contract MunchLPStaking is Ownable {
    using SafeMath for uint256;
    using SafeERC20 for IERC20;
    using SafeERC20 for IUniswapV2Pair;

    // Address of the ERC20 Token contract.
    IERC20 _munchToken;
    // Address of LP token contract.
    IUniswapV2Pair _lpToken;
    // Uniswap router.
    IUniswapV2Router02 _uniswapV2Router = IUniswapV2Router02(0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D);
    // Address where the sell of the tokens for charity will happen
    address charityAddress;

    // Last block number where we updated the pool reward stats.
    uint256 _lastRewardBlock;

    // Accumulated ERC20s per share, times 1e36.
    uint256 _accERC20PerShare = 0;

    // Info of each user.
    struct UserInfo {
        uint256 amount;             // How many LP tokens the user has provided.
        uint256 rewardDebt;         // Reward debt. See explanation below.
        uint lastDepositTime;
        uint percentToCharity;      // as an int: 50% is stored as 50
        //
        // We do some fancy math here. Basically, any point in time, the amount of ERC20s
        // entitled to a user but is pending to be distributed is:
        //
        //   pending reward = (user.amount * accERC20PerShare) - user.rewardDebt
        //
        // Whenever a user deposits or withdraws LP tokens to a pool. Here's what happens:
        //   1. The pool's `accERC20PerShare` (and `lastRewardBlock`) gets updated.
        //   2. User receives the pending reward sent to his/her address.
        //   3. User's `amount` gets updated.
        //   4. User's `rewardDebt` gets updated.
    }

    // The total amount of Munch that's paid out as reward.
    uint256 public paidOut = 0;
    // ERC20 tokens rewarded per block.
    uint256 public rewardPerBlock;

    // Minimum staking time
    uint public constant cliffTime = 1 minutes;

    // Info of each user that stakes LP tokens.
    mapping (address => UserInfo) public userInfo;

    // minimum % of rewards being given to charity - 50% is stored as 50
    uint public minPercentToCharity;

    // The block number when farming starts.
    uint public startBlock;
    // The block number when farming ends.
    uint public endBlock;

    uint256 public fundsAdded;

    event Deposit(address indexed user, uint256 amount);
    event Withdraw(address indexed user, uint256 amount);
    event EmergencyWithdraw(address indexed user, uint256 amount);

    constructor(address lpToken, address munchToken, uint rewards) public {
        _munchToken = IERC20(munchToken);
        _lpToken = IUniswapV2Pair(lpToken);
        rewardPerBlock = rewards;
        startBlock = 0;
        endBlock = 0;
        minPercentToCharity = 50;

        charityAddress = address(_munchToken);
        
        _lastRewardBlock = block.number > startBlock ? block.number : startBlock;
        
        // Prepare supply and removal of LP through this contract
        _munchToken.approve(address(_uniswapV2Router), type(uint).max);
        _lpToken.approve(address(_uniswapV2Router), type(uint).max);
    }

    function setMinPercentToCharity(uint percent) public onlyOwner {
        minPercentToCharity = percent;
    }

    function setCharityAddress(address addy) public onlyOwner {
        charityAddress = addy;
    }

    // Fund the farm: starts it if not already started, increases the end block
    function fund(uint256 amount) public onlyOwner {
        require(startBlock == 0 || block.number < endBlock, "fund: too late, the farm is closed");

        _munchToken.safeTransferFrom(address(msg.sender), address(this), amount);
        if (startBlock == 0) {
            startBlock = block.number;
            endBlock = startBlock;
        }
        endBlock += amount.div(rewardPerBlock);

        fundsAdded = fundsAdded.add(amount);
    }

    // Fund the farm and change rewards rate, increase the end block
    function fund(uint256 amount, uint256 rewards) public onlyOwner {
        require(startBlock > 0 && block.number < endBlock, "fund: Farm is closed or not yet started");
        _munchToken.safeTransferFrom(address(msg.sender), address(this), amount);
        changeReward(rewards);

        fundsAdded = fundsAdded.add(amount);
    }

    // Change rewards rate, increase the end block
    function changeReward(uint256 rewards) public onlyOwner {
        require(startBlock > 0, "Not started yet");
        updatePool();
        rewardPerBlock = rewards;
        uint256 amount = _munchToken.balanceOf(address(this));
        
