Token

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

contract Token {
    string public name;
    string public symbol;
    uint8 public decimals = 18;
    uint256 public totalSupply;

    mapping(address => uint256) private _balances;
    mapping(address => mapping(address => uint256)) private _allowances;

    uint256 private constant MAX_SUPPLY = 1_000_000_000 * 10**18;

    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);

    constructor(
        string memory _name,
        string memory _symbol
    ) {
        name = _name;
        symbol = _symbol;
    }

    function balanceOf(address account) public view returns (uint256) {
        return _balances[account];
    }

    function transfer(address to, uint256 amount) public returns (bool) {
        _transfer(msg.sender, to, amount);
        return true;
    }

    function allowance(address owner, address spender) public view returns (uint256) {
        return _allowances[owner][spender];
    }

    function approve(address spender, uint256 amount) public returns (bool) {
        _approve(msg.sender, spender, amount);
        return true;
    }

    function transferFrom(
        address from,
        address to,
        uint256 amount
    ) public returns (bool) {
        _spendAllowance(from, msg.sender, amount);
        _transfer(from, to, amount);
        return true;
    }

    function freeMint(uint256 amount) external {
        require(totalSupply + amount <= MAX_SUPPLY, "Max supply reached");
        _mint(msg.sender, amount);
    }

    function _transfer(
        address from,
        address to,
        uint256 amount
    ) internal {
        require(to != address(0), "Transfer to zero address");
        require(_balances[from] >= amount, "Insufficient balance");

        _balances[from] -= amount;
        _balances[to] += amount;
        emit Transfer(from, to, amount);
    }

    function _mint(address account, uint256 amount) internal {
        require(account != address(0), "Mint to zero address");
        require(totalSupply + amount <= MAX_SUPPLY, "Max supply reached");

        _balances[account] += amount;
        totalSupply += amount;
        emit Transfer(address(0), account, amount);
    }

    function _approve(
        address owner,
        address spender,
        uint256 amount
    ) internal {
        require(owner != address(0), "Approve from zero address");
        require(spender != address(0), "Approve to zero address");

        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }

    function _spendAllowance(
        address owner,
        address spender,
        uint256 amount
    ) internal {
        uint256 currentAllowance = _allowances[owner][spender];
        require(currentAllowance >= amount, "Insufficient allowance");

        _allowances[owner][spender] = currentAllowance - amount;
    }
}