CircularArcIntersector.h

/**********************************************************************
 *
 * GEOS - Geometry Engine Open Source
 * http://geos.osgeo.org
 *
 * Copyright (C) 2024-2025 ISciences, LLC
 *
 * 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 <array>
#include <cstdint>
 
#include <geos/export.h>
#include <geos/algorithm/LineIntersector.h>
#include <geos/geom/Coordinate.h>
#include <geos/geom/CircularArc.h>
 
namespace geos::algorithm {
 
class GEOS_DLL CircularArcIntersector {
public:
    using CoordinateXY = geom::CoordinateXY;
    using CoordinateXYZM = geom::CoordinateXYZM;
    using CircularArc = geom::CircularArc;
    using Envelope = geom::Envelope;
 
    enum intersection_type : uint8_t {
        NO_INTERSECTION = 0,
        ONE_POINT_INTERSECTION = 1,
        TWO_POINT_INTERSECTION = 2,
        COCIRCULAR_INTERSECTION = 3,
    };
 
    explicit CircularArcIntersector(const geom::PrecisionModel* pm = nullptr)
        : precisionModel(pm)
    {}
 
    intersection_type getResult() const
    {
        return result;
    }
 
    const CoordinateXYZM& getPoint(std::uint8_t i) const
    {
        return intPt[i];
    }
 
    const CircularArc& getArc(std::uint8_t i) const
    {
        return intArc[i];
    }
 
    std::uint8_t getNumPoints() const
    {
        return nPt;
    }
 
    std::uint8_t getNumArcs() const
    {
        return nArc;
    }
 
    void intersects(const CircularArc& arc, const geom::CoordinateSequence& seq, std::size_t pos0, std::size_t pos1, bool useSegEndpoints);
 
    void intersects(const CircularArc& arc1, const CircularArc& arc2);
 
    void intersects(const geom::CoordinateSequence& p, std::size_t p0, std::size_t p1,
                    const geom::CoordinateSequence& q, std::size_t q0, std::size_t q1);
 
private:
    void reset() {
        nPt = 0;
        nArc = 0;
    }
 
    void addCocircularIntersection(double startAngle, double endAngle, int orientation, const CircularArc& arc1, const CircularArc& arc2);
 
    void addArcArcIntersectionPoint(const CoordinateXY& computedIntPt, const CircularArc& arc1, const CircularArc& arc2);
 
    void addArcSegmentIntersectionPoint(const CoordinateXY& computedIntPt, const CircularArc& lhs,
        const geom::CoordinateSequence& seq, std::size_t pos0, std::size_t pos1, bool useSegEndpoints);
 
    static int
    circleIntersects(const CoordinateXY& center, double r, const CoordinateXY& p0, const CoordinateXY& p1, CoordinateXY& isect0, CoordinateXY& isect1);
 
    void computeCocircularIntersection(const CircularArc& arc1, const CircularArc& arc2);
 
    bool hasIntersection(const geom::CoordinateXY& p) const;
 
    std::array<CoordinateXYZM, 2> intPt;
    std::array<CircularArc, 2> intArc;
    const geom::PrecisionModel* precisionModel;
    intersection_type result = NO_INTERSECTION;
    std::uint8_t nPt = 0;
    std::uint8_t nArc = 0;
};
 
}