Target is updated after all resolve tasks finish (#590)

Target is updated after all resolve tasks finish

backend/src/api/model/event_manager.rs

@@ -15,6 +15,8 @@ pub enum EventMessage {
     LibraryScanProgress(LibraryScanSummary),
     // Triggered when MetadataUpdateManager queue drains for an input
     InputMetadataUpdatesCompleted(Arc<str>),
+    // Triggered when MetadataUpdateManager starts a new processing cycle for an input
+    InputMetadataUpdatesStarted(Arc<str>),
 }
 
 pub struct EventManager {

backend/src/api/model/metadata_update_manager.rs

@@ -373,6 +373,11 @@ impl InputWorker {
                 last_queue_log_at = Instant::now()
                     .checked_sub(QUEUE_LOG_INTERVAL + Duration::from_secs(1))
                     .unwrap_or_else(Instant::now);
+                if let Some(app_state) = app_state_weak.as_ref().and_then(Weak::upgrade) {
+                    app_state
+                        .event_manager
+                        .send_event(EventMessage::InputMetadataUpdatesStarted(input_name.clone()));
+                }
                 debug!("Background metadata update queue has entries for input {input_name}; starting processing");
             }
 

backend/src/api/model/update_guard.rs

@@ -29,6 +29,15 @@ impl UpdateGuard {
             .map(|permit| UpdateGuardPermit { _permit: permit })
     }
 
+    pub async fn acquire_playlist_lock(&self) -> Option<UpdateGuardPermit> {
+        self.playlist
+            .clone()
+            .acquire_owned()
+            .await
+            .ok()
+            .map(|permit| UpdateGuardPermit { _permit: permit })
+    }
+
     pub fn try_library(&self) -> Option<UpdateGuardPermit> {
         self.library
             .clone()