/* -*- 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) {

        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);

          ignore_unused_variable_warning(l);

          ignore_unused_variable_warning(pp);

          ignore_unused_variable_warning(e);

          ignore_unused_variable_warning(id);

          ignore_unused_variable_warning(ii);

          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);

          ignore_unused_variable_warning(l);

          ignore_unused_variable_warning(e);

          ignore_unused_variable_warning(id);

          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);

          ignore_unused_variable_warning(l);

          ignore_unused_variable_warning(e);

          ignore_unused_variable_warning(id);

          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