    // Copyright (C) 2007  Davis E. King (davis@dlib.net)
    // License: Boost Software License   See LICENSE.txt for the full license.
    #ifndef DLIB_GRAPH_KERNEl_1_
    #define DLIB_GRAPH_KERNEl_1_

    #include "../serialize.h"
    #include "../noncopyable.h"
    #include "../std_allocator.h"
    #include "../smart_pointers.h"
    #include "../algs.h"
    #include <vector>
    #include "graph_kernel_abstract.h"
    #include "../is_kind.h"

    namespace dlib
    {

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

        template <typename node_type, typename graph, bool is_checked>
        struct graph_checker_helper
        {
            /*!
                This object is used to check preconditions based on the value of is_checked
            !*/

            static void check_neighbor (
                unsigned long edge_index,
                const node_type& self
            )
            {
                // make sure requires clause is not broken
                DLIB_CASSERT(edge_index < self.number_of_neighbors(),
                             "\tnode_type& graph::node_type::neighbor(edge_index)"
                             << "\n\tYou have specified an invalid index"
                             << "\n\tedge_index:            " << edge_index
                             << "\n\tnumber_of_neighbors(): " << self.number_of_neighbors()
                             << "\n\tthis:                  " << &self
                );
            }

            static void check_edge (
                unsigned long edge_index,
                const node_type& self
            )
            {
                // make sure requires clause is not broken
                DLIB_CASSERT(edge_index < self.number_of_neighbors(),
                             "\tE& graph::node_type::edge(edge_index)"
                             << "\n\tYou have specified an invalid index"
                             << "\n\tedge_index:            " << edge_index
                             << "\n\tnumber_of_neighbors(): " << self.number_of_neighbors()
                             << "\n\tthis:                  " << &self
                );
            }

            static void check_node (
                unsigned long index,
                const graph& self
            )
            {
                // make sure requires clause is not broken
                DLIB_CASSERT(index < self.number_of_nodes(),
                             "\tnode_type& graph::node(index)"
                             << "\n\tYou have specified an invalid index"
                             << "\n\tindex:             " << index
                             << "\n\tnumber_of_nodes(): " << self.number_of_nodes()
                             << "\n\tthis:              " << &self
                );
            }

            static void check_has_edge (
                unsigned long node_index1,
                unsigned long node_index2,
                const graph& self
            )
            {
                // make sure requires clause is not broken
                DLIB_CASSERT(node_index1 < self.number_of_nodes() &&
                             node_index2 < self.number_of_nodes(),
                             "\tvoid graph::has_edge(node_index1, node_index2)"
                             << "\n\tYou have specified an invalid index"
                             << "\n\tnode_index1:       " << node_index1
                             << "\n\tnode_index2:       " << node_index2
                             << "\n\tnumber_of_nodes(): " << self.number_of_nodes()
                             << "\n\tthis:              " << &self
                );
            }

            static void check_add_edge (
                unsigned long node_index1,
                unsigned long node_index2,
                const graph& self
            )
            {
                DLIB_CASSERT(node_index1 < self.number_of_nodes() &&
                             node_index2 < self.number_of_nodes(),
                             "\tvoid graph::add_edge(node_index1, node_index2)"
                             << "\n\tYou have specified an invalid index"
                             << "\n\tnode_index1:       " << node_index1
                             << "\n\tnode_index2:       " << node_index2
                             << "\n\tnumber_of_nodes(): " << self.number_of_nodes()
                             << "\n\tthis:              " << &self
                );

                DLIB_CASSERT( self.has_edge(node_index1, node_index2) == false,
                              "\tvoid graph::add_edge(node_index1, node_index2)"
                              << "\n\tYou can't add an edge if it already exists in the graph"
                              << "\n\tnode_index1:       " << node_index1
                              << "\n\tnode_index2:       " << node_index2
                              << "\n\tnumber_of_nodes(): " << self.number_of_nodes()
                              << "\n\tthis:              " << &self
                );

            }

            static void check_remove_edge (
                unsigned long node_index1,
                unsigned long node_index2,
                const graph& self
            )
            {
                DLIB_CASSERT(node_index1 < self.number_of_nodes() &&
                             node_index2 < self.number_of_nodes(),
                             "\tvoid graph::remove_edge(node_index1, node_index2)"
                             << "\n\tYou have specified an invalid index"
                             << "\n\tnode_index1:       " << node_index1
                             << "\n\tnode_index2:       " << node_index2
                             << "\n\tnumber_of_nodes(): " << self.number_of_nodes()
                             << "\n\tthis:              " << &self
                );

