App.tsx

import { StatusBar } from 'expo-status-bar';
import { SafeAreaProvider } from 'react-native-safe-area-context';
import { StatusBar as StatusBarHeight } from 'react-native';
import useCachedResources from './hooks/useCachedResources';
import useColorScheme from './hooks/useColorScheme';
import Navigation from './navigation';
import { MenuProvider } from 'react-native-popup-menu';
import { Amplify, API, Auth, graphqlOperation } from 'aws-amplify'
import awsconfig from './src/aws-exports'
import { withAuthenticator } from 'aws-amplify-react-native'
import { useEffect, useState } from 'react';
import { getUser } from './src/graphql/queries';
import { createUser } from './src/graphql/mutations';
import React from 'react';
import FlashMessage from "react-native-flash-message";

Amplify.configure(awsconfig);


function App() {
  const isLoadingComplete = useCachedResources();
  const [userAdded, setUserAdded] = useState(null);
  const colorScheme = useColorScheme();

  // when App first renders
  useEffect(() => {
    const fetchUser = async () => {
      // get user from Auth
      const userDataAuth = await Auth.currentAuthenticatedUser({ bypassCache: true });
      
      // if user from Auth is successfully fetched
      if (userDataAuth) {
        // fetch this user(using sub as id) from db, if not found in db, add new user to db
        const userDataDB = await API.graphql(graphqlOperation(getUser, { id: userDataAuth.attributes.sub }));
        console.log(userDataDB);

        // Check if user is in db
        if (userDataDB.data.getUser) {
          console.log("User already registered")
          setUserAdded(userDataDB.data.getUser);
          return;
        }
        
        // Default list of modules, personality type and year of study as placeholders
        const newUser = {
          id: userDataAuth.attributes.sub,
          name: userDataAuth.username,
          modules: "CS1101S, MA2001", 
          personalityType: "INTP",
          hobbies: "3, 3, 3, 3",
          year: "Y1",
          imageUri:"https://cdn-icons-png.flaticon.com/512/1/1247.png",
        }

        // Add new user to db
        const userCreated = await API.graphql(graphqlOperation(createUser, { input: newUser }));
        setUserAdded(userCreated.data.createUser);

      }

      
    }

    fetchUser();
  }, []);

  if (!isLoadingComplete || !userAdded) {
    return null;
  } else {
    return (
      <SafeAreaProvider>
        <MenuProvider>
          <Navigation colorScheme={colorScheme} />
          <StatusBar />
        </MenuProvider>
        <FlashMessage position="top" statusBarHeight={StatusBarHeight.currentHeight} icon="auto"/>
      </SafeAreaProvider>
    );
  }
}

export default withAuthenticator(App)