//

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

// 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_BREADTH_FIRST_SEARCH_HPP

#define BOOST_GRAPH_BREADTH_FIRST_SEARCH_HPP

/*

  Breadth First Search Algorithm (Cormen, Leiserson, and Rivest p. 470)

*/

#include <boost/config.hpp>

#include <vector>

#include <boost/pending/queue.hpp>

#include <boost/graph/graph_traits.hpp>

#include <boost/graph/graph_concepts.hpp>

#include <boost/graph/visitors.hpp>

#include <boost/graph/named_function_params.hpp>

namespace boost {

  template <class Visitor, class Graph>

  struct BFSVisitorConcept {

    void constraints() {

      function_requires< CopyConstructibleConcept<Visitor> >();

      vis.initialize_vertex(u, g);

      vis.discover_vertex(u, g);

      vis.examine_vertex(u, g);

      vis.examine_edge(e, g);

      vis.tree_edge(e, g);

      vis.non_tree_edge(e, g);

      vis.gray_target(e, g);

      vis.black_target(e, g);

      vis.finish_vertex(u, g);

    }

    Visitor vis;

    Graph g;

    typename graph_traits<Graph>::vertex_descriptor u;

    typename graph_traits<Graph>::edge_descriptor e;

  };

  template <class IncidenceGraph, class Buffer, class BFSVisitor,

            class ColorMap>

  void breadth_first_visit

    (const IncidenceGraph& g,

     typename graph_traits<IncidenceGraph>::vertex_descriptor s,

     Buffer& Q, BFSVisitor vis, ColorMap color)

  {

    function_requires< IncidenceGraphConcept<IncidenceGraph> >();

    typedef graph_traits<IncidenceGraph> GTraits;

    typedef typename GTraits::vertex_descriptor Vertex;

    typedef typename GTraits::edge_descriptor Edge;

    function_requires< BFSVisitorConcept<BFSVisitor, IncidenceGraph> >();

    function_requires< ReadWritePropertyMapConcept<ColorMap, Vertex> >();

    typedef typename property_traits<ColorMap>::value_type ColorValue;

    typedef color_traits<ColorValue> Color;

    typename GTraits::out_edge_iterator ei, ei_end;

    put(color, s, Color::gray());             vis.discover_vertex(s, g);

    Q.push(s);

    while (! Q.empty()) {

      Vertex u = Q.top(); Q.pop();            vis.examine_vertex(u, g);

      for (tie(ei, ei_end) = out_edges(u, g); ei != ei_end; ++ei) {

        Vertex v = target(*ei, g);            vis.examine_edge(*ei, g);

        ColorValue v_color = get(color, v);

        if (v_color == Color::white()) {      vis.tree_edge(*ei, g);

          put(color, v, Color::gray());       vis.discover_vertex(v, g);

          Q.push(v);

        } else {                              vis.non_tree_edge(*ei, g);

          if (v_color == Color::gray())       vis.gray_target(*ei, g);

          else                                vis.black_target(*ei, g);

        }

      } // end for

      put(color, u, Color::black());          vis.finish_vertex(u, g);

    } // end while

  } // breadth_first_visit

  template <class VertexListGraph, class Buffer, class BFSVisitor,

            class ColorMap>

  void breadth_first_search

    (const VertexListGraph& g,

     typename graph_traits<VertexListGraph>::vertex_descriptor s,

     Buffer& Q, BFSVisitor vis, ColorMap color)

  {

    // Initialization

    typedef typename property_traits<ColorMap>::value_type ColorValue;

    typedef color_traits<ColorValue> Color;

    typename boost::graph_traits<VertexListGraph>::vertex_iterator i, i_end;

    for (tie(i, i_end) = vertices(g); i != i_end; ++i) {

      vis.initialize_vertex(*i, g);

      put(color, *i, Color::white());

    }

    breadth_first_visit(g, s, Q, vis, color);

  }

  template <class Visitors = null_visitor>

  class bfs_visitor {

  public:

    bfs_visitor() { }

    bfs_visitor(Visitors vis) : m_vis(vis) { }

    template <class Vertex, class Graph>

    void initialize_vertex(Vertex u, Graph& g) {

      invoke_visitors(m_vis, u, g, ::boost::on_initialize_vertex());

    }

    template <class Vertex, class Graph>

    void discover_vertex(Vertex u, Graph& g) {

      invoke_visitors(m_vis, u, g, ::boost::on_discover_vertex());

    }

    template <class Vertex, class Graph>

    void examine_vertex(Vertex u, Graph& g) {

      invoke_visitors(m_vis, u, g, ::boost::on_examine_vertex());

    }

    template <class Edge, class Graph>

    void examine_edge(Edge e, Graph& g) {

      invoke_visitors(m_vis, e, g, ::boost::on_examine_edge());

    }

    template <class Edge, class Graph>

    void tree_edge(Edge e, Graph& g) {

      invoke_visitors(m_vis, e, g, ::boost::on_tree_edge());

    }

    template <class Edge, class Graph>

    void non_tree_edge(Edge e, Graph& g) {

      invoke_visitors(m_vis, e, g, ::boost::on_non_tree_edge());

    }

    template <class Edge, class Graph>

    void gray_target(Edge e, Graph& g) {

      invoke_visitors(m_vis, e, g, ::boost::on_gray_target());

