autenticacao.dart

Future<Null> _ensureLoggedIn(String teamID) async {
  if (currentUser == null)
    // Não está logado
    currentUser = await _googleSignIn.signInSilently();
  if (currentUser == null) currentUser = await _googleSignIn.signIn();
  if (await _auth.currentUser() == null) {
    // Verificando se o usuário no Firebase é nulo
    GoogleSignInAuthentication credentials =
        await _googleSignIn.currentUser.authentication;
    // Gerando a chave usando as credenciais do Google
    if (currentUser.id != null) {
      var key = sha1.convert(utf8.encode(currentUser.id));
      _chatUID = key.toString();
      _chatHelper = ChatHelper();
      _chatKey = ChatKey();
      _chatKey.firebaseUser = currentUser.id;
      _chatKey.chat = teamID + "__#__" + key.toString();
      _chatHelper.save(_chatKey);

      // Salvando o usuário localmente
      CurrentUserHelper _userHelper = CurrentUserHelper();
      CurrentUser _user = CurrentUser();
      _user.firebaseToken = credentials.idToken;
      _user.googleToken = currentUser.id;
      _user.token = currentUser.id;
      _user.email = currentUser.email;
      _user.name = currentUser.displayName;
      _userHelper.save(_user);
    }
    final AuthCredential _authCredential =
                          GoogleAuthProvider.getCredential(
                              accessToken: credentials.accessToken, 
                              idToken: credentials.idToken);
    var firebaseAuthUser = await _auth.signInWithCredential(_authCredential);

    // Criar o canal de mensagens no firebase
    _chatHelper = ChatHelper();
    var itens = await _chatHelper.all();
    for (var item in itens) {
      _chatUID = item["chatColumn"];
    }
    Firestore.instance
        .collection("chats")
        .document(_chatUID)
        .setData({"from": currentUser.displayName, "to": teamID.toString()});
  }
}