Added lyrics cache to LyricsManager

Author: Naapperas

src/lyrics.rs

@@ -1,4 +1,5 @@
-use std::sync::Arc;
+use log::trace;
+use std::{cell::RefCell, collections::HashMap, sync::Arc};
 
 use crate::{
     lyrics_fetcher::LyricsFetcher,
@@ -10,26 +11,52 @@ use crate::{
 pub struct LyricsManager {
     queue: Arc<Queue>,
     fetcher: LyricsFetcher,
-    // TODO: add a cache
+    cache: RefCell<HashMap<String, String>>,
 }
 
 impl LyricsManager {
     pub fn new(queue: Arc<Queue>, fetcher: LyricsFetcher) -> Self {
-        LyricsManager { queue, fetcher }
+        LyricsManager {
+            queue,
+            fetcher,
+            cache: RefCell::new(HashMap::new()),
+        }
     }
 
     /// Saves the given lyrics to the user's filesystem.
     ///
     /// Returns an optional message indicating the outcome of this operation.
     pub fn save_lyrics(&self, lyrics: String) -> Option<String> {
-        Some("".to_string())
+        Some(lyrics)
     }
 
     /// Fetches and returns the lyrics of the given track
     pub fn get_lyrics(&self, track: Track) -> String {
-        // TODO: implement caching
+        // TODO: see if this panics later on
+        let track_id = track.id.as_ref().unwrap();
+
+        {
+            // insert new scope so that we can perform both borrows from the RefCell
+            // the immutable borrow present in this scope is dropped,
+            // so it is safe to do another borrow after
+
+            let cache = self.cache.borrow();
+
+            if cache.contains_key(track_id) {
+                trace!("Retrieving cached lyrics for {}", track.title);
+                return cache.get(track_id).unwrap().to_owned();
+            }
+        }
+
+        // if we reach this point it means that the cache does not contain this entry yet, update it
+        let mut cache = self.cache.borrow_mut();
+
+        // make network request to fetch track's lyrics
+        let lyrics = self.fetcher.fetch(&track);
+
+        cache.insert(track_id.to_owned(), lyrics.clone());
 
-        self.fetcher.fetch(&track)
+        lyrics
     }
 
     /// Fetches and returns the lyrics of the currently playing track
@@ -40,13 +67,13 @@ impl LyricsManager {
         }
     }
 
-    /// Returns the track being played currently, or nothing if the user is listening to a podcast episodes
+    /// Returns the track being played currently, or nothing if the user is listening to a podcast episode
     pub fn get_current_track(&self) -> Option<Track> {
         let playable = self.queue.get_current().unwrap();
 
         match playable {
             Playable::Track(track) => Some(track),
-            Playable::Episode(_) => None,
+            _ => None,
         }
     }
 }