using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace MECF.Framework.RT.Core.IoProviders.Siemens.IMessage
{


    /// <summary>
    /// Modbus-Tcp协议支持的消息解析类
    /// </summary>
    public class ModbusTcpMessage : INetMessage
    {
        /// <summary>
        /// 消息头的指令长度
        /// </summary>
        public int ProtocolHeadBytesLength
        {
            get { return 8; }
        }


        /// <summary>
        /// 从当前的头子节文件中提取出接下来需要接收的数据长度
        /// </summary>
        /// <returns>返回接下来的数据内容长度</returns>
        public int GetContentLengthByHeadBytes( )
        {
            /************************************************************************
             * 
             *    说明：为了应对有些特殊的设备，在整个指令的开端会增加一个额外的数据的时候
             * 
             ************************************************************************/
             
            if (HeadBytes?.Length >= ProtocolHeadBytesLength)
            {
                int length = HeadBytes[4] * 256 + HeadBytes[5];
                if (length == 0)
                {
                    byte[] buffer = new byte[ProtocolHeadBytesLength - 1];
                    for (int i = 0; i < buffer.Length; i++)
                    {
                        buffer[i] = HeadBytes[i + 1];
                    }
                    HeadBytes = buffer;
                    return HeadBytes[5] * 256 + HeadBytes[6] - 1;
                }
                else
                {
                    return length - 2;
                }
            }
            else
            {
                return 0;
            }
        }


        /// <summary>
        /// 检查头子节的合法性
        /// </summary>
        /// <param name="token">特殊的令牌，有些特殊消息的验证</param>
        /// <returns>是否成功的结果</returns>
        public bool CheckHeadBytesLegal( byte[] token )
        {
            if (HeadBytes == null) return false;
            if (SendBytes[0] != HeadBytes[0] || SendBytes[1] != HeadBytes[1]) return false;
            return HeadBytes[2] == 0x00 && HeadBytes[3] == 0x00;
        }


        /// <summary>
        /// 获取头子节里的消息标识
        /// </summary>
        /// <returns>消息标识</returns>
        public int GetHeadBytesIdentity( )
        {
            return HeadBytes[0] * 256 + HeadBytes[1];
        }


        /// <summary>
        /// 消息头字节
        /// </summary>
        public byte[] HeadBytes { get; set; }


        /// <summary>
        /// 消息内容字节
        /// </summary>
        public byte[] ContentBytes { get; set; }


        /// <summary>
        /// 发送的字节信息
        /// </summary>
        public byte[] SendBytes { get; set; }


    }
}
