// What To Cook? - PWA Service Worker (v1.1.0)
const CACHE_NAME = 'wtc-cache-v2';
const PRECACHE_URLS = [
  '/',
  '/cookbook',
  '/shopping-list',
  '/manifest.json',
  '/favicon.ico',
  '/static/favicon.svg',
  '/static/cookbook.css',
  '/static/icon-192.png',
  '/static/icon-512.png',
  '/static/apple-touch-icon.png'
];

// Install: Pre-cache shell assets
self.addEventListener('install', (event) => {
  event.waitUntil(
    caches.open(CACHE_NAME).then((cache) => {
      return cache.addAll(PRECACHE_URLS).catch((err) => {
        console.warn('[SW] Pre-caching partial failure, continuing:', err);
      });
    }).then(() => self.skipWaiting())
  );
});

// Activate: Clean up old caches
self.addEventListener('activate', (event) => {
  event.waitUntil(
    caches.keys().then((cacheNames) => {
      return Promise.all(
        cacheNames.map((cacheName) => {
          if (cacheName !== CACHE_NAME) {
            return caches.delete(cacheName);
          }
        })
      );
    }).then(() => self.clients.claim())
  );
});

// Fetch: Strategy
self.addEventListener('fetch', (event) => {
  const req = event.request;
  const url = new URL(req.url);

  // Skip non-GET and WebSocket/API mutation requests
  if (req.method !== 'GET') return;
  if (url.pathname.startsWith('/ws/') || url.pathname.startsWith('/api/')) return;

  // Navigation requests (HTML pages): Network first, fallback to cache
  if (req.mode === 'navigate') {
    event.respondWith(
      fetch(req).then((response) => {
        if (response && response.status === 200) {
          const copy = response.clone();
          caches.open(CACHE_NAME).then((cache) => cache.put(req, copy));
        }
        return response;
      }).catch(async () => {
        const cached = await caches.match(req);
        if (cached) return cached;
        // If exact page not cached, return home or shopping list if available
        if (url.pathname === '/shopping-list') {
          const shopCached = await caches.match('/shopping-list');
          if (shopCached) return shopCached;
        }
        const homeCached = await caches.match('/');
        if (homeCached) return homeCached;
        return new Response('Offline – keine Verbindung vorhanden.', {
          status: 503,
          headers: { 'Content-Type': 'text/plain; charset=utf-8' }
        });
      })
    );
    return;
  }

  // Static assets: Cache-first, then network update
  if (url.pathname.startsWith('/static/') || url.hostname.includes('fonts.googleapis.com') || url.hostname.includes('fonts.gstatic.com')) {
    event.respondWith(
      caches.match(req).then((cached) => {
        if (cached) {
          // In background, refresh cache
          fetch(req).then((networkRes) => {
            if (networkRes && networkRes.status === 200) {
              caches.open(CACHE_NAME).then((cache) => cache.put(req, networkRes));
            }
          }).catch(() => {});
          return cached;
        }
        return fetch(req).then((networkRes) => {
          if (networkRes && networkRes.status === 200) {
            const copy = networkRes.clone();
            caches.open(CACHE_NAME).then((cache) => cache.put(req, copy));
          }
          return networkRes;
        });
      })
    );
    return;
  }
});