using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net.Sockets;
using System.Net;
using System.Threading;

namespace ServerTest
{
    /// <summary>
    /// IOCP SOCKET伺服器
    /// </summary>
    public class IOCPServer : IDisposable
    {
        const int opsToPreAlloc = 2;
        #region Fields
        /// <summary>
        /// 伺服器程式允許的最大客戶端連線數
        /// </summary>
        private int _maxClient;

        /// <summary>
        /// 監聽Socket，用於接受客戶端的連線請求
        /// </summary>
        private Socket _serverSock;

        /// <summary>
        /// 當前的連線的客戶端數
        /// </summary>
        private int _clientCount;

        /// <summary>
        /// 用於每個I/O Socket操作的緩衝區大小
        /// </summary>
        private int _bufferSize = 1024;

        /// <summary>
        /// 訊號量
        /// </summary>
        Semaphore _maxAcceptedClients;

        /// <summary>
        /// 緩衝區管理
        /// </summary>
        BufferManager _bufferManager;

        /// <summary>
        /// 物件池
        /// </summary>
        SocketAsyncEventArgsPool _objectPool;

        private bool disposed = false;

        #endregion

        #region Properties

        /// <summary>
        /// 伺服器是否正在執行
        /// </summary>
        public bool IsRunning { get; private set; }
        /// <summary>
        /// 監聽的IP地址
        /// </summary>
        public IPAddress Address { get; private set; }
        /// <summary>
        /// 監聽的埠
        /// </summary>
        public int Port { get; private set; }
        /// <summary>
        /// 通訊使用的編碼
        /// </summary>
        public Encoding Encoding { get; set; }

        #endregion

        #region Ctors

        /// <summary>
        /// 非同步IOCP SOCKET伺服器
        /// </summary>
        /// <param name="listenPort">監聽的埠</param>
        /// <param name="maxClient">最大的客戶端數量</param>
        public IOCPServer(int listenPort,int maxClient)
            : this(IPAddress.Any, listenPort, maxClient)
        {
        }

        /// <summary>
        /// 非同步Socket TCP伺服器
        /// </summary>
        /// <param name="localEP">監聽的終結點</param>
        /// <param name="maxClient">最大客戶端數量</param>
        public IOCPServer(IPEndPoint localEP, int maxClient)
            : this(localEP.Address, localEP.Port,maxClient)
        {
        }

        /// <summary>
        /// 非同步Socket TCP伺服器
        /// </summary>
        /// <param name="localIPAddress">監聽的IP地址</param>
        /// <param name="listenPort">監聽的埠</param>
        /// <param name="maxClient">最大客戶端數量</param>
        public IOCPServer(IPAddress localIPAddress, int listenPort, int maxClient)
        {
            this.Address = localIPAddress;
            this.Port = listenPort;
            this.Encoding = Encoding.Default;

            _maxClient = maxClient;

            _serverSock = new Socket(localIPAddress.AddressFamily, SocketType.Stream, ProtocolType.Tcp);

            _bufferManager = new BufferManager(_bufferSize * _maxClient * opsToPreAlloc,_bufferSize);

            _objectPool = new SocketAsyncEventArgsPool(_maxClient);

            _maxAcceptedClients = new Semaphore(_maxClient, _maxClient); 
        }

        #endregion


        #region 初始化

        /// <summary>
        /// 初始化函式
        /// </summary>
        public void Init()
        {
            // Allocates one large byte buffer which all I/O operations use a piece of.  This gaurds 
            // against memory fragmentation
            _bufferManager.InitBuffer();

            // preallocate pool of SocketAsyncEventArgs objects
            SocketAsyncEventArgs readWriteEventArg;

            for (int i = 0; i < _maxClient; i++)
            {
                //Pre-allocate a set of reusable SocketAsyncEventArgs
                readWriteEventArg = new SocketAsyncEventArgs();
                readWriteEventArg.Completed += new EventHandler<SocketAsyncEventArgs>(OnIOCompleted);
                readWriteEventArg.UserToken = null;

