/* SPDX-FileCopyrightText: 2018 Blender Authors
 *
 * SPDX-License-Identifier: GPL-2.0-or-later */

/** \file
 * \ingroup bke
 */

#include "BKE_subdiv.hh"

#include "DNA_mesh_types.h"
#include "DNA_modifier_types.h"

#include "BLI_utildefines.h"

#include "BKE_subdiv_modifier.hh"

#include "MEM_guardedalloc.h"

#include "subdiv_converter.hh"

#include "opensubdiv_capi.hh"
#include "opensubdiv_converter_capi.hh"
#ifdef WITH_OPENSUBDIV
#  include "opensubdiv_evaluator.hh"
#  include "opensubdiv_topology_refiner.hh"
#endif

namespace blender::bke::subdiv {

/* --------------------------------------------------------------------
 * Module.
 */

void init()
{
  openSubdiv_init();
}

void exit()
{
  openSubdiv_cleanup();
}

/* --------------------------------------------------------------------
 * Conversion helpers.
 */

FVarLinearInterpolation fvar_interpolation_from_uv_smooth(int uv_smooth)
{
  switch (uv_smooth) {
    case SUBSURF_UV_SMOOTH_NONE:
      return SUBDIV_FVAR_LINEAR_INTERPOLATION_ALL;
    case SUBSURF_UV_SMOOTH_PRESERVE_CORNERS:
      return SUBDIV_FVAR_LINEAR_INTERPOLATION_CORNERS_ONLY;
    case SUBSURF_UV_SMOOTH_PRESERVE_CORNERS_AND_JUNCTIONS:
      return SUBDIV_FVAR_LINEAR_INTERPOLATION_CORNERS_AND_JUNCTIONS;
    case SUBSURF_UV_SMOOTH_PRESERVE_CORNERS_JUNCTIONS_AND_CONCAVE:
      return SUBDIV_FVAR_LINEAR_INTERPOLATION_CORNERS_JUNCTIONS_AND_CONCAVE;
    case SUBSURF_UV_SMOOTH_PRESERVE_BOUNDARIES:
      return SUBDIV_FVAR_LINEAR_INTERPOLATION_BOUNDARIES;
    case SUBSURF_UV_SMOOTH_ALL:
      return SUBDIV_FVAR_LINEAR_INTERPOLATION_NONE;
  }
  BLI_assert_msg(0, "Unknown uv smooth flag");
  return SUBDIV_FVAR_LINEAR_INTERPOLATION_ALL;
}

VtxBoundaryInterpolation vtx_boundary_interpolation_from_subsurf(int boundary_smooth)
{
  switch (boundary_smooth) {
    case SUBSURF_BOUNDARY_SMOOTH_PRESERVE_CORNERS:
      return SUBDIV_VTX_BOUNDARY_EDGE_AND_CORNER;
    case SUBSURF_BOUNDARY_SMOOTH_ALL:
      return SUBDIV_VTX_BOUNDARY_EDGE_ONLY;
  }
  BLI_assert_msg(0, "Unknown boundary smooth flag");
  return SUBDIV_VTX_BOUNDARY_EDGE_ONLY;
}

/* --------------------------------------------------------------------
 * Settings.
 */

bool settings_equal(const Settings *settings_a, const Settings *settings_b)
{
  return (settings_a->is_simple == settings_b->is_simple &&
          settings_a->is_adaptive == settings_b->is_adaptive &&
          settings_a->level == settings_b->level &&
          settings_a->vtx_boundary_interpolation == settings_b->vtx_boundary_interpolation &&
          settings_a->fvar_linear_interpolation == settings_b->fvar_linear_interpolation);
}

/* --------------------------------------------------------------------
 * Construction.
 */

/* Creation from scratch. */

Subdiv *new_from_converter(const Settings *settings, OpenSubdiv_Converter *converter)
{
#ifdef WITH_OPENSUBDIV
  SubdivStats stats;
  stats_init(&stats);
  stats_begin(&stats, SUBDIV_STATS_TOPOLOGY_REFINER_CREATION_TIME);
  OpenSubdiv_TopologyRefinerSettings topology_refiner_settings;
  topology_refiner_settings.level = settings->level;
  topology_refiner_settings.is_adaptive = settings->is_adaptive;
  blender::opensubdiv::TopologyRefinerImpl *osd_topology_refiner = nullptr;
  if (converter->getNumVertices(converter) != 0) {
    osd_topology_refiner = blender::opensubdiv::TopologyRefinerImpl::createFromConverter(
        converter, topology_refiner_settings);
  }
  else {
    /* TODO(sergey): Check whether original geometry had any vertices.
     * The thing here is: OpenSubdiv can only deal with faces, but our
     * side of subdiv also deals with loose vertices and edges. */
  }
  Subdiv *subdiv = MEM_cnew<Subdiv>(__func__);
  subdiv->settings = *settings;
  subdiv->topology_refiner = osd_topology_refiner;
  subdiv->evaluator = nullptr;
  subdiv->displacement_evaluator = nullptr;
  stats_end(&stats, SUBDIV_STATS_TOPOLOGY_REFINER_CREATION_TIME);
  subdiv->stats = stats;
  return subdiv;
#else
  UNUSED_VARS(settings, converter);
  return nullptr;
#endif
}

