pragma solidity ^0.5.0;
pragma experimental ABIEncoderV2;

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 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);
}

contract Context {
    constructor () internal { }
    // solhint-disable-previous-line no-empty-blocks

    function _msgSender() internal view returns (address payable) {
        return msg.sender;
    }

    function _msgData() internal view returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

contract ERC20 is Context, IERC20 {
    using SafeMath for uint256;

    mapping (address => uint256) _balances;

    mapping (address => mapping (address => uint256)) private _allowances;

    uint256 _totalSupply;
    function totalSupply() public view returns (uint256) {
        return _totalSupply;
    }
    function balanceOf(address account) public view returns (uint256) {
        return _balances[account];
    }
    function transfer(address recipient, uint256 amount) public returns (bool) {
        _transfer(_msgSender(), recipient, amount);
        return true;
    }
    function allowance(address owner, address spender) public view returns (uint256) {
        return _allowances[owner][spender];
    }
    function approve(address spender, uint256 amount) public returns (bool) {
        _approve(_msgSender(), spender, amount);
        return true;
    }
    function transferFrom(address sender, address recipient, uint256 amount) public returns (bool) {
        _transfer(sender, recipient, amount);
        _approve(sender, _msgSender(), _allowances[sender][_msgSender()].sub(amount, "ERC20: transfer amount exceeds allowance"));
        return true;
    }
    function increaseAllowance(address spender, uint256 addedValue) public returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].add(addedValue));
        return true;
    }
    function decreaseAllowance(address spender, uint256 subtractedValue) public returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].sub(subtractedValue, "ERC20: decreased allowance below zero"));
        return true;
    }
    function _transfer(address sender, address recipient, uint256 amount) internal {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");

        _balances[sender] = _balances[sender].sub(amount, "ERC20: transfer amount exceeds balance");
        _balances[recipient] = _balances[recipient].add(amount);
        emit Transfer(sender, recipient, amount);
    }
    function _mint(address account, uint256 amount) internal {
        require(account != address(0), "ERC20: mint to the zero address");

        _totalSupply = _totalSupply.add(amount);
        _balances[account] = _balances[account].add(amount);
        emit Transfer(address(0), account, amount);
    }
    function _burn(address account, uint256 amount) internal {
        require(account != address(0), "ERC20: burn from the zero address");

        _balances[account] = _balances[account].sub(amount, "ERC20: burn amount exceeds balance");
        _totalSupply = _totalSupply.sub(amount);
        emit Transfer(account, address(0), amount);
    }
    function _approve(address owner, address spender, uint256 amount) internal {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }
    function _burnFrom(address account, uint256 amount) internal {
        _burn(account, amount);
        _approve(account, _msgSender(), _allowances[account][_msgSender()].sub(amount, "ERC20: burn amount exceeds allowance"));
    }
}

contract ERC20Detailed is IERC20 {
    string private _name;
    string private _symbol;
    uint8 private _decimals;

    constructor (string memory name, string memory symbol, uint8 decimals) public {
        _name = name;
        _symbol = symbol;
        _decimals = decimals;
    }
    function name() public view returns (string memory) {
        return _name;
    }
    function symbol() public view returns (string memory) {
        return _symbol;
    }
    function decimals() public view returns (uint8) {
        return _decimals;
    }
}

contract ReentrancyGuard {
    uint256 private _guardCounter;

    constructor () internal {
        _guardCounter = 1;
    }

    modifier nonReentrant() {
        _guardCounter += 1;
        uint256 localCounter = _guardCounter;
        _;
        require(localCounter == _guardCounter, "ReentrancyGuard: reentrant call");
    }
}

contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);
    constructor () internal {
        _owner = _msgSender();
        emit OwnershipTransferred(address(0), _owner);
    }
    function owner() public view returns (address) {
        return _owner;
    }
    modifier onlyOwner() {
        require(isOwner(), "Ownable: caller is not the owner");
        _;
    }
    function isOwner() public view returns (bool) {
        return _msgSender() == _owner;
    }
    function renounceOwnership() public onlyOwner {
        emit OwnershipTransferred(_owner, address(0));
        _owner = address(0);
    }
    function transferOwnership(address newOwner) public onlyOwner {
        _transferOwnership(newOwner);
    }
    function _transferOwnership(address newOwner) internal {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}

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 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));
    }
    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 Compound {
    function mint ( uint256 mintAmount ) external returns ( uint256 );
    function redeem(uint256 redeemTokens) external returns (uint256);
    function exchangeRateStored() external view returns (uint);
}

// Solidity Interface

interface ICurveFi {

  function get_virtual_price() external view returns (uint256);
  function get_dy(
    int128 i,
    int128 j,
    uint256 dx
  ) external view returns (uint256);
  function get_dy_underlying(
    int128 i,
    int128 j,
    uint256 dx
  ) external view returns (uint256);
  function coins(int128 arg0) external view returns (address);
  function underlying_coins(int128 arg0) external view returns (address);
  function balances(int128 arg0) external view returns (uint256);

