/// <reference types="@sveltejs/kit" />
/// <reference lib="webworker" />

declare let self: ServiceWorkerGlobalScope;

import { build, files, version } from "$service-worker";

const CACHE = `cache-${version}`;
const ASSETS = [...build, ...files];

// install service worker
self.addEventListener("install", (event) => {
  async function addFilesToCache() {
    const cache = await caches.open(CACHE);
    await cache.addAll(ASSETS);
  }

  event.waitUntil(addFilesToCache());
});

self.addEventListener("activate", (event) => {
  async function deleteOldCaches() {
    for (const key of await caches.keys()) {
      if (key !== CACHE) {
        await caches.delete(key);
      }
    }
  }
  event.waitUntil(deleteOldCaches());
});

//listen to fetch events
self.addEventListener("fetch", (event) => {
  if (event.request.method !== "GET") return;

  async function respond() {
    const url = new URL(event.request.url);
    const cache = await caches.open(CACHE);

    //serve build files from cache;
    if (ASSETS.includes(url.pathname)) {
      const cacheResponse = await cache.match(url.pathname);
      if (cacheResponse) {
        return cacheResponse;
      }
    }
    // try the network first
    try {
      const response = await fetch(event.request);
      const isNotExtension = url.protocol === "http:";
      const isSuccess = response.status === 200;

      if (isNotExtension && isSuccess) {
        cache.put(event.request, response.clone());
      }

      return response;
    } catch {
      //fall back to cache
      const cachedResponse = await cache.match(url.pathname);
      if (cachedResponse) {
        return cachedResponse;
      }
    }

    return new Response("Not found", { status: 404 });
  }
});

self.addEventListener("message", (event) => {
  if (event.data && event.data.type === "SKIP_WAITING") {
    self.skipWaiting();
  }
});