//

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

// 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_NEIGHBOR_BREADTH_FIRST_SEARCH_HPP

#define BOOST_GRAPH_NEIGHBOR_BREADTH_FIRST_SEARCH_HPP

/*

  Neighbor Breadth First Search

  Like BFS, but traverses in-edges as well as out-edges.

  (for directed graphs only. use normal BFS for undirected graphs)

*/

#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 NeighborBFSVisitorConcept {

    void constraints() {

      function_requires< CopyConstructibleConcept<Visitor> >();

      vis.initialize_vertex(u, g);

      vis.discover_vertex(u, g);

      vis.examine_vertex(u, g);

      vis.examine_out_edge(e, g);

      vis.examine_in_edge(e, g);

      vis.tree_out_edge(e, g);

      vis.tree_in_edge(e, g);

      vis.non_tree_out_edge(e, g);

      vis.non_tree_in_edge(e, g);

      vis.gray_target(e, g);

      vis.black_target(e, g);

      vis.gray_source(e, g);

      vis.black_source(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 Visitors = null_visitor>

  class neighbor_bfs_visitor {

  public:

    neighbor_bfs_visitor(Visitors vis = Visitors()) : m_vis(vis) { }

    template <class Vertex, class Graph>

    void initialize_vertex(Vertex u, Graph& g) {

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

    }

    template <class Vertex, class Graph>

    void discover_vertex(Vertex u, Graph& g) {

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

    }

    template <class Vertex, class Graph>

    void examine_vertex(Vertex u, Graph& g) {

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

    }

    template <class Edge, class Graph>

    void examine_out_edge(Edge e, Graph& g) {

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

    }

    template <class Edge, class Graph>

    void tree_out_edge(Edge e, Graph& g) {

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

    }

    template <class Edge, class Graph>

    void non_tree_out_edge(Edge e, Graph& g) {

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

    }

    template <class Edge, class Graph>

    void gray_target(Edge e, Graph& g) {

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

    }

    template <class Edge, class Graph>

    void black_target(Edge e, Graph& g) {

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

    }

    template <class Edge, class Graph>

    void examine_in_edge(Edge e, Graph& g) {

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

    }

    template <class Edge, class Graph>

    void tree_in_edge(Edge e, Graph& g) {

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

    }

    template <class Edge, class Graph>

    void non_tree_in_edge(Edge e, Graph& g) {

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

    }

    template <class Edge, class Graph>

    void gray_source(Edge e, Graph& g) {

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

    }

    template <class Edge, class Graph>

    void black_source(Edge e, Graph& g) {

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

    }

    template <class Vertex, class Graph>

    void finish_vertex(Vertex u, Graph& g) {

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

    }

  protected:

    Visitors m_vis;

  };

  template <class Visitors>

  neighbor_bfs_visitor<Visitors>

  make_neighbor_bfs_visitor(Visitors vis) {

    return neighbor_bfs_visitor<Visitors>(vis);

  }

  namespace detail {

    template <class BidirectionalGraph, class Buffer, class BFSVisitor, 

              class ColorMap>

    void neighbor_bfs_impl

      (const BidirectionalGraph& g, 

       typename graph_traits<BidirectionalGraph>::vertex_descriptor s, 

       Buffer& Q, BFSVisitor vis, ColorMap color)

    {

      function_requires< BidirectionalGraphConcept<BidirectionalGraph> >();

      typedef graph_traits<BidirectionalGraph> GTraits;

      typedef typename GTraits::vertex_descriptor Vertex;

      typedef typename GTraits::edge_descriptor Edge;

      function_requires< 

        NeighborBFSVisitorConcept<BFSVisitor, BidirectionalGraph> >();

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

      typedef typename property_traits<ColorMap>::value_type ColorValue;

      typedef color_traits<ColorValue> Color;

      put(color, s, Color::gray());

      vis.discover_vertex(s, g);

      Q.push(s);

      while (! Q.empty()) {

        Vertex u = Q.top();

        Q.pop(); // pop before push to avoid problem if Q is priority_queue.

        vis.examine_vertex(u, g);

        typename GTraits::out_edge_iterator ei, ei_end;

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

          Edge e = *ei;

          vis.examine_out_edge(e, g);

          Vertex v = target(e, g);

          ColorValue v_color = get(color, v);

          if (v_color == Color::white()) {

            vis.tree_out_edge(e, g);

            put(color, v, Color::gray());

            vis.discover_vertex(v, g);

            Q.push(v);

          } else {

            vis.non_tree_out_edge(e, g);

            if (v_color == Color::gray())

              vis.gray_target(e, g);

            else

              vis.black_target(e, g);

          }

        } // for out-edges

        typename GTraits::in_edge_iterator in_ei, in_ei_end;

        for (tie(in_ei, in_ei_end) = in_edges(u, g); 

             in_ei != in_ei_end; ++in_ei) {

          Edge e = *in_ei;

          vis.examine_in_edge(e, g);

          Vertex v = source(e, g);

          ColorValue v_color = get(color, v);

          if (v_color == Color::white()) {

            vis.tree_in_edge(e, g);

            put(color, v, Color::gray());

            vis.discover_vertex(v, g);

            Q.push(v);

          } else {

            vis.non_tree_in_edge(e, g);

            if (v_color == Color::gray())

              vis.gray_source(e, g);

            else

              vis.black_source(e, g);

          }

        } // for in-edges

        put(color, u, Color::black());

        vis.finish_vertex(u, g);

      } // while

    }

    template <class VertexListGraph, class ColorMap, class BFSVisitor,

      class P, class T, class R>

    void neighbor_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);

      // 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) {

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

        vis.initialize_vertex(*i, g);

      }

      neighbor_bfs_impl

        (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 neighbor_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)

      {

        neighbor_bfs_helper

          (g, s, color,

           choose_param(get_param(params, graph_visitor),

                        make_neighbor_bfs_visitor(null_visitor())),

           params);

      }

    };

    template <>

    struct neighbor_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));

        null_visitor null_vis;

        neighbor_bfs_helper

          (g, s, 

           make_iterator_property_map

           (color_vec.begin(), 

            choose_const_pmap(get_param(params, vertex_index), 

                              g, vertex_index), color_vec[0]),

           choose_param(get_param(params, graph_visitor),

                        make_neighbor_bfs_visitor(null_vis)),

           params);

      }

    };

  } // namespace detail

  // Named Parameter Variant

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

  void neighbor_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::neighbor_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 neighbor_breadth_first_visit

    (IncidenceGraph& g,

     typename graph_traits<IncidenceGraph>::vertex_descriptor s,

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

  {

    typedef graph_traits<IncidenceGraph> Traits;

    // Buffer default

    typedef boost::queue<typename Traits::vertex_descriptor> queue_t;

    queue_t Q;

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

    detail::neighbor_bfs_impl

      (g, s,

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

       choose_param(get_param(params, graph_visitor),

                    make_neighbor_bfs_visitor(null_visitor())),

       choose_pmap(get_param(params, vertex_color), g, vertex_color)

       );

  }

} // namespace boost

#endif // BOOST_GRAPH_NEIGHBOR_BREADTH_FIRST_SEARCH_HPP