/*
 Sog 游戏基础库
 2016 by zouwei
 */


using System;
using System.Collections.Concurrent;
using System.Collections.Generic;

using System.Net;
using System.Net.Sockets;


namespace Sog
{
    public class UdpSession:NetSession
    {
        const int UDP_DGRAM_BUFFER_SIZE = 1500;
        const int UDP_BUFFER_SIZE = 1024 * 64;

        private bool m_recvAsyncPending;
        private bool m_sendAsyncPending;
        private object m_recvAsyncLocker;
        private object m_sendAsyncLocker;
        private SocketAsyncEventArgs m_recvAsyncEventArgs;
        private SocketAsyncEventArgs m_sendAsyncEventArgs;

//        private int m_dataLengthInSendQueue = 0;
        
        // udp数据报文的recv buffer
        private byte[] m_dgramBuffer;
        private int m_dgramLen = 0;

        private Kcp kcp;

        private ConcurrentQueue<byte[]> m_outputQueue;

        public UdpSession(Socket socket):base(socket)
        {
            InitSession(this.Output);
        }

        public UdpSession(Socket socket, Action<byte[], int> output):base(socket)
        {
            InitSession(output);
        }

        private void InitSession(Action<byte[], int> output)
        {
            kcp = new Kcp(0, output);
            m_recvBuffer = new byte[UDP_BUFFER_SIZE];
            m_sendBuffer = new byte[UDP_BUFFER_SIZE];
            m_dgramBuffer = new byte[UDP_DGRAM_BUFFER_SIZE];
            m_outputQueue = new ConcurrentQueue<byte[]>();

            InitRecvSendAsyncObject();
        }

        private void InitRecvSendAsyncObject()
        {
            m_recvAsyncLocker = new object();
            m_sendAsyncLocker = new object();

            m_recvAsyncEventArgs = new SocketAsyncEventArgs();
            m_recvAsyncEventArgs.Completed += OnRecvFromAsyncCallback;

            m_sendAsyncEventArgs = new SocketAsyncEventArgs();
            m_sendAsyncEventArgs.Completed += OnSendToAsyncCallback;
        }

        protected override void OnBindSocket()
        {
            InitRecvSendAsyncObject();
			m_remoteEndPoint = (IPEndPoint)m_socket.RemoteEndPoint;
        }

        public void SetRemoteEndPoint(EndPoint remoteEP)
        {
            m_remoteEndPoint = (IPEndPoint)remoteEP;
        }

        public void SetKcpConvId(uint id)
        {
            kcp.Conv = (uint)id;
        }

        public uint GetKcpConvId()
        {
            return kcp.Conv;
        }
		
        public override void CheckSocketAndSendKeepAlive()
        {
            //udp连接的心跳包由客户端来负责主动发起
            //原因是底层kcp开启fast resend模式
            //1、客户端已经断开了，
        }

        public ConcurrentQueue<byte[]> GetOutputQueue()
        {
            return m_outputQueue;
        }

        protected override void CloseSocket()
        {
            TraceLog.Trace("UdpSession.CloseSocket session {0} conv {1}", SessionID, kcp.Conv);

            //todo clear kcp data?
            m_socket = null;
        }

        public override void RecvReadableSocket()
        {
            if(m_socket == null)
            {
                return;
            }

            try
            {
                int iRecvLen = m_socket.ReceiveFrom(m_dgramBuffer, 0, m_dgramBuffer.Length, SocketFlags.None, ref m_remoteEndPoint);
                if(iRecvLen > 0)
                {
                    if (WriteSendRecvLog)
                    {
                        TraceLog.Trace("UdpSession.RecvReadableSocket sessionid {0} recv from remote {1} length {2}"
                            , SessionID, m_remoteEndPoint, iRecvLen);
                    }

                    m_dgramLen = iRecvLen;

                    OnDataReceive(m_dgramBuffer, m_dgramLen);

                    TryReadMessageFromBuffer(false, false);
                }
            }
            catch(SocketException socketex)
            {
                TraceLog.Debug("UdpSession.RecvReadableSocket socket session {0} receive error HResult {1} message {2}"
                    , SessionID, socketex.HResult, socketex.Message);

                Close();
                m_dgramLen = 0;
            }
            catch(Exception ex)
            {
                TraceLog.Error("UdpSession.RecvReadableSocket socket session {0} receive unkonw error, message {1}"
                    , SessionID, ex.Message);

                Close();
                m_dgramLen = 0;
            }
        }


        public override void WriteWriteableSocket()
        {
            if (m_socket == null)
            {
                return;
            }

