nap-r: Personal collection of useful functions

Documented in githelp

#' Look for function use in github source.
#'
#' Search github source for topics to find examples
#' of use of the topic. Based on:
#' https://gist.github.com/hrbrmstr/32e9c140129d7d51db52.
#'
#' @export
#'
#' @param topic, string topic to search for.
#' @param in_cran, whether the cran limiter should be applied. Default TRUE.
#' @return html object containing source code with the topic.
#' @importFrom htmltools HTML
#' @importFrom rvest html_node html_nodes
#' @importFrom XML htmlParse
githelp <- function(topic, in_cran=TRUE) {

  # github search URL base
  base_ext_url <- "https://github.com/search?utf8=%%E2%%9C%%93&q=%s+extension%%3AR"
  ext_url <- sprintf(base_ext_url, topic)

  # if searching with user:cran (the default) add that to the URL
  if (in_cran) ext_url <- paste(ext_url, "+user%3Acran", sep="", collapse="")

  # at the time of writing, "rvest" and "xml2" are undergoing some changes, so
  # accommodate those of us who are on the bleeding edge of the hadleyverse
  # either way, we are just extracting out the results <div> for viewing in
  # the viewer pane (it works in plain ol' R, too)
  pg <- html(ext_url)
  res_div <- paste(capture.output(html_node(pg, "div#code_search_results")), collapse="")

  # clean up the HTML a bit
  res_div <- gsub('How are these search results\\? <a href="/contact">Tell us!</a>', '', res_div)
  # include a link to the results at the top of the viewer
  res_div <- gsub('href="/', 'href="http://github.com/', res_div)
  # build the viewer page, getting CSS from github-proper and hiding some cruft
  for_view <- sprintf('<html><head><link crossorigin="anonymous" href="https://assets-cdn.github.com/assets/github/index-4157068649cead58a7dd42dc9c0f2dc5b01bcc77921bc077b357e48be23aa237.css" media="all" rel="stylesheet" /><style>body{padding:20px}</style></head><body><a href="%s">Show on GitHub</a><hr noshade size=1/>%s</body></html>', ext_url, res_div)
  # this makes it show in the viewer (or browser if you're using plain R)
  html_print(HTML(for_view))

}