// SPDX-FileCopyrightText: Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
// SPDX-FileCopyrightText: Copyright 2008 Sandia Corporation
// SPDX-License-Identifier: LicenseRef-BSD-3-Clause-Sandia-USGov
/**
 * @class   vtkKCoreDecomposition
 * @brief   Compute the k-core decomposition of the input graph.
 *
 *
 * The k-core decomposition is a graph partitioning strategy that is useful for
 * analyzing the structure of large networks. A k-core of a graph G is a maximal
 * connected subgraph of G in which all vertices have degree at least k.  The k-core
 * membership for each vertex of the input graph is found on the vertex data of the
 * output graph as an array named 'KCoreDecompositionNumbers' by default.  The algorithm
 * used to find the k-cores has O(number of graph edges) running time, and is described
 * in the following reference paper.
 *
 * An O(m) Algorithm for Cores Decomposition of Networks
 *   V. Batagelj, M. Zaversnik, 2001
 *
 * @par Thanks:
 * Thanks to Thomas Otahal from Sandia National Laboratories for providing this
 * implementation.
 */

#ifndef vtkKCoreDecomposition_h
#define vtkKCoreDecomposition_h

#include "vtkGraphAlgorithm.h"
#include "vtkInfovisCoreModule.h" // For export macro

VTK_ABI_NAMESPACE_BEGIN
class vtkIntArray;

class VTKINFOVISCORE_EXPORT vtkKCoreDecomposition : public vtkGraphAlgorithm
{
public:
  static vtkKCoreDecomposition* New();

  vtkTypeMacro(vtkKCoreDecomposition, vtkGraphAlgorithm);
  void PrintSelf(ostream& os, vtkIndent indent) override;

  ///@{
  /**
   * Set the output array name. If no output array name is
   * set then the name 'KCoreDecompositionNumbers' is used.
   */
  vtkSetStringMacro(OutputArrayName);
  ///@}

  ///@{
  /**
   * Directed graphs only.  Use only the in edges to
   * compute the vertex degree of a vertex.  The default
   * is to use both in and out edges to compute vertex
   * degree.
   */
  vtkSetMacro(UseInDegreeNeighbors, bool);
  vtkGetMacro(UseInDegreeNeighbors, bool);
  vtkBooleanMacro(UseInDegreeNeighbors, bool);
  ///@}

  ///@{
  /**
   * Directed graphs only.  Use only the out edges to
   * compute the vertex degree of a vertex.  The default
   * is to use both in and out edges to compute vertex
   * degree.
   */
  vtkSetMacro(UseOutDegreeNeighbors, bool);
  vtkGetMacro(UseOutDegreeNeighbors, bool);
  vtkBooleanMacro(UseOutDegreeNeighbors, bool);
  ///@}

  ///@{
  /**
   * Check the input graph for self loops and parallel
   * edges.  The k-core is not defined for graphs that
   * contain either of these.  Default is on.
   */
  vtkSetMacro(CheckInputGraph, bool);
  vtkGetMacro(CheckInputGraph, bool);
  vtkBooleanMacro(CheckInputGraph, bool);
  ///@}

protected:
  vtkKCoreDecomposition();
  ~vtkKCoreDecomposition() override;

  int RequestData(vtkInformation*, vtkInformationVector**, vtkInformationVector*) override;

private:
  char* OutputArrayName;

  bool UseInDegreeNeighbors;
  bool UseOutDegreeNeighbors;
  bool CheckInputGraph;

  // K-core partitioning implementation
  void Cores(vtkGraph* g, vtkIntArray* KCoreNumbers);

  vtkKCoreDecomposition(const vtkKCoreDecomposition&) = delete;
  void operator=(const vtkKCoreDecomposition&) = delete;
};

VTK_ABI_NAMESPACE_END
#endif
