// SPDX-License-Identifier: GPL-3.0

pragma solidity 0.6.12;
pragma experimental ABIEncoderV2;

// Global Enums and Structs



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

// Part: IGenericLender

interface IGenericLender {
    function lenderName() external view returns (string memory);

    function nav() external view returns (uint256);

    function strategy() external view returns (address);

    function apr() external view returns (uint256);

    function weightedApr() external view returns (uint256);

    function withdraw(uint256 amount) external returns (uint256);

    function emergencyWithdraw(uint256 amount) external;

    function deposit() external;

    function withdrawAll() external returns (bool);

    function hasAssets() external view returns (bool);

    function aprAfterDeposit(uint256 amount) external view returns (uint256);

    function setDust(uint256 _dust) external;

    function sweep(address _token) external;
}

// Part: IUni

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

// Part: IWantToEth

interface IWantToEth {
    function wantToEth(uint256 input) external view returns (uint256);

    function ethToWant(uint256 input) external view returns (uint256);
}

// Part: OpenZeppelin/openzeppelin-contracts@3.1.0/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/openzeppelin-contracts@3.1.0/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/openzeppelin-contracts@3.1.0/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/openzeppelin-contracts@3.1.0/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: OpenZeppelin/openzeppelin-contracts@3.1.0/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: iearn-finance/yearn-vaults@0.3.1/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);
}

// Part: iearn-finance/yearn-vaults@0.3.1/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;
    string public metadataURI;

    /**
     * @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 "0.3.1";
    }

    /**
     * @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 UpdatedReportDelay(uint256 delay);

    event UpdatedProfitFactor(uint256 profitFactor);

    event UpdatedDebtThreshold(uint256 debtThreshold);

    event EmergencyExitEnabled();

    event UpdatedMetadataURI(string metadataURI);

    // 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(), "!authorized");
        _;
    }

    /**
     * @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.
     */
    constructor(address _vault) public {
        vault = VaultAPI(_vault);
        want = IERC20(vault.token());
        want.approve(_vault, uint256(-1)); // Give Vault unlimited access (might save gas)
        strategist = msg.sender;
        rewards = msg.sender;
        keeper = msg.sender;
        vault.approve(rewards, uint256(-1)); // Allow rewards to be pulled
    }

    /**
     * @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 `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 UpdatedReportDelay(_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 `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 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.
        debtOutstanding = vault.report(profit, loss, debtPayment);

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

        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);
        // Send it directly back (NOTE: Using `msg.sender` saves some gas here)
        want.transfer(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.transfer(_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).transfer(governance(), IERC20(_token).balanceOf(address(this)));
    }
}

// File: Strategy.sol

/********************
 *
 *   A lender optimisation strategy for any erc20 asset
 *   https://github.com/Grandthrax/yearnV2-generic-lender-strat
 *   v0.3.1
 *
 *   This strategy works by taking plugins designed for standard lending platforms
 *   It automatically chooses the best yield generating platform and adjusts accordingly
 *   The adjustment is sub optimal so there is an additional option to manually set position
 *
 ********************* */

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

    address public constant uniswapRouter = address(0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D);
    address public constant weth = address(0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2);
    uint256 public withdrawalThreshold  = 1e16;
    uint256 public constant SECONDSPERYEAR = 31556952;

    IGenericLender[] public lenders;
    bool public externalOracle = false;
    address public wantToEthOracle;

    constructor(address _vault) public BaseStrategy(_vault) {
        debtThreshold = 100*1e18;

        //we do this horrible thing because you can't compare strings in solidity
        require(keccak256(bytes(apiVersion())) == keccak256(bytes(VaultAPI(_vault).apiVersion())), "WRONG VERSION");
    }

    function setWithdrawalThreshold(uint256 _threshold) external onlyAuthorized {
        withdrawalThreshold = _threshold;
    }

    function setPriceOracle(address _oracle) external onlyAuthorized {
        wantToEthOracle = _oracle;
    }

