init

modules/util/TaskQueue.js

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+const logger = require('@jitsi/logger').getLogger(__filename);
+
+/**
+ * Manages a queue of functions where the current function in progress will
+ * automatically execute the next queued function.
+ */
+export class TaskQueue {
+    /**
+     * Creates a new instance of {@link TaskQueue} and sets initial instance
+     * variable values.
+     */
+    constructor() {
+        this._queue = [];
+        this._currentTask = null;
+
+        this._onTaskComplete = this._onTaskComplete.bind(this);
+    }
+
+    /**
+     * Adds a new function to the queue. It will be immediately invoked if no
+     * other functions are queued.
+     *
+     * @param {Function} taskFunction - The function to be queued for execution.
+     * @private
+     * @returns {void}
+     */
+    enqueue(taskFunction) {
+        this._queue.push(taskFunction);
+        this._executeNext();
+    }
+
+    /**
+     * If no queued task is currently executing, invokes the first task in the
+     * queue if any.
+     *
+     * @private
+     * @returns {void}
+     */
+    _executeNext() {
+        if (this._currentTask) {
+            logger.warn('Task queued while a task is in progress.');
+
+            return;
+        }
+
+        this._currentTask = this._queue.shift() || null;
+
+        if (this._currentTask) {
+            logger.debug('Executing a task.');
+
+            try {
+                this._currentTask(this._onTaskComplete);
+            } catch (error) {
+                logger.error(`Task execution failed: ${error}`);
+                this._onTaskComplete();
+            }
+        }
+    }
+
+    /**
+     * Prepares to invoke the next function in the queue.
+     *
+     * @private
+     * @returns {void}
+     */
+    _onTaskComplete() {
+        this._currentTask = null;
+        logger.debug('Task completed.');
+        this._executeNext();
+    }
+}

modules/util/helpers.js

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+import { TaskQueue } from './TaskQueue';
+
+/**
+ * Create deferred object.
+ *
+ * @returns {{promise, resolve, reject}}
+ */
+export function createDeferred() {
+    const deferred = {};
+
+    deferred.promise = new Promise((resolve, reject) => {
+        deferred.resolve = resolve;
+        deferred.reject = reject;
+    });
+
+    return deferred;
+}
+
+/**
+ * Returns an instance of {@link TaskQueue}.
+ *
+ * @returns {Object}
+ */
+export function createTaskQueue() {
+    return new TaskQueue();
+}