import 'package:flutter/foundation.dart';
import 'dart:async';
import 'dart:convert';
import 'package:http/http.dart' as http;
import 'package:firebase_auth/firebase_auth.dart';
import '../map/map_provider_interface.dart';
import 'route_models.dart';
import 'route_provider.dart';
import 'valhalla_polyline_decoder.dart';

/// Provider integrating with the MotorSignal Node.js routing and places relay.
class ValhallaRouteProvider implements RouteProvider {
  final String backendUrl;
  final http.Client _client;
  final Future<String?> Function()? tokenProvider;

  ValhallaRouteProvider({
    String? backendUrl,
    http.Client? client,
    this.tokenProvider,
  })  : _client = client ?? http.Client(),
        backendUrl = backendUrl ?? _getEffectiveBackendUrl();

  static String _getEffectiveBackendUrl() {
    const definedUrl = String.fromEnvironment('MOTORSIGNAL_API_BASE_URL');
    if (definedUrl.isNotEmpty) {
      return definedUrl;
    }
    if (kReleaseMode) {
      throw StateError('MOTORSIGNAL_API_BASE_URL is not configured for production build.');
    }
    return 'http://10.0.2.2:3000';
  }

  @override
  String get name => 'Stadia Maps (Valhalla)';

  Future<Map<String, String>> _getAuthHeaders() async {
    String? token;
    final customTokenProvider = tokenProvider;
    if (customTokenProvider != null) {
      token = await customTokenProvider();
    } else {
      final user = FirebaseAuth.instance.currentUser;
      if (user == null) {
        throw RouteProviderException(
          'authenticationRequired',
          'User must be authenticated (or signed in as guest) to use cloud routing.',
        );
      }
      try {
        token = await user.getIdToken();
      } catch (e) {
        throw RouteProviderException(
          'authenticationRequired',
          'Failed to acquire authentication token: $e',
        );
      }
    }

    if (token == null || token.isEmpty) {
      throw RouteProviderException(
        'authenticationRequired',
        'User must be authenticated to use cloud routing.',
      );
    }

    return {
      'Authorization': 'Bearer $token',
      'Content-Type': 'application/json',
    };
  }

  void _handleHttpError(http.Response response) {
    if (response.statusCode >= 200 && response.statusCode < 300) return;

    String code = 'providerError';
    String msg = 'An unexpected provider error occurred.';

    try {
      final body = jsonDecode(response.body);
      if (body is Map<String, dynamic>) {
        code = body['error']?.toString() ?? code;
        msg = body['message']?.toString() ?? msg;
      }
    } catch (_) {}

    throw RouteProviderException(code, msg);
  }

  @override
  Future<List<PlaceSearchResult>> searchPlaces(
    String query, {
    AppLatLng? nearLocation,
  }) async {
    final clean = query.trim();
    if (clean.length < 2) return const [];

    final headers = await _getAuthHeaders();

    try {
      final queryParams = <String, String>{
        'query': clean,
      };
      if (nearLocation != null) {
        queryParams['lat'] = nearLocation.latitude.toString();
        queryParams['lng'] = nearLocation.longitude.toString();
      }

      final uri = Uri.parse('$backendUrl/api/places/search')
          .replace(queryParameters: queryParams);

      final response = await _client
          .get(uri, headers: headers)
          .timeout(const Duration(seconds: 8));

      _handleHttpError(response);

      final data = jsonDecode(response.body);
      if (data is! Map<String, dynamic>) return const [];

      final results = data['results'] as List<dynamic>? ?? [];
      final attribution = data['attribution'] as String?;

      return results.whereType<Map<String, dynamic>>().map((r) {
        final lat = (r['latitude'] as num?)?.toDouble();
        final lng = (r['longitude'] as num?)?.toDouble();
        return PlaceSearchResult(
          providerId: r['providerId']?.toString() ?? '',
          primaryText: r['primaryText']?.toString() ?? '',
          secondaryText: r['secondaryText']?.toString() ?? '',
          latitude: lat,
          longitude: lng,
          formattedAddress: r['formattedAddress']?.toString(),
          attribution: attribution,
        );
      }).toList();
    } on TimeoutException {
      throw RouteProviderException(
        'providerTimeout',
        'Place search timed out.',
      );
    } catch (e) {
      if (e is RouteProviderException) rethrow;
      throw RouteProviderException(
        'placeSearchUnavailable',
        'Failed to reach places service: $e',
      );
    }
  }

