<?php
/**
 * Database Connection with PDO Persistent
 *
 * @package ROI_APU_Search
 */

declare(strict_types=1);

// Prevent direct access
if (!defined('ABSPATH')) {
    exit;
}

/**
 * Singleton class for PDO database connection with persistent connections
 */
final class ROI_APU_Search_DB
{
    private static ?self $instance = null;
    private ?PDO $pdo = null;

    /**
     * Get singleton instance
     */
    public static function get_instance(): self
    {
        if (self::$instance === null) {
            self::$instance = new self();
        }
        return self::$instance;
    }

    /**
     * Private constructor
     */
    private function __construct()
    {
        $this->connect();
    }

    /**
     * Establish PDO connection with persistent connection enabled
     */
    private function connect(): void
    {
        if ($this->pdo !== null) {
            return;
        }

        // Get WordPress database credentials
        $host = DB_HOST;
        $name = DB_NAME;
        $user = DB_USER;
        $pass = DB_PASSWORD;
        $charset = defined('DB_CHARSET') ? DB_CHARSET : 'utf8mb4';

        // Handle port in host
        $port = 3306;
        if (strpos($host, ':') !== false) {
            [$host, $port] = explode(':', $host);
            $port = (int) $port;
        }

        $dsn = "mysql:host={$host};port={$port};dbname={$name};charset={$charset}";

        $options = [
            PDO::ATTR_ERRMODE            => PDO::ERRMODE_EXCEPTION,
            PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
            PDO::ATTR_EMULATE_PREPARES   => true, // Same as original buscar-apus (enables reusing :q placeholder)
            PDO::ATTR_PERSISTENT         => true, // Enable persistent connections
        ];

        try {
            $this->pdo = new PDO($dsn, $user, $pass, $options);

            // Set MySQL specific options (same as original buscar-apus)
            $this->pdo->exec("SET NAMES {$charset} COLLATE {$charset}_unicode_ci");
        } catch (PDOException $e) {
            // Log error but don't expose details
            error_log('ROI APU Search DB Error: ' . $e->getMessage());
            throw new RuntimeException('Database connection failed');
        }
    }

    /**
     * Get the PDO instance
     */
    public function get_pdo(): PDO
    {
        if ($this->pdo === null) {
            $this->connect();
        }
        return $this->pdo;
    }

    /**
     * Get WordPress table prefix
     */
    public function get_prefix(): string
    {
        global $table_prefix;
        return $table_prefix ?? 'wp_';
    }

    /**
     * Prevent cloning
     */
    private function __clone()
    {
    }

    /**
     * Prevent unserialization
     */
    public function __wakeup()
    {
        throw new RuntimeException('Cannot unserialize singleton');
    }
}