// SPDX-License-Identifier: MIT

pragma solidity 0.6.12;
pragma experimental ABIEncoderV2;



// Part: IFund

interface IFund {
    function underlying() external view returns (address);

    function fundManager() external view returns (address);

    function relayer() external view returns (address);

    function deposit(uint256 amountWei) external;

    function depositFor(uint256 amountWei, address holder) external;

    function withdraw(uint256 numberOfShares) external;

    function getPricePerShare() external view returns (uint256);

    function totalValueLocked() external view returns (uint256);

    function underlyingBalanceWithInvestmentForHolder(address holder)
        external
        view
        returns (uint256);
}

// Part: IGovernable

interface IGovernable {
    function governance() external view returns (address);
}

// Part: IStrategy

interface IStrategy {
    function name() external pure returns (string memory);

    function version() external pure returns (string memory);

    function underlying() external view returns (address);

    function fund() external view returns (address);

    function creator() external view returns (address);

    function withdrawAllToFund() external;

    function withdrawToFund(uint256 amount) external;

    function investedUnderlyingBalance() external view returns (uint256);

    function doHardWork() external;
}

// Part: IStrategyUnderOptimizer

interface IStrategyUnderOptimizer {
    function aprAfterDeposit(uint256 depositAmount)
        external
        view
        returns (uint256);

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

// Part: OpenZeppelin/openzeppelin-contracts@3.4.0/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) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly { size := extcodesize(account) }
        return size > 0;
    }

    /**
     * @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");
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: value }(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data, string memory errorMessage) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.staticcall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage) private pure returns(bytes memory) {
        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@3.4.0/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@3.4.0/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, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        uint256 c = a + b;
        if (c < a) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b > a) return (false, 0);
        return (true, a - b);
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, 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 (true, 0);
        uint256 c = a * b;
        if (c / a != b) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a / b);
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a % b);
    }

    /**
     * @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) {
        require(b <= a, "SafeMath: subtraction overflow");
        return a - b;
    }

    /**
     * @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) {
        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, reverting 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) {
        require(b > 0, "SafeMath: division by zero");
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting 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) {
        require(b > 0, "SafeMath: modulo by zero");
        return a % b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * 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);
        return a - b;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryDiv}.
     *
     * 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);
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * 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@3.4.0/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");
        }
    }
}

// File: OptimizerStrategyBase.sol

/**
 * This strategy takes an asset, and invests into the best strategy
 */
/**
 * @title This is an optimizer strategy that rotates capital to various strategies.
 * @author Mesh Finance
 * @notice This strategy takes an asset, and invests into the strategy with highest APR
 */
contract OptimizerStrategyBase is IStrategy {
    using SafeERC20 for IERC20;
    using Address for address;
    using SafeMath for uint256;

    event StrategyAddedOptimizer(address indexed strategy);
    event StrategyRemovedOptimizer(address indexed strategy);
    event ActiveStrategyChangedOptimizer(address indexed strategy);

    address internal constant ZERO_ADDRESS = address(0);

    string public constant override name = "OptimizerStrategyBase";
    string public constant override version = "V1";

    address public immutable override underlying;
    address public immutable override fund;
    address public immutable deployer;

    // these tokens cannot be claimed by the governance
    mapping(address => bool) public canNotSweep;

    address[] public strategies;

    address public activeStrategy;

    bool public investActivated;

    constructor(address _fund) public {
        require(_fund != address(0), "Fund cannot be empty");
        fund = _fund;
        address _underlying = IFund(_fund).underlying();
        underlying = _underlying;
        deployer = msg.sender;

        // restricted tokens, can not be swept
        canNotSweep[_underlying] = true;

        investActivated = true;
    }

    function _governance() internal view returns (address) {
        return IGovernable(fund).governance();
    }

    function governance() external view returns (address) {
        return _governance();
    }

    function _fundManager() internal view returns (address) {
        return IFund(fund).fundManager();
    }

    function fundManager() external view returns (address) {
        return _fundManager();
    }

    function _relayer() internal view returns (address) {
        return IFund(fund).relayer();
    }

    function relayer() external view returns (address) {
        return _relayer();
    }

    function creator() external view override returns (address) {
        if (activeStrategy != ZERO_ADDRESS) {
            return IStrategy(activeStrategy).creator();
        }
        return deployer;
    }

    modifier onlyFund() {
        require(msg.sender == fund, "The sender has to be the fund");
        _;
    }

