R/utils_reactiveDirReader.R

In earnaud/MetaShARK-v2: metashark

#' reactiveDirReader
#'
#' Function adapted from `reactivePoll()`. Used to create a reactive data
#' source, which works by periodically polling a directory of non-reactive data
#' sources.
#'
#' @usage
#'
#' files_poll <- reactiveDirReader(path, session, pattern, full_names = FALSE,
#' intervalMillis = 1000)
#'
#' @param repo (character) Path of the target directory to poll.
#' @param session The user session to associate this file reader with, or NULL
#' if none. If non-null, the reader will automatically stop when the session
#' ends.
#' @param pattern (character) an optional regular expression. Only file names
#' which match the regular expression will be returned.
#' @param full_names (logical) a logical value. If TRUE, the directory path is
#' prepended to the file names to give a relative file path. If FALSE, the file
#' names (rather than paths) are returned.
#' @param intervalMillis (integer) Approximate number of milliseconds to wait
#' between calls to checkFunc. This can be either a numeric value, or a
#' function that returns a numeric value.
#'
#' @return
#'
#' A reactive returning the files contained in the target repository. If folders
#' are returned, their content won't be detailed. If no file is to be found,
#' only returns "No files found." through `validate()`.
#'
#' @export
reactiveDirReader <- function(repo, session, pattern, full_names = FALSE,
                              intervalMillis = 1000) {
  files <- reactiveVal(character())

  files_poll <- reactivePoll(
    intervalMillis,
    session,
    function() {
      identical(files(), dir(repo, pattern))
    },
    function() {
      dir(repo, pattern, full.names = full_names)
    }
  )

  observe({
    files(files_poll())
  })


  return(files_poll)
}