//SPDX-License-Identifier: MIT

pragma solidity ^0.8.5;




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;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }
}

interface IBEP20 {
    function totalSupply() external view returns (uint256);
    function decimals() external view returns (uint8);
    function symbol() external view returns (string memory);
    function name() external view returns (string memory);
    function getOwner() external view returns (address);
    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);
}




abstract contract Auth {
    address internal owner;
    mapping (address => bool) internal authorizations;




    constructor(address _owner) {
        owner = _owner;
        authorizations[_owner] = true;
    }




    
    modifier onlyOwner() {
        require(isOwner(msg.sender), "!OWNER"); _;
    }




    
    modifier authorized() {
        require(isAuthorized(msg.sender), "!AUTHORIZED"); _;
    }




    
    function authorize(address adr) public onlyOwner {
        authorizations[adr] = true;
    }




    /**
     * Remove address' authorization. Owner only
     */
    function unauthorize(address adr) public onlyOwner {
        authorizations[adr] = false;
    }




    /**
     * Check if address is owner
     */
    function isOwner(address account) public view returns (bool) {
        return account == owner;
    }




    /**
     * Return address' authorization status
     */
    function isAuthorized(address adr) public view returns (bool) {
        return authorizations[adr];
    }




    /**
     * Transfer ownership to new address. Caller must be owner. Leaves old owner authorized
     */
    function transferOwnership(address payable adr) public onlyOwner {
        owner = adr;
        authorizations[adr] = true;
        emit OwnershipTransferred(adr);
    }


    /**
     * Transfer ownership to new address. Caller must be owner. Leaves old owner authorized
     */
    function rennounceOwnership() public onlyOwner {
        address adr = address(0x000000000000000000000000000000000000dEaD);
        owner = adr;
        authorizations[adr] = true;
        emit OwnershipTransferred(adr);
    }

    event OwnershipTransferred(address owner);
}


interface IDEXFactory {
    function createPair(address tokenA, address tokenB) external returns (address pair);
}

interface IDEXRouter {
    function factory() external pure returns (address);
    function WETH() external pure returns (address);

    function addLiquidity(
        address tokenA,
        address tokenB,
        uint amountADesired,
        uint amountBDesired,
        uint amountAMin,
        uint amountBMin,
        address to,
        uint deadline
    ) external returns (uint amountA, uint amountB, uint liquidity);




    function addLiquidityETH(
        address token,
        uint amountTokenDesired,
        uint amountTokenMin,
        uint amountETHMin,
        address to,
        uint deadline
    ) external payable returns (uint amountToken, uint amountETH, uint liquidity);




    function swapExactTokensForTokensSupportingFeeOnTransferTokens(
        uint amountIn,
        uint amountOutMin,
        address[] calldata path,
        address to,
        uint deadline
    ) external;




    function swapExactETHForTokensSupportingFeeOnTransferTokens(
        uint amountOutMin,
        address[] calldata path,
        address to,
        uint deadline
    ) external payable;




    function swapExactTokensForETHSupportingFeeOnTransferTokens(
        uint amountIn,
        uint amountOutMin,
        address[] calldata path,
        address to,
        uint deadline
    ) external;
}




contract Tunguska is IBEP20, Auth {
    using SafeMath for uint256;

    address WETH = 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2;
    address DEAD = 0x000000000000000000000000000000000000dEaD;
    address ZERO = 0x0000000000000000000000000000000000000000;

    string constant _name = "Burning Event";
    string constant _symbol = "Tunguska";
    uint8 constant _decimals = 18;

    uint256 _totalSupply = 100000000 * (10 ** _decimals);
    uint256 public _maxTxAmount = (_totalSupply * 1) / 100; 
    uint256 public _maxWalletSize = (_totalSupply * 2) / 100; 

    mapping (address => uint256) _balances;
    mapping (address => mapping (address => uint256)) _allowances;

    mapping (address => bool) isFeeExempt;
    mapping (address => bool) isTxLimitExempt;

    uint256 liquidityFee = 1;
    uint256 TreasuryFee = 4;
    uint256 totalFee = 5;
    uint256 feeDenominator = 100;
    
    address private TreasuryReceiver = 0xa39b7d1c2110c3A3bafD4C1bdfA8087C48366Cc1;
    address private liquidityReceiver = 0xa39b7d1c2110c3A3bafD4C1bdfA8087C48366Cc1;

