/* 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 <string.h>
#include <sstream>

#include "SimTKOpenMMCommon.h"
#include "SimTKOpenMMLog.h"
#include "SimTKOpenMMUtilities.h"
#include "ReferenceLJCoulombIxn.h"
#include "ReferenceForce.h"

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

   ReferenceLJCoulombIxn constructor

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

ReferenceLJCoulombIxn::ReferenceLJCoulombIxn( ){

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

   // static const char* methodName = "\nReferenceLJCoulombIxn::ReferenceLJCoulombIxn";

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

}

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

   ReferenceLJCoulombIxn destructor

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

ReferenceLJCoulombIxn::~ReferenceLJCoulombIxn( ){

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

   // static const char* methodName = "\nReferenceLJCoulombIxn::~ReferenceLJCoulombIxn";

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

}

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

   Calculate parameters for LJ Coulomb ixn

   @param c6               c6
   @param c12              c12
   @param q1               q1 charge atom 1
   @param epsfac           epsfacSqrt ????????????/
   @param parameters       output parameters:
										parameter[SigIndex]  = sqrt(c6*c6/c12)
										parameter[EpsIndex]  = 0.5*( (c12/c6)**1/6 )
										parameter[QIndex]    = epsfactorSqrt*q1

   @return ReferenceForce::DefaultReturn

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

int ReferenceLJCoulombIxn::getDerivedParameters( RealOpenMM c6, RealOpenMM c12, RealOpenMM q1,
                                                 RealOpenMM epsfacSqrt,
                                                 RealOpenMM* parameters ) const {

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

   // static const char* methodName = "\nReferenceLJCoulombIxn::getDerivedParameters";

   static const RealOpenMM zero          =  0.0;
   static const RealOpenMM one           =  1.0;
   static const RealOpenMM six           =  6.0;
   static const RealOpenMM half          =  0.5;
   static const RealOpenMM oneSixth      =  one/six;
   static const RealOpenMM oneTweleth    =  half*oneSixth;

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

   if( c12 <= 0.0 ){

      parameters[EpsIndex] = zero;
      parameters[SigIndex] = half;

   } else {
 
      parameters[EpsIndex]    = c6*SQRT( one/c12 );
   
      parameters[SigIndex]    = POW( (c12/c6), oneSixth );
      parameters[SigIndex]   *= half;
   }

   parameters[QIndex]   = epsfacSqrt*q1;

   return ReferenceForce::DefaultReturn;
}

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

   Calculate LJ Coulomb pair ixn

   @param numberOfAtoms    number of atoms
   @param atomCoordinates  atom coordinates
   @param atomParameters   atom parameters                             atomParameters[atomIndex][paramterIndex]
   @param exclusions       atom exclusion indices                      exclusions[atomIndex][atomToExcludeIndex]
                           exclusions[atomIndex][0] = number of exclusions
                           exclusions[atomIndex][1-no.] = atom indices of atoms to excluded from
                           interacting w/ atom atomIndex
   @param fixedParameters  non atom parameters (not currently used)
   @param forces           force array (forces added)
   @param energyByAtom     atom energy
   @param totalEnergy      total energy

   @return ReferenceForce::DefaultReturn
      
   --------------------------------------------------------------------------------------- */
    
int ReferenceLJCoulombIxn::calculatePairIxn( int numberOfAtoms, RealOpenMM** atomCoordinates,
                                             RealOpenMM** atomParameters, int** exclusions,
                                             RealOpenMM* fixedParameters, RealOpenMM** forces,
                                             RealOpenMM* energyByAtom, RealOpenMM* totalEnergy ) const {

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

   // static const char* methodName = "\nReferenceLJCoulombIxn::calculatePairIxn";

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

   static const std::string methodName = "\nReferenceLJCoulombIxn::calculatePairIxn";

   // constants -- reduce Visual Studio warnings regarding conversions between float & double

   static const RealOpenMM zero        =  0.0;
   static const RealOpenMM one         =  1.0;
   static const RealOpenMM two         =  2.0;
   static const RealOpenMM three       =  3.0;
   static const RealOpenMM six         =  6.0;
   static const RealOpenMM twelve      = 12.0;
   static const RealOpenMM oneM        = -1.0;

   static const int threeI             = 3;

   // debug flag

   static const int debug              = -1;

   static const int LastAtomIndex      = 2;

