static/sw.js

const CACHE_NAME = "vomebook-search-v1";

const PRECACHE_URLS = [
  "/",
  "/static/style.css",
  "/static/app.js",
  "/manifest.json"
];

// ── Install: precache app shell ─────────────────────
self.addEventListener("install", (event) => {
  event.waitUntil(
    caches.open(CACHE_NAME).then((cache) => {
      return cache.addAll(PRECACHE_URLS).catch((err) => {
        console.warn("[SW] precache partial failure:", err);
      });
    }).then(() => self.skipWaiting())
  );
});

// ── Activate: clean old caches ──────────────────────
self.addEventListener("activate", (event) => {
  event.waitUntil(
    caches.keys().then((keys) => {
      return Promise.all(
        keys.filter((k) => k !== CACHE_NAME).map((k) => caches.delete(k))
      );
    }).then(() => self.clients.claim())
  );
});

// ── Fetch: cache strategies ─────────────────────────
self.addEventListener("fetch", (event) => {
  const url = new URL(event.request.url);

  // External domains: network only
  if (url.hostname !== self.location.hostname) {
    return;
  }

  // ── API: network first, no caching ────────────────
  if (url.pathname.startsWith("/api/")) {
    return;
  }

  // ── Download proxy: network only ──────────────────
  if (url.pathname.startsWith("/txt/")) {
    return;
  }

  // ── App shell / static: cache first, network update
  event.respondWith(
    caches.match(event.request).then((cached) => {
      const fetchPromise = fetch(event.request).then((response) => {
        if (response.ok && response.status !== 206) {
          const clone = response.clone();
          caches.open(CACHE_NAME).then((cache) => {
            cache.put(event.request, clone);
          });
        }
        return response;
      }).catch(() => cached);
      return cached || fetchPromise;
    })
  );
});