R/deal_with_empty.R

In dataRetrieval: Retrieval Functions for USGS and EPA Hydrology and Water Quality Data

#' Return a data frame if there's an empty response
#'
#' @param return_list data frame returned from walk_pages
#' @param properties A vector of requested columns
#' @param service character, can be any existing collection such
#' as "daily", "monitoring-locations", "time-series-metadata"
#' @param skipGeometry A logical for whether to return geometry
#' @param convertType A logical for whether to convert value to numeric
#'
#' @return data.frame
#' @noRd
#' @examples
#'
#' df <- dataRetrieval:::deal_with_empty(data.frame(NULL),
#'                                       properties = c("time", "value"),
#'                                       service = "daily")
#'
#' df2 <- dataRetrieval:::deal_with_empty(data.frame(NULL),
#'                                       properties = NA,
#'                                       service = "daily")
#'
deal_with_empty <- function(
  return_list,
  properties,
  service,
  skipGeometry,
  convertType,
  no_paging = FALSE
) {
  if (nrow(return_list) == 0) {
    if (all(is.na(properties))) {
      schema <- check_OGC_requests(endpoint = service, type = "schema")
      properties <- names(schema$properties)
    }
    return_list <- data.frame(matrix(nrow = 0, ncol = length(properties)))
    return_list <- lapply(return_list, as.character)
    names(return_list) <- properties

    single_params <- c("datetime", "last_modified", "begin", "end", "time")

    for (i in single_params) {
      if (i %in% names(return_list)) {
        return_list[[i]] <- as.POSIXct(as.character(), origin = "1970-01-01")
      }
    }

    if (convertType && service == "daily") {
      return_list$time <- as.Date(as.character())
    }

    if (convertType && "value" %in% names(return_list)) {
      return_list$value <- as.numeric()
    }

    if (convertType && "contributing_drainage_area" %in% names(return_list)) {
      return_list$contributing_drainage_area <- as.numeric()
    }

    return_list <- data.frame(return_list)
    return_list$geometry <- NULL

    if (!skipGeometry) {
      if (!no_paging) {
        return_list <- sf::st_as_sf(return_list, geometry = sf::st_sfc())
      } else {
        return_list$x <- numeric()
        return_list$y <- numeric()
      }
    }
  }

  return(return_list)
}