const CACHE = 'qbank-v1';

self.addEventListener('install', () => self.skipWaiting());
self.addEventListener('activate', e => e.waitUntil(clients.claim()));

self.addEventListener('fetch', e => {
  // Network-first: serve fresh, fall back to cache for GET requests.
  if (e.request.method !== 'GET') return;
  e.respondWith(
    fetch(e.request)
      .then(res => {
        if (res.ok) {
          const clone = res.clone();
          caches.open(CACHE).then(c => c.put(e.request, clone));
        }
        return res;
      })
      .catch(() => caches.match(e.request))
  );
});