/*=========================================================================
 *
 *  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 itkMovingHistogramMorphologicalGradientImageFilter_h
#define itkMovingHistogramMorphologicalGradientImageFilter_h

#include "itkMovingHistogramImageFilter.h"
#include <map>

namespace itk
{
namespace Function
{
template <typename TInputPixel>
class MorphologicalGradientHistogram
{
public:
  MorphologicalGradientHistogram() = default;

  ~MorphologicalGradientHistogram() = default;

  inline void
  AddBoundary()
  {}

  inline void
  RemoveBoundary()
  {}

  using MapType = std::map<TInputPixel, SizeValueType>;

  inline void
  AddPixel(const TInputPixel & p)
  {
    m_Map[p]++;
  }

  inline void
  RemovePixel(const TInputPixel & p)
  {
    m_Map[p]--;
  }

  inline TInputPixel
  GetValue(const TInputPixel &)
  {
    return GetValue();
  }

  inline TInputPixel
  GetValue()
  {
    // clean the map
    typename MapType::iterator mapIt = m_Map.begin();
    while (mapIt != m_Map.end())
    {
      if (mapIt->second == 0)
      {
        // this value must be removed from the histogram
        // The value must be stored and the iterator updated before removing the
        // value
        // or the iterator is invalidated.
        TInputPixel toErase = mapIt->first;
        ++mapIt;
        m_Map.erase(toErase);
      }
      else
      {
        ++mapIt;
      }
    }

    // and return the value
    if (!m_Map.empty())
    {
      return m_Map.rbegin()->first - m_Map.begin()->first;
    }
    return 0;
  }

  static bool
  UseVectorBasedAlgorithm()
  {
    return false;
  }

  MapType m_Map;
};


template <typename TInputPixel>
class VectorMorphologicalGradientHistogram
{
public:
  VectorMorphologicalGradientHistogram()
  {
    // initialize members need for the vector based algorithm
    m_Vector.resize(NumericTraits<TInputPixel>::max() - NumericTraits<TInputPixel>::NonpositiveMin() + 1, 0);
    m_Max = NumericTraits<TInputPixel>::NonpositiveMin();
    m_Min = NumericTraits<TInputPixel>::max();
    m_Count = 0;
  }

  ~VectorMorphologicalGradientHistogram() = default;

  inline void
  AddBoundary()
  {}

  inline void
  RemoveBoundary()
  {}


  inline void
  AddPixel(const TInputPixel & p)
  {
    m_Vector[p - NumericTraits<TInputPixel>::NonpositiveMin()]++;
    if (p > m_Max)
    {
      m_Max = p;
    }
    if (p < m_Min)
    {
      m_Min = p;
    }
    ++m_Count;
  }

  inline void
  RemovePixel(const TInputPixel & p)
  {
    m_Vector[p - NumericTraits<TInputPixel>::NonpositiveMin()]--;
    --m_Count;
    if (m_Count > 0)
    {
      while (m_Vector[m_Max - NumericTraits<TInputPixel>::NonpositiveMin()] == 0)
      {
        --m_Max;
      }
      while (m_Vector[m_Min - NumericTraits<TInputPixel>::NonpositiveMin()] == 0)
      {
        ++m_Min;
      }
    }
    else
    {
      m_Max = NumericTraits<TInputPixel>::NonpositiveMin();
      m_Min = NumericTraits<TInputPixel>::max();
    }
  }

  inline TInputPixel
  GetValue(const TInputPixel &)
  {
    return GetValue();
  }

  inline TInputPixel
  GetValue()
  {
    if (m_Count > 0)
    {
      return m_Max - m_Min;
    }
    else
    {
      return TInputPixel{};
    }
  }

  static bool
  UseVectorBasedAlgorithm()
  {
    return true;
  }

  std::vector<SizeValueType> m_Vector;
  TInputPixel                m_Min;
  TInputPixel                m_Max;
  SizeValueType              m_Count;
};

/// \cond HIDE_SPECIALIZATION_DOCUMENTATION

// now create MorphologicalGradientHistogram specializations using the VectorMorphologicalGradientHistogram
// as base class

template <>
class MorphologicalGradientHistogram<unsigned char> : public VectorMorphologicalGradientHistogram<unsigned char>
{};

template <>
class MorphologicalGradientHistogram<signed char> : public VectorMorphologicalGradientHistogram<signed char>
{};

template <>
class ITK_TEMPLATE_EXPORT MorphologicalGradientHistogram<bool> : public VectorMorphologicalGradientHistogram<bool>
{};

/// \endcond

} // end namespace Function

/**
 * \class MovingHistogramMorphologicalGradientImageFilter
 * \brief Morphological gradients enhance the variation of pixel
 * intensity in a given neighborhood.
 *
 * Morphological gradient is described in Chapter 3.8.1 of Pierre
 * Soille's book  "Morphological Image Analysis: Principles and
 * Applications", Second Edition, Springer, 2003.
 *
 * \author Gaetan Lehmann. Biologie du Developpement et de la Reproduction, INRA de Jouy-en-Josas, France.
 *
 * \ingroup ImageEnhancement  MathematicalMorphologyImageFilters
 * \ingroup ITKMathematicalMorphology
 */

template <typename TInputImage, typename TOutputImage, typename TKernel>
class MovingHistogramMorphologicalGradientImageFilter
  : public MovingHistogramImageFilter<
      TInputImage,
      TOutputImage,
      TKernel,
      typename Function::MorphologicalGradientHistogram<typename TInputImage::PixelType>>
{
public:
  ITK_DISALLOW_COPY_AND_MOVE(MovingHistogramMorphologicalGradientImageFilter);

  /** Standard class type aliases. */
  using Self = MovingHistogramMorphologicalGradientImageFilter;
  using Superclass =
    MovingHistogramImageFilter<TInputImage,
                               TOutputImage,
                               TKernel,
                               typename Function::MorphologicalGradientHistogram<typename TInputImage::PixelType>>;
  using Pointer = SmartPointer<Self>;
  using ConstPointer = SmartPointer<const Self>;

  /** Standard New method. */
  itkNewMacro(Self);

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

  /** Image related type alias. */
  using InputImageType = TInputImage;
  using OutputImageType = TOutputImage;
  using RegionType = typename TInputImage::RegionType;
  using SizeType = typename TInputImage::SizeType;
  using IndexType = typename TInputImage::IndexType;
  using PixelType = typename TInputImage::PixelType;
  using OffsetType = typename TInputImage::OffsetType;
  using typename Superclass::OutputImageRegionType;
  using OutputPixelType = typename TOutputImage::PixelType;

  using HistogramType = Function::MorphologicalGradientHistogram<PixelType>;

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

  /** Return true if the vector based algorithm is used, and
   * false if the map based algorithm is used */
  static bool
  GetUseVectorBasedAlgorithm()
  {
    return Function::MorphologicalGradientHistogram<typename TInputImage::PixelType>::UseVectorBasedAlgorithm();
  }

protected:
  MovingHistogramMorphologicalGradientImageFilter() = default;
  ~MovingHistogramMorphologicalGradientImageFilter() override = default;
}; // end of class
} // end namespace itk

#endif
