implemented frontend including separate message system; started to implement backend

yjs-poll/node_modules/lib0/queue.js

@@ -0,0 +1,84 @@
+export class QueueNode {
+  constructor () {
+    /**
+     * @type {QueueNode|null}
+     */
+    this.next = null
+  }
+}
+
+/**
+ * @template V
+ */
+export class QueueValue extends QueueNode {
+  /**
+   * @param {V} v
+   */
+  constructor (v) {
+    super()
+    this.v = v
+  }
+}
+
+/**
+ * @template {QueueNode} N
+ */
+export class Queue {
+  constructor () {
+    /**
+     * @type {N | null}
+     */
+    this.start = null
+    /**
+     * @type {N | null}
+     */
+    this.end = null
+  }
+}
+
+/**
+ * @note The queue implementation is experimental and unfinished.
+ * Don't use this in production yet.
+ *
+ * @template {QueueNode} N
+ * @return {Queue<N>}
+ */
+export const create = () => new Queue()
+
+/**
+ * @param {Queue<any>} queue
+ */
+export const isEmpty = queue => queue.start === null
+
+/**
+ * @template {Queue<any>} Q
+ * @param {Q} queue
+ * @param {Q extends Queue<infer N> ? N : never} n
+ */
+export const enqueue = (queue, n) => {
+  if (queue.end !== null) {
+    queue.end.next = n
+    queue.end = n
+  } else {
+    queue.end = n
+    queue.start = n
+  }
+}
+
+/**
+ * @template {QueueNode} N
+ * @param {Queue<N>} queue
+ * @return {N | null}
+ */
+export const dequeue = queue => {
+  const n = queue.start
+  if (n !== null) {
+    // @ts-ignore
+    queue.start = n.next
+    if (queue.start === null) {
+      queue.end = null
+    }
+    return n
+  }
+  return null
+}