/* -*-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.
*/
//osgParticle - Copyright (C) 2002 Marco Jez

#ifndef OSGPARTICLE_PARTICLE_
#define OSGPARTICLE_PARTICLE_ 1

#include <osgParticle/Export>
#include <osgParticle/Interpolator>
#include <osgParticle/range>

#include <osg/ref_ptr>
#include <osg/Vec3>
#include <osg/Vec4>
#include <osg/Matrix>
#include <osg/GL>

namespace osgParticle
{

    /**    Implementation of a <B>particle</B>.
        Objects of this class are particles, they have some graphical properties
        and some physical properties. Particles are created by emitters and then placed
        into Particle Systems, where they live and get updated at each frame.
        Particles can either live forever (lifeTime < 0), or die after a specified
        time (lifeTime >= 0). For each property which is defined as a range of values, a
        "current" value will be evaluated at each frame by interpolating the <I>min</I>
        and <I>max</I> values so that <I>curr_value = min</I> when <I>t == 0</I>, and 
        <I>curr_value = max</I> when <I>t == lifeTime</I>.
        You may customize the interpolator objects to achieve any kind of transition.
        If you want the particle to live forever, set its lifetime to any value <= 0;
        in that case, no interpolation is done to compute real-time properties, and only
        minimum values are used.
    */
    class OSGPARTICLE_EXPORT Particle {
    public:

        enum Shape {
            POINT,            // uses GL_POINTS as primitive
            QUAD,            // uses GL_QUADS as primitive
            QUAD_TRIANGLESTRIP,    // uses GL_TRIANGLE_STRIP as primitive, but each particle needs a glBegin/glEnd pair
            HEXAGON            // may save some filling time, but uses more triangles
        };
        
        Particle();

        /// Get the shape of the particle.
        inline Shape getShape() const;
        
        /// Set the shape of the particle.
        inline void setShape(Shape s);

        /// Get whether the particle is still alive.
        inline bool isAlive() const;
        
        /// Get the life time of the particle (in seconds).
        inline double getLifeTime() const;
        
        /// Get the age of the particle (in seconds).
        inline double getAge() const;
        
        /// Get the minimum and maximum values for polygon size.
        inline const rangef &getSizeRange() const;
        
        /// Get the minimum and maximum values for alpha.
        inline const rangef &getAlphaRange() const;
        
        /// Get the minimum and maximum values for color.
        inline const rangev4 &getColorRange() const;
        
        /// Get the interpolator for computing the size of polygons.
        inline const Interpolator *getSizeInterpolator() const;
        
        /// Get the interpolator for computing alpha values.
        inline const Interpolator *getAlphaInterpolator() const;
        
        /// Get the interpolator for computing color values.
        inline const Interpolator *getColorInterpolator() const;

        /** Get the physical radius of the particle.
            For built-in operators to work correctly, lengths must be expressed in meters.
        */
        inline float getRadius() const;
        
        /** Get the mass of the particle.
            For built-in operators to work correctly, remember that the mass is expressed in kg.
        */
        inline float getMass() const;
        
        /// Get <CODE>1 / getMass()</CODE>.
        inline float getMassInv() const;
        
        /// Get the position vector.
        inline const osg::Vec3 &getPosition() const;
        
        /**    Get the velocity vector.
            For built-in operators to work correctly, remember that velocity components are expressed
            in meters per second.
        */
        inline const osg::Vec3 &getVelocity() const;        
        
        /// Get the previous position (the position before last update).
        inline const osg::Vec3 &getPreviousPosition() const;

        /** Kill the particle on next update
            NOTE: after calling this function, the <CODE>isAlive()</CODE> method will still 
            return true until the particle is updated again.
        */
        inline void kill();
        
        /// Set the life time of the particle.
        inline void setLifeTime(double t);
        
        /// Set the minimum and maximum values for polygon size.
        inline void setSizeRange(const rangef &r);
        
        /// Set the minimum and maximum values for alpha.
        inline void setAlphaRange(const rangef &r);
        
        /// Set the minimum and maximum values for color.
        inline void setColorRange(const rangev4 &r);
        
        /// Set the interpolator for computing size values.
        inline void setSizeInterpolator(Interpolator *ri);
        
        /// Set the interpolator for computing alpha values.        
        inline void setAlphaInterpolator(Interpolator *ai);
        
        /// Set the interpolator for computing color values.
        inline void setColorInterpolator(Interpolator *ci);

        /** Set the physical radius of the particle.
            For built-in operators to work correctly, lengths must be expressed in meters.
        */
        inline void setRadius(float r);
        
        /** Set the mass of the particle.
            For built-in operators to work correctly, remember that the mass is expressed in kg.
        */
        inline void setMass(float m);
        
        /// Set the position vector.        
        inline void setPosition(const osg::Vec3 &p);
        
        /**    Set the velocity vector.
            For built-in operators to work correctly, remember that velocity components are expressed
            in meters per second.
        */
        inline void setVelocity(const osg::Vec3 &v);
        
        /// Add a vector to the velocity vector.
        inline void addVelocity(const osg::Vec3 &dv);
        
        /// Transform position and velocity vectors by a matrix.
        inline void transformPositionVelocity(const osg::Matrix &xform);

