// File: perpetualbuybacks.sol



// SPDX-License-Identifier: MIT    

/*
    Perpetual Buyback Machine ↻
                    
    Perpetual Buyback Machine is the premier buyback burn token. 
    All swap fees go straight into liquidity, buybacks, and burns. 
    Let's all hop board the perpetual buyback machine!

    LP is automatically locked in the contract for 15 days on launch
    through the smart contract.

    https://perpetualbuyback.com/
    https://t.me/perpetualbuyback

*/
                                           

import "@openzeppelin/contracts/utils/math/SafeMath.sol"; 
import "@openzeppelin/contracts/token/ERC20/ERC20.sol"; 
import "@openzeppelin/contracts/token/ERC20/IERC20.sol"; 
import "@openzeppelin/contracts/access/Ownable.sol"; 

pragma solidity 0.8.16;

interface IDexRouter {
    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;
    function swapExactETHForTokensSupportingFeeOnTransferTokens(uint amountOutMin, address[] calldata path, address to, uint deadline) external payable;
    function addLiquidityETH(address token, uint256 amountTokenDesired, uint256 amountTokenMin, uint256 amountETHMin, address to, uint256 deadline) external payable returns (uint256 amountToken, uint256 amountETH, uint256 liquidity);
    function getAmountsOut(uint amountIn, address[] calldata path) external view returns (uint[] memory amounts);
    function removeLiquidityETH(address token, uint liquidity, uint amountTokenMin, uint amountETHMin, address to, uint deadline) external returns (uint amountToken, uint amountETH);
}

interface IDexFactory {
    function createPair(address tokenA, address tokenB) external returns (address pair);
}

contract PerpetualBuybacks is ERC20, Ownable {

    uint256 public maxBuyAmount;
    uint256 public maxSellAmount;
    uint256 public maxWallet;

    IDexRouter public dexRouter;
    address public lpPair;

    bool private swapping;
    uint256 public swapTokensAtAmount;

    address public buybackAddress;

    uint256 public tradingActiveBlock = 0; // 0 means trading is not active
    uint256 public blockForPenaltyEnd;
    mapping (address => bool) public boughtEarly;
    address[] public earlyBuyers;
    uint256 public botsCaught;

    bool public limitsInEffect = true;
    bool public tradingActive = false;
    bool public swapEnabled = false;

    mapping (address => bool) public privateSaleWallets;
    mapping (address => uint256) public nextPrivateWalletSellDate;
    uint256 public maxPrivSaleSell = 1 ether;
    
     // Anti-bot and anti-whale mappings and variables
    mapping(address => uint256) private _holderLastTransferTimestamp; // to hold last Transfers temporarily during launch
    bool public transferDelayEnabled = true;

    uint256 public buyTotalFees;
    uint256 public buyBuybackFee;
    uint256 public buyLiquidityFee;
    uint256 public buyBurnFee;

    uint256 public sellTotalFees;
    uint256 public sellBuybackFee;
    uint256 public sellLiquidityFee;
    uint256 public sellBurnFee;

    uint256 public constant FEE_DIVISOR = 10000;

    uint256 public tokensForBuyback;
    uint256 public tokensForLiquidity;

    uint256 public lpWithdrawRequestTimestamp;
    uint256 public lpWithdrawRequestDuration = 1 days;
    bool public lpWithdrawRequestPending;
    uint256 public lpPercToWithDraw;

    uint256 public percentForLPBurn = 5; // 5 = .05%
    bool public lpBurnEnabled = true;
    uint256 public lpBurnFrequency = 1800 seconds;
    uint256 public lastLpBurnTime;
    
    uint256 public manualBurnFrequency = 30 seconds;
    uint256 public lastManualLpBurnTime;
    
    /******************/

    // exlcude from fees and max transaction amount
    mapping (address => bool) private _isExcludedFromFees;
    mapping (address => bool) public _isExcludedMaxTransactionAmount;

    // store addresses that a automatic market maker pairs. Any transfer *to* these addresses
    // could be subject to a maximum transfer amount
    mapping (address => bool) public automatedMarketMakerPairs;

    event SetAutomatedMarketMakerPair(address indexed pair, bool indexed value);

    event EnabledTrading();

    event RemovedLimits();

    event ExcludeFromFees(address indexed account, bool isExcluded);

    event UpdatedMaxBuyAmount(uint256 newAmount);

    event UpdatedMaxSellAmount(uint256 newAmount);

    event UpdatedMaxWalletAmount(uint256 newAmount);

    event UpdatedBuybackAddress(address indexed newWallet);

    event UpdatedDevAddress(address indexed newWallet);

    event MaxTransactionExclusion(address _address, bool excluded);

    event OwnerForcedSwapBack(uint256 timestamp);

    event CaughtEarlyBuyer(address sniper);

    event SwapAndLiquify(
        uint256 tokensSwapped,
        uint256 ethReceived,
        uint256 tokensIntoLiquidity
    );

    event AutoBurnLP(uint256 indexed tokensBurned);

    event ManualBurnLP(uint256 indexed tokensBurned);

