/*=========================================================================
 *
 *  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 itkPathConstIterator_hxx
#define itkPathConstIterator_hxx

#include "itkOffset.h" // for operator++

namespace itk
{
template <typename TImage, typename TPath>
PathConstIterator<TImage, TPath>::PathConstIterator(const ImageType * imagePtr, const PathType * pathPtr)
  : m_Image(imagePtr)
  , m_Path(pathPtr)
  , m_Region(m_Image->GetLargestPossibleRegion())
  , m_ImageOrigin(m_Image->GetOrigin())
  , m_ImageSpacing(m_Image->GetSpacing())
  , m_ImageSize(m_Region.GetSize().m_InternalArray)
  , m_VisitStartIndexAsLastIndexIfClosed(true)
{
  m_ZeroOffset.Fill(0);
  GoToBegin();
}

template <typename TImage, typename TPath>
PathConstIterator<TImage, TPath> &
PathConstIterator<TImage, TPath>::operator=(const Self & it)
{
  if (this != &it)
  {
    m_Image = it.m_Image; // copy the smart pointer
    m_Path = it.m_Path;   // copy the smart pointer
    m_Region = it.m_Region;
    m_ImageOrigin = it.m_ImageOrigin;
    m_ImageSpacing = it.m_ImageSpacing;
    m_ImageSize = it.m_ImageSize;
    m_CurrentPathPosition = it.m_CurrentPathPosition;
    m_CurrentImageIndex = it.m_CurrentImageIndex;
    m_VisitStartIndexAsLastIndexIfClosed = it.m_VisitStartIndexAsLastIndexIfClosed;
  }
  return *this;
}

template <typename TImage, typename TPath>
void
PathConstIterator<TImage, TPath>::GoToBegin()
{
  // Go the beginning
  m_CurrentPathPosition = m_Path->StartOfInput();

  // But don't visit the first index twice for closed paths (unless told to)
  if (m_VisitStartIndexAsLastIndexIfClosed)
  {
    // Are the first and last indices coincident?
    if (m_Path->EvaluateToIndex(m_Path->EndOfInput()) == m_Path->EvaluateToIndex(m_Path->StartOfInput()))
    {
      // Skip the starting index; we will visit it later.
      m_Path->IncrementInput(m_CurrentPathPosition);
    }
  }
  // Update the other member data
  m_CurrentImageIndex = m_Path->EvaluateToIndex(m_CurrentPathPosition);
  m_IsAtEnd = false;
}

template <typename TImage, typename TPath>
void
PathConstIterator<TImage, TPath>::operator++()
{
  // We need to modify m_CurrentPathPosition, m_CurrentImageIndex, m_IsAtEnd
  const OffsetType offset = m_Path->IncrementInput(m_CurrentPathPosition);
  if (m_ZeroOffset == offset)
  {
    // We tried to go past the end (and we are still there)
    m_IsAtEnd = true;
  }
  else if (!m_Region.IsInside(m_CurrentImageIndex))
  {
    // The new index is outside the acceptable region.  We can iterate no
    // farther, call this the end.  NOTE THAT INPUT IS STILL INCREMENTED.
    m_IsAtEnd = true;
    itkWarningMacro("Path left region; unable to finish tracing it");
  }
  else
  {
    m_CurrentImageIndex += offset;
  }
}
} // end namespace itk

#endif
