/*=========================================================================
 *
 *  Copyright Insight Software Consortium
 *
 *  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
 *
 *         http://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 __itkQuadEdgeMesh_hxx
#define __itkQuadEdgeMesh_hxx
#include "itkQuadEdgeMesh.h"
#include "vcl_limits.h"
#include <vector>

namespace itk
{
template< typename TPixel, unsigned int VDimension, typename TTraits >
const typename QuadEdgeMesh< TPixel, VDimension, TTraits >::PointIdentifier
QuadEdgeMesh< TPixel, VDimension, TTraits >::m_NoPoint =
  std::numeric_limits< PointIdentifier >::max();

template< typename TPixel, unsigned int VDimension, typename TTraits >
const typename QuadEdgeMesh< TPixel, VDimension, TTraits >::CellIdentifier
QuadEdgeMesh< TPixel, VDimension, TTraits >::m_NoFace =
  std::numeric_limits< CellIdentifier >::max();

/**
 * Restore the mesh to its initial state. Useful for data pipeline updates
 * without memory re-allocation.
 */
template< typename TPixel, unsigned int VDimension, typename TTraits >
void
QuadEdgeMesh< TPixel, VDimension, TTraits >
::Initialize()
{
  itkDebugMacro("Mesh Initialize method ");
  Clear();
  Superclass::Initialize();
}

/**
 * Clear all this mesh by deleting all contained edges which as
 * a side effect deletes adjacent faces
 */
template< typename TPixel, unsigned int VDimension, typename TTraits >
void
QuadEdgeMesh< TPixel, VDimension, TTraits >
::Clear()
{
  if ( this->GetEdgeCells() )
    {
    CellsContainerIterator cellIterator = this->GetEdgeCells()->Begin();
    while ( !this->GetEdgeCells()->empty() )
      {
      EdgeCellType *edgeToDelete =
        dynamic_cast< EdgeCellType * >( cellIterator.Value() );
      this->LightWeightDeleteEdge(edgeToDelete);
      cellIterator = this->GetEdgeCells()->Begin();
      }
    }

  // Clear the points potentialy left behind by LightWeightDeleteEdge():
  if ( this->GetPoints() )
    {
    this->GetPoints()->clear();
    }
  this->ClearFreePointAndCellIndexesLists();  // to start at index 0
}

template< typename TPixel, unsigned int VDimension, typename TTraits >
void
QuadEdgeMesh< TPixel, VDimension, TTraits >
::Graft(const DataObject *data)
{
  this->Superclass::Graft(data);
  const Self *mesh = dynamic_cast< const Self * >( data );

  if ( !mesh )
    {
    // pointer could not be cast back down
    itkExceptionMacro( << "itk::QuadEdgeMesh::CopyInformation() cannot cast "
                       << typeid( data ).name() << " to "
                       << typeid( Self * ).name() );
    }

  this->m_FreePointIndexes = mesh->m_FreePointIndexes;
  this->m_FreeCellIndexes = mesh->m_FreeCellIndexes;
  this->ClearCellsContainer();
  this->m_EdgeCellsContainer = mesh->m_EdgeCellsContainer;
  this->m_NumberOfFaces = mesh->m_NumberOfFaces;
  this->m_NumberOfEdges = mesh->m_NumberOfEdges;
}

/**
 * \brief The one and only method to modify the edge connectivity.
 */
template< typename TPixel, unsigned int VDimension, typename TTraits >
typename QuadEdgeMesh< TPixel, VDimension, TTraits >::PointIdentifier
QuadEdgeMesh< TPixel, VDimension, TTraits >
::Splice(QEPrimal *a, QEPrimal *b)
{
  bool            SplitingOrigin = a->IsInOnextRing(b);
  PointIdentifier resultingOriginId;

  if ( SplitingOrigin )
    {
    // see TODO's entry dated 2006-01-24
    /* We consider the following situation which depicts the Onext()
    * ring around the point Origin (which is both a->GetOrigin() and
    * b->GetOrigin():
    *
    *              \         /
    *               \       /
    *               e3     e2              counter-clockwise
    *                 \   /                Onext() order.
    *                  \ /
    *      -----b------Org------a----
    *                  / \
    *                 /   \
    *                /     \
    *               /       \
    *              /         \
    *            e5           e6
    *            /             \
    *           /               \
    *
    * The result of this method is then:
    *
    *         \         /
    *          \       /
    *          e3     e2
    *            \   /
    *             \ /
    * ----b------newOrg
    *
    *                  Org------a-----
    *                  / \
    *                 /   \
    *                /     \
    *               /       \
    *              /         \
    *            e5           e7
    *            /             \
    *           /               \
    */

    // Handle connectivity at QEQuadEdge level:
    a->Splice(b);

    ////////// Handle the geometrical references:
    // Make sure the Origin's edge entry doesn't point to an entry edge
    // that isn't any more in the Onext ring:
    PointIdentifier orgId = a->GetOrigin();
    PointType       org = this->GetPoint(orgId);
    org.SetEdge(a);
    this->SetPoint(orgId, org);

    // Create a newOrigin point by duplicating the geometry of Origin...
    PointType newOrigin  = org;
    newOrigin.SetEdge(b);
    PointIdentifier newOriginId = this->AddPoint(newOrigin);

    // ...and inform Onext ring of b that their Origin() have changed:
    typename QEPrimal::IteratorGeom it;
    for ( it = b->BeginGeomOnext(); it != b->EndGeomOnext(); it++ )
      {
      it.Value()->SetOrigin(newOriginId);
      }
    resultingOriginId = newOriginId;
    }
  else
    {
    // see TODO's entry dated 2006-01-24
    /* We consider the following situation which depicts the Onext()
    * rings around the point Origin = a->GetOrigin() and
    * oldOrigin = b->GetOrigin():
    *
    *         \         /
    *          \       /
    *          e3     e2
    *            \   /
    *             \ /
    * ----b------oldOrg
    *
    *                  Org------a-----
    *                  / \
    *                 /   \
    *                /     \
    *               /       \
    *              /         \
    *            e5           e7
    *            /             \
    *           /               \
    *
    *
    * The result of this method is then:
    *
    *              \         /
    *               \       /
    *               e3     e2              counter-clockwise
    *                 \   /                Onext() order.
    *                  \ /
    *      -----b------Org------a----
    *                  / \
    *                 /   \
    *                /     \
    *               /       \
    *              /         \
    *            e5           e6
    *            /             \
    *           /               \
    *
    * Note: in this case we must handle the geometry first and
    *       then the connectivity.
    */

    // Since this is the geometrical version of Splice() we
    // have additional geometrical information that we should use
    // to check the correctness of the situation.