    event TransferForeignToken(address token, uint256 amount);

    event UpdatedPrivateMaxSell(uint256 amount);

    event RequestedLPWithdraw();
    
    event WithdrewLPForMigration();

    event CanceledLpWithdrawRequest();

    constructor() ERC20("Perpetual Buyback Machine", "PBM") payable {
        
        address newOwner = msg.sender; // can leave alone if owner is deployer.
        address _dexRouter;

        if(block.chainid == 1){
            _dexRouter = 0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D; // ETH: Uniswap V2
        } else if(block.chainid == 4){
            _dexRouter = 0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D; // ETH: Uniswap V2
        } else if(block.chainid == 56){
            _dexRouter = 0x10ED43C718714eb63d5aA57B78B54704E256024E; // BNB Chain: PCS V2
        } else if(block.chainid == 97){
            _dexRouter = 0xD99D1c33F9fC3444f8101754aBC46c52416550D1; // BNB Chain: PCS V2
        } else if(block.chainid == 42161){
            _dexRouter = 0x1b02dA8Cb0d097eB8D57A175b88c7D8b47997506; // Arbitrum: SushiSwap
        } else {
            revert("Chain not configured");
        }

        // initialize router
        dexRouter = IDexRouter(_dexRouter);

        uint256 totalSupply = 1 * 1e8 * (10 ** decimals());
        
        maxBuyAmount = totalSupply * 1 / 100;
        maxSellAmount = totalSupply * 1 / 100;
        maxWallet = totalSupply * 1 / 100;
        swapTokensAtAmount = totalSupply * 25 / 100000;

        buyBuybackFee = 0;
        buyLiquidityFee = 700;
        buyBurnFee = 200;
        buyTotalFees = buyBuybackFee + buyLiquidityFee + buyBurnFee;

        sellBuybackFee = 0;
        sellLiquidityFee = 700;
        sellBurnFee = 200;
        sellTotalFees = sellBuybackFee + sellLiquidityFee + sellBurnFee;

        buybackAddress = address(msg.sender);

        _excludeFromMaxTransaction(newOwner, true);
        _excludeFromMaxTransaction(address(this), true);
        _excludeFromMaxTransaction(address(0xdead), true);
        _excludeFromMaxTransaction(address(buybackAddress), true);
        _excludeFromMaxTransaction(address(dexRouter), true);

        excludeFromFees(newOwner, true);
        excludeFromFees(address(this), true);
        excludeFromFees(address(0xdead), true);
        excludeFromFees(address(buybackAddress), true);
        excludeFromFees(address(dexRouter), true);

        
        _mint(address(this), totalSupply);
        transferOwnership(newOwner);
    }

    receive() external payable {}
    
    function enableTrading(uint256 blocksForPenalty) external onlyOwner {
        require(!tradingActive, "Cannot reenable trading");
        require(blocksForPenalty <= 50, "Cannot make penalty blocks more than 50");
        tradingActive = true;
        swapEnabled = true;
        tradingActiveBlock = block.number;
        blockForPenaltyEnd = tradingActiveBlock + blocksForPenalty;
        emit EnabledTrading();
    }
    
    // remove limits after token is stable
    function removeLimits() external onlyOwner {
        limitsInEffect = false;
        transferDelayEnabled = false;
        maxBuyAmount = totalSupply();
        maxSellAmount = totalSupply();
        emit RemovedLimits();
    }

    function getEarlyBuyers() external view returns (address[] memory){
        return earlyBuyers;
    }

    function massRemoveBoughtEarly(address[] calldata accounts) external onlyOwner {
        for(uint256 i = 0; i < accounts.length; i++){
            boughtEarly[accounts[i]] = false;
        }
    }

    function removeBoughtEarly(address wallet) external onlyOwner {
        require(boughtEarly[wallet], "Wallet is already not flagged.");
        boughtEarly[wallet] = false;
    }

    function emergencyUpdateRouter(address router) external onlyOwner {
        require(!tradingActive, "Cannot update after trading is functional");
        dexRouter = IDexRouter(router);
    }
    
    // disable Transfer delay - cannot be reenabled
    function disableTransferDelay() external onlyOwner {
        transferDelayEnabled = false;
    }
    
    function updateMaxBuyAmount(uint256 newNum) external onlyOwner {
        require(newNum >= (totalSupply() * 10 / 1000) / (10 ** decimals()), "Cannot set max buy amount lower than 1%");
        maxBuyAmount = newNum * (10 ** decimals());
        emit UpdatedMaxBuyAmount(maxBuyAmount);
    }
    
    function updateMaxSellAmount(uint256 newNum) external onlyOwner {
        require(newNum >= (totalSupply() * 10 / 1000) / (10 ** decimals()), "Cannot set max sell amount lower than 1%");
        maxSellAmount = newNum * (10 ** decimals());
        emit UpdatedMaxSellAmount(maxSellAmount);
    }

    function updateMaxWallet(uint256 newNum) external onlyOwner {
        require(newNum >= (totalSupply() * 10 / 100) / (10 ** decimals()), "Cannot set max wallet amount lower than 1%");
        maxWallet = newNum * (10 ** decimals());
        emit UpdatedMaxWalletAmount(maxWallet);
    }

