refactor(preview): improve overall previewer scheduling logic (#415)

television/app.rs

@@ -2,7 +2,7 @@ use rustc_hash::FxHashSet;
 
 use anyhow::Result;
 use tokio::sync::mpsc;
-use tracing::{debug, info, trace};
+use tracing::{debug, trace};
 
 use crate::channels::entry::Entry;
 use crate::channels::TelevisionChannel;
@@ -207,6 +207,9 @@ impl App {
             {
                 for event in event_buf.drain(..) {
                     if let Some(action) = self.convert_event_to_action(event) {
+                        if action != Action::Tick {
+                            debug!("Queuing new action: {action:?}");
+                        }
                         action_tx.send(action)?;
                     }
                 }
@@ -251,7 +254,7 @@ impl App {
     fn convert_event_to_action(&self, event: Event<Key>) -> Option<Action> {
         let action = match event {
             Event::Input(keycode) => {
-                info!("{:?}", keycode);
+                debug!("Converting {:?} to action", keycode);
                 // get action based on keybindings
                 if let Some(action) = self.keymap.get(&keycode) {
                     action.clone()

television/preview/mod.rs

@@ -226,6 +226,16 @@ impl Previewer {
         }
     }
 
+    fn cached(&self, entry: &Entry) -> Option<Arc<Preview>> {
+        match &entry.preview_type {
+            PreviewType::Basic => Some(self.basic.preview(entry)),
+            PreviewType::EnvVar => Some(self.env_var.preview(entry)),
+            PreviewType::Files => self.file.cached(entry),
+            PreviewType::Command(_) => self.command.cached(entry),
+            PreviewType::None => None,
+        }
+    }
+
     // we could use a target scroll here to make the previewer
     // faster, but since it's already running in the background and quite
     // fast for most standard file sizes, plus we're caching the previews,
@@ -235,13 +245,14 @@ impl Previewer {
         entry: &Entry,
         preview_window: Option<Rect>,
     ) -> Option<Arc<Preview>> {
-        // if we haven't acknowledged the request yet, acknowledge it
+        // check if we have a preview for the current request
-        self.requests.push(entry.clone());
+        if let Some(preview) = self.cached(entry) {
-
-        if let Some(preview) = self.dispatch_request(entry, preview_window) {
             return Some(preview);
         }
 
+        // otherwise, if we haven't acknowledged the request yet, acknowledge it
+        self.requests.push(entry.clone());
+
         // lookup request stack and return the most recent preview available
         for request in self.requests.back_to_front() {
             if let Some(preview) =

television/preview/previewers/env.rs

@@ -1,4 +1,3 @@
-use rustc_hash::FxHashMap;
 use std::sync::Arc;
 
 use crate::channels::entry;
@@ -6,7 +5,6 @@ use crate::preview::{Preview, PreviewContent};
 
 #[derive(Debug, Default)]
 pub struct EnvVarPreviewer {
-    cache: FxHashMap<entry::Entry, Arc<Preview>>,
     _config: EnvVarPreviewerConfig,
 }
 
@@ -16,16 +14,11 @@ pub struct EnvVarPreviewerConfig {}
 impl EnvVarPreviewer {
     pub fn new(config: Option<EnvVarPreviewerConfig>) -> Self {
         EnvVarPreviewer {
-            cache: FxHashMap::default(),
             _config: config.unwrap_or_default(),
         }
     }
 
-    pub fn preview(&mut self, entry: &entry::Entry) -> Arc<Preview> {
+    pub fn preview(&self, entry: &entry::Entry) -> Arc<Preview> {
-        // check if we have that preview in the cache
-        if let Some(preview) = self.cache.get(entry) {
-            return preview.clone();
-        }
         let content = entry.value.as_ref().map(|preview| {
             maybe_add_newline_after_colon(preview, &entry.name)
         });
@@ -33,7 +26,8 @@ impl EnvVarPreviewer {
             || 1,
             |c| u16::try_from(c.lines().count()).unwrap_or(u16::MAX),
         );
-        let preview = Arc::new(Preview {
+
+        Arc::new(Preview {
             title: entry.name.clone(),
             content: match content {
                 Some(content) => PreviewContent::PlainTextWrapped(content),
@@ -42,9 +36,7 @@ impl EnvVarPreviewer {
             icon: entry.icon,
             partial_offset: None,
             total_lines,
-        });
+        })
-        self.cache.insert(entry.clone(), preview.clone());
-        preview
     }
 }
 

television/preview/previewers/files.rs

@@ -114,6 +114,7 @@ impl FilePreviewer {
     ) {
         if self.in_flight_previews.lock().contains(&entry.name) {
             trace!("Preview already in flight for {:?}", entry.name);
+            return;
         }
 
         if self.concurrent_preview_tasks.load(Ordering::Relaxed)