Cryo Explorer Ethereum Mainnet

// SPDX-License-Identifier: MIT
pragma solidity =0.8.9;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "./interfaces/IUniswap.sol";

library Liquidity {
    address public constant FACTORY =
        0x5C69bEe701ef814a2B6a3EDD4B1652CB9cc5aA6f;
    address public constant ROUTER = 0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D;
    address public constant WETH = 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2;
    address public constant DEAD_ADDRESS =
        0x000000000000000000000000000000000000dEaD;

    function addLiquidity(
        address _tokenA,
        address _tokenB,
        uint256 _amountA,
        uint256 _amountB,
        address _to
    )
        internal
        returns (
            uint256 amountA,
            uint256 amountB,
            uint256 liquidity
        )
    {
        IERC20(_tokenA).approve(ROUTER, _amountA);
        IERC20(_tokenB).approve(ROUTER, _amountB);
        (amountA, amountB, liquidity) = IUniswapV2Router(ROUTER).addLiquidity(
            _tokenA,
            _tokenB,
            _amountA,
            _amountB,
            0,
            0,
            _to,
            block.timestamp
        );
    }

    function removeLiquidity(
        address _tokenA,
        address _tokenB,
        address _to
    ) internal returns (uint256 amountA, uint256 amountB) {
        address pair = getPair(_tokenA, _tokenB);

        uint256 liquidity = IERC20(pair).balanceOf(address(this));
        IERC20(pair).approve(ROUTER, liquidity);

        (amountA, amountB) = IUniswapV2Router(ROUTER).removeLiquidity(
            _tokenA,
            _tokenB,
            liquidity,
            0,
            0,
            _to,
            block.timestamp
        );
    }

    function swap(
        address _tokenIn,
        address _tokenOut,
        uint256 _amountIn,
        uint256 _slippage,
        address _to
    ) internal returns (uint256) {
        IERC20(_tokenIn).approve(ROUTER, _amountIn);

        address[] memory path;
        if (_tokenIn == WETH || _tokenOut == WETH) {
            path = new address[](2);
            path[0] = _tokenIn;
            path[1] = _tokenOut;
        } else {
            path = new address[](3);
            path[0] = _tokenIn;
            path[1] = WETH;
            path[2] = _tokenOut;
        }

        uint256 _amountOutMin = (IUniswapV2Router(ROUTER).getAmountsOut(
            _amountIn,
            path
        )[path.length - 1] * (1000 - _slippage)) / 1000;

        uint256 balanceBefore = IERC20(_tokenOut).balanceOf(_to);
        IUniswapV2Router(ROUTER)
            .swapExactTokensForTokensSupportingFeeOnTransferTokens(
                _amountIn,
                _amountOutMin,
                path,
                _to,
                block.timestamp
            );
        uint256 balanceAfter = IERC20(_tokenOut).balanceOf(_to);
        return balanceAfter - balanceBefore;
    }

    function getPair(address _tokenA, address _tokenB)
        internal
        view
        returns (address)
    {
        return IUniswapV2Factory(FACTORY).getPair(_tokenA, _tokenB);
    }
}

// SPDX-License-Identifier: MIT
pragma solidity =0.8.9;

import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "../interfaces/IFactory.sol";
import "../Liquidity.sol";

contract THERUGGAME is ERC20, Ownable {
    uint256 private _feesOnContract;
    uint256 public points;
    uint256 public wethReward;
    address public factory;

    mapping(address => uint256) private _credit;
    mapping(address => uint256) private _xDividendPerToken;

    error EliminatedToken();
    error InvalidBribeToken();
    error NotEnoughBalance();
    error NotEnoughRewards();
    error TransferLimitExceeded();

    event Bribe(
        address indexed tokenUsedForBribe,
        address indexed tokenBribed,
        uint256 amount
    );

    constructor(
        string memory _name,
        string memory _symbol,
        uint256 _supply,
        address _factory
    ) ERC20(_name, _symbol) {
        _mint(msg.sender, _supply);
        factory = _factory;
    }

    function _transfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual override {
        address pair = Liquidity.getPair(address(this), Liquidity.WETH);

        if (to != pair && to != address(this) && to != factory) {
            uint256 validTokenTransfer = (totalSupply() / 100) - balanceOf(to);
            if (amount > validTokenTransfer) revert TransferLimitExceeded();
        }

