/* -*-c++-*- */
/* osgEarth - Dynamic map generation toolkit for OpenSceneGraph
 * Copyright 2015 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_ELEVATION_QUERY_H
#define OSGEARTH_ELEVATION_QUERY_H 1

#include <osgEarth/MapFrame>
#include <osgEarth/Containers>
#include <osgEarth/DPLineSegmentIntersector>

namespace osgEarth
{
    class OSGEARTH_EXPORT ElevationQueryCacheReadCallback : public osgUtil::IntersectionVisitor::ReadCallback
    {
        public:
            ElevationQueryCacheReadCallback();

            void setMaximumNumOfFilesToCache(unsigned int maxNumFilesToCache) { _maxNumFilesToCache = maxNumFilesToCache; }
            unsigned int  getMaximumNumOfFilesToCache() const { return _maxNumFilesToCache; }

            void clearDatabaseCache();

            void pruneUnusedDatabaseCache();

            virtual osg::Node* readNodeFile(const std::string& filename);

        protected:

            typedef std::map<std::string, osg::ref_ptr<osg::Node> > FileNameSceneMap;

            unsigned int _maxNumFilesToCache;
            OpenThreads::Mutex  _mutex;
            FileNameSceneMap    _filenameSceneMap;
    };


    /**
     * ElevationQuery (EQ) lets you query the elevation at any point on a map.
     * 
     * Rather than intersecting with a loaded scene graph, EQ uses the osgEarth
     * engine to directly access the best terrain tile for elevation query. You
     * give it the DEM resolution at which you want an elevation point, and it will
     * access the necessary tile and sample it.
     *
     * NOTE: EQ does NOT take into account rendering properties like vertical scale or
     * skirts. If you need a vertical scale, for example, simply scale the resulting
     * elevation value.
     *
     * ElevationQuery is not thread-safe. So not use the same instance of ElevationQuery
     * from multiple threads without mutexing.
     */
    class OSGEARTH_EXPORT ElevationQuery
    {
    public:
        /**
         * Constructs a new elevation manager.
         *
         * @param map
         *      Map against which to perform elevation queries.
         */
        ElevationQuery( const Map* map );
        
        /**
         * Constructs a new elevation manager.
         *
         * @param mapFrame
         *      Map frame against which to perform elevation queries.
         */
        ElevationQuery( const MapFrame& mapFrame );

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

        /**
         * Gets the terrain elevation at a point, given a terrain resolution.
         *
         * @param point
         *      Coordinates for which to query elevation.
         * @param out_elevation
         *      Stores the elevation result in this variable upon success.
         * @param desiredResolution
         *      Optimal resolution of elevation data to use for the query (if available).
         *      Pass in 0 (zero) to use the best available resolution.
         * @param out_resolution
         *      Resolution of the resulting elevation value (if the method returns true).
         * 
         * @return True if the query succeeded, false upon failure.
         */
        bool getElevation(
            const GeoPoint& point,
            double&         out_elevation,
            double          desiredResolution    =0.0,
            double*         out_actualResolution =0L );      

        /** 
         * Gets elevations for a whole array of points, storing the result in the
         * "z" element. If "ignoreZ" is false, the new Z value will be offset by
         * the original Z value.
         */
        bool getElevations(
            std::vector<osg::Vec3d>& points,
            const SpatialReference*  pointsSRS,
            bool                     ignoreZ = true,
            double                   desiredResolution =0.0 );

        /**
         * Gets elevations for a whole array of points, storing the results in the
         * "out_elevations" vector.
         */
        bool getElevations(
            const std::vector<osg::Vec3d>& points,
            const SpatialReference*        pointsSRS,
            std::vector<double>&           out_elevations,
            double                         desiredResolution = 0.0 );

        /**
         * Whether a query should fall back on lower resolution data if no results
         * are available at the requested resolution. Default is true.
         */
        void setFallBackOnNoData(bool value) { _fallBackOnNoData = value; }
        bool getFallBackOnNoData() const { return _fallBackOnNoData; }

        /**
         * Sets the maximum cache size for elevation tiles.
         */
        void setMaxTilesToCache( int value );

        /**
         * Gets the maximum cache size for elevation tiles.
         */
        int getMaxTilesToCache() const;
        
        /**
        * Sets the maximum level override for elevation queries.
        * A value of -1 turns off the override.
        */
        void setMaxLevelOverride(int maxLevelOverride);

        /**
        * Gets the maximum level override for elevation queries.
        */
        int getMaxLevelOverride() const;

        /**
         * Gets the average time per query
         */
        double getAverageQueryTime() const { return _queries > 0.0 ? _totalTime/_queries : 0.0; }

        /**
         * Gets the maximum level of data available at the given point.  If the layers have DataExtents provided they
         * will be queried.  This allows certain areas on the earth to have higher levels of detail
         * than others and avoids unnecessary queries where there isn't high resolution data available.
         * Negative return value means there was no data available at the location.
         */
        int getMaxLevel(double x, double y, const SpatialReference* srs, const Profile* profile, unsigned tileSize) const;

        /** Clear the database cache.*/
        void clearDatabaseCache() { if (_eqcrc.valid()) _eqcrc->clearDatabaseCache(); }

        /** Set the ReadCallback that does the reading of external PagedLOD models, and caching of loaded subgraphs.
          * Note, if you have multiple LineOfSight or HeightAboveTerrain objects in use at one time then you should share a single
          * DatabaseCacheReadCallback between all of them. */
        void setElevationQueryCacheReadCallback(ElevationQueryCacheReadCallback* eqcrc);

        /** Get the ReadCallback that does the reading of external PagedLOD models, and caching of loaded subgraphs.*/
        ElevationQueryCacheReadCallback* getElevationQueryCacheReadCallback() { return _eqcrc.get(); }

    private:
        MapFrame     _mapf;
        unsigned     _maxCacheSize;
        int          _tileSize;        
        int          _maxLevelOverride;
        bool         _fallBackOnNoData;

        typedef LRUCache< TileKey, GeoHeightField > TileCache;
        TileCache _cache;
        double _queries;
        double _totalTime;
        std::vector<ModelLayer*> _patchLayers;
        osg::ref_ptr<DPLineSegmentIntersector> _patchLayersLSI;

        osg::ref_ptr<ElevationQueryCacheReadCallback> _eqcrc;

    private:
        void postCTOR();
        void sync();
        void gatherPatchLayers();

        bool getElevationImpl(            
            const GeoPoint& point,
            double&         out_elevation,
            double          desiredResolution,
            double*         out_actualResolution =0L );
    };

} // namespace osgEarth

#endif // OSGEARTH_ELEVATION_QUERY_H
