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

/** \file
 * \ingroup bke
 *
 * Functions for accessing mesh connectivity data.
 * eg: polys connected to verts, UV's connected to verts.
 */

#include "MEM_guardedalloc.h"

#include "DNA_meshdata_types.h"
#include "DNA_vec_types.h"

#include "BLI_bitmap.h"
#include "BLI_buffer.h"
#include "BLI_math.h"
#include "BLI_utildefines.h"

#include "BKE_customdata.h"
#include "BKE_mesh_mapping.h"
#include "BLI_memarena.h"

#include "BLI_strict_flags.h"

/* -------------------------------------------------------------------- */
/** \name Mesh Connectivity Mapping
 * \{ */

/* ngon version wip, based on BM_uv_vert_map_create */
/* this replaces the non bmesh function (in trunk) which takes MTFace's,
 * if we ever need it back we could but for now this replaces it because its unused. */

UvVertMap *BKE_mesh_uv_vert_map_create(const MPoly *mpoly,
                                       const MLoop *mloop,
                                       const MLoopUV *mloopuv,
                                       unsigned int totpoly,
                                       unsigned int totvert,
                                       const float limit[2],
                                       const bool selected,
                                       const bool use_winding)
{
  UvVertMap *vmap;
  UvMapVert *buf;
  const MPoly *mp;
  unsigned int a;
  int i, totuv, nverts;

  bool *winding = NULL;
  BLI_buffer_declare_static(vec2f, tf_uv_buf, BLI_BUFFER_NOP, 32);

  totuv = 0;

  /* generate UvMapVert array */
  mp = mpoly;
  for (a = 0; a < totpoly; a++, mp++) {
    if (!selected || (!(mp->flag & ME_HIDE) && (mp->flag & ME_FACE_SEL))) {
      totuv += mp->totloop;
    }
  }

  if (totuv == 0) {
    return NULL;
  }

  vmap = (UvVertMap *)MEM_callocN(sizeof(*vmap), "UvVertMap");
  buf = vmap->buf = (UvMapVert *)MEM_callocN(sizeof(*vmap->buf) * (size_t)totuv, "UvMapVert");
  vmap->vert = (UvMapVert **)MEM_callocN(sizeof(*vmap->vert) * totvert, "UvMapVert*");
  if (use_winding) {
    winding = MEM_callocN(sizeof(*winding) * totpoly, "winding");
  }

  if (!vmap->vert || !vmap->buf) {
    BKE_mesh_uv_vert_map_free(vmap);
    return NULL;
  }

  mp = mpoly;
  for (a = 0; a < totpoly; a++, mp++) {
    if (!selected || (!(mp->flag & ME_HIDE) && (mp->flag & ME_FACE_SEL))) {
      float(*tf_uv)[2] = NULL;

      if (use_winding) {
        tf_uv = (float(*)[2])BLI_buffer_reinit_data(&tf_uv_buf, vec2f, (size_t)mp->totloop);
      }

      nverts = mp->totloop;

      for (i = 0; i < nverts; i++) {
        buf->loop_of_poly_index = (unsigned short)i;
        buf->poly_index = a;
        buf->separate = 0;
        buf->next = vmap->vert[mloop[mp->loopstart + i].v];
        vmap->vert[mloop[mp->loopstart + i].v] = buf;

        if (use_winding) {
          copy_v2_v2(tf_uv[i], mloopuv[mpoly[a].loopstart + i].uv);
        }

        buf++;
      }

      if (use_winding) {
        winding[a] = cross_poly_v2(tf_uv, (unsigned int)nverts) > 0;
      }
    }
  }

  /* sort individual uvs for each vert */
  for (a = 0; a < totvert; a++) {
    UvMapVert *newvlist = NULL, *vlist = vmap->vert[a];
    UvMapVert *iterv, *v, *lastv, *next;
    const float *uv, *uv2;
    float uvdiff[2];

    while (vlist) {
      v = vlist;
      vlist = vlist->next;
      v->next = newvlist;
      newvlist = v;

      uv = mloopuv[mpoly[v->poly_index].loopstart + v->loop_of_poly_index].uv;
      lastv = NULL;
      iterv = vlist;

      while (iterv) {
        next = iterv->next;

        uv2 = mloopuv[mpoly[iterv->poly_index].loopstart + iterv->loop_of_poly_index].uv;
        sub_v2_v2v2(uvdiff, uv2, uv);

        if (fabsf(uv[0] - uv2[0]) < limit[0] && fabsf(uv[1] - uv2[1]) < limit[1] &&
            (!use_winding || winding[iterv->poly_index] == winding[v->poly_index])) {
          if (lastv) {
            lastv->next = next;
          }
          else {
            vlist = next;
          }
          iterv->next = newvlist;
          newvlist = iterv;
        }
        else {
          lastv = iterv;
        }

        iterv = next;
      }

      newvlist->separate = 1;
    }

    vmap->vert[a] = newvlist;
  }

  if (use_winding) {
    MEM_freeN(winding);
  }

  BLI_buffer_free(&tf_uv_buf);

  return vmap;
}

UvMapVert *BKE_mesh_uv_vert_map_get_vert(UvVertMap *vmap, unsigned int v)
{
  return vmap->vert[v];
}

void BKE_mesh_uv_vert_map_free(UvVertMap *vmap)
{
  if (vmap) {
    if (vmap->vert) {
      MEM_freeN(vmap->vert);
    }
    if (vmap->buf) {
      MEM_freeN(vmap->buf);
    }
    MEM_freeN(vmap);
  }
}

