#ifndef FESA_FEM_DOF_MANAGER_H_
#define FESA_FEM_DOF_MANAGER_H_

#include <array>
#include <cstddef>
#include <cstdint>
#include <optional>
#include <vector>

#include "fesa/analysis/analysis_model.h"
#include "fesa/math/vector.h"

namespace fesa {

/// @brief Identifies one component in the stable six-DOF node layout.
enum class DofComponent : std::uint8_t {
  kUx,
  kUy,
  kUz,
  kUrx,
  kUry,
  kUrz,
};

/// @brief Stores the stable structural CSR pattern.
struct SparsePattern {
  std::vector<std::size_t> row_offsets;
  std::vector<std::size_t> column_indices;
};

/// @brief Owns full/free/constrained numbering, scatter maps, and CSR pattern.
class DofManager {
 public:
  /// @brief Creates every equation-space mapping for an active model.
  static Result<DofManager> Create(const AnalysisModel& model);

  /// @brief Returns the full node-by-component DOF count.
  std::size_t FullDofCount() const noexcept;
  /// @brief Returns the free-equation count.
  std::size_t FreeDofCount() const noexcept;
  /// @brief Returns the prescribed-DOF count.
  std::size_t ConstrainedDofCount() const noexcept;
  /// @brief Maps a stable node index and component to a full DOF.
  std::size_t FullDof(EntityIndex node, DofComponent component) const;
  /// @brief Returns the free equation for a full DOF when unconstrained.
  std::optional<std::size_t> FreeEquation(std::size_t full_dof) const;
  /// @brief Returns a beam scatter in endpoint/component order.
  const std::array<std::size_t, 12>& ElementScatter(EntityIndex element) const;
  /// @brief Returns a shell scatter in node/component order.
  const std::array<std::size_t, 24>& ShellElementScatter(
      EntityIndex element) const;
  /// @brief Returns free full DOFs in stable increasing order.
  const std::vector<std::size_t>& FreeDofs() const noexcept;
  /// @brief Returns constrained full DOFs in stable increasing order.
  const std::vector<std::size_t>& ConstrainedDofs() const noexcept;
  /// @brief Returns dc in constrained-DOF order.
  const Vector& PrescribedValues() const noexcept;
  /// @brief Returns the full-space structural CSR pattern.
  const SparsePattern& GetSparsePattern() const noexcept;

 private:
  /// @brief Takes ownership of fully validated stable equation mappings.
  DofManager(std::size_t full_dof_count,
             std::vector<std::optional<std::size_t>> free_equations,
             std::vector<std::array<std::size_t, 12>> element_scatters,
             std::vector<std::array<std::size_t, 24>> shell_element_scatters,
             std::vector<std::size_t> free_dofs,
             std::vector<std::size_t> constrained_dofs,
             Vector prescribed_values, SparsePattern sparse_pattern);

  std::size_t full_dof_count_;
  std::vector<std::optional<std::size_t>> free_equations_;
  std::vector<std::array<std::size_t, 12>> element_scatters_;
  std::vector<std::array<std::size_t, 24>> shell_element_scatters_;
  std::vector<std::size_t> free_dofs_;
  std::vector<std::size_t> constrained_dofs_;
  Vector prescribed_values_;
  SparsePattern sparse_pattern_;
};

}  // namespace fesa

#endif  // FESA_FEM_DOF_MANAGER_H_