// -*- c++ -*-

 #ifndef LEMON_GRAPH_H

 #define LEMON_GRAPH_H

 ///\file

 ///\brief Declaration of GraphConcept.

 #include <lemon/invalid.h>

 namespace lemon {

   /// @defgroup empty_graph The GraphConcept class

   /// @{

   /// An empty graph class.

   /// This class provides all the common features of a graph structure,

   /// however completely without implementations and real data structures

   /// behind the interface.

   /// All graph algorithms should compile with this class, but it will not

   /// run properly, of course.

   ///

   /// It can be used for checking the interface compatibility,

   /// or it can serve as a skeleton of a new graph structure.

   /// 

   /// Also, you will find here the full documentation of a certain graph

   /// feature, the documentation of a real graph imlementation

   /// like @ref ListGraph or

   /// @ref SmartGraph will just refer to this structure.

   class GraphConcept

   {

   public:

     /// Defalult constructor.

     GraphConcept() { }

     /// \brief Copy consructor.

     /// 

     /// \todo It is not clear, what we expect from a copy constructor.

     /// E.g. How to assign the nodes/edges to each other? What about maps?

     GraphConcept(const GraphConcept&) { }

     /// \brief The base type of the node iterators.

     ///

     /// This is the base type of each node iterators,

     /// thus each kind of node iterator will convert to this.

     /// Sometimes it is said to be a trivial iterator.

     class Node {

     public:

       /// @warning The default constructor sets the iterator

       /// to an undefined value.

       Node() { }   //FIXME

       // /// Copy constructor.

       // Node(const Node&) { }

       /// \brief Invalid constructor \& conversion.

       /// 

       /// This constructor initializes the iterator to be invalid.

       /// \sa Invalid for more details.

       Node(const Invalid&) { }

       /// Two iterators are equal if and only if they point to the

       /// same object or both are invalid.

       bool operator==(Node n) const { return true; }

       /// \sa \ref operator==(Node n)

       ///

       bool operator!=(Node n) const { return true; }

       bool operator<(Node n) const { return true; }

     };

     /// The base type of the edge iterators.

     class Edge {

     public:

       /// @warning The default constructor sets the iterator

       /// to an undefined value.

       Edge() { }   //FIXME

       // /// Copy constructor.

       // Edge(const Edge&) { }

       /// Initialize the iterator to be invalid

       Edge(const Invalid&) { }

       /// Two iterators are equal if and only if they point to the

       /// same object or both are invalid.

       bool operator==(Edge n) const { return true; }

       bool operator!=(Edge n) const { return true; }

       bool operator<(Edge n) const { return true; }

     };

     //  class SymEdgeIt : public Edge {};

     //  SymEdgeIt &first(SymEdgeIt &, Node) const { return i;}

 //     Node getNext(Node) const {}

 //     InEdgeIt getNext(InEdgeIt) const {}

 //     OutEdgeIt getNext(OutEdgeIt) const {}

 //     //SymEdgeIt getNext(SymEdgeIt) const {}

 //     EdgeIt getNext(EdgeIt) const {}

     //SymEdgeIt &next(SymEdgeIt &) const {}

     /// Gives back the head node of an edge.

     Node head(const Edge&) const { return INVALID; }

     /// Gives back the tail node of an edge.

     Node tail(const Edge&) const { return INVALID; }

     //   Node aNode(SymEdgeIt) const {}

     //   Node bNode(SymEdgeIt) const {}

     /// \brief Checks if a node iterator is valid

     /// 

     /// \todo Maybe, it would be better if iterator converted to

     /// bool directly, as Jacint prefers.

     bool valid(const Node&) const { return true; }

     /// \brief Checks if an edge iterator is valid

     /// 

     /// \todo Maybe, it would be better if iterator converted to

     /// bool directly, as Jacint prefers.

     bool valid(const Edge&) const { return true; }

     /// \brief Gives back the \e id of a node.

