/* -*-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 OSGDB_DATABASEPAGER
#define OSGDB_DATABASEPAGER 1

#include <osg/NodeVisitor>
#include <osg/Group>
#include <osg/PagedLOD>
#include <osg/Drawable>
#include <osg/GraphicsThread>
#include <osg/FrameStamp>
#include <osg/ObserverNodePath>
#include <osg/observer_ptr>

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

#include <osgUtil/IncrementalCompileOperation>

#include <osgDB/SharedStateManager>
#include <osgDB/ReaderWriter>
#include <osgDB/Options>


#include <map>
#include <list>
#include <algorithm>
#include <functional>

namespace osgDB {



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

        typedef OpenThreads::Thread::ThreadPriority ThreadPriority;

        DatabasePager();

        DatabasePager(const DatabasePager& rhs);

        virtual const char* className() const { return "DatabasePager"; }

        /** Create a shallow copy on the DatabasePager.*/
        virtual DatabasePager* clone() const { return new DatabasePager(*this); }

        /** get the prototype singleton used by DatabasePager::create().*/
        static osg::ref_ptr<DatabasePager>& prototype();

        /** create a DatabasePager by cloning DatabasePager::prototype().*/
        static DatabasePager* create();



        /** Add a request to load a node file to end the the database request list.*/
        virtual void requestNodeFile(const std::string& fileName, osg::NodePath& nodePath,
                                     float priority, const osg::FrameStamp* framestamp,
                                     osg::ref_ptr<osg::Referenced>& databaseRequest,
                                     const osg::Referenced* options);

        /** Set the priority of the database pager thread(s).*/
        int setSchedulePriority(OpenThreads::Thread::ThreadPriority priority);

        /** Cancel the database pager thread(s).*/
        virtual int cancel();

        virtual bool isRunning() const;

        /** Clear all internally cached structures.*/
        virtual void clear();

        class OSGDB_EXPORT DatabaseThread : public osg::Referenced, public OpenThreads::Thread
        {
        public:

            enum Mode
            {
                HANDLE_ALL_REQUESTS,
                HANDLE_NON_HTTP,
                HANDLE_ONLY_HTTP
            };

            DatabaseThread(DatabasePager* pager, Mode mode, const std::string& name);

            DatabaseThread(const DatabaseThread& dt, DatabasePager* pager);

            void setName(const std::string& name) { _name = name; }
            const std::string& getName() const { return _name; }

            void setDone(bool done) { _done.exchange(done?1:0); }
            bool getDone() const { return _done!=0; }

            void setActive(bool active) { _active = active; }
            bool getActive() const { return _active; }

            virtual int cancel();

            virtual void run();

        protected:

            virtual ~DatabaseThread();

            OpenThreads::Atomic _done;
            volatile bool       _active;
            DatabasePager*      _pager;
            Mode                _mode;
            std::string         _name;

        };

        void setUpThreads(unsigned int totalNumThreads=2, unsigned int numHttpThreads=1);

        virtual unsigned int addDatabaseThread(DatabaseThread::Mode mode, const std::string& name);

        DatabaseThread* getDatabaseThread(unsigned int i) { return _databaseThreads[i].get(); }

        const DatabaseThread* getDatabaseThread(unsigned int i) const { return _databaseThreads[i].get(); }

        unsigned int getNumDatabaseThreads() const { return _databaseThreads.size(); }

        /** 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; }

        /** 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, unsigned int frameNumber = 0);

        /** Set the incremental compile operation.
          * Used to manage the OpenGL object compilation and merging of subgraphs in a way that avoids overloading
          * the rendering of frame with too many new objects in one frame. */
        void setIncrementalCompileOperation(osgUtil::IncrementalCompileOperation* ico);

        /** Get the incremental compile operation. */
        osgUtil::IncrementalCompileOperation* getIncrementalCompileOperation() { return _incrementalCompileOperation.get(); }


        /** Set whether the database pager should pre compile OpenGL objects before allowing
          * them to be merged into the scene graph.
          * Pre compilation helps reduce the chances of frame drops, but also slows the
          * speed at which tiles are merged as they have to be compiled first.*/
        void setDoPreCompile(bool flag) { _doPreCompile = flag; }

        /** Get whether the database pager should pre compile OpenGL objects before allowing
          * them to be merged into the scene graph.*/
        bool getDoPreCompile() const { return _doPreCompile; }



