/* SPDX-License-Identifier: GPL-2.0-or-later
 * Copyright 2020 Blender Foundation. All rights reserved. */

/** \file
 * \ingroup bke
 */

#include "MEM_guardedalloc.h"

#include "DNA_mesh_types.h"
#include "DNA_meshdata_types.h"
#include "DNA_modifier_types.h"
#include "DNA_scene_types.h"

#include "BKE_customdata.h"
#include "BKE_lib_id.h"
#include "BKE_mesh.h"
#include "BKE_mesh_runtime.h"
#include "BKE_modifier.h"
#include "BKE_multires.h"
#include "BKE_subdiv.h"
#include "BKE_subsurf.h"
#include "BLI_math_vector.h"

#include "DEG_depsgraph_query.h"

#include "multires_reshape.h"

/* -------------------------------------------------------------------- */
/** \name Reshape from object
 * \{ */

bool multiresModifier_reshapeFromVertcos(struct Depsgraph *depsgraph,
                                         struct Object *object,
                                         struct MultiresModifierData *mmd,
                                         const float (*vert_coords)[3],
                                         const int num_vert_coords)
{
  MultiresReshapeContext reshape_context;
  if (!multires_reshape_context_create_from_object(&reshape_context, depsgraph, object, mmd)) {
    return false;
  }
  multires_reshape_store_original_grids(&reshape_context);
  multires_reshape_ensure_grids(object->data, reshape_context.top.level);
  if (!multires_reshape_assign_final_coords_from_vertcos(
          &reshape_context, vert_coords, num_vert_coords)) {
    multires_reshape_context_free(&reshape_context);
    return false;
  }
  multires_reshape_smooth_object_grids_with_details(&reshape_context);
  multires_reshape_object_grids_to_tangent_displacement(&reshape_context);
  multires_reshape_context_free(&reshape_context);
  return true;
}

bool multiresModifier_reshapeFromObject(struct Depsgraph *depsgraph,
                                        struct MultiresModifierData *mmd,
                                        struct Object *dst,
                                        struct Object *src)
{
  struct Scene *scene_eval = DEG_get_evaluated_scene(depsgraph);
  struct Object *src_eval = DEG_get_evaluated_object(depsgraph, src);
  Mesh *src_mesh_eval = mesh_get_eval_final(depsgraph, scene_eval, src_eval, &CD_MASK_BAREMESH);

  int num_deformed_verts;
  float(*deformed_verts)[3] = BKE_mesh_vert_coords_alloc(src_mesh_eval, &num_deformed_verts);

  const bool result = multiresModifier_reshapeFromVertcos(
      depsgraph, dst, mmd, deformed_verts, num_deformed_verts);

  MEM_freeN(deformed_verts);

  return result;
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name Reshape from modifier
 * \{ */

bool multiresModifier_reshapeFromDeformModifier(struct Depsgraph *depsgraph,
                                                struct Object *object,
                                                struct MultiresModifierData *mmd,
                                                struct ModifierData *deform_md)
{
  MultiresModifierData highest_mmd = *mmd;
  highest_mmd.sculptlvl = highest_mmd.totlvl;
  highest_mmd.lvl = highest_mmd.totlvl;
  highest_mmd.renderlvl = highest_mmd.totlvl;

  /* Create mesh for the multires, ignoring any further modifiers (leading
   * deformation modifiers will be applied though). */
  Mesh *multires_mesh = BKE_multires_create_mesh(depsgraph, object, &highest_mmd);
  int num_deformed_verts;
  float(*deformed_verts)[3] = BKE_mesh_vert_coords_alloc(multires_mesh, &num_deformed_verts);

  /* Apply deformation modifier on the multires, */
  const ModifierEvalContext modifier_ctx = {
      .depsgraph = depsgraph,
      .object = object,
      .flag = MOD_APPLY_USECACHE | MOD_APPLY_IGNORE_SIMPLIFY,
  };
  BKE_modifier_deform_verts(
      deform_md, &modifier_ctx, multires_mesh, deformed_verts, multires_mesh->totvert);
  BKE_id_free(NULL, multires_mesh);

  /* Reshaping */
  bool result = multiresModifier_reshapeFromVertcos(
      depsgraph, object, &highest_mmd, deformed_verts, num_deformed_verts);

  /* Cleanup */
  MEM_freeN(deformed_verts);

  return result;
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name Reshape from grids
 * \{ */

bool multiresModifier_reshapeFromCCG(const int tot_level,
                                     Mesh *coarse_mesh,
                                     struct SubdivCCG *subdiv_ccg)
{
  MultiresReshapeContext reshape_context;
  if (!multires_reshape_context_create_from_ccg(
          &reshape_context, subdiv_ccg, coarse_mesh, tot_level)) {
    return false;
  }

  multires_ensure_external_read(coarse_mesh, reshape_context.top.level);

  multires_reshape_store_original_grids(&reshape_context);
  multires_reshape_ensure_grids(coarse_mesh, reshape_context.top.level);
  if (!multires_reshape_assign_final_coords_from_ccg(&reshape_context, subdiv_ccg)) {
    multires_reshape_context_free(&reshape_context);
    return false;
  }
  multires_reshape_smooth_object_grids_with_details(&reshape_context);
  multires_reshape_object_grids_to_tangent_displacement(&reshape_context);
  multires_reshape_context_free(&reshape_context);
  return true;
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name Subdivision
 * \{ */

void multiresModifier_subdivide(Object *object,
                                MultiresModifierData *mmd,
                                const eMultiresSubdivideModeType mode)
{
  const int top_level = mmd->totlvl + 1;
  multiresModifier_subdivide_to_level(object, mmd, top_level, mode);
}

void multiresModifier_subdivide_to_level(struct Object *object,
                                         struct MultiresModifierData *mmd,
                                         const int top_level,
                                         const eMultiresSubdivideModeType mode)
{
  if (top_level <= mmd->totlvl) {
    return;
  }

