using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
using Marshal = System.Runtime.InteropServices.Marshal;

namespace Kawa.Tools.Bitmap
{
	/// <summary>
	/// Abstracts away the retrieval of an image's raw pixel and palette data, and allows reading ZSoft Paintbrush PCX files into Bitmap objects.
	/// </summary>
	public static class BitmapDataTools
	{
		/// <summary>
		/// Extracts the raw pixel data and optionally palette from a 256-color 320 by 200 pixel Bitmap.
		/// </summary>
		/// <param name="from">The name of a bitmap file in any of the formats supported by Bitmap, or ZSoft Paintbrush PCX.</param>
		/// <param name="palette">An array of 768 bytes to recieve the color palette of the Bitmap, or null.</param>
		/// <param name="data">An array of 64000 bytes to recieve the pixel data of the Bitmap.</param>
		public static void GetPixels(string from, ref byte[] palette, ref byte[] data)
		{
			if (from.EndsWith(".pcx", StringComparison.InvariantCultureIgnoreCase))
				GetPixels(ReadPCX(from), ref palette, ref data);
			else
				GetPixels(new System.Drawing.Bitmap(from), ref palette, ref data);
		}

		/// <summary>
		/// Extracts the raw pixel data and optionally palette from a 256-color 320 by 200 pixel Bitmap.
		/// </summary>
		/// <param name="from">A Bitmap object.</param>
		/// <param name="palette">An array of 768 bytes to recieve the color palette of the Bitmap, or null.</param>
		/// <param name="data">An array of 64000 bytes to recieve the pixel data of the Bitmap.</param>
		public static void GetPixels(System.Drawing.Bitmap from, ref byte[] palette, ref byte[] data)
		{
			if (data == null)
				throw new Exception("Need a target array.");
			if (data.Length != 320 * 200)
				throw new Exception("Target array isn't big enough.");
			if (palette != null && palette.Length != 256 * 3)
				throw new Exception("Palette array isn't big enough.");
			var victim = from;
			if (victim.PixelFormat != PixelFormat.Format8bppIndexed)
				throw new Exception("Input images can only be in 256 color format.");
			if (victim.Width != 320 || victim.Height != 200)
				throw new Exception("Input images can only be 320 by 200 pixels in size.");

			if (palette != null)
			{
				for (var i = 0; i < victim.Palette.Entries.Length; i++)
				{
					var color = victim.Palette.Entries[i];
					palette[i * 3 + 0] = color.R;
					palette[i * 3 + 1] = color.G;
					palette[i * 3 + 2] = color.B;
				}
			}

			var bitmapData = victim.LockBits(new Rectangle(0, 0, victim.Width, victim.Height), ImageLockMode.ReadOnly, victim.PixelFormat);
			Marshal.Copy(bitmapData.Scan0, data, 0, 320 * 200);
			victim.UnlockBits(bitmapData);
		}

		/// <summary>
		/// Reads a ZSoft Paintbrush PCX file into a Bitmap. Only supports 256-color version 5 files with a single plane.
		/// </summary>
		/// <param name="from">The name of a PCX file.</param>
		/// <returns>A Bitmap object representation of the PCX file.</returns>
		public static System.Drawing.Bitmap ReadPCX(string from)
		{
			using (var stream = new BinaryReader(File.Open(from, FileMode.Open)))
			{
				if (stream.ReadByte() != 10)
					throw new Exception("Filename says PCX, but first byte doesn't.");
				if (stream.ReadByte() != 5)
					throw new Exception("Wrong PCX version.");
				if (stream.ReadByte() != 1)
					throw new Exception("Wrong PCX encoding.");
				if (stream.ReadByte() != 8)
					throw new Exception("Input images can only be in 256 color format.");
				var winLeft = stream.ReadInt16();
				var winTop = stream.ReadInt16();
				var winRight = stream.ReadInt16();
				var winBottom = stream.ReadInt16();
				var width = winRight + 1;
				var height = winBottom + 1;
				var size = width * height;
				if (width % 8 != 0)
					throw new Exception("Can't work with widths that aren't divisible by 8.");
				stream.ReadInt16(); //HRes
				stream.ReadInt16(); //VRes
				stream.ReadBytes(48); //ColorMap
				stream.ReadByte(); //Reserved
				if (stream.ReadByte() != 1)
					throw new Exception("Input images can only have the one plane.");
				var stride = stream.ReadInt16();
				if (stream.ReadByte() != 1)
					throw new Exception("Unexpected palette interpretation.");

				var bitmap = new System.Drawing.Bitmap(width, height, PixelFormat.Format8bppIndexed);
				var palette = bitmap.Palette;
				stream.BaseStream.Seek(-769, SeekOrigin.End);
				if (stream.ReadByte() != 12)
					throw new Exception("Unexpected byte as palette marker.");
				for (var i = 0; i < 256; i++)
					palette.Entries[i] = Color.FromArgb(255, stream.ReadByte(), stream.ReadByte(), stream.ReadByte());
				bitmap.Palette = palette;

				stream.BaseStream.Seek(128, SeekOrigin.Begin);
				var data = new byte[size];
				for (var i = 0; i < size; i++)
				{
					var b = stream.ReadByte();
					if ((b & 0xC0) == 0xC0)
					{
						var length = b & 0x3F;
						b = stream.ReadByte();
						for (var j = 0; j < length; j++)
							data[i + j] = b;
						i += length - 1;
					}
					else
						data[i] = b;
				}

				var bitmapData = bitmap.LockBits(new Rectangle(0, 0, width, height), ImageLockMode.ReadWrite, PixelFormat.Format8bppIndexed);
				Marshal.Copy(data, 0, bitmapData.Scan0, size);
				bitmap.UnlockBits(bitmapData);
				return bitmap;
			}
		}
	}
}