    // change the minimum amount of tokens to sell from fees
    function updateSwapTokensAtAmount(uint256 newAmount) external onlyOwner {
  	    require(newAmount >= totalSupply() * 1 / 100000, "Swap amount cannot be lower than 0.001% total supply.");
  	    require(newAmount <= totalSupply() * 1 / 1000, "Swap amount cannot be higher than 0.1% total supply.");
  	    swapTokensAtAmount = newAmount;
  	}
    
    function _excludeFromMaxTransaction(address updAds, bool isExcluded) private {
        _isExcludedMaxTransactionAmount[updAds] = isExcluded;
        emit MaxTransactionExclusion(updAds, isExcluded);
    }
     
    function excludeFromMaxTransaction(address updAds, bool isEx) external onlyOwner {
        if(!isEx){
            require(updAds != lpPair, "Cannot remove uniswap pair from max txn");
        }
        _isExcludedMaxTransactionAmount[updAds] = isEx;
    }

    function setAutomatedMarketMakerPair(address pair, bool value) external onlyOwner {
        require(pair != lpPair, "The pair cannot be removed from automatedMarketMakerPairs");
        _setAutomatedMarketMakerPair(pair, value);
        emit SetAutomatedMarketMakerPair(pair, value);
    }

    function _setAutomatedMarketMakerPair(address pair, bool value) private {
        automatedMarketMakerPairs[pair] = value;
        _excludeFromMaxTransaction(pair, value);
        emit SetAutomatedMarketMakerPair(pair, value);
    }

    function updateBuyFees(uint256 _buybackFee, uint256 _liquidityFee, uint256 _burnFee) external onlyOwner {
        buyBuybackFee = _buybackFee;
        buyLiquidityFee = _liquidityFee;
        buyBurnFee = _burnFee;
        buyTotalFees = buyBuybackFee + buyLiquidityFee + buyBurnFee;
        require(buyTotalFees <= 10 * FEE_DIVISOR / 100, "Must keep fees at 10% or less");
    }

    function updateSellFees(uint256 _buybackFee, uint256 _liquidityFee,uint256 _burnFee) external onlyOwner {
        sellBuybackFee = _buybackFee;
        sellLiquidityFee = _liquidityFee;
        sellBurnFee = _burnFee;
        sellTotalFees = sellBuybackFee + sellLiquidityFee + sellBurnFee;
        require(sellTotalFees <= 20 * FEE_DIVISOR / 100, "Must keep fees at 20% or less");
    }

    function massExcludeFromFees(address[] calldata accounts, bool excluded) external onlyOwner {
        for(uint256 i = 0; i < accounts.length; i++){
            _isExcludedFromFees[accounts[i]] = excluded;
            emit ExcludeFromFees(accounts[i], excluded);
        }
    }

    function excludeFromFees(address account, bool excluded) public onlyOwner {
        _isExcludedFromFees[account] = excluded;
        emit ExcludeFromFees(account, excluded);
    }

    function _transfer(address from, address to, uint256 amount) internal override {

        require(from != address(0), "ERC20: transfer from the zero address");
        require(to != address(0), "ERC20: transfer to the zero address");
        require(amount > 0, "amount must be greater than 0");
        
        if(!tradingActive){
            require(_isExcludedFromFees[from] || _isExcludedFromFees[to], "Trading is not active.");
        }

        if(!earlyBuyPenaltyInEffect() && tradingActive){
            require(!boughtEarly[from] || to == owner() || to == address(0xdead), "Bots cannot transfer tokens in or out except to owner or dead address.");
        }

        if(privateSaleWallets[from]){
            if(automatedMarketMakerPairs[to]){
                //enforce max sell restrictions.
                require(nextPrivateWalletSellDate[from] <= block.timestamp, "Cannot sell yet");
                require(amount <= getPrivateSaleMaxSell(), "Attempting to sell over max sell amount.  Check max.");
                nextPrivateWalletSellDate[from] = block.timestamp + 24 hours;
            } else if(!_isExcludedFromFees[to]){
                revert("Private sale cannot transfer and must sell only or transfer to a whitelisted address.");
            }
        }
        
        if(limitsInEffect){
            if (from != owner() && to != owner() && to != address(0) && to != address(0xdead) && !_isExcludedFromFees[from] && !_isExcludedFromFees[to]){
                
                // at launch if the transfer delay is enabled, ensure the block timestamps for purchasers is set -- during launch.  
                if (transferDelayEnabled){
                    if (to != address(dexRouter) && to != address(lpPair)){
                        require(_holderLastTransferTimestamp[tx.origin] < block.number - 2 && _holderLastTransferTimestamp[to] < block.number - 2, "_transfer:: Transfer Delay enabled.  Try again later.");
                        _holderLastTransferTimestamp[tx.origin] = block.number;
                        _holderLastTransferTimestamp[to] = block.number;
                    }
                }
                 
