/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2003 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 OSGDB_DATABASEPAGER
#define OSGDB_DATABASEPAGER 1

#include <osg/NodeVisitor>
#include <osg/Group>
#include <osg/PagedLOD>
#include <osg/Drawable>

#include <OpenThreads/Thread>
#include <OpenThreads/Mutex>
#include <OpenThreads/Condition>

#include <osgDB/Export>

#include <map>
#include <set>

namespace osgDB {

class Block: public osg::Referenced {
    public:
        Block():_released(false) {}

        void block()
        {
            _mut.lock();
            if( !_released )
                _cond.wait(&_mut);
            _mut.unlock();
        }

        void release()
        {
            _mut.lock();
            _released = true;
            _cond.broadcast();
            _mut.unlock();
        }

        void reset()
        {
            _mut.lock();
            _released = false;
            _mut.unlock();
        }

    protected:

        ~Block()
        {
            release();
        }

    private:
        OpenThreads::Mutex _mut;
        OpenThreads::Condition _cond;
        bool _released;
};

/** Database paging class which manages the loading of files in a background thread, 
  * and syncronizing of loaded models with the main scene graph.*/
class OSGDB_EXPORT DatabasePager : public osg::NodeVisitor::DatabaseRequestHandler, public OpenThreads::Thread
{
    public :

        DatabasePager();

        /** Add a request to load a node file to end the the database request list.*/
        virtual void requestNodeFile(const std::string& fileName,osg::Group* group, float priority, const osg::FrameStamp* framestamp);

        /** run does the database paging.*/        
        virtual void run();
        
        
        /** Signal the database thread that the update, cull and draw has begun for a new frame.
          * Note, this is called by the application so that the database pager can go to sleep while the CPU is busy on the main rendering threads. */
        void signalBeginFrame(const osg::FrameStamp* framestamp);
        
        /** Signal the database thread that the update, cull and draw dispatch has completed.
          * Note, this is called by the application so that the database pager can go to wake back up now the main rendering threads are iddle waiting for the next frame.*/
        void signalEndFrame();
        

        /** Add the loaded data to the scene graph.*/
        void addLoadedDataToSceneGraph(double timeStamp);


        /** Find all PagedLOD nodes in a subgraph and register them with 
          * the DatabasePager so it can keep track of expired nodes.
          * note, should be only be called from the update thread. */
        void registerPagedLODs(osg::Node* subgraph);


        /** Set the amount of time that a subgraph will be kept without being visited in the cull traversal
          * before being removed.*/
        void setExpiryDelay(double expiryDelay) { _expiryDelay = expiryDelay; }
        
        /** Get the amount of time that a subgraph will be kept without being visited in the cull traversal
          * before being removed.*/
        double getExpiryDelay() const { return _expiryDelay; }

        /** set whether the removed subgraphs should be deleted in the database thread or not.*/
        void setDeleteRemovedSubgraphsInDatabaseThread(bool flag) { _deleteRemovedSubgraphsInDatabaseThread = flag; }
        
        /** get whether the removed subgraphs should be deleted in the database thread or not.*/
        bool getDeleteRemovedSubgraphsInDatabaseThread() const { return _deleteRemovedSubgraphsInDatabaseThread; }

        /** Iterate through the active PagedLOD nodes children removing 
          * children which havn't been visited since specified expiryTime.
          * note, should be only be called from the update thread. */
        void removeExpiredSubgraphs(double currentFrameTime);
        
        
        /** Turn the compilation of rendering objects for specfied graphics context on (true) or off(false).*/
        void setCompileRenderingObjectsForContexID(unsigned int contextID, bool on);
        
        /** Get whether the compilation of rendering objects for specfied graphics context on (true) or off(false).*/
        bool getCompileRenderingObjectsForContexID(unsigned int contextID);

        /** Compile the rendering objects (display lists,texture objects, VBO's) on loaded subgraph.
          * note, should only be called from the draw thread.*/
        void compileRenderingObjects(osg::State& state,double& availableTime);

        /** Helper class used internally to force the release of texture objects
          * and displace lists.*/
        class OSGDB_EXPORT ReleaseTexturesAndDrawablesVisitor : public osg::NodeVisitor
        {
        public:
            ReleaseTexturesAndDrawablesVisitor():
                osg::NodeVisitor(osg::NodeVisitor::TRAVERSE_ALL_CHILDREN)
            {
            }

            virtual void apply(osg::Node& node);
            virtual void apply(osg::Geode& geode);
            inline void apply(osg::StateSet* stateset);
            inline void apply(osg::Drawable* drawable);

        };

    public:

        typedef std::vector< osg::ref_ptr<osg::PagedLOD> > PagedLODList;

        typedef std::vector< osg::ref_ptr<osg::StateSet> > StateSetList;
        typedef std::vector< osg::ref_ptr<osg::Drawable> > DrawableList;
        typedef std::pair<StateSetList,DrawableList>       DataToCompile;
        typedef std::map< unsigned int, DataToCompile >    DataToCompileMap; 

        typedef std::set<unsigned int>                     ActiveGraphicsContexts;


        
        struct DatabaseRequest : public osg::Referenced
        {
            DatabaseRequest():
                _numOfRequests(0)
            {}
            
            std::string                 _fileName;
            int                         _frameNumberFirstRequest;
            double                      _timestampFirstRequest;
            float                       _priorityFirstRequest;
            int                         _frameNumberLastRequest;
            double                      _timestampLastRequest;
            float                       _priorityLastRequest;
            unsigned int                _numOfRequests;
            osg::ref_ptr<osg::Group>    _groupForAddingLoadedSubgraph;
            osg::ref_ptr<osg::Node>     _loadedModel;
            DataToCompileMap            _dataToCompileMap;
            
        };
        
        typedef std::vector< osg::ref_ptr<DatabaseRequest> > DatabaseRequestList;

    protected :

        virtual ~DatabasePager();

        osg::ref_ptr<Block>             _frameBlock;
        int                             _frameNumber;

        DatabaseRequestList             _fileRequestList;
        OpenThreads::Mutex              _fileRequestListMutex;
        osg::ref_ptr<Block>             _fileRequestListEmptyBlock;
        
        DatabaseRequestList             _dataToCompileList;
        OpenThreads::Mutex              _dataToCompileListMutex;
        
        bool                            _deleteRemovedSubgraphsInDatabaseThread;
        osg::NodeList                   _childrenToDeleteList;
        OpenThreads::Mutex              _childrenToDeleteListMutex;

        DatabaseRequestList             _dataToMergeList;
        OpenThreads::Mutex              _dataToMergeListMutex;
        
        
        PagedLODList                    _pagedLODList;
        
        double                          _expiryDelay;

        ActiveGraphicsContexts          _activeGraphicsContexts;

};

}

#endif