/*
-----------------------------------------------------------------------------
This source file is part of OGRE
(Object-oriented Graphics Rendering Engine)
For the latest info, see http://www.ogre3d.org/

Copyright (c) 2000-2014 Torus Knot Software Ltd

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
-----------------------------------------------------------------------------
*/

#ifndef __Ogre_Page_H__
#define __Ogre_Page_H__

#include "OgrePagingPrerequisites.h"
#include "Threading/OgreThreadHeaders.h"
#include "OgreWorkQueue.h"


namespace Ogre
{
    /** \addtogroup Optional
    *  @{
    */
    /** \defgroup Paging Paging
    *  Render large modular structures
    *  @{
    */

    /** Page class
    */
    class _OgrePagingExport Page : public WorkQueue::RequestHandler, 
        public WorkQueue::ResponseHandler, public PageAlloc
    {
    public:
        typedef std::vector<PageContentCollection*> ContentCollectionList;
    private:
        PageID mID;
        PagedWorldSection* mParent;
        unsigned long mFrameLastHeld;
        ContentCollectionList mContentCollections;
        uint16 mWorkQueueChannel;
        bool mDeferredProcessInProgress;
        bool mModified;

        SceneNode* mDebugNode;
        void updateDebugDisplay();

        struct PageData : public PageAlloc
        {
            ContentCollectionList collectionsToAdd;
        };
        /// Structure for holding background page requests
        struct PageRequest
        {
            Page* srcPage;
            PageRequest(Page* p): srcPage(p) {}
        };
        struct PageResponse
        {
            PageData* pageData;
            PageResponse() : pageData(0) {}
        };



        virtual bool prepareImpl(PageData* dataToPopulate);
        virtual bool prepareImpl(StreamSerialiser& str, PageData* dataToPopulate);
        virtual void loadImpl();

        String generateFilename() const;

    public:
        static const uint32 CHUNK_ID;
        static const uint16 CHUNK_VERSION;

        static const uint32 CHUNK_CONTENTCOLLECTION_DECLARATION_ID;

        Page(PageID pageID, PagedWorldSection* parent);
        virtual ~Page();

        PageManager* getManager() const;
        SceneManager* getSceneManager() const;

        /// If true, it's not safe to access this Page at this time, contents may be changing
        bool isDeferredProcessInProgress() const { return mDeferredProcessInProgress; }

        /// Get the ID of this page, unique within the parent
        virtual PageID getID() const { return mID; }
        /// Get the PagedWorldSection this page belongs to
        virtual PagedWorldSection* getParentSection() const { return mParent; }
        /** Get the frame number in which this Page was last loaded or held.

            A Page that has not been requested to be loaded or held in the recent
            past will be a candidate for removal.
        */
        virtual unsigned long getFrameLastHeld() { return mFrameLastHeld; }
        /// 'Touch' the page to let it know it's being used
        virtual void touch();

        /** Load this page. 
        @param synchronous Whether to force this to happen synchronously.
        */
        virtual void load(bool synchronous);
        /** Unload this page. 
        */
        virtual void unload();


        /** Returns whether this page was 'held' in the last frame, that is
            was it either directly needed, or requested to stay in memory (held - as
            in a buffer region for example). If not, this page is eligible for 
            removal.
        */
        virtual bool isHeld() const;

        /// Save page data to an automatically generated file name
        virtual void save();
        /// Save page data to a file
        virtual void save(const String& filename);
        /// Save page data to a serialiser 
        virtual void save(StreamSerialiser& stream);

        /// Called when the frame starts
        virtual void frameStart(Real timeSinceLastFrame);
        /// Called when the frame ends
        virtual void frameEnd(Real timeElapsed);
        /// Notify a section of the current camera
        virtual void notifyCamera(Camera* cam);

        /** Create a new PageContentCollection within this page.
        This is equivalent to calling PageManager::createContentCollection and 
        then attachContentCollection.
        @param typeName The name of the type of content collection (see PageManager::getContentCollectionFactories)
        */
        virtual PageContentCollection* createContentCollection(const String& typeName);

        /** Destroy a PageContentCollection within this page.
        This is equivalent to calling detachContentCollection and 
            PageManager::destroyContentCollection.
        */
        virtual void destroyContentCollection(PageContentCollection* coll);
        /** Destroy all PageContentCollections within this page.
        */
        virtual void destroyAllContentCollections();
        /// Get the number of content collections
        virtual size_t getContentCollectionCount() const;
        /// Get a content collection
        virtual PageContentCollection* getContentCollection(size_t index);
        /// Get the list of content collections
        const ContentCollectionList& getContentCollectionList() const;

        /// WorkQueue::RequestHandler override
        bool canHandleRequest(const WorkQueue::Request* req, const WorkQueue* srcQ) override;
        /// WorkQueue::RequestHandler override
        WorkQueue::Response* handleRequest(const WorkQueue::Request* req, const WorkQueue* srcQ) override;
        /// WorkQueue::ResponseHandler override
        bool canHandleResponse(const WorkQueue::Response* res, const WorkQueue* srcQ) override;
        /// WorkQueue::ResponseHandler override
        void handleResponse(const WorkQueue::Response* res, const WorkQueue* srcQ) override;


        /// Tell the page that it is modified
        void _notifyModified() { mModified = true; }
        bool isModified() const { return mModified; }

        static const uint16 WORKQUEUE_PREPARE_REQUEST;
        static const uint16 WORKQUEUE_CHANGECOLLECTION_REQUEST;

        /** Function for writing to a stream.
        */
        _OgrePagingExport friend std::ostream& operator <<( std::ostream& o, const Page& p );



    };

    /** @} */
    /** @} */
}

#endif
