/*=========================================================================
 *
 *  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 itkQuadEdgeMeshEulerOperatorJoinVertexFunction_h
#define itkQuadEdgeMeshEulerOperatorJoinVertexFunction_h

#include "itkQuadEdgeMeshFunctionBase.h"

#include <stack>

namespace itk
{
/**
 * \class QuadEdgeMeshEulerOperatorJoinVertexFunction
 *
 * \brief Collapse a given edge by joining its dest and its org.
 *
 * Collapse the argument edge e of Evaluate
 * by joining the two vertices incident to e (i.e. its endpoints).
 * The destination vertex of e is set aside (i.e. disconnected from its
 * edge entry and no edge has this vertex as endpoint). Note that the
 * vertex itself is not removed from the container (and hence there is no
 * loss of geometrical information). On success JoinVertex returns the Id
 * of the disconnected vertex (i.e. the destination of e) and it is up to
 * the caller to "take care" of it.
 *
 * Precondition: the edge should be adjacent at least to an other edge
 * (i.e. not be isolated at both endpoints).
 *
 * \warning JoinVertex.Evaluate( h) and JoinVertex.Evaluate( h->GetSym() )
 * are topologically identical. But their differ in their geometrical
 * result, since JoinVertex removes the destination vertex of the
 * incoming argument. A simple way to visualize this difference is to
 * imagine a mesh constituted of squares laid out on a regular grid
 * and for each such square an added diagonal. No imagine what happens
 * when one operates JoinVertex on a diagonal edge of a corner square
 * (and how it differs with feeding JoinVertex with the opposite edge).
 *
 * \ingroup QEMeshModifierFunctions
 * \ingroup ITKQuadEdgeMesh
 */
template <typename TMesh, typename TQEType>
class ITK_TEMPLATE_EXPORT QuadEdgeMeshEulerOperatorJoinVertexFunction
  : public QuadEdgeMeshFunctionBase<TMesh, TQEType *>
{
public:
  ITK_DISALLOW_COPY_AND_MOVE(QuadEdgeMeshEulerOperatorJoinVertexFunction);

  /** Standard class type aliases. */
  using Self = QuadEdgeMeshEulerOperatorJoinVertexFunction;
  using Pointer = SmartPointer<Self>;
  using ConstPointer = SmartPointer<const Self>;
  using Superclass = QuadEdgeMeshFunctionBase<TMesh, TQEType *>;

  itkNewMacro(Self);
  /** \see LightObject::GetNameOfClass() */
  itkOverrideGetNameOfClassMacro(QuadEdgeMeshEulerOperatorJoinVertexFunction);

  /** Type of QuadEdge with which to apply slicing. */
  using QEType = TQEType;

  using typename Superclass::MeshType;
  using typename Superclass::OutputType;

  using PointIdentifier = typename MeshType::PointIdentifier;
  using CellIdentifier = typename MeshType::CellIdentifier;
  using FaceRefType = typename MeshType::FaceRefType;

  /** Evaluate at the specified input position */
  virtual OutputType
  Evaluate(QEType * e);

  enum EdgeStatusType
  {
    STANDARD_CONFIG = 0,
    EDGE_NULL,                     // 1
    MESH_NULL,                     // 2
    EDGE_ISOLATED,                 // 3
    TOO_MANY_COMMON_VERTICES,      // 4
    TETRAHEDRON_CONFIG,            // 5
    QUADEDGE_ISOLATED,             // 6
    FACE_ISOLATED,                 // 7
    SAMOSA_CONFIG,                 // 8
    EYE_CONFIG,                    // 9
    EDGE_JOINING_DIFFERENT_BORDERS // 10
  };

  itkGetConstMacro(OldPointID, PointIdentifier);
  itkGetConstMacro(EdgeStatus, EdgeStatusType);

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

  void
  PrintSelf(std::ostream & os, Indent indent) const override;

  PointIdentifier m_OldPointID{};

  EdgeStatusType m_EdgeStatus{};

  /**
   * \brief
   * \param[in] e
   * \return The number of common vertices in the 0-ring of e->GetOrigin() and
   * e->GetDestination()
   */
  PointIdentifier
  CommonVertexNeighboor(QEType * e);

  /**
   * \brief
   * \param[in] e
   * \return true if it is a tetrahedron
   * \return false else
   */
  bool
  IsTetrahedron(QEType * e);

  /**
   * \brief
   * \param[in] e
   * \param[in] iWasLeftFace
   * \param[out] oToBeDeleted
   * \return true if the face is isolated
   * \return false else
   */
  bool
  IsFaceIsolated(QEType * e, const bool iWasLeftFace, std::stack<TQEType *> & oToBeDeleted);

  bool
  IsSamosa(QEType * e);

  bool
  IsEye(QEType * e);

  bool
  IsEdgeLinkingTwoDifferentBorders(QEType * e);

  EdgeStatusType
  CheckStatus(QEType * e, std::stack<TQEType *> & oToBeDeleted);

  QEType *
  Process(QEType * e);

  QEType *
  ProcessIsolatedQuadEdge(QEType * e);

  QEType *
  ProcessIsolatedFace(QEType * e, std::stack<QEType *> & EdgesToBeDeleted);
};
} // end namespace itk

#include "itkQuadEdgeMeshEulerOperatorJoinVertexFunction.hxx"

#endif