/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2005 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/ScopedLock>
#include <OpenThreads/Condition>

#include <osgDB/SharedStateManager>
#include <osgDB/Export>

#include <map>
#include <list>

namespace osgDB {

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

        inline void block()
        {
            OpenThreads::ScopedLock<OpenThreads::Mutex> mutlock(_mut);
            if( !_released )
                _cond.wait(&_mut);
        }

        inline void release()
        {
            OpenThreads::ScopedLock<OpenThreads::Mutex> mutlock(_mut);
            if (!_released)
            {
                _released = true;
                _cond.broadcast();
            }
        }

        inline void reset()
        {
            OpenThreads::ScopedLock<OpenThreads::Mutex> mutlock(_mut);
            _released = false;
        }
        
        inline void set(bool doRelease)
        {
            if (doRelease!=_released)
            {
                if (doRelease) release();
                else reset();
            }
        }

    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 :

        typedef OpenThreads::Thread::ThreadPriority ThreadPriority;

        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();
        
        /** Cancel the database pager thread.*/        
        virtual int cancel();
        
        /** Clear all internally cached structures.*/
        virtual void clear();
        
        /** Set whether the database pager thread should be paused or not.*/
        void setDatabasePagerThreadPause(bool pause);
        
        /** Get whether the database pager thread should is paused or not.*/
        bool getDatabasePagerThreadPause() const { return _databasePagerThreadPaused; }
        
        /** Set whether new database request calls are accepted or ignored.*/
        void setAcceptNewDatabaseRequests(bool acceptNewRequests) { _acceptNewRequests = acceptNewRequests; }
        
        /** Get whether new database request calls are accepted or ignored.*/
        bool getAcceptNewDatabaseRequests() const { return _acceptNewRequests; }
        
        /** Set the use of the frame block which, if enabled, blocks the DatabasePager 
          * from executing which the current frame is being drawn.  
          * When a single processor machine is being used it can be useful to block on
          * frame to help prevent the database paging thread from slowing the cull and draw
          * traversals which in turn can cause frame drops.*/
        void setUseFrameBlock(bool useFrameBlock) { _useFrameBlock = useFrameBlock; }
        
        /** Get the whether UseFrameBlock is on or off.*/
        bool getUseFrameBlock() const { return _useFrameBlock; }
        
        Block* getFrameBlock() { return _frameBlock.get(); }

        /** Set the priority of the database pager thread during the frame (i.e. while cull and draw are running.)*/
        void setThreadPriorityDuringFrame(ThreadPriority duringFrame) { _threadPriorityDuringFrame = duringFrame; }

        /** Get the priority of the database pager thread during the frame*/
        ThreadPriority getThreadPriorityDuringFrame() const { return _threadPriorityDuringFrame; }
        
        /** Set the priority of the database pager thread when the frame is not being exectuted (i.e. before or after cull and draw have run.)*/
        void setThreadPriorityOutwithFrame(ThreadPriority outwithFrame)  { _threadPriorityOutwithFrame = outwithFrame; }

        /** Get the priority of the database pager thread when the frame is not being exectuted.*/
        ThreadPriority getThreadPriorityOutwithFrame() const { return _threadPriorityOutwithFrame; }
        
        
        /** Get the number of frames that are currently active.*/
        int getNumFramesActive() const { return _numFramesActive; }

        /** 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. */
        virtual 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.*/
        virtual void signalEndFrame();
        

        /** 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. */
        virtual void registerPagedLODs(osg::Node* subgraph);


        /** Set the target frame rate that the DatabasePager should assume.
          * Typically one would set this to the value refresh rate of your display system i.e. 60Hz.
          * Default value is 100.
          * Usage notes.  The TargetFrameRate and the MinimumTimeAvailableForGLCompileAndDeletePerFrame
          * parameters are not directly used by DatabasePager, but are should be used as a guide for how
          * long to set aside per frame for compiling and deleting OpenGL objects - ie. the value to use 
          * when calling DatabasePager::compileGLObjectgs(state,availableTime,). The longer amount of
          * time to set aside  cthe faster databases will be paged in but with increased chance of frame drops,
          * the lower the amount of time the set aside the slower databases will paged it but with better
          * chance of avoid any frame drops.  The default values are chosen to achieve the later when running
          * on a modern mid to high end  PC. 
          * The way to compute the amount of available time use a scheme such as :
          *    availableTime = maximum(1.0/targetFrameRate - timeTakenDuringUpdateCullAndDraw, minimumTimeAvailableForGLCompileAndDeletePerFrame). 
          */
        void setTargetFrameRate(double tfr) { _targetFrameRate = tfr; }

        /** Get the target frame rate that the DatabasePager should assume.*/
        double getTargetFrameRate() const { return _targetFrameRate; }
        
        /** Set the minimum amount of time (in seconds) that should be made available for compiling and delete OpenGL objects per frame.
          * Default value is 0.001 (1 millisecond). 
          * For usage see notes in setTargetFrameRate.*/
        void setMinimumTimeAvailableForGLCompileAndDeletePerFrame(double ta) { _minimumTimeAvailableForGLCompileAndDeletePerFrame = ta; }

        /** Get the minimum amount of time that should be made available for compiling and delete OpenGL objects per frame.
          * For usage see notes in setTargetFrameRate.*/
        double getMinimumTimeAvailableForGLCompileAndDeletePerFrame() const { return _minimumTimeAvailableForGLCompileAndDeletePerFrame; }

