import 'dart:async';
import 'dart:math' as math;
import 'package:flutter/foundation.dart';
import 'package:flutter/services.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:flutter_tts/flutter_tts.dart';
import 'package:geolocator/geolocator.dart';
import 'package:rxdart/rxdart.dart';
import '../location_service.dart';
import '../sensor_fusion_service.dart';
import '../map/map_provider_interface.dart';
import '../navigation/navigation_session_service.dart';
import 'road_alert_models.dart';
import 'road_alert_providers.dart';
import 'road_alert_compliance.dart';
import 'multi_source_alert_deduplicator.dart';

import '../field_test/field_test_logger.dart';
import '../../models/field_test_event.dart';

final leanStreamOverrideProvider = Provider<Stream<double>?>((ref) => null);

final roadAlertServiceProvider = Provider<RoadAlertService>((ref) {
  final customLeanStream = ref.watch(leanStreamOverrideProvider);
  final service = RoadAlertService(ref, leanStream: customLeanStream);
  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;
  final _alertsController = BehaviorSubject<List<RoadAlert>>.seeded([]);

  StreamSubscription<Position>? _locationSub;
  StreamSubscription<double>? _leanSub;

  DateTime? _lastFetchTime;
  Position? _lastFetchPosition;
  Position? _lastObservedPosition;
  bool _isFetching = false; // Request serialization lock
  DateTime? _lastSpeechTime; // Audio cooldown timer

  double _currentLeanAngle = 0.0;
  DateTime? _lastSteepLeanTime;
  RoadAlert? _deferredAudioAlert;

  List<RoadAlert> _cachedAlerts = [];
  final Set<String> _announcedAlertIds = {};
  final Set<String> _dismissedAlertIds = {};
  Timer? _cleanupTimer;

  Stream<List<RoadAlert>> get alertsStream => _alertsController.stream;
  double get currentLeanAngle => _currentLeanAngle;
  bool get isCornering =>
      _currentLeanAngle > 15.0 ||
      (_lastSteepLeanTime != null &&
          DateTime.now().difference(_lastSteepLeanTime!).inMilliseconds < 1500);
  RoadAlert? get deferredAudioAlert => _deferredAudioAlert;

  RoadAlertService(this._ref, {FlutterTts? tts, Stream<double>? leanStream})
      : _tts = tts ?? FlutterTts() {
    _initTts();
    _startListening(leanStream: leanStream);
    _cleanupTimer = Timer.periodic(const Duration(seconds: 2), (_) {
      _pruneExpiredAlerts();
    });
  }

  void _initTts() {
    try {
      _tts.setLanguage("en-US").catchError((_) => null);
      _tts.setSpeechRate(0.5).catchError((_) => null);
      _tts.setVolume(1.0).catchError((_) => null);
    } catch (e) {
      if (kDebugMode) {
        debugPrint('[RoadAlerts] TTS init warning: $e');
      }
    }
  }

  void _startListening({Stream<double>? leanStream}) {
    if (kDebugMode) {
      debugPrint('[RoadAlerts] Service initialized');
    }
    _locationSub = _ref.read(locationServiceProvider).getFilteredPositionStream().listen((position) {
      _processPosition(position);
    });

    final stream = leanStream ?? (() {
      try {
        return _ref.read(sensorFusionServiceProvider).leanAngleStream;
      } catch (e) {
        if (kDebugMode) {
          debugPrint('[RoadAlerts] Sensor fusion not available: $e');
        }
        return null;
      }
    })();

    if (stream != null) {
      _leanSub = stream.listen(
        (lean) {
          _processLean(lean);
        },
        onError: (err) {
          if (kDebugMode) {
            debugPrint('[RoadAlerts] Lean stream error: $err');
          }
        },
      );
    }
  }

  void _processLean(double lean) {
    _currentLeanAngle = lean.abs();
    final now = DateTime.now();

    if (_currentLeanAngle > 15.0) {
      _lastSteepLeanTime = now;
    } else if (_currentLeanAngle < 10.0) {
      final isUpright = _lastSteepLeanTime == null ||
          now.difference(_lastSteepLeanTime!).inMilliseconds >= 1500;

      if (isUpright && _deferredAudioAlert != null) {
        final alert = _deferredAudioAlert!;
        _deferredAudioAlert = null;

        final pos = _lastObservedPosition;
        if (pos != null) {
          final dist = Geolocator.distanceBetween(
            pos.latitude,
            pos.longitude,
            alert.latitude,
            alert.longitude,
          );
          final isAhead = _isAlertAheadOfRider(pos, alert);
          if (dist <= 400.0 && isAhead) {
            _lastSpeechTime = now;
            _announceAlertAudio(alert);
          }
        }
      }
    }
  }

