phone_login/lib/services/auth_service.dart

import 'package:firebase_auth/firebase_auth.dart';

abstract class AuthService {
  Stream<User?> get user;
  Future<void> signInWithPhoneNumber(String phoneNumber);
  Future<void> verifyOTP(String verificationId, String otp);
  Future<void> signOut();
}

class FirebaseAuthService implements AuthService {
  final FirebaseAuth _firebaseAuth = FirebaseAuth.instance;

  @override
  Stream<User?> get user => _firebaseAuth.authStateChanges();

  @override
  Future<void> signInWithPhoneNumber(String phoneNumber) async {
    await _firebaseAuth.verifyPhoneNumber(
      phoneNumber: phoneNumber,
      verificationCompleted: (PhoneAuthCredential credential) async {
        await _firebaseAuth.signInWithCredential(credential);
      },
      verificationFailed: (FirebaseAuthException e) {
        throw Exception(e.message);
      },
      codeSent: (String verificationId, int? resendToken) {
        // Store verificationId for later use in verifyOTP
        // In a real app, this would be stored in state management
      },
      codeAutoRetrievalTimeout: (String verificationId) {},
    );
  }

  @override
  Future<void> verifyOTP(String verificationId, String otp) async {
    PhoneAuthCredential credential = PhoneAuthProvider.credential(
      verificationId: verificationId,
      smsCode: otp,
    );
    await _firebaseAuth.signInWithCredential(credential);
  }

  @override
  Future<void> signOut() async {
    await _firebaseAuth.signOut();
  }
}