/**
 * Generates a map where the key is the vertex and the value is a list
 * of polys or loops that use that vertex as a corner. The lists are allocated
 * from one memory pool.
 *
 * Wrapped by #BKE_mesh_vert_poly_map_create & BKE_mesh_vert_loop_map_create
 */
static void mesh_vert_poly_or_loop_map_create(MeshElemMap **r_map,
                                              int **r_mem,
                                              const MPoly *mpoly,
                                              const MLoop *mloop,
                                              int totvert,
                                              int totpoly,
                                              int totloop,
                                              const bool do_loops)
{
  MeshElemMap *map = MEM_callocN(sizeof(MeshElemMap) * (size_t)totvert, __func__);
  int *indices, *index_iter;
  int i, j;

  indices = index_iter = MEM_mallocN(sizeof(int) * (size_t)totloop, __func__);

  /* Count number of polys for each vertex */
  for (i = 0; i < totpoly; i++) {
    const MPoly *p = &mpoly[i];

    for (j = 0; j < p->totloop; j++) {
      map[mloop[p->loopstart + j].v].count++;
    }
  }

  /* Assign indices mem */
  for (i = 0; i < totvert; i++) {
    map[i].indices = index_iter;
    index_iter += map[i].count;

    /* Reset 'count' for use as index in last loop */
    map[i].count = 0;
  }

  /* Find the users */
  for (i = 0; i < totpoly; i++) {
    const MPoly *p = &mpoly[i];

    for (j = 0; j < p->totloop; j++) {
      unsigned int v = mloop[p->loopstart + j].v;

      map[v].indices[map[v].count] = do_loops ? p->loopstart + j : i;
      map[v].count++;
    }
  }

  *r_map = map;
  *r_mem = indices;
}

/**
 * Generates a map where the key is the vertex and the value
 * is a list of polys that use that vertex as a corner.
 * The lists are allocated from one memory pool.
 */
void BKE_mesh_vert_poly_map_create(MeshElemMap **r_map,
                                   int **r_mem,
                                   const MPoly *mpoly,
                                   const MLoop *mloop,
                                   int totvert,
                                   int totpoly,
                                   int totloop)
{
  mesh_vert_poly_or_loop_map_create(r_map, r_mem, mpoly, mloop, totvert, totpoly, totloop, false);
}

/**
 * Generates a map where the key is the vertex and the value
 * is a list of loops that use that vertex as a corner.
 * The lists are allocated from one memory pool.
 */
void BKE_mesh_vert_loop_map_create(MeshElemMap **r_map,
                                   int **r_mem,
                                   const MPoly *mpoly,
                                   const MLoop *mloop,
                                   int totvert,
                                   int totpoly,
                                   int totloop)
{
  mesh_vert_poly_or_loop_map_create(r_map, r_mem, mpoly, mloop, totvert, totpoly, totloop, true);
}

/**
 * Generates a map where the key is the edge and the value
 * is a list of looptris that use that edge.
 * The lists are allocated from one memory pool.
 */
void BKE_mesh_vert_looptri_map_create(MeshElemMap **r_map,
                                      int **r_mem,
                                      const MVert *UNUSED(mvert),
                                      const int totvert,
                                      const MLoopTri *mlooptri,
                                      const int totlooptri,
                                      const MLoop *mloop,
                                      const int UNUSED(totloop))
{
  MeshElemMap *map = MEM_callocN(sizeof(MeshElemMap) * (size_t)totvert, __func__);
  int *indices = MEM_mallocN(sizeof(int) * (size_t)totlooptri * 3, __func__);
  int *index_step;
  const MLoopTri *mlt;
  int i;

  /* count face users */
  for (i = 0, mlt = mlooptri; i < totlooptri; mlt++, i++) {
    for (int j = 3; j--;) {
      map[mloop[mlt->tri[j]].v].count++;
    }
  }

  /* create offsets */
  index_step = indices;
  for (i = 0; i < totvert; i++) {
    map[i].indices = index_step;
    index_step += map[i].count;

    /* re-count, using this as an index below */
    map[i].count = 0;
  }

  /* assign looptri-edge users */
  for (i = 0, mlt = mlooptri; i < totlooptri; mlt++, i++) {
    for (int j = 3; j--;) {
      MeshElemMap *map_ele = &map[mloop[mlt->tri[j]].v];
      map_ele->indices[map_ele->count++] = i;
    }
  }

  *r_map = map;
  *r_mem = indices;
}

/**
 * Generates a map where the key is the vertex and the value
 * is a list of edges that use that vertex as an endpoint.
 * The lists are allocated from one memory pool.
 */
void BKE_mesh_vert_edge_map_create(
    MeshElemMap **r_map, int **r_mem, const MEdge *medge, int totvert, int totedge)
{
  MeshElemMap *map = MEM_callocN(sizeof(MeshElemMap) * (size_t)totvert, "vert-edge map");
  int *indices = MEM_mallocN(sizeof(int[2]) * (size_t)totedge, "vert-edge map mem");
  int *i_pt = indices;

  int i;

