/**********************************************************************
 *
 * 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.
 *
 **********************************************************************
 *
 * Last port: algorithm/RayCrossingCounter.java rev. 1.2 (JTS-1.9)
 *
 **********************************************************************/

#include <geos/algorithm/CGAlgorithmsDD.h>
#include <geos/algorithm/RayCrossingCounter.h>
#include <geos/geom/Geometry.h>
#include <geos/geom/Location.h>
#include <geos/geom/Coordinate.h>
#include <geos/geom/CoordinateSequence.h>


namespace geos {
namespace algorithm {
//
// private:
//

//
// protected:
//

//
// public:
//
/*static*/ geom::Location
RayCrossingCounter::locatePointInRing(const geom::CoordinateXY& point,
                                      const geom::CoordinateSequence& ring)
{
    RayCrossingCounter rcc(point);

    for(std::size_t i = 1, ni = ring.size(); i < ni; i++) {
        const geom::CoordinateXY& p1 = ring.getAt<geom::CoordinateXY>(i-1);;
        const geom::CoordinateXY& p2 = ring.getAt<geom::CoordinateXY>(i);

        rcc.countSegment(p1, p2);

        if(rcc.isOnSegment()) {
            return rcc.getLocation();
        }
    }
    return rcc.getLocation();
}

/*static*/ geom::Location
RayCrossingCounter::locatePointInRing(const geom::CoordinateXY& point,
                                      const std::vector<const geom::Coordinate*>& ring)
{
    RayCrossingCounter rcc(point);

    for(std::size_t i = 1, ni = ring.size(); i < ni; i++) {
        const geom::Coordinate& p1 = *ring[ i - 1 ];
        const geom::Coordinate& p2 = *ring[ i ];

        rcc.countSegment(p1, p2);

        if(rcc.isOnSegment()) {
            return rcc.getLocation();
        }
    }
    return rcc.getLocation();
}

void
RayCrossingCounter::countSegment(const geom::CoordinateXY& p1,
                                 const geom::CoordinateXY& p2)
{
    // For each segment, check if it crosses
    // a horizontal ray running from the test point in
    // the positive x direction.

    // check if the segment is strictly to the left of the test point
    if(p1.x < point.x && p2.x < point.x) {
        return;
    }

    // check if the point is equal to the current ring vertex
    if(point.x == p2.x && point.y == p2.y) {
        isPointOnSegment = true;
        return;
    }

    // For horizontal segments, check if the point is on the segment.
    // Otherwise, horizontal segments are not counted.
    if(p1.y == point.y && p2.y == point.y) {
        double minx = p1.x;
        double maxx = p2.x;

        if(minx > maxx) {
            minx = p2.x;
            maxx = p1.x;
        }

        if(point.x >= minx && point.x <= maxx) {
            isPointOnSegment = true;
        }

        return;
    }

    // Evaluate all non-horizontal segments which cross a horizontal ray
    // to the right of the test pt.
    // To avoid double-counting shared vertices, we use the convention that
    // - an upward edge includes its starting endpoint, and excludes its
    //   final endpoint
    // - a downward edge excludes its starting endpoint, and includes its
    //   final endpoint
    if(((p1.y > point.y) && (p2.y <= point.y)) ||
            ((p2.y > point.y) && (p1.y <= point.y))) {
        // For an upward edge, orientationIndex will be positive when p1->p2
        // crosses ray. Conversely, downward edges should have negative sign.
        int sign = CGAlgorithmsDD::orientationIndex(p1, p2, point);
        if(sign == 0) {
            isPointOnSegment = true;
            return;
        }

        if(p2.y < p1.y) {
            sign = -sign;
        }

        // The segment crosses the ray if the sign is strictly positive.
        if(sign > 0) {
            crossingCount++;
        }
    }
}


geom::Location
RayCrossingCounter::getLocation() const
{
    if(isPointOnSegment) {
        return geom::Location::BOUNDARY;
    }

    // The point is in the interior of the ring if the number
    // of X-crossings is odd.
    if((crossingCount % 2) == 1) {
        return geom::Location::INTERIOR;
    }

    return geom::Location::EXTERIOR;
}


bool
RayCrossingCounter::isPointInPolygon() const
{
    return getLocation() != geom::Location::EXTERIOR;
}


} // geos::algorithm
} // geos
