refactor(ads): [PKG-ADS-03] split TypeScript lifecycle and preserve legacy behavior

packages/artplayer-plugin-ads/src/countdown.ts

@@ -0,0 +1,55 @@
+import type { Cleanup } from './types'
+
+export function createCountdown(total: () => number, render: (seconds: number) => void, complete: Cleanup) {
+  let elapsed = 0
+  let ready = false
+  let running = false
+  let closed = false
+  let timer: ReturnType<typeof setTimeout> | undefined
+
+  function schedule(): void {
+    if (!ready || !running || closed || timer !== undefined)
+      return
+    timer = setTimeout(() => {
+      timer = undefined
+      if (closed || !running)
+        return
+      elapsed += 1
+      render(elapsed)
+      if (closed)
+        return
+      if (elapsed >= total())
+        complete()
+      else
+        schedule()
+    }, 1000)
+  }
+
+  function pause(): void {
+    running = false
+    if (timer !== undefined)
+      clearTimeout(timer)
+    timer = undefined
+  }
+
+  return {
+    start() {
+      if (ready || closed)
+        return
+      ready = true
+      running = true
+      schedule()
+    },
+    play() {
+      if (!ready || closed)
+        return
+      running = true
+      schedule()
+    },
+    pause,
+    stop() {
+      closed = true
+      pause()
+    },
+  }
+}