/*
 * 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.
 */

#include "BLI_listbase.h"

#include "DNA_mesh_types.h"
#include "DNA_meshdata_types.h"
#include "DNA_object_types.h"

#include "BKE_attribute_access.hh"
#include "BKE_attribute_math.hh"
#include "BKE_deform.h"
#include "BKE_geometry_set.hh"
#include "BKE_lib_id.h"
#include "BKE_mesh.h"

#include "attribute_access_intern.hh"

/* Can't include BKE_object_deform.h right now, due to an enum forward declaration. */
extern "C" MDeformVert *BKE_object_defgroup_data_create(ID *id);

using blender::fn::GVArray;

/* -------------------------------------------------------------------- */
/** \name Geometry Component Implementation
 * \{ */

MeshComponent::MeshComponent() : GeometryComponent(GEO_COMPONENT_TYPE_MESH)
{
}

MeshComponent::~MeshComponent()
{
  this->clear();
}

GeometryComponent *MeshComponent::copy() const
{
  MeshComponent *new_component = new MeshComponent();
  if (mesh_ != nullptr) {
    new_component->mesh_ = BKE_mesh_copy_for_eval(mesh_, false);
    new_component->ownership_ = GeometryOwnershipType::Owned;
  }
  return new_component;
}

void MeshComponent::clear()
{
  BLI_assert(this->is_mutable());
  if (mesh_ != nullptr) {
    if (ownership_ == GeometryOwnershipType::Owned) {
      BKE_id_free(nullptr, mesh_);
    }
    mesh_ = nullptr;
  }
}

bool MeshComponent::has_mesh() const
{
  return mesh_ != nullptr;
}

/* Clear the component and replace it with the new mesh. */
void MeshComponent::replace(Mesh *mesh, GeometryOwnershipType ownership)
{
  BLI_assert(this->is_mutable());
  this->clear();
  mesh_ = mesh;
  ownership_ = ownership;
}

/* Return the mesh and clear the component. The caller takes over responsibility for freeing the
 * mesh (if the component was responsible before). */
Mesh *MeshComponent::release()
{
  BLI_assert(this->is_mutable());
  Mesh *mesh = mesh_;
  mesh_ = nullptr;
  return mesh;
}

/* Get the mesh from this component. This method can be used by multiple threads at the same
 * time. Therefore, the returned mesh should not be modified. No ownership is transferred. */
const Mesh *MeshComponent::get_for_read() const
{
  return mesh_;
}

/* Get the mesh from this component. This method can only be used when the component is mutable,
 * i.e. it is not shared. The returned mesh can be modified. No ownership is transferred. */
Mesh *MeshComponent::get_for_write()
{
  BLI_assert(this->is_mutable());
  if (ownership_ == GeometryOwnershipType::ReadOnly) {
    mesh_ = BKE_mesh_copy_for_eval(mesh_, false);
    ownership_ = GeometryOwnershipType::Owned;
  }
  return mesh_;
}

bool MeshComponent::is_empty() const
{
  return mesh_ == nullptr;
}

bool MeshComponent::owns_direct_data() const
{
  return ownership_ == GeometryOwnershipType::Owned;
}

void MeshComponent::ensure_owns_direct_data()
{
  BLI_assert(this->is_mutable());
  if (ownership_ != GeometryOwnershipType::Owned) {
    mesh_ = BKE_mesh_copy_for_eval(mesh_, false);
    ownership_ = GeometryOwnershipType::Owned;
  }
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name Attribute Access
 * \{ */

int MeshComponent::attribute_domain_size(const AttributeDomain domain) const
{
  if (mesh_ == nullptr) {
    return 0;
  }
  switch (domain) {
    case ATTR_DOMAIN_CORNER:
      return mesh_->totloop;
    case ATTR_DOMAIN_POINT:
      return mesh_->totvert;
    case ATTR_DOMAIN_EDGE:
      return mesh_->totedge;
    case ATTR_DOMAIN_FACE:
      return mesh_->totpoly;
    default:
      break;
  }
  return 0;
}

namespace blender::bke {

template<typename T>
static void adapt_mesh_domain_corner_to_point_impl(const Mesh &mesh,
                                                   const VArray<T> &old_values,
                                                   MutableSpan<T> r_values)
{
  BLI_assert(r_values.size() == mesh.totvert);
  attribute_math::DefaultMixer<T> mixer(r_values);

  for (const int loop_index : IndexRange(mesh.totloop)) {
    const T value = old_values[loop_index];
    const MLoop &loop = mesh.mloop[loop_index];
    const int point_index = loop.v;
    mixer.mix_in(point_index, value);
  }
  mixer.finalize();
}

static GVArrayPtr adapt_mesh_domain_corner_to_point(const Mesh &mesh, GVArrayPtr varray)
{
  GVArrayPtr new_varray;
  attribute_math::convert_to_static_type(varray->type(), [&](auto dummy) {
    using T = decltype(dummy);
    if constexpr (!std::is_void_v<attribute_math::DefaultMixer<T>>) {
      /* We compute all interpolated values at once, because for this interpolation, one has to
       * iterate over all loops anyway. */
      Array<T> values(mesh.totvert);
      adapt_mesh_domain_corner_to_point_impl<T>(mesh, varray->typed<T>(), values);
      new_varray = std::make_unique<fn::GVArray_For_ArrayContainer<Array<T>>>(std::move(values));
    }
  });
  return new_varray;
}

