Discounts.cpp

#include <iostream>
#include <string_view>
#include <string>
#include <cstdlib>
#include <limits>

// Clear the console.

void clearScreen()
{
	system("cls");
}

// Gives time to user to read the console.

void pauseScreen()
{
	std::cout << "Press Enter to continue...";
	std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
	std::cin.get();
}

// Get value user from console.

double getValue(std::string_view str)
{
	std::cout << str;
	double x{};
	std::cin >> x;
	return x;
}

// Calculates discount based on a maximum and minimum.

double calculateDiscount(double& x, const double& discount)
{
	x -= (x * discount / 100);
	return x;
}

// Validates that the user input is a valid value.

double validatePrice(double& x, const double& max, const double& min)
{
	// If the input isn't a valid value, prompt the user to enter it again.

	while (x < min || x >= max)
	{
		clearScreen();
		x = { getValue("Invalid price!, insert a valid price.\n\nEnter the total purchase: ") };
	}
	return x;

}

int main()
{
	char option{};
	do
	{
		std::cout << "--- MAIN MENU ---\n\n";
		std::cout << "1. Purchase less than $100.\n";
		std::cout << "2. Purchase between $100 and $299.\n";
		std::cout << "3. Purchase greater than or equal $300.\n";
		std::cout << "4. Exit\n\n";
		std::cout << "Insert an option: ";
		std::cin >> option;
		clearScreen();
		switch (option)
		{
		case '1':
		{
			double val{ getValue("Enter the total purchase: ") };
			val = { validatePrice(val, 100, 1) };
			std::cout << "Your purchase is less than $100, there aren't discount...\n\n";
			pauseScreen();
			clearScreen();
			option = 'x';
			break;
		}

		case '2':
		{
			double val{ getValue("Enter the total purchase: ") };
			val = { validatePrice(val, 300, 100) };
			std::cout << "Your discount is 10%. Total price is: " << calculateDiscount(val, 10) << "\n\n";
			pauseScreen();
			clearScreen();
			option = 'x';
			break;
		}

		case '3':
		{
			double val{ getValue("Enter the total purchase: ") };
			val = { validatePrice(val, std::numeric_limits<double>::max(), 300) };
			std::cout << "Your discount is 20%. Total price is: " << calculateDiscount(val, 20) << "\n\n";
			pauseScreen();
			clearScreen();
			option = 'x';
			break;
		}

		case '4':
		{
			clearScreen();
			std::cout << "See you later!\n";
			break;
		}

		default:
			std::cout << "Insert a valid value!\n\n";
			pauseScreen();
			clearScreen();
			option = 'x';
			break;
		}

	} while (option == 'x');
	return 0;
}