namespace DTS.DASLib.Command.SLICE.DownloadCommands
{
    /// <summary>
    /// this is ported from FirmwareTestUtility where it was written by Loc Pham.  It is included for
    /// 10573 implement SW side of single command/streaming download
    /// </summary>
    public class DownloadByteConverter
    {
        public enum DlByteIndex
        {
            Sync = 0,
            Type = 1,
            Command = 2,
            Status = 3,
            Group = 4,
            Id = 5,
            Datalength = 6,
            SequenceNumber = 8,
            HeaderCRC = 10,
            DataCRC = 12,
            DataADCStartOffset = 14,
            DataADCEndOffset = 22,
            DataStart = 30
        }

        public ushort SeqNumber { get; }
        public ushort SeqNumberPrev { get; }
        public ulong DlAdcStartOffset { get; }
        public ulong DlAdcEndOffset { get; }

        public ulong DlStreamSampleNumber { get; }

        public ushort[] DlData { get; }

        public uint[] DlChannels { get; }

        public DownloadByteConverter(byte[] bytes)
        {
            SeqNumber = GetUShort(bytes, (int)DlByteIndex.SequenceNumber);
            DlAdcStartOffset = GetUInt(bytes, (int)DlByteIndex.DataADCStartOffset);
            DlAdcStartOffset = GetULong(bytes, (int)DlByteIndex.DataADCEndOffset);
            DlData = new ushort[(bytes.Length - (int)DlByteIndex.DataStart) / 2];

            if (SeqNumber == 0)
            {
                SeqNumberPrev = 0;
            }
            else
            {
                if (SeqNumberPrev != 0 &&
                    SeqNumberPrev != SeqNumber - 1)
                {
                    System.Diagnostics.Debug.WriteLine("sequence out of order: ");
                    System.Diagnostics.Debug.WriteLine(SeqNumberPrev.ToString());
                    System.Diagnostics.Debug.WriteLine(SeqNumber.ToString());
                }
            }
            SeqNumberPrev = SeqNumber;

            for (var idx = 0; idx < DlData.Length; idx++)
            {
                DlData[idx] = GetDownloadUShort(bytes, (int)(DlByteIndex.DataStart + idx * 2));
            }
        }

        private static ulong GetULong(byte[] bytes, int offset)
        {
            return (ulong)bytes[offset + 7] << 0 |
                  (ulong)bytes[offset + 6] << 8 |
                  (ulong)bytes[offset + 5] << 16 |
                  (ulong)bytes[offset + 4] << 24 |
                  (ulong)bytes[offset + 3] << 32 |
                  (ulong)bytes[offset + 2] << 40 |
                  (ulong)bytes[offset + 1] << 48 |
                  (ulong)bytes[offset + 0] << 56;
        }

        private static ushort GetUShort(byte[] bytes, int offset)
        {
            return (ushort)(bytes[offset + 1] |
                            bytes[offset + 0] << 8);
        }

        private static uint GetUInt(byte[] bytes, int offset)
        {
            return (uint)bytes[offset + 3] << 0 |
                   (uint)bytes[offset + 2] << 8 |
                   (uint)bytes[offset + 1] << 16 |
                   (uint)bytes[offset + 0] << 32;
        }
        /// <summary>
        /// data apparently has a different byte order than parameters, so we have to
        /// rearrange byte order for parameters but not data.
        /// </summary>
        /// <param name="bytes"></param>
        /// <param name="offset"></param>
        /// <returns></returns>
        private static ushort GetDownloadUShort(byte[] bytes, int offset)
        {
            return (ushort)(bytes[offset + 0] | bytes[offset + 1] << 8);
        }

    }
}