if ('serviceWorker' in navigator) {
  navigator.serviceWorker.register('/sw.js')
    .then(() => console.log('SW зарегистрирован'))
    .catch(err => console.error('SW ошибка:', err));
}

const CACHE_NAME = 'app-cache-v1';
const urlsToCache = ['/', '/index.html', '/styles.css'];

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

self.addEventListener('fetch', event => {
  event.respondWith(
    caches.match(event.request)
      .then(response => response || fetch(event.request))
  );
});

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