import 'dart:convert';
import 'package:flutter/cupertino.dart';
import 'package:pubnub/pubnub.dart';
import '../../providers/public_keys_provider.dart';
import '../../providers/utils_singleton.dart';

class PubNubService {
  // ── singleton ─────────────────────────────────────────────────
  static final PubNubService _instance = PubNubService._internal();
  factory PubNubService() => _instance;
  PubNubService._internal();

  // ── internal state ────────────────────────────────────────────
  PubNub? _pubnub;
  Subscription? _subscription;

  Stream<Envelope> get inboundStream => _subscription!.messages;

  // ── init — call after publickeys.loadPublicKeys() ─────────────
  void init() {
    if (!publickeys.guardKey(publickeys.pubnubPublishKey, 'pubnubPublishKey')) return;
    if (!publickeys.guardKey(publickeys.pubnubSubscribeKey, 'pubnubSubscribeKey')) return;

    _pubnub = PubNub(
      defaultKeyset: Keyset(
        publishKey: publickeys.pubnubPublishKey!,
        subscribeKey: publickeys.pubnubSubscribeKey!,
        userId: UserId('${utils.user?.username ?? 'anonymous'}'),
      ),
    );
    print('✅ [PubNubService] initialized');
  }

  bool get isInitialized => _pubnub != null;

  // ── subscribe ─────────────────────────────────────────────────
  void subscribeTo(Set<String> channels) {
    if (!isInitialized) {
      debugPrint('[PubNubService] not initialized — call init() first');
      return;
    }
    _subscription?.dispose();
    _subscription = _pubnub!.subscribe(channels: channels);
    _subscription!.messages.listen((envelope) {
      print('🛈 [PubNub] MSG on ${envelope.channel} ⇢ ${envelope.payload}');
    });
    print('✅ [PubNub] Subscribed to $channels');
  }

  // ── publish ───────────────────────────────────────────────────
  Future<void> publishJson(String channel, Object payload) async {
    if (!isInitialized) {
      debugPrint('[PubNubService] not initialized — call init() first');
      return;
    }
    final encoded = jsonEncode(payload);
    print('⏫ [PubNub] PUBLISH → $channel : $encoded');
    await _pubnub!.channel(channel).publish(encoded);
  }

  Future<void> publishString(String channel, String text) async {
    if (!isInitialized) {
      debugPrint('[PubNubService] not initialized — call init() first');
      return;
    }
    print('⏫ [PubNub] PUBLISH → $channel : $text');
    await _pubnub!.channel(channel).publish(text);
  }

  // ── dispose ───────────────────────────────────────────────────
  Future<void> dispose() async {
    await _subscription?.dispose();
    _pubnub = null;
    print('🛑 [PubNub] disposed');
  }
}

// ── dispatcher — for sending offers ──────────────────────────
// call sendRideOffer() only after publickeys.loadPublicKeys()
Future<void> sendRideOffer({
  required int rideId,
  required String driverUsername,
  String message = 'New ride request',
}) async {
  if (!publickeys.guardKey(publickeys.pubnubPublishKey, 'pubnubPublishKey')) return;
  if (!publickeys.guardKey(publickeys.pubnubSubscribeKey, 'pubnubSubscribeKey')) return;

  final dispatcher = PubNub(
    defaultKeyset: Keyset(
      publishKey: publickeys.pubnubPublishKey!,
      subscribeKey: publickeys.pubnubSubscribeKey!,
      userId: const UserId('dispatcher'),
    ),
  );

  final payload = {
    'rideId': rideId,
    'candidateUsernames': [driverUsername],
    'message': message,
  };

  await dispatcher.channel('offers.drivers').publish(jsonEncode(payload));
  print('Offer $rideId sent to $driverUsername');
}