// File: contracts/AirdropToken.sol



pragma solidity ^0.8.4;

import "@openzeppelin/contracts/interfaces/IERC20.sol";
import "@openzeppelin/contracts/utils/Address.sol";
import "@openzeppelin/contracts/utils/Context.sol";
import "@openzeppelin/contracts/access/Ownable.sol";

//
// $AIRDROP is the first meme coin that redistribute a % of the daily traded volume
//
// Find out more on https://airdropfan.com
//


interface IUniswapV2Factory {
    event PairCreated(address indexed token0, address indexed token1, address pair, uint);

    function feeTo() external view returns (address);
    function feeToSetter() external view returns (address);

    function getPair(address tokenA, address tokenB) external view returns (address pair);
    function allPairs(uint) external view returns (address pair);
    function allPairsLength() external view returns (uint);

    function createPair(address tokenA, address tokenB) external returns (address pair);

    function setFeeTo(address) external;
    function setFeeToSetter(address) external;
}

interface IUniswapV2Pair {
    event Approval(address indexed owner, address indexed spender, uint value);
    event Transfer(address indexed from, address indexed to, uint value);

    function name() external pure returns (string memory);
    function symbol() external pure returns (string memory);
    function decimals() external pure returns (uint8);
    function totalSupply() external view returns (uint);
    function balanceOf(address owner) external view returns (uint);
    function allowance(address owner, address spender) external view returns (uint);

    function approve(address spender, uint value) external returns (bool);
    function transfer(address to, uint value) external returns (bool);
    function transferFrom(address from, address to, uint value) external returns (bool);

    function DOMAIN_SEPARATOR() external view returns (bytes32);
    function PERMIT_TYPEHASH() external pure returns (bytes32);
    function nonces(address owner) external view returns (uint);

    function permit(address owner, address spender, uint value, uint deadline, uint8 v, bytes32 r, bytes32 s) external;

    event Mint(address indexed sender, uint amount0, uint amount1);
    event Burn(address indexed sender, uint amount0, uint amount1, address indexed to);
    event Swap(
        address indexed sender,
        uint amount0In,
        uint amount1In,
        uint amount0Out,
        uint amount1Out,
        address indexed to
    );
    event Sync(uint112 reserve0, uint112 reserve1);

    function MINIMUM_LIQUIDITY() external pure returns (uint);
    function factory() external view returns (address);
    function token0() external view returns (address);
    function token1() external view returns (address);
    function getReserves() external view returns (uint112 reserve0, uint112 reserve1, uint32 blockTimestampLast);
    function price0CumulativeLast() external view returns (uint);
    function price1CumulativeLast() external view returns (uint);
    function kLast() external view returns (uint);

    function mint(address to) external returns (uint liquidity);
    function burn(address to) external returns (uint amount0, uint amount1);
    function swap(uint amount0Out, uint amount1Out, address to, bytes calldata data) external;
    function skim(address to) external;
    function sync() external;

    function initialize(address, address) external;
}

interface IUniswapV2RouterBase {
    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 removeLiquidity(
        address tokenA,
        address tokenB,
        uint liquidity,
        uint amountAMin,
        uint amountBMin,
        address to,
        uint deadline
    ) external returns (uint amountA, uint amountB);
    function removeLiquidityETH(
        address token,
        uint liquidity,
        uint amountTokenMin,
        uint amountETHMin,
        address to,
        uint deadline
    ) external returns (uint amountToken, uint amountETH);
    function removeLiquidityWithPermit(
        address tokenA,
        address tokenB,
        uint liquidity,
        uint amountAMin,
        uint amountBMin,
        address to,
        uint deadline,
        bool approveMax, uint8 v, bytes32 r, bytes32 s
    ) external returns (uint amountA, uint amountB);
    function removeLiquidityETHWithPermit(
        address token,
        uint liquidity,
        uint amountTokenMin,
        uint amountETHMin,
        address to,
        uint deadline,
        bool approveMax, uint8 v, bytes32 r, bytes32 s
    ) external returns (uint amountToken, uint amountETH);
    function swapExactTokensForTokens(
        uint amountIn,
        uint amountOutMin,
        address[] calldata path,
        address to,
        uint deadline
    ) external returns (uint[] memory amounts);
    function swapTokensForExactTokens(
        uint amountOut,
        uint amountInMax,
        address[] calldata path,
        address to,
        uint deadline
    ) external returns (uint[] memory amounts);
    function swapExactETHForTokens(uint amountOutMin, address[] calldata path, address to, uint deadline)
    external
    payable
    returns (uint[] memory amounts);
    function swapTokensForExactETH(uint amountOut, uint amountInMax, address[] calldata path, address to, uint deadline)
    external
    returns (uint[] memory amounts);
    function swapExactTokensForETH(uint amountIn, uint amountOutMin, address[] calldata path, address to, uint deadline)
    external
    returns (uint[] memory amounts);
    function swapETHForExactTokens(uint amountOut, address[] calldata path, address to, uint deadline)
    external
    payable
    returns (uint[] memory amounts);

