Hire someone for custom code

import 'package:firebase_auth/firebase_auth.dart';

Future<bool> verifyOTP(String otpCode, String? verificationId) async {
  final auth = FirebaseAuth.instance;

  if (verificationId == null) {
    print('Error: Verification ID not available. Please request a new OTP.');
    return false;
  }

  try {
    final PhoneAuthCredential phoneAuthCredential =
        PhoneAuthProvider.credential(
            verificationId: verificationId, smsCode: otpCode);

// Sign in the user with the credential
    final userCredential = await auth.signInWithCredential(phoneAuthCredential);

// Ensure the user is authenticated and not a new user
    if (userCredential.user != null &&
        userCredential.additionalUserInfo!.isNewUser == false) {
      try {
// Check if the authenticated user's UID matches the UID in the credential
        if (userCredential.user!.uid == phoneAuthCredential.providerId) {
// Update the phone number of the authenticated user
          await userCredential.user!.updatePhoneNumber(phoneAuthCredential);
          print(
              'Phone number updated successfully for user: ${userCredential.user!.uid}');
          return true; // Indicate successful verification and update
        } else {
          print('Error: User UID does not match credential provider ID.');
          return false; // Indicate UID mismatch error
        }
      } on FirebaseAuthException catch (error) {
        print('Update phone number failed: ${error.code}');
        return false; // Indicate update failure
      }
    } else {
      print('Error: User not authenticated or new user created.');
      return false; // Indicate authentication failure or new user creation
    }
  } on FirebaseAuthException catch (error) {
    print('Verification failed: ${error.code}');
    return false; // Indicate verification failure
  }
}