MINEFLAPPY-GAME/sw.js

/* Mineflappy offline cache.

   The app shell (index.html) is fetched NETWORK-FIRST so a new deploy
   reaches the player immediately; if the network is down it falls back to
   the cached copy. The icons and manifest are cache-first because they
   only change with a version bump. */
const CACHE = 'mineflappy-v2';
const ASSETS = [
  './',
  './index.html',
  './manifest.webmanifest',
  './icon-192.png',
  './icon-512.png',
  './apple-touch-icon.png',
  './favicon-32.png'
];

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

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

function isAppShell(url) {
  return url.pathname.endsWith('/') ||
         url.pathname.endsWith('/index.html') ||
         url.pathname.endsWith('/sw.js');
}

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

  if (isAppShell(url)) {
    /* network first - a redeploy shows up straight away */
    e.respondWith(
      fetch(req).then(res => {
        if (res && res.status === 200) {
          const copy = res.clone();
          caches.open(CACHE).then(c => c.put(req, copy));
        }
        return res;
      }).catch(() => caches.match(req).then(hit => hit || caches.match('./index.html')))
    );
    return;
  }

  /* everything else: cache first, refresh in the background */
  e.respondWith(
    caches.match(req).then(hit => {
      const network = fetch(req).then(res => {
        if (res && res.status === 200 && res.type === 'basic') {
          const copy = res.clone();
          caches.open(CACHE).then(c => c.put(req, copy));
        }
        return res;
      }).catch(() => hit);
      return hit || network;
    })
  );
});