def get_dir_from_zipfile(zip_file, fallback=None):
    """Return the name of the root folder in a zip file.

    :param zip_file: a :class:`zipfile.ZipFile` instance.
    :param fallback: if `None`, the name of the zip file is used. This is
        returned if the zip file contains more than one top-level directory,
        or none at all.
    """
    fallback = fallback or zip_file.filename
    directories = [name for name in zip_file.namelist() if name.endswith("/")
                   and len(PurePath(name).parts) == 1]
    return fallback if len(directories) > 1 else directories[0]
def add_forum(category_id=None):
    form = AddForumForm()

    if form.validate_on_submit():
        form.save()
        flash(_("Forum added."), "success")
        return redirect(url_for("management.forums"))
    else:
        form.groups.data = Group.query.order_by(Group.id.asc()).all()
        if category_id:
            category = Category.query.filter_by(id=category_id).first()
            form.category.data = category

    return render_template("management/forum_form.html", form=form,
                           title=_("Add Forum"))