// SPDX-License-Identifier: MIT

pragma solidity ^0.5.17;

interface IERC20 {
    function totalSupply() external view returns (uint256);
    function balanceOf(address account) external view returns (uint256);
    function transfer(address recipient, uint256 amount) external returns (bool);
    function allowance(address owner, address spender) external view returns (uint256);
    function decimals() external view returns (uint);
    function approve(address spender, uint256 amount) external returns (bool);
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);
    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

library SafeMath {
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }
    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;
    }
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }
    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;

        return c;
    }
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

library Address {
    function isContract(address account) internal view returns (bool) {
        bytes32 codehash;
        bytes32 accountHash = 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470;
        // solhint-disable-next-line no-inline-assembly
        assembly { codehash := extcodehash(account) }
        return (codehash != 0x0 && codehash != accountHash);
    }
    function toPayable(address account) internal pure returns (address payable) {
        return address(uint160(account));
    }
    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");
    }
}

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 {
        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 callOptionalReturn(IERC20 token, bytes memory data) private {
        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");
        }
    }
}

interface Controller {
    function vaults(address) external view returns (address);
    function rewards() external view returns (address);
}

/*

 A strategy must implement the following calls;
 
 - deposit()
 - withdraw(address) must exclude any tokens used in the yield - Controller role - withdraw should return to Controller
 - withdraw(uint) - Controller | Vault role - withdraw should always return to vault
 - withdrawAll() - Controller | Vault role - withdraw should always return to vault
 - balanceOf()
 
 Where possible, strategies must remain as immutable as possible, instead of updating variables, we update the contract by linking it in the controller
 
*/

interface Gauge {
    function deposit(uint) external;
    function balanceOf(address) external view returns (uint);
    function withdraw(uint) external;
}

interface Mintr {
    function mint(address) external;
}

interface Uni {
    function swapExactTokensForTokens(uint, uint, address[] calldata, address, uint) external;
}

interface yERC20 {
  function deposit(uint256 _amount) external;
  function withdraw(uint256 _amount) external;
}

interface ICurveFi {

  function get_virtual_price() external view returns (uint);
  function add_liquidity(
    uint256[4] calldata amounts,
    uint256 min_mint_amount
  ) external;
  function remove_liquidity_imbalance(
    uint256[4] calldata amounts,
    uint256 max_burn_amount
  ) external;
  function remove_liquidity(
    uint256 _amount,
    uint256[4] calldata amounts
  ) external;
  function exchange(
    int128 from, int128 to, uint256 _from_amount, uint256 _min_to_amount
  ) external;
}

interface VoteEscrow {
    function create_lock(uint, uint) external;
    function increase_amount(uint) external;
    function withdraw() external;
}

contract CurveYCRVVoter {
    using SafeERC20 for IERC20;
    using Address for address;
    using SafeMath for uint256;
    
    address constant public want = address(0xdF5e0e81Dff6FAF3A7e52BA697820c5e32D806A8);
    address constant public pool = address(0xFA712EE4788C042e2B7BB55E6cb8ec569C4530c1);
    address constant public mintr = address(0xd061D61a4d941c39E5453435B6345Dc261C2fcE0);
    address constant public crv = address(0xD533a949740bb3306d119CC777fa900bA034cd52);
    
    address constant public escrow = address(0x5f3b5DfEb7B28CDbD7FAba78963EE202a494e2A2);
    
    address public governance;
    address public strategy;
    
    constructor() public {
        governance = msg.sender;
    }
    
    function getName() external pure returns (string memory) {
        return "CurveYCRVVoter";
    }
    
    function setStrategy(address _strategy) external {
        require(msg.sender == governance, "!governance");
        strategy = _strategy;
    }
    
    function deposit() public {
        uint _want = IERC20(want).balanceOf(address(this));
        if (_want > 0) {
            IERC20(want).safeApprove(pool, 0);
            IERC20(want).safeApprove(pool, _want);
            Gauge(pool).deposit(_want);
        }
    }
    
    // Controller only function for creating additional rewards from dust
    function withdraw(IERC20 _asset) external returns (uint balance) {
        require(msg.sender == strategy, "!controller");
        balance = _asset.balanceOf(address(this));
        _asset.safeTransfer(strategy, balance);
    }
    
    // Withdraw partial funds, normally used with a vault withdrawal
    function withdraw(uint _amount) external {
        require(msg.sender == strategy, "!controller");
        uint _balance = IERC20(want).balanceOf(address(this));
        if (_balance < _amount) {
            _amount = _withdrawSome(_amount.sub(_balance));
            _amount = _amount.add(_balance);
        }
        IERC20(want).safeTransfer(strategy, _amount);
    }
    
    // Withdraw all funds, normally used when migrating strategies
    function withdrawAll() external returns (uint balance) {
        require(msg.sender == strategy, "!controller");
        _withdrawAll();
        
        
        balance = IERC20(want).balanceOf(address(this));
        IERC20(want).safeTransfer(strategy, balance);
    }
    
    function _withdrawAll() internal {
        Gauge(pool).withdraw(Gauge(pool).balanceOf(address(this)));
    }
    
    function createLock(uint _value, uint _unlockTime) external {
        require(msg.sender == strategy || msg.sender == governance, "!authorized");
        IERC20(crv).safeApprove(escrow, 0);
        IERC20(crv).safeApprove(escrow, _value);
        VoteEscrow(escrow).create_lock(_value, _unlockTime);
    }
    
    function increaseAmount(uint _value) external {
        require(msg.sender == strategy || msg.sender == governance, "!authorized");
        IERC20(crv).safeApprove(escrow, 0);
        IERC20(crv).safeApprove(escrow, _value);
        VoteEscrow(escrow).increase_amount(_value);
    }
    
    function release() external {
        require(msg.sender == strategy || msg.sender == governance, "!authorized");
        VoteEscrow(escrow).withdraw();
    }
    
    function _withdrawSome(uint256 _amount) internal returns (uint) {
        Gauge(pool).withdraw(_amount);
        return _amount;
    }
    
    function balanceOfWant() public view returns (uint) {
        return IERC20(want).balanceOf(address(this));
    }
    
    function balanceOfPool() public view returns (uint) {
        return Gauge(pool).balanceOf(address(this));
    }
    
    function balanceOf() public view returns (uint) {
        return balanceOfWant()
               .add(balanceOfPool());
    }
    
    function setGovernance(address _governance) external {
        require(msg.sender == governance, "!governance");
        governance = _governance;
    }
    
    function execute(address to, uint value, bytes calldata data) external returns (bool, bytes memory) {
        require(msg.sender == strategy || msg.sender == governance, "!governance");
        (bool success, bytes memory result) = to.call.value(value)(data);
        
        return (success, result);
    }
}