// SPDX-License-Identifier: MIT
pragma solidity 0.7.6;

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.

        uint 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, uint 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,
        uint 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,
        uint 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);
            }
        }
    }
}

interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint);

    /**
     * @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, uint 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 (uint);

    /**
     * @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, uint 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,
        uint 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, uint 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, uint value);
}

interface IFundManager {
    function token() external view returns (address);

    function borrow(uint amount) external returns (uint);

    function repay(uint amount) external returns (uint);

    function report(uint gain, uint loss) external;

    function getDebt(address strategy) external view returns (uint);
}

interface IVaultV3 is IERC20 {
    event Deposit(
        address indexed caller,
        address indexed owner,
        uint assets,
        uint shares
    );

    event Withdraw(
        address indexed caller,
        address indexed receiver,
        address indexed owner,
        uint assets,
        uint shares
    );

    function owner() external view returns (address);

    function asset() external view returns (IERC20);

    function totalAssets() external view returns (uint assets);

    function convertToShares(uint assets) external view returns (uint shares);

    function convertToAssets(uint shares) external view returns (uint assets);

    function maxDeposit(address receiver) external view returns (uint assets);

    function previewDeposit(uint assets) external view returns (uint shares);

    function deposit(uint assets, address receiver) external returns (uint shares);

    function maxMint(address receiver) external view returns (uint shares);

    function previewMint(uint shares) external view returns (uint assets);

    function mint(uint shares, address receiver) external returns (uint assets);

    function maxWithdraw(address owner) external view returns (uint assets);

    function previewWithdraw(uint assets) external view returns (uint shares);

    function withdraw(
        uint assets,
        address receiver,
        address owner
    ) external returns (uint shares);

    function maxRedeem(address owner) external view returns (uint shares);

    function previewRedeem(uint shares) external view returns (uint assets);

    function redeem(
        uint shares,
        address receiver,
        address owner
    ) external returns (uint assets);

    function safeRedeem(
        uint shares,
        address receiver,
        address owner,
        uint minAssets
    ) external returns (uint assets);

    function setBlockDelay(uint8) external;
}

library SafeERC20 {
    using SafeMath for uint;
    using Address for address;

    function safeTransfer(
        IERC20 token,
        address to,
        uint value
    ) internal {
        _callOptionalReturn(
            token,
            abi.encodeWithSelector(token.transfer.selector, to, value)
        );
    }

    function safeTransferFrom(
        IERC20 token,
        address from,
        address to,
        uint 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,
        uint 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,
        uint value
    ) internal {
        uint newAllowance = token.allowance(address(this), spender).add(value);
        _callOptionalReturn(
            token,
            abi.encodeWithSelector(token.approve.selector, spender, newAllowance)
        );
    }

    function safeDecreaseAllowance(
        IERC20 token,
        address spender,
        uint value
    ) internal {
        uint 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"
            );
        }
    }
}

library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint a, uint b) internal pure returns (bool, uint) {
        uint 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(uint a, uint b) internal pure returns (bool, uint) {
        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(uint a, uint b) internal pure returns (bool, uint) {
        // 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);
        uint 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(uint a, uint b) internal pure returns (bool, uint) {
        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(uint a, uint b) internal pure returns (bool, uint) {
        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(uint a, uint b) internal pure returns (uint) {
        uint 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(uint a, uint b) internal pure returns (uint) {
        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(uint a, uint b) internal pure returns (uint) {
        if (a == 0) return 0;
        uint 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(uint a, uint b) internal pure returns (uint) {
        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(uint a, uint b) internal pure returns (uint) {
        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(
        uint a,
        uint b,
        string memory errorMessage
    ) internal pure returns (uint) {
        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(
        uint a,
        uint b,
        string memory errorMessage
    ) internal pure returns (uint) {
        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(
        uint a,
        uint b,
        string memory errorMessage
    ) internal pure returns (uint) {
        require(b > 0, errorMessage);
        return a % b;
    }
}

abstract contract Strategy {
    using SafeERC20 for IERC20;
    using SafeMath for uint;

    event SetNextTimeLock(address nextTimeLock);
    event AcceptTimeLock(address timeLock);
    event SetAdmin(address admin);
    event Authorize(address addr, bool authorized);
    event SetTreasury(address treasury);
    event SetFundManager(address fundManager);

    event Deposit(uint amount, uint borrowed);
    event Repay(uint amount, uint repaid);
    event Withdraw(uint amount, uint withdrawn, uint loss);
    event ClaimRewards(uint profit);
    event Skim(uint total, uint debt, uint profit);
    event Report(uint gain, uint loss, uint free, uint total, uint debt);

