/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2003 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 OSG_TEXTURECUBEMAP
#define OSG_TEXTURECUBEMAP 1

#include <osg/Texture>

#ifndef GL_TEXTURE_CUBE_MAP
#define GL_TEXTURE_CUBE_MAP 0x8513
#endif

namespace osg {

/** TextureCubeMap state class which encapsulates OpenGL texture cubemap functionality. */
class SG_EXPORT TextureCubeMap : public Texture
{

    public :
        
        TextureCubeMap();

        /** Copy constructor using CopyOp to manage deep vs shallow copy. */
        TextureCubeMap(const TextureCubeMap& cm,const CopyOp& copyop=CopyOp::SHALLOW_COPY);

        META_StateAttribute(osg, TextureCubeMap,TEXTURE);
        
        /** Return -1 if *this < *rhs, 0 if *this==*rhs, 1 if *this>*rhs. */
        virtual int compare(const StateAttribute& rhs) const;

        virtual bool getModeUsage(ModeUsage& usage) const
        {
            usage.usesTextureMode(GL_TEXTURE_CUBE_MAP);
            return true;
        }

        enum Face {
            POSITIVE_X=0,
            NEGATIVE_X=1,
            POSITIVE_Y=2,
            NEGATIVE_Y=3,
            POSITIVE_Z=4,
            NEGATIVE_Z=5
        };

        /** Set the texture image for specified face. */
        virtual void setImage(unsigned int face, Image* image);

        /** Get the texture image for specified face. */
        virtual Image* getImage(unsigned int face);

        /** Get the const texture image for specified face. */
        virtual const Image* getImage(unsigned int face) const;

        /** Get the number of images that can be assigned to the Texture. */
        virtual unsigned int getNumImages() const { return 6; }

        inline unsigned int& getModifiedTag(unsigned int face,unsigned int contextID) const
        {
            // get the modified tag for the current contextID.
            return _modifiedTag[face][contextID];
        }

        /** Set the texture width and height. If width or height are zero then
          * the repsective size value is calculated from the source image sizes.
        */
        inline void setTextureSize(int width, int height) const
        {
            _textureWidth = width;
            _textureHeight = height;
        }

        /** Get the texture subload width. */
        inline void getTextureSize(int& width, int& height) const
        {
            width = _textureWidth;
            height = _textureHeight;
        }


        class SG_EXPORT SubloadCallback : public Referenced
        {
            public:
                virtual void load(const TextureCubeMap& texture,State& state) const = 0;
                virtual void subload(const TextureCubeMap& texture,State& state) const = 0;
        };
        
        void setSubloadCallback(SubloadCallback* cb) { _subloadCallback = cb;; }
        
        SubloadCallback* getSubloadCallback() { return _subloadCallback.get(); }

        const SubloadCallback* getSubloadCallback() const { return _subloadCallback.get(); }


        /** Set the number of mip map levels the the texture has been created with.
          * Should only be called within an osg::Texuture::apply() and custom OpenGL texture load.
        */
        void setNumMipmapLevels(unsigned int num) const { _numMipmapLevels=num; }

        /** Get the number of mip map levels the the texture has been created with. */
        unsigned int getNumMipmapLevels() const { return _numMipmapLevels; }        

        /** On first apply (unless already compiled), create the mipmapped
          * texture and bind it. Subsequent apply will simple bind to texture.
        */
        virtual void apply(State& state) const;
        

        /** Extensions class which encapsulates the querying of extensions and
          * associated function pointers, and provides convinience wrappers to 
          * check for the extensions or use the associated functions.
        */
        class SG_EXPORT Extensions : public osg::Referenced
        {
            public:
                Extensions();

                Extensions(const Extensions& rhs);
                
                void lowestCommonDenominator(const Extensions& rhs);
                
                void setupGLExtenions();

                void setCubeMapSupported(bool flag) { _isCubeMapSupported=flag; }
                bool isCubeMapSupported() const { return _isCubeMapSupported; }

            protected:

                ~Extensions() {}
                
                bool    _isCubeMapSupported;

        };
        
        /** Function to call to get the extension of a specified context.
          * If the Exentsion object for that context has not yet been created
          * and the 'createIfNotInitalized' flag been set to false then returns NULL.
          * If 'createIfNotInitalized' is true then the Extensions object is 
          * automatically created. However, in this case the extension object will
          * only be created with the graphics context associated with ContextID.
        */
        static Extensions* getExtensions(unsigned int contextID,bool createIfNotInitalized);

        /** The setExtensions method allows users to override the extensions across graphics contexts.
          * Typically used when you have different extensions supported across graphics pipes
          * but need to ensure that they all use the same low common denominator extensions.
        */
        static void setExtensions(unsigned int contextID,Extensions* extensions);


    protected :

        virtual ~TextureCubeMap();
        
        bool imagesValid() const;
        
        virtual void computeInternalFormat() const;

        ref_ptr<Image> _images[6];

        // subloaded images can have different texture and image sizes.
        mutable GLsizei _textureWidth, _textureHeight;
        
        // number of mip map levels the the texture has been created with,        
        mutable GLsizei _numMipmapLevels;

        ref_ptr<SubloadCallback> _subloadCallback;

        typedef buffered_value<unsigned int> ImageModifiedTag;
        mutable ImageModifiedTag _modifiedTag[6];
};

}

#endif