using System;

using Coffeehouse;

​

namespace Coffeehouse

{

    public class Customer

    {

    }

​

    public class Void

    {

        public Void()

        {

            Console.WriteLine(this.GetType().Name);

        }

    }

​

    public class Water : Void

    {

    }

​

    public class Milk : Void

    {

    }

​

    public class Vanilla : Void

    {

    }

​

    public class Chocolate : Void

    {

    }

​

    public class Strawberry : Void

    {

    }

​

    public class Coffee : Void

    {

    }

​

    public interface IService<Out, In>

    {

        Out Serve(In input);

    }

​

    internal class EmptyOrder<Out> : IService<Out, Customer> where Out : class

    {

        private IService<Out, Customer> _base;

        public EmptyOrder()

        {

        }

​

        public EmptyOrder(IService<Out, Customer> service)

        {

            _base = service;

        }

​

        public Out Serve(Customer input)

        {

            if (_base == null)

                return null;

            var output = _base.Serve(input);

            return output;

        }

    }

​

    internal class WaterOrder<Out> : IService<Water, Customer>

    {

        private IService<Out, Customer> _base;

        public WaterOrder()

        {

        }

​

        public WaterOrder(IService<Out, Customer> service)

        {

            _base = service;

        }

​

        public Water Serve(Customer _)

        {

            if (_base != null)

                _base.Serve(_);

            return new Water();

        }

    }

​

    internal class MilkOrder : IService<Milk, Customer>

    {

        public Milk Serve(Customer _)

        {

            return new Milk();

        }

    }

​

    internal class CoffeeOrder<Out> : IService<Coffee, Customer>

    {

        private IService<Out, Customer> _base;

        public CoffeeOrder()

        {

        }

​

        public CoffeeOrder(IService<Out, Customer> service)

        {

            _base = service;

        }

​

        public Coffee Serve(Customer _)

        {

            if (_base != null)

                _base.Serve(_);

            return new Coffee();

        }

    }

​

    public abstract class CoffeehouseOrder : IService<Void, Customer>

    {

        private IService<Coffee, Customer> _order;

        private IService<Water, Customer> _waterOrder;

        public CoffeehouseOrder() : this(new CoffeeOrder<Void>())

        {

        }

​

        public CoffeehouseOrder(IService<Coffee, Customer> order)

        {

            _order = order;

        }

        public CoffeehouseOrder(IService<Water, Customer> order)

        {

            _waterOrder = order;

        }

​

        public Void Serve(Customer customer)

        {

            Console.WriteLine("---Prepare");

            if (_order != null)

                _order.Serve(customer);

            if (_waterOrder != null)

                _waterOrder.Serve(customer);

            Console.WriteLine("---Served\n");

            return new Void();

        }

    }

​

    /// <summary>

    /// Expresso is a coffee with water

    /// </summary>

    public class ExpressoOrder : CoffeehouseOrder

    {

    }

​

    /// <summary>

    /// Double expresso is an expresso with another expresso added

    /// </summary>

    public class DoubleExpressoOrder : CoffeehouseOrder

    {

    }

​

    /// <summary>

    /// Latte is milk with espresso added

    /// </summary>

    public class LatteOrder : CoffeehouseOrder

    {

    }

​

    /// <summary>

    /// Long black is water with espresso added

    /// </summary>

    public class LongBlackOrder : CoffeehouseOrder

    {

    }

​

    /// <summary>

    /// Cappuccino is an espresso with milk added

    /// </summary>

    public class CappucinoOrder : CoffeehouseOrder

    {

    }

​

    /// <summary>

    /// Americano is an espresso with water added

    /// </summary>

    public class AmericanoOrder : CoffeehouseOrder

    {

    }

}

​

public class Program

{

    public static void Main()

    {

        var customer = new Customer();

        Console.WriteLine("An expresso please !");

        var expressoOrder = new ExpressoOrder();

        expressoOrder.Serve(customer);

        Console.WriteLine("A latte please !");

        var latteOrder = new LatteOrder();

        latteOrder.Serve(customer);

        Console.WriteLine("A double expresso please !");

        var doubleExpressoOrder = new DoubleExpressoOrder();

        doubleExpressoOrder.Serve(customer);

        Console.WriteLine("An americano please !");

        var americanoOrder = new AmericanoOrder();

        americanoOrder.Serve(customer);

    }

}