check if user is already authenticated

lib/main.dart

@@ -1,6 +1,7 @@
 import 'package:flutter/material.dart';
 import 'package:provider/provider.dart';
 import 'package:thegorgeousotp/pages/login_page.dart';
+import 'package:thegorgeousotp/pages/splash_page.dart';
 import 'package:thegorgeousotp/stores/login_store.dart';
 
 void main() => runApp(App());
@@ -20,7 +21,7 @@ class _AppState extends State<App> {
         )
       ],
       child: const MaterialApp(
-        home: LoginPage(),
+        home: SplashPage(),
       ),
     );
   }

lib/pages/home_page.dart

@@ -4,6 +4,7 @@ import 'package:thegorgeousotp/stores/login_store.dart';
 import 'package:thegorgeousotp/theme.dart';
 
 class HomePage extends StatefulWidget {
+  const HomePage({Key key}) : super(key: key);
   @override
   _HomePageState createState() => _HomePageState();
 }

lib/pages/splash_page.dart

@@ -0,0 +1,34 @@
+import 'package:flutter/material.dart';
+import 'package:provider/provider.dart';
+import 'package:thegorgeousotp/pages/home_page.dart';
+import 'package:thegorgeousotp/pages/login_page.dart';
+import 'package:thegorgeousotp/stores/login_store.dart';
+import 'package:thegorgeousotp/theme.dart';
+
+class SplashPage extends StatefulWidget {
+  const SplashPage({Key key}) : super(key: key);
+  @override
+  _SplashPageState createState() => _SplashPageState();
+}
+
+class _SplashPageState extends State<SplashPage> {
+
+  @override
+  void initState() {
+    super.initState();
+    Provider.of<LoginStore>(context, listen: false).isAlreadyAuthenticated().then((result) {
+      if (result) {
+        Navigator.of(context).pushAndRemoveUntil(MaterialPageRoute(builder: (_) => const HomePage()), (Route<dynamic> route) => false);
+      } else {
+        Navigator.of(context).pushAndRemoveUntil(MaterialPageRoute(builder: (_) => const LoginPage()), (Route<dynamic> route) => false);
+      }
+    });
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      backgroundColor: MyColors.primaryColor,
+    );
+  }
+}

lib/stores/login_store.dart

@@ -26,6 +26,16 @@ abstract class LoginStoreBase with Store {
   @observable
   FirebaseUser firebaseUser;
 
+  @action
+  Future<bool> isAlreadyAuthenticated() async {
+    firebaseUser = await _auth.currentUser();
+    if (firebaseUser != null) {
+      return true;
+    } else {
+      return false;
+    }
+  }
+
   @action
   Future<void> getCodeWithPhoneNumber(BuildContext context, String phoneNumber) async {
     isLoginLoading = true;