#region ================== Copyright (c) 2007 Pascal vd Heiden

/*
 * Copyright (c) 2007 Pascal vd Heiden, www.codeimp.com
 * This program is released under GNU General Public License
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 */

#endregion

#region ================== Namespaces

using System.IO;
using CodeImp.DoomBuilder.IO;

#endregion

namespace CodeImp.DoomBuilder.Data
{
	internal static class ImageDataFormat
	{
		// Input guess formats
		public const int UNKNOWN = 0;			// No clue.
		public const int DOOMPICTURE = 1;		// Could be Doom Picture format	(column list rendered data)
		public const int DOOMFLAT = 2;			// Could be Doom Flat format	(raw 8-bit pixel data)
		public const int DOOMCOLORMAP = 3;		// Could be Doom Colormap format (raw 8-bit pixel palette mapping)
		
		// File format signatures
		private static readonly int[] PNG_SIGNATURE = new[] { 137, 80, 78, 71, 13, 10, 26, 10 };
		private static readonly int[] GIF_SIGNATURE = new[] { 71, 73, 70 };
		private static readonly int[] BMP_SIGNATURE = new[] { 66, 77 }; 
		private static readonly int[] DDS_SIGNATURE = new[] { 68, 68, 83, 32 };
		private static readonly int[] JPG_SIGNATURE = new[] { 255, 216, 255 }; //mxd
		private static readonly int[] PCX_SIGNATURE = new[] { 10, 5, 1, 8 }; //mxd

		// This check image data and returns the appropriate image reader
		public static IImageReader GetImageReader(Stream data, int guessformat, Playpal palette)
		{
			if(data == null) return new UnknownImageReader(); //mxd

            // [ZZ] If it's 4096 bytes long, and expected to be a flat, ignore all further checks.
            //      This is __NOT__ the good way to resolve it, but at least it works somewhat.
            //      I don't think if much can be done given the fact that Doom graphics are headerless themselves.
            //      https://forum.zdoom.org/viewtopic.php?p=1047520#p1047520
            if (data.Length == 4096 && guessformat == DOOMFLAT)
            {
                DoomFlatReader flatreader = new DoomFlatReader(palette);
                if (flatreader.Validate(data)) return flatreader;
            }

            // Data long enough to check for signatures?
            if (data.Length > 10) 
			{
				// Check for PNG signature
				if(CheckSignature(data, PNG_SIGNATURE)) return new FileImageReader(DevilImageType.IL_PNG);

				// Check for DDS signature
				if(CheckSignature(data, DDS_SIGNATURE)) return new FileImageReader(DevilImageType.IL_DDS);

				//mxd. Check for PCX signature
				if(CheckSignature(data, PCX_SIGNATURE)) return new FileImageReader(DevilImageType.IL_PCX);

				//mxd. Check for JPG signature
				if(CheckSignature(data, JPG_SIGNATURE)) return new FileImageReader(DevilImageType.IL_JPG);

				//mxd. TGA is VERY special in that it doesn't have a proper signature...
				if(CheckTgaSignature(data)) return new FileImageReader(DevilImageType.IL_TGA);

				// Check for GIF signature
				if(CheckSignature(data, GIF_SIGNATURE)) return new UnknownImageReader(); //mxd. Not supported by (G)ZDoom

				// Check for BMP signature
				if(CheckSignature(data, BMP_SIGNATURE)) return new UnknownImageReader(); //mxd. Not supported by (G)ZDoom
			}
				
			// Could it be a doom picture?
			switch(guessformat) 
			{
				case DOOMPICTURE:
					// Check if data is valid for a doom picture
					data.Seek(0, SeekOrigin.Begin);
					DoomPictureReader picreader = new DoomPictureReader(palette);
					if(picreader.Validate(data)) return picreader;
					break;

				case DOOMFLAT:
					// Check if data is valid for a doom flat
					data.Seek(0, SeekOrigin.Begin);
					DoomFlatReader flatreader = new DoomFlatReader(palette);
					if(flatreader.Validate(data)) return flatreader;
					break;

				case DOOMCOLORMAP:
					// Check if data is valid for a doom colormap
					data.Seek(0, SeekOrigin.Begin);
					DoomColormapReader colormapreader = new DoomColormapReader(palette);
					if(colormapreader.Validate(data)) return colormapreader;
					break;
			}
			
			// Format not supported
			return new UnknownImageReader();
		}

		// This checks a signature as byte array
		// NOTE: Expects the stream position to be at the start of the
		// signature, and expects the stream to be long enough.
		private static bool CheckSignature(Stream data, int[] sig)
		{
			//mxd. Rewind the data first
			data.Seek(0, SeekOrigin.Begin);
			
			// Go for all bytes
			foreach(int s in sig)
			{
				// When byte doesnt match the signature, leave
				if(data.ReadByte() != s) return false;
			}

			// Signature matches
			return true;
		}

		//mxd. This tries to guess if a given image is in TGA format...
		private static bool CheckTgaSignature(Stream data)
		{
			// TGA header is 18 bytes long
			if(data.Length < 18) return false;
			
			// Rewind the data first
			data.Seek(0, SeekOrigin.Begin);

			// Read TGA header
			int idlength = data.ReadByte(); // Can be 0 or the length of ID string, whatever that is
			int colormap = data.ReadByte(); // Can be 0 or 1
			if(colormap != 0 && colormap != 1) return false;

			int imagetype = data.ReadByte(); // Can be 0, 1, 2, 3, 9, 10, 11
			if((imagetype > 3 && imagetype < 9) || imagetype > 11) return false;

			data.Position += 9; // Skip some stuff...

			int width = data.ReadByte() + (data.ReadByte() << 8);
			if(width < 0 || width > 8192) return false;

			int height = data.ReadByte() + (data.ReadByte() << 8);
			if(height < 0 || height > 8192) return false;

			int bitsperpixel = data.ReadByte();  // Can be 8, 16, 24, 32
			return (bitsperpixel == 8 || bitsperpixel == 16 || bitsperpixel == 24 || bitsperpixel == 32);
		}
	}
}