clientbot: track failed KICKs with /NAMES & a timer

Suggested by @cooper.

This tracking system solves the problem of failed relay kicks causing channel desyncs, because what's seen as a successful KICK when PyLink is linked as a service might not forward
successfully on clientbot network. This can be caused due to the clientbot not being opped, the target being immune or having higher access than the clientbot, etc. When a NAMES reply
(delayed in this case) is received for any channel where an initial /WHO has already been received, a JOIN hook will be sent for any users on the kick queue to rejoin them on the relay.

protocols/clientbot.py

@@ -1,5 +1,6 @@
 import time
 import string
+import threading
 
 from pylinkirc import utils, conf
 from pylinkirc.log import log
@@ -22,6 +23,11 @@ class ClientbotWrapperProtocol(Protocol):
         # when ENDOFWHO is received.
         self.who_received = set()
 
+        # This stores channel->Timer object mappings for users that we're waiting for a kick
+        # acknowledgement for. The timer is set to send a NAMES request to the uplink to prevent
+        # things like failed KICK attempts from desyncing plugins like relay.
+        self.kick_queue = {}
+
     def _expandPUID(self, uid):
         """
         Returns the real nick for the given PUID.
@@ -131,6 +137,19 @@ class ClientbotWrapperProtocol(Protocol):
         self.irc.send('KICK %s %s :%s' % (channel, self._expandPUID(target), reason))
 
         # Don't update our state here: wait for the IRCd to send an acknowledgement instead.
+        # There is essentially a 3 second wait to do this, as we send NAMES with a delay
+        # to resync any users lost due to kicks being blocked, etc.
+        if (channel not in self.kick_queue) or (not self.kick_queue[channel][1].is_alive()):
+            # However, only do this if there isn't a NAMES request scheduled already.
+            t = threading.Timer(3, lambda: self.irc.send('NAMES %s' % channel))
+            log.debug('(%s) kick: setting NAMES timer for %s on %s', self.irc.name, target, channel)
+
+            # Store the channel, target UID, and timer object in the internal kick queue.
+            self.kick_queue[channel] = ({target}, t)
+            t.start()
+        else:
+            log.debug('(%s) kick: adding %s to kick queue for channel %s', self.irc.name, target, channel)
+            self.kick_queue[channel][0].add(target)
 
     def message(self, source, target, text, notice=False):
         """Sends messages to the target."""
@@ -306,8 +325,10 @@ class ClientbotWrapperProtocol(Protocol):
             # spawning in order to get a real ident/host.
             idsource = self.irc.nickToUid(nick) or self.spawnClient(nick, server=self.irc.uplink).uid
 
-            # Queue these virtual users to be joined if they're not already in the channel.
-            if idsource not in self.irc.channels[channel].users:
+            # Queue these virtual users to be joined if they're not already in the channel,
+            # or we're waiting for a kick acknowledgment for them.
+            if (idsource not in self.irc.channels[channel].users) or (idsource in \
+                    self.kick_queue.get(channel, ([],))[0]):
                 names.add(idsource)
                 self.irc.users[idsource].channels.add(channel)
 
@@ -325,8 +346,16 @@ class ClientbotWrapperProtocol(Protocol):
         log.debug('(%s) handle_353: adding users %s to %s', self.irc.name, names, channel)
         log.debug('(%s) handle_353: adding modes %s to %s', self.irc.name, modes, channel)
 
-        # We send the hook for JOIN after /who data is received, to enumerate the ident, host, and
-        # real names of users.
+        # Unless /WHO has already been received for the given channel, we generally send the hook
+        # for JOIN after /who data is received, to enumerate the ident, host, and real names of
+        # users.
+        if names and hasattr(self.irc.channels[channel], 'who_received'):
+            # /WHO *HAS* already been received. Send JOIN hooks here because we use this to keep
+            # track of any failed KICK attempts sent by the relay bot.
+            log.debug('(%s) handle_353: sending JOIN hook because /WHO was already received for %s',
+                      self.irc.name, channel)
+            return {'channel': channel, 'users': names, 'modes': self.irc.channels[channel].modes,
+                    'parse_as': "JOIN"}
 
     def handle_352(self, source, command, args):
         """
@@ -378,6 +407,7 @@ class ClientbotWrapperProtocol(Protocol):
         self.who_received.clear()
 
         channel = self.irc.toLower(args[1])
+        self.irc.channels[channel].who_received = True
 
         return {'channel': channel, 'users': users, 'modes': self.irc.channels[channel].modes,
                 'parse_as': "JOIN"}
@@ -405,6 +435,17 @@ class ClientbotWrapperProtocol(Protocol):
         except IndexError:
             reason = ''
 
+        if channel in self.kick_queue:
+            # Remove this client from the kick queue if present there.
+            log.debug('(%s) kick: removing %s from kick queue for channel %s', self.irc.name, target, channel)
+            self.kick_queue[channel][0].discard(target)
+
+            if not self.kick_queue[channel][0]:
+                log.debug('(%s) kick: cancelling kick timer for channel %s (all kicks accounted for)', self.irc.name, channel)
+                # There aren't any kicks that failed to be acknowledged. We can remove the timer now
+                self.kick_queue[channel][1].cancel()
+                del self.kick_queue[channel]
+
         self.part(target, channel, reason)
         return {'channel': channel, 'target': target, 'text': reason}