1 files changed, 47 insertions, 0 deletions

diff --git a/src/api/dashboard/mod.rs b/src/api/dashboard/mod.rs
index 8d954c0..6682cbd 100644
--- a/src/api/dashboard/mod.rs
+++ b/src/api/dashboard/mod.rs
@@ -490,6 +490,7 @@ pub(crate) fn router(state: AppState) -> Router<AppState> {
         .route("/admin/dashboard/events", get(events))
         .route("/admin/dashboard/refresh", post(refresh))
         .route("/admin/dashboard/links", post(set_links))
+        .route("/admin/dashboard/tree", get(writer_tree))
         .layer(Extension(Hub::new(state, closing)))
 }
 
@@ -551,6 +552,52 @@ async fn set_links(
     StatusCode::NO_CONTENT
 }
 
+#[derive(serde::Deserialize)]
+struct TreeQuery {
+    writer: String,
+}
+
+/// `GET /admin/dashboard/tree?writer=…`: the writer's tree (`swarm::tree`), as this node
+/// computes it from the member list and the links members report (whom each reaches;
+/// one that reports none counts as reaching its neighbours by the member list): every
+/// member's parent, `null` for one without. `404` if the writer isn't a member.
+async fn writer_tree(
+    Extension(hub): Extension<Arc<Hub>>,
+    Query(query): Query<TreeQuery>,
+) -> Response {
+    let state = &hub.state;
+    let mut reaches: BTreeMap<String, BTreeSet<String>> = state
+        .links
+        .replies()
+        .into_iter()
+        .map(|(member, _, links)| (member, reached_by(&links)))
+        .collect();
+    reaches.insert(
+        state.local_id().to_owned(),
+        reached_by(&links::own_links(state).await),
+    );
+    let reached = |by: &str, member: &str| {
+        reaches
+            .get(by)
+            .is_none_or(|reached| reached.contains(member))
+    };
+    match crate::swarm::tree::whole(state, &query.writer, &reached) {
+        Some(parents) => {
+            axum::Json(json!({ "writer": query.writer, "parents": parents })).into_response()
+        }
+        None => StatusCode::NOT_FOUND.into_response(),
+    }
+}
+
+/// Whom a member reaches, by its links: those neither dormant nor down.
+fn reached_by(links: &[Link]) -> BTreeSet<String> {
+    links
+        .iter()
+        .filter(|link| !link.dormant && !link.down)
+        .map(|link| link.peer.clone())
+        .collect()
+}
+
 /// `GET /admin/dashboard/state`: the latest snapshot, for a client that wants it whole.
 async fn current_state(Extension(hub): Extension<Arc<Hub>>) -> Response {
     hub.want();