text: import { timestamp, files, shell, routes } from "@sapper/service-worker";
  
  const ASSETS = `cache${timestamp}`;
  
  const to_cache = shell.concat(files);
  const cached = new Set(to_cache);
  
  self.addEventListener("install", (event) => {
    event.waitUntil(
      caches
        .open(ASSETS)
        .then((cache) => cache.addAll(to_cache))
        .then(() => {
          self.skipWaiting();
        })
    );
  });
  
  self.addEventListener("activate", (event) => {
    event.waitUntil(
      caches.keys().then(async (keys) => {
        // delete old caches
        for (const key of keys) {
          if (key !== ASSETS) await caches.delete(key);
        }
  
        self.clients.claim();
      })
    );
  });
  
  self.addEventListener("fetch", (event) => {
    if (event.request.method !== "GET" || event.request.headers.has("range"))
      return;
  
    const url = new URL(event.request.url);
  
    // don"t try to handle e.g. data: URIs
    if (!url.protocol.startsWith("http")) return;
  
    // ignore dev server requests
    if (
      url.hostname === self.location.hostname &&
      url.port !== self.location.port
    )
      return;
  
    // always serve static files and bundler-generated assets from cache
    if (url.host === self.location.host && cached.has(url.pathname)) {
      event.respondWith(caches.match(event.request));
      return;
    }
  
    // for pages, you might want to serve a shell `service-worker-index.html` file,
    // which Sapper has generated for you. It"s not right for every
    // app, but if it"s right for yours then uncomment this section
    /*
  	if (url.origin === self.origin && routes.find(route => route.pattern.test(url.pathname))) {
  		event.respondWith(caches.match("/service-worker-index.html"));
  		return;
  	}
  	*/
  
    if (event.request.cache === "only-if-cached") return;
  
    // for everything else, try the network first, falling back to
    // cache if the user is offline. (If the pages never change, you
    // might prefer a cache-first approach to a network-first one.)
    event.respondWith(
      caches.open(`offline${timestamp}`).then(async (cache) => {
        try {
          const response = await fetch(event.request);
          cache.put(event.request, response.clone());
          return response;
        } catch (err) {
          const response = await cache.match(event.request);
          if (response) return response;
  
          throw err;
        }
      })
    );
  });
  