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());

            // 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 < 4) 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);
            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;
        }
    }
}