    function quote(uint amountA, uint reserveA, uint reserveB) external pure returns (uint amountB);
    function getAmountOut(uint amountIn, uint reserveIn, uint reserveOut) external pure returns (uint amountOut);
    function getAmountIn(uint amountOut, uint reserveIn, uint reserveOut) external pure returns (uint amountIn);
    function getAmountsOut(uint amountIn, address[] calldata path) external view returns (uint[] memory amounts);
    function getAmountsIn(uint amountOut, address[] calldata path) external view returns (uint[] memory amounts);
}

interface IUniswapV2Router is IUniswapV2RouterBase {
    function removeLiquidityETHSupportingFeeOnTransferTokens(
        address token,
        uint liquidity,
        uint amountTokenMin,
        uint amountETHMin,
        address to,
        uint deadline
    ) external returns (uint amountETH);
    function removeLiquidityETHWithPermitSupportingFeeOnTransferTokens(
        address token,
        uint liquidity,
        uint amountTokenMin,
        uint amountETHMin,
        address to,
        uint deadline,
        bool approveMax, uint8 v, bytes32 r, bytes32 s
    ) external returns (uint amountETH);

    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 AirdropToken is Context, IERC20, Ownable {
    using Address for address;

    // strings
    string private _tokenName = "Airdrop";
    string private _tokenSymbol = "AIRDROP";

    // uint256
    uint256 private constant MAX = ~uint256(0);
    uint256 private _totalSupplyT = 10000000000 * 10**18;
    uint256 private _rTotal = (MAX - (MAX % _totalSupplyT));
    uint256 private _tFeeTotal;
    uint8 private _decimals = 18;
    uint256 public _baseFee = 2;
    uint256 private _beforeBaseFee = _baseFee;
    uint256 public _liquidityFee = 8;
    uint256 private _beforeLiquidityFee = _liquidityFee;
    uint256 public _maxTokensForTx = 500000000000 * 10**18;
    uint256 private maxForLiquidity = 20000000 * 10**18;

    // Bool variables
    bool inLiquidityIncrease;  // true when the contract is in the process of increasing liquidity of the pool
    bool public liquidityIncreaseEnabled = true;

    // address
    IUniswapV2Router public immutable uniswapV2Router;
    address public immutable uniswapV2Pair;
    address payable public _stakingAddress;
    address payable public _marketingAddress;
    address[] private _excluded;

    // mappings
    mapping (address => uint256) private _rOwned;
    mapping (address => uint256) private _tOwned;
    mapping (address => mapping (address => uint256)) private _allowances;
    mapping (address => bool) private _isExcludedFromFee;
    mapping (address => bool) private _isExcluded;
    mapping (address => bool) private _allowedLiqIncrModifier;

    event LiquidityIncreaseEnabledUpdated(bool enabled);
    event LiquidityIncrease(
        uint256 tokensSwapped,
        uint256 ethReceived,
        uint256 tokensIntoLiqudity
    );

    modifier pauseBrewerySwap {
        inLiquidityIncrease = true;
        _;
        inLiquidityIncrease = false;
    }

