/* ----------------------------------------------------------------------
   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 "string.h"
#include "stdlib.h"
#include "fix_addforce.h"
#include "atom.h"
#include "update.h"
#include "domain.h"
#include "region.h"
#include "respa.h"
#include "input.h"
#include "variable.h"
#include "memory.h"
#include "error.h"

using namespace LAMMPS_NS;

enum{NONE,CONSTANT,EQUAL,ATOM};

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

FixAddForce::FixAddForce(LAMMPS *lmp, int narg, char **arg) :
  Fix(lmp, narg, arg)
{
  if (narg < 6) error->all("Illegal fix addforce command");

  scalar_flag = 1;
  vector_flag = 1;
  size_vector = 3;
  global_freq = 1;
  extscalar = 1;
  extvector = 1;

  xstr = ystr = zstr = NULL;

  if (strstr(arg[3],"v_") == arg[3]) {
    int n = strlen(&arg[3][2]) + 1;
    xstr = new char[n];
    strcpy(xstr,&arg[3][2]);
  } else {
    xvalue = atof(arg[3]);
    xstyle = CONSTANT;
  }
  if (strstr(arg[4],"v_") == arg[4]) {
    int n = strlen(&arg[4][2]) + 1;
    ystr = new char[n];
    strcpy(ystr,&arg[4][2]);
  } else {
    yvalue = atof(arg[4]);
    ystyle = CONSTANT;
  }
  if (strstr(arg[5],"v_") == arg[5]) {
    int n = strlen(&arg[5][2]) + 1;
    zstr = new char[n];
    strcpy(zstr,&arg[5][2]);
  } else {
    zvalue = atof(arg[5]);
    zstyle = CONSTANT;
  }

  // optional args

  iregion = -1;
  estr = NULL;

  int iarg = 6;
  while (iarg < narg) {
    if (strcmp(arg[iarg],"region") == 0) {
      if (iarg+2 > narg) error->all("Illegal fix addforce command");
      iregion = domain->find_region(arg[iarg+1]);
      if (iregion == -1) error->all("Fix addforce region ID does not exist");
      iarg += 2;
    } else if (strcmp(arg[iarg],"energy") == 0) {
      if (iarg+2 > narg) error->all("Illegal fix addforce command");
      int n = strlen(arg[iarg+1]) + 1;
      estr = new char[n];
      strcpy(estr,arg[iarg+1]);
      iarg += 2;
    } else error->all("Illegal fix addforce command");
  }

  force_flag = 0;
  foriginal[0] = foriginal[1] = foriginal[2] = foriginal[3] = 0.0;

  maxatom = 0;
  sforce = NULL;
}

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

FixAddForce::~FixAddForce()
{
  delete [] xstr;
  delete [] ystr;
  delete [] zstr;
  delete [] estr;
  memory->destroy_2d_double_array(sforce);
}

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

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

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

void FixAddForce::init()
{
  // check variables

  if (xstr) {
    xvar = input->variable->find(xstr);
    if (xvar < 0) error->all("Variable name for fix addforce does not exist");
    if (input->variable->equalstyle(xvar)) xstyle = EQUAL;
    else if (input->variable->atomstyle(xvar)) xstyle = ATOM;
    else error->all("Variable for fix setforce is invalid style");
  }
  if (ystr) {
    yvar = input->variable->find(ystr);
    if (yvar < 0) error->all("Variable name for fix addforce does not exist");
    if (input->variable->equalstyle(yvar)) ystyle = EQUAL;
    else if (input->variable->atomstyle(yvar)) ystyle = ATOM;
    else error->all("Variable for fix setforce is invalid style");
  }
  if (zstr) {
    zvar = input->variable->find(zstr);
    if (zvar < 0) error->all("Variable name for fix addforce does not exist");
    if (input->variable->equalstyle(zvar)) zstyle = EQUAL;
    else if (input->variable->atomstyle(zvar)) zstyle = ATOM;
    else error->all("Variable for fix setforce is invalid style");
  }
  if (estr) {
    evar = input->variable->find(estr);
    if (evar < 0) error->all("Variable name for fix addforce does not exist");
    if (input->variable->atomstyle(evar)) estyle = ATOM;
    else error->all("Variable for fix setforce is invalid style");
  } else estyle = NONE;

  if (xstyle == ATOM || ystyle == ATOM || zstyle == ATOM) 
    varflag = ATOM;
  else if (xstyle == EQUAL || ystyle == EQUAL || zstyle == EQUAL)
    varflag = EQUAL;
  else varflag = CONSTANT;

  if (varflag == CONSTANT && estyle != NONE)
    error->all("Cannot use variable energy with "
	       "constant force in fix addforce");
  if ((varflag == EQUAL || varflag == ATOM) && 
      update->whichflag == 2 && estyle == NONE)
    error->all("Must use variable energy with fix addforce");

  if (strcmp(update->integrate_style,"respa") == 0)
    nlevels_respa = ((Respa *) update->integrate)->nlevels;
}

