/*=========================================================================

  Program:   Insight Segmentation & Registration Toolkit
  Module:    $RCSfile: itkImageReverseConstIterator.h,v $
  Language:  C++
  Date:      $Date: 2005/08/14 19:25:18 $
  Version:   $Revision: 1.8 $

  Copyright (c) Insight Software Consortium. All rights reserved.
  See ITKCopyright.txt or http://www.itk.org/HTML/Copyright.htm for details.

     This software is distributed WITHOUT ANY WARRANTY; without even 
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR 
     PURPOSE.  See the above copyright notices for more information.

=========================================================================*/
#ifndef __itkImageReverseConstIterator_h
#define __itkImageReverseConstIterator_h

#include "itkIndex.h"
#include "itkSize.h"
#include "itkImage.h"
#include "itkImageConstIterator.h"
#include <memory>

namespace itk
{

/** \class ImageReverseConstIterator
 * \brief Multi-dimensional image iterator.
 * 
 * ImageReverseConstIterator is a templated class to represent a
 * multi-dimensional iterator. ImageReverseConstIterator is templated over the
 * dimension of the image and the data type of the image.
 *
 * ImageReverseConstIterator is a base class for all the reverse image
 * iterators. It provides the basic construction and comparison
 * operations.  However, it does not provide mechanisms for moving the
 * iterator.  A subclass of ImageReverseConstIterator must be used to move
 * the iterator.
 * 
 * ImageReverseConstIterator 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 buffer, the size of the region, the start index of the buffer,
 * and the start index of the region. To gain access to this
 * information, ImageReverseConstIterator holds a reference to the image
 * over which it is traversing.
 *
 * ImageReverseConstIterator assumes a particular layout of the image
 * data. In particular, the data is arranged in a 1D array as if it
 * were [][][][slice][row][col] with Index[0] = col, Index[1] = row,
 * Index[2] = slice, etc.
  *
 * \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 http://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 */
template<typename TImage>
class ITK_EXPORT ImageReverseConstIterator
{
public:
  /** Standard class typedefs. */
  typedef ImageReverseConstIterator Self;
  
  /** Dimension of the image the iterator walks.  This constant is needed so
   * functions that are templated over image iterator type (as opposed to
   * being templated over pixel type and dimension) can have compile time
   * access to the dimension of the image that the iterator walks. */
  itkStaticConstMacro(ImageIteratorDimension, unsigned int,
                      TImage::ImageDimension);

  /** Index typedef support. */
  typedef typename TImage::IndexType        IndexType;
  typedef typename TImage::IndexValueType   IndexValueType;
    
  /** Size typedef support. */
  typedef typename TImage::SizeType         SizeType;
  typedef typename TImage::SizeValueType    SizeValueType;
  
  /** Offset typedef support. */
  typedef typename TImage::OffsetType       OffsetType;
  typedef typename TImage::OffsetValueType  OffsetValueType;
  
  /** Region typedef support. */
  typedef typename TImage::RegionType       RegionType;

  /** Image typedef support. */
  typedef TImage   ImageType;

  /** PixelContainer typedef support. Used to refer to the container for
   * the pixel data. While this was already typdef'ed in the superclass
   * it needs to be redone here for this subclass to compile properly with gcc. */
  typedef typename TImage::PixelContainer PixelContainer;
  typedef typename PixelContainer::Pointer PixelContainerPointer;
  
  /** Internal Pixel Type */
  typedef typename TImage::InternalPixelType   InternalPixelType;

  /** External Pixel Type */
  typedef typename TImage::PixelType   PixelType;

  /**  Accessor type that convert data between internal and external
   *  representations. */
  typedef typename TImage::AccessorType     AccessorType;

  /** Functor to choose the appropriate accessor. (for Image vs VectorImage) */
  typedef typename TImage::AccessorFunctorType     AccessorFunctorType;

  /** Default Constructor. Need to provide a default constructor since we
   * provide a copy constructor. */
  ImageReverseConstIterator()
    :m_PixelAccessor(),
     m_PixelAccessorFunctor()
  {
    m_Buffer = 0;
    m_Offset = 0;
    m_BeginOffset = 0;
    m_EndOffset = 0;
    m_PixelAccessorFunctor.SetBegin( m_Buffer );
  }

  /** Default Destructor. */
  virtual ~ImageReverseConstIterator() {};

  /** Copy Constructor. The copy constructor is provided to make sure the
   * handle to the image is properly reference counted. */
  ImageReverseConstIterator(const Self& it)
  {
    m_Image = it.m_Image;     // copy the smart pointer

    m_Region = it.m_Region;
    
    m_Buffer = it.m_Buffer;
    m_Offset = it.m_Offset;
    m_BeginOffset = it.m_BeginOffset;
    m_EndOffset = it.m_EndOffset;
    m_PixelAccessor = it.m_PixelAccessor;
    m_PixelAccessorFunctor = it.m_PixelAccessorFunctor;
    m_PixelAccessorFunctor.SetBegin( m_Buffer );
  }