Subdiv *new_from_mesh(const Settings *settings, const Mesh *mesh)
{
  if (mesh->verts_num == 0) {
    return nullptr;
  }
  OpenSubdiv_Converter converter;
  converter_init_for_mesh(&converter, settings, mesh);
  Subdiv *subdiv = new_from_converter(settings, &converter);
  converter_free(&converter);
  return subdiv;
}

/* Creation with cached-aware semantic. */

Subdiv *update_from_converter(Subdiv *subdiv,
                              const Settings *settings,
                              OpenSubdiv_Converter *converter)
{
#ifdef WITH_OPENSUBDIV
  /* Check if the existing descriptor can be re-used. */
  bool can_reuse_subdiv = true;
  if (subdiv != nullptr && subdiv->topology_refiner != nullptr) {
    if (!settings_equal(&subdiv->settings, settings)) {
      can_reuse_subdiv = false;
    }
    else {
      stats_begin(&subdiv->stats, SUBDIV_STATS_TOPOLOGY_COMPARE);
      can_reuse_subdiv = subdiv->topology_refiner->isEqualToConverter(converter);
      stats_end(&subdiv->stats, SUBDIV_STATS_TOPOLOGY_COMPARE);
    }
  }
  else {
    can_reuse_subdiv = false;
  }
  if (can_reuse_subdiv) {
    return subdiv;
  }
  /* Create new subdiv. */
  if (subdiv != nullptr) {
    free(subdiv);
  }
  return new_from_converter(settings, converter);
#else
  UNUSED_VARS(subdiv, settings, converter);
  return nullptr;
#endif
}

Subdiv *update_from_mesh(Subdiv *subdiv, const Settings *settings, const Mesh *mesh)
{
  OpenSubdiv_Converter converter;
  converter_init_for_mesh(&converter, settings, mesh);
  subdiv = update_from_converter(subdiv, settings, &converter);
  converter_free(&converter);
  return subdiv;
}

/* Memory release. */

void free(Subdiv *subdiv)
{
#ifdef WITH_OPENSUBDIV
  if (subdiv->evaluator != nullptr) {
    const eOpenSubdivEvaluator evaluator_type = subdiv->evaluator->type;
    if (evaluator_type != OPENSUBDIV_EVALUATOR_CPU) {
      /* Let the draw code do the freeing, to ensure that the OpenGL context is valid. */
      BKE_subsurf_modifier_free_gpu_cache_cb(subdiv);
      return;
    }
    delete subdiv->evaluator;
  }
  delete subdiv->topology_refiner;
  displacement_detach(subdiv);
  if (subdiv->cache_.face_ptex_offset != nullptr) {
    MEM_freeN(subdiv->cache_.face_ptex_offset);
  }
  MEM_freeN(subdiv);
#else
  UNUSED_VARS(subdiv);
#endif
}

/* --------------------------------------------------------------------
 * Topology helpers.
 */

int *face_ptex_offset_get(Subdiv *subdiv)
{
#ifdef WITH_OPENSUBDIV
  if (subdiv->cache_.face_ptex_offset != nullptr) {
    return subdiv->cache_.face_ptex_offset;
  }
  const blender::opensubdiv::TopologyRefinerImpl *topology_refiner = subdiv->topology_refiner;
  if (topology_refiner == nullptr) {
    return nullptr;
  }
  const int num_coarse_faces = topology_refiner->base_level().GetNumFaces();
  subdiv->cache_.face_ptex_offset = static_cast<int *>(
      MEM_malloc_arrayN(num_coarse_faces + 1, sizeof(int), __func__));
  int ptex_offset = 0;
  for (int face_index = 0; face_index < num_coarse_faces; face_index++) {
    const int face_size = topology_refiner->base_level().GetFaceVertices(face_index).size();
    const int num_ptex_faces = face_size == 4 ? 1 : face_size;
    subdiv->cache_.face_ptex_offset[face_index] = ptex_offset;
    ptex_offset += num_ptex_faces;
  }
  subdiv->cache_.face_ptex_offset[num_coarse_faces] = ptex_offset;
  return subdiv->cache_.face_ptex_offset;
#else
  UNUSED_VARS(subdiv);
  return nullptr;
#endif
}

}  // namespace blender::bke::subdiv