using System;
using System.Runtime.InteropServices;

namespace CapMachine.Wpf.CanDrive.ZlgCan
{
    /// <summary>
    /// 供 DBC 编解码/Marshal 使用的原生 CAN 帧结构（与 zlgcan can_frame 二进制布局兼容）。
    /// </summary>
    [StructLayout(LayoutKind.Sequential, Pack = 1)]
    public struct ZlgNativeCanFrame
    {
        public uint can_id;
        public byte can_dlc;
        public byte __pad;
        public byte __res0;
        public byte __res1;

        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 8)]
        public byte[] data;

        /// <summary>
        /// 创建 CAN 帧。
        /// </summary>
        /// <param name="canId">can_id（包含扩展帧等标志位）。</param>
        /// <param name="payload">数据（0~8）。</param>
        /// <param name="requestTxEcho">是否请求发送回显。</param>
        /// <returns>原生 CAN 帧。</returns>
        public static ZlgNativeCanFrame Create(uint canId, byte[] payload, bool requestTxEcho)
        {
            var len = Math.Min(8, payload?.Length ?? 0);
            var frame = new ZlgNativeCanFrame
            {
                can_id = canId,
                can_dlc = (byte)len,
                __pad = 0,
                __res0 = 0,
                __res1 = 0,
                data = new byte[8]
            };

            if (len > 0 && payload != null)
            {
                Array.Copy(payload, frame.data, len);
            }

            if (requestTxEcho)
            {
                frame.__pad |= 0x20;
            }

            return frame;
        }
    }

    /// <summary>
    /// 供 DBC 编解码/Marshal 使用的原生 CANFD 帧结构（与 zlgcan canfd_frame 二进制布局兼容）。
    /// </summary>
    [StructLayout(LayoutKind.Sequential, Pack = 1)]
    public struct ZlgNativeCanFdFrame
    {
        public uint can_id;
        public byte len;
        public byte flags;
        public byte __res0;
        public byte __res1;

        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 64)]
        public byte[] data;

        /// <summary>
        /// 创建 CANFD 帧。
        /// </summary>
        /// <param name="canId">can_id（包含扩展帧等标志位）。</param>
        /// <param name="payload">数据（0~64）。</param>
        /// <param name="requestTxEcho">是否请求发送回显。</param>
        /// <returns>原生 CANFD 帧。</returns>
        public static ZlgNativeCanFdFrame Create(uint canId, byte[] payload, bool requestTxEcho)
        {
            var len = Math.Min(64, payload?.Length ?? 0);
            var frame = new ZlgNativeCanFdFrame
            {
                can_id = canId,
                len = (byte)len,
                flags = 0,
                __res0 = 0,
                __res1 = 0,
                data = new byte[64]
            };

            if (len > 0 && payload != null)
            {
                Array.Copy(payload, frame.data, len);
            }

            if (requestTxEcho)
            {
                frame.flags |= 0x20;
            }

            return frame;
        }
    }
}