/* SPDX-FileCopyrightText: 2023 Blender Authors
 *
 * SPDX-License-Identifier: GPL-2.0-or-later */

#include "BLI_array_utils.hh"
#include "BLI_math_color.hh"
#include "BLI_math_quaternion.hh"
#include "BLI_math_vector.hh"

#include "BLI_length_parameterize.hh"
#include "BLI_task.hh"

#include "FN_field.hh"
#include "FN_multi_function_builder.hh"
#include "FN_multi_function_registry.hh"

#include "BKE_attribute_math.hh"
#include "BKE_curves.hh"
#include "BKE_curves_utils.hh"
#include "BKE_deform.hh"
#include "BKE_geometry_fields.hh"

#include "GEO_resample_curves.hh"

namespace blender::geometry {

static fn::Field<int> get_count_input_max_one(const fn::Field<int> &count_field)
{
  return fn::Field<int>(
      fn::FieldOperation::from(fn::multi_function::registry::lookup("max(int, int)"_ustr),
                               {fn::Field<int>(1), count_field}));
}

static int get_count_from_length(const float curve_length,
                                 const float sample_length,
                                 const bool keep_last_segment)
{
  /* Find the number of sampled segments by dividing the total length by
   * the sample length. Then there is one more sampled point than segment. */
  if (UNLIKELY(sample_length == 0.0f)) {
    return 1;
  }
  const int count = int(curve_length / sample_length) + 1;
  return std::max(keep_last_segment ? 2 : 1, count);
}

static fn::Field<int> get_count_input_from_length(const fn::Field<float> &length_field,
                                                  const bool keep_last_segment)
{
  static auto get_count_fn = mf::build::SI3_SO<float, float, bool, int>(
      "Length Input to Count",
      get_count_from_length,
      mf::build::exec_presets::SomeSpanOrSingle<0, 1>());

  auto get_count_op = fn::FieldOperation::from(
      get_count_fn,
      {fn::Field<float>::from_input<bke::CurveLengthFieldInput>(),
       length_field,
       fn::Field<bool>(keep_last_segment)});

  return fn::Field<int>(std::move(get_count_op));
}

/**
 * Return true if the attribute should be copied/interpolated to the result curves.
 * Don't output attributes that correspond to curve types that have no curves in the result.
 */
static bool interpolate_attribute_to_curves(const StringRef name,
                                            const std::array<int, CURVE_TYPES_NUM> &type_counts)
{
  if (bke::attribute_name_is_anonymous(name)) {
    return true;
  }
  if (ELEM(name, "handle_type_left", "handle_type_right", "handle_left", "handle_right")) {
    return type_counts[CURVE_TYPE_BEZIER] != 0;
  }
  if (ELEM(name, "nurbs_weight")) {
    return type_counts[CURVE_TYPE_NURBS] != 0;
  }
  return true;
}

/**
 * Return true if the attribute should be copied to poly curves.
 */
static bool interpolate_attribute_to_poly_curve(const StringRef name)
{
  static const Set<StringRef> no_interpolation{{
      "handle_type_left",
      "handle_type_right",
      "handle_right",
      "handle_left",
      "nurbs_weight",
  }};
  return !no_interpolation.contains(name);
}

/**
 * Retrieve spans from source and result attributes.
 */
static void retrieve_attribute_spans(const Span<StringRef> names,
                                     const CurvesGeometry &src_curves,
                                     CurvesGeometry &dst_curves,
                                     Vector<GVArraySpan> &src_arrays,
                                     Vector<GMutableSpan> &dst_arrays,
                                     Vector<bke::GSpanAttributeWriter> &dst_writers)
{
  const bke::AttributeAccessor src_attributes = src_curves.attributes();
  bke::MutableAttributeAccessor dst_attributes = dst_curves.attributes_for_write();
  for (const int i : names.index_range()) {
    GVArray src_attribute = *src_attributes.lookup(names[i], bke::AttrDomain::Point);
    const bke::AttrType data_type = bke::cpp_type_to_attribute_type(src_attribute.type());

