/* -*- mode: C++; indent-tabs-mode: nil; -*-

  *

  * This file is a part of LEMON, a generic C++ optimization library.

  *

  * Copyright (C) 2003-2009

  * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport

  * (Egervary Research Group on Combinatorial Optimization, 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.

  *

  */

 ///\ingroup concept

 ///\file

 ///\brief Classes for representing paths in digraphs.

 ///

 #ifndef LEMON_CONCEPTS_PATH_H

 #define LEMON_CONCEPTS_PATH_H

 #include <lemon/core.h>

 #include <lemon/concept_check.h>

 namespace lemon {

   namespace concepts {

     /// \addtogroup concept

     /// @{

     /// \brief A skeleton structure for representing directed paths in

     /// a digraph.

     ///

     /// A skeleton structure for representing directed paths in a

     /// digraph.

     /// \tparam GR The digraph type in which the path is.

     ///

     /// In a sense, the path can be treated as a list of arcs. The

     /// lemon path type stores just this list. As a consequence it

     /// cannot enumerate the nodes in the path and the zero length

     /// paths cannot store the source.

     ///

     template <typename GR>

     class Path {

     public:

       /// Type of the underlying digraph.

       typedef GR Digraph;

       /// Arc type of the underlying digraph.

       typedef typename Digraph::Arc Arc;

       class ArcIt;

       /// \brief Default constructor

       Path() {}

       /// \brief Template constructor

       template <typename CPath>

       Path(const CPath& cpath) {}

       /// \brief Template assigment

       template <typename CPath>

       Path& operator=(const CPath& cpath) {

         ::lemon::ignore_unused_variable_warning(cpath);

         return *this;

       }

       /// Length of the path ie. the number of arcs in the path.

       int length() const { return 0;}

       /// Returns whether the path is empty.

       bool empty() const { return true;}

       /// Resets the path to an empty path.

       void clear() {}

       /// \brief LEMON style iterator for path arcs

       ///

       /// This class is used to iterate on the arcs of the paths.

       class ArcIt {

       public:

         /// Default constructor

         ArcIt() {}

         /// Invalid constructor

         ArcIt(Invalid) {}

         /// Constructor for first arc

         ArcIt(const Path &) {}

         /// Conversion to Arc

         operator Arc() const { return INVALID; }

         /// Next arc

         ArcIt& operator++() {return *this;}

         /// Comparison operator

         bool operator==(const ArcIt&) const {return true;}

         /// Comparison operator

         bool operator!=(const ArcIt&) const {return true;}

         /// Comparison operator

         bool operator<(const ArcIt&) const {return false;}

       };

       template <typename _Path>

       struct Constraints {

         void constraints() {

           Path<Digraph> pc;

           _Path p, pp(pc);

           int l = p.length();

           int e = p.empty();

           p.clear();

           p = pc;

           typename _Path::ArcIt id, ii(INVALID), i(p);

           ++i;

           typename Digraph::Arc ed = i;

           e = (i == ii);

           e = (i != ii);

           e = (i < ii);

           ::lemon::ignore_unused_variable_warning(l);

           ::lemon::ignore_unused_variable_warning(pp);

           ::lemon::ignore_unused_variable_warning(e);

           ::lemon::ignore_unused_variable_warning(id);

           ::lemon::ignore_unused_variable_warning(ii);

           ::lemon::ignore_unused_variable_warning(ed);

         }

       };

     };

     namespace _path_bits {

       template <typename _Digraph, typename _Path, typename RevPathTag = void>

       struct PathDumperConstraints {

         void constraints() {

           int l = p.length();

           int e = p.empty();

           typename _Path::ArcIt id, i(p);

           ++i;

           typename _Digraph::Arc ed = i;

           e = (i == INVALID);

           e = (i != INVALID);

           ::lemon::ignore_unused_variable_warning(l);

           ::lemon::ignore_unused_variable_warning(e);

           ::lemon::ignore_unused_variable_warning(id);

           ::lemon::ignore_unused_variable_warning(ed);

         }

         _Path& p;

