// @HEADER
// *****************************************************************************
//        MueLu: A package for multigrid based preconditioning
//
// Copyright 2012 NTESS and the MueLu contributors.
// SPDX-License-Identifier: BSD-3-Clause
// *****************************************************************************
// @HEADER

//
// Note 1: This implementation assumes the following:
//   1. The mesh is square and regular.
//   2. The number of ELEMENTS on the fine grid is even.
//   3. Coarsening by a factor of two.
//
// This should be general enough for 1-3 dimensions, but is originally
// implemented to work with two, so deal with it if there are bugs
// initially.
//
// ASSUMPTIONS TO ELIMINATE:
//   1. none that i can think of currently
//
// Note 2: This factory also generates the coarse grid coordinates.
// TODO: More elegant solution - MueLu_MultiVectorTransferFactory.cpp
// in $MUELU_HOME/src/MueCentral/ perhaps...
//

#ifndef MUELU_GEOINTERPFACTORY_DECL_HPP
#define MUELU_GEOINTERPFACTORY_DECL_HPP

#include "MueLu_ConfigDefs.hpp"
//#include "MueLu_SingleLevelFactoryBase.hpp"
//#include "MueLu_GeoInterpFactory_fwd.hpp"

#include <Xpetra_Matrix_fwd.hpp>
#include <Xpetra_Map_fwd.hpp>
#include <Xpetra_MapFactory_fwd.hpp>
#include <Xpetra_CrsMatrixWrap_fwd.hpp>
#include <Xpetra_MultiVector_fwd.hpp>

#include "MueLu_Level_fwd.hpp"
#include "MueLu_PFactory.hpp"

namespace MueLu {

/*!
  @class GeoInterpFactory class.
  @brief Factory for GMG Q2-Q1-Q2 interpolation
  @ingroup MueLuTransferClasses
*/

template <class Scalar        = DefaultScalar,
          class LocalOrdinal  = DefaultLocalOrdinal,
          class GlobalOrdinal = DefaultGlobalOrdinal,
          class Node          = DefaultNode>
class GeoInterpFactory : public PFactory {
#undef MUELU_GEOINTERPFACTORY_SHORT
#include "MueLu_UseShortNames.hpp"

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

  //! Constructor.
  GeoInterpFactory();

  //! Destructor.
  virtual ~GeoInterpFactory();

  //@}

  //! @name Input
  //@{

  /*! @brief Specifies the data that this class needs, and the factories that generate that data.

      If the Build method of this class requires some data, but the
      generating factory is not specified in DeclareInput, then this
      class will fall back to the settings in FactoryManager.
  */
  void DeclareInput(Level &fineLevel, Level &coarseLevel) const;

  //@}

  //! @name Build methods.
  //@{

  //! Build an object with this factory.
  void Build(Level &fineLevel, Level &coarseLevel) const;

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

  // void BuildCoarseGrid(Level &fineLevel, Level &coarseLevel) const;

  /* For our geometric multigrid needs, we will explicitly build the
     coarse grid here and store it as level data. There are two
     things we care about here: coordinates of the dofs and
     element-dof lists.

     We will assume only that the elements are numbered
     lexicographically, left-to-right, bottom-to-top. The order of
     the degrees of freedom will only be assumed on coarse grids. It
     can be anything on the finest grid (fineLevel.GetLevelID()==1).

     We further assume that the x- and y-components of velocity are
     zippered together: UX1 UY1 UX2 UY2 ETC...
  */

  //@}

 private:
  // No parameters need to be stored... To save "P", use
  //    coarseLevel.Set("P", finalP, this);

};  // class GeoInterpFactory

}  // namespace MueLu

#define MUELU_GEOINTERPFACTORY_SHORT
#endif  // MUELU_GEOINTERPFACTORY_DECL_HPP
