//------------------------------------------------------------------------------
//  此代码版权（除特别声明或在XREF结尾的命名空间的代码）归作者本人若汝棋茗所有
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//  感谢您的下载和使用
//------------------------------------------------------------------------------
//------------------------------------------------------------------------------
using System;
using System.Collections.Generic;
using TouchSocket.Core;
using TouchSocket.Sockets;

namespace TouchSocket.Http.WebSockets
{
    /// <summary>
    /// WebSocket适配器
    /// </summary>
    public class WebSocketDataHandlingAdapter : DataHandlingAdapter
    {
        private WSDataFrame m_dataFrameTemp;

        /// <summary>
        /// 数据包剩余长度
        /// </summary>
        private int m_surPlusLength = 0;

        /// <summary>
        /// 临时包
        /// </summary>
        private ByteBlock m_tempByteBlock;

        /// <summary>
        /// <inheritdoc/>
        /// </summary>
        public override bool CanSplicingSend => false;

        /// <summary>
        /// <inheritdoc/>
        /// </summary>
        public override bool CanSendRequestInfo => false;

        /// <summary>
        /// 解码
        /// </summary>
        /// <param name="dataBuffer"></param>
        /// <param name="offset"></param>
        /// <param name="length"></param>
        /// <param name="dataFrame"></param>
        /// <returns></returns>
        public FilterResult DecodingFromBytes(byte[] dataBuffer, ref int offset, int length, out WSDataFrame dataFrame)
        {
            int index = offset;
            dataFrame = new WSDataFrame();
            dataFrame.RSV1 = dataBuffer[offset].GetBit(6) == 1;
            dataFrame.RSV2 = dataBuffer[offset].GetBit(5) == 1;
            dataFrame.RSV3 = dataBuffer[offset].GetBit(4) == 1;
            dataFrame.FIN = (dataBuffer[offset] >> 7) == 1;
            dataFrame.Opcode = (WSDataType)(dataBuffer[offset] & 0xf);
            dataFrame.Mask = (dataBuffer[++offset] >> 7) == 1;

            int payloadLength = dataBuffer[offset] & 0x7f;
            if (payloadLength < 126)
            {
                offset++;
            }
            else if (payloadLength == 126)
            {
                if (length < 4)
                {
                    offset = index;
                    return FilterResult.Cache;
                }
                payloadLength = TouchSocketBitConverter.BigEndian.ToUInt16(dataBuffer, ++offset);
                offset += 2;
            }
            else if (payloadLength == 127)
            {
                if (length < 12)
                {
                    if (m_tempByteBlock == null)
                    {
                        m_tempByteBlock = new ByteBlock();
                    }
                    m_tempByteBlock.Write(dataBuffer, index, length);
                    offset = index;
                    return FilterResult.GoOn;
                }
                payloadLength = (int)TouchSocketBitConverter.BigEndian.ToUInt64(dataBuffer, ++offset);
                offset += 8;
            }

            dataFrame.PayloadLength = payloadLength;

            if (dataFrame.Mask)
            {
                if (length < (offset - index) + 4)
                {
                    if (m_tempByteBlock == null)
                    {
                        m_tempByteBlock = new ByteBlock();
                    }
                    m_tempByteBlock.Write(dataBuffer, index, length);
                    offset = index;
                    return FilterResult.GoOn;
                }
                dataFrame.MaskingKey = new byte[4];
                dataFrame.MaskingKey[0] = dataBuffer[offset++];
                dataFrame.MaskingKey[1] = dataBuffer[offset++];
                dataFrame.MaskingKey[2] = dataBuffer[offset++];
                dataFrame.MaskingKey[3] = dataBuffer[offset++];
            }

