/*=========================================================================
 *
 *  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 itkPolyLineParametricPath_h
#define itkPolyLineParametricPath_h

#include "itkParametricPath.h"
#include "itkVectorContainer.h"
#include "itkIndex.h"

namespace itk
{
/**
 * \class PolyLineParametricPath
 * \brief  Represent a path of line segments through ND Space
 *
 * This class is intended to represent parametric paths through an image, where
 * the paths are composed of line segments.  Each line segment traverses one
 * unit of input.  A classic application of this class is the representation of
 * contours in 2D images, especially when the contours only need to be
 * approximately correct.  Another use of a path is to guide the movement of an
 * iterator through an image.
 *
 * \sa EllipseParametricPath
 * \sa FourierSeriesPath
 * \sa OrthogonallyCorrectedParametricPath
 * \sa ParametricPath
 * \sa ChainCodePath
 * \sa Path
 * \sa ContinuousIndex
 * \sa Index
 * \sa Offset
 * \sa Vector
 *
 * \ingroup PathObjects
 * \ingroup ITKPath
 *
 * \sphinx
 * \sphinxexample{Filtering/Path/DataStructureForPieceWiseLinearCurve,Data Structure For Piece-Wise Linear Curve}
 * \endsphinx
 */
template <unsigned int VDimension>
class ITK_TEMPLATE_EXPORT PolyLineParametricPath : public ParametricPath<VDimension>
{
public:
  ITK_DISALLOW_COPY_AND_MOVE(PolyLineParametricPath);

  /** Standard class type aliases. */
  using Self = PolyLineParametricPath;
  using Superclass = ParametricPath<VDimension>;
  using Pointer = SmartPointer<Self>;
  using ConstPointer = SmartPointer<const Self>;

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

  /** Input type */
  using typename Superclass::InputType;

  /** Output type */
  using typename Superclass::OutputType;

  /** Basic data-structure types used */
  using typename Superclass::ContinuousIndexType;
  using IndexType = Index<VDimension>;
  using OffsetType = Offset<VDimension>;
  using PointType = Point<double, VDimension>;
  using VectorType = Vector<double, VDimension>;
  using VertexType = ContinuousIndexType;
  using VertexListType = VectorContainer<unsigned int, VertexType>;
  using VertexListPointer = typename VertexListType::Pointer;

  /** Return the location of the parametric path at the specified location. */
  OutputType
  Evaluate(const InputType & input) const override;

  ///** Evaluate the first derivative of the ND output with respect to the 1D
  //  * input.  This is an exact, algebraic function. */
  // virtual VectorType EvaluateDerivative(const InputType & input) const;

  /** Add a vertex (and a connecting line segment to the previous vertex).
   * Adding a vertex has the additional effect of extending the domain of the
   * PolyLineParametricPath by 1.0 (each pair of consecutive vertices is
   * separated by one unit of input). */
  inline void
  AddVertex(const ContinuousIndexType & vertex)
  {
    m_VertexList->InsertElement(m_VertexList->Size(), vertex);
    this->Modified();
  }

  /** Where does the path end?  This value is necessary for IncrementInput() to
   * know how to go to the end of a path.  Since each line segment covers one
   * unit of input, this is the number of vertices - 1. */
  InputType
  EndOfInput() const override
  {
    return m_VertexList->Size() - 1;
  }

  /** New() method for dynamic construction */
  itkNewMacro(Self);

  /** Needed for Pipelining */
  void
  Initialize() override
  {
    m_VertexList->Initialize();
  }

  /** Return the container of Vertices as a const object. */
  itkGetModifiableObjectMacro(VertexList, VertexListType);

  /** This function overrides the superclass IncrementInput and calculates
   *  the next pixel along the path to visit by using the instantaneous
   *  partial derivatives to calculate the timestep needed to move along the
   *  path by one pixel */
  OffsetType
  IncrementInput(InputType & input) const override;

  /** This function overrides the superclass EvaluateDerivative and instead
   *  calculates the instantaneous derivative of input by taking the index
   *  of the previous and next integral timepoints and subtracting them */
  VectorType
  EvaluateDerivative(const InputType & input) const override;

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

private:
  VertexListPointer m_VertexList{};
};
} // end namespace itk

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

#endif