    const CommonVArrayInfo info = src_attribute.common_info();
    if (info.type == CommonVArrayInfo::Type::Single) {
      const bke::AttributeInitValue init(GPointer(src_attribute.type(), info.data));
      dst_attributes.add(names[i], bke::AttrDomain::Point, data_type, init);
      continue;
    }

    src_arrays.append(std::move(src_attribute));

    bke::GSpanAttributeWriter dst_attribute = dst_attributes.lookup_or_add_for_write_only_span(
        names[i], bke::AttrDomain::Point, data_type);
    dst_arrays.append(dst_attribute.span);
    dst_writers.append(std::move(dst_attribute));
  }
}

struct AttributesForResample : NonCopyable, NonMovable {
  Vector<GVArraySpan> src;
  Vector<GMutableSpan> dst;

  Vector<bke::GSpanAttributeWriter> dst_attributes;

  Vector<GVArraySpan> src_no_interpolation;
  Vector<GMutableSpan> dst_no_interpolation;

  Span<float3> src_evaluated_tangents;
  Span<float3> src_evaluated_normals;
  MutableSpan<float3> dst_tangents;
  MutableSpan<float3> dst_normals;
};

/**
 * Gather a set of all generic attribute IDs to copy to the result curves.
 */
static void gather_point_attributes_to_interpolate(
    const CurvesGeometry &src_curves,
    CurvesGeometry &dst_curves,
    AttributesForResample &result,
    const ResampleCurvesOutputAttributeIDs &output_ids)
{
  VectorSet<StringRef> names;
  VectorSet<StringRef> names_no_interpolation;
  src_curves.attributes().foreach_attribute([&](const bke::AttributeIter &iter) {
    if (iter.domain != bke::AttrDomain::Point) {
      return;
    }
    if (iter.data_type == bke::AttrType::String) {
      return;
    }
    if (!interpolate_attribute_to_curves(iter.name, dst_curves.curve_type_counts())) {
      return;
    }
    if (interpolate_attribute_to_poly_curve(iter.name)) {
      names.add_new(iter.name);
    }
    else {
      names_no_interpolation.add_new(iter.name);
    }
  });

  /* Position is handled differently since it has non-generic interpolation for Bezier
   * curves and because the evaluated positions are cached for each evaluated point. */
  names.remove_contained("position");

  retrieve_attribute_spans(
      names, src_curves, dst_curves, result.src, result.dst, result.dst_attributes);

  /* Attributes that aren't interpolated like Bezier handles still have to be copied
   * to the result when there are any unselected curves of the corresponding type. */
  retrieve_attribute_spans(names_no_interpolation,
                           src_curves,
                           dst_curves,
                           result.src_no_interpolation,
                           result.dst_no_interpolation,
                           result.dst_attributes);

  bke::MutableAttributeAccessor dst_attributes = dst_curves.attributes_for_write();
  if (output_ids.tangent_id) {
    result.src_evaluated_tangents = src_curves.evaluated_tangents();
    bke::GSpanAttributeWriter dst_attribute = dst_attributes.lookup_or_add_for_write_only_span(
        *output_ids.tangent_id, bke::AttrDomain::Point, bke::AttrType::Float3);
    result.dst_tangents = dst_attribute.span.typed<float3>();
    result.dst_attributes.append(std::move(dst_attribute));
  }
  if (output_ids.normal_id) {
    result.src_evaluated_normals = src_curves.evaluated_normals();
    bke::GSpanAttributeWriter dst_attribute = dst_attributes.lookup_or_add_for_write_only_span(
        *output_ids.normal_id, bke::AttrDomain::Point, bke::AttrType::Float3);
    result.dst_normals = dst_attribute.span.typed<float3>();
    result.dst_attributes.append(std::move(dst_attribute));
  }
}