    /////////////////////////////////////////////////////////////
    // First, consider the vertices: Origin and oldOrigin must be different.
    PointIdentifier oldOriginId = b->GetOrigin();
    PointIdentifier orgId = a->GetOrigin();

    if ( oldOriginId == orgId )
      {
      itkDebugMacro("Trying to fuse the same point!");
      return ( m_NoPoint );
      }

    /** \todo Compare the geometry of the two points and accept
     * splicing when their geometry matches. We could fix
     * an epsilon threshold distance above which the two points
     * are considered distinct.
     * PointType org = this->GetPoint(orgId);
     */
    PointType oldOrigin = this->GetPoint(oldOriginId);


    /////////////////////////////////////////////////////////////
    /* We are done with the vertices and we might need to consider the
    * possible initial adjacent face[s]. We shall accept to proceed
    * with Splicing if and only if the following conditions are met:
    * [1] a and b both share the SAME Left face,
    * [2] a and b and in the same Lnext() ring,
    * [3] a and b are not too close followers in the Lnext() ring
    *    [this is to avoid to create a face with only two edges which
    *     is equivalent to two different edges adjacent to the same two
    *     vertices].
    *
    *                   V ---<-b---- V
    *                  /              \
    *                 /                \
    *                /              a.Lnext().Lnext()
    *               /                    \
    *              /        Face          \
    *             V                        V
    *              \     a.Splice(b)      /
    *               \     is OK          /
    *                \               a.Lnext()
    *                 \                /
    *                  \              /
    *                   V ----a->--- V
    *
    * Basically, we accept to proceed with spliting if there is a
    * single face on the left and this face is at least an hexagone
    * and the vertices we wish to splice are at least two vertices aside.
    */

    FaceRefType aLeftFace = a->GetLeft();
    FaceRefType bLeftFace = b->GetLeft();

    bool MustReconstructFace = false;
    if ( ( aLeftFace == m_NoFace && bLeftFace != m_NoFace )
         || ( aLeftFace != m_NoFace && bLeftFace == m_NoFace ) )
      {
      itkDebugMacro("Face on one side but not the other. Cancel.");
      return ( m_NoPoint );
      }

    if ( aLeftFace != m_NoFace && bLeftFace != m_NoFace )
      {
      if ( ( aLeftFace == bLeftFace )
           && ( a->GetLnext() != b )
           && ( a->GetLnext()->GetLnext() != b )
           && ( b->GetLnext() != a )
           && ( b->GetLnext()->GetLnext() != a )
           && ( a->IsInLnextRing(b) )
           && ( b->IsInLnextRing(a) ) )
        {
        this->DeleteFace(aLeftFace);
        MustReconstructFace = true;
        }
      else
        {
        itkDebugMacro("Face is not at least and hexagon.");
        return ( m_NoPoint );
        }
      }

    // Notice that when aLeftFace == m_NoFace and bLeftFace == m_NoFace
    // we simply proceed... (with MustReconstructFace initialy set to
    // false.

    ///////////////////////////////////////////////////////////////
    // Handle connectivity at QEQuadEdge level:
    a->Splice(b);

    ///////////////////////////////////////////////////////////////
    // Back to dealing with the geometrical references. First
    // make sure the oldOrigin's edge entry won't be used any more:
    oldOrigin.SetEdge( (QEPrimal *)ITK_NULLPTR );
    this->SetPoint(oldOriginId, oldOrigin);

    // We need to inform the edges ranging from a->Onext() to b that
    // their Origin() have changed. Let's over do it (read, be lazy) and
    // inform the full Onext() ring:
    typename QEPrimal::IteratorGeom it;
    for ( it = a->BeginGeomOnext(); it != a->EndGeomOnext(); it++ )
      {
      it.Value()->SetOrigin(orgId);
      }
    resultingOriginId = oldOriginId;

    ///////////////////////////////////////////////////////////////
    // Now that we are done with the handling of the geometry of
    // vertices proceed with the geometry of the faces. When we
    // are spliting a face (through Splicing) we must construct two
    // new faces:
    if ( MustReconstructFace )
      {
      this->AddFace(a);
      this->AddFace(b);
      }
    }

  this->Modified();
  return resultingOriginId;
}

/**
 */
template< typename TPixel, unsigned int VDimension, typename TTraits >
void QuadEdgeMesh< TPixel, VDimension, TTraits >
::SetCell(CellIdentifier cId, CellAutoPointer & cell)
{
  (void)cId;

  // NOTE ALEX: should add some checking to be sure everything went fine
  EdgeCellType *   qe;
  PolygonCellType *pe;

