#region Copyright & License Information
/*
 * Copyright 2007-2022 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, either version 3 of
 * the License, or (at your option) any later version. For more
 * information, see COPYING.
 */
#endregion

using System;
using System.IO;

namespace OpenRA.Mods.Cnc.FileFormats
{
	public class HvaReader
	{
		public readonly uint FrameCount;
		public readonly uint LimbCount;
		public readonly float[] Transforms;

		public HvaReader(Stream s, string fileName)
		{
			// Index swaps for transposing a matrix
			var ids = new byte[] { 0, 4, 8, 12, 1, 5, 9, 13, 2, 6, 10, 14 };

			s.Seek(16, SeekOrigin.Begin);
			FrameCount = s.ReadUInt32();
			LimbCount = s.ReadUInt32();

			// Skip limb names
			s.Seek(16 * LimbCount, SeekOrigin.Current);
			Transforms = new float[16 * FrameCount * LimbCount];

			var testMatrix = new float[16];
			for (var j = 0; j < FrameCount; j++)
				for (var i = 0; i < LimbCount; i++)
				{
					// Convert to column-major matrices and add the final matrix row
					var c = 16 * (LimbCount * j + i);
					Transforms[c + 3] = 0;
					Transforms[c + 7] = 0;
					Transforms[c + 11] = 0;
					Transforms[c + 15] = 1;

					for (var k = 0; k < 12; k++)
						Transforms[c + ids[k]] = s.ReadFloat();

					Array.Copy(Transforms, 16 * (LimbCount * j + i), testMatrix, 0, 16);
					if (OpenRA.Graphics.Util.MatrixInverse(testMatrix) == null)
						throw new InvalidDataException(
							$"The transformation matrix for HVA file `{fileName}` section {i} frame {j} is invalid because it is not invertible!");
				}
		}

		public static HvaReader Load(string filename)
		{
			using (var s = File.OpenRead(filename))
				return new HvaReader(s, Path.GetFileName(filename));
		}
	}
}