static void copy_or_defaults_for_unselected_curves(const CurvesGeometry &src_curves,
                                                   const IndexMask &unselected_curves,
                                                   const AttributesForResample &attributes,
                                                   CurvesGeometry &dst_curves)
{
  const OffsetIndices src_points_by_curve = src_curves.points_by_curve();
  const OffsetIndices dst_points_by_curve = dst_curves.points_by_curve();
  array_utils::copy_group_to_group(src_points_by_curve,
                                   dst_points_by_curve,
                                   unselected_curves,
                                   src_curves.positions(),
                                   dst_curves.positions_for_write());

  for (const int i : attributes.src.index_range()) {
    array_utils::copy_group_to_group(src_points_by_curve,
                                     dst_points_by_curve,
                                     unselected_curves,
                                     attributes.src[i],
                                     attributes.dst[i]);
  }
  for (const int i : attributes.src_no_interpolation.index_range()) {
    array_utils::copy_group_to_group(src_points_by_curve,
                                     dst_points_by_curve,
                                     unselected_curves,
                                     attributes.src_no_interpolation[i],
                                     attributes.dst_no_interpolation[i]);
  }

  if (!attributes.dst_tangents.is_empty()) {
    bke::curves::fill_points(
        dst_points_by_curve, unselected_curves, float3(0), attributes.dst_tangents);
  }
  if (!attributes.dst_normals.is_empty()) {
    bke::curves::fill_points(
        dst_points_by_curve, unselected_curves, float3(0), attributes.dst_normals);
  }
}

static void normalize_span(MutableSpan<float3> data)
{
  for (const int i : data.index_range()) {
    data[i] = math::normalize(data[i]);
  }
}

static void normalize_curve_point_data(const IndexMaskSegment curve_selection,
                                       const OffsetIndices<int> points_by_curve,
                                       MutableSpan<float3> data)
{
  for (const int i_curve : curve_selection) {
    normalize_span(data.slice(points_by_curve[i_curve]));
  }
}

/**
 * Buffer for temporary evaluated curve data, used for memory reuse between multiple attributes of
 * different types.
 */
struct EvalDataBuffer {
  using AllocatorType = GuardedAlignedAllocator<>;
  /* Use a default alignment that works for all attribute types, and don't use the inline buffer
   * because it doesn't necessarily have the correct alignment. */
  Vector<std::byte, 0, AllocatorType> heap_allocated;
  alignas(AllocatorType::min_alignment) std::array<std::byte, 1024> inline_buffer;

  template<typename T> MutableSpan<T> resize(const int64_t size)
  {
    const int64_t size_in_bytes = sizeof(T) * size;
    if (size_in_bytes <= this->inline_buffer.size()) {
      return MutableSpan<std::byte>(this->inline_buffer).slice(0, size_in_bytes).cast<T>();
    }
    this->heap_allocated.resize(size_in_bytes);
    return this->heap_allocated.as_mutable_span().cast<T>();
  }
};

static void resample_to_uniform(const CurvesGeometry &src_curves,
                                const IndexMask &selection,
                                const ResampleCurvesOutputAttributeIDs &output_ids,
                                CurvesGeometry &dst_curves)
{
  if (src_curves.curves_range().is_empty()) {
    return;
  }

  const OffsetIndices src_points_by_curve = src_curves.points_by_curve();
  const OffsetIndices evaluated_points_by_curve = src_curves.evaluated_points_by_curve();
  const VArray<bool> curves_cyclic = src_curves.cyclic();
  const VArray<int8_t> curve_types = src_curves.curve_types();
  const Span<float3> evaluated_positions = src_curves.evaluated_positions();

  /* All resampled curves are poly curves. */
  dst_curves.fill_curve_types(selection, CURVE_TYPE_POLY);

  MutableSpan<float3> dst_positions = dst_curves.positions_for_write();

  AttributesForResample attributes;
  gather_point_attributes_to_interpolate(src_curves, dst_curves, attributes, output_ids);

  src_curves.ensure_evaluated_lengths();