template<typename T>
static void adapt_mesh_domain_point_to_corner_impl(const Mesh &mesh,
                                                   const VArray<T> &old_values,
                                                   MutableSpan<T> r_values)
{
  BLI_assert(r_values.size() == mesh.totloop);

  for (const int loop_index : IndexRange(mesh.totloop)) {
    const int vertex_index = mesh.mloop[loop_index].v;
    r_values[loop_index] = old_values[vertex_index];
  }
}

static GVArrayPtr adapt_mesh_domain_point_to_corner(const Mesh &mesh, GVArrayPtr varray)
{
  GVArrayPtr new_varray;
  attribute_math::convert_to_static_type(varray->type(), [&](auto dummy) {
    using T = decltype(dummy);
    /* It is not strictly necessary to compute the value for all corners here. Instead one could
     * lazily lookup the mesh topology when a specific index accessed. This can be more efficient
     * when an algorithm only accesses very few of the corner values. However, for the algorithms
     * we currently have, precomputing the array is fine. Also, it is easier to implement. */
    Array<T> values(mesh.totloop);
    adapt_mesh_domain_point_to_corner_impl<T>(mesh, varray->typed<T>(), values);
    new_varray = std::make_unique<fn::GVArray_For_ArrayContainer<Array<T>>>(std::move(values));
  });
  return new_varray;
}

/**
 * \note Theoretically this interpolation does not need to compute all values at once.
 * However, doing that makes the implementation simpler, and this can be optimized in the future if
 * only some values are required.
 */
template<typename T>
static void adapt_mesh_domain_corner_to_face_impl(const Mesh &mesh,
                                                  const VArray<T> &old_values,
                                                  MutableSpan<T> r_values)
{
  BLI_assert(r_values.size() == mesh.totpoly);
  attribute_math::DefaultMixer<T> mixer(r_values);

  for (const int poly_index : IndexRange(mesh.totpoly)) {
    const MPoly &poly = mesh.mpoly[poly_index];
    for (const int loop_index : IndexRange(poly.loopstart, poly.totloop)) {
      const T value = old_values[loop_index];
      mixer.mix_in(poly_index, value);
    }
  }

  mixer.finalize();
}

static GVArrayPtr adapt_mesh_domain_corner_to_face(const Mesh &mesh, GVArrayPtr varray)
{
  GVArrayPtr new_varray;
  attribute_math::convert_to_static_type(varray->type(), [&](auto dummy) {
    using T = decltype(dummy);
    if constexpr (!std::is_void_v<attribute_math::DefaultMixer<T>>) {
      Array<T> values(mesh.totpoly);
      adapt_mesh_domain_corner_to_face_impl<T>(mesh, varray->typed<T>(), values);
      new_varray = std::make_unique<fn::GVArray_For_ArrayContainer<Array<T>>>(std::move(values));
    }
  });
  return new_varray;
}

template<typename T>
static void adapt_mesh_domain_corner_to_edge_impl(const Mesh &mesh,
                                                  const VArray<T> &old_values,
                                                  MutableSpan<T> r_values)
{
  BLI_assert(r_values.size() == mesh.totedge);
  attribute_math::DefaultMixer<T> mixer(r_values);

  for (const int poly_index : IndexRange(mesh.totpoly)) {
    const MPoly &poly = mesh.mpoly[poly_index];

    /* For every edge, mix values from the two adjacent corners (the current and next corner). */
    for (const int loop_index : IndexRange(poly.loopstart, poly.totloop)) {
      const int loop_index_next = (loop_index + 1) % poly.totloop;
      const MLoop &loop = mesh.mloop[loop_index];
      const int edge_index = loop.e;
      mixer.mix_in(edge_index, old_values[loop_index]);
      mixer.mix_in(edge_index, old_values[loop_index_next]);
    }
  }

  mixer.finalize();
}

static GVArrayPtr adapt_mesh_domain_corner_to_edge(const Mesh &mesh, GVArrayPtr varray)
{
  GVArrayPtr new_varray;
  attribute_math::convert_to_static_type(varray->type(), [&](auto dummy) {
    using T = decltype(dummy);
    if constexpr (!std::is_void_v<attribute_math::DefaultMixer<T>>) {
      Array<T> values(mesh.totedge);
      adapt_mesh_domain_corner_to_edge_impl<T>(mesh, varray->typed<T>(), values);
      new_varray = std::make_unique<fn::GVArray_For_ArrayContainer<Array<T>>>(std::move(values));
    }
  });
  return new_varray;
}

template<typename T>
void adapt_mesh_domain_face_to_point_impl(const Mesh &mesh,
                                          const VArray<T> &old_values,
                                          MutableSpan<T> r_values)
{
  BLI_assert(r_values.size() == mesh.totvert);
  attribute_math::DefaultMixer<T> mixer(r_values);

  for (const int poly_index : IndexRange(mesh.totpoly)) {
    const MPoly &poly = mesh.mpoly[poly_index];
    const T value = old_values[poly_index];
    for (const int loop_index : IndexRange(poly.loopstart, poly.totloop)) {
      const MLoop &loop = mesh.mloop[loop_index];
      const int point_index = loop.v;
      mixer.mix_in(point_index, value);
    }
  }

