# The Evolution of Finger: configuration of the finger service

## Introduction

This is the eleventh part of the Twisted tutorial Twisted from Scratch, or The Evolution of Finger .

In this part, we make it easier for non-programmers to configure a finger server. Plugins are discussed further in the Twisted Plugin System howto. Writing twistd plugins is covered in Writing a twistd Plugin, and .tac applications are covered in Using the Twisted Application Framework.

## Plugins

So far, the user had to be somewhat of a programmer to be able to configure stuff. Maybe we can eliminate even that? Move old code to `finger/__init__.py` and…

Full source code for finger module here:

`finger.py`

    # finger.py module

    from zope.interface import Interface, implementer

    from twisted.application import internet, service, strports
    from twisted.internet import defer, endpoints, protocol, reactor
    from twisted.protocols import basic
    from twisted.python import components, log
    from twisted.spread import pb
    from twisted.web import resource, server, xmlrpc
    from twisted.words.protocols import irc

    class IFingerService(Interface):
        def getUser(user):
            """
            Return a deferred returning a L{bytes}.
            """

        def getUsers():
            """
            Return a deferred returning a L{list} of L{bytes}.
            """

    class IFingerSetterService(Interface):
        def setUser(user, status):
            """
            Set the user's status to something.
            """

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

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

            def writeValue(value):
                self.transport.write(value + b"\n")
                self.transport.loseConnection()

            d.addCallback(writeValue)

    class IFingerFactory(Interface):
        def getUser(user):
            """
            Return a deferred returning L{bytes}.
            """

        def buildProtocol(addr):
            """
            Return a protocol returning L{bytes}.
            """

    @implementer(IFingerFactory)
    class FingerFactoryFromService(protocol.ServerFactory):

        protocol = FingerProtocol

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

        def getUser(self, user):
            return self.service.getUser(user)

    components.registerAdapter(FingerFactoryFromService, IFingerService, IFingerFactory)

    class FingerSetterProtocol(basic.LineReceiver):
        def connectionMade(self):
            self.lines = []

        def lineReceived(self, line):
            self.lines.append(line)

        def connectionLost(self, reason):
            if len(self.lines) == 2:
                self.factory.setUser(*self.lines)

    class IFingerSetterFactory(Interface):
        def setUser(user, status):
            """
            Return a deferred returning L{bytes}.
            """

        def buildProtocol(addr):
            """
            Return a protocol returning L{bytes}.
            """

    @implementer(IFingerSetterFactory)
    class FingerSetterFactoryFromService(protocol.ServerFactory):

        protocol = FingerSetterProtocol

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

        def setUser(self, user, status):
            self.service.setUser(user, status)

    components.registerAdapter(
        FingerSetterFactoryFromService, IFingerSetterService, IFingerSetterFactory
    )

    class IRCReplyBot(irc.IRCClient):
        def connectionMade(self):
            self.nickname = self.factory.nickname
            irc.IRCClient.connectionMade(self)

        def privmsg(self, user, channel, msg):
            user = user.split("!")[0]
            if self.nickname.lower() == channel.lower():
                d = self.factory.getUser(msg)
                d.addErrback(catchError)
                d.addCallback(lambda m: f"Status of {msg}: {m}")
                d.addCallback(lambda m: self.msg(user, m))

    class IIRCClientFactory(Interface):

        """
        @ivar nickname
        """

        def getUser(user):
            """
            Return a deferred returning L{bytes}.
            """

        def buildProtocol(addr):
            """
            Return a protocol.
            """

    @implementer(IIRCClientFactory)
    class IRCClientFactoryFromService(protocol.ClientFactory):

        protocol = IRCReplyBot
        nickname = None

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

        def getUser(self, user):
            return self.service.getUser(user)

    components.registerAdapter(
        IRCClientFactoryFromService, IFingerService, IIRCClientFactory
    )

    class UserStatusTree(resource.Resource):

        template = """<html><head><title>Users</title></head><body>
        <h1>Users</h1>
        <ul>
        %(users)s
        </ul>
        </body>
        </html>"""

        def __init__(self, service):
            resource.Resource.__init__(self)
            self.service = service

        def getChild(self, path, request):
            if path == "":
                return self
            elif path == "RPC2":
                return UserStatusXR(self.service)
            else:
                return UserStatus(path, self.service)

        def render_GET(self, request):
            users = self.service.getUsers()

            def cbUsers(users):
                request.write(
                    self.template
                    % {
                        "users": "".join(
                            [
                                # Name should be quoted properly these uses.
                                f'<li><a href="{name}">{name}</a></li>'
                                for name in users
                            ]
                        )
                    }
                )
                request.finish()

