const CACHE_NAME = 'stockfill-cache-v1';
const OFFLINE_URLS = ['/', '/index.html'];

self.addEventListener('install', (event) => {
  event.waitUntil(
    caches.open(CACHE_NAME).then((cache) => {
      return cache.addAll(OFFLINE_URLS);
    }),
  );
});

self.addEventListener('activate', (event) => {
  event.waitUntil(
    caches.keys().then((keys) =>
      Promise.all(
        keys.map((key) => {
          if (key !== CACHE_NAME) {
            return caches.delete(key);
          }
          return undefined;
        }),
      ),
    ),
  );
});

self.addEventListener('fetch', (event) => {
  const { request } = event;
  if (request.method !== 'GET') return;

  event.respondWith(
    fetch(request)
      .then((response) => {
        const copy = response.clone();
        caches.open(CACHE_NAME).then((cache) => cache.put(request, copy));
        return response;
      })
      .catch(async () => {
        const cached = await caches.match(request);
        if (cached) return cached;
        if (request.mode === 'navigate') {
          const fallback = await caches.match('/index.html');
          if (fallback) return fallback;
        }
        throw new Error('Network error');
      }),
  );
});