/*=========================================================================
 *
 *  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 itkImageLinearConstIteratorWithIndex_h
#define itkImageLinearConstIteratorWithIndex_h

#include "itkImageConstIteratorWithIndex.h"

namespace itk
{
/** \class ImageLinearConstIteratorWithIndex
 * \brief A multi-dimensional image iterator that visits image pixels within a
 * region in a "scan-line" order.
 *
 * ImageLinearConstIteratorWithIndex is templated over image type and is
 * constrained to walk within a specified image region. It is designed for
 * line-by-line processing of images.  This iterator walks a linear path along
 * a selected image direction that is parallel to one of the coordinate axes
 * of the image.  The iterator conceptually breaks the image into a set of
 * parallel lines that span the selected image dimension.
 *
 * ImageLinearConstIteratorWithIndex 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 preselected direction
 * constraining the movement to within a region of image. The user can verify
 * when the iterator reaches the boundary of the region along this direction,
 * by calling the IsAtEndOfLine() method. Then it is possible to pass to the
 * next line starting at the first pixel in the row that is part of the region
 * by calling the NextLine() method.
 *
 * This is the typical use of this iterator in a loop:
 *
   \code

   ImageLinearConstIteratorWithIndex<ImageType> it( image, image->GetRequestedRegion() );

   it.SetDirection(2);
   it.GoToBegin();
   while( !it.IsAtEnd() )
   {
     while( !it.IsAtEndOfLine() )
     {
        value = it.Get();  // it.Set() doesn't exist in the Const Iterator
        ++it;
     }
     it.NextLine();
    }

    \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
 *
 * \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
 *
 * \ingroup ITKCommon
 */
template <typename TImage>
class ITK_TEMPLATE_EXPORT ImageLinearConstIteratorWithIndex : public ImageConstIteratorWithIndex<TImage>
{
public:
  /** Standard class type aliases. */
  using Self = ImageLinearConstIteratorWithIndex;
  using Superclass = ImageConstIteratorWithIndex<TImage>;

  /** Index type alias support While this was already typedef'ed in the superclass,
   * it needs to be redone here for this subclass to compile properly with gcc.
   * Note that we have to rescope Index back to itk::Index so that it is not
   * confused with ImageIterator::Index. */
  using IndexType = typename TImage::IndexType;

  /** Region type alias support While this was already typedef'ed in the superclass,
   * it needs to be redone here for this subclass to compile properly with gcc.
   * Note that we have to rescope Region back to itk::ImageRegion so that it
   * is not confused with ImageIterator::Index. */
  using RegionType = typename TImage::RegionType;

  /** Image type alias support While this was already typedef'ed in the superclass,
   * it needs to be redone here for this subclass to compile properly with gcc.
   * Note that we have to rescope Index back to itk::Index so that it is not
   * confused with ImageIterator::Index. */
  using ImageType = TImage;

  /** PixelContainer type alias support Used to refer to the container for
   * the pixel data. While this was already typedef'ed in the superclass,
   * it needs to be redone here for this subclass to compile properly with gcc. */
  using PixelContainer = typename TImage::PixelContainer;
  using PixelContainerPointer = typename PixelContainer::Pointer;

  /** Default constructor. Needed since we provide a cast constructor. */
  ImageLinearConstIteratorWithIndex()
    : ImageConstIteratorWithIndex<TImage>()

  {}

  /** Constructor establishes an iterator to walk a particular image and a
   * particular region of that image. */
  ImageLinearConstIteratorWithIndex(const ImageType * ptr, const RegionType & region);

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

  /** Go to the next line.
   * \sa operator++  \sa operator-- \sa IsAtEndOfLine \sa PreviousLine \sa End */
  inline void
  NextLine();

  /** Go to the previous line.
   * \sa operator++ \sa operator-- \sa IsAtEndOfLine \sa NextLine \sa End */
  inline void
  PreviousLine();

  /** Go to the beginning pixel of the current line.
   * \sa GoToReverseBeginOfLine \sa operator++ \sa operator-- \sa NextLine \sa IsAtEndOfLine */
  void
  GoToBeginOfLine();

