wavelength_app/components/auth/SignInScreen.tsx

import React from "react";
import * as AppleAuthentication from "expo-apple-authentication";
import { StyleSheet, Alert } from "react-native";
import { ThemedView } from "@/components/theme/Theme";
import { useColorScheme } from "@/hooks/useColorScheme";
import * as Notifications from "expo-notifications";
import Constants from "expo-constants";
import { saveUser, saveInitialData } from "@/components/services/SecureStore";
import type { InitialData, User } from "@/constants/Types";

const SignInScreen({onSignIn}: {onSignIn: () => void}) => {
  const scheme = useColorScheme() ?? 'dark';

  const handleAppleSignIn = async () => {
    try {
      const credential = await AppleAuthentication.signInAsync({
        requestedScopes: [
          AppleAuthentication.AppleAuthenticationScope.EMAIL,
          AppleAuthentication.AppleAuthenticationScope.FULL_NAME,
        ],
      });
      const projectId = Constants.expoConfig?.extra?.eas?.projectId;
      if (!projectId) throw new Error('Project ID not found in eas.json');

      const pushToken = await Notifications.getExpoPushTokenAsync({
        projectId: projectId,
      });
      console.log(
        credential.user, credential.email, credential.fullName?.givenName,
        credential.fullName?.familyName, pushToken
      );

      const initialData = await
        fetch(`${process.env.NEXT_PUBLIC_API_URL}/api/users/getUserByAppleId` +
        `?appleId=${credential.user}`, {
        method: 'GET',
        headers: {
          'Content-Type': 'application/json',
          'x-api-key': process.env.NEXT_PUBLIC_API_KEY ?? '',
        },
      });
      console.log(initialData);
      if (initialData.status === 404 || !initialData.ok) {
        if (!credential.user || !credential.email ||
            !credential.fullName?.givenName || !credential.fullName?.familyName ||
            !pushToken || credential.email.length === 0) {
          Alert.alert(
            'Sign in error',
            'Unable to create an account. ' + 
              'Remove App from Sign in with Apple & try again.',
          );
          throw new Error(
            'Incomplete user data. This shouldn\'t happen & means that user has ' +
              'previously signed in with Apple, but their user data did not ' +
              'save in the database.'
          );
        }

        const userResponse = await
          fetch(`${process.env.NEXT_PUBLIC_API_URL}/api/users/createUser`, {
          method: 'POST',
          headers: {
            'Content-Type': 'application/json',
            'x-api-key': process.env.NEXT_PUBLIC_API_KEY ?? '',
          },
          body: JSON.stringify({
            appleId: credential.user,
            email: credential.email,
            fullName:
              `${credential.fullName?.givenName} ${credential.fullName?.familyName}`,
            pushToken: pushToken,
          }),
        });
        if (!userResponse.ok) {
          const errorBody = await userResponse.text();
          console.error(
            'API error: No user returned: ',
            userResponse.status, errorBody
          );
          throw new Error(`Failed to create user: ${userResponse.status} ${errorBody}`);
        }
        const user: User = await userResponse.json() as User;
        await saveUser(user);
      } else if (initialData.ok) {
        const allData: InitialData = await initialData.json() as InitialData;
        console.log('Existing user found! Saving data...');

        if (allData.user.pushToken !== pushToken.data) {
          const updatePushTokenResponse = 
            await fetch(`${process.env.NEXT_PUBLIC_API_URL}/api/users/updatePushToken`, {
            method: 'POST',
            headers: {
              'Content-Type': 'application/json',
              'x-api-key': process.env.NEXT_PUBLIC_API_KEY ?? '',
            },
            body: JSON.stringify({
              userId: allData.user.id,
              pushToken: pushToken.data,
            }),
          });
          if (!updatePushTokenResponse.ok) {
            throw new Error(
              `Failed to update push token: ${updatePushTokenResponse.status}`
            );
          }
        } else {
          console.log('Push token is up to date.');
        }
        allData.user.pushToken = pushToken.data;
        await saveInitialData(allData);
      }
      onSignIn();
    } catch (error) {
      console.error('Error signing in:', error);
      if (error.code === 'ERR_REQUEST_CANCELLED') {
        Alert.alert('Sign in error', 'Sign in was cancelled.');
      } else {
        Alert.alert(
          'Sign in error',
          'An error occurred while signing in. Please try again or contact support.'
        );
      }
    }
  };

  return (
    <ThemedView style={styles.container}>
      <AppleAuthentication.AppleAuthenticationButton
        buttonType={AppleAuthentication.AppleAuthenticationButtonType.SIGN_IN}
        buttonStyle={(scheme === 'light') ?
          AppleAuthentication.AppleAuthenticationButtonStyle.BLACK :
          AppleAuthentication.AppleAuthenticationButtonStyle.WHITE
        }
        cornerRadius={5}
        style={styles.button}
        onPress={handleAppleSignIn}
      />
    </ThemedView>
  );
};
export default SignInScreen;

const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    alignItems: 'center',
  },
  button: {
    width: 200,
    height: 45,
  },
});