// SPDX-License-Identifier: BUSL-1.1
pragma solidity 0.6.12;

import "@openzeppelin/contracts/math/SafeMath.sol";
import "@openzeppelin/contracts/math/Math.sol";
import "@openzeppelin/contracts/utils/ReentrancyGuard.sol";
import "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";

import "./libraries/MathExt.sol";
import "./libraries/FeeFomula.sol";
import "./libraries/ERC20Permit.sol";

import "./interfaces/IDMMFactory.sol";
import "./interfaces/IDMMCallee.sol";
import "./interfaces/IDMMPool.sol";
import "./interfaces/IERC20Metadata.sol";
import "./VolumeTrendRecorder.sol";

contract DMMPool is IDMMPool, ERC20Permit, ReentrancyGuard, VolumeTrendRecorder {
    using SafeMath for uint256;
    using SafeERC20 for IERC20;

    uint256 internal constant MAX_UINT112 = 2**112 - 1;
    uint256 internal constant BPS = 10000;

    struct ReserveData {
        uint256 reserve0;
        uint256 reserve1;
        uint256 vReserve0;
        uint256 vReserve1; // only used when isAmpPool = true
    }

    uint256 public constant MINIMUM_LIQUIDITY = 10**3;
    /// @dev To make etherscan auto-verify new pool, these variables are not immutable
    IDMMFactory public override factory;
    IERC20 public override token0;
    IERC20 public override token1;

    /// @dev uses single storage slot, accessible via getReservesData
    uint112 internal reserve0;
    uint112 internal reserve1;
    uint32 public override ampBps;
    /// @dev addition param only when amplification factor > 1
    uint112 internal vReserve0;
    uint112 internal vReserve1;

    /// @dev vReserve0 * vReserve1, as of immediately after the most recent liquidity event
    uint256 public override kLast;

    event Mint(address indexed sender, uint256 amount0, uint256 amount1);
    event Burn(address indexed sender, uint256 amount0, uint256 amount1, address indexed to);
    event Swap(
        address indexed sender,
        uint256 amount0In,
        uint256 amount1In,
        uint256 amount0Out,
        uint256 amount1Out,
        address indexed to,
        uint256 feeInPrecision
    );
    event Sync(uint256 vReserve0, uint256 vReserve1, uint256 reserve0, uint256 reserve1);

    constructor() public ERC20Permit("KyberDMM LP", "DMM-LP", "1") VolumeTrendRecorder(0) {
        factory = IDMMFactory(msg.sender);
    }

    // called once by the factory at time of deployment
    function initialize(
        IERC20 _token0,
        IERC20 _token1,
        uint32 _ampBps
    ) external {
        require(msg.sender == address(factory), "DMM: FORBIDDEN");
        token0 = _token0;
        token1 = _token1;
        ampBps = _ampBps;
    }

    /// @dev this low-level function should be called from a contract
    ///                 which performs important safety checks
    function mint(address to) external override nonReentrant returns (uint256 liquidity) {
        (bool isAmpPool, ReserveData memory data) = getReservesData();
        ReserveData memory _data;
        _data.reserve0 = token0.balanceOf(address(this));
        _data.reserve1 = token1.balanceOf(address(this));
        uint256 amount0 = _data.reserve0.sub(data.reserve0);
        uint256 amount1 = _data.reserve1.sub(data.reserve1);

        bool feeOn = _mintFee(isAmpPool, data);
        uint256 _totalSupply = totalSupply(); // gas savings, must be defined here since totalSupply can update in _mintFee
        if (_totalSupply == 0) {
            if (isAmpPool) {
                uint32 _ampBps = ampBps;
                _data.vReserve0 = _data.reserve0.mul(_ampBps) / BPS;
                _data.vReserve1 = _data.reserve1.mul(_ampBps) / BPS;
            }
            liquidity = MathExt.sqrt(amount0.mul(amount1)).sub(MINIMUM_LIQUIDITY);
            _mint(address(-1), MINIMUM_LIQUIDITY); // permanently lock the first MINIMUM_LIQUIDITY tokens
        } else {
            liquidity = Math.min(
                amount0.mul(_totalSupply) / data.reserve0,
                amount1.mul(_totalSupply) / data.reserve1
            );
            if (isAmpPool) {
                uint256 b = liquidity.add(_totalSupply);
                _data.vReserve0 = Math.max(data.vReserve0.mul(b) / _totalSupply, _data.reserve0);
                _data.vReserve1 = Math.max(data.vReserve1.mul(b) / _totalSupply, _data.reserve1);
            }
        }
        require(liquidity > 0, "DMM: INSUFFICIENT_LIQUIDITY_MINTED");
        _mint(to, liquidity);