            //清空
            m_noWriteableCheckCount = 0;

            if (m_sendDataLeft == 0)
            {
                CopySendBuffer();
            }

            if (m_sendDataLeft > 0)
            {
                // 消息转存到kcp内部的send queue，queue中每个packet长度不超过mss
                int ret = kcp.Send(m_sendBuffer, 0, m_sendDataLeft);
                if (ret == 0)
                {
                    TotalSendLength += m_sendDataLeft;
                    LastSendDataTimeSecond = AppTime.GetNowSysSecond();

                    if (WriteSendRecvLog)
                    {
                        TraceLog.Trace("UdpSession.WriteWriteableSocket sessionid {0} send remote {1} length {2} dataLengthInSendQueue {3}"
                            , SessionID, m_remoteEndPoint, m_sendDataLeft, m_dataLengthInSendQueue);
                    }

                    m_sendDataLeft = 0;
                }
                else
                {
                    if (WriteSendRecvLog)
                    {
                        TraceLog.Trace("UdpSession.WriteWriteableSocket kcp send fail, ret {0}", ret);
                    }
                }
            }
            else
            {
                if (WriteSendRecvLog)
                {
                    TraceLog.Trace("UdpSession.WriteWriteableSocket send remote no data");
                }
            }
        }

        public override void StartRecvAsync()
        {
            TraceLog.Trace("UdpSession.StartRecvAsync socket session {0}", SessionID);

            if (m_socket == null)
            {
                return;
            }

            lock (m_recvAsyncLocker)
            {
                if (m_recvAsyncPending)
                {
                    return;
                }

                m_recvAsyncPending = true;
            }

            DoRecvFromAsync();
        }

        private void DoRecvFromAsync()
        {
            try
            {
                TraceLog.Trace("UdpSession.DoRecvFromAsync socket session {0} m_alreadyRecvLength {1}", SessionID, m_alreadyRecvLength);

                m_recvAsyncEventArgs.SetBuffer(m_dgramBuffer, 0, m_dgramBuffer.Length);

                bool pending = m_socket.ReceiveFromAsync(m_recvAsyncEventArgs);
                if (!pending)
                {
                    OnRecvFromAsyncCallback(null, m_recvAsyncEventArgs);
                }
            }
            catch (SocketException socketex)
            {
                TraceLog.Debug("UdpSession.DoRecvFromAsync socket session {0} receive error HResult {1} message {2}"
                    , SessionID, socketex.HResult, socketex.Message);

                Close();

                lock (m_recvAsyncLocker)
                {
                    m_recvAsyncPending = false;
                }
            }
            catch (Exception ex)
            {
                TraceLog.Error("UdpSession.DoRecvFromAsync socket session {0} receive unkonw error, message {1}"
                    , SessionID, ex.Message);

                Close();

                lock (m_recvAsyncLocker)
                {
                    m_recvAsyncPending = false;
                }
            }
        }

        private void OnRecvFromAsyncCallback(object sender, SocketAsyncEventArgs args)
        {
            //错误
            if (args.SocketError != SocketError.Success || args.BytesTransferred <= 0)
            {
                TraceLog.Debug("UdpSession.OnRecvFromAsyncCallback socket session {0} receive error {1} "
                    , SessionID, args.SocketError);

                Close();

                lock (m_recvAsyncLocker)
                {
                    m_recvAsyncPending = false;
                }
                return;
            }

            m_dgramLen = args.BytesTransferred;

            if (WriteSendRecvLog)
            {
                TraceLog.Trace("UdpSession.OnRecvFromAsyncCallback sessionid {0} recv from remote {1} length {2}"
                    , SessionID, m_remoteEndPoint, m_dgramLen);
            }

            OnDataReceive(m_dgramBuffer, m_dgramLen);

            //继续接收消息
            DoRecvFromAsync();
        }

        public void OnDataReceive(byte[] data, int length)
        {
            TraceLog.TraceDetail("UdpSession.OnDataReceive kcp conv {0} input data length {1}"
                , kcp.Conv, length);

            if (length >= Kcp.IKCP_OVERHEAD)
            {
                uint conv = 0;
                Kcp.ikcp_decode32u(data, 0, ref conv);

                // conv不一致，无效的信息，端口被重用了
                if (conv != kcp.Conv)
                {
                    TraceLog.Error("UdpSession.OnDataReceive recv conv {0} local conv {1} not equal, drop data"
                        , conv, kcp.Conv);
                    return;
                }
            }
            else
            {
                TraceLog.Error("UdpSession.OnDataReceive conv {0} invalid recv len {1}"
                    , kcp.Conv, length);
                return;
            }


            kcp.Input(data, length);

            int count = 0;
            while (count < 10)
            {
                count++;

                int recvLength = kcp.Recv(m_recvBuffer, m_alreadyRecvLength, m_recvBuffer.Length - m_alreadyRecvLength);
                if (recvLength < 0)
                {
                    break;
                }

