R/ct_perform_request.R

In ropensci/comtradr: Interface with the United Nations Comtrade API

#' Performs the request to the Comtrade API
#'
#' This function is internally called by `ct_get_data()` and performs the
#' request constructed by `ct_build_request()` and returns an error body with
#' the respective error returned by the Comtrade API.
#' By default throttles all requests to 1 request per 6 seconds,
#' or 10 requests per minute, but it adjusts automatically if the
#' API asks for longer waiting times.
#'
#' @param req a valid comtrade request built by the `ct_build_request()`
#' function
#'
#' @noRd
#' @returns JSON data from comtrade, data.frame with results or error codes.
#' @inheritParams ct_get_data
ct_perform_request <- function(req, requests_per_second, verbose = FALSE) {
  if (verbose) {
    cli::cli_inform(c("i" = "Performing request, which can take a few seconds, depending on the amount of data queried.")) # nolint
  }

  comtrade_is_transient <- function(resp) {
    (httr2::resp_status(resp) == 403 &&
      httr2::resp_header(resp, "Retry-After") != "0") ||
      (httr2::resp_status(resp) == 429 &&
        httr2::resp_header(resp, "Retry-After") != "0")
  }

  comtrade_after <- function(resp) {
    time <- as.numeric(httr2::resp_header(resp, "Retry-After"))
    time
  }

  resp <- req |>
    httr2::req_error(body = comtrade_error_body) |>
    httr2::req_throttle(rate = requests_per_second) |>
    httr2::req_retry(
      is_transient = comtrade_is_transient,
      after = comtrade_after,
      max_tries = 2
    ) |>
    httr2::req_perform()

  if (verbose) {
    cli::cli_inform(c("v" = "Got a response object from UN Comtrade. Use `process = F` if there is an error after this step to find issues with the response object.")) # nolint
  }

  return(resp)
}

comtrade_error_body <- function(resp) {
  if (!is.null(httr2::resp_header(resp, "Content-Type"))) {
    if (stringr::str_detect(httr2::resp_header(resp, "Content-Type"), "json")) {
      body <- httr2::resp_body_json(resp, simplifyVector = TRUE)

      message <- body$errorObject$errorMessage
      if (!is.null(message)) {
        message <- c(message)
      }
      return(message)
    } else if (stringr::str_detect(
      httr2::resp_header(
        resp,
        "Content-Type"
      ),
      "text"
    )) {
      body <- httr2::resp_body_string(resp)

      if (stringr::str_detect(body, "Request URL Too Long")) {
        message <-
          c("You might have provided too many parameters and the URL got too long.") # nolint
        return(message)
      } else if (stringr::str_detect(
        body,
        "The resource you are looking for has been removed"
      )) { # nolint
        message <-
          c(
            "The original message is: ",
            body,
            "But most likely you have exceeded the character value for the api."
          )
        return(message)
      }
    }
  }
}