  mixer.finalize();
}

static GVArrayPtr adapt_mesh_domain_face_to_point(const Mesh &mesh, GVArrayPtr varray)
{
  GVArrayPtr new_varray;
  attribute_math::convert_to_static_type(varray->type(), [&](auto dummy) {
    using T = decltype(dummy);
    if constexpr (!std::is_void_v<attribute_math::DefaultMixer<T>>) {
      Array<T> values(mesh.totvert);
      adapt_mesh_domain_face_to_point_impl<T>(mesh, varray->typed<T>(), values);
      new_varray = std::make_unique<fn::GVArray_For_ArrayContainer<Array<T>>>(std::move(values));
    }
  });
  return new_varray;
}

template<typename T>
void adapt_mesh_domain_face_to_corner_impl(const Mesh &mesh,
                                           const VArray<T> &old_values,
                                           MutableSpan<T> r_values)
{
  BLI_assert(r_values.size() == mesh.totloop);

  for (const int poly_index : IndexRange(mesh.totpoly)) {
    const MPoly &poly = mesh.mpoly[poly_index];
    MutableSpan<T> poly_corner_values = r_values.slice(poly.loopstart, poly.totloop);
    poly_corner_values.fill(old_values[poly_index]);
  }
}

static GVArrayPtr adapt_mesh_domain_face_to_corner(const Mesh &mesh, GVArrayPtr varray)
{
  GVArrayPtr new_varray;
  attribute_math::convert_to_static_type(varray->type(), [&](auto dummy) {
    using T = decltype(dummy);
    if constexpr (!std::is_void_v<attribute_math::DefaultMixer<T>>) {
      Array<T> values(mesh.totloop);
      adapt_mesh_domain_face_to_corner_impl<T>(mesh, varray->typed<T>(), values);
      new_varray = std::make_unique<fn::GVArray_For_ArrayContainer<Array<T>>>(std::move(values));
    }
  });
  return new_varray;
}

template<typename T>
void adapt_mesh_domain_face_to_edge_impl(const Mesh &mesh,
                                         const VArray<T> &old_values,
                                         MutableSpan<T> r_values)
{
  BLI_assert(r_values.size() == mesh.totedge);
  attribute_math::DefaultMixer<T> mixer(r_values);

  for (const int poly_index : IndexRange(mesh.totpoly)) {
    const MPoly &poly = mesh.mpoly[poly_index];
    const T value = old_values[poly_index];
    for (const int loop_index : IndexRange(poly.loopstart, poly.totloop)) {
      const MLoop &loop = mesh.mloop[loop_index];
      mixer.mix_in(loop.e, value);
    }
  }
  mixer.finalize();
}

static GVArrayPtr adapt_mesh_domain_face_to_edge(const Mesh &mesh, GVArrayPtr varray)
{
  GVArrayPtr new_varray;
  attribute_math::convert_to_static_type(varray->type(), [&](auto dummy) {
    using T = decltype(dummy);
    if constexpr (!std::is_void_v<attribute_math::DefaultMixer<T>>) {
      Array<T> values(mesh.totedge);
      adapt_mesh_domain_face_to_edge_impl<T>(mesh, varray->typed<T>(), values);
      new_varray = std::make_unique<fn::GVArray_For_ArrayContainer<Array<T>>>(std::move(values));
    }
  });
  return new_varray;
}

/**
 * \note Theoretically this interpolation does not need to compute all values at once.
 * However, doing that makes the implementation simpler, and this can be optimized in the future if
 * only some values are required.
 */
template<typename T>
static void adapt_mesh_domain_point_to_face_impl(const Mesh &mesh,
                                                 const VArray<T> &old_values,
                                                 MutableSpan<T> r_values)
{
  BLI_assert(r_values.size() == mesh.totpoly);
  attribute_math::DefaultMixer<T> mixer(r_values);

  for (const int poly_index : IndexRange(mesh.totpoly)) {
    const MPoly &poly = mesh.mpoly[poly_index];
    for (const int loop_index : IndexRange(poly.loopstart, poly.totloop)) {
      MLoop &loop = mesh.mloop[loop_index];
      const int point_index = loop.v;
      mixer.mix_in(poly_index, old_values[point_index]);
    }
  }
  mixer.finalize();
}

static GVArrayPtr adapt_mesh_domain_point_to_face(const Mesh &mesh, GVArrayPtr varray)
{
  GVArrayPtr new_varray;
  attribute_math::convert_to_static_type(varray->type(), [&](auto dummy) {
    using T = decltype(dummy);
    if constexpr (!std::is_void_v<attribute_math::DefaultMixer<T>>) {
      Array<T> values(mesh.totpoly);
      adapt_mesh_domain_point_to_face_impl<T>(mesh, varray->typed<T>(), values);
      new_varray = std::make_unique<fn::GVArray_For_ArrayContainer<Array<T>>>(std::move(values));
    }
  });
  return new_varray;
}

