/**********************************************************************
 *
 * GEOS - Geometry Engine Open Source
 * http://geos.osgeo.org
 *
 * Copyright (C) 2011 Sandro Santilli <strk@kbt.io>
 *
 * 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.
 *
 **********************************************************************
 *
 * Last port: operation/union/UnaryUnionOp.java r320 (JTS-1.12)
 *
 **********************************************************************/

#pragma once

#include <memory>
#include <vector>

#include <geos/export.h>
#include <geos/geom/GeometryFactory.h>
#include <geos/geom/Point.h>
#include <geos/geom/LineString.h>
#include <geos/geom/Polygon.h>
#include <geos/geom/util/GeometryExtracter.h>
#include <geos/operation/union/CascadedPolygonUnion.h>

#ifdef _MSC_VER
#pragma warning(push)
#pragma warning(disable: 4251) // warning C4251: needs to have dll-interface to be used by clients of class
#endif

// Forward declarations
namespace geos {
namespace geom {
class GeometryFactory;
class Geometry;
}
}

namespace geos {
namespace operation { // geos::operation
namespace geounion {  // geos::operation::geounion

/** \brief
 * Unions a collection of Geometry or a single Geometry
 * (which may be a collection) together.
 *
 * By using this special-purpose operation over a collection of
 * geometries it is possible to take advantage of various optimizations
 * to improve performance.
 * Heterogeneous [GeometryCollections](@ref geom::GeometryCollection)
 * are fully supported.
 *
 * The result obeys the following contract:
 *
 * - Unioning a set of overlapping [Polygons](@ref geom::Polygon) has the effect
 *   of merging the areas (i.e. the same effect as
 *   iteratively unioning all individual polygons together).
 * - Unioning a set of [LineStrings](@ref geom::LineString) has the effect of
 *   **fully noding** and **dissolving** the input linework.
 *   In this context "fully noded" means that there will be a node or
 *   endpoint in the output for every endpoint or line segment crossing
 *   in the input.
 *   "Dissolved" means that any duplicate (e.g. coincident) line segments
 *   or portions of line segments will be reduced to a single line segment
 *   in the output.
 *   This is consistent with the semantics of the
 *   [Geometry::Union(Geometry* )](@ref geom::Geometry::Union())
 *   operation. If **merged** linework is required, the
 *   [LineMerger](@ref operation::linemerge::LineMerger) class
 *   can be used.
 * - Unioning a set of [Points](@ref geom::Point) has the effect of merging
 *   all identical points (producing a set with no duplicates).
 *
 * `UnaryUnion` always operates on the individual components of
 * MultiGeometries.
 * So it is possible to use it to "clean" invalid self-intersecting
 * MultiPolygons (although the polygon components must all still be
 * individually valid.)
 */
class GEOS_DLL UnaryUnionOp {
public:

    template <typename T>
    static std::unique_ptr<geom::Geometry>
    Union(const T& geoms)
    {
        UnaryUnionOp op(geoms);
        return op.Union();
    }

    template <class T>
    static std::unique_ptr<geom::Geometry>
    Union(const T& geoms,
          geom::GeometryFactory& geomFact)
    {
        UnaryUnionOp op(geoms, geomFact);
        return op.Union();
    }

    static std::unique_ptr<geom::Geometry>
    Union(const geom::Geometry& geom)
    {
        UnaryUnionOp op(geom);
        return op.Union();
    }

    template <class T>
    UnaryUnionOp(const T& geoms, geom::GeometryFactory& geomFactIn)
        : geomFact(&geomFactIn)
        , unionFunction(&defaultUnionFunction)
    {
        extractGeoms(geoms);
    }

    template <class T>
    UnaryUnionOp(const T& geoms)
        : geomFact(nullptr)
        , unionFunction(&defaultUnionFunction)
    {
        extractGeoms(geoms);
    }

    UnaryUnionOp(const geom::Geometry& geom)
        : geomFact(geom.getFactory())
        , unionFunction(&defaultUnionFunction)
    {
        extract(geom);
    }

    void setUnionFunction(UnionStrategy* unionFun)
    {
        unionFunction = unionFun;
    }

    /**
     * \brief
     * Gets the union of the input geometries.
     *
     * If no input geometries were provided, an empty GEOMETRYCOLLECTION is returned.
     *
     * @return a Geometry containing the union
     * @return an empty GEOMETRYCOLLECTION if no geometries were provided
     *         in the input
     */
    std::unique_ptr<geom::Geometry> Union();

private:

    template <typename T>
    void
    extractGeoms(const T& geoms)
    {
        for(typename T::const_iterator
                i = geoms.begin(),
                e = geoms.end();
                i != e;
                ++i) {
            const geom::Geometry* geom = *i;
            extract(*geom);
        }
    }

    void
    extract(const geom::Geometry& geom)
    {
        using namespace geom::util;

        if(! geomFact) {
            geomFact = geom.getFactory();
        }

        GeometryExtracter::extract<geom::Polygon>(geom, polygons);
        GeometryExtracter::extract<geom::LineString>(geom, lines);
        GeometryExtracter::extract<geom::Point>(geom, points);
    }

    /**
     * Computes a unary union with no extra optimization,
     * and no short-circuiting.
     * Due to the way the overlay operations
     * are implemented, this is still efficient in the case of linear
     * and puntal geometries.
     * Uses robust version of overlay operation
     * to ensure identical behaviour to the <tt>union(Geometry)</tt> operation.
     *
     * @param g0 a geometry
     * @return the union of the input geometry
     */
    std::unique_ptr<geom::Geometry>
    unionNoOpt(const geom::Geometry& g0)
    {
        if(! empty.get()) {
            empty = geomFact->createEmptyGeometry();
        }
        return unionFunction->Union(&g0, empty.get());
    }

    /**
     * Computes the union of two geometries,
     * either of both of which may be null.
     *
     * @param g0 a Geometry (ownership transferred)
     * @param g1 a Geometry (ownership transferred)
     * @return the union of the input(s)
     * @return null if both inputs are null
     */
    std::unique_ptr<geom::Geometry> unionWithNull(
        std::unique_ptr<geom::Geometry> g0,
        std::unique_ptr<geom::Geometry> g1
        );

    // Members
    std::vector<const geom::Polygon*> polygons;
    std::vector<const geom::LineString*> lines;
    std::vector<const geom::Point*> points;

    const geom::GeometryFactory* geomFact;
    std::unique_ptr<geom::Geometry> empty;

    UnionStrategy* unionFunction;
    ClassicUnionStrategy defaultUnionFunction;

};


} // namespace geos::operation::union
} // namespace geos::operation
} // namespace geos

#ifdef _MSC_VER
#pragma warning(pop)
#endif