import 'dart:io';

void main() {
  List<Map<String, double>> incomeList = [];
  List<Map<String, double>> expenseList = [];
  const double TAX_RATE = 0.15;
  
  print('Welcome to the Budget Management Application!');
  
  while (true) {
    print('\nPlease choose an option:');
    print('1. Add income');
    print('2. Add expense');
    print('3. View summary');
    print('4. Exit');
    
    stdout.write('Enter your choice: ');
    String? choiceInput = stdin.readLineSync();
    
    if (choiceInput == null || choiceInput.isEmpty) {
      print('Invalid input. Please try again.');
      continue;
    }
    
    int choice = int.tryParse(choiceInput) ?? 0;
    
    switch (choice) {
      case 1:
        stdout.write('Enter income description: ');
        String? desc = stdin.readLineSync();
        stdout.write('Enter income amount: ');
        String? amountInput = stdin.readLineSync();
        double amount = double.tryParse(amountInput ?? '') ?? 0.0;
        
        if (amount > 0 && desc != null && desc.isNotEmpty) {
          incomeList.add({'description': desc, 'amount': amount});
          print('Income added!');
        } else {
          print('Invalid amount or description. Amount must be positive.');
        }
        break;
      
      case 2:
        stdout.write('Enter expense description: ');
        String? desc = stdin.readLineSync();
        stdout.write('Enter expense amount: ');
        String? amountInput = stdin.readLineSync();
        double amount = double.tryParse(amountInput ?? '') ?? 0.0;
        
        if (amount > 0 && desc != null && desc.isNotEmpty) {
          expenseList.add({'description': desc, 'amount': amount});
          print('Expense added!');
        } else {
          print('Invalid amount or description. Amount must be positive.');
        }
        break;
      
      case 3:
        double totalIncome = incomeList.fold(0.0, (sum, item) => sum + item['amount']!);
        double totalExpense = expenseList.fold(0.0, (sum, item) => sum + item['amount']!);
        double net = totalIncome - totalExpense;
        
        print('\nSummary:');
        print('Total income: \$${totalIncome.toStringAsFixed(2)}');
        print('Total expenses: \$${totalExpense.toStringAsFixed(2)}');
        
        if (net > 0) {
          print('Net profit: \$${net.toStringAsFixed(2)}');
          double tax = net * TAX_RATE;
          print('Tax to be paid: \$${tax.toStringAsFixed(2)}');
        } else if (net < 0) {
          print('Net loss: \$${(-net).toStringAsFixed(2)}');
        } else {
          print('Net balance: \$0.00');
        }
        break;
      
      case 4:
        print('Exiting the application. Goodbye!');
        exit(0);
      
      default:
        print('Invalid choice. Please try again.');
    }
  }
}