/* -*-c++-*- */
/* osgEarth - Geospatial SDK for OpenSceneGraph
 * Copyright 2020 Pelican Mapping
 * http://osgearth.org
 *
 * osgEarth is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>
 */

#ifndef OSGEARTHSYMBOLOGY_INSTANCE_SYMBOL_H
#define OSGEARTHSYMBOLOGY_INSTANCE_SYMBOL_H 1

#include <climits>

#include <osgEarth/Common>
#include <osgEarth/Symbol>
#include <osgEarth/Tags>
#include <osgEarth/Expression>
#include <osg/Vec3f>

namespace osgEarth
{
    class IconSymbol;
    class ModelSymbol;
    namespace Util {
        class InstanceResource;
    }

    /**
     * Base class for symbols that represent an instance of an external resource
     * like an icon or a model and can be placed at a location.
     */
    class OSGEARTH_EXPORT InstanceSymbol : public TaggableWithConfig<Symbol>
    {
    public:
        /**
         * Controls the placement of the instance.
         */
        enum Placement
        {
            /** Places an instance at each feature point (default) */
            PLACEMENT_VERTEX,

            /** Places one instance at the centroid of the feature. */
            PLACEMENT_CENTROID,

            /** Places instances at regular intervals within/along the feature geometry,
                according to density. */
            PLACEMENT_INTERVAL,

            /** Scatter instances randomly within/along feature, according to density. */
            PLACEMENT_RANDOM
        };

    public:

        InstanceSymbol(const InstanceSymbol& rhs,const osg::CopyOp& copyop=osg::CopyOp::SHALLOW_COPY);

        /** dtor */
        virtual ~InstanceSymbol() { }

        /** URI of the instance to use for substitution. */
        optional<StringExpression>& url() { return _url; }
        const optional<StringExpression>& url() const { return _url; }

        /** Name of the resource library to use with this symbol (optional) */
        optional<StringExpression>& library() { return _library; }
        const optional<StringExpression>& library() const { return _library; }   

        /** How to map feature geometry to instance placement. (default is PLACEMENT_CENTROID) */
        optional<Placement>& placement() { return _placement; }
        const optional<Placement>& placement() const { return _placement; }

        /** For PLACEMENT_RANDOM/INTERVAL, the scattering density in instances per sqkm */
        optional<float>& density() { return _density; }
        const optional<float>& density() const { return _density; }

        /** Model instance scale factor */
        optional<NumericExpression>& scale() { return _scale; }
        const optional<NumericExpression>& scale() const { return _scale; }

        /** Seeding value for the randomizer */
        optional<unsigned>& randomSeed() { return _randomSeed; }
        const optional<unsigned>& randomSeed() const { return _randomSeed; }

        /** URI alias map for embedded resources */
        optional<URIAliasMap>& uriAliasMap() { return _uriAliasMap; }
        const optional<URIAliasMap>& uriAliasMap() const { return _uriAliasMap; }

        /** Expression that returns custom geometry as a GeoJSON string. 
            You will typically use this as a script that takes the input geometry
            to dumps out a new geometry for model substitution. */
        optional<StringExpression>& script() { return _script; }
        const optional<StringExpression>& script() const { return _script; }

    public: // conversions to built-in base classes, for convenience.

        const IconSymbol* asIcon() const;
        const ModelSymbol* asModel() const;

    public:
        virtual Config getConfig() const;
        virtual void mergeConfig( const Config& conf );

    public: // internal
        /** Creates a new (empty) resource appropriate for this symbol */
        virtual InstanceResource* createResource() const =0;

    protected:
        InstanceSymbol( const Config& conf =Config() );

    protected:
        optional<StringExpression>   _url;
        optional<StringExpression>   _library;
        optional<NumericExpression>  _scale;
        optional<Placement>          _placement;
        optional<float>              _density;
        optional<unsigned>           _randomSeed;
        optional<URIAliasMap>        _uriAliasMap;
        optional<StringExpression>   _script;
    };
} // namespace osgEarth

#endif // OSGEARTHSYMBOLOGY_MARKER_SYMBOL_H