ফ্লাটার অ্যাপে গুগল অথেনটিকেশন

import 'package:flutter/material.dart';
import 'package:google_sign_in/google_sign_in.dart';

void main() => runApp(const MyApp());

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      title: 'Google Sign-In Demo',
      home: SignInTest(),
    );
  }
}
class SignInTest extends StatefulWidget {
  const SignInTest({super.key});
  @override
  State<SignInTest> createState() => _SignInTestState();
}

class _SignInTestState extends State<SignInTest> {
  final GoogleSignIn _googleSignIn = GoogleSignIn.instance;
  GoogleSignInAccount? _user;
  bool _isInitialized = false;

  @override
  void initState() {
    super.initState();
    _initializeGoogleSignIn();
  }

  Future<void> _initializeGoogleSignIn() async {
    try {
      // Initialize GoogleSignIn - scopes are now requested via authorizationClient
      // serverClientId is required for authentication
      await _googleSignIn.initialize(serverClientId: 'asdf-asdf.apps.googleusercontent.com');
      _isInitialized = true;
      
      // Listen to authentication events
      _listenForAuthChanges();
      
      // Attempt to restore previous session
      await _restorePreviousSession();
    } catch (e) {
      debugPrint('Failed to initialize Google Sign-In: $e');
    }
  }

  void _listenForAuthChanges() {
    _googleSignIn.authenticationEvents.listen((event) {
      if (event is GoogleSignInAuthenticationEventSignIn) {
        setState(() => _user = event.user);
      } else if (event is GoogleSignInAuthenticationEventSignOut) {
        setState(() => _user = null);
      }
    }, onError: (error) {
      debugPrint('Authentication error: $error');
    });
  }

  Future<void> _restorePreviousSession() async {
    if (!_isInitialized) return;
    
    try {
      final future = _googleSignIn.attemptLightweightAuthentication();
      if (future != null) {
        final currentUser = await future;
        if (currentUser != null && mounted) {
          setState(() => _user = currentUser);
        }
      }
    } catch (e) {
      debugPrint('Failed to restore session: $e');
    }
  }

  Future<void> _signIn() async {
    if (!_isInitialized) {
      debugPrint('Google Sign-In not initialized yet');
      return;
    }
    
    try {
      final user = await _googleSignIn.authenticate(
        scopeHint: ['email', 'profile'],
      );
      if (mounted) {
        setState(() => _user = user);
      }
    } catch (e) {
      debugPrint('Sign-in error: $e');
      // Show error to user
      if (mounted) {
        ScaffoldMessenger.of(context).showSnackBar(
          SnackBar(content: Text('Sign-in failed: ${e.toString()}')),
        );
      }
    }
  }

  Future<void> _signOut() async {
    if (!_isInitialized) return;
    
    try {
      await _googleSignIn.signOut();
      setState(() => _user = null);
    } catch (e) {
      debugPrint('Sign-out error: $e');
    }
  }

  @override
  Widget build(BuildContext context) {
    final user = _user;
    return Scaffold(
      appBar: AppBar(title: const Text('Google Sign-In  Test')),
      body: Center(
        child: user == null
            ? ElevatedButton(
                onPressed: _signIn,
                child: const Text('Sign in with Google'),
              )
            : Column(
                mainAxisSize: MainAxisSize.min,
                children: [
                  if (user.photoUrl != null)
                    CircleAvatar(
                      backgroundImage: NetworkImage(user.photoUrl!),
                      radius: 40,
                    ),
                  const SizedBox(height: 16),
                  Text('Signed in as: ${user.displayName ?? 'No name'}'),
                  Text(user.email),
                  const SizedBox(height: 16),
                  ElevatedButton(
                    onPressed: _signOut,
                    style: ElevatedButton.styleFrom(backgroundColor: Colors.red),
                    child: const Text('Sign Out'),
                  ),
                ],
              ),
      ),
    );
  }
}