api: add support for shallow store reads

1 files changed, 37 insertions, 0 deletions

diff --git a/src/api/store.rs b/src/api/store.rs
index d0fc807..7e8caed 100644
--- a/src/api/store.rs
+++ b/src/api/store.rs
@@ -32,6 +32,10 @@ pub(crate) struct ReadQuery {
     /// to base a replacing remake on exactly what was read.
     #[serde(default)]
     heads: bool,
+    /// What's there, one level deep (`store::read_shallow`), to browse a large store a
+    /// level at a time.
+    #[serde(default)]
+    shallow: bool,
 }
 
 #[derive(Debug, Deserialize)]
@@ -54,6 +58,9 @@ pub(crate) async fn get_store_root(
     headers: HeaderMap,
     Query(query): Query<ReadQuery>,
 ) -> Result<Response, StatusCode> {
+    if query.shallow {
+        return shallow(&state, Vec::new(), true, &query).await;
+    }
     let accept = headers.get(ACCEPT).cloned();
     let want_conflicts = query.conflicts;
 
@@ -91,6 +98,9 @@ pub(crate) async fn get_store_entry(
     Query(query): Query<ReadQuery>,
 ) -> Result<Response, StatusCode> {
     let path = parse_key_path(&key)?;
+    if query.shallow {
+        return shallow(&state, path, false, &query).await;
+    }
 
     let accept = headers.get(ACCEPT).cloned();
     let want_conflicts = query.conflicts;
@@ -121,6 +131,33 @@ pub(crate) async fn get_store_entry(
     mark_source(response, source, heads)
 }
 
+/// `?shallow=true`: what's at `path`, one level deep, as JSON (`store::read_shallow`);
+/// with conflicts asked for too, `400`. `unready_live` as `render_read` has it.
+async fn shallow(
+    state: &AppState,
+    path: Vec<String>,
+    unready_live: bool,
+    query: &ReadQuery,
+) -> Result<Response, StatusCode> {
+    if query.conflicts {
+        return Err(StatusCode::BAD_REQUEST);
+    }
+    let (response, source, heads) = state
+        .render_read(
+            unready_live,
+            query.heads,
+            move |doc| store::read_shallow(doc, &path),
+            move |result| {
+                let value = result
+                    .map_err(|e| store_status(e, "Failed to read store path"))?
+                    .ok_or(StatusCode::NOT_FOUND)?;
+                response_for_value(&value, None)
+            },
+        )
+        .await?;
+    mark_source(response, source, heads)
+}
+
 /// Header on reads served from the pre-rejoin document; its value is that epoch.
 const STALE_HEADER: &str = "x-continuum-stale";