refactor new hls vtt private methods in track extensions

lib/av_player/track_extensions.rb

@@ -5,7 +5,7 @@
 
 module BerkeleyLibrary
   module AV
-    class Track
+    class Track # rubocop:disable Metrics/ClassLength
       include BerkeleyLibrary::Logging
 
       COLLECTION_RE = %r{(^[^/]+)/}
@@ -78,20 +78,25 @@ def build_mpeg_dash_uri
 
       def find_hls_vtt_uri
         return unless hls_uri_exists?
-        return unless (hls_manifest = do_get(hls_uri, ignore_errors: true))
+        return unless (hls_manifest_uri = hls_uri)
+        return unless (hls_manifest = do_get(hls_manifest_uri, ignore_errors: true))
+        return unless (subtitle_list_uri = find_hls_subtitle_list_uri(hls_manifest))
+        return unless (hls_subtitle_list = do_get(subtitle_list_uri, ignore_errors: true))
 
-        playlist = M3u8::Playlist.read(hls_manifest)
-        vtt_manifest = playlist.items.find { |p| p.group_id == 'subs' }
-        hls_vtt_manifest_uri = hls_uri.merge(vtt_manifest.uri)
-
-        return unless (hls_vtt_manifest = do_get(hls_vtt_manifest_uri, ignore_errors: true))
-
-        vtt_playlist = M3u8::Playlist.read(hls_vtt_manifest)
+        vtt_playlist = M3u8::Playlist.read(hls_subtitle_list)
         return unless (hls_vtt_path_relative = vtt_playlist.items.first.segment)
 
         hls_uri.merge(hls_vtt_path_relative)
       end
 
+      def find_hls_subtitle_list_uri(manifest)
+        return unless (playlist = M3u8::Playlist.read(manifest))
+        return unless (subtitle_list = playlist.items.find { |p| p.group_id == 'subs' })
+        return unless (subtitle_list_uri = subtitle_list.uri)
+
+        hls_uri.merge(subtitle_list_uri)
+      end
+
       def find_dash_vtt_uri
         return unless (dash_uri = mpeg_dash_uri)
         return unless (dash_manifest = do_get(dash_uri, ignore_errors: true))