api: Add getReadReceipts binding (GET messages/{message_id}/read_receipts)

We'll use this for #5367, "Make it possible to view read receipts".

Author: chrisbobbe

src/api/index.js

@@ -55,6 +55,7 @@ import createUser from './users/createUser';
 import getUserProfile from './users/getUserProfile';
 import updateUserStatus from './users/updateUserStatus';
 import getFileTemporaryUrl from './messages/getFileTemporaryUrl';
+import getReadReceipts from './messages/getReadReceipts';
 
 export {
   fetchServerEmojiData,
@@ -104,4 +105,5 @@ export {
   getUserProfile,
   updateUserStatus,
   getFileTemporaryUrl,
+  getReadReceipts,
 };

src/api/messages/getReadReceipts.js

@@ -0,0 +1,37 @@
+/* @flow strict-local */
+import invariant from 'invariant';
+
+import type { Auth, ApiResponseSuccess } from '../transportTypes';
+import { apiGet } from '../apiFetch';
+import type { UserId } from '../idTypes';
+
+type ServerApiResponseReadReceipts = {|
+  ...$Exact<ApiResponseSuccess>,
+  +user_ids: $ReadOnlyArray<UserId>,
+|};
+
+/**
+ * See https://zulip.com/api/get-read-receipts
+ *
+ * Should only be called for servers with FL 137+.
+ */
+// TODO(server-6.0): Stop mentioning a FL 137 condition.
+export default async (
+  auth: Auth,
+  args: {|
+    +message_id: number,
+  |},
+
+  // TODO(#4659): Don't get this from callers.
+  zulipFeatureLevel: number,
+): Promise<$ReadOnlyArray<UserId>> => {
+  invariant(zulipFeatureLevel >= 137, 'api.getReadReceipts called for unsupporting server');
+
+  const { message_id } = args;
+  const response: ServerApiResponseReadReceipts = await apiGet(
+    auth,
+    `messages/${message_id}/read_receipts`,
+  );
+
+  return response.user_ids;
+};