using System;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        var calculator = new SubscriptionCalculator();

        var discountValue = calculator.Calculate((decimal)100.5, 2, 6);

        var discountValue1 = calculator.Calculate((decimal)100.5, MembershipType.SimpleCustomer, 6);

        Console.WriteLine("Discounted value for six years is " + discountValue);

        Console.WriteLine("Discounted value for six years is " + discountValue1);   

    }

}

​

​

public class MembershipSubscriptionDiscount

{

    private static readonly MembershipSubscriptionDiscount NotRegisteredSubscriptionDiscount = new MembershipSubscriptionDiscount(MembershipType.NotRegistered, 0);

    private static readonly MembershipSubscriptionDiscount SimpleCustomerSubscriptionDiscount = new MembershipSubscriptionDiscount(MembershipType.SimpleCustomer, 10);

    private static readonly MembershipSubscriptionDiscount ValuableCustomerSubscriptionDiscount = new MembershipSubscriptionDiscount(MembershipType.ValuableCustomer, 30);

    private static readonly MembershipSubscriptionDiscount MostValuableCustomerSubscriptionDiscount = new MembershipSubscriptionDiscount(MembershipType.MostValuableCustomer, 50);

    private static readonly MembershipSubscriptionDiscount GoldSubscriptionDiscount = new MembershipSubscriptionDiscount(MembershipType.Gold, 60);

​

    public static readonly MembershipSubscriptionDiscount[] KnownMembershipSubscriptionDiscounts = new MembershipSubscriptionDiscount[] {

        NotRegisteredSubscriptionDiscount,

        SimpleCustomerSubscriptionDiscount,

        ValuableCustomerSubscriptionDiscount,

        MostValuableCustomerSubscriptionDiscount,

        GoldSubscriptionDiscount

    };

​

    private MembershipSubscriptionDiscount(MembershipType membershipType, decimal discountRate)

    {

        MembershipType = membershipType;

        DiscountRate = discountRate;

    }

​

    public MembershipType MembershipType { get; private set; }

    public decimal DiscountRate { get; private set; }

}

​

public enum MembershipType

{

    NotRegistered = 1,

    SimpleCustomer = 2,

    ValuableCustomer = 3,

    MostValuableCustomer = 4,

    Gold = 5

}

​

public interface ISubscriptionCalculator

{

    decimal Calculate(decimal amount, MembershipType membershipType, int years);

    decimal Calculate(decimal amount, int discountType, int years);

}

​

//    NotRegistered = 1,

//    SimpleCustomer = 2, (10%)

//    ValuableCustomer = 3 (30%)

//    MostValuableCustomer =  4 (50%)

// NEW REQUIREMENT: Add a new membership type of gold customer where discount is 60%

public class SubscriptionCalculator : ISubscriptionCalculator

{

    public decimal Calculate(decimal amount, MembershipType membershipType, int years)

    {

        if (amount <= 0)

            throw new ArgumentOutOfRangeException("'{nameof(amount)}' must be greater than 0.");

        if (years < 0)

            throw new ArgumentOutOfRangeException("'{nameof(years)}' must be greater than 0.");

​

        var membershipSubscriptionDiscount = MembershipSubscriptionDiscount.KnownMembershipSubscriptionDiscounts.FirstOrDefault(m => m.MembershipType == membershipType);

        if (membershipSubscriptionDiscount == null)

            throw new ArgumentException("Unable to find subscription discount for membership type '{membershipType}'.");

​

        var yearBasedDiscountRate = years > 5 ? (decimal) 5 / 100 : (decimal) years / 100;

​

        return amount * (1 - membershipSubscriptionDiscount.DiscountRate / 100) * (1 - yearBasedDiscountRate);

    }

​

    public decimal Calculate(decimal amount, int discountType, int years)

    {

        decimal result = 0;

        decimal disc = (years > 5) ? (decimal)5 / 100 : (decimal)years / 100;

        if (discountType == 1)

        {

            result = amount;

        }

        else if (discountType == 2)

        {

            result = (amount - (0.1m * amount)) - disc * (amount - (0.1m * amount));

        }

        else if (discountType == 3)

        {

            result = (0.7m * amount) - disc * (0.7m * amount);

        }

        else if (discountType == 4)

        {

            result = (amount - (0.5m * amount)) - disc * (amount - (0.5m * amount));

        }

        return result;

    }

}

​

​