    modifier onlyWithLiqIncrPermission {
        require(_allowedLiqIncrModifier[msg.sender], "Only allowed users can edit this status");
        _;
    }

    constructor (address payable stakingAddress) public {
        _stakingAddress = stakingAddress;
        _marketingAddress = stakingAddress;
        _rOwned[_msgSender()] = _rTotal;
        IUniswapV2Router _uniswapV2Router = IUniswapV2Router(0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D);
        // Make Uni pair for token
        uniswapV2Pair = IUniswapV2Factory(_uniswapV2Router.factory())
        .createPair(address(this), _uniswapV2Router.WETH());
        uniswapV2Router = _uniswapV2Router;
        //exclude from fees
        _isExcludedFromFee[owner()] = true;
        _allowedLiqIncrModifier[owner()] = true;
        _isExcludedFromFee[address(this)] = true;
        // say we moved funds
        emit Transfer(address(0), _msgSender(), _totalSupplyT);
    }

    function transferFrom(address sender, address recipient, uint256 amount) public override returns (bool) {
        _transfer(sender, recipient, amount);
        _approve(sender, _msgSender(), _allowances[sender][_msgSender()] - amount);
        return true;
    }

    function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender] + addedValue);
        return true;
    }

    function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender] - subtractedValue);
        return true;
    }

    function isNotInReward(address account) public view returns (bool) {
        return _isExcluded[account];
    }

    function totalFees() public view returns (uint256) {
        return _tFeeTotal;
    }

    function withdraw(uint256 tAmount) public {
        address caller = _msgSender();
        require(!_isExcluded[caller], "Excluded addresses cannot call this function");
        (uint256 rAmount,,,,,) = _getAllValues(tAmount);
        _rOwned[caller] = _rOwned[caller] - rAmount;
        _rTotal = _rTotal - rAmount;
        _tFeeTotal = _tFeeTotal + tAmount;
    }

    function reflectFromToken(uint256 tAmount, bool removeTransferFee) public view returns(uint256) {
        require(tAmount <= _totalSupplyT, "Amount must be less than supply");
        if (!removeTransferFee) {
            (uint256 rAmount,,,,,) = _getAllValues(tAmount);
            return rAmount;
        } else {
            (,uint256 rTransferAmount,,,,) = _getAllValues(tAmount);
            return rTransferAmount;
        }
    }

    function tokenFromReflection(uint256 rAmount) public view returns(uint256) {
        require(rAmount <= _rTotal, "Amount must be less than total reflections");
        uint256 currentRate =  _getCurrentRate();
        return rAmount/currentRate;
    }

    function excludeFromReward(address account) public onlyOwner() {
        require(!_isExcluded[account], "Account is already excluded");
        if(_rOwned[account] > 0) {
            _tOwned[account] = tokenFromReflection(_rOwned[account]);
        }
        _isExcluded[account] = true;
        _excluded.push(account);
    }

    function includeInReward(address account) external onlyOwner() {
        require(_isExcluded[account], "Account is already excluded");
        for (uint256 i = 0; i < _excluded.length; i++) {
            if (_excluded[i] == account) {
                _excluded[i] = _excluded[_excluded.length - 1];
                _tOwned[account] = 0;
                _isExcluded[account] = false;
                _excluded.pop();
                break;
            }
        }
    }
    function _transferBothExcluded(address sender, address recipient, uint256 tAmount) private {
        (uint256 rAmount, uint256 rTransferAmount, uint256 rFee, uint256 tTransferAmount, uint256 tFee, uint256 tLiquidity) = _getAllValues(tAmount);
        _tOwned[sender] = _tOwned[sender] - tAmount;
        _rOwned[sender] = _rOwned[sender] - rAmount;
        _tOwned[recipient] = _tOwned[recipient] + tTransferAmount;
        _rOwned[recipient] = _rOwned[recipient] + rTransferAmount;
        _takeLiquidity(tLiquidity);
        _reflectFee(rFee, tFee);
        emit Transfer(sender, recipient, tTransferAmount);
    }

