import 'dart:io' show stdout, stdin;

void main() {
  // Lists to store income and expenses
  List<Map<String, dynamic>> incomeList = [];
  List<Map<String, dynamic>> expenseList = [];
  
  // Tax rate constant
  const double taxRate = 0.15;
  
  print('Welcome to the Budget Management Application!');
  
  // Main program loop
  while (true) {
    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();
    
    switch (choice) {
      case '1':
        addIncome(incomeList);
        break;
        
      case '2':
        addExpense(expenseList);
        break;
        
      case '3':
        viewSummary(incomeList, expenseList, taxRate);
        break;
        
      case '4':
        print('Exiting the application. Goodbye!');
        return;
        
      default:
        print('Invalid choice! Please enter a number between 1 and 4.');
    }
  }
}

void addIncome(List<Map<String, dynamic>> incomeList) {
  stdout.write('Enter income description: ');
  String? description = stdin.readLineSync();
  
  if (description == null || description.isEmpty) {
    print('Invalid description!');
    return;
  }
  
  stdout.write('Enter income amount: ');
  String? amountInput = stdin.readLineSync();
  
  try {
    double amount = double.parse(amountInput!);
    
    // Input validation - no negative amounts
    if (amount <= 0) {
      print('Invalid amount! Please enter a positive number.');
      return;
    }
    
    // Add income to list
    incomeList.add({
      'description': description,
      'amount': amount
    });
    
    print('Income added successfully!');
    
  } catch (e) {
    print('Invalid amount! Please enter a valid number.');
  }
}

void addExpense(List<Map<String, dynamic>> expenseList) {
  stdout.write('Enter expense description: ');
  String? description = stdin.readLineSync();
  
  if (description == null || description.isEmpty) {
    print('Invalid description!');
    return;
  }
  
  stdout.write('Enter expense amount: ');
  String? amountInput = stdin.readLineSync();
  
  try {
    double amount = double.parse(amountInput!);
    
    // Input validation - no negative amounts
    if (amount <= 0) {
      print('Invalid amount! Please enter a positive number.');
      return;
    }
    
    // Add expense to list
    expenseList.add({
      'description': description,
      'amount': amount
    });
    
    print('Expense added successfully!');
    
  } catch (e) {
    print('Invalid amount! Please enter a valid number.');
  }
}

void viewSummary(List<Map<String, dynamic>> incomeList, List<Map<String, dynamic>> expenseList, double taxRate) {
  print('\n=== BUDGET SUMMARY ===');
  
  // Calculate totals
  double totalIncome = calculateTotal(incomeList);
  double totalExpenses = calculateTotal(expenseList);
  double netProfit = totalIncome - totalExpenses;
  
  // Display income details
  print('\nINCOME:');
  if (incomeList.isEmpty) {
    print('  No income recorded');
  } else {
    for (var income in incomeList) {
      print('  - ${income['description']}: \$${income['amount']}');
    }
  }
  print('  Total income: \$${totalIncome.toStringAsFixed(2)}');
  
  // Display expense details
  print('\nEXPENSES:');
  if (expenseList.isEmpty) {
    print('  No expenses recorded');
  } else {
    for (var expense in expenseList) {
      print('  - ${expense['description']}: \$${expense['amount']}');
    }
  }
  print('  Total expenses: \$${totalExpenses.toStringAsFixed(2)}');
  
  // Display net profit/loss
  print('\nNET RESULT:');
  if (netProfit >= 0) {
    print('  Net profit: \$${netProfit.toStringAsFixed(2)}');
  } else {
    print('  Net loss: \$${netProfit.abs().toStringAsFixed(2)}');
  }
  
  // Tax calculation using ternary operator (only if profitable)
  double taxAmount = netProfit > 0 ? netProfit * taxRate : 0;
  
  if (taxAmount > 0) {
    print('  Tax to be paid (${(taxRate * 100).toInt()}%): \$${taxAmount.toStringAsFixed(2)}');
    double profitAfterTax = netProfit - taxAmount;
    print('  Profit after tax: \$${profitAfterTax.toStringAsFixed(2)}');
  }
}

double calculateTotal(List<Map<String, dynamic>> list) {
  double total = 0;
  for (var item in list) {
    total += item['amount'];
  }
  return total;
}