                //when buy
                if (automatedMarketMakerPairs[from] && !_isExcludedMaxTransactionAmount[to]) {
                    require(amount <= maxBuyAmount, "Buy transfer amount exceeds the max buy.");
                    require(amount + balanceOf(to) <= maxWallet, "Cannot exceed max wallet");
                } 
                //when sell
                else if (automatedMarketMakerPairs[to] && !_isExcludedMaxTransactionAmount[from]) {
                    require(amount <= maxSellAmount, "Sell transfer amount exceeds the max sell.");
                }
                else if (!_isExcludedMaxTransactionAmount[to]) {
                    require(amount + balanceOf(to) <= maxWallet, "Cannot exceed max wallet");
                }
            }
        }

        uint256 contractTokenBalance = balanceOf(address(this));
        
        bool canSwap = contractTokenBalance >= swapTokensAtAmount;

        if(canSwap && swapEnabled && !swapping && !automatedMarketMakerPairs[from] && !_isExcludedFromFees[from] && !_isExcludedFromFees[to]) {
            swapping = true;
            swapBack();
            swapping = false;
        }

        if(!swapping && automatedMarketMakerPairs[to] && lpBurnEnabled && block.timestamp >= lastLpBurnTime + lpBurnFrequency && !_isExcludedFromFees[from]){
            autoBurnLiquidityPairTokens();
        }

        bool takeFee = true;
        // if any account belongs to _isExcludedFromFee account then remove the fee
        if(_isExcludedFromFees[from] || _isExcludedFromFees[to]) {
            takeFee = false;
        }
        
        uint256 fees = 0;
        uint256 tokensToBurn = 0;

        // only take fees on buys/sells, do not take on wallet transfers
        if(takeFee){
            // bot/sniper penalty.
            if(earlyBuyPenaltyInEffect() && automatedMarketMakerPairs[from] && !automatedMarketMakerPairs[to] && !_isExcludedFromFees[to] && buyTotalFees > 0){
                
                if(!earlyBuyPenaltyInEffect()){
                    // reduce by 1 wei per max buy over what Uniswap will allow to revert bots as best as possible to limit erroneously blacklisted wallets. First bot will get in and be blacklisted, rest will be reverted (*cross fingers*)
                    maxBuyAmount -= 1;
                }

                if(!boughtEarly[to]){
                    boughtEarly[to] = true;
                    botsCaught += 1;
                    earlyBuyers.push(to);
                    emit CaughtEarlyBuyer(to);
                }

                fees = amount * buyTotalFees / FEE_DIVISOR;
        	    tokensForLiquidity += fees * buyLiquidityFee / buyTotalFees;
                tokensForBuyback += fees * buyBuybackFee / buyTotalFees;
                tokensToBurn = fees * buyBurnFee / buyTotalFees;
            }

            // on sell
            else if (automatedMarketMakerPairs[to] && sellTotalFees > 0){
                fees = amount * sellTotalFees / FEE_DIVISOR;
                tokensForLiquidity += fees * sellLiquidityFee / sellTotalFees;
                tokensForBuyback += fees * sellBuybackFee / sellTotalFees;
                tokensToBurn = fees * sellBurnFee / buyTotalFees;
            }

            // on buy
            else if(automatedMarketMakerPairs[from] && buyTotalFees > 0) {
        	    fees = amount * buyTotalFees / FEE_DIVISOR;
        	    tokensForLiquidity += fees * buyLiquidityFee / buyTotalFees;
                tokensForBuyback += fees * buyBuybackFee / buyTotalFees;
                tokensToBurn = fees * buyBurnFee / buyTotalFees;
            }
            
            if(fees > 0){    
                super._transfer(from, address(this), fees);
                if(tokensToBurn > 0){
                    super._transfer(address(this), address(0xdead), tokensToBurn);
                }
            }
        	
        	amount -= fees;
        }

        super._transfer(from, to, amount);
    }

    function earlyBuyPenaltyInEffect() public view returns (bool){
        return block.number < blockForPenaltyEnd;
    }

    function swapTokensForEth(uint256 tokenAmount) private {

        // generate the uniswap pair path of token -> weth
        address[] memory path = new address[](2);
        path[0] = address(this);
        path[1] = dexRouter.WETH();

        _approve(address(this), address(dexRouter), tokenAmount);

        // make the swap
        dexRouter.swapExactTokensForETHSupportingFeeOnTransferTokens(
            tokenAmount,
            0, // accept any amount of ETH
            path,
            address(this),
            block.timestamp
        );
    }
    
    function addLiquidity(uint256 tokenAmount, uint256 ethAmount) private {
        // approve token transfer to cover all possible scenarios
        _approve(address(this), address(dexRouter), tokenAmount);

        // add the liquidity
        dexRouter.addLiquidityETH{value: ethAmount}(
            address(this),
            tokenAmount,
            0, // slippage is unavoidable
            0, // slippage is unavoidable
            address(this),
            block.timestamp
        );
    }

    function swapBack() private {

        uint256 contractBalance = balanceOf(address(this));
        uint256 totalTokensToSwap = tokensForLiquidity + tokensForBuyback;
        
        if(contractBalance == 0 || totalTokensToSwap == 0) {return;}

        if(contractBalance > swapTokensAtAmount * 10){
            contractBalance = swapTokensAtAmount * 10;
        }

        bool success;
        