        _withdrawToCredit(from);
        _withdrawToCredit(to);

        if (
            (pair == to && from != address(this) && from != factory) ||
            (pair == from && to != address(this) && to != factory)
        ) {
            uint256 totalTax = burnTax() + cultTax() + rewardTax() + trgTax();
            uint256 feeAmount = (amount * totalTax) / 10000;
            super._transfer(from, address(this), feeAmount);

            _feesOnContract += feeAmount;

            if (from != pair) {
                uint256 swappedCult = _buyAndBurnToken(
                    cult(),
                    (_feesOnContract * cultTax()) / totalTax
                );
                uint256 swappedTrg = _buyAndBurnToken(
                    trg(),
                    (_feesOnContract * trgTax()) / totalTax
                );
                uint256 swappedWeth = Liquidity.swap(
                    address(this),
                    Liquidity.WETH,
                    (_feesOnContract * rewardTax()) / totalTax,
                    slippage(),
                    factory
                );
                uint256 burnAmount = (_feesOnContract * burnTax()) / totalTax;
                super._transfer(
                    address(this),
                    Liquidity.DEAD_ADDRESS,
                    burnAmount
                );

                wethReward += swappedWeth;
                points += swappedCult + swappedTrg + (burnAmount * 100000);
                _feesOnContract = 0;
            } else {
                uint256 validTokenTransfer = (totalSupply() / 100) -
                    balanceOf(to);
                if (amount > validTokenTransfer) revert TransferLimitExceeded();
            }

            return super._transfer(from, to, amount - feeAmount);
        } else return super._transfer(from, to, amount);
    }

    function _buyAndBurnToken(address _tokenOut, uint256 _amountIn)
        private
        returns (uint256)
    {
        if (_amountIn > 0) {
            uint256 swappedAmount = Liquidity.swap(
                address(this),
                _tokenOut,
                _amountIn,
                slippage(),
                address(this)
            );
            transferIERC20(_tokenOut, Liquidity.DEAD_ADDRESS, swappedAmount);

            return swappedAmount;
        }
        return 0;
    }

    function _withdrawToCredit(address _user) private {
        address pair = Liquidity.getPair(address(this), Liquidity.WETH);
        if (
            _user == pair ||
            _user == Liquidity.DEAD_ADDRESS ||
            _user == address(this)
        ) return;

        uint256 recipientBalance = balanceOf(_user);
        if (recipientBalance != 0) {
            uint256 amount = ((dividendPerToken() - _xDividendPerToken[_user]) *
                recipientBalance) / 1e18;
            _credit[_user] += amount;
        }
        _xDividendPerToken[_user] = dividendPerToken();
    }

    function pendingRewards(address _user) public view returns (uint256) {
        address pair = Liquidity.getPair(address(this), Liquidity.WETH);
        if (_user == Liquidity.DEAD_ADDRESS || _user == pair) return 0;

        uint256 userBalance = balanceOf(_user);
        if (userBalance == 0) return 0;

        uint256 amount = ((dividendPerToken() - _xDividendPerToken[_user]) *
            userBalance) / 1e18;
        return amount += _credit[_user];
    }

    function claimReward() external {
        uint256 userReward = pendingRewards(msg.sender);
        if (userReward == 0) revert NotEnoughRewards();