  /* Count number of edges for each vertex */
  for (i = 0; i < totedge; i++) {
    map[medge[i].v1].count++;
    map[medge[i].v2].count++;
  }

  /* Assign indices mem */
  for (i = 0; i < totvert; i++) {
    map[i].indices = i_pt;
    i_pt += map[i].count;

    /* Reset 'count' for use as index in last loop */
    map[i].count = 0;
  }

  /* Find the users */
  for (i = 0; i < totedge; i++) {
    const unsigned int v[2] = {medge[i].v1, medge[i].v2};

    map[v[0]].indices[map[v[0]].count] = i;
    map[v[1]].indices[map[v[1]].count] = i;

    map[v[0]].count++;
    map[v[1]].count++;
  }

  *r_map = map;
  *r_mem = indices;
}

/**
 * A version of #BKE_mesh_vert_edge_map_create that references connected vertices directly
 * (not their edges).
 */
void BKE_mesh_vert_edge_vert_map_create(
    MeshElemMap **r_map, int **r_mem, const MEdge *medge, int totvert, int totedge)
{
  MeshElemMap *map = MEM_callocN(sizeof(MeshElemMap) * (size_t)totvert, "vert-edge map");
  int *indices = MEM_mallocN(sizeof(int[2]) * (size_t)totedge, "vert-edge map mem");
  int *i_pt = indices;

  int i;

  /* Count number of edges for each vertex */
  for (i = 0; i < totedge; i++) {
    map[medge[i].v1].count++;
    map[medge[i].v2].count++;
  }

  /* Assign indices mem */
  for (i = 0; i < totvert; i++) {
    map[i].indices = i_pt;
    i_pt += map[i].count;

    /* Reset 'count' for use as index in last loop */
    map[i].count = 0;
  }

  /* Find the users */
  for (i = 0; i < totedge; i++) {
    const unsigned int v[2] = {medge[i].v1, medge[i].v2};

    map[v[0]].indices[map[v[0]].count] = (int)v[1];
    map[v[1]].indices[map[v[1]].count] = (int)v[0];

    map[v[0]].count++;
    map[v[1]].count++;
  }

  *r_map = map;
  *r_mem = indices;
}

/**
 * Generates a map where the key is the edge and the value is a list of loops that use that edge.
 * Loops indices of a same poly are contiguous and in winding order.
 * The lists are allocated from one memory pool.
 */
void BKE_mesh_edge_loop_map_create(MeshElemMap **r_map,
                                   int **r_mem,
                                   const MEdge *UNUSED(medge),
                                   const int totedge,
                                   const MPoly *mpoly,
                                   const int totpoly,
                                   const MLoop *mloop,
                                   const int totloop)
{
  MeshElemMap *map = MEM_callocN(sizeof(MeshElemMap) * (size_t)totedge, "edge-poly map");
  int *indices = MEM_mallocN(sizeof(int) * (size_t)totloop * 2, "edge-poly map mem");
  int *index_step;
  const MPoly *mp;
  int i;

  /* count face users */
  for (i = 0, mp = mpoly; i < totpoly; mp++, i++) {
    const MLoop *ml;
    int j = mp->totloop;
    for (ml = &mloop[mp->loopstart]; j--; ml++) {
      map[ml->e].count += 2;
    }
  }

  /* create offsets */
  index_step = indices;
  for (i = 0; i < totedge; i++) {
    map[i].indices = index_step;
    index_step += map[i].count;

    /* re-count, using this as an index below */
    map[i].count = 0;
  }

  /* assign loop-edge users */
  for (i = 0, mp = mpoly; i < totpoly; mp++, i++) {
    const MLoop *ml;
    MeshElemMap *map_ele;
    const int max_loop = mp->loopstart + mp->totloop;
    int j = mp->loopstart;
    for (ml = &mloop[j]; j < max_loop; j++, ml++) {
      map_ele = &map[ml->e];
      map_ele->indices[map_ele->count++] = j;
      map_ele->indices[map_ele->count++] = j + 1;
    }
    /* last edge/loop of poly, must point back to first loop! */
    map_ele->indices[map_ele->count - 1] = mp->loopstart;
  }

  *r_map = map;
  *r_mem = indices;
}

/**
 * Generates a map where the key is the edge and the value
 * is a list of polygons that use that edge.
 * The lists are allocated from one memory pool.
 */
void BKE_mesh_edge_poly_map_create(MeshElemMap **r_map,
                                   int **r_mem,
                                   const MEdge *UNUSED(medge),
                                   const int totedge,
                                   const MPoly *mpoly,
                                   const int totpoly,
                                   const MLoop *mloop,
                                   const int totloop)
{
  MeshElemMap *map = MEM_callocN(sizeof(MeshElemMap) * (size_t)totedge, "edge-poly map");
  int *indices = MEM_mallocN(sizeof(int) * (size_t)totloop, "edge-poly map mem");
  int *index_step;
  const MPoly *mp;
  int i;

  /* count face users */
  for (i = 0, mp = mpoly; i < totpoly; mp++, i++) {
    const MLoop *ml;
    int j = mp->totloop;
    for (ml = &mloop[mp->loopstart]; j--; ml++) {
      map[ml->e].count++;
    }
  }

  /* create offsets */
  index_step = indices;
  for (i = 0; i < totedge; i++) {
    map[i].indices = index_step;
    index_step += map[i].count;