                DLIB_CASSERT( self.has_edge(node_index1, node_index2) == true,
                              "\tvoid graph::remove_edge(node_index1, node_index2)"
                              << "\n\tYou can't remove an edge if it isn't in the graph"
                              << "\n\tnode_index1:       " << node_index1
                              << "\n\tnode_index2:       " << node_index2
                              << "\n\tnumber_of_nodes(): " << self.number_of_nodes()
                              << "\n\tthis:              " << &self
                );

            }

            static void check_remove_node (
                unsigned long index,
                const graph& self
            )
            {
                // make sure requires clause is not broken
                DLIB_CASSERT(index < self.number_of_nodes(),
                             "\tvoid graph::remove_node(index)"
                             << "\n\tYou have specified an invalid index"
                             << "\n\tindex:             " << index
                             << "\n\tnumber_of_nodes(): " << self.number_of_nodes()
                             << "\n\tthis:              " << &self
                );
            }
        };

        template <typename node_type, typename graph>
        struct graph_checker_helper <node_type, graph, false>
        {
            static inline void check_edge ( unsigned long , const node_type& ) { }
            static inline void check_neighbor ( unsigned long , const node_type& ) { }
            static inline void check_node ( unsigned long , const graph& ) { }
            static inline void check_has_edge ( unsigned long , unsigned long , const graph& ) { }
            static inline void check_add_edge ( unsigned long , unsigned long , const graph& ) { }
            static inline void check_remove_edge ( unsigned long , unsigned long , const graph& ) { }
            static inline void check_remove_node ( unsigned long , const graph& ) { }
        };

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

        template <
            typename T,
            typename E = char,
            typename mem_manager = default_memory_manager,
            bool is_checked = true
            >
        class graph_kernel_1 : noncopyable
        {

            /*!
                INITIAL VALUE
                    - nodes.size() == 0

                CONVENTION
                    - nodes.size() == number_of_nodes()
                    - for all valid i:
                        - *nodes[i] == node(i)
                        - nodes[i]->neighbors.size() == nodes[i]->number_of_neighbors(i)
                        - nodes[i]->idx == i == nodes[i]->index()
                        - for all valid n:
                            - nodes[i]->neighbors[n] == pointer to the n'th parent node of i
                            - *nodes[i]->neighbors[n] == node(i).neighbor(n)
                            - *nodes[i]->edges[n] == node(i).edge(n)
            !*/

        public:
            struct node_type;

        private:
            typedef graph_checker_helper<node_type, graph_kernel_1, is_checked> checker;

        public:

            typedef T type;
            typedef E edge_type;
            typedef mem_manager mem_manager_type;

            graph_kernel_1(
            ) {}

            virtual ~graph_kernel_1(
            ) {}

            void clear(
            ) { nodes.clear(); }

            void set_number_of_nodes (
                unsigned long new_size
            );

            unsigned long number_of_nodes (
            ) const { return nodes.size(); }

            node_type& node (
                unsigned long index
            ) { checker::check_node(index,*this); return *nodes[index]; }

            const node_type& node (
                unsigned long index
            ) const { checker::check_node(index,*this); return *nodes[index]; }

            bool has_edge (
                unsigned long node_index1,
                unsigned long node_index2
            ) const;

            void add_edge (
                unsigned long node_index1,
                unsigned long node_index2
            );

            void remove_edge (
                unsigned long node_index1,
                unsigned long node_index2
            );

            unsigned long add_node (
            );

            void remove_node (
                unsigned long index
            );

            void swap (
                graph_kernel_1& item
            ) { nodes.swap(item.nodes); }

        public:

            struct node_type
            {
                T data;
                typedef graph_kernel_1 graph_type;

                unsigned long index(
                ) const { return idx; }

                unsigned long number_of_neighbors (
                ) const { return neighbors.size(); }

                const node_type& neighbor (
                    unsigned long edge_index
                ) const { checker::check_neighbor(edge_index,*this);  return *neighbors[edge_index]; }

                node_type& neighbor (
                    unsigned long edge_index
                ) { checker::check_neighbor(edge_index,*this);  return *neighbors[edge_index]; }

                const E& edge (
                    unsigned long edge_index
                ) const { checker::check_edge(edge_index,*this);  return *edges[edge_index]; }

