/*=========================================================================
 *
 *  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 itkQuadEdgeMeshBoundaryEdgesMeshFunction_hxx
#define itkQuadEdgeMeshBoundaryEdgesMeshFunction_hxx

#include "itkQuadEdgeMesh.h" // Just to mark the dependence towards this class.

namespace itk
{
template <typename TMesh>
auto
QuadEdgeMeshBoundaryEdgesMeshFunction<TMesh>::Evaluate(const InputType & mesh) const -> OutputType
{
  // Push on a list all the non internal edges:
  using CellsContainerConstIterator = typename MeshType::CellsContainerConstIterator;
  std::set<QEPrimal *> boundaryList;

  CellsContainerConstIterator cellIterator = mesh.GetEdgeCells()->Begin();
  CellsContainerConstIterator cellEnd = mesh.GetEdgeCells()->End();

  while (cellIterator != cellEnd)
  {
    if (auto * cell = dynamic_cast<EdgeCellType *>(cellIterator.Value()))
    {
      QEPrimal * edge = cell->GetQEGeom();
      if (!edge->IsInternal())
      {
        boundaryList.insert(edge);
      }
    }
    ++cellIterator;
  }

  auto ResultList = new EdgeListType;
  while (!boundaryList.empty())
  {
    // Pop the first edge of list and make sure it has no face
    // on its left [because we want to follow the boundary with
    // GeometricalQuadEdge::Lnext()]:
    auto       b = boundaryList.begin();
    QEPrimal * bdryEdge = *b;
    boundaryList.erase(b);
    if (bdryEdge->IsLeftSet())
    {
      bdryEdge = bdryEdge->GetSym();
    }
    if (bdryEdge->IsLeftSet())
    {
      itkWarningMacro("Entry edge has not face adjacency.");
      delete ResultList;
      return ((OutputType) nullptr);
    }

    // Store this edge as representative of its Lnext() ring i.e.
    // representative of the boundary:
    ResultList->push_back(bdryEdge);

    // Follow, with Lnext(), the boundary while removing edges
    // from boundary list:
    typename QEPrimal::IteratorGeom bIt = bdryEdge->BeginGeomLnext();
    typename QEPrimal::IteratorGeom bEnd = bdryEdge->EndGeomLnext();

    while (bIt != bEnd)
    {
      // Only one of the following will be effective (but we have
      // no way to know which one):
      b = boundaryList.find(bIt.Value());

      if (b != boundaryList.end())
      {
        boundaryList.erase(b);
      }

      b = boundaryList.find(bIt.Value()->GetSym());

      if (b != boundaryList.end())
      {
        boundaryList.erase(b);
      }

      ++bIt;
    }
  }

  return ResultList;
}
} // namespace itk

#endif
