//=======================================================================
// Copyright 2002 Indiana University.
// Authors: Andrew Lumsdaine, Lie-Quan Lee, Jeremy G. Siek
//
// Distributed under the Boost Software License, Version 1.0. (See
// accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
//=======================================================================

#ifndef BOOST_CREATE_CONDENSATION_GRAPH_HPP
#define BOOST_CREATE_CONDENSATION_GRAPH_HPP

#include <boost/graph/graph_traits.hpp>
#include <boost/property_map/property_map.hpp>

namespace boost {

  template <typename Graph, typename ComponentLists, 
    typename ComponentNumberMap,
    typename CondensationGraph, typename EdgeMultiplicityMap>
  void create_condensation_graph(const Graph& g, 
                                 const ComponentLists& components,
                                 ComponentNumberMap component_number,
                                 CondensationGraph& cg,
                                 EdgeMultiplicityMap edge_mult_map)
  {
    typedef typename graph_traits<Graph>::vertex_descriptor vertex;
    typedef typename graph_traits<Graph>::vertices_size_type size_type;
    typedef typename graph_traits<CondensationGraph>::vertex_descriptor 
      cg_vertex;
    std::vector<cg_vertex> to_cg_vertex(components.size());
    for (size_type s = 0; s < components.size(); ++s)
      to_cg_vertex[s] = add_vertex(cg);

    for (size_type si = 0; si < components.size(); ++si) {
      cg_vertex s = to_cg_vertex[si];
      std::vector<cg_vertex> adj;
      for (size_type i = 0; i < components[si].size(); ++i) {
        vertex u = components[s][i];
        typename graph_traits<Graph>::adjacency_iterator v, v_end;
        for (boost::tie(v, v_end) = adjacent_vertices(u, g); v != v_end; ++v) {
          cg_vertex t = to_cg_vertex[component_number[*v]];
          if (s != t) // Avoid loops in the condensation graph
            adj.push_back(t);
        }
      }
      std::sort(adj.begin(), adj.end());
      if (! adj.empty()) {
        size_type i = 0;
        cg_vertex t = adj[i];
        typename graph_traits<CondensationGraph>::edge_descriptor e;
        bool inserted;
        boost::tie(e, inserted) = add_edge(s, t, cg);
        put(edge_mult_map, e, 1);
        ++i;
        while (i < adj.size()) {
          if (adj[i] == t)
            put(edge_mult_map, e, get(edge_mult_map, e) + 1);
          else {
            t = adj[i];
            boost::tie(e, inserted) = add_edge(s, t, cg);
            put(edge_mult_map, e, 1);
          }
          ++i;
        }
      }
    }
  }
  
  template <typename Graph, typename ComponentLists, 
    typename ComponentNumberMap, typename CondensationGraph>
  void create_condensation_graph(const Graph& g, 
                                 const ComponentLists& components,
                                 ComponentNumberMap component_number,
                                 CondensationGraph& cg)
  {
    create_condensation_graph(g, components, component_number, cg, 
                              dummy_property_map());
  }

} // namespace boost

#endif // BOOST_CREATE_CONDENSATION_GRAPH_HPP