/**********************************************************************

 *

 * 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>

#include <geos/algorithm/CGAlgorithmsDD.h>

#include <geos/algorithm/Orientation.h>

#include <geos/algorithm/Angle.h>

using geos::algorithm::Angle;

using geos::algorithm::Orientation;

namespace geos {

namespace geom { // geos::geom

bool

Triangle::isIsoceles()

{

    double len0 = p1.distance(p2);

    double len1 = p0.distance(p2);

    double len2 = p0.distance(p1);

    if (len0 == len1 || len1 == len2 || len2 == len0)

        return true;

    else

        return false;

}

void

Triangle::inCentre(CoordinateXY& 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 = CoordinateXY(inCentreX, inCentreY);

}

CoordinateXY

Triangle::inCentre(const CoordinateXY& p0,

        const CoordinateXY& p1,

        const CoordinateXY& p2)

{

    Triangle tri(p0, p1, p2);

    CoordinateXY result;

    tri.inCentre(result);

    return result;

}

void

Triangle::circumcentre(CoordinateXY& 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 = CoordinateXY(ccx, ccy);

}

double

Triangle::circumradius(

    const CoordinateXY& a,

    const CoordinateXY& b,

    const CoordinateXY& c)

{

    double A = a.distance(b);

    double B = b.distance(c);

    double C = c.distance(a);

    double triArea = area(a, b, c);

    if (triArea == 0.0)

        return std::numeric_limits<double>::infinity();

    return (A * B * C) / (4 * triArea);

}

void

Triangle::circumcentreDD(CoordinateXY& result)

{

    result = algorithm::CGAlgorithmsDD::circumcentreDD(p0, p1, p2);

}

/* public static */

const CoordinateXY

Triangle::circumcentre(const CoordinateXY& p0, const CoordinateXY& p1, const CoordinateXY& p2)

{

    Triangle t(p0, p1, p2);

    CoordinateXY c;

    t.circumcentre(c);

    return c;

}

/* private */

double

Triangle::det(double m00, double m01, double m10, double m11) const

{

    return m00 * m11 - m01 * m10;

}

/* public static */

bool

Triangle::isAcute(const CoordinateXY& a, const CoordinateXY& b, const CoordinateXY& c)

{

    if (!Angle::isAcute(a, b, c))

        return false;

    if (!Angle::isAcute(b, c, a))

        return false;

    if (!Angle::isAcute(c, a, b))

        return false;

    return true;

}

/* public static */

bool

Triangle::isCCW(const CoordinateXY& a, const CoordinateXY& b, const CoordinateXY& c)

{

    return Orientation::COUNTERCLOCKWISE == Orientation::index(a, b, c);

}

/* public static */

bool

Triangle::intersects(const CoordinateXY& a, const CoordinateXY& b, const CoordinateXY& c, const CoordinateXY& p)

{

    int exteriorIndex = isCCW(a, b, c) ?

        Orientation::CLOCKWISE : Orientation::COUNTERCLOCKWISE;

    if (exteriorIndex == Orientation::index(a, b, p))

        return false;

    if (exteriorIndex == Orientation::index(b, c, p))

        return false;

    if (exteriorIndex == Orientation::index(c, a, p))

        return false;

    return true;

}

/* public static */

double

Triangle::length(const CoordinateXY& a, const CoordinateXY& b, const CoordinateXY& c)

{

    return a.distance(b) + b.distance(c) + c.distance(a);

}

/* public */

double

Triangle::length() const

{

    return length(p0, p1, p2);

}

/* public static */

double

Triangle::area(const CoordinateXY& a, const CoordinateXY& b, const CoordinateXY& c)

{

    return std::abs(((c.x - a.x) * (b.y - a.y) - (b.x - a.x) * (c.y - a.y)) / 2);

}

/* public */

double

Triangle::area() const

{

    return area(p0, p1, p2);

}

/* public static */

double

Triangle::longestSideLength(const CoordinateXY& a, const CoordinateXY& b, const CoordinateXY& c)

{

    double lenAB = a.distance(b);

    double lenBC = b.distance(c);

    double lenCA = c.distance(a);

    double maxLen = lenAB;

    if (lenBC > maxLen)

        maxLen = lenBC;

    if (lenCA > maxLen)

        maxLen = lenCA;

    return maxLen;

}

} // namespace geos::geom

} // namespace geos