feat: Leave room when a transcriber is detected on joining.

src/main/java/org/jitsi/jigasi/JvbConference.java

@@ -51,6 +51,7 @@
 import org.jivesoftware.smack.packet.*;
 import org.jivesoftware.smackx.disco.*;
 import org.jivesoftware.smackx.disco.packet.*;
+import org.jivesoftware.smackx.muc.filter.*;
 import org.jivesoftware.smackx.muc.packet.*;
 import org.jivesoftware.smackx.nick.packet.*;
 import org.jivesoftware.smackx.xdata.packet.*;
@@ -447,6 +448,12 @@ private ExtensionElement addSupportedFeatures(
      */
     private final VisitorsMessagesListener visitorsMessagesListener = new VisitorsMessagesListener();
 
+    /**
+     * The Presence listener we use to monitor the initial participants when joining. We need this only when in
+     * transcriber mode. To make sure there is a single transcriber in the room.
+     */
+    private final ChatRoomPresenceListener presenceListener = new ChatRoomPresenceListener();
+
     /**
      * The features for the current xmpp provider we will use later adding to the room presence we send.
      */
@@ -964,35 +971,30 @@ public void joinConferenceRoom()
 
             if (mucRoom instanceof ChatRoomJabberImpl)
             {
+                ChatRoomJabberImpl chatRoom = (ChatRoomJabberImpl)mucRoom;
+
                 String displayName = gatewaySession.getMucDisplayName();
                 if (displayName != null)
                 {
-                    ((ChatRoomJabberImpl)mucRoom).addPresencePacketExtensions(
-                        new Nick(displayName));
+                    chatRoom.addPresencePacketExtensions(new Nick(displayName));
                 }
                 else
                 {
-                    logger.error(this.callContext
-                        + " No display name to use...");
+                    logger.error(this.callContext + " No display name to use...");
                 }
 
-                String region = JigasiBundleActivator.getConfigurationService()
-                    .getString(LOCAL_REGION_PNAME);
+                String region = JigasiBundleActivator.getConfigurationService().getString(LOCAL_REGION_PNAME);
                 if (StringUtils.isNotEmpty(region))
                 {
                     JitsiParticipantRegionPacketExtension rpe = new JitsiParticipantRegionPacketExtension();
                     rpe.setRegionId(region);
 
-                    ((ChatRoomJabberImpl)mucRoom)
-                        .addPresencePacketExtensions(rpe);
+                    chatRoom.addPresencePacketExtensions(rpe);
                 }
 
-                ((ChatRoomJabberImpl)mucRoom)
-                    .addPresencePacketExtensions(
-                        new ColibriStatsExtension.Stat(
-                            ColibriStatsExtension.VERSION,
-                            CurrentVersionImpl.VERSION.getApplicationName()
-                                + " " + CurrentVersionImpl.VERSION));
+                chatRoom.addPresencePacketExtensions(new ColibriStatsExtension.Stat(
+                    ColibriStatsExtension.VERSION,
+                        CurrentVersionImpl.VERSION.getApplicationName() + " " + CurrentVersionImpl.VERSION));
 
                 // creates an extension to hold all headers, as when using
                 // addPresencePacketExtensions it requires unique extensions
@@ -1011,15 +1013,22 @@ public void joinConferenceRoom()
                     });
                 if (!initiator.getChildExtensions().isEmpty())
                 {
-                    ((ChatRoomJabberImpl)mucRoom).addPresencePacketExtensions(initiator);
+                    chatRoom.addPresencePacketExtensions(initiator);
                 }
 
-                ((ChatRoomJabberImpl)mucRoom).addPresencePacketExtensions(this.features);
+                chatRoom.addPresencePacketExtensions(this.features);
+
+                if (this.isTranscriber)
+                {
+                    getConnection().addAsyncStanzaListener(
+                            presenceListener,
+                            new AndFilter(
+                                FromMatchesFilter.create(chatRoom.getIdentifierAsJid()), StanzaTypeFilter.PRESENCE));
+                }
             }
             else
             {
-                logger.error(this.callContext
-                    + " Cannot set presence extensions as chatRoom "
+                logger.error(this.callContext + " Cannot set presence extensions as chatRoom "
                     + "is not an instance of ChatRoomJabberImpl");
             }
 
@@ -2803,4 +2812,39 @@ public void processStanza(Stanza stanza)
 
             processVisitorsJson(jsonMsg.getJson());
         }
-    }}
+    }
+
+    /**
+     * Listens for presence packets.
+     */
+    private class ChatRoomPresenceListener
+        implements StanzaListener
+    {
+        /**
+         * Processes an incoming presence packet.
+         * @param packet the incoming packet.
+         */
+        @Override
+        public void processStanza(Stanza packet)
+        {
+            if (!(packet instanceof Presence) || packet.getError() != null)
+            {
+                logger.warn("Unable to handle packet: " + packet);
+                return;
+            }
+
+            Presence presence = (Presence) packet;
+            if (MUCUserStatusCodeFilter.STATUS_110_PRESENCE_TO_SELF.accept(presence))
+            {
+                getConnection().removeAsyncStanzaListener(this);
+            }
+            else if (Util.isTranscriberJigasi(presence))
+            {
+                getConnection().removeAsyncStanzaListener(this);
+
+                logger.warn(callContext + " Detected another transcriber in the room, will leave!");
+                stop();
+            }
+        }
+    }
+}

src/main/java/org/jitsi/jigasi/util/Util.java

@@ -31,6 +31,7 @@
 import org.jitsi.xmpp.extensions.jitsimeet.*;
 import org.jivesoftware.smack.bosh.*;
 import org.jivesoftware.smack.packet.*;
+import org.jivesoftware.smackx.muc.packet.*;
 import org.json.simple.*;
 import org.json.simple.parser.*;
 
@@ -314,6 +315,26 @@ private static boolean checkForFeature(ChatRoomMemberJabberImpl member, String f
         return features.getFeatureExtensions().stream().anyMatch(f -> f.getVar().equals(feature));
     }
 
+    /**
+     * Checks for the transcriber feature in presence.
+     * @param presence the presence to check,
+     * @return <tt>true</tt> when the presence is from a transcriber.
+     */
+    public static boolean isTranscriberJigasi(Presence presence)
+    {
+        FeaturesExtension features = presence.getExtension(FeaturesExtension.class);
+        MUCUser mucUser = (MUCUser) presence.getExtensionElement("x", "http://jabber.org/protocol/muc#user");
+
+        if (features == null || mucUser == null || mucUser.getItem() == null
+            || !getTrustedDomains().contains(mucUser.getItem().getJid().asDomainBareJid().toString()))
+        {
+            return false;
+        }
+
+        return features.getFeatureExtensions().stream()
+            .anyMatch(f -> f.getVar().equals(TRANSCRIBER_FEATURE_NAME));
+    }
+
     /**
      * Checks for the transcriber feature in presence.
      * @param member the member to check