fix: Handles max occupants reached from a visitor node.

When we receive the error from a visitor node, we need to restore the previous configuration, reconnect to the main prosody and be ready to try to rejoin again (from prejoin screen).

conference.js

@@ -58,6 +58,7 @@ import {
     commonUserLeftHandling,
     getConferenceOptions,
     getVisitorOptions,
+    restoreConferenceOptions,
     sendLocalParticipant
 } from './react/features/base/conference/functions';
 import { overwriteConfig } from './react/features/base/config/actions';
@@ -402,10 +403,28 @@ class ConferenceConnector {
             room.leave(CONFERENCE_LEAVE_REASONS.UNRECOVERABLE_ERROR).then(() => connection.disconnect());
             break;
 
-        case JitsiConferenceErrors.CONFERENCE_MAX_USERS:
+        case JitsiConferenceErrors.CONFERENCE_MAX_USERS: {
             APP.UI.notifyMaxUsersLimitReached();
-            break;
 
+            // in case of max users(it can be from a visitor node), let's restore
+            // oldConfig if any as we will be back to the main prosody
+            const newConfig = restoreConferenceOptions(APP.store.getState());
+
+            if (newConfig) {
+                APP.store.dispatch(overwriteConfig(newConfig))
+                    .then(this._conference.leaveRoom())
+                    .then(() => {
+                        _connectionPromise = connect(this._conference.roomName);
+
+                        return _connectionPromise;
+                    })
+                    .then(con => {
+                        APP.connection = connection = con;
+                    });
+            }
+
+            break;
+        }
         case JitsiConferenceErrors.INCOMPATIBLE_SERVER_VERSIONS:
             APP.store.dispatch(reloadWithStoredParams());
             break;

react/features/base/conference/functions.ts

@@ -254,6 +254,33 @@ export function getConferenceOptions(stateful: IStateful) {
     return options;
 }
 
+/**
+ * Returns the restored conference options if anything is available to be restored or undefined.
+ *
+ * @param {IStateful} stateful - The redux store state.
+ * @returns {Object?}
+ */
+export function restoreConferenceOptions(stateful: IStateful) {
+    const config = toState(stateful)['features/base/config'];
+
+    if (config.oldConfig) {
+        return {
+            hosts: {
+                domain: config.oldConfig.hosts.domain,
+                muc: config.oldConfig.hosts.muc
+            },
+            focusUserJid: config.oldConfig.focusUserJid,
+            disableFocus: false,
+            bosh: config.oldConfig.bosh,
+            websocket: config.oldConfig.websocket,
+            oldConfig: undefined
+        };
+    }
+
+    // nothing to return
+    return;
+}
+
 /**
  * Override the global config (that is, window.config) with XMPP configuration required to join as a visitor.
  *
@@ -284,7 +311,8 @@ export function getVisitorOptions(stateful: IStateful, params: Array<string>) {
                 focusUserJid: focusJid,
                 bosh: config.oldConfig.bosh && appendURLParam(config.oldConfig.bosh, 'customusername', username),
                 websocket: config.oldConfig.websocket
-                    && appendURLParam(config.oldConfig.websocket, 'customusername', username)
+                    && appendURLParam(config.oldConfig.websocket, 'customusername', username),
+                oldConfig: undefined // clears it up
             };
         }
 
@@ -296,6 +324,7 @@ export function getVisitorOptions(stateful: IStateful, params: Array<string>) {
             domain: config.hosts.domain,
             muc: config.hosts.muc
         },
+        focusUserJid: config.focusUserJid,
         bosh: config.bosh,
         websocket: config.websocket
     };

react/features/base/conference/middleware.any.js

@@ -52,7 +52,8 @@ import {
     _removeLocalTracksFromConference,
     forEachConference,
     getCurrentConference,
-    getVisitorOptions
+    getVisitorOptions,
+    restoreConferenceOptions
 } from './functions';
 import logger from './logger';
 
@@ -177,6 +178,23 @@ function _conferenceFailed({ dispatch, getState }, next, action) {
 
         break;
     }
+    case JitsiConferenceErrors.CONFERENCE_MAX_USERS: {
+        if (typeof APP === 'undefined') {
+            // in case of max users(it can be from a visitor node), let's restore
+            // oldConfig if any as we will be back to the main prosody
+            const newConfig = restoreConferenceOptions(getState);
+
+            if (newConfig) {
+                dispatch(overwriteConfig(newConfig))
+                    .then(dispatch(conferenceWillLeave(conference)))
+                    .then(conference.leave())
+                    .then(dispatch(disconnect()))
+                    .then(dispatch(connect()));
+            }
+        }
+
+        break;
+    }
     case JitsiConferenceErrors.OFFER_ANSWER_FAILED:
         sendAnalytics(createOfferAnswerFailedEvent());
         break;

react/features/base/config/reducer.ts

@@ -86,6 +86,7 @@ export interface IConfigState extends IConfig {
     error?: Error;
     oldConfig?: {
         bosh?: string;
+        focusUserJid?: string;
         hosts: {
             domain: string;
             muc: string;