   RealOpenMM deltaR[2][ReferenceForce::LastDeltaRIndex];

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

   // allocate and initialize exclusion array

   int* exclusionIndices = new int[numberOfAtoms];
   for( int ii = 0; ii < numberOfAtoms; ii++ ){
      exclusionIndices[ii] = -1;
   }

   for( int ii = 0; ii < numberOfAtoms; ii++ ){

      // set exclusions

      for( int jj = 1; jj <= exclusions[ii][0]; jj++ ){
         exclusionIndices[exclusions[ii][jj]] = ii;
      }
     
      // loop over atom pairs

      for( int jj = ii+1; jj < numberOfAtoms; jj++ ){

         if( exclusionIndices[jj] != ii ){

            // get deltaR, R2, and R between 2 atoms

            ReferenceForce::getDeltaR( atomCoordinates[jj], atomCoordinates[ii], deltaR[0] );  

            RealOpenMM inverseR  = one/(deltaR[0][ReferenceForce::RIndex]);
            RealOpenMM sig       = atomParameters[ii][SigIndex] +  atomParameters[jj][SigIndex];
            RealOpenMM sig2      = inverseR*sig;
                       sig2     *= sig2;
            RealOpenMM sig6      = sig2*sig2*sig2;
             
            RealOpenMM eps       = atomParameters[ii][EpsIndex]*atomParameters[jj][EpsIndex];
            RealOpenMM dEdR      = eps*( twelve*sig6 - six )*sig6;
                       dEdR     += atomParameters[ii][QIndex]*atomParameters[jj][QIndex]*inverseR;
                       dEdR     *= inverseR*inverseR;
         
            // accumulate forces
         
            for( int kk = 0; kk < 3; kk++ ){
               RealOpenMM force  = dEdR*deltaR[0][kk];
               forces[ii][kk]   += force;
               forces[jj][kk]   -= force;
            }
         
            RealOpenMM energy = 0.0;
         
            // accumulate energies
         
            *totalEnergy += energy;
            if( energyByAtom ){
               energyByAtom[ii] += energy;
               energyByAtom[jj] += energy;
            }
         
            // debug 
         
            if( debug == ii ){
               static bool printHeader = false;
               std::stringstream message;
               message << methodName;
               message << std::endl;
               int pairArray[2] = { ii, jj };
               if( !printHeader  ){  
                  printHeader = true;
                  message << std::endl;
                  message << methodName.c_str() << " a0 k [c q p s] r1 r2  angle dt rp p[] dot cosine angle dEdR*r F[]" << std::endl;
               }   
         
               message << std::endl;
               for( int kk = 0; kk < 2; kk++ ){
                  message << " Atm " << pairArray[kk] << " [" << atomCoordinates[pairArray[kk]][0] << " " << atomCoordinates[pairArray[kk]][1] << " " << atomCoordinates[pairArray[kk]][2] << "] ";
               }
               message << std::endl << " Delta:";
               for( int kk = 0; kk < (LastAtomIndex - 1); kk++ ){
                  message << " [";
                  for( int jj = 0; jj < ReferenceForce::LastDeltaRIndex; jj++ ){
                     message << deltaR[kk][jj] << " ";
                  }
                  message << "]";
               }
               message << std::endl;
         
               for( int kk = 0; kk < 2; kk++ ){
                  message << " p" << pairArray[kk] << " [";
                  message << atomParameters[pairArray[kk]][0] << " " << atomParameters[pairArray[kk]][1] << " " << atomParameters[pairArray[kk]][2];
                  message << "]";
               }
              message << std::endl;
         
               message << " dEdR=" << dEdR;
               message << " E=" << energy << " force factors: ";
               message << "F=compute force; f=cumulative force";
         
               message << std::endl << "  ";
               message << " f" << ii << "[";
               SimTKOpenMMUtilities::formatRealStringStream( message, deltaR[0], threeI, dEdR );
               message << "]";

               for( int kk = 0; kk < 2; kk++ ){
                  message << " F" <<  pairArray[kk] << " [";
                  SimTKOpenMMUtilities::formatRealStringStream( message, forces[pairArray[kk]], threeI );
                  message << "]";
               }
         
               SimTKOpenMMLog::printMessage( message );
            }
         }
      }
   }

   delete[] exclusionIndices;

   return ReferenceForce::DefaultReturn;
}