       }
     }
 
-    fileprivate var parentTransformer: PreviewReducer?
+    fileprivate let baseServerUrl: URL
   }
 }


    typealias Pair = StateActionPair<UuidState<MainWindow.State>, MainWindow.Action>

    func reduce(_ source: Observable<Pair>) -> Observable<Pair> {
      return source.map { pair in
        guard let baseServerUrl = self.parentTransformer?.baseServerUrl else {
          return pair
        }

        var state = pair.state.payload

        switch pair.action {

            return pair
          }

          state.preview = PreviewUtils.state(for: pair.state.uuid, baseUrl: self.baseServerUrl, buffer: buffer)

        case .close:
          state.preview = PreviewUtils.state(for: .none, baseUrl: self.baseServerUrl)

        default:
          return pair
