# Read from file
from twisted.application import service, strports
from twisted.internet import protocol, reactor, defer
from twisted.protocols import basic

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

        def onError(err):
            return b'Internal error in server'
        d.addErrback(onError)

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


class FingerService(service.Service):
    def __init__(self, filename):
        self.users = {}
        self.filename = filename

    def _read(self):
        with open(self.filename, "rb") as f:
            for line in f:
                user, status = line.split(b':', 1)
                user = user.strip()
                status = status.strip()
                self.users[user] = status
        self.call = reactor.callLater(30, self._read)

    def startService(self):
        self._read()
        service.Service.startService(self)

    def stopService(self):
        service.Service.stopService(self)
        self.call.cancel()

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

    def getFingerFactory(self):
        f = protocol.ServerFactory()
        f.protocol = FingerProtocol
        f.getUser = self.getUser
        return f


application = service.Application('finger', uid=1, gid=1)
f = FingerService('/etc/users')
finger = strports.service("tcp:79", f.getFingerFactory())

finger.setServiceParent(service.IServiceCollection(application))
f.setServiceParent(service.IServiceCollection(application))