                TotalRecvLength += recvLength;
                LastRecvDataTimeSecond = AppTime.GetNowSysSecond();
                m_alreadyRecvLength += recvLength;

                if (WriteSendRecvLog)
                {
                    TraceLog.Trace("UdpSession.OnDataReceive session {0} try recv remote {1}, realy recv length {2} left length {3}"
                        , SessionID, m_remoteEndPoint, recvLength, m_alreadyRecvLength);
                }

                TryReadMessageFromBuffer(false, false);
            }
        }

        //对于服务器目前没用
        public override void StartSendAsync()
        {
            if (m_socket == null)
            {
                return;
            }

            if (m_outputQueue.Count == 0)
            {
                return;
            }

            if (m_remoteEndPoint == null)
            {
                TraceLog.Trace("UdpSession.StartSendAsync session {0} remote ip is null", SessionID);
                return;
            }

            lock (m_sendAsyncLocker)
            {
                if (m_sendAsyncPending)
                {
                    return;
                }

                m_sendAsyncPending = true;
            }

            DoSendToAsync();
        }

        private void DoSendToAsync()
        {
            try
            {
                if (m_outputQueue.TryDequeue(out byte[] buffer))
                {
                    if (true)
                    {
                        uint conv = 0;
                        byte cmd = 0;
                        uint sn = 0;
                        uint len = 0;
                        Kcp.ikcp_decode32u(buffer, 0, ref conv);
                        Kcp.ikcp_decode8u(buffer, 4, ref cmd);
                        Kcp.ikcp_decode32u(buffer, 12, ref sn);
                        Kcp.ikcp_decode32u(buffer, 20, ref len);

                        if (cmd == 81)  //data
                        {
                            TraceLog.TraceDetail("UdpSession.DoSendToAsync conv {0} sn {1} data len {2}"
                                , conv, sn, len);
                        }
                        else if (cmd == 82)  //ack
                        {
                            TraceLog.TraceDetail("UdpSession.DoSendToAsync conv {0} sn {1} ack"
                                , conv, sn);
                        }
                    }

                    m_sendAsyncEventArgs.RemoteEndPoint = m_remoteEndPoint;
                    m_sendAsyncEventArgs.SetBuffer(buffer, 0, buffer.Length);

                    if (! m_socket.SendToAsync(m_sendAsyncEventArgs))
                    {
                        OnSendToAsyncCallback(null, m_sendAsyncEventArgs);
                    }
                }
                else
                {
                    lock (m_sendAsyncLocker)
                    {
                        m_sendAsyncPending = false;
                    }
                }
            }
            catch (SocketException ex)
            {
                // 底层buffer不够
                TraceLog.Error("UdpSession.DoSendToAsync socket session {0} send erro, errorcode {1} message {2}"
                    , SessionID, ex.SocketErrorCode, ex.Message);

                Close();

                lock (m_sendAsyncLocker)
                {
                    m_sendAsyncPending = false;
                }
            }
            catch (Exception ex)
            {
                TraceLog.Error("UdpSession.DoSendToAsync socket session {0} send erro, message {1}", SessionID, ex.Message);

                Close();

                lock (m_sendAsyncLocker)
                {
                    m_sendAsyncPending = false;
                }
            }
        }

        private void OnSendToAsyncCallback(object sender, SocketAsyncEventArgs args)
        {
            int iSendBytes = args.BytesTransferred;

            if (args.SocketError != SocketError.Success || args.BytesTransferred <= 0)
            {
                TraceLog.Debug("UdpSession.OnSendToAsyncCallback socket session {0} error {1}"
                    , SessionID, args.SocketError);

                Close();

                lock (m_sendAsyncLocker)
                {
                    m_sendAsyncPending = false;
                }

                return;
            }

            LastSendDataTimeSecond = AppTime.GetNowSysSecond();

            if (WriteSendRecvLog)
            {
                TraceLog.Trace("UdpSession.OnSendToAsyncCallback session {0} try send remote {1} length {2} left length {3} dataLengthInSendQueue {4}"
                    , SessionID, m_remoteEndPoint, iSendBytes, m_sendDataLeft, m_dataLengthInSendQueue);
            }

            DoSendToAsync();
        }

        private void Output(byte[] data, int len)
        {
            byte[] packet = new byte[len];
            Array.Copy(data, 0, packet, 0, len);
            m_outputQueue.Enqueue(packet);

            TraceLog.TraceDetail("UdpSession.Output session {0} output queue num {1}"
                , SessionID, m_outputQueue.Count);
        }

        public void Update(long timeMs)
        {
            if (kcp.State == 0)
            {
                kcp.Update((uint) timeMs);
            }

            if (kcp.State == -1 && IsSocketClosed == false)
            {
                TraceLog.Trace("UdpSession.Update session {0} conv {1} dead link, close session"
                    , SessionID, kcp.Conv);

                Close();
            }
        }
    }
}