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

   LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator

   http://lammps.sandia.gov, Sandia National Laboratories

   Steve Plimpton, sjplimp@sandia.gov

   Copyright (2003) Sandia Corporation.  Under the terms of Contract

   DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains

   certain rights in this software.  This software is distributed under 

   the GNU General Public License.

   See the README file in the top-level LAMMPS directory.

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

#include "stdio.h"

#include "string.h"

#include "fix_external.h"

#include "atom.h"

#include "update.h"

#include "memory.h"

#include "error.h"

using namespace LAMMPS_NS;

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

FixExternal::FixExternal(LAMMPS *lmp, int narg, char **arg) :

  Fix(lmp, narg, arg)

{

  if (narg != 3) error->all("Illegal fix external command");

  callback = NULL;

  nmax = 0;

  fexternal = NULL;

}

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

FixExternal::~FixExternal()

{

  memory->destroy_2d_double_array(fexternal);

}

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

int FixExternal::setmask()

{

  int mask = 0;

  mask |= POST_FORCE;

  return mask;

}

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

void FixExternal::init()

{

  if (callback == NULL) error->all("Fix external callback function not set");

}

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

void FixExternal::setup(int vflag)

{

  post_force(vflag);

}

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

void FixExternal::post_force(int vflag)

{

  if (atom->nlocal > nmax) {

    memory->destroy_2d_double_array(fexternal);

    nmax = atom->nmax;

    fexternal = memory->create_2d_double_array(nmax,3,"external:fexternal");

  }

  // invoke the callback in driver program

  // it will fill fexternal with forces

  (this->callback)(ptr_caller,update->ntimestep,

		   atom->nlocal,atom->tag,atom->x,fexternal);

  // add forces from fexternal to atoms in group

  double **f = atom->f;

  int *mask = atom->mask;

  int nlocal = atom->nlocal;

  for (int i = 0; i < nlocal; i++)

    if (mask[i] & groupbit) {

      f[i][0] += fexternal[i][0];

      f[i][1] += fexternal[i][1];

      f[i][2] += fexternal[i][2];

    }

}

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

   external caller sets a callback function to invoke in post_force()

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

void FixExternal::set_callback(FnPtr caller_callback, void *caller_ptr)

{

  callback = caller_callback;

  ptr_caller = caller_ptr;

}

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

   LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator

   http://lammps.sandia.gov, Sandia National Laboratories

   Steve Plimpton, sjplimp@sandia.gov

   Copyright (2003) Sandia Corporation.  Under the terms of Contract

   DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains

   certain rights in this software.  This software is distributed under 

   the GNU General Public License.

   See the README file in the top-level LAMMPS directory.

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

#ifdef FIX_CLASS

FixStyle(external,FixExternal)

#else

#ifndef LMP_FIX_EXTERNAL_H

#define LMP_FIX_EXTERNAL_H

#include "fix.h"

namespace LAMMPS_NS {

class FixExternal : public Fix {

 public:

  FixExternal(class LAMMPS *, int, char **);

  ~FixExternal();

  int setmask();

  void init();

  void setup(int);

  void post_force(int);

  typedef void (*FnPtr)(void *, int, int, int *, double **, double **);

  void set_callback(FnPtr, void *);

 private:

  FnPtr callback;

  void *ptr_caller;

  int nmax;

  double **fexternal;

};

}

#endif

#endif