/*=========================================================================
 *
 *  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 itkLevelSetEquationAdvectionTerm_h
#define itkLevelSetEquationAdvectionTerm_h

#include "itkLevelSetEquationTermBase.h"
#include "itkZeroFluxNeumannBoundaryCondition.h"
#include "itkConstNeighborhoodIterator.h"
#include "itkVector.h"
#include "vnl/vnl_matrix_fixed.h"

namespace itk
{
/**
 *  \class LevelSetEquationAdvectionTerm
 *  \brief Derived class to represents an advection term in the level-set evolution PDE
 *
 *  \f[
 *  AdvectionImage\left( p \right) \bullet \nabla \phi\left( p \right)
 *  \f]
 *
 *  \li \f$ AdvectionImage \left( p \right) \f$ is the advection image provided by the user.
 *  \li \f$ \cdot \bullet \cdot \f$ denotes the usual dot product
 *  \li \f$ \nabla \phi \f$ denotes the gradient of the level set function \f$ \phi \f$.
 *
 * The advection image can be directly provided by the user; or by
 * default, it is computed as the gradient of the input image. In this last
 * case, it can be smoothed by the means of DerivativeSigma.
 *
 *  \tparam TInput Input Image Type
 *  \tparam TLevelSetContainer Level set function container type
 *  \ingroup ITKLevelSetsv4
 */
template< typename TInput, // Input image or mesh
          typename TLevelSetContainer >
class LevelSetEquationAdvectionTerm :
    public LevelSetEquationTermBase< TInput, TLevelSetContainer >
{
public:
  typedef LevelSetEquationAdvectionTerm                           Self;
  typedef SmartPointer< Self >                                    Pointer;
  typedef SmartPointer< const Self >                              ConstPointer;
  typedef LevelSetEquationTermBase< TInput, TLevelSetContainer >  Superclass;

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

  /** Run-time type information */
  itkTypeMacro( LevelSetEquationAdvectionTerm,
                LevelSetEquationTermBase );

  typedef typename Superclass::InputImageType     InputImageType;
  typedef typename Superclass::InputImagePointer  InputImagePointer;
  typedef typename Superclass::InputPixelType     InputPixelType;
  typedef typename Superclass::InputPixelRealType InputPixelRealType;

  typedef typename Superclass::LevelSetContainerType      LevelSetContainerType;
  typedef typename Superclass::LevelSetContainerPointer   LevelSetContainerPointer;
  typedef typename Superclass::LevelSetType               LevelSetType;
  typedef typename Superclass::LevelSetPointer            LevelSetPointer;
  typedef typename Superclass::LevelSetOutputPixelType    LevelSetOutputPixelType;
  typedef typename Superclass::LevelSetOutputRealType     LevelSetOutputRealType;
  typedef typename Superclass::LevelSetInputIndexType     LevelSetInputIndexType;
  typedef typename Superclass::LevelSetGradientType       LevelSetGradientType;
  typedef typename Superclass::LevelSetHessianType        LevelSetHessianType;
  typedef typename Superclass::LevelSetIdentifierType     LevelSetIdentifierType;
  typedef typename Superclass::LevelSetDataType           LevelSetDataType;

  typedef typename Superclass::HeavisideType         HeavisideType;
  typedef typename Superclass::HeavisideConstPointer HeavisideConstPointer;

  itkStaticConstMacro(ImageDimension, unsigned int, InputImageType::ImageDimension);

  typedef LevelSetGradientType  VectorType;

  typedef Image< VectorType, itkGetStaticConstMacro(ImageDimension) > AdvectionImageType;
  typedef typename AdvectionImageType::Pointer                        AdvectionImagePointer;


  void SetAdvectionImage( AdvectionImageType* iImage );
  itkGetModifiableObjectMacro(AdvectionImage, AdvectionImageType );

  itkSetMacro( DerivativeSigma, LevelSetOutputRealType );
  itkGetMacro( DerivativeSigma, LevelSetOutputRealType );

  /** Neighborhood radius type */
  typedef ZeroFluxNeumannBoundaryCondition< InputImageType > DefaultBoundaryConditionType;
  typedef typename ConstNeighborhoodIterator< InputImageType >::RadiusType RadiusType;
  typedef ConstNeighborhoodIterator< InputImageType, DefaultBoundaryConditionType > NeighborhoodType;

  typedef Vector< LevelSetOutputRealType, itkGetStaticConstMacro(ImageDimension) > NeighborhoodScalesType;

  /** \todo to be documented. */
  virtual void Update() ITK_OVERRIDE;

  /** Initialize the parameters in the terms prior to an iteration */
  virtual void InitializeParameters() ITK_OVERRIDE;

  /** \todo to be documented. */
  virtual void Initialize( const LevelSetInputIndexType& ) ITK_OVERRIDE;

  /** Supply updates at pixels to keep the term parameters always updated */
  virtual void UpdatePixel( const LevelSetInputIndexType& iP,
                            const LevelSetOutputRealType& oldValue,
                            const LevelSetOutputRealType& newValue ) ITK_OVERRIDE;

protected:
  LevelSetEquationAdvectionTerm();

  virtual ~LevelSetEquationAdvectionTerm();

  AdvectionImagePointer m_AdvectionImage;

  /** Return the spatial speed dependence a given pixel location
   * Usually, it is constant across the image domain */
  VectorType AdvectionSpeed( const LevelSetInputIndexType& iP ) const;

  /** Returns the term contribution for a given location iP, i.e.
   *  \f$ \omega_i( p ) \f$. */
  virtual LevelSetOutputRealType Value( const LevelSetInputIndexType& iP ) ITK_OVERRIDE;
  virtual LevelSetOutputRealType Value( const LevelSetInputIndexType& iP,
                                        const LevelSetDataType& iData ) ITK_OVERRIDE;

  LevelSetOutputRealType m_NeighborhoodScales[ImageDimension];

private:
  LevelSetEquationAdvectionTerm( const Self& ) ITK_DELETE_FUNCTION;
  void operator = ( const Self& ) ITK_DELETE_FUNCTION;

  LevelSetOutputRealType m_DerivativeSigma;

  bool m_AutoGenerateAdvectionImage;

  void GenerateAdvectionImage();
};

}

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

#endif
