// File: @openzeppelin/contracts/token/ERC20/IERC20.sol

pragma solidity ^0.5.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP. Does not include
 * the optional functions; to access them see {ERC20Detailed}.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

// File: @openzeppelin/contracts/utils/Address.sol

pragma solidity ^0.5.5;

/**
 * @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 Converts an `address` into `address payable`. Note that this is
     * simply a type cast: the actual underlying value is not changed.
     *
     * _Available since v2.4.0._
     */
    function toPayable(address account) internal pure returns (address payable) {
        return address(uint160(account));
    }

    /**
     * @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].
     *
     * _Available since v2.4.0._
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        // solhint-disable-next-line avoid-call-value
        (bool success, ) = recipient.call.value(amount)("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }
}

// File: @openzeppelin/contracts/math/SafeMath.sol

pragma solidity ^0.5.0;

/**
 * @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.
     *
     * _Available since v2.4.0._
     */
    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.
     *
     * _Available since v2.4.0._
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        // Solidity only automatically asserts when dividing by 0
        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.
     *
     * _Available since v2.4.0._
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

// File: @openzeppelin/contracts/token/ERC20/SafeERC20.sol

pragma solidity ^0.5.0;




/**
 * @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 ERC20;` 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));
    }

    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.

        // A Solidity high level call has three parts:
        //  1. The target address is checked to verify it contains contract code
        //  2. The call itself is made, and success asserted
        //  3. The return value is decoded, which in turn checks the size of the returned data.
        // solhint-disable-next-line max-line-length
        require(address(token).isContract(), "SafeERC20: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = address(token).call(data);
        require(success, "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: contracts/hardworkInterface/IStrategy.sol

pragma solidity 0.5.16;

interface IStrategy {
    
    function unsalvagableTokens(address tokens) external view returns (bool);
    
    function governance() external view returns (address);
    function controller() external view returns (address);
    function underlying() external view returns (address);
    function vault() external view returns (address);

    function withdrawAllToVault() external;
    function withdrawToVault(uint256 amount) external;

    function investedUnderlyingBalance() external view returns (uint256); // itsNotMuch()

    // should only be called by controller
    function salvage(address recipient, address token, uint256 amount) external;

    function doHardWork() external;
    function depositArbCheck() external view returns(bool);
}

// File: contracts/Storage.sol

pragma solidity 0.5.16;

contract Storage {

  address public governance;
  address public controller;

  constructor() public {
    governance = msg.sender;
  }

  modifier onlyGovernance() {
    require(isGovernance(msg.sender), "Not governance");
    _;
  }

  function setGovernance(address _governance) public onlyGovernance {
    require(_governance != address(0), "new governance shouldn't be empty");
    governance = _governance;
  }

  function setController(address _controller) public onlyGovernance {
    require(_controller != address(0), "new controller shouldn't be empty");
    controller = _controller;
  }

  function isGovernance(address account) public view returns (bool) {
    return account == governance;
  }

  function isController(address account) public view returns (bool) {
    return account == controller;
  }
}

// File: contracts/Governable.sol

pragma solidity 0.5.16;


contract Governable {

  Storage public store;

  constructor(address _store) public {
    require(_store != address(0), "new storage shouldn't be empty");
    store = Storage(_store);
  }

  modifier onlyGovernance() {
    require(store.isGovernance(msg.sender), "Not governance");
    _;
  }

  function setStorage(address _store) public onlyGovernance {
    require(_store != address(0), "new storage shouldn't be empty");
    store = Storage(_store);
  }

  function governance() public view returns (address) {
    return store.governance();
  }
}

// File: contracts/Controllable.sol

pragma solidity 0.5.16;


contract Controllable is Governable {

  constructor(address _storage) Governable(_storage) public {
  }

  modifier onlyController() {
    require(store.isController(msg.sender), "Not a controller");
    _;
  }

  modifier onlyControllerOrGovernance(){
    require((store.isController(msg.sender) || store.isGovernance(msg.sender)),
      "The caller must be controller or governance");
    _;
  }

  function controller() public view returns (address) {
    return store.controller();
  }
}

// File: contracts/hardworkInterface/IMigrator.sol

pragma solidity 0.5.16;

interface IMigrator {
    function pullFromStrategy() external;
}

// File: contracts/hardworkInterface/IVault.sol

pragma solidity 0.5.16;

interface IVault {

    function underlyingBalanceInVault() external view returns (uint256);
    function underlyingBalanceWithInvestment() external view returns (uint256);

