protocols/gossipsub: Add public accessors (#1677)

Co-authored-by: Toralf Wittner <tw@dtex.org>
Co-authored-by: Max Inden <mail@max-inden.de>

protocols/gossipsub/CHANGELOG.md

@@ -1,5 +1,7 @@
 # 0.21.0 [unreleased]
 
+- Add public API to list topics and peers. [PR 1677](https://github.com/libp2p/rust-libp2p/pull/1677).
+
 - Add message signing and extended privacy/validation configurations. [PR 1583](https://github.com/libp2p/rust-libp2p/pull/1583).
 
 - `Debug` instance for `Gossipsub`. [PR 1673](https://github.com/libp2p/rust-libp2p/pull/1673).

protocols/gossipsub/src/behaviour.rs

@@ -221,6 +221,25 @@ impl Gossipsub {
         }
     }
 
+    /// Lists the hashes of the topics we are currently subscribed to.
+    pub fn topics(&self) -> impl Iterator<Item = &TopicHash> {
+        self.mesh.keys()
+    }
+
+    /// Lists peers for a certain topic hash.
+    pub fn peers(&self, topic_hash: &TopicHash) -> impl Iterator<Item = &PeerId> {
+        self.mesh.get(topic_hash).into_iter().map(|x| x.into_iter()).flatten()
+    }
+
+    /// Lists all peers for any topic.
+    pub fn all_peers(&self) -> impl Iterator<Item = &PeerId> {
+        let mut res = BTreeSet::new();
+        for peers in self.mesh.values() {
+            res.extend(peers);
+        }
+        res.into_iter()
+    }
+
     /// Subscribe to a topic.
     ///
     /// Returns true if the subscription worked. Returns false if we were already subscribed.
@@ -1508,10 +1527,10 @@ impl fmt::Debug for Gossipsub {
 impl fmt::Debug for PublishConfig {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
-            PublishConfig::Signing { author, .. } => f.write_fmt(format_args!("PublishConfig::Signing({})", author)), 
-            PublishConfig::Author(author) => f.write_fmt(format_args!("PublishConfig::Author({})", author)), 
-            PublishConfig::RandomAuthor => f.write_fmt(format_args!("PublishConfig::RandomAuthor")), 
-            PublishConfig::Anonymous => f.write_fmt(format_args!("PublishConfig::Anonymous")), 
+            PublishConfig::Signing { author, .. } => f.write_fmt(format_args!("PublishConfig::Signing({})", author)),
+            PublishConfig::Author(author) => f.write_fmt(format_args!("PublishConfig::Author({})", author)),
+            PublishConfig::RandomAuthor => f.write_fmt(format_args!("PublishConfig::RandomAuthor")),
+            PublishConfig::Anonymous => f.write_fmt(format_args!("PublishConfig::Anonymous")),
         }
     }
 }

protocols/gossipsub/src/behaviour/tests.rs

@@ -895,4 +895,27 @@ mod tests {
         // Peers should be removed to reach mesh_n
         assert_eq!(gs.mesh.get(&topics[0]).unwrap().len(), config.mesh_n);
     }
+
+    // Some very basic test of public api methods.
+    #[test]
+    fn test_public_api() {
+        let (gs, peers, topic_hashes) =
+            build_and_inject_nodes(4, vec![String::from("topic1")], true);
+        let peers = peers.into_iter().collect::<BTreeSet<_>>();
+
+        assert_eq!(
+            gs.topics().cloned().collect::<Vec<_>>(), topic_hashes,
+            "Expected topics to match registered topic."
+        );
+
+        assert_eq!(
+            gs.peers(&TopicHash::from_raw("topic1")).cloned().collect::<BTreeSet<_>>(), peers,
+            "Expected peers for a registered topic to contain all peers."
+        );
+
+        assert_eq!(
+            gs.all_peers().cloned().collect::<BTreeSet<_>>(), peers,
+            "Expected all_peers to contain all peers."
+        );
+    }
 }