Circle.h

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/*
 * LSST Data Management System
 * Copyright 2014-2015 AURA/LSST.
 *
 * This product includes software developed by the
 * LSST Project (http://www.lsst.org/).
 *
 * 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 LSST License Statement and
 * the GNU General Public License along with this program.  If not,
 * see <https://www.lsstcorp.org/LegalNotices/>.
 */

#ifndef LSST_SPHGEOM_CIRCLE_H_
#define LSST_SPHGEOM_CIRCLE_H_


#include <iosfwd>

#include "Region.h"
#include "UnitVector3d.h"


namespace lsst {
namespace sphgeom {

class Circle : public Region {
public:
    static constexpr uint8_t TYPE_CODE = 'c';

    static Circle empty() { return Circle(); }

    static Circle full() { return Circle(UnitVector3d::Z(), 4.0); }

    static double squaredChordLengthFor(Angle openingAngle);

    static Angle openingAngleFor(double squaredChordLength);

    Circle() :
        _center(UnitVector3d::Z()),
        _squaredChordLength(-1.0),
        _openingAngle(-1.0)
    {}

    explicit Circle(UnitVector3d const & c) :
        _center(c),
        _squaredChordLength(0.0),
        _openingAngle(0.0)
    {}

    Circle(UnitVector3d const & c, Angle a) :
        _center(c),
        _squaredChordLength(squaredChordLengthFor(a)),
        _openingAngle(a)
    {}

    Circle(UnitVector3d const & c, double cl2) :
        _center(c),
        _squaredChordLength(cl2),
        _openingAngle(openingAngleFor(cl2))
    {}

    bool operator==(Circle const & c) const {
        return (isEmpty() && c.isEmpty()) ||
               (isFull() && c.isFull()) ||
               (_center == c._center &&
                _squaredChordLength == c._squaredChordLength &&
                _openingAngle == c._openingAngle);
    }
    bool operator!=(Circle const & c) const { return !(*this == c); }

    bool isEmpty() const {
        // Return true when _squaredChordLength is negative or NaN.
        return !(_squaredChordLength >= 0.0);
    }

    bool isFull() const { return _squaredChordLength >= 4.0; }

    UnitVector3d const & getCenter() const { return _center; }

    double getSquaredChordLength() const { return _squaredChordLength; }

    Angle getOpeningAngle() const { return _openingAngle; }

    bool contains(Circle const & x) const;

    bool isDisjointFrom(UnitVector3d const & x) const { return !contains(x); }
    bool isDisjointFrom(Circle const & x) const;

    bool intersects(UnitVector3d const & x) const { return contains(x); }
    bool intersects(Circle const & x) const { return !isDisjointFrom(x); }

    bool isWithin(UnitVector3d const &) const { return isEmpty(); }
    bool isWithin(Circle const & x) const { return x.contains(*this); }

    Circle & clipTo(UnitVector3d const & x);
    Circle & clipTo(Circle const & x);

    Circle clippedTo(UnitVector3d const & x) const {
        return Circle(*this).clipTo(x);
    }

    Circle clippedTo(Circle const & x) const {
        return Circle(*this).clipTo(x);
    }

    Circle & expandTo(UnitVector3d const & x);
    Circle & expandTo(Circle const & x);

    Circle expandedTo(UnitVector3d const & x) const {
        return Circle(*this).expandTo(x);
    }

    Circle expandedTo(Circle const & x) const {
        return Circle(*this).expandTo(x);
    }

    Circle & dilateBy(Angle r);
    Circle dilatedBy(Angle r) const { return Circle(*this).dilateBy(r); }
    Circle & erodeBy(Angle r) { return dilateBy(-r); }
    Circle erodedBy(Angle r) const { return dilatedBy(-r); }

    double getArea() const {
        return PI * std::max(0.0, std::min(_squaredChordLength, 4.0));
    }

    Circle & complement();

    Circle complemented() const { return Circle(*this).complement(); }

    Relationship relate(UnitVector3d const & v) const;

    // Region interface
    std::unique_ptr<Region> clone() const override {
        return std::unique_ptr<Circle>(new Circle(*this));
    }

    Box getBoundingBox() const override;
    Box3d getBoundingBox3d() const override;
    Circle getBoundingCircle() const override { return *this; }

    bool contains(UnitVector3d const & v) const override {
        return isFull() ||
               (v - _center).getSquaredNorm() <= _squaredChordLength;
    }

    Relationship relate(Region const & r) const override {
        // Dispatch on the type of r.
        return invert(r.relate(*this));
    }

    Relationship relate(Box const &) const override;
    Relationship relate(Circle const &) const override;
    Relationship relate(ConvexPolygon const &) const override;
    Relationship relate(Ellipse const &) const override;

    std::vector<uint8_t> encode() const override;

    static std::unique_ptr<Circle> decode(std::vector<uint8_t> const & s) {
        return decode(s.data(), s.size());
    }
    static std::unique_ptr<Circle> decode(uint8_t const * buffer, size_t n);

private:
    static constexpr size_t ENCODED_SIZE = 41;

    UnitVector3d _center;
    double _squaredChordLength;
    Angle _openingAngle;
};

std::ostream & operator<<(std::ostream &, Circle const &);

}} // namespace lsst::sphgeom

#endif // LSST_SPHGEOM_CIRCLE_H_