#ifndef SCROLLHELPER_H_

#define SCROLLHELPER_H_

#include <QPropertyAnimation>

#include <QRectF>

#include <QPoint>

#include <QTime>

#include <QTimer>

#include "uitimer.h"

namespace GVA {

class ScrollHelper: public QObject

{

    Q_OBJECT

public:

    enum ScrollMode {

        ReadyMode = 0,

        PanScrollMode,

        KineticScrollMode

    };

    enum ScrollState {

        IdleState = 0,   // no scrolling

        ActiveState, // scroll poins added

        WaitState    // no new scroll points

    };

    enum ScrollProperty {

        Geometry,

        Position,

        Velocity

    };

    ScrollHelper(QObject* scrolledWidget);

    ~ScrollHelper();

    void scroll(QPointF& delta);

    bool isScrolling();

    void panFromOvershoot();

    void setFlickDurationLimits(int minDuration, int midDuration, int maxDuration);

    void setFlickSpeedLimits(qreal minSpeed, qreal midSpeed, qreal maxSpeed);

    void setDeceleration(qreal decel);

    qreal getDeceleration();

    void kineticScroll(QPointF& speed);

    QSizeF viewportSize();

    void setViewportSize(const QSizeF& size);

    void setFlickLimits(qreal minFlick, qreal midFlick, qreal maxFlick);

    void stopScrollNoSignal();

public slots:

    void stopScroll();    

    void scrollTimerCallback();

    void scrollAnimationStateChanged(QAbstractAnimation::State newState,

                                     QAbstractAnimation::State);

signals:

    void scrollFinished();

private:

    void reset();

    void doScroll(QPointF& delta);

    QPointF getScrollPos();

    QPointF getMaxScrollPos();

    void setScrollPos(QPointF& pos);

    bool clampScrollPosition(QPointF& scrollPos);

    void startScrollAnimation(QPointF& scrollPos, QPointF& targetPos,

                              int duration, QEasingCurve::Type& easingCurveType);

    int calcScrollDuration(const QPointF& speed, const QPointF& delta);

    int calcScrollDuration(qreal motionFactor);

    QPointF calcTargetScrollPosAndDuration(const QPointF& speed,

                                           const QPointF& scrollPos, int& duration);

    qreal calcMotionFactor(const qreal speed);

    QPointF calcDeceleration(const QPointF& initSpeed, const QPointF& distance, long time);

    QPointF speedForNextInterval(const QPointF& initSpeed, long timeInterval, const QPointF& decel);

private:

    ScrollMode          m_scrollMode;

    ScrollState         m_scrollState;

    QPointF             m_scrollDelta;

    QPointF             m_curScrollPos;

    QPropertyAnimation* m_scrollAnimation;

    UiTimer*            m_scrollTimer;

    QObject*            m_scrolledWidget;

    int                 m_minFlickDuration;

    int                 m_maxFlickDuration;

    int                 m_midFlickDuration;

    qreal               m_minFlickSpeed;

    qreal               m_maxFlickSpeed;

    qreal               m_midFlickSpeed;

    qreal               m_decel;

    QPointF             m_decelVec;

    QSizeF              m_viewportSize;

    qreal               m_maxFlickInViewportUnits;

    qreal               m_minFlickInViewportUnits;

    qreal               m_midFlickInViewportUnits;

    bool                m_lockToY;

    bool                m_lockToX;

    QPointF             m_targetScrollPos;

    QPointF             m_startScrollPos;

    QPointF             m_kineticSpeed;

    long                m_scrollTotalDuration;

    long                m_scrollDuration;

    QEasingCurve::Type  m_easingCurveType;

    QEasingCurve*       m_easingCurve;

    QEasingCurve*       m_easingCurveOvershoot;

    QEasingCurve*       m_curEasingCurve;

};

}

#endif /* SCROLLHELPER_H_ */