                E& edge (
                    unsigned long edge_index
                ) { checker::check_edge(edge_index,*this);  return *edges[edge_index]; }

            private:
                friend class graph_kernel_1;
                typedef std_allocator<node_type*,mem_manager> alloc_type;
                typedef std_allocator<shared_ptr<E>,mem_manager> alloc_edge_type;
                std::vector<node_type*,alloc_type> neighbors;
                std::vector<shared_ptr<E>,alloc_edge_type> edges;
                unsigned long idx;
            };

        private:

            typedef std_allocator<shared_ptr<node_type>,mem_manager> alloc_type;
            typedef std::vector<shared_ptr<node_type>, alloc_type> vector_type;
            vector_type nodes;
        };

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

        template <
            typename T,
            typename E,
            typename mem_manager,
            bool is_checked
            >
        inline void swap (
            graph_kernel_1<T,E,mem_manager,is_checked>& a,
            graph_kernel_1<T,E,mem_manager,is_checked>& b
        ) { a.swap(b); }

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

        template <
            typename T,
            typename E,
            typename mem_manager,
            bool is_checked
            >
        struct is_graph<graph_kernel_1<T,E,mem_manager, is_checked> >
        {
            static const bool value = true;
        };

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

        template <
            typename T,
            typename E,
            typename mem_manager,
            bool is_checked
            >
        void serialize (
            const graph_kernel_1<T,E,mem_manager,is_checked>& item,
            std::ostream& out
        )
        {
            try
            {
                serialize(item.number_of_nodes(), out);

                // serialize each node
                for (unsigned long i = 0; i < item.number_of_nodes(); ++i)
                {
                    serialize(item.node(i).data, out);

                    // serialize all the edges
                    for (unsigned long n = 0; n < item.node(i).number_of_neighbors(); ++n)
                    {
                        // only serialize edges that we haven't already serialized
                        if (item.node(i).neighbor(n).index() >= i)
                        {
                            serialize(item.node(i).neighbor(n).index(), out);
                            serialize(item.node(i).edge(n), out);
                        }
                    }
                    const unsigned long stop_mark = 0xFFFFFFFF;
                    serialize(stop_mark, out);
                }
            }
            catch (serialization_error& e)
            {
                throw serialization_error(e.info + "\n   while serializing object of type graph_kernel_1");
            }
        }

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

        template <
            typename T,
            typename E,
            typename mem_manager,
            bool is_checked
            >
        void deserialize (
            graph_kernel_1<T,E,mem_manager,is_checked>& item,
            std::istream& in
        )
        {
            try
            {
                unsigned long size;
                deserialize(size, in);

                item.clear();
                item.set_number_of_nodes(size);

                // deserialize each node
                for (unsigned long i = 0; i < item.number_of_nodes(); ++i)
                {
                    deserialize(item.node(i).data, in);

                    const unsigned long stop_mark = 0xFFFFFFFF;
                    // Add all the edges going to this node's neighbors
                    unsigned long index;
                    deserialize(index, in);
                    while (index != stop_mark)
                    {
                        item.add_edge(i, index);
                        // find the edge
                        unsigned long j = 0;
                        for (j = 0; j < item.node(i).number_of_neighbors(); ++j)
                            if (item.node(i).neighbor(j).index() == index)
                                break;

                        deserialize(item.node(i).edge(j), in);
                        deserialize(index, in);
                    }

                }
            }
            catch (serialization_error& e)
            {
                throw serialization_error(e.info + "\n   while deserializing object of type graph_kernel_1");
            }
        }

    // ----------------------------------------------------------------------------------------
    // ----------------------------------------------------------------------------------------
    //                             member function definitions
    // ----------------------------------------------------------------------------------------
    // ----------------------------------------------------------------------------------------

        template <
            typename T,
            typename E,
            typename mem_manager,
            bool is_checked
            >
        void graph_kernel_1<T,E,mem_manager,is_checked>::
        set_number_of_nodes (
            unsigned long new_size
        )
        {
            try
            {
                nodes.resize(new_size);
                for (unsigned long i = 0; i < nodes.size(); ++i)
                {
                    nodes[i].reset(new node_type);
                    nodes[i]->idx = i;
                }
            }
            catch (...)
            {
                clear();
                throw;
            }
        }