  /** Constructor establishes an iterator to walk a particular image and a
   * particular region of that image. */
  ImageReverseConstIterator(ImageType *ptr,
                const RegionType &region)
  {
    unsigned long offset;
    m_Image = ptr;
    m_Buffer = m_Image->GetBufferPointer();
    m_Region = region;

    // Compute the end offset, one pixel before the first pixel
    offset = m_Image->ComputeOffset( m_Region.GetIndex() );
    m_EndOffset = offset-1;
    
    // Compute the begin offset, the last pixel in the region
    IndexType ind(m_Region.GetIndex());
    SizeType size(m_Region.GetSize());
    for (unsigned int i=0; i < TImage::ImageDimension; ++i)
      {
      ind[i] += (size[i] - 1);
      }
    m_BeginOffset = m_Image->ComputeOffset( ind );
    m_Offset = m_BeginOffset;

    m_PixelAccessor = ptr->GetPixelAccessor();
    m_PixelAccessorFunctor.SetPixelAccessor( m_PixelAccessor );
    m_PixelAccessorFunctor.SetBegin( m_Buffer );
  }
  
  /** Constructor that can be used to cast from an ImageConstIterator to an
   * ImageRegionReverseIterator. Many routines return an ImageConstIterator
   * but for a particular task, you may want an
   * ImageRegionReverseIterator.  Rather than provide overloaded APIs
   * that return different types of Iterators, itk returns
   * ImageConstIterators and uses constructors to cast from an
   * ImageConstIterator to a ImageRegionReverseIterator. */
  ImageReverseConstIterator( const ImageConstIterator<TImage> &it)
  {
    m_Image = it.GetImage();
    m_Region = it.GetRegion();
    m_Buffer = m_Image->GetBufferPointer();
    
    IndexType ind = it.GetIndex();

    m_Offset = m_Image->ComputeOffset( ind );

    // Compute the end offset, one pixel before the first pixel
    m_EndOffset = m_Image->ComputeOffset( m_Region.GetIndex() ) - 1;
    
    // Compute the begin offset, the last pixel in the region
    IndexType regInd(m_Region.GetIndex());
    SizeType regSize(m_Region.GetSize());
    for (unsigned int i=0; i < TImage::ImageDimension; ++i)
      {
      regInd[i] += (regSize[i] - 1);
      }
    m_BeginOffset = m_Image->ComputeOffset( regInd );
    
    m_PixelAccessor = m_Image->GetPixelAccessor();
    m_PixelAccessorFunctor.SetPixelAccessor( m_PixelAccessor );
    m_PixelAccessorFunctor.SetBegin( m_Buffer );
  }

  /** operator= is provided to make sure the handle to the image is properly
   * reference counted. */
  Self &operator=(const Self& it)
  {
    m_Image = it.m_Image;     // copy the smart pointer
    m_Region = it.m_Region;
    
    m_Buffer = it.m_Buffer;
    m_Offset = it.m_Offset;
    m_BeginOffset = it.m_BeginOffset;
    m_EndOffset = it.m_EndOffset;
    m_PixelAccessor = it.m_PixelAccessor;
    m_PixelAccessorFunctor.SetPixelAccessor( m_PixelAccessor );
    m_PixelAccessorFunctor.SetBegin( m_Buffer );
    return *this;
  }
  
  /** operator= is provided to make sure the handle to the image is properly
   * reference counted. */
  Self &operator=(const ImageConstIterator<TImage>& it)
  {
    m_Image = it.GetImage();
    m_Region = it.GetRegion();
    m_Buffer = m_Image->GetBufferPointer();
    
    IndexType ind = it.GetIndex();

    m_Offset = m_Image->ComputeOffset( ind );

    // Compute the end offset, one pixel before the first pixel
    m_EndOffset = m_Image->ComputeOffset( m_Region.GetIndex() ) - 1;
    
    // Compute the begin offset, the last pixel in the region
    IndexType regInd(m_Region.GetIndex());
    SizeType regSize(m_Region.GetSize());
    for (unsigned int i=0; i < TImage::ImageDimension; ++i)
      {
      regInd[i] += (regSize[i] - 1);
      }
    m_BeginOffset = m_Image->ComputeOffset( regInd );
    
    m_PixelAccessor = m_Image->GetPixelAccessor();
    m_PixelAccessorFunctor.SetPixelAccessor( m_PixelAccessor );
    m_PixelAccessorFunctor.SetBegin( m_Buffer );
    
    return *this;
  }
  
  /** Get the dimension (size) of the index. */
  static unsigned int GetImageIteratorDimension() 
    {return TImage::ImageDimension;}

  /** Comparison operator. Two iterators are the same if they "point to" the
   * same memory location */
  bool
  operator!=(const Self &it) const
    {
    // two iterators are the same if they "point to" the same memory location
    return (m_Buffer + m_Offset) != (it.m_Buffer + it.m_Offset);
    };