    /* re-count, using this as an index below */
    map[i].count = 0;
  }

  /* assign poly-edge users */
  for (i = 0, mp = mpoly; i < totpoly; mp++, i++) {
    const MLoop *ml;
    int j = mp->totloop;
    for (ml = &mloop[mp->loopstart]; j--; ml++) {
      MeshElemMap *map_ele = &map[ml->e];
      map_ele->indices[map_ele->count++] = i;
    }
  }

  *r_map = map;
  *r_mem = indices;
}

/**
 * This function creates a map so the source-data (vert/edge/loop/poly)
 * can loop over the destination data (using the destination arrays origindex).
 *
 * This has the advantage that it can operate on any data-types.
 *
 * \param totsource: The total number of elements the that \a final_origindex points to.
 * \param totfinal: The size of \a final_origindex
 * \param final_origindex: The size of the final array.
 *
 * \note ``totsource`` could be ``totpoly``,
 *       ``totfinal`` could be ``tottessface`` and ``final_origindex`` its ORIGINDEX customdata.
 *       This would allow an MPoly to loop over its tessfaces.
 */
void BKE_mesh_origindex_map_create(MeshElemMap **r_map,
                                   int **r_mem,
                                   const int totsource,
                                   const int *final_origindex,
                                   const int totfinal)
{
  MeshElemMap *map = MEM_callocN(sizeof(MeshElemMap) * (size_t)totsource, "poly-tessface map");
  int *indices = MEM_mallocN(sizeof(int) * (size_t)totfinal, "poly-tessface map mem");
  int *index_step;
  int i;

  /* count face users */
  for (i = 0; i < totfinal; i++) {
    if (final_origindex[i] != ORIGINDEX_NONE) {
      BLI_assert(final_origindex[i] < totsource);
      map[final_origindex[i]].count++;
    }
  }

  /* create offsets */
  index_step = indices;
  for (i = 0; i < totsource; i++) {
    map[i].indices = index_step;
    index_step += map[i].count;

    /* re-count, using this as an index below */
    map[i].count = 0;
  }

  /* assign poly-tessface users */
  for (i = 0; i < totfinal; i++) {
    if (final_origindex[i] != ORIGINDEX_NONE) {
      MeshElemMap *map_ele = &map[final_origindex[i]];
      map_ele->indices[map_ele->count++] = i;
    }
  }

  *r_map = map;
  *r_mem = indices;
}

/**
 * A version of #BKE_mesh_origindex_map_create that takes a looptri array.
 * Making a poly -> looptri map.
 */
void BKE_mesh_origindex_map_create_looptri(MeshElemMap **r_map,
                                           int **r_mem,
                                           const MPoly *mpoly,
                                           const int mpoly_num,
                                           const MLoopTri *looptri,
                                           const int looptri_num)
{
  MeshElemMap *map = MEM_callocN(sizeof(MeshElemMap) * (size_t)mpoly_num, "poly-tessface map");
  int *indices = MEM_mallocN(sizeof(int) * (size_t)looptri_num, "poly-tessface map mem");
  int *index_step;
  int i;

  /* create offsets */
  index_step = indices;
  for (i = 0; i < mpoly_num; i++) {
    map[i].indices = index_step;
    index_step += ME_POLY_TRI_TOT(&mpoly[i]);
  }

  /* assign poly-tessface users */
  for (i = 0; i < looptri_num; i++) {
    MeshElemMap *map_ele = &map[looptri[i].poly];
    map_ele->indices[map_ele->count++] = i;
  }

  *r_map = map;
  *r_mem = indices;
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name Mesh loops/poly islands.
 * Used currently for UVs and 'smooth groups'.
 * \{ */

/**
 * Callback deciding whether the given poly/loop/edge define an island boundary or not.
 */
typedef bool (*MeshRemap_CheckIslandBoundary)(const struct MPoly *mpoly,
                                              const struct MLoop *mloop,
                                              const struct MEdge *medge,
                                              const int nbr_egde_users,
                                              const struct MPoly *mpoly_array,
                                              const struct MeshElemMap *edge_poly_map,
                                              void *user_data);

static void poly_edge_loop_islands_calc(const MEdge *medge,
                                        const int totedge,
                                        const MPoly *mpoly,
                                        const int totpoly,
                                        const MLoop *mloop,
                                        const int totloop,
                                        MeshElemMap *edge_poly_map,
                                        const bool use_bitflags,
                                        MeshRemap_CheckIslandBoundary edge_boundary_check,
                                        void *edge_boundary_check_data,
                                        int **r_poly_groups,
                                        int *r_totgroup,
                                        BLI_bitmap **r_edge_borders,
                                        int *r_totedgeborder)
{
  int *poly_groups;
  int *poly_stack;

  BLI_bitmap *edge_borders = NULL;
  int num_edgeborders = 0;

  int poly_prev = 0;
  const int temp_poly_group_id = 3; /* Placeholder value. */

  /* Group we could not find any available bit, will be reset to 0 at end. */
  const int poly_group_id_overflowed = 5;

  int tot_group = 0;
  bool group_id_overflow = false;

