/* -*- 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