/*=========================================================================
 *
 *  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 itkLandweberDeconvolutionImageFilter_h
#define itkLandweberDeconvolutionImageFilter_h

#include "itkIterativeDeconvolutionImageFilter.h"

#include "itkComplexConjugateImageAdaptor.h"
#include "itkTernaryGeneratorImageFilter.h"

namespace itk
{
namespace Functor
{
/**
 * \class LandweberMethod
 * \brief Functor class for computing a Landweber iteration.
 * \ingroup ITKDeconvolution
 */
template <typename TInput1, typename TInput2, typename TInput3, typename TOutput>
class ITK_TEMPLATE_EXPORT LandweberMethod
{
public:
  bool
  operator==(const LandweberMethod &) const
  {
    return true;
  }

  ITK_UNEQUAL_OPERATOR_MEMBER_FUNCTION(LandweberMethod);

  inline TOutput
  operator()(const TInput1 & estimateFT, const TInput2 & kernelFT, const TInput2 & inputFT) const
  {
    return m_Alpha * std::conj(kernelFT) * inputFT +
           (NumericTraits<typename TInput1::value_type>::OneValue() - m_Alpha * std::norm(kernelFT)) * estimateFT;
  }

  typename TInput1::value_type m_Alpha;
};
} // end namespace Functor

/**
 * \class LandweberDeconvolutionImageFilter
 * \brief Deconvolve an image using the Landweber deconvolution
 * algorithm.
 *
 * This filter implements the Landweber deconvolution algorithm as
 * defined in \cite bertero1998. The algorithm assumes that the input
 * image has been formed by a linear shift-invariant system with a
 * known kernel.
 *
 * The Landweber algorithm converges to a solution that minimizes the
 * sum of squared errors \f$||f \otimes h - g||\f$ where \f$f\f$ is
 * the estimate of the unblurred image, \f$\otimes\f$ is the
 * convolution operator, \f$h\f$ is the blurring kernel, and \f$g\f$ is
 * the blurred input image. As such, it is best suited for images that
 * have zero-mean Gaussian white noise.
 *
 * This is the base implementation of the Landweber algorithm. It may
 * produce results with negative values. For a version of this
 * algorithm that enforces a positivity constraint on each
 * intermediate solution, see ProjectedLandweberDeconvolutionImageFilter.
 *
 * This code was adapted from the Insight Journal contribution:
 *
 * "Deconvolution: infrastructure and reference algorithms"
 * by Gaetan Lehmann
 * https://doi.org/10.54294/tvgfv1
 *
 * \author Gaetan Lehmann, Biologie du Developpement et de la Reproduction, INRA de Jouy-en-Josas, France
 * \author Cory Quammen, The University of North Carolina at Chapel Hill
 *
 * \ingroup ITKDeconvolution
 * \sa IterativeDeconvolutionImageFilter
 * \sa RichardsonLucyDeconvolutionImageFilter
 * \sa ProjectedLandweberDeconvolutionImageFilter
 */
template <typename TInputImage,
          typename TKernelImage = TInputImage,
          typename TOutputImage = TInputImage,
          typename TInternalPrecision = double>
class ITK_TEMPLATE_EXPORT LandweberDeconvolutionImageFilter
  : public IterativeDeconvolutionImageFilter<TInputImage, TKernelImage, TOutputImage, TInternalPrecision>
{
public:
  ITK_DISALLOW_COPY_AND_MOVE(LandweberDeconvolutionImageFilter);

  /** Standard type alias. */
  using Self = LandweberDeconvolutionImageFilter;
  using Superclass = IterativeDeconvolutionImageFilter<TInputImage, TKernelImage, TOutputImage, TInternalPrecision>;
  using Pointer = SmartPointer<Self>;
  using ConstPointer = SmartPointer<const Self>;

  /** Other useful type alias. */
  using InputImageType = TInputImage;
  using KernelImageType = TKernelImage;
  using OutputImageType = TOutputImage;

  /** Internal types used by the FFT filters. */
  using typename Superclass::InternalImageType;
  using typename Superclass::InternalImagePointerType;
  using typename Superclass::InternalComplexType;
  using typename Superclass::InternalComplexImageType;
  using typename Superclass::InternalComplexImagePointerType;

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

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

  /** Set/get relaxation factor. */
  /** @ITKStartGrouping */
  itkSetMacro(Alpha, double);
  itkGetMacro(Alpha, double);
  /** @ITKEndGrouping */
protected:
  LandweberDeconvolutionImageFilter();
  ~LandweberDeconvolutionImageFilter() override;

  void
  Initialize(ProgressAccumulator * progress, float progressWeight, float iterationProgressWeight) override;

  void
  Iteration(ProgressAccumulator * progress, float iterationProgressWeight) override;

  void
  Finish(ProgressAccumulator * progress, float progressWeight) override;

  using typename Superclass::FFTFilterType;
  using typename Superclass::IFFTFilterType;

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

private:
  double m_Alpha{};

  InternalComplexImagePointerType m_TransformedInput{};

  using LandweberFunctor =
    Functor::LandweberMethod<InternalComplexType, InternalComplexType, InternalComplexType, InternalComplexType>;
  using LandweberFilterType = TernaryGeneratorImageFilter<InternalComplexImageType,
                                                          InternalComplexImageType,
                                                          InternalComplexImageType,
                                                          InternalComplexImageType>;

  typename LandweberFilterType::Pointer m_LandweberFilter{};
  typename IFFTFilterType::Pointer      m_IFFTFilter{};
};

} // end namespace itk

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

#endif
