/*=========================================================================
 *
 *  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 itkLevelSetEvolutionUpdateLevelSetsThreader_hxx
#define itkLevelSetEvolutionUpdateLevelSetsThreader_hxx


#include "itkImageRegionIterator.h"

namespace itk
{

template <typename TImage, typename TLevelSetEvolution>
void
LevelSetEvolutionUpdateLevelSetsThreader<LevelSetDenseImage<TImage>,
                                         ThreadedImageRegionPartitioner<TImage::ImageDimension>,
                                         TLevelSetEvolution>::BeforeThreadedExecution()
{
  this->m_RMSChangeAccumulatorPerThread.resize(this->GetNumberOfWorkUnitsUsed());

  for (ThreadIdType ii = 0, maxThreads = this->GetNumberOfWorkUnitsUsed(); ii < maxThreads; ++ii)
  {
    this->m_RMSChangeAccumulatorPerThread[ii].ResetToZero();
  }
}

template <typename TImage, typename TLevelSetEvolution>
void
LevelSetEvolutionUpdateLevelSetsThreader<LevelSetDenseImage<TImage>,
                                         ThreadedImageRegionPartitioner<TImage::ImageDimension>,
                                         TLevelSetEvolution>::ThreadedExecution(const DomainType & imageSubRegion,
                                                                                const ThreadIdType threadId)
{
  typename LevelSetContainerType::Iterator levelSetContainerIt =
    this->m_Associate->m_LevelSetContainerIteratorToProcessWhenThreading;
  typename LevelSetContainerType::ConstIterator levelSetUpdateContainerIt =
    this->m_Associate->m_LevelSetUpdateContainerIteratorToProcessWhenThreading;

  // This is for single level set analysis, so we only process the first level
  // set.
  typename LevelSetType::Pointer levelSet = levelSetContainerIt->GetLevelSet();
  typename LevelSetType::Pointer levelSetUpdate = levelSetUpdateContainerIt->GetLevelSet();

  typename LevelSetImageType::Pointer      levelSetImage = levelSet->GetModifiableImage();
  typename LevelSetImageType::ConstPointer levelSetUpdateImage = levelSetUpdate->GetImage();

  ImageRegionIterator<LevelSetImageType>      levelSetImageIt(levelSetImage, imageSubRegion);
  ImageRegionConstIterator<LevelSetImageType> levelSetUpdateImageIt(levelSetUpdateImage, imageSubRegion);
  levelSetImageIt.GoToBegin();
  levelSetUpdateImageIt.GoToBegin();

  while (!levelSetImageIt.IsAtEnd())
  {
    const LevelSetOutputRealType & p = this->m_Associate->m_Dt * levelSetUpdateImageIt.Get();
    levelSetImageIt.Set(levelSetImageIt.Get() + p);

    this->m_RMSChangeAccumulatorPerThread[threadId] += p * p;

    ++levelSetImageIt;
    ++levelSetUpdateImageIt;
  }
}

template <typename TImage, typename TLevelSetEvolution>
void
LevelSetEvolutionUpdateLevelSetsThreader<LevelSetDenseImage<TImage>,
                                         ThreadedImageRegionPartitioner<TImage::ImageDimension>,
                                         TLevelSetEvolution>::AfterThreadedExecution()
{
  for (ThreadIdType ii = 0, maxThreads = this->GetNumberOfWorkUnitsUsed(); ii < maxThreads; ++ii)
  {
    this->m_Associate->m_RMSChangeAccumulator += this->m_RMSChangeAccumulatorPerThread[ii].GetSum();
  }
}

} // end namespace itk

#endif