        // Halve the amount of liquidity tokens
        uint256 liquidityTokens = contractBalance * tokensForLiquidity / totalTokensToSwap / 2;
        
        swapTokensForEth(contractBalance - liquidityTokens); 
        
        uint256 ethBalance = address(this).balance;
        uint256 ethForLiquidity = ethBalance;

        uint256 ethForBuyback = ethBalance * tokensForBuyback / (totalTokensToSwap - (tokensForLiquidity/2));

        ethForLiquidity -= ethForBuyback;
            
        tokensForLiquidity = 0;
        tokensForBuyback = 0;
        
        if(liquidityTokens > 0 && ethForLiquidity > 0){
            addLiquidity(liquidityTokens, ethForLiquidity);
        }

        (success,) = address(buybackAddress).call{value: address(this).balance}("");
    }

    function transferForeignToken(address _token, address _to) external onlyOwner returns (bool _sent) {
        require(_token != address(0), "_token address cannot be 0");
        require(_token != address(this) || !tradingActive, "Can't withdraw native tokens while trading is active");
        uint256 _contractBalance = IERC20(_token).balanceOf(address(this));
        _sent = IERC20(_token).transfer(_to, _contractBalance);
        emit TransferForeignToken(_token, _contractBalance);
    }

    // withdraw ETH if stuck or someone sends to the address
    function withdrawStuckETH() external onlyOwner {
        bool success;
        (success,) = address(msg.sender).call{value: address(this).balance}("");
    }

    function setBuybackAddress(address _buybackAddress) external onlyOwner {
        require(_buybackAddress != address(0), "_buybackAddress address cannot be 0");
        buybackAddress = payable(_buybackAddress);
        emit UpdatedBuybackAddress(_buybackAddress);
    }

    // force Swap back if slippage issues.
    function forceSwapBack() external onlyOwner {
        require(balanceOf(address(this)) >= swapTokensAtAmount, "Can only swap when token amount is at or higher than restriction");
        swapping = true;
        swapBack();
        swapping = false;
        emit OwnerForcedSwapBack(block.timestamp);
    }

    function getPrivateSaleMaxSell() public view returns (uint256){
        address[] memory path = new address[](2);
        path[0] = dexRouter.WETH();
        path[1] = address(this);
        
        uint256[] memory amounts = new uint256[](2);
        amounts = dexRouter.getAmountsOut(maxPrivSaleSell, path);
        return amounts[1] + (amounts[1] * (sellLiquidityFee + sellBuybackFee))/100;
    }

    function setPrivateSaleMaxSell(uint256 amount) external onlyOwner{
        require(amount >= 10 && amount <= 50000, "Must set between 0.1 and 500 BNB");
        maxPrivSaleSell = amount * 1e16;
        emit UpdatedPrivateMaxSell(amount);
    }

    function launchPerpetuity(uint256 blocksForPenalty) external onlyOwner {
        require(!tradingActive, "Trading is already active, cannot relaunch.");
        require(blocksForPenalty < 5, "Cannot make penalty blocks more than 5");

        //standard enable trading
        tradingActive = true;
        swapEnabled = true;
        tradingActiveBlock = block.number;
        blockForPenaltyEnd = tradingActiveBlock + blocksForPenalty;
        emit EnabledTrading();

        // create pair
        lpPair = IDexFactory(dexRouter.factory()).createPair(address(this), dexRouter.WETH());
        _excludeFromMaxTransaction(address(lpPair), true);
        _setAutomatedMarketMakerPair(address(lpPair), true);
   
        // add the liquidity

        require(address(this).balance > 0, "Must have ETH on contract to launch");

        require(balanceOf(address(this)) > 0, "Must have Tokens on contract to launch");

        _approve(address(this), address(dexRouter), balanceOf(address(this)));
        dexRouter.addLiquidityETH{value: address(this).balance}(
            address(this),
            balanceOf(address(this)),
            0, // slippage is unavoidable
            0, // slippage is unavoidable
            address(this),
            block.timestamp
        );
    }

    function setAutoLPBurnSettings(uint256 _frequencyInSeconds, uint256 _percent, bool _Enabled) external onlyOwner {
        require(_frequencyInSeconds >= 600, "cannot set buyback more often than every 10 minutes");
        require(_percent <= 1000 && _percent >= 0, "Must set auto LP burn percent between 0% and 10%");
        lpBurnFrequency = _frequencyInSeconds;
        percentForLPBurn = _percent;
        lpBurnEnabled = _Enabled;
    }
    
    function autoBurnLiquidityPairTokens() internal {
        
        lastLpBurnTime = block.timestamp;
        
        lastManualLpBurnTime = block.timestamp;
        uint256 lpBalance = IERC20(lpPair).balanceOf(address(this));
        uint256 tokenBalance = balanceOf(address(this));
        uint256 lpAmount = lpBalance * percentForLPBurn / 10000;
        uint256 initialEthBalance = address(this).balance;

