import 'dart:io';

void main() {
  print("=== Welcome to the Budget Management System ===");

  // Lists to store income and expenses
  List<Map<String, double>> incomeList = [];
  List<Map<String, double>> expenseList = [];

  bool running = true;

  while (running) {
    print("\nChoose an option:");
    print("1) Add Income");
    print("2) Add Expense");
    print("3) View Summary");
    print("4) Exit");

    stdout.write("Your choice: ");
    String? choice = stdin.readLineSync();

    if (choice == null) continue;

    // Control flow using if/else
    if (choice == "1") {
      _addEntry(isIncome: true, list: incomeList);
    } else if (choice == "2") {
      _addEntry(isIncome: false, list: expenseList);
    } else if (choice == "3") {
      _viewSummary(incomeList, expenseList);
    } else if (choice == "4") {
      print("Exiting program... Goodbye!");
      running = false;
    } else {
      print("Invalid option. Try again.");
    }
  }
}

// Function to add income or expense
void _addEntry({
  required bool isIncome,
  required List<Map<String, double>> list,
}) {
  stdout.write("Enter description: ");
  String? description = stdin.readLineSync();

  if (description == null || description.trim().isEmpty) {
    print("Description cannot be empty.");
    return;
  }

  stdout.write("Enter amount: ");
  String? amountInput = stdin.readLineSync();

  double? amount = double.tryParse(amountInput ?? "");

  // Input validation
  if (amount == null || amount < 0) {
    print("Invalid amount. Must be a positive number.");
    return;
  }

  list.add({description: amount});
  print("${isIncome ? "Income" : "Expense"} added successfully.");
}

// Function to calculate and display summary
void _viewSummary(
  List<Map<String, double>> incomeList,
  List<Map<String, double>> expenseList,
) {
  double totalIncome = 0;
  double totalExpenses = 0;

  // Calculate totals
  for (var entry in incomeList) {
    totalIncome += entry.values.first;
  }
  for (var entry in expenseList) {
    totalExpenses += entry.values.first;
  }

  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)}");

    // Optional tax calculation using ternary operator
    double tax = net > 0 ? net * 0.15 : 0;
    print("Tax (15%): \$${tax.toStringAsFixed(2)}");
    print("Profit after tax: \$${(net - tax).toStringAsFixed(2)}");
  } else if (net < 0) {
    print("Your net loss is \$${net.abs().toStringAsFixed(2)}");
    print("No tax applied due to loss.");
  } else {
    print("You broke even. No profit, no loss.");
  }
}