/**********************************************************************
 *
 * GEOS - Geometry Engine Open Source
 * http://geos.osgeo.org
 *
 * Copyright (C) 2001-2002 Vivid Solutions Inc.
 *
 * This is free software; you can redistribute and/or modify it under
 * the terms of the GNU Lesser General Public Licence as published
 * by the Free Software Foundation.
 * See the COPYING file for more information.
 *
 **********************************************************************/

#include <geos/geom/Triangle.h>
#include <geos/geom/Coordinate.h>

namespace geos {
namespace geom { // geos::geom


void
Triangle::inCentre(Coordinate& result)
{
	// the lengths of the sides, labelled by their opposite vertex
	double len0 = p1.distance(p2);
	double len1 = p0.distance(p2);
	double len2 = p0.distance(p1);
	double circum = len0 + len1 + len2;
	double inCentreX = (len0 * p0.x + len1 * p1.x +len2 * p2.x)  / circum;
	double inCentreY = (len0 * p0.y + len1 * p1.y +len2 * p2.y)  / circum;

	result = Coordinate(inCentreX, inCentreY);
}

void Triangle::circumcentre(Coordinate& result)
{
	double cx = p2.x;
	double cy = p2.y;
	double ax = p0.x - cx;
	double ay = p0.y - cy;
	double bx = p1.x - cx;
	double by = p1.y - cy;

	double denom = 2 * det(ax,ay,bx,by);
	double numx = det(ay , ax * ax + ay * ay , by , bx * bx + by * by);
	double numy = det(ax, ax * ax + ay * ay, bx, bx * bx + by * by);

	double ccx = cx - numx / denom;
	double ccy = cy + numy / denom;

	result = Coordinate(ccx,ccy);
}

double Triangle::det(double m00 , double m01 , double m10 , double m11) const
{
	return m00 * m11 - m01 * m10;
}


} // namespace geos::geom
} // namespace geos