  // The QuadEdgeMeshCellTypes first
  if ( ( qe = dynamic_cast< EdgeCellType * >( cell.GetPointer() ) ) )
    {
    // NOTE ALEX: here
    this->AddEdge( qe->GetQEGeom()->GetOrigin(),
                   qe->GetQEGeom()->GetDestination() );
    cell.ReleaseOwnership();
    delete qe;
    }
  else if ( ( pe = dynamic_cast< PolygonCellType * >( cell.GetPointer() ) ) )
    {
    PointIdList             points;
    PointIdInternalIterator pit = pe->InternalPointIdsBegin();
    PointIdInternalIterator pend = pe->InternalPointIdsEnd();
    while ( pit != pend )
      {
      points.push_back(*pit);
      ++pit;
      }
    // NOTE ALEX: here
    this->AddFaceWithSecurePointList(points);
    cell.ReleaseOwnership();
    delete pe;
    }
  else // non-QE cell, i.e. original itk cells for example
    {
    PointIdentifier numPoint = cell->GetNumberOfPoints();
    PointIdIterator pointId = cell->PointIdsBegin();
    PointIdIterator endId = cell->PointIdsEnd();
    // Edge
    if ( numPoint == 2 )
      {
      if ( ( pointId ) && ( endId ) && ( pointId != endId ) )
        {
        PointIdIterator temp = pointId++;
        // NOTE ALEX: here
        this->AddEdge(*pointId, *temp);
        }
      }
    // polygons
    else if ( cell->GetDimension() == 2 )
      {
      PointIdList points;
      while ( pointId != endId )
        {
        points.push_back(*pointId);
        ++pointId;
        }
      // NOTE ALEX: here
      this->AddFace(points);
      }
    cell.ReleaseOwnership();
    delete ( cell.GetPointer() );
    }
}

/**
 */
template< typename TPixel, unsigned int VDimension, typename TTraits >
typename QuadEdgeMesh< TPixel, VDimension, TTraits >::PointIdentifier
QuadEdgeMesh< TPixel, VDimension, TTraits >
::FindFirstUnusedPointIndex()
{
  PointIdentifier pid = 0;
  PointIdentifier maxpid = this->GetNumberOfPoints();

  if ( !m_FreePointIndexes.empty() )
    {
    // find the first valid free ID
    do
      {
      pid = m_FreePointIndexes.front();
      if ( pid < maxpid )
        {
        m_FreePointIndexes.pop();
        return ( pid );
        }
      else
        {
        m_FreePointIndexes.pop();
        }
      }
    while ( !m_FreePointIndexes.empty() );
    }

  if ( m_FreePointIndexes.empty() )
    {
    pid = this->GetNumberOfPoints();
    if ( pid != 0 )
      {
      PointsContainerConstIterator last = this->GetPoints()->End();
      last--;
      pid = last.Index() + 1;
      }
    }
  return ( pid );
}


/**
 *  The point container being a map, after deleting a point
 *  it is very likely that one index will be missing.
 *  This method "squeeze" the indexes by relocating the points
 *  and their data from the end of their respective container
 *  to the "empty" locations.
 */
template< typename TPixel, unsigned int VDimension, typename TTraits >
void
QuadEdgeMesh< TPixel, VDimension, TTraits >
::SqueezePointsIds()
{

  // sanity check
  if( m_FreePointIndexes.size() == 0 )
    {
    return;
    }

  // Get hold on the last point in the container
  PointsContainerPointer points = this->GetPoints();
  PointsContainerConstIterator last = points->End();
  --last;

  // Check if there is any data
  PointDataContainerPointer pointData = this->GetPointData();
  bool HasPointData = ( pointData->Size() != 0 );

  // if there is get hold on the last point's data
  PointDataContainerIterator lastData = pointData->End();
  if( HasPointData )
    {
    --lastData;
    }

  // Some Temp var to be used in the while loop
  PointIdentifier FilledPointID;
  QEType* EdgeRingEntry;
  QEType* EdgeRingIter;

  // for all the free indexes and while there is any gap
  while( ( m_FreePointIndexes.size() != 0 )
    && ( last.Index() >= this->GetNumberOfPoints() ) )
    {

    // duplicate last point into the empty slot and pop the id from freeID list
    FilledPointID = AddPoint( GetPoint( last.Index( ) ) );

    // same thing for the data if any
    if( HasPointData )
      {
      pointData->SetElement(
        FilledPointID,
        pointData->GetElement( lastData.Index( ) )
        );
      }

    // make sure that all the edges/faces now refer to the new ID
    // i.e. enforce the integrity at the QE level now.
    EdgeRingEntry = GetPoint( last.Index( ) ).GetEdge( );
    if( EdgeRingEntry )
      {
      EdgeRingIter  = EdgeRingEntry;
      do
        {
        EdgeRingIter->SetOrigin( FilledPointID );
        EdgeRingIter = EdgeRingIter->GetOnext( );
        }
      while( EdgeRingIter != EdgeRingEntry );
      }

    // pop the duplicated point from the container, increment iterator
    points->DeleteIndex( last.Index( ) );
    last = points->End();
    --last;

    // same thing for data, if any
    if( HasPointData )
      {
      pointData->DeleteIndex( lastData.Index() );
      lastData = pointData->End();
      --lastData;
      }

    }

}

/**
 */
template< typename TPixel, unsigned int VDimension, typename TTraits >
typename QuadEdgeMesh< TPixel, VDimension, TTraits >::PointIdentifier
QuadEdgeMesh< TPixel, VDimension, TTraits >
::AddPoint(const PointType & p)
{
  PointIdentifier pid = this->FindFirstUnusedPointIndex();

  this->SetPoint(pid, p);
  return ( pid );
}

/**
 */
template< typename TPixel, unsigned int VDimension, typename TTraits >
void QuadEdgeMesh< TPixel, VDimension, TTraits >
::DeletePoint(const PointIdentifier & pid)
{
  // We suppose point index is valid
  // otherwise we should test with
  // this->GetPoints()->IndexExists( pid );
  PointType pointToDelete = this->GetPoint( pid);

  // Check that there is no cell that use this point anymore
  // i.e. that the o-next-ring is empty
  if( pointToDelete.GetEdge() )
    {
    itkDebugMacro("Point is not isolated.");
    return;
    }

  // Remove the point from the points container
  this->GetPoints()->DeleteIndex( pid );

  // Check if there is associated poindata and eventually delete them
  if( this->GetPointData()->Size() > 0 )
    {
    this->GetPointData()->DeleteIndex( pid );
    }

  // store the delete index to later squeeze the ID list
  // needed to write files that expect incremental IDs
  // like vtk
  m_FreePointIndexes.push( pid );
}

