import 'package:flutter/foundation.dart';

import '../models/auth.dart';

/// Shared operation lifecycle adapted from Sendico's ChangeNotifier providers.
/// Reset invalidates pending results; it does not cancel service-side work.
abstract class AuthProvider extends ChangeNotifier {
  AuthState _state = const AuthState.idle();
  int _generation = 0;
  bool _disposed = false;
  AuthState get state => _state;

  @protected
  Future<void> run(Future<AuthResult> Function() operation) async {
    if (_disposed || _state.isLoading) return;
    final generation = ++_generation;
    _state = const AuthState.loading();
    notifyListeners();
    try {
      final result = await operation();
      if (_disposed || generation != _generation) return;
      _state = AuthState.success(result);
    } catch (error) {
      if (_disposed || generation != _generation) return;
      // Never retain or expose arbitrary exceptions that may contain credentials.
      _state = AuthState.failure(
        error is AuthException ? error.code : AuthError.unexpected,
      );
    }
    if (!_disposed && generation == _generation) notifyListeners();
  }

  void reset() {
    if (_disposed) return;
    ++_generation;
    _state = const AuthState.idle();
    notifyListeners();
  }

  @override
  void dispose() {
    _disposed = true;
    ++_generation;
    super.dispose();
  }
}