     /// 

     /// \warning Not all graph structures provide this feature.

     ///

     int id(const Node&) const { return 0; }

     /// \brief Gives back the \e id of an edge.

     ///

     /// \warning Not all graph structures provide this feature.

     ///

     int id(const Edge&) const { return 0; }

     //void setInvalid(Node &) const {};

     //void setInvalid(Edge &) const {};

     /// \brief Add a new node to the graph.

     ///

     /// \return the new node.

     Node addNode() { return INVALID; }

     /// \brief Add a new edge to the graph.

     ///

     /// Add a new edge to the graph with tail node \c tail

     /// and head node \c head.

     /// \return the new edge.

     Edge addEdge(const Node& tail, const Node& head) { return INVALID; }

     /// \brief Resets the graph.

     /// 

     /// This function deletes all edges and nodes of the graph.

     /// It also frees the memory allocated to store them.

     /// \todo What happens with the maps?

     void clear() { }

     /// Read/write/reference map of the nodes to type \c T.

     /// Read/write/reference map of the nodes to type \c T.

     /// \sa MemoryMapConcept

     /// \todo We may need copy constructor

     /// \todo We may need conversion from other nodetype

     /// \todo We may need operator=

     /// \warning Making maps that can handle bool type (NodeMap<bool>)

     /// needs extra attention!

     template<class T> class NodeMap

     {

     public:

       typedef T ValueType;

       typedef Node KeyType;

       NodeMap(const GraphConcept& g) { }

       NodeMap(const GraphConcept& g, T t) { }

       template<typename TT> NodeMap(const NodeMap<TT>& m) { }

       /// Sets the value of a node.

       /// Sets the value associated with node \c i to the value \c t.

       ///

       void set(Node i, T t) {}

       /// Gets the value of a node.

       T get(Node i) const {return *(T*)0;}  //FIXME: Is it necessary

       T &operator[](Node i) {return *(T*)0;}

       const T &operator[](Node i) const {return *(T*)0;}

       /// Updates the map if the graph has been changed

       /// \todo Do we need this?

       ///

       void update() { }

       //void update(T a) { }   //FIXME: Is it necessary

     };

     ///Read/write/reference map of the edges to type \c T.

     /// Read/write/reference map of the edges to type \c T.

     /// It behaves exactly in the same way as \ref NodeMap.

     /// \sa NodeMap

     /// \sa MemoryMapConcept

     /// \todo We may need copy constructor

     /// \todo We may need conversion from other edgetype

     /// \todo We may need operator=

     template<class T> class EdgeMap

     {

     public:

       typedef T ValueType;

       typedef Edge KeyType;

       EdgeMap(const GraphConcept& g) {}

       EdgeMap(const GraphConcept& g, T t) {}

       void set(Edge i, T t) {}

       T get(Edge i) const {return *(T*)0;}

       T &operator[](Edge i) {return *(T*)0;}

       void update() { }

       //void update(T a) { }   //FIXME: Is it necessary

     };

   };

   /// \brief Node-iterable graph concept.

   ///

   /// A graph class which provides functions to 

   /// iterate on its nodes.

   class NodeIterableGraphConcept : virtual public GraphConcept

   {

   public:

     /// \brief This iterator goes trough the nodes of the graph.

     ///

     /// This iterator goes trough the \e nodes of the graph.

     /// Its usage is quite simple, for example you can count the number

     /// of nodes in graph \c g of type \c Graph as follows.

     /// \code

     /// int count=0;

     /// for(Graph::NodeIt n(g); g.valid(n); g.next(n)) ++count;

     /// \endcode

     class NodeIt : public Node {

     public:

       /// @warning The default constructor sets the iterator.

       /// to an undefined value.

       NodeIt() { }

       // /// Copy constructor

       //NodeIt(const NodeIt& n) { }

       /// Initialize the iterator to be invalid.

