/*=========================================================================
 *
 *  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 itkLabelOverlayFunctor_h
#define itkLabelOverlayFunctor_h

#include "itkLabelToRGBFunctor.h"
#include "itkMath.h"

namespace itk
{
namespace Functor
{
/**
 * \class LabelOverlayFunctor
 *  \brief Functor for applying a colormap to a label image and combine it
 * with a grayscale image
 *
 * This functor class used internally by LabelOverlayImageFilter
 *
 * This code was contributed in the Insight Journal paper:
 * "The watershed transform in ITK - discussion and new developments"
 * by Beare R., Lehmann G.
 * https://www.insight-journal.org/browse/publication/92
 *
 * \author Gaetan Lehmann. Biologie du Developpement et de la Reproduction,
 * INRA de Jouy-en-Josas, France.
 *
 * \sa LabelOverlayImageFilter LabelToRGBFunctor
 *
 * \ingroup ITKImageFusion
 */
template <typename TInputPixel, typename TLabel, typename TRGBPixel>
class LabelOverlayFunctor
{
public:
  LabelOverlayFunctor()
  {
    // provide some default value for external use (outside
    // LabelOverlayFunctorImageFilter) Inside LabelOverlayFunctorImageFilter,
    // the values are always initialized
    m_Opacity = 1.0;
    m_BackgroundValue = TLabel{};
  }

  inline TRGBPixel
  operator()(const TInputPixel & p1, const TLabel & p2) const
  {
    TRGBPixel rgbPixel;
    NumericTraits<TRGBPixel>::SetLength(rgbPixel, 3);

    if (p2 == m_BackgroundValue)
    {
      // value is background
      // return a gray pixel with the same intensity than the input pixel
      auto p = static_cast<typename TRGBPixel::ValueType>(p1);
      rgbPixel[0] = p;
      rgbPixel[1] = p;
      rgbPixel[2] = p;
      return rgbPixel;
    }

    // taint the input pixel with the colored one returned by
    // the color functor.
    TRGBPixel opaque = m_RGBFunctor(p2);
    // the following has been unrolled due to a bug with apple's
    // llvm-gcc-4.2 build 5658
    const double p1_blend = p1 * (1.0 - m_Opacity);
    rgbPixel[0] = static_cast<typename TRGBPixel::ValueType>(opaque[0] * m_Opacity + p1_blend);
    rgbPixel[1] = static_cast<typename TRGBPixel::ValueType>(opaque[1] * m_Opacity + p1_blend);
    rgbPixel[2] = static_cast<typename TRGBPixel::ValueType>(opaque[2] * m_Opacity + p1_blend);

    return rgbPixel;
  }

  bool
  operator==(const LabelOverlayFunctor & other) const
  {
    return Math::ExactlyEquals(m_Opacity, other.m_Opacity) && m_BackgroundValue == other.m_BackgroundValue &&
           m_RGBFunctor == other.m_RGBFunctor;
  }

  ITK_UNEQUAL_OPERATOR_MEMBER_FUNCTION(LabelOverlayFunctor);

  ~LabelOverlayFunctor() = default;

  void
  SetOpacity(double opacity)
  {
    m_Opacity = opacity;
  }

  void
  SetBackgroundValue(TLabel v)
  {
    m_BackgroundValue = v;
    m_RGBFunctor.SetBackgroundValue(v);
  }

  void
  ResetColors()
  {
    m_RGBFunctor.ResetColors();
  }

  unsigned int
  GetNumberOfColors() const
  {
    return m_RGBFunctor.GetNumberOfColors();
  }

  /** type of the color component */
  using ComponentType = typename TRGBPixel::ComponentType;

  void
  AddColor(unsigned char r, unsigned char g, unsigned char b)
  {
    m_RGBFunctor.AddColor(r, g, b);
  }

protected:
private:
  double m_Opacity;
  TLabel m_BackgroundValue;

  typename Functor::LabelToRGBFunctor<TLabel, TRGBPixel> m_RGBFunctor;
};
} // end namespace Functor
} // end namespace itk

#endif