using System;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Caching.Memory;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

namespace CacheEntryRepro
{
    class Program
    {
        static async Task Main(string[] args)
        {
            var builder = Host.CreateDefaultBuilder().ConfigureWebHostDefaults(whb =>
                whb.ConfigureServices(s => s.AddMemoryCache())
                    .Configure(app =>
                    {
                        app.UseRouting();
                        app.UseEndpoints(erb => { erb.MapGet("/", hc => RequestDelegate(hc)); });
                    }));
            await builder.Build().RunAsync();
        }

        private static async Task RequestDelegate(HttpContext context)
        {
            var cache = context.RequestServices.GetRequiredService<IMemoryCache>();
            int processors = Environment.ProcessorCount;
            var tasks = new Task[processors];
            for (int i = 0; i < 1000; i++)
            {
                for (int j = 0; j < processors; j++)
                {
                    tasks[j] = AddCacheEntry(cache);
                }

                await Task.WhenAll(tasks);
            }

            context.Response.StatusCode = StatusCodes.Status200OK;
            await context.Response.StartAsync();
            await context.Response.WriteAsync("Done");
            await context.Response.CompleteAsync();
        }

        private static Task AddCacheEntry(IMemoryCache cache)
        {
            var guid = Guid.NewGuid();
            using var entry = cache.CreateEntry(guid.ToString());
            entry.Size = 1;
            entry.SlidingExpiration = TimeSpan.FromMinutes(1);
            entry.Value = Guid.NewGuid();
            return Task.CompletedTask;
        }
    }
}