       NodeIt(const Invalid&) { }

       /// \brief This constructor sets the iterator to first node.

       ///

       /// This constructor set the iterator to the first 

       /// node of the graph \c g.

       ///

       ///@param g the graph

       NodeIt(const GraphConcept& g) { }

     };

     /// The first node.

     NodeIt &first(NodeIt &i) const { return i; }

     /// Go to the next node.

     NodeIt &next(NodeIt &i) const { return i; }

   };

   /// \brief Edge-iterable graph concept.

   ///

   /// A graph class which provides functions to 

   /// iterate on its edges.

   class EdgeIterableGraphConcept : virtual public GraphConcept

   {

   public:

     /// \brief This iterator goes trough the edges of the graph.

     ///

     /// This iterator goes trough the \e edges of the graph.

     /// Its usage is quite simple, for example you can count the number

     /// of edges in graph \c g of type \c Graph as follows.

     /// \code

     /// int count=0;

     /// for(Graph::EdgeIt e(g); g.valid(e); g.next(e)) ++count;

     /// \endcode

     class EdgeIt : public Edge {

     public:

       /// @warning The default constructor sets the iterator.

       /// to an undefined value.

       EdgeIt() { }

       // /// Copy constructor

       // EdgeIt(const EdgeIt&) { }

       /// Initialize the iterator to be invalid.

       EdgeIt(const Invalid&) { }

       /// \brief This constructor sets the iterator to first edge.

       ///

       /// This constructor set the iterator to the first 

       /// edge of the graph \c g.

       ///

       ///@param g the graph

       EdgeIt(const GraphConcept& g) { }

     };

     /// The first edge.

     EdgeIt &first(EdgeIt &i) const { return i; }

     /// Go to the next edge.

     EdgeIt &next(EdgeIt &i) const { return i; }

   };

   /// \brief Out-edge-iterable graph concept.

   ///

   /// A graph class which provides functions to 

   /// iterate on out-edges of any node.

   class OutEdgeIterableGraphConcept : virtual public GraphConcept

   {

   public:

     /// \brief This iterator goes trough the outgoing edges of a node.

     ///

     /// This iterator goes trough the \e outgoing edges of a certain node

     /// of a graph.

     /// Its usage is quite simple, for example you can count the number

     /// of outgoing edges of a node \c n

     /// in graph \c g of type \c Graph as follows.

     /// \code

     /// int count=0;

     /// for(Graph::OutEdgeIt e(g, n); g.valid(e); g.next(e)) ++count;

     /// \endcode

     class OutEdgeIt : public Edge {

     public:

       /// @warning The default constructor sets the iterator.

       /// to an undefined value.

       OutEdgeIt() { }

       /// Initialize the iterator to be invalid.

       OutEdgeIt(const Invalid&) { }

       /// \brief This constructor sets the iterator to first outgoing edge.

       ///

       /// This constructor set the iterator to the first outgoing edge of

       /// node

       ///@param n the node

       ///@param g the graph

       OutEdgeIt(const GraphConcept& g, const Node& n) { }

     };

     /// The first outgoing edge.

     OutEdgeIt &first(OutEdgeIt &i, const Node& n) const { return i; }

     /// Go to the next outgoing edge.

     OutEdgeIt &next(OutEdgeIt &i) const { return i; }

     Node aNode(const OutEdgeIt&) const { return Node(); }

     Node bNode(const OutEdgeIt&) const { return Node(); }

   };

   /// \brief In-edge-iterable graph concept.

   ///

   /// A Graph class which provides a function to 

   /// iterate on in-edges of any node.

   class InEdgeIterableGraphConcept : virtual public GraphConcept

   {

   public:

     /// \brief This iterator goes trough the incoming edges of a node.

     /// 

     /// This iterator goes trough the \e incoming edges of a certain node

     /// of a graph.