        /** Set the target maximum number of PagedLOD to maintain in memory.
          * Note, if more than the target number are required for rendering of a frame then these active PagedLOD are excempt from being expiried.
          * But once the number of active drops back below the target the inactive PagedLOD will be trimmed back to the target number.*/
        void setTargetMaximumNumberOfPageLOD(unsigned int target) { _targetMaximumNumberOfPageLOD = target; }

        /** Get the target maximum number of PagedLOD to maintain in memory.*/
        unsigned int getTargetMaximumNumberOfPageLOD() const { return _targetMaximumNumberOfPageLOD; }


        /** 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; }

        enum DrawablePolicy
        {
            DO_NOT_MODIFY_DRAWABLE_SETTINGS,
            USE_DISPLAY_LISTS,
            USE_VERTEX_BUFFER_OBJECTS,
            USE_VERTEX_ARRAYS
        };

        /** Set how loaded drawables should be handled w.r.t their display list/vertex buffer object/vertex array settings.*/
        void setDrawablePolicy(DrawablePolicy policy) { _drawablePolicy = policy; }

        /** Get how loaded drawables should be handled w.r.t their display list/vertex buffer object/vertex array settings.*/
        DrawablePolicy getDrawablePolicy() const { return _drawablePolicy; }


        /** Set whether newly loaded textures should have a PixelBufferObject assigned to them to aid download to the GPU.*/
        void setApplyPBOToImages(bool assignPBOToImages) { _assignPBOToImages = assignPBOToImages; }

        /** Get whether newly loaded textures should have a PixelBufferObject assigned to them..*/
        bool getApplyPBOToImages() const { return _assignPBOToImages; }


        /** 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(const osg::FrameStamp& frameStamp);

        /** Report how many items are in the _fileRequestList queue */
        unsigned int getFileRequestListSize() const { return _fileRequestQueue->size() + _httpRequestQueue->size(); }

        /** Report how many items are in the _dataToCompileList queue */
        unsigned int getDataToCompileListSize() const { return _dataToCompileList->size(); }

        /** Report how many items are in the _dataToMergeList queue */
        unsigned int getDataToMergeListSize() const { return _dataToMergeList->size(); }

        /** Report whether any requests are in the pager.*/
        bool getRequestsInProgress() const;

        /** Get the minimum time between the first request for a tile to be loaded and the time of its merge into the main scene graph.*/
        double getMinimumTimeToMergeTile() const { return _minimumTimeToMergeTile; }

        /** Get the maximum time between the first request for a tile to be loaded and the time of its merge into the main scene graph.*/
        double getMaximumTimeToMergeTile() const { return _maximumTimeToMergeTile; }

        /** Get the average time between the first request for a tile to be loaded and the time of its merge into the main scene graph.*/
        double getAverageTimeToMergeTiles() const { return (_numTilesMerges > 0) ? _totalTimeToMergeTiles/static_cast<double>(_numTilesMerges) : 0; }

        /** Reset the Stats variables.*/
        void resetStats();

        typedef std::set< osg::ref_ptr<osg::StateSet> >                 StateSetList;
        typedef std::vector< osg::ref_ptr<osg::Drawable> >              DrawableList;

        class ExpirePagedLODsVisitor;

        typedef std::list<  osg::ref_ptr<osg::Object> > ObjectList;

        struct PagedLODList : public osg::Referenced
        {
            virtual PagedLODList* clone() = 0;
            virtual void clear() = 0;
            virtual unsigned int size() = 0;
            virtual void removeExpiredChildren(int numberChildrenToRemove, double expiryTime, unsigned int expiryFrame, ObjectList& childrenRemoved, bool visitActive) = 0;
            virtual void removeNodes(osg::NodeList& nodesToRemove) = 0;
            virtual void insertPagedLOD(const osg::observer_ptr<osg::PagedLOD>& plod) = 0;
            virtual bool containsPagedLOD(const osg::observer_ptr<osg::PagedLOD>& plod) const = 0;
        };


    protected:

        virtual ~DatabasePager();

        friend class DatabaseThread;
        friend struct DatabaseRequest;

        struct RequestQueue;

        struct OSGDB_EXPORT DatabaseRequest : public osg::Referenced
        {
            DatabaseRequest():
                osg::Referenced(true),
                _valid(false),
                _frameNumberFirstRequest(0),
                _timestampFirstRequest(0.0),
                _priorityFirstRequest(0.f),
                _frameNumberLastRequest(0),
                _timestampLastRequest(0.0),
                _priorityLastRequest(0.0f),
                _numOfRequests(0),
                _groupExpired(false)
            {}

            void invalidate();