  /* Sampling arbitrary attributes works by first interpolating them to the curve's standard
   * "evaluated points" and then interpolating that result with the uniform samples. This is
   * potentially wasteful when down-sampling a curve to many fewer points. There are two possible
   * solutions: only sample the necessary points for interpolation, or first sample curve
   * parameter/segment indices and evaluate the curve directly. */
  Array<int> sample_indices(dst_curves.points_num());
  Array<float> sample_factors(dst_curves.points_num());

  const OffsetIndices dst_points_by_curve = dst_curves.points_by_curve();

  /* Use a "for each group of curves: for each attribute: for each curve" pattern to work on
   * smaller sections of data that ideally fit into CPU cache better than simply one attribute at a
   * time or one curve at a time. */
  selection.foreach_segment(
      [&](const IndexMaskSegment selection_segment) {
        EvalDataBuffer evaluated_buffer;

        /* Gather uniform samples based on the accumulated lengths of the original curve. */
        for (const int i_curve : selection_segment) {
          const bool cyclic = curves_cyclic[i_curve];
          const IndexRange dst_points = dst_points_by_curve[i_curve];
          const Span<float> lengths = src_curves.evaluated_lengths_for_curve(i_curve, cyclic);
          if (lengths.is_empty()) {
            /* Handle curves with only one evaluated point. */
            sample_indices.as_mutable_span().slice(dst_points).fill(0);
            sample_factors.as_mutable_span().slice(dst_points).fill(0.0f);
          }
          else {
            length_parameterize::sample_uniform(
                lengths,
                !curves_cyclic[i_curve],
                sample_indices.as_mutable_span().slice(dst_points),
                sample_factors.as_mutable_span().slice(dst_points));
          }
        }

        /* For every attribute, evaluate attributes from every curve in the range in the original
         * curve's "evaluated points", then use linear interpolation to sample to the result. */
        for (const int i_attribute : attributes.dst.index_range()) {
          const CPPType &type = attributes.src[i_attribute].type();
          bke::attribute_math::to_static_type(type, [&]<typename T>() {
            if constexpr (!std::is_same_v<T, std::string>) {
              Span<T> src = attributes.src[i_attribute].typed<T>();
              MutableSpan<T> dst = attributes.dst[i_attribute].typed<T>();

              for (const int i_curve : selection_segment) {
                const IndexRange src_points = src_points_by_curve[i_curve];
                const IndexRange dst_points = dst_points_by_curve[i_curve];

                if (curve_types[i_curve] == CURVE_TYPE_POLY) {
                  length_parameterize::interpolate(src.slice(src_points),
                                                   sample_indices.as_span().slice(dst_points),
                                                   sample_factors.as_span().slice(dst_points),
                                                   dst.slice(dst_points));
                }
                else {
                  MutableSpan evaluated = evaluated_buffer.resize<T>(
                      evaluated_points_by_curve[i_curve].size());
                  src_curves.interpolate_to_evaluated(i_curve, src.slice(src_points), evaluated);

                  length_parameterize::interpolate(evaluated.as_span(),
                                                   sample_indices.as_span().slice(dst_points),
                                                   sample_factors.as_span().slice(dst_points),
                                                   dst.slice(dst_points));
                }
              }
            }
          });
        }

        auto interpolate_evaluated_data = [&](const Span<float3> src, MutableSpan<float3> dst) {
          for (const int i_curve : selection_segment) {
            const IndexRange src_points = evaluated_points_by_curve[i_curve];
            const IndexRange dst_points = dst_points_by_curve[i_curve];
            length_parameterize::interpolate(src.slice(src_points),
                                             sample_indices.as_span().slice(dst_points),
                                             sample_factors.as_span().slice(dst_points),
                                             dst.slice(dst_points));
          }
        };

        /* Interpolate the evaluated positions to the resampled curves. */
        interpolate_evaluated_data(evaluated_positions, dst_positions);

        if (!attributes.dst_tangents.is_empty()) {
          interpolate_evaluated_data(attributes.src_evaluated_tangents, attributes.dst_tangents);
          normalize_curve_point_data(
              selection_segment, dst_points_by_curve, attributes.dst_tangents);
        }
        if (!attributes.dst_normals.is_empty()) {
          interpolate_evaluated_data(attributes.src_evaluated_normals, attributes.dst_normals);
          normalize_curve_point_data(
              selection_segment, dst_points_by_curve, attributes.dst_normals);
        }

