// No reload or permission prompt is implicit: the app knows about unsaved work
// and whether the person actually asked to enable notifications.
export async function register({ url = "/sw.js", scope, onUpdate = () => {} } = {}) {
  if (!globalThis.navigator?.serviceWorker) return null;
  const registration = await navigator.serviceWorker.register(url, {
    ...(scope ? { scope } : {}),
    updateViaCache: "none",
  });
  const seen = new WeakSet();
  const notify = () => {
    const worker = registration.waiting;
    if (worker && !seen.has(worker)) {
      seen.add(worker);
      onUpdate(registration);
    }
  };
  const watch = () => {
    registration.installing?.addEventListener("statechange", notify);
    notify();
  };
  registration.addEventListener("updatefound", watch);
  watch();
  return registration;
}

// Activation affects the registration shared by all tabs. Call only after the
// app has resolved unsaved work across those tabs; this helper never reloads.
export function activateUpdate(registration) {
  if (!registration?.waiting) return false;
  registration.waiting.postMessage({ type: "rastrillo:pwa:activate" });
  return true;
}