using System;
using System.Collections.Generic;

namespace WzorceProjektowe
{
    public enum Genre{
        Sport,
        Politics,
        Economy,
        Science
    }

    public interface IObserver{
        void Update(ISubject subject);
    }

    public interface ISubject{
        void Attach(IObserver observer);
        //
        //
    }

    public class NewsAgency : ISubject{
        public string NewsHeadline;
        public Genre State;

        public void setNewsHeadline(Genre state, string news){
            this.NewsHeadline = news;
            this.State = state;
        }

        private List<IObserver> Observers = new List<IObserver>();

        //
        //
        //
         public void Attach(IObserver observer){
            this.Observers.Add(observer);
        }

        public void Detach(IObserver observer){
            this.Observers.Remove(observer);
        }

        public void Notify(){
            foreach (var observer in Observers){
                observer.Update(this);
            }
        }
    }

    class DailyEconomy : IObserver{
        public void Update(ISubject subject){
            if ((subject as NewsAgency).State == Genre.Economy){
                Console.WriteLine($"DailyEconomy publikuje artykuł \"{(subject as NewsAgency).NewsHeadline}\"");
            }
        }
    }
     class NewYorkTimes : IObserver{
        public void Update(ISubject subject){
            if ((subject as NewsAgency).State == Genre.Economy || (subject as NewsAgency).State == Genre.Science || (subject as NewsAgency).State == Genre.Sport){
                Console.WriteLine($"NewYorkTimes  publikuje artykuł \"{(subject as NewsAgency).NewsHeadline}\"");
            }
        }
    }
     class NationalGeographic : IObserver{
        public void Update(ISubject subject){
            if ((subject as NewsAgency).State == Genre.Science){
                Console.WriteLine($"NationalGeographic  publikuje artykuł \"{(subject as NewsAgency).NewsHeadline}\"");
            }
        }
    }


    class Program{
        static void Main(string[] args){
            var newsAgency = new NewsAgency();

            var dailyEconomy = new DailyEconomy();
            var newYork = new NewYorkTimes();
            var nationalGeographic = new NationalGeographic();
            newsAgency.Attach(dailyEconomy);
            newsAgency.Attach(newYork);
            newsAgency.Attach(nationalGeographic);

            newsAgency.setNewsHeadline(Genre.Economy, "USA is going bancrupt!");
            newsAgency.Notify();
            newsAgency.setNewsHeadline(Genre.Science, "Life on Alpha Centauri");
            newsAgency.Notify();
            newsAgency.setNewsHeadline(Genre.Sport, "Adam Małysz is the greatest sportsman in the history of mankind");
            newsAgency.Notify();
            newsAgency.setNewsHeadline(Genre.Economy, "CD Project RED value has grown by 500% in 2020");
            newsAgency.Notify();
            newsAgency.setNewsHeadline(Genre.Science, "Kirkendall effect causing airplanes' engine deteriorate");
            newsAgency.Notify();
            newsAgency.Detach(dailyEconomy);
            newsAgency.setNewsHeadline(Genre.Economy, "Texas is going bancrupt!");
            newsAgency.Notify();

            //deatach?
        }
    }
}