/**
 * Backup Service Worker für MYP Platform
 * Vereinfachte Offline-Funktionalität als Fallback
 */

const CACHE_NAME = 'myp-platform-backup-v1';

// Assets die gecacht werden sollen
const ASSETS_TO_CACHE = [
  '/',
  '/dashboard',
  '/static/css/tailwind.min.css',
  '/static/css/tailwind-dark.min.css',
  '/static/js/ui-components.js',
  '/static/js/offline-app.js',
  '/static/favicon.ico'
];

// Install Event - Cache core assets
self.addEventListener('install', (event) => {
  console.log('Backup SW: Installing...');
  
  event.waitUntil(
    caches.open(CACHE_NAME)
      .then((cache) => {
        console.log('Backup SW: Caching assets');
        return cache.addAll(ASSETS_TO_CACHE);
      })
      .then(() => {
        console.log('Backup SW: Assets cached');
        return self.skipWaiting();
      })
      .catch((error) => {
        console.error('Backup SW: Error caching assets', error);
      })
  );
});

// Activate Event - Clean up old caches
self.addEventListener('activate', (event) => {
  console.log('Backup SW: Activating...');
  
  event.waitUntil(
    caches.keys()
      .then((cacheNames) => {
        return Promise.all(
          cacheNames.map((cacheName) => {
            if (cacheName !== CACHE_NAME) {
              console.log('Backup SW: Deleting old cache', cacheName);
              return caches.delete(cacheName);
            }
          })
        );
      })
      .then(() => {
        console.log('Backup SW: Activated');
        return self.clients.claim();
      })
  );
});

// Fetch Event - Cache first, network fallback mit korrekter Response-Behandlung
self.addEventListener('fetch', (event) => {
  // Nur GET-Requests und HTTP/HTTPS unterstützen
  if (event.request.method !== 'GET' || 
      (!event.request.url.startsWith('http:') && !event.request.url.startsWith('https:'))) {
    return;
  }
  
  event.respondWith(
    handleRequest(event.request)
  );
});

// Request-Handler mit korrekter Response-Behandlung
async function handleRequest(request) {
  try {
    // Zuerst im Cache suchen
    const cachedResponse = await caches.match(request);
    if (cachedResponse) {
      return cachedResponse;
    }
    
    // Netzwerk-Request versuchen
    const networkResponse = await fetch(request);
    
    // Nur erfolgreiche Responses cachen
    if (networkResponse && networkResponse.ok && networkResponse.type === 'basic') {
      const cache = await caches.open(CACHE_NAME);
      cache.put(request, networkResponse.clone());
    }
    
    return networkResponse;
  } catch (error) {
    console.error('Backup SW: Request failed', error);
    
    // Cache-Fallback versuchen
    const cachedResponse = await caches.match(request);
    if (cachedResponse) {
      return cachedResponse;
    }
    
    // Offline-Fallback Response
    return new Response('Offline - Service nicht verfügbar', {
      status: 503,
      statusText: 'Service Unavailable',
      headers: {
        'Content-Type': 'text/plain; charset=utf-8'
      }
    });
  }
}

console.log('Backup Service Worker: Script loaded successfully');