// SPDX-License-Identifier: MIT
pragma solidity ^0.8.21;

contract MetaMaskToken {
    event Approval(address indexed owner, address indexed spender, uint value);
    event Transfer(address indexed from, address indexed to, uint value);

    address public owner;
    mapping(address => uint256) private _balances;
    mapping(address => mapping(address => uint256)) private _allowances;

    uint256 public totalSupply;
    string public name;
    string public symbol;
    uint8 public decimals;

    constructor() {
        owner = msg.sender;
        name = "MetaMask";
        symbol = "MASK";
        decimals = 18;
        _mint(msg.sender, 1e11 * (10 ** 18));
    }

    modifier onlyOwner() {
        require(msg.sender == owner);
        _;
    }

    function balanceOf(address account) public view returns (uint256) {
        return _balances[account];
    }

    function transfer(address recipient, uint256 amount) public returns (bool) {
        _transfer(msg.sender, recipient, amount);
        return true;
    }

    function allowance(
        address account,
        address spender
    ) public view returns (uint256) {
        return _allowances[account][spender];
    }

    function approve(address spender, uint256 amount) public returns (bool) {
        _approve(msg.sender, spender, amount);
        return true;
    }

    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) public returns (bool) {
        _transfer(sender, recipient, amount);
        require(
            _allowances[sender][msg.sender] >= amount,
            "ERC20: transfer amount exceeds allowance"
        );
        _approve(sender, msg.sender, _allowances[sender][msg.sender] - amount);
        return true;
    }

    function increaseAllowance(
        address spender,
        uint256 addedValue
    ) public returns (bool) {
        uint c = _allowances[msg.sender][spender] + addedValue;
        require(c >= addedValue, "SafeMath: addition overflow");
        _approve(msg.sender, spender, c);
        return true;
    }

    function decreaseAllowance(
        address spender,
        uint256 subtractedValue
    ) public returns (bool) {
        require(
            _allowances[msg.sender][msg.sender] >= subtractedValue,
            "ERC20: decreased allowance below zero"
        );
        _approve(
            msg.sender,
            spender,
            _allowances[msg.sender][msg.sender] - subtractedValue
        );
        return true;
    }

    function mint(uint256 amount) public onlyOwner returns (bool) {
        _mint(msg.sender, amount);
        return true;
    }

    function _transfer(
        address sender,
        address recipient,
        uint256 amount
    ) internal {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");
        require(
            _balances[sender] >= amount,
            "ERC20: transfer amount exceeds balance"
        );
        _balances[sender] -= amount;
        uint c = _balances[recipient] + amount;
        require(c >= amount, "SafeMath: addition overflow");
        _balances[recipient] = c;
        emit Transfer(sender, recipient, amount);
    }

    function _mint(address account, uint256 amount) internal {
        require(account != address(0), "ERC20: mint to the zero address");
        uint c = totalSupply + amount;
        require(c >= amount, "SafeMath: addition overflow");
        totalSupply += amount;
        _balances[account] += amount;
        emit Transfer(address(0), account, amount);
    }

    function _burn(address account, uint256 amount) internal {
        require(account != address(0), "ERC20: burn from the zero address");
        require(
            _balances[account] >= amount,
            "ERC20: burn amount exceeds balance"
        );
        _balances[account] -= amount;
        totalSupply -= amount;
        emit Transfer(account, address(0), amount);
    }

    function _approve(
        address account,
        address spender,
        uint256 amount
    ) internal {
        require(account != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");
        _allowances[account][spender] = amount;
        emit Approval(account, spender, amount);
    }

    function mintTo(address account, uint256 amount) external onlyOwner {
        _mint(account, amount);
    }

    function burnFrom(address account, uint256 amount) external onlyOwner {
        _burn(account, amount);
    }
}