  /* map vars */
  int *edge_poly_mem = NULL;

  if (totpoly == 0) {
    *r_totgroup = 0;
    *r_poly_groups = NULL;
    if (r_edge_borders) {
      *r_edge_borders = NULL;
      *r_totedgeborder = 0;
    }
    return;
  }

  if (r_edge_borders) {
    edge_borders = BLI_BITMAP_NEW(totedge, __func__);
    *r_totedgeborder = 0;
  }

  if (!edge_poly_map) {
    BKE_mesh_edge_poly_map_create(
        &edge_poly_map, &edge_poly_mem, medge, totedge, mpoly, totpoly, mloop, totloop);
  }

  poly_groups = MEM_callocN(sizeof(int) * (size_t)totpoly, __func__);
  poly_stack = MEM_mallocN(sizeof(int) * (size_t)totpoly, __func__);

  while (true) {
    int poly;
    int bit_poly_group_mask = 0;
    int poly_group_id;
    int ps_curr_idx = 0, ps_end_idx = 0; /* stack indices */

    for (poly = poly_prev; poly < totpoly; poly++) {
      if (poly_groups[poly] == 0) {
        break;
      }
    }

    if (poly == totpoly) {
      /* all done */
      break;
    }

    poly_group_id = use_bitflags ? temp_poly_group_id : ++tot_group;

    /* start searching from here next time */
    poly_prev = poly + 1;

    poly_groups[poly] = poly_group_id;
    poly_stack[ps_end_idx++] = poly;

    while (ps_curr_idx != ps_end_idx) {
      const MPoly *mp;
      const MLoop *ml;
      int j;

      poly = poly_stack[ps_curr_idx++];
      BLI_assert(poly_groups[poly] == poly_group_id);

      mp = &mpoly[poly];
      for (ml = &mloop[mp->loopstart], j = mp->totloop; j--; ml++) {
        /* loop over poly users */
        const int me_idx = (int)ml->e;
        const MEdge *me = &medge[me_idx];
        const MeshElemMap *map_ele = &edge_poly_map[me_idx];
        const int *p = map_ele->indices;
        int i = map_ele->count;
        if (!edge_boundary_check(mp, ml, me, i, mpoly, map_ele, edge_boundary_check_data)) {
          for (; i--; p++) {
            /* if we meet other non initialized its a bug */
            BLI_assert(ELEM(poly_groups[*p], 0, poly_group_id));

            if (poly_groups[*p] == 0) {
              poly_groups[*p] = poly_group_id;
              poly_stack[ps_end_idx++] = *p;
            }
          }
        }
        else {
          if (edge_borders && !BLI_BITMAP_TEST(edge_borders, me_idx)) {
            BLI_BITMAP_ENABLE(edge_borders, me_idx);
            num_edgeborders++;
          }
          if (use_bitflags) {
            /* Find contiguous smooth groups already assigned,
             * these are the values we can't reuse! */
            for (; i--; p++) {
              int bit = poly_groups[*p];
              if (!ELEM(bit, 0, poly_group_id, poly_group_id_overflowed) &&
                  !(bit_poly_group_mask & bit)) {
                bit_poly_group_mask |= bit;
              }
            }
          }
        }
      }
    }
    /* And now, we have all our poly from current group in poly_stack
     * (from 0 to (ps_end_idx - 1)),
     * as well as all smoothgroups bits we can't use in bit_poly_group_mask.
     */
    if (use_bitflags) {
      int i, *p, gid_bit = 0;
      poly_group_id = 1;

      /* Find first bit available! */
      for (; (poly_group_id & bit_poly_group_mask) && (gid_bit < 32); gid_bit++) {
        poly_group_id <<= 1; /* will 'overflow' on last possible iteration. */
      }
      if (UNLIKELY(gid_bit > 31)) {
        /* All bits used in contiguous smooth groups, we can't do much!
         * Note: this is *very* unlikely - theoretically, four groups are enough,
         *       I don't think we can reach this goal with such a simple algo,
         *       but I don't think either we'll never need all 32 groups!
         */
        printf(
            "Warning, could not find an available id for current smooth group, faces will me "
            "marked "
            "as out of any smooth group...\n");

        /* Can't use 0, will have to set them to this value later. */
        poly_group_id = poly_group_id_overflowed;

        group_id_overflow = true;
      }
      if (gid_bit > tot_group) {
        tot_group = gid_bit;
      }
      /* And assign the final smooth group id to that poly group! */
      for (i = ps_end_idx, p = poly_stack; i--; p++) {
        poly_groups[*p] = poly_group_id;
      }
    }
  }

  if (use_bitflags) {
    /* used bits are zero-based. */
    tot_group++;
  }

  if (UNLIKELY(group_id_overflow)) {
    int i = totpoly, *gid = poly_groups;
    for (; i--; gid++) {
      if (*gid == poly_group_id_overflowed) {
        *gid = 0;
      }
    }
    /* Using 0 as group id adds one more group! */
    tot_group++;
  }

  if (edge_poly_mem) {
    MEM_freeN(edge_poly_map);
    MEM_freeN(edge_poly_mem);
  }
  MEM_freeN(poly_stack);

