2 files changed, 63 insertions, 15 deletions

diff --git a/src/api/mod.rs b/src/api/mod.rs
index 3f60cd6..1f178e7 100644
--- a/src/api/mod.rs
+++ b/src/api/mod.rs
@@ -49,6 +49,7 @@ pub(crate) fn router(
             "/store/{*key}",
             get(store::get_store_entry)
                 .put(store::put_store_entry)
+                .post(store::post_store_entry)
                 .delete(store::delete_store_entry),
         )
         .route("/stream", get(store::stream_store_root))
@@ -197,6 +198,7 @@ pub(crate) fn store_status(error: StoreError, context: &str) -> StatusCode {
     match error {
         StoreError::Conflict => StatusCode::CONFLICT,
         StoreError::NotFound => StatusCode::NOT_FOUND,
+        StoreError::NotAList | StoreError::PastTheEnd { .. } => StatusCode::CONFLICT,
         other => {
             error!(error = %format!("{other:#}"), "{context}");
             StatusCode::INTERNAL_SERVER_ERROR
diff --git a/src/api/store.rs b/src/api/store.rs
index 7e8caed..89123e2 100644
--- a/src/api/store.rs
+++ b/src/api/store.rs
@@ -39,6 +39,13 @@ pub(crate) struct ReadQuery {
 }
 
 #[derive(Debug, Deserialize)]
+pub(crate) struct InsertQuery {
+    /// Where in the list: the items from there on move up one. At the end without one,
+    /// or with `-1`.
+    index: Option<i64>,
+}
+
+#[derive(Debug, Deserialize)]
 pub(crate) struct DeleteQuery {
     #[serde(default)]
     prune: bool,
@@ -202,7 +209,19 @@ pub(crate) async fn put_store_entry(
     }
 
     let path = parse_write_path(&state, &user, &key, "PUT")?;
+    let value = body_value(&headers, &body)?;
+
+    let written = value.clone();
+    state
+        .mutate_doc(move |doc| store::write_path(doc, &path, &written))
+        .await
+        .map_err(|e| store_status(e, "Failed to write store value"))?;
 
+    response_for_value(&value, headers.get(ACCEPT))
+}
+
+/// A write's body as a value: JSON (the default), or text as a string.
+fn body_value(headers: &HeaderMap, body: &Bytes) -> Result<JsonValue, StatusCode> {
     let content_type = headers
         .get(CONTENT_TYPE)
         .and_then(|value| value.to_str().ok())
@@ -211,24 +230,51 @@ pub(crate) async fn put_store_entry(
         .next()
         .unwrap_or("")
         .trim();
-
-    let value = match content_type {
+    match content_type {
         "application/json" => {
-            serde_json::from_slice::<JsonValue>(&body).map_err(|_| StatusCode::BAD_REQUEST)?
+            serde_json::from_slice::<JsonValue>(body).map_err(|_| StatusCode::BAD_REQUEST)
         }
-        "text/plain" => JsonValue::String(
-            String::from_utf8(body.to_vec()).map_err(|_| StatusCode::BAD_REQUEST)?,
-        ),
-        _ => return Err(StatusCode::UNSUPPORTED_MEDIA_TYPE),
-    };
-
-    let written = value.clone();
-    state
-        .mutate_doc(move |doc| store::write_path(doc, &path, &written))
-        .await
-        .map_err(|e| store_status(e, "Failed to write store value"))?;
+        "text/plain" => String::from_utf8(body.to_vec())
+            .map(JsonValue::String)
+            .map_err(|_| StatusCode::BAD_REQUEST),
+        _ => Err(StatusCode::UNSUPPORTED_MEDIA_TYPE),
+    }
+}
 
-    response_for_value(&value, headers.get(ACCEPT))
+/// `POST /store/{key}`: inserts the body into the list at `key` (`store::insert_path`),
+/// at `?index=` or at the end; `201` with where it went (`{"index": n}`). No list there,
+/// or an index past its end: `409`, saying which.
+pub(crate) async fn post_store_entry(
+    State(state): State<AppState>,
+    Extension(user): Extension<AuthenticatedUser>,
+    Path(key): Path<String>,
+    Query(query): Query<InsertQuery>,
+    headers: HeaderMap,
+    body: Bytes,
+) -> Result<Response, StatusCode> {
+    if !state.is_ready().await {
+        return Err(StatusCode::SERVICE_UNAVAILABLE);
+    }
+    let path = parse_write_path(&state, &user, &key, "POST")?;
+    let index = match query.index {
+        None | Some(-1) => None,
+        Some(index) => Some(usize::try_from(index).map_err(|_| StatusCode::BAD_REQUEST)?),
+    };
+    let value = body_value(&headers, &body)?;
+    let inserted = state
+        .mutate_doc(move |doc| store::insert_path(doc, &path, index, &value))
+        .await;
+    match inserted {
+        Ok(index) => Ok((
+            StatusCode::CREATED,
+            axum::Json(serde_json::json!({ "index": index })),
+        )
+            .into_response()),
+        Err(error @ (StoreError::NotAList | StoreError::PastTheEnd { .. })) => {
+            Ok((StatusCode::CONFLICT, error.to_string()).into_response())
+        }
+        Err(error) => Err(store_status(error, "Failed to insert into a list")),
+    }
 }
 
 /// `DELETE /store/{key}`.