/* ----------------------------------------------------------------------
   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_wall_region.h"

#include "atom.h"
#include "domain.h"
#include "error.h"
#include "math_const.h"
#include "math_special.h"
#include "region.h"
#include "respa.h"
#include "update.h"

#include <cmath>
#include <cstring>

using namespace LAMMPS_NS;
using namespace FixConst;
using MathConst::MY_2PI;
using MathConst::MY_SQRT2;
using MathSpecial::powint;

enum { LJ93, LJ126, LJ1043, COLLOID, HARMONIC, MORSE };

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

FixWallRegion::FixWallRegion(LAMMPS *lmp, int narg, char **arg) :
    Fix(lmp, narg, arg), idregion(nullptr), region(nullptr)
{
  if (narg < 8) utils::missing_cmd_args(FLERR, "fix wall/region", error);

  scalar_flag = 1;
  vector_flag = 1;
  size_vector = 3;
  global_freq = 1;
  extscalar = 1;
  extvector = 1;
  energy_global_flag = 1;
  virial_global_flag = virial_peratom_flag = 1;
  respa_level_support = 1;
  ilevel_respa = 0;

  // parse args

  region = domain->get_region_by_id(arg[3]);
  if (!region) error->all(FLERR, "Region {} for fix wall/region does not exist", arg[3]);
  idregion = utils::strdup(arg[3]);

  if (strcmp(arg[4], "lj93") == 0)
    style = LJ93;
  else if (strcmp(arg[4], "lj126") == 0)
    style = LJ126;
  else if (strcmp(arg[4], "lj1043") == 0)
    style = LJ1043;
  else if (strcmp(arg[4], "colloid") == 0)
    style = COLLOID;
  else if (strcmp(arg[4], "harmonic") == 0)
    style = HARMONIC;
  else if (strcmp(arg[4], "morse") == 0)
    style = MORSE;
  else
    error->all(FLERR, "Unknown fix wall/region style {}", arg[4]);

  if (style != COLLOID) dynamic_group_allow = 1;

  if (style == MORSE) {
    if (narg != 9) error->all(FLERR, "Illegal fix wall/region morse command");

    epsilon = utils::numeric(FLERR, arg[5], false, lmp);
    alpha = utils::numeric(FLERR, arg[6], false, lmp);
    sigma = utils::numeric(FLERR, arg[7], false, lmp);
    cutoff = utils::numeric(FLERR, arg[8], false, lmp);

  } else {
    if (narg != 8) error->all(FLERR, "Illegal fix wall/region command");

    epsilon = utils::numeric(FLERR, arg[5], false, lmp);
    sigma = utils::numeric(FLERR, arg[6], false, lmp);
    cutoff = utils::numeric(FLERR, arg[7], false, lmp);
  }

  if (cutoff <= 0.0) error->all(FLERR, "Fix wall/region cutoff <= 0.0");

  eflag = 0;
  ewall[0] = ewall[1] = ewall[2] = ewall[3] = 0.0;
}

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

FixWallRegion::~FixWallRegion()
{
  delete[] idregion;
}

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

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

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

void FixWallRegion::init()
{
  // set index and check validity of region

  region = domain->get_region_by_id(idregion);
  if (!region) error->all(FLERR, "Region {} for fix wall/region does not exist", idregion);

  // error checks for style COLLOID
  // ensure all particles in group are extended particles

  if (style == COLLOID) {
    if (!atom->radius_flag)
      error->all(FLERR, "Fix wall/region colloid requires atom attribute radius");

    double *radius = atom->radius;
    int *mask = atom->mask;
    int nlocal = atom->nlocal;

    int flag = 0;
    for (int i = 0; i < nlocal; i++)
      if (mask[i] & groupbit)
        if (radius[i] == 0.0) flag = 1;

    int flagall;
    MPI_Allreduce(&flag, &flagall, 1, MPI_INT, MPI_SUM, world);
    if (flagall) error->all(FLERR, "Fix wall/region colloid requires only extended particles");
  }

