/*=========================================================================
 *
 *  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 itkLevelSetEquationTermContainer_h
#define itkLevelSetEquationTermContainer_h

#include "itkLevelSetEquationTermBase.h"
#include "itkObject.h"

#include <atomic>
#include <map>
#include <string>
#include <unordered_map>

namespace itk
{
/**
 *  \class LevelSetEquationTermContainer
 *  \brief Class for container holding the terms of a given level set update equation
 *
 *  \tparam TInputImage Input image or speed image or feature image for segmentation
 *  \tparam TLevelSetContainer Container holding all the level set functions
 *
 *  \ingroup ITKLevelSetsv4
 */
template <typename TInputImage, typename TLevelSetContainer>
class ITK_TEMPLATE_EXPORT LevelSetEquationTermContainer : public Object
{
public:
  ITK_DISALLOW_COPY_AND_MOVE(LevelSetEquationTermContainer);

  using Self = LevelSetEquationTermContainer;
  using Pointer = SmartPointer<Self>;
  using ConstPointer = SmartPointer<const Self>;
  using Superclass = Object;

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

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

  using TermIdType = unsigned int;

  using InputImageType = TInputImage;
  using InputImagePointer = typename InputImageType::Pointer;

  using LevelSetContainerType = TLevelSetContainer;
  using LevelSetContainerPointer = typename LevelSetContainerType::Pointer;

  using LevelSetType = typename LevelSetContainerType::LevelSetType;
  using LevelSetPointer = typename LevelSetContainerType::LevelSetPointer;

  using LevelSetIdentifierType = typename LevelSetContainerType::LevelSetIdentifierType;
  using LevelSetOutputPixelType = typename LevelSetContainerType::OutputType;
  using LevelSetOutputRealType = typename LevelSetContainerType::OutputRealType;
  using LevelSetDataType = typename LevelSetContainerType::LevelSetDataType;
  using LevelSetInputIndexType = typename LevelSetContainerType::InputIndexType;
  using LevelSetGradientType = typename LevelSetContainerType::GradientType;
  using LevelSetHessianType = typename LevelSetContainerType::HessianType;

  using TermType = LevelSetEquationTermBase<InputImageType, LevelSetContainerType>;
  using TermPointer = typename TermType::Pointer;

  /** Set/Get the input image to be segmented. */
  /** @ITKStartGrouping */
  itkSetObjectMacro(Input, InputImageType);
  itkGetModifiableObjectMacro(Input, InputImageType);
  /** @ITKEndGrouping */
  itkSetMacro(CurrentLevelSetId, LevelSetIdentifierType);
  itkGetMacro(CurrentLevelSetId, LevelSetIdentifierType);

  itkSetObjectMacro(LevelSetContainer, LevelSetContainerType);
  itkGetModifiableObjectMacro(LevelSetContainer, LevelSetContainerType);

  /** Add a term to the end of the container  */
  void
  PushTerm(TermType * iTerm);

  /** Replace the pointer to the term with the given id */
  void
  AddTerm(const TermIdType & iId, TermType * iTerm);

  /** Get the term with the given id */
  TermType *
  GetTerm(const TermIdType & iId);

  /** Get the term with the given name */
  TermType *
  GetTerm(const std::string & iName);

  /** \todo  */
  void
  Initialize(const LevelSetInputIndexType & iP);

  /** Supply the update at a given pixel location to update the term parameters */
  void
  UpdatePixel(const LevelSetInputIndexType & iP,
              const LevelSetOutputRealType & oldValue,
              const LevelSetOutputRealType & newValue);

  /** Initialize the term parameters prior to the start of an iteration */
  void
  InitializeParameters();

  /** Evaluate the term at a given pixel location */
  LevelSetOutputRealType
  Evaluate(const LevelSetInputIndexType & iP);

  LevelSetOutputRealType
  Evaluate(const LevelSetInputIndexType & iP, const LevelSetDataType & iData);

  /** Update the term parameters at end of iteration */
  void
  Update();

