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

  *

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

  *

  * Copyright (C) 2003-2008

  * 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.

  *

  */

 #ifndef LEMON_BITS_ALTERATION_NOTIFIER_H

 #define LEMON_BITS_ALTERATION_NOTIFIER_H

 #include <vector>

 #include <list>

 #include <lemon/bits/utility.h>

 ///\ingroup graphbits

 ///\file

 ///\brief Observer notifier for graph alteration observers.

 namespace lemon {

   /// \ingroup graphbits

   ///

   /// \brief Notifier class to notify observes about alterations in

   /// a container.

   ///

   /// The simple graph's can be refered as two containers, one node container

   /// and one edge container. But they are not standard containers they

   /// does not store values directly they are just key continars for more

   /// value containers which are the node and edge maps.

   ///

   /// The graph's node and edge sets can be changed as we add or erase

   /// nodes and edges in the graph. Lemon would like to handle easily

   /// that the node and edge maps should contain values for all nodes or

   /// edges. If we want to check on every indicing if the map contains

   /// the current indicing key that cause a drawback in the performance

   /// in the library. We use another solution we notify all maps about

   /// an alteration in the graph, which cause only drawback on the

   /// alteration of the graph.

   ///

   /// This class provides an interface to the container. The \e first() and \e

   /// next() member functions make possible to iterate on the keys of the

   /// container. The \e id() function returns an integer id for each key.

   /// The \e maxId() function gives back an upper bound of the ids.

   ///

   /// For the proper functonality of this class, we should notify it

   /// about each alteration in the container. The alterations have four type

   /// as \e add(), \e erase(), \e build() and \e clear(). The \e add() and

   /// \e erase() signals that only one or few items added or erased to or

   /// from the graph. If all items are erased from the graph or from an empty

   /// graph a new graph is builded then it can be signaled with the

   /// clear() and build() members. Important rule that if we erase items

   /// from graph we should first signal the alteration and after that erase

   /// them from the container, on the other way on item addition we should

   /// first extend the container and just after that signal the alteration.

   ///

   /// The alteration can be observed with a class inherited from the

   /// \e ObserverBase nested class. The signals can be handled with

   /// overriding the virtual functions defined in the base class.  The

   /// observer base can be attached to the notifier with the

   /// \e attach() member and can be detached with detach() function. The

   /// alteration handlers should not call any function which signals

   /// an other alteration in the same notifier and should not

   /// detach any observer from the notifier.

   ///

   /// Alteration observers try to be exception safe. If an \e add() or

   /// a \e clear() function throws an exception then the remaining

   /// observeres will not be notified and the fulfilled additions will

   /// be rolled back by calling the \e erase() or \e clear()

   /// functions. Thence the \e erase() and \e clear() should not throw

   /// exception. Actullay, it can be throw only

   /// \ref AlterationObserver::ImmediateDetach ImmediateDetach

   /// exception which detach the observer from the notifier.

   ///

   /// There are some place when the alteration observing is not completly

   /// reliable. If we want to carry out the node degree in the graph

   /// as in the \ref InDegMap and we use the reverseEdge that cause

   /// unreliable functionality. Because the alteration observing signals

   /// only erasing and adding but not the reversing it will stores bad

   /// degrees. The sub graph adaptors cannot signal the alterations because

   /// just a setting in the filter map can modify the graph and this cannot

   /// be watched in any way.

   ///

   /// \param _Container The container which is observed.

   /// \param _Item The item type which is obserbved.

   template <typename _Container, typename _Item>

   class AlterationNotifier {

   public:

     typedef True Notifier;

     typedef _Container Container;

     typedef _Item Item;

     /// \brief Exception which can be called from \e clear() and

     /// \e erase().

     ///

     /// From the \e clear() and \e erase() function only this

     /// exception is allowed to throw. The exception immediatly

     /// detaches the current observer from the notifier. Because the

     /// \e clear() and \e erase() should not throw other exceptions

     /// it can be used to invalidate the observer.

     struct ImmediateDetach {};

     /// \brief ObserverBase is the base class for the observers.

     ///

     /// ObserverBase is the abstract base class for the observers.

     /// It will be notified about an item was inserted into or

     /// erased from the graph.

     ///

     /// The observer interface contains some pure virtual functions

     /// to override. The add() and erase() functions are

     /// to notify the oberver when one item is added or

     /// erased.