  Future<void> _processPosition(Position position) async {
    _lastObservedPosition = position;
    final isEnabled = _ref.read(roadAlertsEnabledProvider);
    if (!isEnabled) {
      if (_cachedAlerts.isNotEmpty) {
        _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);
    final hereApiKey = _ref.read(hereApiKeyProvider);
    final wazeApiKey = _ref.read(wazeApiKeyProvider);
    final complianceEnabled = _ref.read(jurisdictionComplianceEnabledProvider);
    final leanInterlockEnabled = _ref.read(leanInterlockEnabledProvider);

    // Request serialization check: prevent overlapping queries
    bool shouldFetch = false;
    if (!_isFetching) {
      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) {
      _isFetching = true;
      _lastFetchTime = now;
      _lastFetchPosition = position;
      try {
        await _fetchAlertsFromProviders(
          position.latitude,
          position.longitude,
          radiusMeters,
          tomtomApiKey: tomtomApiKey,
          communityApiKey: communityApiKey,
          hereApiKey: hereApiKey,
          wazeApiKey: wazeApiKey,
        );
      } finally {
        _isFetching = false;
      }
    }

    // Process cached alerts & filter out expired ones
    final List<RoadAlert> inRangeAlerts = [];
    for (var alert in _cachedAlerts) {
      if (alert.expiresAt != null && alert.expiresAt!.isBefore(now)) {
        continue;
      }

      if (!enabledCategories.contains(alert.category)) {
        continue;
      }

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

      if (dist <= radiusMeters * 1.5) {
        inRangeAlerts.add(alert.copyWith(distanceFromUser: dist));
      }
    }

    // Deduplicate across heterogeneous sources (Swarm, Zyla, GA511, OSM, etc.)
    final deduplicatedAlerts = MultiSourceAlertDeduplicator.deduplicate(
      inRangeAlerts,
      dismissedIds: _dismissedAlertIds,
    );

    // Apply jurisdictional regulatory compliance (US standard, France danger zone, Germany/Switzerland prohibited)
    final compliantList = RoadAlertCompliance.applyCompliance(
      deduplicatedAlerts,
      userLat: position.latitude,
      userLng: position.longitude,
      complianceEnabled: complianceEnabled,
    );

    final navSession = _ref.read(navigationSessionProvider);
    final hasActiveRoute = navSession.isNavigating &&
        navSession.calculationResult != null &&
        navSession.calculationResult!.geometry.length >= 2;

    compliantList.sort((a, b) {
      if (hasActiveRoute) {
        final geom = navSession.calculationResult!.geometry;
        final aOnRoute = RouteCorridorAlertFilter.isAlertAheadOnRoute(
          userLat: position.latitude,
          userLng: position.longitude,
          alertLat: a.latitude,
          alertLng: a.longitude,
          geometry: geom,
        );
        final bOnRoute = RouteCorridorAlertFilter.isAlertAheadOnRoute(
          userLat: position.latitude,
          userLng: position.longitude,
          alertLat: b.latitude,
          alertLng: b.longitude,
          geometry: geom,
        );
        if (aOnRoute && !bOnRoute) return -1;
        if (!aOnRoute && bOnRoute) return 1;
      }
      return (a.distanceFromUser ?? 0).compareTo(b.distanceFromUser ?? 0);
    });

    _cachedAlerts = compliantList;
    _alertsController.add(compliantList);

