?using System;
using System.Collections;
using System.Collections.Specialized;
using System.Text;
using System.Threading;
using System.Net.Sockets;
using System.Net;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Formatters.Binary;
using System.IO;

namespace EasyChat_Server
{
    class Listener
    {

        #region 字段定義

        /// <summary>
        /// 服務器程序使用的端口，默認為8888
        /// </summary>
        private int _port = 8888;

        /// <summary>
        /// 接收數據緩沖區大小64K 
        /// </summary>
        private const int _maxPacket = 64 * 1024;

        /// <summary>
        /// 服務器端的監聽器
        /// </summary>
        private TcpListener _tcpl = null;

        /// <summary>
        /// 保存所有客戶端會話的哈希表
        /// </summary>
        private Hashtable _transmit_tb = new Hashtable();

        #endregion
        

        #region 服務器方法

        /// <summary>
        /// 關閉監聽器并釋放資源
        /// </summary>
        public void Close()
        {
            if (_tcpl != null)
            {
                _tcpl.Stop();
            }
            //關閉客戶端連接并清理資源
            if (_transmit_tb.Count != 0)
            {
                foreach (Socket session in _transmit_tb.Values)
                {
                    session.Shutdown(SocketShutdown.Both);
                }
                _transmit_tb.Clear();
                _transmit_tb = null;
            }
        }

        /// <summary>
        /// 配置監聽端口號
        /// </summary>
        public void GetConfig()
        {
            string portParam;
            Console.Write("請輸入監聽端口，直接回車則接受默認端口8888: ");
            portParam = Console.ReadLine();
            if (portParam != string.Empty)
            {
                if (!int.TryParse(portParam, out _port) || _port < 1023 || _port > 65535)
                {
                    _port = 8888;
                    Console.WriteLine("端口號不合法,默認端口號被接受!");
                }
            }
        }

        /// <summary>
        /// 序列化在線列表，向客戶端返回序列化后的字節數組
        /// </summary>
        /// <returns>序列化后的字節數組</returns>
        private byte[] SerializeOnlineList()
        {
            StringCollection onlineList = new StringCollection();
            foreach (object o in _transmit_tb.Keys)
            {
                onlineList.Add(o as string);
            }
            IFormatter format = new BinaryFormatter();
            MemoryStream stream = new MemoryStream();
            format.Serialize(stream, onlineList);
            byte[] ret = stream.ToArray();
            stream.Close();
            return ret;
        }

        /// <summary>
        /// 提取命令
        /// 格式為兩個一位整數拼接成的字符串。
        /// 第一位為0表示客戶機向服務器發送的命令，為1表示服務器向客戶機發送的命令。
        /// 第二位表示命令的含義，具體如下：
        /// "01"-離線
        /// "02"-請求在線列表
        /// "03"-請求對所有人閃屏振動
        /// "04"-請求對指定用戶閃屏振動
        /// "05"-請求廣播消息
        /// default-轉發給指定用戶
        /// </summary>
        /// <param name="s">要解析的包含命令的byte數組，只提取前兩個字節</param>
        /// <returns>拼接成的命令</returns>
        private string DecodingBytes(byte[] s)
        {
            return string.Concat(s[0].ToString(), s[1].ToString());
        }

