"use client";

/**
 * ServiceWorkerRegistrar — registers the app's service worker for everyone on
 * load (not just when a user opts into push). The same `/sw.js` now also
 * powers the Save-offline feature (caching page HTML + assets), so it must be
 * active regardless of push. The `?bff=` query matches the push registration
 * exactly (see lib/push.ts) so there's a single registration / scope, and push
 * subscription management keeps working.
 */

import { useEffect } from "react";
import { precacheOfflineLibrary } from "@/lib/offline";

const BFF_BASE = process.env.NEXT_PUBLIC_BFF_URL || "http://localhost:8080";

export function ServiceWorkerRegistrar() {
  useEffect(() => {
    if (typeof navigator === "undefined" || !("serviceWorker" in navigator)) {
      return;
    }
    const register = () => {
      navigator.serviceWorker
        .register(`/sw.js?bff=${encodeURIComponent(BFF_BASE)}`)
        .then(() => {
          // Precache the offline library so it works as the SW navigation
          // fallback even if the user never opens it online.
          void precacheOfflineLibrary();
        })
        .catch(() => {
          /* registration is best-effort; the app works online without it */
        });
    };
    // Defer past first paint so it never competes with hydration.
    if (document.readyState === "complete") {
      register();
      return;
    }
    window.addEventListener("load", register, { once: true });
    return () => window.removeEventListener("load", register);
  }, []);

  return null;
}