refactor(mediabunny): [PKG-MB-04] checkpoint typed shim and event cleanup

packages/artplayer-proxy-mediabunny/src/EventTarget.ts

@@ -0,0 +1,44 @@
+export type MediaEvent = Event & { detail: unknown }
+export type MediaListener = (event: MediaEvent) => unknown
+
+export default class EventTarget {
+  declare listeners: Map<string, MediaListener[]>
+  #closed = false
+
+  constructor() {
+    this.listeners = new Map()
+  }
+
+  addEventListener(type: string, fn: MediaListener): void {
+    if (this.#closed)
+      return
+    if (!this.listeners.has(type))
+      this.listeners.set(type, [])
+    this.listeners.get(type)?.push(fn)
+  }
+
+  removeEventListener(type: string, fn: MediaListener): void {
+    const list = this.listeners.get(type)
+    if (!list)
+      return
+    const index = list.indexOf(fn)
+    if (index >= 0)
+      list.splice(index, 1)
+  }
+
+  emit(type: string, detail?: unknown): void {
+    if (this.#closed)
+      return
+    const event = Object.assign(new Event(type), { detail })
+    // Keep historical live-array forEach semantics and uncaught listener exceptions.
+    this.listeners.get(type)?.forEach((fn) => {
+      if (!this.#closed)
+        fn(event)
+    })
+  }
+
+  destroy(): void {
+    this.#closed = true
+    this.listeners.clear()
+  }
+}