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module autosaver;

import QtCore.QObject;
import QtCore.QBasicTimer;
import QtCore.QTime;

import QtCore.QDir;
import QtCore.QCoreApplication;
import QtCore.QMetaObject;
import QtDebug;

const uint AUTOSAVE_IN  = 1000 * 3  // seconds
const uint MAXWAIT = 1000 * 15 // seconds

/*
    This class will call the save() slot on the parent object when the parent changes.
    It will wait several seconds after changed() to combining multiple changes and
    prevent continuous writing to disk.
  */
class AutoSaver : public QObject {

Q_OBJECT

public:
    this(QObject *parent)
{
	super(parent);
    Q_ASSERT(parent);
}
    ~this();
{
    if (m_timer.isActive())
        qWarning() << "AutoSaver: still active when destroyed, changes not saved.";
}
    void saveIfNeccessary()
{
    if (!m_timer.isActive())
        return;
    m_timer.stop();
    m_firstChange = QTime();
    if (!QMetaObject::invokeMethod(parent(), "save", Qt::DirectConnection)) {
        qWarning() << "AutoSaver: error invoking slot save() on parent";
    }
}

public slots:
    void changeOccurred();
{
    if (m_firstChange.isNull())
        m_firstChange.start();

    if (m_firstChange.elapsed() > MAXWAIT) {
        saveIfNeccessary();
    } else {
        m_timer.start(AUTOSAVE_IN, this);
    }
}

protected:
    void timerEvent(QTimerEvent *event)
{
    if (event.timerId() == m_timer.timerId()) {
        saveIfNeccessary();
    } else {
        QObject::timerEvent(event);
    }
}


private:
    QBasicTimer m_timer;
    QTime m_firstChange;
}