/* -*-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 OSGSIM_OVERLAYNODE
#define OSGSIM_OVERLAYNODE 1

#include <osg/buffered_value>
#include <osg/Camera>
#include <osg/Texture2D>
#include <osg/TexGenNode>
#include <osg/Geode>

#include <osgUtil/CullVisitor>

#include <osgSim/Export>

namespace osgSim {

/** OverlayNode is for creating texture overlays on scenes, with the overlay texture being generated
  * by pre rendering an Overlay Subgraph to a texture, then projecting this resulting texture on the scene.*/
class OSGSIM_EXPORT OverlayNode : public osg::Group
{
    public :

        enum OverlayTechnique
        {
            OBJECT_DEPENDENT_WITH_ORTHOGRAPHIC_OVERLAY,
            VIEW_DEPENDENT_WITH_ORTHOGRAPHIC_OVERLAY,
            VIEW_DEPENDENT_WITH_PERSPECTIVE_OVERLAY,
        };

        OverlayNode(OverlayTechnique technique=OBJECT_DEPENDENT_WITH_ORTHOGRAPHIC_OVERLAY);

        OverlayNode(const OverlayNode& es, const osg::CopyOp& copyop=osg::CopyOp::SHALLOW_COPY);
            
        META_Node(osgSim, OverlayNode);
        
        virtual void traverse(osg::NodeVisitor& nv);


        void setOverlayTechnique(OverlayTechnique technique);
        OverlayTechnique getOverlayTechnique() const { return _overlayTechnique; }

        /** Set the implementation to be used when creating the overlay texture. */
        void setRenderTargetImplementation(osg::Camera::RenderTargetImplementation impl);

        /** Set the overlay subgraph which will be rendered to texture.*/
        void setOverlaySubgraph(osg::Node* node);
        
        /** Get the overlay subgraph which will be rendered to texture.*/
        osg::Node* getOverlaySubgraph() { return _overlaySubgraph.get(); }

        /** Get the const overlay subgraph which will be render to texture.*/
        const osg::Node* getOverlaySubgraph() const { return _overlaySubgraph.get(); }
        

        /** Inform the OverlayNode that the overlay texture needs to be updated.*/
        void dirtyOverlayTexture();
        
        /** Set whether the OverlayNode should update the overlay texture on every frame.*/
        void setContinuousUpdate(bool update) { _continuousUpdate = update; }

        /** Get whether the OverlayNode should update the overlay texture on every frame.*/
        bool getContinuousUpdate() const { return _continuousUpdate; }

        /** Set the base height that the overlay subgraph will be projected down to.
          * Normally you'll set this to just below ground level, if you set it too high
          * then the overlay texture can end up being clipped in certain viewing directions,
          * while if its too low then there will be a limit to how close you can get to the
          * terrain before pixaltion becomes an issue.*/
        void setOverlayBaseHeight(double baseHeight) { _overlayBaseHeight = baseHeight; }

        /** Get the base height that the overlay subgraph will be projected down to.*/
        double getOverlayBaseHeight() const { return _overlayBaseHeight; }

        /** Set the clear color to use when rendering the overlay subgraph.*/
        void setOverlayClearColor(const osg::Vec4& color) { _overlayClearColor = _overlayClearColor; }

        /** Get the clear color to use when rendering the overlay subgraph.*/
        const osg::Vec4& getOverlayClearColor() const { return _overlayClearColor; }

        /** Set the TexEnv mode used to combine the overlay texture with the base color/texture of the OverlayNode's decorate subgraph.*/
        void setTexEnvMode(GLenum mode);
        
        /** Get the TexEnv mode used to combine the overlay texture with the base color/texture of the OverlayNode's decorate subgraph.*/
        GLenum getTexEnvMode() const { return _texEnvMode; }

        /** Set the texture unit that the texture should be assigned to.*/
        void setOverlayTextureUnit(unsigned int unit);