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

        template <
            typename T,
            typename E,
            typename mem_manager,
            bool is_checked
            >
        bool graph_kernel_1<T,E,mem_manager,is_checked>::
        has_edge (
            unsigned long node_index1,
            unsigned long node_index2
        ) const
        {
            checker::check_has_edge(node_index1, node_index2, *this);

            node_type& n = *nodes[node_index1];

            // search all the child nodes to see if there is a link to the right node
            for (unsigned long i = 0; i < n.neighbors.size(); ++i)
            {
                if (n.neighbors[i]->idx == node_index2)
                    return true;
            }

            return false;
        }

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

        template <
            typename T,
            typename E,
            typename mem_manager,
            bool is_checked
            >
        void graph_kernel_1<T,E,mem_manager,is_checked>::
        add_edge (
            unsigned long node_index1,
            unsigned long node_index2
        )
        {
            checker::check_add_edge(node_index1, node_index2, *this);
            try
            {
                node_type& n1 = *nodes[node_index1];
                node_type& n2 = *nodes[node_index2];

                n1.neighbors.push_back(&n2);

                shared_ptr<E> e(new E);
                n1.edges.push_back(e);

                // don't add this twice if this is an edge from node_index1 back to itself
                if (node_index1 != node_index2)
                {
                    n2.neighbors.push_back(&n1);
                    n2.edges.push_back(e);
                }
            }
            catch (...)
            {
                clear();
                throw;
            }
        }

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

        template <
            typename T,
            typename E,
            typename mem_manager,
            bool is_checked
            >
        void graph_kernel_1<T,E,mem_manager,is_checked>::
        remove_edge (
            unsigned long node_index1,
            unsigned long node_index2
        )
        {
            checker::check_remove_edge(node_index1, node_index2, *this);

            node_type& n1 = *nodes[node_index1];
            node_type& n2 = *nodes[node_index2];

            // remove the record of the link from n1
            unsigned long pos = static_cast<unsigned long>(find(n1.neighbors.begin(), n1.neighbors.end(), &n2) - n1.neighbors.begin());
            n1.neighbors.erase(n1.neighbors.begin() + pos);
            n1.edges.erase(n1.edges.begin() + pos);

            // check if this is an edge that goes from node_index1 back to itself
            if (node_index1 != node_index2)
            {
                // remove the record of the link from n2
                unsigned long pos = static_cast<unsigned long>(find(n2.neighbors.begin(), n2.neighbors.end(), &n1) - n2.neighbors.begin());
                n2.neighbors.erase(n2.neighbors.begin() + pos);
                n2.edges.erase(n2.edges.begin() + pos);
            }
        }

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

        template <
            typename T,
            typename E,
            typename mem_manager,
            bool is_checked
            >
        unsigned long graph_kernel_1<T,E,mem_manager,is_checked>::
        add_node (
        )
        {
            try
            {
                shared_ptr<node_type> n(new node_type);
                n->idx = nodes.size();
                nodes.push_back(n);
                return n->idx;
            }
            catch (...)
            {
                clear();
                throw;
            }
        }

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

        template <
            typename T,
            typename E,
            typename mem_manager,
            bool is_checked
            >
        void graph_kernel_1<T,E,mem_manager,is_checked>::
        remove_node (
            unsigned long index
        )
        {
            checker::check_remove_node(index,*this);

            node_type& n = *nodes[index];

            // remove all edges pointing to this node from its neighbors
            for (unsigned long i = 0; i < n.neighbors.size(); ++i)
            {
                // remove the edge from this specific parent
                unsigned long pos = static_cast<unsigned long>(find(n.neighbors[i]->neighbors.begin(), n.neighbors[i]->neighbors.end(), &n) -
                                    n.neighbors[i]->neighbors.begin());
                n.neighbors[i]->neighbors.erase(n.neighbors[i]->neighbors.begin() + pos);
                n.neighbors[i]->edges.erase(n.neighbors[i]->edges.begin() + pos);
            }

            // now remove this node by replacing it with the last node in the nodes vector
            nodes[index] = nodes[nodes.size()-1];

            // update the index for the node we just moved
            nodes[index]->idx = index;

            // now remove the duplicated node at the end of the vector
            nodes.pop_back();
        }

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

    }

    #endif // DLIB_GRAPH_KERNEl_1_