    // Privilege - time lock >= admin >= authorized addresses
    address public timeLock;
    address public nextTimeLock;
    address public admin;
    address public treasury; // Profit is sent to this address

    // authorization other than time lock and admin
    mapping(address => bool) public authorized;

    IERC20 public immutable token;
    IFundManager public fundManager;

    // Performance fee sent to treasury
    uint public perfFee = 1000;
    uint private constant PERF_FEE_CAP = 2000; // Upper limit to performance fee
    uint internal constant PERF_FEE_MAX = 10000;

    bool public claimRewardsOnMigrate = true;

    constructor(
        address _token,
        address _fundManager,
        address _treasury
    ) {
        // Don't allow accidentally sending perf fee to 0 address
        require(_treasury != address(0), "treasury = 0 address");

        timeLock = msg.sender;
        admin = msg.sender;
        treasury = _treasury;

        require(
            IFundManager(_fundManager).token() == _token,
            "fund manager token != token"
        );

        fundManager = IFundManager(_fundManager);
        token = IERC20(_token);

        IERC20(_token).safeApprove(_fundManager, type(uint).max);
    }

    modifier onlyTimeLock() {
        require(msg.sender == timeLock, "!time lock");
        _;
    }

    modifier onlyTimeLockOrAdmin() {
        require(msg.sender == timeLock || msg.sender == admin, "!auth");
        _;
    }

    modifier onlyAuthorized() {
        require(
            msg.sender == timeLock || msg.sender == admin || authorized[msg.sender],
            "!auth"
        );
        _;
    }

    modifier onlyFundManager() {
        require(msg.sender == address(fundManager), "!fund manager");
        _;
    }

    /*
    @notice Set next time lock
    @param _nextTimeLock Address of next time lock
    @dev nextTimeLock can become timeLock by calling acceptTimeLock()
    */
    function setNextTimeLock(address _nextTimeLock) external onlyTimeLock {
        // Allow next time lock to be zero address (cancel next time lock)
        nextTimeLock = _nextTimeLock;
        emit SetNextTimeLock(_nextTimeLock);
    }

    /*
    @notice Set timeLock to msg.sender
    @dev msg.sender must be nextTimeLock
    */
    function acceptTimeLock() external {
        require(msg.sender == nextTimeLock, "!next time lock");
        timeLock = msg.sender;
        nextTimeLock = address(0);
        emit AcceptTimeLock(msg.sender);
    }

    /*
    @notice Set admin
    @param _admin Address of admin
    */
    function setAdmin(address _admin) external onlyTimeLockOrAdmin {
        require(_admin != address(0), "admin = 0 address");
        admin = _admin;
        emit SetAdmin(_admin);
    }

    /*
    @notice Set authorization
    @param _addr Address to authorize
    @param _authorized Boolean
    */
    function authorize(address _addr, bool _authorized) external onlyTimeLockOrAdmin {
        require(_addr != address(0), "addr = 0 address");
        authorized[_addr] = _authorized;
        emit Authorize(_addr, _authorized);
    }

    /*
    @notice Set treasury
    @param _treasury Address of treasury
    */
    function setTreasury(address _treasury) external onlyTimeLockOrAdmin {
        // Don't allow accidentally sending perf fee to 0 address
        require(_treasury != address(0), "treasury = 0 address");
        treasury = _treasury;
        emit SetTreasury(_treasury);
    }

