refactor(vtt-thumbnail): [PKG-VTT-THUMB-04] type runtime data and resource boundaries

packages/artplayer-plugin-vtt-thumbnail/src/lifetime.ts

@@ -0,0 +1,54 @@
+import type { Events } from 'artplayer'
+import type { Cleanup, Lifetime, LifetimeHost, OwnedEvent } from './types'
+
+export default function createLifetime(art: LifetimeHost): Lifetime {
+  let closed = Boolean(art.isDestroy)
+  const cleanups = new Set<Cleanup>()
+  let cancel!: Cleanup
+  const cancelled = new Promise<void>((resolve) => {
+    cancel = resolve
+  })
+  const lifetime: Lifetime = {
+    get closed() { return closed },
+    own(cleanup) {
+      if (closed)
+        run(cleanup)
+      else
+        cleanups.add(cleanup)
+      return () => cleanups.delete(cleanup)
+    },
+    listen<Name extends OwnedEvent>(name: Name, callback: (...args: Events[Name]) => unknown) {
+      if (closed)
+        return
+      lifetime.own(() => art.off(name, callback))
+      art.on(name, callback)
+    },
+    wait<Value>(value: Value | PromiseLike<Value>) { return Promise.race([value, cancelled]) },
+    dispose() {
+      if (closed)
+        return
+      closed = true
+      cancel()
+      const pending = [...cleanups].reverse()
+      cleanups.clear()
+      for (const cleanup of pending)
+        run(cleanup)
+    },
+  }
+  function run(cleanup: Cleanup) {
+    try {
+      cleanup()
+    }
+    catch (error) {
+      console.warn('Failed to clean up VTT thumbnails:', error)
+    }
+  }
+  try {
+    lifetime.listen('destroy', lifetime.dispose)
+  }
+  catch (error) {
+    lifetime.dispose()
+    throw error
+  }
+  return lifetime
+}