Comprehensive comparison for Mobile Development technology in applications

import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'dart:convert';
import 'dart:async';

// Model class for User
class User {
  final String id;
  final String email;
  final String name;
  final String? avatarUrl;

  User({
    required this.id,
    required this.email,
    required this.name,
    this.avatarUrl,
  });

  factory User.fromJson(Map<String, dynamic> json) {
    return User(
      id: json['id'] as String,
      email: json['email'] as String,
      name: json['name'] as String,
      avatarUrl: json['avatar_url'] as String?,
    );
  }
}

// Authentication Service with error handling
class AuthService {
  static const String _baseUrl = 'https://api.example.com';
  static const Duration _timeout = Duration(seconds: 30);

  Future<User> login(String email, String password) async {
    try {
      final response = await http
          .post(
            Uri.parse('$_baseUrl/auth/login'),
            headers: {'Content-Type': 'application/json'},
            body: jsonEncode({'email': email, 'password': password}),
          )
          .timeout(_timeout);

      if (response.statusCode == 200) {
        final data = jsonDecode(response.body);
        return User.fromJson(data['user']);
      } else if (response.statusCode == 401) {
        throw Exception('Invalid credentials');
      } else {
        throw Exception('Login failed: ${response.statusCode}');
      }
    } on TimeoutException {
      throw Exception('Connection timeout. Please try again.');
    } catch (e) {
      throw Exception('Network error: $e');
    }
  }
}

// Login Screen Widget
class LoginScreen extends StatefulWidget {
  const LoginScreen({Key? key}) : super(key: key);

  @override
  State<LoginScreen> createState() => _LoginScreenState();
}

class _LoginScreenState extends State<LoginScreen> {
  final _formKey = GlobalKey<FormState>();
  final _emailController = TextEditingController();
  final _passwordController = TextEditingController();
  final _authService = AuthService();
  bool _isLoading = false;
  String? _errorMessage;

  @override
  void dispose() {
    _emailController.dispose();
    _passwordController.dispose();
    super.dispose();
  }

  Future<void> _handleLogin() async {
    if (!_formKey.currentState!.validate()) return;

    setState(() {
      _isLoading = true;
      _errorMessage = null;
    });

    try {
      final user = await _authService.login(
        _emailController.text.trim(),
        _passwordController.text,
      );

      if (mounted) {
        Navigator.pushReplacementNamed(
          context,
          '/home',
          arguments: user,
        );
      }
    } catch (e) {
      if (mounted) {
        setState(() {
          _errorMessage = e.toString().replaceAll('Exception: ', '');
        });
      }
    } finally {
      if (mounted) {
        setState(() {
          _isLoading = false;
        });
      }
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Login')),
      body: Padding(
        padding: const EdgeInsets.all(16.0),
        child: Form(
          key: _formKey,
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              TextFormField(
                controller: _emailController,
                decoration: const InputDecoration(
                  labelText: 'Email',
                  border: OutlineInputBorder(),
                ),
                keyboardType: TextInputType.emailAddress,
                validator: (value) {
                  if (value == null || value.isEmpty) {
                    return 'Please enter your email';
                  }
                  if (!value.contains('@')) {
                    return 'Please enter a valid email';
                  }
                  return null;
                },
              ),
              const SizedBox(height: 16),
              TextFormField(
                controller: _passwordController,
                decoration: const InputDecoration(
                  labelText: 'Password',
                  border: OutlineInputBorder(),
                ),
                obscureText: true,
                validator: (value) {
                  if (value == null || value.isEmpty) {
                    return 'Please enter your password';
                  }
                  if (value.length < 6) {
                    return 'Password must be at least 6 characters';
                  }
                  return null;
                },
              ),
              if (_errorMessage != null)
                Padding(
                  padding: const EdgeInsets.only(top: 16),
                  child: Text(
                    _errorMessage!,
                    style: const TextStyle(color: Colors.red),
                  ),
                ),
              const SizedBox(height: 24),
              SizedBox(
                width: double.infinity,
                child: ElevatedButton(
                  onPressed: _isLoading ? null : _handleLogin,
                  child: _isLoading
                      ? const CircularProgressIndicator()
                      : const Text('Login'),
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }
}