ChannelLogger: rewrite relayed messages echoed by the server

The former code worked only with emulated echo-message, as it depends
on internal tags.
In case echo-message (and labeled-response) is enabled, rely on
remembering the label instead.

plugins/ChannelLogger/plugin.py

@@ -68,6 +68,10 @@ class ChannelLogger(callbacks.Plugin):
         self.flusher = self.flush
         world.flushers.append(self.flusher)
 
+        # 10 minutes is long enough to be confident the server won't send
+        # messages after they timeouted.
+        self._emitted_relayed_msgs = utils.structures.ExpiringDict(10*60)
+
     def die(self):
         for log in self._logs():
             log.close()
@@ -190,7 +194,19 @@ class ChannelLogger(callbacks.Plugin):
                 nick = msg.nick or irc.nick
                 rewriteRelayed = self.registryValue('rewriteRelayed',
                                                     channel, irc.network)
-                if rewriteRelayed and msg.tagged('ChannelLogger__relayed'):
+                if msg.tagged('ChannelLogger__relayed'):
+                    wasRelayed = True
+                elif 'label' in msg.server_tags:
+                    label = msg.server_tags['label']
+                    if label in self._emitted_relayed_msgs:
+                        del self._emitted_relayed_msgs[label]
+                        wasRelayed = True
+                    else:
+                        wasRelayed = False
+                else:
+                    wasRelayed = False
+
+                if rewriteRelayed and wasRelayed:
                     (nick, text) = text.split(' ', 1)
                     nick = nick[1:-1]
                     msg.args = (recipients, text)
@@ -284,9 +300,24 @@ class ChannelLogger(callbacks.Plugin):
         # Gotta catch my own messages *somehow* :)
         # Let's try this little trick...
         if msg.command in ('PRIVMSG', 'NOTICE'):
-            # Other messages should be sent back to us.
-            if msg.tagged('relayedMsg'):
-                msg.tag('ChannelLogger__relayed')
+            rewriteRelayed = self.registryValue(
+                'rewriteRelayed', msg.channel, irc.network)
+            if rewriteRelayed and  'echo-message' in self.state.capabilities_ack:
+                assert 'labeled-response' in self.state.capabilities_ack, \
+                    'echo-message was negotiated without labeled-response.'
+                # If we negotiated the echo-message cap, we have to remember
+                # this message was relayed when the server sends it back to us.
+                if 'label' not in msg.server_tags:
+                    msg.server_tags['label'] = ircutils.makeLabel()
+                if msg.tagged('relayedMsg'):
+                    # Remember this was a relayed message, in case
+                    # rewriteRelayed is True.
+                    self._emitted_relayed_msgs[msg.server_tags['label']] = True
+            else:
+                # Else, we can simply rely on internal tags, because echos are
+                # simulated.
+                if msg.tagged('relayedMsg'):
+                    m.tag('ChannelLogger__relayed')
         return msg