/* -*- C++ -*-

  *

  * src/lemon/undir_graph_extender.h - Part of LEMON, a generic C++

  * optimization library

  *

  * Copyright (C) 2004 Egervary Jeno Kombinatorikus Optimalizalasi

  * Kutatocsoport (Egervary Combinatorial Optimization Research Group,

  * EGRES).

  *

  * Permission to use, modify and distribute this software is granted

  * provided that this copyright notice appears in all copies. For

  * precise terms see the accompanying LICENSE file.

  *

  * This software is provided "AS IS" with no warranty of any kind,

  * express or implied, and with no claim as to its suitability for any

  * purpose.

  *

  */

 #ifndef LEMON_UNDIR_GRAPH_EXTENDER_H

 #define LEMON_UNDIR_GRAPH_EXTENDER_H

 #include <lemon/invalid.h>

 namespace lemon {

   template <typename _Base>

   class UndirGraphExtender : public _Base {

     typedef _Base Parent;

     typedef UndirGraphExtender Graph;

   public:

     typedef typename Parent::Edge UndirEdge;

     typedef typename Parent::Node Node;

     class Edge : public UndirEdge {

       friend class UndirGraphExtender;

     protected:

       // FIXME: Marci use opposite logic in his graph wrappers. It would

       // be reasonable to syncronize...

       bool forward;

     public:

       Edge() {}

       /// Construct a direct edge from undirect edge and a direction.

       Edge(const UndirEdge &ue, bool _forward) :

 	UndirEdge(ue), forward(_forward) {}

       /// Invalid edge constructor

       Edge(Invalid i) : UndirEdge(i), forward(false) {}

       bool operator==(const Edge &that) const {

 	return forward==that.forward && UndirEdge(*this)==UndirEdge(that);

       }

       bool operator!=(const Edge &that) const {

 	return forward!=that.forward || UndirEdge(*this)!=UndirEdge(that);

       }

       bool operator<(const Edge &that) const {

 	return forward<that.forward ||

 	  (!(that.forward<forward) && UndirEdge(*this)<UndirEdge(that));

       }

     };

     /// \brief Returns the Edge of opposite direction.

     ///

     /// \bug Is this a good name for this? Or "reverse" is better?

     Edge opposite(const Edge &e) const {

       return Edge(e,!e.forward);

     }

     /// Source of the given Edge.

     Node source(const Edge &e) const {

       return e.forward ? Parent::source(e) : Parent::target(e);

     }

     /// \todo Shouldn't the "source" of an undirected edge be called "aNode"

     /// or something???

     using Parent::source;

     /// Target of the given Edge.

     Node target(const Edge &e) const {

       return e.forward ? Parent::target(e) : Parent::source(e);

     }

     /// \todo Shouldn't the "target" of an undirected edge be called "bNode"

     /// or something???

     using Parent::target;

     /// Returns whether the given directed edge is same orientation as the

     /// corresponding undirected edge.

     ///

     /// \todo reference to the corresponding point of the undirected graph

     /// concept. "What does the direction of an undirected edge mean?"

     bool forward(const Edge &e) const { return e.forward; }

     Node oppsiteNode(const Node &n, const Edge &e) const {

       if( n == Parent::source(e))

 	return Parent::target(e);

       else if( n == Parent::target(e))

 	return Parent::source(e);

       else

 	return INVALID;

     }

     using Parent::first;

     void first(Edge &e) const {

       Parent::first(e);

       e.forward=true;

     }

     using Parent::next;

     void next(Edge &e) const {

       if( e.forward ) {

 	e.forward = false;

       }

       else {

 	Parent::next(e);

 	e.forward = true;

       }

     }

     void firstOut(Edge &e, const Node &n) const {

       Parent::firstOut(e,n);

       if( UndirEdge(e) != INVALID ) {

 	e.forward = true;

       }

       else {

 	Parent::firstIn(e,n);

 	e.forward = false;

       }

     }

     void firstIn(Edge &e, const Node &n) const {

       Parent::firstIn(e,n);

       if( UndirEdge(e) != INVALID ) {

 	e.forward = true;

       }

       else {

 	Parent::firstOut(e,n);

 	e.forward = false;

       }

     }

     void nextOut(Edge &e) const {

       if( e.forward ) {

 	Parent::nextOut(e);

 	if( UndirEdge(e) == INVALID ) {

 	  Parent::firstIn(e, Parent::source(e));

 	  e.forward = false;

 	}

       }

       else {

 	Parent::nextIn(e);

       }

     }

     void nextIn(Edge &e) const {

       if( e.forward ) {

 	Parent::nextIn(e);

 	if( UndirEdge(e) == INVALID ) {

 	  Parent::firstOut(e, Parent::target(e));

 	  e.forward = false;

 	}

       }

       else {

 	Parent::nextOut(e);

       }

     }

     // Miscellaneous stuff:

     /// \todo these methods (id, maxEdgeId) should be moved into separate

     /// Extender

     using Parent::id;

     int id(const Edge &e) const {

       return 2 * Parent::id(e) + int(e.forward);

     }

     int maxId(Edge = INVALID) const {

       return 2 * Parent::maxId(typename Parent::Edge()) + 1;

     }

     int maxId(UndirEdge = INVALID) const {

       return Parent::maxId(typename Parent::Edge());

     }

   };

 }

 #endif // LEMON_UNDIR_GRAPH_EXTENDER_H