// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

using System;
using System.Buffers;
using System.IO.Pipelines;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using BenchmarkDotNet.Attributes;
using Microsoft.AspNetCore.Http.Features;
using Microsoft.AspNetCore.Server.Kestrel.Core;
using Microsoft.AspNetCore.Server.Kestrel.Core.Internal;
using Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http;
using Microsoft.AspNetCore.Testing;

namespace Microsoft.AspNetCore.Server.Kestrel.Performance
{
    public class Http1WritingBenchmark
    {
        // Standard completed task
        private static readonly Func<object, Task> _syncTaskFunc = (obj) => Task.CompletedTask;
        // Non-standard completed task
        private static readonly Task _psuedoAsyncTask = Task.FromResult(27);
        private static readonly Func<object, Task> _psuedoAsyncTaskFunc = (obj) => _psuedoAsyncTask;

        private readonly TestHttp1Connection _http1Connection;
        private (IPipeConnection Transport, IPipeConnection Application) _pair;

        private readonly byte[] _writeData;

        public Http1WritingBenchmark()
        {
            _http1Connection = MakeHttp1Connection();
            _writeData = Encoding.ASCII.GetBytes("Hello, World!");
        }

        [Params(true, false)]
        public bool WithHeaders { get; set; }

        [Params(true, false)]
        public bool Chunked { get; set; }

        [Params(Startup.None, Startup.Sync, Startup.Async)]
        public Startup OnStarting { get; set; }

        [IterationSetup]
        public void Setup()
        {
            _http1Connection.Reset();
            if (Chunked)
            {
                _http1Connection.RequestHeaders.Add("Transfer-Encoding", "chunked");
            }
            else
            {
                _http1Connection.RequestHeaders.ContentLength = _writeData.Length;
            }

            if (!WithHeaders)
            {
                _http1Connection.FlushAsync().GetAwaiter().GetResult();
            }

            ResetState();
        }

        private void ResetState()
        {
            if (WithHeaders)
            {
                _http1Connection.ResetState();

                switch (OnStarting)
                {
                    case Startup.Sync:
                        _http1Connection.OnStarting(_syncTaskFunc, null);
                        break;
                    case Startup.Async:
                        _http1Connection.OnStarting(_psuedoAsyncTaskFunc, null);
                        break;
                }
            }
        }

        [Benchmark]
        public Task WriteAsync()
        {
            ResetState();

            return _http1Connection.ResponseBody.WriteAsync(_writeData, 0, _writeData.Length, default(CancellationToken));
        }

        private TestHttp1Connection MakeHttp1Connection()
        {
            using (var memoryPool = new MemoryPool())
            {
                var pair = PipeFactory.CreateConnectionPair(memoryPool);
                _pair = pair;

                var serviceContext = new ServiceContext
                {
                    DateHeaderValueManager = new DateHeaderValueManager(),
                    ServerOptions = new KestrelServerOptions(),
                    Log = new MockTrace(),
                    HttpParser = new HttpParser<Http1ParsingHandler>()
                };

                var http1Connection = new TestHttp1Connection(new Http1ConnectionContext
                {
                    ServiceContext = serviceContext,
                    ConnectionFeatures = new FeatureCollection(),
                    MemoryPool = memoryPool,
                    Application = pair.Application,
                    Transport = pair.Transport
                });

                http1Connection.Reset();
                http1Connection.InitializeStreams(MessageBody.ZeroContentLengthKeepAlive);

                return http1Connection;
            }
        }

        [IterationCleanup]
        public void Cleanup()
        {
            var reader = _pair.Application.Input;
            if (reader.TryRead(out var readResult))
            {
                reader.Advance(readResult.Buffer.End);
            }
        }

        public enum Startup
        {
            None,
            Sync,
            Async
        }
    }
}