perf(backend): optimize subtitles detection performance (#2637)

files/file.go

@@ -29,20 +29,21 @@ const PermDir = 0755
 // FileInfo describes a file.
 type FileInfo struct {
 	*Listing
-	Fs        afero.Fs          `json:"-"`
-	Path      string            `json:"path"`
-	Name      string            `json:"name"`
-	Size      int64             `json:"size"`
-	Extension string            `json:"extension"`
-	ModTime   time.Time         `json:"modified"`
-	Mode      os.FileMode       `json:"mode"`
-	IsDir     bool              `json:"isDir"`
-	IsSymlink bool              `json:"isSymlink"`
-	Type      string            `json:"type"`
-	Subtitles []string          `json:"subtitles,omitempty"`
-	Content   string            `json:"content,omitempty"`
-	Checksums map[string]string `json:"checksums,omitempty"`
-	Token     string            `json:"token,omitempty"`
+	Fs         afero.Fs          `json:"-"`
+	Path       string            `json:"path"`
+	Name       string            `json:"name"`
+	Size       int64             `json:"size"`
+	Extension  string            `json:"extension"`
+	ModTime    time.Time         `json:"modified"`
+	Mode       os.FileMode       `json:"mode"`
+	IsDir      bool              `json:"isDir"`
+	IsSymlink  bool              `json:"isSymlink"`
+	Type       string            `json:"type"`
+	Subtitles  []string          `json:"subtitles,omitempty"`
+	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.
@@ -294,13 +295,21 @@ 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 {
-		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()))
-			}
+	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()))
 		}
 	}
 }
@@ -340,15 +349,16 @@ func (i *FileInfo) readListing(checker rules.Checker, readHeader bool) error {
 		}
 
 		file := &FileInfo{
-			Fs:        i.Fs,
-			Name:      name,
-			Size:      f.Size(),
-			ModTime:   f.ModTime(),
-			Mode:      f.Mode(),
-			IsDir:     f.IsDir(),
-			IsSymlink: isSymlink,
-			Extension: filepath.Ext(name),
-			Path:      fPath,
+			Fs:         i.Fs,
+			Name:       name,
+			Size:       f.Size(),
+			ModTime:    f.ModTime(),
+			Mode:       f.Mode(),
+			IsDir:      f.IsDir(),
+			IsSymlink:  isSymlink,
+			Extension:  filepath.Ext(name),
+			Path:       fPath,
+			currentDir: dir,
 		}
 
 		if file.IsDir {