/*=========================================================================
 *
 *  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 itkLevelSetEquationChanAndVeseExternalTerm_hxx
#define itkLevelSetEquationChanAndVeseExternalTerm_hxx


namespace itk
{
template <typename TInput, typename TLevelSetContainer>
LevelSetEquationChanAndVeseExternalTerm<TInput, TLevelSetContainer>::LevelSetEquationChanAndVeseExternalTerm()
{
  this->m_TermName = "External Chan And Vese term";
  this->m_RequiredData.insert("Value");
  this->m_DomainMapImageFilter = nullptr;
  this->m_CacheImage = nullptr;
}

template <typename TInput, typename TLevelSetContainer>
void
LevelSetEquationChanAndVeseExternalTerm<TInput, TLevelSetContainer>::ComputeProduct(const LevelSetInputIndexType & iP,
                                                                                    LevelSetOutputRealType &       prod)
{
  this->ComputeProductTerm(iP, prod);
  LevelSetPointer        levelSet = this->m_LevelSetContainer->GetLevelSet(this->m_CurrentLevelSetId);
  LevelSetOutputRealType value = levelSet->Evaluate(iP);
  prod *= -(1 - this->m_Heaviside->Evaluate(-value));
}

template <typename TInput, typename TLevelSetContainer>
void
LevelSetEquationChanAndVeseExternalTerm<TInput, TLevelSetContainer>::ComputeProductTerm(
  const LevelSetInputIndexType & iP,
  LevelSetOutputRealType &       prod)
{
  prod = -1 * NumericTraits<LevelSetOutputRealType>::OneValue();

  if (this->m_LevelSetContainer->HasDomainMap())
  {
    if (this->m_DomainMapImageFilter == nullptr)
    {
      this->m_DomainMapImageFilter = this->m_LevelSetContainer->GetModifiableDomainMapFilter();
      this->m_CacheImage = this->m_DomainMapImageFilter->GetOutput();
    }
    const LevelSetIdentifierType id = this->m_CacheImage->GetPixel(iP);

    using DomainMapType = typename DomainMapImageFilterType::DomainMapType;
    const DomainMapType domainMap = this->m_DomainMapImageFilter->GetDomainMap();
    auto                levelSetMapItr = domainMap.find(id);

    if (levelSetMapItr != domainMap.end())
    {
      const IdListType * idList = levelSetMapItr->second.GetIdList();

      LevelSetIdentifierType kk;
      LevelSetPointer        levelSet;
      LevelSetOutputRealType value;

      auto idListIt = idList->begin();
      while (idListIt != idList->end())
      {
        //! \todo Fix me for string identifiers
        kk = *idListIt - 1;
        if (kk != this->m_CurrentLevelSetId)
        {
          levelSet = this->m_LevelSetContainer->GetLevelSet(kk);
          value = levelSet->Evaluate(iP);
          prod *= (NumericTraits<LevelSetOutputRealType>::OneValue() - this->m_Heaviside->Evaluate(-value));
        }
        ++idListIt;
      }
    }
  }
  else
  {
    LevelSetIdentifierType kk;
    LevelSetPointer        levelSet;
    LevelSetOutputRealType value;

    typename LevelSetContainerType::Iterator lsIt = this->m_LevelSetContainer->Begin();

    while (lsIt != this->m_LevelSetContainer->End())
    {
      kk = lsIt->GetIdentifier();
      if (kk != this->m_CurrentLevelSetId)
      {
        levelSet = this->m_LevelSetContainer->GetLevelSet(kk);
        value = levelSet->Evaluate(iP);
        prod *= (NumericTraits<LevelSetOutputRealType>::OneValue() - this->m_Heaviside->Evaluate(-value));
      }
      ++lsIt;
    }
  }
}

template <typename TInput, typename TLevelSetContainer>
void
LevelSetEquationChanAndVeseExternalTerm<TInput, TLevelSetContainer>::UpdatePixel(
  const LevelSetInputIndexType & iP,
  const LevelSetOutputRealType & oldValue,
  const LevelSetOutputRealType & newValue)
{
  // Compute the product factor
  LevelSetOutputRealType prod;

  this->ComputeProductTerm(iP, prod);

  // For each affected h val: h val = new hval (this will dirty some cvals)
  InputPixelType input = this->m_Input->GetPixel(iP);

  const LevelSetOutputRealType oldH = this->m_Heaviside->Evaluate(-oldValue);
  const LevelSetOutputRealType newH = this->m_Heaviside->Evaluate(-newValue);
  const LevelSetOutputRealType change = oldH - newH; //(1 - newH) - (1 - oldH);

  // Determine the change in the product factor
  const LevelSetOutputRealType productChange = -(prod * change);

  this->m_TotalH += change;
  this->m_TotalValue += input * productChange;
}

} // namespace itk

#endif
