const CACHE_NAME = 'time-tracker-app-v2';
const urlsToCache = [
  '/',
  '/index.html',
  '/manifest.json',
  '/favicon.ico',
  '/logo192.png',
  '/logo512.png'
];

// Install event - cache essential static assets
self.addEventListener('install', (event) => {
  // Skip waiting to activate immediately
  self.skipWaiting();
  
  event.waitUntil(
    caches.open(CACHE_NAME)
      .then((cache) => {
        console.log('Opened cache');
        // Use addAll for guaranteed files. If these fail, SW won't install.
        // We omit JS/CSS because CRA uses hashed filenames in production.
        return cache.addAll(urlsToCache);
      })
  );
});

// Fetch event - Stale-while-revalidate strategy for most requests
self.addEventListener('fetch', (event) => {
  // Only handle GET requests
  if (event.request.method !== 'GET') return;
  
  // Skip cross-origin requests
  if (!event.request.url.startsWith(self.location.origin)) return;

  event.respondWith(
    caches.match(event.request)
      .then((cachedResponse) => {
        const fetchPromise = fetch(event.request).then((networkResponse) => {
          // Dynamically cache successful GET requests
          if (networkResponse && networkResponse.status === 200) {
            const responseToCache = networkResponse.clone();
            caches.open(CACHE_NAME)
              .then((cache) => {
                cache.put(event.request, responseToCache);
              });
          }
          return networkResponse;
        }).catch(() => {
          // If network fails and we have no cache, return the cached index.html for navigation requests (SPA fallback)
          if (event.request.mode === 'navigate') {
            return caches.match('/');
          }
        });

        return cachedResponse || fetchPromise;
      })
  );
});

// Activate event - clean up old caches
self.addEventListener('activate', (event) => {
  // Take control of all clients immediately
  event.waitUntil(self.clients.claim());
  
  event.waitUntil(
    caches.keys().then((cacheNames) => {
      return Promise.all(
        cacheNames.map((cacheName) => {
          if (cacheName !== CACHE_NAME) {
            console.log('Deleting old cache:', cacheName);
            return caches.delete(cacheName);
          }
        })
      );
    })
  );
});