                // assign a byte buffer from the buffer pool to the SocketAsyncEventArg object
                _bufferManager.SetBuffer(readWriteEventArg);

                // add SocketAsyncEventArg to the pool
                _objectPool.Push(readWriteEventArg);
            }

        }

        #endregion

        #region Start
        /// <summary>
        /// 啟動
        /// </summary>
        public void Start()
        {
            if (!IsRunning)
            {
                Init();
                IsRunning = true;
                IPEndPoint localEndPoint = new IPEndPoint(Address, Port);
                // 建立監聽socket
                _serverSock = new Socket(localEndPoint.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
                //_serverSock.ReceiveBufferSize = _bufferSize;
                //_serverSock.SendBufferSize = _bufferSize;
                if (localEndPoint.AddressFamily == AddressFamily.InterNetworkV6)
                {
                    // 配置監聽socket為 dual-mode (IPv4 & IPv6) 
                    // 27 is equivalent to IPV6_V6ONLY socket option in the winsock snippet below,
                    _serverSock.SetSocketOption(SocketOptionLevel.IPv6, (SocketOptionName)27, false);
                    _serverSock.Bind(new IPEndPoint(IPAddress.IPv6Any, localEndPoint.Port));
                }
                else
                {
                    _serverSock.Bind(localEndPoint);
                }
                // 開始監聽
                _serverSock.Listen(this._maxClient);
                // 在監聽Socket上投遞一個接受請求。
                StartAccept(null);
            }
        }
        #endregion

        #region Stop

        /// <summary>
        /// 停止服務
        /// </summary>
        public void Stop()
        {
            if (IsRunning)
            {
                IsRunning = false;
                _serverSock.Close();
                //TODO 關閉對所有客戶端的連線

            }
        }

        #endregion


        #region Accept

        /// <summary>
        /// 從客戶端開始接受一個連線操作
        /// </summary>
        private void StartAccept(SocketAsyncEventArgs asyniar)
        {
            if (asyniar == null)
            {
                asyniar = new SocketAsyncEventArgs();
                asyniar.Completed += new EventHandler<SocketAsyncEventArgs>(OnAcceptCompleted);
            }
            else
            {
                //socket must be cleared since the context object is being reused
                asyniar.AcceptSocket = null;
            }
            _maxAcceptedClients.WaitOne();
            if (!_serverSock.AcceptAsync(asyniar))
            {
                ProcessAccept(asyniar);
                //如果I/O掛起等待非同步則觸發AcceptAsyn_Asyn_Completed事件
                //此時I/O操作同步完成，不會觸發Asyn_Completed事件，所以指定BeginAccept()方法
            }
        }

        /// <summary>
        /// accept 操作完成時回撥函式
        /// </summary>
        /// <param name="sender">Object who raised the event.</param>
        /// <param name="e">SocketAsyncEventArg associated with the completed accept operation.</param>
        private void OnAcceptCompleted(object sender, SocketAsyncEventArgs e)
        {
            ProcessAccept(e);
        }

        /// <summary>
        /// 監聽Socket接受處理
        /// </summary>
        /// <param name="e">SocketAsyncEventArg associated with the completed accept operation.</param>
        private void ProcessAccept(SocketAsyncEventArgs e)
        {
            if (e.SocketError == SocketError.Success)
            {
                Socket s = e.AcceptSocket;//和客戶端關聯的socket
                if (s.Connected)
                {
                    try
                    {
                        
                        Interlocked.Increment(ref _clientCount);//原子操作加1
                        SocketAsyncEventArgs asyniar = _objectPool.Pop();
                        asyniar.UserToken = s;

                        Log4Debug(String.Format("客戶 {0} 連入, 共有 {1} 個連線。", s.RemoteEndPoint.ToString(), _clientCount));
                        