    // Approach Audio Warning with lean-angle cornering safety interlock and speech cooldown
    for (var updatedAlert in compliantList) {
      final key = '${updatedAlert.providerId}_${updatedAlert.id}';
      final dist = updatedAlert.distanceFromUser ?? 999999.0;
      if (audioEnabled && dist <= 400.0 && !_announcedAlertIds.contains(key)) {
        final isAhead = _isAlertAheadOfRider(position, updatedAlert);
        if (isAhead) {
          final isCornering = _currentLeanAngle > 15.0 ||
              (_lastSteepLeanTime != null &&
                  now.difference(_lastSteepLeanTime!).inMilliseconds < 1500);

          if (leanInterlockEnabled && isCornering) {
            _deferredAudioAlert = updatedAlert;
            _announcedAlertIds.add(key);
            try {
              _ref.read(fieldTestLoggerProvider).log(
                eventType: FieldTestEventType.roadAlertReceived,
                severity: EventSeverity.info,
                message: 'Alert audio deferred: cornering at ${_currentLeanAngle.toStringAsFixed(1)}° lean',
                metadata: {
                  'category': updatedAlert.category.displayName,
                  'leanAngle': _currentLeanAngle,
                  'distance': dist,
                },
              );
            } catch (_) {}
          } else {
            final speechTime = DateTime.now();
            if (_lastSpeechTime == null || speechTime.difference(_lastSpeechTime!).inSeconds >= 4) {
              _lastSpeechTime = speechTime;
              _announcedAlertIds.add(key);
              _announceAlertAudio(updatedAlert);
            }
          }
        }
      }
    }
  }

  bool _isAlertAheadOfRider(Position userPos, RoadAlert alert) {
    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;

    return delta <= 100.0;
  }

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

    if (kDebugMode) {
      debugPrint('[RoadAlerts] Fetching alerts from ${providers.length} providers...');
    }

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

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

        try {
          for (var a in fetched) {
            _ref.read(fieldTestLoggerProvider).log(
              eventType: FieldTestEventType.roadAlertReceived,
              severity: EventSeverity.info,
              message: '[${provider.id}] ${a.category.displayName}: ${a.description}',
              metadata: {
                'providerId': provider.id,
                'category': a.category.displayName,
                'distanceMeters': a.distanceFromUser,
              },
            );
          }
        } catch (_) {}
      } catch (e) {
        if (kDebugMode) {
          debugPrint('[RoadAlerts] Provider ${provider.id} error: $e');
        }
        try {
          _ref.read(fieldTestLoggerProvider).log(
            eventType: FieldTestEventType.networkError,
            severity: EventSeverity.warning,
            message: 'Road alert provider ${provider.id} failure: $e',
          );
        } catch (_) {}
      }
    }

    _cachedAlerts = newAlerts;
    if (kDebugMode) {
      debugPrint('[RoadAlerts] Active cached alerts count: ${_cachedAlerts.length}');
    }
  }

  void _announceAlertAudio(RoadAlert alert) {
    final audioMode = _ref.read(roadAlertAudioModeProvider);
    if (audioMode == RoadAlertAudioMode.tacticalTone) {
      _playTacticalTone(alert);
      return;
    }

    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.pothole:
        phrase = "Severe pothole ahead.";
        break;
      case RoadAlertCategory.debris:
        phrase = "Road debris ahead.";
        break;
      case RoadAlertCategory.disabledVehicle:
        phrase = "Disabled vehicle reported ahead.";
        break;
      case RoadAlertCategory.weatherHazard:
        phrase = "Weather hazard reported ahead.";
        break;
      case RoadAlertCategory.other:
        phrase = "Traffic alert ahead.";
        break;
    }

    if (kDebugMode) {
      debugPrint('[RoadAlerts] Announcing audio alert: $phrase');
    }

    try {
      _tts.speak(phrase).catchError((e) {
        if (kDebugMode) {
          debugPrint('[RoadAlerts] TTS speak error: $e');
        }
        return null;
      });
      _ref.read(fieldTestLoggerProvider).log(
        eventType: FieldTestEventType.ttsAnnounced,
        severity: EventSeverity.info,
        message: 'TTS Announced: "$phrase"',
      );
    } catch (e) {
      if (kDebugMode) {
        debugPrint('[RoadAlerts] TTS speak error: $e');
      }
      _ref.read(fieldTestLoggerProvider).log(
        eventType: FieldTestEventType.audioFailure,
        severity: EventSeverity.warning,
        message: 'TTS error speaking "$phrase": $e',
      );
    }
  }

