/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2005 Robert Osfield 
 * Copyright (C) 2003-2005 3Dlabs Inc. Ltd.
 * Copyright (C) 2004-2005 Nathan Cournia
 *
 * This application is open source and may be redistributed and/or modified   
 * freely and without restriction, both in commericial and non commericial
 * applications, as long as this copyright notice is maintained.
 * 
 * This application 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.
*/

/* file:   include/osg/Shader
 * author: Mike Weiblen 2005-06-15
*/

#ifndef OSG_SHADER
#define OSG_SHADER 1


#include <osg/GL2Extensions>
#include <osg/Object>
#include <osg/buffered_value>

#include <set>

namespace osg {

class Program;

///////////////////////////////////////////////////////////////////////////
/** osg::Shader is an application-level abstraction of an OpenGL glShader.
  * It is a container to load the shader source code text and manage its
  * compilation.
  * An osg::Shader may be attached to more than one osg::Program.
  * Shader will automatically manage per-context instancing of the
  * internal objects, if that is necessary for a particular display
  * configuration.
  */

class OSG_EXPORT Shader : public osg::Object
{
    public:

        enum Type {
            VERTEX = GL_VERTEX_SHADER,
            FRAGMENT = GL_FRAGMENT_SHADER,
            UNDEFINED = -1
        };

        Shader( Type type = UNDEFINED);
        Shader( Type type, const std::string& source );

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

        META_Object(osg, Shader);

        int compare(const Shader& rhs) const;

        bool setType( Type t );
        

        /** Load the Shader's source code text from a string. */
        void setShaderSource( const std::string& sourceText );

        /** Read shader source from file and then constructor shader of specified type.
          * Return the resulting Shader or 0 if no valid shader source code be read.*/
        static Shader* readShaderFile( Type type, const std::string& fileName );

        /** Load the Shader's source code text from a file. */
        bool loadShaderSourceFromFile( const std::string& fileName );

        /** Query the shader's source code text */
        inline const std::string& getShaderSource() const { return _shaderSource; }

        /** Get the Shader type as an enum. */
        inline Type getType() const { return _type; }

        /** Get the Shader type as a descriptive string. */
        const char* getTypename() const;

        /** release OpenGL objects in specified graphics context if State
            object is passed, otherwise release OpenGL objects for all graphics context if
            State object pointer NULL.*/
        void releaseGLObjects(osg::State* state=0) const;

        /** Mark our PCSs as needing recompilation.
          * Also mark Programs that depend on us as needing relink */
        void dirtyShader();        

        /** If needed, compile the PCS's glShader */
        void compileShader(unsigned int contextID) const;

        /** For a given GL context, attach a glShader to a glProgram */
        void attachShader(unsigned int contextID, GLuint program) const;

        /** Query InfoLog from a glShader */
        bool getGlShaderInfoLog(unsigned int contextID, std::string& log) const;

        /** Mark internal glShader for deletion.
          * Deletion requests are queued tuntil they can be executed
          * in the proper GL context. */
        static void deleteGlShader(unsigned int contextID, GLuint shader);

        /** flush all the cached glShaders which need to be deleted
          * in the OpenGL context related to contextID.*/
        static void flushDeletedGlShaders(unsigned int contextID,double currentTime, double& availableTime);

        static Shader::Type getTypeId( const std::string& tname );

    protected:
        /** PerContextShader (PCS) is an OSG-internal encapsulation of glShader per-GL context. */
        class PerContextShader : public osg::Referenced
        {
            public:
                PerContextShader(const Shader* shader, unsigned int contextID);

                GLuint getHandle() const {return _glShaderHandle;}

                void requestCompile();
                void compileShader();
                bool needsCompile() const {return _needsCompile;}
                bool isCompiled() const {return _isCompiled;}
                bool getInfoLog( std::string& infoLog ) const;

                /** Attach our glShader to a glProgram */
                void attachShader(GLuint program) const;

                /** Detach our glShader from a glProgram */
                void detachShader(GLuint program) const;

            protected:        /*methods*/
                ~PerContextShader();

            protected:        /*data*/
                /** Pointer to our parent osg::Shader */
                const Shader* _shader;
                /** Pointer to this context's extension functions. */
                osg::ref_ptr<osg::GL2Extensions> _extensions;
                /** Handle to the actual glShader. */
                GLuint _glShaderHandle;
                /** Does our glShader need to be recompiled? */
                bool _needsCompile;
                /** Is our glShader successfully compiled? */
                bool _isCompiled;
                const unsigned int _contextID;

            private:
                PerContextShader();        // disallowed
                PerContextShader(const PerContextShader&);        // disallowed
                PerContextShader& operator=(const PerContextShader&);        // disallowed
        };

    protected:        /*methods*/
        virtual ~Shader();

        PerContextShader* getPCS(unsigned int contextID) const;

        friend class osg::Program;
        bool addProgramRef( osg::Program* program );
        bool removeProgramRef( osg::Program* program );

    protected:        /*data*/
        Type _type;
        std::string _shaderSource;
        /** osg::Programs that this osg::Shader is attached to */
        typedef std::set< osg::Program* > ProgramSet;
        ProgramSet _programSet;
        mutable osg::buffered_value< osg::ref_ptr<PerContextShader> > _pcsList;

    private:
        Shader& operator=(const Shader&);        // disallowed
};

}

#endif

/*EOF*/