/* Offline app shell for the Interval Timer PWA. */

const CACHE = 'interval-timer-v1';

const ASSETS = [
  './',
  './index.html',
  './styles.css',
  './app.js',
  './manifest.webmanifest',
  './icons/icon-192.png',
  './icons/icon-512.png',
  './icons/icon-maskable-512.png',
];

self.addEventListener('install', (event) => {
  event.waitUntil(
    caches.open(CACHE)
      .then((cache) => cache.addAll(ASSETS))
      .then(() => self.skipWaiting())
  );
});

self.addEventListener('activate', (event) => {
  event.waitUntil(
    caches.keys()
      .then((keys) => Promise.all(keys.filter((k) => k !== CACHE).map((k) => caches.delete(k))))
      .then(() => self.clients.claim())
  );
});

self.addEventListener('fetch', (event) => {
  const { request } = event;
  if (request.method !== 'GET' || new URL(request.url).origin !== self.location.origin) return;

  // Navigations: try the network, fall back to the cached shell when offline.
  if (request.mode === 'navigate') {
    event.respondWith(
      fetch(request)
        .then((response) => {
          const copy = response.clone();
          caches.open(CACHE).then((cache) => cache.put('./index.html', copy));
          return response;
        })
        .catch(() => caches.match('./index.html'))
    );
    return;
  }

  // Everything else: cache first, refresh in the background.
  event.respondWith(
    caches.match(request).then((cached) => {
      const network = fetch(request)
        .then((response) => {
          if (response && response.status === 200 && response.type === 'basic') {
            const copy = response.clone();
            caches.open(CACHE).then((cache) => cache.put(request, copy));
          }
          return response;
        })
        .catch(() => cached);
      return cached || network;
    })
  );
});