/*=========================================================================
 *
 *  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 itkImageRegionConstIteratorWithOnlyIndex_h
#define itkImageRegionConstIteratorWithOnlyIndex_h

#include "itkImageConstIteratorWithOnlyIndex.h"

namespace itk
{
/** \class ImageRegionConstIteratorWithOnlyIndex
 * \brief A multi-dimensional iterator templated over image type that walks
 * an image region and is specialized to keep track of its index location
 * and safely support images of type ImageBase.
 *
 * The "WithOnlyIndex" family of iterators was designed for algorithms that use only
 * the locations of image pixels in calculations. Unlike
 * ImageRegionIterator, which calculates an index only when requested,
 * ImageRegionIteratorWithOnlyIndex maintains its index location as a member
 * variable that is updated during increment and decrement operations.
 * Iteration speed is penalized, but index queries become more efficient.
 *
 * ImageRegionConstIteratorWithOnlyIndex is a multi-dimensional iterator,
 * requiring more information be specified before the iterator can be
 * used than conventional iterators. Whereas the std::vector::iterator
 * from the STL only needs to be passed a pointer to establish the
 * iterator, the multi-dimensional image iterator needs a pointer,
 * the size of the region, and the start index of the region. To gain access to this
 * information, ImageRegionConstIteratorWithOnlyIndex holds a reference to the
 * image over which it is traversing.
 *
 * ImageRegionConstIteratorWithOnlyIndex assumes a particular layout of
 * the image data. The is arranged in a 1D array as if it were
 * [][][][slice][row][col] with Index[0] = col, Index[1] = row,
 * Index[2] = slice, etc.
 *
 * operator++ provides a simple syntax for walking around a region of
 * a multidimensional image. operator++ iterates across a row, constraining
 * the movement to within a region of image. When the iterator reaches
 * the boundary of the region along a row, the iterator automatically
 * wraps to the next row, starting at the first pixel in the row that is
 * part of the region. This allows for simple processing loops of the form:
 *
   \code

    IteratorType it( image, image->GetRequestedRegion() );

    it.Begin();

    while( ! it.IsAtEnd() )
    {
      std::cout << it.GetIndex() << std::endl;
      ++it;
    }

   \endcode
 *
 *  It also can be used for walking in the reverse direction like
 *
   \code

    IteratorType it( image, image->GetRequestedRegion() );

    it.End();

    while( !it.IsAtBegin() )
    {
      std::cout << it.GetIndex() << std::endl;
      --it;
    }

   \endcode
 *
 * \par MORE INFORMATION
 *
 * For a complete description of the ITK Image Iterators and their API, please
 * see the Iterators chapter in the ITK Software Guide.  The ITK Software Guide
 * is available in print and as a free .pdf download from https://www.itk.org.
 *
 * \ingroup ImageIterators
 *
 * Index-only iterators:
 *
 * \sa ImageRandomConstIteratorWithOnlyIndex
 * \sa ConstNeighborhoodIteratorWithOnlyIndex
 *
 * Pixel data-access iterators:
 *
 * \sa ImageConstIterator \sa ConditionalConstIterator
 * \sa ConstNeighborhoodIterator \sa ConstShapedNeighborhoodIterator
 * \sa ConstSliceIterator  \sa CorrespondenceDataStructureIterator
 * \sa FloodFilledFunctionConditionalConstIterator
 * \sa FloodFilledImageFunctionConditionalConstIterator
 * \sa FloodFilledImageFunctionConditionalIterator
 * \sa FloodFilledSpatialFunctionConditionalConstIterator
 * \sa FloodFilledSpatialFunctionConditionalIterator
 * \sa ImageConstIterator \sa ImageConstIteratorWithIndex
 * \sa ImageIterator \sa ImageIteratorWithIndex
 * \sa ImageLinearConstIteratorWithIndex  \sa ImageLinearIteratorWithIndex
 * \sa ImageRandomConstIteratorWithIndex  \sa ImageRandomIteratorWithIndex
 * \sa ImageRegionConstIterator \sa ImageRegionConstIteratorWithIndex
 * \sa ImageRegionExclusionConstIteratorWithIndex
 * \sa ImageRegionExclusionIteratorWithIndex
 * \sa ImageRegionIterator  \sa ImageRegionIteratorWithIndex
 * \sa ImageRegionReverseConstIterator  \sa ImageRegionReverseIterator
 * \sa ImageReverseConstIterator  \sa ImageReverseIterator
 * \sa ImageSliceConstIteratorWithIndex  \sa ImageSliceIteratorWithIndex
 * \sa NeighborhoodIterator \sa PathConstIterator  \sa PathIterator
 * \sa ShapedNeighborhoodIterator  \sa SliceIterator
 * \sa ImageConstIteratorWithIndex
 * \sa ImageRegionIndexRange
 *
 * \ingroup ITKCommon
 *
 */
template <typename TImage>
class ITK_TEMPLATE_EXPORT ImageRegionConstIteratorWithOnlyIndex : public ImageConstIteratorWithOnlyIndex<TImage>
{
public:
  /** Standard class type aliases. */
  using Self = ImageRegionConstIteratorWithOnlyIndex;
  using Superclass = ImageConstIteratorWithOnlyIndex<TImage>;

