using System;
using System.Diagnostics;
using System.Linq.Expressions;
using System.Reflection;
using System.Reflection.Emit;
using Xunit;

namespace ReflectionPerformance
{
    public class PerformanceRunner
    {
        public class Address { public String City { get; set; } }
        
        [Fact]
        public void RunAll()
        {
            // Remember to run it in RELEASE-mode (it makes a big difference)
            var address = new Address {City = "Trondheim"};

            Run("Normal property access", () => { var city = address.City; });

            var cityPropertyInfo = typeof (Address).GetProperty("City");
            Run("With reflection", () => cityPropertyInfo.GetValue(address, new object[0]));

            Expression<Func<Address, string>> expression = x => x.City;
            var func = expression.Compile();
            Run("Invoke compiled expression", () => func.Invoke(address));

            RunLong("Compile Expression and invoke", () =>
                         {
                             var compiledFunction = expression.Compile();
                             compiledFunction.Invoke(address);
                         });

            var emitDelegate = GetEmitDelegate();
            Run("Emit: run compiled statement", ()=>emitDelegate(address));
            RunLong("Emit: Create statement, compile, run",()=>Emit(address));
        }

        public void Emit(Address address)
        {
            var del = GetEmitDelegate();
            del(address);

        }

        private Func<Address, string> GetEmitDelegate()
        {
            var dm = new DynamicMethod("TestMethod", typeof(String), new [] {typeof(Address) }, typeof(Address).Module);

            MethodInfo getCity = typeof(Address).GetProperty("City").GetGetMethod();

            ILGenerator il = dm.GetILGenerator();
            il.Emit(OpCodes.Ldarg_0);
            il.EmitCall(OpCodes.Call, getCity, null);
            il.Emit(OpCodes.Ret);

            return (Func<Address, String>)dm.CreateDelegate(typeof(Func<Address, String>));
        }

        private const int timesToRun = 1000000;
        private void Run(String label, Action action)
        {
            var timer = new Stopwatch();
            timer.Start();
            for (int i = 0; i < timesToRun; i++)
            {
                action();
            }
            timer.Stop();
            Console.WriteLine(timer.ElapsedTicks.ToString().PadLeft(10) + " : " + label);
        }

        private void RunLong(String label, Action action)
        {
            var timer = new Stopwatch();
            timer.Start();
            for (int i = 0; i < timesToRun/100; i++)
            {
                action();
            }
            timer.Stop();
            Console.WriteLine((timer.ElapsedTicks * 100).ToString().PadLeft(10) + " : " + label);
        }
    }
}