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// Copyright (C) 2004, 2006 International Business Machines and others.
// All Rights Reserved.
// This code is published under the Common Public License.
//
// $Id: IpObserver.hpp 1019 2007-06-24 03:52:34Z andreasw $
//
// Authors:  Carl Laird, Andreas Waechter     IBM    2004-08-13

#ifndef __IPOBSERVER_HPP__
#define __IPOBSERVER_HPP__

#include "IpUtils.hpp"
#include <vector>
#include <algorithm>

//#define IP_DEBUG_OBSERVER
#if COIN_IPOPT_CHECKLEVEL > 2
# define IP_DEBUG_OBSERVER
#endif
#ifdef IP_DEBUG_OBSERVER
# include "IpDebug.hpp"
#endif

namespace Ipopt
{
  class Subject;

  class Observer
  {
  public:
#ifdef IP_DEBUG_OBSERVER

    static const Index dbg_verbosity;
#endif

    Observer()
    {}

    virtual ~Observer();

    enum NotifyType
    {
      NT_All,
      NT_BeingDestroyed,
      NT_Changed
    };

  protected:
    void RequestAttach(NotifyType notify_type, const Subject* subject);

    void RequestDetach(NotifyType notify_type, const Subject* subject);

    virtual void RecieveNotification(NotifyType notify_type, const Subject* subject)=0;

  private:
    Observer(const Observer&);

    void operator=(const Observer&);

    std::vector<const Subject*> subjects_;

    void ProcessNotification(NotifyType notify_type, const Subject* subject);

    friend class Subject;
  };

  class Subject
  {
  public:
#ifdef IP_DEBUG_OBSERVER

    static const Index dbg_verbosity;
#endif

    Subject()
    {}

    virtual ~Subject();


    void AttachObserver(Observer::NotifyType notify_type, Observer* observer) const;

    void DetachObserver(Observer::NotifyType notify_type, Observer* observer) const;

  protected:

    void Notify(Observer::NotifyType notify_type) const;

  private:
    Subject(const Subject&);

    void operator=(const Subject&);

    mutable std::vector<Observer*> observers_;

  };

  /* inline methods */
  inline
  Observer::~Observer()
  {
#ifdef IP_DEBUG_OBSERVER
    DBG_START_METH("Observer::~Observer", dbg_verbosity);
    if (DBG_VERBOSITY()>=1) {
      for (Index i=0; i<(Index)subjects_.size(); i++) {
        DBG_PRINT((1,"subjects_[%d] = 0x%x\n", i, subjects_[i]));
      }
    }
#endif
    // Detach all subjects
    for (Int i=(Int)(subjects_.size()-1); i>=0; i--) {
#ifdef IP_DEBUG_OBSERVER
      DBG_PRINT((1,"About to detach subjects_[%d] = 0x%x\n", i, subjects_[i]));
#endif

      RequestDetach(NT_All, subjects_[i]);
    }
  }

  inline
  void Observer::RequestAttach(NotifyType notify_type, const Subject* subject)
  {
#ifdef IP_DEBUG_OBSERVER
    DBG_START_METH("Observer::RequestAttach", dbg_verbosity);

    // Add the subject to the list if it does not already exist
    std::vector<const Subject*>::iterator attached_subject;
    attached_subject = std::find(subjects_.begin(), subjects_.end(), subject);
    DBG_ASSERT(attached_subject == subjects_.end());
    DBG_ASSERT(subject);
#endif

    // add the subject to the list
    subjects_.push_back(subject);
    // Attach the observer to the subject
    subject->AttachObserver(notify_type, this);
  }

  inline
  void Observer::RequestDetach(NotifyType notify_type, const Subject* subject)
  {
#ifdef IP_DEBUG_OBSERVER
    DBG_START_METH("Observer::RequestDetach", dbg_verbosity);
    DBG_PRINT((1, "Requesting detach of subject: 0x%x\n", subject));
    DBG_ASSERT(subject);
#endif

    if (subject) {
      std::vector<const Subject*>::iterator attached_subject;
      attached_subject = std::find(subjects_.begin(), subjects_.end(), subject);
#ifdef IP_DEBUG_OBSERVER

      DBG_ASSERT(attached_subject != subjects_.end());
#endif

      if (attached_subject != subjects_.end()) {
#ifdef IP_DEBUG_OBSERVER
        DBG_PRINT((1, "Removing subject: 0x%x from the list\n", subject));
#endif

        subjects_.erase(attached_subject);
      }

      // Detach the observer from the subject
      subject->DetachObserver(notify_type, this);
    }
  }

  inline
  void Observer::ProcessNotification(NotifyType notify_type, const Subject* subject)
  {
#ifdef IP_DEBUG_OBSERVER
    DBG_START_METH("Observer::ProcessNotification", dbg_verbosity);
    DBG_ASSERT(subject);
#endif

    if (subject) {
      std::vector<const Subject*>::iterator attached_subject;
      attached_subject = std::find(subjects_.begin(), subjects_.end(), subject);

      // We must be processing a notification for a
      // subject that was previously attached.
#ifdef IP_DEBUG_OBSERVER

      DBG_ASSERT(attached_subject != subjects_.end());
#endif

      this->RecieveNotification(notify_type, subject);

      if (notify_type == NT_BeingDestroyed) {
        // the subject is going away, remove it from our list
        subjects_.erase(attached_subject);
      }
    }
  }

  inline
  Subject::~Subject()
  {
#ifdef IP_DEBUG_OBSERVER
    DBG_START_METH("Subject::~Subject", dbg_verbosity);
#endif

    std::vector<Observer*>::iterator iter;
    for (iter = observers_.begin(); iter != observers_.end(); iter++) {
      (*iter)->ProcessNotification(Observer::NT_BeingDestroyed, this);
    }
  }

  inline
  void Subject::AttachObserver(Observer::NotifyType notify_type, Observer* observer) const
  {
#ifdef IP_DEBUG_OBSERVER
    DBG_START_METH("Subject::AttachObserver", dbg_verbosity);
    // current implementation notifies all observers of everything
    // they must filter the notifications that they are not interested
    // in (i.e. a hub, not a router)
    DBG_ASSERT(observer);

    std::vector<Observer*>::iterator attached_observer;
    attached_observer = std::find(observers_.begin(), observers_.end(), observer);
    DBG_ASSERT(attached_observer == observers_.end());

    DBG_ASSERT(observer);
#endif

    observers_.push_back(observer);
  }

  inline
  void Subject::DetachObserver(Observer::NotifyType notify_type, Observer* observer) const
  {
#ifdef IP_DEBUG_OBSERVER
    DBG_START_METH("Subject::DetachObserver", dbg_verbosity);
    DBG_ASSERT(observer);
#endif

    if (observer) {
      std::vector<Observer*>::iterator attached_observer;
      attached_observer = std::find(observers_.begin(), observers_.end(), observer);
#ifdef IP_DEBUG_OBSERVER

      DBG_ASSERT(attached_observer != observers_.end());
#endif

      if (attached_observer != observers_.end()) {
        observers_.erase(attached_observer);
      }
    }
  }

  inline
  void Subject::Notify(Observer::NotifyType notify_type) const
  {
#ifdef IP_DEBUG_OBSERVER
    DBG_START_METH("Subject::Notify", dbg_verbosity);
#endif

    std::vector<Observer*>::iterator iter;
    for (iter = observers_.begin(); iter != observers_.end(); iter++) {
      (*iter)->ProcessNotification(notify_type, this);
    }
  }


} // namespace Ipopt

#endif

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