  /**
   * Index type alias support While these were already typedef'ed in the superclass
   * they need to be redone here for this subclass to compile properly with gcc.
   */
  /** Types inherited from the Superclass */
  using typename Superclass::IndexType;
  using typename Superclass::SizeType;
  using typename Superclass::OffsetType;
  using typename Superclass::RegionType;
  using typename Superclass::ImageType;

  /** Default constructor. Needed since we provide a cast constructor. */
  ImageRegionConstIteratorWithOnlyIndex()
    : ImageConstIteratorWithOnlyIndex<TImage>()
  {}

  /** Constructor establishes an iterator to walk a particular image and a
   * particular region of that image. */
  ImageRegionConstIteratorWithOnlyIndex(const TImage * ptr, const RegionType & region)
    : ImageConstIteratorWithOnlyIndex<TImage>(ptr, region)
  {}

  /** Constructor that can be used to cast from an ImageIterator to an
   * ImageRegionConstIteratorWithOnlyIndex. Many routines return an ImageIterator but for a
   * particular task, you may want an ImageRegionConstIteratorWithOnlyIndex.  Rather than
   * provide overloaded APIs that return different types of Iterators, itk
   * returns ImageIterators and uses constructors to cast from an
   * ImageIterator to a ImageRegionConstIteratorWithOnlyIndex. */
  ImageRegionConstIteratorWithOnlyIndex(const ImageConstIteratorWithOnlyIndex<TImage> & it)
  {
    this->ImageConstIteratorWithOnlyIndex<TImage>::operator=(it);
  }

  /** Increment (prefix) the fastest moving dimension of the iterator's index.
   * This operator will constrain the iterator within the region (i.e. the
   * iterator will automatically wrap from the end of the row of the region
   * to the beginning of the next row of the region) up until the iterator
   * tries to moves past the last pixel of the region.  Here, the iterator
   * will be set to be one pixel past the end of the region.
   * \sa operator-- */
  Self &
  operator++();

  /** Decrement (prefix) the fastest moving dimension of the iterator's index.
   * This operator will constrain the iterator within the region (i.e. the
   * iterator will automatically wrap from the beginning of the row of the
   * region to the end of the previous row of the region) up until the iterator
   * tries to moves past the first pixel of the region.  Here, the iterator
   * will be set to be one pixel past the beginning of the region.
   * \sa operator++ */
  Self &
  operator--();
};
} // end namespace itk

#ifndef ITK_MANUAL_INSTANTIATION
#  include "itkImageRegionConstIteratorWithOnlyIndex.hxx"
#endif

#endif
