import 'dart:async';
import 'dart:math' as math;
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:flutter_tts/flutter_tts.dart';
import 'package:geolocator/geolocator.dart';
import '../location_service.dart';
import 'road_alert_models.dart';
import 'road_alert_providers.dart';

final roadAlertServiceProvider = Provider<RoadAlertService>((ref) {
  final service = RoadAlertService(ref);
  ref.onDispose(() => service.dispose());
  return service;
});

final activeAlertsStreamProvider = StreamProvider<List<RoadAlert>>((ref) {
  return ref.watch(roadAlertServiceProvider).alertsStream;
});

class RoadAlertService {
  final Ref _ref;
  final FlutterTts _tts = FlutterTts();
  final _alertsController = StreamController<List<RoadAlert>>.broadcast();

  StreamSubscription<Position>? _locationSub;

  DateTime? _lastFetchTime;
  Position? _lastFetchPosition;
  List<RoadAlert> _cachedAlerts = [];
  final Set<String> _announcedAlertIds = {};

  Stream<List<RoadAlert>> get alertsStream => _alertsController.stream;

  RoadAlertService(this._ref) {
    _initTts();
    _startListening();
  }

  void _initTts() {
    _tts.setLanguage("en-US");
    _tts.setSpeechRate(0.5);
    _tts.setVolume(1.0);
  }

  void _startListening() {
    _locationSub = _ref.read(locationServiceProvider).getFilteredPositionStream().listen((position) {
      _processPosition(position);
    });
  }

  Future<void> _processPosition(Position position) async {
    final isEnabled = _ref.read(roadAlertsEnabledProvider);
    if (!isEnabled) {
      _cachedAlerts = [];
      _alertsController.add([]);
      return;
    }

    final now = DateTime.now();
    final radiusMeters = _ref.read(alertRadiusMetersProvider);
    final audioEnabled = _ref.read(audioAlertsEnabledProvider);
    final enabledCategories = _ref.read(enabledCategoriesProvider);
    final tomtomApiKey = _ref.read(tomtomApiKeyProvider);
    final communityApiKey = _ref.read(communityApiKeyProvider);

    // Throttle fetches: query every 45s OR when moved > 500m
    bool shouldFetch = false;
    if (_lastFetchTime == null || now.difference(_lastFetchTime!).inSeconds >= 45) {
      shouldFetch = true;
    } else if (_lastFetchPosition != null) {
      final dist = Geolocator.distanceBetween(
        _lastFetchPosition!.latitude,
        _lastFetchPosition!.longitude,
        position.latitude,
        position.longitude,
      );
      if (dist > 500.0) {
        shouldFetch = true;
      }
    }

    if (shouldFetch) {
      _lastFetchTime = now;
      _lastFetchPosition = position;
      await _fetchAlertsFromProviders(
        position.latitude,
        position.longitude,
        radiusMeters,
        tomtomApiKey: tomtomApiKey,
        communityApiKey: communityApiKey,
      );
    }

    final Map<String, RoadAlert> deduplicated = {};
    for (var alert in _cachedAlerts) {
      // Expiration check
      if (alert.expiresAt != null && alert.expiresAt!.isBefore(now)) {
        continue;
      }

      // Category toggle check
      if (!enabledCategories.contains(alert.category)) {
        continue;
      }

      final dist = Geolocator.distanceBetween(
        position.latitude,
        position.longitude,
        alert.latitude,
        alert.longitude,
      );

      if (dist <= radiusMeters * 1.5) {
        final updatedAlert = alert.copyWith(distanceFromUser: dist);
        final key = '${alert.providerId}_${alert.id}';
        deduplicated[key] = updatedAlert;

        // Approach Audio Warning: check distance (< 400m), cooldown, and direction relevance
        if (audioEnabled && dist <= 400.0 && !_announcedAlertIds.contains(key)) {
          final isAhead = _isAlertAheadOfRider(position, alert);
          if (isAhead) {
            _announcedAlertIds.add(key);
            _announceAlertAudio(updatedAlert);
          }
        }
      }
    }

    final resultList = deduplicated.values.toList()
      ..sort((a, b) => (a.distanceFromUser ?? 0).compareTo(b.distanceFromUser ?? 0));

    _cachedAlerts = resultList;
    _alertsController.add(resultList);
  }

  bool _isAlertAheadOfRider(Position userPos, RoadAlert alert) {
    // If rider speed < 2.0 m/s (standing still), assume alert is relevant
    if (userPos.speed < 2.0) return true;

    final riderHeading = userPos.heading;
    final bearingToAlert = Geolocator.bearingBetween(
      userPos.latitude,
      userPos.longitude,
      alert.latitude,
      alert.longitude,
    );

    double delta = (bearingToAlert - riderHeading).abs();
    if (delta > 180) delta = 360 - delta;

    // Relevant if alert is within ±100 degrees of rider's heading (in front or side)
    return delta <= 100.0;
  }

  Future<void> _fetchAlertsFromProviders(
    double lat,
    double lng,
    double radiusMeters, {
    required String tomtomApiKey,
    required String communityApiKey,
  }) async {
    final providers = _ref.read(activeRoadAlertProviders);
    final List<RoadAlert> newAlerts = [];

    for (var provider in providers) {
      try {
        String? key;
        if (provider.id == 'tomtom') key = tomtomApiKey;
        if (provider.id == 'community_traffic') key = communityApiKey;

        final fetched = await provider.getAlerts(
          latitude: lat,
          longitude: lng,
          radiusMeters: radiusMeters,
          apiKey: key,
        );
        newAlerts.addAll(fetched);
      } catch (_) {}
    }

    _cachedAlerts = newAlerts;
  }

  void _announceAlertAudio(RoadAlert alert) {
    String phrase;
    switch (alert.category) {
      case RoadAlertCategory.police:
        phrase = "Police report ahead.";
        break;
      case RoadAlertCategory.speedCamera:
        phrase = "Speed camera reported ahead.";
        break;
      case RoadAlertCategory.accident:
        phrase = "Accident reported ahead.";
        break;
      case RoadAlertCategory.hazard:
        phrase = "Road hazard ahead.";
        break;
      case RoadAlertCategory.roadClosure:
        phrase = "Road closure ahead.";
        break;
      case RoadAlertCategory.construction:
        phrase = "Construction zone ahead.";
        break;
      case RoadAlertCategory.traffic:
        phrase = "Traffic delay ahead.";
        break;
      case RoadAlertCategory.other:
        phrase = "Traffic alert ahead.";
        break;
    }
    _tts.speak(phrase);
  }

  void dispose() {
    _locationSub?.cancel();
    _alertsController.close();
    _tts.stop();
  }
}