  Mesh *coarse_mesh = object->data;
  if (coarse_mesh->totloop == 0) {
    /* If there are no loops in the mesh implies there is no CD_MDISPS as well. So can early output
     * from here as there is nothing to subdivide. */
    return;
  }

  MultiresReshapeContext reshape_context;

  /* There was no multires at all, all displacement is at 0. Can simply make sure all mdisps grids
   * are allocated at a proper level and return. */
  const bool has_mdisps = CustomData_has_layer(&coarse_mesh->ldata, CD_MDISPS);
  if (!has_mdisps) {
    CustomData_add_layer(&coarse_mesh->ldata, CD_MDISPS, CD_CALLOC, NULL, coarse_mesh->totloop);
  }

  /* NOTE: Subdivision happens from the top level of the existing multires modifier. If it is set
   * to 0 and there is mdisps layer it would mean that the modifier went out of sync with the data.
   * This happens when, for example, linking modifiers from one object to another.
   *
   * In such cases simply ensure grids to be the proper level.
   *
   * If something smarter is needed it is up to the operators which does data synchronization, so
   * that the mdisps layer is also synchronized. */
  if (!has_mdisps || top_level == 1 || mmd->totlvl == 0) {
    multires_reshape_ensure_grids(coarse_mesh, top_level);
    if (ELEM(mode, MULTIRES_SUBDIVIDE_LINEAR, MULTIRES_SUBDIVIDE_SIMPLE)) {
      multires_subdivide_create_tangent_displacement_linear_grids(object, mmd);
    }
    else {
      multires_set_tot_level(object, mmd, top_level);
    }
    return;
  }

  multires_flush_sculpt_updates(object);

  if (!multires_reshape_context_create_from_modifier(&reshape_context, object, mmd, top_level)) {
    return;
  }

  multires_reshape_store_original_grids(&reshape_context);
  multires_reshape_ensure_grids(coarse_mesh, reshape_context.top.level);
  multires_reshape_assign_final_elements_from_orig_mdisps(&reshape_context);

  /* Free original grids which makes it so smoothing with details thinks all the details were
   * added against base mesh's limit surface. This is similar behavior to as if we've done all
   * displacement in sculpt mode at the old top level and then propagated to the new top level. */
  multires_reshape_free_original_grids(&reshape_context);

  if (ELEM(mode, MULTIRES_SUBDIVIDE_LINEAR, MULTIRES_SUBDIVIDE_SIMPLE)) {
    multires_reshape_smooth_object_grids(&reshape_context, mode);
  }
  else {
    multires_reshape_smooth_object_grids_with_details(&reshape_context);
  }

  multires_reshape_object_grids_to_tangent_displacement(&reshape_context);
  multires_reshape_context_free(&reshape_context);

  multires_set_tot_level(object, mmd, top_level);
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name Apply base
 * \{ */

void multiresModifier_base_apply(struct Depsgraph *depsgraph,
                                 Object *object,
                                 MultiresModifierData *mmd)
{
  multires_force_sculpt_rebuild(object);

  MultiresReshapeContext reshape_context;
  if (!multires_reshape_context_create_from_object(&reshape_context, depsgraph, object, mmd)) {
    return;
  }

  multires_reshape_store_original_grids(&reshape_context);

  /* At this point base_mesh is object's mesh, the subdiv is initialized to the deformed state of
   * the base mesh.
   * Store coordinates of top level grids in object space which will define true shape we would
   * want to reshape to after modifying the base mesh. */
  multires_reshape_assign_final_coords_from_mdisps(&reshape_context);

  /* For modifying base mesh we only want to consider deformation caused by multires displacement
   * and ignore all deformation which might be caused by deformation modifiers leading the multires
   * one.
   * So refine the subdiv to the original mesh vertices positions, which will also need to make
   * it so object space displacement is re-evaluated for them (as in, can not re-use any knowledge
   * from the final coordinates in the object space ). */
  multires_reshape_apply_base_refine_from_base(&reshape_context);

  /* Modify original mesh coordinates. This happens in two steps:
   * - Coordinates are set to their final location, where they are intended to be in the final
   *   result.
   * - Heuristic moves them a bit, kind of canceling out the effect of subsurf (so then when
   *   multires modifier applies subsurf vertices are placed at the desired location). */
  multires_reshape_apply_base_update_mesh_coords(&reshape_context);
  multires_reshape_apply_base_refit_base_mesh(&reshape_context);

  /* Reshape to the stored final state.
   * Not that the base changed, so the subdiv is to be refined to the new positions. Unfortunately,
   * this can not be done foe entirely cheap: if there were deformation modifiers prior to the
   * multires they need to be re-evaluated for the new base mesh. */
  multires_reshape_apply_base_refine_from_deform(&reshape_context);
  multires_reshape_object_grids_to_tangent_displacement(&reshape_context);

  multires_reshape_context_free(&reshape_context);
}

/** \} */