/*
 * Copyright (C) 2012 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef EventSender_h
#define EventSender_h

#include "platform/Timer.h"
#include "platform/heap/Handle.h"
#include "wtf/Vector.h"
#include "wtf/text/AtomicString.h"

namespace blink {

template <typename T>
class EventSender final : public GarbageCollectedFinalized<EventSender<T>> {
  WTF_MAKE_NONCOPYABLE(EventSender);

 public:
  static EventSender* create(const AtomicString& eventType) {
    return new EventSender(eventType);
  }

  const AtomicString& eventType() const { return m_eventType; }
  void dispatchEventSoon(T*);
  void cancelEvent(T*);
  void dispatchPendingEvents();

#if DCHECK_IS_ON()
  bool hasPendingEvents(T* sender) const {
    return m_dispatchSoonList.find(sender) != kNotFound ||
           m_dispatchingList.find(sender) != kNotFound;
  }
#endif

  DEFINE_INLINE_TRACE() {
    visitor->trace(m_dispatchSoonList);
    visitor->trace(m_dispatchingList);
  }

 private:
  explicit EventSender(const AtomicString& eventType);

  void timerFired(TimerBase*) { dispatchPendingEvents(); }

  AtomicString m_eventType;
  Timer<EventSender<T>> m_timer;
  HeapVector<Member<T>> m_dispatchSoonList;
  HeapVector<Member<T>> m_dispatchingList;
};

template <typename T>
EventSender<T>::EventSender(const AtomicString& eventType)
    : m_eventType(eventType), m_timer(this, &EventSender::timerFired) {}

template <typename T>
void EventSender<T>::dispatchEventSoon(T* sender) {
  m_dispatchSoonList.append(sender);
  if (!m_timer.isActive())
    m_timer.startOneShot(0, BLINK_FROM_HERE);
}

template <typename T>
void EventSender<T>::cancelEvent(T* sender) {
  // Remove instances of this sender from both lists.
  // Use loops because we allow multiple instances to get into the lists.
  size_t size = m_dispatchSoonList.size();
  for (size_t i = 0; i < size; ++i) {
    if (m_dispatchSoonList[i] == sender)
      m_dispatchSoonList[i] = nullptr;
  }
  size = m_dispatchingList.size();
  for (size_t i = 0; i < size; ++i) {
    if (m_dispatchingList[i] == sender)
      m_dispatchingList[i] = nullptr;
  }
}

template <typename T>
void EventSender<T>::dispatchPendingEvents() {
  // Need to avoid re-entering this function; if new dispatches are
  // scheduled before the parent finishes processing the list, they
  // will set a timer and eventually be processed.
  if (!m_dispatchingList.isEmpty())
    return;

  m_timer.stop();

  m_dispatchingList.swap(m_dispatchSoonList);
  size_t size = m_dispatchingList.size();
  for (size_t i = 0; i < size; ++i) {
    if (T* sender = m_dispatchingList[i]) {
      m_dispatchingList[i] = nullptr;
      sender->dispatchPendingEvent(this);
    }
  }
  m_dispatchingList.clear();
}

}  // namespace blink

#endif  // EventSender_h
