    // Copyright (C) 2012  Davis E. King (davis@dlib.net)
    // License: Boost Software License   See LICENSE.txt for the full license.
    #ifndef DLIB_GENERAL_FLOW_GRaPH_Hh_
    #define DLIB_GENERAL_FLOW_GRaPH_Hh_

    #include "../graph_utils.h"

    namespace dlib
    {

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

        namespace impl
        {

            template <
                typename directed_graph_type
                >
            class general_flow_graph
            {
                /*!
                    this is a utility class used by dlib::min_cut to convert a directed_graph
                    into the kind of flow graph expected by the min_cut object's main block
                    of code.
                !*/

                directed_graph_type& g;

                typedef typename directed_graph_type::node_type node_type;
                typedef typename directed_graph_type::type node_label;

            public:

                general_flow_graph(
                    directed_graph_type& g_
                ) : g(g_)
                {
                }

                class out_edge_iterator
                {
                    friend class general_flow_graph;
                    unsigned long idx; // base node idx
                    unsigned long cnt; // count over the neighbors of idx
                public:

                    out_edge_iterator(
                    ):idx(0),cnt(0) {}

                    out_edge_iterator(
                        unsigned long idx_,
                        unsigned long cnt_
                    ):idx(idx_),cnt(cnt_)
                    {}

                    bool operator!= (
                        const out_edge_iterator& item
                    ) const { return cnt != item.cnt; }

                    out_edge_iterator& operator++(
                    )
                    {
                        ++cnt;
                        return *this;
                    }
                };

                class in_edge_iterator
                {

                    friend class general_flow_graph;
                    unsigned long idx; // base node idx
                    unsigned long cnt; // count over the neighbors of idx
                public:

                    in_edge_iterator(
                    ):idx(0),cnt(0) {}

                    in_edge_iterator(
                        unsigned long idx_,
                        unsigned long cnt_
                    ):idx(idx_),cnt(cnt_)
                    {}

                    bool operator!= (
                        const in_edge_iterator& item
                    ) const { return cnt != item.cnt; }

                    in_edge_iterator& operator++(
                    )
                    {
                        ++cnt;
                        return *this;
                    }
                };

                unsigned long number_of_nodes (
                ) const { return g.number_of_nodes(); }

                out_edge_iterator out_begin(
                    const unsigned long& it
                ) const { return out_edge_iterator(it, 0); }

                in_edge_iterator in_begin(
                    const unsigned long& it
                ) const { return in_edge_iterator(it, 0); }

                out_edge_iterator out_end(
                    const unsigned long& it
                ) const { return out_edge_iterator(it, g.node(it).number_of_children()); }

                in_edge_iterator in_end(
                    const unsigned long& it
                ) const { return in_edge_iterator(it, g.node(it).number_of_parents()); }

                unsigned long node_id (
                    const out_edge_iterator& it
                ) const { return g.node(it.idx).child(it.cnt).index(); }
                unsigned long node_id (
                    const in_edge_iterator& it
                ) const { return g.node(it.idx).parent(it.cnt).index(); }

                typedef typename directed_graph_type::edge_type edge_type;

                edge_type get_flow (const unsigned long& it1,     const unsigned long& it2) const
                {
                    return edge(g, it1, it2);
                }
                edge_type get_flow (const out_edge_iterator& it) const
                {
                    return g.node(it.idx).child_edge(it.cnt);
                }
                edge_type get_flow (const in_edge_iterator& it) const
                {
                    return g.node(it.idx).parent_edge(it.cnt);
                }

                void adjust_flow (
                    const unsigned long& it1,
                    const unsigned long& it2,
                    const edge_type& value
                )
                {
                    edge(g, it1, it2) += value;
                    edge(g, it2, it1) -= value;
                }

                void set_label (
                    const unsigned long& it,
                    node_label value
                )
                {
                    g.node(it).data = value;
                }

                node_label get_label (
                    const unsigned long& it
                ) const
                {
                    return g.node(it).data;
                }

            };

        }

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

    }

    #endif // DLIB_GENERAL_FLOW_GRaPH_Hh_