// File: token.sol



/*

Telegram - https://t.me/Smmbot_portal
Telegram bot - https://t.me/smmerc_bot
Website - https://smmbot.tech/
Twitter - https://twitter.com/smmbot_erc

*/


// SPDX-License-Identifier: No License
pragma solidity 0.8.19;

import "./ERC20.sol";
import "./ERC20Burnable.sol";
import "./Ownable.sol";
import "./Initializable.sol";
import "./IUniswapV2Factory.sol";
import "./IUniswapV2Pair.sol";
import "./IUniswapV2Router01.sol";
import "./IUniswapV2Router02.sol";

contract SmmBOT is ERC20, ERC20Burnable, Ownable, Initializable {
    
    uint256 public swapThreshold;
    
    uint256 private _devtaxPending;

    address public devtaxAddress;
    uint16[3] public devtaxFees;

    mapping (address => bool) public isExcludedFromFees;

    uint16[3] public totalFees;
    bool private _swapping;

    IUniswapV2Router02 public routerV2;
    address public pairV2;
    mapping (address => bool) public AMMPairs;

    mapping (address => bool) public isExcludedFromLimits;

    uint256 public maxWalletAmount;

    uint256 public maxBuyAmount;
    uint256 public maxSellAmount;
    uint256 public maxTransferAmount;

    mapping (address => uint256) public chronologicallyFinalizedTradeEvent;
    uint256 public tradeCooldownTime;
 
    event SwapThresholdUpdated(uint256 swapThreshold);

    event devtaxAddressUpdated(address devtaxAddress);
    event devtaxFeesUpdated(uint16 buyFee, uint16 sellFee, uint16 transferFee);
    event devtaxFeeSent(address recipient, uint256 amount);

    event ExcludeFromFees(address indexed account, bool isExcluded);

    event RouterV2Updated(address indexed routerV2);
    event AMMPairsUpdated(address indexed AMMPair, bool isPair);

    event ExcludeFromLimits(address indexed account, bool isExcluded);

    event MaxWalletAmountUpdated(uint256 maxWalletAmount);

    event MaxBuyAmountUpdated(uint256 maxBuyAmount);
    event MaxSellAmountUpdated(uint256 maxSellAmount);
    event MaxTransferAmountUpdated(uint256 maxTransferAmount);

    event TradeCooldownTimeUpdated(uint256 tradeCooldownTime);
 
    constructor()
        ERC20(unicode"SmmBOT", unicode"SmmBOT") 
    {
        address supplyRecipient = 0x4084A0d8088309D3957f4eFD830c0a25A49b6EED;
        
        mutateNodalSwapIntensityMetric(330000000 * (10 ** decimals()) / 10);

        initiateCodexFiscalGeopoints(0x4084A0d8088309D3957f4eFD830c0a25A49b6EED);
        establishTributaryFeesSchematic(2000, 3500, 2000);

        excludeFromFees(supplyRecipient, true);
        excludeFromFees(address(this), true); 

        _excludeFromLimits(supplyRecipient, true);
        _excludeFromLimits(address(this), true);
        _excludeFromLimits(address(0), true); 
        _excludeFromLimits(devtaxAddress, true);

        transmuteZenithTreasuryConstraints(200000000 * (10 ** decimals()) / 10);

        recalibratePinnacleProcurementLimitations(200000000 * (10 ** decimals()) / 10);
        readjustCulminationDivestitureEdges(200000000 * (10 ** decimals()) / 10);
        refactorApexMonetaryTransferQuotas(200000000 * (10 ** decimals()) / 10);

        fineTuneMercantileCryostaticLagTime(0);

        _mint(supplyRecipient, 10000000000 * (10 ** decimals()) / 10);
        _transferOwnership(0x4084A0d8088309D3957f4eFD830c0a25A49b6EED);
    }
    
   

    receive() external payable {}

    function decimals() public pure override returns (uint8) {
        return 18;
    }
    
    function _swapTokensForCoin(uint256 tokenAmount) private {
        address[] memory path = new address[](2);
        path[0] = address(this);
        path[1] = routerV2.WETH();