            users.addCallback(cbUsers)

            def ebUsers(err):
                log.err(err, "UserStatusTree failed")
                request.finish()

            users.addErrback(ebUsers)
            return server.NOT_DONE_YET

    components.registerAdapter(UserStatusTree, IFingerService, resource.IResource)

    class UserStatus(resource.Resource):

        template = """<html><head><title>%(title)s</title></head>
        <body><h1>%(name)s</h1><p>%(status)s</p></body></html>"""

        def __init__(self, user, service):
            resource.Resource.__init__(self)
            self.user = user
            self.service = service

        def render_GET(self, request):
            status = self.service.getUser(self.user)

            def cbStatus(status):
                request.write(
                    self.template
                    % {"title": self.user, "name": self.user, "status": status}
                )
                request.finish()

            status.addCallback(cbStatus)

            def ebStatus(err):
                log.err(err, "UserStatus failed")
                request.finish()

            status.addErrback(ebStatus)
            return server.NOT_DONE_YET

    class UserStatusXR(xmlrpc.XMLRPC):
        def __init__(self, service):
            xmlrpc.XMLRPC.__init__(self)
            self.service = service

        def xmlrpc_getUser(self, user):
            return self.service.getUser(user)

        def xmlrpc_getUsers(self):
            return self.service.getUsers()

    class IPerspectiveFinger(Interface):
        def remote_getUser(username):
            """
            Return a user's status.
            """

        def remote_getUsers():
            """
            Return a user's status.
            """

    @implementer(IPerspectiveFinger)
    class PerspectiveFingerFromService(pb.Root):
        def __init__(self, service):
            self.service = service

        def remote_getUser(self, username):
            return self.service.getUser(username)

        def remote_getUsers(self):
            return self.service.getUsers()

    components.registerAdapter(
        PerspectiveFingerFromService, IFingerService, IPerspectiveFinger
    )

    @implementer(IFingerService)
    class FingerService(service.Service):
        def __init__(self, filename):
            self.filename = filename

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

        def getUsers(self):
            return defer.succeed(self.users.keys())

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

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

    # Easy configuration

    def makeService(config):
        # finger on port 79
        s = service.MultiService()
        f = FingerService(config["file"])
        h = strports.service("tcp:1079", IFingerFactory(f))
        h.setServiceParent(s)

        # website on port 8000
        r = resource.IResource(f)
        r.templateDirectory = config["templates"]
        site = server.Site(r)
        j = strports.service("tcp:8000", site)
        j.setServiceParent(s)

        # ssl on port 443
        #    if config.get('ssl'):
        #        k = strports.service(
        #            "ssl:port=443:certKey=cert.pem:privateKey=key.pem", site
        #        )
        #        k.setServiceParent(s)

        # irc fingerbot
        if "ircnick" in config:
            i = IIRCClientFactory(f)
            i.nickname = config["ircnick"]
            ircserver = config["ircserver"]
            b = internet.ClientService(
                endpoints.HostnameEndpoint(reactor, ircserver, 6667), i
            )
            b.setServiceParent(s)

        # Pespective Broker on port 8889
        if "pbport" in config:
            m = internet.StreamServerEndpointService(
                endpoints.TCP4ServerEndpoint(reactor, int(config["pbport"])),
                pb.PBServerFactory(IPerspectiveFinger(f)),
            )
            m.setServiceParent(s)

        return s

`tap.py`

    # finger/tap.py
    import finger

    from twisted.application import internet, service
    from twisted.internet import interfaces
    from twisted.python import usage

    class Options(usage.Options):

        optParameters = [
            ["file", "f", "/etc/users"],
            ["templates", "t", "/usr/share/finger/templates"],
            ["ircnick", "n", "fingerbot"],
            ["ircserver", None, "irc.freenode.net"],
            ["pbport", "p", 8889],
        ]

        optFlags = [["ssl", "s"]]

    def makeService(config):
        return finger.makeService(config)

And register it all:

`finger_tutorial.py`

    from twisted.application.service import ServiceMaker

    finger = ServiceMaker("finger", "finger.tap", "Run a finger service", "finger")

Note that the second argument to `ServiceMaker` ,``finger.tap`` , is a reference to a module (`finger/tap.py` ), not to a filename.

And now, the following works

    % sudo twistd -n finger --file=/etc/users --ircnick=fingerbot

For more details about this, see the twistd plugin documentation .