refactor(rtc): add readable()

packages/agora-rtc-react/src/store.ts

@@ -0,0 +1,53 @@
+import type { Disposer } from "./utils";
+
+/** Callback to inform of a value updates. */
+export type Subscriber<T> = (value: T) => void;
+
+/** Start and stop notification callbacks. */
+export type StartStopNotifier<T> = (set: Subscriber<T>) => Disposer | void;
+
+/** Readable interface for subscribing. */
+export interface Readable<T> {
+  /**
+   * Subscribe on value changes.
+   * @param run subscription callback
+   */
+  subscribe(this: void, run: Subscriber<T>): Disposer;
+}
+
+export function readable<T>(value: T, start: StartStopNotifier<T>): Readable<T> {
+  let stop: Disposer | null | undefined;
+  const subscribers = new Set<Subscriber<T>>();
+
+  function set(newValue: T) {
+    if (!Object.is(value, newValue)) {
+      value = newValue;
+      if (stop) {
+        for (const subscriber of subscribers) {
+          subscriber(value);
+        }
+      }
+    }
+  }
+
+  function subscribe(run: Subscriber<T>) {
+    subscribers.add(run);
+    if (subscribers.size === 1) {
+      stop = start(set) || noop;
+    }
+    run(value);
+    return () => {
+      subscribers.delete(run);
+      if (subscribers.size === 0 && stop) {
+        stop();
+        stop = null;
+      }
+    };
+  }
+
+  return { subscribe };
+}
+
+function noop() {
+  // noop
+}