// -*- c++ -*-
#ifndef HUGO_GRAPH_H
#define HUGO_GRAPH_H

///\file
///\brief Declaration of GraphConcept.

#include <hugo/invalid.h>

namespace hugo {

  /// @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-eraseable graph concept.
  ///
  /// A graph class which provides a function to 
  /// delete any of its nodes.
  class NodeEraseableGraphConcept : virtual public GraphConcept
  {
  public:
    /// Deletes a node.
    void erase(const Node& n) { }
  };


  /// \brief Edge-eraseable graph concept.
  /// 
  /// A graph class which provides a function to delete any 
  /// of its edges.
  class EdgeEraseableGraphConcept : 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 : public NodeIterableGraphConcept,
				  public EdgeIterableGraphConcept, 
				  public OutEdgeIterableGraphConcept, 
				  public InEdgeIterableGraphConcept {
  public:
    FullFeatureGraphConcept() { }
  };
  
  /// @}

} //namespace hugo



// 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 // HUGO_GRAPH_H