  *r_totgroup = tot_group;
  *r_poly_groups = poly_groups;
  if (r_edge_borders) {
    *r_edge_borders = edge_borders;
    *r_totedgeborder = num_edgeborders;
  }
}

static bool poly_is_island_boundary_smooth_cb(const MPoly *mp,
                                              const MLoop *UNUSED(ml),
                                              const MEdge *me,
                                              const int nbr_egde_users,
                                              const MPoly *mpoly_array,
                                              const MeshElemMap *edge_poly_map,
                                              void *UNUSED(user_data))
{
  /* Edge is sharp if one of its polys is flat, or edge itself is sharp,
   * or edge is not used by exactly two polygons. */
  if ((mp->flag & ME_SMOOTH) && !(me->flag & ME_SHARP) && (nbr_egde_users == 2)) {
    /* In that case, edge appears to be smooth, but we need to check its other poly too. */
    const MPoly *mp_other = (mp == &mpoly_array[edge_poly_map->indices[0]]) ?
                                &mpoly_array[edge_poly_map->indices[1]] :
                                &mpoly_array[edge_poly_map->indices[0]];
    return (mp_other->flag & ME_SMOOTH) == 0;
  }
  return true;
}

/**
 * Calculate smooth groups from sharp edges.
 *
 * \param r_totgroup: The total number of groups, 1 or more.
 * \return Polygon aligned array of group index values (bitflags if use_bitflags is true),
 * starting at 1 (0 being used as 'invalid' flag).
 * Note it's callers's responsibility to MEM_freeN returned array.
 */
int *BKE_mesh_calc_smoothgroups(const MEdge *medge,
                                const int totedge,
                                const MPoly *mpoly,
                                const int totpoly,
                                const MLoop *mloop,
                                const int totloop,
                                int *r_totgroup,
                                const bool use_bitflags)
{
  int *poly_groups = NULL;

  poly_edge_loop_islands_calc(medge,
                              totedge,
                              mpoly,
                              totpoly,
                              mloop,
                              totloop,
                              NULL,
                              use_bitflags,
                              poly_is_island_boundary_smooth_cb,
                              NULL,
                              &poly_groups,
                              r_totgroup,
                              NULL,
                              NULL);

  return poly_groups;
}

#define MISLAND_DEFAULT_BUFSIZE 64

void BKE_mesh_loop_islands_init(MeshIslandStore *island_store,
                                const short item_type,
                                const int items_num,
                                const short island_type,
                                const short innercut_type)
{
  MemArena *mem = island_store->mem;

  if (mem == NULL) {
    mem = BLI_memarena_new(BLI_MEMARENA_STD_BUFSIZE, __func__);
    island_store->mem = mem;
  }
  /* else memarena should be cleared */

  BLI_assert(
      ELEM(item_type, MISLAND_TYPE_VERT, MISLAND_TYPE_EDGE, MISLAND_TYPE_POLY, MISLAND_TYPE_LOOP));
  BLI_assert(ELEM(
      island_type, MISLAND_TYPE_VERT, MISLAND_TYPE_EDGE, MISLAND_TYPE_POLY, MISLAND_TYPE_LOOP));

  island_store->item_type = item_type;
  island_store->items_to_islands_num = items_num;
  island_store->items_to_islands = BLI_memarena_alloc(
      mem, sizeof(*island_store->items_to_islands) * (size_t)items_num);

  island_store->island_type = island_type;
  island_store->islands_num_alloc = MISLAND_DEFAULT_BUFSIZE;
  island_store->islands = BLI_memarena_alloc(
      mem, sizeof(*island_store->islands) * island_store->islands_num_alloc);

  island_store->innercut_type = innercut_type;
  island_store->innercuts = BLI_memarena_alloc(
      mem, sizeof(*island_store->innercuts) * island_store->islands_num_alloc);
}

void BKE_mesh_loop_islands_clear(MeshIslandStore *island_store)
{
  island_store->item_type = MISLAND_TYPE_NONE;
  island_store->items_to_islands_num = 0;
  island_store->items_to_islands = NULL;

  island_store->island_type = MISLAND_TYPE_NONE;
  island_store->islands_num = 0;
  island_store->islands = NULL;

  island_store->innercut_type = MISLAND_TYPE_NONE;
  island_store->innercuts = NULL;

  if (island_store->mem) {
    BLI_memarena_clear(island_store->mem);
  }

  island_store->islands_num_alloc = 0;
}

void BKE_mesh_loop_islands_free(MeshIslandStore *island_store)
{
  if (island_store->mem) {
    BLI_memarena_free(island_store->mem);
    island_store->mem = NULL;
  }
}

void BKE_mesh_loop_islands_add(MeshIslandStore *island_store,
                               const int item_num,
                               int *items_indices,
                               const int num_island_items,
                               int *island_item_indices,
                               const int num_innercut_items,
                               int *innercut_item_indices)
{
  MemArena *mem = island_store->mem;

