#if NET452
using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.Runtime.InteropServices;
using System.Threading.Tasks;

namespace Unosquare.Swan.Formatters {
  /// <summary>
  /// Represents a buffer of bytes containing pixels in BGRA byte order
  /// loaded from an image that is passed on to the constructor.
  /// Data contains all the raw bytes (without scanline left-over bytes)
  /// where they can be quickly changed and then a new bitmap
  /// can be created from the byte data.
  /// </summary>
  public class BitmapBuffer {
    /// <summary>
    /// A constant representing the number of
    /// bytes per pixel in the pixel data. This is
    /// always 4 but it is kept here for readability.
    /// </summary>
    public const Int32 BytesPerPixel = 4;

    /// <summary>
    /// The blue byte offset within a pixel offset. This is 0.
    /// </summary>
    public const Int32 BOffset = 0;

    /// <summary>
    /// The green byte offset within a pixel offset.  This is 1.
    /// </summary>
    public const Int32 GOffset = 1;

    /// <summary>
    /// The red byte offset within a pixel offset.  This is 2.
    /// </summary>
    public const Int32 ROffset = 2;

    /// <summary>
    /// The alpha byte offset within a pixel offset.  This is 3.
    /// </summary>
    public const Int32 AOffset = 3;

    /// <summary>
    /// Initializes a new instance of the <see cref="BitmapBuffer"/> class.
    /// Data will not contain left-over stride bytes
    /// </summary>
    /// <param name="sourceImage">The source image.</param>
    public BitmapBuffer(Image sourceImage) {
      // Acquire or create the source bitmap in a manageable format
      Boolean disposeSourceBitmap = false;
      if(!(sourceImage is Bitmap sourceBitmap) || sourceBitmap.PixelFormat != this.PixelFormat) {
        sourceBitmap = new Bitmap(sourceImage.Width, sourceImage.Height, this.PixelFormat);
        using(Graphics g = Graphics.FromImage(sourceBitmap)) {
          g.DrawImage(sourceImage, 0, 0);
        }

        // We created this bitmap. Make sure we clear it from memory
        disposeSourceBitmap = true;
      }

      // Lock the bits
      BitmapData sourceDataLocker = sourceBitmap.LockBits(
          new Rectangle(0, 0, sourceBitmap.Width, sourceBitmap.Height),
          ImageLockMode.ReadOnly,
          sourceBitmap.PixelFormat);

      // Set basic properties
      this.ImageWidth = sourceBitmap.Width;
      this.ImageHeight = sourceBitmap.Height;
      this.LineStride = sourceDataLocker.Stride;

      // State variables
      this.LineLength = sourceBitmap.Width * BytesPerPixel; // may or may not be equal to the Stride
      this.Data = new Byte[this.LineLength * sourceBitmap.Height];

      // copy line by line in order to ignore the useless left-over stride
      _ = Parallel.For(0, sourceBitmap.Height, y => {
        IntPtr sourceAddress = sourceDataLocker.Scan0 + sourceDataLocker.Stride * y;
        Int32 targetAddress = y * this.LineLength;
        Marshal.Copy(sourceAddress, this.Data, targetAddress, this.LineLength);
      });

      // finally unlock the bitmap
      sourceBitmap.UnlockBits(sourceDataLocker);

      // dispose the source bitmap if we had to create it
      if(disposeSourceBitmap) {
        sourceBitmap.Dispose();
      }
    }

    /// <summary>
    /// Contains all the bytes of the pixel data
    /// Each horizontal scanline is represented by LineLength
    /// rather than by LinceStride. The left-over stride bytes
    /// are removed.
    /// </summary>
    public Byte[] Data {
      get;
    }

    /// <summary>
    /// Gets the width of the image.
    /// </summary>
    public Int32 ImageWidth {
      get;
    }

    /// <summary>
    /// Gets the height of the image.
    /// </summary>
    public Int32 ImageHeight {
      get;
    }

    /// <summary>
    /// Gets the pixel format. This will always be Format32bppArgb.
    /// </summary>
    public PixelFormat PixelFormat { get; } = PixelFormat.Format32bppArgb;

    /// <summary>
    /// Gets the length in bytes of a line of pixel data.
    /// Basically the same as Line Length except Stride might be a little larger as
    /// some bitmaps might be DWORD-algned.
    /// </summary>
    public Int32 LineStride {
      get;
    }

    /// <summary>
    /// Gets the length in bytes of a line of pixel data.
    /// Basically the same as Stride except Stride might be a little larger as
    /// some bitmaps might be DWORD-algned.
    /// </summary>
    public Int32 LineLength {
      get;
    }

    /// <summary>
    /// Gets the index of the first byte in the BGRA pixel data for the given image coordinates.
    /// </summary>
    /// <param name="x">The x.</param>
    /// <param name="y">The y.</param>
    /// <returns>Index of the first byte in the BGRA pixel.</returns>
    /// <exception cref="ArgumentOutOfRangeException">
    /// x
    /// or
    /// y.
    /// </exception>
    public Int32 GetPixelOffset(Int32 x, Int32 y) {
      if(x < 0 || x > this.ImageWidth) {
        throw new ArgumentOutOfRangeException(nameof(x));
      }

      if(y < 0 || y > this.ImageHeight) {
        throw new ArgumentOutOfRangeException(nameof(y));
      }

      return y * this.LineLength + x * BytesPerPixel;
    }

    /// <summary>
    /// Converts the pixel data bytes held in the buffer
    /// to a 32-bit RGBA bitmap.
    /// </summary>
    /// <returns>Pixel data for a graphics image and its attribute.</returns>
    public Bitmap ToBitmap() {
      Bitmap bitmap = new Bitmap(this.ImageWidth, this.ImageHeight, this.PixelFormat);
      BitmapData bitLocker = bitmap.LockBits(new Rectangle(0, 0, bitmap.Width, bitmap.Height), ImageLockMode.WriteOnly, bitmap.PixelFormat);

      _ = Parallel.For(0, bitmap.Height, y => {
        Int32 sourceOffset = this.GetPixelOffset(0, y);
        IntPtr targetOffset = bitLocker.Scan0 + y * bitLocker.Stride;
        Marshal.Copy(this.Data, sourceOffset, targetOffset, bitLocker.Width);
      });

      bitmap.UnlockBits(bitLocker);

      return bitmap;
    }
  }
}
#endif