/* -*- c++ -*---------------------------------------------------------------
   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.
------------------------------------------------------------------------- */
/* ----------------------------------------------------------------------
   Contributing author:  Axel Kohlmeyer (Temple U)
------------------------------------------------------------------------- */

#include "ndx2group.h"

#include "atom.h"
#include "comm.h"
#include "error.h"
#include "group.h"
#include "tokenizer.h"

#include <exception>

using namespace LAMMPS_NS;
static constexpr int BUFLEN = 4096;

// read file until next section "name" or any next section if name == ""

static std::string find_section(FILE *fp, const std::string &name)
{
  char linebuf[BUFLEN];

  if (!fgets(linebuf, BUFLEN, fp)) throw TokenizerException("Read error", utils::getsyserror());
  while (!feof(fp)) {
    if (utils::strmatch(linebuf, "^\\s*\\[.*\\]\\s*$")) {
      auto words = Tokenizer(linebuf).as_vector();
      if (words.size() != 3)
        throw TokenizerException("Invalid group name in index file",
                                 utils::trim(utils::strfind(linebuf, "[^\\[^\\]]+")));
      if (name.empty() || (name == words[1])) return words[1];
    }
    fgets(linebuf, BUFLEN, fp);
  }
  return "";
}

static std::vector<tagint> read_section(FILE *fp, std::string &name)
{
  char linebuf[BUFLEN];
  std::vector<tagint> tagbuf;

  while (fgets(linebuf, BUFLEN, fp)) {
    // start of new section. we are done, update "name"
    if (utils::strmatch(linebuf, "^\\s*\\[.*\\]\\s*$")) {
      auto words = Tokenizer(linebuf).as_vector();
      if (words.size() != 3)
        throw TokenizerException("Invalid group name in index file",
                                 utils::trim(utils::strfind(linebuf, "[^\\[^\\]]+")));
      name = words[1];
      return tagbuf;
    }
    ValueTokenizer values(linebuf);
    while (values.has_next()) tagbuf.push_back(values.next_tagint());
  }
  // set empty name to indicate end of file
  name = "";
  return tagbuf;
}

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

void Ndx2Group::command(int narg, char **arg)
{
  int len;
  bigint num;
  FILE *fp;
  std::string name, next;

  if (narg < 1) utils::missing_cmd_args(FLERR, "ndx2group", error);
  if (atom->tag_enable == 0) error->all(FLERR, "Must have atom IDs for ndx2group command");
  if (atom->map_style == Atom::MAP_NONE)
    error->all(FLERR, "Must have an atom map for ndx2group command");
  if (comm->me == 0) {
    fp = fopen(arg[0], "r");
    if (fp == nullptr)
      error->one(FLERR, "Cannot open index file for reading: {}", utils::getsyserror());
    utils::logmesg(lmp, "Reading groups from index file {}:\n", arg[0]);
  }

  if (narg == 1) {    // restore all groups

    if (comm->me == 0) {
      try {
        name = find_section(fp, "");
      } catch (std::exception &e) {
        error->one(FLERR, e.what());
      }

      while (!name.empty()) {
        // skip over group "all", which is called "System" in gromacs
        if (name == "System") {
          try {
            name = find_section(fp, "");
          } catch (std::exception &e) {
            error->one(FLERR, e.what());
          }
          continue;
        }

        utils::logmesg(lmp, " Processing group '{}'\n", name);
        len = name.size() + 1;
        MPI_Bcast(&len, 1, MPI_INT, 0, world);
        if (len > 1) {
          MPI_Bcast((void *) name.c_str(), len, MPI_CHAR, 0, world);

          // read tags for atoms in group and broadcast
          std::vector<tagint> tags;
          try {
            tags = read_section(fp, next);
          } catch (std::exception &e) {
            error->one(FLERR, e.what());
          }
          num = tags.size();
          MPI_Bcast(&num, 1, MPI_LMP_BIGINT, 0, world);
          MPI_Bcast((void *) tags.data(), num, MPI_LMP_TAGINT, 0, world);
          create(name, tags);
          name = next;
        }
      }
      len = -1;
      MPI_Bcast(&len, 1, MPI_INT, 0, world);

    } else {

      while (true) {
        MPI_Bcast(&len, 1, MPI_INT, 0, world);
        if (len < 0) break;
        if (len > 1) {
          char *buf = new char[len];
          MPI_Bcast(buf, len, MPI_CHAR, 0, world);
          MPI_Bcast(&num, 1, MPI_LMP_BIGINT, 0, world);
          auto *tbuf = new tagint[num];
          MPI_Bcast(tbuf, num, MPI_LMP_TAGINT, 0, world);
          create(buf, std::vector<tagint>(tbuf, tbuf + num));
          delete[] buf;
          delete[] tbuf;
        }
      }
    }

  } else {    // restore selected groups

    for (int idx = 1; idx < narg; ++idx) {
      if (comm->me == 0) {

        // find named section, search from beginning of file
        rewind(fp);
        try {
          name = find_section(fp, arg[idx]);
        } catch (std::exception &e) {
          error->one(FLERR, e.what());
        }
        utils::logmesg(lmp, " {} group '{}'\n", name.size() ? "Processing" : "Skipping", arg[idx]);
        len = name.size() + 1;
        MPI_Bcast(&len, 1, MPI_INT, 0, world);
        if (len > 1) {
          MPI_Bcast((void *) name.c_str(), len, MPI_CHAR, 0, world);

          // read tags for atoms in group and broadcast
          std::vector<tagint> tags;
          try {
            tags = read_section(fp, next);
          } catch (std::exception &e) {
            error->one(FLERR, e.what());
          }
          num = tags.size();
          MPI_Bcast(&num, 1, MPI_LMP_BIGINT, 0, world);
          MPI_Bcast((void *) tags.data(), num, MPI_LMP_TAGINT, 0, world);
          create(name, tags);
          name = next;
        }
      } else {
        MPI_Bcast(&len, 1, MPI_INT, 0, world);
        if (len > 1) {
          char *buf = new char[len];
          MPI_Bcast(buf, len, MPI_CHAR, 0, world);
          MPI_Bcast(&num, 1, MPI_LMP_BIGINT, 0, world);
          auto *tbuf = new tagint[num];
          MPI_Bcast(tbuf, num, MPI_LMP_TAGINT, 0, world);
          create(buf, std::vector<tagint>(tbuf, tbuf + num));
          delete[] buf;
          delete[] tbuf;
        }
      }
    }
  }
  if (comm->me == 0) fclose(fp);
}

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

void Ndx2Group::create(const std::string &name, const std::vector<tagint> &tags)
{
  // wipe out all members if the group exists. gid==0 is group "all"
  int gid = group->find(name);
  if (gid > 0) group->assign(name + " clear");

  // map from global to local
  const int nlocal = atom->nlocal;
  int *flags = (int *) calloc(nlocal, sizeof(int));
  for (bigint i = 0; i < (int) tags.size(); ++i) {
    const int id = atom->map(tags[i]);
    if (id < nlocal && id >= 0) flags[id] = 1;
  }
  group->create(name, flags);
  free(flags);
}
