feat(audio): set audio content type (#8416)

* feat(audio): set audio content type

Signed-off-by: Ettore Di Giacinto <mudler@localai.io>

* chore: add tests

Signed-off-by: Ettore Di Giacinto <mudler@localai.io>

---------

Signed-off-by: Ettore Di Giacinto <mudler@localai.io>

pkg/audio/identify.go

@@ -0,0 +1,130 @@
+package audio
+
+import (
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/dhowden/tag"
+	"github.com/mudler/xlog"
+)
+
+// extensionFromFileType returns the file extension for tag.FileType.
+func extensionFromFileType(ft tag.FileType) string {
+	switch ft {
+	case tag.FLAC:
+		return "flac"
+	case tag.MP3:
+		return "mp3"
+	case tag.OGG:
+		return "ogg"
+	case tag.M4A:
+		return "m4a"
+	case tag.M4B:
+		return "m4b"
+	case tag.M4P:
+		return "m4p"
+	case tag.ALAC:
+		return "m4a"
+	case tag.DSF:
+		return "dsf"
+	default:
+		return ""
+	}
+}
+
+// contentTypeFromFileType returns the MIME type for tag.FileType.
+func contentTypeFromFileType(ft tag.FileType) string {
+	switch ft {
+	case tag.FLAC:
+		return "audio/flac"
+	case tag.MP3:
+		return "audio/mpeg"
+	case tag.OGG:
+		return "audio/ogg"
+	case tag.M4A, tag.M4B, tag.M4P, tag.ALAC:
+		return "audio/mp4"
+	case tag.DSF:
+		return "audio/dsd"
+	default:
+		return ""
+	}
+}
+
+// Identify reads from r and returns the detected audio extension and Content-Type.
+// It uses github.com/dhowden/tag to identify the format from the stream.
+// Returns ("", "", err) if the format could not be identified.
+func Identify(r io.ReadSeeker) (ext string, contentType string, err error) {
+	_, fileType, err := tag.Identify(r)
+	if err != nil || fileType == tag.UnknownFileType {
+		return "", "", err
+	}
+	ext = extensionFromFileType(fileType)
+	contentType = contentTypeFromFileType(fileType)
+	if ext == "" || contentType == "" {
+		return "", "", nil
+	}
+	return ext, contentType, nil
+}
+
+// ContentTypeFromExtension returns the MIME type for common audio file extensions.
+// Use as a fallback when Identify fails or when the file is not openable.
+func ContentTypeFromExtension(path string) string {
+	ext := strings.ToLower(strings.TrimPrefix(filepath.Ext(path), "."))
+	switch ext {
+	case "flac":
+		return "audio/flac"
+	case "mp3":
+		return "audio/mpeg"
+	case "wav":
+		return "audio/wav"
+	case "ogg":
+		return "audio/ogg"
+	case "m4a", "m4b", "m4p":
+		return "audio/mp4"
+	case "webm":
+		return "audio/webm"
+	default:
+		return ""
+	}
+}
+
+// NormalizeAudioFile opens the file at path, identifies its format with tag.Identify,
+// and renames the file to have the correct extension if the current one does not match.
+// It returns the path to use (possibly the renamed file) and the Content-Type to set.
+// If identification fails, returns (path, ContentTypeFromExtension(path)).
+func NormalizeAudioFile(path string) (finalPath string, contentType string) {
+	finalPath = path
+	f, err := os.Open(path)
+	if err != nil {
+		contentType = ContentTypeFromExtension(path)
+		return finalPath, contentType
+	}
+	defer f.Close()
+
+	ext, ct, identifyErr := Identify(f)
+	if identifyErr != nil || ext == "" || ct == "" {
+		contentType = ContentTypeFromExtension(path)
+		return finalPath, contentType
+	}
+	contentType = ct
+
+	currentExt := strings.ToLower(strings.TrimPrefix(filepath.Ext(path), "."))
+	if currentExt == ext {
+		return finalPath, contentType
+	}
+
+	dir := filepath.Dir(path)
+	base := filepath.Base(path)
+	baseNoExt := strings.TrimSuffix(base, filepath.Ext(base))
+	if baseNoExt == "" {
+		baseNoExt = base
+	}
+	newPath := filepath.Join(dir, baseNoExt+"."+ext)
+	if renameErr := os.Rename(path, newPath); renameErr != nil {
+		xlog.Debug("Could not rename audio file to match type", "from", path, "to", newPath, "error", renameErr)
+		return finalPath, contentType
+	}
+	return newPath, contentType
+}