import 'dart:io';

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

  List<Map<String, dynamic>> incomes = [];
  List<Map<String, dynamic>> expenses = [];

  while (true) {
    print('\nMenu:');
    print('1. Add Income');
    print('2. Add Expense');
    print('3. View Summary (Total income, Total expenses, Net)');
    print('4. Exit');

    stdout.write('Choose an option (1-4): ');
    String? choice = stdin.readLineSync();

    if (choice == null) {
      print('Invalid input. Try again.');
      continue;
    }

    if (choice == '1') {
      stdout.write('Enter income description: ');
      String? desc = stdin.readLineSync() ?? '';
      double? amount = _readPositiveDouble('Enter income amount: ');
      if (amount == null) {
        print('Cancelled adding income.');
        continue;
      }
      incomes.add({'description': desc, 'amount': amount});
      print('Income added: $desc — \$${amount.toStringAsFixed(2)}');
    } else if (choice == '2') {
      stdout.write('Enter expense description: ');
      String? desc = stdin.readLineSync() ?? '';
      double? amount = _readPositiveDouble('Enter expense amount: ');
      if (amount == null) {
        print('Cancelled adding expense.');
        continue;
      }
      expenses.add({'description': desc, 'amount': amount});
      print('Expense added: $desc — \$${amount.toStringAsFixed(2)}');
    } else if (choice == '3') {
      double totalIncome = incomes.fold(
        0.0,
        (s, e) => s + (e['amount'] as double),
      );
      double totalExpenses = expenses.fold(
        0.0,
        (s, e) => s + (e['amount'] as double),
      );
      double net = totalIncome - totalExpenses;

      print('\n--- Budget Summary ---');
      print('Total Income: \$${totalIncome.toStringAsFixed(2)}');
      print('Total Expenses: \$${totalExpenses.toStringAsFixed(2)}');
      if (net >= 0) {
        print('Your net profit is \$${net.toStringAsFixed(2)}');
      } else {
        print('Your net loss is \$${(net.abs()).toStringAsFixed(2)}');
      }

      double tax = net > 0 ? net * 0.15 : 0.0;
      if (net > 0) {
        print('Tax to pay (15% of profit): \$${tax.toStringAsFixed(2)}');
      } else {
        print('No tax due (no profit).');
      }

      print('-----------------------\n');
    } else if (choice == '4') {
      print('Exiting Budget Manager. Goodbye!');
      break;
    } else {
      print('Invalid choice — pick 1-4.');
    }
  }
}

double? _readPositiveDouble(String prompt) {
  while (true) {
    stdout.write(prompt);
    String? input = stdin.readLineSync();
    if (input == null || input.trim().isEmpty) return null;
    double? value = double.tryParse(input);
    if (value == null) {
      print('Please enter a numeric value.');
      continue;
    }
    if (value < 0) {
      print('Amount cannot be negative. Try again.');
      continue;
    }
    return value;
  }
}