/*=========================================================================
 *
 *  Copyright Insight Software Consortium
 *
 *  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
 *
 *         http://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:
  using Self = SmoothingQuadEdgeMeshFilter;
  using Pointer = SmartPointer< Self >;
  using ConstPointer = SmartPointer< const Self >;
  using Superclass = QuadEdgeMeshToQuadEdgeMeshFilter< TInputMesh, TOutputMesh >;

  /** Run-time type information (and related methods).   */
  itkTypeMacro(SmoothingQuadEdgeMeshFilter, QuadEdgeMeshToQuadEdgeMeshFilter);
  /** 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 */
  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;

private:
  SmoothingQuadEdgeMeshFilter(const Self &) = delete;
  void operator=(const Self &) = delete;
};
}

#include "itkSmoothingQuadEdgeMeshFilter.hxx"
#endif
