/**
 * Från
 * https://developer.mozilla.org/en-US/docs/Web/Progressive_web_apps/Offline_Service_workers (2021-06-09)
 * https://web.dev/offline-cookbook/
 */
 const cacheKey = 'cache-v1';

 const cacheArray = [
   '/index.html',
   '/manifest.json',
   '/favicon.ico',
   '/icons/icon-72x72.png',
   '/icons/icon-96x96.png',
   '/icons/icon-128x128.png',
   '/icons/icon-144x144.png',
   '/icons/icon-152x152.png',
   '/icons/icon-180x180.png',
   '/icons/icon-192x192.png',
   '/icons/icon-32x32.png',
   '/icons/icon-48x48.png',
   '/icons/icon-512x512.png',
   '/css/style.css',
   '/js/script.js'
 ];

 self.addEventListener('install', event => {
   console.log('Attempting to install service worker and cache static assets');
   event.waitUntil(
     caches.open(cacheKey)
     .then(cache => {
       return cache.addAll(cacheArray);
     })
   );
 });

 /** Rensar cache */
self.addEventListener('activate', (e) => {
  e.waitUntil(caches.keys().then((keyList) => {
    return Promise.all(keyList.map((key) => {
      if (key === cacheKey) { return; }
      return caches.delete(key);
    }))
  }));
});

 /** cache-filer först, upddaterar cache från servern */
 self.addEventListener('fetch', function (event) {
   if (!(event.request.url.indexOf('http') === 0)) return; 
   event.respondWith(
     caches.open(cacheKey).then(function (cache) {
       return cache.match(event.request).then(function (response) {
         var fetchPromise = fetch(event.request).then(function (networkResponse) {
           cache.put(event.request, networkResponse.clone());
           return networkResponse;
         });
         return response || fetchPromise;
       });
     }),
   );
 });