using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Collections.Generic;
using System.Threading;

namespace Cnblogs.Ajax
{
	/// <summary>
	/// Summary description for ChatRoom
	/// </summary>
	public class ChatRoom // 界面不好看，同步問題上可能會有問題，本想完全重新寫，但是最終擋不住AJAX框架的誘惑
	{
		private static readonly long ClearUserInterval = 300000;
		private static readonly TimeSpan ExpiringInterval = new TimeSpan(0, 10, 0);
		private static readonly int MessageLimit = 50;

		private static ChatRoom _Instance = new ChatRoom();

		public static ChatRoom Instance
		{
			get
			{
				return _Instance;
			}
		}

		private Dictionary<string, ChattingUser> chatingUsers = null;
		private LinkedList<ChatMessage> chatMessage = null;
		private Timer timer = null;
		private object mutex = new object();

		public ChatRoom()
		{
			this.chatingUsers = new Dictionary<string, ChattingUser>();
			this.chatMessage = new LinkedList<ChatMessage>();

			TimerCallback callback = new TimerCallback(this.OnClearExpiredUser);
			this.timer = new Timer(callback, null, ClearUserInterval, ClearUserInterval);
		}

		public bool UserIsChatting(string userName)
		{
			return this.chatingUsers.ContainsKey(userName);
		}

		public ChattingUser GetUser(string userName)
		{
			return this.chatingUsers[userName];
		}

		public void AddUser(string userName, string password)
		{
			lock (mutex)
			{
				this.chatingUsers[userName] = new ChattingUser(userName, password);
			}
		}

		private void OnClearExpiredUser(object state)
		{
			lock (mutex)
			{
				List<ChattingUser> expiredUsers = new List<ChattingUser>();

				foreach (ChattingUser user in this.chatingUsers.Values)
				{
					if (user.IsExpired(ExpiringInterval))
					{
						expiredUsers.Add(user);
					}
				}

				foreach (ChattingUser user in expiredUsers)
				{
					this.chatingUsers.Remove(user.Name);
				}
			}
		}

		public void SendMessage(string userName, string message)
		{
			lock (mutex)
			{
				if (this.chatMessage.Count >= MessageLimit)
				{
					this.chatMessage.RemoveFirst();
				}

				this.chatMessage.AddLast(new ChatMessage(userName, message));
			}
		}

		public IEnumerable<ChatMessage> GetAllMessages()
		{
			return this.chatMessage;
		}

		public IEnumerable<ChattingUser> GetAllUsers()
		{
			return this.chatingUsers.Values;
		}
	}
}