Display warning messages if fails to parse sr report (#2543)

platform/core/src/classes/PubSub.js

@@ -0,0 +1,75 @@
+const _subscriptions = Symbol('subscriptions');
+const _lastSubscriptionId = Symbol('lastSubscriptionId');
+
+/**
+ * Class to implement publish/subscribe pattern
+ *
+ * @class
+ * @classdesc Pub/sub mechanism
+ */
+export default class PubSub {
+  constructor() {
+    this[_subscriptions] = {};
+    this[_lastSubscriptionId] = 0;
+  }
+
+  /**
+   * Subscribe to event
+   *
+   * @param {string} eventName Event name
+   * @param {Function} callback Callback function
+   * @returns {void}
+   */
+  subscribe(eventName, callback) {
+    if (eventName === undefined) {
+      throw new Error('Event name is required');
+    }
+
+    if (typeof callback !== 'function') {
+      throw new Error('Callback must be a function');
+    }
+
+    if (!this[_subscriptions].hasOwnProperty(eventName)) {
+      this[_subscriptions][eventName] = {};
+    }
+
+    const subscriptionId = `sub${this[_lastSubscriptionId]++}`;
+    this[_subscriptions][eventName][subscriptionId] = callback;
+  }
+
+  /**
+   * Removes a subscription
+   *
+   * @param {string} eventName Event name
+   * @param {Function} [callback] Callback function
+   * @returns {void}
+   */
+  unsubscribe(eventName, callback) {
+    const callbacks = this[_subscriptions][eventName] || {};
+    for (let subscriptionId in callbacks) {
+      if (!callback) {
+        delete callbacks[subscriptionId];
+      } else if (callbacks[subscriptionId] === callback) {
+        delete callbacks[subscriptionId];
+      }
+    }
+  }
+
+  /**
+   * Publish event to all subscriptions
+   *
+   * @param {String} eventName Event name
+   * @param {any} [payload] Data that will be published
+   * @returns {void}
+   */
+  publish(eventName, ...payload) {
+    if (eventName === undefined) {
+      throw new Error('Event name is required');
+    }
+
+    const callbacks = this[_subscriptions][eventName] || {};
+    for (let subscriptionId in callbacks) {
+      callbacks[subscriptionId](...payload);
+    }
+  }
+}