refactor(core): CORE-06 type media surfaces and playback hosts

packages/artplayer/src/player/playingMix.ts

@@ -0,0 +1,14 @@
+import type { MediaHost } from '../media/hosts'
+import type { MediaState } from '../media/types'
+import { def } from '../utils'
+
+export default function playingMix(art: MediaHost<Omit<MediaState, 'duration'>>): asserts art is MediaHost<Omit<MediaState, 'duration'>> & { readonly playing: boolean } {
+  const { $video } = art.template
+  def(art, 'playing', {
+    get: () => {
+      if (typeof $video.playing === 'boolean')
+        return $video.playing
+      return !!($video.currentTime > 0 && !$video.paused && !$video.ended && $video.readyState > 2)
+    },
+  })
+}