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#include "qquicksinglepointhandler_p.h"

QT_BEGIN_NAMESPACE
Q_DECLARE_LOGGING_CATEGORY(DBG_TOUCH_TARGET)

/*!
    \qmltype SinglePointHandler
    \qmlabstract
    \preliminary
    \instantiates QQuickSinglePointHandler
    \inherits PointerDeviceHandler
    \inqmlmodule Qt.labs.handlers
    \ingroup qtquick-handlers
    \brief Abstract handler for single-point Pointer Events.

    An intermediate class (not registered as a QML type)
    for the most common handlers: those which expect only a single point.
    wantsPointerEvent() will choose the first point which is inside the
    \l target item, and return true as long as the event contains that point.
    Override handleEventPoint() to implement a single-point handler.
*/

QQuickSinglePointHandler::QQuickSinglePointHandler(QObject *parent)
  : QQuickPointerDeviceHandler(parent)
  , m_acceptedButtons(Qt::LeftButton)
  , m_ignoreAdditionalPoints(false)
{
}

bool QQuickSinglePointHandler::wantsPointerEvent(QQuickPointerEvent *event)
{
    if (!QQuickPointerDeviceHandler::wantsPointerEvent(event))
        return false;
    if (event->device()->pointerType() != QQuickPointerDevice::Finger &&
            (event->buttons() & m_acceptedButtons) == 0 && (event->button() & m_acceptedButtons) == 0)
        return false;

    if (m_pointInfo.m_id) {
        // We already know which one we want, so check whether it's there.
        // It's expected to be an update or a release.
        // If we no longer want it, cancel the grab.
        int candidatePointCount = 0;
        bool missing = true;
        QQuickEventPoint *point = nullptr;
        int c = event->pointCount();
        for (int i = 0; i < c; ++i) {
            QQuickEventPoint *p = event->point(i);
            const bool found = (p->pointId() == m_pointInfo.m_id);
            if (found)
                missing = false;
            if (wantsEventPoint(p)) {
                ++candidatePointCount;
                if (found)
                    point = p;
            }
        }
        if (missing)
            qCWarning(DBG_TOUCH_TARGET) << this << "pointId" << hex << m_pointInfo.m_id
                << "is missing from current event, but was neither canceled nor released";
        if (point) {
            if (candidatePointCount == 1 || (candidatePointCount > 1 && m_ignoreAdditionalPoints)) {
                point->setAccepted();
                return true;
            } else {
                point->cancelAllGrabs(this);
            }
        } else {
            return false;
        }
    } else {
        // We have not yet chosen a point; choose the first one for which wantsEventPoint() returns true.
        int candidatePointCount = 0;
        int c = event->pointCount();
        QQuickEventPoint *chosen = nullptr;
        for (int i = 0; i < c; ++i) {
            QQuickEventPoint *p = event->point(i);
            if (!p->exclusiveGrabber() && wantsEventPoint(p)) {
                if (!chosen)
                    chosen = p;
                ++candidatePointCount;
            }
        }
        if (chosen && candidatePointCount == 1) {
            m_pointInfo.m_id = chosen->pointId();
            chosen->setAccepted();
        }
    }
    return m_pointInfo.m_id;
}

void QQuickSinglePointHandler::handlePointerEventImpl(QQuickPointerEvent *event)
{
    QQuickPointerDeviceHandler::handlePointerEventImpl(event);
    QQuickEventPoint *currentPoint = event->pointById(m_pointInfo.m_id);
    Q_ASSERT(currentPoint);
    if (!m_pointInfo.m_id || !currentPoint->isAccepted()) {
        reset();
    } else {
        m_pointInfo.reset(currentPoint);
        handleEventPoint(currentPoint);
        if (currentPoint->state() == QQuickEventPoint::Released) {
            setExclusiveGrab(currentPoint, false);
            reset();
        }
        emit pointChanged();
    }
}

void QQuickSinglePointHandler::onGrabChanged(QQuickPointerHandler *grabber, QQuickEventPoint::GrabState stateChange, QQuickEventPoint *point)
{
    if (grabber != this)
        return;
    switch (stateChange) {
    case QQuickEventPoint::GrabExclusive:
        m_pointInfo.m_sceneGrabPosition = point->sceneGrabPosition();
        setActive(true);
        QQuickPointerHandler::onGrabChanged(grabber, stateChange, point);
        break;
    case QQuickEventPoint::GrabPassive:
        m_pointInfo.m_sceneGrabPosition = point->sceneGrabPosition();
        QQuickPointerHandler::onGrabChanged(grabber, stateChange, point);
        break;
    case QQuickEventPoint::OverrideGrabPassive:
        return; // don't emit
    case QQuickEventPoint::UngrabPassive:
    case QQuickEventPoint::UngrabExclusive:
    case QQuickEventPoint::CancelGrabPassive:
    case QQuickEventPoint::CancelGrabExclusive:
        // the grab is lost or relinquished, so the point is no longer relevant
        QQuickPointerHandler::onGrabChanged(grabber, stateChange, point);
        reset();
        break;
    }
    emit singlePointGrabChanged();
}

void QQuickSinglePointHandler::setIgnoreAdditionalPoints(bool v)
{
    m_ignoreAdditionalPoints = v;
}

void QQuickSinglePointHandler::moveTarget(QPointF pos, QQuickEventPoint *point)
{
    target()->setPosition(pos);
    m_pointInfo.m_scenePosition = point->scenePosition();
    m_pointInfo.m_position = target()->mapFromScene(m_pointInfo.m_scenePosition);
}

/*!
    \qmlproperty int QtQuick::SinglePointHandler::acceptedButtons

    The mouse buttons which can activate this Pointer Handler.

    By default, this property is set to \l {QtQuick::MouseEvent::button} {Qt.LeftButton}.
    It can be set to an OR combination of mouse buttons, and will ignore events
    from other buttons.

    For example, a control could be made to respond to left and right clicks
    in different ways, with two handlers:

    \qml
    Item {
        TapHandler {
            onTapped: console.log("left clicked")
        }
        TapHandler {
            acceptedButtons: Qt.RightButton
            onTapped: console.log("right clicked")
        }
    }
    \endqml

    \note Tapping on a touchscreen or tapping the stylus on a graphics tablet
    emulates clicking the left mouse button. This behavior can be altered via
    \l {PointerDeviceHandler::acceptedDevices}{acceptedDevices} or
    \l {PointerDeviceHandler::acceptedPointerTypes}{acceptedPointerTypes}.
*/
void QQuickSinglePointHandler::setAcceptedButtons(Qt::MouseButtons buttons)
{
    if (m_acceptedButtons == buttons)
        return;

    m_acceptedButtons = buttons;
    emit acceptedButtonsChanged();
}

void QQuickSinglePointHandler::reset()
{
    setActive(false);
    m_pointInfo.reset();
}

/*!
    \readonly
    \qmlproperty HandlerPoint QtQuick::SinglePointHandler::point

    The event point currently being handled. When no point is currently being
    handled, this object is reset to default values (all coordinates are 0).
*/

QT_END_NAMESPACE