#' @rdname render_reports
#' @inheritParams bookdown::render_book
#' @export
render_report <- function(input,
                          output_dir,
                          output_format = Sys.getenv("BOOKDOWN_FORMAT", "bookdown::gitbook"),
                          clean_cache = FALSE,
                          ...) {

  stopifnot(output_format %in% c("bookdown::gitbook", "bookdown::pdf_book"))

  if (output_format == "bookdown::pdf_book") {
    if (!requireNamespace("tinytex", quietly=TRUE)) install.packages("tinytex")
  }
  message("output_format=", output_format)

  if (clean_cache) {
    cache_dir <- list.files(path = input,
                            pattern = "_cache$",
                            include.dirs = TRUE,
                            full.names = TRUE)
    unlink(cache_dir, recursive = TRUE)
  }
  cfg_bookdown <-
    yaml::read_yaml(file.path(input, "_bookdown.yml"))
  unlink(file.path(input, paste0(cfg_bookdown$book_filename, ".*")))
  attached_packages <- (.packages())
  bookdown::render_book(input,
                        output_format =  output_format,
                        output_dir = output_dir,
                        envir =  new.env(),
                        ...)
  # detach all packages used in the knit
  sapply(
    setdiff((.packages()), attached_packages),
    function(x) detach(paste0("package:", x),
                       unload = TRUE,
                       character.only = TRUE))
  invisible()
}