/* -*- C++ -*-

  * src/lemon/notifier.h - Part of LEMON, a generic C++ optimization library

  *

  * Copyright (C) 2005 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_ALTERATION_OBSERVER_REGISTRY_H

 #define LEMON_ALTERATION_OBSERVER_REGISTRY_H

 #include <vector>

 #include <algorithm>

 ///\ingroup graphmaps

 ///\file

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

 namespace lemon {

   /// \addtogroup graphmaps

   /// @{

   /// Registry class to register objects observes alterations in the graph.

   /// This class is a registry for the objects which observe the

   /// alterations in a container. The alteration observers can be attached

   /// to and detached from the registry. The observers have to inherit

   /// from the \ref AlterationNotifier::ObserverBase and override

   /// the virtual functions in that.

   ///

   /// The most important application of the alteration observing is the

   /// dynamic map implementation when the observers are observing the

   /// alterations in the graph.

   ///

   /// \param _Item The item type what the observers are observing, usually

   /// edge or node.

   ///

   /// \author Balazs Dezso

   template <typename _Item>

   class AlterationNotifier {

   public:

     typedef _Item Item;

     /// 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. 

     /// 

     /// \author Balazs Dezso

     class ObserverBase {

     protected:

       typedef AlterationNotifier Registry;

       friend class AlterationNotifier;

       /// Default constructor.

       /// Default constructor for ObserverBase.

       /// 

       ObserverBase() : registry(0) {}

       virtual ~ObserverBase() {}

       /// Attaches the observer into an AlterationNotifier.

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

       ///

       void attach(AlterationNotifier& r) {

 	registry = &r;

 	registry->attach(*this);

       }

       /// Detaches the observer into an AlterationNotifier.

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

       ///

       void detach() {

 	if (registry) {

 	  registry->detach(*this);

 	}

       }

       /// Gives back a pointer to the registry what the map attached into.

       /// This function gives back a pointer to the registry what the map

       /// attached into.

       ///

       Registry* getRegistry() const { return const_cast<Registry*>(registry); }

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

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

     private:

       ObserverBase(const ObserverBase& copy);

       ObserverBase& operator=(const ObserverBase& copy);

     protected:

       Registry* registry;

       int registry_index;

     public:

       /// \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 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 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:

     typedef std::vector<ObserverBase*> Container; 

     Container container;

   public:

     /// Default constructor.

     ///

     /// The default constructor of the AlterationNotifier. 

     /// It creates an empty registry.

     AlterationNotifier() {}

     /// Copy Constructor of the AlterationNotifier. 

     /// Copy constructor of the AlterationNotifier. 

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

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

     AlterationNotifier(const AlterationNotifier&) {}

     /// Assign operator.

     /// Assign operator for the AlterationNotifier. 

     /// It makes the notifier only empty because the copiable

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

     AlterationNotifier& operator=(const AlterationNotifier&) {

       typename Container::iterator it;

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

 	(*it)->registry = 0;

       }

     }

     /// Destructor.

     /// Destructor of the AlterationNotifier.

     ///

     ~AlterationNotifier() {

       typename Container::iterator it;

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

 	(*it)->registry = 0;

       }

     }

   protected:

     void attach(ObserverBase& observer) {

       container.push_back(&observer);

       observer.registry = this;

       observer.registry_index = container.size()-1;

     } 

     void detach(ObserverBase& base) {

       container.back()->registry_index = base.registry_index; 

       container[base.registry_index] = container.back();

       container.pop_back();

       base.registry = 0;

     }

   public:

     /// Notifies all the registered observers about an Item added to the container.

     /// It notifies all the registered observers about an Item added to the container.

     /// 

     void add(const Item& key) {

       typename Container::iterator it;

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

 	(*it)->add(key);

       }

     }	

     /// Notifies all the registered observers about an Item erased from the container.

     /// It notifies all the registered observers about an Item erased from the container.

     /// 

     void erase(const Item& key) {

       typename Container::iterator it;

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

 	(*it)->erase(key);

       }

     }

     /// Notifies all the registered observers about the container is built.

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

     /// from an empty container.

     void build() {

       typename Container::iterator it;

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

 	(*it)->build();

       }

     }

     /// Notifies all the registered observers about all Items are erased.

     /// Notifies all the registered observers about all Items are erased

     /// from the container.

     void clear() {

       typename Container::iterator it;

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

 	(*it)->clear();

       }

     }

   };

   /// \brief Class to extend a graph with the functionality of alteration

   /// observing.

   ///

   /// AlterableGraphExtender extends the _Base graphs functionality with

   /// the possibility of alteration observing. It defines two observer

   /// registrys for the nodes and mapes.

   /// 

   /// \todo Document what "alteration observing" is. And probably find a

   /// better (shorter) name.

   ///

   /// \param _Base is the base class to extend.

   ///

   /// \pre _Base is conform to the BaseGraphComponent concept.

   ///

   /// \post AlterableGraphExtender<_Base> is conform to the

   /// AlterableGraphComponent concept.

   ///

   /// \author Balazs Dezso

   template <typename _Base> 

   class AlterableGraphExtender : public _Base {

   public:

     typedef AlterableGraphExtender Graph;

     typedef _Base Parent;

     typedef typename Parent::Node Node;

     typedef typename Parent::Edge Edge;

     /// The edge observer registry.

     typedef AlterationNotifier<Edge> EdgeNotifier;

     /// The node observer registry.

     typedef AlterationNotifier<Node> NodeNotifier;

   protected:

     mutable EdgeNotifier edge_notifier;

     mutable NodeNotifier node_notifier;

   public:

     /// \brief Gives back the edge alteration notifier.

     ///

     /// Gives back the edge alteration notifier.

     EdgeNotifier& getNotifier(Edge) const {

       return edge_notifier;

     }

     /// \brief Gives back the node alteration notifier.

     ///

     /// Gives back the node alteration notifier.

     NodeNotifier& getNotifier(Node) const {

       return node_notifier;

     }

     ~AlterableGraphExtender() {

       node_notifier.clear();

       edge_notifier.clear();

     }

   };

   /// \brief Class to extend an undirected graph with the functionality of

   /// alteration observing.

   ///

   /// \todo Document.

   ///

   /// \sa AlterableGraphExtender

   ///

   /// \bug This should be done some other way. Possibilities: template

   /// specialization (not very easy, if at all possible); some kind of

   /// enable_if boost technique?

   template <typename _Base> 

   class AlterableUndirGraphExtender

     : public AlterableGraphExtender<_Base> {

   public:

     typedef AlterableUndirGraphExtender Graph;

     typedef AlterableGraphExtender<_Base> Parent;

     typedef typename Parent::UndirEdge UndirEdge;

     /// The edge observer registry.

     typedef AlterationNotifier<UndirEdge> UndirEdgeNotifier;

   protected:

     mutable UndirEdgeNotifier undir_edge_notifier;

   public:

     using Parent::getNotifier;

     UndirEdgeNotifier& getNotifier(UndirEdge) const {

       return undir_edge_notifier;

     }

     ~AlterableUndirGraphExtender() {

       undir_edge_notifier.clear();

     }

   };

 /// @}

 }

 #endif