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#include <QtCore>
#include <qaccelerometer.h>

QTM_USE_NAMESPACE

namespace arrows{
    static const QString ARROW_UP="^", ARROW_DOWN="v", ARROW_LEFT="<",ARROW_RIGHT=">", ARROW_TO=".", ARROW_FROM="x";
}

class AccelerometerFilter : public QAccelerometerFilter
{
public:

    bool filter(QAccelerometerReading *reading)
    {
        QString arrow = getArrowKey(reading->x(), reading->y(), reading->z());
        if (arrow!=exArrow){
            qDebug() << "direction:" << arrow;
            exArrow = arrow;
        }
        return false; // don't store the reading in the sensor
    }

private:
    QString exArrow;
    static const qreal THRESHOLD;

    QString getArrowKey(qreal x, qreal y, qreal z){

        // axis_z: TO or FROM
        if (abs(y)<THRESHOLD && abs(x)<THRESHOLD) return z>0?(arrows::ARROW_FROM):(arrows::ARROW_TO);

        // axis_x: LEFT or RIGHT
        if (abs(x)>abs(y)) return x>0?(arrows::ARROW_LEFT):(arrows::ARROW_RIGHT);

        // axis_y: UP or DOWN
        return y>0?(arrows::ARROW_DOWN):(arrows::ARROW_UP);
    }

    static qreal abs(qreal value) {return value<0?-value:value;}
};

const qreal AccelerometerFilter::THRESHOLD = 0.3;

int main(int argc, char **argv)
{
    QCoreApplication app(argc, argv);
    QAccelerometer sensor;
    if (!sensor.connectToBackend()) {
        qWarning("No Accelerometer available!");
        return 1;
    }
    AccelerometerFilter filter;
    sensor.addFilter(&filter);
    sensor.start();

    return app.exec();
}