/* -*-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.
*/
//osgFX - Copyright (C) 2003 Marco Jez

#ifndef OSGFX_TECHNIQUE_
#define OSGFX_TECHNIQUE_

#include <osgFX/Export>

#include <osg/Referenced>
#include <osg/State>
#include <osg/Group>
#include <osg/NodeVisitor>

#include <vector>
#include <string>

/**
 An helper macro that defines the methods techniqueName() and 
 techniqueDescription() making them return the strings passed as parameters.
 */
#define META_Technique(name, description) \
    inline virtual const char *techniqueName() { return name; } \
    inline virtual const char *techniqueDescription() { return description; }


namespace osgFX
{

    /**
     This is the base class for effect techniques. A technique represents one
     of the possible ways to implement a special effect. This base class is
     abstract, you will have to subclass your own techniques for your custom
     effects.
     Derived classes will have to implement the define_passes() method to
     configure the rendering pass(es) that make up the technique. Usually
     you will create one StateSet object for each rendering pass and then
     you'll call addPass(stateset).
     The validate() method should return true if the technique is valid within
     the current rendering context, false otherwise. The default implementation
     of validate() calls getRequiredExtensions() and tests whether all required
     extensions are supported or not, returning false if at least one extension
     is not supported.
     */
    class OSGFX_EXPORT Technique: public osg::Referenced {
    public:
        Technique();

        /** get the name of this technique */
        virtual const char *techniqueName()        { return "Default"; }

        /** get a brief description of this technique */
        virtual const char *techniqueDescription() { return "This is the default technique"; }

        /**
         collect the GL extension strings which are required for this technique
         to work properly. This method is called from the default implementation
         of validate().
         */
        virtual void getRequiredExtensions(std::vector<std::string> & /*extensions*/) const {};

        /**
         tests whether this technique is valid for the current rendering context.
         The default behavior is to call getRequiredExtensions() and check for
         extension availability.
         */
        virtual bool validate(osg::State &) const;

        /** get the number of rendering passes defined in this technique */
        inline int getNumPasses() const;

        /** get the Group object associated to the i-th pass */
        inline osg::Group *getPassGroup(int i);

        /** get the const Group object associated to the i-th pass */
        inline const osg::Group *getPassGroup(int i) const;

        /** get the StateSet object associated to the i-th pass */
        inline osg::StateSet *getPassStateSet(int i);

        /** get the const StateSet object associated to the i-th pass */
        inline const osg::StateSet *getPassStateSet(int i) const;

        /** 
         traverses the child nodes with multipass if necessary.
         Don't call this method directly as it is called by osgFX::Effect
         */
        virtual void accept(osg::NodeVisitor &nv, osg::Node *child);

    protected:
        Technique(const Technique &): osg::Referenced() {}    // copying is nonsense ;)
        virtual ~Technique() {}
        Technique &operator=(const Technique &)  { return *this; }

        /** force rebuilding of pass nodes on next traversal */
        inline void dirtyPasses();

        /** optional: return a node that overrides the child node on a specified pass */
        inline virtual osg::Node *getOverrideChild(int)  { return 0; }

        /** create a new pass node, add it to the technique and associate a StateSet */
        void addPass(osg::StateSet *ss = 0);

        /**
         add a new pass to the technique specifying an user-defined pass node.
         You should call this version of addPass() only when you need to gain direct
         control over the pass node (i.e. for setting up a cull callback); otherwise
         please use addPass(StateSet*) and let the class create the pass node for you.
        */
        void addPass(osg::Group *pass);

        /**
         get the control node which holds the user's subgraph.
         You may want to do something on it like applying a cull callback.
         */
        inline osg::Group *getControlNode();

        /** get the const control node which holds the user's subgraph */
        inline const osg::Group *getControlNode() const;

        /**
         define the rendering passes that make up this technique. You must
         implement this method in derived classes to add the required passes.
         */
        virtual void define_passes() = 0;

    private:
        bool passes_defined_;

        osg::ref_ptr<osg::Group> control_node_;
        osg::ref_ptr<osg::Node> prev_child_;
    };

    // INLINE METHODS

    inline int Technique::getNumPasses() const
    {
        return static_cast<int>(control_node_->getNumChildren());
    }

    inline osg::Group *Technique::getPassGroup(int i)
    {
        return static_cast<osg::Group *>(control_node_->getChild(i));
    }

    inline const osg::Group *Technique::getPassGroup(int i) const
    {
        return static_cast<const osg::Group *>(control_node_->getChild(i));
    }

    inline osg::StateSet *Technique::getPassStateSet(int i)
    {
        return control_node_->getChild(i)->getStateSet();
    }

    inline const osg::StateSet *Technique::getPassStateSet(int i) const
    {
        return control_node_->getChild(i)->getStateSet();
    }
    
    inline osg::Group *Technique::getControlNode()
    {
        return control_node_.get();
    }

    inline const osg::Group *Technique::getControlNode() const
    {
        return control_node_.get();
    }
    
    inline void Technique::dirtyPasses()
    {
        passes_defined_ = false;
    }

}

#endif