/**
 */
template< typename TPixel, unsigned int VDimension, typename TTraits >
typename QuadEdgeMesh< TPixel, VDimension, TTraits >::PointType
QuadEdgeMesh< TPixel, VDimension, TTraits >
::GetPoint(const PointIdentifier & pid) const
{
  return ( this->GetPoints()->GetElement(pid) );
}

/**
 */
template< typename TPixel, unsigned int VDimension, typename TTraits >
typename QuadEdgeMesh< TPixel, VDimension, TTraits >::VectorType
QuadEdgeMesh< TPixel, VDimension, TTraits >
::GetVector(const PointIdentifier & pid) const
{
  return ( this->GetPoint(pid).GetVectorFromOrigin() );
}

/**
 */
template< typename TPixel, unsigned int VDimension, typename TTraits >
typename QuadEdgeMesh< TPixel, VDimension, TTraits >::CellIdentifier
QuadEdgeMesh< TPixel, VDimension, TTraits >
::FindFirstUnusedCellIndex()
{
  CellIdentifier cid;

  if ( m_FreeCellIndexes.size() == 0 )
    {
    cid = this->GetNumberOfCells();

    if ( cid != 0 )
      {
      CellsContainerIterator last = this->GetCells()->End();
      last--;
      cid = last.Index() + 1;
      }
    }
  else
    {
    cid = m_FreeCellIndexes.front();
    m_FreeCellIndexes.pop();
    }

  return ( cid );
}

/**
 *\brief  Construct a new edge ending at points with identifiers given
 *        as arguments.
 * @param  orgPid first endpoint (origin) of the edge to Add.
 * @param destPid second endpoint (destination) of the edge to Add.
 * @sa \ref GeometricalQuadEdge::InsertAfterNextBorderEdgeWithUnsetLeft
 */
template< typename TPixel, unsigned int VDimension, typename TTraits >
typename QuadEdgeMesh< TPixel, VDimension, TTraits >::QEPrimal *
QuadEdgeMesh< TPixel, VDimension, TTraits >
::AddEdge(const PointIdentifier & orgPid, const PointIdentifier & destPid)
{
  // Make sure the points are different
  if ( orgPid == destPid )
    {
    itkDebugMacro("Creating an edge between the same point.");
    return ( (QEPrimal *)ITK_NULLPTR );
    }

  // Make sure the points are already in the QuadEdgeMesh container:
  if ( !( this->GetPoints()->IndexExists(orgPid) )
       || !( this->GetPoints()->IndexExists(destPid) ) )
    {
    itkDebugMacro("One of the points not in the PointSet.");
    return ( (QEPrimal *)ITK_NULLPTR );
    }

  // Make sure the edge is not already in the container
  QEPrimal *e = this->FindEdge(orgPid, destPid);
  if ( e != (QEPrimal *)ITK_NULLPTR )
    {
    itkDebugMacro("Edge already in QuadEdgeMesh.");
    return e;
    }

  // Check if the points have room to receive a new edge
  QEPrimal *eOrigin     = this->GetPoint(orgPid).GetEdge();

  if ( eOrigin )
    {
    if ( eOrigin->IsOriginInternal() )
      {
      itkDebugMacro("No room for a new edge in the Origin() ring.");
      return ( (QEPrimal *)ITK_NULLPTR );
      }
    }

  QEPrimal *eDestination = this->GetPoint(destPid).GetEdge();

  if ( eDestination )
    {
    if ( eDestination->IsOriginInternal() )
      {
      itkDebugMacro("No room for a new edge in the Destination() ring.");
      return ( (QEPrimal *)ITK_NULLPTR );
      }
    }

  return AddEdgeWithSecurePointList(orgPid, destPid);
}

template< typename TPixel, unsigned int VDimension, typename TTraits >
typename QuadEdgeMesh< TPixel, VDimension, TTraits >::QEPrimal *
QuadEdgeMesh< TPixel, VDimension, TTraits >
::AddEdgeWithSecurePointList(const PointIdentifier & orgPid, const PointIdentifier & destPid)
{
  PointsContainerPointer points = this->GetPoints();

  PointType& pOrigin       = points->ElementAt(orgPid);
  PointType& pDestination  = points->ElementAt(destPid);

  QEPrimal *eOrigin       = pOrigin.GetEdge();
  QEPrimal *eDestination  = pDestination.GetEdge();

  // Ok, there's room and the points exist
  EdgeCellType *newEdge = new EdgeCellType();
  QEPrimal *    newEdgeGeom = newEdge->GetQEGeom();

  newEdgeGeom->SetOrigin (orgPid);
  newEdgeGeom->SetDestination(destPid);

  if ( !eOrigin )
    {
    pOrigin.SetEdge(newEdgeGeom);
    }
  else
    {
    eOrigin->InsertAfterNextBorderEdgeWithUnsetLeft(newEdgeGeom);
    }

  if ( !eDestination )
    {
    pDestination.SetEdge( newEdgeGeom->GetSym() );
    }
  else
    {
    eDestination->InsertAfterNextBorderEdgeWithUnsetLeft(
      newEdgeGeom->GetSym() );
    }

  // Add it to the container
  this->PushOnContainer(newEdge);

  return ( newEdgeGeom );
}

/**
 */
template< typename TPixel, unsigned int VDimension, typename TTraits >
void
QuadEdgeMesh< TPixel, VDimension, TTraits >
::PushOnContainer(EdgeCellType *newEdge)
{
  CellIdentifier eid = 0;

  if ( this->GetEdgeCells()->size() > 0 )
    {
    CellsContainerConstIterator last = this->GetEdgeCells()->End();
    --last;
    eid = last.Index() + 1;
    }
  newEdge->SetIdent(eid);
  CellAutoPointer pEdge;
  pEdge.TakeOwnership(newEdge);
  this->SetEdgeCell(eid, pEdge);
  m_NumberOfEdges++;
}

