/* -*-c++-*- */
/* osgEarth - Geospatial SDK for OpenSceneGraph
 * Copyright 2008-2013 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 OSGEARTH_EXTENSION_H
#define OSGEARTH_EXTENSION_H 1

#include <osgEarth/Common>
#include <osgEarth/Config>
#include <osgEarth/PluginLoader>
#include <osg/Object>
#include <osgDB/Options>
#include <osgDB/ReaderWriter>
#include <osgDB/FileNameUtils>
#include <osgDB/Registry>

    
#define META_OE_Extension(NS, CLASS, SLUG) \
    META_Object(NS, CLASS); \
    CLASS (const CLASS & rhs, const osg::CopyOp& op) { } \
    virtual const char* getConfigKey() const { return #SLUG ; }

namespace osgEarth
{
    /**
     * An Extension is an object that can be loaded on demand (from a plugin) 
     * and can have multiple object-specific interfaces. Its main function is
     * to enable activation and configuration of a plugin feature from an
     * osgEarth .earth file.
     *
     * For example, the pattern for declaring an Extension that connects to a
     * MapNode looks like:
     *
     *   public MyExtension : public Extension,
     *                        public ExtensionInterface<MapNode>
     *
     * You can implement more than one interface. This one would connect to a
     * MapNode and to a UI Control:
     *
     *   public MyExtension : public Extension,
     *                        public ExtensionInterface<MapNode>,
     *                        public ExtensionInterface<Control>
     *
     * You can register an Extension so that one can activate and configure it
     * from a .earth file. Use the registration macro:
     *
     *   REGISTER_OSGEARTH_EXTENSION( osgearth_extension, ExtentionClassName );
     *
     * Where the string "extension" in osgearth_extension is the key string 
     * that will appear in the earth file under the <map> element.
     */
    class OSGEARTH_EXPORT Extension : public osg::Object // header-only
    {
    public:
        META_OE_Extension(osgEarth, Extension, extension);

        /**
         * Sets DB options that this extension should use when doing IO operations.
         */
        virtual void setDBOptions(const osgDB::Options* readOptions) { }

        /**
         * Gets the configuration options that can be used to re-configure
         * this Extension. Necessary for serialization.
         */
        virtual const ConfigOptions& getConfigOptions() const;

        /**
         * Convenience function for casting the extension to another one of its
         * interfaces.
         */
        template<typename T> T* as() { return dynamic_cast<T*>(this); }
        template<typename T> const T* as() const { return dynamic_cast<T*>(this); }

    protected:
        Extension();

    protected:
        virtual ~Extension() { }

    public:
        /**
         * Attempts to create an instance of an named extension.
         */
        static Extension* create(const std::string& name, const ConfigOptions& options);

        /**
         * Fetch configuration options from a plugin loader
         */
        static const ConfigOptions& getConfigOptions(const osgDB::Options*);

    private:
        ConfigOptions _defaultOptions;
    };

    
    /**
     * This template lets you create object-specific interfaces in an extension.
     */
    template<typename T> class ExtensionInterface
    {
    public:
        /**
         * Connects the extension to an object.
         */
        virtual bool connect(T* object) =0;

        /**
         * Disconnects the extension from an object. This should be the
         * same object used to call connect().
         */
        virtual bool disconnect(T* object) =0;
        
        /**
         * Cast a base extension to this interface, or return NULL
         * if the extenstion doesn't implemenent this inteface.
         */
        static ExtensionInterface<T>* get(Extension* e) {
            return dynamic_cast< ExtensionInterface<T>* >(e);
        }
    };

} // namespace osgEarth

#define REGISTER_OSGEARTH_EXTENSION(PLUGINNAME, CLASS) \
    extern "C" void osgdb_##PLUGINNAME(void) {} \
    static osgEarth::RegisterPluginLoader< osgEarth::PluginLoader<CLASS, osgEarth::Extension> > g_proxy_##CLASS_##PLUGINNAME( #PLUGINNAME );

#endif