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

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

#include "BKE_mesh.h"

#include "node_geometry_util.hh"

namespace blender::nodes::node_geo_input_mesh_face_area_cc {

static void node_declare(NodeDeclarationBuilder &b)
{
  b.add_output<decl::Float>(N_("Area"))
      .field_source()
      .description(N_("The surface area of each of the mesh's faces"));
}

static VArray<float> construct_face_area_gvarray(const MeshComponent &component,
                                                 const eAttrDomain domain)
{
  const Mesh *mesh = component.get_for_read();
  if (mesh == nullptr) {
    return {};
  }

  auto area_fn = [mesh](const int i) -> float {
    const MPoly *mp = &mesh->mpoly[i];
    return BKE_mesh_calc_poly_area(mp, &mesh->mloop[mp->loopstart], mesh->mvert);
  };

  return component.attributes()->adapt_domain<float>(
      VArray<float>::ForFunc(mesh->totpoly, area_fn), ATTR_DOMAIN_FACE, domain);
}

class FaceAreaFieldInput final : public GeometryFieldInput {
 public:
  FaceAreaFieldInput() : GeometryFieldInput(CPPType::get<float>(), "Face Area Field")
  {
    category_ = Category::Generated;
  }

  GVArray get_varray_for_context(const GeometryComponent &component,
                                 const eAttrDomain domain,
                                 IndexMask UNUSED(mask)) const final
  {
    if (component.type() == GEO_COMPONENT_TYPE_MESH) {
      const MeshComponent &mesh_component = static_cast<const MeshComponent &>(component);
      return construct_face_area_gvarray(mesh_component, domain);
    }
    return {};
  }

  uint64_t hash() const override
  {
    /* Some random constant hash. */
    return 1346334523;
  }

  bool is_equal_to(const fn::FieldNode &other) const override
  {
    return dynamic_cast<const FaceAreaFieldInput *>(&other) != nullptr;
  }
};

static void node_geo_exec(GeoNodeExecParams params)
{
  params.set_output("Area", Field<float>(std::make_shared<FaceAreaFieldInput>()));
}

}  // namespace blender::nodes::node_geo_input_mesh_face_area_cc

void register_node_type_geo_input_mesh_face_area()
{
  namespace file_ns = blender::nodes::node_geo_input_mesh_face_area_cc;

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