/**
 */
template< typename TPixel, unsigned int VDimension, typename TTraits >
void
QuadEdgeMesh< TPixel, VDimension, TTraits >
::DeleteEdge(const PointIdentifier & orgPid, const PointIdentifier & destPid)
{
  // Check if the edge exists
  QEPrimal *e = this->FindEdge(orgPid, destPid);

  if ( e == (QEPrimal *)ITK_NULLPTR )
    {
    itkDebugMacro("Edge missing in mesh.");
    return;
    }

  this->DeleteEdge(e);
}

/**
 */
template< typename TPixel, unsigned int VDimension, typename TTraits >
void
QuadEdgeMesh< TPixel, VDimension, TTraits >
::DeleteEdge(QEPrimal *e)
{
  const PointIdentifier & orgPid  = e->GetOrigin();
  const PointIdentifier & destPid = e->GetDestination();

  PointsContainerPointer points = this->GetPoints();

  // Check if the Origin point's edge ring entry should be changed
  PointType& pOrigin = points->ElementAt(orgPid);

  if ( pOrigin.GetEdge() == e )
    {
    if ( !e->IsOriginDisconnected() )
      {
      pOrigin.SetEdge( e->GetOprev() );
      }
    else
      {
      pOrigin.SetEdge( (QEPrimal *)ITK_NULLPTR );
      }
    }

  // Same for the Destination point
  PointType& pDestination = points->ElementAt(destPid);

  if ( pDestination.GetEdge() == e->GetSym() )
    {
    if ( !e->IsDestinationDisconnected() )
      {
      pDestination.SetEdge( e->GetLnext() );
      }
    else
      {
      pDestination.SetEdge( (QEPrimal *)ITK_NULLPTR );
      }
    }

  // This container serves to avoid the MS .net bug when
  // one wants to delete a map element using a map::iterator.
  // Normally, if we delete a map element using an iterator,
  // it should keep the iterator validity but .net doesn't
  // like it, so we delay the cell deletion to a later loop.
  typedef std::list< CellIdentifier > DeleteCellsCont;
  DeleteCellsCont cellsToDelete;

  // Delete all references to 'e' in the cell container
  CellsContainerIterator cit = this->GetCells()->Begin();
  const CellsContainerIterator cend = this->GetCells()->End();

  while ( cit != cend )
    {
    PolygonCellType *pcell = dynamic_cast< PolygonCellType * >( cit.Value() );
    bool             toDelete = false;
    if ( pcell != (PolygonCellType *)ITK_NULLPTR )
      {
      QEPrimal *edge = pcell->GetEdgeRingEntry();
      typename QEPrimal::IteratorGeom it  = edge->BeginGeomLnext();
      const typename QEPrimal::IteratorGeom end = edge->EndGeomLnext();

      while ( it != end && !toDelete )
        {
        toDelete = ( ( it.Value() == e )
                     || ( it.Value()->GetSym() == e ) );
        ++it;
        }

      if ( toDelete )
        {
        --m_NumberOfFaces;
        // handle QE level, i.e. for the polygon, just unset the faces
        it = edge->BeginGeomLnext();
        while ( it != end )
          {
          it.Value()->UnsetLeft();
          ++it;
          }
        }
      }

    // if the current face is to be deleted,
    // put it in the second container
    // and keep the Id for next cell insertion
    if ( toDelete )
      {
      cellsToDelete.push_back( cit.Index() );
      m_FreeCellIndexes.push( cit.Index() );
      }
    ++cit;
    }

  // we checked all the cells i nthe container
  // now delete the elements in the map
  typename DeleteCellsCont::iterator dit = cellsToDelete.begin();
  const typename DeleteCellsCont::iterator dend = cellsToDelete.end();
  while ( dit != dend )
    {
    const CellType *cellToBeDeleted = this->GetCells()->GetElement(*dit);
    delete cellToBeDeleted;
    this->GetCells()->DeleteIndex(*dit);
    ++dit;
    }

  // now delete the edge in the edge container
  CellType *edgeCellToDelete = this->GetEdgeCells()->ElementAt( e->GetIdent() );
  this->GetEdgeCells()->DeleteIndex( e->GetIdent() );
  delete edgeCellToDelete;
  --m_NumberOfEdges;

  // Now, disconnect it and let the garbage collector do the rest
  this->Modified();
}

/**
 * Delete the incoming edge and all LOCAL references to this edge.
 * By local we mean the ones we can reasonably be aware of i.e.
 * the adjacent faces (that we also delete) and the adjacent points
 * (when the incoming edge is their Onext ring entry).
 * This is to be opposed to \ref DeleteEdge that searches for ALL
 * references to the incoming edge (which is a much heavier process
 * because one as to make an exhaustive search in the CellContainer).
 * \note: when deleting the adjacent faces we also handle the
 *        suppression of the references to those faces in the Lnext()
 *        and Rnext() rings.
 * \warning Nothing is done to remove the potential isolated points
 *        left by this edge deletion (the caller might want to recycle
 *        them). Hence it is the caller's responsibility to manage the
 *        clean-up of adjacent points (when necessary).
 */
template< typename TPixel, unsigned int VDimension, typename TTraits >
void
QuadEdgeMesh< TPixel, VDimension, TTraits >
::LightWeightDeleteEdge(EdgeCellType *edgeCell)
{
  if ( !edgeCell )
    {
    return;
    }

  QEPrimal *e = edgeCell->GetQEGeom();

  if ( !e )
    {
    return;
    }
  const PointIdentifier & orgPid  = e->GetOrigin();
  const PointIdentifier & destPid = e->GetDestination();

  PointsContainerPointer points = this->GetPoints();

  if ( orgPid != e->m_NoPoint &&  destPid != e->m_NoPoint )
    {
    // ------------------------------------------------------------------
    // First make sure the points are not pointing to the edge we are
    // trying to delete.

