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

// 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_GRAPH_DAG_SHORTEST_PATHS_HPP

#define BOOST_GRAPH_DAG_SHORTEST_PATHS_HPP

#include <boost/graph/topological_sort.hpp>

#include <boost/graph/dijkstra_shortest_paths.hpp>

// single-source shortest paths for a Directed Acyclic Graph (DAG)

namespace boost {

  // Initalize distances and call depth first search

  template <class VertexListGraph, class DijkstraVisitor, 

            class DistanceMap, class WeightMap, class ColorMap, 

            class PredecessorMap,

            class Compare, class Combine, 

            class DistInf, class DistZero>

  inline void

  dag_shortest_paths

    (const VertexListGraph& g,

     typename graph_traits<VertexListGraph>::vertex_descriptor s, 

     DistanceMap distance, WeightMap weight, ColorMap color,

     PredecessorMap pred,

     DijkstraVisitor vis, Compare compare, Combine combine, 

     DistInf inf, DistZero zero)

  {

    typedef typename graph_traits<VertexListGraph>::vertex_descriptor Vertex;

    std::vector<Vertex> rev_topo_order;

    rev_topo_order.reserve(num_vertices(g));

    // Call 'depth_first_visit', not 'topological_sort', because we don't

    // want to traverse the entire graph, only vertices reachable from 's',

    // and 'topological_sort' will traverse everything. The logic below

    // is the same as for 'topological_sort', only we call 'depth_first_visit'

    // and 'topological_sort' calls 'depth_first_search'.

    topo_sort_visitor<std::back_insert_iterator<std::vector<Vertex> > >

        topo_visitor(std::back_inserter(rev_topo_order));

    depth_first_visit(g, s, topo_visitor, color);

    typename graph_traits<VertexListGraph>::vertex_iterator ui, ui_end;

    for (tie(ui, ui_end) = vertices(g); ui != ui_end; ++ui) {

      put(distance, *ui, inf);

      put(pred, *ui, *ui);

    }

    put(distance, s, zero);

    vis.discover_vertex(s, g);

    typename std::vector<Vertex>::reverse_iterator i;

    for (i = rev_topo_order.rbegin(); i != rev_topo_order.rend(); ++i) {

      Vertex u = *i;

      vis.examine_vertex(u, g);

      typename graph_traits<VertexListGraph>::out_edge_iterator e, e_end;

      for (tie(e, e_end) = out_edges(u, g); e != e_end; ++e) {

        vis.discover_vertex(target(*e, g), g);

        bool decreased = relax(*e, g, weight, pred, distance, 

                               combine, compare);

        if (decreased)

          vis.edge_relaxed(*e, g);

        else

          vis.edge_not_relaxed(*e, g);

      }

      vis.finish_vertex(u, g);      

    }

  }

  namespace detail {

    // Defaults are the same as Dijkstra's algorithm

    // Handle Distance Compare, Combine, Inf and Zero defaults

    template <class VertexListGraph, class DijkstraVisitor, 

      class DistanceMap, class WeightMap, class ColorMap, 

      class IndexMap, class Params>

    inline void

    dag_sp_dispatch2

      (const VertexListGraph& g,

       typename graph_traits<VertexListGraph>::vertex_descriptor s, 

       DistanceMap distance, WeightMap weight, ColorMap color, IndexMap id,

       DijkstraVisitor vis, const Params& params)

    {

      typedef typename property_traits<DistanceMap>::value_type D;

      dummy_property_map p_map;

      dag_shortest_paths

        (g, s, distance, weight, color, 

         choose_param(get_param(params, vertex_predecessor), p_map),

         vis, 

         choose_param(get_param(params, distance_compare_t()), std::less<D>()),

         choose_param(get_param(params, distance_combine_t()), closed_plus<D>()),

         choose_param(get_param(params, distance_inf_t()), 

                      (std::numeric_limits<D>::max)()),

         choose_param(get_param(params, distance_zero_t()), 

                      D()));

    }

    // Handle DistanceMap and ColorMap defaults

    template <class VertexListGraph, class DijkstraVisitor, 

              class DistanceMap, class WeightMap, class ColorMap,

              class IndexMap, class Params>

    inline void

    dag_sp_dispatch1

      (const VertexListGraph& g,

       typename graph_traits<VertexListGraph>::vertex_descriptor s, 

       DistanceMap distance, WeightMap weight, ColorMap color, IndexMap id,

       DijkstraVisitor vis, const Params& params)

    {

      typedef typename property_traits<WeightMap>::value_type T;

      typename std::vector<T>::size_type n;

      n = is_default_param(distance) ? num_vertices(g) : 1;

      std::vector<T> distance_map(n);

      n = is_default_param(color) ? num_vertices(g) : 1;

      std::vector<default_color_type> color_map(n);

      dag_sp_dispatch2

        (g, s, 

         choose_param(distance, 

                      make_iterator_property_map(distance_map.begin(), id,

                                                 distance_map[0])),

         weight, 

         choose_param(color,

                      make_iterator_property_map(color_map.begin(), id, 

                                                 color_map[0])),

         id, vis, params);

    }

  } // namespace detail 

  template <class VertexListGraph, class Param, class Tag, class Rest>

  inline void

  dag_shortest_paths

    (const VertexListGraph& g,

     typename graph_traits<VertexListGraph>::vertex_descriptor s,

     const bgl_named_params<Param,Tag,Rest>& params)

  {

    // assert that the graph is directed...

    null_visitor null_vis;

    detail::dag_sp_dispatch1

      (g, s, 

       get_param(params, vertex_distance),

       choose_const_pmap(get_param(params, edge_weight), g, edge_weight),

       get_param(params, vertex_color),

       choose_const_pmap(get_param(params, vertex_index), g, vertex_index),

       choose_param(get_param(params, graph_visitor),

                    make_dijkstra_visitor(null_vis)),

       params);

  }

} // namespace boost

#endif // BOOST_GRAPH_DAG_SHORTEST_PATHS_HPP