feat(uploads): preview storage paths, detect templates, attach covers and withdraw batches

services/api/internal/uploads/batch.go

@@ -26,6 +26,30 @@ type BatchPatch struct {
 
 const maxCoverBytes = 8 << 20
 
+// createCover writes a new immutable cover before the quota transaction; Create removes it on failure.
+func (s *Service) createCover(data []byte) (*string, error) {
+	if data == nil {
+		return nil, nil
+	}
+	if len(data) > maxCoverBytes {
+		return nil, apperr.Validation("cover_base64", "validation.cover_too_large", "cover is larger than 8 MB", nil)
+	}
+	ext, ok := coverExt(data)
+	if !ok {
+		return nil, apperr.Validation("cover_base64", "validation.cover_type", "cover must be jpeg, png or webp", nil)
+	}
+	rel := path.Join("covers", newID().String()+ext)
+	abs := s.stagingAbs(rel)
+	if err := os.MkdirAll(filepath.Dir(abs), 0o755); err != nil {
+		return nil, err
+	}
+	if err := os.WriteFile(abs, data, 0o644); err != nil {
+		_ = os.Remove(abs)
+		return nil, err
+	}
+	return &rel, nil
+}
+
 // UpdateBatch применяет исполнителя, альбом, год и обложку к файлам пачки на рассмотрении.
 func (s *Service) UpdateBatch(ctx context.Context, id uuid.UUID, in BatchPatch) ([]File, error) {
 	if _, err := principal(ctx, auth.PermReviewUploads); err != nil {