import 'dart:io';

const double taxRate = 0.15;

void main() {
  print('Welcome to the Budget Management Application!');

  List<Map<String, double>> incomeList = [];
  List<Map<String, double>> expenseList = [];

  bool running = true;

  while (running) {
    print('\nPlease choose an option:');
    print('1. Add income');
    print('2. Add expense');
    print('3. View summary');
    print('4. Exit');

    stdout.write('\nEnter your choice: ');
    String choice = stdin.readLineSync()?.trim() ?? '';

    if (choice == '1') {
      stdout.write('Enter income description: ');
      String desc = (stdin.readLineSync() ?? '').trim();
      double amount = _readAmount('Enter income amount: ');
      incomeList.add({desc: amount});
      print('Income added!');
    } else if (choice == '2') {
      stdout.write('Enter expense description: ');
      String desc = (stdin.readLineSync() ?? '').trim();
      double amount = _readAmount('Enter expense amount: ');
      expenseList.add({desc: amount});
      print('Expense added!');
    } else if (choice == '3') {
      double totalIncome = _sumList(incomeList);
      double totalExpenses = _sumList(expenseList);
      double net = totalIncome - totalExpenses;

      print('\nSummary:');
      print('Total income: \$${totalIncome.toStringAsFixed(2)}');
      print('Total expenses: \$${totalExpenses.toStringAsFixed(2)}');

      if (net > 0) {
        print('Your net profit is \$${net.toStringAsFixed(2)}');
      } else if (net < 0) {
        print('Your net loss is \$${(-net).toStringAsFixed(2)}');
      } else {
        print('You are breaking even (no profit, no loss).');
      }

      double tax = net > 0 ? net * taxRate : 0.0;
      if (tax > 0) {
        print('Tax to be paid: \$${tax.toStringAsFixed(2)}');
      }
    } else if (choice == '4') {
      running = false;
      print('Exiting the application. Goodbye!');
    } else {
      print('Invalid choice. Please try again.');
    }
  }
}

double _readAmount(String prompt) {
  while (true) {
    stdout.write(prompt);
    String input = stdin.readLineSync()?.trim() ?? '';
    double? value = double.tryParse(input);
    if (value != null && value >= 0) {
      return value;
    }
    print('Invalid amount! Please enter a non-negative number.');
  }
}

double _sumList(List<Map<String, double>> list) {
  double total = 0.0;
  for (var entry in list) {
    if (entry.values.isNotEmpty) {
      total += entry.values.first;
    }
  }
  return total;
}