/*=========================================================================
 *
 *  Copyright Insight Software Consortium
 *
 *  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
 *
 *         http://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 itkContourDirectedMeanDistanceImageFilter_h
#define itkContourDirectedMeanDistanceImageFilter_h

#include "itkImageToImageFilter.h"
#include "itkNumericTraits.h"
#include "itkArray.h"
#include "itkImage.h"

namespace itk
{
/** \class ContourDirectedMeanDistanceImageFilter
 * \brief Computes the directed Mean distance between the boundaries of
 * non-zero pixel regions of two images.
 *
 * ContourDirectedMeanDistanceImageFilter computes the distance between the set
 * non-zero pixels of two images using the following formula:
 * \f[ h(A,B) = \mathrm{mean}_{a \in A} \min_{b \in B} \| a - b\| \f]
 * where \f$A\f$ and \f$B\f$ are respectively the set of non-zero pixels
 * in the first and second input images. It identifies the point \f$ a \in A \f$
 * that is farthest from any point of \f$B\f$ and measures the distance from \f$a\f$
 * to the nearest neighbor in \f$B\f$. Note that this function is not
 * is not symmetric and hence is not a true distance.
 *
 * In particular, this filter uses the SignedMaurerDistanceMapImageFilter
 * inside to compute distance map from all non-zero pixels in the second image.
 * It then computes the mean distance (in pixels) within the boundary pixels
 *  of non-zero regions in the first image.
 *
 * This filter requires the largest possible region of the first image and the
 * same corresponding region in the second image. It behaves as filter with
 * two input and one output. Thus it can be inserted in a pipeline with other
 * filters. The filter passes the first input through unmodified.
 *
 * This filter is templated over the two input image type. It assume
 * both image have the same number of dimensions.
 *
 * \sa SignedMaurerDistanceMapImageFilter
 *
 * \ingroup MultiThreaded
 *
 * \author Teo Popa, ISIS Center, Georgetown University
 *
 * \ingroup ITKDistanceMap
 */
template< typename TInputImage1, typename TInputImage2 >
class ITK_TEMPLATE_EXPORT ContourDirectedMeanDistanceImageFilter:
  public ImageToImageFilter< TInputImage1, TInputImage1 >
{
public:
  ITK_DISALLOW_COPY_AND_ASSIGN(ContourDirectedMeanDistanceImageFilter);

  /** Standard Self type alias */
  using Self = ContourDirectedMeanDistanceImageFilter;
  using Superclass = ImageToImageFilter< TInputImage1, TInputImage1 >;
  using Pointer = SmartPointer< Self >;
  using ConstPointer = SmartPointer< const Self >;

  /** Method for creation through the object factory. */
  itkNewMacro(Self);

  /** Runtime information support. */
  itkTypeMacro(ContourDirectedMeanDistanceImageFilter, ImageToImageFilter);

  /** Image related type alias. */
  using InputImage1Type = TInputImage1;
  using InputImage2Type = TInputImage2;
  using InputImage1Pointer = typename TInputImage1::Pointer;
  using InputImage2Pointer = typename TInputImage2::Pointer;
  using InputImage1ConstPointer = typename TInputImage1::ConstPointer;
  using InputImage2ConstPointer = typename TInputImage2::ConstPointer;

  using RegionType = typename TInputImage1::RegionType;
  using SizeType = typename TInputImage1::SizeType;
  using IndexType = typename TInputImage1::IndexType;

  using InputImage1PixelType = typename TInputImage1::PixelType;
  using InputImage2PixelType = typename TInputImage2::PixelType;

  /** Image related type alias. */
  static constexpr unsigned int ImageDimension = TInputImage1::ImageDimension;

  /** Type to use form computations. */
  using RealType = typename NumericTraits< InputImage1PixelType >::RealType;

  /** Set the first input. */
  void SetInput1(const InputImage1Type *image);

  /** Set the second input. */
  void SetInput2(const InputImage2Type *image);

  /** Get the first input. */
  const InputImage1Type * GetInput1();

  /** Get the second input. */
  const InputImage2Type * GetInput2();

  /** Return the computed directed Mean distance. */
  itkGetConstMacro(ContourDirectedMeanDistance, RealType);

  /** Set if image spacing should be used in computing distances. */
  itkSetMacro( UseImageSpacing, bool );
  itkGetConstMacro( UseImageSpacing, bool );

#ifdef ITK_USE_CONCEPT_CHECKING
  // Begin concept checking
  itkConceptMacro( InputHasNumericTraitsCheck,
                   ( Concept::HasNumericTraits< InputImage1PixelType > ) );
  // End concept checking
#endif

protected:
  ContourDirectedMeanDistanceImageFilter();
  ~ContourDirectedMeanDistanceImageFilter() override = default;
  void PrintSelf(std::ostream & os, Indent indent) const override;

  /** Pass the input through unmodified. Do this by Grafting in the
    AllocateOutputs method. */
  void AllocateOutputs() override;

  /** Initialize some accumulators before the threads run. */
  void BeforeThreadedGenerateData() override;

  /** Do final mean and variance computation from data accumulated in threads.
    */
  void AfterThreadedGenerateData() override;

  /** Multi-thread version GenerateData. */
  void  ThreadedGenerateData(const RegionType &
                             outputRegionForThread,
                             ThreadIdType threadId) override;

  void DynamicThreadedGenerateData( const RegionType & ) override
  {
    itkExceptionMacro("This class requires threadId so it must use classic multi-threading model");
  }

  // Override since the filter needs all the data for the algorithm
  void GenerateInputRequestedRegion() override;

  // Override since the filter produces all of its output
  void EnlargeOutputRequestedRegion(DataObject *data) override;

private:
  using DistanceMapType = Image< RealType, Self::ImageDimension >;

  typename DistanceMapType::Pointer m_DistanceMap;

  Array< RealType >       m_MeanDistance;
  Array< IdentifierType > m_Count;
  RealType                m_ContourDirectedMeanDistance;
  bool                    m_UseImageSpacing;
}; // end of class
} // end namespace itk

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

#endif
