baton/frontend/sw.js

'use strict';

const CACHE_NAME = 'baton-v4';

// App shell assets to precache
const APP_SHELL = [
  '/',
  '/index.html',
  '/app.js',
  '/style.css',
  '/manifest.json',
  '/icons/icon-192.png',
  '/icons/icon-512.png',
];

// Install: precache app shell + skipWaiting so new SW activates immediately
self.addEventListener('install', (event) => {
  self.skipWaiting();
  event.waitUntil(
    caches.open(CACHE_NAME).then((cache) => cache.addAll(APP_SHELL))
  );
});

// Activate: delete stale caches + claim open clients (decision: skipWaiting + clients.claim)
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: cache-first for app shell; API calls pass through to network
self.addEventListener('fetch', (event) => {
  if (event.request.method !== 'GET') return;

  const url = new URL(event.request.url);

  // Never intercept API calls — they must always reach the server
  if (url.pathname.startsWith('/api/')) return;

  event.respondWith(
    caches.match(event.request).then((cached) => {
      if (cached) return cached;

      return fetch(event.request).then((response) => {
        if (response && response.status === 200) {
          const clone = response.clone();
          caches.open(CACHE_NAME).then((cache) => cache.put(event.request, clone));
        }
        return response;
      });
    })
  );
});