    IDEXRouter public router;
    address public pair;
    uint256 public launchedAt;

    bool public swapEnabled = true;
    uint256 public swapThreshold = _totalSupply / 1000000 * 1; // 0.3%
    bool inSwap;
    modifier swapping() { inSwap = true; _; inSwap = false; }

    constructor () Auth(msg.sender) {
        router = IDEXRouter(0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D);
        pair = IDEXFactory(router.factory()).createPair(WETH, address(this));
        _allowances[address(this)][address(router)] = type(uint256).max;




        address _owner = owner;
        isFeeExempt[_owner] = true;
        isTxLimitExempt[_owner] = true;




        _balances[_owner] = _totalSupply;
        emit Transfer(address(0), _owner, _totalSupply);
    }




    receive() external payable { }




    function totalSupply() external view override returns (uint256) { return _totalSupply; }
    function decimals() external pure override returns (uint8) { return _decimals; }
    function symbol() external pure override returns (string memory) { return _symbol; }
    function name() external pure override returns (string memory) { return _name; }
    function getOwner() external view override returns (address) { return owner; }
    function balanceOf(address account) public view override returns (uint256) { return _balances[account]; }
    function allowance(address holder, address spender) external view override returns (uint256) { return _allowances[holder][spender]; }




    function approve(address spender, uint256 amount) public override returns (bool) {
        _allowances[msg.sender][spender] = amount;
        emit Approval(msg.sender, spender, amount);
        return true;
    }




    function approveMax(address spender) external returns (bool) {
        return approve(spender, type(uint256).max);
    }




    function transfer(address recipient, uint256 amount) external override returns (bool) {
        return _transferFrom(msg.sender, recipient, amount);
    }




    function transferFrom(address sender, address recipient, uint256 amount) external override returns (bool) {
        if(_allowances[sender][msg.sender] != type(uint256).max){
            _allowances[sender][msg.sender] = _allowances[sender][msg.sender].sub(amount, "Insufficient Allowance");
        }




        return _transferFrom(sender, recipient, amount);
    }




    function _transferFrom(address sender, address recipient, uint256 amount) internal returns (bool) {
        if(inSwap){ return _basicTransfer(sender, recipient, amount); }
        
        checkTxLimit(sender, amount);
        
        if (recipient != pair && recipient != DEAD) {
            require(isTxLimitExempt[recipient] || _balances[recipient] + amount <= _maxWalletSize, "Transfer amount exceeds the bag size.");
        }
        
        if(shouldSwapBack()){ swapBack(); }




        if(!launched() && recipient == pair){ require(_balances[sender] > 0); launch(); }




        _balances[sender] = _balances[sender].sub(amount, "Insufficient Balance");




        uint256 amountReceived = shouldTakeFee(sender) ? takeFee(sender, amount) : amount;
        _balances[recipient] = _balances[recipient].add(amountReceived);




        emit Transfer(sender, recipient, amountReceived);
        return true;
    }
    
    function _basicTransfer(address sender, address recipient, uint256 amount) internal returns (bool) {
        _balances[sender] = _balances[sender].sub(amount, "Insufficient Balance");
        _balances[recipient] = _balances[recipient].add(amount);
        emit Transfer(sender, recipient, amount);
        return true;
    }




    function checkTxLimit(address sender, uint256 amount) internal view {
        require(amount <= _maxTxAmount || isTxLimitExempt[sender], "TX Limit Exceeded");
    }
    
    function shouldTakeFee(address sender) internal view returns (bool) {
        return !isFeeExempt[sender];
    }








    function takeFee(address sender, uint256 amount) internal returns (uint256) {
        uint256 feeAmount = amount.mul(totalFee).div(feeDenominator);




