auth.dart

import 'dart:async';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:google_sign_in/google_sign_in.dart';


class Auth {
  final GoogleSignIn _googleSignIn = GoogleSignIn();
  final FirebaseAuth _auth = FirebaseAuth.instance;

  static final Auth _instance = Auth._internal();

  FirebaseUser user;

  factory Auth() {
    return _instance;
  }

  Auth._internal();

  Future<FirebaseUser> googleSignIn() async {
    final GoogleSignInAccount googleUser = await _googleSignIn.signIn();
    final GoogleSignInAuthentication googleAuth = await googleUser.authentication;

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

    final FirebaseUser user = (await _auth.signInWithCredential(credential)).user;
    print("signed in " + user.displayName);
    this.user = user;
    return user;
  }

  Future<FirebaseUser> getCurrentUser() async {
    FirebaseUser user = await _auth.currentUser();
    this.user = user;
    return user;
  }

  Future<void> signOut() async {
    return _auth.signOut();
  }
}