import 'package:flutter/widgets.dart';

sealed class AuthenticationState {
  const AuthenticationState();
  bool authenticated();
}

class Unauthenticated extends AuthenticationState {
  @override
  bool authenticated() {
    return false;
  }
}

class Authenticated extends AuthenticationState {
  final String token;
  final String username;
  const Authenticated(this.token, this.username);

  @override
  bool authenticated() {
    return true;
  }
}

class AuthenticationModel extends ChangeNotifier {
  AuthenticationState _state = Unauthenticated();

  AuthenticationState get state => _state;

  set state(AuthenticationState newState) {
    _state = newState;
    notifyListeners();
  }
}

String? usernameValidator(String? value) {
  if (value == null || value.trim().length < 3) {
    return 'Please enter a valid username.';
  }
  return null;
}

String? passwordValidator(String? value) {
  if (value == null || value.length < 8) {
    return 'Please enter a valid password.';
  }
  return null;
}