  @override
  Future<ResolvedPlace> resolvePlace(String placeId) async {
    final cleanId = placeId.trim();
    if (cleanId.isEmpty) {
      throw RouteProviderException(
        'invalidRequest',
        'Place ID cannot be empty.',
      );
    }

    final headers = await _getAuthHeaders();

    try {
      final uri = Uri.parse('$backendUrl/api/places/resolve')
          .replace(queryParameters: {'placeId': cleanId});

      final response = await _client
          .get(uri, headers: headers)
          .timeout(const Duration(seconds: 8));

      _handleHttpError(response);

      final data = jsonDecode(response.body);
      if (data is! Map<String, dynamic>) {
        throw RouteProviderException(
          'placeNotFound',
          'Invalid response from place resolution.',
        );
      }

      return ResolvedPlace(
        providerId: data['providerId']?.toString() ?? cleanId,
        displayName: data['displayName']?.toString() ?? 'Unknown Place',
        formattedAddress: data['formattedAddress']?.toString(),
        latitude: (data['latitude'] as num).toDouble(),
        longitude: (data['longitude'] as num).toDouble(),
        attribution: data['attribution']?.toString(),
      );
    } on TimeoutException {
      throw RouteProviderException(
        'providerTimeout',
        'Place resolution timed out.',
      );
    } catch (e) {
      if (e is RouteProviderException) rethrow;
      throw RouteProviderException(
        'placeSearchUnavailable',
        'Failed to resolve place: $e',
      );
    }
  }

  @override
  Future<RouteCalculationResult> calculateRoute(
    List<RouteStop> stops, {
    bool avoidHighways = false,
    bool avoidTolls = false,
    bool avoidFerries = false,
  }) async {
    final ordered = List<RouteStop>.from(stops);
    ordered.sort((a, b) => a.order.compareTo(b.order));

    if (ordered.length < 2) {
      throw RouteProviderException(
        'invalidRequest',
        'At least 2 stops are required to calculate a route.',
      );
    }
    if (ordered.length > 25) {
      throw RouteProviderException(
        'invalidRequest',
        'A maximum of 25 stops is allowed.',
      );
    }

    final headers = await _getAuthHeaders();

    final locations = ordered
        .map((s) => {
              'lat': s.latitude,
              'lon': s.longitude,
              'type': 'break',
            })
        .toList();

    try {
      final uri = Uri.parse('$backendUrl/api/routes/calculate');
      final response = await _client
          .post(
            uri,
            headers: headers,
            body: jsonEncode({
              'locations': locations,
              'options': {
                'avoid_highways': avoidHighways,
                'avoid_tolls': avoidTolls,
                'avoid_ferries': avoidFerries,
              }
            }),
          )
          .timeout(const Duration(seconds: 15));

      _handleHttpError(response);

      final data = jsonDecode(response.body);
      if (data is! Map<String, dynamic>) {
        throw RouteProviderException(
          'routeUnavailable',
          'Malformed response from route calculation.',
        );
      }

      final encodedPolyline = data['encodedPolyline'] as String? ?? '';
      final distanceMeters =
          (data['distanceMeters'] as num?)?.toDouble() ?? 0.0;
      final durationSeconds =
          (data['durationSeconds'] as num?)?.toInt();
      final warningsRaw = data['warnings'] as List<dynamic>? ?? [];

      final geometry = ValhallaPolylineDecoder.decode(encodedPolyline);
      final straightLineDist =
          MotorSignalRoute.calculateTotalDistanceMeters(ordered);

      return RouteCalculationResult(
        straightLineDistanceMeters: straightLineDist,
        estimatedDistanceMeters: distanceMeters,
        estimatedDurationSeconds: durationSeconds,
        geometry: geometry,
        isStraightLine: false,
        providerName: name,
        warnings: warningsRaw.map((e) => e.toString()).toList(),
      );
    } on TimeoutException {
      throw RouteProviderException(
        'providerTimeout',
        'Route calculation timed out.',
      );
    } catch (e) {
      if (e is RouteProviderException) rethrow;
      throw RouteProviderException(
        'routeUnavailable',
        'Failed to calculate route: $e',
      );
    }
  }
}