// Copyright (c) Six Labors.
// Licensed under the Apache License, Version 2.0.

using System.IO;
using BenchmarkDotNet.Attributes;
using SixLabors.ImageSharp.Formats.Jpeg;
using SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder;
using SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder.ColorConverters;
using SixLabors.ImageSharp.IO;
using SixLabors.ImageSharp.Tests;
using SDSize = System.Drawing.Size;

namespace SixLabors.ImageSharp.Benchmarks.Codecs.Jpeg
{
    [Config(typeof(Config.ShortMultiFramework))]
    public class DecodeJpegParseStreamOnly
    {
        [Params(TestImages.Jpeg.BenchmarkSuite.Lake_Small444YCbCr)]
        public string TestImage { get; set; }

        private string TestImageFullPath => Path.Combine(TestEnvironment.InputImagesDirectoryFullPath, this.TestImage);

        private byte[] jpegBytes;

        [GlobalSetup]
        public void Setup()
            => this.jpegBytes = File.ReadAllBytes(this.TestImageFullPath);

        [Benchmark(Baseline = true, Description = "System.Drawing FULL")]
        public SDSize JpegSystemDrawing()
        {
            using var memoryStream = new MemoryStream(this.jpegBytes);
            using var image = System.Drawing.Image.FromStream(memoryStream);
            return image.Size;
        }

        [Benchmark(Description = "JpegDecoderCore.ParseStream")]
        public void ParseStream()
        {
            using var memoryStream = new MemoryStream(this.jpegBytes);
            using var bufferedStream = new BufferedReadStream(Configuration.Default, memoryStream);

            var decoder = new JpegDecoderCore(Configuration.Default, new JpegDecoder { IgnoreMetadata = true });
            var scanDecoder = new HuffmanScanDecoder(bufferedStream, new NoopSpectralConverter(), cancellationToken: default);
            decoder.ParseStream(bufferedStream, scanDecoder, cancellationToken: default);
            decoder.Dispose();
        }

        // We want to test only stream parsing and scan decoding, we don't need to convert spectral data to actual pixels
        // Nor we need to allocate final pixel buffer
        // Note: this still introduces virtual method call overhead for baseline interleaved images
        // There's no way to eliminate it as spectral conversion is built into the scan decoding loop for memory footprint reduction
        private class NoopSpectralConverter : SpectralConverter
        {
            public override void ConvertStrideBaseline()
            {
            }

            public override void InjectFrameData(JpegFrame frame, IRawJpegData jpegData)
            {
            }

            public override JpegColorConverter GetConverter(JpegFrame frame, IRawJpegData jpegData) => JpegColorConverter.GetConverter(jpegData.ColorSpace, frame.Precision);
        }
    }
}

/*
BenchmarkDotNet=v0.13.0, OS=Windows 10.0.19042.1083 (20H2/October2020Update)
Intel Core i7-6700K CPU 4.00GHz (Skylake), 1 CPU, 8 logical and 4 physical cores
.NET SDK=6.0.100-preview.3.21202.5
  [Host]     : .NET Core 3.1.13 (CoreCLR 4.700.21.11102, CoreFX 4.700.21.11602), X64 RyuJIT
  Job-VAJCIU : .NET Core 2.1.26 (CoreCLR 4.6.29812.02, CoreFX 4.6.29812.01), X64 RyuJIT
  Job-INPXCR : .NET Core 3.1.13 (CoreCLR 4.700.21.11102, CoreFX 4.700.21.11602), X64 RyuJIT
  Job-JRCLOJ : .NET Framework 4.8 (4.8.4390.0), X64 RyuJIT

IterationCount=3  LaunchCount=1  WarmupCount=3
|                      Method |        Job |              Runtime |             TestImage |     Mean |     Error |    StdDev | Ratio |   Gen 0 | Gen 1 | Gen 2 | Allocated |
|---------------------------- |----------- |--------------------- |---------------------- |---------:|----------:|----------:|------:|--------:|------:|------:|----------:|
|       'System.Drawing FULL' | Job-VAJCIU |        .NET Core 2.1 | Jpg/baseline/Lake.jpg | 5.196 ms | 0.7520 ms | 0.0412 ms |  1.00 | 46.8750 |     - |     - | 210,768 B |
| JpegDecoderCore.ParseStream | Job-VAJCIU |        .NET Core 2.1 | Jpg/baseline/Lake.jpg | 3.467 ms | 0.0784 ms | 0.0043 ms |  0.67 |       - |     - |     - |  12,416 B |
|                             |            |                      |                       |          |           |           |       |         |       |       |           |
|       'System.Drawing FULL' | Job-INPXCR |        .NET Core 3.1 | Jpg/baseline/Lake.jpg | 5.201 ms | 0.4105 ms | 0.0225 ms |  1.00 |       - |     - |     - |     183 B |
| JpegDecoderCore.ParseStream | Job-INPXCR |        .NET Core 3.1 | Jpg/baseline/Lake.jpg | 3.349 ms | 0.0468 ms | 0.0026 ms |  0.64 |       - |     - |     - |  12,408 B |
|                             |            |                      |                       |          |           |           |       |         |       |       |           |
|       'System.Drawing FULL' | Job-JRCLOJ | .NET Framework 4.7.2 | Jpg/baseline/Lake.jpg | 5.164 ms | 0.6524 ms | 0.0358 ms |  1.00 | 46.8750 |     - |     - | 211,571 B |
| JpegDecoderCore.ParseStream | Job-JRCLOJ | .NET Framework 4.7.2 | Jpg/baseline/Lake.jpg | 4.548 ms | 0.3357 ms | 0.0184 ms |  0.88 |       - |     - |     - |  12,480 B |
*/