         PathDumperConstraints() {}

       };

       template <typename _Digraph, typename _Path>

       struct PathDumperConstraints<

         _Digraph, _Path,

         typename enable_if<typename _Path::RevPathTag, void>::type

       > {

         void constraints() {

           int l = p.length();

           int e = p.empty();

           typename _Path::RevArcIt id, i(p);

           ++i;

           typename _Digraph::Arc ed = i;

           e = (i == INVALID);

           e = (i != INVALID);

           ::lemon::ignore_unused_variable_warning(l);

           ::lemon::ignore_unused_variable_warning(e);

           ::lemon::ignore_unused_variable_warning(id);

           ::lemon::ignore_unused_variable_warning(ed);

         }

         _Path& p;

         PathDumperConstraints() {}

       };

     }

     /// \brief A skeleton structure for path dumpers.

     ///

     /// A skeleton structure for path dumpers. The path dumpers are

     /// the generalization of the paths. The path dumpers can

     /// enumerate the arcs of the path wheter in forward or in

     /// backward order.  In most time these classes are not used

     /// directly rather it used to assign a dumped class to a real

     /// path type.

     ///

     /// The main purpose of this concept is that the shortest path

     /// algorithms can enumerate easily the arcs in reverse order.

     /// If we would like to give back a real path from these

     /// algorithms then we should create a temporarly path object. In

     /// LEMON such algorithms gives back a path dumper what can

     /// assigned to a real path and the dumpers can be implemented as

     /// an adaptor class to the predecessor map.

     ///

     /// \tparam GR The digraph type in which the path is.

     ///

     /// The paths can be constructed from any path type by a

     /// template constructor or a template assignment operator.

     template <typename GR>

     class PathDumper {

     public:

       /// Type of the underlying digraph.

       typedef GR Digraph;

       /// Arc type of the underlying digraph.

       typedef typename Digraph::Arc Arc;

       /// Length of the path ie. the number of arcs in the path.

       int length() const { return 0;}

       /// Returns whether the path is empty.

       bool empty() const { return true;}

       /// \brief Forward or reverse dumping

       ///

       /// If the RevPathTag is defined and true then reverse dumping

       /// is provided in the path dumper. In this case instead of the

       /// ArcIt the RevArcIt iterator should be implemented in the

       /// dumper.

       typedef False RevPathTag;

       /// \brief LEMON style iterator for path arcs

       ///

       /// This class is used to iterate on the arcs of the paths.

       class ArcIt {

       public:

         /// Default constructor

         ArcIt() {}

         /// Invalid constructor

         ArcIt(Invalid) {}

         /// Constructor for first arc

         ArcIt(const PathDumper&) {}

         /// Conversion to Arc

         operator Arc() const { return INVALID; }

         /// Next arc

         ArcIt& operator++() {return *this;}

         /// Comparison operator

         bool operator==(const ArcIt&) const {return true;}

         /// Comparison operator

         bool operator!=(const ArcIt&) const {return true;}

         /// Comparison operator

         bool operator<(const ArcIt&) const {return false;}

       };

       /// \brief LEMON style iterator for path arcs

       ///

       /// This class is used to iterate on the arcs of the paths in

       /// reverse direction.

       class RevArcIt {

       public:

         /// Default constructor

         RevArcIt() {}

         /// Invalid constructor

         RevArcIt(Invalid) {}

         /// Constructor for first arc

         RevArcIt(const PathDumper &) {}

         /// Conversion to Arc

         operator Arc() const { return INVALID; }

         /// Next arc

         RevArcIt& operator++() {return *this;}

         /// Comparison operator

         bool operator==(const RevArcIt&) const {return true;}

         /// Comparison operator

         bool operator!=(const RevArcIt&) const {return true;}

         /// Comparison operator

         bool operator<(const RevArcIt&) const {return false;}

       };

       template <typename _Path>

       struct Constraints {

         void constraints() {

           function_requires<_path_bits::

             PathDumperConstraints<Digraph, _Path> >();

         }

       };

     };

     ///@}

   }

 } // namespace lemon

 #endif