/* SPDX-FileCopyrightText: 2023 Blender Authors
 *
 * SPDX-License-Identifier: GPL-2.0-or-later */
#include "IO_subdiv_disabler.hh"

#include "BLI_listbase.h"

#include "DEG_depsgraph.hh"
#include "DEG_depsgraph_query.hh"

#include "DNA_layer_types.h"
#include "DNA_mesh_types.h"
#include "DNA_modifier_types.h"
#include "DNA_object_types.h"

#include "BKE_layer.hh"
#include "BKE_modifier.hh"

namespace blender::io {

ModifierData *SubdivModifierDisabler::get_subdiv_modifier(Scene *scene,
                                                          const Object *ob,
                                                          ModifierMode mode)
{
  /* Returns the last subdiv modifier associated with an object,
   * if that modifier should be disabled.
   * We do not disable the subdiv modifier if other modifiers are
   * applied after it, with the sole exception of particle modifiers,
   * which are allowed.
   * Returns nullptr if there is not any subdiv modifier to disable.
   */

  ModifierData *md = static_cast<ModifierData *>(ob->modifiers.last);

  for (; md; md = md->prev) {
    /* Ignore disabled modifiers. */
    if (!BKE_modifier_is_enabled(scene, md, mode)) {
      continue;
    }

    if (md->type == eModifierType_Subsurf) {
      SubsurfModifierData *smd = reinterpret_cast<SubsurfModifierData *>(md);

      if (smd->subdivType == ME_CC_SUBSURF) {
        /* This is a Catmull-Clark modifier. */
        return md;
      }

      /* Not Catmull-Clark, so ignore it. */
      return nullptr;
    }

    /* If any modifier other than a particle system exists after the
     * subdiv modifier, then abort. */
    if (md->type != eModifierType_ParticleSystem) {
      return nullptr;
    }
  }

  return nullptr;
}

SubdivModifierDisabler::SubdivModifierDisabler(Depsgraph *depsgraph) : depsgraph_(depsgraph) {}

SubdivModifierDisabler::~SubdivModifierDisabler()
{
  /* Enable previously disabled modifiers. */
  for (ModifierData *modifier : disabled_modifiers_) {
    modifier->mode &= ~eModifierMode_DisableTemporary;
  }

  /* Update object to render with restored modifiers in the viewport. */
  for (Object *object : modified_objects_) {
    DEG_id_tag_update(&object->id, ID_RECALC_GEOMETRY);
  }
}

void SubdivModifierDisabler::disable_modifiers()
{
  eEvaluationMode eval_mode = DEG_get_mode(depsgraph_);
  const ModifierMode mode = eval_mode == DAG_EVAL_VIEWPORT ? eModifierMode_Realtime :
                                                             eModifierMode_Render;

  Scene *scene = DEG_get_input_scene(depsgraph_);
  ViewLayer *view_layer = DEG_get_input_view_layer(depsgraph_);

  BKE_view_layer_synced_ensure(scene, view_layer);
  LISTBASE_FOREACH (Base *, base, BKE_view_layer_object_bases_get(view_layer)) {
    Object *object = base->object;

    if (object->type != OB_MESH) {
      continue;
    }

    /* Check if a subdiv modifier exists, and should be disabled. */
    ModifierData *mod = get_subdiv_modifier(scene, object, mode);
    if (!mod) {
      continue;
    }

    /* This might disable more modifiers than necessary, as it doesn't take restrictions like
     * "export selected objects only" into account. However, with the subdivisions disabled,
     * moving to a different frame is also going to be faster, so in the end this is probably
     * a good thing to do. */
    disable_modifier(mod);
    modified_objects_.append(object);
    DEG_id_tag_update(&object->id, ID_RECALC_GEOMETRY);
  }
}

void SubdivModifierDisabler::disable_modifier(ModifierData *mod)
{
  mod->mode |= eModifierMode_DisableTemporary;
  disabled_modifiers_.append(mod);
}

}  // namespace blender::io
