using System.Runtime.CompilerServices;
using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Jobs;
using PerfectNumbers.Core;

namespace EvenPerfectBitScanner.Benchmarks;

[SimpleJob(RuntimeMoniker.Net80, launchCount: 1, warmupCount: 1, iterationCount: 5)]
[MemoryDiagnoser]
public class Mod3ULongBenchmarks
{
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    private static ulong Mod3(ulong value) =>
        ((uint)(value & ULongExtensions.WordBitMask)
         + (uint)((value >> 16) & ULongExtensions.WordBitMask)
         + (uint)((value >> 32) & ULongExtensions.WordBitMask)
         + (uint)((value >> 48) & ULongExtensions.WordBitMask)) % 3UL;

    [Params(3UL, 8191UL, 131071UL, 2147483647UL, ulong.MaxValue - 17UL)]
    public ulong Value { get; set; }

    /// <summary>
    /// `% 3` baseline; delivered 0.259-0.286 ns for the standard values (0.2640 ns at 3, 0.2599 ns at 8191, 0.2620 ns at 131071,
    /// 0.2858 ns at 2147483647) and 0.4916 ns near ulong.Max.
    /// </summary>
    [Benchmark(Baseline = true)]
    public ulong ModuloOperator()
    {
        return Value % 3UL;
    }

    /// <summary>
    /// Byte-slice helper; measured 0.441 ns at value 3, 0.437 ns at 8191, 0.438 ns at 131071, 0.436 ns at 2147483647, and 0.448 ns
    /// near ulong.Max—about 1.5-1.7x slower than the `%` baseline but still sub-nanosecond.
    /// </summary>
    [Benchmark]
    public ulong ExtensionMethod()
    {
        return Mod3(Value);
    }
}