/**
 * \note Theoretically this interpolation does not need to compute all values at once.
 * However, doing that makes the implementation simpler, and this can be optimized in the future if
 * only some values are required.
 */
template<typename T>
static void adapt_mesh_domain_point_to_edge_impl(const Mesh &mesh,
                                                 const VArray<T> &old_values,
                                                 MutableSpan<T> r_values)
{
  BLI_assert(r_values.size() == mesh.totedge);
  attribute_math::DefaultMixer<T> mixer(r_values);

  for (const int edge_index : IndexRange(mesh.totedge)) {
    const MEdge &edge = mesh.medge[edge_index];
    mixer.mix_in(edge_index, old_values[edge.v1]);
    mixer.mix_in(edge_index, old_values[edge.v2]);
  }

  mixer.finalize();
}

static GVArrayPtr adapt_mesh_domain_point_to_edge(const Mesh &mesh, GVArrayPtr varray)
{
  GVArrayPtr new_varray;
  attribute_math::convert_to_static_type(varray->type(), [&](auto dummy) {
    using T = decltype(dummy);
    if constexpr (!std::is_void_v<attribute_math::DefaultMixer<T>>) {
      Array<T> values(mesh.totedge);
      adapt_mesh_domain_point_to_edge_impl<T>(mesh, varray->typed<T>(), values);
      new_varray = std::make_unique<fn::GVArray_For_ArrayContainer<Array<T>>>(std::move(values));
    }
  });
  return new_varray;
}

template<typename T>
void adapt_mesh_domain_edge_to_corner_impl(const Mesh &mesh,
                                           const VArray<T> &old_values,
                                           MutableSpan<T> r_values)
{
  BLI_assert(r_values.size() == mesh.totloop);
  attribute_math::DefaultMixer<T> mixer(r_values);

  for (const int poly_index : IndexRange(mesh.totpoly)) {
    const MPoly &poly = mesh.mpoly[poly_index];

    /* For every corner, mix the values from the adjacent edges on the face. */
    for (const int loop_index : IndexRange(poly.loopstart, poly.totloop)) {
      const int loop_index_prev = loop_index - 1 + (loop_index == poly.loopstart) * poly.totloop;
      const MLoop &loop = mesh.mloop[loop_index];
      const MLoop &loop_prev = mesh.mloop[loop_index_prev];
      mixer.mix_in(loop_index, old_values[loop.e]);
      mixer.mix_in(loop_index, old_values[loop_prev.e]);
    }
  }

  mixer.finalize();
}

static GVArrayPtr adapt_mesh_domain_edge_to_corner(const Mesh &mesh, GVArrayPtr varray)
{
  GVArrayPtr new_varray;
  attribute_math::convert_to_static_type(varray->type(), [&](auto dummy) {
    using T = decltype(dummy);
    if constexpr (!std::is_void_v<attribute_math::DefaultMixer<T>>) {
      Array<T> values(mesh.totloop);
      adapt_mesh_domain_edge_to_corner_impl<T>(mesh, varray->typed<T>(), values);
      new_varray = std::make_unique<fn::GVArray_For_ArrayContainer<Array<T>>>(std::move(values));
    }
  });
  return new_varray;
}

template<typename T>
static void adapt_mesh_domain_edge_to_point_impl(const Mesh &mesh,
                                                 const VArray<T> &old_values,
                                                 MutableSpan<T> r_values)
{
  BLI_assert(r_values.size() == mesh.totvert);
  attribute_math::DefaultMixer<T> mixer(r_values);

  for (const int edge_index : IndexRange(mesh.totedge)) {
    const MEdge &edge = mesh.medge[edge_index];
    const T value = old_values[edge_index];
    mixer.mix_in(edge.v1, value);
    mixer.mix_in(edge.v2, value);
  }

  mixer.finalize();
}

static GVArrayPtr adapt_mesh_domain_edge_to_point(const Mesh &mesh, GVArrayPtr varray)
{
  GVArrayPtr new_varray;
  attribute_math::convert_to_static_type(varray->type(), [&](auto dummy) {
    using T = decltype(dummy);
    if constexpr (!std::is_void_v<attribute_math::DefaultMixer<T>>) {
      Array<T> values(mesh.totvert);
      adapt_mesh_domain_edge_to_point_impl<T>(mesh, varray->typed<T>(), values);
      new_varray = std::make_unique<fn::GVArray_For_ArrayContainer<Array<T>>>(std::move(values));
    }
  });
  return new_varray;
}

/**
 * \note Theoretically this interpolation does not need to compute all values at once.
 * However, doing that makes the implementation simpler, and this can be optimized in the future if
 * only some values are required.
 */
template<typename T>
static void adapt_mesh_domain_edge_to_face_impl(const Mesh &mesh,
                                                const VArray<T> &old_values,
                                                MutableSpan<T> r_values)
{
  BLI_assert(r_values.size() == mesh.totpoly);
  attribute_math::DefaultMixer<T> mixer(r_values);

  for (const int poly_index : IndexRange(mesh.totpoly)) {
    const MPoly &poly = mesh.mpoly[poly_index];
    for (const int loop_index : IndexRange(poly.loopstart, poly.totloop)) {
      const MLoop &loop = mesh.mloop[loop_index];
      mixer.mix_in(poly_index, old_values[loop.e]);
    }
  }

  mixer.finalize();
}

static GVArrayPtr adapt_mesh_domain_edge_to_face(const Mesh &mesh, GVArrayPtr varray)
{
  GVArrayPtr new_varray;
  attribute_math::convert_to_static_type(varray->type(), [&](auto dummy) {
    using T = decltype(dummy);
    if constexpr (!std::is_void_v<attribute_math::DefaultMixer<T>>) {
      Array<T> values(mesh.totpoly);
      adapt_mesh_domain_edge_to_face_impl<T>(mesh, varray->typed<T>(), values);
      new_varray = std::make_unique<fn::GVArray_For_ArrayContainer<Array<T>>>(std::move(values));
    }
  });
  return new_varray;
}