    function excludeFromFee(address account) public onlyOwner {
        _isExcludedFromFee[account] = true;
    }

    function includeInFee(address account) public onlyOwner {
        _isExcludedFromFee[account] = false;
    }

    function setTaxFeePercent(uint256 taxFee) external onlyOwner() {
        _baseFee = taxFee;
    }

    function setLiquidityFeePercent(uint256 liquidityFee) external onlyOwner() {
        _liquidityFee = liquidityFee;
    }

    function setMaxTxPercent(uint256 maxTxPercent) external onlyOwner() {
        _maxTokensForTx = (_totalSupplyT * maxTxPercent)/(10**2);
    }

    function setLiquidityIncreaseEnabled(bool _enabled) external onlyWithLiqIncrPermission {
        liquidityIncreaseEnabled = _enabled;
        emit LiquidityIncreaseEnabledUpdated(_enabled);
    }

    function toggleLiquidityIncreaseEnabledModifier(address _newAdd, bool _enabled) public onlyOwner {
        _allowedLiqIncrModifier[_newAdd] = _enabled;
    }

    function _getAllValues(uint256 tAmount) private view returns (uint256, uint256, uint256, uint256, uint256, uint256) {
        (uint256 tTransferAmount, uint256 tFee, uint256 tLiquidity) = _getTValues(tAmount);
        (uint256 rAmount, uint256 rTransferAmount, uint256 rFee) = _getRValues(tAmount, tFee, tLiquidity, _getCurrentRate());
        return (rAmount, rTransferAmount, rFee, tTransferAmount, tFee, tLiquidity);
    }

    function _getTValues(uint256 tAmount) private view returns (uint256, uint256, uint256) {
        uint256 tFee = calculateTaxFee(tAmount);
        uint256 tLiquidity = calculateLiquidityFee(tAmount);
        uint256 tTransferAmount = tAmount - tFee - tLiquidity;
        return (tTransferAmount, tFee, tLiquidity);
    }

    receive() external payable {}

    function _reflectFee(uint256 rFee, uint256 tFee) private {
        _rTotal = _rTotal - rFee;
        _tFeeTotal = _tFeeTotal + tFee;
    }

    function _getCurrentSupply() private view returns(uint256, uint256) {
        uint256 rSupply = _rTotal;
        uint256 tSupply = _totalSupplyT;
        for (uint256 i = 0; i < _excluded.length; i++) {
            if (_rOwned[_excluded[i]] > rSupply || _tOwned[_excluded[i]] > tSupply) return (_rTotal, _totalSupplyT);
            rSupply = rSupply - _rOwned[_excluded[i]];
            tSupply = tSupply - _tOwned[_excluded[i]];
        }
        if (rSupply < _rTotal/_totalSupplyT) return (_rTotal, _totalSupplyT);
        return (rSupply, tSupply);
    }

    function _getRValues(uint256 tAmount, uint256 tFee, uint256 tLiquidity, uint256 currentRate) private pure returns (uint256, uint256, uint256) {
        uint256 rAmount = tAmount * currentRate;
        uint256 rFee = tFee * currentRate;
        uint256 rLiquidity = tLiquidity * currentRate;
        uint256 rTransferAmount = rAmount - rFee - rLiquidity;
        return (rAmount, rTransferAmount, rFee);
    }

    function removeAllFee() private {
        if(_baseFee == 0 && _liquidityFee == 0) return;
        _beforeBaseFee = _baseFee;
        _beforeLiquidityFee = _liquidityFee;
        _baseFee = 0;
        _liquidityFee = 0;
    }

    function calculateTaxFee(uint256 _amount) private view returns (uint256) {
        return (_amount * _baseFee) / (10**2);
    }

    function calculateLiquidityFee(uint256 _amount) private view returns (uint256) {
        return (_amount * _liquidityFee) / (10**2);
    }

    function sendFundsToWallet(uint256 amount) private {
        swapTokensForEth(amount);
        uint balance = address(this).balance;
        _stakingAddress.transfer(balance / 2);
        _marketingAddress.transfer(balance / 2);
    }

