TreeTest.h

/*
 *
 * This file is part of Tulip (http://tulip.labri.fr)
 *
 * Authors: David Auber and the Tulip development Team
 * from LaBRI, University of Bordeaux
 *
 * Tulip is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License
 * as published by the Free Software Foundation, either version 3
 * of the License, or (at your option) any later version.
 *
 * Tulip is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details.
 *
 */

#ifndef TULIP_TREETEST_H
#define TULIP_TREETEST_H

#include <tulip/tuliphash.h>
#include <tulip/Observable.h>
#include <tulip/Graph.h>

namespace tlp {

class PluginProgress;
/**
 * @ingroup Checks
 * @brief Performs test to check whether a graph is a simple or rooted tree.
 * From wikipedia: "A tree is an undirected graph in which any two vertices are connected by exactly
 *one simple path."
 * Free trees have no designated root, while rooted trees do.
 **/
class TLP_SCOPE TreeTest : private Observable {
public:
  /**
   * @brief Checks if the graph is a rooted tree (i.e. one node is designated as the root).
   *
   * @param graph The graph to check is a tree.
   * @return bool True if the graph is a tree, false otherwise.
   **/
  static bool isTree(const Graph *graph);

  /**
   *  Returns true if the graph is a topological tree
   *  (i.e. if the graph was undirected, there would be no cycle),
   *  false otherwise.
   */
  /**
   * @brief Checks if the graph is a topological tree (i.e. if the graph was undirected, there would
   *be no cycle).
   *
   * @param graph The graph to check is a free tree.
   * @return bool True if the graph is a free tree, false otherwise.
   **/
  static bool isFreeTree(const Graph *graph);

  /**
   * Turns a free tree into a rooted tree.
   */
  /**
   * @brief Makes a free tree into a rooted tree.
   *
   * @param freeTree The free tree to make a rooted tree.
   * @param root The root of the tree.
   * @return void
   **/
  static void makeRootedTree(Graph *freeTree, node root);

  /**
   * @brief Computes a rooted tree from the graph.
   * If the graph is a rooted tree, the input graph is returned as is.
   * If the graphs is a free tree, a rooted clone subgraph is returned.
   * If the graph is connected, a rooted spanning tree of a clone subgraph is returned
   * If the graph is not connected, computes a tree for each of the connected components of a clone
   *subgraph, adds a simple source and returns the clone.
   *
   * @param graph The graph to compute a tree on.
   * @param pluginProgress reports progress on the computation. Defaults to 0.
   * @return :Graph* If the input graph is a rooted tree, returns it as is, otherwise a clone
   *subgraph transformed into a rooted tree.
   **/
  static Graph *computeTree(Graph *graph, PluginProgress *pluginProgress = nullptr);

  /**
   * @brief Removes subgraphs created during tree computation.
   * If graph and tree are the same graph, does nothing.
   *
   * @param graph The graph to clean from tree subgraphs.
   * @param tree The tree subgraph to remove.
   * @return void
   * @note this deletes the root of the graph from graph's root (i.e. calls
   *graph->getRoot()->delNode()).
   **/
  static void cleanComputedTree(Graph *graph, Graph *tree);

private:
  TreeTest();

  bool compute(const Graph *graph);

  bool isFreeTree(const Graph *graph, node curRoot);

  // override Observable::treatEvent
  void treatEvent(const Event &) override;

  /**
   * @brief Singleton instance of this class.
   **/
  static TreeTest *instance;
  /**
   * @brief Stored results for graphs. When a graph is updated, its entry is removed from the
   *hashmap.
   **/
  TLP_HASH_MAP<const Graph *, bool> resultsBuffer;
};
} // namespace tlp
#endif