
/* Portions copyright (c) 2006 Stanford University and Simbios.
 * Contributors: Pande Group
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject
 * to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS, CONTRIBUTORS OR COPYRIGHT HOLDERS BE
 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

#include <cstring>
#include <sstream>

#include "../SimTKUtilities/SimTKOpenMMCommon.h"
#include "../SimTKUtilities/SimTKOpenMMLog.h"
#include "../SimTKUtilities/SimTKOpenMMUtilities.h"
#include "ReferenceForce.h"

#include <cstdio>

/**---------------------------------------------------------------------------------------

   ReferenceForce constructor

   --------------------------------------------------------------------------------------- */

ReferenceForce::ReferenceForce( ){

   // ---------------------------------------------------------------------------------------

   // static const char* methodName = "\nReferenceForce::ReferenceForce";

   // ---------------------------------------------------------------------------------------

}

/**---------------------------------------------------------------------------------------

   ReferenceForce destructor

   --------------------------------------------------------------------------------------- */

ReferenceForce::~ReferenceForce( ){

   // ---------------------------------------------------------------------------------------

   // static const char* methodName = "\nReferenceForce::~ReferenceForce";

   // ---------------------------------------------------------------------------------------

}

/**---------------------------------------------------------------------------------------

   Given two coordinates on a periodic lattice, return the difference between them.

   --------------------------------------------------------------------------------------- */

RealOpenMM ReferenceForce::periodicDifference(RealOpenMM val1, RealOpenMM val2, RealOpenMM period) {
    RealOpenMM diff = val1-val2;
    RealOpenMM base = (RealOpenMM) (floor(diff/period+0.5)*period);
    return diff-base;

}


/**---------------------------------------------------------------------------------------

   Get deltaR and distance and distance**2 between atomI and atomJ (static method)
   deltaR: j - i

   @param atomCoordinatesI    atom i coordinates
   @param atomCoordinatesI    atom j coordinates
   @param deltaR              deltaX, deltaY, deltaZ, R2, R upon return

   @return ReferenceForce::DefaultReturn

   --------------------------------------------------------------------------------------- */

int ReferenceForce::getDeltaR( const RealOpenMM* atomCoordinatesI, const RealOpenMM* atomCoordinatesJ,
                               RealOpenMM* deltaR ){

   // ---------------------------------------------------------------------------------------

   // static const std::string methodName = "\nReferenceForce::getDeltaR";

   // ---------------------------------------------------------------------------------------

   deltaR[XIndex]    = atomCoordinatesJ[0] - atomCoordinatesI[0];
   deltaR[YIndex]    = atomCoordinatesJ[1] - atomCoordinatesI[1];
   deltaR[ZIndex]    = atomCoordinatesJ[2] - atomCoordinatesI[2];

   deltaR[R2Index]   = DOT3( deltaR, deltaR );
   deltaR[RIndex]    = (RealOpenMM) SQRT( deltaR[R2Index] );

   return ReferenceForce::DefaultReturn;
}

/**---------------------------------------------------------------------------------------

   Get deltaR and distance and distance**2 between atomI and atomJ, assuming periodic
   boundary conditions (static method); deltaR: j - i

   @param atomCoordinatesI    atom i coordinates
   @param atomCoordinatesI    atom j coordinates
   @param boxSize             X, Y, and Z sizes of the periodic box
   @param deltaR              deltaX, deltaY, deltaZ, R2, R upon return

   @return ReferenceForce::DefaultReturn

   --------------------------------------------------------------------------------------- */

int ReferenceForce::getDeltaRPeriodic( const RealOpenMM* atomCoordinatesI, const RealOpenMM* atomCoordinatesJ,
                               const RealOpenMM* boxSize, RealOpenMM* deltaR ){

   // ---------------------------------------------------------------------------------------

   // static const std::string methodName = "\nReferenceForce::getDeltaR";

   // ---------------------------------------------------------------------------------------

   deltaR[XIndex]    = periodicDifference(atomCoordinatesJ[0], atomCoordinatesI[0], boxSize[0]);
   deltaR[YIndex]    = periodicDifference(atomCoordinatesJ[1], atomCoordinatesI[1], boxSize[1]);
   deltaR[ZIndex]    = periodicDifference(atomCoordinatesJ[2], atomCoordinatesI[2], boxSize[2]);

   deltaR[R2Index]   = DOT3( deltaR, deltaR );
   deltaR[RIndex]    = (RealOpenMM) SQRT( deltaR[R2Index] );

   return ReferenceForce::DefaultReturn;
}

/**---------------------------------------------------------------------------------------

   Get deltaR between atomI and atomJ (static method); deltaR: j - i

   @param atomCoordinatesI    atom i coordinates
   @param atomCoordinatesI    atom j coordinates
   @param deltaR              deltaX, deltaY, deltaZ upon return

   @return ReferenceForce::DefaultReturn

   --------------------------------------------------------------------------------------- */

int ReferenceForce::getDeltaROnly( const RealOpenMM* atomCoordinatesI,
                                   const RealOpenMM* atomCoordinatesJ,
                                   RealOpenMM* deltaR ){

   // ---------------------------------------------------------------------------------------

   // static const std::string methodName = "\nReferenceForce::getDeltaR";

   // ---------------------------------------------------------------------------------------

   deltaR[XIndex]    = atomCoordinatesJ[0] - atomCoordinatesI[0];
   deltaR[YIndex]    = atomCoordinatesJ[1] - atomCoordinatesI[1];
   deltaR[ZIndex]    = atomCoordinatesJ[2] - atomCoordinatesI[2];

   return ReferenceForce::DefaultReturn;
}
