HalfEdge.h

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/**********************************************************************
 *
 * GEOS - Geometry Engine Open Source
 * http://geos.osgeo.org
 *
 * Copyright (C) 2020 Paul Ramsey <pramsey@cleverelephant.ca>
 *
 * 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.
 *
 **********************************************************************/


#pragma once

#include <geos/export.h>
#include <string>
#include <cassert>
#include <geos/geom/Coordinate.h>

// Forward declarations
namespace geos {
namespace geom {
class Coordinate;
}
}

namespace geos {
namespace edgegraph { // geos.edgegraph

class GEOS_DLL HalfEdge {

private:

    /* members */
    geom::Coordinate m_orig;
    HalfEdge* m_sym;
    HalfEdge* m_next;


    void setSym(HalfEdge* e) { m_sym = e; };

    HalfEdge* insertionEdge(HalfEdge* eAdd);

    void insertAfter(HalfEdge* e);

    const HalfEdge* findLowest() const;

protected:

    virtual const geom::Coordinate& directionPt() const { return dest(); };


public:

    HalfEdge(const geom::Coordinate& p_orig) :
        m_orig(p_orig)
    {};

    virtual ~HalfEdge() {};

    static HalfEdge* create(const geom::Coordinate& p0, const geom::Coordinate& p1);

    void link(HalfEdge* p_sym);

    const geom::Coordinate& orig() const { return m_orig; };

    const geom::Coordinate& dest() const { return m_sym->m_orig; }

    double directionX() const { return directionPt().x - m_orig.x; }

    double directionY() const { return directionPt().y - m_orig.y; }

    HalfEdge* sym() const { return m_sym; };

    HalfEdge* next() const { return m_next; };

    HalfEdge* prev() const { return m_sym->next()->m_sym; };

    HalfEdge* oNext() const { return m_sym->m_next; };

    void setNext(HalfEdge* e) { m_next = e; };

    HalfEdge* find(const geom::Coordinate& dest);

    bool equals(const geom::Coordinate& p0, const geom::Coordinate& p1) const;

    void insert(HalfEdge* eAdd);

    bool isEdgesSorted() const;

    int compareAngularDirection(const HalfEdge* e) const;
    int compareTo(const HalfEdge* e) const { return compareAngularDirection(e); };

    int degree();

    HalfEdge* prevNode();

    friend std::ostream& operator<< (std::ostream& os, const HalfEdge& el);
    static void toStringNode(const HalfEdge* he, std::ostream& os);

};


} // namespace geos.edgegraph
} // namespace geos