        /* Fill the default value for non-interpolating attributes that still must be copied. */
        for (GMutableSpan dst : attributes.dst_no_interpolation) {
          for (const int i_curve : selection_segment) {
            const IndexRange dst_points = dst_points_by_curve[i_curve];
            dst.type().value_initialize_n(dst.slice(dst_points).data(), dst_points.size());
          }
        }
      },
      exec_mode::grain_size(512));

  IndexMaskMemory memory;
  const IndexMask unselected = selection.complement(src_curves.curves_range(), memory);
  copy_or_defaults_for_unselected_curves(src_curves, unselected, attributes, dst_curves);

  for (bke::GSpanAttributeWriter &attribute : attributes.dst_attributes) {
    attribute.finish();
  }
}

static CurvesGeometry resample_to_uniform(const CurvesGeometry &src_curves,
                                          const fn::FieldContext &field_context,
                                          const fn::Field<bool> &selection_field,
                                          const fn::Field<int> &count_field,
                                          const ResampleCurvesOutputAttributeIDs &output_ids)
{
  if (src_curves.curves_range().is_empty()) {
    return {};
  }
  const OffsetIndices src_points_by_curve = src_curves.points_by_curve();

  CurvesGeometry dst_curves = bke::curves::copy_only_curve_domain(src_curves);
  /* Copy vertex groups from source curves to allow copying vertex group attributes. */
  BKE_defgroup_copy_list(&dst_curves.vertex_group_names, &src_curves.vertex_group_names);
  MutableSpan<int> dst_offsets = dst_curves.offsets_for_write();

  fn::FieldEvaluator evaluator{field_context, src_curves.curves_num()};
  evaluator.set_selection(selection_field);
  evaluator.add_with_destination(count_field, dst_offsets.drop_back(1));
  evaluator.evaluate();
  const IndexMask selection = evaluator.get_evaluated_selection_as_mask();
  IndexMaskMemory memory;
  const IndexMask unselected = selection.complement(src_curves.curves_range(), memory);

  /* Fill the counts for the curves that aren't selected and accumulate the counts into offsets. */
  offset_indices::copy_group_sizes(src_points_by_curve, unselected, dst_offsets);
  if (!offset_indices::accumulate_counts_to_offsets_with_overflow_check(dst_offsets)) {
    return {};
  }
  dst_curves.resize(dst_offsets.last(), dst_curves.curves_num());

  resample_to_uniform(src_curves, selection, output_ids, dst_curves);

  bke::curves::nurbs::copy_custom_knots(src_curves, selection, dst_curves);
  return dst_curves;
}

CurvesGeometry resample_to_count(const CurvesGeometry &src_curves,
                                 const IndexMask &selection,
                                 const VArray<int> &counts,
                                 const ResampleCurvesOutputAttributeIDs &output_ids)
{
  if (src_curves.curves_range().is_empty()) {
    return {};
  }
  const OffsetIndices src_points_by_curve = src_curves.points_by_curve();

  CurvesGeometry dst_curves = bke::curves::copy_only_curve_domain(src_curves);
  /* Copy vertex groups from source curves to allow copying vertex group attributes. */
  BKE_defgroup_copy_list(&dst_curves.vertex_group_names, &src_curves.vertex_group_names);
  MutableSpan<int> dst_offsets = dst_curves.offsets_for_write();

  array_utils::copy(counts, selection, dst_offsets);

  IndexMaskMemory memory;
  const IndexMask unselected = selection.complement(src_curves.curves_range(), memory);

