/* ScummVM - Graphic Adventure Engine
 *
 * ScummVM 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 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 3 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, see <http://www.gnu.org/licenses/>.
 *
 */

/*
 * This file is based on WME Lite.
 * http://dead-code.org/redir.php?target=wmelite
 * Copyright (c) 2011 Jan Nedoma
 */

#include "engines/wintermute/math/math_util.h"
#include "common/scummsys.h"

#ifdef ENABLE_WME3D
#include "common/util.h"
#endif

namespace Wintermute {

//////////////////////////////////////////////////////////////////////////
float MathUtil::round(float val) {
	float result = floor(val);
	if (val - result >= 0.5f) {
		result += 1.0;
	}
	return result;
}

//////////////////////////////////////////////////////////////////////////
float MathUtil::roundUp(float val) {
	float result = floor(val);
	if (val - result > 0) {
		result += 1.0;
	}
	return result;
}

#ifdef ENABLE_WME3D
bool lineIntersectsTriangle(const Math::Vector3d &origin, const Math::Vector3d &direction,
							const Math::Vector3d &v0, const Math::Vector3d &v1, const Math::Vector3d &v2,
							float &t, float &u, float &v) {
	const float epsilon = 0.0001f;

	Math::Vector3d edge1 = v1 - v0;
	Math::Vector3d edge2 = v2 - v0;

	Math::Vector3d pVector = Math::Vector3d::crossProduct(direction, edge2);

	float det = Math::Vector3d::dotProduct(edge1, pVector);

	if (ABS(det) < epsilon) {
		return false;
	}

	Math::Vector3d tVector = origin - v0;
	u = Math::Vector3d::dotProduct(tVector, pVector) / det;

	if (u < 0.0f || u > 1.0f) {
		return false;
	}

	Math::Vector3d qVector = Math::Vector3d::crossProduct(tVector, edge1);
	v = Math::Vector3d::dotProduct(direction, qVector) / det;

	if (v < 0.0f || u + v > 1.0f) {
		return false;
	}

	t = Math::Vector3d::dotProduct(edge2, qVector) / det;

	Math::Vector3d intersectionPoint = origin + direction * t;
	t = intersectionPoint.x();
	u = intersectionPoint.y();
	v = intersectionPoint.z();
	return true;
}

bool lineSegmentIntersectsTriangle(const Math::Vector3d &lineStart, const Math::Vector3d &lineEnd,
								   const Math::Vector3d &v0, const Math::Vector3d &v1, const Math::Vector3d &v2,
								   Math::Vector3d &intersection, float &distance) {
	const float epsilon = 0.0001f;

	Math::Vector3d edge1 = v1 - v0;
	Math::Vector3d edge2 = v2 - v1;

	Math::Vector3d planeNormal = Math::Vector3d::crossProduct(edge1, edge2);
	planeNormal.normalize();

	Math::Vector3d lineDirection = lineEnd - lineStart;

	float lineLength = Math::Vector3d::dotProduct(lineDirection, planeNormal);

	if (ABS(lineLength) < epsilon) {
		return false;
	}

	float distFromPlane = Math::Vector3d::dotProduct(v0 - lineStart, planeNormal);
	float relativeDistance = distFromPlane / lineLength;

	if (relativeDistance < 0.0f || relativeDistance > 1.0f) {
		return false;
	}

	distance = relativeDistance;
	intersection = lineStart + lineDirection * relativeDistance;

	return true;
}

#endif

} // End of namespace Wintermute