From f2351bfcf2abf2a2097730cb53f31299774866f9 Mon Sep 17 00:00:00 2001
From: alexpasmantier <alex.pasmant@gmail.com>
Date: Mon, 7 Oct 2024 18:53:20 +0200
Subject: [PATCH] preview caches and ringsets

---
 TODO.md                            |  1 +
 src/components/previewers/cache.rs | 68 ++++++++++++++++++------------
 2 files changed, 41 insertions(+), 28 deletions(-)

diff --git a/TODO.md b/TODO.md
index fc8df69..a95ac67 100644
--- a/TODO.md
+++ b/TODO.md
@@ -13,6 +13,7 @@
 - [x] async finder search
 - [x] use nucleo for env
 - [ ] better keymaps
+- [ ] mutualize placeholder previews in cache (really not a priority)
 
 ## feature ideas
 - [ ] some sort of iterative fuzzy file explorer (preview contents of folders on the right, enter to go in etc.) maybe
diff --git a/src/components/previewers/cache.rs b/src/components/previewers/cache.rs
index 22a15fc..11ce937 100644
--- a/src/components/previewers/cache.rs
+++ b/src/components/previewers/cache.rs
@@ -8,69 +8,81 @@ use tracing::debug;
 use crate::components::previewers::Preview;
 
 /// A ring buffer that also keeps track of the keys it contains to avoid duplicates.
-struct SetRingBuffer<T> {
+///
+/// I'm planning on using this as a backend LRU-cache for the preview cache.
+/// Basic idea:
+/// - When a new key is pushed, if it's already in the buffer, do nothing.
+/// - If the buffer is full, remove the oldest key and push the new key.
+struct RingSet<T> {
     ring_buffer: VecDeque<T>,
     known_keys: HashSet<T>,
     capacity: usize,
 }
 
-impl<T> SetRingBuffer<T>
+impl<T> RingSet<T>
 where
     T: Eq + std::hash::Hash + Clone + std::fmt::Debug,
 {
     pub fn with_capacity(capacity: usize) -> Self {
-        SetRingBuffer {
+        RingSet {
             ring_buffer: VecDeque::with_capacity(capacity),
             known_keys: HashSet::with_capacity(capacity),
             capacity,
         }
     }
 
-    // TODO: finish this
-    pub fn push(&mut self, key: T) -> Option<T> {
+    /// Push a new item to the back of the buffer, removing the oldest item if the buffer is full.
+    /// Returns the item that was removed, if any.
+    /// If the item is already in the buffer, do nothing and return None.
+    pub fn push(&mut self, item: T) -> Option<T> {
         // If the key is already in the buffer, do nothing
-        if self.contains(&key) {
-            debug!("Key already in ring buffer: {:?}", key);
+        if self.contains(&item) {
+            debug!("Key already in ring buffer: {:?}", item);
             return None;
         }
-        // If the buffer is full, remove the oldest key
+        let mut popped_key = None;
+        // If the buffer is full, remove the oldest key (e.g. pop from the front of the buffer)
         if self.ring_buffer.len() >= self.capacity {
-            self.pop();
+            popped_key = self.pop();
         }
-        // finally, push the new key
-        self.ring_buffer.push_back(key.clone());
-        self.known_keys.insert(key);
-        None
+        // finally, push the new key to the back of the buffer
+        self.ring_buffer.push_back(item.clone());
+        self.known_keys.insert(item);
+        popped_key
     }
 
-    pub fn pop(&mut self) -> Option<T> {
-        if let Some(key) = self.ring_buffer.pop_front() {
-            debug!("Removing key from ring buffer: {:?}", key);
-            self.known_keys.remove(&key);
-            Some(key)
+    fn pop(&mut self) -> Option<T> {
+        if let Some(item) = self.ring_buffer.pop_front() {
+            debug!("Removing key from ring buffer: {:?}", item);
+            self.known_keys.remove(&item);
+            Some(item)
         } else {
             None
         }
     }
 
-    pub fn contains(&self, key: &T) -> bool {
+    fn contains(&self, key: &T) -> bool {
         self.known_keys.contains(key)
     }
 }
 
+/// Default size of the preview cache.
+/// This does seem kind of arbitrary for now, will need to play around with it.
 const DEFAULT_PREVIEW_CACHE_SIZE: usize = 100;
 
 /// A cache for previews.
+/// The cache is implemented as a LRU cache with a fixed size.
 pub struct PreviewCache {
     entries: HashMap<String, Arc<Preview>>,
-    set_ring_buffer: SetRingBuffer<String>,
+    ring_set: RingSet<String>,
 }
 
 impl PreviewCache {
-    pub fn new(max_size: usize) -> Self {
+    /// Create a new preview cache with the given capacity.
+    pub fn new(capacity: usize) -> Self {
         PreviewCache {
             entries: HashMap::new(),
-            set_ring_buffer: SetRingBuffer::with_capacity(max_size),
+            ring_set: RingSet::with_capacity(capacity),
         }
     }
 
@@ -78,15 +90,15 @@ impl PreviewCache {
         self.entries.get(key).cloned()
     }
 
+    /// Insert a new preview into the cache.
+    /// If the cache is full, the oldest entry will be removed.
+    /// If the key is already in the cache, the preview will be updated.
     pub fn insert(&mut self, key: String, preview: Arc<Preview>) {
         debug!("Inserting preview into cache: {}", key);
         self.entries.insert(key.clone(), preview.clone());
-        self.set_ring_buffer.push(key);
-        if self.entry_buffer.len() >= self.max_size {
-            if let Some(oldest_key) = self.entry_buffer.pop_front() {
-                debug!("Cache full, removing oldest entry: {}", oldest_key);
-                self.entries.remove(&oldest_key);
-            }
+        if let Some(oldest_key) = self.ring_set.push(key) {
+            debug!("Cache full, removing oldest entry: {}", oldest_key);
+            self.entries.remove(&oldest_key);
         }
     }
 }