/* Service worker: app-shell cache-first, API network-first met timeout en fallback op de laatste response. */

const VERSION = 'weerscherm-v12';
const SHELL = [
  './',
  './index.html',
  './styles.css',
  './app.js',
  './format.js',
  './icons.js',
  './manifest.webmanifest',
  './icons/icon.svg',
  './icons/icon-180.png',
  './icons/icon-192.png',
  './icons/icon-512.png',
];
const API_PREFIX = '/api/';
const DATA_PATH = '/api/data.php';
const API_TIMEOUT_MS = 8000;

self.addEventListener('install', (event) => {
  event.waitUntil(
    caches.open(VERSION).then((cache) => cache.addAll(SHELL)).then(() => self.skipWaiting()),
  );
});

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

self.addEventListener('fetch', (event) => {
  const req = event.request;
  if (req.method !== 'GET') return;
  const url = new URL(req.url);
  if (url.origin !== self.location.origin) return;

  if (url.pathname.includes(API_PREFIX)) {
    event.respondWith(networkFirst(req));
  } else {
    event.respondWith(cacheFirst(req));
  }
});

async function networkFirst(req) {
  const cache = await caches.open(VERSION);
  const url = new URL(req.url);
  // Sleutel zonder querystring: het radarbeeld krijgt elke paar minuten een andere ?t=, en zonder
  // normaliseren zou de cache vollopen met varianten en zou offline nooit een treffer geven.
  const key = url.origin + url.pathname;
  const controller = new AbortController();
  const timer = setTimeout(() => controller.abort(), API_TIMEOUT_MS);
  try {
    const res = await fetch(req, { signal: controller.signal, cache: 'no-store' });
    if (res.ok) {
      cache.put(key, res.clone());
    }
    return res;
  } catch (err) {
    const cached = await cache.match(key);
    if (cached) {
      const headers = new Headers(cached.headers);
      headers.set('X-From-Cache', '1');
      return new Response(await cached.arrayBuffer(), { status: 200, statusText: 'OK', headers });
    }
    if (url.pathname.endsWith(DATA_PATH)) {
      return new Response(JSON.stringify({ errors: ['offline'] }), {
        status: 503,
        headers: { 'Content-Type': 'application/json; charset=utf-8', 'Cache-Control': 'no-store' },
      });
    }
    return new Response('offline', { status: 503, headers: { 'Cache-Control': 'no-store' } });
  } finally {
    clearTimeout(timer);
  }
}

async function cacheFirst(req) {
  const cache = await caches.open(VERSION);
  const cached = await cache.match(req, { ignoreSearch: true });
  if (cached) return cached;
  const res = await fetch(req);
  if (res.ok) {
    cache.put(req, res.clone());
  }
  return res;
}