/*******************************************************************************
 * This file is part of SWIFT.
 * Coypright (c) 2016 Matthieu Schaller (matthieu.schaller@durham.ac.uk)
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published
 * by the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 ******************************************************************************/
#ifndef SWIFT_DEFAULT_GRAVITY_IO_H
#define SWIFT_DEFAULT_GRAVITY_IO_H

#include "io_properties.h"
#include "kick.h"

INLINE static void convert_gpart_pos(const struct engine* e,
                                     const struct gpart* gp, double ret[3]) {

  const struct space* s = e->s;
  if (s->periodic) {
    ret[0] = box_wrap(gp->x[0], 0.0, s->dim[0]);
    ret[1] = box_wrap(gp->x[1], 0.0, s->dim[1]);
    ret[2] = box_wrap(gp->x[2], 0.0, s->dim[2]);
  } else {
    ret[0] = gp->x[0];
    ret[1] = gp->x[1];
    ret[2] = gp->x[2];
  }
}

INLINE static void convert_gpart_vel(const struct engine* e,
                                     const struct gpart* gp, float ret[3]) {

  const int with_cosmology = (e->policy & engine_policy_cosmology);
  const struct cosmology* cosmo = e->cosmology;
  const integertime_t ti_current = e->ti_current;
  const double time_base = e->time_base;
  const float dt_kick_grav_mesh = e->dt_kick_grav_mesh_for_io;

  const integertime_t ti_beg = get_integer_time_begin(ti_current, gp->time_bin);
  const integertime_t ti_end = get_integer_time_end(ti_current, gp->time_bin);

  /* Get time-step since the last kick */
  const float dt_kick_grav =
      kick_get_grav_kick_dt(ti_beg, ti_current, time_base, with_cosmology,
                            cosmo) -
      kick_get_grav_kick_dt(ti_beg, (ti_beg + ti_end) / 2, time_base,
                            with_cosmology, cosmo);

  /* Extrapolate the velocites to the current time */
  ret[0] = gp->v_full[0] + gp->a_grav[0] * dt_kick_grav;
  ret[1] = gp->v_full[1] + gp->a_grav[1] * dt_kick_grav;
  ret[2] = gp->v_full[2] + gp->a_grav[2] * dt_kick_grav;

  /* Extrapolate the velocites to the current time (mesh forces) */
  ret[0] += gp->a_grav_mesh[0] * dt_kick_grav_mesh;
  ret[1] += gp->a_grav_mesh[1] * dt_kick_grav_mesh;
  ret[2] += gp->a_grav_mesh[2] * dt_kick_grav_mesh;

  /* Conversion from internal units to peculiar velocities */
  ret[0] *= cosmo->a_inv;
  ret[1] *= cosmo->a_inv;
  ret[2] *= cosmo->a_inv;
}

/**
 * @brief Specifies which g-particle fields to read from a dataset
 *
 * @param gparts The g-particle array.
 * @param list The list of i/o properties to read.
 * @param num_fields The number of i/o fields to read.
 */
INLINE static void darkmatter_read_particles(struct gpart* gparts,
                                             struct io_props* list,
                                             int* num_fields) {

  /* Say how much we want to read */
  *num_fields = 4;

  /* List what we want to read */
  list[0] = io_make_input_field("Coordinates", DOUBLE, 3, COMPULSORY,
                                UNIT_CONV_LENGTH, gparts, x);
  list[1] = io_make_input_field("Velocities", FLOAT, 3, COMPULSORY,
                                UNIT_CONV_SPEED, gparts, v_full);
  list[2] = io_make_input_field("Masses", FLOAT, 1, COMPULSORY, UNIT_CONV_MASS,
                                gparts, mass);
  list[3] = io_make_input_field("ParticleIDs", ULONGLONG, 1, COMPULSORY,
                                UNIT_CONV_NO_UNITS, gparts, id_or_neg_offset);
}

/**
 * @brief Specifies which g-particle fields to write to a dataset
 *
 * @param gparts The g-particle array.
 * @param list The list of i/o properties to write.
 * @param num_fields The number of i/o fields to write.
 */
INLINE static void darkmatter_write_particles(const struct gpart* gparts,
                                              struct io_props* list,
                                              int* num_fields) {

  /* Say how much we want to write */
  *num_fields = 4;

  /* List what we want to write */
  list[0] = io_make_output_field_convert_gpart(
      "Coordinates", DOUBLE, 3, UNIT_CONV_LENGTH, 1.f, gparts,
      convert_gpart_pos, "Co-moving position of the particles");

  list[1] = io_make_output_field_convert_gpart(
      "Velocities", FLOAT, 3, UNIT_CONV_SPEED, 0.f, gparts, convert_gpart_vel,
      "Peculiar velocities of the stars. This is a * dx/dt where x is the "
      "co-moving position of the particles.");

  list[2] = io_make_output_field("Masses", FLOAT, 1, UNIT_CONV_MASS, 0.f,
                                 gparts, mass, "Masses of the particles");

  list[3] = io_make_output_field(
      "ParticleIDs", ULONGLONG, 1, UNIT_CONV_NO_UNITS, 0.f, gparts,
      id_or_neg_offset, "Unique ID of the particles");
}

#endif /* SWIFT_DEFAULT_GRAVITY_IO_H */
