/**
 * Service Worker — КЛГ АСУ ТК v2.
 * Стратегия: network-first для API, cache-first для статики.
 * Offline fallback для всех страниц.
 */
const CACHE_NAME = 'klg-v2';
const STATIC_CACHE = 'klg-static-v2';
const API_CACHE = 'klg-api-v2';

const SHELL_URLS = [
  '/', '/dashboard', '/login', '/offline',
  '/aircraft', '/airworthiness', '/airworthiness-core',
  '/maintenance', '/defects', '/personnel-plg',
  '/calendar', '/risks', '/checklists', '/regulator',
];

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

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

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

  // API requests: network-first with cache fallback
  if (url.pathname.startsWith('/api/')) {
    event.respondWith(
      fetch(request)
        .then((response) => {
          // Cache GET responses for offline
          if (request.method === 'GET' && response.ok) {
            const clone = response.clone();
            caches.open(API_CACHE).then((cache) => cache.put(request, clone));
          }
          return response;
        })
        .catch(() => caches.match(request))
    );
    return;
  }

  // Static assets: cache-first
  if (url.pathname.match(/\.(js|css|png|jpg|svg|woff2?)$/)) {
    event.respondWith(
      caches.match(request).then((cached) =>
        cached || fetch(request).then((response) => {
          const clone = response.clone();
          caches.open(STATIC_CACHE).then((cache) => cache.put(request, clone));
          return response;
        })
      )
    );
    return;
  }

  // Pages: network-first with offline fallback
  event.respondWith(
    fetch(request)
      .then((response) => {
        const clone = response.clone();
        caches.open(CACHE_NAME).then((cache) => cache.put(request, clone));
        return response;
      })
      .catch(() =>
        caches.match(request).then((cached) => cached || caches.match('/offline'))
      )
  );
});