/*
 * 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.
 */

#pragma once

#include "Timer.h"
#include <wtf/Vector.h>
#include <wtf/WeakPtr.h>

namespace WebCore {

class Page;

template<typename T> class EventSender {
    WTF_MAKE_NONCOPYABLE(EventSender); WTF_MAKE_FAST_ALLOCATED;
public:
    explicit EventSender(const AtomString& eventType);

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

#if ASSERT_ENABLED
    bool hasPendingEvents(T& sender) const
    {
        return m_dispatchSoonList.find(&sender) != notFound || m_dispatchingList.find(&sender) != notFound;
    }
#endif

private:
    void timerFired() { dispatchPendingEvents(nullptr); }

    AtomString m_eventType;
    Timer m_timer;
    Vector<WeakPtr<T>> m_dispatchSoonList;
    Vector<WeakPtr<T>> m_dispatchingList;
};

template<typename T> EventSender<T>::EventSender(const AtomString& 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_s);
}

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.
    for (auto& event : m_dispatchSoonList) {
        if (event == &sender)
            event = nullptr;
    }
    for (auto& event : m_dispatchingList) {
        if (event == &sender)
            event = nullptr;
    }
}

template<typename T> void EventSender<T>::dispatchPendingEvents(Page* page)
{
    // 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_dispatchSoonList.checkConsistency();

    m_dispatchingList = std::exchange(m_dispatchSoonList, { });
    for (auto& event : m_dispatchingList) {
        if (auto sender = event.get()) {
            event = nullptr;
            if (!page || sender->document().page() == page)
                sender->dispatchPendingEvent(this);
            else
                dispatchEventSoon(*sender);
        }
    }
    m_dispatchingList.clear();
}

} // namespace WebCore