//C++ header - Open Scene Graph - Copyright (C) 1998-2002 Robert Osfield
//Distributed under the terms of the GNU Library General Public License (LGPL)
//as published by the Free Software Foundation.
//osgParticle - Copyright (C) 2002 Marco Jez

#ifndef OSGPARTICLE_OPERATOR_
#define OSGPARTICLE_OPERATOR_ 1

#include <osgParticle/Program>

#include <osg/CopyOp>
#include <osg/Object>
#include <osg/Matrix>

namespace osgParticle
{

    // forward declaration to avoid including the whole header file
    class Particle;

    /** An abstract base class used by <CODE>ModularProgram</CODE> to perform operations on particles before they are updated. 
        To implement a new operator, derive from this class and override the <CODE>operate()</CODE> method.
        You should also override the <CODE>beginOperate()</CODE> method to query the calling program for the reference frame
        used, and initialize the right transformations if needed.
    */
    class Operator: public osg::Object {        
    public:
        inline Operator();
        inline Operator(const Operator &copy, const osg::CopyOp &copyop = osg::CopyOp::SHALLOW_COPY);

        virtual const char *libraryName() const { return "osgParticle"; }
        virtual const char *className() const { return "Operator"; }
        virtual bool isSameKindAs(const osg::Object *obj) const { return dynamic_cast<const Operator *>(obj) != 0; }
        
        /// Get whether this operator is enabled.
        inline bool isEnabled() const;
        
        /// Enable or disable this operator.
        inline void setEnabled(bool v);
        
        /**    Do something on a particle. 
            This method is called by <CODE>ModularProgram</CODE> objects to perform some operations
            on the particles. You must override it in descendant classes. Common operations
            consist of modifying the particle's velocity vector. The <CODE>dt</CODE> parameter is
            the time elapsed from last operation.            
        */
        virtual void operate(Particle *P, double dt) = 0;
        
        /** Do something before processing particles via the <CODE>operate()</CODE> method.
            Overriding this method could be necessary to query the calling <CODE>Program</CODE> object
            for the current reference frame. If the reference frame is RELATIVE_TO_PARENTS, then your
            class should prepare itself to do all operations in local coordinates.
        */
        virtual void beginOperate(Program *) {}
        
        /// Do something after all particles have been processed.
        virtual void endOperate() {}

    protected:
        virtual ~Operator() {}
        Operator &operator=(const Operator &) { return *this; }
        
    private:
        bool enabled_;        
    };
    
    // INLINE FUNCTIONS
    
    inline Operator::Operator()
    : osg::Object(), enabled_(true)
    {
    }
    
    inline Operator::Operator(const Operator &copy, const osg::CopyOp &copyop)
    : osg::Object(copy, copyop), enabled_(copy.enabled_)
    {
    }
    
    inline bool Operator::isEnabled() const    
    {
        return enabled_;
    }
    
    inline void Operator::setEnabled(bool v)
    {
        enabled_ = v;
    }


}

#endif