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//        MueLu: A package for multigrid based preconditioning
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// @HEADER
#ifndef MUELU_RAPSHIFTFACTORY_DECL_HPP
#define MUELU_RAPSHIFTFACTORY_DECL_HPP

#include <string>

#include <Xpetra_Matrix_fwd.hpp>
#include <Xpetra_CrsMatrix_fwd.hpp>
#include <Xpetra_MatrixFactory_fwd.hpp>
#include <Xpetra_Vector_fwd.hpp>
#include <Xpetra_VectorFactory_fwd.hpp>

#include "MueLu_ConfigDefs.hpp"
#include "MueLu_RAPShiftFactory_fwd.hpp"

#include "MueLu_FactoryBase_fwd.hpp"
#include "MueLu_Level_fwd.hpp"
#include "MueLu_PerfUtils_fwd.hpp"
#include "MueLu_TwoLevelFactoryBase.hpp"
#include "MueLu_Utilities_fwd.hpp"

namespace MueLu {
  /*!
    @class RAPShiftFactory
    @brief Factory for building coarse grid matrices, when the matrix
           is of the form K+a*M. Useful when you want to change the shift
           variable ("a") at every level. Each level must store the stiffness
           matrix K and mass matrix M separately.
  */
  template <class Scalar = double, class LocalOrdinal = int, class GlobalOrdinal = LocalOrdinal, class Node = KokkosClassic::DefaultNode::DefaultNodeType>
  class RAPShiftFactory : public TwoLevelFactoryBase {
#undef MUELU_RAPSHIFTFACTORY_SHORT
#include "MueLu_UseShortNames.hpp"

  public:
    //! @name Constructors/Destructors.
    //@{

    RAPShiftFactory();

    virtual ~RAPShiftFactory() { }

    //@}

    //! @name Input
    //@{

    void DeclareInput(Level &fineLevel, Level &coarseLevel) const;

    //@}

    //! @name Build methods.
    //@{
    void Build(Level &fineLevel, Level &coarseLevel) const;
    //@}

    //! @name Handling of user-defined transfer factories
    //@{

    //! Indicate that the restriction operator action should be implicitly defined by the transpose of the prolongator.
    void SetImplicitTranspose(bool const &implicit) {
      implicitTranspose_ = implicit;
    }

    //! Indicate that zero entries on the diagonal of Ac shall be repaired (i.e. if A(i,i) == 0.0 set A(i,i) = 1.0)
    void SetRepairZeroDiagonal(bool const &repairZeroDiagonals) {
      repairZeroDiagonals_ = repairZeroDiagonals;
      if(repairZeroDiagonals_) checkAc_ = true; // make sure that plausibility check is performed. Otherwise SetRepairZeroDiagonal(true) has no effect.
    }

    //! Indicate that a simple plausibility check shall be done for Ac after building RAP
    void SetPlausibilityCheck(bool const &checkAc) {
      checkAc_ = checkAc;
    }

    void SetShifts(std::vector<Scalar>& shifts) {
      shifts_.clear();
      shifts_ = shifts;
    }

    //@}

    //@{
    /*! @brief Add transfer factory in the end of list of transfer factories in RepartitionAcFactory.

    Transfer factories are derived from TwoLevelFactoryBase and project some data from the fine level to
    the next coarser level.
    */
    void AddTransferFactory(const RCP<const FactoryBase>& factory);

    // TODO add a function to remove a specific transfer factory?

    //! Returns number of transfer factories.
    size_t NumTransferFactories() const { return transferFacts_.size(); }

    //@}

  private:

    //! @name internal plausibility check methods
    void CheckMainDiagonal(RCP<Matrix> & Ac) const;

    //! If true, the action of the restriction operator action is implicitly defined by the transpose of the prolongator.
    bool implicitTranspose_;

    //! If true, perform a basic plausibility check on Ac (default = false)
    //! note, that the repairZeroDiagonals_ flag is only valid for checkAc_ == true
    bool checkAc_;

    //! If true, the CheckMainDiagonal routine automatically repairs zero entries on main diagonal (default = false)
    //! i.e. if A(i,i) == 0.0 set A(i,i) = 1.0
    //! note, that the repairZeroDiagonals_ flag is only valid for checkAc_ == true
    bool repairZeroDiagonals_;

    //! list of user-defined transfer Factories
    std::vector<RCP<const FactoryBase> > transferFacts_;

    // vector of shifting terms
    std::vector<Scalar> shifts_;

  }; //class RAPShiftFactory

} //namespace MueLu

#define MUELU_RAPSHIFTFACTORY_SHORT
#endif // MUELU_RAPSHIFTFACTORY_DECL_HPP
