common/Hardware/Common.Hardware.SIRT/SIRTMessage.cs

namespace Common.Hardware.SIRT
{
    using System;

    using static SIRTConstants;

    public class SIRTMessage
    {
        private byte[] bytes;
        private bool buildCRC;

        public SIRTMessage()
        {
            this.bytes = new byte[MIN_LEN];
            this.bytes[0] = PC_SIRT;
            this.buildCRC = true;
        }

        public SIRTMessage(byte[] bytes)
        {
            if (bytes is null)
            {
                bytes = Array.Empty<byte>();
            }

            var length = Math.Max(MIN_LEN, bytes.Length);

            this.bytes = new byte[length];

            if (bytes.Length > 0)
            {
                Array.Copy(bytes, 0, this.bytes, 0, bytes.Length);
            }
        }

        public byte Direction
        {
            get => this.bytes[DIR_IX];
            set => this.bytes[DIR_IX] = value;
        }

        public byte Command
        {
            get => this.bytes[CMD_IX];
            set => this.bytes[CMD_IX] = value;
        }

        public byte P1
        {
            get => this.bytes[P1_IX];
            set => this.bytes[P1_IX] = value;
        }

        public byte P2
        {
            get => this.bytes[P2_IX];
            set => this.bytes[P2_IX] = value;
        }

        public uint Address
        {
            get => this.bytes.GetAddress(ADDR_IX);
            set => this.bytes.SetAddress(ADDR_IX, value);
        }

        public byte Length
        {
            get => this.bytes[LEN_IX];
            set => this.bytes[LEN_IX] = value;
        }

        public byte[] Payload
        {
            get
            {
                var payload = new byte[this.Length];

                Array.Copy(bytes, DATA_IX, payload, 0, this.Length);

                return payload;
            }
            set
            {
                var payload = value ?? Array.Empty<byte>();
                this.Length = (byte)payload.Length;

                Array.Resize(ref this.bytes, MIN_LEN + this.Length);
                Array.Clear(this.bytes, DATA_IX, this.bytes.Length - DATA_IX);
                Array.Copy(payload, 0, this.bytes, DATA_IX, this.Length);
            }
        }

        public ushort Crc
        {
            get => this.bytes.GetCrc(this.bytes.Length - 3);
            set => this.bytes.SetCrc(this.bytes.Length - 3, value);
        }

        public byte End
        {
            get => this.bytes[this.bytes.Length - 1];
            set => this.bytes[this.bytes.Length - 1] = value;
        }

        public string SirtId { get; set; }

        public int Frequency { get; set; }

        public DateTimeOffset Timestamp { get; set; } = DateTimeOffset.UtcNow;

        public override string ToString()  => $"{this.SirtId}|{this.Frequency:000}|{BitConverter.ToString(this.GetBytes())}";

        public byte[] GetBytes()
        {
            if (this.buildCRC)
            {
                this.Crc = this.bytes.CRCCCITT(1, this.bytes.Length - 3);
            }

            this.End = MSG_END;

            return this.bytes;
        }

        public static implicit operator SIRTMessage(byte[] bytes)
            => new SIRTMessage(bytes);

        public static implicit operator byte[] (SIRTMessage message)
            => message?.GetBytes() ?? Array.Empty<byte>();
    }
}