using System;
using System.IO;
using System.Reflection;
using System.Windows.Forms;
using Blacklight.Core;
using Blacklight.Core.Cameras;
using SharpDX.Direct3D9;

namespace Blacklight.SharpDX9.PerformanceTests
{
    /// <summary>
    /// Draws the comparison scenes and writes what the GPU produced for each to a file, so two builds of the shader can
    /// be checked for drawing the same picture.
    /// </summary>
    public static class ImageDump
    {
        public const string Argument = "--dump-images";
        public const int Width = 640;
        public const int Height = 480;

        private const int BytesPerPixel = 8;

        /// <summary>
        /// Gets the scene target the last frame was drawn into, which the window handle keeps to itself.
        /// </summary>
        public static SharpDX9SceneTarget SceneTargetOf(SharpDX9WindowHandle handle)
        {
            FieldInfo field = typeof(SharpDX9WindowHandle).GetField(
                "_sceneTarget", BindingFlags.Instance | BindingFlags.NonPublic);
            return (SharpDX9SceneTarget)field.GetValue(handle);
        }

        /// <summary>
        /// Writes the scene target's linear half float RGBA pixels, row by row, to `path`.
        /// </summary>
        public static void Capture(SharpDX9WindowHandle handle, string path)
        {
            Device device = handle.Backend.GraphicsDevice;
            Surface target = SceneTargetOf(handle).Surface;
            SurfaceDescription description = target.Description;
            using (Surface readable = Surface.CreateOffscreenPlain(
                device, description.Width, description.Height, description.Format, Pool.SystemMemory))
            {
                device.GetRenderTargetData(target, readable);
                SharpDX.DataRectangle rectangle = readable.LockRectangle(LockFlags.ReadOnly);
                try
                {
                    var row = new byte[description.Width * BytesPerPixel];
                    using (var file = new FileStream(path, FileMode.Create))
                    {
                        for (int y = 0; y < description.Height; ++y)
                        {
                            System.Runtime.InteropServices.Marshal.Copy(
                                rectangle.DataPointer + y * rectangle.Pitch, row, 0, row.Length);
                            file.Write(row, 0, row.Length);
                        }
                    }
                }
                finally
                {
                    readable.UnlockRectangle();
                }
            }
        }

        public static int Run(string directory)
        {
            Directory.CreateDirectory(directory);
            using (var window = new Form())
            using (var module = new Module { VerticalSync = VerticalSyncMode.Off })
            {
                window.ClientSize = new System.Drawing.Size(Width, Height);
                var handle = (SharpDX9WindowHandle)module.CreateDrawableSurfaceOnWindow(window.Handle);
                try
                {
                    var context = new SceneContext
                    {
                        Handle = handle,
                        Sheet = SpriteSheet.Create(handle, ImageScene.BuildFrames(premultiplied: false),
                            new System.Drawing.Size(ImageScene.FrameSide, ImageScene.FrameSide), borderSize: 0),
                        PremultipliedSheet = SpriteSheet.Create(handle, ImageScene.BuildFrames(premultiplied: true),
                            new System.Drawing.Size(ImageScene.FrameSide, ImageScene.FrameSide), borderSize: 0),
                        FillTexture = handle.CreateTexture(ImageScene.BuildChecker()),
                    };
                    var camera = new ScreenSpaceCamera(handle);

                    Console.WriteLine($"{handle.Width}x{handle.Height}");
                    foreach (ImageScene imageScene in ImageScene.All())
                    {
                        Scene scene = imageScene.Build(context);
                        handle.FrameReset();
                        handle.DrawScene(scene, camera);
                        handle.SubmitDrawCalls();
                        Capture(handle, Path.Combine(directory, imageScene.Name + ".f16"));
                    }
                }
                finally
                {
                    handle.Dispose();
                }
            }

            return 0;
        }
    }
}