// GoF: - Facade

using System;

​

//Subsystem

public class BaseDiscountService

{

    public double GetDiscount(int id) => id > 100 ? 0.9 : 0.95;

}

​

//Subsystem

public class OrderService

{

    public bool HasEnoughOrders(int id) => id > 50;

}

//Subsystem

public class DayOfWeekService

{

    // Andditional discount on Sundays

    public double GetDayOfWeekDiscount() => DateTime.Now.DayOfWeek == DayOfWeek.Sunday ? 0.9 : 1.0;

}

//Facade

public class DiscountFacade

{

    private BaseDiscountService _baseDiscountSvc = new();

    private OrderService _orderSvc = new();

    private DayOfWeekService _dayofweekSvc = new();

    public double GetDiscount(int customerId)

    {

        if(_orderSvc.HasEnoughOrders(customerId))

        {

            return _baseDiscountSvc.GetDiscount(customerId) * _dayofweekSvc.GetDayOfWeekDiscount();

        }

        else return 1.0;

    }

}

​

public class Program

{

    public static void Main()

    {   

        DiscountFacade discountFacade = new();

        Console.WriteLine(discountFacade.GetDiscount(10));

        Console.WriteLine(discountFacade.GetDiscount(60));

        Console.WriteLine(discountFacade.GetDiscount(110));

    }

}