const CACHE_NAME = "apicore-shell-v3";

self.addEventListener("install", () => {
  self.skipWaiting();
});

self.addEventListener("activate", (event) => {
  event.waitUntil(
    caches
      .keys()
      .then((keys) =>
        Promise.all(keys.filter((key) => key !== CACHE_NAME).map((key) => caches.delete(key))),
      )
      .then(() => self.clients.claim()),
  );
});

self.addEventListener("fetch", (event) => {
  const { request } = event;

  if (request.method !== "GET") {
    return;
  }

  const url = new URL(request.url);

  // /api/runtime-config tells the app which backend origin to use - it
  // must always be fetched live. A stale cached value would point the app
  // at the wrong (or no longer running) backend, which is worse than no
  // cache at all.
  if (url.pathname === "/api/runtime-config") {
    return;
  }

  // Same-origin static assets/pages, or the real backend API. The backend
  // runs on its own origin (API_URL, injected at runtime via
  // /api/runtime-config) rather than this app's own origin, so it can't be
  // matched by origin the way static assets are - matched by path instead,
  // since every backend call goes through /api/v1/. Without this, colonies,
  // apiaries, tasks etc. were never cached at all: a beekeeper opening the
  // app with no signal at an apiary saw nothing, not even data they had
  // already loaded minutes earlier on the same device.
  const isCacheable =
    url.origin === self.location.origin || url.pathname.includes("/api/v1/");
  if (!isCacheable) {
    return;
  }

  // Page navigations must never be answered with a synthetic Response.error() -
  // Chrome/Edge render that as a native "This page couldn't load" interstitial
  // instead of the app. Let the browser handle navigations directly; only
  // static assets/API data go through the offline-cache fallback below.
  if (request.mode === "navigate") {
    return;
  }

  event.respondWith(
    fetch(request)
      .then((response) => {
        // Never cache an error response (e.g. a 401 hit right as an access
        // token expired, before refresh could kick in) - it would otherwise
        // get served back later as if it were still the current state.
        if (!response.ok) {
          return response;
        }
        const responseClone = response.clone();
        return caches
          .open(CACHE_NAME)
          .then((cache) => cache.put(request, responseClone))
          .then(() => response);
      })
      .catch(() => caches.match(request).then((cached) => cached || Response.error())),
  );
});