/*=========================================================================
 *
 *  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 itkRegionBasedLevelSetFunction_h
#define itkRegionBasedLevelSetFunction_h

#include "itkFiniteDifferenceFunction.h"
#include "itkRegularizedHeavisideStepFunction.h"
#include "vnl/vnl_matrix_fixed.h"

namespace itk
{
/** \class RegionBasedLevelSetFunction
 *
 * \brief LevelSet function that computes a speed image based on regional integrals
 *
 * This class implements a level set function that computes the speed image by
 * integrating values on the image domain.
 *
 * Based on the paper:
 *
 *        "An active contour model without edges"
 *         T. Chan and L. Vese.
 *         In Scale-Space Theories in Computer Vision, pages 141-151, 1999.
 *
 * \author Mosaliganti K., Smith B., Gelas A., Gouaillard A., Megason S.
 *
 *  This code was taken from the Insight Journal paper:
 *
 *      "Cell Tracking using Coupled Active Surfaces for Nuclei and Membranes"
 *      https://www.insight-journal.org/browse/publication/642
 *
 *  That is based on the papers:
 *
 *      "Level Set Segmentation: Active Contours without edge"
 *      https://www.insight-journal.org/browse/publication/322
 *
 *      and
 *
 *      "Level set segmentation using coupled active surfaces"
 *      https://www.insight-journal.org/browse/publication/323
 *
 * NOTE: The convention followed is
 * inside of the level-set function is negative and outside is positive.
 * \ingroup ITKReview
 */
template <typename TInput,   // LevelSetImageType
          typename TFeature, // FeatureImageType
          typename TSharedData>
class ITK_TEMPLATE_EXPORT RegionBasedLevelSetFunction : public FiniteDifferenceFunction<TInput>
{
public:
  ITK_DISALLOW_COPY_AND_MOVE(RegionBasedLevelSetFunction);

  /** Standard class type aliases. */
  using Self = RegionBasedLevelSetFunction;
  using Superclass = FiniteDifferenceFunction<TInput>;
  using Pointer = SmartPointer<Self>;
  using ConstPointer = SmartPointer<const Self>;

  static constexpr unsigned int ImageDimension = Superclass::ImageDimension;

  // itkNewMacro() is not provided since this is an abstract class.

  /** \see LightObject::GetNameOfClass() */
  itkOverrideGetNameOfClassMacro(RegionBasedLevelSetFunction);

  /** Extract some parameters from the superclass. */
  using TimeStepType = double;
  using typename Superclass::ImageType;
  using typename Superclass::PixelType;
  using ScalarValueType = PixelType;
  using typename Superclass::RadiusType;
  using typename Superclass::NeighborhoodType;
  using typename Superclass::NeighborhoodScalesType;
  using typename Superclass::FloatOffsetType;
  using VectorType = FixedArray<ScalarValueType, Self::ImageDimension>;

  /* This structure is derived from LevelSetFunction and stores intermediate
  values for computing time step sizes */
  struct GlobalDataStruct
  {
    GlobalDataStruct()
    {
      ScalarValueType null_value{};

      m_MaxCurvatureChange = null_value;
      m_MaxAdvectionChange = null_value;
      m_MaxGlobalChange = null_value;
    }

    ~GlobalDataStruct() = default;

    vnl_matrix_fixed<ScalarValueType, Self::ImageDimension, Self::ImageDimension> m_dxy;

    ScalarValueType m_dx[Self::ImageDimension];

    ScalarValueType m_dx_forward[Self::ImageDimension];
    ScalarValueType m_dx_backward[Self::ImageDimension];

    ScalarValueType m_GradMagSqr;
    ScalarValueType m_GradMag;

    ScalarValueType m_MaxCurvatureChange;
    ScalarValueType m_MaxAdvectionChange;
    ScalarValueType m_MaxGlobalChange;
  };

  using InputImageType = TInput;
  using InputImageConstPointer = typename InputImageType::ConstPointer;
  using InputImagePointer = typename InputImageType::Pointer;
  using InputPixelType = typename InputImageType::PixelType;
  using InputIndexType = typename InputImageType::IndexType;
  using InputIndexValueType = typename InputImageType::IndexValueType;
  using InputSizeType = typename InputImageType::SizeType;
  using InputSizeValueType = typename InputImageType::SizeValueType;
  using InputRegionType = typename InputImageType::RegionType;
  using InputPointType = typename InputImageType::PointType;

  using FeatureImageType = TFeature;
  using FeatureImageConstPointer = typename FeatureImageType::ConstPointer;
  using FeaturePixelType = typename FeatureImageType::PixelType;
  using FeatureIndexType = typename FeatureImageType::IndexType;
  using FeatureSpacingType = typename FeatureImageType::SpacingType;
  using FeatureOffsetType = typename FeatureImageType::OffsetType;

  using SharedDataType = TSharedData;
  using SharedDataPointer = typename SharedDataType::Pointer;

  using HeavisideFunctionType = HeavisideStepFunctionBase<InputPixelType, InputPixelType>;
  using HeavisideFunctionConstPointer = typename HeavisideFunctionType::ConstPointer;

  void
  SetDomainFunction(const HeavisideFunctionType * f)
  {
    this->m_DomainFunction = f;
  }

  virtual void
  Initialize(const RadiusType & r)
  {
    this->SetRadius(r);

