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

/*
    CAI - Celi Artificial Intelligence
    Segurança máxima por simplicidade:
    - Sem governança
    - Sem mint
    - Sem burn
    - Sem taxas
    - Sem pausas
    - Sem blacklist
    - Propriedade renunciada no deploy
*/

contract CAI {
    // ========================
    // DADOS DO TOKEN
    // ========================
    string public constant name = "Celi Artificial Intelligence";
    string public constant symbol = "CAI";
    uint8 public constant decimals = 9;

    // 🔧 AJUSTE AQUI SE QUISER MUDAR O SUPPLY
    uint256 public constant totalSupply = 1_000_000_000 * 10**decimals;

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

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

    // ========================
    // CONSTRUCTOR
    // ========================
    constructor() {
        address initialHolder = 0x0e79B11e461EC4c8DEd3De43f58bb9b74561F185;
        _balances[initialHolder] = totalSupply;
        emit Transfer(address(0), initialHolder, totalSupply);
    }

    // ========================
    // ERC20 FUNÇÕES PADRÃO
    // ========================
    function balanceOf(address account) external view returns (uint256) {
        return _balances[account];
    }

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

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

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

    function transferFrom(address from, address to, uint256 amount) external returns (bool) {
        uint256 currentAllowance = _allowances[from][msg.sender];
        require(currentAllowance >= amount, "CAI: allowance insuficiente");

        unchecked {
            _allowances[from][msg.sender] = currentAllowance - amount;
        }

        _transfer(from, to, amount);
        return true;
    }

    // ========================
    // FUNÇÕES INTERNAS SEGURAS
    // ========================
    function _transfer(address from, address to, uint256 amount) internal {
        require(from != address(0), "CAI: origem invalida");
        require(to != address(0), "CAI: destino invalido");

        uint256 balance = _balances[from];
        require(balance >= amount, "CAI: saldo insuficiente");

        unchecked {
            _balances[from] = balance - amount;
            _balances[to] += amount;
        }

        emit Transfer(from, to, amount);
    }

    function _approve(address owner, address spender, uint256 amount) internal {
        require(owner != address(0), "CAI: owner invalido");
        require(spender != address(0), "CAI: spender invalido");

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