credit-card-helper.cs

namespace Parking.Application.Core.Helpers;

public static class CardTypeHelper
{
    public static string GetCardType(string? cardNumber)
    {
        cardNumber = cardNumber?.Replace(" ", "").Replace("-", "");

        if (string.IsNullOrEmpty(cardNumber))
            return "Unknown";
        
        if (Regex.IsMatch(cardNumber, @"^4[0-9]{12}(?:[0-9]{3})?$"))
            return "Visa";

        if (Regex.IsMatch(cardNumber, @"^5[1-5][0-9]{14}$") ||
            Regex.IsMatch(cardNumber, @"^2(2[2-9][0-9]{2}|[3-6][0-9]{3}|7[01][0-9]{2}|7200)[0-9]{10}$"))
            return "MasterCard";

        if (Regex.IsMatch(cardNumber, @"^3[47][0-9]{13}$"))
            return "AmericanExpress";

        if (Regex.IsMatch(cardNumber, @"^6(?:011|5[0-9]{2})[0-9]{12}$"))
            return "Discover";

        return "Unknown";
    }
}