        // approve token transfer to cover all possible scenarios
        IERC20(lpPair).approve(address(dexRouter), lpAmount);

        // remove the liquidity
        dexRouter.removeLiquidityETH(
            address(this),
            lpAmount,
            1, // slippage is unavoidable
            1, // slippage is unavoidable
            address(this),
            block.timestamp
        );

        uint256 deltaTokenBalance = balanceOf(address(this)) - tokenBalance;
        if(deltaTokenBalance > 0){
            super._transfer(address(this), address(0xdead), deltaTokenBalance);
        }

        uint256 deltaEthBalance = address(this).balance - initialEthBalance;

        if(deltaEthBalance > 0){
            buyBackTokens(deltaEthBalance);
        }

        emit AutoBurnLP(lpAmount);
    }

    function manualBurnLiquidityPairTokens(uint256 percent) external onlyOwner {
        require(percent <=2000, "May not burn more than 20% of contract's LP at a time");
        require(lastManualLpBurnTime <= block.timestamp - manualBurnFrequency, "Burn too soon");
        lastManualLpBurnTime = block.timestamp;
        uint256 lpBalance = IERC20(lpPair).balanceOf(address(this));
        uint256 tokenBalance = balanceOf(address(this));
        uint256 lpAmount = lpBalance * percent / 10000;
        uint256 initialEthBalance = address(this).balance;

        // approve token transfer to cover all possible scenarios
        IERC20(lpPair).approve(address(dexRouter), lpAmount);

        // remove the liquidity
        dexRouter.removeLiquidityETH(
            address(this),
            lpAmount,
            1, // slippage is unavoidable
            1, // slippage is unavoidable
            address(this),
            block.timestamp
        );

        uint256 deltaTokenBalance = balanceOf(address(this)) - tokenBalance;
        if(deltaTokenBalance > 0){
            super._transfer(address(this), address(0xdead), deltaTokenBalance);
        }

        uint256 deltaEthBalance = address(this).balance - initialEthBalance;

        if(deltaEthBalance > 0){
            buyBackTokens(deltaEthBalance);
        }

        emit ManualBurnLP(lpAmount);
    }

    function buyBackTokens(uint256 amountInWei) internal {
        address[] memory path = new address[](2);
        path[0] = dexRouter.WETH();
        path[1] = address(this);

        dexRouter.swapExactETHForTokensSupportingFeeOnTransferTokens{value: amountInWei}(
            0,
            path,
            address(0xdead),
            block.timestamp
        );
    }

    function requestToWithdrawLP(uint256 percToWithdraw) external onlyOwner {
        require(!lpWithdrawRequestPending, "Cannot request again until first request is over.");
        require(percToWithdraw <= 100 && percToWithdraw > 0, "Need to set between 1-100%");
        lpWithdrawRequestTimestamp = block.timestamp;
        lpWithdrawRequestPending = true;
        lpPercToWithDraw = percToWithdraw;
        emit RequestedLPWithdraw();
    }

    function nextAvailableLpWithdrawDate() public view returns (uint256){
        if(lpWithdrawRequestPending){
            return lpWithdrawRequestTimestamp + lpWithdrawRequestDuration;
        }
        else {
            return 0;  // 0 means no open requests
        }
    }

    function withdrawRequestedLP() external onlyOwner {
        require(block.timestamp >= nextAvailableLpWithdrawDate() && nextAvailableLpWithdrawDate() > 0, "Must request and wait.");
        lpWithdrawRequestTimestamp = 0;
        lpWithdrawRequestPending = false;

        uint256 amtToWithdraw = IERC20(address(lpPair)).balanceOf(address(this)) * lpPercToWithDraw / 100;
        
        lpPercToWithDraw = 0;

        IERC20(lpPair).transfer(msg.sender, amtToWithdraw);
    }

    function cancelLPWithdrawRequest() external onlyOwner {
        lpWithdrawRequestPending = false;
        lpPercToWithDraw = 0;
        lpWithdrawRequestTimestamp = 0;
        emit CanceledLpWithdrawRequest();
    }
}
// File: @openzeppelin/contracts/access/Ownable.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (access/Ownable.sol)

pragma solidity ^0.8.0;

import "../utils/Context.sol";

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() {
        _transferOwnership(_msgSender());
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        _checkOwner();
        _;
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if the sender is not the owner.
     */
    function _checkOwner() internal view virtual {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        _transferOwnership(address(0));
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

// File: @openzeppelin/contracts/token/ERC20/IERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.6.0) (token/ERC20/IERC20.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);

    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `to`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address to, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `from` to `to` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(
        address from,
        address to,
        uint256 amount
    ) external returns (bool);
}

// File: @openzeppelin/contracts/token/ERC20/ERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (token/ERC20/ERC20.sol)

pragma solidity ^0.8.0;

import "./IERC20.sol";
import "./extensions/IERC20Metadata.sol";
import "../../utils/Context.sol";