    // function store() external view returns (address);
    function governance() external view returns (address);
    function controller() external view returns (address);
    function underlying() external view returns (address);
    function strategy() external view returns (address);

    function setStrategy(address _strategy) external;
    function setVaultFractionToInvest(uint256 numerator, uint256 denominator) external;

    function deposit(uint256 amountWei) external;
    function depositFor(uint256 amountWei, address holder) external;

    function withdrawAll() external;
    function withdraw(uint256 numberOfShares) external;
    function getPricePerFullShare() external view returns (uint256);

    function underlyingBalanceWithInvestmentForHolder(address holder) view external returns (uint256);

    // hard work should be callable only by the controller (by the hard worker) or by governance
    function doHardWork() external;
    function rebalance() external;
}

// File: contracts/strategies/VaultMigratorStrategy.sol

pragma solidity 0.5.16;










contract VaultMigratorStrategy is IStrategy, Controllable {
  using SafeERC20 for IERC20;
  using Address for address;
  using SafeMath for uint256;

  IERC20 public underlying;
  IVault public vault;
  address public newVault;
  address public migrator;
  mapping(address => bool) public unsalvagableTokens;

  constructor(
    address _storage,
    address _underlying,
    address _vault,
    address _newVault
  ) public
  Controllable(_storage) {
    require(_underlying != address(0), "_underlying cannot be empty");
    require(_vault != address(0), "_vault cannot be empty");
    require(_newVault != address(0), "_newVault cannot be empty");

    require(IVault(_newVault).underlying() == _underlying, "underlying must match");

    unsalvagableTokens[_underlying] = true;
    underlying = IERC20(_underlying);
    vault = IVault(_vault);
    newVault = _newVault;
  }

  modifier restricted() {
    require(msg.sender == address(vault) || msg.sender == address(controller()) || msg.sender == address(governance()),
      "The sender has to be the controller or vault or governance");
    _;
  }

  function depositArbCheck() public view returns(bool) {
    return false; // disable deposits
  }

  modifier onlyVault() {
    require(msg.sender == address(vault), "The caller must be the vault");
    _;
  }

  /*
  * Returns the total amount.
  */
  function investedUnderlyingBalance() view public returns (uint256) {
    return underlying.balanceOf(address(this));
  }

  /*
  * Invests all tokens that were accumulated so far
  */
  function investAllUnderlying() public {
    // a no-op
  }

  function setMigrator(address _migrator) external onlyGovernance {
    migrator = _migrator;
  }

  function rebalance() public {
    // a no-op
  }

  /*
  * withdraws to the vault (in case migration is aborted)
  */
  function withdrawAllToVault() external restricted {
    uint256 balance = IERC20(underlying).balanceOf(address(this));
    IERC20(underlying).safeTransfer(address(vault), balance);
  }

  /*
  * Cashes some amount out and withdraws to the vault
  */
  function withdrawToVault(uint256 amountWei) external restricted {
    revert("Withdraws through this strategy are disabled");
  }

  // initiates the migration. Assumes all underling balance is already
  // in the strategy (transferred from the vault by doHardWork)
  function migrateToNewVault() external onlyGovernance {
    uint256 entireUnderlyingBalance = underlying.balanceOf(address(this));

    uint256 newVaultBalanceBefore = underlying.balanceOf(newVault);
    underlying.safeApprove(newVault, 0);
    underlying.safeApprove(newVault, entireUnderlyingBalance);
    IVault(newVault).deposit(entireUnderlyingBalance);
    require(underlying.balanceOf(newVault).sub(newVaultBalanceBefore) == entireUnderlyingBalance, "underlying balance mismatch");

    uint256 entireShareBalance = IERC20(newVault).balanceOf(address(this));

    require(migrator != address(0), "Migrator not set!");
    uint256 migratorBalanceBefore = IERC20(newVault).balanceOf(migrator);
    IERC20(newVault).safeApprove(migrator, 0);
    IERC20(newVault).safeApprove(migrator, entireShareBalance);
    IMigrator(migrator).pullFromStrategy();
    require(IERC20(newVault).balanceOf(migrator).sub(migratorBalanceBefore) == entireShareBalance, "share balance mismatch");
  }

  function doHardWork() external onlyVault {
    // a no-op
  }

  // should only be called by controller
  function salvage(address destination, address token, uint256 amount) external restricted {
    require(!unsalvagableTokens[token], "token is defined as not salvageable");
    IERC20(token).safeTransfer(destination, amount);
  }
}