#ifndef FESA_SOLVERS_EIGEN_MKL_FEAST_EIGEN_SOLVER_H_
#define FESA_SOLVERS_EIGEN_MKL_FEAST_EIGEN_SOLVER_H_

#include "fesa/solvers/eigen/eigen_solver.h"

namespace fesa {

/// @brief Adapts standard and symmetric-definite sparse pencils to FEAST.
class MklFeastEigenSolver final : public EigenSolver {
 public:
  /// @brief Computes all validated interval pairs for a requested lowest-mode
  /// prefix.
  /// @param whitened_operator Symmetric physical-lambda operator after
  /// whitening.
  /// @param requested_modes Number of lowest modes eventually exposed by the
  /// caller.
  /// @param zero_operator_scale Positive physical scale used only when A is
  /// exactly zero.
  /// @return Sorted all-c eigenpairs in physical lambda units or a solver
  /// failure.
  /// @note The implementation fixes oneMKL local thread count to one during
  /// every call.
  Result<FeastEigenResult> Solve(const SparseMatrix& whitened_operator,
                                std::size_t requested_modes,
                                double zero_operator_scale) const override;
  /// @brief Solves the original sparse symmetric definite K/M pencil.
  /// @param mass_lower_bound Certified positive lower spectral bound of M,
  /// including floating-point assembly uncertainty; never a diagonal estimate.
  /// @param classification_scale Positive max |Kii|/Mii in physical units.
  /// @note Eigenvectors are mass-normalized. For this API the historical
  /// whitened_residuals field contains original-pencil eta_r; no whitening
  /// is performed. Intervals/eigenvalues in normalized backend evidence use
  /// classification_scale, while eigenvalues are returned in physical units.
  Result<FeastEigenResult> SolveGeneralized(const SparseMatrix& stiffness,
                                            const SparseMatrix& mass,
                                           std::size_t requested_modes,
                                            double mass_lower_bound,
                                            double classification_scale) const override;

 private:
  /// @brief Shares deterministic count/search controls without changing
  /// pencils.
  Result<FeastEigenResult> SolveImpl(const SparseMatrix& stiffness,
                                     const SparseMatrix* mass,
                                    std::size_t requested_modes,
                                     double physical_scale,
                                     double mass_lower_bound) const;
};

}  // namespace fesa

#endif  // FESA_SOLVERS_EIGEN_MKL_FEAST_EIGEN_SOLVER_H_