import 'dart:io'; 
void main() { 
// Lists to store income and expense entries 
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 loop for user interaction 
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(); 
if (choice == '1') { 
// Add income 
addIncome(incomeList); 
       
    } else if (choice == '2') { 
      // Add expense 
      addExpense(expenseList); 
       
    } else if (choice == '3') { 
      // View summary 
      viewSummary(incomeList, expenseList, taxRate); 
       
    } else if (choice == '4') { 
      // Exit program 
      print('Exiting the application. Goodbye!'); 
      break; 
       
    } else { 
      print('Invalid choice! Please enter a number between 1 and 4.'); 
    } 
  } 
} 
 
// Function to add income 
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; 
} 
double amount = getValidAmount('Enter income amount: '); 
if (amount > 0) { 
incomeList.add({ 
'description': description, 
'amount': amount 
}); 
print('Income added!'); 
} else { 
print('Income amount must be positive!'); 
} 
} 
// Function to add expense 
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; 
} 
   
  double amount = getValidAmount('Enter expense amount: '); 
   
  if (amount > 0) { 
    expenseList.add({ 
      'description': description, 
      'amount': amount 
    }); 
    print('Expense added!'); 
  } else { 
    print('Expense amount must be positive!'); 
  } 
} 
 
// Function to get valid amount from user 
double getValidAmount(String prompt) { 
  while (true) { 
    stdout.write(prompt); 
    String? amountInput = stdin.readLineSync(); 
     
    try { 
      double amount = double.parse(amountInput!); 
      if (amount >= 0) { 
        return amount; 
      } else { 
        print('Amount cannot be negative! Please enter a positive value.'); 
} 
} catch (e) { 
print('Invalid input! Please enter a valid number.'); 
} 
} 
} 
// Function to calculate total from a list 
double calculateTotal(List<Map<String, dynamic>> list) { 
double total = 0; 
for (var item in list) { 
total += item['amount']; 
} 
return total; 
} 
// Function to view summary 
void viewSummary(List<Map<String, dynamic>> incomeList, List<Map<String, 
dynamic>> expenseList, double taxRate) { 
double totalIncome = calculateTotal(incomeList); 
double totalExpenses = calculateTotal(expenseList); 
double netProfit = totalIncome - totalExpenses; 
print('\nSummary:'); 
print('Total income: \$${totalIncome.toStringAsFixed(2)}'); 
print('Total expenses: \$${totalExpenses.toStringAsFixed(2)}'); 
if (netProfit >= 0) { 
print('Net profit: \$${netProfit.toStringAsFixed(2)}'); 
// Tax calculation using ternary operator (only if profitable) 
double tax = netProfit > 0 ? netProfit * taxRate : 0; 
if (tax > 0) { 
print('Tax to be paid: \$${tax.toStringAsFixed(2)}'); 
} 
} else { 
print('Net loss: \$${netProfit.abs().toStringAsFixed(2)}'); 
} 
// Display detailed lists if available 
if (incomeList.isNotEmpty) { 
print('\nIncome Details:'); 
for (var income in incomeList) { 
print('- ${income['description']}: \$${income['amount'].toStringAsFixed(2)}'); 
} 
} 
if (expenseList.isNotEmpty) { 
print('\nExpense Details:'); 
for (var expense in expenseList) { 
print('- ${expense['description']}: \$${expense['amount'].toStringAsFixed(2)}'); 
    } 
  } 
}