}  // namespace blender::bke

blender::fn::GVArrayPtr MeshComponent::attribute_try_adapt_domain(
    blender::fn::GVArrayPtr varray,
    const AttributeDomain from_domain,
    const AttributeDomain to_domain) const
{
  if (!varray) {
    return {};
  }
  if (varray->size() == 0) {
    return {};
  }
  if (from_domain == to_domain) {
    return varray;
  }

  switch (from_domain) {
    case ATTR_DOMAIN_CORNER: {
      switch (to_domain) {
        case ATTR_DOMAIN_POINT:
          return blender::bke::adapt_mesh_domain_corner_to_point(*mesh_, std::move(varray));
        case ATTR_DOMAIN_FACE:
          return blender::bke::adapt_mesh_domain_corner_to_face(*mesh_, std::move(varray));
        case ATTR_DOMAIN_EDGE:
          return blender::bke::adapt_mesh_domain_corner_to_edge(*mesh_, std::move(varray));
        default:
          break;
      }
      break;
    }
    case ATTR_DOMAIN_POINT: {
      switch (to_domain) {
        case ATTR_DOMAIN_CORNER:
          return blender::bke::adapt_mesh_domain_point_to_corner(*mesh_, std::move(varray));
        case ATTR_DOMAIN_FACE:
          return blender::bke::adapt_mesh_domain_point_to_face(*mesh_, std::move(varray));
        case ATTR_DOMAIN_EDGE:
          return blender::bke::adapt_mesh_domain_point_to_edge(*mesh_, std::move(varray));
        default:
          break;
      }
      break;
    }
    case ATTR_DOMAIN_FACE: {
      switch (to_domain) {
        case ATTR_DOMAIN_POINT:
          return blender::bke::adapt_mesh_domain_face_to_point(*mesh_, std::move(varray));
        case ATTR_DOMAIN_CORNER:
          return blender::bke::adapt_mesh_domain_face_to_corner(*mesh_, std::move(varray));
        case ATTR_DOMAIN_EDGE:
          return blender::bke::adapt_mesh_domain_face_to_edge(*mesh_, std::move(varray));
        default:
          break;
      }
      break;
    }
    case ATTR_DOMAIN_EDGE: {
      switch (to_domain) {
        case ATTR_DOMAIN_CORNER:
          return blender::bke::adapt_mesh_domain_edge_to_corner(*mesh_, std::move(varray));
        case ATTR_DOMAIN_POINT:
          return blender::bke::adapt_mesh_domain_edge_to_point(*mesh_, std::move(varray));
        case ATTR_DOMAIN_FACE:
          return blender::bke::adapt_mesh_domain_edge_to_face(*mesh_, std::move(varray));
        default:
          break;
      }
      break;
    }
    default:
      break;
  }

  return {};
}

static Mesh *get_mesh_from_component_for_write(GeometryComponent &component)
{
  BLI_assert(component.type() == GEO_COMPONENT_TYPE_MESH);
  MeshComponent &mesh_component = static_cast<MeshComponent &>(component);
  return mesh_component.get_for_write();
}

static const Mesh *get_mesh_from_component_for_read(const GeometryComponent &component)
{
  BLI_assert(component.type() == GEO_COMPONENT_TYPE_MESH);
  const MeshComponent &mesh_component = static_cast<const MeshComponent &>(component);
  return mesh_component.get_for_read();
}

namespace blender::bke {

template<typename StructT, typename ElemT, ElemT (*GetFunc)(const StructT &)>
static GVArrayPtr make_derived_read_attribute(const void *data, const int domain_size)
{
  return std::make_unique<fn::GVArray_For_DerivedSpan<StructT, ElemT, GetFunc>>(
      Span<StructT>((const StructT *)data, domain_size));
}

template<typename StructT,
         typename ElemT,
         ElemT (*GetFunc)(const StructT &),
         void (*SetFunc)(StructT &, ElemT)>
static GVMutableArrayPtr make_derived_write_attribute(void *data, const int domain_size)
{
  return std::make_unique<fn::GVMutableArray_For_DerivedSpan<StructT, ElemT, GetFunc, SetFunc>>(
      MutableSpan<StructT>((StructT *)data, domain_size));
}

static float3 get_vertex_position(const MVert &vert)
{
  return float3(vert.co);
}

static void set_vertex_position(MVert &vert, float3 position)
{
  copy_v3_v3(vert.co, position);
}

static void tag_normals_dirty_when_writing_position(GeometryComponent &component)
{
  Mesh *mesh = get_mesh_from_component_for_write(component);
  if (mesh != nullptr) {
    mesh->runtime.cd_dirty_vert |= CD_MASK_NORMAL;
  }
}

static int get_material_index(const MPoly &mpoly)
{
  return static_cast<int>(mpoly.mat_nr);
}

static void set_material_index(MPoly &mpoly, int index)
{
  mpoly.mat_nr = static_cast<short>(std::clamp(index, 0, SHRT_MAX));
}

