/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/**
 * Copyright (C) 2014 Named Data Networking Project
 * See COPYING for copyright and distribution information.
 */

#ifndef NFD_UTIL_EVENT_EMITTER_HPP
#define NFD_UTIL_EVENT_EMITTER_HPP

#include "common.hpp"

namespace ndn {

struct empty {};

/** \class EventEmitter
 *  \brief provides a lightweight event system
 *
 *  To declare an event:
 *    EventEmitter<TArgs> m_eventName;
 *  To subscribe to an event:
 *    eventSource->m_eventName += eventHandler;
 *    Multiple functions can subscribe to the same event.
 *  To trigger an event:
 *    m_eventName(args);
 *  To clear event subscriptions:
 *    m_eventName.clear();
 */

// four arguments
template<typename T1 = empty, typename T2 = empty,
    typename T3 = empty, typename T4 = empty>
class EventEmitter : noncopyable
{
public:
  /// represents a handler that can subscribe to the event
  typedef function<void(const T1&, const T2&,
                               const T3&, const T4&)> Handler;
  
  /// adds an subscription
  void
  operator+=(Handler handler);
  
  /// returns true if there is no subscription,
  /// otherwise returns false
  bool
  isEmpty();
  
  /// clears all subscriptions
  void
  clear();
  
  /// triggers the event
  void
  operator()(const T1& a1, const T2& a2, const T3& a3, const T4& a4);

private:
  /// stores all subscribed handlers
  std::vector<Handler> m_handlers;
};

// zero argument
template<>
class EventEmitter<empty, empty, empty, empty> : noncopyable
{
public:
  typedef function<void()> Handler;
  
  void
  operator+=(Handler handler);

  bool
  isEmpty();

  void
  clear();
  
  void
  operator()();

private:
  std::vector<Handler> m_handlers;
};


// one argument
template<typename T1>
class EventEmitter<T1, empty, empty, empty> : noncopyable
{
public:
  typedef function<void(const T1&)> Handler;
  
  void
  operator+=(Handler handler);

  bool
  isEmpty();

  void
  clear();
  
  void
  operator()(const T1& a1);

private:
  std::vector<Handler> m_handlers;
};


// two arguments
template<typename T1, typename T2>
class EventEmitter<T1, T2, empty, empty> : noncopyable
{
public:
  typedef function<void(const T1&, const T2&)> Handler;
  
  void
  operator+=(Handler handler);

  bool
  isEmpty();

  void
  clear();
  
  void
  operator()(const T1& a1, const T2& a2);

private:
  std::vector<Handler> m_handlers;
};


// three arguments
template<typename T1, typename T2, typename T3>
class EventEmitter<T1, T2, T3, empty> : noncopyable
{
public:
  typedef function<void(const T1&, const T2&, const T3&)> Handler;
  
  void
  operator+=(Handler handler);

  bool
  isEmpty();

  void
  clear();
  
  void
  operator()(const T1& a1, const T2& a2, const T3& a3);

private:
  std::vector<Handler> m_handlers;
};


// zero argument

inline void
EventEmitter<empty, empty, empty, empty>::operator+=(Handler handler)
{
  m_handlers.push_back(handler);
}

inline bool
EventEmitter<empty, empty, empty, empty>::isEmpty()
{
  return m_handlers.empty();
}

inline void
EventEmitter<empty, empty, empty, empty>::clear()
{
  return m_handlers.clear();
}

inline void
EventEmitter<empty, empty, empty, empty>::operator()()
{
  std::vector<Handler>::iterator it;
  for (it = m_handlers.begin(); it != m_handlers.end(); ++it) {
    (*it)();
  }
}

// one argument

template<typename T1>
inline void
EventEmitter<T1, empty, empty, empty>::operator+=(Handler handler)
{
  m_handlers.push_back(handler);
}

template<typename T1>
inline bool
EventEmitter<T1, empty, empty, empty>::isEmpty()
{
  return m_handlers.empty();
}

template<typename T1>
inline void
EventEmitter<T1, empty, empty, empty>::clear()
{
  return m_handlers.clear();
}

template<typename T1>
inline void
EventEmitter<T1, empty, empty, empty>::operator()(const T1& a1)
{
  typename std::vector<Handler>::iterator it;
  for (it = m_handlers.begin(); it != m_handlers.end(); ++it) {
    (*it)(a1);
  }
}

// two arguments

template<typename T1, typename T2>
inline void
EventEmitter<T1, T2, empty, empty>::operator+=(Handler handler)
{
  m_handlers.push_back(handler);
}

template<typename T1, typename T2>
inline bool
EventEmitter<T1, T2, empty, empty>::isEmpty()
{
  return m_handlers.empty();
}

template<typename T1, typename T2>
inline void
EventEmitter<T1, T2, empty, empty>::clear()
{
  return m_handlers.clear();
}

template<typename T1, typename T2>
inline void
EventEmitter<T1, T2, empty, empty>::operator()
    (const T1& a1, const T2& a2)
{
  typename std::vector<Handler>::iterator it;
  for (it = m_handlers.begin(); it != m_handlers.end(); ++it) {
    (*it)(a1, a2);
  }
}

// three arguments

template<typename T1, typename T2, typename T3>
inline void
EventEmitter<T1, T2, T3, empty>::operator+=(Handler handler)
{
  m_handlers.push_back(handler);
}

template<typename T1, typename T2, typename T3>
inline bool
EventEmitter<T1, T2, T3, empty>::isEmpty()
{
  return m_handlers.empty();
}

template<typename T1, typename T2, typename T3>
inline void
EventEmitter<T1, T2, T3, empty>::clear()
{
  return m_handlers.clear();
}

template<typename T1, typename T2, typename T3>
inline void
EventEmitter<T1, T2, T3, empty>::operator()
    (const T1& a1, const T2& a2, const T3& a3)
{
  typename std::vector<Handler>::iterator it;
  for (it = m_handlers.begin(); it != m_handlers.end(); ++it) {
    (*it)(a1, a2, a3);
  }
}

// four arguments

template<typename T1, typename T2, typename T3, typename T4>
inline void
EventEmitter<T1, T2, T3, T4>::operator+=(Handler handler)
{
  m_handlers.push_back(handler);
}

template<typename T1, typename T2, typename T3, typename T4>
inline bool
EventEmitter<T1, T2, T3, T4>::isEmpty()
{
  return m_handlers.empty();
}

template<typename T1, typename T2, typename T3, typename T4>
inline void
EventEmitter<T1, T2, T3, T4>::clear()
{
  return m_handlers.clear();
}

template<typename T1, typename T2, typename T3, typename T4>
inline void
EventEmitter<T1, T2, T3, T4>::operator()
    (const T1& a1, const T2& a2, const T3& a3, const T4& a4)
{
  typename std::vector<Handler>::iterator it;
  for (it = m_handlers.begin(); it != m_handlers.end(); ++it) {
    (*it)(a1, a2, a3, a4);
  }
}


} // namespace ndn

#endif // NFD_UTIL_EVENT_EMITTER_HPP