/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2006 Robert Osfield
 *
 * This library is open source and may be redistributed and/or modified under
 * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or
 * (at your option) any later version.  The full license is in LICENSE file
 * included with this distribution, and on the openscenegraph.org website.
 *
 * This library 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
 * OpenSceneGraph Public License for more details.
*/

#ifndef OSGSIM_ELEVATIONSLICE
#define OSGSIM_ELEVATIONSLICE 1

#include <osgUtil/IntersectionVisitor>

// include so we can get access to the DatabaseCacheReadCallback
#include <osgSim/LineOfSight>

namespace osgSim {

/** Helper class for setting up and acquiring height above terrain intersections with terrain.
  * By default assigns a osgSim::DatabaseCacheReadCallback that enables automatic loading
  * of external PagedLOD tiles to ensure that the highest level of detail is used in intersections.
  * This automatic loading of tiles is done by the intersection traversal that is done within
  * the computeIntersections(..) method, so can result in long intersection times when external
  * tiles have to be loaded.
  * The external loading of tiles can be disabled by removing the read callback, this is done by
  * calling the setDatabaseCacheReadCallback(DatabaseCacheReadCallback*) method with a value of 0.*/
class OSGSIM_EXPORT ElevationSlice
{
    public :


        ElevationSlice();

        /** Set the start point of the slice.*/
        void setStartPoint(const osg::Vec3d& startPoint) { _startPoint = startPoint; }

        /** Get the start point of the slice.*/
        const osg::Vec3d& getStartPoint() const { return _startPoint; }

        /** Set the end point of the slice.*/
        void setEndPoint(const osg::Vec3d& endPoint) { _endPoint = endPoint; }

        /** Get the end point of the slice.*/
        const osg::Vec3d& getEndPoint() const { return _endPoint; }


        typedef std::vector<osg::Vec3d> Vec3dList;

        /** Get the intersections in the form of a vector of Vec3d. */
        const Vec3dList& getIntersections() const  { return _intersections; }

        typedef std::pair<double,double> DistanceHeight;
        typedef std::vector<DistanceHeight> DistanceHeightList;

        /** Get the intersections in the form a vector of pair<double,double> representing distance along the slice and height. */
        const DistanceHeightList& getDistanceHeightIntersections() const { return _distanceHeightIntersections; }


        /** Compute the intersections with the specified scene graph, the results are stored in vectors of Vec3d.
          * Note, if the topmost node is a CoordinateSystemNode then the input points are assumed to be geocentric,
          * with the up vector defined by the EllipsoidModel attached to the CoordinateSystemNode.
          * If the topmost node is not a CoordinateSystemNode then a local coordinates frame is assumed, with a local up vector. */
        void computeIntersections(osg::Node* scene, osg::Node::NodeMask traversalMask=0xffffffff);

        /** Compute the vertical distance between the specified scene graph and a single HAT point.*/
        static Vec3dList computeElevationSlice(osg::Node* scene, const osg::Vec3d& startPoint, const osg::Vec3d& endPoint, osg::Node::NodeMask traversalMask=0xffffffff);


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

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

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

    protected :


        osg::Vec3d                              _startPoint;
        osg::Vec3d                              _endPoint;
        Vec3dList                               _intersections;
        DistanceHeightList                      _distanceHeightIntersections;

        osg::ref_ptr<DatabaseCacheReadCallback> _dcrc;
        osgUtil::IntersectionVisitor            _intersectionVisitor;


};

}

#endif
