/*=========================================================================
 *
 *  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 itkBSplineControlPointImageFilter_h
#define itkBSplineControlPointImageFilter_h

#include "itkImageToImageFilter.h"
#include "itkBSplineKernelFunction.h"
#include "itkCoxDeBoorBSplineKernelFunction.h"
#include "itkFixedArray.h"
#include "itkPointSet.h"
#include "itkVariableSizeMatrix.h"
#include "itkVector.h"
#include "itkVectorContainer.h"

#include "vnl/vnl_matrix.h"
#include "vnl/vnl_vector.h"

namespace itk
{

/**
 * \class BSplineControlPointImageFilter
 *
 * \brief Process a given a B-spline grid of control points.
 *
 * \par  The output of the class itkBSplineScatteredDataPointSetToImageFilter
 * is a control point grid defining a B-spline object.  This class is used to
 * hold various routines meant to operate on that control point grid.  In
 * addition to specifying the control point grid as the input, the user
 * must also supply the spline order and the parametric domain (i.e. size,
 * domain, origin, direction, spacing).  The output of the filter is the sampled
 * B-spline object.
 *
 * This code was contributed in the Insight Journal paper:
 * "N-D C^k B-Spline Scattered Data Approximation"
 * by Nicholas J. Tustison, James C. Gee
 * https://www.insight-journal.org/browse/publication/57
 *
 * \author Nicholas J. Tustison
 * \ingroup ITKImageGrid
 */

template <typename TInputImage, typename TOutputImage = TInputImage>
class ITK_TEMPLATE_EXPORT BSplineControlPointImageFilter : public ImageToImageFilter<TInputImage, TOutputImage>
{
public:
  ITK_DISALLOW_COPY_AND_MOVE(BSplineControlPointImageFilter);

  using Self = BSplineControlPointImageFilter;
  using Superclass = ImageToImageFilter<TInputImage, TOutputImage>;
  using Pointer = SmartPointer<Self>;
  using ConstPointer = SmartPointer<const Self>;

  /** Method for creation through the object factory. */
  itkNewMacro(Self);

  /** \see LightObject::GetNameOfClass() */
  itkOverrideGetNameOfClassMacro(BSplineControlPointImageFilter);

  /** Extract dimension from input image. */
  static constexpr unsigned int ImageDimension = TInputImage::ImageDimension;

  using ControlPointLatticeType = TInputImage;
  using OutputImageType = TOutputImage;

  /** Image type alias support */
  using PixelType = typename OutputImageType::PixelType;
  using RegionType = typename OutputImageType::RegionType;
  using IndexType = typename OutputImageType::IndexType;
  using PointType = typename OutputImageType::PointType;
  using OutputImageRegionType = typename OutputImageType::RegionType;

  using SpacingType = typename OutputImageType::SpacingType;
  using OriginType = typename OutputImageType::PointType;
  using SizeType = typename OutputImageType::SizeType;
  using DirectionType = typename OutputImageType::DirectionType;

  /** Other type alias */
  using RealType = float;
  using RealImageType = Image<RealType, Self::ImageDimension>;
  using RealImagePointer = typename RealImageType::Pointer;

  using ArrayType = FixedArray<unsigned int, Self::ImageDimension>;
  using RealArrayType = FixedArray<RealType, Self::ImageDimension>;

  /** PointSet type alias support */
  using PointSetType = PointSet<PixelType, Self::ImageDimension>;
  using PointDataType = typename PointSetType::PixelType;
  using PointDataContainerType = typename PointSetType::PointDataContainer;
  using PointDataImageType = Image<PointDataType, Self::ImageDimension>;
  using PointDataImagePointer = typename PointDataImageType::Pointer;

  /** Interpolation kernel type (default spline order = 3) */
  using KernelType = CoxDeBoorBSplineKernelFunction<3>;
  using KernelOrder0Type = BSplineKernelFunction<0>;
  using KernelOrder1Type = BSplineKernelFunction<1>;
  using KernelOrder2Type = BSplineKernelFunction<2>;
  using KernelOrder3Type = BSplineKernelFunction<3>;

  /**
   * Set the spline order of the B-spline object for all parametric dimensions.
   * Default = 3.
   */
  void
  SetSplineOrder(unsigned int);

  /**
   * Set the spline order array where each element of the array corresponds to
   * a single parametric dimension of the B-spline object.  Default = 3.
   */
  void SetSplineOrder(ArrayType);

  /**
   * Get the spline order array of the B-spline object.  Default = 3.
   */
  itkGetConstReferenceMacro(SplineOrder, ArrayType);

