Fetch latest build artifact from gitlab and install as R package.

install-gitlab.R

#' Install an R package hosted as a build artifact on gitlab
#' 
#' Gitlab supports the storage of build artifacts which may be utilized as
#' distribution mechanism for code binaries. Applying this to scheme to R, a
#' build task may be defined (for example for each tagged commit), yielding a
#' .zip file of the tar.gz package produced by R CMD build. This function
#' fetches the most recent build artifact and installs it as a package.
#'
#' @param gitlab A string representing the base url of the gitlab host
#' @param name   The name of the package repository
#' @param token  The user token, required for accessing the gitlab REST api
#' @param ...    All further arguments are passed to install.packages
#'
#' @return NULL
#'
install.gitlab <- function(gitlab, name, token, ...) {

  library(httr)

  base  <- paste0(gitlab, "/api/v3/")
  resp  <- GET(paste0(base, "projects"), add_headers("PRIVATE-TOKEN"=token))
  json  <- content(resp)

  id.project <- lapply(json, function(project, name) {
    if(project$name == name) return(project$id)
    else return(NULL)
  }, name=name)
  id.project <- unlist(id.project)
  if(length(id.project) != 1) warning("expecting to find exactly 1 repo match.")

  resp  <- GET(paste0(base, "projects/", id.project, "/builds"),
               add_headers("PRIVATE-TOKEN"=token))
  json  <- content(resp)

  build <- lapply(json, function(build) {
    if(!is.null(build$artifacts_file$filename)) {
      id   <- build$id
      date <- build$started_at
      date <- gsub(paste0("^([0-9]{4}-[0-9]{2}-[0-9]{2}T[0-9]{2}:[0-9]{2}:",
                          "[0-9]{2}\\.[0-9]+[+-][0-9]{2}):([0-9]{2})$"),
                   "\\1\\2", date)
      date <- as.POSIXct(strptime(date, "%Y-%m-%dT%H:%M:%OS%z"))
      return(list(id, date))
    }
    else return(NULL)
  })

  build <- lapply(build, data.frame)
  build <- do.call(rbind.data.frame, build)
  colnames(build) <- c("build_id", "build_date")
  latest <- build$build_id[tail(order(build$build_date), n=1)]

  resp  <- GET(paste0(base, "projects/", id.project, "/builds/", latest,
                      "/artifacts"),
               add_headers("PRIVATE-TOKEN"=token))

  tempdir <- paste0(tempdir(), "/build_", name)
  tmpexis <- dir.exists(tempdir)
  if(!tmpexis) dir.create(tempdir)
  tempzip <- paste0(tempdir, "/", name, ".zip")
  if(file.exists(tempzip)) stop(".zip already exists in temp dir.")
  temptar <- list.files(tempdir, pattern="*.tar.gz", full.names=T)
  if(length(temptar) != 0) stop("some .tar.gz already exists in temp dir.")
  writeBin(content(resp, "raw"), tempzip)
  unzip(tempzip, exdir=tempdir)
  temptar <- list.files(tempdir, pattern="*.tar.gz", full.names=T)
  if(length(temptar) != 1) stop("expecting exactly 1 .tar.gz file in temp dir.")

  install.packages(pkgs=temptar, repos=NULL, type="source", ...)

  if(tmpexis) unlink(c(tempzip, temptar))
  else unlink(tempdir, recursive=T)

  return(invisible(NULL))
}