fix Queue, tweaks on relay.ts and make relay.test.ts pass.

utils.ts

@@ -94,11 +94,11 @@ export function insertEventIntoAscendingList(sortedArray: Event[], event: Event)
 
 export class QueueNode<V> {
   public value: V
-  public next: QueueNode<V> | null
+  public next: QueueNode<V> | null = null
+  public prev: QueueNode<V> | null = null
 
   constructor(message: V) {
     this.value = message
-    this.next = null
   }
 }
 
@@ -114,9 +114,17 @@ export class Queue<V> {
   enqueue(value: V): boolean {
     const newNode = new QueueNode(value)
     if (!this.last) {
+      // list is empty
       this.first = newNode
       this.last = newNode
+    } else if (this.last === this.first) {
+      // list has a single element
+      this.last = newNode
+      this.last.prev = this.first
+      this.first.next = newNode
     } else {
+      // list has elements, add as last
+      newNode.prev = this.last
       this.last.next = newNode
       this.last = newNode
     }
@@ -126,10 +134,16 @@ export class Queue<V> {
   dequeue(): V | null {
     if (!this.first) return null
 
-    let prev = this.first
-    this.first = prev.next
-    prev.next = null
+    if (this.first === this.last) {
+      const target = this.first
+      this.first = null
+      this.last = null
+      return target.value
+    }
 
-    return prev.value
+    const target = this.first
+    this.first = target.next
+
+    return target.value
   }
 }