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

    //management functions
    //add lenders for the strategy to choose between
    // only governance to stop strategist adding dodgy lender
    function addLender(address a) public onlyGovernance {
        IGenericLender n = IGenericLender(a);
        require(n.strategy() == address(this), "Undocked Lender");

        for (uint256 i = 0; i < lenders.length; i++) {
            require(a != address(lenders[i]), "Already Added");
        }
        lenders.push(n);
    }

    //but strategist can remove for safety
    function safeRemoveLender(address a) public onlyAuthorized {
        _removeLender(a, false);
    }

    function forceRemoveLender(address a) public onlyAuthorized {
        _removeLender(a, true);
    }

    //force removes the lender even if it still has a balance
    function _removeLender(address a, bool force) internal {
        for (uint256 i = 0; i < lenders.length; i++) {
            if (a == address(lenders[i])) {
                bool allWithdrawn = lenders[i].withdrawAll();

                if (!force) {
                    require(allWithdrawn, "WITHDRAW FAILED");
                }

                //put the last index here
                //remove last index
                if (i != lenders.length - 1) {
                    lenders[i] = lenders[lenders.length - 1];
                }

                //pop shortens array by 1 thereby deleting the last index
                lenders.pop();

                //if balance to spend we might as well put it into the best lender
                if (want.balanceOf(address(this)) > 0) {
                    adjustPosition(0);
                }
                return;
            }
        }
        require(false, "NOT LENDER");
    }

    //we could make this more gas efficient but it is only used by a view function
    struct lendStatus {
        string name;
        uint256 assets;
        uint256 rate;
        address add;
    }

    //Returns the status of all lenders attached the strategy
    function lendStatuses() public view returns (lendStatus[] memory) {
        lendStatus[] memory statuses = new lendStatus[](lenders.length);
        for (uint256 i = 0; i < lenders.length; i++) {
            lendStatus memory s;
            s.name = lenders[i].lenderName();
            s.add = address(lenders[i]);
            s.assets = lenders[i].nav();
            s.rate = lenders[i].apr();
            statuses[i] = s;
        }

        return statuses;
    }

    // lent assets plus loose assets
    function estimatedTotalAssets() public view override returns (uint256) {
        uint256 nav = lentTotalAssets();
        nav = nav.add(want.balanceOf(address(this)));

        return nav;
    }

    function numLenders() public view returns (uint256) {
        return lenders.length;
    }

    //the weighted apr of all lenders. sum(nav * apr)/totalNav
    function estimatedAPR() public view returns (uint256) {
        uint256 bal = estimatedTotalAssets();
        if (bal == 0) {
            return 0;
        }

        uint256 weightedAPR = 0;

        for (uint256 i = 0; i < lenders.length; i++) {
            weightedAPR = weightedAPR.add(lenders[i].weightedApr());
        }

        return weightedAPR.div(bal);
    }

    //Estimates the impact on APR if we add more money. It does not take into account adjusting position
    function _estimateDebtLimitIncrease(uint256 change) internal view returns (uint256) {
        uint256 highestAPR = 0;
        uint256 aprChoice = 0;
        uint256 assets = 0;

        for (uint256 i = 0; i < lenders.length; i++) {
            uint256 apr = lenders[i].aprAfterDeposit(change);
            if (apr > highestAPR) {
                aprChoice = i;
                highestAPR = apr;
                assets = lenders[i].nav();
            }
        }

        uint256 weightedAPR = highestAPR.mul(assets.add(change));

        for (uint256 i = 0; i < lenders.length; i++) {
            if (i != aprChoice) {
                weightedAPR = weightedAPR.add(lenders[i].weightedApr());
            }
        }

        uint256 bal = estimatedTotalAssets().add(change);

        return weightedAPR.div(bal);
    }

    //Estimates debt limit decrease. It is not accurate and should only be used for very broad decision making
    function _estimateDebtLimitDecrease(uint256 change) internal view returns (uint256) {
        uint256 lowestApr = uint256(-1);
        uint256 aprChoice = 0;

