/* -*- mode: C++; indent-tabs-mode: nil; -*-

 *

 * This file is a part of LEMON, a generic C++ optimization library.

 *

 * Copyright (C) 2003-2009

 * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport

 * (Egervary Research Group on Combinatorial Optimization, EGRES).

 *

 * Permission to use, modify and distribute this software is granted

 * provided that this copyright notice appears in all copies. For

 * precise terms see the accompanying LICENSE file.

 *

 * This software is provided "AS IS" with no warranty of any kind,

 * express or implied, and with no claim as to its suitability for any

 * purpose.

 *

 */

#ifndef LEMON_NAUTY_READER_H

#define LEMON_NAUTY_READER_H

#include <vector>

#include <iostream>

#include <string>

/// \ingroup nauty_group

/// \file

/// \brief Nauty file reader.

namespace lemon {

  /// \ingroup nauty_group

  ///

  /// \brief Nauty file reader

  ///

  /// The \e geng program is in the \e gtools suite of the nauty

  /// package. This tool can generate all non-isomorphic undirected

  /// graphs of several classes with given node number (e.g.

  /// general, connected, biconnected, triangle-free, 4-cycle-free,

  /// bipartite and graphs with given edge number and degree

  /// constraints). This function reads a \e nauty \e graph6 \e format

  /// line from the given stream and builds it in the given graph.

  ///

  /// The site of nauty package: http://cs.anu.edu.au/~bdm/nauty/

  ///

  /// For example, the number of all non-isomorphic planar graphs

  /// can be computed with the following code.

  ///\code

  /// int num = 0;

  /// SmartGraph graph;

  /// while (readNautyGraph(graph, std::cin)) {

  ///   PlanarityChecking<SmartGraph> pc(graph);

  ///   if (pc.run()) ++num;

  /// }

  /// std::cout << "Number of planar graphs: " << num << std::endl;

  ///\endcode

  ///

  /// The nauty files are quite huge, therefore instead of the direct

  /// file generation pipelining is recommended. For example,

  ///\code

  /// ./geng -c 10 | ./num_of_planar_graphs

  ///\endcode

  template <typename Graph>

  std::istream& readNautyGraph(Graph& graph, std::istream& is = std::cin) {

    graph.clear();

    std::string line;

    if (getline(is, line)) {

      int index = 0;

      int n;

      if (line[index] == '>') {

        index += 10;

      }

      char c = line[index++]; c -= 63;

      if (c != 63) {

        n = int(c);

      } else {

        c = line[index++]; c -= 63;

        n = (int(c) << 12);

        c = line[index++]; c -= 63;

        n |= (int(c) << 6);

        c = line[index++]; c -= 63;

        n |= int(c);

      }

      std::vector<typename Graph::Node> nodes;

      for (int i = 0; i < n; ++i) {

        nodes.push_back(graph.addNode());

      }

      int bit = -1;

      for (int j = 0; j < n; ++j) {

        for (int i = 0; i < j; ++i) {

          if (bit == -1) {

            c = line[index++]; c -= 63;

            bit = 5;

          }

          bool b = (c & (1 << (bit--))) != 0;

          if (b) {

            graph.addEdge(nodes[i], nodes[j]);

          }

        }

      }

    }

    return is;

  }

}

#endif