import 'dart:io';

void main() {
  List<Map<String, double>> incomeList = [];
  List<Map<String, double>> expenseList = [];

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

  while (true) {
    print('\nSelect an option:');
    print('1. Add Income');
    print('2. Add Expense');
    print('3. View Net Profit/Loss');
    print('4. Exit');

    String? choice = stdin.readLineSync();

    if (choice == '1') {
      addIncome(incomeList);
    } else if (choice == '2') {
      addExpense(expenseList);
    } else if (choice == '3') {
      viewNetProfitOrLoss(incomeList, expenseList);
    } else if (choice == '4') {
      print('Thank you for using the Budget Management Application!');
      break;
    } else {
      print('Invalid choice, please try again.');
    }
  }
}

void addIncome(List<Map<String, double>> incomeList) {
  print('Enter income description:');
  String? description = stdin.readLineSync();
  
  print('Enter income amount:');
  double? amount = _getValidAmount();
  
  if (description != null && amount != null) {
    incomeList.add({description: amount});
    print('Income added: $description - \$${amount}');
  }
}

void addExpense(List<Map<String, double>> expenseList) {
  print('Enter expense description:');
  String? description = stdin.readLineSync();
  
  print('Enter expense amount:');
  double? amount = _getValidAmount();
  
  if (description != null && amount != null) {
    expenseList.add({description: amount});
    print('Expense added: $description - \$${amount}');
  }
}

void viewNetProfitOrLoss(List<Map<String, double>> incomeList, List<Map<String, double>> expenseList) {
  double totalIncome = incomeList.fold(0, (sum, income) => sum + income.values.first);
  double totalExpenses = expenseList.fold(0, (sum, expense) => sum + expense.values.first);

  double netProfitOrLoss = totalIncome - totalExpenses;

  if (netProfitOrLoss > 0) {
    double tax = netProfitOrLoss * 0.15;
    print('Your net profit is \$${netProfitOrLoss}');
    print('Tax to be paid: \$${tax.toStringAsFixed(2)}');
  } else if (netProfitOrLoss < 0) {
    print('Your net loss is \$${netProfitOrLoss.abs()}');
  } else {
    print('You broke even, no profit or loss.');
  }
}

double? _getValidAmount() {
  double? amount;
  while (true) {
    try {
      String? input = stdin.readLineSync();
      amount = double.tryParse(input ?? '');
      if (amount != null && amount >= 0) {
        break;
      } else {
        print('Please enter a valid non-negative amount.');
      }
    } catch (e) {
      print('Invalid input. Please enter a valid amount.');
    }
  }
  return amount;
}