// 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 dRewards {
    function withdraw(uint) external;
    function getReward() external;
    function stake(uint) external;
    function balanceOf(address) external view returns (uint);
    function exit() external;
}

interface dERC20 {
  function mint(address, uint256) external;
  function redeem(address, uint) external;
  function getTokenBalance(address) external view returns (uint);
  function getExchangeRate() external view returns (uint);
}

interface Uni {
    function swapExactTokensForTokens(uint, uint, address[] calldata, address, uint) external;
}

contract StrategyDForceUSDT {
    using SafeERC20 for IERC20;
    using Address for address;
    using SafeMath for uint256;
    
    address constant public want = address(0xdAC17F958D2ee523a2206206994597C13D831ec7);
    address constant public d = address(0x868277d475E0e475E38EC5CdA2d9C83B5E1D9fc8);
    address constant public pool = address(0x324EebDAa45829c6A8eE903aFBc7B61AF48538df);
    address constant public df = address(0x431ad2ff6a9C365805eBaD47Ee021148d6f7DBe0);
    address constant public uni = address(0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D);
    address constant public weth = address(0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2); // used for df <> weth <> usdc route
    
    uint public performanceFee = 30000;
    uint constant public performanceMax = 30000;
    
    uint public withdrawalFee = 50;
    uint constant public withdrawalMax = 10000;
    
    address public governance;
    address public controller;
    address public strategist;
    
    constructor(address _controller) public {
        governance = msg.sender;
        strategist = msg.sender;
        controller = _controller;
    }
    
    function getName() external pure returns (string memory) {
        return "StrategyDForceUSDT";
    }
    
    function setStrategist(address _strategist) external {
        require(msg.sender == governance, "!governance");
        strategist = _strategist;
    }
    
    function setWithdrawalFee(uint _withdrawalFee) external {
        require(msg.sender == governance, "!governance");
        withdrawalFee = _withdrawalFee;
    }
    
    function setPerformanceFee(uint _performanceFee) external {
        require(msg.sender == governance, "!governance");
        performanceFee = _performanceFee;
    }
    
    function deposit() public {
        uint _want = IERC20(want).balanceOf(address(this));
        if (_want > 0) {
            IERC20(want).safeApprove(d, 0);
            IERC20(want).safeApprove(d, _want);
            dERC20(d).mint(address(this), _want);
        }
        
        uint _d = IERC20(d).balanceOf(address(this));
        if (_d > 0) {
            IERC20(d).safeApprove(pool, 0);
            IERC20(d).safeApprove(pool, _d);
            dRewards(pool).stake(_d);
        }
        
    }
    
    // Controller only function for creating additional rewards from dust
    function withdraw(IERC20 _asset) external returns (uint balance) {
        require(msg.sender == controller, "!controller");
        require(want != address(_asset), "want");
        require(d != address(_asset), "d");
        balance = _asset.balanceOf(address(this));
        _asset.safeTransfer(controller, balance);
    }
    
    // Withdraw partial funds, normally used with a vault withdrawal
    function withdraw(uint _amount) external {
        require(msg.sender == controller, "!controller");
        uint _balance = IERC20(want).balanceOf(address(this));
        if (_balance < _amount) {
            _amount = _withdrawSome(_amount.sub(_balance));
            _amount = _amount.add(_balance);
        }
        
        uint _fee = _amount.mul(withdrawalFee).div(withdrawalMax);
        
        
        IERC20(want).safeTransfer(Controller(controller).rewards(), _fee);
        address _vault = Controller(controller).vaults(address(want));
        require(_vault != address(0), "!vault"); // additional protection so we don't burn the funds
        
        IERC20(want).safeTransfer(_vault, _amount.sub(_fee));
    }
    
    // Withdraw all funds, normally used when migrating strategies
    function withdrawAll() external returns (uint balance) {
        require(msg.sender == controller, "!controller");
        _withdrawAll();
        
        
        balance = IERC20(want).balanceOf(address(this));
        
        address _vault = Controller(controller).vaults(address(want));
        require(_vault != address(0), "!vault"); // additional protection so we don't burn the funds
        IERC20(want).safeTransfer(_vault, balance);
    }
    
    function _withdrawAll() internal {
        dRewards(pool).exit();
        uint _d = IERC20(d).balanceOf(address(this));
        if (_d > 0) {
            dERC20(d).redeem(address(this),_d);
        }
    }
    
    function harvest() public {
        require(msg.sender == strategist || msg.sender == governance, "!authorized");
        dRewards(pool).getReward();
        uint _df = IERC20(df).balanceOf(address(this));
        if (_df > 0) {
            IERC20(df).safeApprove(uni, 0);
            IERC20(df).safeApprove(uni, _df);
            
            address[] memory path = new address[](3);
            path[0] = df;
            path[1] = weth;
            path[2] = want;
            
            Uni(uni).swapExactTokensForTokens(_df, uint(0), path, address(this), now.add(1800));
        }
        uint _want = IERC20(want).balanceOf(address(this));
        if (_want > 0) {
            uint _fee = _want.mul(performanceFee).div(performanceMax);
            IERC20(want).safeTransfer(Controller(controller).rewards(), _fee);
            deposit();
        }
    }
    
    function _withdrawSome(uint256 _amount) internal returns (uint) {
        uint _d = _amount.mul(1e18).div(dERC20(d).getExchangeRate());
        uint _before = IERC20(d).balanceOf(address(this));
        dRewards(pool).withdraw(_d);
        uint _after = IERC20(d).balanceOf(address(this));
        uint _withdrew = _after.sub(_before);
        _before = IERC20(want).balanceOf(address(this));
        dERC20(d).redeem(address(this), _withdrew);
        _after = IERC20(want).balanceOf(address(this));
        _withdrew = _after.sub(_before);
        return _withdrew;
    }
    
    function balanceOfWant() public view returns (uint) {
        return IERC20(want).balanceOf(address(this));
    }
    
    function balanceOfPool() public view returns (uint) {
        return (dRewards(pool).balanceOf(address(this))).mul(dERC20(d).getExchangeRate()).div(1e18);
    }
    
    function getExchangeRate() public view returns (uint) {
        return dERC20(d).getExchangeRate();
    }
    
    function balanceOfD() public view returns (uint) {
        return dERC20(d).getTokenBalance(address(this));
    }
    
    function balanceOf() public view returns (uint) {
        return balanceOfWant()
               .add(balanceOfD())
               .add(balanceOfPool());
    }
    
    function setGovernance(address _governance) external {
        require(msg.sender == governance, "!governance");
        governance = _governance;
    }
    
    function setController(address _controller) external {
        require(msg.sender == governance, "!governance");
        controller = _controller;
    }
}