<?php
// db/config.php

// --- Database Credentials ---
// --> IMPORTANT: Replace with your actual database credentials
define('DB_HOST', getenv('DB_HOST') ?: '127.0.0.1');
define('DB_PORT', getenv('DB_PORT') ?: 3306);
define('DB_NAME', getenv('DB_NAME') ?: 'localdb');
define('DB_USER', getenv('DB_USER') ?: 'user');
define('DB_PASS', getenv('DB_PASS') ?: 'password');

/**
 * 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 !== null) {
        return $pdo;
    }

    $dsn = 'mysql:host=' . DB_HOST . ';port=' . DB_PORT . ';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 {
        $pdo = new PDO($dsn, DB_USER, DB_PASS, $options);
        return $pdo;
    } catch (PDOException $e) {
        // In a real application, you would log this error and show a generic message.
        // For development, it's useful to see the error.
        error_log('Database Connection Error: ' . $e->getMessage());
        // Never show detailed errors in production
        // die('Database connection failed. Please check configuration.');
        return null;
    }
}