# Read username, output from non-empty factory, drop connections
# Use deferreds, to minimize synchronicity assumptions

from twisted.internet import defer, endpoints, protocol, reactor
from twisted.protocols import basic


class FingerProtocol(basic.LineReceiver):
    def lineReceived(self, user):
        d = self.factory.getUser(user)

        def onError(err):
            return "Internal error in server"

        d.addErrback(onError)

        def writeResponse(message):
            self.transport.write(message + b"\r\n")
            self.transport.loseConnection()

        d.addCallback(writeResponse)


class FingerFactory(protocol.ServerFactory):
    protocol = FingerProtocol

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

    def getUser(self, user):
        return defer.succeed(self.users.get(user, b"No such user"))


fingerEndpoint = endpoints.serverFromString(reactor, "tcp:1079")
fingerEndpoint.listen(FingerFactory({b"moshez": b"Happy and well"}))
reactor.run()