sw.js

const CACHE_NAME = "loadcalc-v1";
const PRECACHE_URLS = [
  "./",
  "./index.html",
  "./style.css",
  "./script.js",
  "./calculations.js",
];

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

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

self.addEventListener("fetch", (event) => {
  // Cache-first for same-origin requests; pass through everything else.
  if (!event.request.url.startsWith(self.location.origin)) return;
  event.respondWith(
    caches
      .match(event.request)
      .then((cached) => cached || fetch(event.request)),
  );
});