simplify audio locking with local refcell rather than thread local

src/main.rs

@@ -19,10 +19,6 @@ const HUE_KEY: &str = include_str!("../hue.key");
 const BUTTON_PIN: u8 = 26;
 const CHANNEL_VEC_SIZE: usize = 32;
 
-thread_local! {
-  static AUDIO_CHILD: RefCell<Option<process::Child>> = RefCell::new(None);
-}
-
 #[tokio::main(basic_scheduler)]
 async fn main() {
   pretty_env_logger::init_timed();
@@ -36,13 +32,15 @@ async fn main() {
   pin.set_async_interrupt(Trigger::FallingEdge, move |_| button_pressed(&clients))
      .expect("set interrupt");
 
-  let reqwest = &reqwest::Client::new();
   let (tx, rx) = mpsc::channel(1);
   events_clients.lock().unwrap().push(tx);
+
+  let reqwest = &reqwest::Client::new();
+  let audio_child = &RefCell::new(None);
   let hue_busy = &Cell::new(false);
   let pushes = rx.for_each_concurrent(2, |()| async move {
-    if !audio_busy() {
-      play_chime()
+    if !audio_busy(&audio_child) {
+      play_chime(&audio_child)
     } else { debug!("doorbell still ringing, not playing new chime"); }
 
     if !hue_busy.replace(true) {
@@ -107,25 +105,23 @@ async fn warp(clients: Arc<Mutex<SmallVec<[mpsc::Sender<()>; CHANNEL_VEC_SIZE]>>
   warp::serve(routes).run(([0, 0, 0, 0], 8060)).await;
 }
 
-fn audio_busy() -> bool {
-  AUDIO_CHILD.with(|cell| {
-    if let Some(ref mut audio_child) = *cell.borrow_mut() {
+fn audio_busy(audio_child: &RefCell<Option<process::Child>>) -> bool {
+  if let Some(ref mut audio_child) = *audio_child.borrow_mut() {
     if let Ok(None) = audio_child.try_wait() {
       return true;
     }
   }
   false
-  })
 }
 
-fn play_chime() {
+fn play_chime(audio_child: &RefCell<Option<process::Child>>) {
   trace!("Playing doorbell chime");
   match process::Command::new("mplayer")
                          .arg(OUTDOOR_CHIME_FILE)
                          .stdout(process::Stdio::null())
                          .stderr(process::Stdio::null())
                          .spawn() {
-    Ok(child) => { AUDIO_CHILD.with(|cell| cell.replace(Some(child))); },
+    Ok(child) => { audio_child.replace(Some(child)); },
     Err(err) => error!("Error playing outdoor chime: {}", err)
   };
 }