subscriber.py

import re
 
def slugify(string, delim="-"):
    """ Return a (naively) normalized slug of a string"""
    words = re.split(r"\W+", string.lower())
    return delim.join(words).strip("-")
 
class Provider(object):
    """ A provider holds its publishers alongside their
    subscribers and can run the published content to
    the appropriate subscribers"""
 
    def __init__(self):
        self.queue = []
        self.publishers = {}
 
    def notify(self, content):
        self.queue.append(content)
 
    def subscribe(self, subscriber, publisher):
        self.publishers.setdefault(publisher.slug, []).append(subscriber)
 
    def unsubscribe(self, subscriber, publisher):
        self.publishers[publisher].remove(subscriber)
 
    def update(self):
        # item = (content, slug)
        for item in self.queue:
            for sub in self.publishers.get(item[1], []):
                sub.run(item[0])
        self.queue = []
 
 
class Publisher(object):
    def __init__(self, name, provider):
        self.name = name
        self.slug = slugify(self.name)
        self.provider = provider
 
    def publish(self, content):
        self.provider.notify((content, self.slug))
 
 
class Subscriber(object):
    def __init__(self, name, provider):
        self.name = name
        self.provider = provider
 
    def subscribe(self, publisher):
        self.provider.subscribe(self, publisher)
 
    def run(self, content):
        # just a demonstration of the subscriber's capabilities
        print("[{}]: I got '{}' ({})".format(self.name, 
            content.slug, content.publisher.name))
 
 
class Content(object):
    def __init__(self, publisher, name, data={}):
        self.publisher = publisher
        self.name = name
        self.slug = slugify(self.name)
        self.data = data
 
 
def main():
    # create a new provider
    sky = Provider()
 
    # add a publisher
    movies = Publisher("Sky Movies", sky)
    atlantic = Publisher("Sky Atlantic", sky)
 
    # add a subscriber and give him a subscription
    guy = Subscriber("guy", sky)
    guy.subscribe(movies)
    guy.subscribe(atlantic)
 
    bob = Subscriber("bob", sky)
    bob.subscribe(movies)
 
    # publish some dummy content
    movies.publish(Content(movies, "film"))
 
    atlantic.publish(Content(atlantic, "american show"))
 
    # update the provider and send the queued content
    # to the appropriate subscribers
    sky.update()
 
if __name__ == '__main__':
    main()