def __init__(self, messages):
"""Create a new application that expects to have plugins that implement
a listener and messager for each message in messages.
"""
self.dispatcher = Dispatcher()
self.needed_listeners = set(messages)
self.needed_listeners.add('APP_START')
self.needed_messengers = set(messages)
self.needed_messengers.add('APP_STOP')
self.valid = False
class Application(object):
"""An application is defined as a set of messages that will be generated and
responded to by plugins, and a Dispatcher that handles communication between
plugins.
Applications expect, at the least, a Plugin that listens for 'APP_START',
and one that generates 'APP_STOP'
"""
def __init__(self, messages):
"""Create a new application that expects to have plugins that implement
a listener and messager for each message in messages.
"""
self.dispatcher = Dispatcher()
self.needed_listeners = set(messages)
self.needed_listeners.add('APP_START')
self.needed_messengers = set(messages)
self.needed_messengers.add('APP_STOP')
self.valid = False
def register(self, plugin):
"""Take a feather.plugin.Plugin and tell our dispatcher about it.
Plugins are expected to provide a list of the messages that they
listen for and generate. If registering this plugin makes it so we have
at least one plugin listening for and generating our expected messages,
set self.valid to true
"""
self.needed_listeners -= plugin.listeners
self.needed_messengers -= plugin.messengers
if self.needed_messengers == self.needed_listeners == set():
self.valid = True
self.dispatcher.register(plugin)
def start(self):
"""If we have a set of plugins that provide our expected listeners and
messengers, tell our dispatcher to start up. Otherwise, raise
InvalidApplication
"""
if not self.valid:
err = ("\nMessengers and listeners that still need set:\n\n"
"messengers : %s\n\n"
"listeners : %s\n")
raise InvalidApplication(err % (self.needed_messengers,
self.needed_listeners))
self.dispatcher.start()
