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

namespace SomeBench
{
  public class Program
  {
    static void Main()
    {
      BenchmarkRunner.Run<Program>();
    }

    Random _random;
    MethodInfo _invoker;
    Bar _barFunc;
    Bar _barExpressionFunc;
    [GlobalSetup]
    public void GlobalSetup()
    {
      _random = new Random((int)DateTime.Now.Ticks);
      _invoker = typeof(Foo).GetMethod("Bar", BindingFlags.Public | BindingFlags.Static);
      _barFunc = (Bar) Delegate.CreateDelegate(typeof(Bar), _invoker);
      var paramExpr = Expression.Parameter(typeof(int));
      var invokeExpr = Expression.Call(_invoker, paramExpr);
      var lambda = Expression.Lambda<Bar>(invokeExpr, paramExpr);
      _barExpressionFunc = lambda.Compile();
    }

    [Benchmark(Baseline = true)]
    public void DirectCall()
    {
      _ = Foo.Bar(_random.Next());
    }

    [Benchmark]
    public void ReflectionCall()
    {
      _ = (string) _invoker.Invoke(null, new object[] {_random.Next()});
    }

    [Benchmark]
    public void DelegateCall()
    {
      _ = _barFunc(_random.Next());
    }

    [Benchmark]
    public void ExpressionCall()
    {
      _ = _barExpressionFunc(_random.Next());
    }
  }

  public delegate string Bar(int n);

  public class Foo
  {
    public static string Bar(int n) => n.ToString(CultureInfo.InvariantCulture);
  }
}

/*
|         Method |     Mean |     Error |    StdDev | Ratio |
|--------------- |---------:|----------:|----------:|------:|
|     DirectCall | 106.9 ns | 0.1416 ns | 0.1255 ns |  1.00 |
| ReflectionCall | 287.1 ns | 0.4297 ns | 0.4020 ns |  2.69 |
|   DelegateCall | 109.3 ns | 0.1600 ns | 0.1497 ns |  1.02 |
| ExpressionCall | 118.7 ns | 0.1811 ns | 0.1694 ns |  1.11 |
*/