/* -*-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 OSGVIEWER_RENDERER
#define OSGVIEWER_RENDERER 1

#include <osg/Timer>
#include <osgDB/DatabasePager>
#include <osgUtil/SceneView>
#include <osgViewer/Export>

namespace osgViewer {

class OSGVIEWER_EXPORT OpenGLQuerySupport
{
    public:
        OpenGLQuerySupport();

        typedef std::pair<GLuint, int> QueryFrameNumberPair;
        typedef std::list<QueryFrameNumberPair> QueryFrameNumberList;
        typedef std::vector<GLuint> QueryList;

        void setStartTick(osg::Timer_t startTick) { _startTick = startTick; }
        osg::Timer_t getStartTick() const { return _startTick; }

        void checkQuery(osg::Stats* stats);
        
        GLuint createQueryObject();
        void beginQuery(int frameNumber);
        void endQuery();
        void initialize(osg::State* state);

    protected:

        osg::Timer_t                                _startTick;
        bool                                        _initialized;
        bool                                        _timerQuerySupported;
        const osg::Drawable::Extensions*            _extensions;
        QueryFrameNumberList                        _queryFrameNumberList;
        QueryList                                   _availableQueryObjects;
        double                                      _previousQueryTime;

};

class OSGVIEWER_EXPORT Renderer : public osg::GraphicsOperation, public OpenGLQuerySupport
{
    public:

        Renderer(osg::Camera* camera);

        osgUtil::SceneView* getSceneView(unsigned int i) { return _sceneView[i].get(); }

        void setDone(bool done) { _done = done; }
        bool getDone() { return _done; }

        void setGraphicsThreadDoesCull(bool flag);
        bool getGraphicsThreadDoesCull() const { return _graphicsThreadDoesCull; }

        virtual void cull();
        virtual void draw();
        virtual void cull_draw();

        virtual void operator () (osg::Object* object);
        
        virtual void operator () (osg::GraphicsContext* context);

        virtual void release();
        

        /** 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). 
          *
          * Note, the actual TargetFrameRate used is the minimum of this value and that set in the DatabasePager. */
        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.
          *
          * Note, the actual TargetFrameRate used is the minimum of this value and that set in the DatabasePager. */
        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; }

        /** FlushTimeRatio governs how much of the spare time in each frame is used for flushing deleted OpenGL objects.
          * Default value is 0.5, valid range is 0.1 to 0.9.*/
        void setFlushTimeRatio(double ratio) { _flushTimeRatio = ratio; }
        double getFlushTimeRatio() const { return _flushTimeRatio; }

        /** ConservativeTimeRatio governs how much of the measured spare time in each frame is used for flushing deleted and compile new OpenGL objects.
          * Default value is 0.5, valid range is 0.1 to 1.0.
          * A ratio near 1.0 will lead to paged databases being compiled and merged quicker but increase the chances of frame drop.
          * A ratio near 0.1 will lead to paged databases being compiled and merged closer but reduse the chances of frame drop.*/
        void setConservativeTimeRatio(double ratio) { _conservativeTimeRatio = ratio; }
        double getConservativeTimeRatio() const { return _conservativeTimeRatio; }

    protected:
    
        virtual ~Renderer();

        virtual void updateSceneView(osgUtil::SceneView* sceneView);        
        virtual void flushAndCompile(double currentElapsedFrameTime, osgUtil::SceneView* sceneView, osgDB::DatabasePager* databasePager, osg::GraphicsThread* compileThread);

        double _targetFrameRate;
        double _minimumTimeAvailableForGLCompileAndDeletePerFrame;
        double _flushTimeRatio;
        double _conservativeTimeRatio;

        osg::observer_ptr<osg::Camera>                      _camera;
        
        bool                                                _done;
        bool                                                _graphicsThreadDoesCull;
        
        osg::ref_ptr<osgUtil::SceneView>                    _sceneView[2];
        
        osg::ref_ptr<osg::FlushDeletedGLObjectsOperation>   _flushOperation;
    

        struct OSGVIEWER_EXPORT TheadSafeQueue
        {
            OpenThreads::Mutex _mutex;
            OpenThreads::Block _block;
            typedef std::list<osgUtil::SceneView*> SceneViewList;
            SceneViewList _queue;
            
            TheadSafeQueue();
            ~TheadSafeQueue();
            
            void release()
            {
                _block.release();
            }
            
            osgUtil::SceneView* takeFront();
            
            void add(osgUtil::SceneView* sv);
        };


        TheadSafeQueue _availableQueue;
        TheadSafeQueue _drawQueue;

};

}

#endif