/*
 Sog 游戏基础库
 2016 by zouwei
 */


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


namespace Sog
{
    public class UdpClientSession:ClientSession
    {
        private const int SOCKET_BUFFER_SIZE = 1024 * 1024;
        private const int TMP_RECV_BUFFER_SIZE = 1500;

        protected UdpSession udpSession;

        private long lastUdpConnectTime;
        private int udpConnectNum;

        //todo 握手阶段优化
        // 握手阶段用来临时收发信息的buffer，最多是8个字节的临时数据
        private byte[] m_tmpRecvBuffer;
        private byte[] m_tmpSendBuffer;

        public UdpClientSession(ClientSessionSettings settings):base(settings, SessionNetSelectMode.Synchronous)
        {
            AllockSocket();
            udpSession = new UdpSession(m_socketClient);
            NetSessionObj = udpSession;
        }


        private void AllockSocket()
        {
            m_socketClient = new Socket(settings.RemoteEndPoint.AddressFamily, 
                SocketType.Dgram, ProtocolType.Udp);

            // set recv buffer
            m_socketClient.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReceiveBuffer, SOCKET_BUFFER_SIZE);
            m_socketClient.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.SendBuffer, SOCKET_BUFFER_SIZE);
            m_socketClient.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, (int)1);
        }


        public override void Connect()
        {
            TraceLog.Trace("UdpClientSession.Connect remote {0}", settings.RemoteEndPoint);

            m_isConnected = false;
            m_isConnecting = true;

            try
            {
                udpConnectNum++;
                lastUdpConnectTime = AppTime.GetNowSysMs();
                m_socketClient.Connect(settings.RemoteEndPoint);

                if (m_tmpSendBuffer == null)
                {
                    m_tmpSendBuffer = new byte[4];
                }
                Kcp.ikcp_encode32u(m_tmpSendBuffer, 0, (uint) KcpProtocalType.SYN);

                // send will block socket
                m_socketClient.Send(m_tmpSendBuffer, 4, SocketFlags.None);
            }
            catch (SocketException ex)
            {
                TraceLog.Error("UdpClientSession.Connect {0}, SocketErrorCode {1} message {2}",
                    settings.RemoteEndPoint, ex.SocketErrorCode, ex.Message);
            }
            catch (Exception ex)
            {
                TraceLog.Error("UdpClientSession.Connect {0} fail, exception {1}"
                    , settings.RemoteEndPoint, ex);
            }
        }

        public override void Reconnect()
        {
            TraceLog.Trace("UdpClientSession.Reconnect remote {0}", settings.RemoteEndPoint);

            // 重连时m_socketClient如果不是null，要丢掉session中未发送和未解析的信息
            if (m_socketClient != null)
            {
                TraceLog.Error("UdpClientSession.Reconnect close old socket");
                CloseSession();
            }

            //重连的时候重新allock socket，linux下必须如此
            AllockSocket();

            Connect();
        }

        private void UpdateConnect(long nowMs)
        {
            if (!m_isConnecting)
            {
                return;
            }

            // 超时无应答connect失败
            if (lastUdpConnectTime > 0 && nowMs >= lastUdpConnectTime + 1500)
            {
                SessionEventArgs arg = new SessionEventArgs();
                arg.Session = NetSessionObj;
                OnConnectFail(arg);
                return;
            }

            try
            {
                bool bReadable = m_socketClient.Poll(0, SelectMode.SelectRead);
                if (bReadable)
                {
                    if (m_tmpRecvBuffer == null)
                    {
                        m_tmpRecvBuffer = new byte[TMP_RECV_BUFFER_SIZE];
                    }

                    int len = m_socketClient.Receive(m_tmpRecvBuffer);
                    if (len == 8)
                    {
                        if (udpSession.GetKcpConvId() != 0)
                        {
                            TraceLog.Error("UdpConnect socket recv from {0} len {1} invalid session"
                                , m_socketClient.RemoteEndPoint, len);
                            return;
                        }

                        uint proto = 0;
                        uint conv = 0;
                        Kcp.ikcp_decode32u(m_tmpRecvBuffer, 0, ref proto);
                        Kcp.ikcp_decode32u(m_tmpRecvBuffer, 4, ref conv);
                        if (proto != 2)
                        {
                            TraceLog.Error("UdpConnect socket recv from {0} len {1} invalid proto {2}"
                                , m_socketClient.RemoteEndPoint, len, proto);
                            return;
                        }

                        udpSession.SetKcpConvId(conv);

                        OnUdpConnectSucc();
                    }
                    else
                    {
                        TraceLog.Error("UdpConnect socket recv from {0} invalid connect msg len {1}"
                            , m_socketClient.RemoteEndPoint, len);
                    }
                }
            }
            catch (Exception ex)
            {
                TraceLog.Exception(ex);
            }
        }

        protected void UpdateReadWrite(long nowMs)
        {
            if (! m_isConnected || NetSessionObj.IsSocketClosed)
            {
                return;
            }

            UpdateSynchronousMode();

            udpSession.Update(nowMs);
        }

        protected virtual void UpdateSynchronousMode()
        {
            if (NetSessionObj.IsSocketClosed)
            {
                SocketErrorOnUpdate();
                return;
            }

            bool bError = m_socketClient.Poll(0, SelectMode.SelectError);
            if (bError)
            {
                SocketErrorOnUpdate();
                return;
            }

            bool bReadable = m_socketClient.Poll(0, SelectMode.SelectRead);
            if (bReadable)
            {
                NetSessionObj.RecvReadableSocket();
            }

            //todo udp keepalive
            NetSessionObj.CheckSocketAndSendKeepAlive();

            //write出错的情况下，write调用之后有可能socket会被关闭
            if (NetSessionObj.IsSocketClosed)
            {
                SocketErrorOnUpdate();
                return;
            }

            if (NetSessionObj.IsHaveDataNeedSend())
            {
                NetSessionObj.WriteWriteableSocket();
            }

            NetSessionObj.StartSendAsync();

            //write出错的情况下，write调用之后有可能socket会被关闭
            if (NetSessionObj.IsSocketClosed)
            {
                SocketErrorOnUpdate();
            }
        }

        public override void Update(long nowMs)
        {
            UpdateConnect(nowMs);
            UpdateReadWrite(nowMs);
        }

        private void OnUdpConnectSucc()
        {
            m_tmpSendBuffer = null;
            m_tmpRecvBuffer = null;

            ConnectSucc();
        }

        protected override void CloseSession()
        {
            TraceLog.Trace("UdpClientSession.CloseSession conv {0}", udpSession.GetKcpConvId());

            SendDisconnectMsg();

            m_isConnected = false;
            m_isConnecting = false;

            //丢弃正在发送和接收的数据，关闭socket
            NetSessionObj.Close();
            m_socketClient = null;
        }

        private void SendDisconnectMsg()
        {
            uint conv = udpSession.GetKcpConvId();
            if (conv > 0 && m_socketClient != null)
            {
                if (m_socketClient.Poll(0, SelectMode.SelectWrite))
                {
                    if (m_tmpSendBuffer == null)
                    {
                        m_tmpSendBuffer = new byte[4];
                    }

                    Kcp.ikcp_encode32u(m_tmpSendBuffer, 0, (uint) KcpProtocalType.FIN);
                    Kcp.ikcp_encode32u(m_tmpSendBuffer, 4, conv);
                    // send will block socket
                    m_socketClient.Send(m_tmpSendBuffer, 8, SocketFlags.None);
                }
            }
        }
    }
}