Updates for Firebase Google signin

Flutter google signin

import 'package:firebase_auth/firebase_auth.dart';
import 'package:google_sign_in/google_sign_in.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:rxdart/rxdart.dart';

class AuthService {
  final GoogleSignIn _googleSignIn = GoogleSignIn();
  final FirebaseAuth _auth = FirebaseAuth.instance;
  final Firestore _db = Firestore.instance;

  Stream<FirebaseUser> user; // firebase user
  Stream<Map<String, dynamic>> profile; // custom user data in Firestore
  PublishSubject loading = PublishSubject();

  // constructor
  AuthService() {
    user = _auth.onAuthStateChanged;

    profile = user.switchMap((FirebaseUser u) {
      if (u != null) {
        return _db
            .collection('users')
            .document(u.uid)
            .snapshots()
            .map((snap) => snap.data);
      } else {
        return Stream.value({});
      }
    });
  }

  Future<FirebaseUser> googleSignIn() async {
    try {
      loading.add(true);
      GoogleSignInAccount googleSignInAccount = await _googleSignIn.signIn();
      GoogleSignInAuthentication googleAuth =
          await googleSignInAccount.authentication;

      final AuthCredential credential = GoogleAuthProvider.getCredential(
        accessToken: googleAuth.accessToken,
        idToken: googleAuth.idToken,
      );

      final AuthResult authResult =
          await _auth.signInWithCredential(credential);

      FirebaseUser user = authResult.user;

      updateUserData(user);
      print("user name: ${user.displayName}");

      loading.add(false);
      return user;
    } catch (error) {
      return error;
    }
  }

  void updateUserData(FirebaseUser user) async {
    DocumentReference ref = _db.collection('users').document(user.uid);

    return ref.setData({
      'uid': user.uid,
      'email': user.email,
      'photoURL': user.photoUrl,
      'displayName': user.displayName,
      'lastSeen': DateTime.now()
    }, merge: true);
  }

  Future<String> signOut() async {
    try {
      await _auth.signOut();
      return 'SignOut';
    } catch (e) {
      return e.toString();
    }
  }
}

// TODO refactor global to InheritedWidget
final AuthService authService = AuthService();