Finger 的演变：清理 Finger 代码

简介

这是 Twisted 教程的第三部分 从头开始使用 Twisted，或 Finger 的演变 。

在本教程的这一部分中，我们将清理我们的代码，使其更接近可读且可扩展的风格。

编写可读代码

应用程序的最后一个版本有很多 hack。我们避免了子类化，不支持诸如通过 Web 进行用户列表之类的功能，并删除了所有空行——所有这些都是为了使代码更短。在这里，我们退一步，对更自然地进行子类化的内容进行子类化，使应该占用多行的内容占用多行，等等。这展示了一种更好的 Twisted 应用程序开发风格，尽管之前阶段的 hack 有时会在一次性原型中使用。

finger18.tac

# Do everything properly
import html

from twisted.application import internet, service, strports
from twisted.internet import defer, endpoints, protocol, reactor
from twisted.protocols import basic
from twisted.web import resource, server, static, xmlrpc
from twisted.words.protocols import irc


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"\r\n")
            self.transport.loseConnection()

        d.addCallback(writeValue)


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.encode("ascii"))
            d.addErrback(catchError)
            d.addCallback(lambda m: f"Status of {msg}: {m}")
            d.addCallback(lambda m: self.msg(user, m))


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

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

        def formatUsers(users):
            l = [f'<li><a href="{user}">{user}</a></li>' for user in users]
            return "<ul>" + "".join(l) + "</ul>"

        d.addCallback(formatUsers)
        d.addCallback(request.write)
        d.addCallback(lambda _: request.finish())
        return server.NOT_DONE_YET

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


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

    def render_GET(self, request):
        d = self.service.getUser(self.user)
        d.addCallback(html.escape)
        d.addCallback(lambda m: "<h1>%s</h1>" % self.user + "<p>%s</p>" % m)
        d.addCallback(request.write)
        d.addCallback(lambda _: request.finish())
        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)


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

    def _read(self):
        self.users.clear()
        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(list(self.users.keys()))

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

    def getResource(self):
        r = UserStatusTree(self)
        x = UserStatusXR(self)
        r.putChild("RPC2", x)
        return r

    def getIRCBot(self, nickname):
        f = protocol.ClientFactory()
        f.protocol = IRCReplyBot
        f.nickname = nickname
        f.getUser = self.getUser
        return f

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

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


application = service.Application("finger", uid=1, gid=1)
f = FingerService("/etc/users")
serviceCollection = service.IServiceCollection(application)
f.setServiceParent(serviceCollection)
strports.service("tcp:79", f.getFingerFactory()).setServiceParent(serviceCollection)
strports.service("tcp:8000", server.Site(f.getResource())).setServiceParent(
    serviceCollection
)
internet.ClientService(
    endpoints.clientFromString(reactor, "tcp:irc.freenode.org:6667"),
    f.getIRCBot("fingerbot"),
).setServiceParent(serviceCollection)