  // setup coefficients for each style

  if (style == LJ93) {
    coeff1 = 6.0 / 5.0 * epsilon * powint(sigma, 9);
    coeff2 = 3.0 * epsilon * powint(sigma, 3);
    coeff3 = 2.0 / 15.0 * epsilon * powint(sigma, 9);
    coeff4 = epsilon * powint(sigma, 3);
    double rinv = 1.0 / cutoff;
    double r2inv = rinv * rinv;
    double r4inv = r2inv * r2inv;
    offset = coeff3 * r4inv * r4inv * rinv - coeff4 * r2inv * rinv;
  } else if (style == LJ126) {
    coeff1 = 48.0 * epsilon * powint(sigma, 12);
    coeff2 = 24.0 * epsilon * powint(sigma, 6);
    coeff3 = 4.0 * epsilon * powint(sigma, 12);
    coeff4 = 4.0 * epsilon * powint(sigma, 6);
    double r2inv = 1.0 / (cutoff * cutoff);
    double r6inv = r2inv * r2inv * r2inv;
    offset = r6inv * (coeff3 * r6inv - coeff4);
  } else if (style == LJ1043) {
    coeff1 = MY_2PI * 2.0 / 5.0 * epsilon * powint(sigma, 10);
    coeff2 = MY_2PI * epsilon * powint(sigma, 4);
    coeff3 = MY_2PI * MY_SQRT2 / 3.0 * epsilon * powint(sigma, 3);
    coeff4 = 0.61 / MY_SQRT2 * sigma;
    coeff5 = coeff1 * 10.0;
    coeff6 = coeff2 * 4.0;
    coeff7 = coeff3 * 3.0;
    double rinv = 1.0 / cutoff;
    double r2inv = rinv * rinv;
    double r4inv = r2inv * r2inv;
    offset = coeff1 * r4inv * r4inv * r2inv - coeff2 * r4inv - coeff3 * powint(cutoff + coeff4, -3);
  } else if (style == MORSE) {
    coeff1 = 2 * epsilon * alpha;
    double alpha_dr = -alpha * (cutoff - sigma);
    offset = epsilon * (exp(2.0 * alpha_dr) - 2.0 * exp(alpha_dr));
  } else if (style == COLLOID) {
    coeff1 = -4.0 / 315.0 * epsilon * powint(sigma, 6);
    coeff2 = -2.0 / 3.0 * epsilon;
    coeff3 = epsilon * powint(sigma, 6) / 7560.0;
    coeff4 = epsilon / 6.0;
    double rinv = 1.0 / cutoff;
    double r2inv = rinv * rinv;
    double r4inv = r2inv * r2inv;
    offset = coeff3 * r4inv * r4inv * rinv - coeff4 * r2inv * rinv;
  }

  if (utils::strmatch(update->integrate_style, "^respa")) {
    ilevel_respa = (dynamic_cast<Respa *>(update->integrate))->nlevels - 1;
    if (respa_level >= 0) ilevel_respa = MIN(respa_level, ilevel_respa);
  }
}

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

void FixWallRegion::setup(int vflag)
{
  if (utils::strmatch(update->integrate_style, "^respa")) {
    auto respa = dynamic_cast<Respa *>(update->integrate);
    respa->copy_flevel_f(ilevel_respa);
    post_force_respa(vflag, ilevel_respa, 0);
    respa->copy_f_flevel(ilevel_respa);
  } else {
    post_force(vflag);
  }
}

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

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

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

void FixWallRegion::post_force(int vflag)
{
  int i, m, n;
  double rinv, fx, fy, fz, tooclose;
  double delx, dely, delz, v[6];

  double **x = atom->x;
  double **f = atom->f;
  double *radius = atom->radius;
  int *mask = atom->mask;
  int nlocal = atom->nlocal;

  region->prematch();

  int onflag = 0;

  // virial setup

  v_init(vflag);

  // region->match() ensures particle is in region or on surface, else error
  // if returned contact dist r = 0, is on surface, also an error
  // in COLLOID case, r <= radius is an error
  // initilize ewall after region->prematch(),
  //   so a dynamic region can access last timestep values

  eflag = 0;
  ewall[0] = ewall[1] = ewall[2] = ewall[3] = 0.0;

  for (i = 0; i < nlocal; i++)
    if (mask[i] & groupbit) {
      if (!region->match(x[i][0], x[i][1], x[i][2])) {
        onflag = 1;
        continue;
      }
      if (style == COLLOID)
        tooclose = radius[i];
      else
        tooclose = 0.0;

      n = region->surface(x[i][0], x[i][1], x[i][2], cutoff);

      for (m = 0; m < n; m++) {
        if (region->contact[m].r <= tooclose) {
          onflag = 1;
          continue;
        } else
          rinv = 1.0 / region->contact[m].r;

        if (style == LJ93)
          lj93(region->contact[m].r);
        else if (style == LJ126)
          lj126(region->contact[m].r);
        else if (style == LJ1043)
          lj1043(region->contact[m].r);
        else if (style == MORSE)
          morse(region->contact[m].r);
        else if (style == COLLOID)
          colloid(region->contact[m].r, radius[i]);
        else
          harmonic(region->contact[m].r);

        delx = region->contact[m].delx;
        dely = region->contact[m].dely;
        delz = region->contact[m].delz;
        fx = fwall * delx * rinv;
        fy = fwall * dely * rinv;
        fz = fwall * delz * rinv;
        f[i][0] += fx;
        f[i][1] += fy;
        f[i][2] += fz;
        ewall[1] -= fx;
        ewall[2] -= fy;
        ewall[3] -= fz;
        ewall[0] += eng;
        if (evflag) {
          v[0] = fx * delx;
          v[1] = fy * dely;
          v[2] = fz * delz;
          v[3] = fx * dely;
          v[4] = fx * delz;
          v[5] = fy * delz;
          v_tally(i, v);
        }
      }
    }

  if (onflag) error->one(FLERR, "Particle outside surface of region used in fix wall/region");
}

