/*
 * Copyright 2011, Blender Foundation.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 */

/*
 * Adapted from code with license:
 * 
 * Copyright (c) 2002, Industrial Light & Magic, a division of Lucas
 * Digital Ltd. LLC. All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 * * Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * * Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in
 *   the documentation and/or other materials provided with the
 *   distribution.
 * * Neither the name of Industrial Light & Magic nor the names of its
 *   contributors may be used to endorse or promote products derived
 *   from this software without specific prior written permission. 
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "util_math.h"
#include "util_transform.h"

CCL_NAMESPACE_BEGIN

static bool transform_matrix4_gj_inverse(float R[][4], float M[][4])
{
	/* forward elimination */
	for(int i = 0; i < 4; i++) {
		int pivot = i;
		float pivotsize = M[i][i];

		if(pivotsize < 0)
			pivotsize = -pivotsize;

		for(int j = i + 1; j < 4; j++) {
			float tmp = M[j][i];

			if(tmp < 0)
				tmp = -tmp;

			if(tmp > pivotsize) {
				pivot = j;
				pivotsize = tmp;
			}
		}

		if(pivotsize == 0)
			return false;

		if(pivot != i) {
			for(int j = 0; j < 4; j++) {
				float tmp;

				tmp = M[i][j];
				M[i][j] = M[pivot][j];
				M[pivot][j] = tmp;

				tmp = R[i][j];
				R[i][j] = R[pivot][j];
				R[pivot][j] = tmp;
			}
		}

		for(int j = i + 1; j < 4; j++) {
			float f = M[j][i] / M[i][i];

			for(int k = 0; k < 4; k++) {
				M[j][k] -= f*M[i][k];
				R[j][k] -= f*R[i][k];
			}
		}
	}

	/* backward substitution */
	for(int i = 3; i >= 0; --i) {
		float f;

		if((f = M[i][i]) == 0)
			return false;

		for(int j = 0; j < 4; j++) {
			M[i][j] /= f;
			R[i][j] /= f;
		}

		for(int j = 0; j < i; j++) {
			f = M[j][i];

			for(int k = 0; k < 4; k++) {
				M[j][k] -= f*M[i][k];
				R[j][k] -= f*R[i][k];
			}
		}
	}

	return true;
}

Transform transform_inverse(const Transform& tfm)
{
	union { Transform T; float M[4][4]; } R, M;
	
	R.T = transform_identity();
	M.T = tfm;

	if(!transform_matrix4_gj_inverse(R.M, M.M))
		return transform_identity();

	return R.T;
}

CCL_NAMESPACE_END