        for (uint256 i = 0; i < lenders.length; i++) {
            uint256 apr = lenders[i].aprAfterDeposit(change);
            if (apr < lowestApr) {
                aprChoice = i;
                lowestApr = apr;
            }
        }

        uint256 weightedAPR = 0;

        for (uint256 i = 0; i < lenders.length; i++) {
            if (i != aprChoice) {
                weightedAPR = weightedAPR.add(lenders[i].weightedApr());
            } else {
                uint256 asset = lenders[i].nav();
                if (asset < change) {
                    //simplistic. not accurate
                    change = asset;
                }
                weightedAPR = weightedAPR.add(lowestApr.mul(change));
            }
        }
        uint256 bal = estimatedTotalAssets().add(change);
        return weightedAPR.div(bal);
    }

    //estimates highest and lowest apr lenders. Public for debugging purposes but not much use to general public
    function estimateAdjustPosition()
        public
        view
        returns (
            uint256 _lowest,
            uint256 _lowestApr,
            uint256 _highest,
            uint256 _potential
        )
    {
        //all loose assets are to be invested
        uint256 looseAssets = want.balanceOf(address(this));

        // our simple algo
        // get the lowest apr strat
        // cycle through and see who could take its funds plus want for the highest apr
        _lowestApr = uint256(-1);
        _lowest = 0;
        uint256 lowestNav = 0;
        for (uint256 i = 0; i < lenders.length; i++) {
            if (lenders[i].hasAssets()) {
                uint256 apr = lenders[i].apr();
                if (apr < _lowestApr) {
                    _lowestApr = apr;
                    _lowest = i;
                    lowestNav = lenders[i].nav();
                }
            }
        }

        uint256 toAdd = lowestNav.add(looseAssets);

        uint256 highestApr = 0;
        _highest = 0;

        for (uint256 i = 0; i < lenders.length; i++) {
            uint256 apr;
            apr = lenders[i].aprAfterDeposit(looseAssets);

            if (apr > highestApr) {
                highestApr = apr;
                _highest = i;
            }
        }

        //if we can improve apr by withdrawing we do so
        _potential = lenders[_highest].aprAfterDeposit(toAdd);
    }

    //gives estiomate of future APR with a change of debt limit. Useful for governance to decide debt limits
    function estimatedFutureAPR(uint256 newDebtLimit) public view returns (uint256) {
        uint256 oldDebtLimit = vault.strategies(address(this)).totalDebt;
        uint256 change;
        if (oldDebtLimit < newDebtLimit) {
            change = newDebtLimit - oldDebtLimit;
            return _estimateDebtLimitIncrease(change);
        } else {
            change = oldDebtLimit - newDebtLimit;
            return _estimateDebtLimitDecrease(change);
        }
    }

    //cycle all lenders and collect balances
    function lentTotalAssets() public view returns (uint256) {
        uint256 nav = 0;
        for (uint256 i = 0; i < lenders.length; i++) {
            nav = nav.add(lenders[i].nav());
        }
        return nav;
    }

    //we need to free up profit plus _debtOutstanding.
    //If _debtOutstanding is more than we can free we get as much as possible
    // should be no way for there to be a loss. we hope...
    function prepareReturn(uint256 _debtOutstanding)
        internal
        override
        returns (
            uint256 _profit,
            uint256 _loss,
            uint256 _debtPayment
        )
    {
        _profit = 0;
        _loss = 0; //for clarity
        _debtPayment = _debtOutstanding;

        uint256 lentAssets = lentTotalAssets();

        uint256 looseAssets = want.balanceOf(address(this));

        uint256 total = looseAssets.add(lentAssets);

        if (lentAssets == 0) {
            //no position to harvest or profit to report
            if (_debtPayment > looseAssets) {
                //we can only return looseAssets
                _debtPayment = looseAssets;
            }

            return (_profit, _loss, _debtPayment);
        }

        uint256 debt = vault.strategies(address(this)).totalDebt;

        if (total > debt) {
            _profit = total - debt;
            uint256 amountToFree = _profit.add(_debtPayment);