        _update(isAmpPool, _data);
        if (feeOn) kLast = getK(isAmpPool, _data);
        emit Mint(msg.sender, amount0, amount1);
    }

    /// @dev this low-level function should be called from a contract
    /// @dev which performs important safety checks
    /// @dev user must transfer LP token to this contract before call burn
    function burn(address to)
        external
        override
        nonReentrant
        returns (uint256 amount0, uint256 amount1)
    {
        (bool isAmpPool, ReserveData memory data) = getReservesData(); // gas savings
        IERC20 _token0 = token0; // gas savings
        IERC20 _token1 = token1; // gas savings

        uint256 balance0 = _token0.balanceOf(address(this));
        uint256 balance1 = _token1.balanceOf(address(this));
        require(balance0 >= data.reserve0 && balance1 >= data.reserve1, "DMM: UNSYNC_RESERVES");
        uint256 liquidity = balanceOf(address(this));

        bool feeOn = _mintFee(isAmpPool, data);
        uint256 _totalSupply = totalSupply(); // gas savings, must be defined here since totalSupply can update in _mintFee
        amount0 = liquidity.mul(balance0) / _totalSupply; // using balances ensures pro-rata distribution
        amount1 = liquidity.mul(balance1) / _totalSupply; // using balances ensures pro-rata distribution
        require(amount0 > 0 && amount1 > 0, "DMM: INSUFFICIENT_LIQUIDITY_BURNED");
        _burn(address(this), liquidity);
        _token0.safeTransfer(to, amount0);
        _token1.safeTransfer(to, amount1);
        ReserveData memory _data;
        _data.reserve0 = _token0.balanceOf(address(this));
        _data.reserve1 = _token1.balanceOf(address(this));
        if (isAmpPool) {
            uint256 b = Math.min(
                _data.reserve0.mul(_totalSupply) / data.reserve0,
                _data.reserve1.mul(_totalSupply) / data.reserve1
            );
            _data.vReserve0 = Math.max(data.vReserve0.mul(b) / _totalSupply, _data.reserve0);
            _data.vReserve1 = Math.max(data.vReserve1.mul(b) / _totalSupply, _data.reserve1);
        }
        _update(isAmpPool, _data);
        if (feeOn) kLast = getK(isAmpPool, _data); // data are up-to-date
        emit Burn(msg.sender, amount0, amount1, to);
    }

    /// @dev this low-level function should be called from a contract
    /// @dev which performs important safety checks
    function swap(
        uint256 amount0Out,
        uint256 amount1Out,
        address to,
        bytes calldata callbackData
    ) external override nonReentrant {
        require(amount0Out > 0 || amount1Out > 0, "DMM: INSUFFICIENT_OUTPUT_AMOUNT");
        (bool isAmpPool, ReserveData memory data) = getReservesData(); // gas savings
        require(
            amount0Out < data.reserve0 && amount1Out < data.reserve1,
            "DMM: INSUFFICIENT_LIQUIDITY"
        );

