Add support to getNarrowFromNotificationData for group narrows

For this to work we need to parse a string of comma delimited
numbers of the recipients. This data is not yet passed to the
function; we keep the function flexible and functional by making
the parameter of `usersById` optional.`

src/types.js

@@ -98,6 +98,10 @@ export type User = {
   isBot: boolean,
 };
 
+export type UserIdMap = {
+  [userId: string]: User,
+};
+
 export type PresenceAggregated = {
   client: string,
   status: UserStatus,

src/utils/__tests__/notificationsCommon-test.js

@@ -1,5 +1,5 @@
 import { getNarrowFromNotificationData } from '../notificationsCommon';
-import { homeNarrow, topicNarrow, privateNarrow } from '../narrow';
+import { homeNarrow, topicNarrow, privateNarrow, groupNarrow } from '../narrow';
 
 describe('getNarrowFromNotificationData', () => {
   test('unknown notification data returns home narrow', () => {
@@ -26,4 +26,21 @@ describe('getNarrowFromNotificationData', () => {
     const narrow = getNarrowFromNotificationData(notification);
     expect(narrow).toEqual(privateNarrow('mark@example.com'));
   });
+
+  test('on notification for a group message returns a group narrow', () => {
+    const notification = {
+      recipient_type: 'private',
+      pm_users: '1,2,4',
+    };
+    const usersById = {
+      '1': { email: 'me@example.com' },
+      '2': { email: 'mark@example.com' },
+      '4': { email: 'john@example.com' },
+    };
+    const expectedNarrow = groupNarrow(['me@example.com', 'mark@example.com', 'john@example.com']);
+
+    const narrow = getNarrowFromNotificationData(notification, usersById);
+
+    expect(narrow).toEqual(expectedNarrow);
+  });
 });

src/utils/notificationsCommon.js

@@ -1,10 +1,26 @@
 /* @flow */
-import { homeNarrow, topicNarrow, privateNarrow } from '../utils/narrow';
-import type { Notification } from '../types';
-
-export const getNarrowFromNotificationData = (data: Notification) =>
-  !data || !data.recipient_type
-    ? homeNarrow
-    : data.recipient_type === 'stream'
-      ? topicNarrow(data.stream, data.topic)
-      : privateNarrow(data.sender_email);
+import type { Notification, NotificationGroup, UserIdMap } from '../types';
+import { homeNarrow, topicNarrow, privateNarrow, groupNarrow } from '../utils/narrow';
+
+const getGroupNarrowFromNotificationData = (data: NotificationGroup, usersById: UserIdMap = {}) => {
+  const userIds = data.pm_users.split(',');
+  const userEmails = userIds.map(x => usersById[x].email);
+  return groupNarrow(userEmails);
+};
+
+export const getNarrowFromNotificationData = (data: Notification, usersById: UserIdMap = {}) => {
+  if (!data || !data.recipient_type) {
+    return homeNarrow;
+  }
+
+  if (data.recipient_type === 'stream') {
+    return topicNarrow(data.stream, data.topic);
+  }
+
+  // $FlowFixMe
+  if (!data.pm_users) {
+    return privateNarrow(data.sender_email);
+  }
+
+  return getGroupNarrowFromNotificationData(data, usersById);
+};