/// <reference no-default-lib="true"/>
/// <reference lib="esnext" />
/// <reference lib="webworker" />
/// <reference types="@sveltejs/kit" />

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

const sw = self as unknown as ServiceWorkerGlobalScope;

const SHELL_CACHE = `shell-${version}`;
const MODEL_CACHE = "birdnet-models";

// Precache the app shell and lightweight static files.
// Model binaries and label JSON are excluded — they're too large to cache at
// install time and are instead cached on first use via the fetch handler.
const SHELL_ASSETS = [
  ...build,
  ...files.filter((f) => !f.startsWith("/models/") && f !== "/robots.txt"),
  "/",
];

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

sw.addEventListener("activate", (event) => {
  event.waitUntil(
    caches.keys().then((keys) =>
      Promise.all(
        keys
          .filter((k) => k !== SHELL_CACHE && k !== MODEL_CACHE)
          .map((k) => caches.delete(k)),
      ),
    ),
  );
  sw.clients.claim();
});

sw.addEventListener("fetch", (event) => {
  const { request } = event;
  const url = new URL(request.url);

  if (request.method !== "GET" || url.origin !== sw.location.origin) return;

  // Model files: cache-first with a stable cache that outlives app updates.
  if (url.pathname.startsWith("/models/")) {
    event.respondWith(
      caches.open(MODEL_CACHE).then(async (cache) => {
        const cached = await cache.match(request);
        if (cached) return cached;
        const response = await fetch(request);
        cache.put(request, response.clone());
        return response;
      }),
    );
    return;
  }

  // Everything else: serve from shell cache when available, fall back to
  // network, and for navigation failures return the cached root as SPA shell.
  event.respondWith(
    caches.match(request).then(async (cached) => {
      if (cached) return cached;
      try {
        return await fetch(request);
      } catch {
        if (request.mode === "navigate") {
          return (
            (await caches.match("/")) ??
            new Response("Offline", { status: 503 })
          );
        }
        return new Response("Offline", { status: 503 });
      }
    }),
  );
});