`%||%` <- function(a, b) if (is.null(a)) b else a

is_named <- function(x) {
  all(has_names(x))
}

has_names <- function(x) {
  nms <- names(x)
  if (is.null(nms)) {
    rep(FALSE, length(x))
  } else {
    !(is.na(nms) | nms == "")
  }
}

# non smart quote version of sQuote
quote_str <- function(x, quote = "\"") {
  if (!length(x)) {
    return(character(0))
  }

  paste0(quote, x, quote)
}

is_installed <- function(pkg) {
  requireNamespace(pkg, quietly = TRUE)
}

need_package <- function(pkg) {
  if (is_installed(pkg)) return(invisible())

  stop("Please install ", pkg, " package", call. = FALSE)
}

# Format the C bitwise flags for display in Rd. The input object is a named
# integer vector with a 'description' character vector attribute that
# corresponds to each flag.
describe_options <- function(x) {
  paste0("\\describe{\n",
    paste0("  \\item{", names(x), "}{", attr(x, "description"), "}", collapse = "\n"),
  "\n}")
}

s_quote <- function(x) paste0("'", x, "'")

# Similar to match.arg, but returns character() with NULL or empty input and
# errors if any of the inputs are not found (fixing
# https://bugs.r-project.org/bugzilla3/show_bug.cgi?id=16659)
parse_options <- function(arg, options) {
  if (is.numeric(arg)) {
    return(as.integer(arg))
  }

  if (is.null(arg) || !nzchar(arg)) {
    return(0L)
  }

  # set duplicates.ok = TRUE so any duplicates are counted differently than
  # non-matches, then take only unique results
  i <- pmatch(arg, names(options), duplicates.ok = TRUE)
  if (any(is.na(i))) {
    stop(sprintf("`options` %s is not a valid option, should be one of %s",
      s_quote(arg[is.na(i)][1L]),
      paste(s_quote(names(options)), collapse = ", ")),
      call. = FALSE)
  }
  sum(options[unique(i)])
}

#' Get path to a xml2 example
#'
#' xml2 comes bundled with a number of sample files in its \sQuote{inst/extdata}
#' directory. This function makes them easy to access.
#' @param path Name of file. If \code{NULL}, the example files will be listed.
#' @export
xml2_example <- function(path = NULL) {
  if (is.null(path)) {
    dir(system.file("extdata", package = "xml2"))
  } else {
    system.file("extdata", path, package = "xml2", mustWork = TRUE)
  }
}