import 'dart:async';
import 'dart:convert';
import 'package:flutter/foundation.dart';
import 'package:mqtt_client/mqtt_client.dart';
import 'package:mqtt_client/mqtt_server_client.dart';
import 'package:miler/views/helpers/constants/mqtt_constants.dart';
import 'package:shared_preferences/shared_preferences.dart';

class MilerMqttService {
  static final MilerMqttService _instance = MilerMqttService._internal();

  factory MilerMqttService() {
    return _instance;
  }

  MilerMqttService._internal();

  MqttServerClient? _client;
  bool _isConnected = false;
  String? _currentRiderId;

  bool get isConnected => _isConnected;

  Future<void> connect() async {
    if (_isConnected) return;

    final prefs = await SharedPreferences.getInstance();
    final riderIdLong = prefs.getInt('userId') ?? prefs.getInt('userid');
    if (riderIdLong == null || riderIdLong <= 0) {
      debugPrint('[MQTT] Cannot connect: No rider ID found in preferences.');
      return;
    }
    _currentRiderId = riderIdLong.toString();

    const host = MqttConstants.brokerHost;
    // Append a small random or "bg" suffix if we want to allow simultaneous connections
    // from UI and Background Isolates.
    final clientId =
        'rider_${_currentRiderId}_${DateTime.now().millisecondsSinceEpoch % 1000}';

    _client = MqttServerClient(host, clientId);
    _client!.port = MqttConstants.brokerPort;
    _client!.keepAlivePeriod = 30; // 30 seconds
    _client!.autoReconnect = true;
    _client!.logging(on: false);

    // --- LAST WILL AND TESTAMENT (LWT) ---
    // If the app crashes or loses internet unexpectedly, the broker will publish this.
    final lwtTopic = MqttConstants.topicRiderStatus.replaceAll(
      '{riderId}',
      _currentRiderId!,
    );
    _client!.onDisconnected = _onDisconnected;
    _client!.onConnected = _onConnected;
    _client!.onAutoReconnect = _onAutoReconnect;
    _client!.onSubscribed = _onSubscribed;

    final connMessage = MqttConnectMessage()
        .withClientIdentifier(clientId)
        .authenticateAs(MqttConstants.username, MqttConstants.passwordString)
        .withWillTopic(lwtTopic)
        .withWillMessage(MqttConstants.statusOffline)
        .withWillQos(MqttQos.atLeastOnce)
        .withWillRetain()
        .startClean();

    _client!.connectionMessage = connMessage;

    try {
      debugPrint('[MQTT] Connecting to $host...');
      await _client!.connect();
    } catch (e) {
      debugPrint('[MQTT] Connection failed: $e');
      _disconnect();
    }
  }

  void _onConnected() {
    _isConnected = true;
    debugPrint('[MQTT] Connected successfully.');
    _publishStatus(MqttConstants.statusOnline);
  }

  void _onDisconnected() {
    _isConnected = false;
    debugPrint('[MQTT] Disconnected from broker.');
  }

  void _onAutoReconnect() {
    debugPrint('[MQTT] Auto-reconnecting...');
  }

  void _onSubscribed(String topic) {
    debugPrint('[MQTT] Subscribed to topic: $topic');
  }

  void _disconnect() {
    _client?.disconnect();
    _onDisconnected();
  }

  void _publishStatus(String status) {
    if (!_isConnected || _currentRiderId == null) return;

    final topic = MqttConstants.topicRiderStatus.replaceAll(
      '{riderId}',
      _currentRiderId!,
    );
    final builder = MqttClientPayloadBuilder();
    builder.addString(status);

    _client!.publishMessage(
      topic,
      MqttQos.atLeastOnce,
      builder.payload!,
      retain: true,
    );
    debugPrint('[MQTT] Published status: $status to $topic');
  }

  // --- PUBLIC API ---

  /// Updates the rider's status (Online, Offline, Idle)
  void updateStatus(String status) {
    _publishStatus(status);
  }

  /// Updates the rider's profile (name, context, tokens etc.)
  void publishProfile(Map<String, dynamic> profileData) {
    if (!_isConnected || _currentRiderId == null) return;

    final topic = MqttConstants.topicRiderProfile.replaceAll(
      '{riderId}',
      _currentRiderId!,
    );
    final builder = MqttClientPayloadBuilder();
    builder.addString(jsonEncode(profileData));

    _client!.publishMessage(
      topic,
      MqttQos.atLeastOnce,
      builder.payload!,
      retain: true,
    );
    debugPrint('[MQTT] Published profile to $topic');
  }

  /// Publishes location data
  void publishLocation(Map<String, dynamic> locationData) {
    if (!_isConnected || _currentRiderId == null) return;

    final topic = MqttConstants.topicRiderLocation.replaceAll(
      '{riderId}',
      _currentRiderId!,
    );
    final builder = MqttClientPayloadBuilder();
    builder.addString(jsonEncode(locationData));

    _client!.publishMessage(topic, MqttQos.atMostOnce, builder.payload!);
    // Avoid excessive logging for high-frequency location updates
  }

  /// Publishes telemetry data (Battery, GPS Signal, Rider Logs etc.)
  void publishTelemetry(Map<String, dynamic> telemetryData) {
    if (!_isConnected || _currentRiderId == null) return;

    final topic = MqttConstants.topicRiderTelemetry.replaceAll(
      '{riderId}',
      _currentRiderId!,
    );
    final builder = MqttClientPayloadBuilder();
    builder.addString(jsonEncode(telemetryData));

    _client!.publishMessage(topic, MqttQos.atLeastOnce, builder.payload!);
    debugPrint('[MQTT] Published telemetry data.');
  }

  /// Publishes arbitrary logs or events
  void publishLog(String eventName, Map<String, dynamic> data) {
    if (!_isConnected || _currentRiderId == null) return;

    final topic =
        '${MqttConstants.topicRiderLogs.replaceAll('{riderId}', _currentRiderId!)}/$eventName';
    final builder = MqttClientPayloadBuilder();
    builder.addString(jsonEncode(data));

    _client!.publishMessage(topic, MqttQos.atLeastOnce, builder.payload!);
    debugPrint('[MQTT] Published log: $eventName');
  }

  /// Generic publish to doormile/riders/{id}/{subTopic}
  void publish(String subTopic, dynamic data) {
    if (!_isConnected || _currentRiderId == null) return;

    final topic = 'doormile/riders/$_currentRiderId/$subTopic';
    final builder = MqttClientPayloadBuilder();
    if (data is String) {
      builder.addString(data);
    } else {
      builder.addString(jsonEncode(data));
    }

    _client!.publishMessage(topic, MqttQos.atLeastOnce, builder.payload!);
    debugPrint('[MQTT] Published to $topic');
  }
}