/*   []----------------------------------------[]
      |               Harmonic.h               |
     []----------------------------------------[]
      |                                        |
      |   AUTHOR:    MFSomers 2005.            |
      |   USE:       Defines a harmonic type   |
      |               interaction...           |
      |                                        |
     []----------------------------------------[]
*/

// Copyright (C) 2005 M.F. Somers, Theoretical Chemistry Department, Leiden University
//
// This 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.
//
// http://www.gnu.org/licenses/lgpl.txt

#if !defined(__HARMONIC_INCLUDED__)

#define __HARMONIC_INCLUDED__

#include "Global.h"
#include "Vector.h"
#include "Constants.h"
#include "ClassicalDynamics.h"

#include "PointPair.h"
#include "Bending.h"
#include "Torsional.h"

/* --------------------------------------------------------- */
/* Defines a harmonic pointpair interaction between particles */

class   HarmonicInteraction;
typedef HarmonicInteraction *HarmonicInteractionPointer;

class HarmonicInteraction : public PointPairInteraction
                            {
		 	     public:
			     
			     inline HarmonicInteraction( double TheFactor, double TheR, unsigned int TheId = GET_NEW_ID, Vector *UsePeriodicBox = NULL ) : PointPairInteraction( TheId, UsePeriodicBox )
			     {
			      InteractionFactor = TheFactor;
			      R = TheR;
			      Type = AHarmonicInteraction;
			     };
			     inline HarmonicInteraction( HarmonicInteraction& I ) : PointPairInteraction( I )
			     {
			      InteractionFactor = I.InteractionFactor;
			      R = I.R;
			     }

			     virtual HarmonicInteraction& operator=( HarmonicInteraction& I )
			     {
			      if( &I == &(*this) ) return( (*this) );
			      PointPairInteraction::operator=( I );
			      InteractionFactor = I.InteractionFactor;
			      R = I.R;
			      return( (*this) );
			     } 			    
			     virtual HarmonicInteractionPointer Clone()
		             {
		              return( new HarmonicInteraction( (*this) ) );
		             }
		             virtual HarmonicInteractionPointer Create( double TheFactor = 1.0, double TheR = 1.0, unsigned int TheId = GET_NEW_ID, Vector *UsePeriodicBox = NULL )
		             {
		              return( new HarmonicInteraction( TheFactor, TheR, TheId ) );
		             }			    
				    
			     virtual double PointPairPotential( Particle& P1, Particle& P2 );
			     virtual Vector PointPairForce( Particle& P1, Particle& P2 );
			    
			     double InteractionFactor, R;        /* V(r) = 0.5 * TheFactor * (r-R)^2 */
			    };
			   
/* --------------------------------------------------------- */

#endif