Twisted Timeout Etude (with Deferred) 1

# A solution to exercise 1 of the Twisted tutorial at http://krondo.com/blog/?p=1778

# class PoetryProtocol is the only thing changed from get-poetry client 4.0

class PoetryTimeoutError(Exception): pass

class PoetryProtocol(Protocol):

    poem = ''

    def connectionMade(self):
        port = self.transport.getPeer().port
        self.onTime = None
        # poetry downloads on even numbered ports time out after 1 sec
        # just another of the ways the universe is stacked against poetry
        if not port % 2:
            self.onTime = True
            from twisted.internet import reactor
            self.timer = reactor.callLater(1, self.timeout)

    def timeout(self):
        self.onTime = False
        self.transport.loseConnection()

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

    def connectionLost(self, reason):
        if self.onTime is not None:
            if self.onTime == True:
                self.timer.cancel()
            else:
                err = PoetryTimeoutError('Evil timeout stole your poetry again!')
                self.factory.deferred.errback(Failure(err))
                return
        self.poemReceived(self.poem)

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