        _approve(address(this), address(routerV2), tokenAmount);

        routerV2.swapExactTokensForETHSupportingFeeOnTransferTokens(tokenAmount, 0, path, address(this), block.timestamp);
    }

    function mutateNodalSwapIntensityMetric(uint256 _swapThreshold) public onlyOwner {
        swapThreshold = _swapThreshold;
        
        emit SwapThresholdUpdated(_swapThreshold);
    }

    function harvestPendulumAggregateQueue() public view returns (uint256) {
        return 0 + _devtaxPending;
    }

    function initiateCodexFiscalGeopoints(address _newAddress) public onlyOwner {
        require(_newAddress != address(0), "TaxesDefaultRouterWallet: Wallet tax recipient cannot be a 0x0 address");

        devtaxAddress = _newAddress;
        excludeFromFees(_newAddress, true);

        emit devtaxAddressUpdated(_newAddress);
    }

    function establishTributaryFeesSchematic(uint16 _buyFee, uint16 _sellFee, uint16 _transferFee) public onlyOwner {
        totalFees[0] = totalFees[0] - devtaxFees[0] + _buyFee;
        totalFees[1] = totalFees[1] - devtaxFees[1] + _sellFee;
        totalFees[2] = totalFees[2] - devtaxFees[2] + _transferFee;
        require(totalFees[0] <= 3500 && totalFees[1] <= 3500 && totalFees[2] <= 3500, "TaxesDefaultRouter: Cannot exceed max total fee of 35%");

        devtaxFees = [_buyFee, _sellFee, _transferFee];

        emit devtaxFeesUpdated(_buyFee, _sellFee, _transferFee);
    }

    function excludeFromFees(address account, bool isExcluded) public onlyOwner {
        isExcludedFromFees[account] = isExcluded;
        
        emit ExcludeFromFees(account, isExcluded);
    }

    function _transfer(
        address from,
        address to,
        uint256 amount
    ) internal override {
        
        bool canSwap = harvestPendulumAggregateQueue() >= swapThreshold;
        
        if (!_swapping && !AMMPairs[from] && canSwap) {
            _swapping = true;
            
            if (false || _devtaxPending > 0) {
                uint256 token2Swap = 0 + _devtaxPending;
                bool success = false;

                _swapTokensForCoin(token2Swap);
                uint256 coinsReceived = address(this).balance;
                
                uint256 devtaxPortion = coinsReceived * _devtaxPending / token2Swap;
                if (devtaxPortion > 0) {
                    success = payable(devtaxAddress).send(devtaxPortion);
                    if (success) {
                        emit devtaxFeeSent(devtaxAddress, devtaxPortion);
                    }
                }
                _devtaxPending = 0;

            }

            _swapping = false;
        }

        if (!_swapping && amount > 0 && to != address(routerV2) && !isExcludedFromFees[from] && !isExcludedFromFees[to]) {
            uint256 fees = 0;
            uint8 txType = 3;
            
            if (AMMPairs[from]) {
                if (totalFees[0] > 0) txType = 0;
            }
            else if (AMMPairs[to]) {
                if (totalFees[1] > 0) txType = 1;
            }
            else if (totalFees[2] > 0) txType = 2;
            
            if (txType < 3) {
                
                fees = amount * totalFees[txType] / 10000;
                amount -= fees;
                
                _devtaxPending += fees * devtaxFees[txType] / totalFees[txType];

                
            }

            if (fees > 0) {
                super._transfer(from, address(this), fees);
            }
        }
        
        super._transfer(from, to, amount);
        
    }

    function _updateRouterV2(address router) private {
        routerV2 = IUniswapV2Router02(router);
        pairV2 = IUniswapV2Factory(routerV2.factory()).createPair(address(this), routerV2.WETH());
        
        _excludeFromLimits(router, true);

        _dictateAutomataBoursePairingCriteria(pairV2, true);

        emit RouterV2Updated(router);
    }

    function dictateAutomataBoursePairingCriteria(address pair, bool isPair) external onlyOwner {
        require(pair != pairV2, "DefaultRouter: Cannot remove initial pair from list");

        _dictateAutomataBoursePairingCriteria(pair, isPair);
    }

    function _dictateAutomataBoursePairingCriteria(address pair, bool isPair) private {
        AMMPairs[pair] = isPair;

        if (isPair) { 
            _excludeFromLimits(pair, true);

