import 'dart:async';
import 'dart:convert';
import 'package:flutter/foundation.dart';
import 'package:get/get.dart';
import 'package:connectivity_plus/connectivity_plus.dart';
import 'package:flutter_secure_storage/flutter_secure_storage.dart';
import 'package:http/http.dart' as http;
import '../models/workout.dart';
import '../utils/hmac_utility.dart';
import 'database_service.dart';

/// محرك المزامنة التلقائي
/// يراقب الاتصال بالإنترنت ويرسل التمارين المحفوظة محلياً عند توفر الشبكة
class SyncService extends GetxService {
  final DatabaseService _db = Get.find<DatabaseService>();
  final _storage = const FlutterSecureStorage();
  final _connectivity = Connectivity();

  StreamSubscription? _connectivitySub;
  Timer? _syncTimer;

  final _isSyncing = false.obs;
  final _isOnline = false.obs;
  final _pendingCount = 0.obs;

  bool get isSyncing => _isSyncing.value;
  bool get isOnline => _isOnline.value;
  int get pendingCount => _pendingCount.value;

  static const String _apiEndpointKey = 'api_endpoint';
  static const String _apiKeyKey = 'api_key';
  static const String _apiSecretKey = 'api_secret';

  @override
  Future<void> onInit() async {
    super.onInit();
    await _checkConnectivity();
    _startConnectivityMonitor();
    _startPeriodicSync();
    await _updatePendingCount();
  }

  // ─── Connectivity Monitoring ──────────────────────────────────

  Future<void> _checkConnectivity() async {
    final results = await _connectivity.checkConnectivity();
    _isOnline.value = !results.contains(ConnectivityResult.none);
  }

  void _startConnectivityMonitor() {
    _connectivitySub = _connectivity.onConnectivityChanged.listen(
      (List<ConnectivityResult> results) {
        final wasOffline = !_isOnline.value;
        _isOnline.value = !results.contains(ConnectivityResult.none);

        // Came back online → trigger sync
        if (wasOffline && _isOnline.value) {
          debugPrint('[SYNC] Back online — triggering sync');
          syncPendingWorkouts();
        }
      },
    );
  }

  void _startPeriodicSync() {
    // Check for pending syncs every 2 minutes
    _syncTimer = Timer.periodic(
      const Duration(minutes: 2),
      (_) {
        if (_isOnline.value && !_isSyncing.value) {
          syncPendingWorkouts();
        }
      },
    );
  }

  // ─── Credentials Management ───────────────────────────────────

  Future<void> saveCredentials({
    required String apiEndpoint,
    required String apiKey,
    required String apiSecret,
  }) async {
    await _storage.write(key: _apiEndpointKey, value: apiEndpoint);
    await _storage.write(key: _apiKeyKey, value: apiKey);
    await _storage.write(key: _apiSecretKey, value: apiSecret);
  }

  Future<Map<String, String?>> getCredentials() async {
    return {
      'endpoint': await _storage.read(key: _apiEndpointKey),
      'apiKey': await _storage.read(key: _apiKeyKey),
      'apiSecret': await _storage.read(key: _apiSecretKey),
    };
  }

  Future<bool> hasCredentials() async {
    final creds = await getCredentials();
    return creds['apiKey'] != null &&
        creds['apiKey']!.isNotEmpty &&
        creds['apiSecret'] != null &&
        creds['apiSecret']!.isNotEmpty;
  }

  // ─── Sync Operations ─────────────────────────────────────────

  /// Queue a workout for sync
  Future<void> queueWorkout(Workout workout) async {
    final payload = jsonEncode(workout.toApiPayload());
    await _db.enqueueSync(workout.id, payload);
    await _updatePendingCount();

    // Try immediate sync if online
    if (_isOnline.value) {
      syncPendingWorkouts();
    }
  }

  /// Process all pending sync items
  Future<void> syncPendingWorkouts() async {
    if (_isSyncing.value) return;
    _isSyncing.value = true;

    try {
      final creds = await getCredentials();
      if (creds['endpoint'] == null || creds['apiKey'] == null ||
          creds['apiSecret'] == null) {
        debugPrint('[SYNC] No API credentials configured');
        return;
      }

      final pendingItems = await _db.getPendingSyncs();
      if (pendingItems.isEmpty) return;

      debugPrint('[SYNC] Processing ${pendingItems.length} pending items');

      for (final item in pendingItems) {
        await _syncSingleItem(
          id: item['id'] as int,
          workoutId: item['workout_id'] as String,
          payload: item['payload'] as String,
          endpoint: creds['endpoint']!,
          apiKey: creds['apiKey']!,
          apiSecret: creds['apiSecret']!,
        );
      }

      await _db.removeSentFromQueue();
      await _updatePendingCount();
    } catch (e) {
      debugPrint('[SYNC] Error during sync: $e');
    } finally {
      _isSyncing.value = false;
    }
  }

  Future<void> _syncSingleItem({
    required int id,
    required String workoutId,
    required String payload,
    required String endpoint,
    required String apiKey,
    required String apiSecret,
  }) async {
    try {
      final headers = HmacUtility.buildHeaders(
        apiKey: apiKey,
        apiSecret: apiSecret,
        payload: payload,
      );

      final response = await http
          .post(
            Uri.parse('$endpoint/api/v1/workouts'),
            headers: headers,
            body: payload,
          )
          .timeout(const Duration(seconds: 30));

      if (response.statusCode == 201) {
        await _db.updateSyncQueueItem(id, 'sent');
        await _db.updateSyncStatus(
          workoutId,
          SyncStatus.synced,
          syncedAt: DateTime.now(),
        );
        debugPrint('[SYNC] ✅ Workout $workoutId synced');
      } else {
        await _db.updateSyncQueueItem(
          id,
          'failed',
          errorMessage: 'HTTP ${response.statusCode}: ${response.body}',
        );
        debugPrint('[SYNC] ❌ Failed: ${response.statusCode}');
      }
    } catch (e) {
      await _db.updateSyncQueueItem(id, 'failed', errorMessage: e.toString());
      debugPrint('[SYNC] ❌ Error: $e');
    }
  }

  Future<void> _updatePendingCount() async {
    final items = await _db.getPendingSyncs();
    _pendingCount.value = items.length;
  }

  @override
  void onClose() {
    _connectivitySub?.cancel();
    _syncTimer?.cancel();
    super.onClose();
  }
}