#ifndef FESA_LOADS_SHELL_SURFACE_PRESSURE_H_
#define FESA_LOADS_SHELL_SURFACE_PRESSURE_H_

#include <array>
#include <string>

#include "fesa/core/status.h"
#include "fesa/math/vector3.h"
#include "fesa/model/model_types.h"

namespace fesa {

/// @brief Selects the surface geometry used to evaluate uniform pressure.
enum class SurfacePressureConfiguration { kReference, kCurrent };

/// @brief Supplies one four-node shell facet pressure evaluation.
struct ShellSurfacePressureInput {
  std::array<Vector3, 4> reference_coordinates;
  std::array<Vector3, 4> translational_displacements;
  ShellSurfaceSide side;
  double pressure_magnitude;
  double load_factor;
  SurfacePressureConfiguration configuration;
  SourceLocation location;
  std::string entity_identity;
};

/// @brief Stores one fixed-order pressure force and external tangent.
struct ShellSurfacePressureContribution {
  std::array<double, 24> force;
  std::array<double, 24 * 24> external_tangent;
};

/// @brief Evaluates one four-node reference or follower surface pressure.
/// @param input Geometry, pressure, side, load factor, and diagnostic identity.
/// @return A finite 24-DOF force and external tangent or a structured failure.
/// @note Translation DOFs occupy components zero through two of each node.
/// @warning The returned tangent is the positive derivative of external force.
Result<ShellSurfacePressureContribution> EvaluateShellSurfacePressure(
    const ShellSurfacePressureInput& input);

}  // namespace fesa

#endif  // FESA_LOADS_SHELL_SURFACE_PRESSURE_H_