/* SPDX-License-Identifier: GPL-2.0-or-later */

/** \file
 * \ingroup bmesh
 *
 * Fill in geometry with the attributes of their adjacent data.
 */

#include "BLI_linklist_stack.h"
#include "BLI_utildefines.h"

#include "bmesh.h"

#include "intern/bmesh_operators_private.h" /* own include */

/**
 * Check if all other loops are tagged.
 */
static bool bm_loop_is_all_radial_tag(BMLoop *l)
{
  BMLoop *l_iter;
  l_iter = l->radial_next;
  do {
    if (BM_elem_flag_test(l_iter->f, BM_ELEM_TAG) == 0) {
      return false;
    }
  } while ((l_iter = l_iter->radial_next) != l);

  return true;
}

/**
 * Callback to run on source-loops for #BM_face_copy_shared
 */
static bool bm_loop_is_face_untag(const BMLoop *l, void *UNUSED(user_data))
{
  return (BM_elem_flag_test(l->f, BM_ELEM_TAG) == 0);
}

/**
 * Copy all attributes from adjacent untagged faces.
 */
static void bm_face_copy_shared_all(BMesh *bm,
                                    BMLoop *l,
                                    const bool use_normals,
                                    const bool use_data)
{
  BMLoop *l_other = l->radial_next;
  BMFace *f = l->f, *f_other;
  while (BM_elem_flag_test(l_other->f, BM_ELEM_TAG)) {
    l_other = l_other->radial_next;
  }
  f_other = l_other->f;

  if (use_data) {
    /* copy face-attrs */
    BM_elem_attrs_copy(bm, bm, f_other, f);

    /* copy loop-attrs */
    BM_face_copy_shared(bm, f, bm_loop_is_face_untag, NULL);
  }

  if (use_normals) {
    /* copy winding (flipping) */
    if (l->v == l_other->v) {
      BM_face_normal_flip(bm, f);
    }
  }
}

/**
 * Flood fill attributes.
 */
static uint bmesh_face_attribute_fill(BMesh *bm, const bool use_normals, const bool use_data)
{
  BLI_LINKSTACK_DECLARE(loop_queue_prev, BMLoop *);
  BLI_LINKSTACK_DECLARE(loop_queue_next, BMLoop *);

  BMFace *f;
  BMIter iter;
  BMLoop *l;

  uint face_tot = 0;

  BLI_LINKSTACK_INIT(loop_queue_prev);
  BLI_LINKSTACK_INIT(loop_queue_next);

  BM_ITER_MESH (f, &iter, bm, BM_FACES_OF_MESH) {
    if (BM_elem_flag_test(f, BM_ELEM_TAG)) {
      BMLoop *l_iter, *l_first;
      l_iter = l_first = BM_FACE_FIRST_LOOP(f);
      do {
        if (bm_loop_is_all_radial_tag(l_iter) == false) {
          BLI_LINKSTACK_PUSH(loop_queue_prev, l_iter);
        }
      } while ((l_iter = l_iter->next) != l_first);
    }
  }

  while (BLI_LINKSTACK_SIZE(loop_queue_prev)) {
    while ((l = BLI_LINKSTACK_POP(loop_queue_prev))) {
      /* check we're still un-assigned */
      if (BM_elem_flag_test(l->f, BM_ELEM_TAG)) {
        BMLoop *l_iter;

        BM_elem_flag_disable(l->f, BM_ELEM_TAG);

        l_iter = l->next;
        do {
          BMLoop *l_radial_iter = l_iter->radial_next;
          if (l_radial_iter != l_iter) {
            do {
              if (BM_elem_flag_test(l_radial_iter->f, BM_ELEM_TAG)) {
                BLI_LINKSTACK_PUSH(loop_queue_next, l_radial_iter);
              }
            } while ((l_radial_iter = l_radial_iter->radial_next) != l_iter);
          }
        } while ((l_iter = l_iter->next) != l);

        /* do last because of face flipping */
        bm_face_copy_shared_all(bm, l, use_normals, use_data);
        face_tot += 1;
      }
    }

    BLI_LINKSTACK_SWAP(loop_queue_prev, loop_queue_next);
  }

  BLI_LINKSTACK_FREE(loop_queue_prev);
  BLI_LINKSTACK_FREE(loop_queue_next);

  return face_tot;
}

void bmo_face_attribute_fill_exec(BMesh *bm, BMOperator *op)
{
  const bool use_normals = BMO_slot_bool_get(op->slots_in, "use_normals");
  const bool use_data = BMO_slot_bool_get(op->slots_in, "use_data");

  int face_tot;

  BM_mesh_elem_hflag_disable_all(bm, BM_FACE, BM_ELEM_TAG, false);

  /* do inline */
  BMO_slot_buffer_hflag_enable(bm, op->slots_in, "faces", BM_FACE, BM_ELEM_TAG, false);

  /* now we can copy adjacent data */
  face_tot = bmesh_face_attribute_fill(bm, use_normals, use_data);

  if (face_tot != BMO_slot_buffer_len(op->slots_in, "faces")) {
    /* any remaining tags will be skipped */
    BMO_slot_buffer_from_enabled_hflag(
        bm, op, op->slots_out, "faces_fail.out", BM_FACE, BM_ELEM_TAG);
  }
}