import 'dart:io';

void main() {
  print("=== SIMPLE BUDGET MANAGEMENT SYSTEM ===");

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

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

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

    if (choice == null) continue;

    if (choice == "4") {
      print("Exiting Budget System. Goodbye!");
      break;
    }

    if (choice == "1") {
      // Add Income
      stdout.write("Enter income description: ");
      String? desc = stdin.readLineSync();

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

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

      if (amount == null || amount < 0) {
        print("Invalid amount. Please enter a positive number.");
      } else {
        incomeList.add({desc ?? "Income": amount});
        print("Income added successfully.");
      }

    } else if (choice == "2") {
      // Add Expense
      stdout.write("Enter expense description: ");
      String? desc = stdin.readLineSync();

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

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

      if (amount == null || amount < 0) {
        print("Invalid amount. Please enter a positive number.");
      } else {
        expenseList.add({desc ?? "Expense": amount});
        print("Expense added successfully.");
      }

    } else if (choice == "3") {
      // View Summary
      double totalIncome = 0;
      double totalExpenses = 0;

      for (var item in incomeList) {
        totalIncome += item.values.first;
      }

      for (var item in expenseList) {
        totalExpenses += item.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 (15%)
        double tax = net > 0 ? net * 0.15 : 0;
        print("Tax to be paid (15%): \$${tax.toStringAsFixed(2)}");

      } else if (net < 0) {
        print("Your net loss is \$${net.abs().toStringAsFixed(2)}");
      } else {
        print("You broke even this month.");
      }

    } else {
      print("Invalid choice. Please select a valid option.");
    }
  }
}