        /// <summary>
        /// 線程執行體,轉發消息
        /// </summary>
        /// <param name="obj">傳遞給線程執行體的用戶名，用以與用戶通信</param>
        private void ThreadFunc(object obj)
        {
            //通過轉發表得到當前用戶套接字
            Socket clientSkt = _transmit_tb[obj] as Socket;
            while (true)
            {
                try
                {
                    //接受第一個數據包。
                    //僅有兩種情況，一為可以識別的命令格式，否則為要求轉發給指定用戶的用戶名。
                    //這里的實現不夠優雅，但不失為此簡單模型的一個解決之道。
                    byte[] _cmdBuff = new byte[128];
                    clientSkt.Receive(_cmdBuff);
                    string _cmd = DecodingBytes(_cmdBuff);
                    /// "01"-離線
                    /// "02"-請求在線列表
                    /// "03"-請求對所有人閃屏振動
                    /// "04"-請求對指定用戶閃屏振動
                    /// "05"-請求廣播消息
                    /// default-轉發給指定用戶
                    switch (_cmd)
                    {
                        case "01":
                            {
                                _transmit_tb.Remove(obj);
                                string svrlog = string.Format("[系統消息]用戶 {0} 在 {1} 已斷開... 當前在線人數: {2}\r\n\r\n", obj, DateTime.Now, _transmit_tb.Count);
                                Console.WriteLine(svrlog);
                                //向所有客戶機發送系統消息
                                foreach (DictionaryEntry de in _transmit_tb)
                                {
                                    string _clientName = de.Key as string;
                                    Socket _clientSkt = de.Value as Socket;
                                    _clientSkt.Send(Encoding.Unicode.GetBytes(svrlog));
                                }
                                Thread.CurrentThread.Abort();
                                break;
                            }
                        case "02":
                            {
                                byte[] onlineBuff = SerializeOnlineList();
                                //先發送響應信號，用于客戶機的判斷，"11"表示服務發給客戶機的更新在線列表的命令
                                clientSkt.Send(new byte[] { 1, 1 });
                                clientSkt.Send(onlineBuff);
                                break;
                            }
                        case "03":
                            {
                                string displayTxt = string.Format("[系統提示]用戶 {0} 向您發送了一個閃屏振動。\r\n\r\n", obj);
                                foreach (DictionaryEntry de in _transmit_tb)
                                {
                                    string _clientName = de.Key as string;
                                    Socket _clientSkt = de.Value as Socket;
                                    if (!_clientName.Equals(obj))
                                    {
                                        //先發送響應信號，用于客戶機的判斷，"12"表示服務發給客戶機的閃屏振動的命令
                                        _clientSkt.Send(new byte[] { 1, 2 });
                                        _clientSkt.Send(Encoding.Unicode.GetBytes(displayTxt));
                                    }
                                }
                                break;
                            }
                        case "04":
                            {
                                string _receiver = null;
                                byte[] _receiverBuff = new byte[128];
                                clientSkt.Receive(_receiverBuff);
                                _receiver = Encoding.Unicode.GetString(_receiverBuff).TrimEnd('\0');
                                string displayTxt = string.Format("[系統提示]用戶 {0} 向您發送了一個閃屏振動。\r\n\r\n", obj);
                                //通過轉發表查找接收方的套接字
                                if (_transmit_tb.ContainsKey(_receiver))
                                {
                                    Socket receiverSkt = _transmit_tb[_receiver] as Socket;
                                    receiverSkt.Send(new byte[] { 1, 2 });
                                    receiverSkt.Send(Encoding.Unicode.GetBytes(displayTxt));
                                }
                                else
                                {
                                    string sysMessage = string.Format("[系統消息]您剛才的閃屏振動沒有發送成功。\r\n可能原因：用戶 {0} 已離線或者網絡阻塞。\r\n\r\n", _receiver);
                                    clientSkt.Send(Encoding.Unicode.GetBytes(sysMessage));
                                }
                                break;
                            }
                        case "05":
                            {
                                byte[] _msgBuff = new byte[_maxPacket];
                                clientSkt.Receive(_msgBuff);
                                foreach (DictionaryEntry de in _transmit_tb)
                                {
                                    string _clientName = de.Key as string;
                                    Socket _clientSkt = de.Value as Socket;
                                    if (!_clientName.Equals(obj))
                                    {
                                        _clientSkt.Send(_msgBuff);
                                    }
                                }
                                break;
                            }
                        default:
                            {
                                //以上都不是則表明第一個包是接收方用戶名，繼續接受第二個消息正文數據包
                                string _receiver = Encoding.Unicode.GetString(_cmdBuff).TrimEnd('\0');
                                byte[] _packetBuff = new byte[_maxPacket];
                                clientSkt.Receive(_packetBuff);
                                if (_transmit_tb.ContainsKey(_receiver))
                                {
                                    //通過轉發表查找接收方的套接字
                                    Socket receiverSkt = _transmit_tb[_receiver] as Socket;
                                    receiverSkt.Send(_packetBuff);
                                }
                                else
                                {
                                    string sysMessage = string.Format("[系統消息]您剛才的內容沒有發送成功。\r\n可能原因：用戶 {0} 已離線或者網絡阻塞。\r\n\r\n", _receiver);
                                    clientSkt.Send(Encoding.Unicode.GetBytes(sysMessage));
                                }
                                break;
                            }
                    }
                }
                catch (SocketException)
                {
                    _transmit_tb.Remove(obj);
                    string svrlog = string.Format("[系統消息]用戶 {0} 的客戶端在 {1} 意外終止！當前在線人數：{2}\r\n\r\n", obj, DateTime.Now, _transmit_tb.Count);
                    Console.WriteLine(svrlog);
                    //向所有客戶機發送系統消息
                    foreach (DictionaryEntry de in _transmit_tb)
                    {
                        string _clientName = de.Key as string;
                        Socket _clientSkt = de.Value as Socket;
                        _clientSkt.Send(Encoding.Unicode.GetBytes(svrlog));
                    }
                    Console.WriteLine();
                    Thread.CurrentThread.Abort();
                }
            }
        }

        /// <summary>
        /// 啟動監聽，輪詢監聽客戶機請求并將客戶端套接字存入轉發表
        /// </summary>
        public void StartUp()
        {
            IPAddress _ip = Dns.GetHostAddresses(Dns.GetHostName())[0];
            _tcpl = new TcpListener(_ip, _port);
            _tcpl.Start();
            Console.WriteLine("服務器已啟動，正在監聽...\n");
            Console.WriteLine(string.Format("服務器IP：{0}\t端口號：{1}\n", _ip, _port));
            while (true)
            {
                byte[] packetBuff = new byte[_maxPacket];
                Socket newClient = _tcpl.AcceptSocket();
                newClient.Receive(packetBuff);
                string userName = Encoding.Unicode.GetString(packetBuff).TrimEnd('\0');
                //驗證是否為唯一用戶
                if (_transmit_tb.Count != 0 && _transmit_tb.ContainsKey(userName))
                {
                    newClient.Send(Encoding.Unicode.GetBytes("cmd::Failed"));
                    continue;
                }
                else
                {
                    newClient.Send(Encoding.Unicode.GetBytes("cmd::Successful"));
                }
                //將新連接加入轉發表并創建線程為其服務
                _transmit_tb.Add(userName, newClient);
                string svrlog = string.Format("[系統消息]新用戶 {0} 在 {1} 已連接... 當前在線人數: {2}\r\n\r\n", userName, DateTime.Now, _transmit_tb.Count);
                Console.WriteLine(svrlog);
                
                Thread clientThread = new Thread(new ParameterizedThreadStart(ThreadFunc));
                clientThread.Start(userName);
                //向所有客戶機發送系統消息
                foreach (DictionaryEntry de in _transmit_tb)
                {
                    string _clientName = de.Key as string;
                    Socket _clientSkt = de.Value as Socket;
                    if (!_clientName.Equals(userName))
                    {
                        _clientSkt.Send(Encoding.Unicode.GetBytes(svrlog));
                    }
                }
            }
        }

        #endregion
    }
}