/*
  This file is part of p4est.
  p4est is a C library to manage a collection (a forest) of multiple
  connected adaptive quadtrees or octrees in parallel.

  Copyright (C) 2010 The University of Texas System
  Written by Carsten Burstedde, Lucas C. Wilcox, and Tobin Isaac

  p4est is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation; either version 2 of the License, or
  (at your option) any later version.

  p4est 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 General Public License
  along with p4est; if not, write to the Free Software Foundation, Inc.,
  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/

/** \file p4est_iterate.h
 *
 * Iteration over mesh topology via callbacks
 *
 * \ingroup p4est
 */

#ifndef P4EST_ITERATE_H
#define P4EST_ITERATE_H

#include <p4est.h>
#include <p4est_ghost.h>

SC_EXTERN_C_BEGIN;

/** The information that is available to the user-defined p4est_iter_volume_t
 * callback function.
 *
 * \a treeid gives the index in \a p4est->trees of the tree to which
 *    \a quad belongs.
 * \a quadid gives the index of \a quad within \a tree's quadrants array.
 */
typedef struct p4est_iter_volume_info
{
  p4est_t            *p4est;
  p4est_ghost_t      *ghost_layer;
  p4est_quadrant_t   *quad;    /**< the quadrant of the callback */
  p4est_locidx_t      quadid;  /**< id in \a quad's tree array (see
                                    p4est_tree_t) */
  p4est_topidx_t      treeid;  /**< the tree containing \a quad */
}
p4est_iter_volume_info_t;

/** The prototype for a function that p4est_iterate will execute at every
 * quadrant local to the current process.
 * \param [in] info          information about a quadrant provided to the user
 * \param [in,out] user_data the user context passed to p4est_iterate()
 */
typedef void        (*p4est_iter_volume_t) (p4est_iter_volume_info_t * info,
                                            void *user_data);

/** Information about one side of a face in the forest.
 *
 * If a \a quad is local
 * (\a is_ghost is false), then its \a quadid indexes the tree's quadrant
 * array; otherwise, it indexes the ghosts array. If the face is hanging, then
 * the quadrants are listed in z-order.  If a quadrant should be present, but
 * it is not included in the ghost layer, then quad = NULL, is_ghost is true,
 * and quadid = -1.
 */
typedef struct p4est_iter_face_side
{
  p4est_topidx_t      treeid;          /**< the tree on this side */
  int8_t              face;            /**< which quadrant side the face
                                            touches */
  int8_t              is_hanging;      /**< boolean: one full quad (0) or
                                            two smaller quads (1) */
  union p4est_iter_face_side_data
  {
    struct
    {
      int8_t              is_ghost;    /**< boolean: local (0) or ghost (1) */
      p4est_quadrant_t   *quad;        /**< the actual quadrant */
      p4est_locidx_t      quadid;      /**< index in tree or ghost array */
    }
    full; /**< if \a is_hanging = 0,
               use is.full to access per-quadrant data */
    struct
    {
      int8_t              is_ghost[2]; /**< boolean: local (0) or ghost (1) */
      p4est_quadrant_t   *quad[2];     /**< the actual quadrant */
      p4est_locidx_t      quadid[2];   /**< index in tree or ghost array */
    }
    hanging; /**< if \a is_hanging = 1,
                  use is.hanging to access per-quadrant data */
  }
  is;
}
p4est_iter_face_side_t;

/** The information that is available to the user-defined p4est_iter_face_t
 * callback.
 *
 * The orientation is 0 if the face is within one tree; otherwise, it is the
 * same as the orientation value between the two trees given in the
 * connectivity.  If the face is on the outside boundary of the forest, then
 * there is only one side.  If tree_boundary is false, the face is on the
 * interior of a tree.  When tree_boundary is false, sides[0] contains the
 * lowest z-order quadrant that touches the face.
 * When tree_boundary is true, its value is P4EST_CONNECT_FACE.
 */
typedef struct p4est_iter_face_info
{
  p4est_t            *p4est;
  p4est_ghost_t      *ghost_layer;
  int8_t              orientation; /**< the orientation of the sides to each
                                        other, as in the definition of
                                        p4est_connectivity_t */
  int8_t              tree_boundary; /**< boolean: interior face (0),
                                          boundary face (1) */
  sc_array_t          sides;    /* array of p4est_iter_face_side_t type */
}
p4est_iter_face_info_t;

/** The prototype for a function that p4est_iterate will execute wherever two
 * quadrants share a face: the face can be a 2:1 hanging face, it does not have
 * to be conformal.
 *
 * \param [in] info          information about a quadrant provided to the user
 * \param [in,out] user_data the user context passed to p4est_iterate()
 *
 * \note the forest must be face balanced for p4est_iterate() to execute a
 * callback function on faces (see p4est_balance()).
 */
typedef void        (*p4est_iter_face_t) (p4est_iter_face_info_t * info,
                                          void *user_data);

/** Information about one side of a corner in the forest.  If a \a quad is local
 * (\a is_ghost is false), then its \a quadid indexes the tree's quadrant array;
 * otherwise, it indexes the ghosts array. If a quadrant should be present, but
 * it is not included in the ghost layer, then quad = NULL, is_ghost is true,
 * and quadid = -1.
 *
 * the \a faces field provides some additional information about the local
 * topology: if side[i]->faces[j] == side[k]->faces[l], this indicates that
 * there is a common face between these two sides of the corner.
 */
typedef struct p4est_iter_corner_side
{
  p4est_topidx_t      treeid;   /**< the tree that contains \a quad */
  int8_t              corner;   /**< which of the quadrant's corners touches
                                     this corner */
  int8_t              is_ghost; /**< boolean: local (0) or ghost (1) */
  p4est_quadrant_t   *quad;
  p4est_locidx_t      quadid;   /**< the index in the tree or ghost array */
  int8_t              faces[2]; /**< internal work data */
}
p4est_iter_corner_side_t;

