#' Activate and deactivate development mode
#'
#' @description
#' `r lifecycle::badge("deprecated")`
#'
#' We no longer recommend `dev_mode()` and it will be removed in a future
#' release of devtools. Instead, we now rely on [load_all()] to test drive an
#' in-development package. If you really like the idea of corralling
#' experimental packages in a special library, you might enjoy
#' `withr::local_libpaths()`. If you are concerned about different projects
#' interfering with each other through the use of a shared library, consider
#' using the [renv package](https://rstudio.github.io/renv/).
#'
#' Original description: When activated, `dev_mode` creates a new library for
#' storing installed packages. This new library is automatically created when
#' `dev_mode` is activated if it does not already exist. This allows you to test
#' development packages in a sandbox, without interfering with the other
#' packages you have installed.
#'
#' @param on turn dev mode on (`TRUE`) or off (`FALSE`).  If omitted will guess
#'   based on whether or not `path` is in [.libPaths()]
#' @param path directory to library.
#' @export
#' @keywords internal
#' @examples
#' \dontrun{
#' dev_mode()
#' dev_mode()
#' }
dev_mode <- local({
  .prompt <- NULL

  function(on = NULL, path = getOption("devtools.path")) {
    lifecycle::deprecate_warn("2.4.6", "dev_mode()")
    lib_paths <- .libPaths()

    path <- path_real(path)
    if (is.null(on)) {
      on <- !(path %in% lib_paths)
    }

    if (on) {
      if (!file_exists(path)) {
        dir_create(path)
      }
      if (!file_exists(path)) {
        cli::cli_abort("Failed to create {.path {path}}")
      }

      if (!is_library(path)) {
        cli::cli_warn(c(
          "{.path {path}} does not appear to be a library.",
          "Are sure you specified the correct directory?"
        ))
      }

      cli::cli_inform(c(v = "Dev mode: ON"))
      options(dev_path = path)

      if (is.null(.prompt)) {
        .prompt <<- getOption("prompt")
      }
      options(prompt = paste("d> "))

      .libPaths(c(path, lib_paths))
    } else {
      cli::cli_inform(c(v = "Dev mode: OFF"))
      options(dev_path = NULL)

      if (!is.null(.prompt)) {
        options(prompt = .prompt)
      }
      .prompt <<- NULL

      .libPaths(setdiff(lib_paths, path))
    }
  }
})

is_library <- function(path) {
  # empty directories can be libraries
  if (length(dir_ls(path)) == 0) {
    return(TRUE)
  }

  # otherwise check that the directories are compiled R directories -
  # i.e. that they contain a Meta directory
  dirs <- dir_ls(path, type = "directory")

  has_pkg_dir <- function(path) length(dir_ls(path, regexp = "Meta")) > 0
  help_dirs <- vapply(dirs, has_pkg_dir, logical(1))

  all(help_dirs)
}