    // Dummy neighborhood.
    NeighborhoodType it;
    it.SetRadius(r);

    // Find the center index of the neighborhood.
    m_Center = it.Size() / 2;

    // Get the stride length for each axis.
    for (unsigned int i = 0; i < ImageDimension; ++i)
    {
      m_xStride[i] = it.GetStride(i);
    }
  }

#if !defined(ITK_WRAPPING_PARSER)
  void
  SetSharedData(SharedDataPointer sharedDataIn)
  {
    this->m_SharedData = sharedDataIn;
  }
#endif

  void
  UpdateSharedData(bool forceUpdate);

  void *
  GetGlobalDataPointer() const override
  {
    return new GlobalDataStruct;
  }

  TimeStepType
  ComputeGlobalTimeStep(void * GlobalData) const override;

  /** Compute the equation value. */
  PixelType
  ComputeUpdate(const NeighborhoodType & neighborhood,
                void *                   globalData,
                const FloatOffsetType & = FloatOffsetType(0.0)) override;

  void
  SetInitialImage(InputImageType * f)
  {
    m_InitialImage = f;
  }

  virtual const FeatureImageType *
  GetFeatureImage() const
  {
    return m_FeatureImage.GetPointer();
  }
  virtual void
  SetFeatureImage(const FeatureImageType * f)
  {
    m_FeatureImage = f;

    FeatureSpacingType spacing = m_FeatureImage->GetSpacing();
    for (unsigned int i = 0; i < ImageDimension; ++i)
    {
      this->m_InvSpacing[i] = 1 / spacing[i];
    }
  }

  /** Advection field.  Default implementation returns a vector of zeros. */
  virtual VectorType
  AdvectionField(const NeighborhoodType &, const FloatOffsetType &, GlobalDataStruct * = 0) const
  {
    return this->m_ZeroVectorConstant;
  }

  /** Nu. Area regularization values */
  void
  SetAreaWeight(const ScalarValueType & nu)
  {
    this->m_AreaWeight = nu;
  }
  ScalarValueType
  GetAreaWeight() const
  {
    return this->m_AreaWeight;
  }

  /** Lambda1. Internal intensity difference weight */
  void
  SetLambda1(const ScalarValueType & lambda1)
  {
    this->m_Lambda1 = lambda1;
  }
  ScalarValueType
  GetLambda1() const
  {
    return this->m_Lambda1;
  }

  /** Lambda2. External intensity difference weight */
  void
  SetLambda2(const ScalarValueType & lambda2)
  {
    this->m_Lambda2 = lambda2;
  }
  ScalarValueType
  GetLambda2() const
  {
    return this->m_Lambda2;
  }

  /** Gamma. Overlap penalty */
  void
  SetOverlapPenaltyWeight(const ScalarValueType & gamma)
  {
    this->m_OverlapPenaltyWeight = gamma;
  }
  ScalarValueType
  GetOverlapPenaltyWeight() const
  {
    return this->m_OverlapPenaltyWeight;
  }

  /** Gamma. Scales all curvature weight values */
  virtual void
  SetCurvatureWeight(const ScalarValueType c)
  {
    m_CurvatureWeight = c;
  }
  ScalarValueType
  GetCurvatureWeight() const
  {
    return m_CurvatureWeight;
  }

  void
  SetAdvectionWeight(const ScalarValueType & iA)
  {
    this->m_AdvectionWeight = iA;
  }
  ScalarValueType
  GetAdvectionWeight() const
  {
    return this->m_AdvectionWeight;
  }

  /** Weight of the laplacian smoothing term */
  void
  SetReinitializationSmoothingWeight(const ScalarValueType c)
  {
    m_ReinitializationSmoothingWeight = c;
  }
  ScalarValueType
  GetReinitializationSmoothingWeight() const
  {
    return m_ReinitializationSmoothingWeight;
  }

  /** Volume matching weight.  */
  void
  SetVolumeMatchingWeight(const ScalarValueType & tau)
  {
    this->m_VolumeMatchingWeight = tau;
  }
  ScalarValueType
  GetVolumeMatchingWeight() const
  {
    return this->m_VolumeMatchingWeight;
  }

  /** Pixel Volume = Number of pixels inside the level-set  */
  void
  SetVolume(const ScalarValueType & volume)
  {
    this->m_Volume = volume;
  }
  ScalarValueType
  GetVolume() const
  {
    return this->m_Volume;
  }

  /** Set function id.  */
  void
  SetFunctionId(const unsigned int iFid)
  {
    this->m_FunctionId = iFid;
  }

  void
  ReleaseGlobalDataPointer(void * GlobalData) const override
  {
    delete (GlobalDataStruct *)GlobalData;
  }

  virtual ScalarValueType
  ComputeCurvature(const NeighborhoodType &, const FloatOffsetType &, GlobalDataStruct * gd);