        ReserveData memory newData;
        {
            // scope for _token{0,1}, avoids stack too deep errors
            IERC20 _token0 = token0;
            IERC20 _token1 = token1;
            require(to != address(_token0) && to != address(_token1), "DMM: INVALID_TO");
            if (amount0Out > 0) _token0.safeTransfer(to, amount0Out); // optimistically transfer tokens
            if (amount1Out > 0) _token1.safeTransfer(to, amount1Out); // optimistically transfer tokens
            if (callbackData.length > 0)
                IDMMCallee(to).dmmSwapCall(msg.sender, amount0Out, amount1Out, callbackData);
            newData.reserve0 = _token0.balanceOf(address(this));
            newData.reserve1 = _token1.balanceOf(address(this));
            if (isAmpPool) {
                newData.vReserve0 = data.vReserve0.add(newData.reserve0).sub(data.reserve0);
                newData.vReserve1 = data.vReserve1.add(newData.reserve1).sub(data.reserve1);
            }
        }
        uint256 amount0In = newData.reserve0 > data.reserve0 - amount0Out
            ? newData.reserve0 - (data.reserve0 - amount0Out)
            : 0;
        uint256 amount1In = newData.reserve1 > data.reserve1 - amount1Out
            ? newData.reserve1 - (data.reserve1 - amount1Out)
            : 0;
        require(amount0In > 0 || amount1In > 0, "DMM: INSUFFICIENT_INPUT_AMOUNT");
        uint256 feeInPrecision = verifyBalanceAndUpdateEma(
            amount0In,
            amount1In,
            isAmpPool ? data.vReserve0 : data.reserve0,
            isAmpPool ? data.vReserve1 : data.reserve1,
            isAmpPool ? newData.vReserve0 : newData.reserve0,
            isAmpPool ? newData.vReserve1 : newData.reserve1
        );

        _update(isAmpPool, newData);
        emit Swap(msg.sender, amount0In, amount1In, amount0Out, amount1Out, to, feeInPrecision);
    }

    /// @dev force balances to match reserves
    function skim(address to) external nonReentrant {
        token0.safeTransfer(to, token0.balanceOf(address(this)).sub(reserve0));
        token1.safeTransfer(to, token1.balanceOf(address(this)).sub(reserve1));
    }

    /// @dev force reserves to match balances
    function sync() external override nonReentrant {
        (bool isAmpPool, ReserveData memory data) = getReservesData();
        bool feeOn = _mintFee(isAmpPool, data);
        ReserveData memory newData;
        newData.reserve0 = IERC20(token0).balanceOf(address(this));
        newData.reserve1 = IERC20(token1).balanceOf(address(this));
        // update virtual reserves if this is amp pool
        if (isAmpPool) {
            uint256 _totalSupply = totalSupply();
            uint256 b = Math.min(
                newData.reserve0.mul(_totalSupply) / data.reserve0,
                newData.reserve1.mul(_totalSupply) / data.reserve1
            );
            newData.vReserve0 = Math.max(data.vReserve0.mul(b) / _totalSupply, newData.reserve0);
            newData.vReserve1 = Math.max(data.vReserve1.mul(b) / _totalSupply, newData.reserve1);
        }
        _update(isAmpPool, newData);
        if (feeOn) kLast = getK(isAmpPool, newData);
    }

    /// @dev returns data to calculate amountIn, amountOut
    function getTradeInfo()
        external
        virtual
        override
        view
        returns (
            uint112 _reserve0,
            uint112 _reserve1,
            uint112 _vReserve0,
            uint112 _vReserve1,
            uint256 feeInPrecision
        )
    {
        // gas saving to read reserve data
        _reserve0 = reserve0;
        _reserve1 = reserve1;
        uint32 _ampBps = ampBps;
        _vReserve0 = vReserve0;
        _vReserve1 = vReserve1;
        if (_ampBps == BPS) {
            _vReserve0 = _reserve0;
            _vReserve1 = _reserve1;
        }
        uint256 rFactorInPrecision = getRFactor(block.number);
        feeInPrecision = getFinalFee(FeeFomula.getFee(rFactorInPrecision), _ampBps);
    }

    /// @dev returns reserve data to calculate amount to add liquidity
    function getReserves() external override view returns (uint112 _reserve0, uint112 _reserve1) {
        _reserve0 = reserve0;
        _reserve1 = reserve1;
    }

    function name() public override view returns (string memory) {
        IERC20Metadata _token0 = IERC20Metadata(address(token0));
        IERC20Metadata _token1 = IERC20Metadata(address(token1));
        return string(abi.encodePacked("KyberDMM LP ", _token0.symbol(), "-", _token1.symbol()));
    }

    function symbol() public override view returns (string memory) {
        IERC20Metadata _token0 = IERC20Metadata(address(token0));
        IERC20Metadata _token1 = IERC20Metadata(address(token1));
        return string(abi.encodePacked("DMM-LP ", _token0.symbol(), "-", _token1.symbol()));
    }