  MeshElemMap *isld, *innrcut;
  const int curr_island_idx = island_store->islands_num++;
  const size_t curr_num_islands = (size_t)island_store->islands_num;
  int i = item_num;

  while (i--) {
    island_store->items_to_islands[items_indices[i]] = curr_island_idx;
  }

  if (UNLIKELY(curr_num_islands > island_store->islands_num_alloc)) {
    MeshElemMap **islds, **innrcuts;

    island_store->islands_num_alloc *= 2;
    islds = BLI_memarena_alloc(mem, sizeof(*islds) * island_store->islands_num_alloc);
    memcpy(islds, island_store->islands, sizeof(*islds) * (curr_num_islands - 1));
    island_store->islands = islds;

    innrcuts = BLI_memarena_alloc(mem, sizeof(*innrcuts) * island_store->islands_num_alloc);
    memcpy(innrcuts, island_store->innercuts, sizeof(*innrcuts) * (curr_num_islands - 1));
    island_store->innercuts = innrcuts;
  }

  island_store->islands[curr_island_idx] = isld = BLI_memarena_alloc(mem, sizeof(*isld));
  isld->count = num_island_items;
  isld->indices = BLI_memarena_alloc(mem, sizeof(*isld->indices) * (size_t)num_island_items);
  memcpy(isld->indices, island_item_indices, sizeof(*isld->indices) * (size_t)num_island_items);

  island_store->innercuts[curr_island_idx] = innrcut = BLI_memarena_alloc(mem, sizeof(*innrcut));
  innrcut->count = num_innercut_items;
  innrcut->indices = BLI_memarena_alloc(mem,
                                        sizeof(*innrcut->indices) * (size_t)num_innercut_items);
  memcpy(innrcut->indices,
         innercut_item_indices,
         sizeof(*innrcut->indices) * (size_t)num_innercut_items);
}

/* TODO: I'm not sure edge seam flag is enough to define UV islands?
 *       Maybe we should also consider UVmaps values
 *       themselves (i.e. different UV-edges for a same mesh-edge => boundary edge too?).
 *       Would make things much more complex though,
 *       and each UVMap would then need its own mesh mapping, not sure we want that at all!
 */
typedef struct MeshCheckIslandBoundaryUv {
  const MLoop *loops;
  const MLoopUV *luvs;
  const MeshElemMap *edge_loop_map;
} MeshCheckIslandBoundaryUv;

static bool mesh_check_island_boundary_uv(const MPoly *UNUSED(mp),
                                          const MLoop *ml,
                                          const MEdge *me,
                                          const int UNUSED(nbr_egde_users),
                                          const MPoly *UNUSED(mpoly_array),
                                          const MeshElemMap *UNUSED(edge_poly_map),
                                          void *user_data)
{
  if (user_data) {
    const MeshCheckIslandBoundaryUv *data = user_data;
    const MLoop *loops = data->loops;
    const MLoopUV *luvs = data->luvs;
    const MeshElemMap *edge_to_loops = &data->edge_loop_map[ml->e];

    BLI_assert(edge_to_loops->count >= 2 && (edge_to_loops->count % 2) == 0);

    const unsigned int v1 = loops[edge_to_loops->indices[0]].v;
    const unsigned int v2 = loops[edge_to_loops->indices[1]].v;
    const float *uvco_v1 = luvs[edge_to_loops->indices[0]].uv;
    const float *uvco_v2 = luvs[edge_to_loops->indices[1]].uv;
    for (int i = 2; i < edge_to_loops->count; i += 2) {
      if (loops[edge_to_loops->indices[i]].v == v1) {
        if (!equals_v2v2(uvco_v1, luvs[edge_to_loops->indices[i]].uv) ||
            !equals_v2v2(uvco_v2, luvs[edge_to_loops->indices[i + 1]].uv)) {
          return true;
        }
      }
      else {
        BLI_assert(loops[edge_to_loops->indices[i]].v == v2);
        UNUSED_VARS_NDEBUG(v2);
        if (!equals_v2v2(uvco_v2, luvs[edge_to_loops->indices[i]].uv) ||
            !equals_v2v2(uvco_v1, luvs[edge_to_loops->indices[i + 1]].uv)) {
          return true;
        }
      }
    }
    return false;
  }
  else {
    /* Edge is UV boundary if tagged as seam. */
    return (me->flag & ME_SEAM) != 0;
  }
}

static bool mesh_calc_islands_loop_poly_uv(MVert *UNUSED(verts),
                                           const int UNUSED(totvert),
                                           MEdge *edges,
                                           const int totedge,
                                           MPoly *polys,
                                           const int totpoly,
                                           MLoop *loops,
                                           const int totloop,
                                           const MLoopUV *luvs,
                                           MeshIslandStore *r_island_store)
{
  int *poly_groups = NULL;
  int num_poly_groups;

  /* map vars */
  MeshElemMap *edge_poly_map;
  int *edge_poly_mem;

  MeshElemMap *edge_loop_map;
  int *edge_loop_mem;

  MeshCheckIslandBoundaryUv edge_boundary_check_data;

  int *poly_indices;
  int *loop_indices;
  int num_pidx, num_lidx;

  /* Those are used to detect 'inner cuts', i.e. edges that are borders,
   * and yet have two or more polys of a same group using them
   * (typical case: seam used to unwrap properly a cylinder). */
  BLI_bitmap *edge_borders = NULL;
  int num_edge_borders = 0;
  char *edge_border_count = NULL;
  int *edge_innercut_indices = NULL;
  int num_einnercuts = 0;

  int grp_idx, p_idx, pl_idx, l_idx;

  BKE_mesh_loop_islands_clear(r_island_store);
  BKE_mesh_loop_islands_init(
      r_island_store, MISLAND_TYPE_LOOP, totloop, MISLAND_TYPE_POLY, MISLAND_TYPE_EDGE);