    // Check if the Origin point's edge ring entry is the edge we are
    // trying to delete. When this is the case shift the Origin edge entry
    // to another edge and when no other edge is available leave it
    // to NULL.
    PointType& pOrigin = points->ElementAt(orgPid);

    if ( pOrigin.GetEdge() == e )
      {
      if ( !e->IsOriginDisconnected() )
        {
        pOrigin.SetEdge( e->GetOprev() );
        }
      else
        {
        pOrigin.SetEdge( (QEPrimal *)ITK_NULLPTR );
        }
      }

    // Same thing for the Destination point:
    PointType& pDestination = points->ElementAt(destPid);

    if ( pDestination.GetEdge() == e->GetSym() )
      {
      if ( !e->IsDestinationDisconnected() )
        {
        pDestination.SetEdge( e->GetLnext() );
        }
      else
        {
        pDestination.SetEdge( (QEPrimal *)ITK_NULLPTR );
        }
      }
    // ------------------------------------------------------------------
    // Second we need to destroy the adjacent faces (both GetLeft()
    // and GetRight() when they exist) because their very definition
    // makes reference to the edge we are trying to delete:
    if ( e->IsLeftSet() )
      {
      this->DeleteFace( e->GetLeft() );
      }

    if ( e->IsRightSet() )
      {
      this->DeleteFace( e->GetRight() );
      }

    /////////////////////////////////////////////////////////////////
    // Third we need to remove from the container the EdgeCell
    // representing the edge we are trying to destroy at the itk
    // level.
    this->GetEdgeCells()->DeleteIndex( edgeCell->GetIdent() );
    edgeCell->SetIdent(0);

    // Eventually, we disconnect (at the QuadEdge level) the edge we
    // are trying to delete and we delete it.
    e->Disconnect();
    }

  --m_NumberOfEdges;
  delete edgeCell;
  this->Modified();
}

template< typename TPixel, unsigned int VDimension, typename TTraits >
void
QuadEdgeMesh< TPixel, VDimension, TTraits >
::LightWeightDeleteEdge(QEPrimal *e)
{
  if ( !e )
    {
    return;
    }
  const PointIdentifier & orgPid  = e->GetOrigin();
  if ( orgPid == e->m_NoPoint )
    {
    // org not set
    return;
    }

  const PointIdentifier & destPid = e->GetDestination();
  if ( destPid == e->m_NoPoint )
    {
    // dest not set
    return;
    }

  CellIdentifier LineIdent = e->GetIdent();
  if ( LineIdent != m_NoPoint )
    {
    EdgeCellType *edgeCell = dynamic_cast< EdgeCellType * >( this->GetEdgeCells()->GetElement(LineIdent) );
    this->LightWeightDeleteEdge(edgeCell);
    }
  else
    {
    itkDebugMacro("Edge Not found. LineIdent not set?");
    return;
    }
}

/**
 */
template< typename TPixel, unsigned int VDimension, typename TTraits >
void
QuadEdgeMesh< TPixel, VDimension, TTraits >
::DeleteFace(FaceRefType faceToDelete)
{
  CellsContainerPointer cells = this->GetCells();
  CellType* c;

  if( !cells->GetElementIfIndexExists( faceToDelete, &c ) )
    {
    itkDebugMacro("No such face in container");
    return;
    }

  PolygonCellType *cellToDelete = dynamic_cast< PolygonCellType * >( c );
  if ( !cellToDelete )
    {
    itkDebugMacro("This Id does not correspond to a face (should be an edge)");
    return;
    }

  // Iterate on the edges adjacent to face and remove references to
  // to this face:
  QEPrimal *e = cellToDelete->GetEdgeRingEntry();

  if ( faceToDelete != e->GetLeft() )
    {
    e = e->GetSym();
    }

  if ( faceToDelete != e->GetLeft() )
    {
    itkDebugMacro("Neither e nor e->Sym() are the correct face");
    return;
    }

  typename QEPrimal::IteratorGeom       it  = e->BeginGeomLnext();
  const typename QEPrimal::IteratorGeom end = e->EndGeomLnext();

  while( it != end )
    {
    it.Value()->UnsetLeft();
    ++it;
    }

  cells->DeleteIndex(faceToDelete);
  delete cellToDelete;

  --m_NumberOfFaces;

  this->Modified();
}

/**
 */
template< typename TPixel, unsigned int VDimension, typename TTraits >
typename QuadEdgeMesh< TPixel, VDimension, TTraits >::QEPrimal *
QuadEdgeMesh< TPixel, VDimension, TTraits >
::GetEdge() const
{
  if ( this->GetEdgeCells()->size() == 0 )
    {
    return ( (QEPrimal *)ITK_NULLPTR );
    }

  const CellsContainer* edgeCells = this->GetEdgeCells();
  CellsContainerConstIterator cit = edgeCells->Begin();
  EdgeCellType* e = dynamic_cast< EdgeCellType * >( cit.Value() );

  return ( e->GetQEGeom() );
}

/**
 */
template< typename TPixel, unsigned int VDimension, typename TTraits >
typename QuadEdgeMesh< TPixel, VDimension, TTraits >::QEPrimal *
QuadEdgeMesh< TPixel, VDimension, TTraits >
::GetEdge(const CellIdentifier & eid) const
{
  CellType* c;

  if( !this->GetEdgeCells()->GetElementIfIndexExists( eid, &c ) )
    {
    itkDebugMacro("No such edge in container");
    return ( (QEPrimal *)ITK_NULLPTR );
    }

  EdgeCellType *e = dynamic_cast< EdgeCellType * >( c );
  return ( e->GetQEGeom() );
}

/**
 */
template< typename TPixel, unsigned int VDimension, typename TTraits >
typename QuadEdgeMesh< TPixel, VDimension, TTraits >::QEPrimal *
QuadEdgeMesh< TPixel, VDimension, TTraits >
::FindEdge(const PointIdentifier & pid0) const
{
  PointType p = this->GetPoint(pid0);

  return ( p.GetEdge() );
}

/**
 */
template< typename TPixel, unsigned int VDimension, typename TTraits >
typename QuadEdgeMesh< TPixel, VDimension, TTraits >::QEPrimal *
QuadEdgeMesh< TPixel, VDimension, TTraits >
::FindEdge(const PointIdentifier & pid0, const PointIdentifier & pid1) const
{
  QEPrimal *initialEdge = this->GetPoint(pid0).GetEdge();

  if ( initialEdge )
    {
    typename QEPrimal::IteratorGeom it  = initialEdge->BeginGeomOnext();
    typename QEPrimal::IteratorGeom end = initialEdge->EndGeomOnext();
    while ( it != end )
      {
      if ( it.Value()->GetDestination() == pid1 )
        {
        return ( dynamic_cast< QEPrimal * >( it.Value() ) );
        }
      ++it;
      }
    }
  return ( static_cast< QEPrimal * >( ITK_NULLPTR ) );
}

