get-poetry.py

# This is the Twisted Get Poetry Now! client, version 5.0

import optparse, random, sys

from twisted.internet import defer
from twisted.internet.protocol import Protocol, ClientFactory


def parse_args():
    usage = """usage: %prog [options] [hostname]:port ...

This is the Get Poetry Now! client, Twisted version 5.0
Run it like this:

  python get-poetry.py port1 port2 port3 ...

If you are in the base directory of the twisted-intro package,
you could run it like this:

  python twisted-client-5/get-poetry.py 10001 10002 10003

to grab poetry from servers on ports 10001, 10002, and 10003.

Of course, there need to be servers listening on those ports
for that to work.
"""

    parser = optparse.OptionParser(usage)

    _, addresses = parser.parse_args()

    if not addresses:
        print(parser.format_help())
        parser.exit()

    def parse_address(addr):
        if ':' not in addr:
            host = '127.0.0.1'
            port = addr
        else:
            host, port = addr.split(':', 1)

        if not port.isdigit():
            parser.error('Ports must be integers.')

        return host, int(port)

    return list(map(parse_address, addresses))


class PoetryProtocol(Protocol):

    poem = b''

    def dataReceived(self, data):
        self.poem += data

    def connectionLost(self, reason):
        self.poemReceived(self.poem)

    def poemReceived(self, poem):
        self.factory.poem_finished(poem)


class PoetryClientFactory(ClientFactory):

    protocol = PoetryProtocol

    def __init__(self, deferred):
        self.deferred = deferred

    def poem_finished(self, poem):
        if self.deferred is not None:
            d, self.deferred = self.deferred, None
            d.callback(poem)

    def clientConnectionFailed(self, connector, reason):
        if self.deferred is not None:
            d, self.deferred = self.deferred, None
            d.errback(reason)


def get_poetry(host, port):
    """
    Download a poem from the given host and port. This function
    returns a Deferred which will be fired with the complete text of
    the poem or a Failure if the poem could not be downloaded.
    """
    d = defer.Deferred()
    from twisted.internet import reactor
    factory = PoetryClientFactory(d)
    reactor.connectTCP(host, port, factory)
    return d


class GibberishError(Exception): pass

def cummingsify(poem):
    """
    Randomly do one of the following:

    1. Return a cummingsified version of the poem.
    2. Raise a GibberishError.
    3. Raise a ValueError.
    """

    def success():
        return poem.lower()

    def gibberish():
        raise GibberishError()

    def bug():
        raise ValueError()

    poem = poem.decode('utf8')
    return random.choice([success, gibberish, bug])()


def poetry_main():
    addresses = parse_args()

    from twisted.internet import reactor

    poems = []
    errors = []

    def try_to_cummingsify(poem):
        try:
            return cummingsify(poem)
        except GibberishError:
            raise
        except:
            print('Cummingsify failed!')
            return poem

    def got_poem(poem):
        print(poem)
        poems.append(poem)

    def poem_failed(err):
        print('The poem download failed.', file=sys.stderr)
        errors.append(err)

    def poem_done(_):
        if len(poems) + len(errors) == len(addresses):
            reactor.stop()

    for address in addresses:
        host, port = address
        d = get_poetry(host, port)
        d.addCallback(try_to_cummingsify)
        d.addCallbacks(got_poem, poem_failed)
        d.addBoth(poem_done)

    reactor.run()


if __name__ == '__main__':
    poetry_main()