swarm: announce to whom writers can't reach

1 files changed, 29 insertions, 18 deletions

diff --git a/src/swarm/topology/mod.rs b/src/swarm/topology/mod.rs
index 30fa56e..946fc33 100644
--- a/src/swarm/topology/mod.rs
+++ b/src/swarm/topology/mod.rs
@@ -133,31 +133,42 @@ pub(crate) fn is_neighbour(state: &AppState, peer: &str) -> bool {
 pub(crate) fn intended_graph(state: &AppState) -> Option<BTreeMap<String, BTreeSet<String>>> {
     let view = state.neighbours.read_or_recover();
     let view = view.as_ref()?;
-    let unreachable = |member: &str| view.unreachable.contains(member);
-    let stable = |member: &str| view.stable.contains(member);
     let graph = view
         .members
         .iter()
-        .map(|member| {
-            let neighbours = if member == state.local_id() {
-                view.neighbours.clone()
-            } else {
-                let own = view.transports.get(member).cloned().unwrap_or_default();
-                neighbours_across(
-                    &view.transports,
-                    member,
-                    &own,
-                    view.k,
-                    &unreachable,
-                    &stable,
-                )
-            };
-            (member.clone(), neighbours)
-        })
+        .map(|member| (member.clone(), view.neighbours_of(state.local_id(), member)))
         .collect();
     Some(graph)
 }
 
+/// `member`'s neighbours as the member list makes them, as this node sees it (as in
+/// `intended_graph`); None until the view is known, or for one the list doesn't have.
+pub(crate) fn neighbours_of(state: &AppState, member: &str) -> Option<BTreeSet<String>> {
+    let view = state.neighbours.read_or_recover();
+    let view = view.as_ref()?;
+    view.members
+        .iter()
+        .any(|listed| listed == member)
+        .then(|| view.neighbours_of(state.local_id(), member))
+}
+
+impl NeighbourView {
+    fn neighbours_of(&self, local: &str, member: &str) -> BTreeSet<String> {
+        if member == local {
+            return self.neighbours.clone();
+        }
+        let own = self.transports.get(member).cloned().unwrap_or_default();
+        neighbours_across(
+            &self.transports,
+            member,
+            &own,
+            self.k,
+            &|member| self.unreachable.contains(member),
+            &|member| self.stable.contains(member),
+        )
+    }
+}
+
 /// How the neighbours changed.
 pub(crate) struct NeighbourChange {
     pub(crate) added: Vec<String>,