  /* Fill the counts for the curves that aren't selected and accumulate the counts into offsets. */
  offset_indices::copy_group_sizes(src_points_by_curve, unselected, dst_offsets);
  /* We assume the counts are at least 1. */
  BLI_assert(std::all_of(dst_offsets.begin(),
                         dst_offsets.drop_back(1).end(),
                         [&](const int count) { return count > 0; }));
  offset_indices::accumulate_counts_to_offsets(dst_offsets);
  dst_curves.resize(dst_offsets.last(), dst_curves.curves_num());

  resample_to_uniform(src_curves, selection, output_ids, dst_curves);

  bke::curves::nurbs::copy_custom_knots(src_curves, selection, dst_curves);
  return dst_curves;
}

CurvesGeometry resample_to_count(const CurvesGeometry &src_curves,
                                 const fn::FieldContext &field_context,
                                 const fn::Field<bool> &selection_field,
                                 const fn::Field<int> &count_field,
                                 const ResampleCurvesOutputAttributeIDs &output_ids)
{
  return resample_to_uniform(src_curves,
                             field_context,
                             selection_field,
                             get_count_input_max_one(count_field),
                             output_ids);
}

CurvesGeometry resample_to_length(const CurvesGeometry &src_curves,
                                  const IndexMask &selection,
                                  const VArray<float> &sample_lengths,
                                  const ResampleCurvesOutputAttributeIDs &output_ids,
                                  const bool keep_last_segment)
{
  if (src_curves.curves_range().is_empty()) {
    return {};
  }
  const OffsetIndices src_points_by_curve = src_curves.points_by_curve();
  const VArray<bool> curves_cyclic = src_curves.cyclic();

  CurvesGeometry dst_curves = bke::curves::copy_only_curve_domain(src_curves);
  /* Copy vertex groups from source curves to allow copying vertex group attributes. */
  BKE_defgroup_copy_list(&dst_curves.vertex_group_names, &src_curves.vertex_group_names);
  MutableSpan<int> dst_offsets = dst_curves.offsets_for_write();

  src_curves.ensure_evaluated_lengths();
  selection.foreach_index(
      [&](const int curve_i) {
        const float curve_length = src_curves.evaluated_length_total_for_curve(
            curve_i, curves_cyclic[curve_i]);
        dst_offsets[curve_i] = get_count_from_length(
            curve_length, sample_lengths[curve_i], keep_last_segment);
      },
      exec_mode::grain_size(1024));

  IndexMaskMemory memory;
  const IndexMask unselected = selection.complement(src_curves.curves_range(), memory);

  /* Fill the counts for the curves that aren't selected and accumulate the counts into offsets. */
  offset_indices::copy_group_sizes(src_points_by_curve, unselected, dst_offsets);
  offset_indices::accumulate_counts_to_offsets(dst_offsets);
  dst_curves.resize(dst_offsets.last(), dst_curves.curves_num());

  resample_to_uniform(src_curves, selection, output_ids, dst_curves);

  bke::curves::nurbs::copy_custom_knots(src_curves, selection, dst_curves);
  return dst_curves;
}

CurvesGeometry resample_to_length(const CurvesGeometry &src_curves,
                                  const fn::FieldContext &field_context,
                                  const fn::Field<bool> &selection_field,
                                  const fn::Field<float> &segment_length_field,
                                  const ResampleCurvesOutputAttributeIDs &output_ids,
                                  const bool keep_last_segment)
{
  return resample_to_uniform(src_curves,
                             field_context,
                             selection_field,
                             get_count_input_from_length(segment_length_field, keep_last_segment),
                             output_ids);
}

CurvesGeometry resample_to_evaluated(const CurvesGeometry &src_curves,
                                     const IndexMask &selection,
                                     const ResampleCurvesOutputAttributeIDs &output_ids)
{
  if (src_curves.curves_range().is_empty()) {
    return {};
  }
  const OffsetIndices src_points_by_curve = src_curves.points_by_curve();
  const OffsetIndices src_evaluated_points_by_curve = src_curves.evaluated_points_by_curve();
  const Span<float3> evaluated_positions = src_curves.evaluated_positions();

  IndexMaskMemory memory;
  const IndexMask unselected = selection.complement(src_curves.curves_range(), memory);

