/*******************************************************************************
 * 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_BLACK_HOLES_H
#define SWIFT_DEFAULT_BLACK_HOLES_H

#include <float.h>

/* Local includes */
#include "black_holes_properties.h"
#include "black_holes_struct.h"
#include "dimension.h"
#include "kernel_hydro.h"
#include "minmax.h"

/**
 * @brief Computes the gravity time-step of a given black hole particle.
 *
 * @param bp Pointer to the s-particle data.
 */
__attribute__((always_inline)) INLINE static float black_holes_compute_timestep(
    const struct bpart* const bp) {

  return FLT_MAX;
}

/**
 * @brief Initialises the b-particles for the first time
 *
 * This function is called only once just after the ICs have been
 * read in to do some conversions.
 *
 * @param bp The particle to act upon
 * @param props The properties of the black holes model.
 */
__attribute__((always_inline)) INLINE static void black_holes_first_init_bpart(
    struct bpart* bp, const struct black_holes_props* props) {

  bp->time_bin = 0;
}

/**
 * @brief Prepares a b-particle for its interactions
 *
 * @param bp The particle to act upon
 */
__attribute__((always_inline)) INLINE static void black_holes_init_bpart(
    struct bpart* bp) {

#ifdef DEBUG_INTERACTIONS_BLACK_HOLES
  for (int i = 0; i < MAX_NUM_OF_NEIGHBOURS_STARS; ++i)
    bp->ids_ngbs_density[i] = -1;
  bp->num_ngb_density = 0;
#endif

  bp->density.wcount = 0.f;
  bp->density.wcount_dh = 0.f;
}

/**
 * @brief Predict additional particle fields forward in time when drifting
 *
 * @param bp The particle
 * @param dt_drift The drift time-step for positions.
 */
__attribute__((always_inline)) INLINE static void black_holes_predict_extra(
    struct bpart* restrict bp, float dt_drift) {}

/**
 * @brief Sets the values to be predicted in the drifts to their values at a
 * kick time
 *
 * @param bp The particle.
 */
__attribute__((always_inline)) INLINE static void
black_holes_reset_predicted_values(struct bpart* restrict bp) {}

/**
 * @brief Kick the additional variables
 *
 * @param bp The particle to act upon
 * @param dt The time-step for this kick
 */
__attribute__((always_inline)) INLINE static void black_holes_kick_extra(
    struct bpart* bp, float dt) {}

/**
 * @brief Finishes the calculation of density on black holes
 *
 * @param bp The particle to act upon
 * @param cosmo The current cosmological model.
 */
__attribute__((always_inline)) INLINE static void black_holes_end_density(
    struct bpart* bp, const struct cosmology* cosmo) {

  /* Some smoothing length multiples. */
  const float h = bp->h;
  const float h_inv = 1.0f / h;                       /* 1/h */
  const float h_inv_dim = pow_dimension(h_inv);       /* 1/h^d */
  const float h_inv_dim_plus_one = h_inv_dim * h_inv; /* 1/h^(d+1) */

  /* Finish the calculation by inserting the missing h-factors */
  bp->density.wcount *= h_inv_dim;
  bp->density.wcount_dh *= h_inv_dim_plus_one;
}

/**
 * @brief Sets all particle fields to sensible values when the #spart has 0
 * ngbs.
 *
 * @param bp The particle to act upon
 * @param cosmo The current cosmological model.
 */
__attribute__((always_inline)) INLINE static void
black_holes_bpart_has_no_neighbours(struct bpart* restrict bp,
                                    const struct cosmology* cosmo) {

  /* Some smoothing length multiples. */
  const float h = bp->h;
  const float h_inv = 1.0f / h;                 /* 1/h */
  const float h_inv_dim = pow_dimension(h_inv); /* 1/h^d */

  /* Re-set problematic values */
  bp->density.wcount = kernel_root * h_inv_dim;
  bp->density.wcount_dh = 0.f;
}

/**
 * @brief Update the properties of a black hole particles by swallowing
 * a gas particle.
 *
 * @param bp The #bpart to update.
 * @param p The #part that is swallowed.
 * @param xp The #xpart that is swallowed.
 * @param cosmo The current cosmological model.
 */
__attribute__((always_inline)) INLINE static void black_holes_swallow_part(
    struct bpart* bp, const struct part* p, const struct xpart* xp,
    const struct cosmology* cosmo) {

  /* Nothing to do here: No swallowing in the default model */
}

/**
 * @brief Update the properties of a black hole particles by swallowing
 * a BH particle.
 *
 * @param bpi The #bpart to update.
 * @param bpj The #bpart that is swallowed.
 * @param cosmo The current cosmological model.
 */
__attribute__((always_inline)) INLINE static void black_holes_swallow_bpart(
    struct bpart* bpi, const struct bpart* bpj, const struct cosmology* cosmo) {

  /* Nothing to do here: No merging in the default model */
}

/**
 * @brief Compute the accretion rate of the black hole and all the quantites
 * required for the feedback loop.
 *
 * Nothing to do here.
 *
 * @param bp The black hole particle.
 * @param props The properties of the black hole scheme.
 * @param constants The physical constants (in internal units).
 * @param cosmo The cosmological model.
 * @param dt The time-step size (in physical internal units).
 */
__attribute__((always_inline)) INLINE static void black_holes_prepare_feedback(
    struct bpart* restrict bp, const struct black_holes_props* props,
    const struct phys_const* constants, const struct cosmology* cosmo,
    const double dt) {}

/**
 * @brief Reset acceleration fields of a particle
 *
 * This is the equivalent of hydro_reset_acceleration.
 * We do not compute the acceleration on black hole, therefore no need to use
 * it.
 *
 * @param bp The particle to act upon
 */
__attribute__((always_inline)) INLINE static void black_holes_reset_feedback(
    struct bpart* restrict bp) {

#ifdef DEBUG_INTERACTIONS_BLACK_HOLES
  for (int i = 0; i < MAX_NUM_OF_NEIGHBOURS_STARS; ++i)
    bp->ids_ngbs_force[i] = -1;
  bp->num_ngb_force = 0;
#endif
}

/**
 * @brief Initialise a BH particle that has just been seeded.
 *
 * @param bp The #bpart to initialise.
 * @param props The properties of the black hole scheme.
 * @param constants The physical constants in internal units.
 * @param cosmo The current cosmological model.
 * @param p The #part that became a black hole.
 */
INLINE static void black_holes_create_from_gas(
    struct bpart* bp, const struct black_holes_props* props,
    const struct phys_const* constants, const struct cosmology* cosmo,
    const struct part* p) {

  /* First initialisation */
  black_holes_init_bpart(bp);
}

#endif /* SWIFT_DEFAULT_BLACK_HOLES_H */