static bool get_shade_smooth(const MPoly &mpoly)
{
  return mpoly.flag & ME_SMOOTH;
}

static void set_shade_smooth(MPoly &mpoly, bool value)
{
  SET_FLAG_FROM_TEST(mpoly.flag, value, ME_SMOOTH);
}

static float2 get_loop_uv(const MLoopUV &uv)
{
  return float2(uv.uv);
}

static void set_loop_uv(MLoopUV &uv, float2 co)
{
  copy_v2_v2(uv.uv, co);
}

static ColorGeometry4f get_loop_color(const MLoopCol &col)
{
  ColorGeometry4b encoded_color = ColorGeometry4b(col.r, col.g, col.b, col.a);
  ColorGeometry4f linear_color = encoded_color.decode();
  return linear_color;
}

static void set_loop_color(MLoopCol &col, ColorGeometry4f linear_color)
{
  ColorGeometry4b encoded_color = linear_color.encode();
  col.r = encoded_color.r;
  col.g = encoded_color.g;
  col.b = encoded_color.b;
  col.a = encoded_color.a;
}

static float get_crease(const MEdge &edge)
{
  return edge.crease / 255.0f;
}

static void set_crease(MEdge &edge, float value)
{
  edge.crease = round_fl_to_uchar_clamp(value * 255.0f);
}

class VMutableArray_For_VertexWeights final : public VMutableArray<float> {
 private:
  MDeformVert *dverts_;
  const int dvert_index_;

 public:
  VMutableArray_For_VertexWeights(MDeformVert *dverts, const int totvert, const int dvert_index)
      : VMutableArray<float>(totvert), dverts_(dverts), dvert_index_(dvert_index)
  {
  }

  float get_impl(const int64_t index) const override
  {
    return get_internal(dverts_, dvert_index_, index);
  }

  void set_impl(const int64_t index, const float value) override
  {
    MDeformWeight *weight = BKE_defvert_ensure_index(&dverts_[index], dvert_index_);
    weight->weight = value;
  }

  static float get_internal(const MDeformVert *dverts, const int dvert_index, const int64_t index)
  {
    if (dverts == nullptr) {
      return 0.0f;
    }
    const MDeformVert &dvert = dverts[index];
    for (const MDeformWeight &weight : Span(dvert.dw, dvert.totweight)) {
      if (weight.def_nr == dvert_index) {
        return weight.weight;
      }
    }
    return 0.0f;
  }
};

class VArray_For_VertexWeights final : public VArray<float> {
 private:
  const MDeformVert *dverts_;
  const int dvert_index_;

 public:
  VArray_For_VertexWeights(const MDeformVert *dverts, const int totvert, const int dvert_index)
      : VArray<float>(totvert), dverts_(dverts), dvert_index_(dvert_index)
  {
  }

  float get_impl(const int64_t index) const override
  {
    return VMutableArray_For_VertexWeights::get_internal(dverts_, dvert_index_, index);
  }
};

/**
 * This provider makes vertex groups available as float attributes.
 */
class VertexGroupsAttributeProvider final : public DynamicAttributesProvider {
 public:
  ReadAttributeLookup try_get_for_read(const GeometryComponent &component,
                                       const AttributeIDRef &attribute_id) const final
  {
    BLI_assert(component.type() == GEO_COMPONENT_TYPE_MESH);
    if (!attribute_id.is_named()) {
      return {};
    }
    const MeshComponent &mesh_component = static_cast<const MeshComponent &>(component);
    const Mesh *mesh = mesh_component.get_for_read();
    if (mesh == nullptr) {
      return {};
    }
    const std::string name = attribute_id.name();
    const int vertex_group_index = BLI_findstringindex(
        &mesh->vertex_group_names, name.c_str(), offsetof(bDeformGroup, name));
    if (vertex_group_index < 0) {
      return {};
    }
    if (mesh->dvert == nullptr) {
      static const float default_value = 0.0f;
      return {std::make_unique<fn::GVArray_For_SingleValueRef>(
                  CPPType::get<float>(), mesh->totvert, &default_value),
              ATTR_DOMAIN_POINT};
    }
    return {std::make_unique<fn::GVArray_For_EmbeddedVArray<float, VArray_For_VertexWeights>>(
                mesh->totvert, mesh->dvert, mesh->totvert, vertex_group_index),
            ATTR_DOMAIN_POINT};
  }

  WriteAttributeLookup try_get_for_write(GeometryComponent &component,
                                         const AttributeIDRef &attribute_id) const final
  {
    BLI_assert(component.type() == GEO_COMPONENT_TYPE_MESH);
    if (!attribute_id.is_named()) {
      return {};
    }
    MeshComponent &mesh_component = static_cast<MeshComponent &>(component);
    Mesh *mesh = mesh_component.get_for_write();
    if (mesh == nullptr) {
      return {};
    }

    const std::string name = attribute_id.name();
    const int vertex_group_index = BLI_findstringindex(
        &mesh->vertex_group_names, name.c_str(), offsetof(bDeformGroup, name));
    if (vertex_group_index < 0) {
      return {};
    }
    if (mesh->dvert == nullptr) {
      BKE_object_defgroup_data_create(&mesh->id);
    }
    else {
      /* Copy the data layer if it is shared with some other mesh. */
      mesh->dvert = (MDeformVert *)CustomData_duplicate_referenced_layer(
          &mesh->vdata, CD_MDEFORMVERT, mesh->totvert);
    }
    return {
        std::make_unique<
            fn::GVMutableArray_For_EmbeddedVMutableArray<float, VMutableArray_For_VertexWeights>>(
            mesh->totvert, mesh->dvert, mesh->totvert, vertex_group_index),
        ATTR_DOMAIN_POINT};
  }

