import 'dart:io';

const double TAX_RATE = 0.15;

void main() {
  // قوائم تخزين الدخل والمصروفات: كل عنصر هو Map حيث المفتاح = الوصف، القيمة = المبلغ
  List<Map<String, double>> incomeList = [];
  List<Map<String, double>> expenseList = [];

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

  bool running = true;
  while (running) {
    showMenu();
    stdout.write('\nEnter your choice: ');
    String? input = stdin.readLineSync();
    int? choice = input != null ? int.tryParse(input.trim()) : null;

    if (choice == null) {
      print('Invalid input. Please enter a number between 1 and 4.\n');
      continue;
    }

    if (choice == 1) {
      // Add income
      stdout.write('Enter income description: ');
      String? desc = stdin.readLineSync();
      if (desc == null || desc.trim().isEmpty) {
        print('Description cannot be empty.\n');
        continue;
      }
      stdout.write('Enter income amount: ');
      String? amtStr = stdin.readLineSync();
      double? amount = _parsePositiveDouble(amtStr);
      if (amount == null) {
        print('Invalid amount. Please enter a non-negative number.\n');
        continue;
      }
      incomeList.add({desc.trim(): amount});
      print('Income added!\n');
    } else if (choice == 2) {
      // Add expense
      stdout.write('Enter expense description: ');
      String? desc = stdin.readLineSync();
      if (desc == null || desc.trim().isEmpty) {
        print('Description cannot be empty.\n');
        continue;
      }
      stdout.write('Enter expense amount: ');
      String? amtStr = stdin.readLineSync();
      double? amount = _parsePositiveDouble(amtStr);
      if (amount == null) {
        print('Invalid amount. Please enter a non-negative number.\n');
        continue;
      }
      expenseList.add({desc.trim(): amount});
      print('Expense added!\n');
    } else if (choice == 3) {
      // View summary
      double totalIncome = _sumAmounts(incomeList);
      double totalExpenses = _sumAmounts(expenseList);
      double net = totalIncome - totalExpenses;
      print('\nSummary:');
      print('Total income: \$${_formatMoney(totalIncome)}');
      print('Total expenses: \$${_formatMoney(totalExpenses)}');
      if (net >= 0) {
        print('Net profit: \$${_formatMoney(net)}');
      } else {
        print('Net loss: \$${_formatMoney(net.abs())}');
      }
      // حساب الضريبة (15%) باستخدام ternary: تُحسب فقط لو كانت ربح
      double tax = net > 0 ? net * TAX_RATE : 0.0;
      if (tax > 0) {
        print('Tax to be paid (15%): \$${_formatMoney(tax)}');
      }
      print('');
    } else if (choice == 4) {
      print('Exiting the application.');
      running = false;
    } else {
      print('Choice out of range. Please choose between 1 and 4.\n');
    }
  }
}

void showMenu() {
  print('Please choose an option:');
  print('1. Add income');
  print('2. Add expense');
  print('3. View summary');
  print('4. Exit');
}

/// يحسب مجموع المبالغ داخل قائمة من Map<String,double>
double _sumAmounts(List<Map<String, double>> list) {
  double total = 0.0;
  for (var map in list) {
    for (var value in map.values) {
      total += value;
    }
  }
  return total;
}

/// يحاول تحويل النص إلى double ويتحقق أنه غير سالب.
/// يرجع null إذا فشل أو كان سالباً.
double? _parsePositiveDouble(String? s) {
  if (s == null) return null;
  double? val = double.tryParse(s.trim());
  if (val == null) return null;
  if (val < 0) return null;
  return val;
}

/// تنسيق مبالغ بعرض رقمين بعد الفاصلة (للطباعة)
String _formatMoney(double v) {
  return v.toStringAsFixed(2);
}