R/as.location.R

In finch: Parse Darwin Core Files

#' Convert a path or URL to a location object
#'
#' @export
#'
#' @param x Input, a path or URL
#' @param ... Ignored.
#' @examples
#' # A zip file
#' file <- system.file("examples/0000154-150116162929234.zip",
#'   package = "finch")
#' as.location(file)
#'
#' # A directory
#' dir <- system.file("examples/0000154-150116162929234",
#'   package = "finch")
#' as.location(dir)
#'
#' # A URL
#' as.location("https://httpbin.org/get")
as.location <- function(x, ...) UseMethod("as.location")

#' @export
#' @rdname as.location
as.location.character <- function(x, ...) check_location(x, ...)

#' @export
#' @rdname as.location
as.location.location <- function(x, ...) x

check_location <- function(x, ...){
  if (is.url(x)) {
    as_location(x, "url")
  } else {
    if ( !file.exists(x) )
      stop("File does not exist. Create it, or fix the path.")
    if ( file.info(x)$isdir )
      as_location(path.expand(x), "dir")
    else
      as_location(path.expand(x), "file")
  }
}

as_location <- function(x, type){
  structure(x, class = "location", type = type)
}

#' @export
#' @rdname as.location
print.location <- function(x, ...){
  cat("<location>", "\n")
  cat("   Type: ", attr(x, "type"), "\n")
  cat("   Location: ", x[[1]], "\n")
}

is.url <- function(x, ...){
  grepl("https?://", x)
}