import 'dart:convert';

import 'package:shared_preferences/shared_preferences.dart';

import '../models/auth_session.dart';
import 'local_seed_repository.dart';

abstract class AuthRepository {
  Future<AuthSession?> restoreSession();
  Future<AuthSession> signIn({required String email, required String password});
  Future<AuthSession> signUp({required String name, required String email, required String password});
  Future<void> signOut();
}

class LocalAuthRepository implements AuthRepository {
  const LocalAuthRepository();

  static const String _tokenKey = 'auth_token';
  static const String _emailKey = 'auth_email';
  static const String _nameKey = 'auth_name';
  static const String _sessionKey = 'auth_session_json';
  static const String _usersKey = 'auth_users_json';

  @override
  Future<AuthSession?> restoreSession() async {
    final prefs = await SharedPreferences.getInstance();
    final sessionJson = prefs.getString(_sessionKey);
    if (sessionJson != null && sessionJson.trim().isNotEmpty) {
      final decoded = jsonDecode(sessionJson);
      if (decoded is Map<String, dynamic>) {
        final token = decoded['token']?.toString();
        final email = decoded['email']?.toString();
        final name = decoded['displayName']?.toString();
        if (token != null && email != null && token.isNotEmpty && email.isNotEmpty) {
          return AuthSession(token: token, email: email, displayName: name ?? email);
        }
      }
    }

    final token = prefs.getString(_tokenKey);
    final email = prefs.getString(_emailKey);
    final name = prefs.getString(_nameKey);

    if (token == null || email == null) {
      return null;
    }

    return AuthSession(token: token, email: email, displayName: name ?? email);
  }

  @override
  Future<AuthSession> signIn({required String email, required String password}) {
    return _authenticate(
      endpoint: '/auth/login',
      body: <String, dynamic>{'email': email, 'password': password},
    );
  }

  @override
  Future<AuthSession> signUp({required String name, required String email, required String password}) {
    return _authenticate(
      endpoint: '/auth/register',
      body: <String, dynamic>{'name': name, 'email': email, 'password': password},
    );
  }

  Future<AuthSession> _authenticate({required String endpoint, required Map<String, dynamic> body}) async {
    final email = body['email']?.toString().trim();
    final password = body['password']?.toString();
    if (email == null || password == null || email.isEmpty) {
      throw AuthException('Ingresa correo y contraseña válidos.');
    }

    final seedData = await LocalSeedRepository.instance.load();
    final profile = seedData.profileForCredentials(email, password);
    if (profile != null) {
      final session = AuthSession(
        token: 'local-${profile.email}',
        email: profile.email,
        displayName: profile.name,
      );
      await _persistSession(session);
      return session;
    }

    final localUsers = await _loadLocalUsers();
    final normalizedEmail = email.toLowerCase();
    final localMatch = localUsers.where((user) {
      final userEmail = user['email']?.toString().trim().toLowerCase();
      final userPassword = user['password']?.toString();
      return userEmail == normalizedEmail && userPassword == password;
    }).toList(growable: false);

    if (localMatch.isNotEmpty) {
      final user = localMatch.first;
      final displayName = user['name']?.toString().trim();
      final session = AuthSession(
        token: 'local-${email.toLowerCase()}',
        email: email,
        displayName: displayName == null || displayName.isEmpty ? email : displayName,
      );
      await _persistSession(session);
      return session;
    }

    if (endpoint == '/auth/register') {
      final displayName = body['name']?.toString().trim();
      final alreadyInSeed = seedData.profileForCredentials(email, password) != null ||
          seedData.demoProfiles.any((profile) => profile.email.trim().toLowerCase() == normalizedEmail);
      final alreadyInLocal = localUsers.any((user) => user['email']?.toString().trim().toLowerCase() == normalizedEmail);
      if (alreadyInSeed || alreadyInLocal) {
        throw AuthException('Este correo ya está registrado.');
      }

      final createdUser = <String, dynamic>{
        'name': displayName == null || displayName.isEmpty ? email : displayName,
        'email': email,
        'password': password,
        'createdAt': DateTime.now().toIso8601String(),
      };
      await _saveLocalUsers(<Map<String, dynamic>>[...localUsers, createdUser]);

      final session = AuthSession(
        token: 'local-$email',
        email: email,
        displayName: displayName == null || displayName.isEmpty ? email : displayName,
      );
      await _persistSession(session);
      return session;
    }

    throw AuthException('Usuario o contraseña no encontrados en los perfiles locales.');
  }

  Future<void> _persistSession(AuthSession session) async {
    final prefs = await SharedPreferences.getInstance();
    await prefs.setString(_tokenKey, session.token);
    await prefs.setString(_emailKey, session.email);
    await prefs.setString(_nameKey, session.displayName);
    await prefs.setString(
      _sessionKey,
      jsonEncode(
        <String, dynamic>{
          'token': session.token,
          'email': session.email,
          'displayName': session.displayName,
        },
      ),
    );
  }

  Future<List<Map<String, dynamic>>> _loadLocalUsers() async {
    final prefs = await SharedPreferences.getInstance();
    final raw = prefs.getString(_usersKey);
    if (raw == null || raw.trim().isEmpty) {
      return <Map<String, dynamic>>[];
    }

    final decoded = jsonDecode(raw);
    if (decoded is! List) {
      return <Map<String, dynamic>>[];
    }

    return decoded.whereType<Map<String, dynamic>>().toList(growable: false);
  }

  Future<void> _saveLocalUsers(List<Map<String, dynamic>> users) async {
    final prefs = await SharedPreferences.getInstance();
    await prefs.setString(_usersKey, jsonEncode(users));
  }

  @override
  Future<void> signOut() async {
    final prefs = await SharedPreferences.getInstance();
    await prefs.remove(_tokenKey);
    await prefs.remove(_emailKey);
    await prefs.remove(_nameKey);
    await prefs.remove(_sessionKey);
  }
}

class AuthException implements Exception {
  AuthException(this.message);

  final String message;

  @override
  String toString() => message;
}