#region Copyright & License Information
/*
 * Copyright 2007-2011 The OpenRA Developers (see AUTHORS)
 * This file is part of OpenRA, which is free software. It is made
 * available to you under the terms of the GNU General Public License
 * as published by the Free Software Foundation. For more information,
 * see COPYING.
 */
#endregion

using System.Collections.Generic;
using System.Drawing;
using System.IO;
using System.Linq;

namespace OpenRA.FileFormats
{
	public class ImageHeader
	{
		public uint Offset;
		public Format Format;

		public uint RefOffset;
		public Format RefFormat;
		public ImageHeader RefImage;

		public byte[] Image;

		public ImageHeader() { }

		public ImageHeader( BinaryReader reader )
		{
			var data = reader.ReadUInt32();
			Offset = data & 0xffffff;
			Format = (Format)(data >> 24);

			RefOffset = reader.ReadUInt16();
			RefFormat = (Format)reader.ReadUInt16();
		}

		public static readonly int SizeOnDisk = 8;

		public void WriteTo(BinaryWriter writer)
		{
			writer.Write(Offset | ((uint)Format << 24));
			writer.Write((ushort)RefOffset);
			writer.Write((ushort)RefFormat);
		}
	}

	public enum Format { Format20 = 0x20, Format40 = 0x40, Format80 = 0x80 }

	public class ShpReader
	{
		public readonly int ImageCount;
		public readonly ushort Width;
		public readonly ushort Height;

		public Size Size { get { return new Size(Width, Height); } }

		readonly List<ImageHeader> headers = new List<ImageHeader>();

		int recurseDepth = 0;

		public ShpReader( Stream stream )
		{
			using( var reader = new BinaryReader( stream ) )
			{
				ImageCount = reader.ReadUInt16();
				reader.ReadUInt16();
				reader.ReadUInt16();
				Width = reader.ReadUInt16();
				Height = reader.ReadUInt16();
				reader.ReadUInt32();

				for( int i = 0 ; i < ImageCount ; i++ )
					headers.Add( new ImageHeader( reader ) );

				new ImageHeader( reader ); // end-of-file header
				new ImageHeader( reader ); // all-zeroes header

				var offsets = headers.ToDictionary(h => h.Offset, h =>h);

				for( int i = 0 ; i < ImageCount ; i++ )
				{
					var h = headers[ i ];
					if( h.Format == Format.Format20 )
						h.RefImage = headers[ i - 1 ];

					else if( h.Format == Format.Format40 )
						if( !offsets.TryGetValue( h.RefOffset, out h.RefImage ) )
							throw new InvalidDataException( "Reference doesnt point to image data {0}->{1}".F(h.Offset, h.RefOffset) );
				}

				foreach( ImageHeader h in headers )
					Decompress( stream, h );
			}
		}

		public ImageHeader this[ int index ]
		{
			get { return headers[ index ]; }
		}

		void Decompress( Stream stream, ImageHeader h )
		{
			if( recurseDepth > ImageCount )
				throw new InvalidDataException( "Format20/40 headers contain infinite loop" );

			switch( h.Format )
			{
				case Format.Format20:
				case Format.Format40:
					{
						if( h.RefImage.Image == null )
						{
							++recurseDepth;
							Decompress( stream, h.RefImage );
							--recurseDepth;
						}

						h.Image = CopyImageData( h.RefImage.Image );
						Format40.DecodeInto(ReadCompressedData(stream, h), h.Image);
						break;
					}
				case Format.Format80:
					{
						var imageBytes = new byte[ Width * Height ];
						Format80.DecodeInto( ReadCompressedData( stream, h ), imageBytes );
						h.Image = imageBytes;
						break;
					}
				default:
					throw new InvalidDataException();
			}
		}

		static byte[] ReadCompressedData( Stream stream, ImageHeader h )
		{
			stream.Position = h.Offset;
			// Actually, far too big. There's no length field with the correct length though :(
			var compressedLength = (int)( stream.Length - stream.Position );

			var compressedBytes = new byte[ compressedLength ];
			stream.Read( compressedBytes, 0, compressedLength );

			return compressedBytes;
		}

		byte[] CopyImageData( byte[] baseImage )
		{
			var imageData = new byte[ Width * Height ];
			for( int i = 0 ; i < Width * Height ; i++ )
				imageData[ i ] = baseImage[ i ];

			return imageData;
		}

		public IEnumerable<ImageHeader> Frames { get { return headers; } }

		public static ShpReader Load(string filename)
		{
			using (var s = File.OpenRead(filename))
				return new ShpReader(s);
		}
	}
}