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

 *

 * 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 <geos/geom/Envelope.h>

#include <geos/geom/CoordinateSequence.h>

// Forward declarations

namespace geos {

namespace geom {

class Coordinate;

class CoordinateSequence;

}

}

namespace geos {      // geos.

namespace operation { // geos.operation

namespace overlayng { // geos.operation.overlayng

/**

 * Clips rings of points to a rectangle.

 * Uses a variant of Cohen-Sutherland clipping.

 *

 * In general the output is not topologically valid.

 * In particular, the output may contain coincident non-noded line segments

 * along the clip rectangle sides.

 * However, the output is sufficiently well-structured

 * that it can be used as input to the {@link OverlayNG} algorithm

 * (which is able to process coincident linework due

 * to the need to handle topology collapse under precision reduction).

 *

 * Because of the likelihood of creating

 * extraneous line segments along the clipping rectangle sides,

 * this class is not suitable for clipping linestrings.

 *

 * The clipping envelope should be generated using {@link RobustClipEnvelopeComputer},

 * to ensure that intersecting line segments are not perturbed

 * by clipping.

 * This is required to ensure that the overlay of the

 * clipped geometry is robust and correct (i.e. the same as

 * if clipping was not used).

 *

 * @see LineLimiter

 *

 * @author Martin Davis

 *

 */

class GEOS_DLL RingClipper {

    using Coordinate = geos::geom::Coordinate;

    using CoordinateSequence = geos::geom::CoordinateSequence;

    using Envelope = geos::geom::Envelope;

private:

    // Constants

    static constexpr int BOX_LEFT = 3;

    static constexpr int BOX_TOP = 2;

    static constexpr int BOX_RIGHT = 1;

    static constexpr int BOX_BOTTOM = 0;

    // Members

    const Envelope clipEnv;

    // Methods

    /**

    * Clips line to the axis-parallel line defined by a single box edge.

    */

    std::unique_ptr<CoordinateSequence> clipToBoxEdge(const CoordinateSequence* pts, int edgeIndex, bool closeRing) const;

    /**

    * Computes the intersection point of a segment

    * with an edge of the clip box.

    * The segment must be known to intersect the edge.

    */

    void intersection(const Coordinate& a, const Coordinate& b, int edgeIndex, Coordinate& rsltPt) const;

    double intersectionLineY(const Coordinate& a, const Coordinate& b, double y) const;

    double intersectionLineX(const Coordinate& a, const Coordinate& b, double x) const;

    bool isInsideEdge(const Coordinate& p, int edgeIndex) const;

public:

    RingClipper(const Envelope* env)

        : clipEnv(*env)

        {};

    /**

    * Clips a list of points to the clipping rectangle box.

    */

    std::unique_ptr<CoordinateSequence> clip(const CoordinateSequence* cs) const;

};

} // namespace geos.operation.overlayng

} // namespace geos.operation

} // namespace geos