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

void FixAddForce::setup(int vflag)
{
  if (strcmp(update->integrate_style,"verlet") == 0)
    post_force(vflag);
  else {
    ((Respa *) update->integrate)->copy_flevel_f(nlevels_respa-1);
    post_force_respa(vflag,nlevels_respa-1,0);
    ((Respa *) update->integrate)->copy_f_flevel(nlevels_respa-1);
  }
}

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

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

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

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

  // reallocate sforce array if necessary

  if ((varflag == ATOM || estyle == ATOM) && nlocal > maxatom) {
    maxatom = atom->nmax;
    memory->destroy_2d_double_array(sforce);
    sforce = memory->create_2d_double_array(maxatom,4,"addforce:sforce");
  }

  // foriginal[0] = "potential energy" for added force
  // foriginal[123] = force on atoms before extra force added

  foriginal[0] = foriginal[1] = foriginal[2] = foriginal[3] = 0.0;
  force_flag = 0;

  // constant force
  // potential energy = - x dot f

  if (varflag == CONSTANT) {
    for (int i = 0; i < nlocal; i++)
      if (mask[i] & groupbit) {
	if (iregion >= 0 && 
	    !domain->regions[iregion]->match(x[i][0],x[i][1],x[i][2]))
	  continue;
	
	foriginal[0] -= xvalue*x[i][0] + yvalue*x[i][1] + zvalue*x[i][2];
	foriginal[1] += f[i][0];
	foriginal[2] += f[i][1];
	foriginal[3] += f[i][2];
	f[i][0] += xvalue;
	f[i][1] += yvalue;
	f[i][2] += zvalue;
      }

  // variable force
  // potential energy = evar if defined, else 0.0

  } else {
    if (xstyle == EQUAL) xvalue = input->variable->compute_equal(xvar);
    else if (xstyle == ATOM)
      input->variable->compute_atom(xvar,igroup,&sforce[0][0],4,0);
    if (ystyle == EQUAL) yvalue = input->variable->compute_equal(yvar);
    else if (ystyle == ATOM) 
      input->variable->compute_atom(yvar,igroup,&sforce[0][1],4,0);
    if (zstyle == EQUAL) zvalue = input->variable->compute_equal(zvar);
    else if (zstyle == ATOM)
      input->variable->compute_atom(zvar,igroup,&sforce[0][2],4,0);
    if (estyle == ATOM)
      input->variable->compute_atom(evar,igroup,&sforce[0][3],4,0);

    for (int i = 0; i < nlocal; i++)
      if (mask[i] & groupbit) {
	if (iregion >= 0 && 
	    !domain->regions[iregion]->match(x[i][0],x[i][1],x[i][2]))
	  continue;
	
	if (estyle == ATOM) foriginal[0] += sforce[i][3];
	foriginal[1] += f[i][0];
	foriginal[2] += f[i][1];
	foriginal[3] += f[i][2];
	if (xstyle == ATOM) f[i][0] += sforce[i][0];
	else if (xstyle) f[i][0] += xvalue;
	if (ystyle == ATOM) f[i][1] += sforce[i][1];
	else if (ystyle) f[i][1] += yvalue;
	if (zstyle == ATOM) f[i][2] += sforce[i][2];
	else if (zstyle) f[i][2] += zvalue;
      }
  }
}

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

void FixAddForce::post_force_respa(int vflag, int ilevel, int iloop)
{
  if (ilevel == nlevels_respa-1) post_force(vflag);
}

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

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

/* ----------------------------------------------------------------------
   potential energy of added force
------------------------------------------------------------------------- */

double FixAddForce::compute_scalar()
{
  // only sum across procs one time

  if (force_flag == 0) {
    MPI_Allreduce(foriginal,foriginal_all,4,MPI_DOUBLE,MPI_SUM,world);
    force_flag = 1;
  }
  return foriginal_all[0];
}

/* ----------------------------------------------------------------------
   return components of total force on fix group before force was changed
------------------------------------------------------------------------- */

double FixAddForce::compute_vector(int n)
{
  // only sum across procs one time

  if (force_flag == 0) {
    MPI_Allreduce(foriginal,foriginal_all,4,MPI_DOUBLE,MPI_SUM,world);
    force_flag = 1;
  }
  return foriginal_all[n+1];
}

/* ----------------------------------------------------------------------
   memory usage of local atom-based array
------------------------------------------------------------------------- */

double FixAddForce::memory_usage()
{
  double bytes = 0.0;
  if (varflag == ATOM) bytes = atom->nmax*4 * sizeof(double);
  return bytes;
}