added queue classes

utils.ts

@@ -109,3 +109,79 @@ export function insertEventIntoAscendingList(
 
   return sortedArray
 }
+
+export class MessageNode {
+  private _value: string;
+  private _next: MessageNode|null;
+
+  public get value(): string {
+    return this._value;
+  }
+  public set value(message: string) {
+    this._value = message;
+  }
+  public get next(): MessageNode|null {
+    return this._next;
+  }
+  public set next(node: MessageNode|null) {
+    this._next = node;
+  }
+
+  constructor(message: string) {
+    this._value = message;
+    this._next = null;
+  }
+}
+
+export class MessageQueue {
+  private _first: MessageNode|null;
+  private _last: MessageNode|null;
+
+  public get first(): MessageNode|null {
+    return this._first;
+  }
+  public set first(messageNode: MessageNode|null) {
+    this._first = messageNode;
+  }
+  public get last(): MessageNode|null {
+    return this._last;
+  }
+  public set last(messageNode: MessageNode|null) {
+    this._last = messageNode;
+  }
+  private _size: number;
+  public get size(): number {
+    return this._size;
+  }
+  public set size(v: number) {
+    this._size = v;
+  }
+
+  constructor() {
+    this._first = null;
+    this._last = null;
+    this._size = 0;
+  }
+  enqueue(message: string): boolean {
+    const newNode = new MessageNode(message);
+    if (this._size == 0 || !this._last) {
+      this._first = newNode;
+      this._last = newNode;
+    } else {
+        this._last.next = newNode;
+        this._last = newNode;
+    }
+    this._size++;
+    return true;
+  }
+  dequeue(): string|null {
+     if (this._size == 0 || !this._first) return null;
+
+     let prev = this._first;
+     this._first = prev.next;
+     prev.next = null;
+
+     this._size--;
+     return prev.value;
+   }
+}