  /** \brief Laplacian smoothing speed can be used to spatially modify the
    effects of laplacian smoothing of the level set function */
  virtual ScalarValueType
  LaplacianSmoothingSpeed(const NeighborhoodType &, const FloatOffsetType &, GlobalDataStruct * = 0) const
  {
    return NumericTraits<ScalarValueType>::OneValue();
  }

  /** \brief Curvature speed can be used to spatially modify the effects of
    curvature . The default implementation returns one. */
  virtual ScalarValueType
  CurvatureSpeed(const NeighborhoodType &, const FloatOffsetType &, GlobalDataStruct * = 0) const
  {
    return NumericTraits<ScalarValueType>::OneValue();
  }

  /** This method must be defined in a subclass to implement a working function
   * object.  This method is called before the solver begins its work to
   * produce the speed image used as the level set function's Advection field
   * term.  See LevelSetFunction for more information. */
  virtual void
  CalculateAdvectionImage()
  {}

protected:
  RegionBasedLevelSetFunction();
  ~RegionBasedLevelSetFunction() override = default;

  /** The initial level set image */
  InputImageConstPointer m_InitialImage{};

  /** The feature image */
  FeatureImageConstPointer m_FeatureImage{};

  SharedDataPointer m_SharedData{};

  HeavisideFunctionConstPointer m_DomainFunction{};

  /** Area regularization weight */
  ScalarValueType m_AreaWeight{};

  /** Internal functional of the level set weight */
  ScalarValueType m_Lambda1{};

  /** External functional of the level set weight */
  ScalarValueType m_Lambda2{};

  /** Overlap Penalty Weight */
  ScalarValueType m_OverlapPenaltyWeight{};

  /** Volume Regularization Weight */
  ScalarValueType m_VolumeMatchingWeight{};

  /** Volume Constraint in pixels */
  ScalarValueType m_Volume{};

  /** Curvature Regularization Weight */
  ScalarValueType m_CurvatureWeight{};

  ScalarValueType m_AdvectionWeight{};

  /** Laplacian Regularization Weight */
  ScalarValueType m_ReinitializationSmoothingWeight{};

  unsigned int m_FunctionId{};

  std::slice      x_slice[Self::ImageDimension];
  OffsetValueType m_Center{};
  OffsetValueType m_xStride[Self::ImageDimension]{};
  double          m_InvSpacing[Self::ImageDimension]{};

  static double m_WaveDT;
  static double m_DT;

  void
  ComputeHImage();

  /** \brief Compute the global term as a combination of the internal, external,
    overlapping and volume regularization terms.  */
  ScalarValueType
  ComputeGlobalTerm(const ScalarValueType & imagePixel, const InputIndexType & inputIndex);

  /** \brief Compute the internal term
  \param[in] iValue Feature Image Value
  \param[in] iIdx Feature Image Index
  */
  virtual ScalarValueType
  ComputeInternalTerm(const FeaturePixelType & iValue, const FeatureIndexType & iIdx) = 0;

  /** \brief Compute the external term
  \param[in] iValue Feature Image Value
  \param[in] iIdx Feature Image Index */
  virtual ScalarValueType
  ComputeExternalTerm(const FeaturePixelType & iValue, const FeatureIndexType & iIdx) = 0;

  /** \brief Compute the overlap term
  \param[in] featIndex
  \param[out] pr = \f$ \prod_{i \neq j} H(\phi_i)\f$
  \return OverlapTerm = \f$ \sum_{i \neq j} H(\phi_i)\f$ */
  virtual ScalarValueType
  ComputeOverlapParameters(const FeatureIndexType & featIndex, ScalarValueType & pr) = 0;

  /** \brief Compute the overlap term
      \return \f$ \int_{p \in \Omega} H(\phi_i) dp - this->Volume \f$
      \note the volume regularization does not depend on the spacing.
        So the volume must be set in number of pixels (not in real world unit). */
  ScalarValueType
  ComputeVolumeRegularizationTerm();

  /** \brief Compute the laplacian term
      \return \f$ \Delta \phi - \div(\frac{\nabla \phi}{|\nabla \phi|}) \f$
      For details see

      \par REFERENCE
      Li, C.M. and Xu, C.Y. and Gui, C. and Fox, M.D.
      "Level Set Evolution without Re-Initialization: A New Variational Formulation",
      CVPR05. 2005. pp. 430-436.
  */

  /** \brief Compute the laplacian
  \return \f$ \Delta \phi \f$ */
  ScalarValueType
  ComputeLaplacian(GlobalDataStruct * gd);

  /** \brief Compute Hessian Matrix */
  void
  ComputeHessian(const NeighborhoodType & it, GlobalDataStruct * globalData);

  /** \brief Compute Parameters for the inner and outer parts. */
  virtual void
  ComputeParameters() = 0;

  /** \brief Update and save the inner and outer parameters in the shared data
    structure. */
  virtual void
  UpdateSharedDataParameters() = 0;

  bool m_UpdateC{};

  /** This method's only purpose is to initialize the zero vector
   * constant. */
  static VectorType
  InitializeZeroVectorConstant();

  /** Zero vector constant. */
  static VectorType m_ZeroVectorConstant;
};
} // end namespace itk

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

#endif