    modifier onlyFundManager() {
        require(
            msg.sender == _fundManager(),
            "The sender has to be the fund manager"
        );
        _;
    }

    modifier onlyFundOrGovernance() {
        require(
            msg.sender == fund || msg.sender == _governance(),
            "The sender has to be the governance or fund"
        );
        _;
    }

    modifier onlyFundManagerOrGovernance() {
        require(
            msg.sender == _fundManager() || msg.sender == _governance(),
            "The sender has to be the governance or fund manager"
        );
        _;
    }

    modifier onlyFundManagerOrRelayer() {
        require(
            msg.sender == _fundManager() || msg.sender == _relayer(),
            "The sender has to be the relayer or fund manager"
        );
        _;
    }

    /**
     * @notice Allows Governance/Fund Manager to stop/start investing from this strategy to active strategies
     * @dev Used for emergencies
     * @param _investActivated Set investment to True/False
     */
    function setInvestActivated(bool _investActivated)
        external
        onlyFundManagerOrGovernance
    {
        investActivated = _investActivated;
    }

    /**
     * @notice Withdraws an underlying asset from the strategy to the fund in the specified amount.
     * It tries to withdraw from this optimizer contract if this has enough balance.
     * Otherwise, we withdraw from the active strategy.
     * @param underlyingAmount Underlying amount to withdraw to fund
     */
    function withdrawToFund(uint256 underlyingAmount)
        external
        override
        onlyFund
    {
        uint256 underlyingBalanceBefore =
            IERC20(underlying).balanceOf(address(this));

        if (underlyingBalanceBefore >= underlyingAmount) {
            IERC20(underlying).safeTransfer(fund, underlyingAmount);
            return;
        }

        if (activeStrategy != ZERO_ADDRESS) {
            IStrategy(activeStrategy).withdrawToFund(
                underlyingAmount.sub(underlyingBalanceBefore)
            );
        }

        // we can transfer the asset to the fund
        uint256 underlyingBalance = IERC20(underlying).balanceOf(address(this));
        if (underlyingBalance > 0) {
            if (underlyingAmount < underlyingBalance) {
                IERC20(underlying).safeTransfer(fund, underlyingAmount);
                _investAllUnderlying();
            } else {
                IERC20(underlying).safeTransfer(fund, underlyingBalance);
            }
        }
    }

    /**
     * @notice Withdraws all assets from the active strategy and transfers all underlying to fund.
     */
    function withdrawAllToFund() external override onlyFund {
        if (activeStrategy != ZERO_ADDRESS) {
            IStrategy(activeStrategy).withdrawAllToFund();
        }
        uint256 underlyingBalance = IERC20(underlying).balanceOf(address(this));
        if (underlyingBalance > 0) {
            IERC20(underlying).safeTransfer(fund, underlyingBalance);
        }
    }

    /**
     * @notice This selects new active strategy based on APR
     * @dev If active strategy is changed, funds are withdrawn from current active strategy
     */
    function _selectActiveStrategy() internal {
        if (strategies.length > 0) {
            uint256 highestApr = 0;
            address highestAprStrategy;

            uint256 underlyingBalance =
                IERC20(underlying).balanceOf(address(this));

            for (uint256 i = 0; i < strategies.length; i++) {
                uint256 apr;
                apr = IStrategyUnderOptimizer(strategies[i]).aprAfterDeposit(
                    underlyingBalance
                );
                if (apr > highestApr) {
                    highestApr = apr;
                    highestAprStrategy = strategies[i];
                }
            }

            if (highestAprStrategy != activeStrategy) {
                if (activeStrategy != ZERO_ADDRESS) {
                    IStrategy(activeStrategy).withdrawAllToFund();
                }
                activeStrategy = highestAprStrategy;
                emit ActiveStrategyChangedOptimizer(activeStrategy);
            }
        } else {
            if (activeStrategy != ZERO_ADDRESS) {
                activeStrategy = ZERO_ADDRESS;
                emit ActiveStrategyChangedOptimizer(activeStrategy);
            }
        }
    }

    /**
     * @notice Invests all underlying assets into active strategy
     */
    function _investAllUnderlying() internal {
        if (!investActivated) {
            return;
        }

        uint256 underlyingBalance = IERC20(underlying).balanceOf(address(this));

        if (activeStrategy != ZERO_ADDRESS) {
            if (underlyingBalance > 0) {
                // deposits the entire balance to active strategy
                IERC20(underlying).safeTransfer(
                    activeStrategy,
                    underlyingBalance
                );
            }
            IStrategy(activeStrategy).doHardWork();
        }
    }

