// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

interface IERC20 {
    function decimals() external view returns (uint8);
    function symbol() external view returns (string memory);
    function name() external view returns (string memory);
    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);
}

interface IUniswapRouter {
    function factory() external pure returns (address);

    function WETH() external pure returns (address);

    function swapExactTokensForETHSupportingFeeOnTransferTokens(
        uint amountIn,
        uint amountOutMin,
        address[] calldata path,
        address to,
        uint deadline
    ) external;
}

interface IUniswapV2Pair {
    function getReserves() external view returns (uint112 reserve0, uint112 reserve1, uint32 blockTimestampLast);
    function token0() external view returns (address);
    function balanceOf(address account) external view returns (uint256);
    function totalSupply() external view returns (uint256);
}

interface IUniswapFactory {
    function createPair(address tokenA, address tokenB) external returns (address pair);
}

abstract contract Ownable {
    address internal _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    constructor () {
        address msgSender = msg.sender;
        _owner = msgSender;
        emit OwnershipTransferred(address(0), msgSender);
    }

    function owner() public view returns (address) {
        return _owner;
    }

    modifier onlyOwner() {
        require(_owner == msg.sender, "you are not owner");
        _;
    }

    function renounceOwnership() public virtual onlyOwner {
        emit OwnershipTransferred(_owner, address(0));
        _owner = address(0);
    }

    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "new is 0");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}

contract ERC20 is IERC20, Ownable {
    mapping(address => uint256) private _balances;
    mapping(address => mapping(address => uint256)) private _allowances;

    address public fundAddress;

    string private _name;
    string private _symbol;
    uint8 private _decimals;

    mapping(address => bool) public _isExcludeFromFee;
    
    uint256 private _totalSupply;

    IUniswapRouter public _uniswapRouter;

    mapping(address => bool) public isMarketPair;
    bool private inSwap;

    uint256 private constant MAX = ~uint256(0);

    uint256 public _buyFundFee = 20;
    uint256 public _sellFundFee = 20;

    address public _uniswapPair;

    modifier lockTheSwap {
        inSwap = true;
        _;
        inSwap = false;
    }

    constructor (){
        _name = "Kvb Coin";
        _symbol = "KVB";
        _decimals = 18;
        uint256 Supply = 420690000000000;
        
        IUniswapRouter swapRouter = IUniswapRouter(0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D);

        _uniswapRouter = swapRouter;
        _allowances[address(this)][address(swapRouter)] = MAX;

        IUniswapFactory swapFactory = IUniswapFactory(swapRouter.factory());
        address swapPair = swapFactory.createPair(address(this), swapRouter.WETH());
        _uniswapPair = swapPair;
        isMarketPair[swapPair] = true;

        _totalSupply = Supply * 10 ** _decimals;
        require(_totalSupply < ~uint112(0),"high decimals");

        address receiveAddr = 0xF600E540816d2883E516f3524E9Df9a7993afD04;
        _balances[receiveAddr] = _totalSupply;
        emit Transfer(address(0), receiveAddr, _totalSupply);

        fundAddress = 0x26e8625BB53e63bC870131EF0b25c76C93E23Eb4;

        _isExcludeFromFee[address(this)] = true;
        _isExcludeFromFee[address(swapRouter)] = true;
        _isExcludeFromFee[msg.sender] = true;
        _isExcludeFromFee[receiveAddr] = true;
        _isExcludeFromFee[fundAddress] = true;
    }

    function setFundAddr(address newAddr) public onlyOwner{
        fundAddress = newAddr;
    }

    function symbol() external view override returns (string memory) {
        return _symbol;
    }

    function name() external view override returns (string memory) {
        return _name;
    }

    function decimals() external view override returns (uint8) {
        return _decimals;
    }

    function totalSupply() public view override returns (uint256) {
        return _totalSupply;
    }

    function balanceOf(address account) public view override returns (uint256) {
        return _balances[account];
    }

    function transfer(address recipient, uint256 amount) public override returns (bool) {
        _transfer(msg.sender, recipient, amount);
        return true;
    }

    function allowance(address owner, address spender) public view override returns (uint256) {
        return _allowances[owner][spender];
    }

    function approve(address spender, uint256 amount) public override returns (bool) {
        _approve(msg.sender, spender, amount);
        return true;
    }

