sw.js

const CACHE_NAME = 'scicalc-v2';
const ASSETS = [
  './',
  './index.html',
  './manifest.json',
  './icon.svg'
];

// Install: cache all app files
self.addEventListener('install', (e) => {
  e.waitUntil(
    caches.open(CACHE_NAME)
      .then(cache => cache.addAll(ASSETS))
      .then(() => self.skipWaiting())
  );
});

// Activate: clean up old caches
self.addEventListener('activate', (e) => {
  e.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, fall back to cache (so updates arrive immediately)
self.addEventListener('fetch', (e) => {
  e.respondWith(
    fetch(e.request).then(response => {
      if (response.ok) {
        const clone = response.clone();
        caches.open(CACHE_NAME).then(cache => cache.put(e.request, clone));
      }
      return response;
    }).catch(() => caches.match(e.request))
  );
});