    /*
    @notice Set performance fee
    @param _fee Performance fee
    */
    function setPerfFee(uint _fee) external onlyTimeLockOrAdmin {
        require(_fee <= PERF_FEE_CAP, "fee > cap");
        perfFee = _fee;
    }

    function setFundManager(address _fundManager) external onlyTimeLock {
        if (address(fundManager) != address(0)) {
            token.safeApprove(address(fundManager), 0);
        }

        require(
            IFundManager(_fundManager).token() == address(token),
            "new fund manager token != token"
        );

        fundManager = IFundManager(_fundManager);
        token.safeApprove(_fundManager, type(uint).max);

        emit SetFundManager(_fundManager);
    }

    /*
    @notice Set `claimRewardsOnMigrate`. If `false` skip call to `claimRewards`
            when `migrate` is called.
    @param _claimRewards Boolean to call or skip call to `claimRewards`
    */
    function setClaimRewardsOnMigrate(bool _claimRewards) external onlyTimeLockOrAdmin {
        claimRewardsOnMigrate = _claimRewards;
    }

    /*
    @notice Transfer funds from `_from` address. Used for migration.
    @param _from Address to transfer token from
    @param _amount Amount of token to transfer
    */
    function transferTokenFrom(address _from, uint _amount) external onlyAuthorized {
        token.safeTransferFrom(_from, address(this), _amount);
    }

    /*
    @notice Returns approximate amount of token locked in this contract
    @dev Output may vary depending on price pulled from external DeFi contracts
    */
    function totalAssets() external view virtual returns (uint);

    /*
    @notice Deposit into strategy
    @param _amount Amount of token to deposit from fund manager
    @param _min Minimum amount borrowed
    */
    function deposit(uint _amount, uint _min) external virtual;

    /*
    @notice Withdraw token from this contract
    @dev Only callable by fund manager
    @dev Returns current loss = debt to fund manager - total assets
    */
    function withdraw(uint _amount) external virtual returns (uint);

    /*
    @notice Repay fund manager
    @param _amount Amount of token to repay to fund manager
    @param _min Minimum amount repaid
    @dev Call report after this to report any loss
    */
    function repay(uint _amount, uint _min) external virtual;

    /*
    @notice Claim any reward tokens, sell for token
    @param _minProfit Minumum amount of token to gain from selling rewards
    */
    function claimRewards(uint _minProfit) external virtual;

    /*
    @notice Free up any profit over debt
    */
    function skim() external virtual;

    /*
    @notice Report gain or loss back to fund manager
    @param _minTotal Minimum value of total assets.
               Used to protect against price manipulation.
    @param _maxTotal Maximum value of total assets Used
               Used to protect against price manipulation.  
    */
    function report(uint _minTotal, uint _maxTotal) external virtual;

    /*
    @notice Claim rewards, skim and report
    @param _minProfit Minumum amount of token to gain from selling rewards
    @param _minTotal Minimum value of total assets.
               Used to protect against price manipulation.
    @param _maxTotal Maximum value of total assets Used
               Used to protect against price manipulation.  
    */
    function harvest(
        uint _minProfit,
        uint _minTotal,
        uint _maxTotal
    ) external virtual;

    /*
    @notice Migrate to new version of this strategy
    @param _strategy Address of new strategy
    @dev Only callable by fund manager
    */
    function migrate(address _strategy) external virtual;

    /*
    @notice Transfer token accidentally sent here back to admin
    @param _token Address of token to transfer
    */
    function sweep(address _token) external virtual;
}

contract StrategyVaultV3 is Strategy {
    using SafeERC20 for IERC20;
    using SafeMath for uint;

    IVaultV3 public immutable V3;

    uint16 public slip = 950;
    uint16 public constant SLIP_BASIS = 1000;

    constructor(
        address _token,
        address _fundManager,
        address _treasury,
        IVaultV3 _V3
    ) Strategy(_token, _fundManager, _treasury) {
        require(_token == address(_V3.asset()), "token != asset");
        V3 = _V3;
    }

    function totalAssets() public view override returns (uint) {
        return
            token.balanceOf(address(this)) +
            V3.previewRedeem(V3.balanceOf(address(this)));
    }

    function deposit(uint _amount, uint _min) external override onlyAuthorized {
        require(_amount > 0, "deposit = 0");

        uint borrowed = fundManager.borrow(_amount);
        require(borrowed >= _min, "borrowed < min");

        uint balance = token.balanceOf(address(this));
        require(balance > 0, "balance = 0");

        _checkApproval(token, address(V3), _amount);
        V3.deposit(balance, address(this));
    }

    function _withdraw(uint _amount) private returns (uint available) {
        // first, check from balance
        uint bal = token.balanceOf(address(this));
        if (bal >= _amount) return _amount;

        uint total = totalAssets();
        _amount = _amount > total ? total : _amount;

