#ifndef OSG_LIGHT
#define OSG_LIGHT 1

#include <osg/GL>
#include <osg/OSG>
#include <osg/Vec4>

namespace osg {

/** Light state class which encapsulates OpenGL glLight() functionality.*/
class SG_EXPORT Light : public Object
{
    public :

        Light();
        
        /** return a static instance of an osg::Light, to be used as prototype
            for loading lights.*/
        static Light* instance();

        /** return a shallow copy of a node, with Object* return type.*/
        virtual Object* clone() const { return new Light(); }

        virtual bool isSameKindAs(Object* obj) { return dynamic_cast<Light*>(obj)!=NULL; }

        /** return the name of the node's class type.*/
        virtual const char* className() const { return "Light"; }



	/**
	 * Turn the light on.
	 * Calling this method doesn't directly affect OpenGL's lighting mode.
	 */
        void on( void ) { _on = true; }

	/**
	 * Turn the light off.
	 * Calling this method doesn't directly affect OpenGL's lighting mode.
	 */
	void off( void ) { _on = false; }

	/** Enable OpenGL's Lighting mode. */
        static void enable( void );

	/** Disable OpenGL's Lighting mode. */
        static void disable( void );

	/** Apply the light's state to the OpenGL state machine. */
        void apply( void );

	/** Set the ambient component of the light. */
        void setAmbient( const Vec4& ambient ) { _ambient = ambient; }

	/** Get the ambient component of the light. */
        const Vec4& getAmbient() const { return _ambient; }

	/** Set the diffuse component of the light. */
        void setDiffuse( const Vec4& diffuse ) { _diffuse = diffuse; }

	/** Get the diffuse component of the light. */
        const Vec4& getDiffuse() const { return _diffuse; }

	/** Set the specular component of the light. */
        void setSpecular( const Vec4& specular ) { _specular = specular; }

	/** Get the specular component of the light. */
        const Vec4& getSpecular() const { return _specular; }

	/** Set the position of the light. */	
        void setPosition( const Vec4& position ) { _position = position; }

	/** Get the position of the light. */	
        const Vec4& getPosition() const { return _position; }

	/** Set the direction of the light. */	
        void setDirection( const Vec3& direction ) { _direction = direction; }

	/** Get the direction of the light. */	
        const Vec3& getDirection() const { return _direction; }

	/** Set the constant attenuation of the light. */
        void setConstantAttenuation( float constant_attenuation )     { _constant_attenuation = constant_attenuation; }

	/** Get the constant attenuation of the light. */
        float setConstantAttenuation() const { return _constant_attenuation; }

	/** Set the linear attenuation of the light. */
        void setLinearAttenuation ( float linear_attenuation )        { _linear_attenuation = linear_attenuation; }

	/** Get the linear attenuation of the light. */
        float getLinearAttenuation () const { return _linear_attenuation; }

	/** Set the quadratic attenuation of the light. */
        void setQuadraticAttenuation ( float quadratic_attenuation )  { _quadratic_attenuation = quadratic_attenuation; }

	/** Get the quadratic attenuation of the light. */
        float getQuadraticAttenuation()  const { return _quadratic_attenuation; }

	/** Set the spot exponent of the light. */
        void setSpotExponent( float spot_exponent )                   { _spot_exponent = spot_exponent; }

	/** Get the spot exponent of the light. */
        float getSpotExponent() const { return _spot_exponent; }

	/** Set the spot cutoff of the light. */
        void setSpotCutoff( float spot_cutoff )                       { _spot_cutoff = spot_cutoff; }

	/** Get the spot cutoff of the light. */
        float getSpotCutoff()                                         { return _spot_cutoff; }

	/**
	 * Capture the lighting settings of the current OpenGL state
	 * and store them in this object.
	 */
        void captureLightState();

    protected :
    
        virtual ~Light( void );

	/** Initialize the light's settings with some decent defaults. */
        void init( void );

        int _lightnum;                           // OpenGL light number
        bool _on;                                // on/off state
        Vec4 _ambient;                           // r, g, b, w
        Vec4 _diffuse;                           // r, g, b, w
        Vec4 _specular;                          // r, g, b, w
        Vec4 _position;                          // x, y, z, w
        Vec3 _direction;                         // x, y, z
        float _constant_attenuation;             // constant
        float _linear_attenuation;               // linear
        float _quadratic_attenuation;            // quadratic
        float _spot_exponent;                    // exponent
        float _spot_cutoff;                      // spread

        static int _currentLightNum;             // current max. OpenGL light number
};

};

#endif