import 'dart:io';

 void main() {
     // Constants for temperature range
       const int minTemp = 15;
     const int maxTemp = 30;

     // Initialize device statuses
     String lightsStatus = 'off';
     int thermostatTemp = 20;
     String securityStatus = 'disarmed';

    bool running = true;

     while (running) {
       print('\nSmart Home Automation System');
       print('1. Turn lights on/off');
       print('2. Set thermostat temperature');
       print('3. Arm/disarm security system');
       print('4. View system status');
       print('5. Exit');
       stdout.write('Choose an option (1-5): ');

        String? input = stdin.readLineSync();
        int? choice = int.tryParse(input ?? '');

        if (choice == null || choice < 1 || choice > 5) {
          print('Invalid choice. Please enter a number between 1 and 5.');
          continue;
            }

             // Use if/else for main user choices
    if (choice == 1) {
      // Toggle lights
      lightsStatus = (lightsStatus == 'off') ? 'on' : 'off';
      print('Lights are now ${lightsStatus.toUpperCase()}.');
    } else if (choice == 2) {
      // Set thermostat temperature
      stdout.write('Enter temperature (${minTemp}°C to ${maxTemp}°C): ');
      String? tempInput = stdin.readLineSync();
       int? temp = int.tryParse(tempInput ?? '');
      if (temp == null || temp < minTemp || temp > maxTemp) {
        print('Invalid temperature. Please enter a value between $minTemp and $maxTemp.');
      } else {
        thermostatTemp = temp;
        print('Thermostat set to ${thermostatTemp}°C.');
       }
       } else if (choice == 3) {
      // Toggle security system
      securityStatus = (securityStatus == 'disarmed') ? 'armed' : 'disarmed';
      print('Security system is now ${securityStatus.toUpperCase()}.');
    } else if (choice == 4) {
      // View system status with string interpolation and operations
      String lightsDisplay = lightsStatus.toUpperCase();
      String securityDisplay = securityStatus.toUpperCase();
      String tempMessage = '$thermostatTemp°C';

       // FizzBuzz-like logic for temperature
      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('System Status:');
      print('Lights: $lightsDisplay');
      print('Thermostat: $tempMessage');
      print('Security System: $securityDisplay');
    } else if (choice == 5) {
      // Exit
      running = false;
      print('Exiting the Smart Home Automation System. Goodbye!');
       }
     }
   }