from logger import Logger


class EventDriver(Logger):
    """
    The event driver receives driver-specific messages, which are delegated to
    the root area in the form of common events such as 'piont_down' pr
    'point_up'.
    """
    def __init__(self, root_area=None):
        self.root_area = root_area

    def get_root_area(self):
        return self.root_area

    def set_root_area(self, area):
        self.root_area = area

    def delegate_event(self, event):
        """
        Delegate an event that has been triggered by the event driver to the
        area tree.
        """
        if self.root_area.contains_event(event):
            self.root_area.delegate_event(event)

    def start(self):
        """
        Start the event loop. A root area is needed to be able to delegate
        events, so check if it exists first.
        """
        if not self.root_area:
            raise ValueError('Cannot start event server without root area.')

        self.start_loop()

    def start_loop(self):
        """
        Start the event loop.
        """
        raise NotImplementedError

    def stop(self):
        """
        Stop the event loop.
        """
        raise NotImplementedError

    def run(self):
        """
        Execute a single loop iteration. If implemented, this method provides a
        way to run the driver within another event loop.
        """
        raise NotImplementedError