//============================================================================
//  Copyright (c) Kitware, Inc.
//  All rights reserved.
//  See LICENSE.txt for details.
//
//  This software is distributed WITHOUT ANY WARRANTY; without even
//  the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
//  PURPOSE.  See the above copyright notice for more information.
//============================================================================
// Copyright (c) 2018, The Regents of the University of California, through
// Lawrence Berkeley National Laboratory (subject to receipt of any required approvals
// from the U.S. Dept. of Energy).  All rights reserved.
//
// Redistribution and use in source and binary forms, with or without modification,
// are permitted provided that the following conditions are met:
//
// (1) Redistributions of source code must retain the above copyright notice, this
//     list of conditions and the following disclaimer.
//
// (2) Redistributions in binary form must reproduce the above copyright notice,
//     this list of conditions and the following disclaimer in the documentation
//     and/or other materials provided with the distribution.
//
// (3) Neither the name of the University of California, Lawrence Berkeley National
//     Laboratory, U.S. Dept. of Energy nor the names of its contributors may be
//     used to endorse or promote products derived from this software without
//     specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
// IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
// INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
// BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
// OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
// OF THE POSSIBILITY OF SUCH DAMAGE.
//
//=============================================================================
//
//  This code is an extension of the algorithm presented in the paper:
//  Parallel Peak Pruning for Scalable SMP Contour Tree Computation.
//  Hamish Carr, Gunther Weber, Christopher Sewell, and James Ahrens.
//  Proceedings of the IEEE Symposium on Large Data Analysis and Visualization
//  (LDAV), October 2016, Baltimore, Maryland.
//
//  The PPP2 algorithm and software were jointly developed by
//  Hamish Carr (University of Leeds), Gunther H. Weber (LBNL), and
//  Oliver Ruebel (LBNL)
//==============================================================================

#ifndef vtk_m_worklet_contourtree_distributed_bract_maker_compress_regularised_nodes_resolve_root_worklet_h
#define vtk_m_worklet_contourtree_distributed_bract_maker_compress_regularised_nodes_resolve_root_worklet_h

#include <vtkm/filter/scalar_topology/worklet/contourtree_augmented/Types.h>
#include <vtkm/worklet/WorkletMapField.h>

namespace vtkm
{
namespace worklet
{
namespace contourtree_distributed
{
namespace bract_maker
{

/// Step 1 of IdentifyRegularisedSupernodes
class CompressRegularisedNodesResolveRootWorklet : public vtkm::worklet::WorkletMapField
{
public:
  using ControlSignature = void(FieldIn newIndex,           // input
                                WholeArrayInOut newSuperarc // input/output
  );
  using ExecutionSignature = void(_1, _2);
  using InputDomain = _1;

  // Default Constructor
  VTKM_EXEC_CONT
  CompressRegularisedNodesResolveRootWorklet() {}

  template <typename InOutFieldPortalType>
  VTKM_EXEC void operator()(const vtkm::Id& newIndex,
                            const InOutFieldPortalType& newSuperarcPortal) const
  {
    // per kept vertex
    // retrieve it to register
    vtkm::Id newInbound = newSuperarcPortal.Get(newIndex);

    // if it doesn't exist, do nothing
    if (vtkm::worklet::contourtree_augmented::NoSuchElement(newInbound))
    {
      return;
    }

    // if there is no loopback, do nothing
    if (newSuperarcPortal.Get(newInbound) != newIndex)
    {
      return;
    }

    // if there is loopback and we're the lower one, substitute NULL
    if (newIndex < newInbound)
    {
      newSuperarcPortal.Set(newIndex,
                            (vtkm::Id)vtkm::worklet::contourtree_augmented::NO_SUCH_ELEMENT);
    }

    // In serial this worklet implements the following operation
    /*
    for (indexType newIndex = 0; newIndex < nKept; newIndex++)
      { // per kept vertex
      // retrieve it to register
      indexType newInbound = newSuperarc[newIndex];

      // if it doesn't exist, do nothing
      if (noSuchElement(newInbound))
        continue;

      // if there is no loopback, do nothing
      if (newSuperarc[newInbound] != newIndex)
        continue;

      // if there is loopback and we're the lower one, substitute NULL
      if (newIndex < newInbound)
        newSuperarc[newIndex] = NO_SUCH_ELEMENT;
      } // per kept vertex
    */
  }
}; // CompressRegularisedNodesResolveRootWorklet


} // namespace bract_maker
} // namespace contourtree_distributed
} // namespace worklet
} // namespace vtkm

#endif
