#ifndef FESA_ELEMENTS_ELEMENT_CAPABILITIES_H_
#define FESA_ELEMENTS_ELEMENT_CAPABILITIES_H_

#include <array>
#include <cstddef>

#include "fesa/elements/element.h"
#include "fesa/elements/thermal_element_layout.h"
#include "fesa/math/vector3.h"

namespace fesa {

class Hex8Element;
class Mitc4Shell;
class NonlinearMitc4Shell;
class NonlinearMitc4Inertia;
class ThermalShell;
struct Hex8Response;
struct Hex8HighLowResponse;
struct Mitc4Stiffness;
struct Mitc4Mass;
struct NonlinearMitc4TrialDofs;
struct NonlinearMitc4InternalEquilibrium;
struct NonlinearMitc4ExternalDrillingConstraint;
struct NonlinearMitc4InertiaEvaluation;
struct ThermalShellRecovery;

/// @brief Evaluates immutable shell trials; accepted history belongs to the procedure.
class ShellTrialElement {
 public:
  virtual ~ShellTrialElement() = default;
  /// @brief Returns stable source-local node/component order, never equations.
  virtual const ElementDofLayout& DofLayout() const noexcept = 0;
  /// @brief Returns the complete force/tangent/recovery at a fixed-global trial.
  /// @param coordinate_direction Optional 24-vector for D2(f_int)[v,v].
  /// @note Failure preserves the kernel, caller inputs and earlier responses.
  virtual Result<NonlinearMitc4InternalEquilibrium> EvaluateTrial(
      const NonlinearMitc4TrialDofs& trial,
      const Vector* coordinate_direction = nullptr) const = 0;
  /// @copydoc NonlinearMitc4Shell::EvaluateExternalDrillingConstraint
  virtual Result<NonlinearMitc4ExternalDrillingConstraint>
  EvaluateExternalDrillingConstraint(
      std::size_t node, const Vector3& phi, const Vector3& phi_dot,
      const Vector3& force, const Vector3& force_rate,
      const Vector3& force_acceleration) const = 0;
};

/// @brief Borrows the same immutable shell kernel for every trial operation.
/// @note The kernel must outlive this adapter and remain at its bound address.
class Mitc4TrialAdapter final : public ShellTrialElement {
 public:
  Mitc4TrialAdapter(ElementDofLayout layout, const NonlinearMitc4Shell& kernel);
  const ElementDofLayout& DofLayout() const noexcept override;
  Result<NonlinearMitc4InternalEquilibrium> EvaluateTrial(
      const NonlinearMitc4TrialDofs& trial,
      const Vector* coordinate_direction = nullptr) const override;
  Result<NonlinearMitc4ExternalDrillingConstraint>
  EvaluateExternalDrillingConstraint(
      std::size_t node, const Vector3& phi, const Vector3& phi_dot,
      const Vector3& force, const Vector3& force_rate,
      const Vector3& force_acceleration) const override;

 private:
  ElementDofLayout layout_;
  const NonlinearMitc4Shell& kernel_;
};

/// @brief Keeps complete paired solid responses and reference mass typed.
class SolidTrialElement : public Element {
 public:
  ~SolidTrialElement() override = default;
  /// @copydoc Hex8Element::EvaluateLinear
  virtual Result<Hex8Response> EvaluateLinear(const Vector& u) const = 0;
  /// @copydoc Hex8Element::EvaluateNonlinear
  virtual Result<Hex8Response> EvaluateNonlinear(const Vector& u) const = 0;
  /// @copydoc Hex8Element::EvaluateLinearHighLow
  virtual Result<Hex8HighLowResponse> EvaluateLinearHighLow(
      const Vector& high, const Vector& low) const = 0;
  /// @copydoc Hex8Element::EvaluateNonlinearHighLow
  virtual Result<Hex8HighLowResponse> EvaluateNonlinearHighLow(
      const Vector& high, const Vector& low) const = 0;
  /// @copydoc Hex8Element::ComputeMass
  virtual Result<ElementStiffnessContribution> ComputeMass() const = 0;
  /// @brief Returns fixed Gauss weights used by the frequency mass bound.
  virtual std::array<double, 8> ReferenceWeights() const noexcept = 0;
};

/// @brief Borrows one stable Hex8 kernel shared by all local operations.
/// @note The kernel must outlive this adapter and remain at its bound address.
class Hex8TrialAdapter final : public SolidTrialElement {
 public:
  explicit Hex8TrialAdapter(const Hex8Element& kernel);
  const ElementDofLayout& DofLayout() const noexcept override;
  Result<ElementStiffnessContribution> ComputeStiffness() const override;
  Result<ElementResultBundle> Recover(const Vector& u) const override;
  Result<Hex8Response> EvaluateLinear(const Vector& u) const override;
  Result<Hex8Response> EvaluateNonlinear(const Vector& u) const override;
  Result<Hex8HighLowResponse> EvaluateLinearHighLow(
      const Vector& high, const Vector& low) const override;
  Result<Hex8HighLowResponse> EvaluateNonlinearHighLow(
      const Vector& high, const Vector& low) const override;
  Result<ElementStiffnessContribution> ComputeMass() const override;
  std::array<double, 8> ReferenceWeights() const noexcept override;

 private:
  const Hex8Element& kernel_;
};

