// -*- c++ -*-

#ifndef HUGO_EMPTYGRAPH_H

#define HUGO_EMPTYGRAPH_H

#include <invalid.h>

/// The namespace of HugoLib

namespace hugo {

  // @defgroup empty_graph The GraphSkeleton class

  // @{

  /// An empty graph class.

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

  /// however completely without implementations or 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 GraphSkeleton

  {

  public:

    /// The base type of the node iterators.

    /// This \c Node is the base type of each node iterators,

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

    class Node {

    public:

      /// @warning The default constructor sets the iterator

      /// to an undefined value.

      Node() {}   //FIXME

      /// Invalid constructor \& conversion.

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

      /// \sa Invalid for more details.

      Node(Invalid) {}

      //Node(const Node &) {}

      /// 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; }

    };

    /// This iterator goes through each node.

    class NodeIt : public Node {

    public:

      /// @warning The default constructor sets the iterator

      /// to an undefined value.

      NodeIt() {} //FIXME

      /// Invalid constructor \& conversion.

      /// Initialize the iterator to be invalid

      /// \sa Invalid for more details.

      NodeIt(Invalid) {}

      /// Sets the iterator to the first node of \c G.

      NodeIt(const GraphSkeleton &G) {}

      /// @warning The default constructor sets the iterator

      /// to an undefined value.

      NodeIt(const NodeIt &) {}

    };

    /// The base type of the edge iterators.

    class Edge {

    public:

      /// @warning The default constructor sets the iterator

      /// to an undefined value.

      Edge() {}   //FIXME

      /// Initialize the iterator to be invalid

      Edge(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; }

    };

    /// This iterator goes trought the outgoing edges of a certain graph.

    class OutEdgeIt : public Edge {

    public:

      /// @warning The default constructor sets the iterator

      /// to an undefined value.

      OutEdgeIt() {}

      /// Initialize the iterator to be invalid

      OutEdgeIt(Invalid) {}

      /// 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 GraphSkeleton & G, Node n) {}

    };

    class InEdgeIt : public Edge {

    public:

      /// @warning The default constructor sets the iterator

      /// to an undefined value.

      InEdgeIt() {}

      /// Initialize the iterator to be invalid

      InEdgeIt(Invalid) {}

      InEdgeIt(const GraphSkeleton &, Node) {}    

    };

    //  class SymEdgeIt : public Edge {};

    class EdgeIt : public Edge {

    public:

      /// @warning The default constructor sets the iterator

      /// to an undefined value.

      EdgeIt() {}

      /// Initialize the iterator to be invalid

      EdgeIt(Invalid) {}

      EdgeIt(const GraphSkeleton &) {}

    };

    /// First node of the graph.

    /// \post \c i and the return value will be the first node.

    ///

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

    /// The first outgoing edge.

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

    /// The first incoming edge.

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

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

    /// The first edge of the Graph.

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

//     Node getNext(Node) const {}

//     InEdgeIt getNext(InEdgeIt) const {}

//     OutEdgeIt getNext(OutEdgeIt) const {}

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

//     EdgeIt getNext(EdgeIt) const {}

    /// Go to the next node.

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

    /// Go to the next incoming edge.

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

    /// Go to the next outgoing edge.

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

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

    /// Go to the next edge.

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

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

    Node head(Edge) const { return INVALID; }

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

    Node tail(Edge) const { return INVALID; }

    //   Node aNode(InEdgeIt) const {}

    //   Node aNode(OutEdgeIt) const {}

    //   Node aNode(SymEdgeIt) const {}

    //   Node bNode(InEdgeIt) const {}

    //   Node bNode(OutEdgeIt) const {}

    //   Node bNode(SymEdgeIt) const {}

    /// Checks if a node iterator is valid

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

    /// Checks if an edge iterator is valid

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

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

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

    ///

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

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

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

    ///

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

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

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

    ///Add a new node to the graph.

    /// \return the new node.

    Node addNode() { return INVALID;}

    ///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(Node tail, Node head) { return INVALID;}

    /// Deletes a node.

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

    ///

    void erase(Node n) {}

    /// Deletes an edge.

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

    ///

    void erase(Edge e) {}

    /// Reset the graph.

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

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

    void clear() {}

    int nodeNum() const { return 0;}

    int edgeNum() const { return 0;}

    GraphSkeleton() {}

    GraphSkeleton(const GraphSkeleton &G) {}

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

    /// \todo We may need copy constructor

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

    /// \todo We may need operator=

    template<class T> class NodeMap

    {

    public:

      typedef T ValueType;

      typedef Node KeyType;

      NodeMap(const GraphSkeleton &G) {}

      NodeMap(const GraphSkeleton &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 map of the edges to type \c T.

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

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

    template<class T> class EdgeMap

    {

    public:

      typedef T ValueType;

      typedef Edge KeyType;

      EdgeMap(const GraphSkeleton &G) {}

      EdgeMap(const GraphSkeleton &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

    };

  };

  // @}

} //namespace hugo

// class EmptyBipGraph : public Graph Skeleton

// {

//   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 // HUGO_EMPTYGRAPH_H