/* -*- 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 The concept of paths

 ///

 #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.

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

     /// LEMON path types just store this list. As a consequence, they cannot

     /// enumerate the nodes on the path directly and a zero length path

     /// cannot store its source node.

     ///

     /// The arcs of a path should be stored in the order of their directions,

     /// i.e. the target node of each arc should be the same as the source

     /// node of the next arc. This consistency could be checked using

     /// \ref checkPath().

     /// The source and target nodes of a (consistent) path can be obtained

     /// using \ref pathSource() and \ref pathTarget().

     ///

     /// A path can be constructed from another path of any type using the

     /// copy constructor or the assignment operator.

     ///

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

     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 copy constructor

       template <typename CPath>

       Path(const CPath& cpath) {}

       /// \brief Template assigment operator

       template <typename CPath>

       Path& operator=(const CPath& cpath) {

         ::lemon::ignore_unused_variable_warning(cpath);

         return *this;

       }

       /// Length of the path, i.e. the number of arcs on 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 enumerating the arcs of a path.

       ///

       /// LEMON style iterator class for enumerating the arcs of a path.

       class ArcIt {

       public:

         /// Default constructor

         ArcIt() {}

         /// Invalid constructor

         ArcIt(Invalid) {}

         /// Sets the iterator to the first arc of the given path

         ArcIt(const Path &) {}

         /// Conversion to \c 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, they can enumerate the arcs

     /// of the path either in forward or in backward order.

     /// These classes are typically not used directly, they are rather

     /// used to be assigned to a real path type.

     ///

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

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

     /// In LEMON, such algorithms give back a (reverse) path dumper that

     /// can be assigned to a real path. The dumpers can be implemented as

     /// an adaptor class to the predecessor map.

     ///

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

     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, i.e. the number of arcs on the path.

       int length() const { return 0;}

       /// Returns whether the path is empty.

       bool empty() const { return true;}

       /// \brief Forward or reverse dumping

       ///

       /// If this tag is defined to be \c True, then reverse dumping

       /// is provided in the path dumper. In this case, \c RevArcIt

       /// iterator should be implemented instead of \c ArcIt iterator.

       typedef False RevPathTag;

       /// \brief LEMON style iterator for enumerating the arcs of a path.

       ///

       /// LEMON style iterator class for enumerating the arcs of a path.

       class ArcIt {

       public:

         /// Default constructor

         ArcIt() {}

         /// Invalid constructor

         ArcIt(Invalid) {}

         /// Sets the iterator to the first arc of the given path

         ArcIt(const PathDumper&) {}

         /// Conversion to \c 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 enumerating the arcs of a path

       /// in reverse direction.

       ///

       /// LEMON style iterator class for enumerating the arcs of a path

       /// in reverse direction.

       class RevArcIt {

       public:

         /// Default constructor

         RevArcIt() {}

         /// Invalid constructor

         RevArcIt(Invalid) {}

         /// Sets the iterator to the last arc of the given path

         RevArcIt(const PathDumper &) {}

         /// Conversion to \c 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