                        if (!s.ReceiveAsync(asyniar))//投遞接收請求
                        {
                            ProcessReceive(asyniar);
                        }
                    }
                    catch (SocketException ex)
                    {
                        Log4Debug(String.Format("接收客戶 {0} 資料出錯, 異常資訊： {1} 。", s.RemoteEndPoint, ex.ToString()));
                        //TODO 異常處理
                    }
                    //投遞下一個接受請求
                    StartAccept(e);
                }
            }
        }

        #endregion

        #region 傳送資料

        /// <summary>
        /// 非同步的傳送資料
        /// </summary>
        /// <param name="e"></param>
        /// <param name="data"></param>
        public void Send(SocketAsyncEventArgs e, byte[] data)
        {
            if (e.SocketError == SocketError.Success)
            {
                Socket s = e.AcceptSocket;//和客戶端關聯的socket
                if (s.Connected)
                {
                    Array.Copy(data, 0, e.Buffer, 0, data.Length);//設定傳送資料

                    //e.SetBuffer(data, 0, data.Length); //設定傳送資料
                    if (!s.SendAsync(e))//投遞傳送請求，這個函式有可能同步傳送出去，這時返回false，並且不會引發SocketAsyncEventArgs.Completed事件
                    {
                        // 同步傳送時處理髮送完成事件
                        ProcessSend(e);
                    }
                    else
                    {
                        CloseClientSocket(e);
                    }
                }
            }
        }

        /// <summary>
        /// 同步的使用socket傳送資料
        /// </summary>
        /// <param name="socket"></param>
        /// <param name="buffer"></param>
        /// <param name="offset"></param>
        /// <param name="size"></param>
        /// <param name="timeout"></param>
        public void Send(Socket socket, byte[] buffer, int offset, int size, int timeout)
        {
            socket.SendTimeout = 0;
            int startTickCount = Environment.TickCount;
            int sent = 0; // how many bytes is already sent
            do
            {
                if (Environment.TickCount > startTickCount + timeout)
                {
                    //throw new Exception("Timeout.");
                }
                try
                {
                    sent += socket.Send(buffer, offset + sent, size - sent, SocketFlags.None);
                }
                catch (SocketException ex)
                {
                    if (ex.SocketErrorCode == SocketError.WouldBlock ||
                    ex.SocketErrorCode == SocketError.IOPending ||
                    ex.SocketErrorCode == SocketError.NoBufferSpaceAvailable)
                    {
                        // socket buffer is probably full, wait and try again
                        Thread.Sleep(30);
                    }
                    else
                    {
                        throw ex; // any serious error occurr
                    }
                }
            } while (sent < size);
        }


        /// <summary>
        /// 傳送完成時處理函式
        /// </summary>
        /// <param name="e">與傳送完成操作相關聯的SocketAsyncEventArg物件</param>
        private void ProcessSend(SocketAsyncEventArgs e)
        {
            if (e.SocketError == SocketError.Success)
            {
                Socket s = (Socket)e.UserToken;

                //TODO
            }
            else
            {
                CloseClientSocket(e);
            }
        }

        #endregion

        #region 接收資料


        /// <summary>
        ///接收完成時處理函式
        /// </summary>
        /// <param name="e">與接收完成操作相關聯的SocketAsyncEventArg物件</param>
        private void ProcessReceive(SocketAsyncEventArgs e)
        {
            if (e.SocketError == SocketError.Success)//if (e.BytesTransferred > 0 && e.SocketError == SocketError.Success)
            {
                // 檢查遠端主機是否關閉連線
                if (e.BytesTransferred > 0)
                {
                    Socket s = (Socket)e.UserToken;
                    //判斷所有需接收的資料是否已經完成
                    if (s.Available == 0)
                    {
                        //從偵聽者獲取接收到的訊息。 
                        //String received = Encoding.ASCII.GetString(e.Buffer, e.Offset, e.BytesTransferred);
                        //echo the data received back to the client
                        //e.SetBuffer(e.Offset, e.BytesTransferred);

