from rdflib import events


class AddedEvent(events.Event):
    pass


class RemovedEvent(events.Event):
    pass


def subscribe_to(source, target):
    target.subscribe(AddedEvent, source._add_handler)
    target.subscribe(RemovedEvent, source._remove_handler)


def subscribe_all(caches):
    for cache in caches:
        for other in caches:
            if other != cache:
                subscribe_to(cache, other)


class Cache(events.Dispatcher):
    def __init__(self, data=None):
        if data is None:
            data = {}
        self._data = data
        self.subscribe(AddedEvent, self._add_handler)
        self.subscribe(RemovedEvent, self._remove_handler)

    def _add_handler(self, event):
        self._data[event.key] = event.value

    def _remove_handler(self, event):
        del self._data[event.key]

    def __getitem__(self, key):
        return self._data[key]

    def __setitem__(self, key, value):
        self.dispatch(AddedEvent(key=key, value=value))

    def __delitem__(self, key):
        self.dispatch(RemovedEvent(key=key))

    def __contains__(self, key):
        return key in self._data

    has_key = __contains__


class TestEvent:
    def testEvents(self):
        c1 = Cache()
        c2 = Cache()
        c3 = Cache()
        subscribe_all([c1, c2, c3])
        c1["bob"] = "uncle"
        assert c2["bob"] == "uncle"
        assert c3["bob"] == "uncle"
        del c3["bob"]
        assert ("bob" in c1) is False
        assert ("bob" in c2) is False
