"use client";

import { initializeApp, getApps, type FirebaseApp } from "firebase/app";
import {
  getMessaging,
  getToken,
  onMessage,
  type Messaging,
} from "firebase/messaging";

let app: FirebaseApp | null = null;
let messaging: Messaging | null = null;

export function initFirebase() {
  if (typeof window === "undefined") return;

  const {
    NEXT_PUBLIC_FIREBASE_API_KEY,
    NEXT_PUBLIC_FIREBASE_AUTH_DOMAIN,
    NEXT_PUBLIC_FIREBASE_PROJECT_ID,
    NEXT_PUBLIC_FIREBASE_STORAGE_BUCKET,
    NEXT_PUBLIC_FIREBASE_MESSAGING_SENDER_ID,
    NEXT_PUBLIC_FIREBASE_APP_ID,
  } = process.env;

  if (
    !NEXT_PUBLIC_FIREBASE_API_KEY ||
    !NEXT_PUBLIC_FIREBASE_PROJECT_ID
  ) {
    console.warn(
      "Firebase config not fully provided. Browser push notifications will be disabled.",
    );
    return;
  }

  if (getApps().length === 0) {
    app = initializeApp({
      apiKey: NEXT_PUBLIC_FIREBASE_API_KEY,
      authDomain: NEXT_PUBLIC_FIREBASE_AUTH_DOMAIN,
      projectId: NEXT_PUBLIC_FIREBASE_PROJECT_ID,
      storageBucket: NEXT_PUBLIC_FIREBASE_STORAGE_BUCKET,
      messagingSenderId: NEXT_PUBLIC_FIREBASE_MESSAGING_SENDER_ID,
      appId: NEXT_PUBLIC_FIREBASE_APP_ID,
    });
  } else {
    app = getApps()[0];
  }

  try {
    messaging = getMessaging(app);
  } catch (err) {
    console.warn("Failed to initialize Firebase Messaging", err);
  }
}

export function getFirebaseMessaging(): Messaging | null {
  return messaging;
}

/**
 * Request notification permission and retrieve the FCM registration token.
 * Returns the token string, or null if permission is not granted or FCM is unavailable.
 */
export async function registerFcmToken(): Promise<string | null> {
  if (!messaging) {
    console.warn("Firebase Messaging not initialized");
    return null;
  }

  try {
    const permission = await Notification.requestPermission();
    if (permission !== "granted") {
      console.warn("Notification permission not granted");
      return null;
    }

    const token = await getToken(messaging, {
      vapidKey: process.env.NEXT_PUBLIC_FIREBASE_VAPID_KEY,
    });

    if (!token) {
      console.warn("Failed to retrieve FCM token");
      return null;
    }

    return token;
  } catch (err) {
    console.warn("Failed to register FCM token", err);
    return null;
  }
}

/**
 * Listen for foreground messages and dispatch a custom event so the UI can react.
 */
export function onForegroundMessage(
  callback: (payload: any) => void,
): (() => void) | null {
  if (!messaging) return null;
  const unsubscribe = onMessage(messaging, (payload) => {
    callback(payload);
  });
  return unsubscribe;
}