implemented frontend including separate message system; started to implement backend

yjs-poll/node_modules/lib0/cache.js

@@ -0,0 +1,206 @@
+/* eslint-env browser */
+
+/**
+ * An implementation of a map which has keys that expire.
+ *
+ * @module cache
+ */
+
+import * as list from './list.js'
+import * as map from './map.js'
+import * as time from './time.js'
+
+/**
+ * @template K, V
+ *
+ * @implements {list.ListNode}
+ */
+class Entry {
+  /**
+   * @param {K} key
+   * @param {V | Promise<V>} val
+   */
+  constructor (key, val) {
+    /**
+     * @type {this | null}
+     */
+    this.prev = null
+    /**
+     * @type {this | null}
+     */
+    this.next = null
+    this.created = time.getUnixTime()
+    this.val = val
+    this.key = key
+  }
+}
+
+/**
+ * @template K, V
+ */
+export class Cache {
+  /**
+   * @param {number} timeout
+   */
+  constructor (timeout) {
+    this.timeout = timeout
+    /**
+     * @type list.List<Entry<K, V>>
+     */
+    this._q = list.create()
+    /**
+     * @type {Map<K, Entry<K, V>>}
+     */
+    this._map = map.create()
+  }
+}
+
+/**
+ * @template K, V
+ *
+ * @param {Cache<K, V>} cache
+ * @return {number} Returns the current timestamp
+ */
+export const removeStale = cache => {
+  const now = time.getUnixTime()
+  const q = cache._q
+  while (q.start && now - q.start.created > cache.timeout) {
+    cache._map.delete(q.start.key)
+    list.popFront(q)
+  }
+  return now
+}
+
+/**
+ * @template K, V
+ *
+ * @param {Cache<K, V>} cache
+ * @param {K} key
+ * @param {V} value
+ */
+export const set = (cache, key, value) => {
+  const now = removeStale(cache)
+  const q = cache._q
+  const n = cache._map.get(key)
+  if (n) {
+    list.removeNode(q, n)
+    list.pushEnd(q, n)
+    n.created = now
+    n.val = value
+  } else {
+    const node = new Entry(key, value)
+    list.pushEnd(q, node)
+    cache._map.set(key, node)
+  }
+}
+
+/**
+ * @template K, V
+ *
+ * @param {Cache<K, V>} cache
+ * @param {K} key
+ * @return {Entry<K, V> | undefined}
+ */
+const getNode = (cache, key) => {
+  removeStale(cache)
+  const n = cache._map.get(key)
+  if (n) {
+    return n
+  }
+}
+
+/**
+ * @template K, V
+ *
+ * @param {Cache<K, V>} cache
+ * @param {K} key
+ * @return {V | undefined}
+ */
+export const get = (cache, key) => {
+  const n = getNode(cache, key)
+  return n && !(n.val instanceof Promise) ? n.val : undefined
+}
+
+/**
+ * @template K, V
+ *
+ * @param {Cache<K, V>} cache
+ * @param {K} key
+ */
+export const refreshTimeout = (cache, key) => {
+  const now = time.getUnixTime()
+  const q = cache._q
+  const n = cache._map.get(key)
+  if (n) {
+    list.removeNode(q, n)
+    list.pushEnd(q, n)
+    n.created = now
+  }
+}
+
+/**
+ * Works well in conjunktion with setIfUndefined which has an async init function.
+ * Using getAsync & setIfUndefined ensures that the init function is only called once.
+ *
+ * @template K, V
+ *
+ * @param {Cache<K, V>} cache
+ * @param {K} key
+ * @return {V | Promise<V> | undefined}
+ */
+export const getAsync = (cache, key) => {
+  const n = getNode(cache, key)
+  return n ? n.val : undefined
+}
+
+/**
+ * @template K, V
+ *
+ * @param {Cache<K, V>} cache
+ * @param {K} key
+ */
+export const remove = (cache, key) => {
+  const n = cache._map.get(key)
+  if (n) {
+    list.removeNode(cache._q, n)
+    cache._map.delete(key)
+    return n.val && !(n.val instanceof Promise) ? n.val : undefined
+  }
+}
+
+/**
+ * @template K, V
+ *
+ * @param {Cache<K, V>} cache
+ * @param {K} key
+ * @param {function():Promise<V>} init
+ * @param {boolean} removeNull Optional argument that automatically removes values that resolve to null/undefined from the cache.
+ * @return {Promise<V> | V}
+ */
+export const setIfUndefined = (cache, key, init, removeNull = false) => {
+  removeStale(cache)
+  const q = cache._q
+  const n = cache._map.get(key)
+  if (n) {
+    return n.val
+  } else {
+    const p = init()
+    const node = new Entry(key, p)
+    list.pushEnd(q, node)
+    cache._map.set(key, node)
+    p.then(v => {
+      if (p === node.val) {
+        node.val = v
+      }
+      if (removeNull && v == null) {
+        remove(cache, key)
+      }
+    })
+    return p
+  }
+}
+
+/**
+ * @param {number} timeout
+ */
+export const create = timeout => new Cache(timeout)