<?php
// db/config.php

// --- Database Credentials ---
// Note: In a real production environment, use environment variables
// or a secure secrets management system instead of hardcoding credentials.
define('DB_HOST', '127.0.0.1');
define('DB_NAME', 'webapp_db');
define('DB_USER', 'webapp_user');
define('DB_PASS', 'password'); // IMPORTANT: Use a strong, unique password in production

/**
 * Establishes a PDO database connection.
 *
 * @return PDO|null A PDO connection object on success, or null on failure.
 */
function db_connect() {
    static $pdo = null;

    if ($pdo instanceof PDO) {
        return $pdo;
    }

    $dsn = 'mysql:host=' . DB_HOST . ';dbname=' . DB_NAME . ';charset=utf8mb4';
    $options = [
        PDO::ATTR_ERRMODE            => PDO::ERRMODE_EXCEPTION,
        PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
        PDO::ATTR_EMULATE_PREPARES   => false,
    ];

    try {
        // Create a new database and user if they don't exist.
        // This is for demonstration purposes to make setup easier.
        // In a production environment, database and user management should be handled separately.
        $rootPdo = new PDO('mysql:host=' . DB_HOST, 'root', '');
        $rootPdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
        $rootPdo->exec('CREATE DATABASE IF NOT EXISTS ' . DB_NAME);
        $rootPdo->exec("CREATE USER IF NOT EXISTS '" . DB_USER . "'@'localhost' IDENTIFIED BY '" . DB_PASS . "'");
        $rootPdo->exec('GRANT ALL PRIVILEGES ON ' . DB_NAME . '.* TO '' . DB_USER . ''@'localhost'');
        $rootPdo = null;

        $pdo = new PDO($dsn, DB_USER, DB_PASS, $options);
        return $pdo;
    } catch (PDOException $e) {
        // In a real app, you would log this error and show a generic error page.
        // For development, it's useful to see the error.
        error_log('Database Connection Error: ' . $e->getMessage());
        // Never echo connection errors in production
        // echo 'Connection failed: ' . $e->getMessage();
        return null;
    }
}