/**
 */
template< typename TPixel, unsigned int VDimension, typename TTraits >
typename QuadEdgeMesh< TPixel, VDimension, TTraits >::EdgeCellType *
QuadEdgeMesh< TPixel, VDimension, TTraits >
::FindEdgeCell(const PointIdentifier & pid0, const PointIdentifier & pid1) const
{
  EdgeCellType *result = (EdgeCellType *)ITK_NULLPTR;
  QEPrimal *    EdgeGeom = FindEdge(pid0, pid1);

  if ( EdgeGeom != (QEPrimal *)ITK_NULLPTR )
    {
    CellIdentifier LineIdent = EdgeGeom->GetIdent();
    if ( LineIdent != m_NoPoint )
      {
      result = dynamic_cast< EdgeCellType * >(
        this->GetEdgeCells()->GetElement(LineIdent) );
      }
    }
  return ( result );
}

/**
 */
template< typename TPixel, unsigned int VDimension, typename TTraits >
typename QuadEdgeMesh< TPixel, VDimension, TTraits >::QEPrimal *
QuadEdgeMesh< TPixel, VDimension, TTraits >
::AddFace(const PointIdList & points)
{
  size_t N = points.size();

#ifndef NDEBUG

  // Check that there are no duplicate points
  for ( size_t i = 0; i < N; i++ )
    {
    typename PointIdList::const_iterator itr = points.begin();
    typename PointIdList::const_iterator end = points.end();
    PointIdentifier count = NumericTraits< PointIdentifier >::Zero;
    const PointIdentifier pointId = points[i];
    while ( itr != end )
      {
      if ( *itr == pointId )
        {
        ++count;
        }
      ++itr;
      }
    if ( count != 1 )
      {
      itkDebugMacro("Point " << i << " is duplicated");
      return ( (QEPrimal *)NULL );
      }
    }

  PointsContainerPointer pointsContainer = this->GetPoints();

  // Check that all points exist
  for ( size_t i = 0; i < N; i++ )
    {
    if ( !pointsContainer->IndexExists(points[i]) )
      {
      itkDebugMacro("Point " << i << " is missing in the mesh");
      return (QEPrimal *)NULL;
      }
    }
#endif

  // Check if existing edges have no face on the left.
  for ( size_t i = 0; i < N; i++ )
    {
    PointIdentifier pid0 = points[i];
    PointIdentifier pid1 = points[ ( i + 1 ) % N ];

    QEPrimal *edge = this->FindEdge(pid0, pid1);

    if ( edge )
      {
      if ( edge->IsLeftSet() )
        {
        itkDebugMacro("Edge [" << i << " " << ( ( i + 1 ) % N )
                               << " has a left face.");
        return (QEPrimal *)ITK_NULLPTR;
        }
      }
    }

  return AddFaceWithSecurePointList(points);
}

/**
 */
template< typename TPixel, unsigned int VDimension, typename TTraits >
typename QuadEdgeMesh< TPixel, VDimension, TTraits >::QEPrimal *
QuadEdgeMesh< TPixel, VDimension, TTraits >
::AddFaceWithSecurePointList(const PointIdList & points)
{
  return AddFaceWithSecurePointList(points, true);
}

/**
 */
template< typename TPixel, unsigned int VDimension, typename TTraits >
typename QuadEdgeMesh< TPixel, VDimension, TTraits >::QEPrimal *
QuadEdgeMesh< TPixel, VDimension, TTraits >
::AddFaceWithSecurePointList(const PointIdList & points, bool CheckEdges)
{
  const PointIdentifier numberOfPoints = static_cast< PointIdentifier >( points.size() );

  typedef std::vector< QEPrimal * > QEList;
  QEList FaceQEList( numberOfPoints, ITK_NULLPTR );

  // Now create edge list and create missing edges if needed.
  for ( PointIdentifier i = 0; i < numberOfPoints; i++ )
    {
    PointIdentifier pid0 = points[i];
    PointIdentifier pid1 = points[( i + 1 ) % numberOfPoints];
    QEPrimal *      edge = this->FindEdge(pid0, pid1);

    if ( !edge && CheckEdges )
      {
      QEPrimal *entry = this->AddEdgeWithSecurePointList(pid0, pid1);
      if ( entry == (QEPrimal *)ITK_NULLPTR )
        {
        return ( entry );
        }
      FaceQEList[i] = entry;
      }
    else
      {
      //FIXME throw exception here if !edge
      FaceQEList[i] = edge;
      }
    }

  // Reorder all Onext rings
  QEPrimal *e1;
  QEPrimal *e0 = FaceQEList.back();

  typename QEList::iterator fIt = FaceQEList.begin();
  typename QEList::iterator fEnd = FaceQEList.end();

  while( fIt != fEnd )
    {
    e1 = e0->GetSym();
    e0 = *fIt;

    e0->ReorderOnextRingBeforeAddFace(e1);
    ++fIt;
    }

  // all edges are ready to receive a face on the left
  QEPrimal *entry = FaceQEList.front();

  if ( !entry )
    {
    // FIXME throw exception here instead
    itkDebugMacro("entry == NULL");
    return (QEPrimal *)ITK_NULLPTR;
    }

  this->AddFace(entry);

  return ( entry );
}

/**
 * We here make the strong assumption that the caller was wise enough
 * to build/handle the connectivity at the QE level. This method
 * simply creates a new PolygonCell and assigns it as the left face
 * of all edges in the Lnext ring of the incoming argument.
 */
template< typename TPixel, unsigned int VDimension, typename TTraits >
void
QuadEdgeMesh< TPixel, VDimension, TTraits >
::AddFace(QEPrimal *entry)
{
  // Create the cell and add it to the container
  PolygonCellType *faceCell = new PolygonCellType(entry);
  CellIdentifier   fid = this->FindFirstUnusedCellIndex();

  faceCell->SetIdent(fid);