        /**    Update the particle (don't call this method manually).
            This method is called automatically by <CODE>ParticleSystem::update()</CODE>; it
            updates the graphical properties of the particle for the current time,
            checks whether the particle is still alive, and then updates its position
            by computing <I>P = P + V * dt</I> (where <I>P</I> is the position and <I>V</I> is the velocity).
        */
        bool update(double dt);

        /// Perform some pre-rendering tasks. Called automatically by particle systems.
        inline void beginRender() const;
        
        /// Render the particle. Called automatically by particle systems.
        void render(const osg::Vec3 &xpos, const osg::Vec3 &px, const osg::Vec3 &py, float scale = 1.0f) const;
        
        /// Perform some post-rendering tasks. Called automatically by particle systems.
        inline void endRender() const;
        
        /// Get the current (interpolated) polygon size. Valid only after the first call to update().
        inline float getCurrentSize() const;

    private:
        Shape shape_;

        rangef sr_;
        rangef ar_;
        rangev4 cr_;

        osg::ref_ptr<Interpolator> si_;
        osg::ref_ptr<Interpolator> ai_;
        osg::ref_ptr<Interpolator> ci_;

        bool alive_;
        bool mustdie_;
        double lifetime_;

        float radius_;
        float mass_;
        float massinv_;
        osg::Vec3 prev_pos_;
        osg::Vec3 position_;
        osg::Vec3 velocity_;

        double t0_;        

        float current_size_;
        float current_alpha_;
        osg::Vec4 current_color_;
    };

    // INLINE FUNCTIONS

    inline Particle::Shape Particle::getShape() const
    {
        return shape_;
    }

    inline void Particle::setShape(Shape s)
    {
        shape_ = s;
    }

    inline bool Particle::isAlive() const
    {
        return alive_;
    }

    inline double Particle::getLifeTime() const
    {
        return lifetime_;
    }
    
    inline double Particle::getAge() const
    {
        return t0_;
    }
    
    inline float Particle::getRadius() const
    {
        return radius_;
    }
    
    inline void Particle::setRadius(float r)
    {
        radius_ = r;
    }

    inline const rangef &Particle::getSizeRange() const
    {
        return sr_;
    }

    inline const rangef &Particle::getAlphaRange() const
    {
        return ar_;
    }

    inline const rangev4 &Particle::getColorRange() const
    {
        return cr_;
    }

    inline const Interpolator *Particle::getSizeInterpolator() const
    {
        return si_.get();
    }

    inline const Interpolator *Particle::getAlphaInterpolator() const
    {
        return ai_.get();
    }

    inline const Interpolator *Particle::getColorInterpolator() const
    {
        return ci_.get();
    }

    inline const osg::Vec3 &Particle::getPosition() const
    {
        return position_;
    }

    inline const osg::Vec3 &Particle::getVelocity() const
    {
        return velocity_;
    }
    
    inline const osg::Vec3 &Particle::getPreviousPosition() const
    {
        return prev_pos_;
    }

    inline void Particle::kill()
    {
        mustdie_ = true;
    }

    inline void Particle::setLifeTime(double t)
    {
        lifetime_ = t;
    }

    inline void Particle::setSizeRange(const rangef &r)
    {
        sr_ = r;
    }

    inline void Particle::setAlphaRange(const rangef &r)
    {
        ar_ = r;
    }

    inline void Particle::setColorRange(const rangev4 &r)
    {
        cr_ = r;
    }

    inline void Particle::setSizeInterpolator(Interpolator *ri)
    {
        si_ = ri;
    }

    inline void Particle::setAlphaInterpolator(Interpolator *ai)
    {
        ai_ = ai;
    }

    inline void Particle::setColorInterpolator(Interpolator *ci)
    {
        ci_ = ci;
    }

    inline void Particle::setPosition(const osg::Vec3 &p)
    {
        position_ = p;
    }

    inline void Particle::setVelocity(const osg::Vec3 &v)
    {
        velocity_ = v;
    }

    inline void Particle::addVelocity(const osg::Vec3 &v)
    {
        velocity_ += v;
    }

    inline void Particle::transformPositionVelocity(const osg::Matrix &xform)
    {
        // this should be optimized!

        osg::Vec3 p1 = position_ + velocity_;
                
        position_ = xform.preMult(position_);
        p1 = xform.preMult(p1);
        
        velocity_ = p1 - position_;
    }
    
    inline float Particle::getMass() const
    {
        return mass_;
    }
    
    inline float Particle::getMassInv() const
    {
        return massinv_;
    }
    
    inline void Particle::setMass(float m)
    {
        mass_ = m;
        massinv_ = 1 / m;
    }
    
    inline void Particle::beginRender() const
    {
        switch (shape_)
        {
        case POINT:
            glBegin(GL_POINTS);
            break;
        case QUAD:
            glBegin(GL_QUADS);
            break;
        default: ;
        }
    }
    
    inline void Particle::endRender() const
    {
        switch (shape_)
        {        
        case POINT:
        case QUAD:
            glEnd();
            break;
        default: ;
        }
    }
    
    inline float Particle::getCurrentSize() const
    {
        return current_size_;
    }


}

#endif