  // 0 = cDAI, 1 - cUSDC
  function add_liquidity(
    uint256[2] calldata amounts,
    uint256 deadline
  ) external;
  function exchange(
    int128 i,
    int128 j,
    uint256 dx,
    uint256 min_dy,
    uint256 deadline
  ) external;
  function exchange_underlying(
    int128 i,
    int128 j,
    uint256 dx,
    uint256 min_dy,
    uint256 deadline
  ) external;
  function remove_liquidity(
    uint256 _amount,
    uint256 deadline,
    uint256[2] calldata min_amounts
  ) external;
  function remove_liquidity_imbalance(
    uint256[2] calldata amounts,
    uint256 deadline
  ) external;
}

contract yCRV is ERC20, ERC20Detailed, ReentrancyGuard, Ownable {
  using SafeERC20 for IERC20;
  using Address for address;
  using SafeMath for uint256;

  uint256 public pool;
  address public token;
  address public cDAI;
  address public apr;
  address public curve;
  address public curveToken;

  constructor () public ERC20Detailed("yCRV", "cDAI/cUSDC", 18) {
    token = address(0x6B175474E89094C44Da98b954EedeAC495271d0F);
    apr = address(0x318135fbD0b40D48fCEF431CCdF6C7926450edFB);
    cDAI = address(0x5d3a536E4D6DbD6114cc1Ead35777bAB948E3643);
    curve = address(0x2e60CF74d81ac34eB21eEff58Db4D385920ef419);
    curveToken = address(0x3740fb63ab7a09891d7c0d4299442A551D06F5fD);
    approveToken();
  }

  function set_new_TOKEN(address _new_TOKEN) public onlyOwner {
      token = _new_TOKEN;
  }
  function set_new_APR(address _new_APR) public onlyOwner {
      apr = _new_APR;
  }
  function set_new_cDAI(address _new_cDAI) public onlyOwner {
      cDAI = _new_cDAI;
  }
  function set_new_curveToken(address _new_set_new_curveToken) public onlyOwner {
      curveToken = _new_set_new_curveToken;
  }

  function() external payable {

  }

  function approveToken() public {
      IERC20(token).approve(cDAI, uint(-1));
      IERC20(cDAI).approve(curve, uint(-1));
  }
  function balanceCompound() public view returns (uint256) {
      return IERC20(cDAI).balanceOf(address(this));
  }
  function supplyCompound(uint amount) public {
      require(Compound(cDAI).mint(amount) == 0, "COMPOUND: supply failed");
  }
  function withdrawCompound(uint amount) internal {
      require(Compound(cDAI).redeem(amount) == 0, "COMPOUND: withdraw failed");
  }

  // Invest ETH
  function invest(uint256 _amount)
      external
      nonReentrant
  {
      require(_amount > 0, "deposit must be greater than 0");
      pool = calcPoolValueInToken();

      IERC20(token).transferFrom(msg.sender, address(this), _amount);
      // Got DAI
      supplyCompound(_amount);
      ICurveFi(curve).add_liquidity([balanceCompound(),0],now.add(1800));

      // Calculate pool shares
      uint256 shares = 0;
      if (pool == 0) {
        shares = _amount;
        pool = _amount;
      } else {
        shares = (_amount.mul(_totalSupply)).div(pool);
      }
      pool = calcPoolValueInToken();
      _mint(msg.sender, shares);
  }

  // Invest self eth from external profits
  function investSelf()
      external
      nonReentrant
      onlyOwner
  {
      uint b = IERC20(token).balanceOf(address(this));
      require(b > 0, "deposit must be greater than 0");
      supplyCompound(b);
      ICurveFi(curve).add_liquidity([b,0],now.add(1800));
      pool = calcPoolValueInToken();
  }

  function calcPoolValueInToken() public view returns (uint) {
    uint256 price = ICurveFi(curve).get_virtual_price();
    uint256 supply = IERC20(curveToken).balanceOf(address(this));
    return price.mul(supply).div(1e18);
  }

  function withdraw(uint256 _amount) internal {
    // _amount is amount of yCRV
    // exchangeRateStored.div(1e18).mul(_amountOfCDai) = DAI
    uint256 dai = _amount.mul(getPricePerFullShare()).div(1e18);
    uint256 compoundDai = dai.mul(1e18).div(Compound(cDAI).exchangeRateStored());
    ICurveFi(curve).remove_liquidity_imbalance([compoundDai,0], now.add(1800));
    withdrawCompound(compoundDai);
  }

  function getPricePerFullShare() public view returns (uint) {
    uint _pool = calcPoolValueInToken();
    return _pool.mul(1e18).div(_totalSupply);
  }

  // Redeem any invested tokens from the pool
  function redeem(uint256 _shares)
      external
      nonReentrant
  {
      require(_shares > 0, "withdraw must be greater than 0");

      uint256 ibalance = balanceOf(msg.sender);
      require(_shares <= ibalance, "insufficient balance");

      // Could have over value from cTokens
      pool = calcPoolValueInToken();
      // Calc eth to redeem before updating balances
      uint256 r = (pool.mul(_shares)).div(_totalSupply);


      _balances[msg.sender] = _balances[msg.sender].sub(_shares, "redeem amount exceeds balance");
      _totalSupply = _totalSupply.sub(_shares);

      emit Transfer(msg.sender, address(0), _shares);

      // Check balance
      uint256 b = IERC20(token).balanceOf(address(this));
      if (b < r) {
        withdraw(r);
      }

      IERC20(token).transfer(msg.sender, r);
      pool = calcPoolValueInToken();
  }

  // incase of half-way error
  function inCaseTokenGetsStuck(IERC20 _TokenAddress) onlyOwner public {
      uint qty = _TokenAddress.balanceOf(address(this));
      _TokenAddress.transfer(msg.sender, qty);
  }
  // incase of half-way error
  function inCaseETHGetsStuck() onlyOwner public{
      (bool result, ) = msg.sender.call.value(address(this).balance)("");
      require(result, "transfer of ETH failed");
  }
}