  // Associate the above generated CellIndex as the default FaceRefType
  // of the new face [ i.e. use the itk level CellIdentifier as the
  // GeometricalQuadEdge::m_Origin of dual edges (edges of type QEDual) ].
  typename QEPrimal::IteratorGeom it  = entry->BeginGeomLnext();
  typename QEPrimal::IteratorGeom end = entry->EndGeomLnext();

  while( it != end )
    {
    it.Value()->SetLeft(fid);
    ++it;
    }

  ++m_NumberOfFaces;
  CellAutoPointer face;
  face.TakeOwnership(faceCell);
  this->Superclass::SetCell(fid, face);
}

/**
 * Add a triangle face to this QuadEdgeMesh.
 * @param aPid \ref PointIdentifier of first point
 * @param bPid \ref PointIdentifier of second point
 * @param cPid \ref PointIdentifier of third point
 */
template< typename TPixel, unsigned int VDimension, typename TTraits >
typename QuadEdgeMesh< TPixel, VDimension, TTraits >::QEPrimal *
QuadEdgeMesh< TPixel, VDimension, TTraits >
::AddFaceTriangle(
  const PointIdentifier & aPid,
  const PointIdentifier & bPid,
  const PointIdentifier & cPid)
{
  PointIdList points( 3 );

  points[0] = aPid;
  points[1] = bPid;
  points[2] = cPid;
  return this->AddFace(points);
}

/**
 */
template< typename TPixel, unsigned int VDimension, typename TTraits >
QuadEdgeMesh< TPixel, VDimension, TTraits >
::QuadEdgeMesh():m_NumberOfFaces(0), m_NumberOfEdges(0)
{
  m_EdgeCellsContainer = CellsContainer::New();
}

template< typename TPixel, unsigned int VDimension, typename TTraits >
QuadEdgeMesh< TPixel, VDimension, TTraits >
::~QuadEdgeMesh()
{
  this->ClearCellsContainer();
}

template< typename TPixel, unsigned int VDimension, typename TTraits >
void
QuadEdgeMesh< TPixel, VDimension, TTraits >
::ClearCellsContainer()
{
  if ( m_EdgeCellsContainer->GetReferenceCount() == 1 )
    {
    CellsContainerIterator EdgeCell = m_EdgeCellsContainer->Begin();
    CellsContainerIterator EdgeEnd  = m_EdgeCellsContainer->End();
    while ( EdgeCell != EdgeEnd )
      {
      const CellType *EdgeCellToBeDeleted = EdgeCell->Value();
      delete EdgeCellToBeDeleted;
      ++EdgeCell;
      }
    m_EdgeCellsContainer->Initialize();
    }
}

/**
 */
template< typename TPixel, unsigned int VDimension, typename TTraits >
typename QuadEdgeMesh< TPixel, VDimension, TTraits >::CoordRepType
QuadEdgeMesh< TPixel, VDimension, TTraits >
::ComputeEdgeLength(QEPrimal *e)
{
  const PointsContainer *points = this->GetPoints();

  const PointType org  = points->GetElement( e->GetOrigin() );
  const PointType dest = points->GetElement( e->GetDestination() );

  return org.EuclideanDistanceTo(dest);
}

/**
 * \brief Compute the total number of USED points. This differs from
 * \ref Mesh::GetNumberOfPoints() that will return the total number of
 * points including the ones that have no entry in the edge ring.
 *
 * \note This method is an optional utility of the class: its
 * understanding is not useful at first contact with the class.
 */
template< typename TPixel, unsigned int VDimension, typename TTraits >
typename QuadEdgeMesh< TPixel, VDimension, TTraits >::PointIdentifier
QuadEdgeMesh< TPixel, VDimension, TTraits >
::ComputeNumberOfPoints() const
{
  const PointsContainer *points = this->GetPoints();

  if ( !points )
    {
    itkDebugMacro("No point container");
    return ( 0 );
    }

  PointIdentifier  numberOfPoints = NumericTraits<PointIdentifier>::Zero;
  PointsContainerConstIterator pointIterator = points->Begin();
  PointsContainerConstIterator pointEnd = points->End();

  while ( pointIterator != pointEnd )
    {
    if ( pointIterator.Value().GetEdge() )
      {
      ++numberOfPoints;
      }
    ++pointIterator;
    }

  return ( numberOfPoints );
}

/**
 * \brief Compute the total number of faces.
 *
 * \note This method is an optional utility of the class: its
 * understanding is not useful at first contact with the class.
 */
template< typename TPixel, unsigned int VDimension, typename TTraits >
typename QuadEdgeMesh< TPixel, VDimension, TTraits >::CellIdentifier
QuadEdgeMesh< TPixel, VDimension, TTraits >
::ComputeNumberOfFaces() const
{
  CellIdentifier  numberOfFaces = NumericTraits<CellIdentifier>::Zero;
  CellsContainerConstIterator cellIterator = this->GetCells()->Begin();
  CellsContainerConstIterator cellEnd      = this->GetCells()->End();

  PointIdentifier NumOfPoints;

  while ( cellIterator != cellEnd )
    {
    NumOfPoints = cellIterator.Value()->GetNumberOfPoints();
    if ( NumOfPoints > 2 )
      {
      ++numberOfFaces;
      }
    ++cellIterator;
    }

  return ( numberOfFaces );
}

/**
 * \brief Compute the total number of edges.
 *
 * \note This method is an optional utility of the class: it's
 *       understanding is not useful at first contact with the class.
 */
template< typename TPixel, unsigned int VDimension, typename TTraits >
typename QuadEdgeMesh< TPixel, VDimension, TTraits >::CellIdentifier
QuadEdgeMesh< TPixel, VDimension, TTraits >
::ComputeNumberOfEdges() const
{
  return static_cast< CellIdentifier >( this->GetEdgeCells()->size() );
}
} // namespace itk

#endif