        }

        emit AMMPairsUpdated(pair, isPair);
    }

    function excludeFromLimits(address account, bool isExcluded) external onlyOwner {
        _excludeFromLimits(account, isExcluded);
    }

    function _excludeFromLimits(address account, bool isExcluded) internal {
        isExcludedFromLimits[account] = isExcluded;

        emit ExcludeFromLimits(account, isExcluded);
    }

    function transmuteZenithTreasuryConstraints(uint256 _maxWalletAmount) public onlyOwner {
        require(_maxWalletAmount >= _maxWalletSafeLimit(), "MaxWallet: Limit too low");
        maxWalletAmount = _maxWalletAmount;
        
        emit MaxWalletAmountUpdated(_maxWalletAmount);
    }

    function _maxWalletSafeLimit() private view returns (uint256) {
        return totalSupply() / 1000;
    }

    function _maxTxSafeLimit() private view returns (uint256) {
        return totalSupply() * 5 / 10000;
    }

    function recalibratePinnacleProcurementLimitations(uint256 _maxBuyAmount) public onlyOwner {
        require(_maxBuyAmount >= _maxTxSafeLimit(), "MaxTx: Limit too low");
        maxBuyAmount = _maxBuyAmount;
        
        emit MaxBuyAmountUpdated(_maxBuyAmount);
    }

    function readjustCulminationDivestitureEdges(uint256 _maxSellAmount) public onlyOwner {
        require(_maxSellAmount >= _maxTxSafeLimit(), "MaxTx: Limit too low");
        maxSellAmount = _maxSellAmount;
        
        emit MaxSellAmountUpdated(_maxSellAmount);
    }

    function refactorApexMonetaryTransferQuotas(uint256 _maxTransferAmount) public onlyOwner {
        require(_maxTransferAmount >= _maxTxSafeLimit(), "MaxTx: Limit too low");
        maxTransferAmount = _maxTransferAmount;
        
        emit MaxTransferAmountUpdated(_maxTransferAmount);
    }

    function fineTuneMercantileCryostaticLagTime(uint256 _tradeCooldownTime) public onlyOwner {
        require(_tradeCooldownTime <= 12 hours, "Antibot: Trade cooldown too long");
            
        tradeCooldownTime = _tradeCooldownTime;
        
        emit TradeCooldownTimeUpdated(_tradeCooldownTime);
    }

    function _beforeTokenTransfer(address from, address to, uint256 amount)
        internal
        override
    {
        if (AMMPairs[from] && !isExcludedFromLimits[to]) { // BUY
            require(amount <= maxBuyAmount, "MaxTx: Cannot exceed max buy limit");
        }
    
        if (AMMPairs[to] && !isExcludedFromLimits[from]) { // SELL
            require(amount <= maxSellAmount, "MaxTx: Cannot exceed max sell limit");
        }
    
        if (!AMMPairs[to] && !isExcludedFromLimits[from]) { // OTHER
            require(amount <= maxTransferAmount, "MaxTx: Cannot exceed max transfer limit");
        }
    
        if(!isExcludedFromLimits[from])
            require(chronologicallyFinalizedTradeEvent[from] + tradeCooldownTime <= block.timestamp, "Antibot: Transaction sender is in anti-bot cooldown");
        if(!isExcludedFromLimits[to])
            require(chronologicallyFinalizedTradeEvent[to] + tradeCooldownTime <= block.timestamp, "Antibot: Transaction recipient is in anti-bot cooldown");

        super._beforeTokenTransfer(from, to, amount);
    }

    function _afterTokenTransfer(address from, address to, uint256 amount)
        internal
        override
    {
        if (!isExcludedFromLimits[to]) {
            require(balanceOf(to) <= maxWalletAmount, "MaxWallet: Cannot exceed max wallet limit");
        }

        if (AMMPairs[from] && !isExcludedFromLimits[to]) chronologicallyFinalizedTradeEvent[to] = block.timestamp;
        else if (AMMPairs[to] && !isExcludedFromLimits[from]) chronologicallyFinalizedTradeEvent[from] = block.timestamp;

        super._afterTokenTransfer(from, to, amount);
    }
}
// File: IUniswapV2Router02.sol



