Ayay/SHH.CameraService/Core/NetSenders/NetMQProtocolExtensions.cs

using MessagePack;
using NetMQ;
using SHH.Contracts;

namespace SHH.CameraService
{
    /// <summary>
    /// 负责将业务契约转换为 ZeroMQ 传输协议
    /// </summary>
    public static class NetMQProtocolExtensions
    {
        private const string PROTOCOL_HEADER = "SHH_V1";

        /// <summary>
        /// 扩展方法：将 Payload 转为 NetMQMessage
        /// 使用方法：var msg = payload.ToNetMqMessage();
        /// </summary>
        public static NetMQMessage ToNetMqMessage(this VideoPayload payload)
        {
            var msg = new NetMQMessage();

            // Frame 0: 协议魔数
            msg.Append(PROTOCOL_HEADER);

            ////// Frame 1: 元数据 JSON
            ////msg.Append(payload.GetMetadataJson());

            // ★★★ 修复点：在序列化之前，手动更新 Payload 的标志位 ★★★
            payload.HasOriginalImage = (payload.OriginalImageBytes != null && payload.OriginalImageBytes.Length > 0);
            payload.HasTargetImage = (payload.TargetImageBytes != null && payload.TargetImageBytes.Length > 0);

            // Frame 1: Metadata (MessagePack)
            byte[] metaBytes = MessagePackSerializer.Serialize(payload);
            msg.Append(metaBytes);

            // Frame 2: 原始图 (保持帧位对齐，无数据则发空帧)
            if (payload.HasOriginalImage && payload.OriginalImageBytes != null)
                msg.Append(payload.OriginalImageBytes);
            else
                msg.Append(Array.Empty<byte>());

            // Frame 3: 处理图
            if (payload.HasTargetImage && payload.TargetImageBytes != null)
                msg.Append(payload.TargetImageBytes);
            else
                msg.Append(Array.Empty<byte>());

            return msg;
        }

        /// <summary>
        /// 扩展方法：从 NetMQMessage 还原 Payload
        /// </summary>
        public static VideoPayload ToVideoPayload(this NetMQMessage msg)
        {
            if (msg == null || msg.FrameCount < 2) return null;

            // Frame 0 Check
            if (msg[0].ConvertToString() != PROTOCOL_HEADER) return null;

            //// Frame 1: Metadata
            //string json = msg[1].ConvertToString();
            //var payload = VideoPayload.FromMetadataJson(json);

            // [新代码] 直接从二进制还原
            // ToByteArray() 虽然会产生一次拷贝，但对于 Metadata 这种小数据影响微乎其微
            // 相比 JSON 解析 String 的开销，这已经非常快了
            var payload = MessagePackSerializer.Deserialize<VideoPayload>(msg[1].ToByteArray());
            if (payload == null) return null;

            // Frame 2: Raw Image
            // 利用 BufferSize 避免不必要的内存拷贝，如果长度为0则跳过
            if (payload.HasOriginalImage && msg[2].BufferSize > 0)
            {
                payload.OriginalImageBytes = msg[2].ToByteArray();
            }

            // Frame 3: Processed Image
            if (payload.HasTargetImage && msg[3].BufferSize > 0)
            {
                payload.TargetImageBytes = msg[3].ToByteArray();
            }

            return payload;
        }
    }
}