     /// Its usage is quite simple, for example you can count the number

     /// of incoming edges of a node \c n

     /// in graph \c g of type \c Graph as follows.

     /// \code

     /// int count=0;

     /// for(Graph::InEdgeIt e(g, n); g.valid(e); g.next(e)) ++count;

     /// \endcode

     class InEdgeIt : public Edge {

     public:

       /// @warning The default constructor sets the iterator

       /// to an undefined value.

       InEdgeIt() { }

       /// Initialize the iterator to be invalid

       InEdgeIt(const Invalid&) { }

       /// \brief This constructor sets the iterator to first incomig edge.

       /// 

       /// This constructor set the iterator to the first incomig edge of

       /// node

       ///@param n the node

       ///@param g the graph

       InEdgeIt(const GraphConcept& g, const Node& n) { }

     };

     /// The first incoming edge.

     InEdgeIt &first(InEdgeIt &i, const Node& n) const { return i; }

     /// Go to the next incoming edge.

     InEdgeIt &next(InEdgeIt &i) const { return i; }

     Node aNode(const InEdgeIt&) const { return Node(); }

     Node bNode(const InEdgeIt&) const { return Node(); }

   };

   /// \brief Node-erasable graph concept.

   ///

   /// A graph class which provides a function to 

   /// delete any of its nodes.

   class NodeErasableGraphConcept : virtual public GraphConcept

   {

   public:

     /// Deletes a node.

     void erase(const Node& n) { }

   };

   /// \brief Edge-erasable graph concept.

   /// 

   /// A graph class which provides a function to delete any 

   /// of its edges.

   class EdgeErasableGraphConcept : virtual public GraphConcept

   {

   public:

     /// Deletes a node.

     void erase(const Edge& n) { }

   };

   /// \brief An empty graph class which provides a function to 

   /// get the number of its nodes.

   /// 

   /// This graph class provides a function for getting the number of its 

   /// nodes. 

   /// Clearly, for physical graph structures it can be expected to have such a 

   /// function. For wrappers or graphs which are given in an implicit way, 

   /// the implementation can be circumstantial, that is why this composes a 

   /// separate concept.

   class NodeCountingGraphConcept : virtual public GraphConcept

   {

   public:

     /// Returns the number of nodes.

     int nodeNum() const { return 0; }

   };

   /// \brief An empty graph class which provides a function to 

   /// get the number of its edges.

   /// 

   /// This graph class provides a function for getting the number of its 

   /// edges. 

   /// Clearly, for physical graph structures it can be expected to have such a 

   /// function. For wrappers or graphs which are given in an implicit way, 

   /// the implementation can be circumstantial, that is why this composes a 

   /// separate concept.

   class EdgeCountingGraphConcept : virtual public GraphConcept

   {

   public:

     /// Returns the number of edges.

     int edgeNum() const { return 0; }

   };

   class FullFeatureGraphConcept : virtual public NodeIterableGraphConcept,

 				  virtual public EdgeIterableGraphConcept, 

 				  virtual public OutEdgeIterableGraphConcept, 

 				  virtual public InEdgeIterableGraphConcept, 

 				  virtual public NodeCountingGraphConcept {

   public:

     FullFeatureGraphConcept() { }

     using EdgeIterableGraphConcept::next;

     using NodeIterableGraphConcept::next;

     using OutEdgeIterableGraphConcept::next;    

     using InEdgeIterableGraphConcept::next;

   };

   /// @}

 } //namespace lemon

 // class EmptyBipGraph : public Graph Concept

 // {

 //   class ANode {};

 //   class BNode {};

 //   ANode &next(ANode &) {}

 //   BNode &next(BNode &) {}

 //   ANode &getFirst(ANode &) const {}

 //   BNode &getFirst(BNode &) const {}

 //   enum NodeClass { A = 0, B = 1 };

 //   NodeClass getClass(Node n) {}

 // }

 #endif // LEMON_GRAPH_H