            //we need to add outstanding to our profit
            //dont need to do logic if there is nothiing to free
            if (amountToFree > 0 && looseAssets < amountToFree) {
                //withdraw what we can withdraw
                _withdrawSome(amountToFree.sub(looseAssets));
                uint256 newLoose = want.balanceOf(address(this));

                //if we dont have enough money adjust _debtOutstanding and only change profit if needed
                if (newLoose < amountToFree) {
                    if (_profit > newLoose) {
                        _profit = newLoose;
                        _debtPayment = 0;
                    } else {
                        _debtPayment = Math.min(newLoose - _profit, _debtPayment);
                    }
                }
            }
        } else {
            //serious loss should never happen but if it does lets record it accurately
            _loss = debt - total;
            uint256 amountToFree = _loss.add(_debtPayment);

            if (amountToFree > 0 && looseAssets < amountToFree) {
                //withdraw what we can withdraw

                _withdrawSome(amountToFree.sub(looseAssets));
                uint256 newLoose = want.balanceOf(address(this));

                //if we dont have enough money adjust _debtOutstanding and only change profit if needed
                if (newLoose < amountToFree) {
                    if (_loss > newLoose) {
                        _loss = newLoose;
                        _debtPayment = 0;
                    } else {
                        _debtPayment = Math.min(newLoose - _loss, _debtPayment);
                    }
                }
            }
        }
    }

    /*
     * Key logic.
     *   The algorithm moves assets from lowest return to highest
     *   like a very slow idiots bubble sort
     *   we ignore debt outstanding for an easy life
     */
    function adjustPosition(uint256 _debtOutstanding) internal override {

        _debtOutstanding; //ignored. we handle it in prepare return
        //emergency exit is dealt with at beginning of harvest
        if (emergencyExit) {
            return;
        }

        //we just keep all money in want if we dont have any lenders
        if (lenders.length == 0) {
            return;
        }

        (uint256 lowest, uint256 lowestApr, uint256 highest, uint256 potential) = estimateAdjustPosition();

        if (potential > lowestApr) {
            //apr should go down after deposit so wont be withdrawing from self
            lenders[lowest].withdrawAll();
        }

        uint256 bal = want.balanceOf(address(this));
        if (bal > 0) {
            want.safeTransfer(address(lenders[highest]), bal);
            lenders[highest].deposit();
        }
    }

    struct lenderRatio {
        address lender;
        //share x 1000
        uint16 share;
    }

    //share must add up to 1000. 500 means 50% etc
    function manualAllocation(lenderRatio[] memory _newPositions) public onlyAuthorized {
        uint256 share = 0;

        for (uint256 i = 0; i < lenders.length; i++) {
            lenders[i].withdrawAll();
        }

        uint256 assets = want.balanceOf(address(this));

        for (uint256 i = 0; i < _newPositions.length; i++) {
            bool found = false;

            //might be annoying and expensive to do this second loop but worth it for safety
            for (uint256 j = 0; j < lenders.length; j++) {
                if (address(lenders[j]) == _newPositions[i].lender) {
                    found = true;
                }
            }
            require(found, "NOT LENDER");

            share = share.add(_newPositions[i].share);
            uint256 toSend = assets.mul(_newPositions[i].share).div(1000);
            want.safeTransfer(_newPositions[i].lender, toSend);
            IGenericLender(_newPositions[i].lender).deposit();
        }

        require(share == 1000, "SHARE!=1000");
    }

    //cycle through withdrawing from worst rate first
    function _withdrawSome(uint256 _amount) internal returns (uint256 amountWithdrawn) {

        if(lenders.length == 0){
            return 0;
        }

        //dont withdraw dust
        if (_amount < withdrawalThreshold) {
            return 0;
        }

