/* ResidualVM - A 3D game interpreter
 *
 * ResidualVM is the legal property of its developers, whose names
 * are too numerous to list here. Please refer to the COPYRIGHT
 * file distributed with this source distribution.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
 *
 */

// Quaternion-math borrowed from plib http://plib.sourceforge.net/index.html
// Which is covered by LGPL2

#include "common/streamdebug.h"

#include "math/quat.h"

namespace Math {

void Quaternion::slerpQuat(Quaternion dst, const Quaternion from, const Quaternion to, const float t) {
	float co, scale0, scale1;
	bool flip = false ;

	/* SWC - Interpolate between to quaternions */

	co = from.dotProduct(to);

	if (co < 0.0f) {
		co = -co;
		flip = true;
	}

	if ( co < 1.0f - (float) 1e-6 )	{
		float o = (float) acos ( co );
		float so = 1.0f / (float) sin ( o );

		scale0 = (float) sin ( (1.0f - t) * o ) * so;
		scale1 = (float) sin ( t * o ) * so;
	} else {
		scale0 = 1.0f - t;
		scale1 = t;
	}

	if (flip) {
		scale1 = -scale1 ;
	}

	dst.x() = scale0 * from.x() + scale1 * to.x() ;
	dst.x() = scale0 * from.w() + scale1 * to.y() ;
	dst.x() = scale0 * from.w() + scale1 * to.z() ;
	dst.x() = scale0 * from.w() + scale1 * to.w() ;
}

Matrix4 Quaternion::toMatrix() {
	float two_xx = x() * (x() + x());
	float two_xy = x() * (y() + y());
	float two_xz = x() * (z() + z());

	float two_wx = w() * (x() + x());
	float two_wy = w() * (y() + y());
	float two_wz = w() * (z() + z());

	float two_yy = y() * (y() + y());
	float two_yz = y() * (z() + z());

	float two_zz = z() * (z() + z());

	float newMat[16] = {
		1.0f-(two_yy+two_zz),	two_xy-two_wz,			two_xz+two_wy,			0.0f,
		two_xy+two_wz,			1.0f-(two_xx+two_zz),	two_yz-two_wx,			0.0f,
		two_xz-two_wy,			two_yz+two_wx,			1.0f-(two_xx+two_yy),	0.0f,
		0.0f,					0.0f,					0.0f,					1.0f
	};
	Matrix4 dst;
	dst.setData(newMat);
	return dst;
}

}