add currently playing cache to spotify

src/main/java/cc/fascinated/bat/service/SpotifyService.java

@@ -36,6 +36,13 @@ public class SpotifyService {
             .expiration(30, TimeUnit.MINUTES)
             .build();
 
+    /**
+     * A cache of the currently playing track for each user.
+     */
+    private final Map<BatUser, CurrentlyPlaying> currentlyPlayingCache = ExpiringMap.builder()
+            .expiration(30, TimeUnit.SECONDS)
+            .build();
+
     /**
      * The client ID.
      */
@@ -98,7 +105,12 @@ public class SpotifyService {
      */
     @SneakyThrows
     public CurrentlyPlaying getCurrentlyPlayingTrack(BatUser user) {
-        return getSpotifyApi(user).getUsersCurrentlyPlayingTrack().build().execute();
+        if (currentlyPlayingCache.containsKey(user)) {
+            return currentlyPlayingCache.get(user);
+        }
+        CurrentlyPlaying currentlyPlaying = getSpotifyApi(user).getUsersCurrentlyPlayingTrack().build().execute();
+        currentlyPlayingCache.put(user, currentlyPlaying);
+        return currentlyPlaying;
     }
 
     /**
@@ -191,7 +203,7 @@ public class SpotifyService {
             AuthorizationCodeCredentials credentials = api.authorizationCodeRefresh().build().execute();
             profile.setAccessToken(credentials.getAccessToken());
             profile.setExpiresAt(System.currentTimeMillis() + (credentials.getExpiresIn() * 1000));
-            log.info("Refreshed Spotify token for user {}", user.getName());
+            log.info("Refreshed Spotify token for user \"{}\"", user.getName());
         } catch (SpotifyWebApiException ex) {
             log.error("Failed to refresh Spotify token", ex);
         }