            bool valid() const { return _valid; }

            bool                        _valid;
            std::string                 _fileName;
            unsigned int                _frameNumberFirstRequest;
            double                      _timestampFirstRequest;
            float                       _priorityFirstRequest;
            unsigned int                _frameNumberLastRequest;
            double                      _timestampLastRequest;
            float                       _priorityLastRequest;
            unsigned int                _numOfRequests;

            osg::observer_ptr<osg::Node>        _terrain;
            osg::observer_ptr<osg::Group>       _group;

            osg::ref_ptr<osg::Node>             _loadedModel;
            osg::ref_ptr<Options>               _loadOptions;

            osg::observer_ptr<osgUtil::IncrementalCompileOperation::CompileSet> _compileSet;
            bool                        _groupExpired; // flag used only in update thread

            bool isRequestCurrent (int frameNumber) const
            {
                return _valid && (frameNumber - _frameNumberLastRequest <= 1);
            }
        };


        struct OSGDB_EXPORT RequestQueue : public osg::Referenced
        {
        public:

            RequestQueue(DatabasePager* pager);

            void add(DatabaseRequest* databaseRequest);
            void remove(DatabaseRequest* databaseRequest);

            void addNoLock(DatabaseRequest* databaseRequest);

            void takeFirst(osg::ref_ptr<DatabaseRequest>& databaseRequest);

            /// prune all the old requests and then return true if requestList left empty
            bool pruneOldRequestsAndCheckIfEmpty();

            virtual void updateBlock() {}

            void invalidate(DatabaseRequest* dr);

            bool empty();

            unsigned int size();

            void clear();


            typedef std::list< osg::ref_ptr<DatabaseRequest> > RequestList;
            void swap(RequestList& requestList);

            DatabasePager*              _pager;
            RequestList                 _requestList;
            OpenThreads::Mutex          _requestMutex;
            unsigned int                _frameNumberLastPruned;

        protected:
            virtual ~RequestQueue();
        };


        typedef std::vector< osg::ref_ptr<DatabaseThread> > DatabaseThreadList;

        struct OSGDB_EXPORT ReadQueue : public RequestQueue
        {
            ReadQueue(DatabasePager* pager, const std::string& name);

            void block() { _block->block(); }

            void release() { _block->release(); }

            virtual void updateBlock();


            osg::ref_ptr<osg::RefBlock> _block;

            std::string                 _name;

            OpenThreads::Mutex          _childrenToDeleteListMutex;
            ObjectList                  _childrenToDeleteList;
        };

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

        struct DatabasePagerCompileCompletedCallback;
        friend struct DatabasePagerCompileCompletedCallback;

        class FindPagedLODsVisitor;
        friend class FindPagedLODsVisitor;

        struct SortFileRequestFunctor;
        friend struct SortFileRequestFunctor;


        OpenThreads::Mutex              _run_mutex;
        OpenThreads::Mutex              _dr_mutex;
        bool                            _startThreadCalled;

        void compileCompleted(DatabaseRequest* databaseRequest);

        /** 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. */
        virtual void removeExpiredSubgraphs(const osg::FrameStamp &frameStamp);

        /** Add the loaded data to the scene graph.*/
        void addLoadedDataToSceneGraph(const osg::FrameStamp &frameStamp);


        bool                            _done;
        bool                            _acceptNewRequests;
        bool                            _databasePagerThreadPaused;

        DatabaseThreadList              _databaseThreads;

        int                             _numFramesActive;
        mutable OpenThreads::Mutex      _numFramesActiveMutex;
        OpenThreads::Atomic             _frameNumber;

        osg::ref_ptr<ReadQueue>         _fileRequestQueue;
        osg::ref_ptr<ReadQueue>         _httpRequestQueue;
        osg::ref_ptr<RequestQueue>      _dataToCompileList;
        osg::ref_ptr<RequestQueue>      _dataToMergeList;

        DrawablePolicy                  _drawablePolicy;

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

        bool                            _deleteRemovedSubgraphsInDatabaseThread;


        osg::ref_ptr<PagedLODList>      _activePagedLODList;

        unsigned int                    _targetMaximumNumberOfPageLOD;

        bool                            _doPreCompile;
        osg::ref_ptr<osgUtil::IncrementalCompileOperation>  _incrementalCompileOperation;


        double                          _minimumTimeToMergeTile;
        double                          _maximumTimeToMergeTile;
        double                          _totalTimeToMergeTiles;
        unsigned int                    _numTilesMerges;
};

}

#endif