        _credit[msg.sender] = 0;
        _xDividendPerToken[msg.sender] = dividendPerToken();
        transferIERC20(Liquidity.WETH, msg.sender, userReward);
    }

    function bribe(address _token, uint256 _amount) external {
        bool isRugged = IFactory(factory).isValidBribe(address(this));
        if (isRugged) revert EliminatedToken();

        if (
            (_token != cult() && _token != trg()) ||
            trgTax() == 0 ||
            cultTax() == 0
        ) revert InvalidBribeToken();

        if (balanceOfIERC20(_token, msg.sender) < _amount)
            revert NotEnoughBalance();

        uint256 beforeBalance = balanceOfIERC20(_token, address(this));
        IERC20(_token).transferFrom(msg.sender, address(this), _amount);
        uint256 balanceDifference = balanceOfIERC20(_token, address(this)) -
            beforeBalance;

        uint256 amountToBurn = balanceDifference / 2;
        uint256 amountForHolders = balanceDifference - amountToBurn;

        transferIERC20(_token, Liquidity.DEAD_ADDRESS, amountToBurn);

        if (_token == trg()) transferIERC20(trg(), sTrg(), amountForHolders);
        if (_token == cult()) transferIERC20(cult(), dCult(), amountForHolders);

        points += (_amount * 3) / 2;

        emit Bribe(_token, address(this), _amount);
    }

    function balanceOfIERC20(address _token, address _user)
        private
        view
        returns (uint256)
    {
        return IERC20(_token).balanceOf(_user);
    }

    function transferIERC20(
        address _token,
        address _to,
        uint256 _amount
    ) private returns (bool) {
        return IERC20(_token).transfer(_to, _amount);
    }

    function dividendPerToken() public view returns (uint256) {
        return IFactory(factory).dividendPerToken(address(this));
    }

    function cult() public view returns (address) {
        return IFactory(factory).cult();
    }

    function dCult() public view returns (address) {
        return IFactory(factory).dCult();
    }

    function trg() public view returns (address) {
        return IFactory(factory).trg();
    }

    function sTrg() public view returns (address) {
        return IFactory(factory).sTrg();
    }

    function slippage() public view returns (uint256) {
        return IFactory(factory).slippage();
    }

    function burnTax() public view returns (uint256) {
        return IFactory(factory).burnTax();
    }

    function cultTax() public view returns (uint256) {
        return IFactory(factory).cultTax();
    }

    function rewardTax() public view returns (uint256) {
        return IFactory(factory).rewardTax();
    }

    function trgTax() public view returns (uint256) {
        return IFactory(factory).trgTax();
    }
}

// SPDX-License-Identifier: MIT
pragma solidity =0.8.9;

interface IFactory {
    function cult() external view returns (address);

    function dCult() external view returns (address);

    function trg() external view returns (address);

    function sTrg() external view returns (address);

    function dividendPerToken(address) external view returns (uint256);

    function burnTax() external view returns (uint256);

    function cultTax() external view returns (uint256);

    function rewardTax() external view returns (uint256);

    function trgTax() external view returns (uint256);

    function isValidBribe(address) external view returns (bool);

    function slippage() external view returns (uint256);
}

// SPDX-License-Identifier: MIT
pragma solidity =0.8.9;

interface IUniswapV2Router {
    function addLiquidity(
        address tokenA,
        address tokenB,
        uint256 amountADesired,
        uint256 amountBDesired,
        uint256 amountAMin,
        uint256 amountBMin,
        address to,
        uint256 deadline
    )
        external
        returns (
            uint256 amountA,
            uint256 amountB,
            uint256 liquidity
        );

    function getAmountsOut(uint256 amountIn, address[] memory path)
        external
        view
        returns (uint256[] memory amounts);

    function removeLiquidity(
        address tokenA,
        address tokenB,
        uint256 liquidity,
        uint256 amountAMin,
        uint256 amountBMin,
        address to,
        uint256 deadline
    ) external returns (uint256 amountA, uint256 amountB);

    function swapExactTokensForTokensSupportingFeeOnTransferTokens(
        uint256 amountIn,
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external;
}

interface IUniswapV2Factory {
    function getPair(address tokenA, address tokenB)
        external
        view
        returns (address pair);
}

// 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;
    }
}

// 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);
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (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.openzeppelin.com/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;
            // 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 {}
}

// 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);
}

// 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);
}