  bool try_delete(GeometryComponent &component, const AttributeIDRef &attribute_id) const final
  {
    BLI_assert(component.type() == GEO_COMPONENT_TYPE_MESH);
    if (!attribute_id.is_named()) {
      return false;
    }
    MeshComponent &mesh_component = static_cast<MeshComponent &>(component);
    Mesh *mesh = mesh_component.get_for_write();
    if (mesh == nullptr) {
      return true;
    }

    const std::string name = attribute_id.name();
    const int vertex_group_index = BLI_findstringindex(
        &mesh->vertex_group_names, name.c_str(), offsetof(bDeformGroup, name));
    if (vertex_group_index < 0) {
      return false;
    }
    if (mesh->dvert == nullptr) {
      return true;
    }
    for (MDeformVert &dvert : MutableSpan(mesh->dvert, mesh->totvert)) {
      MDeformWeight *weight = BKE_defvert_find_index(&dvert, vertex_group_index);
      BKE_defvert_remove_group(&dvert, weight);
    }
    return true;
  }

  bool foreach_attribute(const GeometryComponent &component,
                         const AttributeForeachCallback callback) const final
  {
    BLI_assert(component.type() == GEO_COMPONENT_TYPE_MESH);
    const MeshComponent &mesh_component = static_cast<const MeshComponent &>(component);
    const Mesh *mesh = mesh_component.get_for_read();
    if (mesh == nullptr) {
      return true;
    }

    LISTBASE_FOREACH (const bDeformGroup *, group, &mesh->vertex_group_names) {
      if (!callback(group->name, {ATTR_DOMAIN_POINT, CD_PROP_FLOAT})) {
        return false;
      }
    }
    return true;
  }

  void foreach_domain(const FunctionRef<void(AttributeDomain)> callback) const final
  {
    callback(ATTR_DOMAIN_POINT);
  }
};

/**
 * This provider makes face normals available as a read-only float3 attribute.
 */
class NormalAttributeProvider final : public BuiltinAttributeProvider {
 public:
  NormalAttributeProvider()
      : BuiltinAttributeProvider(
            "normal", ATTR_DOMAIN_FACE, CD_PROP_FLOAT3, NonCreatable, Readonly, NonDeletable)
  {
  }

  GVArrayPtr try_get_for_read(const GeometryComponent &component) const final
  {
    const MeshComponent &mesh_component = static_cast<const MeshComponent &>(component);
    const Mesh *mesh = mesh_component.get_for_read();
    if (mesh == nullptr) {
      return {};
    }

    /* Use existing normals if possible. */
    if (!(mesh->runtime.cd_dirty_poly & CD_MASK_NORMAL) &&
        CustomData_has_layer(&mesh->pdata, CD_NORMAL)) {
      const void *data = CustomData_get_layer(&mesh->pdata, CD_NORMAL);

      return std::make_unique<fn::GVArray_For_Span<float3>>(
          Span<float3>((const float3 *)data, mesh->totpoly));
    }

    Array<float3> normals(mesh->totpoly);
    for (const int i : IndexRange(mesh->totpoly)) {
      const MPoly *poly = &mesh->mpoly[i];
      BKE_mesh_calc_poly_normal(poly, &mesh->mloop[poly->loopstart], mesh->mvert, normals[i]);
    }

    return std::make_unique<fn::GVArray_For_ArrayContainer<Array<float3>>>(std::move(normals));
  }

  GVMutableArrayPtr try_get_for_write(GeometryComponent &UNUSED(component)) const final
  {
    return {};
  }

  bool try_delete(GeometryComponent &UNUSED(component)) const final
  {
    return false;
  }

  bool try_create(GeometryComponent &UNUSED(component),
                  const AttributeInit &UNUSED(initializer)) const final
  {
    return false;
  }

  bool exists(const GeometryComponent &component) const final
  {
    return component.attribute_domain_size(ATTR_DOMAIN_FACE) != 0;
  }
};

/**
 * In this function all the attribute providers for a mesh component are created. Most data in this
 * function is statically allocated, because it does not change over time.
 */
static ComponentAttributeProviders create_attribute_providers_for_mesh()
{
  static auto update_custom_data_pointers = [](GeometryComponent &component) {
    Mesh *mesh = get_mesh_from_component_for_write(component);
    if (mesh != nullptr) {
      BKE_mesh_update_customdata_pointers(mesh, false);
    }
  };