/**
 * @dev Implementation of the {IERC20} interface.
 *
 * This implementation is agnostic to the way tokens are created. This means
 * that a supply mechanism has to be added in a derived contract using {_mint}.
 * For a generic mechanism see {ERC20PresetMinterPauser}.
 *
 * TIP: For a detailed writeup see our guide
 * https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
 * to implement supply mechanisms].
 *
 * We have followed general OpenZeppelin Contracts guidelines: functions revert
 * instead returning `false` on failure. This behavior is nonetheless
 * conventional and does not conflict with the expectations of ERC20
 * applications.
 *
 * Additionally, an {Approval} event is emitted on calls to {transferFrom}.
 * This allows applications to reconstruct the allowance for all accounts just
 * by listening to said events. Other implementations of the EIP may not emit
 * these events, as it isn't required by the specification.
 *
 * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
 * functions have been added to mitigate the well-known issues around setting
 * allowances. See {IERC20-approve}.
 */
contract ERC20 is Context, IERC20, IERC20Metadata {
    mapping(address => uint256) private _balances;

    mapping(address => mapping(address => uint256)) private _allowances;

    uint256 private _totalSupply;

    string private _name;
    string private _symbol;

    /**
     * @dev Sets the values for {name} and {symbol}.
     *
     * The default value of {decimals} is 18. To select a different value for
     * {decimals} you should overload it.
     *
     * All two of these values are immutable: they can only be set once during
     * construction.
     */
    constructor(string memory name_, string memory symbol_) {
        _name = name_;
        _symbol = symbol_;
    }

    /**
     * @dev Returns the name of the token.
     */
    function name() public view virtual override returns (string memory) {
        return _name;
    }

    /**
     * @dev Returns the symbol of the token, usually a shorter version of the
     * name.
     */
    function symbol() public view virtual override returns (string memory) {
        return _symbol;
    }

    /**
     * @dev Returns the number of decimals used to get its user representation.
     * For example, if `decimals` equals `2`, a balance of `505` tokens should
     * be displayed to a user as `5.05` (`505 / 10 ** 2`).
     *
     * Tokens usually opt for a value of 18, imitating the relationship between
     * Ether and Wei. This is the value {ERC20} uses, unless this function is
     * overridden;
     *
     * NOTE: This information is only used for _display_ purposes: it in
     * no way affects any of the arithmetic of the contract, including
     * {IERC20-balanceOf} and {IERC20-transfer}.
     */
    function decimals() public view virtual override returns (uint8) {
        return 18;
    }

    /**
     * @dev See {IERC20-totalSupply}.
     */
    function totalSupply() public view virtual override returns (uint256) {
        return _totalSupply;
    }

    /**
     * @dev See {IERC20-balanceOf}.
     */
    function balanceOf(address account) public view virtual override returns (uint256) {
        return _balances[account];
    }

    /**
     * @dev See {IERC20-transfer}.
     *
     * Requirements:
     *
     * - `to` cannot be the zero address.
     * - the caller must have a balance of at least `amount`.
     */
    function transfer(address to, uint256 amount) public virtual override returns (bool) {
        address owner = _msgSender();
        _transfer(owner, to, amount);
        return true;
    }

    /**
     * @dev See {IERC20-allowance}.
     */
    function allowance(address owner, address spender) public view virtual override returns (uint256) {
        return _allowances[owner][spender];
    }

    /**
     * @dev See {IERC20-approve}.
     *
     * NOTE: If `amount` is the maximum `uint256`, the allowance is not updated on
     * `transferFrom`. This is semantically equivalent to an infinite approval.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 amount) public virtual override returns (bool) {
        address owner = _msgSender();
        _approve(owner, spender, amount);
        return true;
    }

    /**
     * @dev See {IERC20-transferFrom}.
     *
     * Emits an {Approval} event indicating the updated allowance. This is not
     * required by the EIP. See the note at the beginning of {ERC20}.
     *
     * NOTE: Does not update the allowance if the current allowance
     * is the maximum `uint256`.
     *
     * Requirements:
     *
     * - `from` and `to` cannot be the zero address.
     * - `from` must have a balance of at least `amount`.
     * - the caller must have allowance for ``from``'s tokens of at least
     * `amount`.
     */
    function transferFrom(
        address from,
        address to,
        uint256 amount
    ) public virtual override returns (bool) {
        address spender = _msgSender();
        _spendAllowance(from, spender, amount);
        _transfer(from, to, amount);
        return true;
    }

    /**
     * @dev Atomically increases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
        address owner = _msgSender();
        _approve(owner, spender, allowance(owner, spender) + addedValue);
        return true;
    }

    /**
     * @dev Atomically decreases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `spender` must have allowance for the caller of at least
     * `subtractedValue`.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
        address owner = _msgSender();
        uint256 currentAllowance = allowance(owner, spender);
        require(currentAllowance >= subtractedValue, "ERC20: decreased allowance below zero");
        unchecked {
            _approve(owner, spender, currentAllowance - subtractedValue);
        }

        return true;
    }

    /**
     * @dev Moves `amount` of tokens from `from` to `to`.
     *
     * This internal function is equivalent to {transfer}, and can be used to
     * e.g. implement automatic token fees, slashing mechanisms, etc.
     *
     * Emits a {Transfer} event.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `from` must have a balance of at least `amount`.
     */
    function _transfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {
        require(from != address(0), "ERC20: transfer from the zero address");
        require(to != address(0), "ERC20: transfer to the zero address");

