/*=========================================================================
 *
 *  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 itkAttributeKeepNObjectsLabelMapFilter_hxx
#define itkAttributeKeepNObjectsLabelMapFilter_hxx

#include "itkProgressReporter.h"


namespace itk
{

template <typename TImage, typename TAttributeAccessor>
AttributeKeepNObjectsLabelMapFilter<TImage, TAttributeAccessor>::AttributeKeepNObjectsLabelMapFilter()
{
  m_ReverseOrdering = false;
  m_NumberOfObjects = 1;
  // create the output image for the removed objects
  this->SetNumberOfRequiredOutputs(2);
  this->SetNthOutput(1, static_cast<TImage *>(this->MakeOutput(1).GetPointer()));
}


template <typename TImage, typename TAttributeAccessor>
void
AttributeKeepNObjectsLabelMapFilter<TImage, TAttributeAccessor>::GenerateData()
{
  // Allocate the output
  this->AllocateOutputs();

  ImageType * output = this->GetOutput();
  ImageType * output2 = this->GetOutput(1);

  // set the background value for the second output - this is not done in the superclasses
  output2->SetBackgroundValue(output->GetBackgroundValue());

  ProgressReporter progress(this, 0, 2 * output->GetNumberOfLabelObjects());

  // get the label objects in a vector, so they can be sorted
  using VectorType = typename std::vector<typename LabelObjectType::Pointer>;
  VectorType labelObjects;
  labelObjects.reserve(output->GetNumberOfLabelObjects());
  for (typename ImageType::Iterator it(output); !it.IsAtEnd(); ++it)
  {
    labelObjects.push_back(it.GetLabelObject());
    progress.CompletedPixel();
  }

  // instantiate the comparator and sort the vector
  if (m_NumberOfObjects < output->GetNumberOfLabelObjects())
  {
    auto end = labelObjects.begin() + m_NumberOfObjects;
    if (m_ReverseOrdering)
    {
      ReverseComparator comparator;
      std::nth_element(labelObjects.begin(), end, labelObjects.end(), comparator);
    }
    else
    {
      Comparator comparator;
      std::nth_element(labelObjects.begin(), end, labelObjects.end(), comparator);
    }
    //   progress.CompletedPixel();

    // and move the last objects to the second output
    for (typename VectorType::const_iterator it = end; it != labelObjects.end(); ++it)
    {
      output->RemoveLabelObject(*it);
      output2->AddLabelObject(*it);
      progress.CompletedPixel();
    }
  }
}


template <typename TImage, typename TAttributeAccessor>
void
AttributeKeepNObjectsLabelMapFilter<TImage, TAttributeAccessor>::PrintSelf(std::ostream & os, Indent indent) const
{
  Superclass::PrintSelf(os, indent);

  os << indent << "ReverseOrdering: " << m_ReverseOrdering << std::endl;
  os << indent << "NumberOfObjects: " << m_NumberOfObjects << std::endl;
}

} // end namespace itk
#endif
