observer.h

///\file

/******************************************************************************
The MIT License(MIT)

Embedded Template Library.
https://github.com/ETLCPP/etl

Copyright(c) 2014 jwellbelove

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******************************************************************************/

#ifndef __ETL_OBSERVER__
#define __ETL_OBSERVER__

//*****************************************************************************
///\defgroup observer observer
/// A templated implementation to simplify the creation of the observer pattern
/// and attempts to eliminate certain runtime errors by turning them into compile errors.
/// The pattern consists of two template classes.
/// \li <b>Observer</b><br>
/// This template may take up to eight notification types.
/// Each notification type will generate a pure virtual 'notification'
/// function. The class that inherits from this *must* define all
/// of the 'notification' function overloads otherwise the object will
/// remain 'abstract' and will not compile.
/// This ensures that no overload can be forgotten.<br>
///
/// \li <b>observable</b><br>
/// The class derived from this will be observed by the above class.
/// It keeps a list of registered observers and will notify all
/// of them with the notifications.
///\ingroup patterns
//*****************************************************************************

#include <algorithm>
#include "vector.h"
#include "exception.h"

#ifndef ETL_THROW_EXCEPTIONS
#include "error_handler.h"
#endif

namespace etl
{
  //***************************************************************************
  ///\ingroup observer
  /// The base class for observer exceptions.
  //***************************************************************************
  class observer_exception : public exception
  {
  public:

    observer_exception(const char* what)
      : exception(what)
    {
    }
  };

  //***************************************************************************
  ///\ingroup observer
  /// The exception thrown when the observer list is full.
  //***************************************************************************
  class observer_list_full : public observer_exception
  {
  public:

    observer_list_full()
      : observer_exception("observer: list full")
    {
    }
  };

  //*********************************************************************
  /// The object that is being observed.
  ///\tparam TObserver     The observer type.
  ///\tparam MAX_OBSERVERS The maximum number of observers that can be accomodated.
  ///\ingroup observer
  //*********************************************************************
  template <typename TObserver, const size_t MAX_OBSERVERS>
  class observable
  {
  public:

    typedef size_t size_type;

    typedef etl::vector<TObserver*, MAX_OBSERVERS> Observer_List;

    //*****************************************************************
    /// Add an observer to the list.
    /// If ETL_THROW_EXCEPTIONS is defined then an etl::observable_observer_list_full
    /// is emitted if the observer list is already full.
    ///\param observer A reference to the observer.
    //*****************************************************************
    void add_observer(TObserver& observer)
    {
		  // See if we already have it in our list.
      typename Observer_List::const_iterator i_observer = std::find(observer_list.begin(),
                                                                    observer_list.end(),
                                                                    &observer);

		  // Not there?
      if (i_observer == observer_list.end())
      {
        // Is there enough room?
        if (!observer_list.full())
        {
          // Add it.
          observer_list.push_back(&observer);
        }
#ifdef ETL_THROW_EXCEPTIONS
        else
        {
          throw observer_list_full();
        }
#else
        else
        {
          error_handler::error(observer_list_full());
        }
#endif
      }
    }

    //*****************************************************************
    /// Remove a particular observer from the list.
    ///\param observer A reference to the observer.
    //*****************************************************************
    void remove_observer(TObserver& observer)
    {
      // See if we have it in our list.
      typename Observer_List::iterator i_observer = std::find(observer_list.begin(),
                                                              observer_list.end(),
                                                              &observer);

      // Found it?
      if (i_observer != observer_list.end())
      {
        // Erase it.
        observer_list.erase(i_observer);
      }
    }

    //*****************************************************************
    /// Clear all observers from the list.
    //*****************************************************************
    void clear_observers()
    {
      observer_list.clear();
    }

    //*****************************************************************
    /// Returns the number of observers.
    //*****************************************************************
    size_type number_of_observers() const
    {
      return observer_list.size();
    }

    //*****************************************************************
    /// Notify all of the observers, sending them the notification.
    ///\tparam TNotification the notification type.
    ///\param n The notification.
    //*****************************************************************
    template <typename TNotification>
    void notify_observers(TNotification n)
    {
      for (size_t i = 0; i < observer_list.size(); ++i)
      {
        observer_list[i]->notification(n);
      }
    }

  private:

