"""Class-based event handlers
"""
import zope.event

registry = {}

def handler(event_class, handler=None):
    if handler is None:
        return lambda func: handler(event_class, func)

    if not registry:
        zope.event.subscribers.append(dispatch)

    if event_class not in registry:
        registry[event_class] = [handler]
    else:
        registry[event_class].append(handler)

def dispatch(event):
    for event_class in event.__class__.__mro__:
        for handler in registry.get(event_class, ()):
            handler(event)