     ///

     /// The build() and clear() members are to notify the observer

     /// about the container is built from an empty container or

     /// is cleared to an empty container.

     class ObserverBase {

     protected:

       typedef AlterationNotifier Notifier;

       friend class AlterationNotifier;

       /// \brief Default constructor.

       ///

       /// Default constructor for ObserverBase.

       ///

       ObserverBase() : _notifier(0) {}

       /// \brief Constructor which attach the observer into notifier.

       ///

       /// Constructor which attach the observer into notifier.

       ObserverBase(AlterationNotifier& nf) {

         attach(nf);

       }

       /// \brief Constructor which attach the obserever to the same notifier.

       ///

       /// Constructor which attach the obserever to the same notifier as

       /// the other observer is attached to.

       ObserverBase(const ObserverBase& copy) {

         if (copy.attached()) {

           attach(*copy.notifier());

         }

       }

       /// \brief Destructor

       virtual ~ObserverBase() {

         if (attached()) {

           detach();

         }

       }

       /// \brief Attaches the observer into an AlterationNotifier.

       ///

       /// This member attaches the observer into an AlterationNotifier.

       ///

       void attach(AlterationNotifier& nf) {

         nf.attach(*this);

       }

       /// \brief Detaches the observer into an AlterationNotifier.

       ///

       /// This member detaches the observer from an AlterationNotifier.

       ///

       void detach() {

         _notifier->detach(*this);

       }

       /// \brief Gives back a pointer to the notifier which the map

       /// attached into.

       ///

       /// This function gives back a pointer to the notifier which the map

       /// attached into.

       ///

       Notifier* notifier() const { return const_cast<Notifier*>(_notifier); }

       /// Gives back true when the observer is attached into a notifier.

       bool attached() const { return _notifier != 0; }

     private:

       ObserverBase& operator=(const ObserverBase& copy);

     protected:

       Notifier* _notifier;

       typename std::list<ObserverBase*>::iterator _index;

       /// \brief The member function to notificate the observer about an

       /// item is added to the container.

       ///

       /// The add() member function notificates the observer about an item

       /// is added to the container. It have to be overrided in the

       /// subclasses.

       virtual void add(const Item&) = 0;

       /// \brief The member function to notificate the observer about

       /// more item is added to the container.

       ///

       /// The add() member function notificates the observer about more item

       /// is added to the container. It have to be overrided in the

       /// subclasses.

       virtual void add(const std::vector<Item>& items) = 0;

       /// \brief The member function to notificate the observer about an

       /// item is erased from the container.

       ///

       /// The erase() member function notificates the observer about an

       /// item is erased from the container. It have to be overrided in

       /// the subclasses.

       virtual void erase(const Item&) = 0;

       /// \brief The member function to notificate the observer about

       /// more item is erased from the container.

       ///

       /// The erase() member function notificates the observer about more item

       /// is erased from the container. It have to be overrided in the

       /// subclasses.

       virtual void erase(const std::vector<Item>& items) = 0;

       /// \brief The member function to notificate the observer about the

       /// container is built.

       ///

       /// The build() member function notificates the observer about the

       /// container is built from an empty container. It have to be

       /// overrided in the subclasses.

       virtual void build() = 0;

       /// \brief The member function to notificate the observer about all

       /// items are erased from the container.

       ///

       /// The clear() member function notificates the observer about all

       /// items are erased from the container. It have to be overrided in

       /// the subclasses.

       virtual void clear() = 0;

     };

   protected:

     const Container* container;

     typedef std::list<ObserverBase*> Observers;

     Observers _observers;

   public:

     /// \brief Default constructor.

     ///

     /// The default constructor of the AlterationNotifier.

     /// It creates an empty notifier.

     AlterationNotifier()

       : container(0) {}

     /// \brief Constructor.

     ///

     /// Constructor with the observed container parameter.

     AlterationNotifier(const Container& _container)

       : container(&_container) {}

     /// \brief Copy Constructor of the AlterationNotifier.

     ///

     /// Copy constructor of the AlterationNotifier.

     /// It creates only an empty notifier because the copiable

     /// notifier's observers have to be registered still into that notifier.

     AlterationNotifier(const AlterationNotifier& _notifier)

       : container(_notifier.container) {}

     /// \brief Destructor.

     ///

     /// Destructor of the AlterationNotifier.

     ///

     ~AlterationNotifier() {

       typename Observers::iterator it;

       for (it = _observers.begin(); it != _observers.end(); ++it) {

         (*it)->_notifier = 0;

       }

     }

     /// \brief Sets the container.

