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#include "private/qdeclarativeflipable_p.h"

#include "private/qdeclarativeitem_p.h"
#include "private/qdeclarativeguard_p.h"

#include <qdeclarativeinfo.h>

#include <QtGui/qgraphicstransform.h>

QT_BEGIN_NAMESPACE

class QDeclarativeFlipablePrivate : public QDeclarativeItemPrivate
{
    Q_DECLARE_PUBLIC(QDeclarativeFlipable)
public:
    QDeclarativeFlipablePrivate() : current(QDeclarativeFlipable::Front), front(0), back(0) {}

    void updateSceneTransformFromParent();
    void setBackTransform();

    QDeclarativeFlipable::Side current;
    QDeclarativeGuard<QGraphicsObject> front;
    QDeclarativeGuard<QGraphicsObject> back;

    bool wantBackXFlipped;
    bool wantBackYFlipped;
};

/*!
    \qmlclass Flipable QDeclarativeFlipable
    \since 4.7
    \ingroup qml-basic-interaction-elements

    \brief The Flipable item provides a surface that can be flipped.
    \inherits Item

    Flipable is an item that can be visibly "flipped" between its front and
    back sides. It is used together with \l Rotation and \l {State}/\l {Transition} to
    produce a flipping effect.

    Here is a Flipable that flips whenever it is clicked:

    \snippet doc/src/snippets/declarative/flipable.qml 0

    \image flipable.gif

    The \l Rotation element is used to specify the angle and axis of the flip.
    When \c flipped is \c true, the item changes to the "back" state, where
    the angle is changed to 180 degrees to produce the flipping effect. 
    Finally, the \l Transition creates the animation that changes the
    angle over one second: when the item changes between its "back" and 
    default states, the NumberAnimation animates the angle between
    its old and new values.

    See the \l {QML States} and \l {QML Animation} documentation for more
    details on state changes and how animations work within transitions.
    
    \sa {declarative/ui-components/flipable}{Flipable example}
*/

QDeclarativeFlipable::QDeclarativeFlipable(QDeclarativeItem *parent)
: QDeclarativeItem(*(new QDeclarativeFlipablePrivate), parent)
{
}

QDeclarativeFlipable::~QDeclarativeFlipable()
{
}

/*!
  \qmlproperty Item Flipable::front
  \qmlproperty Item Flipable::back

  The front and back sides of the flipable.
*/

QGraphicsObject *QDeclarativeFlipable::front()
{
    Q_D(const QDeclarativeFlipable);
    return d->front;
}

void QDeclarativeFlipable::setFront(QGraphicsObject *front)
{
    Q_D(QDeclarativeFlipable);
    if (d->front) {
        qmlInfo(this) << tr("front is a write-once property");
        return;
    }
    d->front = front;
    d->front->setParentItem(this);
    if (Back == d->current)
        d->front->setOpacity(0.);
}

QGraphicsObject *QDeclarativeFlipable::back()
{
    Q_D(const QDeclarativeFlipable);
    return d->back;
}

void QDeclarativeFlipable::setBack(QGraphicsObject *back)
{
    Q_D(QDeclarativeFlipable);
    if (d->back) {
        qmlInfo(this) << tr("back is a write-once property");
        return;
    }
    d->back = back;
    d->back->setParentItem(this);
    if (Front == d->current)
        d->back->setOpacity(0.);
    connect(back, SIGNAL(widthChanged()),
            this, SLOT(retransformBack()));
    connect(back, SIGNAL(heightChanged()),
            this, SLOT(retransformBack()));
}

void QDeclarativeFlipable::retransformBack()
{
    Q_D(QDeclarativeFlipable);
    if (d->current == QDeclarativeFlipable::Back && d->back)
        d->setBackTransform();
}

/*!
  \qmlproperty enumeration Flipable::side

  The side of the Flippable currently visible. Possible values are \c
  Flippable.Front and \c Flippable.Back.
*/
QDeclarativeFlipable::Side QDeclarativeFlipable::side() const
{
    Q_D(const QDeclarativeFlipable);
    if (d->dirtySceneTransform)
        const_cast<QDeclarativeFlipablePrivate *>(d)->ensureSceneTransform();

    return d->current;
}

// determination on the currently visible side of the flipable
// has to be done on the complete scene transform to give
// correct results.
void QDeclarativeFlipablePrivate::updateSceneTransformFromParent()
{
    Q_Q(QDeclarativeFlipable);

    QDeclarativeItemPrivate::updateSceneTransformFromParent();
    QPointF p1(0, 0);
    QPointF p2(1, 0);
    QPointF p3(1, 1);

    QPointF scenep1 = sceneTransform.map(p1);
    QPointF scenep2 = sceneTransform.map(p2);
    QPointF scenep3 = sceneTransform.map(p3);
    p1 = q->mapToParent(p1);
    p2 = q->mapToParent(p2);
    p3 = q->mapToParent(p3);

    qreal cross = (scenep1.x() - scenep2.x()) * (scenep3.y() - scenep2.y()) -
                  (scenep1.y() - scenep2.y()) * (scenep3.x() - scenep2.x());

    wantBackYFlipped = p1.x() >= p2.x();
    wantBackXFlipped = p2.y() >= p3.y();

    QDeclarativeFlipable::Side newSide;
    if (cross > 0) {
        newSide = QDeclarativeFlipable::Back;
    } else {
        newSide = QDeclarativeFlipable::Front;
    }

    if (newSide != current) {
        current = newSide;
        if (current == QDeclarativeFlipable::Back && back)
            setBackTransform();
        if (front)
            front->setOpacity((current==QDeclarativeFlipable::Front)?1.:0.);
        if (back)
            back->setOpacity((current==QDeclarativeFlipable::Back)?1.:0.);
        emit q->sideChanged();
    }
}

/* Depends on the width/height of the back item, and so needs reevaulating
   if those change.
*/
void QDeclarativeFlipablePrivate::setBackTransform()
{
    QTransform mat;
    QGraphicsItemPrivate *dBack = QGraphicsItemPrivate::get(back);
    mat.translate(dBack->width()/2,dBack->height()/2);
    if (dBack->width() && wantBackYFlipped)
        mat.rotate(180, Qt::YAxis);
    if (dBack->height() && wantBackXFlipped)
        mat.rotate(180, Qt::XAxis);
    mat.translate(-dBack->width()/2,-dBack->height()/2);
    back->setTransform(mat);
}

QT_END_NAMESPACE