namespace System.Runtime.Intrinsics.X86;

public abstract class Gfni : Sse41
{
    public static bool IsSupported { get; }

    public static Vector128<byte> GaloisFieldAffineTransformInverse(Vector128<byte> x, Vector128<byte> a, [ConstantExpected] byte b);
    public static Vector128<byte> GaloisFieldAffineTransform(Vector128<byte> x, Vector128<byte> a, [ConstantExpected] byte b);
    public static Vector128<byte> GaloisFieldMultiply(Vector128<byte> left, Vector128<byte> right);

    public abstract class X64 : Sse41.X64
    {
        public static bool IsSupported { get; }
    }

    public abstract class V256
    {
        public static new bool IsSupported { get; }

        public static Vector256<byte> GaloisFieldAffineTransformInverse(Vector256<byte> x, Vector256<byte> a, [ConstantExpected] byte b);
        public static Vector256<byte> GaloisFieldAffineTransform(Vector256<byte> x, Vector256<byte> a, [ConstantExpected] byte b);
        public static Vector256<byte> GaloisFieldMultiply(Vector256<byte> left, Vector256<byte> right);
    }

    public abstract class V512
    {
        public static new bool IsSupported { get; }

        public static Vector512<byte> GaloisFieldAffineTransformInverse(Vector512<byte> x, Vector512<byte> a, [ConstantExpected] byte b);
        public static Vector512<byte> GaloisFieldAffineTransform(Vector512<byte> x, Vector512<byte> a, [ConstantExpected] byte b);
        public static Vector512<byte> GaloisFieldMultiply(Vector512<byte> left, Vector512<byte> right);
    }
}

// https://wunkolo.github.io/post/2020/11/gf2p8affineqb-bit-reversal/
public static Vector128<byte> ReverseBits128(Vector128<byte> value)
{
    var xmm0 = Gfni.GaloisFieldAffineTransform(value, Vector128.Create(0b10000000_01000000_00100000_00010000_00001000_00000100_00000010_00000001ul).AsByte(), 0);
    return Ssse3.Shuffle(xmm0, Vector128.Create(15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, byte.MinValue));
}