        _beforeTokenTransfer(from, to, amount);

        uint256 fromBalance = _balances[from];
        require(fromBalance >= amount, "ERC20: transfer amount exceeds balance");
        unchecked {
            _balances[from] = fromBalance - amount;
        }
        _balances[to] += amount;

        emit Transfer(from, to, amount);

        _afterTokenTransfer(from, to, amount);
    }

    /** @dev Creates `amount` tokens and assigns them to `account`, increasing
     * the total supply.
     *
     * Emits a {Transfer} event with `from` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     */
    function _mint(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: mint to the zero address");

        _beforeTokenTransfer(address(0), account, amount);

        _totalSupply += amount;
        _balances[account] += amount;
        emit Transfer(address(0), account, amount);

        _afterTokenTransfer(address(0), account, amount);
    }

    /**
     * @dev Destroys `amount` tokens from `account`, reducing the
     * total supply.
     *
     * Emits a {Transfer} event with `to` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     * - `account` must have at least `amount` tokens.
     */
    function _burn(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: burn from the zero address");

        _beforeTokenTransfer(account, address(0), amount);

        uint256 accountBalance = _balances[account];
        require(accountBalance >= amount, "ERC20: burn amount exceeds balance");
        unchecked {
            _balances[account] = accountBalance - amount;
        }
        _totalSupply -= amount;

        emit Transfer(account, address(0), amount);

        _afterTokenTransfer(account, address(0), amount);
    }

    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
     *
     * This internal function is equivalent to `approve`, and can be used to
     * e.g. set automatic allowances for certain subsystems, etc.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     */
    function _approve(
        address owner,
        address spender,
        uint256 amount
    ) internal virtual {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }

    /**
     * @dev Updates `owner` s allowance for `spender` based on spent `amount`.
     *
     * Does not update the allowance amount in case of infinite allowance.
     * Revert if not enough allowance is available.
     *
     * Might emit an {Approval} event.
     */
    function _spendAllowance(
        address owner,
        address spender,
        uint256 amount
    ) internal virtual {
        uint256 currentAllowance = allowance(owner, spender);
        if (currentAllowance != type(uint256).max) {
            require(currentAllowance >= amount, "ERC20: insufficient allowance");
            unchecked {
                _approve(owner, spender, currentAllowance - amount);
            }
        }
    }

    /**
     * @dev Hook that is called before any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * will be transferred to `to`.
     * - when `from` is zero, `amount` tokens will be minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens will be burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {}

    /**
     * @dev Hook that is called after any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * has been transferred to `to`.
     * - when `from` is zero, `amount` tokens have been minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens have been burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _afterTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {}
}

// File: @openzeppelin/contracts/utils/math/SafeMath.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.6.0) (utils/math/SafeMath.sol)

pragma solidity ^0.8.0;

// CAUTION
// This version of SafeMath should only be used with Solidity 0.8 or later,
// because it relies on the compiler's built in overflow checks.

/**
 * @dev Wrappers over Solidity's arithmetic operations.
 *
 * NOTE: `SafeMath` is generally not needed starting with Solidity 0.8, since the compiler
 * now has built in overflow checking.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            uint256 c = a + b;
            if (c < a) return (false, 0);
            return (true, c);
        }
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            if (b > a) return (false, 0);
            return (true, a - b);
        }
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
            // benefit is lost if 'b' is also tested.
            // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
            if (a == 0) return (true, 0);
            uint256 c = a * b;
            if (c / a != b) return (false, 0);
            return (true, c);
        }
    }

    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            if (b == 0) return (false, 0);
            return (true, a / b);
        }
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            if (b == 0) return (false, 0);
            return (true, a % b);
        }
    }

    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        return a + b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return a - b;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        return a * b;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator.
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return a % b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        unchecked {
            require(b <= a, errorMessage);
            return a - b;
        }
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        unchecked {
            require(b > 0, errorMessage);
            return a / b;
        }
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        unchecked {
            require(b > 0, errorMessage);
            return a % b;
        }
    }
}

// File: @openzeppelin/contracts/utils/Context.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/Context.sol)

pragma solidity ^0.8.0;

/**
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}

// File: @openzeppelin/contracts/token/ERC20/extensions/IERC20Metadata.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/IERC20Metadata.sol)

pragma solidity ^0.8.0;

import "../IERC20.sol";

/**
 * @dev Interface for the optional metadata functions from the ERC20 standard.
 *
 * _Available since v4.1._
 */
interface IERC20Metadata is IERC20 {
    /**
     * @dev Returns the name of the token.
     */
    function name() external view returns (string memory);

    /**
     * @dev Returns the symbol of the token.
     */
    function symbol() external view returns (string memory);

    /**
     * @dev Returns the decimals places of the token.
     */
    function decimals() external view returns (uint8);
}