1 files changed, 35 insertions, 0 deletions
diff --git a/src/swarm/tree.rs b/src/swarm/tree.rs
index 0aef94c..81004e8 100644
--- a/src/swarm/tree.rs
+++ b/src/swarm/tree.rs
@@ -370,6 +370,41 @@ pub(crate) async fn own_parent(state: &AppState, writer: &str) -> Option<String>
     parent(&graph, &distance, &reached, &round_trip, state.local_id()).map(str::to_owned)
 }
 
+/// Where we are in `writer`'s tree, as we see it: our distance from the writer, our
+/// parent (`parent`), and the neighbours we reach that come before us (whom we could
+/// take). None while the member list isn't known, or the writer or we aren't in it.
+#[cfg(test)]
+pub(crate) struct Place {
+    pub(crate) distance: u32,
+    pub(crate) parent: Option<String>,
+    pub(crate) before: Vec<String>,
+}
+
+#[cfg(test)]
+pub(crate) async fn own_place(state: &AppState, writer: &str) -> Option<Place> {
+    let (graph, distance) = distances(state, topology::pair_key(writer))?;
+    let known = known_reaches(state, &graph).await;
+    let reached = |by: &str, member: &str| known.reached(by, member);
+    let round_trip = |by: &str, member: &str| known.round_trip(by, member);
+    let me = state.local_id();
+    let its_rank = rank(&graph, &distance, &reached, me)?;
+    let before = graph
+        .get(me)
+        .into_iter()
+        .flatten()
+        .filter(|candidate| {
+            rank(&graph, &distance, &reached, candidate).is_some_and(|r| r < its_rank)
+                && reached(me, candidate)
+        })
+        .cloned()
+        .collect();
+    Some(Place {
+        distance: distance[me],
+        parent: parent(&graph, &distance, &reached, &round_trip, me).map(str::to_owned),
+        before,
+    })
+}
+
 /// `Latencies` of our own tree, by `latency(from, to)` in milliseconds; None while the
 /// member list isn't known, or we aren't in it, or the tree reaches nobody.
 #[cfg(test)]