        /** Get the texture unit that the texture should be assigned to.*/
        unsigned int getOverlayTextureUnit() const { return _textureUnit; }
        
        /** Set the texture size hint. The size hint is used to request a texture of specified size.*/
        void setOverlayTextureSizeHint(unsigned int size);

        /** Get the texture size hint.*/
        unsigned int getOverlayTextureSizeHint() const { return _textureSizeHint; }
        
        
        /** Set whether to use a mutex to ensure ref() and unref() are thread safe.*/
        virtual void setThreadSafeRefUnref(bool threadSafe);

        /** Resize any per context GLObject buffers to specified size. */
        virtual void resizeGLObjectBuffers(unsigned int /*maxSize*/);

        /** If State is non-zero, this function releases any associated OpenGL objects for
           * the specified graphics context. Otherwise, releases OpenGL objexts
           * for all graphics contexts. */
        virtual void releaseGLObjects(osg::State* = 0) const;

    protected :

        virtual ~OverlayNode() {}
        
        void init();
        void init_OBJECT_DEPENDENT_WITH_ORTHOGRAPHIC_OVERLAY();
        void init_VIEW_DEPENDENT_WITH_ORTHOGRAPHIC_OVERLAY();
        void init_VIEW_DEPENDENT_WITH_PERSPECTIVE_OVERLAY();
        
        void traverse_OBJECT_DEPENDENT_WITH_ORTHOGRAPHIC_OVERLAY(osg::NodeVisitor& nv);
        void traverse_VIEW_DEPENDENT_WITH_ORTHOGRAPHIC_OVERLAY(osg::NodeVisitor& nv);
        void traverse_VIEW_DEPENDENT_WITH_PERSPECTIVE_OVERLAY(osg::NodeVisitor& nv);


        void updateMainSubgraphStateSet();

        typedef osg::buffered_value< int > TextureObjectValidList;
        
        mutable TextureObjectValidList _textureObjectValidList;

        OverlayTechnique _overlayTechnique;


        // overlay subgraph is render to a texture
        osg::ref_ptr<osg::Node>         _overlaySubgraph;

        osg::ref_ptr<osg::StateSet>     _overlayStateSet;
        osg::ref_ptr<osg::StateSet>     _mainStateSet;
        
        // texture to render to, and to read from.
        GLenum                          _texEnvMode;
        unsigned int                    _textureUnit;
        unsigned int                    _textureSizeHint;
        osg::Vec4                       _overlayClearColor;

        bool                            _continuousUpdate;
        double                          _overlayBaseHeight;
        bool                            _updateCamera;
        
        osg::Camera::RenderTargetImplementation _renderTargetImpl;

    private:
        
        struct OverlayData
        {

            void setThreadSafeRefUnref(bool threadSafe);
            void resizeGLObjectBuffers(unsigned int maxSize);
            void releaseGLObjects(osg::State* state= 0) const;

            osg::ref_ptr<osg::Camera>       _camera;
            osg::ref_ptr<osg::StateSet>     _overlayStateSet;
            osg::ref_ptr<osg::StateSet>     _mainSubgraphStateSet;
            osg::ref_ptr<osg::TexGenNode>   _texgenNode;
            osg::ref_ptr<osg::Texture2D>    _texture;
            osg::Polytope                   _textureFrustum;
            osg::ref_ptr<osg::Geode>        _geode;

            osg::ref_ptr<osg::Program>      _mainSubgraphProgram;
            
            osg::ref_ptr<osg::Uniform>      _y0;
            osg::ref_ptr<osg::Uniform>      _lightingEnabled;
        };
        
        typedef std::map<osgUtil::CullVisitor*, OverlayData> OverlayDataMap;
        
        OpenThreads::Mutex              _overlayDataMapMutex;
        OverlayDataMap                  _overlayDataMap;
        
        OverlayData& getOverlayData(osgUtil::CullVisitor* cv);
        
};

}

#endif