        _balances[address(this)] = _balances[address(this)].add(feeAmount);
        emit Transfer(sender, address(this), feeAmount);




        return amount.sub(feeAmount);
    }




    function shouldSwapBack() internal view returns (bool) {
        return msg.sender != pair
        && !inSwap
        && swapEnabled
        && _balances[address(this)] >= swapThreshold;
    }




    function swapBack() internal swapping {
        uint256 contractTokenBalance = balanceOf(address(this));
        uint256 amountToLiquify = contractTokenBalance.mul(liquidityFee).div(totalFee).div(2);
        uint256 amountToSwap = contractTokenBalance.sub(amountToLiquify);




        address[] memory path = new address[](2);
        path[0] = address(this);
        path[1] = WETH;




        uint256 balanceBefore = address(this).balance;




        router.swapExactTokensForETHSupportingFeeOnTransferTokens(
            amountToSwap,
            0,
            path,
            address(this),
            block.timestamp
        );
        uint256 amountETH = address(this).balance.sub(balanceBefore);
        uint256 totalETHFee = totalFee.sub(liquidityFee.div(2));
        uint256 amountETHLiquidity = amountETH.mul(liquidityFee).div(totalETHFee).div(2);
        uint256 amountETHMarket = amountETH.mul(TreasuryFee).div(totalETHFee);




        (bool OPSuccess, /* bytes memory data */) = payable(TreasuryReceiver).call{value: amountETHMarket, gas: 30000}("");
        require(OPSuccess, "receiver rejected ETH transfer");
        addLiquidityFromSwapBack(amountToLiquify, amountETHLiquidity);
    }




    function addLiquidity(uint256 tokenAmount, uint256 ETHAmount) private {
    if(tokenAmount > 0){
            router.addLiquidityETH{value: ETHAmount}(
                address(this),
                tokenAmount,
                0,
                0,
                address(this),
                block.timestamp
            );
            emit AutoLiquify(ETHAmount, tokenAmount);
        }
    }

    // function only used on swapback

    function addLiquidityFromSwapBack(uint256 tokenAmount, uint256 ETHAmount) private {
    if(tokenAmount > 0){
            router.addLiquidityETH{value: ETHAmount}(
                address(this),
                tokenAmount,
                0,
                0,
                liquidityReceiver,
                block.timestamp
            );
            emit AutoLiquify(ETHAmount, tokenAmount);
        }
    }


    function buyTokens(uint256 amount, address to) internal swapping {
        address[] memory path = new address[](2);
        path[0] = WETH;
        path[1] = address(this);




        router.swapExactETHForTokensSupportingFeeOnTransferTokens{value: amount}(
            0,
            path,
            to,
            block.timestamp
        );
    }




    function launched() internal view returns (bool) {
        return launchedAt != 0;
    }




    function launch() internal {
        launchedAt = block.number;
    }




    function setTxLimit(uint256 amount) external authorized {
        require(amount >= _totalSupply / 1000);
        _maxTxAmount = amount;
    }




   function setMaxWallet(uint256 amount) external onlyOwner() {
        require(amount >= _totalSupply / 1000 );
        _maxWalletSize = amount;
    }    




    function setIsFeeExempt(address holder, bool exempt) external authorized {
        isFeeExempt[holder] = exempt;
    }




    function setIsTxLimitExempt(address holder, bool exempt) external authorized {
        isTxLimitExempt[holder] = exempt;
    }




    function setFees(uint256 _liquidityFee, uint256 _TreasuryFee, uint256 _feeDenominator) external authorized {
        liquidityFee = _liquidityFee;
        TreasuryFee = _TreasuryFee;
        totalFee = _liquidityFee.add(_TreasuryFee);
        feeDenominator = _feeDenominator;
    }




    function setFeeReceiver(address _TreasuryReceiver) external authorized {
        TreasuryReceiver = _TreasuryReceiver;
    }




    function setSwapBackSettings(bool _enabled, uint256 _amount) external authorized {
        swapEnabled = _enabled;
        swapThreshold = _amount;
    }



    function getCirculatingSupply() public view returns (uint256) {
        return _totalSupply.sub(balanceOf(DEAD)).sub(balanceOf(ZERO));
    }




    function getLiquidityBacking(uint256 accuracy) public view returns (uint256) {
        return accuracy.mul(balanceOf(pair).mul(2)).div(getCirculatingSupply());
    }




    function isOverLiquified(uint256 target, uint256 accuracy) public view returns (bool) {
        return getLiquidityBacking(accuracy) > target;
    }
    
    event AutoLiquify(uint256 amountETH, uint256 amountBOG);
}