using Microsoft.Diagnostics.NETCore.Client;
using Microsoft.Diagnostics.Tracing;
using Microsoft.Diagnostics.Tracing.Analysis;
using Microsoft.Diagnostics.Tracing.Analysis.GC;
using Microsoft.Diagnostics.Tracing.Parsers.Clr;
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Diagnostics.Tracing;
using System.Runtime.InteropServices;
using System.Threading;
using System.Threading.Tasks;

namespace SampleApp
{
    class Program
    {
        static List<object> s_objects = new List<object>();

        static void Main(string[] args)
        {
            GCEventPipeMonitor monitor = new GCEventPipeMonitor();
            monitor.Start();
            Task.Run(AllocateMemory);
            Console.ReadLine();
        }

        static void AllocateMemory()
        {
            while(true)
            {
                s_objects.Add(new byte[50_000]);
                Thread.Sleep(10);
            }
        }
    }


    public class GCEventPipeMonitor
    {
        DiagnosticsClient _client;
        EventPipeSession _session;
        public void Start()
        {
            Task.Run(() =>
            {
                int pid = Process.GetCurrentProcess().Id;
                _client = new DiagnosticsClient(pid);
                _session = _client.StartEventPipeSession(new EventPipeProvider[]
                {
                    new EventPipeProvider("Microsoft-Windows-DotNETRuntime", EventLevel.Informational, 0x1)
                },
                requestRundown: false,
                circularBufferMB: 5);
                EventPipeEventSource source = new EventPipeEventSource(_session.EventStream);
                source.NeedLoadedDotNetRuntimes();
                source.AddCallbackOnProcessStart(delegate (TraceProcess proc)
                {
                    proc.AddCallbackOnDotNetRuntimeLoad(delegate (TraceLoadedDotNetRuntime runtime)
                    {
                        runtime.GCEnd += delegate (TraceProcess p, TraceGC gc)
                        {
                            Console.WriteLine($"GC#{gc.Number} Gen2 Fragmentation is: {gc.GenFragmentationPercent(Gens.Gen2):g2}%");
                        };
                    });
                });
                source.Process();
            });
        }
    }
}

/* Example output
GC#1 Gen2 Fragmentation is: 0%
GC#2 Gen2 Fragmentation is: 3.9%
GC#3 Gen2 Fragmentation is: 0%
GC#5 Gen2 Fragmentation is: 1.9%
GC#4 Gen2 Fragmentation is: 1.9%
GC#6 Gen2 Fragmentation is: 0%
GC#7 Gen2 Fragmentation is: 1.2%
GC#8 Gen2 Fragmentation is: 0%
GC#9 Gen2 Fragmentation is: 0.9%
GC#10 Gen2 Fragmentation is: 0%
GC#12 Gen2 Fragmentation is: 0.74%
GC#11 Gen2 Fragmentation is: 0.77%
GC#13 Gen2 Fragmentation is: 0%
GC#14 Gen2 Fragmentation is: 0.67%
*/