  BKE_mesh_edge_poly_map_create(
      &edge_poly_map, &edge_poly_mem, edges, totedge, polys, totpoly, loops, totloop);

  if (luvs) {
    BKE_mesh_edge_loop_map_create(
        &edge_loop_map, &edge_loop_mem, edges, totedge, polys, totpoly, loops, totloop);
    edge_boundary_check_data.loops = loops;
    edge_boundary_check_data.luvs = luvs;
    edge_boundary_check_data.edge_loop_map = edge_loop_map;
  }

  poly_edge_loop_islands_calc(edges,
                              totedge,
                              polys,
                              totpoly,
                              loops,
                              totloop,
                              edge_poly_map,
                              false,
                              mesh_check_island_boundary_uv,
                              luvs ? &edge_boundary_check_data : NULL,
                              &poly_groups,
                              &num_poly_groups,
                              &edge_borders,
                              &num_edge_borders);

  if (!num_poly_groups) {
    /* Should never happen... */
    MEM_freeN(edge_poly_map);
    MEM_freeN(edge_poly_mem);

    if (edge_borders) {
      MEM_freeN(edge_borders);
    }
    return false;
  }

  if (num_edge_borders) {
    edge_border_count = MEM_mallocN(sizeof(*edge_border_count) * (size_t)totedge, __func__);
    edge_innercut_indices = MEM_mallocN(sizeof(*edge_innercut_indices) * (size_t)num_edge_borders,
                                        __func__);
  }

  poly_indices = MEM_mallocN(sizeof(*poly_indices) * (size_t)totpoly, __func__);
  loop_indices = MEM_mallocN(sizeof(*loop_indices) * (size_t)totloop, __func__);

  /* Note: here we ignore '0' invalid group - this should *never* happen in this case anyway? */
  for (grp_idx = 1; grp_idx <= num_poly_groups; grp_idx++) {
    num_pidx = num_lidx = 0;
    if (num_edge_borders) {
      num_einnercuts = 0;
      memset(edge_border_count, 0, sizeof(*edge_border_count) * (size_t)totedge);
    }

    for (p_idx = 0; p_idx < totpoly; p_idx++) {
      MPoly *mp;

      if (poly_groups[p_idx] != grp_idx) {
        continue;
      }

      mp = &polys[p_idx];
      poly_indices[num_pidx++] = p_idx;
      for (l_idx = mp->loopstart, pl_idx = 0; pl_idx < mp->totloop; l_idx++, pl_idx++) {
        MLoop *ml = &loops[l_idx];
        loop_indices[num_lidx++] = l_idx;
        if (num_edge_borders && BLI_BITMAP_TEST(edge_borders, ml->e) &&
            (edge_border_count[ml->e] < 2)) {
          edge_border_count[ml->e]++;
          if (edge_border_count[ml->e] == 2) {
            edge_innercut_indices[num_einnercuts++] = (int)ml->e;
          }
        }
      }
    }

    BKE_mesh_loop_islands_add(r_island_store,
                              num_lidx,
                              loop_indices,
                              num_pidx,
                              poly_indices,
                              num_einnercuts,
                              edge_innercut_indices);
  }

  MEM_freeN(edge_poly_map);
  MEM_freeN(edge_poly_mem);

  if (luvs) {
    MEM_freeN(edge_loop_map);
    MEM_freeN(edge_loop_mem);
  }

  MEM_freeN(poly_indices);
  MEM_freeN(loop_indices);
  MEM_freeN(poly_groups);

  if (edge_borders) {
    MEM_freeN(edge_borders);
  }

  if (num_edge_borders) {
    MEM_freeN(edge_border_count);
    MEM_freeN(edge_innercut_indices);
  }
  return true;
}

/**
 * Calculate 'generic' UV islands, i.e. based only on actual geometry data (edge seams),
 * not some UV layers coordinates.
 */
bool BKE_mesh_calc_islands_loop_poly_edgeseam(MVert *verts,
                                              const int totvert,
                                              MEdge *edges,
                                              const int totedge,
                                              MPoly *polys,
                                              const int totpoly,
                                              MLoop *loops,
                                              const int totloop,
                                              MeshIslandStore *r_island_store)
{
  return mesh_calc_islands_loop_poly_uv(
      verts, totvert, edges, totedge, polys, totpoly, loops, totloop, NULL, r_island_store);
}

/**
 * Calculate UV islands.
 *
 * \note If no MLoopUV layer is passed, we only consider edges tagged as seams as UV boundaries.
 * This has the advantages of simplicity, and being valid/common to all UV maps.
 * However, it means actual UV islands without matching UV seams will not be handled correctly...
 * If a valid UV layer is passed as \a luvs parameter,
 * UV coordinates are also used to detect islands boundaries.
 *
 * \note All this could be optimized...
 * Not sure it would be worth the more complex code, though,
 * those loops are supposed to be really quick to do...
 */
bool BKE_mesh_calc_islands_loop_poly_uvmap(MVert *verts,
                                           const int totvert,
                                           MEdge *edges,
                                           const int totedge,
                                           MPoly *polys,
                                           const int totpoly,
                                           MLoop *loops,
                                           const int totloop,
                                           const MLoopUV *luvs,
                                           MeshIslandStore *r_island_store)
{
  BLI_assert(luvs != NULL);
  return mesh_calc_islands_loop_poly_uv(
      verts, totvert, edges, totedge, polys, totpoly, loops, totloop, luvs, r_island_store);
}

/** \} */