// JGA Prag 2026 — Service Worker
// Cache-Strategie:
//   • Eigene HTML/JS/CSS  → network-first (immer frisch laden, Fallback Cache offline)
//   • Map-Tiles (OSM)     → cache-first (für Offline-Karten)
//   • Externe APIs (OSRM) → network-only (kein Cache)
const CACHE_VERSION = 'jga-2026-v4';
const TILE_CACHE = 'jga-2026-tiles-v4';
const PAGE_CACHE = 'jga-2026-pages-v4';

// Nur Map-Tiles werden offline gecached — KEINE eigenen HTML-Files
const PRECACHE_URLS = [
  './manifest.json'
];

// Install: nur manifest precachen, KEINE HTML-Files
self.addEventListener('install', (event) => {
  event.waitUntil(
    caches.open(PAGE_CACHE)
      .then(cache => cache.addAll(PRECACHE_URLS))
      .then(() => self.skipWaiting())
  );
});

// Activate: alle alten Caches (inkl. v3, v2, v1) löschen
self.addEventListener('activate', (event) => {
  event.waitUntil(
    caches.keys()
      .then(keys => Promise.all(
        keys
          .filter(k => k !== CACHE_VERSION && k !== TILE_CACHE && k !== PAGE_CACHE)
          .map(k => caches.delete(k))
      ))
      .then(async () => {
        // Auch alte Tile- und Page-Caches aufräumen
        const old = await caches.keys();
        await Promise.all(
          old
            .filter(k => k.startsWith('jga-2026-') && k !== CACHE_VERSION && k !== TILE_CACHE && k !== PAGE_CACHE)
            .map(k => caches.delete(k))
        );
        await self.clients.claim();
      })
  );
});

// Fetch-Handler
self.addEventListener('fetch', (event) => {
  const req = event.request;
  if (req.method !== 'GET') return;

  const url = new URL(req.url);

  // ─── Externe APIs (OSRM, Open-Meteo) → network-only, kein Cache ───
  if (url.origin !== self.location.origin) {
    // Map-Tiles (OSM / Carto / unpkg Leaflet) → cache-first
    if (
      url.hostname.includes('openstreetmap') ||
      url.hostname.includes('cartocdn') ||
      url.hostname.includes('tile.openstreetmap')
    ) {
      event.respondWith(cacheFirst(req, TILE_CACHE));
      return;
    }
    // Alles andere extern → einfach durch, kein Caching
    return; // default browser behavior
  }

  // ─── Eigene Files (HTML/JS/CSS/JSON) → network-first ───
  // Immer versuchen frisch zu laden, nur bei Offline-Fallback aus Cache
  event.respondWith(networkFirst(req, PAGE_CACHE));
});

// Network-first: frisch vom Netz, Fallback auf Cache (offline)
async function networkFirst(request, cacheName) {
  const cache = await caches.open(cacheName);
  try {
    const response = await fetch(request, { cache: 'no-store' });
    if (response.ok) {
      cache.put(request, response.clone());
    }
    return response;
  } catch (err) {
    const cached = await cache.match(request);
    if (cached) return cached;
    // Letzter Fallback: index.html (für SPA-ähnliches Verhalten)
    if (request.mode === 'navigate') {
      const fallback = await cache.match('./index.html');
      if (fallback) return fallback;
    }
    throw err;
  }
}

// Cache-first: aus Cache, Fallback aufs Netz (für Tiles)
async function cacheFirst(request, cacheName) {
  const cache = await caches.open(cacheName);
  const cached = await cache.match(request);
  if (cached) return cached;
  try {
    const response = await fetch(request);
    if (response.ok) {
      cache.put(request, response.clone());
    }
    return response;
  } catch (err) {
    // Tile offline + nicht im Cache → leere 503
    return new Response('', { status: 503, statusText: 'Tile offline' });
  }
}

// Clients über neues Update benachrichtigen
self.addEventListener('message', (event) => {
  if (event.data && event.data.type === 'SKIP_WAITING') {
    self.skipWaiting();
  }
});