import 'dart:io';

void main() {
  List<Map<String, double>> income = [];
  List<Map<String, double>> expense = [];
  const tax = 0.15;

  print('Welcome to Budget Management!');
  while (true) {
    print('\n1) Add income\n2) Add expense\n3) View summary\n4) Exit');
    stdout.write('Choose: ');
    switch (stdin.readLineSync()) {
      case '1':
        stdout.write('Income description: ');
        String desc = stdin.readLineSync() ?? '';
        stdout.write('Amount: ');
        double? amt = double.tryParse(stdin.readLineSync() ?? '');
        if (amt != null && amt >= 0) income.add({desc: amt});
        break;
      case '2':
        stdout.write('Expense description: ');
        String desc = stdin.readLineSync() ?? '';
        stdout.write('Amount: ');
        double? amt = double.tryParse(stdin.readLineSync() ?? '');
        if (amt != null && amt >= 0) expense.add({desc: amt});
        break;
      case '3':
        double inc = income.fold(0, (s, e) => s + e.values.first);
        double exp = expense.fold(0, (s, e) => s + e.values.first);
        double net = inc - exp;
        print('\nTotal income: \$${inc.toStringAsFixed(2)}');
        print('Total expenses: \$${exp.toStringAsFixed(2)}');
        print(net >= 0
            ? 'Net profit: \$${net.toStringAsFixed(2)}'
            : 'Net loss: \$${(-net).toStringAsFixed(2)}');
        double taxAmt = net > 0 ? net * tax : 0;
        if (taxAmt > 0) print('Tax (15%): \$${taxAmt.toStringAsFixed(2)}');
        break;
      case '4':
        print('Goodbye!');
        return;
      default:
        print('Invalid choice.');
    }
  }
}