                        byte[] data = new byte[e.BytesTransferred];
                        Array.Copy(e.Buffer, e.Offset, data, 0, data.Length);//從e.Buffer塊中複製資料出來，保證它可重用

                        string info=Encoding.Default.GetString(data);
                        Log4Debug(String.Format("收到 {0} 資料為 {1}",s.RemoteEndPoint.ToString(),info));
                        //TODO 處理資料

                        //增加伺服器接收的總位元組數。
                    }

                    if (!s.ReceiveAsync(e))//為接收下一段資料，投遞接收請求，這個函式有可能同步完成，這時返回false，並且不會引發SocketAsyncEventArgs.Completed事件
                    {
                        //同步接收時處理接收完成事件
                        ProcessReceive(e);
                    }
                }
            }
            else
            {
                CloseClientSocket(e);
            }
        }

        #endregion

        #region 回撥函式

        /// <summary>
        /// 當Socket上的傳送或接收請求被完成時，呼叫此函式
        /// </summary>
        /// <param name="sender">激發事件的物件</param>
        /// <param name="e">與傳送或接收完成操作相關聯的SocketAsyncEventArg物件</param>
        private void OnIOCompleted(object sender, SocketAsyncEventArgs e)
        {
            // Determine which type of operation just completed and call the associated handler.
            switch (e.LastOperation)
            {
                case SocketAsyncOperation.Accept:
                    ProcessAccept(e);
                    break;
                case SocketAsyncOperation.Receive:
                    ProcessReceive(e);
                    break;
                default:
                    throw new ArgumentException("The last operation completed on the socket was not a receive or send");
            }
        }

        #endregion

        #region Close
        /// <summary>
        /// 關閉socket連線
        /// </summary>
        /// <param name="e">SocketAsyncEventArg associated with the completed send/receive operation.</param>
        private void CloseClientSocket(SocketAsyncEventArgs e)
        {
            Log4Debug(String.Format("客戶 {0} 斷開連線!",((Socket)e.UserToken).RemoteEndPoint.ToString()));
            Socket s = e.UserToken as Socket;
            CloseClientSocket(s, e);
        }

        /// <summary>
        /// 關閉socket連線
        /// </summary>
        /// <param name="s"></param>
        /// <param name="e"></param>
        private void CloseClientSocket(Socket s, SocketAsyncEventArgs e)
        {
            try
            {
                s.Shutdown(SocketShutdown.Send);
            }
            catch (Exception)
            {
                // Throw if client has closed, so it is not necessary to catch.
            }
            finally
            {
                s.Close();
            }
            Interlocked.Decrement(ref _clientCount);
            _maxAcceptedClients.Release();
            _objectPool.Push(e);//SocketAsyncEventArg 物件被釋放，壓入可重用佇列。
        }
        #endregion

        #region Dispose
        /// <summary>
        /// Performs application-defined tasks associated with freeing, 
        /// releasing, or resetting unmanaged resources.
        /// </summary>
        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        /// <summary>
        /// Releases unmanaged and - optionally - managed resources
        /// </summary>
        /// <param name="disposing"><c>true</c> to release 
        /// both managed and unmanaged resources; <c>false</c> 
        /// to release only unmanaged resources.</param>
        protected virtual void Dispose(bool disposing)
        {
            if (!this.disposed)
            {
                if (disposing)
                {
                    try
                    {
                        Stop();
                        if (_serverSock != null)
                        {
                            _serverSock = null;
                        }
                    }
                    catch (SocketException ex)
                    {
                        //TODO 事件
                    }
                }
                disposed = true;
            }
        }
        #endregion

        public void Log4Debug(string msg)
        {
            Console.WriteLine("notice:"+msg);
        }

    }
}