  /** Return the CFL contribution of the current term */
  LevelSetOutputRealType
  ComputeCFLContribution() const;

  void
  ComputeRequiredData(const LevelSetInputIndexType & iP, LevelSetDataType & ioData);

protected:
  using MapTermContainerType = std::map<TermIdType, TermPointer>;
  using MapTermContainerIteratorType = typename MapTermContainerType::iterator;
  using MapTermContainerConstIteratorType = typename MapTermContainerType::const_iterator;

public:
  class Iterator;
  friend class Iterator;

  class ConstIterator
  {
  public:
    ConstIterator() = default;
    ConstIterator(const MapTermContainerConstIteratorType & it)
      : m_Iterator(it)
    {}
    ~ConstIterator() = default;
    ConstIterator(const Iterator & it)
      : m_Iterator(it.m_Iterator)
    {}
    ConstIterator &
    operator*()
    {
      return *this;
    }
    ConstIterator *
    operator->()
    {
      return this;
    }
    ConstIterator &
    operator++()
    {
      ++m_Iterator;
      return *this;
    }
    ConstIterator
    operator++(int)
    {
      ConstIterator tmp(*this);
      ++(*this);
      return tmp;
    }
    ConstIterator &
    operator--()
    {
      --m_Iterator;
      return *this;
    }
    ConstIterator
    operator--(int)
    {
      ConstIterator tmp(*this);
      --(*this);
      return tmp;
    }
    bool
    operator==(const Iterator & it) const
    {
      return m_Iterator == it.m_Iterator;
    }

    ITK_UNEQUAL_OPERATOR_MEMBER_FUNCTION(Iterator);

    bool
    operator==(const ConstIterator & it) const
    {
      return m_Iterator == it.m_Iterator;
    }

    ITK_UNEQUAL_OPERATOR_MEMBER_FUNCTION(ConstIterator);

    [[nodiscard]] TermIdType
    GetIdentifier() const
    {
      return m_Iterator->first;
    }

    [[nodiscard]] TermType *
    GetTerm() const
    {
      return m_Iterator->second;
    }

  private:
    MapTermContainerConstIteratorType m_Iterator;
    friend class Iterator;
  };

  class Iterator
  {
  public:
    Iterator() = default;
    Iterator(const MapTermContainerIteratorType & it)
      : m_Iterator(it)
    {}
    Iterator(const ConstIterator & it)
      : m_Iterator(it.m_Iterator)
    {}
    ~Iterator() = default;

    Iterator &
    operator*()
    {
      return *this;
    }
    Iterator *
    operator->()
    {
      return this;
    }

    Iterator &
    operator++()
    {
      ++m_Iterator;
      return *this;
    }
    Iterator
    operator++(int)
    {
      Iterator tmp(*this);
      ++(*this);
      return tmp;
    }
    Iterator &
    operator--()
    {
      --m_Iterator;
      return *this;
    }
    Iterator
    operator--(int)
    {
      Iterator tmp(*this);
      --(*this);
      return tmp;
    }

    bool
    operator==(const Iterator & it) const
    {
      return m_Iterator == it.m_Iterator;
    }

    ITK_UNEQUAL_OPERATOR_MEMBER_FUNCTION(Iterator);

    bool
    operator==(const ConstIterator & it) const
    {
      return m_Iterator == it.m_Iterator;
    }

    ITK_UNEQUAL_OPERATOR_MEMBER_FUNCTION(ConstIterator);

    [[nodiscard]] TermIdType
    GetIdentifier() const
    {
      return m_Iterator->first;
    }

    [[nodiscard]] TermType *
    GetTerm() const
    {
      return m_Iterator->second;
    }

  private:
    MapTermContainerIteratorType m_Iterator;
    friend class ConstIterator;
  };

  Iterator
  Begin();
  Iterator
  End();

  ConstIterator
  Begin() const;
  ConstIterator
  End() const;

protected:
  LevelSetEquationTermContainer();

  ~LevelSetEquationTermContainer() override = default;

  LevelSetIdentifierType   m_CurrentLevelSetId{};
  LevelSetContainerPointer m_LevelSetContainer{};

  InputImagePointer m_Input{};

  using HashMapStringTermContainerType = std::unordered_map<std::string, TermPointer>;

  HashMapStringTermContainerType m_NameContainer{};

  using RequiredDataType = typename TermType::RequiredDataType;
  RequiredDataType m_RequiredData{};

  MapTermContainerType m_Container{};

  using MapCFLContainerType = std::map<TermIdType, std::atomic<LevelSetOutputRealType>>;
  using MapCFLContainerIterator = typename MapCFLContainerType::iterator;
  using MapCFLContainerConstIterator = typename MapCFLContainerType::const_iterator;

  MapCFLContainerType m_TermContribution{};
};

} // namespace itk
#ifndef ITK_MANUAL_INSTANTIATION
#  include "itkLevelSetEquationTermContainer.hxx"
#endif

#endif // itkLevelSetEquationTermContainer_h
