import 'package:shared_preferences/shared_preferences.dart';
import 'dart:convert';

class TokenStorageService {
  static final TokenStorageService _instance = TokenStorageService._internal();
  factory TokenStorageService() => _instance;
  TokenStorageService._internal();

  // Storage keys
  static const String _preEnrollmentKey = 'pre_enrollment_data';
  static const String _postEnrollmentKey = 'post_enrollment_data';
  static const String _selectedBranchKey = 'selected_branch';
  static const String _decodedTokenKey = 'decoded_token';

  // In-memory cache
  List<dynamic>? _preEnrollmentData;
  List<dynamic>? _postEnrollmentData;
  Map<String, dynamic>? _selectedBranch;
  Map<String, dynamic>? _decodedToken;

  // Initialize - Load data from storage
  Future<void> initialize() async {
    final prefs = await SharedPreferences.getInstance();

    final preData = prefs.getString(_preEnrollmentKey);
    if (preData != null) {
      _preEnrollmentData = json.decode(preData);
    }

    final postData = prefs.getString(_postEnrollmentKey);
    if (postData != null) {
      _postEnrollmentData = json.decode(postData);
    }

    final branchData = prefs.getString(_selectedBranchKey);
    if (branchData != null) {
      _selectedBranch = json.decode(branchData);
    }

    final tokenData = prefs.getString(_decodedTokenKey);
    if (tokenData != null) {
      _decodedToken = json.decode(tokenData);
    }
  }

  // Save enrollment data
  Future<void> saveEnrollmentData(List<dynamic> preData, List<dynamic> postData) async {
    _preEnrollmentData = preData;
    _postEnrollmentData = postData;

    final prefs = await SharedPreferences.getInstance();
    await prefs.setString(_preEnrollmentKey, json.encode(preData));
    await prefs.setString(_postEnrollmentKey, json.encode(postData));
  }

  // Get combined unique branches
  List<Map<String, dynamic>> getCombinedBranches() {
    List<Map<String, dynamic>> combined = [];
    Set<String> seenTokens = {};
    Set<String> seenIds = {};

    // Add pre-enrollment data
    if (_preEnrollmentData != null) {
      for (var item in _preEnrollmentData!) {
        String token = item['token']?.toString() ?? '';
        String uniqueId = '${item['id']}_${item['client_id']}_${item['client_branch_id']}';

        if (seenIds.contains(uniqueId)) continue;
        if (token.isNotEmpty && seenTokens.contains(token)) continue;

        if (token.isNotEmpty) seenTokens.add(token);
        seenIds.add(uniqueId);

        combined.add({...item, 'enrollment_type': 'pre'});
      }
    }

    // Add post-enrollment data
    if (_postEnrollmentData != null) {
      for (var item in _postEnrollmentData!) {
        String token = item['token']?.toString() ?? '';
        String uniqueId = '${item['id']}_${item['client_id']}_${item['client_branch_id']}';

        if (seenIds.contains(uniqueId)) continue;
        if (token.isNotEmpty && seenTokens.contains(token)) continue;

        if (token.isNotEmpty) seenTokens.add(token);
        seenIds.add(uniqueId);

        combined.add({...item, 'enrollment_type': 'post'});
      }
    }

    return combined;
  }

  // Save selected branch and decode token
  Future<void> saveSelectedBranch(Map<String, dynamic> branch) async {
    _selectedBranch = branch;

    String token = branch['token']?.toString() ?? '';
    if (token.isNotEmpty) {
      _decodedToken = _decodeJWT(token);
    } else {
      _decodedToken = null;
    }

    final prefs = await SharedPreferences.getInstance();
    await prefs.setString(_selectedBranchKey, json.encode(branch));

    if (_decodedToken != null) {
      await prefs.setString(_decodedTokenKey, json.encode(_decodedToken));
    }
  }

  // Decode JWT token
  Map<String, dynamic>? _decodeJWT(String token) {
    try {
      final parts = token.split('.');
      if (parts.length != 3) return null;

      final payload = parts[1];
      var normalized = base64Url.normalize(payload);
      var decoded = utf8.decode(base64Url.decode(normalized));

      return json.decode(decoded);
    } catch (e) {
      print('Error decoding token: $e');
      return null;
    }
  }

  // Getters
  Map<String, dynamic>? getSelectedBranch() => _selectedBranch;
  Map<String, dynamic>? getDecodedToken() => _decodedToken;
  String? getCurrentToken() => _selectedBranch?['token'];

  bool isLoggedIn() {
    return _selectedBranch != null &&
        _selectedBranch!['token'] != null &&
        _selectedBranch!['token'].toString().isNotEmpty;
  }

  // Clear all data (logout)
  Future<void> clearAll() async {
    _preEnrollmentData = null;
    _postEnrollmentData = null;
    _selectedBranch = null;
    _decodedToken = null;

    final prefs = await SharedPreferences.getInstance();
    await prefs.remove(_preEnrollmentKey);
    await prefs.remove(_postEnrollmentKey);
    await prefs.remove(_selectedBranchKey);
    await prefs.remove(_decodedTokenKey);
  }
}