/** The information that is available to the user-defined p4est_iter_corner_t
 * callback.
 *
 * If tree_boundary is false, the corner is on the interior of a tree.
 * When tree_boundary is false, sides[0] contains the lowest z-order quadrant
 * that touches the corner.
 * When tree_boundary is true, its value is P4EST_CONNECT_FACE/CORNER
 * depending on the location of the corner relative to the tree.
 */
typedef struct p4est_iter_corner_info
{
  p4est_t            *p4est;
  p4est_ghost_t      *ghost_layer;
  int8_t              tree_boundary; /**< boolean: interior face (0),
                                           boundary face (1) */
  sc_array_t          sides; /**< array of type p4est_iter_corner_side_t type */
}
p4est_iter_corner_info_t;

/** The prototype for a function that p4est_iterate will execute wherever
 * quadrants meet at a conformal corner
 *
 * i.e. the callback will not execute on a hanging corner.
 *
 * \param [in] info          information about a quadrant provided to the user
 * \param [in,out] user_data the user context passed to p4est_iterate()
 *
 * \note the forest does not need to be corner balanced for p4est_iterate() to
 * correctly execute a callback function at corners, only face balanced (see
 * p4est_balance()).
 */
typedef void        (*p4est_iter_corner_t) (p4est_iter_corner_info_t * info,
                                            void *user_data);

/** Execute user supplied callbacks at every volume, face, and corner in the
 * local forest.
 *
 * p4est_iterate executes the user-supplied callback functions at every
 * volume, face, and corner in the local forest. The ghost_layer may be NULL.
 * The \a user_data pointer is not touched by p4est_iterate, but is passed to
 * each of the callbacks.  Any of the callbacks may be NULL.
 * The callback functions are interspersed with each other, i.e. some face
 * callbacks will occur between volume callbacks, and some corner callbacks
 * will occur between face callbacks:
 *
 * 1) volume callbacks occur in the sorted Morton-index order.
 * 2) a face callback is not executed until after the volume callbacks have
 *    been executed for the quadrants that share it.
 * 3) a corner callback is not executed until the face callbacks have been
 *    executed for all faces that touch the corner.
 * 4) it is not always the case that every face callback for a given quadrant
 *    is executed before any of the corner callbacks.
 * 5) callbacks are not executed at faces or corners that only involve ghost
 *    quadrants, i.e. that are not adjacent in the local section of the
 *    forest.
 *
 * \param[in] p4est          the forest
 * \param[in] ghost_layer    optional: when not given, callbacks at the
 *                           boundaries of the local partition cannot provide
 *                           quadrant data about ghost quadrants: missing
 *                           (p4est_quadrant_t *) pointers are set to NULL,
 *                           missing indices are set to -1.
 * \param[in,out] user_data  optional context to supply to each callback
 * \param[in] iter_volume    callback function for every quadrant's interior
 * \param[in] iter_face      callback function for every face between
 *                           quadrants
 * \param[in] iter_corner    callback function for every corner between
 *                           quadrants
 */
void                p4est_iterate (p4est_t * p4est,
                                   p4est_ghost_t * ghost_layer,
                                   void *user_data,
                                   p4est_iter_volume_t iter_volume,
                                   p4est_iter_face_t iter_face,
                                   p4est_iter_corner_t iter_corner);

/** Return a pointer to a iter_corner_side array element indexed by a int.
 */
/*@unused@*/
static inline p4est_iter_corner_side_t *
p4est_iter_cside_array_index_int (sc_array_t * array, int it)
{
  P4EST_ASSERT (array->elem_size == sizeof (p4est_iter_corner_side_t));
  P4EST_ASSERT (it >= 0 && (size_t) it < array->elem_count);

  return (p4est_iter_corner_side_t *)
    (array->array + sizeof (p4est_iter_corner_side_t) * it);
}

/** Return a pointer to a iter_corner_side array element indexed by a size_t.
 */
/*@unused@*/
static inline p4est_iter_corner_side_t *
p4est_iter_cside_array_index (sc_array_t * array, size_t it)
{
  P4EST_ASSERT (array->elem_size == sizeof (p4est_iter_corner_side_t));
  P4EST_ASSERT (it < array->elem_count);

  return (p4est_iter_corner_side_t *)
    (array->array + sizeof (p4est_iter_corner_side_t) * it);
}

/** Return a pointer to a iter_face_side array element indexed by a int.
 */
/*@unused@*/
static inline p4est_iter_face_side_t *
p4est_iter_fside_array_index_int (sc_array_t * array, int it)
{
  P4EST_ASSERT (array->elem_size == sizeof (p4est_iter_face_side_t));
  P4EST_ASSERT (it >= 0 && (size_t) it < array->elem_count);

  return (p4est_iter_face_side_t *)
    (array->array + sizeof (p4est_iter_face_side_t) * it);
}

/** Return a pointer to a iter_face_side array element indexed by a size_t.
 */
/*@unused@*/
static inline p4est_iter_face_side_t *
p4est_iter_fside_array_index (sc_array_t * array, size_t it)
{
  P4EST_ASSERT (array->elem_size == sizeof (p4est_iter_face_side_t));
  P4EST_ASSERT (it < array->elem_count);

  return (p4est_iter_face_side_t *)
    (array->array + sizeof (p4est_iter_face_side_t) * it);
}

SC_EXTERN_C_END;

#endif /* !P4EST_ITERATE_H */
