perf(file): optimize performance of detectSubtitles function in file.go

- Improve performance of the detectSubtitles function in the file.go file for querying subtitle files
- Enhance user experience, especially when filebrowser supports network file systems in the future

files/file.go

@@ -43,6 +43,7 @@ type FileInfo struct {
 	Content    string            `json:"content,omitempty"`
 	Checksums  map[string]string `json:"checksums,omitempty"`
 	Token      string            `json:"token,omitempty"`
+	currentDir []os.FileInfo     `json:"-"`
 }
 
 // FileOptions are the options when getting a file info.
@@ -294,15 +295,23 @@ func (i *FileInfo) detectSubtitles() {
 	// detect multiple languages. Base*.vtt
 	// TODO: give subtitles descriptive names (lang) and track attributes
 	parentDir := strings.TrimRight(i.Path, i.Name)
-	dir, err := afero.ReadDir(i.Fs, parentDir)
-	if err == nil {
+	var dir []os.FileInfo
+	if len(i.currentDir) > 0 {
+		dir = i.currentDir
+	} else {
+		var err error
+		dir, err = afero.ReadDir(i.Fs, parentDir)
+		if err != nil {
+			return
+		}
+	}
+
 	base := strings.TrimSuffix(i.Name, ext)
 	for _, f := range dir {
 		if !f.IsDir() && strings.HasPrefix(f.Name(), base) && strings.HasSuffix(f.Name(), ".vtt") {
 			i.Subtitles = append(i.Subtitles, path.Join(parentDir, f.Name()))
 		}
 	}
-	}
 }
 
 func (i *FileInfo) readListing(checker rules.Checker, readHeader bool) error {
@@ -349,6 +358,7 @@ func (i *FileInfo) readListing(checker rules.Checker, readHeader bool) error {
 			IsSymlink:  isSymlink,
 			Extension:  filepath.Ext(name),
 			Path:       fPath,
+			currentDir: dir,
 		}
 
 		if file.IsDir {