/* ----------------------------------------------------------------------
   LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
   https://www.lammps.org/, Sandia National Laboratories
   LAMMPS development team: developers@lammps.org

   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 "fix_lineforce.h"

#include "atom.h"
#include "error.h"
#include "respa.h"
#include "update.h"

#include <cmath>

using namespace LAMMPS_NS;
using namespace FixConst;

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

FixLineForce::FixLineForce(LAMMPS *lmp, int narg, char **arg) : Fix(lmp, narg, arg)
{
  dynamic_group_allow = 1;

  if (narg != 6) error->all(FLERR, "Illegal fix lineforce command");
  xdir = utils::numeric(FLERR, arg[3], false, lmp);
  ydir = utils::numeric(FLERR, arg[4], false, lmp);
  zdir = utils::numeric(FLERR, arg[5], false, lmp);

  double len = sqrt(xdir * xdir + ydir * ydir + zdir * zdir);
  if (len == 0.0) error->all(FLERR, "Illegal fix lineforce command");

  xdir /= len;
  ydir /= len;
  zdir /= len;
}

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

int FixLineForce::setmask()
{
  int mask = 0;
  mask |= POST_FORCE;
  mask |= POST_FORCE_RESPA;
  mask |= MIN_POST_FORCE;
  return mask;
}

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

void FixLineForce::setup(int vflag)
{
  if (utils::strmatch(update->integrate_style, "^verlet"))
    post_force(vflag);
  else {
    int nlevels_respa = (dynamic_cast<Respa *>(update->integrate))->nlevels;
    for (int ilevel = 0; ilevel < nlevels_respa; ilevel++) {
      (dynamic_cast<Respa *>(update->integrate))->copy_flevel_f(ilevel);
      post_force_respa(vflag, ilevel, 0);
      (dynamic_cast<Respa *>(update->integrate))->copy_f_flevel(ilevel);
    }
  }
}

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

void FixLineForce::min_setup(int vflag)
{
  post_force(vflag);
}

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

void FixLineForce::post_force(int /*vflag*/)
{
  double **f = atom->f;
  int *mask = atom->mask;
  int nlocal = atom->nlocal;

  double dot;
  for (int i = 0; i < nlocal; i++)
    if (mask[i] & groupbit) {
      dot = f[i][0] * xdir + f[i][1] * ydir + f[i][2] * zdir;
      f[i][0] = dot * xdir;
      f[i][1] = dot * ydir;
      f[i][2] = dot * zdir;
    }
}

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

void FixLineForce::post_force_respa(int vflag, int /*ilevel*/, int /*iloop*/)
{
  post_force(vflag);
}

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

void FixLineForce::min_post_force(int vflag)
{
  post_force(vflag);
}