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

tests/test_sync.py

@@ -378,6 +378,57 @@ def test_sync_peer_discovery():
         shutil.rmtree(dir_c)
 
 
+def test_announce_handler():
+    """Announce handler should auto-discover peers."""
+    dir_a = tempfile.mkdtemp()
+    try:
+        fdb = ForumDB(dir_a)
+        from tinyweb_forum.sync import _ForumAnnounceHandler
+
+        # Mock identity — RNS identity.hash returns bytes
+        class MockIdentity:
+            def __init__(self, h):
+                self._hash_hex = h
+            @property
+            def hash(self):
+                return bytes.fromhex(self._hash_hex)
+
+        local_hex = "aa" * 16
+        peer_hex = "bb" * 16
+
+        handler = _ForumAnnounceHandler(fdb, MockIdentity(local_hex))
+
+        class MockAnnouncedIdentity:
+            def __init__(self, h):
+                self._hash_hex = h
+            @property
+            def hash(self):
+                return bytes.fromhex(self._hash_hex)
+
+        # Announce from a peer
+        handler.received_announce(
+            destination_hash=bytes.fromhex(peer_hex),
+            announced_identity=MockAnnouncedIdentity(peer_hex),
+            app_data=b"tinyweb-forum",
+        )
+
+        known = [r["instance_hash"] for r in fdb.get_synced_instances()]
+        assert peer_hex in known, "peer should be added to sync list"
+
+        # Announce from ourselves should be ignored
+        handler.received_announce(
+            destination_hash=bytes.fromhex(local_hex),
+            announced_identity=MockAnnouncedIdentity(local_hex),
+            app_data=b"tinyweb-forum",
+        )
+
+        known = [r["instance_hash"] for r in fdb.get_synced_instances()]
+        assert known.count(local_hex) == 0, "own announce should be ignored"
+    finally:
+        import shutil
+        shutil.rmtree(dir_a)
+
+
 if __name__ == "__main__":
     test_sync_thread()
     test_sync_reply()
@@ -388,4 +439,5 @@ if __name__ == "__main__":
     test_sync_block_gossip()
     test_sync_updated_content()
     test_sync_peer_discovery()
+    test_announce_handler()
     print("all sync tests passed")

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: