App.tsx

import React, { useEffect, useState } from "react";
import { NavigationContainer } from "@react-navigation/native";
import { createNativeStackNavigator } from "@react-navigation/native-stack";
import { onAuthStateChanged, User } from "firebase/auth";
import { auth } from "./firebase";

import LoginScreen from "./src/screens/LoginScreen";
import HomeScreen from "./src/screens/HomeScreen";

export type RootStackParamList = {
  Login: undefined;
  Home: undefined;
};

const Stack = createNativeStackNavigator<RootStackParamList>();

export default function App() {
  const [user, setUser] = useState<User | null>(null);
  const [loading, setLoading] = useState(true);

  useEffect(() => {
    const unsubscribe = onAuthStateChanged(auth, (currentUser) => {
      setUser(currentUser);
      setLoading(false);
    });
    return unsubscribe;
  }, []);

  if (loading) return null; // can show splash later

  return (
    <NavigationContainer>
      <Stack.Navigator>
        {user ? (
          <Stack.Screen name="Home" component={HomeScreen} />
        ) : (
          <Stack.Screen name="Login" component={LoginScreen} />
        )}
      </Stack.Navigator>
    </NavigationContainer>
  );
}