/*=========================================================================
 *
 *  Copyright NumFOCUS
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *         https://www.apache.org/licenses/LICENSE-2.0.txt
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 *=========================================================================*/
#ifndef itkSmoothingQuadEdgeMeshFilter_h
#define itkSmoothingQuadEdgeMeshFilter_h

#include "itkDelaunayConformingQuadEdgeMeshFilter.h"
#include "itkQuadEdgeMeshParamMatrixCoefficients.h"

namespace itk
{
/** \class SmoothingQuadEdgeMeshFilter
 *
 * \brief QuadEdgeMesh Smoothing Filter
 *
 * This filter adjusts point coordinates using Laplacian smoothing. The
 * effect is to "relax" the mesh, making the cells better shaped and the
 * vertices more evenly distributed.
 *
 * For one iteration the location of one vertex is computed as follows:
 * \f[
 * \boldsymbol{ v' }_i = v_i + m_RelaxationFactor \cdot \frac{ \sum_j w_{ij} ( \boldsymbol{ v_j } - \boldsymbol{ v_i } )
 * }{ \sum_j w_{ij} } \f]
 *
 * where \f$ w_{ij} \f$ is computed by the means of the set functor
 * CoefficientsComputation
 *
 * This process is then repeated for m_NumberOfIterations (the more iterations,
 * the smoother the output mesh will be).
 *
 * At each iteration, one can run DelaunayConformingQuadEdgeMeshFilter
 * resulting a more regular (in terms of connectivity) and smoother mesh.
 * Depending on the mesh size and configuration it could be an expensive
 * process to run it at each iterations, especially if the number of iterations
 * is large.  Note that one can still run N iterations without
 * DelaunayConformingQuadEdgeMeshFilter, then run this filter and apply this
 * process M times.
 *
 *
 * \ingroup ITKQuadEdgeMeshFiltering
 */

template <typename TInputMesh, typename TOutputMesh = TInputMesh>
class ITK_TEMPLATE_EXPORT SmoothingQuadEdgeMeshFilter : public QuadEdgeMeshToQuadEdgeMeshFilter<TInputMesh, TOutputMesh>
{
public:
  ITK_DISALLOW_COPY_AND_MOVE(SmoothingQuadEdgeMeshFilter);

  using Self = SmoothingQuadEdgeMeshFilter;
  using Pointer = SmartPointer<Self>;
  using ConstPointer = SmartPointer<const Self>;
  using Superclass = QuadEdgeMeshToQuadEdgeMeshFilter<TInputMesh, TOutputMesh>;

  /** \see LightObject::GetNameOfClass() */
  itkOverrideGetNameOfClassMacro(SmoothingQuadEdgeMeshFilter);
  /** New macro for creation of through a Smart Pointer   */
  itkNewMacro(Self);

  using InputMeshType = TInputMesh;
  using InputMeshPointer = typename InputMeshType::Pointer;

  using OutputMeshType = TOutputMesh;
  using OutputMeshPointer = typename OutputMeshType::Pointer;
  using OutputEdgeCellType = typename OutputMeshType::EdgeCellType;
  using OutputPolygonCellType = typename OutputMeshType::PolygonCellType;
  using OutputQEType = typename OutputMeshType::QEType;
  using OutputPointIdentifier = typename OutputMeshType::PointIdentifier;
  using OutputPointType = typename OutputMeshType::PointType;
  using OutputVectorType = typename OutputPointType::VectorType;
  using OutputCoordType = typename OutputPointType::CoordRepType;
  using OutputPointsContainer = typename OutputMeshType::PointsContainer;
  using OutputPointsContainerPointer = typename OutputMeshType::PointsContainerPointer;
  using OutputPointsContainerIterator = typename OutputMeshType::PointsContainerIterator;
  using OutputCellsContainerPointer = typename OutputMeshType::CellsContainerPointer;
  using OutputCellsContainerIterator = typename OutputMeshType::CellsContainerIterator;

  static constexpr unsigned int PointDimension = OutputMeshType::PointDimension;

  using CoefficientsComputation = MatrixCoefficients<OutputMeshType>;

  void
  SetCoefficientsMethod(CoefficientsComputation * iMethod);

  /** Set/Get the number of iterations */
  itkSetMacro(NumberOfIterations, unsigned int);
  itkGetConstMacro(NumberOfIterations, unsigned int);

  /** Set/Get if DelaunayConformingQuadEdgeMeshFilter is used at the end of each iterations */
  itkBooleanMacro(DelaunayConforming);
  itkSetMacro(DelaunayConforming, bool);
  itkGetConstMacro(DelaunayConforming, bool);

  /** Set/Get relaxation factor applied for each iteration */
  itkSetMacro(RelaxationFactor, OutputCoordType);
  itkGetConstMacro(RelaxationFactor, OutputCoordType);

protected:
  SmoothingQuadEdgeMeshFilter();
  ~SmoothingQuadEdgeMeshFilter() override;
  void
  PrintSelf(std::ostream & os, Indent indent) const override;

  CoefficientsComputation * m_CoefficientsMethod{};

  using InputOutputDelaunayConformingType = DelaunayConformingQuadEdgeMeshFilter<InputMeshType, OutputMeshType>;
  using InputOutputDelaunayConformingPointer = typename InputOutputDelaunayConformingType::Pointer;

  InputOutputDelaunayConformingPointer m_InputDelaunayFilter{};

  using OutputDelaunayConformingType = DelaunayConformingQuadEdgeMeshFilter<OutputMeshType, OutputMeshType>;
  using OutputDelaunayConformingPointer = typename OutputDelaunayConformingType::Pointer;

  OutputDelaunayConformingPointer m_OutputDelaunayFilter{};

  bool m_DelaunayConforming{};

  unsigned int m_NumberOfIterations{};

  OutputCoordType m_RelaxationFactor{};

  void
  GenerateData() override;
};
} // namespace itk

#include "itkSmoothingQuadEdgeMeshFilter.hxx"
#endif