    /// The list of observers.
    Observer_List observer_list;
  };

  //*********************************************************************
  /// The observer interface for eight notification types.
  ///\ingroup observer
  //*********************************************************************
  template <typename T1,
            typename T2  = void,
            typename T3  = void,
            typename T4  = void,
            typename T5  = void,
            typename T6  = void,
            typename T7  = void,
            typename T8  = void>
  class observer
  {
  public:
    virtual ~observer() {}
    virtual void notification(T1) = 0;
    virtual void notification(T2) = 0;
    virtual void notification(T3) = 0;
    virtual void notification(T4) = 0;
    virtual void notification(T5) = 0;
    virtual void notification(T6) = 0;
    virtual void notification(T7) = 0;
    virtual void notification(T8) = 0;
  };

  //*********************************************************************
  /// The observer interface for seven notification types.
  ///\ingroup observer
  //*********************************************************************
  template <typename T1,
            typename T2,
            typename T3,
            typename T4,
            typename T5,
            typename T6,
            typename T7>
  class observer<T1, T2, T3, T4, T5, T6, T7>
  {
  public:

    virtual ~observer() {}
    virtual void notification(T1) = 0;
    virtual void notification(T2) = 0;
    virtual void notification(T3) = 0;
    virtual void notification(T4) = 0;
    virtual void notification(T5) = 0;
    virtual void notification(T6) = 0;
    virtual void notification(T7) = 0;
  };

  //*********************************************************************
  /// The observer interface for six notification types.
  ///\ingroup observer
  //*********************************************************************
  template <typename T1,
            typename T2,
            typename T3,
            typename T4,
            typename T5,
            typename T6>
  class observer<T1, T2, T3, T4, T5, T6>
  {
  public:

    virtual ~observer() {}
    virtual void notification(T1) = 0;
    virtual void notification(T2) = 0;
    virtual void notification(T3) = 0;
    virtual void notification(T4) = 0;
    virtual void notification(T5) = 0;
    virtual void notification(T6) = 0;
  };

  //*********************************************************************
  /// The observer interface for five notification types.
  ///\ingroup observer
  //*********************************************************************
  template <typename T1,
            typename T2,
            typename T3,
            typename T4,
            typename T5>
  class observer<T1, T2, T3, T4, T5>
  {
  public:

    virtual ~observer() {}
    virtual void notification(T1) = 0;
    virtual void notification(T2) = 0;
    virtual void notification(T3) = 0;
    virtual void notification(T4) = 0;
    virtual void notification(T5) = 0;
  };

  //*********************************************************************
  /// The observer interface for four notification types.
  ///\ingroup observer
  //*********************************************************************
  template <typename T1,
            typename T2,
            typename T3,
            typename T4>
  class observer<T1, T2, T3, T4>
  {
  public:

    virtual ~observer() {}
    virtual void notification(T1) = 0;
    virtual void notification(T2) = 0;
    virtual void notification(T3) = 0;
    virtual void notification(T4) = 0;
  };

  //*********************************************************************
  /// The observer interface for three notification types.
  ///\ingroup observer
  //*********************************************************************
  template <typename T1,
            typename T2,
            typename T3>
  class observer<T1, T2, T3>
  {
  public:

    virtual ~observer() {}
    virtual void notification(T1) = 0;
    virtual void notification(T2) = 0;
    virtual void notification(T3) = 0;
  };

  //*********************************************************************
  /// The observer interface for two notification types.
  ///\ingroup observer
  //*********************************************************************
  template <typename T1,
            typename T2>
  class observer<T1, T2>
  {
  public:

    virtual ~observer() {}
    virtual void notification(T1) = 0;
    virtual void notification(T2) = 0;
  };

  //*********************************************************************
  /// The observer interface for one notification type.
  ///\ingroup observer
  //*********************************************************************
  template <typename T1>
  class observer<T1>
  {
  public:

    virtual ~observer() {}
    virtual void notification(T1) = 0;
  };
}

#endif