truly public forum: auto-discover other instances via RNS announce handler

tinyweb_forum/sync.py

@@ -8,6 +8,24 @@ SYNC_INTERVAL = 300  # 5 minutes
 REQUEST_TIMEOUT = 60
 
 
+class _ForumAnnounceHandler:
+    """Receives announces from other forum instances and auto-discovers them."""
+
+    aspect_filter = FORUM_APP
+    receive_path_responses = False
+
+    def __init__(self, fdb, identity):
+        self.fdb = fdb
+        self.my_hash = identity.hash.hex() if identity else "local"
+
+    def received_announce(self, destination_hash, announced_identity, app_data):
+        if announced_identity is None:
+            return
+        peer_hash = announced_identity.hash.hex()
+        if peer_hash and peer_hash != self.my_hash:
+            self.fdb.add_known_peer(peer_hash)
+
+
 class ForumSync:
     def __init__(self, fdb, identity, reticulum, handlers_ref):
         self.fdb = fdb
@@ -15,6 +33,7 @@ class ForumSync:
         self.reticulum = reticulum
         self.handlers_ref = handlers_ref
         self.destination = None
+        self._announce_handler = None
         self._running = False
         self._thread = None
 
@@ -30,13 +49,21 @@ class ForumSync:
             response_generator=self._rns_handler,
             allow=RNS.Destination.ALLOW_ALL,
         )
-        self.destination.announce()
+        self.destination.announce(app_data=FORUM_APP.encode("utf-8"))
+        # Auto-discover other forum instances via announces
+        self._announce_handler = _ForumAnnounceHandler(self.fdb, self.identity)
+        RNS.Transport.register_announce_handler(self._announce_handler)
         self._running = True
         self._thread = threading.Thread(target=self._sync_loop, daemon=True)
         self._thread.start()
 
     def stop(self):
         self._running = False
+        if self._announce_handler:
+            try:
+                RNS.Transport.deregister_announce_handler(self._announce_handler)
+            except Exception:
+                pass
 
     def _rns_handler(self, path, data, request_id, link_id, remote_identity, requested_at):
         if remote_identity: