/*=========================================================================
 *
 *  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 itkFastMarchingImageFilter_hxx
#define itkFastMarchingImageFilter_hxx

#include "itkImageRegionIterator.h"
#include "itkNumericTraits.h"
#include <algorithm>

namespace itk
{
template <typename TLevelSet, typename TSpeedImage>
FastMarchingImageFilter<TLevelSet, TSpeedImage>::FastMarchingImageFilter()
  : m_TrialHeap()
{
  this->ProcessObject::SetNumberOfRequiredInputs(0);

  m_OutputRegion.SetSize(OutputSizeType::Filled(16));
  m_OutputRegion.SetIndex({ { 0 } });

  m_OutputOrigin.Fill(0.0);
  m_OutputSpacing.Fill(1.0);
  m_OutputDirection.SetIdentity();
  m_OverrideOutputInformation = false;

  m_AlivePoints = nullptr;
  m_OutsidePoints = nullptr;
  m_TrialPoints = nullptr;
  m_ProcessedPoints = nullptr;

  m_SpeedConstant = 1.0;
  m_InverseSpeed = -1.0;
  m_LabelImage = LabelImageType::New();

  m_LargeValue = static_cast<PixelType>(NumericTraits<PixelType>::max() / 2.0);
  m_StoppingValue = static_cast<double>(m_LargeValue);
  m_CollectPoints = false;

  m_NormalizationFactor = 1.0;
}

template <typename TLevelSet, typename TSpeedImage>
void
FastMarchingImageFilter<TLevelSet, TSpeedImage>::PrintSelf(std::ostream & os, Indent indent) const
{
  Superclass::PrintSelf(os, indent);
  os << indent << "Alive points: " << m_AlivePoints.GetPointer() << std::endl;
  os << indent << "Trial points: " << m_TrialPoints.GetPointer() << std::endl;
  os << indent << "Speed constant: " << m_SpeedConstant << std::endl;
  os << indent << "Stopping value: " << m_StoppingValue << std::endl;
  os << indent << "Large Value: " << static_cast<typename NumericTraits<PixelType>::PrintType>(m_LargeValue)
     << std::endl;
  os << indent << "Normalization Factor: " << m_NormalizationFactor << std::endl;
  os << indent << "Collect points: " << m_CollectPoints << std::endl;
  os << indent << "OverrideOutputInformation: ";
  os << m_OverrideOutputInformation << std::endl;
  os << indent << "OutputRegion: " << m_OutputRegion << std::endl;
  os << indent << "OutputOrigin:  " << m_OutputOrigin << std::endl;
  os << indent << "OutputSpacing: " << m_OutputSpacing << std::endl;
  os << indent << "OutputDirection: " << m_OutputDirection << std::endl;
}

template <typename TLevelSet, typename TSpeedImage>
void
FastMarchingImageFilter<TLevelSet, TSpeedImage>::GenerateOutputInformation()
{
  // copy output information from input image
  Superclass::GenerateOutputInformation();

  // use user-specified output information
  if (this->GetInput() == nullptr || m_OverrideOutputInformation)
  {
    LevelSetPointer output = this->GetOutput();
    output->SetLargestPossibleRegion(m_OutputRegion);
    output->SetOrigin(m_OutputOrigin);
    output->SetSpacing(m_OutputSpacing);
    output->SetDirection(m_OutputDirection);
  }
}

template <typename TLevelSet, typename TSpeedImage>
void
FastMarchingImageFilter<TLevelSet, TSpeedImage>::EnlargeOutputRequestedRegion(DataObject * output)
{
  // enlarge the requested region of the output
  // to the whole data set
  TLevelSet * imgData;

  imgData = dynamic_cast<TLevelSet *>(output);
  if (imgData)
  {
    imgData->SetRequestedRegionToLargestPossibleRegion();
  }
  else
  {
    // Pointer could not be cast to TLevelSet *
    itkWarningMacro("itk::FastMarchingImageFilter"
                    << "::EnlargeOutputRequestedRegion cannot cast " << typeid(output).name() << " to "
                    << typeid(TLevelSet *).name());
  }
}

template <typename TLevelSet, typename TSpeedImage>
void
FastMarchingImageFilter<TLevelSet, TSpeedImage>::Initialize(LevelSetImageType * output)
{
  // allocate memory for the output buffer
  output->SetBufferedRegion(output->GetRequestedRegion());
  output->Allocate();

  // cache some buffered region information
  m_BufferedRegion = output->GetBufferedRegion();
  m_StartIndex = m_BufferedRegion.GetIndex();
  m_LastIndex = m_StartIndex + m_BufferedRegion.GetSize();
  typename LevelSetImageType::OffsetType offset;
  offset.Fill(1);
  m_LastIndex -= offset;

  // allocate memory for the PointTypeImage
  m_LabelImage->CopyInformation(output);
  m_LabelImage->SetBufferedRegion(output->GetBufferedRegion());
  m_LabelImage->Allocate();

  // set all output value to infinity
  using OutputIterator = ImageRegionIterator<LevelSetImageType>;

  PixelType outputPixel;
  outputPixel = m_LargeValue;

  for (OutputIterator outIt(output, output->GetBufferedRegion()); !outIt.IsAtEnd(); ++outIt)
  {
    outIt.Set(outputPixel);
  }

  // set all points type to FarPoint
  using LabelIterator = ImageRegionIterator<LabelImageType>;

  LabelIterator typeIt(m_LabelImage, m_LabelImage->GetBufferedRegion());

  while (!typeIt.IsAtEnd())
  {
    typeIt.Set(LabelEnum::FarPoint);
    ++typeIt;
  }

  // process input alive points
  AxisNodeType  node;
  NodeIndexType idx;

  if (m_AlivePoints)
  {
    typename NodeContainer::ConstIterator pointsIter = m_AlivePoints->Begin();
    typename NodeContainer::ConstIterator pointsEnd = m_AlivePoints->End();

    while (pointsIter != pointsEnd)
    {
      // get node from alive points container
      node = pointsIter.Value();
      idx = node.GetIndex();

      // check if node index is within the output level set
      if (m_BufferedRegion.IsInside(idx))
      {
        // make this an alive point
        m_LabelImage->SetPixel(idx, LabelEnum::AlivePoint);

        outputPixel = node.GetValue();
        output->SetPixel(idx, outputPixel);
      }

      ++pointsIter;
    }
  }

  if (m_OutsidePoints)
  {
    typename NodeContainer::ConstIterator pointsIter = m_OutsidePoints->Begin();
    typename NodeContainer::ConstIterator pointsEnd = m_OutsidePoints->End();

    while (pointsIter != pointsEnd)
    {
      // get node from alive points container
      node = pointsIter.Value();
      idx = node.GetIndex();

      // check if node index is within the output level set
      if (m_BufferedRegion.IsInside(idx))
      {
        // make this an alive point
        m_LabelImage->SetPixel(idx, LabelEnum::OutsidePoint);

        outputPixel = node.GetValue();
        output->SetPixel(idx, outputPixel);
      }

      ++pointsIter;
    }
  }

  // make sure the heap is empty
  while (!m_TrialHeap.empty())
  {
    m_TrialHeap.pop();
  }

  // process the input trial points
  if (m_TrialPoints)
  {
    typename NodeContainer::ConstIterator pointsIter = m_TrialPoints->Begin();
    typename NodeContainer::ConstIterator pointsEnd = m_TrialPoints->End();

    while (pointsIter != pointsEnd)
    {
      // get node from trial points container
      node = pointsIter.Value();
      idx = node.GetIndex();

      // check if node index is within the output level set
      if (m_BufferedRegion.IsInside(idx))
      {
        // make this an initial trial point
        m_LabelImage->SetPixel(idx, LabelEnum::InitialTrialPoint);

        outputPixel = node.GetValue();
        output->SetPixel(idx, outputPixel);

        m_TrialHeap.push(node);
      }
      ++pointsIter;
    }
  }
}

template <typename TLevelSet, typename TSpeedImage>
void
FastMarchingImageFilter<TLevelSet, TSpeedImage>::GenerateData()
{
  if (m_NormalizationFactor < itk::Math::eps)
  {
    ExceptionObject err(__FILE__, __LINE__);
    err.SetLocation(ITK_LOCATION);
    err.SetDescription("Normalization Factor is null or negative");
    throw err;
  }

  LevelSetPointer        output = this->GetOutput();
  SpeedImageConstPointer speedImage = this->GetInput();

  this->Initialize(output);

  if (m_CollectPoints)
  {
    m_ProcessedPoints = NodeContainer::New();
  }

  // process points on the heap
  AxisNodeType node;
  double       currentValue;
  double       oldProgress = 0;

  this->UpdateProgress(0.0); // Send first progress event

  // CACHE
  while (!m_TrialHeap.empty())
  {
    // get the node with the smallest value
    node = m_TrialHeap.top();
    m_TrialHeap.pop();

    // does this node contain the current value ?
    currentValue = static_cast<double>(output->GetPixel(node.GetIndex()));

    if (Math::ExactlyEquals(node.GetValue(), currentValue))
    {
      // is this node already alive ?
      if (m_LabelImage->GetPixel(node.GetIndex()) != LabelEnum::AlivePoint)
      {
        if (currentValue > m_StoppingValue)
        {
          this->UpdateProgress(1.0);
          break;
        }

        if (m_CollectPoints)
        {
          m_ProcessedPoints->InsertElement(m_ProcessedPoints->Size(), node);
        }

        // set this node as alive
        m_LabelImage->SetPixel(node.GetIndex(), LabelEnum::AlivePoint);

        // update its neighbors
        this->UpdateNeighbors(node.GetIndex(), speedImage, output);

        // Send events every certain number of points.
        const double newProgress = currentValue / m_StoppingValue;
        if (newProgress - oldProgress > 0.01) // update every 1%
        {
          this->UpdateProgress(newProgress);
          oldProgress = newProgress;
          if (this->GetAbortGenerateData())
          {
            this->InvokeEvent(AbortEvent());
            this->ResetPipeline();
            ProcessAborted e(__FILE__, __LINE__);
            e.SetDescription("Process aborted.");
            e.SetLocation(ITK_LOCATION);
            throw e;
          }
        }
      }
    }
  }
}

template <typename TLevelSet, typename TSpeedImage>
void
FastMarchingImageFilter<TLevelSet, TSpeedImage>::UpdateNeighbors(const IndexType &      index,
                                                                 const SpeedImageType * speedImage,
                                                                 LevelSetImageType *    output)
{
  IndexType neighIndex = index;


  for (unsigned int j = 0; j < SetDimension; ++j)
  {
    // update left neighbor
    if (index[j] > m_StartIndex[j])
    {
      neighIndex[j] = index[j] - 1;
    }

    LabelEnum label = m_LabelImage->GetPixel(neighIndex);

    if ((label != LabelEnum::AlivePoint) && (label != LabelEnum::InitialTrialPoint) &&
        (label != LabelEnum::OutsidePoint))
    {
      this->UpdateValue(neighIndex, speedImage, output);
    }

    // update right neighbor
    if (index[j] < m_LastIndex[j])
    {
      neighIndex[j] = index[j] + 1;
    }

    label = m_LabelImage->GetPixel(neighIndex);

    if ((label != LabelEnum::AlivePoint) && (label != LabelEnum::InitialTrialPoint) &&
        (label != LabelEnum::OutsidePoint))
    {
      this->UpdateValue(neighIndex, speedImage, output);
    }

    // reset neighIndex
    neighIndex[j] = index[j];
  }
}

template <typename TLevelSet, typename TSpeedImage>
double
FastMarchingImageFilter<TLevelSet, TSpeedImage>::UpdateValue(const IndexType &      index,
                                                             const SpeedImageType * speedImage,
                                                             LevelSetImageType *    output)
{
  IndexType neighIndex = index;

  PixelType neighValue;

  // just to make sure the index is initialized (really cautious)
  AxisNodeType node;
  node.SetIndex(index);

  for (unsigned int j = 0; j < SetDimension; ++j)
  {
    node.SetValue(m_LargeValue);

    // find smallest valued neighbor in this dimension
    for (int s = -1; s < 2; s = s + 2)
    {
      neighIndex[j] = index[j] + s;

      // make sure neighIndex is not outside from the image
      if ((neighIndex[j] > m_LastIndex[j]) || (neighIndex[j] < m_StartIndex[j]))
      {
        continue;
      }

      if (m_LabelImage->GetPixel(neighIndex) == LabelEnum::AlivePoint)
      {
        neighValue = static_cast<PixelType>(output->GetPixel(neighIndex));

        // let's find the minimum value given a direction j
        if (node.GetValue() > neighValue)
        {
          node.SetValue(neighValue);
          node.SetIndex(neighIndex);
        }
      }
    }

    // put the minimum neighbor onto the heap
    m_NodesUsed[j] = node;
    m_NodesUsed[j].SetAxis(j);

    // reset neighIndex
    neighIndex[j] = index[j];
  }

  // sort the local list
  std::sort(m_NodesUsed, m_NodesUsed + SetDimension);

  // solve quadratic equation
  auto solution = static_cast<double>(m_LargeValue);

  double aa(0.0);
  double bb(0.0);
  double cc(m_InverseSpeed);

  if (speedImage)
  {
    cc = static_cast<double>(speedImage->GetPixel(index)) / m_NormalizationFactor;
    cc = -1.0 * itk::Math::sqr(1.0 / cc);
  }

  OutputSpacingType spacing = /* this->GetOutput() */ output->GetSpacing();

  double discrim;

  for (unsigned int j = 0; j < SetDimension; ++j)
  {
    node = m_NodesUsed[j];
    const auto value = static_cast<double>(node.GetValue());

    if (solution >= value)
    {
      const int axis = node.GetAxis();
      // spaceFactor = \frac{1}{spacing[axis]^2}
      const double spaceFactor = itk::Math::sqr(1.0 / spacing[axis]);
      aa += spaceFactor;
      bb += value * spaceFactor;
      cc += itk::Math::sqr(value) * spaceFactor;

      discrim = itk::Math::sqr(bb) - aa * cc;
      if (discrim < 0.0)
      {
        // Discriminant of quadratic eqn. is negative
        ExceptionObject err(__FILE__, __LINE__);
        err.SetLocation(ITK_LOCATION);
        err.SetDescription("Discriminant of quadratic equation is negative");
        throw err;
      }

      solution = (std::sqrt(discrim) + bb) / aa;
    }
    else
    {
      break;
    }
  }

  if (solution < m_LargeValue)
  {
    // write solution to m_OutputLevelSet
    auto outputPixel = static_cast<PixelType>(solution);
    output->SetPixel(index, outputPixel);

    // insert point into trial heap
    m_LabelImage->SetPixel(index, LabelEnum::TrialPoint);
    node.SetValue(outputPixel);
    node.SetIndex(index);
    m_TrialHeap.push(node);
  }

  return solution;
}
} // namespace itk

#endif
