uint256 callCostinEth)
        public
        view
        override
        returns (bool)
    {
        // only check if we need to earmark on vaults we know are problematic
        if (checkEarmark) {
            // don't harvest if we need to earmark convex rewards
            if (needsEarmarkReward()) {
                return false;
            }
        }

        // harvest if we have a profit to claim at our upper limit without considering gas price
        uint256 claimableProfit = claimableProfitInUsdt();
        if (claimableProfit > harvestProfitMax) {
            return true;
        }

        // check if the base fee gas price is higher than we allow. if it is, block harvests.
        if (!isBaseFeeAcceptable()) {
            return false;
        }

        // trigger if we want to manually harvest, but only if our gas price is acceptable
        if (forceHarvestTriggerOnce) {
            return true;
        }

        // harvest if we have a sufficient profit to claim, but only if our gas price is acceptable
        if (claimableProfit > harvestProfitMin) {
            return true;
        }

        // otherwise, we don't harvest
        return false;
    }

    // we will need to add rewards token here if we have them
    function claimableProfitInUsdt() internal view returns (uint256) {
        // calculations pulled directly from CVX's contract for minting CVX per CRV claimed
        uint256 totalCliffs = 1_000;
        uint256 maxSupply = 100 * 1_000_000 * 1e18; // 100mil
        uint256 reductionPerCliff = 100_000 * 1e18; // 100,000
        uint256 supply = convexToken.totalSupply();
        uint256 mintableCvx;

        uint256 cliff = supply.div(reductionPerCliff);
        uint256 _claimableBal = claimableBalance();
        //mint if below total cliffs
        if (cliff < totalCliffs) {
            //for reduction% take inverse of current cliff
            uint256 reduction = totalCliffs.sub(cliff);
            //reduce
            mintableCvx = _claimableBal.mul(reduction).div(totalCliffs);

            //supply cap check
            uint256 amtTillMax = maxSupply.sub(supply);
            if (mintableCvx > amtTillMax) {
                mintableCvx = amtTillMax;
            }
        }

        address[] memory usd_path = new address[](3);
        usd_path[0] = address(crv);
        usd_path[1] = address(weth);
        usd_path[2] = address(usdt);

        uint256 crvValue;
        if (_claimableBal > 0) {
            uint256[] memory crvSwap =
                IUniswapV2Router02(sushiswap).getAmountsOut(
                    _claimableBal,
                    usd_path
                );
            crvValue = crvSwap[crvSwap.length - 1];
        }

        usd_path[0] = address(convexToken);
        uint256 cvxValue;
        if (mintableCvx > 0) {
            uint256[] memory cvxSwap =
                IUniswapV2Router02(sushiswap).getAmountsOut(
                    mintableCvx,
                    usd_path
                );
            cvxValue = cvxSwap[cvxSwap.length - 1];
        }

        return crvValue.add(cvxValue);
    }

    // check if the current baseFee is below our external target
    function isBaseFeeAcceptable() internal view returns (bool) {
        return
            IBaseFee(0xb5e1CAcB567d98faaDB60a1fD4820720141f064F)
                .isCurrentBaseFeeAcceptable();
    }

    // check if someone needs to earmark rewards on convex before keepers harvest again
    function needsEarmarkReward() public view returns (bool needsEarmark) {
        // check if there is any CRV we need to earmark
        uint256 crvExpiry = rewardsContract.periodFinish();
        if (crvExpiry < block.timestamp) {
            return true;
        }
    }

    /* ========== SETTERS ========== */

    // These functions are useful for setting parameters of the strategy that may need to be adjusted.

    // Set optimal token to sell harvested funds for depositing to Curve.
    // Default is DAI, but can be set to USDC or USDT as needed by strategist or governance.
    function setOptimal(uint256 _optimal) external onlyAuthorized {
        if (_optimal == 0) {
            targetStable = address(dai);
        } else if (_optimal == 1) {
            targetStable = address(usdc);
        } else if (_optimal == 2) {
            targetStable = address(usdt);
        } else {
            revert("incorrect token");
        }
    }

    // determine whether we will check if our convex rewards need to be earmarked
    function setCheckEarmark(bool _checkEarmark) external onlyAuthorized {
        checkEarmark = _checkEarmark;
    }

    // set the fee pool we'd like to swap through for CRV on UniV3 (1% = 10_000)
    function setUniFees(uint24 _stableFee) external onlyAuthorized {
        uniStableFee = _stableFee;
    }
}