  /**
   * Set/Get the boolean array indicating the periodicity of the B-spline object.
   * This array of 0/1 values defines whether a particular dimension of the
   * parametric space is to be considered periodic or not. For example, if you
   * are using interpolating along a 1D closed curve, the array type will have
   * size 1, and you should set the first element of this array to the value
   * "1". In the case that you were interpolating in a planar surface with
   * cylindrical topology, the array type will have two components, and you
   * should set to "1" the component that goes around the cylinder, and set to
   * "0" the component that goes from the top of the cylinder to the bottom.
   * This will indicate the periodicity of that parameter to the filter.
   * Internally, in order to make periodic the domain of the parameter, the
   * filter will reuse some of the points at the beginning of the domain as if
   * they were also located at the end of the domain. The number of points to
   * be reused will depend on the spline order. As a user, you don't need to
   * replicate the points, the filter will do this for you. */
  itkSetMacro(CloseDimension, ArrayType);
  itkGetConstReferenceMacro(CloseDimension, ArrayType);

  /**
   * Set/Get the parametric spacing of the B-spline object domain.
   */
  itkSetMacro(Spacing, SpacingType);
  itkGetConstMacro(Spacing, SpacingType);

  /**
   * Set/Get the parametric origin of the B-spline object domain.
   */
  itkSetMacro(Origin, OriginType);
  itkGetConstMacro(Origin, OriginType);

  /**
   * Set/Get the parametric size of the B-spline object domain.
   */
  itkSetMacro(Size, SizeType);
  itkGetConstMacro(Size, SizeType);

  /**
   * Set the sampled object direction.  Note that this is not used in any of the
   * calculations in this class.  The only reason why it is included is due
   * to the fact that we use the image class to represent the B-spline
   * parametric domain (due to the maturity of the image class and the
   * wealth of helper functions associated with it).  This is where the
   * incongruence between the B-spline parametric domain and the concept of an
   * image is most obvious.  An ITK image is a representation of a physical
   * object thus it also exists in physical space which includes orientation.
   * However, it can be argued that the parametric domain, per se, does not
   * exist in physical space and it is only a parametric mapping which allows
   * us to go from the parametric space to the physical space.  Therefore,
   * the direction is not used.
   */
  itkSetMacro(Direction, DirectionType);

  /**
   * Get the sampled B-spline object direction.
   */
  itkGetConstMacro(Direction, DirectionType);

  /**
   * Generate a refined control point lattice from the input control point
   * lattice such that the resolution is doubled for each level.  This is
   * further described in the references.  Note that if one sets the number
   * of refinement levels to all 1's, the control point lattice is not increased
   * in resolution.  Doubling the resolution starts at 2 refinement levels.
   */
  typename ControlPointLatticeType::Pointer RefineControlPointLattice(ArrayType);

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

  /** Multi-threaded function which generates the output sampled B-spline object. */
  void
  DynamicThreadedGenerateData(const OutputImageRegionType &) override;


private:
  /**
   * Before splitting, we need to allocate memory for the output sampled
   * B-spline object based on the multi-threading functionality
   */
  void
  BeforeThreadedGenerateData() override;

  /**
   * Based on the way CollapsePhiLattice() is written, we want to split on the
   * the last dimension.
   */
  unsigned int
  SplitRequestedRegion(unsigned int, unsigned int, OutputImageRegionType &) override;

  /**
   * Sub-function used by GenerateOutputImageFast() to generate the sampled
   * B-spline object quickly.
   */
  void
  CollapsePhiLattice(PointDataImageType *, PointDataImageType *, const RealType, const unsigned int);

  /**
   * Private function to handle the internal ivars.
   */
  void SetNumberOfLevels(ArrayType);

  /** Parameters for the output image. */
  SizeType      m_Size{};
  SpacingType   m_Spacing{};
  OriginType    m_Origin{};
  DirectionType m_Direction{};

  bool         m_DoMultilevel{ false };
  unsigned int m_MaximumNumberOfLevels{ 1 };
  ArrayType    m_NumberOfControlPoints{};
  ArrayType    m_CloseDimension{};
  ArrayType    m_SplineOrder{};
  ArrayType    m_NumberOfLevels{};

  vnl_matrix<RealType> m_RefinedLatticeCoefficients[ImageDimension]{};

  typename KernelType::Pointer       m_Kernel[ImageDimension]{};
  typename KernelOrder0Type::Pointer m_KernelOrder0{};
  typename KernelOrder1Type::Pointer m_KernelOrder1{};
  typename KernelOrder2Type::Pointer m_KernelOrder2{};
  typename KernelOrder3Type::Pointer m_KernelOrder3{};

  RealType m_BSplineEpsilon{ static_cast<RealType>(1e-3) };

  inline typename RealImageType::IndexType
  NumberToIndex(unsigned int number, typename RealImageType::SizeType size)
  {
    typename RealImageType::IndexType k;
    k[0] = 1;

    for (unsigned int i = 1; i < ImageDimension; ++i)
    {
      k[i] = size[ImageDimension - i - 1] * k[i - 1];
    }
    typename RealImageType::IndexType index;
    for (unsigned int i = 0; i < ImageDimension; ++i)
    {
      index[ImageDimension - i - 1] = static_cast<unsigned int>(number / k[ImageDimension - i - 1]);
      number %= k[ImageDimension - i - 1];
    }
    return index;
  }
};

} // end namespace itk

#ifndef ITK_MANUAL_INSTANTIATION
#  include "itkBSplineControlPointImageFilter.hxx"
#endif

#endif
