using FxpConvert.Common;
using System.Runtime.CompilerServices;

namespace NIFPGA
{
    public sealed class FPGAArrayFXPReadProperty : FPGABaseProperty
    {
        Interop.NiFpgaDll_ReadArrayU8 Read;
        private NiFpga_FxpTypeInfo _TypeInfo;
        private IFxpConvert _Convert;
        private ulong[] tempbuffer = new ulong[0];
        private ulong[] tempvalue = new ulong[0];
        private double[] doubles = new double[0];
        internal FPGAArrayFXPReadProperty(FPGASession session, uint indicator, uint count, NiFpga_FxpTypeInfo typeInfo, IFxpConvert convert) : base(session, indicator, true)
        {
            _Convert = convert;
            Count = count;
            tempvalue = new ulong[count];
            doubles = new double[count];
            _TypeInfo = typeInfo;
            tempbuffer = new ulong[(int)Math.Ceiling(typeInfo.wordLength * count / (8*8.0))];
            Read = _Session.GetDelegate<Interop.NiFpgaDll_ReadArrayU8>();
        }

        private double[] GetData()
        {
            _Session.CheckResult(Read(_Session.Session, Indicator, ref Unsafe.As<ulong, byte>(ref tempbuffer[0]), (uint)tempbuffer.Length * 8));

            int tempdatalen = Unsafe.SizeOf<ulong>() * 8;
            ulong mask = (1ul << _TypeInfo.wordLength) - 1;
            for (int i = 0; i < Count; i++)
            {
                int index = i * _TypeInfo.wordLength / tempdatalen;
                int bitindex = tempdatalen - (i * _TypeInfo.wordLength % tempdatalen);
                if (bitindex >= _TypeInfo.wordLength)
                {
                    tempvalue[i] = (tempbuffer[index] >> (bitindex - _TypeInfo.wordLength)) & mask;
                }
                else
                {
                    tempvalue[i] = (((tempbuffer[index] & ((1ul << bitindex) - 1)) << (_TypeInfo.wordLength - bitindex)) | (tempbuffer[index + 1] >> (tempdatalen - (_TypeInfo.wordLength - bitindex))));
                }
            }

            _Convert.FxpConvertToDouble(ref tempvalue[0], _TypeInfo, ref doubles[0], Count);
            return doubles;
        }
        public uint Count { get; }
        public double[] Value { get => GetData(); }
    }
}