kicad/libs/kimath/include/geometry/circle.h

/*
 * This program source code file is part of KiCad, a free EDA CAD application.
 *
 * Copyright (C) 2021 Roberto Fernandez Bautista <roberto.fer.bau@gmail.com>
 * Copyright (C) 2021 KiCad Developers, see AUTHORS.txt for contributors.
 *
 * This program is free software: you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation, either version 3 of the License, or (at your
 * option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#ifndef __CIRCLE_H
#define __CIRCLE_H

#include <math/vector2d.h> // for VECTOR2I
#include <vector>          // for std::vector

class SEG;

/**
 * Represent basic circle geometry with utility geometry functions.
 */
class CIRCLE
{
public:
    CIRCLE();

    CIRCLE( const VECTOR2I& aCenter, int aRadius );

    CIRCLE( const CIRCLE& aOther );

    /**
     * Construct this circle such that it is tangent to the given segments and passes through the
     * given point, generating the solution which can be used to fillet both segments.
     *
     * The caller is responsible for ensuring it is providing a solvable problem. This function will
     * assert if this is not the case.
     *
     * @param aLineA is the first tangent line. Treated as an infinite line except for the purpose
     *               of selecting the solution to return.
     * @param aLineB is the second tangent line. Treated as an infinite line except for the purpose
     *               of selecting the solution to return.
     * @param aP is the point to pass through.
     * @return this circle.
     */
    CIRCLE& ConstructFromTanTanPt( const SEG& aLineA, const SEG& aLineB, const VECTOR2I& aP );

    /**
     * Return true if aP is on the circumference of this circle. Note that there is an accepted
     * margin of error of SHAPE::MIN_PRECISION_IU to account for integer rounding errors.
     *
     * @param aP A point to test
     * @return true if aP is on the circumference.
    */
    bool Contains( const VECTOR2I& aP ) const;

    /**
     * Compute the point on the circumference of the circle that is the closest to aP.
     *
     * In other words: finds the intersection point of this circle and a line that passes through
     * both this circle's center and aP.
     *
     * @param aP.
     * @return nearest point to aP.
     */
    VECTOR2I NearestPoint( const VECTOR2I& aP ) const;

    /**
     * Compute the point (floating point version) on the circumference of the circle that
     * is the closest to aP.
     *
     * In other words: finds the intersection point of this circle and a line that passes through
     * both this circle's center and aP.
     *
     * @param aP.
     * @return nearest point to aP.
     */
    VECTOR2D NearestPoint( const VECTOR2D& aP ) const;

    /**
     * Compute the intersection points between this circle and \a aCircle.
     *
     * @param aCircle The other circle to intersect with this.
     * @return std::vector containing:
     *           - 0 elements if the circles do not intersect.
     *           - 1 element if the circles are tangent.
     *           - 2 elements if the circles intersect.
     */
    std::vector<VECTOR2I> Intersect( const CIRCLE& aCircle ) const;

    /**
     * Compute the intersection points between this circle and \a aSeg.
     *
     * @param aSeg The segment to intersect with this circle (end points ignored).
     * @return std::vector containing up to two intersection points.
     */
    std::vector<VECTOR2I> Intersect( const SEG& aSeg ) const;

    /**
     * Compute the intersection points between this circle and aLine.
     *
     * @param aLine The line to intersect with this circle (end points ignored).
     * @return std::vector containing:
     *           - 0 elements if there is no intersection.
     *           - 1 element if the line is tangent to the circle.
     *           - 2 elements if the line intersects the circle.
     */
    std::vector<VECTOR2I> IntersectLine( const SEG& aLine ) const;

    /**
     * Check whether point aP is inside this circle.
     *
     * @param aP The point to check.
     * @return true if the point is inside, false otherwise.
     */
    bool Contains( const VECTOR2I& aP );

    int      Radius; ///< Public to make access simpler
    VECTOR2I Center; ///< Public to make access simpler
};

#endif // __CIRCLE_H