    }

    template <class Edge, class Graph>

    void black_target(Edge e, Graph& g) {

      invoke_visitors(m_vis, e, g, ::boost::on_black_target());

    }

    template <class Vertex, class Graph>

    void finish_vertex(Vertex u, Graph& g) {

      invoke_visitors(m_vis, u, g, ::boost::on_finish_vertex());

    }

    BOOST_GRAPH_EVENT_STUB(on_initialize_vertex,bfs)

    BOOST_GRAPH_EVENT_STUB(on_discover_vertex,bfs)

    BOOST_GRAPH_EVENT_STUB(on_examine_vertex,bfs)

    BOOST_GRAPH_EVENT_STUB(on_examine_edge,bfs)

    BOOST_GRAPH_EVENT_STUB(on_tree_edge,bfs)

    BOOST_GRAPH_EVENT_STUB(on_non_tree_edge,bfs)

    BOOST_GRAPH_EVENT_STUB(on_gray_target,bfs)

    BOOST_GRAPH_EVENT_STUB(on_black_target,bfs)

    BOOST_GRAPH_EVENT_STUB(on_finish_vertex,bfs)

  protected:

    Visitors m_vis;

  };

  template <class Visitors>

  bfs_visitor<Visitors>

  make_bfs_visitor(Visitors vis) {

    return bfs_visitor<Visitors>(vis);

  }

  typedef bfs_visitor<> default_bfs_visitor;

  namespace detail {

    template <class VertexListGraph, class ColorMap, class BFSVisitor,

      class P, class T, class R>

    void bfs_helper

      (VertexListGraph& g,

       typename graph_traits<VertexListGraph>::vertex_descriptor s,

       ColorMap color,

       BFSVisitor vis,

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

    {

      typedef graph_traits<VertexListGraph> Traits;

      // Buffer default

      typedef typename Traits::vertex_descriptor Vertex;

      typedef boost::queue<Vertex> queue_t;

      queue_t Q;

      detail::wrap_ref<queue_t> Qref(Q);

      breadth_first_search

        (g, s,

         choose_param(get_param(params, buffer_param_t()), Qref).ref,

         vis, color);

    }

    //-------------------------------------------------------------------------

    // Choose between default color and color parameters. Using

    // function dispatching so that we don't require vertex index if

    // the color default is not being used.

    template <class ColorMap>

    struct bfs_dispatch {

      template <class VertexListGraph, class P, class T, class R>

      static void apply

      (VertexListGraph& g,

       typename graph_traits<VertexListGraph>::vertex_descriptor s,

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

       ColorMap color)

      {

        bfs_helper

          (g, s, color,

           choose_param(get_param(params, graph_visitor),

                        make_bfs_visitor(null_visitor())),

           params);

      }

    };

    template <>

    struct bfs_dispatch<detail::error_property_not_found> {

      template <class VertexListGraph, class P, class T, class R>

      static void apply

      (VertexListGraph& g,

       typename graph_traits<VertexListGraph>::vertex_descriptor s,

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

       detail::error_property_not_found)

      {

        std::vector<default_color_type> color_vec(num_vertices(g));

        default_color_type c = white_color;

        null_visitor null_vis;

        bfs_helper

          (g, s,

           make_iterator_property_map

           (color_vec.begin(),

            choose_const_pmap(get_param(params, vertex_index),

                              g, vertex_index), c),

           choose_param(get_param(params, graph_visitor),

                        make_bfs_visitor(null_vis)),

           params);

      }

    };

  } // namespace detail

  // Named Parameter Variant

  template <class VertexListGraph, class P, class T, class R>

  void breadth_first_search

    (const VertexListGraph& g,

     typename graph_traits<VertexListGraph>::vertex_descriptor s,

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

  {

    // The graph is passed by *const* reference so that graph adaptors

    // (temporaries) can be passed into this function. However, the

    // graph is not really const since we may write to property maps

    // of the graph.

    VertexListGraph& ng = const_cast<VertexListGraph&>(g);

    typedef typename property_value< bgl_named_params<P,T,R>,

      vertex_color_t>::type C;

    detail::bfs_dispatch<C>::apply(ng, s, params,

                                   get_param(params, vertex_color));

  }

  // This version does not initialize colors, user has to.

  template <class IncidenceGraph, class P, class T, class R>

  void breadth_first_visit

    (const IncidenceGraph& g,

     typename graph_traits<IncidenceGraph>::vertex_descriptor s,

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

  {

    // The graph is passed by *const* reference so that graph adaptors

    // (temporaries) can be passed into this function. However, the

    // graph is not really const since we may write to property maps

    // of the graph.

    IncidenceGraph& ng = const_cast<IncidenceGraph&>(g);

    typedef graph_traits<IncidenceGraph> Traits;

    // Buffer default

    typedef typename Traits::vertex_descriptor vertex_descriptor;

    typedef boost::queue<vertex_descriptor> queue_t;

    queue_t Q;

    detail::wrap_ref<queue_t> Qref(Q);

    breadth_first_visit

      (ng, s,

       choose_param(get_param(params, buffer_param_t()), Qref).ref,

       choose_param(get_param(params, graph_visitor),

                    make_bfs_visitor(null_visitor())),

       choose_pmap(get_param(params, vertex_color), ng, vertex_color)

       );

  }

} // namespace boost

#endif // BOOST_GRAPH_BREADTH_FIRST_SEARCH_HPP