refactor(canvas): [PKG-CANVAS-03] own media and frame lifecycle in strict TypeScript

packages/artplayer-proxy-canvas/src/scheduler.ts

@@ -0,0 +1,69 @@
+export function createFrameScheduler(draw: (valid: () => boolean) => Promise<void>, active: () => boolean) {
+  let running = false
+  let closed = false
+  let busy = false
+  let pending = false
+  let generation = 0
+  let frame: number | null = null
+
+  function cancel(): void {
+    if (frame !== null)
+      cancelAnimationFrame(frame)
+    frame = null
+  }
+
+  function drain(): void {
+    if (busy || closed || !active())
+      return
+    if (pending) {
+      pending = false
+      busy = true
+      const version = generation
+      const valid = () => !closed && active() && generation === version
+      const complete = () => {
+        busy = false
+        drain()
+      }
+      // An observer throwing must not leave the scheduler busy or reject unhandled.
+      void draw(valid).then(complete, complete)
+    }
+    else if (running && frame === null) {
+      frame = requestAnimationFrame(() => {
+        frame = null
+        pending = true
+        drain()
+      })
+    }
+  }
+
+  function request(): void {
+    if (closed || !active())
+      return
+    generation++
+    pending = true
+    cancel()
+    drain()
+  }
+
+  function stop(): void {
+    running = false
+    pending = false
+    generation++
+    cancel()
+  }
+
+  return {
+    request,
+    start() {
+      if (running || closed || !active())
+        return
+      running = true
+      request()
+    },
+    stop,
+    destroy() {
+      closed = true
+      stop()
+    },
+  }
+}