using System;
using System.Collections.Generic;
using System.Text;

namespace ConsoleSmaple
{
    class Program
    {
        static void Main(string[] args)
        {
            Commodity aCommodity1 = new Commodity("中华牙膏", 12);
            Commodity aCommodity2 = new Commodity("李宁运动服",300);
            Console.WriteLine(string.Format("当前中华牙膏的价格：{0}",aCommodity1.Price.ToString()));
            Console.WriteLine(string.Format("当前李宁运动服的价格：{0}", aCommodity2.Price.ToString()));
            Console.WriteLine();

            Buyer aBuyer1 = new Buyer(1);
            Buyer aBuyer2 = new Buyer(2);

            Subscriber subscriber = new Subscriber();
            subscriber.Subscribe(aBuyer1, aCommodity1);
            subscriber.Subscribe(aBuyer1, aCommodity2);
            subscriber.Subscribe(aBuyer2, aCommodity1);
            subscriber.Subscribe(aBuyer2, aCommodity2);

            aCommodity1.Price = 15;

            Console.WriteLine("取消部分订阅....");
            subscriber.CancelSubscribe(aBuyer1, aCommodity2);
            subscriber.CancelSubscribe(aBuyer2, aCommodity1);


            aCommodity2.Price = 1000;

            Console.WriteLine();
            Console.WriteLine("Press Enter to Exit");
            Console.ReadLine();
        }
    }


    public delegate void ChangePriceEventHandler(object sender, EventArgs e);

    /// <summary>
    /// 商品类
    /// </summary>
    public class Commodity
    {
        private long _price;
        private string _name;

        public string Name
        {
            get { return _name; }
            set { _name = value; }
        }
        public long Price
        {
            get { return _price; }
            set
            {
                if (value != _price)
                {
                    _price = value;
                    OnChangePrice();
                }
            }
        }

        public event ChangePriceEventHandler ChangePrice;

        public Commodity(string name, long price)
        {
            _name = name;
            _price = price;
        }

        private void OnChangePrice()
        {
            ChangePriceEventHandler temp = ChangePrice;
            if (temp != null)
            {
                temp(this, EventArgs.Empty);
            }
        }
    }

    /// <summary>
    /// 买家类
    /// </summary>
    public class Buyer
    {
        private int _id;

        public int ID
        {
            get { return _id; }
            set { _id = value; }
        }

        public Buyer(int Id)
        {
            _id = Id;
        }
    }

    /// <summary>
    /// 商品集合类
    /// </summary>
    public class CommodityCollection : List<Commodity>
    {

    }

    /// <summary>
    /// 类似一个买家与商品的关系表;
    /// </summary>
    public class BuyerRefCommodityCollection : Dictionary<Buyer, CommodityCollection>
    {
        
    }

    /// <summary>
    /// 所有用户订阅与取消订阅都在这里实现；
    /// 
    /// 如果是多种订阅和取消订阅的方式
    /// 可以抽象此类，变为多种策略实现；
    /// </summary>
    public class Subscriber
    {
        private BuyerRefCommodityCollection _ref = new BuyerRefCommodityCollection();
        private NormalNotity _notify = new NormalNotity();

        /// <summary>
        /// 订阅商品
        /// </summary>
        /// <param name="aCommodity">商品</param>
        public void Subscribe(Buyer buyer, Commodity aCommodity)
        {
            if (_ref.ContainsKey(buyer))
            {
                CommodityCollection list = _ref[buyer];
                list.Add(aCommodity);
            }
            else
            {
                CommodityCollection list = new CommodityCollection();
                list.Add(aCommodity);
                _ref.Add(buyer, list);
            }
            aCommodity.ChangePrice += new ChangePriceEventHandler(aCommodity_ChangePrice);
        }

        /// <summary>
        /// 取消订阅商品
        /// </summary>
        /// <param name="aCommodity">商品</param>
        public void CancelSubscribe(Buyer buyer, Commodity aCommodity)
        {
            if (_ref.ContainsKey(buyer))
            {
                CommodityCollection list = _ref[buyer];
                list.Remove(aCommodity);
                aCommodity.ChangePrice -= new ChangePriceEventHandler(aCommodity_ChangePrice);
            }
        }

        void aCommodity_ChangePrice(object sender, EventArgs e)
        {
            Commodity aCommodity = sender as Commodity;
            foreach (KeyValuePair<Buyer, CommodityCollection> item in _ref)
            {
                CommodityCollection list = item.Value;
                foreach (Commodity commodity in list)
                {
                    if (commodity == aCommodity) //这里可以重载操作符（比如通过商品名称判断是否相等）；
                    {
                        _notify.SendNotity(item.Key, commodity);
                    }
                }
            }
        }

    }

    /// <summary>
    /// 如果是多种通知用户价格变更的方式
    /// 则可以抽象此类，变为多种策略实现；，比如可以改为邮件通知；
    /// </summary>
    public class NormalNotity
    {
        /// <summary>
        /// 发送通知
        /// </summary>
        /// <param name="buyer"></param>
        /// <param name="aCommodity"></param>
        public void SendNotity(Buyer buyer, Commodity aCommodity)
        {
            Console.WriteLine(string.Format("用户[{0}] 获取 {1} 的最新价格为：{2}", buyer.ID, aCommodity.Name, aCommodity.Price.ToString()));
        }
    }


}