/*
-----------------------------------------------------------------------------
This source file is part of OGRE 
	(Object-oriented Graphics Rendering Engine)
For the latest info, see http://www.ogre3d.org/

Copyright (c) 2000-2006 Torus Knot Software Ltd
Also see acknowledgements in Readme.html

This program is free software; you can redistribute it and/or modify it under 
the terms of the GNU Lesser General Public License as published by the Free Software 
Foundation; either version 2 of the License, or (at your option) any later 
version.

This program 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 GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with 
this program; if not, write to the Free Software Foundation, Inc., 59 Temple 
Place - Suite 330, Boston, MA 02111-1307, USA, or go to 
http://www.gnu.org/copyleft/lesser.txt.

You may alternatively use this source under the terms of a specific version of
the OGRE Unrestricted License provided you have obtained such a license from
Torus Knot Software Ltd.
-----------------------------------------------------------------------------
*/
#ifndef __ParticleAffector_H__
#define __ParticleAffector_H__

#include "OgrePrerequisites.h"
#include "OgreString.h"
#include "OgreStringInterface.h"


namespace Ogre {

    /** Abstract class defining the interface to be implemented by particle affectors.
    @remarks
        Particle affectors modify particles in a particle system over their lifetime. They can be
        grouped into types, e.g. 'vector force' affectors, 'fader' affectors etc; each type will 
        modify particles in a different way, using different parameters.
    @par
        Because there are so many types of affectors you could use, OGRE chooses not to dictate
        the available types. It comes with some in-built, but allows plugins or applications to extend the affector types available.
        This is done by subclassing ParticleAffector to have the appropriate emission behaviour you want,
        and also creating a subclass of ParticleAffectorFactory which is responsible for creating instances 
        of your new affector type. You register this factory with the ParticleSystemManager using
        addAffectorFactory, and from then on affectors of this type can be created either from code or through
        text particle scripts by naming the type.
    @par
        This same approach is used for ParticleEmitters (which are the source of particles in a system).
        This means that OGRE is particularly flexible when it comes to creating particle system effects,
        with literally infinite combinations of affector and affector types, and paramters within those
        types.
    */
    class _OgreExport ParticleAffector : public StringInterface
    {
    protected:
        /// Name of the type of affector, MUST be initialised by subclasses
        String mType;

        /** Internal method for setting up the basic parameter definitions for a subclass. 
        @remarks
            Because StringInterface holds a dictionary of parameters per class, subclasses need to
            call this to ask the base class to add it's parameters to their dictionary as well.
            Can't do this in the constructor because that runs in a non-virtual context.
        @par
            The subclass must have called it's own createParamDictionary before calling this method.
        */
        void addBaseParameters(void) { /* actually do nothing - for future possible use */ }

        ParticleSystem* mParent;
    public:
        ParticleAffector(ParticleSystem* parent): mParent(parent) {}

        /** Virtual destructor essential. */
        virtual ~ParticleAffector();

        /** Method called to allow the affector to initialize all newly created particles in the system.
        @remarks
            This is where the affector gets the chance to initialize it's effects to the particles of a system.
            The affector is expected to initialize some or all of the particles in the system
            passed to it, depending on the affector's approach.
        @param
            pParticle Pointer to a Particle to initialize.
        */
		virtual void _initParticle(Particle* pParticle) { /* by default do nothing */ }

        /** Method called to allow the affector to 'do it's stuff' on all active particles in the system.
        @remarks
            This is where the affector gets the chance to apply it's effects to the particles of a system.
            The affector is expected to apply it's effect to some or all of the particles in the system
            passed to it, depending on the affector's approach.
        @param
            pSystem Pointer to a ParticleSystem to affect.
        @param
            timeElapsed The number of seconds which have elapsed since the last call.
        */
        virtual void _affectParticles(ParticleSystem* pSystem, Real timeElapsed) = 0;

        /** Returns the name of the type of affector. 
        @remarks
            This property is useful for determining the type of affector procedurally so another
            can be created.
        */
        const String &getType(void) const { return mType; }

    };

}


#endif