        /** Set the maximum number of OpenGL objects that the page should attempt to compile per frame.
          * Note, Lower values reduces chances of a frame drop but lower the rate that database will be paged in at.
          * Default value is 8. */
        void setMaximumNumOfObjectsToCompilePerFrame(unsigned int num) { _maximumNumOfObjectsToCompilePerFrame = num; }

        /** Get the maximum number of OpenGL objects that the page should attempt to compile per frame.*/
        unsigned int getMaximumNumOfObjectsToCompilePerFrame() const { return _maximumNumOfObjectsToCompilePerFrame; }


        /** 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; }


        /** set whether newly loaded textures should have their UnrefImageDataAfterApply set to a specified value.*/
        void setUnrefImageDataAfterApplyPolicy(bool changeAutoUnRef, bool valueAutoUnRef) { _changeAutoUnRef = changeAutoUnRef; _valueAutoUnRef = valueAutoUnRef; }

        /** get whether newly loaded textures should have their UnrefImageDataAfterApply set to a specified value.*/
        void getUnrefImageDataAfterApplyPolicy(bool& changeAutoUnRef, bool& valueAutoUnRef) const { changeAutoUnRef = _changeAutoUnRef; valueAutoUnRef = _valueAutoUnRef; }


        /** set whether newly loaded textures should have their MaxAnisotopy set to a specified value.*/
        void setMaxAnisotropyPolicy(bool changeAnisotropy, float valueAnisotropy) { _changeAnisotropy = changeAnisotropy; _valueAnisotropy = valueAnisotropy; }

        /** set whether newly loaded textures should have their MaxAnisotopy set to a specified value.*/
        void getMaxAnisotropyPolicy(bool& changeAnisotropy, float& valueAnisotropy) const { changeAnisotropy = _changeAnisotropy; valueAnisotropy = _valueAnisotropy; }


        /** Return true if there are pending updates to the scene graph that require a call to updateSceneGraph(double). */
        bool requiresUpdateSceneGraph() const;
        
        /** Merge the changes to the scene graph by calling calling removeExpiredSubgraphs then addLoadedDataToSceneGraph.
          * Note, must only be called from single thread update phase. */
        virtual void updateSceneGraph(double currentFrameTime)
        {
            removeExpiredSubgraphs(currentFrameTime);
            addLoadedDataToSceneGraph(currentFrameTime);
        }
        
        
        /** Turn the compilation of rendering objects for specfied graphics context on (true) or off(false). */
        void setCompileGLObjectsForContextID(unsigned int contextID, bool on);
        
        /** Get whether the compilation of rendering objects for specfied graphics context on (true) or off(false). */
        bool getCompileGLObjectsForContextID(unsigned int contextID);

        /** Return true if there are pending compile operations that are required.
          * If requiresCompileGLObjects() return true the application should call compileGLObjects() .*/
        bool requiresCompileGLObjects() const;

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

        typedef std::list< osg::ref_ptr<osg::PagedLOD> >   PagedLODList;
        typedef std::set< 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;

    protected:

        virtual ~DatabasePager();


        friend struct DatabaseRequest;
        
        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;
        typedef std::vector<  osg::ref_ptr<osg::Object> > ObjectList;

        // forward declare inner helper classes
        class FindCompileableGLObjectsVisitor;
        friend class FindCompileableGLObjectsVisitor;
        
        class FindPagedLODsVisitor;
        friend class FindPagedLODsVisitor;

        struct SortFileRequestFunctor;
        friend struct SortFileRequestFunctor;

        
        OpenThreads::Mutex              _run_mutex;
        bool                            _startThreadCalled;

        
        osg::ref_ptr<Block>             _databasePagerThreadBlock;

        inline void updateDatabasePagerThreadBlock()
        {
            _databasePagerThreadBlock->set(
                (!_fileRequestList.empty() || !_childrenToDeleteList.empty()) && !_databasePagerThreadPaused);
        }
        
        inline void updateFrameBlock(int delta)
        {
            OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_numFramesActiveMutex);
            _numFramesActive += delta;
            _frameBlock->set(_numFramesActive==0);
        }


        /** 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);

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


        bool                            _done;
        bool                            _acceptNewRequests;
        bool                            _databasePagerThreadPaused;
    
        bool                            _useFrameBlock;
        int                             _numFramesActive;
        mutable OpenThreads::Mutex      _numFramesActiveMutex;
        osg::ref_ptr<Block>             _frameBlock;
        int                             _frameNumber;

        ThreadPriority                  _threadPriorityDuringFrame;
        ThreadPriority                  _threadPriorityOutwithFrame;

        DatabaseRequestList             _fileRequestList;
        mutable OpenThreads::Mutex      _fileRequestListMutex;
        
        DatabaseRequestList             _dataToCompileList;
        mutable OpenThreads::Mutex      _dataToCompileListMutex;

        bool                            _changeAutoUnRef;
        bool                            _valueAutoUnRef;
        bool                            _changeAnisotropy;
        float                           _valueAnisotropy;

        bool                            _deleteRemovedSubgraphsInDatabaseThread;
        ObjectList                      _childrenToDeleteList;
        mutable OpenThreads::Mutex      _childrenToDeleteListMutex;

        DatabaseRequestList             _dataToMergeList;
        mutable OpenThreads::Mutex      _dataToMergeListMutex;
        
        
        PagedLODList                    _activePagedLODList;
        PagedLODList                    _inactivePagedLODList;
        
        double                          _expiryDelay;

        ActiveGraphicsContexts          _activeGraphicsContexts;
        
        double                          _targetFrameRate;
        double                          _minimumTimeAvailableForGLCompileAndDeletePerFrame;
        unsigned int                    _maximumNumOfObjectsToCompilePerFrame;
};

}

#endif
