using System.Diagnostics;

namespace Nerfed.Runtime.Systems.Synthetic;

internal static class DummyWorkloadRunner
{
    public static int Run(TimeSpan duration, DummyWorkloadMode mode, int seed)
    {
        return mode switch
        {
            DummyWorkloadMode.Sleep => Sleep(duration, seed),
            DummyWorkloadMode.Compute => Compute(duration, seed),
            _ => Spin(duration, seed),
        };
    }

    private static int Sleep(TimeSpan duration, int seed)
    {
        if (duration > TimeSpan.Zero)
        {
            Thread.Sleep(duration);
        }

        return seed;
    }

    private static int Spin(TimeSpan duration, int seed)
    {
        Stopwatch stopwatch = Stopwatch.StartNew();
        int value = seed;
        while (stopwatch.Elapsed < duration)
        {
            value = unchecked((value * 1664525) + 1013904223);
            Thread.SpinWait(128);
        }

        return value;
    }

    private static int Compute(TimeSpan duration, int seed)
    {
        Stopwatch stopwatch = Stopwatch.StartNew();
        int value = seed;
        while (stopwatch.Elapsed < duration)
        {
            for (int i = 0; i < 2048; i++)
            {
                value = unchecked((value << 5) - value + i);
            }
        }

        return value;
    }
}