feat: send analytics event when conference is rejoined

react/features/analytics/AnalyticsEvents.js

     };
 }
 
+/**
+ * Creates an event which indicates that the same conference has been rejoined.
+ *
+ * @param {string} url - The full conference URL.
+ * @param {number} lastConferenceDuration - How many seconds user stayed in the previous conference.
+ * @param {number} timeSinceLeft - How many seconds since the last conference was left.
+ * @returns {Object} The event in a format suitable for sending via sendAnalytics.
+ */
+export function createRejoinedEvent({ url, lastConferenceDuration, timeSinceLeft }) {
+    return {
+        action: 'rejoined',
+        attributes: {
+            lastConferenceDuration,
+            timeSinceLeft,
+            url
+        }
+    };
+}
+
 /**
  * Creates an event which specifies that the "confirm" button on the remote
  * mute dialog has been clicked.

react/features/app/components/AbstractApp.js

 import '../../follow-me';
 import { OverlayContainer } from '../../overlay';
 
+// Enable rejoin analytics
+import '../../rejoin';
+
 import { appNavigate } from '../actions';
 import { getDefaultURL } from '../functions';
 

react/features/rejoin/index.js

+import './middleware';

react/features/rejoin/middleware.js

+import { createRejoinedEvent, sendAnalytics } from '../analytics';
+
+import { StateListenerRegistry } from '../base/redux';
+
+StateListenerRegistry.register(
+    /* selector */ state => {
+        const recentList = state['features/recent-list'];
+
+        // Return the most recent conference entry
+        return recentList && recentList.length && recentList[recentList.length - 1];
+    },
+    // eslint-disable-next-line no-empty-pattern
+    /* listener */ (newMostRecent, { }, prevMostRecent) => {
+        if (prevMostRecent && newMostRecent) {
+
+            // Send the rejoined event just before the duration is reset on the most recent entry
+            if (prevMostRecent.conference === newMostRecent.conference && newMostRecent.duration === 0) {
+                sendAnalytics(
+                    createRejoinedEvent({
+                        lastConferenceDuration: prevMostRecent.duration / 1000,
+                        timeSinceLeft: (Date.now() - (prevMostRecent.date + prevMostRecent.duration)) / 1000,
+                        url: prevMostRecent.conference
+                    })
+                );
+            }
+        }
+    });