R/format_URL_parameters.R

In searchdiscovery/cjar: R Client for 'Customer Journey Analytics' ('CJA') API

#' Format list as query parameters
#'
#' Pretty much ripped straight from `httr`, but it's not exported there so I
#' had to do this.
#'
#' I'm going to add some functionality here to automatically collapse vector
#' inputs into a single comma-separated string. This is used in probably all
#' cases. In cases where it isn't used, the programmer can pre-collapse the
#' input to prevent automatic conversion to a comma-separated string.
#'
#' But that raises a question: how should `NA`s and `NULL`s be handled? The case
#' will be this:
#'
#' - All `NA`s is not allowed
#' - `NULL` is omitted by `purrr::compact`
#' - Some `NA`s will be converted to the string "NA" and passed onto the API
#'
#' @param elements Named list of query parameters
#'
#' @return String, `x` formatted as a parameter list
#' @noRd
format_URL_parameters <- function(elements) {
  if (length(elements) == 0) {
    return("")
  }

  stopifnot(is.list(elements))

  if (!is_fully_named_list(elements)) {
    stop("All components of query must be named", call. = FALSE)
  }

  # Remove NULL elements
  elements <- purrr::compact(elements)
  names <- utils::URLencode(names(elements), reserved = TRUE)

  # Handle NAs and collapse vectors into single strings
  elements <- lapply(elements, function(elem) {
    assertthat::assert_that(is.null(elem) | !all(is.na(elem)))
    paste(elem, collapse = ",")
  })


  values <- vapply(
    elements,
    function(x) {
      if (inherits(x, "AsIs"))
        return(x)
      utils::URLencode(as.character(x), reserved = TRUE)
    },
    character(1))

  paste0(names, "=", values, collapse = "&")
}



is_fully_named_list <- function(l) {
  if (length(names(l)[names(l) != ""]) != length(l)) {
    FALSE
  } else {
    TRUE
  }
}