windwiderstand/src/service-worker.ts

/// <reference types="@sveltejs/kit" />
/// <reference no-default-lib="true"/>
/// <reference lib="esnext" />
/// <reference lib="webworker" />
import { build, files, version } from "$service-worker";

const sw = self as unknown as ServiceWorkerGlobalScope;

const CACHE = `ww-cache-${version}`;
// Vom Build erzeugte Assets + statische Dateien (Icons, Manifest, Fonts…).
const PRECACHE = [...build, ...files];

sw.addEventListener("install", (event) => {
  event.waitUntil(
    caches
      .open(CACHE)
      .then((cache) => cache.addAll(PRECACHE))
      .then(() => sw.skipWaiting()),
  );
});

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

sw.addEventListener("fetch", (event) => {
  const req = event.request;
  if (req.method !== "GET") return;

  const url = new URL(req.url);
  // Nur same-origin — CMS-/Cross-Origin-Requests (dynamischer Content) nicht cachen.
  if (url.origin !== sw.location.origin) return;

  // Precache-Assets → cache-first (unveränderlich pro Version).
  if (PRECACHE.includes(url.pathname)) {
    event.respondWith(caches.match(req).then((r) => r ?? fetch(req)));
    return;
  }

  // Seiten → network-first, bei Offline aus Cache; sonst Hinweis.
  if (req.mode === "navigate") {
    event.respondWith(
      (async () => {
        try {
          const res = await fetch(req);
          const cache = await caches.open(CACHE);
          cache.put(req, res.clone());
          return res;
        } catch {
          const cached = await caches.match(req);
          return (
            cached ??
            new Response("Du bist offline. Diese Seite wurde noch nicht geladen.", {
              status: 503,
              headers: { "Content-Type": "text/plain; charset=utf-8" },
            })
          );
        }
      })(),
    );
  }
});