AnkiId.cs

using System.Buffers.Binary;
using System.Security.Cryptography;
using System.Text;
 
namespace AnkiIO;

public static class AnkiId
{
    private static long last = DateTimeOffset.UtcNow.ToUnixTimeMilliseconds() * 1_000;

    public static long New() => Interlocked.Increment(ref last);

    public static long FromStableValue(string scope, string value)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(scope);
        ArgumentException.ThrowIfNullOrWhiteSpace(value);
        var bytes = SHA256.HashData(Encoding.UTF8.GetBytes(scope + "\0" + value));
        return (BinaryPrimitives.ReadInt64LittleEndian(bytes) & long.MaxValue) is var result && result != 0 ? result : 1;
    }
}