#define MAKE_MUTABLE_CUSTOM_DATA_GETTER(NAME) \
  [](GeometryComponent &component) -> CustomData * { \
    Mesh *mesh = get_mesh_from_component_for_write(component); \
    return mesh ? &mesh->NAME : nullptr; \
  }
#define MAKE_CONST_CUSTOM_DATA_GETTER(NAME) \
  [](const GeometryComponent &component) -> const CustomData * { \
    const Mesh *mesh = get_mesh_from_component_for_read(component); \
    return mesh ? &mesh->NAME : nullptr; \
  }

  static CustomDataAccessInfo corner_access = {MAKE_MUTABLE_CUSTOM_DATA_GETTER(ldata),
                                               MAKE_CONST_CUSTOM_DATA_GETTER(ldata),
                                               update_custom_data_pointers};
  static CustomDataAccessInfo point_access = {MAKE_MUTABLE_CUSTOM_DATA_GETTER(vdata),
                                              MAKE_CONST_CUSTOM_DATA_GETTER(vdata),
                                              update_custom_data_pointers};
  static CustomDataAccessInfo edge_access = {MAKE_MUTABLE_CUSTOM_DATA_GETTER(edata),
                                             MAKE_CONST_CUSTOM_DATA_GETTER(edata),
                                             update_custom_data_pointers};
  static CustomDataAccessInfo face_access = {MAKE_MUTABLE_CUSTOM_DATA_GETTER(pdata),
                                             MAKE_CONST_CUSTOM_DATA_GETTER(pdata),
                                             update_custom_data_pointers};

#undef MAKE_CONST_CUSTOM_DATA_GETTER
#undef MAKE_MUTABLE_CUSTOM_DATA_GETTER

  static BuiltinCustomDataLayerProvider position(
      "position",
      ATTR_DOMAIN_POINT,
      CD_PROP_FLOAT3,
      CD_MVERT,
      BuiltinAttributeProvider::NonCreatable,
      BuiltinAttributeProvider::Writable,
      BuiltinAttributeProvider::NonDeletable,
      point_access,
      make_derived_read_attribute<MVert, float3, get_vertex_position>,
      make_derived_write_attribute<MVert, float3, get_vertex_position, set_vertex_position>,
      tag_normals_dirty_when_writing_position);

  static NormalAttributeProvider normal;

  static BuiltinCustomDataLayerProvider material_index(
      "material_index",
      ATTR_DOMAIN_FACE,
      CD_PROP_INT32,
      CD_MPOLY,
      BuiltinAttributeProvider::NonCreatable,
      BuiltinAttributeProvider::Writable,
      BuiltinAttributeProvider::NonDeletable,
      face_access,
      make_derived_read_attribute<MPoly, int, get_material_index>,
      make_derived_write_attribute<MPoly, int, get_material_index, set_material_index>,
      nullptr);

  static BuiltinCustomDataLayerProvider shade_smooth(
      "shade_smooth",
      ATTR_DOMAIN_FACE,
      CD_PROP_BOOL,
      CD_MPOLY,
      BuiltinAttributeProvider::NonCreatable,
      BuiltinAttributeProvider::Writable,
      BuiltinAttributeProvider::NonDeletable,
      face_access,
      make_derived_read_attribute<MPoly, bool, get_shade_smooth>,
      make_derived_write_attribute<MPoly, bool, get_shade_smooth, set_shade_smooth>,
      nullptr);

  static BuiltinCustomDataLayerProvider crease(
      "crease",
      ATTR_DOMAIN_EDGE,
      CD_PROP_FLOAT,
      CD_MEDGE,
      BuiltinAttributeProvider::NonCreatable,
      BuiltinAttributeProvider::Writable,
      BuiltinAttributeProvider::NonDeletable,
      edge_access,
      make_derived_read_attribute<MEdge, float, get_crease>,
      make_derived_write_attribute<MEdge, float, get_crease, set_crease>,
      nullptr);

  static NamedLegacyCustomDataProvider uvs(
      ATTR_DOMAIN_CORNER,
      CD_PROP_FLOAT2,
      CD_MLOOPUV,
      corner_access,
      make_derived_read_attribute<MLoopUV, float2, get_loop_uv>,
      make_derived_write_attribute<MLoopUV, float2, get_loop_uv, set_loop_uv>);

  static NamedLegacyCustomDataProvider vertex_colors(
      ATTR_DOMAIN_CORNER,
      CD_PROP_COLOR,
      CD_MLOOPCOL,
      corner_access,
      make_derived_read_attribute<MLoopCol, ColorGeometry4f, get_loop_color>,
      make_derived_write_attribute<MLoopCol, ColorGeometry4f, get_loop_color, set_loop_color>);

  static VertexGroupsAttributeProvider vertex_groups;
  static CustomDataAttributeProvider corner_custom_data(ATTR_DOMAIN_CORNER, corner_access);
  static CustomDataAttributeProvider point_custom_data(ATTR_DOMAIN_POINT, point_access);
  static CustomDataAttributeProvider edge_custom_data(ATTR_DOMAIN_EDGE, edge_access);
  static CustomDataAttributeProvider face_custom_data(ATTR_DOMAIN_FACE, face_access);

  return ComponentAttributeProviders({&position, &material_index, &shade_smooth, &normal, &crease},
                                     {&uvs,
                                      &vertex_colors,
                                      &corner_custom_data,
                                      &vertex_groups,
                                      &point_custom_data,
                                      &edge_custom_data,
                                      &face_custom_data});
}

}  // namespace blender::bke

const blender::bke::ComponentAttributeProviders *MeshComponent::get_attribute_providers() const
{
  static blender::bke::ComponentAttributeProviders providers =
      blender::bke::create_attribute_providers_for_mesh();
  return &providers;
}

/** \} */