  void _playTacticalTone(RoadAlert alert) {
    if (kDebugMode) {
      debugPrint('[RoadAlerts] Playing tactical tone chirp for ${alert.category.displayName}');
    }
    try {
      SystemSound.play(SystemSoundType.alert);
      if (alert.category == RoadAlertCategory.police ||
          alert.severity == RoadAlertSeverity.high ||
          alert.severity == RoadAlertSeverity.critical) {
        Future.delayed(const Duration(milliseconds: 140), () {
          SystemSound.play(SystemSoundType.alert);
        });
      }
      _ref.read(fieldTestLoggerProvider).log(
        eventType: FieldTestEventType.ttsAnnounced,
        severity: EventSeverity.info,
        message: 'Tactical tone chirp played for ${alert.category.displayName}',
        metadata: {
          'category': alert.category.displayName,
          'severity': alert.severity.name,
          'distance': alert.distanceFromUser,
        },
      );
    } catch (e) {
      if (kDebugMode) {
        debugPrint('[RoadAlerts] Tactical tone error: $e');
      }
    }
  }

  void triggerTestAlert({RoadAlertCategory category = RoadAlertCategory.police}) {
    final now = DateTime.now();
    final pos = _lastFetchPosition;
    
    // 150 meters ahead of current location
    final lat = pos != null ? pos.latitude + 0.0012 : 34.0620;
    final lng = pos != null ? pos.longitude + 0.0008 : -85.2330;

    final testAlert = RoadAlert(
      id: 'test_alert_${now.millisecondsSinceEpoch}',
      providerId: 'diagnostic_test',
      category: category,
      latitude: lat,
      longitude: lng,
      description: 'TEST ALERT: ${category.displayName} reported ahead (Diagnostic Verification)',
      roadName: 'Test Way / Simulation',
      reportedAt: now,
      expiresAt: now.add(const Duration(seconds: 12)),
      lastUpdated: now,
      distanceFromUser: 150.0,
      source: 'Internal Pipeline Test',
      sourceType: RoadAlertSourceType.providerReported,
    );

    if (kDebugMode) {
      debugPrint('[RoadAlerts] [TEST ALERT] Injected: ${testAlert.description}');
    }

    _cachedAlerts = [testAlert, ..._cachedAlerts.where((a) => !a.id.startsWith('test_alert_'))];
    _alertsController.add(_cachedAlerts);

    final phrase = "TEST ALERT: ${category.displayName} reported ahead.";
    try {
      _tts.speak(phrase).catchError((_) => null);
      _ref.read(fieldTestLoggerProvider).log(
        eventType: FieldTestEventType.ttsAnnounced,
        severity: EventSeverity.info,
        message: 'TTS Test Alert: "$phrase"',
      );
    } catch (e) {
      if (kDebugMode) {
        debugPrint('[RoadAlerts] TTS speak error for test alert: $e');
      }
    }
  }

  /// Dismisses a specific alert by ID and prevents it from re-appearing
  void dismissAlert(String alertId) {
    _dismissedAlertIds.add(alertId);
    _cachedAlerts = _cachedAlerts.where((a) => a.id != alertId && '${a.providerId}_${a.id}' != alertId).toList();
    _alertsController.add(_cachedAlerts);
    if (kDebugMode) {
      debugPrint('[RoadAlerts] Manually dismissed alert $alertId');
    }
  }

  /// Clears all cached alerts immediately
  void clearAllAlerts() {
    _cachedAlerts = [];
    _alertsController.add([]);
    if (kDebugMode) {
      debugPrint('[RoadAlerts] Cleared all cached alerts');
    }
  }

  /// Periodically prunes expired or dismissed alerts even when stationary
  void _pruneExpiredAlerts() {
    if (_cachedAlerts.isEmpty) return;
    final now = DateTime.now();
    final initialCount = _cachedAlerts.length;

    _cachedAlerts = _cachedAlerts.where((alert) {
      final key = '${alert.providerId}_${alert.id}';
      if (_dismissedAlertIds.contains(alert.id) || _dismissedAlertIds.contains(key)) {
        return false;
      }
      if (alert.expiresAt != null && alert.expiresAt!.isBefore(now)) {
        return false;
      }
      return true;
    }).toList();

    if (_cachedAlerts.length != initialCount) {
      if (kDebugMode) {
        debugPrint('[RoadAlerts] Pruned expired/dismissed alerts (remaining: ${_cachedAlerts.length})');
      }
      _alertsController.add(_cachedAlerts);
    }
  }

