#ifndef FESA_MODEL_SHELL_GEOMETRY_H_
#define FESA_MODEL_SHELL_GEOMETRY_H_

#include <array>
#include <cstddef>
#include <vector>

#include "fesa/core/status.h"
#include "fesa/model/model_types.h"

namespace fesa {

/// @brief Classifies a mandatory shell-geometry validation location.
enum class ShellGeometryPointKind { kCenter, kStiffness, kTying, kRecovery };

/// @brief Identifies one deterministic shell-geometry validation point.
struct ShellGeometryValidationPoint {
  ShellGeometryPointKind kind;
  std::size_t location_index;
  std::array<double, 3> natural_coordinates;
};

/// @brief Stores deterministic preprocessing data for one shell element.
struct ShellElementGeometryData {
  EntityIndex element_index;
  std::array<double, 3> normal_candidate;
  double surface_area_weight;
};

/// @brief Owns preprocessed shell node frames and element geometry data.
struct ShellGeometry {
  std::vector<ShellNodeInitialFrame> nodal_frames;
  std::vector<ShellElementGeometryData> element_data;
};

/// @brief Returns the complete fixed validation-point inventory.
/// @note Ordering is center, stiffness, tying, then recovery identity.
const std::array<ShellGeometryValidationPoint, 17>&
ShellGeometryValidationPoints() noexcept;

/// @brief Builds deterministic nodal frames and validates shell geometry.
/// @param nodes Source nodes indexed by stable EntityIndex.
/// @param elements Shell definitions in stable source order.
/// @param sections Shell sections used for thickness validation.
/// @return Validated geometry or a structured model failure.
Result<ShellGeometry> PreprocessShellGeometry(
    const std::vector<Node>& nodes,
    const std::vector<Mitc4ShellDefinition>& elements,
    const std::vector<ShellSection>& sections);

}  // namespace fesa

#endif  // FESA_MODEL_SHELL_GEOMETRY_H_