import 'dart:async';
import 'package:flutter_test/flutter_test.dart';
import 'package:firebase_auth/firebase_auth.dart' as fb;
import 'package:motorcycle_dash/services/auth/auth_service.dart';

class MockFirebaseAuth implements fb.FirebaseAuth {
  fb.User? _currentUser;
  final StreamController<fb.User?> _authStateChangesController = StreamController<fb.User?>.broadcast();
  int signInAnonymouslyCallCount = 0;
  bool shouldThrowOnSignIn = false;

  MockFirebaseAuth(this._currentUser);

  @override
  fb.User? get currentUser => _currentUser;

  @override
  Stream<fb.User?> authStateChanges() async* {
    yield _currentUser;
    yield* _authStateChangesController.stream;
  }

  @override
  Future<fb.UserCredential> signInAnonymously() async {
    signInAnonymouslyCallCount++;
    if (shouldThrowOnSignIn) {
      throw fb.FirebaseAuthException(code: 'network-error', message: 'Network disconnected');
    }
    await Future.delayed(const Duration(milliseconds: 50));
    final user = MockUser('new_anon', true, null);
    _currentUser = user;
    _authStateChangesController.add(user);
    return MockUserCredential(user);
  }

  @override
  dynamic noSuchMethod(Invocation invocation) {
    if (invocation.isGetter) return null;
    return super.noSuchMethod(invocation);
  }
}

class MockUser implements fb.User {
  @override
  final String uid;
  @override
  final bool isAnonymous;
  @override
  final String? email;
  @override
  final bool emailVerified = false;
  @override
  final fb.UserMetadata metadata;
  @override
  final List<fb.UserInfo> providerData = const [];

  MockUser(this.uid, this.isAnonymous, this.email) : metadata = MockUserMetadata();

  @override
  dynamic noSuchMethod(Invocation invocation) {
    if (invocation.isGetter) return null;
    return super.noSuchMethod(invocation);
  }
}

class MockUserMetadata implements fb.UserMetadata {
  @override
  DateTime? get creationTime => DateTime.now();
  @override
  DateTime? get lastSignInTime => DateTime.now();

  @override
  dynamic noSuchMethod(Invocation invocation) {
    if (invocation.isGetter) return null;
    return super.noSuchMethod(invocation);
  }
}

class MockUserCredential implements fb.UserCredential {
  @override
  final fb.User? user;

  MockUserCredential(this.user);

  @override
  dynamic noSuchMethod(Invocation invocation) {
    if (invocation.isGetter) return null;
    return super.noSuchMethod(invocation);
  }
}

void main() {
  group('AuthService ensureBackendIdentity Tests', () {
    test('current registered user -> reused, no anonymous sign-in', () async {
      final fakeUser = MockUser('reg_123', false, 'test@example.com');
      final fakeAuth = MockFirebaseAuth(fakeUser);
      final service = FirebaseAuthService(firebaseAuth: fakeAuth);
      await Future.delayed(Duration.zero); // allow init to run

      await service.ensureBackendIdentity();

      expect(fakeAuth.signInAnonymouslyCallCount, 0);
      expect(service.currentUser?.isAnonymous, false);
      expect(service.currentUser?.uid, 'reg_123');
    });

    test('current anonymous user -> reused', () async {
      final fakeUser = MockUser('anon_123', true, null);
      final fakeAuth = MockFirebaseAuth(fakeUser);
      final service = FirebaseAuthService(firebaseAuth: fakeAuth);
      await Future.delayed(Duration.zero);

      await service.ensureBackendIdentity();

      expect(fakeAuth.signInAnonymouslyCallCount, 0);
      expect(service.currentUser?.isAnonymous, true);
    });

    test('null user -> one anonymous sign-in', () async {
      final fakeAuth = MockFirebaseAuth(null);
      final service = FirebaseAuthService(firebaseAuth: fakeAuth);
      await Future.delayed(Duration.zero);

      await service.ensureBackendIdentity();

      expect(fakeAuth.signInAnonymouslyCallCount, 1);
      expect(service.currentState.user?.uid, 'new_anon');
    });

    test('two simultaneous requests -> only one anonymous sign-in', () async {
      final fakeAuth = MockFirebaseAuth(null);
      final service = FirebaseAuthService(firebaseAuth: fakeAuth);
      await Future.delayed(Duration.zero);

      final future1 = service.ensureBackendIdentity();
      final future2 = service.ensureBackendIdentity();

      await Future.wait([future1, future2]);

      expect(fakeAuth.signInAnonymouslyCallCount, 1);
      expect(service.currentState.user?.uid, 'new_anon');
    });

    test('anonymous sign-in failure -> explicit provider/auth error', () async {
      final fakeAuth = MockFirebaseAuth(null);
      fakeAuth.shouldThrowOnSignIn = true;
      final service = FirebaseAuthService(firebaseAuth: fakeAuth);
      await Future.delayed(Duration.zero);

      expect(
        () => service.ensureBackendIdentity(),
        throwsA(isA<Exception>().having((e) => e.toString(), 'msg', contains('Network disconnected')))
      );
    });
  });
}