updateGdCache <- function(local_folder, cloud_folder){
  #     
  cache_fname <- "gdrive_sig.Rds"
  # 0.  memoise     
  getGdriveFolder <- memoise(function(gdrive_folder){
    drive_ls(as_id(gdrive_folder), recursive = FALSE)
  })

  # 1.        
  cloud_gdrive_sig <- purrr::possibly(getGdriveFolder, NULL)(cloud_folder)
  #          ,     
  if(is.null(cloud_gdrive_sig)) {
    message("Some Google Drive issues happened. Can't update cache")
    return()
  }
  # 2.       
  fdir <- if(fs::is_dir(local_folder)) local_folder else fs::path_dir(local_folder)

  # 3.       
  local_files <- fs::dir_ls(fdir, recurse = FALSE) %>%
    fs::path_file()

  # 4.        
  local_gdrive_sig <- purrr::possibly(readRDS, NULL, quiet = TRUE)(fs::path(fdir, cache_fname))
  if(is.null(local_gdrive_sig)){
    #    ,   ,     
    #  ,   
    local_gdrive_sig <- cloud_gdrive_sig %>%
      dplyr::filter(row_number() == -1)
  }
  #         
  local_gdrive_sig <- local_gdrive_sig %>%
    dplyr::filter(name %in% local_files)

  # 5.      ,    ,   
  #  ,       
  reconcile_tbl <- cloud_gdrive_sig %>%
    dplyr::rename(drive_resource_cloud = drive_resource) %>%
    dplyr::left_join(local_gdrive_sig, by = c("name", "id")) %>%
    tidyr::hoist(drive_resource_cloud, cloud_modified_time = "modifiedTime") %>%
    tidyr::hoist(drive_resource, local_modified_time = "modifiedTime") %>%
    # TODO:   ,       
    #       = NA
    dplyr::mutate(not_in_sync = is.na(local_modified_time) | cloud_modified_time != local_modified_time)

  # 6.    
  syncFile <- function(fpath, id){
    res <- purrr::possibly(drive_download, otherwise = NULL)(as_id(id), path = fpath, overwrite = TRUE, verbose = TRUE)
    ifelse(is.null(res), FALSE, TRUE)
  }
  #  ,        ,   
  sync_gdrive_sig <- reconcile_tbl %>%
    dplyr::filter(not_in_sync == TRUE) %>%
    dplyr::mutate(fpath = fs::path(fdir, name)) %>%
    dplyr::mutate(sync_status = purrr::map2_lgl(fpath, id, syncFile)) %>%
    dplyr::select(name, id, sync_status)

  # 7.      ,   
  #   
  cloud_gdrive_sig %>%
    #   
    dplyr::anti_join(dplyr::filter(sync_gdrive_sig, sync_status == FALSE), by = c("name", "id")) %>%
    saveRDS(fs::path(fdir, cache_fname))
}