    /**
     * @notice This selects new active strategy based on APR and invests all the underlying there.
     * @dev If active strategy is changed, funds are first withdrawn from current active strategy
     */
    function doHardWork() external override onlyFund {
        _selectActiveStrategy();
        _investAllUnderlying();
    }

    /**
     * @notice Adds a new strategy to select active strategy from.
     * @param newStrategy Strategy to add
     */
    function addStrategy(address newStrategy) external onlyFundManager {
        require(newStrategy != ZERO_ADDRESS, "newStrategy cannot be empty");
        // The strategies added in optimizer treat optimizer as fund.
        require(
            IStrategy(newStrategy).fund() == address(this),
            "The strategy does not belong to this optimizer"
        );
        for (uint256 i = 0; i < strategies.length; i++) {
            require(
                newStrategy != strategies[i],
                "The strategy is already added in this optimizer"
            );
        }

        strategies.push(newStrategy);

        emit StrategyAddedOptimizer(newStrategy);
    }

    /**
     * @notice Removes the strategy from the optimizer.
     * If it is an active strategy, funds are withdrawn from it, and reinvested in the newly selected active strategy.
     * @param strategy Strategy to remove
     */
    function removeStrategy(address strategy)
        external
        onlyFundManagerOrGovernance
    {
        require(strategy != ZERO_ADDRESS, "strategy cannot be empty");

        for (uint256 i = 0; i < strategies.length; i++) {
            if (strategy == strategies[i]) {
                IStrategy(strategy).withdrawAllToFund();
                if (i != strategies.length - 1) {
                    strategies[i] = strategies[strategies.length - 1];
                }
                strategies.pop();
                if (strategy == activeStrategy) {
                    activeStrategy = ZERO_ADDRESS;
                    _selectActiveStrategy();
                }
                _investAllUnderlying();
                emit StrategyRemovedOptimizer(strategy);
                return;
            }
        }

        require(false, "This strategy is not part of this optimizer");
    }

    //we could make this more gas efficient but it is only used by a view function
    struct Strategy {
        string name;
        address strategy;
        uint256 investedUnderlyingBalance;
        uint256 apr;
    }

    /**
     * @notice Returns the details of all the strategies in the optimiser
     * @return Array of Strategy struct
     */
    function getStrategies() public view returns (Strategy[] memory) {
        Strategy[] memory _strategies = new Strategy[](strategies.length);
        for (uint256 i = 0; i < strategies.length; i++) {
            Strategy memory s;
            s.name = IStrategy(strategies[i]).name();
            s.strategy = strategies[i];
            s.investedUnderlyingBalance = IStrategy(strategies[i])
                .investedUnderlyingBalance();
            s.apr = IStrategyUnderOptimizer(strategies[i]).apr();
            _strategies[i] = s;
        }

        return _strategies;
    }

    /**
     * @notice No tokens apart from underlying asset should ever be stored on this contract.
     * Any tokens that are sent here by mistake are recoverable by owner.
     * @dev Not applicable for ETH, different function needs to be written
     * @param  _token  Token address that needs to be recovered
     * @param  _sweepTo  Address to which tokens are sent
     */
    function sweep(address _token, address _sweepTo) external {
        require(_governance() == msg.sender, "Not governance");
        require(!canNotSweep[_token], "Token is restricted");
        require(_sweepTo != address(0), "Can not sweep to zero address");
        IERC20(_token).safeTransfer(
            _sweepTo,
            IERC20(_token).balanceOf(address(this))
        );
    }

    /**
     * @notice Returns the underlying invested balance. This is the underlying amount based on active strategy,
     * plus the current balance of the underlying asset.
     * @return Total balance invested in the strategy
     */
    function investedUnderlyingBalance()
        external
        view
        override
        returns (uint256)
    {
        uint256 underlyingBalanceinActiveStrategy;

        if (activeStrategy != ZERO_ADDRESS) {
            underlyingBalanceinActiveStrategy = IStrategy(activeStrategy)
                .investedUnderlyingBalance();
        }

        return
            underlyingBalanceinActiveStrategy.add(
                IERC20(underlying).balanceOf(address(this))
            );
    }
}