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

namespace NIFPGA
{
    public sealed class FPGAArrayFXPReadProperty : FPGABaseProperty
    {
        private object _Locker = new object();
        Interop.NiFpgaDll_ReadArrayU8 Read;
        private NiFpga_FxpTypeInfo _TypeInfo;
        private IFxpConvert _Convert;
        private uint bytescount = 0;
        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))];
            bytescount = (uint)Math.Ceiling(typeInfo.wordLength * count / 8.0);
            Read = _Session.GetDelegate<Interop.NiFpgaDll_ReadArrayU8>();
        }

        private double[] GetData()
        {
            lock (_Locker)
            {
                _Session.CheckResult(Read(_Session.Session, Indicator, ref Unsafe.As<ulong, byte>(ref tempbuffer[0]), bytescount));
                for (int i = 0; i < tempbuffer.Length; i++)
                {
                    tempbuffer[i] = BinaryPrimitives.ReverseEndianness(tempbuffer[i]);
                }

                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(); }
    }
}