pattern decorator C# example

Program.cs

using System.Text;

namespace CoffeeShop
{
    // розміри чашок у мілілітрах
    internal enum Size { Small = 80, Medium = 180, Large = 280, ExtraLarge = 500 }

    // базовий абстрактний напій
    internal abstract class Beverage
    {
        protected Size size;
        protected double price;
        protected string? description;

        public Size GetSize() => size;

        public double GetPrice() => price;

        public string? GetDescription() => description;

        public void Print()
        {
            Console.WriteLine($"{description} = {price:F2} грн");
        }
    }

    // чорний чай - конкретний базовий напій без добавок
    internal class BlackTea : Beverage
    {
        public BlackTea(Size size)
        {
            this.size = size;
            description = "чорний чай з пакетика";
            price = size switch
            {
                Size.Medium => 35,
                Size.Large => 45,
                _ => throw new ArgumentException("неправильний розмір чашки")
            };
        }
    }

    // зелений чай - конкретний базовий напій без добавок
    internal class GreenTea : Beverage
    {
        public GreenTea()
        {
            size = Size.Medium;
            description = "зелений листовий чай";
            price = 55;
        }
    }

    // еспресо - конкретний базовий напій без добавок
    internal class Espresso : Beverage
    {
        public Espresso()
        {
            size = Size.Small;
            description = "мала порція міцної кави";
            price = 45;
        }
    }

    // базова абстрактна добавка
    internal abstract class Condiment : Beverage
    {
        protected Beverage? beverage;
    }

    // молоко
    internal class MilkCondiment : Condiment
    {
        public MilkCondiment(Beverage beverage)
        {
            this.beverage = beverage;
            description = $"{this.beverage.GetDescription()} + молоко (5 грн)";
            price = this.beverage.GetPrice() + 5;
            size = this.beverage.GetSize();
        }

        public MilkCondiment() // молоко може бути основою напою
        {
            beverage = this;
            description = "склянка молока";
            price = 15;
            size = Size.Medium;
        }
    }

    // шоколад
    internal class ChocolateCondiment : Condiment
    {
        public ChocolateCondiment(Beverage beverage)
        {
            this.beverage = beverage;
            description = $"{this.beverage.GetDescription()} + шоколад (8 грн)";
            price = this.beverage.GetPrice() + 8;
            size = this.beverage.GetSize();
        }
    }

    // цукор
    internal class SugarCondiment : Condiment
    {
        public SugarCondiment(Beverage beverage)
        {
            this.beverage = beverage;
            description = $"{this.beverage.GetDescription()} + цукор (2 грн)";
            price = this.beverage.GetPrice() + 2;
            size = this.beverage.GetSize();
        }
    }

    internal static class Program
    {
        private static void Main()
        {
            Console.OutputEncoding = Encoding.UTF8;

            var espresso = new Espresso();
            var blackTea = new BlackTea(Size.Large);
            var greenTea = new GreenTea();
            espresso.Print();
            blackTea.Print();
            greenTea.Print();
            Console.WriteLine("================================================");
            var cappuccino = new SugarCondiment(new MilkCondiment(new Espresso()));
            cappuccino.Print();
            var chocolateCappuccino = new ChocolateCondiment(cappuccino);
            chocolateCappuccino.Print();
            var extraSweetBlackTea = new SugarCondiment(new SugarCondiment(new SugarCondiment(new BlackTea(Size.Large))));
            extraSweetBlackTea.Print();
            var glassOfMilk = new MilkCondiment();
            glassOfMilk.Print();
        }
    }
}