spike: feat(notifications): prioritize based on type (appearance) (#2188)

* feat(notifications): prioritize based on type (appearance)

* squash: add return description to doc

react/features/notifications/constants.js

@@ -10,3 +10,16 @@ export const NOTIFICATION_TYPE = {
     SUCCESS: 'success',
     WARNING: 'warning'
 };
+
+/**
+ * A mapping of notification type to priority of display.
+ *
+ * @enum {number}
+ */
+export const NOTIFICATION_TYPE_PRIORITIES = {
+    [NOTIFICATION_TYPE.ERROR]: 5,
+    [NOTIFICATION_TYPE.INFO]: 3,
+    [NOTIFICATION_TYPE.NORMAL]: 3,
+    [NOTIFICATION_TYPE.SUCCESS]: 3,
+    [NOTIFICATION_TYPE.WARNING]: 4
+};

react/features/notifications/reducer.js

@@ -5,6 +5,7 @@ import {
     SET_NOTIFICATIONS_ENABLED,
     SHOW_NOTIFICATION
 } from './actionTypes';
+import { NOTIFICATION_TYPE_PRIORITIES } from './constants';
 
 /**
  * The initial state of the feature notifications.
@@ -43,17 +44,55 @@ ReducerRegistry.register('features/notifications',
         case SHOW_NOTIFICATION:
             return {
                 ...state,
-                notifications: [
-                    ...state.notifications,
-                    {
+                notifications:
+                    _insertNotificationByPriority(state.notifications, {
                         component: action.component,
                         props: action.props,
                         timeout: action.timeout,
                         uid: action.uid
-                    }
-                ]
+                    })
             };
         }
 
         return state;
     });
+
+/**
+ * Creates a new notification queue with the passed in notification placed at
+ * the end of other notifications with higher or the same priority.
+ *
+ * @param {Object[]} notifications - The queue of notifications to be displayed.
+ * @param {Object} notification - The new notification to add to the queue.
+ * @private
+ * @returns {Object[]} A new array with an updated order of the notification
+ * queue.
+ */
+function _insertNotificationByPriority(notifications, notification) {
+    const newNotificationPriority
+        = NOTIFICATION_TYPE_PRIORITIES[notification.props.appearance] || 0;
+
+    // Default to putting the new notification at the end of the queue.
+    let insertAtLocation = notifications.length;
+
+    // Find where to insert the new notification based on priority. Do not
+    // insert at the front of the queue so that the user can finish acting on
+    // any notification currently being read.
+    for (let i = 1; i < notifications.length; i++) {
+        const queuedNotification = notifications[i];
+        const queuedNotificationPriority
+            = NOTIFICATION_TYPE_PRIORITIES[queuedNotification.props.appearance]
+                || 0;
+
+        if (queuedNotificationPriority < newNotificationPriority) {
+            insertAtLocation = i;
+            break;
+        }
+    }
+
+    // Create a copy to avoid mutation and insert the notification.
+    const copyOfNotifications = notifications.slice();
+
+    copyOfNotifications.splice(insertAtLocation, 0, notification);
+
+    return copyOfNotifications;
+}