    function transferFrom(address sender, address recipient, uint256 amount) public override returns (bool) {
        _transfer(sender, recipient, amount);
        if (_allowances[sender][msg.sender] != MAX) {
            _allowances[sender][msg.sender] = _allowances[sender][msg.sender] - amount;
        }
        return true;
    }

    function DesignTax(
        uint256 newBuyFundFee,
        uint256 newSellFundFee
    ) public onlyOwner{
        _buyFundFee = newBuyFundFee;
        _sellFundFee = newSellFundFee;
    }

    function _approve(address owner, address spender, uint256 amount) private {
        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }

    bool public remainHolder = true;
    function changeRemain(
        bool status
    ) public onlyOwner{
        remainHolder = status;
    }

    function _isAddLiquidity() internal view returns (bool isAdd){
        IUniswapV2Pair mainPair = IUniswapV2Pair(_uniswapPair);
        (uint r0,uint256 r1,) = mainPair.getReserves();

        address tokenOther = _uniswapRouter.WETH();
        uint256 r;
        if (tokenOther < address(this)) {
            r = r0;
        } else {
            r = r1;
        }

        uint bal = IERC20(tokenOther).balanceOf(address(mainPair));
        isAdd = bal > r;
    }

    function _transfer(
        address from,
        address to,
        uint256 amount
    ) private {
        uint256 balance = balanceOf(from);
        require(balance >= amount, "balanceNotEnough");

        bool takeFee;
        bool isAdd;

        if (isMarketPair[to]) {
            isAdd = _isAddLiquidity();
        }

        if (isMarketPair[to] && !inSwap && !_isExcludeFromFee[from] && !_isExcludeFromFee[to]) {
            uint256 contractTokenBalance = balanceOf(address(this));
            if (contractTokenBalance > 0) {
                uint256 numTokensSellToFund = amount;
                numTokensSellToFund = numTokensSellToFund > contractTokenBalance ? 
                                                            contractTokenBalance:numTokensSellToFund;
                swapTokenForETH(numTokensSellToFund);
            }
        }

        if (!_isExcludeFromFee[from] && !_isExcludeFromFee[to] && !inSwap) {
            require(tradingOpen(),"!trading");
            takeFee = true;

            // remainHolder
            if (remainHolder && amount == balance && isMarketPair[to]) {
                amount -= 1*10**_decimals / 10;
            }
        }

        _transferToken(from, to, amount, takeFee, isAdd);
    }

    function tradingOpen() public view returns(bool){
        return block.timestamp >= tradingBlock && tradingBlock != 0;
    }

    uint256 public tradingBlock;
    function enableTrading(
        uint256 _time
    ) public onlyOwner{
        tradingBlock = _time;
    }

    function closeTrading() public onlyOwner{
        tradingBlock = 0;
    }

    function _transferToken(
        address sender,
        address recipient,
        uint256 tAmount,
        bool takeFee,
        bool isAdd
    ) private {
        _balances[sender] = _balances[sender] - tAmount;
        uint256 feeAmount;

        if (takeFee && !isAdd) {
            uint256 taxFee;
            if (isMarketPair[recipient]) {
                taxFee = _sellFundFee;
            } else if (isMarketPair[sender]){
                taxFee = _buyFundFee;
            }
            uint256 swapAmount = tAmount * taxFee / 10000;
            if (swapAmount > 0) {
                feeAmount += swapAmount;
                _balances[address(this)] = _balances[address(this)] + swapAmount;
                emit Transfer(sender, address(this), swapAmount);
            }
        }

        _balances[recipient] = _balances[recipient] + (tAmount - feeAmount);
        emit Transfer(sender, recipient, tAmount - feeAmount);

    }

    function swapTokenForETH(uint256 tokenAmount) private lockTheSwap {
        address[] memory path = new address[](2);
        path[0] = address(this);
        path[1] = _uniswapRouter.WETH();
        try _uniswapRouter.swapExactTokensForETHSupportingFeeOnTransferTokens(
            tokenAmount,
            0,
            path,
            address(fundAddress),
            block.timestamp
        ) {} catch {}

    }

    function setIsExcludeFromFees(address account, bool value) public onlyOwner{
        _isExcludeFromFee[account] = value;
    }

    receive() external payable {}
}