import sys, traceback

class EventDispatcher:

    def __init__(self, *event_names):

        self._events = {}

        self._listname = 0

        for n in event_names:

            self._events[n] = {}

    def add_handler(self, name, listener, listener_name=None):

        # TODO add proper checks and specific exception if event is not supported

        if not listener_name:

            listener_name = '__auto__name__{}'.format(self._listname)

            self._listname += 1

        self._events[name][listener_name] = listener

    def remove_handler(self, name, listener_name=None):

        # TODO add proper checks and specific exception if event is not supported

        if listener_name:

            del self._events[name][listener_name]

        else:

            self._events[name].clear()

    def dispatch(self, name, *args, **kwargs):

        # TODO add special exceptions for StopPropagation and PreventDefault

        for e in self._events[name].values():

            try:

                e(*args, **kwargs)

            except Exception:

                sys.stderr.write(traceback.format_exc())