        amountWithdrawn = 0;
        //most situations this will only run once. Only big withdrawals will be a gas guzzler
        uint256 j = 0;
        while (amountWithdrawn < _amount) {
            uint256 lowestApr = uint256(-1);
            uint256 lowest = 0;
            for (uint256 i = 0; i < lenders.length; i++) {
                if (lenders[i].hasAssets()) {
                    uint256 apr = lenders[i].apr();
                    if (apr < lowestApr) {
                        lowestApr = apr;
                        lowest = i;
                    }
                }
            }
            if (!lenders[lowest].hasAssets()) {
                return amountWithdrawn;
            }
            amountWithdrawn = amountWithdrawn.add(lenders[lowest].withdraw(_amount - amountWithdrawn));
            j++;
            //dont want infinite loop
            if (j >= 6) {
                return amountWithdrawn;
            }
        }
    }

    /*
     * Liquidate as many assets as possible to `want`, irregardless of slippage,
     * up to `_amountNeeded`. Any excess should be re-invested here as well.
     */
    function liquidatePosition(uint256 _amountNeeded) internal override returns (uint256 _amountFreed, uint256 _loss) {
        uint256 _balance = want.balanceOf(address(this));

        if (_balance >= _amountNeeded) {
            //if we don't set reserve here withdrawer will be sent our full balance
            return (_amountNeeded, 0);
        } else {
            uint256 received = _withdrawSome(_amountNeeded - _balance).add(_balance);
            if (received >= _amountNeeded) {
                return (_amountNeeded, 0);
            } else {
                return (received, 0);
            }
        }
    }

    function harvestTrigger(uint256 callCost) public override view returns (bool) {
        uint256 wantCallCost = _callCostToWant(callCost);

        return super.harvestTrigger(wantCallCost);
    }

    function ethToWant(uint256 _amount) internal view returns (uint256) {
        address[] memory path = new address[](2);
        path = new address[](2);
        path[0] = weth;
        path[1] = address(want);

        uint256[] memory amounts = IUni(uniswapRouter).getAmountsOut(_amount, path);

        return amounts[amounts.length - 1];
    }

    function _callCostToWant(uint256 callCost) internal view returns (uint256) {
        uint256 wantCallCost;

        //three situations
        //1 currency is eth so no change.
        //2 we use uniswap swap price
        //3 we use external oracle
        if (address(want) == weth) {
            wantCallCost = callCost;
        } else if (wantToEthOracle == address(0)) {
            wantCallCost = ethToWant(callCost);
        } else {
            wantCallCost = IWantToEth(wantToEthOracle).ethToWant(callCost);
        }

        return wantCallCost;
    }

    function tendTrigger(uint256 callCost) public view override returns (bool) {
        // make sure to call tendtrigger with same callcost as harvestTrigger
        if (harvestTrigger(callCost)) {
            return false;
        }

        //now let's check if there is better apr somewhere else.
        //If there is and profit potential is worth changing then lets do it
        (uint256 lowest, uint256 lowestApr, , uint256 potential) = estimateAdjustPosition();

        //if protential > lowestApr it means we are changing horses
        if (potential > lowestApr) {
            uint256 nav = lenders[lowest].nav();

            //To calculate our potential profit increase we work out how much extra
            //we would make in a typical harvest interlude. That is maxReportingDelay
            //then we see if the extra profit is worth more than the gas cost * profitFactor

            //safe math not needed here
            //apr is scaled by 1e18 so we downscale here
            uint256 profitIncrease = (nav.mul(potential) - nav.mul(lowestApr)).div(1e18).mul(maxReportDelay).div(SECONDSPERYEAR);

            uint256 wantCallCost = _callCostToWant(callCost);

            return (wantCallCost.mul(profitFactor) < profitIncrease);
        }
    }

    /*
     * revert if we can't withdraw full balance
     */
    function prepareMigration(address _newStrategy) internal override {
        uint256 outstanding = vault.strategies(address(this)).totalDebt;
        (, uint256 loss, uint256 wantBalance) = prepareReturn(outstanding);
    }

    function protectedTokens() internal view override returns (address[] memory) {
        address[] memory protected = new address[](1);
        protected[0] = address(want);
        return protected;
    }
}