<?php
function db_connect() {
    static $pdo;
    if ($pdo) {
        return $pdo;
    }

    // Database configuration
    $host = getenv('DB_HOST') ?: '127.0.0.1';
    $port = getenv('DB_PORT') ?: '3306';
    $dbname = getenv('DB_NAME') ?: 'lamp_app_db';
    $user = getenv('DB_USER') ?: 'lamp_app_user';
    $pass = getenv('DB_PASS') ?: 'lamp_app_pass';
    $charset = 'utf8mb4';

    $dsn = "mysql:host=$host;port=$port;dbname=$dbname;charset=$charset";
    $options = [
        PDO::ATTR_ERRMODE            => PDO::ERRMODE_EXCEPTION,
        PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
        PDO::ATTR_EMULATE_PREPARES   => false,
    ];

    try {
        $pdo = new PDO($dsn, $user, $pass, $options);
        return $pdo;
    } catch (\PDOException $e) {
        throw new \PDOException($e->getMessage(), (int)$e->getCode());
    }
}

function db_init() {
    $pdo = db_connect();
    $sql = "
    CREATE TABLE IF NOT EXISTS students (
        id INT AUTO_INCREMENT PRIMARY KEY,
        first_name VARCHAR(100) NOT NULL,
        last_name VARCHAR(100) NOT NULL,
        date_of_birth DATE,
        email VARCHAR(100),
        phone_number VARCHAR(20),
        created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
    );
    ";
    $pdo->exec($sql);
}