// ==========================================================================
//  Squidex Headless CMS
// ==========================================================================
//  Copyright (c) Squidex UG (haftungsbeschraenkt)
//  All rights reserved. Licensed under the MIT license.
// ==========================================================================

using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Xunit;
using Xunit.Abstractions;

namespace TestSuite.LoadTests
{
    public static class Run
    {
        public static async Task Parallel(int numUsers, int numIterationsPerUser, Func<Task> action, int expectedAvg = 100, ITestOutputHelper testOutput = null)
        {
            await action();

            var elapsedMs = new ConcurrentBag<long>();

            var errors = 0;

            async Task RunAsync()
            {
                for (var i = 0; i < numIterationsPerUser; i++)
                {
                    try
                    {
                        var watch = Stopwatch.StartNew();

                        await action();

                        watch.Stop();

                        elapsedMs.Add(watch.ElapsedMilliseconds);
                    }
                    catch
                    {
                        Interlocked.Increment(ref errors);
                    }
                }
            }

            var tasks = new List<Task>();

            for (var i = 0; i < numUsers; i++)
            {
                tasks.Add(Task.Run(RunAsync));
            }

            await Task.WhenAll(tasks);

            var count = elapsedMs.Count;

            var avg = elapsedMs.Average();

            if (testOutput != null)
            {
                testOutput.WriteLine("Total Errors: {0}/{1}", errors, numUsers * numIterationsPerUser);
                testOutput.WriteLine("Total Count: {0}/{1}", count, numUsers * numIterationsPerUser);

                testOutput.WriteLine(string.Empty);
                testOutput.WriteLine("Performance Average: {0}", avg);
                testOutput.WriteLine("Performance Max: {0}", elapsedMs.Max());
                testOutput.WriteLine("Performance Min: {0}", elapsedMs.Min());
            }

            Assert.InRange(avg, 0, expectedAvg);
        }
    }
}