import 'dart:convert';
import 'package:http/http.dart' as http;
import 'package:shared_preferences/shared_preferences.dart';
import '../core/constants.dart';

class AuthService {
  static const _tokenKey = 'access_token';

  /// Intenta hacer login. Devuelve null si ok, o un mensaje de error.
  Future<String?> login(String email, String password) async {
    try {
      final response = await http.post(
        Uri.parse('$kApiBase/login'),
        headers: {'Content-Type': 'application/json'},
        body: jsonEncode({'email': email, 'password': password}),
      );

      if (response.statusCode == 200) {
        final data = jsonDecode(response.body) as Map<String, dynamic>;
        final token = data['access_token'] as String?;
        if (token != null) {
          await _saveToken(token);
          return null; // éxito
        }
        return 'Respuesta inesperada del servidor';
      } else if (response.statusCode == 401) {
        return 'Email o contraseña incorrectos';
      } else {
        return 'Error del servidor (${response.statusCode})';
      }
    } catch (_) {
      return 'No se pudo conectar con el servidor';
    }
  }

  Future<void> logout() async {
    final prefs = await SharedPreferences.getInstance();
    await prefs.remove(_tokenKey);
  }

  Future<String?> getToken() async {
    final prefs = await SharedPreferences.getInstance();
    return prefs.getString(_tokenKey);
  }

  Future<bool> isLoggedIn() async => (await getToken()) != null;

  Future<void> _saveToken(String token) async {
    final prefs = await SharedPreferences.getInstance();
    await prefs.setString(_tokenKey, token);
  }
}