Budget App


import 'dart:io';

const double taxRate = 0.15;

void main() {
final List<Map<String, double>> incomeList = [];
final List<Map<String, double>> expenseList = [];

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

while (true) {
print('\nPlease choose an option:');
print('1. Add income');
print('2. Add expense');
print('3. View summary');
print('4. Exit');

final choice = _readInt('Enter your choice: ');

if (choice == 1) {
final desc = _readString('Enter income description: ');
final amount = _readPositiveDouble('Enter income amount: ');
incomeList.add({desc: amount});
print('Income added!');
} else if (choice == 2) {
final desc = _readString('Enter expense description: ');
final amount = _readPositiveDouble('Enter expense amount: ');
expenseList.add({desc: amount});
print('Expense added!');
} else if (choice == 3) {
final totalIncome = _sumList(incomeList);
final totalExpenses = _sumList(expenseList);
final net = totalIncome - totalExpenses;

print('\nSummary:');
print('Total income: \$${totalIncome.toStringAsFixed(2)}');
print('Total expenses: \$${totalExpenses.toStringAsFixed(2)}');

if (net >= 0) {
print('Net profit: \$${net.toStringAsFixed(2)}');
} else {
print('Net loss: \$${(-net).toStringAsFixed(2)}');
}

// Optional tax (ternary): tax only if profitable
final tax = (net > 0) ? net * taxRate : 0.0;
if (tax > 0) {
print('Tax to be paid: \$${tax.toStringAsFixed(2)}');
}
} else if (choice == 4) {
print('Exiting the application. Goodbye!');
break;
} else {
print('Invalid choice. Please try again.');
}
}
}

double _sumList(List<Map<String, double>> list) {
double sum = 0.0;
for (final entry in list) {
for (final value in entry.values) {
sum += value;
}
}
return sum;
}

int _readInt(String prompt) {
while (true) {
stdout.write(prompt);
final input = stdin.readLineSync();
final value = int.tryParse(input ?? '');
if (value != null) return value;
print('Please enter a valid number.');
}
}

String _readString(String prompt) {
while (true) {
stdout.write(prompt);
final input = stdin.readLineSync();
final value = (input ?? '').trim();
if (value.isNotEmpty) return value;
print('Input cannot be empty.');
}
}

double _readPositiveDouble(String prompt) {
while (true) {
stdout.write(prompt);
final input = stdin.readLineSync();
final value = double.tryParse(input ?? '');
// logical & relational operators for validation
if (value != null && value >= 0) return value;
print('Please enter a valid non-negative number.');
}
}