    function _setMarketingAddress(address payable marketingAddress) external onlyOwner() {
        _marketingAddress = marketingAddress;
    }

    function _setMaxForLiquidity(uint _newMax) external onlyOwner() {
        maxForLiquidity = _newMax;
    }

    function restoreAllFee() private {
        _baseFee = _beforeBaseFee;
        _liquidityFee = _beforeLiquidityFee;
    }

    function isExcludedFromFee(address account) public view returns(bool) {
        return _isExcludedFromFee[account];
    }

    function _approve(address owner, address spender, uint256 amount) private {
        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);
    }

    function addLiquidity(uint256 tokenAmount, uint256 ethAmount) private {
        _approve(address(this), address(uniswapV2Router), tokenAmount);
        uniswapV2Router.addLiquidityETH{value: ethAmount}(
            address(this), tokenAmount, 0,  0, owner(), block.timestamp
        );
    }

    function _transfer( address from, address to, uint256 amount ) private {
        require(from != address(0), "ERC20: transfer from the zero address");
        require(amount > 0, "Transfer amount must be greater than zero");
        if(from != owner() && to != owner())
            require(amount <= _maxTokensForTx, "You are transferring out too much! Reduce the amount.");
        uint256 contractTokenBalance = balanceOf(address(this));
        if(contractTokenBalance >= _maxTokensForTx) contractTokenBalance = _maxTokensForTx;
        bool overMinTokenBalance = contractTokenBalance >= maxForLiquidity;
        if ( overMinTokenBalance && !inLiquidityIncrease && from != uniswapV2Pair && liquidityIncreaseEnabled ) {
            contractTokenBalance = maxForLiquidity;
            uniswapAndAddLiquidity(contractTokenBalance);
        }
        bool takeFee = true;
        if(_isExcludedFromFee[from] || _isExcludedFromFee[to]) takeFee = false;
        _tokenTransfer(from,to,amount,takeFee);
    }

    function uniswapAndAddLiquidity(uint256 contractTokenBalance) private pauseBrewerySwap {
        uint256 halfToLiquify = contractTokenBalance / 4;
        uint256 otherHalfToLiquify = contractTokenBalance / 4;
        uint256 portionForFees = contractTokenBalance - halfToLiquify - otherHalfToLiquify;
        uint256 initialBalance = address(this).balance;
        swapTokensForEth(halfToLiquify);
        uint256 newBalance = address(this).balance - initialBalance;
        addLiquidity(otherHalfToLiquify, newBalance);
        sendFundsToWallet(portionForFees);
        emit LiquidityIncrease(halfToLiquify, newBalance, otherHalfToLiquify);
    }

    function swapTokensForEth(uint256 tokenAmount) private {
        address[] memory path = new address[](2);
        path[0] = address(this);
        path[1] = uniswapV2Router.WETH();
        _approve(address(this), address(uniswapV2Router), tokenAmount);
        uniswapV2Router.swapExactTokensForETHSupportingFeeOnTransferTokens(
            tokenAmount,
            0,
            path,
            address(this),
            block.timestamp
        );
    }

    function _transferStandard(address sender, address recipient, uint256 tAmount) private {
        (uint256 rAmount, uint256 rTransferAmount, uint256 rFee, uint256 tTransferAmount, uint256 tFee, uint256 tLiquidity) = _getAllValues(tAmount);
        _rOwned[sender] = _rOwned[sender] - rAmount;
        _rOwned[recipient] = _rOwned[recipient] + rTransferAmount;
        _takeLiquidity(tLiquidity);
        _reflectFee(rFee, tFee);
        emit Transfer(sender, recipient, tTransferAmount);
    }

    function _transferToExcluded(address sender, address recipient, uint256 tAmount) private {
        (uint256 rAmount, uint256 rTransferAmount, uint256 rFee, uint256 tTransferAmount, uint256 tFee, uint256 tLiquidity) = _getAllValues(tAmount);
        _rOwned[sender] = _rOwned[sender] - rAmount;
        _tOwned[recipient] = _tOwned[recipient] + tTransferAmount;
        _rOwned[recipient] = _rOwned[recipient] + rTransferAmount;
        _takeLiquidity(tLiquidity);
        _reflectFee(rFee, tFee);
        emit Transfer(sender, recipient, tTransferAmount);
    }

