/*=========================================================================
 *
 *  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 itkSimilarityIndexImageFilter_h
#define itkSimilarityIndexImageFilter_h

#include "itkImageToImageFilter.h"
#include "itkNumericTraits.h"
#include "itkArray.h"

namespace itk
{
/**
 * \class SimilarityIndexImageFilter
 * \brief Measures the similarity between the set of non-zero pixels of
 * two images.
 *
 * SimilarityIndexImageFilter measures the similarity between the set
 * non-zero pixels of two images using the following formula:
 * \f[ S = \frac{2 | A \cap B |}{|A| + |B|} \f]
 * where \f$A\f$ and \f$B\f$ are respectively the set of non-zero pixels
 * in the first and second input images. Operator \f$|\cdot|\f$ represents
 * the size of a set and \f$\cap\f$ represents the intersection of two sets.
 *
 * The measure is derived from a reliability measure known as the kappa
 * statistic. \f$S\f$ is sensitive to both differences in size and in
 * location and have been in the literature for comparing two segmentation masks.
 * For more information see \cite zijdenbos1994.
 *
 * This filter requires the largest possible region of the first image
 * and the same corresponding region in the second image.
 * It behaves as filter with
 * two input and one output. Thus it can be inserted in a pipeline with
 * other filters. The filter passes the first input through unmodified.
 *
 * This filter is templated over the two input image type. It assume
 * both image have the same number of dimensions.
 *
 * \ingroup MultiThreaded
 * \ingroup ITKImageCompare
 */
template <typename TInputImage1, typename TInputImage2>
class ITK_TEMPLATE_EXPORT SimilarityIndexImageFilter : public ImageToImageFilter<TInputImage1, TInputImage1>
{
public:
  ITK_DISALLOW_COPY_AND_MOVE(SimilarityIndexImageFilter);

  /** Standard Self type alias */
  using Self = SimilarityIndexImageFilter;
  using Superclass = ImageToImageFilter<TInputImage1, TInputImage1>;
  using Pointer = SmartPointer<Self>;
  using ConstPointer = SmartPointer<const Self>;

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

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

  /** Image related type alias. */
  using InputImage1Type = TInputImage1;
  using InputImage2Type = TInputImage2;
  using InputImage1Pointer = typename TInputImage1::Pointer;
  using InputImage2Pointer = typename TInputImage2::Pointer;
  using InputImage1ConstPointer = typename TInputImage1::ConstPointer;
  using InputImage2ConstPointer = typename TInputImage2::ConstPointer;

  using RegionType = typename TInputImage1::RegionType;
  using SizeType = typename TInputImage1::SizeType;
  using IndexType = typename TInputImage1::IndexType;

  using InputImage1PixelType = typename TInputImage1::PixelType;
  using InputImage2PixelType = typename TInputImage2::PixelType;

  /** Image related type alias. */
  static constexpr unsigned int ImageDimension = TInputImage1::ImageDimension;

  /** Type to use form computations. */
  using RealType = typename NumericTraits<InputImage1PixelType>::RealType;

  /** Set the first input. */
  void
  SetInput1(const InputImage1Type * image)
  {
    this->SetInput(image);
  }

  /** Set the second input. */
  void
  SetInput2(const InputImage2Type * image);

  /** Get the first input. */
  const InputImage1Type *
  GetInput1()
  {
    return this->GetInput();
  }

  /** Get the second input. */
  const InputImage2Type *
  GetInput2();

  /** Return the computed similarity index. */
  itkGetConstMacro(SimilarityIndex, RealType);

  itkConceptMacro(Input1HasNumericTraitsCheck, (Concept::HasNumericTraits<InputImage1PixelType>));
  itkConceptMacro(Input2HasNumericTraitsCheck, (Concept::HasNumericTraits<InputImage2PixelType>));

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

  /** Pass the input through unmodified. Do this by Grafting in the
   * AllocateOutputs method. */
  void
  AllocateOutputs() override;

  /** Initialize some accumulators before the threads run. */
  void
  BeforeThreadedGenerateData() override;

  /** Do final mean and variance computation from data accumulated in threads.
   */
  void
  AfterThreadedGenerateData() override;

  /** Multi-thread version GenerateData. */
  void
  ThreadedGenerateData(const RegionType & outputRegionForThread, ThreadIdType threadId) override;

  void
  DynamicThreadedGenerateData(const RegionType &) override
  {
    itkExceptionStringMacro("This class requires threadId so it must use classic multi-threading model");
  }

  // Override since the filter needs all the data for the algorithm
  void
  GenerateInputRequestedRegion() override;

  // Override since the filter produces all of its output
  void
  EnlargeOutputRequestedRegion(DataObject * data) override;

private:
  RealType m_SimilarityIndex{};

  Array<SizeValueType> m_CountOfImage1{};
  Array<SizeValueType> m_CountOfImage2{};
  Array<SizeValueType> m_CountOfIntersection{};
}; // end of class
} // end namespace itk

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

#endif
