<?php
class Database {
    private static $instance = null;
    private $pdo;
    private $settingsCache = [];
    
    private function __construct() {
        try {
            $this->pdo = new PDO(
                "mysql:host=" . DB_HOST . ";dbname=" . DB_NAME . ";charset=utf8mb4",
                DB_USER,
                DB_PASS,
                [
                    PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
                    PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
                    PDO::ATTR_EMULATE_PREPARES => false
                ]
            );
        } catch (PDOException $e) {
            die("Datenbankverbindung fehlgeschlagen: " . $e->getMessage());
        }
    }
    
    public static function getInstance() {
        if (self::$instance === null) {
            self::$instance = new self();
        }
        return self::$instance;
    }
    
    public function getConnection() {
        return $this->pdo;
    }
    
    // Helper-Methode für Queries
    public function query($sql, $params = []) {
        $stmt = $this->pdo->prepare($sql);
        $stmt->execute($params);
        return $stmt;
    }
    
    // Helper für einzelnen Datensatz
    public function fetchOne($sql, $params = []) {
        $stmt = $this->query($sql, $params);
        return $stmt->fetch();
    }
    
    // Helper für mehrere Datensätze
    public function fetchAll($sql, $params = []) {
        $stmt = $this->query($sql, $params);
        return $stmt->fetchAll();
    }
    
    // Helper für Insert/Update mit Rückgabe der ID
    public function execute($sql, $params = []) {
        $this->query($sql, $params);
        return $this->pdo->lastInsertId();
    }
    
    // Settings-Helper
    public function getSetting($key, $default = null) {
        if (array_key_exists($key, $this->settingsCache)) {
            return $this->settingsCache[$key] ?? $default;
        }
        $result = $this->fetchOne("SELECT setting_value FROM settings WHERE setting_key = ?", [$key]);
        $value = $result ? $result['setting_value'] : null;
        $this->settingsCache[$key] = $value;
        return $value ?? $default;
    }

    public function setSetting($key, $value) {
        $this->query(
            "INSERT INTO settings (setting_key, setting_value) VALUES (?, ?)
             ON DUPLICATE KEY UPDATE setting_value = VALUES(setting_value)",
            [$key, $value]
        );
        $this->settingsCache[$key] = $value;
    }
}