class TreeHeader : public QHeaderView
{
public:
    TreeHeader(QWidget *parent = nullptr) noexcept;

    QAction *getModeAction(const QString &sActionTitle) const;

    void addModeAction(QAction *action, eTreeMode mode, QAction *before = nullptr);

protected:
    /// Override the context menu event
    void contextMenuEvent(QContextMenuEvent *event) override;

    /// The context menu
    QMenu *m_pContextMenu = nullptr;

private:
    /// Setups connections and necessary data for the given action
    void setupAction(QAction *action, eTreeMode eMode) const;

}; // class TreeHeader

TreeHeader::TreeHeader(QWidget *parent /* = nullptr */) noexcept
    : QHeaderView(Qt::Horizontal, parent)
    , m_pContextMenu(new QMenu(this))
{
    std::vector<std::pair<eTreeMode, QString>> mapModeToName;
    mapModeToName.emplace_back(eTreeMode::Mode1, QString("By %1").arg(mode1));
    mapModeToName.emplace_back(eTreeMode::Mode2, QString("By %1").arg(mode2));

    // create the default actions
    for (const auto &pair : mapModeToName)
    {
        // add the action to the menu and setup necessary properties to it
        setupAction(m_pContextMenu->addAction(pair.second), pair.first);
    }

    setTextElideMode(Qt::ElideRight);
    setStretchLastSection(true);
}

QAction *TreeHeader::getModeAction(const QString &sActionTitle) const
{
    for (const auto pAction : m_pContextMenu->actions())
    {
        if (pAction->text() == sActionTitle)
            return pAction;
    }
    return nullptr;
}

void TreeHeader::addModeAction(QAction *action, eTreeMode mode, QAction *before /* = nullptr */)
{
    if (!action) return;

    // add the action at appropriate position
    if (before)
        m_pContextMenu->insertAction(before, action);
    else
        m_pContextMenu->addAction(action);

    // setup necessary properties to the action
    setupAction(action, mode);
}

void TreeHeader::contextMenuEvent(QContextMenuEvent *event)
{
    if (auto pTree = static_cast<TreeView *>(parentWidget()))
    {
        // make sure we have a populated tree
        if (!(pTree->getTreeModel() && pTree->getTreeModel()->hasChildren())) return;

        // show the context menu only for the first column which specifies the grouping mode
        if (logicalIndexAt(event->pos()) == 0)
        {
            // get the current mode
            auto eMode = pTree->getMode();

            // set correct checked states of the actions
            for (const auto pAction : m_pContextMenu->actions())
                pAction->setChecked(eMode == static_cast<eTreeMode>(pAction->data().toInt()));

            // and show the menu
            m_pContextMenu->exec(event->globalPos());
        }
    }
}

void TreeHeader::setupAction(QAction *action, eTreeMode eMode) const
{
    // make the action checkable and check it, if necessary
    action->setCheckable(true);

    // set the action's checked state and make necessary connections
    if (auto pTree = dynamic_cast<TreeView *>(parentWidget()))
    {
        action->setChecked(pTree->getMode() == eMode);

        // set up a connection to process to mode change
        if (auto pView = dynamic_cast<TreeViewContainer *>(pTree->parentWidget()))
        {
            // setup a connection to process mode change
            connect(action, &QAction::triggered, pView, &TreeViewContainer::onModeChanged);
        }
    }

    // set the mode as data
    action->setData(eMode);
}