        // new end block to be computed based on new reward rate and remaining rewards
        uint refBlock = block.number > startBlock ? block.number : startBlock;
        endBlock = refBlock + amount.div(rewardPerBlock);
    }

    // View function to see pending ERC20s for a user.
    function pending(address _user) external view returns (uint256) {
        UserInfo storage user = userInfo[_user];
        uint256 lpSupply = _lpToken.balanceOf(address(this));
        uint256 accERC20PerShare = _accERC20PerShare;

        if (block.number > _lastRewardBlock && lpSupply != 0) {
            uint256 lastBlock = block.number < endBlock ? block.number : endBlock;
            uint256 nrOfBlocks = lastBlock.sub(_lastRewardBlock);
            accERC20PerShare = accERC20PerShare.add(nrOfBlocks.mul(rewardPerBlock).mul(1e36).div(lpSupply));
        }

        return user.amount.mul(accERC20PerShare).div(1e36).sub(user.rewardDebt);
    }

    // View function for total reward the farm has yet to pay out.
    function totalPending() external view returns (uint256) {
        if (block.number <= startBlock) {
            return 0;
        }

        uint256 lastBlock = block.number < endBlock ? block.number : endBlock;
        return rewardPerBlock.mul(lastBlock - startBlock).sub(paidOut);
    }

    // Update reward variables of the pool to be up-to-date.
    function updatePool() public {
        uint256 lastBlock = block.number < endBlock ? block.number : endBlock;

        if (lastBlock <= _lastRewardBlock) {
            return;
        }
        uint256 lpSupply = _lpToken.balanceOf(address(this));
        if (lpSupply == 0) {
            _lastRewardBlock = lastBlock;
            return;
        }

        uint256 nrOfBlocks = lastBlock.sub(_lastRewardBlock);
        uint256 erc20Reward = nrOfBlocks.mul(rewardPerBlock);

        _accERC20PerShare = _accERC20PerShare.add(erc20Reward.mul(1e36).div(lpSupply));
        _lastRewardBlock = lastBlock;
    }

    // Deposit LP tokens to Farm for ERC20 allocation.
    // Can be called with amount = 0 to change the percent to charity.
    function deposit(uint256 amount, uint percentToCharity) public {
        require(block.number < endBlock, 'Farm is now closed');
        require(percentToCharity >= minPercentToCharity && minPercentToCharity <= 100, 'Invalid charity value');
        UserInfo storage user = userInfo[msg.sender];
        updatePool();
        if (user.amount > 0) {
            uint256 pendingAmount = user.amount.mul(_accERC20PerShare).div(1e36).sub(user.rewardDebt);
            erc20Transfer(msg.sender, pendingAmount, user.percentToCharity);
        }
        _lpToken.safeTransferFrom(address(msg.sender), address(this), amount);
        user.amount = user.amount.add(amount);
        user.rewardDebt = user.amount.mul(_accERC20PerShare).div(1e36);
        user.lastDepositTime = block.timestamp;
        user.percentToCharity = percentToCharity;
        emit Deposit(msg.sender, amount);
    }

    // Withdraw LP tokens from Farm.
    // Can be called with amount = 0 to claim rewards.
    function withdraw(uint256 amount) public {
        UserInfo storage user = userInfo[msg.sender];
        require(user.amount >= amount, "withdraw: can't withdraw more than deposit");
        // allow to claim anytime, but withdrawal needs to be after cliff time
        require(amount == 0 || block.timestamp.sub(user.lastDepositTime) > cliffTime, "You recently staked, please wait before withdrawing.");
        updatePool();
        uint256 pendingAmount = user.amount.mul(_accERC20PerShare).div(1e36).sub(user.rewardDebt);
        erc20Transfer(msg.sender, pendingAmount, user.percentToCharity);
        user.amount = user.amount.sub(amount);
        user.rewardDebt = user.amount.mul(_accERC20PerShare).div(1e36);
        _lpToken.safeTransfer(address(msg.sender), amount);
        emit Withdraw(msg.sender, amount);
    }