    function verifyBalanceAndUpdateEma(
        uint256 amount0In,
        uint256 amount1In,
        uint256 beforeReserve0,
        uint256 beforeReserve1,
        uint256 afterReserve0,
        uint256 afterReserve1
    ) internal virtual returns (uint256 feeInPrecision) {
        // volume = beforeReserve0 * amount1In / beforeReserve1 + amount0In (normalized into amount in token 0)
        uint256 volume = beforeReserve0.mul(amount1In).div(beforeReserve1).add(amount0In);
        uint256 rFactorInPrecision = recordNewUpdatedVolume(block.number, volume);
        feeInPrecision = getFinalFee(FeeFomula.getFee(rFactorInPrecision), ampBps);
        // verify balance update matches with fomula
        uint256 balance0Adjusted = afterReserve0.mul(PRECISION);
        balance0Adjusted = balance0Adjusted.sub(amount0In.mul(feeInPrecision));
        balance0Adjusted = balance0Adjusted / PRECISION;
        uint256 balance1Adjusted = afterReserve1.mul(PRECISION);
        balance1Adjusted = balance1Adjusted.sub(amount1In.mul(feeInPrecision));
        balance1Adjusted = balance1Adjusted / PRECISION;
        require(
            balance0Adjusted.mul(balance1Adjusted) >= beforeReserve0.mul(beforeReserve1),
            "DMM: K"
        );
    }

    /// @dev update reserves
    function _update(bool isAmpPool, ReserveData memory data) internal {
        reserve0 = safeUint112(data.reserve0);
        reserve1 = safeUint112(data.reserve1);
        if (isAmpPool) {
            assert(data.vReserve0 >= data.reserve0 && data.vReserve1 >= data.reserve1); // never happen
            vReserve0 = safeUint112(data.vReserve0);
            vReserve1 = safeUint112(data.vReserve1);
        }
        emit Sync(data.vReserve0, data.vReserve1, data.reserve0, data.reserve1);
    }

    /// @dev if fee is on, mint liquidity equivalent to configured fee of the growth in sqrt(k)
    function _mintFee(bool isAmpPool, ReserveData memory data) internal returns (bool feeOn) {
        (address feeTo, uint16 governmentFeeBps) = factory.getFeeConfiguration();
        feeOn = feeTo != address(0);
        uint256 _kLast = kLast; // gas savings
        if (feeOn) {
            if (_kLast != 0) {
                uint256 rootK = MathExt.sqrt(getK(isAmpPool, data));
                uint256 rootKLast = MathExt.sqrt(_kLast);
                if (rootK > rootKLast) {
                    uint256 numerator = totalSupply().mul(rootK.sub(rootKLast)).mul(
                        governmentFeeBps
                    );
                    uint256 denominator = rootK.add(rootKLast).mul(5000);
                    uint256 liquidity = numerator / denominator;
                    if (liquidity > 0) _mint(feeTo, liquidity);
                }
            }
        } else if (_kLast != 0) {
            kLast = 0;
        }
    }

    /// @dev gas saving to read reserve data
    function getReservesData() internal view returns (bool isAmpPool, ReserveData memory data) {
        data.reserve0 = reserve0;
        data.reserve1 = reserve1;
        isAmpPool = ampBps != BPS;
        if (isAmpPool) {
            data.vReserve0 = vReserve0;
            data.vReserve1 = vReserve1;
        }
    }

    function getFinalFee(uint256 feeInPrecision, uint32 _ampBps) internal pure returns (uint256) {
        if (_ampBps <= 20000) {
            return feeInPrecision;
        } else if (_ampBps <= 50000) {
            return (feeInPrecision * 20) / 30;
        } else if (_ampBps <= 200000) {
            return (feeInPrecision * 10) / 30;
        } else {
            return (feeInPrecision * 4) / 30;
        }
    }

    function getK(bool isAmpPool, ReserveData memory data) internal pure returns (uint256) {
        return isAmpPool ? data.vReserve0 * data.vReserve1 : data.reserve0 * data.reserve1;
    }

    function safeUint112(uint256 x) internal pure returns (uint112) {
        require(x <= MAX_UINT112, "DMM: OVERFLOW");
        return uint112(x);
    }
}