store the original uploaded file name as metadata

tools/filesystem/filesystem.go

@@ -133,8 +133,17 @@ func (s *System) UploadMultipart(fh *multipart.FileHeader, fileKey string) error
 	// rewind
 	f.Seek(0, io.SeekStart)
 
+	originalName := fh.Filename
+	if len(originalName) > 255 {
+		// keep only the first 255 chars as a very rudimentary measure
+		// to prevent the metadata to grow too big in size
+		originalName = originalName[:255]
+	}
 	opts := &blob.WriterOptions{
 		ContentType: mt.String(),
+		Metadata: map[string]string{
+			"original_filename": fh.Filename,
+		},
 	}
 
 	w, err := s.bucket.NewWriter(s.ctx, fileKey, opts)

tools/filesystem/filesystem_test.go

@@ -162,14 +162,24 @@ func TestFileSystemUploadMultipart(t *testing.T) {
 	}
 	defer fs.Close()
 
-	uploadErr := fs.UploadMultipart(fh, "newdir/newkey.txt")
+	fileKey := "newdir/newkey.txt"
+
+	uploadErr := fs.UploadMultipart(fh, fileKey)
 	if uploadErr != nil {
 		t.Fatal(uploadErr)
 	}
 
-	if exists, _ := fs.Exists("newdir/newkey.txt"); !exists {
+	if exists, _ := fs.Exists(fileKey); !exists {
 		t.Fatalf("Expected newdir/newkey.txt to exist")
 	}
+
+	attrs, err := fs.Attributes(fileKey)
+	if err != nil {
+		t.Fatalf("Failed to fetch file attributes: %v", err)
+	}
+	if name, ok := attrs.Metadata["original_filename"]; !ok || name != "test" {
+		t.Fatalf("Expected original_filename to be %q, got %q", "test", name)
+	}
 }
 
 func TestFileSystemUpload(t *testing.T) {