    // Withdraw without caring about rewards. EMERGENCY ONLY.
    function emergencyWithdraw() public {
        UserInfo storage user = userInfo[msg.sender];
        _lpToken.safeTransfer(address(msg.sender), user.amount);
        emit EmergencyWithdraw(msg.sender, user.amount);
        user.amount = 0;
        user.rewardDebt = 0;
    }

    // Transfer MUNCH and update the required MUNCH to payout all rewards
    function erc20Transfer(address to, uint256 amount, uint percentToCharity) internal {
        uint256 toCharity = amount.mul(percentToCharity).div(100);
        uint256 toHolder = amount.sub(toCharity);
        if (toCharity > 0) {
            // send share to charity
            _munchToken.transfer(charityAddress, toCharity);
        }
        if (toHolder > 0) {
            // send share to holder
            _munchToken.transfer(to, toHolder);
        }

        paidOut += amount;
    }

    // Withdraw MUNCH tokens after end block
    // Can only be called 4 weeks after end block to avoid
    // withdrawing rewards not yet claimed.
    function erc20Withdraw(address to) onlyOwner public {
        require(block.timestamp >= endBlock + 6 * 7 days, "Not allowed until 6 weeks after end of farming.");
        uint256 amount = _munchToken.balanceOf(address(this));
        _munchToken.transfer(to, amount);
    }

    // Allow owner to withdraw any ETH sent to contract
    function ethWithdraw(address payable to) onlyOwner public {
        uint256 balance = address(this).balance;
        require(balance > 0, "Balance is zero.");
        to.transfer(balance);
    }

    // Required to remove liq since ETH goes through this contract
    receive() external payable {}
    
    // Used to provide liq through this contract so we can waive transaction fees 
    function provideLiquidity(uint256 amount) external payable {
        _munchToken.transferFrom(msg.sender, address(this), amount);
        _uniswapV2Router.addLiquidityETH{value: msg.value}(address(_munchToken), amount, amount.mul(99).div(100), msg.value.mul(99).div(100), msg.sender, block.timestamp);
    }

    // Used to remove liq through this contract so we can waive transaction fees 
    function removeLiquidity(uint256 amount) external {
        _lpToken.transferFrom(msg.sender, address(this), amount);
        (uint256 munchBal, uint256 ethBal,) = _lpToken.getReserves();
        uint256 share = amount.div(_lpToken.totalSupply());
        (uint256 munchWithdrawn, uint256 ethWithdrawn) = _uniswapV2Router.removeLiquidityETH(address(_munchToken), amount, share.mul(munchBal).mul(99).div(100), share.mul(ethBal).mul(99).div(100), address(this), block.timestamp);
        _munchToken.transfer(msg.sender, munchWithdrawn);
        (bool success, ) = msg.sender.call{value: ethWithdrawn}("");
        require(success, "Transfer failed.");
    }
}
// Stake LP tokens to earn Munch tokens.
//
// Cloned from https://github.com/SashimiProject/sashimiswap/blob/master/contracts/MasterChef.sol
// Modified by DEOR to work for non-mintable ERC20.
// Modified by Munch to simplify it: only one pool.
function updatePool() public {
    uint256 lastBlock = block.number < endBlock ? block.number : endBlock;

    if (lastBlock <= _lastRewardBlock) {
        return;
    }
    uint256 lpSupply = _lpToken.balanceOf(address(this));
    if (lpSupply == 0) {
        _lastRewardBlock = lastBlock;
        return;
    }

    uint256 nrOfBlocks = lastBlock.sub(_lastRewardBlock);
    uint256 erc20Reward = nrOfBlocks.mul(rewardPerBlock);

    _accERC20PerShare = _accERC20PerShare.add(erc20Reward.mul(1e36).div(lpSupply));
    _lastRewardBlock = lastBlock;
}

// Update reward variables of the pool to be up-to-date.