/*=========================================================================
 *
 *  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 itkScalarToRGBPixelFunctor_hxx
#define itkScalarToRGBPixelFunctor_hxx

#include "itkByteSwapper.h"

namespace itk::Functor
{
template <typename TScalar>
ScalarToRGBPixelFunctor<TScalar>::ScalarToRGBPixelFunctor()
{
  m_ColorIndex[0] = 0;
  m_ColorIndex[1] = 0;
  m_ColorIndex[2] = 0;
  const auto scalarSize = static_cast<unsigned int>(sizeof(ScalarType));
  for (unsigned int i = 0; i < scalarSize && i < 3; ++i)
  {
    m_ColorIndex[i] = i;
  }

#ifdef ITK_WORDS_BIGENDIAN
  m_UseMSBForHashing = true;
#else
  m_UseMSBForHashing = false;
#endif
}

template <typename TScalar>
auto
ScalarToRGBPixelFunctor<TScalar>::operator()(const TScalar & v) const -> RGBPixelType
{
  TScalar      buf = v;
  const auto * bytes = reinterpret_cast<const unsigned char *>(&buf);

  if (this->m_UseMSBForHashing)
  { // swap bytes
    // always swap regardless of system endianness
    if constexpr (ByteSwapper<TScalar>::SystemIsBigEndian())
    {
      ByteSwapper<TScalar>::SwapFromSystemToLittleEndian(&buf);
    }
    else
    {
      ByteSwapper<TScalar>::SwapFromSystemToBigEndian(&buf);
    }
  }

  RGBPixelType ans;

  ans[0] = static_cast<RGBComponentType>(bytes[m_ColorIndex[0]] * 3);
  ans[1] = static_cast<RGBComponentType>((bytes[m_ColorIndex[0]] + bytes[m_ColorIndex[1]]) * 5);
  ans[2] = static_cast<RGBComponentType>((bytes[m_ColorIndex[0]] + bytes[m_ColorIndex[2]]));

  return ans;
}
} // namespace itk::Functor

#endif