  /** Comparison operator. Two iterators are the same if they "point to" the
   * same memory location */
  bool
  operator==(const Self &it) const
    {
    // two iterators are the same if they "point to" the same memory location
    return (m_Buffer + m_Offset) == (it.m_Buffer + it.m_Offset);
    };
  
#if 0
  /** I am not sure what the semantics of <=, <, >, >= should be for reverse
   * iterators.  So, I am taking them out for now. */

  
  /** Comparison operator. An iterator is "less than" another if it "points to"
   * a lower memory location. */
  bool
  operator<=(const Self &it) const
    {
    // an iterator is "less than" another if it "points to" a lower
    // memory location
    return (m_Buffer + m_Offset) <= (it.m_Buffer + it.m_Offset);
    };

  /** Comparison operator. An iterator is "less than" another if it "points to"
   * a lower memory location. */
  bool
  operator<(const Self &it) const
    {
    // an iterator is "less than" another if it "points to" a lower
    // memory location
    return (m_Buffer + m_Offset) < (it.m_Buffer + it.m_Offset);
    };

  /** Comparison operator. An iterator is "greater than" another if it
   * "points to" a higher location. */
  bool
  operator>=(const Self &it) const
    {
    // an iterator is "greater than" another if it "points to" a higher
    // memory location
    return (m_Buffer + m_Offset) >= (it.m_Buffer + it.m_Offset);
    };

  /** Comparison operator. An iterator is "greater than" another if it
   * "points to" a higher location. */
  bool
  operator>(const Self &it) const
    {
    // an iterator is "greater than" another if it "points to" a higher
    // memory location
    return (m_Buffer + m_Offset) > (it.m_Buffer + it.m_Offset);
    };
#endif

  
  /** Get the index. This provides a read only reference to the index.
   * This causes the index to be calculated from pointer arithmetic and is
   * therefore an expensive operation.
   * \sa SetIndex */
  const IndexType GetIndex()
    { return m_Image->ComputeIndex( m_Offset );  }

  /** Set the index. No bounds checking is performed.
   * \sa GetIndex */
  virtual void SetIndex(const IndexType &ind)
    { m_Offset = m_Image->ComputeOffset( ind ); }


  /** Get the region that this iterator walks. ImageReverseConstIterators know the
   * beginning and the end of the region of the image to iterate over. */
  const RegionType& GetRegion() const
    { return m_Region; };

  /** Get the pixel value */
  const PixelType Get(void) const  
    { return m_PixelAccessorFunctor.Get(*(m_Buffer+m_Offset)); }
  
  /** Set the pixel value */
  void Set( const PixelType & value) const  
    { m_PixelAccessorFunctor.Set(*(m_Buffer+m_Offset),value); }

  /** Return a const reference to the pixel 
   * This method will provide the fastest access to pixel
   * data, but it will NOT support ImageAdaptors. */
  const PixelType & Value(void) const  
    { return *(m_Buffer+m_Offset); }
 
  /** Return a reference to the pixel 
   * This method will provide the fastest access to pixel
   * data, but it will NOT support ImageAdaptors. */
  PixelType & Value(void) 
    { return *(m_Buffer+m_Offset); }

  /** Return an iterator for the beginning of the region. "Begin" for a reverse
   * iterator is the last pixel in the region.
   * \deprecated Use GoToBegin() instead */
  Self Begin() const;

 /** Move an iterator to the beginning of the region. "Begin" for a reverse
  * iterator is the last pixel in the region. */
  void GoToBegin()
    {
    m_Offset = m_BeginOffset;
    };

  /** Return an iterator for the end of the region. "End" for a reverse iterator
   * is one pixel before the first pixel in the region.
  * \deprecated Use GoToEnd() instead */
  Self End() const;

 /** Move an iterator to the end of the region. "End" for a reverse iterator
  * is defined as one pixel before the first pixel in the region. */
  void GoToEnd()
    {
    m_Offset = m_EndOffset;
    };

  /** Is the iterator at the beginning of the (reverse) region? "Begin" for
   * a reverse iterator is the last pixel in the region. */
  bool IsAtBegin()
    {
    return (m_Offset == m_BeginOffset);
    }

  /** Is the iterator at the end of the (reverse) region? "End" for a reverse
   * iterator is one pixel before the first pixel in the region. */
  bool IsAtEnd()
    {
    return (m_Offset == m_EndOffset);
    }
  
protected: //made protected so other iterators can access 
  typename ImageType::ConstWeakPointer    m_Image;
  RegionType                          m_Region;      // region to iterate over
  
  unsigned long  m_Offset;
  unsigned long  m_BeginOffset; // offset to last pixel in region
  unsigned long  m_EndOffset;   // offset to one pixel before first pixel

  const InternalPixelType        *m_Buffer;

  AccessorType                    m_PixelAccessor;
  AccessorFunctorType             m_PixelAccessorFunctor;
};

} // end namespace itk

#ifndef ITK_MANUAL_INSTANTIATION
#include "itkImageReverseConstIterator.txx"
#endif

#endif 