  void simulateAlert(RoadAlert alert) {
    if (!_ref.read(roadAlertsEnabledProvider)) return;
    final now = DateTime.now();
    final key = '${alert.providerId}_${alert.id}';
    if ((alert.expiresAt != null && alert.expiresAt!.isBefore(now)) ||
        _dismissedAlertIds.contains(alert.id) ||
        _dismissedAlertIds.contains(key)) {
      return;
    }
    _cachedAlerts = [
      alert,
      ..._cachedAlerts.where(
        (existing) =>
            existing.id != alert.id || existing.providerId != alert.providerId,
      ),
    ];
    _alertsController.add(_cachedAlerts);
    if (_ref.read(audioAlertsEnabledProvider)) {
      final leanInterlock = _ref.read(leanInterlockEnabledProvider);
      if (leanInterlock && isCornering) {
        _deferredAudioAlert = alert;
      } else {
        _announceAlertAudio(alert);
      }
    }
  }

  void dispose() {
    if (kDebugMode) {
      debugPrint('[RoadAlerts] Disposing service resources');
    }
    _cleanupTimer?.cancel();
    _locationSub?.cancel();
    _leanSub?.cancel();
    _alertsController.close();
    try {
      _tts.stop().catchError((_) => null);
    } catch (_) {}
  }
}

/// Helper to evaluate route corridor proximity and ahead-of-rider geometry.
class RouteCorridorAlertFilter {
  /// Computes minimum cross-track perpendicular distance in meters from point to route polyline.
  static double minDistanceToPolyline(
    double alertLat,
    double alertLng,
    List<AppLatLng> geometry,
  ) {
    if (geometry.isEmpty) return double.infinity;
    if (geometry.length == 1) {
      return Geolocator.distanceBetween(
        alertLat,
        alertLng,
        geometry.first.latitude,
        geometry.first.longitude,
      );
    }

    double minDistance = double.infinity;
    final cosLat = math.cos(alertLat * math.pi / 180.0);

    for (int i = 0; i < geometry.length - 1; i++) {
      final p1 = geometry[i];
      final p2 = geometry[i + 1];

      final dx = (p2.longitude - p1.longitude) * 111320.0 * cosLat;
      final dy = (p2.latitude - p1.latitude) * 111320.0;
      final segLengthSq = dx * dx + dy * dy;

      final ax = (alertLng - p1.longitude) * 111320.0 * cosLat;
      final ay = (alertLat - p1.latitude) * 111320.0;

      if (segLengthSq == 0.0) {
        final dist = math.sqrt(ax * ax + ay * ay);
        if (dist < minDistance) minDistance = dist;
        continue;
      }

      final t = ((ax * dx + ay * dy) / segLengthSq).clamp(0.0, 1.0);
      final projX = t * dx;
      final projY = t * dy;

      final dist = math.sqrt((ax - projX) * (ax - projX) + (ay - projY) * (ay - projY));
      if (dist < minDistance) {
        minDistance = dist;
      }
    }
    return minDistance;
  }

  /// Evaluates whether an alert is along and ahead of the user's active route corridor.
  static bool isAlertAheadOnRoute({
    required double userLat,
    required double userLng,
    required double alertLat,
    required double alertLng,
    required List<AppLatLng> geometry,
    double maxCrossTrackMeters = 80.0,
    double maxAheadMeters = 1200.0,
  }) {
    if (geometry.length < 2) return false;

    final crossTrack = minDistanceToPolyline(alertLat, alertLng, geometry);
    if (crossTrack > maxCrossTrackMeters) return false;

    int userSeg = 0;
    double minUserDist = double.infinity;
    int alertSeg = 0;
    double minAlertDist = double.infinity;

    for (int i = 0; i < geometry.length; i++) {
      final du = Geolocator.distanceBetween(userLat, userLng, geometry[i].latitude, geometry[i].longitude);
      if (du < minUserDist) {
        minUserDist = du;
        userSeg = i;
      }
      final da = Geolocator.distanceBetween(alertLat, alertLng, geometry[i].latitude, geometry[i].longitude);
      if (da < minAlertDist) {
        minAlertDist = da;
        alertSeg = i;
      }
    }

    if (alertSeg < userSeg) return false;

    final directDist = Geolocator.distanceBetween(userLat, userLng, alertLat, alertLng);
    return directDist <= maxAheadMeters;
  }
}