/* SPDX-License-Identifier: GPL-2.0-or-later */

#include "BLI_task.hh"

#include "BKE_mesh.h"

#include "node_geometry_util.hh"

namespace blender::nodes::node_geo_mesh_topology_corners_of_face_cc {

static void node_declare(NodeDeclarationBuilder &b)
{
  b.add_input<decl::Int>(N_("Face Index"))
      .implicit_field(implicit_field_inputs::index)
      .description(N_("The face to retrieve data from. Defaults to the face from the context"));
  b.add_input<decl::Float>(N_("Weights"))
      .supports_field()
      .hide_value()
      .description(N_("Values used to sort the face's corners. Uses indices by default"));
  b.add_input<decl::Int>(N_("Sort Index"))
      .min(0)
      .supports_field()
      .description(N_("Which of the sorted corners to output"));
  b.add_output<decl::Int>(N_("Corner Index"))
      .dependent_field()
      .description(N_("A corner of the face, chosen by the sort index"));
  b.add_output<decl::Int>(N_("Total"))
      .dependent_field()
      .description(N_("The number of corners in the face"));
}

class CornersOfFaceInput final : public bke::MeshFieldInput {
  const Field<int> face_index_;
  const Field<int> sort_index_;
  const Field<float> sort_weight_;

 public:
  CornersOfFaceInput(Field<int> face_index, Field<int> sort_index, Field<float> sort_weight)
      : bke::MeshFieldInput(CPPType::get<int>(), "Corner of Face"),
        face_index_(std::move(face_index)),
        sort_index_(std::move(sort_index)),
        sort_weight_(std::move(sort_weight))
  {
    category_ = Category::Generated;
  }

  GVArray get_varray_for_context(const Mesh &mesh,
                                 const eAttrDomain domain,
                                 const IndexMask mask) const final
  {
    const Span<MPoly> polys = mesh.polys();

    const bke::MeshFieldContext context{mesh, domain};
    fn::FieldEvaluator evaluator{context, &mask};
    evaluator.add(face_index_);
    evaluator.add(sort_index_);
    evaluator.evaluate();
    const VArray<int> face_indices = evaluator.get_evaluated<int>(0);
    const VArray<int> indices_in_sort = evaluator.get_evaluated<int>(1);

    const bke::MeshFieldContext corner_context{mesh, ATTR_DOMAIN_CORNER};
    fn::FieldEvaluator corner_evaluator{corner_context, mesh.totloop};
    corner_evaluator.add(sort_weight_);
    corner_evaluator.evaluate();
    const VArray<float> all_sort_weights = corner_evaluator.get_evaluated<float>(0);

    Array<int> corner_of_face(mask.min_array_size());
    threading::parallel_for(mask.index_range(), 1024, [&](const IndexRange range) {
      /* Reuse arrays to avoid allocation. */
      Array<float> sort_weights;
      Array<int> sort_indices;

      for (const int selection_i : mask.slice(range)) {
        const int poly_i = face_indices[selection_i];
        const int index_in_sort = indices_in_sort[selection_i];
        if (!polys.index_range().contains(poly_i)) {
          corner_of_face[selection_i] = 0;
          continue;
        }

        const MPoly &poly = polys[poly_i];
        const IndexRange corners(poly.loopstart, poly.totloop);

        /* Retrieve the weights for each corner. */
        sort_weights.reinitialize(corners.size());
        all_sort_weights.materialize_compressed(IndexMask(corners),
                                                sort_weights.as_mutable_span());

        /* Sort a separate array of compressed indices corresponding to the compressed weights.
         * This allows using `materialize_compressed` to avoid virtual function call overhead
         * when accessing values in the sort weights. However, it means a separate array of
         * indices within the compressed array is necessary for sorting. */
        sort_indices.reinitialize(corners.size());
        std::iota(sort_indices.begin(), sort_indices.end(), 0);
        std::stable_sort(sort_indices.begin(), sort_indices.end(), [&](int a, int b) {
          return sort_weights[a] < sort_weights[b];
        });

        const int index_in_sort_wrapped = mod_i(index_in_sort, corners.size());
        corner_of_face[selection_i] = corners[sort_indices[index_in_sort_wrapped]];
      }
    });

    return VArray<int>::ForContainer(std::move(corner_of_face));
  }

  uint64_t hash() const final
  {
    return 6927982716657;
  }

  bool is_equal_to(const fn::FieldNode &other) const final
  {
    if (const auto *typed = dynamic_cast<const CornersOfFaceInput *>(&other)) {
      return typed->face_index_ == face_index_ && typed->sort_index_ == sort_index_ &&
             typed->sort_weight_ == sort_weight_;
    }
    return false;
  }

  std::optional<eAttrDomain> preferred_domain(const Mesh & /*mesh*/) const final
  {
    return ATTR_DOMAIN_FACE;
  }
};

static int get_poly_totloop(const MPoly &poly)
{
  return poly.totloop;
}

class CornersOfFaceCountInput final : public bke::MeshFieldInput {
 public:
  CornersOfFaceCountInput() : bke::MeshFieldInput(CPPType::get<int>(), "Face Corner Count")
  {
    category_ = Category::Generated;
  }

  GVArray get_varray_for_context(const Mesh &mesh,
                                 const eAttrDomain domain,
                                 const IndexMask /*mask*/) const final
  {
    if (domain != ATTR_DOMAIN_FACE) {
      return {};
    }
    return VArray<int>::ForDerivedSpan<MPoly, get_poly_totloop>(mesh.polys());
  }

  uint64_t hash() const final
  {
    return 8345908765432698;
  }

  bool is_equal_to(const fn::FieldNode &other) const final
  {
    if (dynamic_cast<const CornersOfFaceCountInput *>(&other)) {
      return true;
    }
    return false;
  }

  std::optional<eAttrDomain> preferred_domain(const Mesh & /*mesh*/) const final
  {
    return ATTR_DOMAIN_FACE;
  }
};

static void node_geo_exec(GeoNodeExecParams params)
{
  const Field<int> face_index = params.extract_input<Field<int>>("Face Index");
  if (params.output_is_required("Total")) {
    params.set_output("Total",
                      Field<int>(std::make_shared<FieldAtIndexInput>(
                          face_index,
                          Field<int>(std::make_shared<CornersOfFaceCountInput>()),
                          ATTR_DOMAIN_FACE)));
  }
  if (params.output_is_required("Corner Index")) {
    params.set_output("Corner Index",
                      Field<int>(std::make_shared<CornersOfFaceInput>(
                          face_index,
                          params.extract_input<Field<int>>("Sort Index"),
                          params.extract_input<Field<float>>("Weights"))));
  }
}

}  // namespace blender::nodes::node_geo_mesh_topology_corners_of_face_cc

void register_node_type_geo_mesh_topology_corners_of_face()
{
  namespace file_ns = blender::nodes::node_geo_mesh_topology_corners_of_face_cc;

  static bNodeType ntype;
  geo_node_type_base(
      &ntype, GEO_NODE_MESH_TOPOLOGY_CORNERS_OF_FACE, "Corners of Face", NODE_CLASS_INPUT);
  ntype.geometry_node_execute = file_ns::node_geo_exec;
  ntype.declare = file_ns::node_declare;
  nodeRegisterType(&ntype);
}