/****************************************************************************
**
** Copyright (C) 2015 Paul Lemire (paul.lemire350@gmail.com)
** Contact: https://www.qt.io/licensing/
**
** This file is part of the Qt3D module of the Qt Toolkit.
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** General Public License version 3 as published by the Free Software
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** packaging of this file. Please review the following information to
** ensure the GNU Lesser General Public License version 3 requirements
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** Alternatively, this file may be used under the terms of the GNU
** General Public License version 2.0 or (at your option) the GNU General
** Public license version 3 or any later version approved by the KDE Free
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****************************************************************************/

#include "qeventfilterservice_p.h"

#include <QtCore/QMap>
#include <QtCore/QObject>
#include <QtCore/QVector>

#include <Qt3DCore/private/qabstractserviceprovider_p.h>

QT_BEGIN_NAMESPACE

namespace {
    struct FilterPriorityPair
    {
        QObject *filter;
        int priority;
    };

    bool operator <(const FilterPriorityPair &a, const FilterPriorityPair &b)
    {
        return a.priority < b.priority;
    }
}

Q_DECLARE_TYPEINFO(FilterPriorityPair, Q_PRIMITIVE_TYPE);

namespace Qt3DCore {

namespace {

class InternalEventListener : public QObject
{
    Q_OBJECT
public:
    explicit InternalEventListener(QEventFilterServicePrivate *filterService, QObject *parent = nullptr);
    bool eventFilter(QObject *obj, QEvent *e) Q_DECL_FINAL;
    QEventFilterServicePrivate* m_filterService;
};

} // anonymous


class QEventFilterServicePrivate : public QAbstractServiceProviderPrivate
{
public:
    QEventFilterServicePrivate()
        : QAbstractServiceProviderPrivate(QServiceLocator::EventFilterService, QStringLiteral("Default event filter service implementation"))
    {}

    Q_DECLARE_PUBLIC(QEventFilterService)

    void registerEventFilter(QObject *eventFilter, int priority)
    {
        for (int i = 0, m = m_eventFilters.size(); i < m; ++i)
            if (m_eventFilters.at(i).priority == priority)
                return;

        FilterPriorityPair fpPair;
        fpPair.filter = eventFilter;
        fpPair.priority = priority;
        m_eventFilters.push_back(fpPair);
        std::sort(m_eventFilters.begin(), m_eventFilters.end());
    }

    void unregisterEventFilter(QObject *eventFilter)
    {
        QVector<FilterPriorityPair>::iterator it = m_eventFilters.begin();
        const QVector<FilterPriorityPair>::iterator end = m_eventFilters.end();
        while (it != end) {
            if (it->filter == eventFilter) {
                m_eventFilters.erase(it);
                return;
            }
            ++it;
        }
    }

    QScopedPointer<InternalEventListener> m_eventDispatcher;
    QVector<FilterPriorityPair> m_eventFilters;
};

/* !\internal
    \class Qt3DCore::QEventFilterService
    \inmodule Qt3DCore

    \brief Allows to register event filters with a priority.

    The QEventFilterService class allows registering prioritized event filters.
    Events are dispatched to the event filter with the highest priority first,
    and then propagates to lower priority event filters if the event wasn't
    accepted.
 */

QEventFilterService::QEventFilterService()
    : QAbstractServiceProvider(*new QEventFilterServicePrivate())
{
}

QEventFilterService::~QEventFilterService()
{
}

// Note: event filters can only be registered to QObject in the same thread
void QEventFilterService::initialize(QObject *eventSource)
{
    Q_D(QEventFilterService);
    if (eventSource == nullptr) {
        d->m_eventDispatcher.reset();
    } else {
        d->m_eventDispatcher.reset(new InternalEventListener(d));
        eventSource->installEventFilter(d->m_eventDispatcher.data());
    }
}

void QEventFilterService::shutdown(QObject *eventSource)
{
    Q_D(QEventFilterService);
    if (eventSource && d->m_eventDispatcher.data())
        eventSource->removeEventFilter(d->m_eventDispatcher.data());
}

void QEventFilterService::registerEventFilter(QObject *eventFilter, int priority)
{
    Q_D(QEventFilterService);
    d->registerEventFilter(eventFilter, priority);
}

void QEventFilterService::unregisterEventFilter(QObject *eventFilter)
{
    Q_D(QEventFilterService);
    d->unregisterEventFilter(eventFilter);
}

namespace{

InternalEventListener::InternalEventListener(QEventFilterServicePrivate *filterService, QObject *parent)
    : QObject(parent),
      m_filterService(filterService)
{
}

bool InternalEventListener::eventFilter(QObject *obj, QEvent *e)
{
    for (int i = m_filterService->m_eventFilters.size() - 1; i >= 0; --i) {
        const FilterPriorityPair &fPPair = m_filterService->m_eventFilters.at(i);
        if (fPPair.filter->eventFilter(obj, e))
            return true;
    }
    return false;
}
}

} // Qt3DCore

QT_END_NAMESPACE

#include "qeventfilterservice.moc"
