using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;
using System;
using System.Diagnostics;
using System.Linq.Expressions;
using System.Reflection;

[MemoryDiagnoser(false)]
[HideColumns("Error", "StdDev", "Median")]
public class Program
{
    public static void Main(string[] args) => BenchmarkSwitcher.FromAssembly(typeof(Program).Assembly).Run(args);

    private Action<Activity, string> _setter;

    [GlobalSetup]
    public void Setup()
    {
        Activity.DefaultIdFormat = ActivityIdFormat.W3C;
        _setter = BuildSetter<Activity, string>(typeof(Activity).GetField("_id", BindingFlags.NonPublic | BindingFlags.Instance));
    }

    [Benchmark]
    public void Test()
    {
        using Activity activity = new Activity("Test");
        activity.Start();
        Action<Activity, string> setter = _setter;
        for (int i = 0; i < 100_000; i++)
        {
            _ = activity.Id;
            setter(activity, null);
        }
        activity.Stop();
    }

    private static Action<TSource, TArg> BuildSetter<TSource, TArg>(FieldInfo field)
    {
        ParameterExpression target = Expression.Parameter(typeof(TSource));
        ParameterExpression value = Expression.Parameter(typeof(TArg));
        return Expression.Lambda<Action<TSource, TArg>>(
            Expression.Assign(Expression.Field(target, field), value),
            target,
            value).Compile();
    }
}