  CurvesGeometry dst_curves = bke::curves::copy_only_curve_domain(src_curves);
  /* Copy vertex groups from source curves to allow copying vertex group attributes. */
  BKE_defgroup_copy_list(&dst_curves.vertex_group_names, &src_curves.vertex_group_names);
  dst_curves.fill_curve_types(selection, CURVE_TYPE_POLY);
  MutableSpan<int> dst_offsets = dst_curves.offsets_for_write();
  offset_indices::copy_group_sizes(src_evaluated_points_by_curve, selection, dst_offsets);
  offset_indices::copy_group_sizes(src_points_by_curve, unselected, dst_offsets);
  offset_indices::accumulate_counts_to_offsets(dst_offsets);
  const OffsetIndices dst_points_by_curve = dst_curves.points_by_curve();

  dst_curves.resize(dst_offsets.last(), dst_curves.curves_num());

  MutableSpan<float3> dst_positions = dst_curves.positions_for_write();

  AttributesForResample attributes;
  gather_point_attributes_to_interpolate(src_curves, dst_curves, attributes, output_ids);

  src_curves.ensure_can_interpolate_to_evaluated();
  selection.foreach_segment(
      [&](const IndexMaskSegment selection_segment) {
        /* Evaluate generic point attributes directly to the result attributes. */
        for (const int i_attribute : attributes.dst.index_range()) {
          for (const int i_curve : selection_segment) {
            const IndexRange src_points = src_points_by_curve[i_curve];
            const IndexRange dst_points = dst_points_by_curve[i_curve];
            src_curves.interpolate_to_evaluated(i_curve,
                                                attributes.src[i_attribute].slice(src_points),
                                                attributes.dst[i_attribute].slice(dst_points));
          }
        }

        auto copy_evaluated_data = [&](const Span<float3> src, MutableSpan<float3> dst) {
          for (const int i_curve : selection_segment) {
            const IndexRange src_points = src_evaluated_points_by_curve[i_curve];
            const IndexRange dst_points = dst_points_by_curve[i_curve];
            dst.slice(dst_points).copy_from(src.slice(src_points));
          }
        };

        /* Copy the evaluated positions to the selected curves. */
        copy_evaluated_data(evaluated_positions, dst_positions);

        if (!attributes.dst_tangents.is_empty()) {
          copy_evaluated_data(attributes.src_evaluated_tangents, attributes.dst_tangents);
          normalize_curve_point_data(
              selection_segment, dst_points_by_curve, attributes.dst_tangents);
        }
        if (!attributes.dst_normals.is_empty()) {
          copy_evaluated_data(attributes.src_evaluated_normals, attributes.dst_normals);
          normalize_curve_point_data(
              selection_segment, dst_points_by_curve, attributes.dst_normals);
        }

        /* Fill the default value for non-interpolating attributes that still must be copied. */
        for (GMutableSpan dst : attributes.dst_no_interpolation) {
          for (const int i_curve : selection_segment) {
            const IndexRange dst_points = dst_points_by_curve[i_curve];
            dst.type().value_initialize_n(dst.slice(dst_points).data(), dst_points.size());
          }
        }
      },
      exec_mode::grain_size(512));

  copy_or_defaults_for_unselected_curves(src_curves, unselected, attributes, dst_curves);

  for (bke::GSpanAttributeWriter &attribute : attributes.dst_attributes) {
    attribute.finish();
  }

  bke::curves::nurbs::copy_custom_knots(src_curves, selection, dst_curves);
  return dst_curves;
}

CurvesGeometry resample_to_evaluated(const CurvesGeometry &src_curves,
                                     const fn::FieldContext &field_context,
                                     const fn::Field<bool> &selection_field,
                                     const ResampleCurvesOutputAttributeIDs &output_ids)
{
  if (src_curves.curves_range().is_empty()) {
    return {};
  }
  fn::FieldEvaluator evaluator{field_context, src_curves.curves_num()};
  evaluator.set_selection(selection_field);
  evaluator.evaluate();
  return resample_to_evaluated(
      src_curves, evaluator.get_evaluated_selection_as_mask(), output_ids);
}

}  // namespace blender::geometry
