using System;

public class Program

{

    public static void Main()

    {

        ITalker talker = new ConsoleTalker();

        talker.say("hello world");

        /*

        talker = new YellingDecorator(talker);

        talker.say("hello world");

        talker = new FrenchDecorator(talker);

        talker.say("hello world");      

        */

    }

    public interface ITalker {

        void say(string message);

    }   

    public class ConsoleTalker : ITalker {

        public ConsoleTalker(){

        }

        public void say(string message){

            Console.WriteLine(message);

        }       

    }

    public abstract class BaseDecoratorTalker : ITalker {

        protected ITalker wrappee;

        public BaseDecoratorTalker(ITalker wrappee){

            this.wrappee = wrappee;

        }

        public abstract void say(string message);

    }

    public class YellingDecorator : BaseDecoratorTalker{

        public YellingDecorator(ITalker wrappee):base(wrappee){

        }

        public override void say(string message){

            var yelledMessage = message.ToUpper();

            wrappee.say(yelledMessage);

        }       

    }

    public class FrenchDecorator : BaseDecoratorTalker{

        public FrenchDecorator(ITalker wrappee):base(wrappee){

        }

        public override void say(string message){

            var frenchMessage = message.Replace("hello", "bonjour");

            wrappee.say(frenchMessage);

        }       

    }

}