            ByteBlock byteBlock = new ByteBlock(payloadLength);
            dataFrame.PayloadData = byteBlock;

            int surlen = length - (offset - index);
            if (payloadLength <= surlen)
            {
                byteBlock.Write(dataBuffer, offset, payloadLength);
                offset += payloadLength;
            }
            else
            {
                byteBlock.Write(dataBuffer, offset, surlen);
                offset += surlen;
            }

            return FilterResult.Success;
        }

        /// <summary>
        /// 当接收到数据时处理数据
        /// </summary>
        /// <param name="byteBlock">数据流</param>
        protected override void PreviewReceived(ByteBlock byteBlock)
        {
            byte[] buffer = byteBlock.Buffer;
            int r = byteBlock.Len;

            if (m_tempByteBlock != null)
            {
                m_tempByteBlock.Write(buffer, 0, r);
                buffer = m_tempByteBlock.ToArray();
                r = m_tempByteBlock.Pos;
                m_tempByteBlock.Dispose();
                m_tempByteBlock = null;
            }

            if (m_dataFrameTemp == null)
            {
                SplitPackage(buffer, 0, r);
            }
            else
            {
                if (m_surPlusLength == r)
                {
                    m_dataFrameTemp.PayloadData.Write(buffer, 0, m_surPlusLength);
                    PreviewHandle(m_dataFrameTemp);
                    m_dataFrameTemp = null;
                    m_surPlusLength = 0;
                }
                else if (m_surPlusLength < r)
                {
                    m_dataFrameTemp.PayloadData.Write(buffer, 0, m_surPlusLength);
                    PreviewHandle(m_dataFrameTemp);
                    m_dataFrameTemp = null;
                    SplitPackage(buffer, m_surPlusLength, r);
                }
                else
                {
                    m_dataFrameTemp.PayloadData.Write(buffer, 0, r);
                    m_surPlusLength -= r;
                }
            }
        }

        /// <summary>
        /// 当发送数据前处理数据
        /// </summary>
        /// <param name="buffer"></param>
        /// <param name="offset"></param>
        /// <param name="length"></param>
        protected override void PreviewSend(byte[] buffer, int offset, int length)
        {
            GoSend(buffer, offset, length);
        }

        /// <summary>
        /// <inheritdoc/>
        /// </summary>
        /// <param name="transferBytes"></param>
        protected override void PreviewSend(IList<ArraySegment<byte>> transferBytes)
        {
            throw new System.NotImplementedException();//因为设置了不支持拼接发送，所以该方法可以不实现。
        }

        /// <summary>
        /// <inheritdoc/>
        /// </summary>
        /// <param name="requestInfo"></param>
        protected override void PreviewSend(IRequestInfo requestInfo)
        {
            throw new NotImplementedException();
        }

        /// <summary>
        /// <inheritdoc/>
        /// </summary>
        protected override void Reset()
        {
            m_tempByteBlock = null;
            m_dataFrameTemp = null;
            m_surPlusLength = 0;
            base.Reset();
        }

        private void PreviewHandle(WSDataFrame dataFrame)
        {
            try
            {
                if (dataFrame.Mask)
                {
                    WSTools.DoMask(dataFrame.PayloadData.Buffer, 0, dataFrame.PayloadData.Buffer, 0, dataFrame.PayloadData.Len, dataFrame.MaskingKey);
                }
                GoReceived(null, dataFrame);
            }
            finally
            {
                dataFrame.Dispose();
            }
        }

        /// <summary>
        /// 分解包
        /// </summary>
        /// <param name="dataBuffer"></param>
        /// <param name="offset"></param>
        /// <param name="length"></param>
        private void SplitPackage(byte[] dataBuffer, int offset, int length)
        {
            while (offset < length)
            {
                if (length - offset < 2)
                {
                    if (m_tempByteBlock == null)
                    {
                        m_tempByteBlock = new ByteBlock();
                    }
                    m_tempByteBlock.Write(dataBuffer, offset, length - offset);
                    return;
                }

                switch (DecodingFromBytes(dataBuffer, ref offset, length - offset, out WSDataFrame dataFrame))
                {
                    case FilterResult.Cache:
                        {
                            if (m_tempByteBlock == null)
                            {
                                m_tempByteBlock = new ByteBlock();
                            }
                            m_tempByteBlock.Write(dataBuffer, offset, length - offset);
                            return;
                        }
                    case FilterResult.Success:
                        {
                            if (dataFrame.PayloadLength == dataFrame.PayloadData.Len)
                            {
                                PreviewHandle(dataFrame);
                            }
                            else
                            {
                                m_surPlusLength = dataFrame.PayloadLength - dataFrame.PayloadData.Len;
                                m_dataFrameTemp = dataFrame;
                            }
                        }
                        break;

                    case FilterResult.GoOn:
                    default:
                        return;
                }
            }
        }
    }
}