void main() {
  bool lightsOn = false;
  int thermostatTemp = 20;
  bool securityArmed = false;

  const int minTemp = 15;
  const int maxTemp = 30;

  print('Welcome to the Smart Home System!');

  while (true) {
    print('\nPlease choose an action:');
    print('1. Toggle lights');
    print('2. Set thermostat temperature');
    print('3. Arm/disarm security system');
    print('4. View system status');
    print('5. Exit');

    String? choice = stdin.readLineSync();

    switch (choice) {
      case '1':
        lightsOn = !lightsOn;
        print('Lights are now ${lightsOn ? 'ON' : 'OFF'}.');
        break;

      case '2':
        print('Set thermostat temperature ($minTemp°C – $maxTemp°C):');
        String? input = stdin.readLineSync();
        int? temp = int.tryParse(input!);

        if (temp != null && temp >= minTemp && temp <= maxTemp) {
          thermostatTemp = temp;
          print('Thermostat set to ${thermostatTemp}°C.');
        } else {
          print('Invalid temperature. Please enter a value between $minTemp and $maxTemp.');
        }
        break;

      case '3':
        securityArmed = !securityArmed;
        print('Security system is now ${securityArmed ? 'ARMED' : 'DISARMED'}.');
        break;

      case '4':
        String tempMessage = thermostatTemp.toString() + '°C';
        if (thermostatTemp % 3 == 0 && thermostatTemp % 5 == 0) {
          tempMessage += ' – Perfect Day';
        } else if (thermostatTemp % 3 == 0) {
          tempMessage += ' – Cool Day';
        } else if (thermostatTemp % 5 == 0) {
          tempMessage += ' – Warm Day';
        }

        print('\nSystem Status:');
        print('- Lights: ${lightsOn ? 'ON' : 'OFF'}');
        print('- Thermostat: $tempMessage');
        print('- Security System: ${securityArmed ? 'ARMED' : 'DISARMED'}');
        break;

      case '5':
        print('Exiting the system. Goodbye!');
        return;

      default:
        print('Invalid choice. Please try again.');
    }
  }
}