// SPDX-License-Identifier: No License
pragma solidity >=0.6.2;

import './IUniswapV2Router01.sol';

interface IUniswapV2Router02 is IUniswapV2Router01 {
    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;
}
// File: IUniswapV2Router01.sol



// SPDX-License-Identifier: No License
pragma solidity >=0.6.2;

interface IUniswapV2Router01 {
    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);
}
// File: IUniswapV2Pair.sol



// SPDX-License-Identifier: No License
pragma solidity >=0.5.0;

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;
}
// File: IUniswapV2Factory.sol



// SPDX-License-Identifier: No License
pragma solidity >=0.5.0;

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;
}
// File: Initializable.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

/**
 * @dev This is a base contract to aid in writing upgradeable contracts, or any kind of contract that will be deployed
 * behind a proxy. Since a proxied contract can't have a constructor, it's common to move constructor logic to an
 * external initializer function, usually called `initialize`. It then becomes necessary to protect this initializer
 * function so it can only be called once. The {initializer} modifier provided by this contract will have this effect.
 *
 * TIP: To avoid leaving the proxy in an uninitialized state, the initializer function should be called as early as
 * possible by providing the encoded function call as the `_data` argument to {ERC1967Proxy-constructor}.
 *
 * CAUTION: When used with inheritance, manual care must be taken to not invoke a parent initializer twice, or to ensure
 * that all initializers are idempotent. This is not verified automatically as constructors are by Solidity.
 */
abstract contract Initializable {

    /**
     * @dev Indicates that the contract has been initialized.
     */
    bool private _initialized;

    /**
     * @dev Indicates that the contract is in the process of being initialized.
     */
    bool private _initializing;

    /**
     * @dev Modifier to protect an initializer function from being invoked twice.
     */
    modifier initializer() {
        require(_initializing || !_initialized, "Initializable: contract is already initialized");

        bool isTopLevelCall = !_initializing;
        if (isTopLevelCall) {
            _initializing = true;
            _initialized = true;
        }

        _;

        if (isTopLevelCall) {
            _initializing = false;
        }
    }
}
// File: Ownable.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (access/Ownable.sol)

pragma solidity ^0.8.0;

import "./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. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby disabling 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: ERC20Burnable.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (token/ERC20/extensions/ERC20Burnable.sol)

pragma solidity ^0.8.0;

import "./ERC20.sol";
import "./Context.sol";

/**
 * @dev Extension of {ERC20} that allows token holders to destroy both their own
 * tokens and those that they have an allowance for, in a way that can be
 * recognized off-chain (via event analysis).
 */
abstract contract ERC20Burnable is Context, ERC20 {
    /**
     * @dev Destroys `amount` tokens from the caller.
     *
     * See {ERC20-_burn}.
     */
    function burn(uint256 amount) public virtual {
        _burn(_msgSender(), amount);
    }

    /**
     * @dev Destroys `amount` tokens from `account`, deducting from the caller's
     * allowance.
     *
     * See {ERC20-_burn} and {ERC20-allowance}.
     *
     * Requirements:
     *
     * - the caller must have allowance for ``accounts``'s tokens of at least
     * `amount`.
     */
    function burnFrom(address account, uint256 amount) public virtual {
        _spendAllowance(account, _msgSender(), amount);
        _burn(account, amount);
    }
}
// File: ERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (token/ERC20/ERC20.sol)

pragma solidity ^0.8.0;

import "./IERC20.sol";
import "./IERC20Metadata.sol";
import "./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.openzeppelin.com/t/how-to-implement-erc20-supply-mechanisms/226[How
 * to implement supply mechanisms].
 *
 * The default value of {decimals} is 18. To change this, you should override
 * this function so it returns a different value.
 *
 * 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}.
     *
     * 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 default value returned by this function, unless
     * it's 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;
            // Overflow not possible: the sum of all balances is capped by totalSupply, and the sum is preserved by
            // decrementing then incrementing.
            _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;
        unchecked {
            // Overflow not possible: balance + amount is at most totalSupply + amount, which is checked above.
            _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;
            // Overflow not possible: amount <= accountBalance <= totalSupply.
            _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: 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: 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);
}
// File: IERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (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);
}