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

void FixWallRegion::post_force_respa(int vflag, int ilevel, int /* iloop */)
{
  if (ilevel == ilevel_respa) post_force(vflag);
}

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

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

/* ----------------------------------------------------------------------
   energy of wall interaction
------------------------------------------------------------------------- */

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

  if (eflag == 0) {
    MPI_Allreduce(ewall, ewall_all, 4, MPI_DOUBLE, MPI_SUM, world);
    eflag = 1;
  }
  return ewall_all[0];
}

/* ----------------------------------------------------------------------
   components of force on wall
------------------------------------------------------------------------- */

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

  if (eflag == 0) {
    MPI_Allreduce(ewall, ewall_all, 4, MPI_DOUBLE, MPI_SUM, world);
    eflag = 1;
  }
  return ewall_all[n + 1];
}

/* ----------------------------------------------------------------------
   LJ 9/3 interaction for particle with wall
   compute eng and fwall = magnitude of wall force
------------------------------------------------------------------------- */

void FixWallRegion::lj93(double r)
{
  double rinv = 1.0 / r;
  double r2inv = rinv * rinv;
  double r4inv = r2inv * r2inv;
  double r10inv = r4inv * r4inv * r2inv;
  fwall = coeff1 * r10inv - coeff2 * r4inv;
  eng = coeff3 * r4inv * r4inv * rinv - coeff4 * r2inv * rinv - offset;
}

/* ----------------------------------------------------------------------
   LJ 12/6 interaction for particle with wall
   compute eng and fwall = magnitude of wall force
------------------------------------------------------------------------- */

void FixWallRegion::lj126(double r)
{
  double rinv = 1.0 / r;
  double r2inv = rinv * rinv;
  double r6inv = r2inv * r2inv * r2inv;
  fwall = r6inv * (coeff1 * r6inv - coeff2) * rinv;
  eng = r6inv * (coeff3 * r6inv - coeff4) - offset;
}

/* ----------------------------------------------------------------------
   LJ 10/4/3 interaction for particle with wall
   compute eng and fwall = magnitude of wall force
------------------------------------------------------------------------- */

void FixWallRegion::lj1043(double r)
{
  double rinv = 1.0 / r;
  double r2inv = rinv * rinv;
  double r4inv = r2inv * r2inv;
  double r10inv = r4inv * r4inv * r2inv;
  fwall = coeff5 * r10inv * rinv - coeff6 * r4inv * rinv - coeff7 * powint(r + coeff4, -4);
  eng = coeff1 * r10inv - coeff2 * r4inv - coeff3 * powint(r + coeff4, -3) - offset;
}

/* ----------------------------------------------------------------------
   Morse interaction for particle with wall
   compute eng and fwall = magnitude of wall force
------------------------------------------------------------------------- */

void FixWallRegion::morse(double r)
{
  double dr = r - sigma;
  double dexp = exp(-alpha * dr);
  fwall = coeff1 * (dexp * dexp - dexp);
  eng = epsilon * (dexp * dexp - 2.0 * dexp) - offset;
}

/* ----------------------------------------------------------------------
   colloid interaction for finite-size particle of rad with wall
   compute eng and fwall = magnitude of wall force
------------------------------------------------------------------------- */

void FixWallRegion::colloid(double r, double rad)
{
  double new_coeff2 = coeff2 * rad * rad * rad;
  double diam = 2.0 * rad;

  double rad2 = rad * rad;
  double rad4 = rad2 * rad2;
  double rad8 = rad4 * rad4;
  double delta2 = rad2 - r * r;
  double rinv = 1.0 / delta2;
  double r2inv = rinv * rinv;
  double r4inv = r2inv * r2inv;
  double r8inv = r4inv * r4inv;
  fwall = coeff1 *
          (rad8 * rad + 27.0 * rad4 * rad2 * rad * r * r + 63.0 * rad4 * rad * powint(r, 4) +
           21.0 * rad2 * rad * powint(r, 6)) *
          r8inv -
      new_coeff2 * r2inv;

  double r2 = 0.5 * diam - r;
  double rinv2 = 1.0 / r2;
  double r2inv2 = rinv2 * rinv2;
  double r4inv2 = r2inv2 * r2inv2;
  double r3 = r + 0.5 * diam;
  double rinv3 = 1.0 / r3;
  double r2inv3 = rinv3 * rinv3;
  double r4inv3 = r2inv3 * r2inv3;
  eng = coeff3 *
          ((-3.5 * diam + r) * r4inv2 * r2inv2 * rinv2 +
           (3.5 * diam + r) * r4inv3 * r2inv3 * rinv3) -
      coeff4 * ((-diam * r + r2 * r3 * (log(-r2) - log(r3))) * (-rinv2) * rinv3) - offset;
}

/* ----------------------------------------------------------------------
   harmonic interaction for particle with wall
   compute eng and fwall = magnitude of wall force
------------------------------------------------------------------------- */

void FixWallRegion::harmonic(double r)
{
  double dr = cutoff - r;
  fwall = 2.0 * epsilon * dr;
  eng = epsilon * dr * dr;
}
