//

//=======================================================================

// Copyright 1997, 1998, 1999, 2000 University of Notre Dame.

// 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_GRAPH_TOPOLOGICAL_SORT_HPP

#define BOOST_GRAPH_TOPOLOGICAL_SORT_HPP

#include <boost/config.hpp>

#include <boost/property_map.hpp>

#include <boost/graph/depth_first_search.hpp>

#include <boost/graph/visitors.hpp>

#include <boost/graph/exception.hpp>

namespace boost { 

  // Topological sort visitor

  //

  // This visitor merely writes the linear ordering into an

  // OutputIterator. The OutputIterator could be something like an

  // ostream_iterator, or it could be a back/front_insert_iterator.

  // Note that if it is a back_insert_iterator, the recorded order is

  // the reverse topological order. On the other hand, if it is a

  // front_insert_iterator, the recorded order is the topological

  // order.

  //

  template <typename OutputIterator>

  struct topo_sort_visitor : public dfs_visitor<>

  {

    topo_sort_visitor(OutputIterator _iter)

      : m_iter(_iter) { }

    template <typename Edge, typename Graph>

    void back_edge(const Edge& u, Graph&) { throw not_a_dag(); }

    template <typename Vertex, typename Graph> 

    void finish_vertex(const Vertex& u, Graph&) { *m_iter++ = u; }

    OutputIterator m_iter;

  };

  // Topological Sort

  //

  // The topological sort algorithm creates a linear ordering

  // of the vertices such that if edge (u,v) appears in the graph,

  // then u comes before v in the ordering. The graph must

  // be a directed acyclic graph (DAG). The implementation

  // consists mainly of a call to depth-first search.

  //

  template <typename VertexListGraph, typename OutputIterator,

    typename P, typename T, typename R>

  void topological_sort(VertexListGraph& g, OutputIterator result,

                        const bgl_named_params<P, T, R>& params)

  {

    typedef topo_sort_visitor<OutputIterator> TopoVisitor;

    depth_first_search(g, params.visitor(TopoVisitor(result)));

  }

  template <typename VertexListGraph, typename OutputIterator>

  void topological_sort(VertexListGraph& g, OutputIterator result)

  {

    topological_sort(g, result, 

                     bgl_named_params<int, buffer_param_t>(0)); // bogus

  }

} // namespace boost

#endif /*BOOST_GRAPH_TOPOLOGICAL_SORT_H*/