const CACHE_NAME = 'podcast-mindmap-v2';

// Core assets to cache immediately
const CORE_ASSETS = [
  '/',
  '/index.html',
  '/d3.v7.min.js',
  '/manifest.json'
];

// Install: cache core assets
self.addEventListener('install', event => {
  event.waitUntil(
    caches.open(CACHE_NAME)
      .then(cache => cache.addAll(CORE_ASSETS))
      .then(() => self.skipWaiting())
  );
});

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

// Fetch: network-first for API, cache-first for static assets
self.addEventListener('fetch', event => {
  const url = new URL(event.request.url);

  // Skip non-GET requests
  if (event.request.method !== 'GET') return;

  // API calls: network-first with no cache
  if (url.pathname.startsWith('/api/')) {
    event.respondWith(
      fetch(event.request).catch(() =>
        new Response(JSON.stringify({ error: 'offline' }), {
          headers: { 'Content-Type': 'application/json' }
        })
      )
    );
    return;
  }

  // App shell (index.html): network-first, sonst kommen Code-Updates erst beim
  // uebernaechsten Reload an. Cache-Fallback bleibt fuer Offline-Betrieb erhalten.
  if (url.pathname === '/' || url.pathname === '/index.html') {
    event.respondWith(
      fetch(event.request).then(resp => {
        if (resp.ok) {
          const clone = resp.clone();
          caches.open(CACHE_NAME).then(cache => cache.put(event.request, clone));
        }
        return resp;
      }).catch(() => caches.match(event.request))
    );
    return;
  }

  // Audio files: network-first, cache on success (optional offline playback)
  if (url.pathname.startsWith('/audio/')) {
    event.respondWith(
      fetch(event.request).then(resp => {
        // Only cache complete responses (not range requests)
        if (resp.status === 200) {
          const clone = resp.clone();
          caches.open(CACHE_NAME).then(cache => cache.put(event.request, clone));
        }
        return resp;
      }).catch(() => caches.match(event.request))
    );
    return;
  }

  // Static assets + JSON data: stale-while-revalidate
  event.respondWith(
    caches.match(event.request).then(cached => {
      const fetchPromise = fetch(event.request).then(resp => {
        if (resp.ok) {
          const clone = resp.clone();
          caches.open(CACHE_NAME).then(cache => cache.put(event.request, clone));
        }
        return resp;
      }).catch(() => cached);

      return cached || fetchPromise;
    })
  );
});