  /** Go to the beginning pixel of the current line.
   * \sa GoToBeginOfLine \sa operator++ \sa operator-- \sa NextLine \sa IsAtEndOfLine */
  void
  GoToReverseBeginOfLine();

  /** Go to the past end pixel of the current line.
   * \sa GoToBeginOfLine \sa operator++ \sa operator-- \sa NextLine \sa IsAtEndOfLine */
  void
  GoToEndOfLine();

  /** Test if the index is at the end of line */
  inline bool
  IsAtEndOfLine() const
  {
    return this->m_PositionIndex[m_Direction] >= this->m_EndIndex[m_Direction];
  }

  /** Test if the index is at the begin of line */
  inline bool
  IsAtReverseEndOfLine() const
  {
    return this->m_PositionIndex[m_Direction] < this->m_BeginIndex[m_Direction];
  }

  /** Set the direction of movement */
  inline void
  SetDirection(unsigned int direction)
  {
    if (direction >= TImage::ImageDimension)
    {
      itkGenericExceptionMacro("In image of dimension " << TImage::ImageDimension << " Direction " << direction
                                                        << " was selected");
    }
    m_Direction = direction;
    m_Jump = this->m_OffsetTable[m_Direction];
  }

  /** get the direction of movement */
  unsigned int
  GetDirection()
  {
    return m_Direction;
  }

  /** Increment (prefix) the selected dimension.
   * No bounds checking is performed. \sa GetIndex \sa operator-- */
  inline Self &
  operator++()
  {
    this->m_PositionIndex[m_Direction]++;
    this->m_Position += m_Jump;
    return *this;
  }

  /** Decrement (prefix) the selected dimension.
   * No bounds checking is performed.  \sa GetIndex \sa operator++ */
  inline Self &
  operator--()
  {
    this->m_PositionIndex[m_Direction]--;
    this->m_Position -= m_Jump;
    return *this;
  }

private:
  OffsetValueType m_Jump{ 0 };
  unsigned int    m_Direction{ 0 };
};

//----------------------------------------------------------------------
//  Go to next line
//----------------------------------------------------------------------
template <typename TImage>
inline void
ImageLinearConstIteratorWithIndex<TImage>::NextLine()
{
  this->m_Position -=
    this->m_OffsetTable[m_Direction] * (this->m_PositionIndex[m_Direction] - this->m_BeginIndex[m_Direction]);

  this->m_PositionIndex[m_Direction] = this->m_BeginIndex[m_Direction];

  for (unsigned int n = 0; n < TImage::ImageDimension; ++n)
  {
    this->m_Remaining = false;

    if (n == m_Direction)
    {
      continue;
    }

    this->m_PositionIndex[n]++;
    if (this->m_PositionIndex[n] < this->m_EndIndex[n])
    {
      this->m_Position += this->m_OffsetTable[n];
      this->m_Remaining = true;
      break;
    }
    else
    {
      this->m_Position -= this->m_OffsetTable[n] * (this->m_Region.GetSize()[n] - 1);
      this->m_PositionIndex[n] = this->m_BeginIndex[n];
    }
  }
}

//----------------------------------------------------------------------
//  Pass to the last pixel on the previous line
//----------------------------------------------------------------------
template <typename TImage>
inline void
ImageLinearConstIteratorWithIndex<TImage>::PreviousLine()
{
  this->m_Position +=
    this->m_OffsetTable[m_Direction] * (this->m_EndIndex[m_Direction] - 1 - this->m_PositionIndex[m_Direction]);

  this->m_PositionIndex[m_Direction] = this->m_EndIndex[m_Direction] - 1;

  for (unsigned int n = 0; n < TImage::ImageDimension; ++n)
  {
    this->m_Remaining = false;

    if (n == m_Direction)
    {
      continue;
    }

    this->m_PositionIndex[n]--;
    if (this->m_PositionIndex[n] >= this->m_BeginIndex[n])
    {
      this->m_Position -= this->m_OffsetTable[n];
      this->m_Remaining = true;
      break;
    }
    else
    {
      this->m_Position += this->m_OffsetTable[n] * (this->m_Region.GetSize()[n] - 1);
      this->m_PositionIndex[n] = this->m_EndIndex[n] - 1;
    }
  }
}
} // end namespace itk

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

#endif