    function _getCurrentRate() private view returns(uint256) {
        (uint256 rSupply, uint256 tSupply) = _getCurrentSupply();
        return rSupply/tSupply;
    }

    function _takeLiquidity(uint256 tLiquidity) private {
        uint256 currentRate =  _getCurrentRate();
        uint256 rLiquidity = tLiquidity * currentRate;
        _rOwned[address(this)] = _rOwned[address(this)] + rLiquidity;
        if(_isExcluded[address(this)])
            _tOwned[address(this)] = _tOwned[address(this)] + tLiquidity;
    }

    function _tokenTransfer(address sender, address recipient, uint256 amount,bool takeFee) private {
        if(!takeFee)
            removeAllFee();
        if (_isExcluded[sender] && !_isExcluded[recipient]) _transferFromExcluded(sender, recipient, amount);
        else if (!_isExcluded[sender] && _isExcluded[recipient]) _transferToExcluded(sender, recipient, amount);
        else if (!_isExcluded[sender] && !_isExcluded[recipient])  _transferStandard(sender, recipient, amount);
        else if (_isExcluded[sender] && _isExcluded[recipient]) _transferBothExcluded(sender, recipient, amount);
        else _transferStandard(sender, recipient, amount);
        if(!takeFee) restoreAllFee();
    }

    function _transferFromExcluded(address sender, address recipient, uint256 tAmount) private {
        (uint256 rAmount, uint256 rTransferAmount, uint256 rFee, uint256 tTransferAmount, uint256 tFee, uint256 tLiquidity) = _getAllValues(tAmount);
        _tOwned[sender] = _tOwned[sender] - tAmount;
        _rOwned[sender] = _rOwned[sender] - rAmount;
        _rOwned[recipient] = _rOwned[recipient] + rTransferAmount;
        _takeLiquidity(tLiquidity);
        _reflectFee(rFee, tFee);
        emit Transfer(sender, recipient, tTransferAmount);
    }

    function name() public view returns (string memory) {
        return _tokenName;
    }

    function symbol() public view returns (string memory) {
        return _tokenSymbol;
    }

    function decimals() public view returns (uint8) {
        return _decimals;
    }

    function totalSupply() public view override returns (uint256) {
        return _totalSupplyT;
    }

    function balanceOf(address account) public view override returns (uint256) {
        if (_isExcluded[account]) return _tOwned[account];
        return tokenFromReflection(_rOwned[account]);
    }

    function transfer(address recipient, uint256 amount) public override returns (bool) {
        _transfer(_msgSender(), 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(_msgSender(), spender, amount);
        return true;
    }

}
// File: @openzeppelin/contracts/interfaces/IERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "../token/ERC20/IERC20.sol";

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



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        assembly {
            size := extcodesize(account)
        }
        return size > 0;
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        (bool success, ) = recipient.call{value: amount}("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain `call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionCall(target, data, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value
    ) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        require(isContract(target), "Address: call to non-contract");

        (bool success, bytes memory returndata) = target.call{value: value}(data);
        return verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");

        (bool success, bytes memory returndata) = target.staticcall(data);
        return verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");

        (bool success, bytes memory returndata) = target.delegatecall(data);
        return verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Tool to verifies that a low level call was successful, and revert if it wasn't, either by bubbling the
     * revert reason using the provided one.
     *
     * _Available since v4.3._
     */
    function verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal pure returns (bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

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



// SPDX-License-Identifier: MIT

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/access/Ownable.sol



// SPDX-License-Identifier: MIT

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() {
        _setOwner(_msgSender());
    }

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

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

    function _setOwner(address newOwner) private {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

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



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @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 `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, 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 `sender` to `recipient` 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 sender,
        address recipient,
        uint256 amount
    ) external returns (bool);

    /**
     * @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);
}