/// @brief Returns the complete physical inertia response in fixed chart DOFs.
class ShellInertiaElement {
 public:
  virtual ~ShellInertiaElement() = default;
  virtual const ElementDofLayout& DofLayout() const noexcept = 0;
  /// @copydoc NonlinearMitc4Inertia::Evaluate
  virtual Result<NonlinearMitc4InertiaEvaluation> Evaluate(
      const NonlinearMitc4TrialDofs& trial, const Vector& velocity24,
      const Vector& physical_acceleration24) const = 0;
};

/// @brief Borrows immutable inertia geometry, never shared mutable scratch.
/// @note The kernel must outlive this adapter and remain at its bound address.
class Mitc4InertiaAdapter final : public ShellInertiaElement {
 public:
  Mitc4InertiaAdapter(ElementDofLayout layout,
                      const NonlinearMitc4Inertia& kernel);
  const ElementDofLayout& DofLayout() const noexcept override;
  Result<NonlinearMitc4InertiaEvaluation> Evaluate(
      const NonlinearMitc4TrialDofs& trial, const Vector& velocity24,
      const Vector& physical_acceleration24) const override;

 private:
  ElementDofLayout layout_;
  const NonlinearMitc4Inertia& kernel_;
};

/// @brief Keeps DS4 DOFs 11-15 and all four-by-six flux traces independent.
class ThermalElement {
 public:
  virtual ~ThermalElement() = default;
  /// @brief Returns node-major stations 11-15 and original source identity.
  virtual const ThermalElementDofLayout& DofLayout() const noexcept = 0;
  /// @copydoc ThermalShell::Conductivity
  virtual const Matrix& Conductivity() const noexcept = 0;
  /// @copydoc ThermalShell::Capacity
  virtual const Matrix& Capacity() const noexcept = 0;
  /// @copydoc ThermalShell::ConductivityError
  virtual const Matrix& ConductivityError() const noexcept = 0;
  /// @copydoc ThermalShell::CapacityError
  virtual const Matrix& CapacityError() const noexcept = 0;
  /// @copydoc ThermalShell::Recover
  virtual Result<ThermalShellRecovery> Recover(
      const std::array<double, 20>& temperature) const = 0;
};

/// @brief Borrows the same DS4 kernel for matrices, intervals and recovery.
/// @note The kernel must outlive this adapter and remain at its bound address.
class Ds4ThermalAdapter final : public ThermalElement {
 public:
  explicit Ds4ThermalAdapter(const ThermalShell& kernel);
  const ThermalElementDofLayout& DofLayout() const noexcept override;
  const Matrix& Conductivity() const noexcept override;
  const Matrix& Capacity() const noexcept override;
  const Matrix& ConductivityError() const noexcept override;
  const Matrix& CapacityError() const noexcept override;
  Result<ThermalShellRecovery> Recover(
      const std::array<double, 20>& temperature) const override;

 private:
  ThermalElementDofLayout layout_;
  const ThermalShell& kernel_;
};

/// @brief Supplies shell frequency operators with their distinct mass contract.
class ShellReferenceElement : public Element {
 public:
  ~ShellReferenceElement() override = default;
  /// @copydoc Mitc4Shell::Stiffness
  virtual Result<Mitc4Stiffness> Stiffness() const = 0;
  /// @copydoc Mitc4Shell::Mass
  virtual Result<Mitc4Mass> Mass(double density) const = 0;
  /// @brief Returns the actual immutable reference-kernel drilling formulation.
  virtual Mitc4DrillingMode DrillingMode() const noexcept = 0;
};

/// @brief Borrows the same linear MITC4 kernel for stiffness and recovery.
/// @note The kernel must outlive this adapter and remain at its bound address.
class Mitc4ReferenceAdapter final : public ShellReferenceElement {
 public:
  explicit Mitc4ReferenceAdapter(const Mitc4Shell& kernel);
  const ElementDofLayout& DofLayout() const noexcept override;
  Result<ElementStiffnessContribution> ComputeStiffness() const override;
  Result<ElementResultBundle> Recover(const Vector& u) const override;
  Result<Mitc4Stiffness> Stiffness() const override;
  Result<Mitc4Mass> Mass(double density) const override;
  Mitc4DrillingMode DrillingMode() const noexcept override;

 private:
  const Mitc4Shell& kernel_;
};

}  // namespace fesa

#endif  // FESA_ELEMENTS_ELEMENT_CAPABILITIES_H_