     ///

     /// Sets the container.

     void setContainer(const Container& _container) {

       container = &_container;

     }

   protected:

     AlterationNotifier& operator=(const AlterationNotifier&);

   public:

     /// \brief First item in the container.

     ///

     /// Returns the first item in the container. It is

     /// for start the iteration on the container.

     void first(Item& item) const {

       container->first(item);

     }

     /// \brief Next item in the container.

     ///

     /// Returns the next item in the container. It is

     /// for iterate on the container.

     void next(Item& item) const {

       container->next(item);

     }

     /// \brief Returns the id of the item.

     ///

     /// Returns the id of the item provided by the container.

     int id(const Item& item) const {

       return container->id(item);

     }

     /// \brief Returns the maximum id of the container.

     ///

     /// Returns the maximum id of the container.

     int maxId() const {

       return container->maxId(Item());

     }

   protected:

     void attach(ObserverBase& observer) {

       observer._index = _observers.insert(_observers.begin(), &observer);

       observer._notifier = this;

     }

     void detach(ObserverBase& observer) {

       _observers.erase(observer._index);

       observer._index = _observers.end();

       observer._notifier = 0;

     }

   public:

     /// \brief Notifies all the registed observers about an item added to

     /// the container.

     ///

     /// It notifies all the registed observers about an item added to

     /// the container.

     ///

     void add(const Item& item) {

       typename Observers::reverse_iterator it;

       try {

         for (it = _observers.rbegin(); it != _observers.rend(); ++it) {

           (*it)->add(item);

         }

       } catch (...) {

         typename Observers::iterator jt;

         for (jt = it.base(); jt != _observers.end(); ++jt) {

           (*jt)->erase(item);

         }

         throw;

       }

     }

     /// \brief Notifies all the registed observers about more item added to

     /// the container.

     ///

     /// It notifies all the registed observers about more item added to

     /// the container.

     ///

     void add(const std::vector<Item>& items) {

       typename Observers::reverse_iterator it;

       try {

         for (it = _observers.rbegin(); it != _observers.rend(); ++it) {

           (*it)->add(items);

         }

       } catch (...) {

         typename Observers::iterator jt;

         for (jt = it.base(); jt != _observers.end(); ++jt) {

           (*jt)->erase(items);

         }

         throw;

       }

     }

     /// \brief Notifies all the registed observers about an item erased from

     /// the container.

     ///

     /// It notifies all the registed observers about an item erased from

     /// the container.

     ///

     void erase(const Item& item) throw() {

       typename Observers::iterator it = _observers.begin();

       while (it != _observers.end()) {

         try {

           (*it)->erase(item);

           ++it;

         } catch (const ImmediateDetach&) {

           it = _observers.erase(it);

           (*it)->_index = _observers.end();

           (*it)->_notifier = 0;

         }

       }

     }

     /// \brief Notifies all the registed observers about more item erased

     /// from the container.

     ///

     /// It notifies all the registed observers about more item erased from

     /// the container.

     ///

     void erase(const std::vector<Item>& items) {

       typename Observers::iterator it = _observers.begin();

       while (it != _observers.end()) {

         try {

           (*it)->erase(items);

           ++it;

         } catch (const ImmediateDetach&) {

           it = _observers.erase(it);

           (*it)->_index = _observers.end();

           (*it)->_notifier = 0;

         }

       }

     }

     /// \brief Notifies all the registed observers about the container is

     /// built.

     ///

     /// Notifies all the registed observers about the container is built

     /// from an empty container.

     void build() {

       typename Observers::reverse_iterator it;

       try {

         for (it = _observers.rbegin(); it != _observers.rend(); ++it) {

           (*it)->build();

         }

       } catch (...) {

         typename Observers::iterator jt;

         for (jt = it.base(); jt != _observers.end(); ++jt) {

           (*jt)->clear();

         }

         throw;

       }

     }

     /// \brief Notifies all the registed observers about all items are

     /// erased.

     ///

     /// Notifies all the registed observers about all items are erased

     /// from the container.

     void clear() {

       typename Observers::iterator it = _observers.begin();

       while (it != _observers.end()) {

         try {

           (*it)->clear();

           ++it;

         } catch (const ImmediateDetach&) {

           it = _observers.erase(it);

           (*it)->_index = _observers.end();

           (*it)->_notifier = 0;

         }

       }

     }

   };

 }

 #endif