R/gs_png.R

In muschellij2/leanbuild: Tools for Creating Automated Courses

#' Get Google Slide PNG URL
#'
#' @param url URL to Google Slide
#'
#' @return A character vector of URLs
#' @export
#'
#' @examples
#' url = paste0("https://docs.google.com/presentation/d/",
#' "12DPZgPteQBwgal6kSPP58zhPhjZ7QSPZLe3NkA8M3eo/edit",
#' "#slide=id.gc8648f14c3_0_397&t=4")
#' id = ariExtra::get_slide_id(url)
#' gs_png_url(url)
gs_png_url = function(url) {
  id = ariExtra::get_slide_id(url)
  slide_id = get_slide_page(url)
  gs_png_id(id, slide_id)
}

gs_png_id = function(id, slide_id) {
  if (any(grepl("^id[.]", slide_id))) {
    warning("slide ids usually don't have format of id.gc*, ",
            "you should likely remove the id.")
  }
  paste0("https://docs.google.com/presentation/d/",
         id,
         "/export/png?id=", id,
         "&pageid=", slide_id)
}

#' @export
#' @rdname gs_png_url
get_slide_page = function(url) {
  parsed = httr::parse_url(url)
  slide_id = parsed$query$pageid
  if (length(slide_id) == 0 || nchar(slide_id) == 0) {
    fragment = parsed$fragment
    slide_id = sub("slide=(.*)", "\\1", fragment)
    slide_id = sub("&.*", "", slide_id)
    slide_id = sub("^id[.]", "", slide_id)
  }
  stopifnot(length(slide_id) > 0 && nchar(slide_id) > 0)
  slide_id
}

#' @export
#' @rdname gs_png_url
#' @param output_dir path to output png
#' @param overwrite should the slide PNG be overwritten?
gs_png_download = function(url, output_dir = ".", overwrite = TRUE) {
  id = ariExtra::get_slide_id(url)
  slide_id = get_slide_page(url)
  url = gs_png_url(url)
  dir.create(output_dir, recursive = TRUE, showWarnings = FALSE)
  outfile = file.path(output_dir, paste0(id, "_", slide_id, ".png"))
  if (!file.exists(outfile) || overwrite) {
    curl::curl_download(url, destfile = outfile, quiet = FALSE)
  }
  stopifnot(file.exists(outfile))
  outfile
}

#' @export
#' @rdname gs_png_url
#' @param ... for \code{include_slide}, options passed to
#' [knitr::include_graphics()]
include_slide = function(url,
                         output_dir =  knitr::opts_chunk$get("fig.path"),
                         overwrite = TRUE, ...) {
  outfile = gs_png_download(url, output_dir, overwrite = overwrite)
  knitr::include_graphics(outfile, ...)
}