feat(ui): epoch-based debounce cancels stale search results

crates/k-launcher-ui/src/app.rs

@@ -27,6 +27,7 @@ pub struct KLauncherApp {
     selected: usize,
     cfg: AppearanceCfg,
     error: Option<String>,
+    search_epoch: u64,
 }
 
 impl KLauncherApp {
@@ -43,6 +44,7 @@ impl KLauncherApp {
             selected: 0,
             cfg,
             error: None,
+            search_epoch: 0,
         }
     }
 }
@@ -50,7 +52,7 @@ impl KLauncherApp {
 #[derive(Debug, Clone)]
 pub enum Message {
     QueryChanged(String),
-    ResultsReady(Arc<Vec<SearchResult>>),
+    ResultsReady(u64, Arc<Vec<SearchResult>>),
     KeyPressed(KeyEvent),
 }
 
@@ -60,14 +62,21 @@ fn update(state: &mut KLauncherApp, message: Message) -> Task<Message> {
             state.error = None;
             state.query = q.clone();
             state.selected = 0;
+            state.search_epoch += 1;
+            let epoch = state.search_epoch;
             let engine = state.engine.clone();
             Task::perform(
-                async move { engine.search(&q).await },
-                |results| Message::ResultsReady(Arc::new(results)),
+                async move {
+                    tokio::time::sleep(std::time::Duration::from_millis(50)).await;
+                    (epoch, engine.search(&q).await)
+                },
+                |(epoch, results)| Message::ResultsReady(epoch, Arc::new(results)),
             )
         }
-        Message::ResultsReady(results) => {
+        Message::ResultsReady(epoch, results) => {
+            if epoch == state.search_epoch {
                 state.results = results;
+            }
             Task::none()
         }
         Message::KeyPressed(event) => {