        // how much to withdraw from v3
        uint need = _amount - bal;

        uint shares = V3.previewWithdraw(need);
        uint received = V3.safeRedeem(
            shares,
            address(this),
            address(this),
            need.mul(slip).div(SLIP_BASIS)
        );

        return bal + received;
    }

    function withdraw(uint _amount)
        external
        override
        onlyFundManager
        returns (uint loss)
    {
        require(_amount > 0, "withdraw = 0");

        uint available = _withdraw(_amount);
        uint debt = fundManager.getDebt(address(this));

        uint total = totalAssets();
        if (debt > total) loss = debt - total;

        if (available > 0) token.safeTransfer(msg.sender, available);
        emit Withdraw(_amount, available, loss);
    }

    function repay(uint _amount, uint _min) external override onlyAuthorized {
        require(_amount > 0, "repay = 0");
        uint available = _withdraw(_amount);
        uint repaid = fundManager.repay(available);
        require(repaid >= _min, "repaid < min");

        emit Repay(_amount, repaid);
    }

    /// nothing as compounding is handled in v3
    function claimRewards(uint _minProfit) external override onlyAuthorized {}

    function _skim() private {
        uint total = totalAssets();
        uint debt = fundManager.getDebt(address(this));
        require(total > debt, "total <= debt");

        uint profit = total - debt;
        // reassign to actual amount withdrawn
        profit = _withdraw(profit);

        emit Skim(total, debt, profit);
    }

    function skim() external override onlyAuthorized {
        _skim();
    }

    function _report(uint _minTotal, uint _maxTotal) private {
        uint total = totalAssets();
        require(total >= _minTotal, "total < min");
        require(total <= _maxTotal, "total > max");

        uint gain = 0;
        uint loss = 0;
        uint free = 0; // balance of token
        uint debt = fundManager.getDebt(address(this));
        if (total > debt) {
            gain = total - debt;

            free = token.balanceOf(address(this));
            if (gain > free) {
                gain = free;
            }
        } else {
            loss = debt - total;
        }

        if (gain > 0 || loss > 0) {
            fundManager.report(gain, loss);
        }

        emit Report(gain, loss, free, total, debt);
    }

    function report(uint _minTotal, uint _maxTotal) external override onlyAuthorized {
        _report(_minTotal, _maxTotal);
    }

    function harvest(
        uint _minProfit,
        uint _minTotal,
        uint _maxTotal
    ) external override onlyAuthorized {
        _skim();
        _report(_minTotal, _maxTotal);
    }

    function migrate(address _strategy) external override onlyFundManager {
        Strategy strat = Strategy(_strategy);
        require(address(strat.token()) == address(token), "strategy token != token");
        require(
            address(strat.fundManager()) == address(fundManager),
            "strategy fund manager != fund manager"
        );

        uint bal = _withdraw(type(uint).max);
        token.safeApprove(_strategy, bal);
        strat.transferTokenFrom(address(this), bal);
    }

    /*
    @notice Transfer token accidentally sent here to admin
    @param _token Address of token to transfer
    */
    function sweep(address _token) external override onlyAuthorized {
        require(_token != address(token), "protected token");
        require(_token != address(V3), "protected token");
        IERC20(_token).safeTransfer(admin, IERC20(_token).balanceOf(address(this)));
    }

    function setSlip(uint16 _slip) external onlyAuthorized {
        require(_slip <= SLIP_BASIS, "slip > max");
        slip = _slip;
    }

    function _checkApproval(
        IERC20 _token,
        address _spender,
        uint _amount
    ) internal {
        uint approval = _token.allowance(address(this), _spender);
        if (approval > _amount) return;
        _token.safeApprove(_spender, 0);
        _token.safeApprove(_spender, type(uint).max);
    }
}

contract StrategyVaultV3Usdc is StrategyVaultV3 {
    constructor(address _fundManager, address _treasury)
        StrategyVaultV3(
            0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48,
            _fundManager,
            _treasury,
            IVaultV3(0x09DAb27cC3758040eea0f7b51df2Aee14bc003D6)
        )
    {}
}