R/prepare_test_message.R

In blastula: Easily Send HTML Email Messages

#' Prepare a email test message object
#'
#' Create an email test message object, which is helpful for sending a test
#' message with the `smtp_send()` function.
#'
#' @param incl_ggplot An option to include a ggplot plot within the body of the
#'   test message. This requires that the \pkg{ggplot2} package is installed. By
#'   default, this is `FALSE`.
#' @param incl_image An option to include a test image within the body of the
#'   test message. By default, this is `FALSE`.
#' @return An `email_message` object.
#'
#' @examples
#' # Create a credentials file to send
#' # a test message via Gmail's SMTP
#' # (this file is named "gmail_secret")
#'
#' # create_smtp_creds_file(
#' #   file = "gmail_secret",
#' #   user = "sender@email.com",
#' #   provider = "gmail"
#' # )
#'
#' # Send oneself a test message to
#' # test these new SMTP settings and
#' # to ensure that the message appears
#' # correctly in the email client
#'
#' # prepare_test_message() %>%
#' #   smtp_send(
#' #     from = "sender@email.com",
#' #     to = "sender@email.com",
#' #     subject = "Test Message",
#' #     credentials = creds_file(
#' #       file = "gmail_secret"
#' #       )
#' #     )
#'
#' @export
prepare_test_message <- function(
    incl_ggplot = FALSE,
    incl_image = FALSE
) {

  # nocov start

  test_message_text <-
c(
"## This a Test Message", "",
"This message was prepared using the blastula R package, where
you can use Markdown formatting to **embolden** text or to add *emphasis*."
)

  # Include an image if requested
  if (isTRUE(incl_image)) {

    image_include <-
      system.file("img", "pexels-photo-267151.jpeg", package = "blastula") %>%
      add_image()

    test_message_text <-
      c(
        test_message_text,
        "",
        "There are helpers to add things like images:",
        "", image_include, ""
      )
  }

  # Include a ggplot if requested
  if (isTRUE(incl_ggplot)) {

    # If the `ggplot2` package is available, then
    # use the `ggplot2::ggsave()` function
    if (requireNamespace("ggplot2", quietly = TRUE)) {

      # Set a seed to make the plot reproducible
      set.seed(23)

      # Create a ggplot object with `qplot()`
      ggplot_object <-
        ggplot2::qplot(
          x = stats::rnorm(1000, 150, 6.6),
          geom = "histogram",
          breaks = seq(130, 170, 2),
          colour = I("black"),
          fill = I("white"),
          xlab = "x",
          ylab = "y"
        )

      test_message_text <-
        c(
          test_message_text,
          "We can add a ggplot plot with `add_ggplot()`:",
          "", add_ggplot(ggplot_object), ""
        )

    } else {

      stop(
        "Please ensure that the `ggplot2` package is installed before ",
        "using `add_ggplot()`.",
        call. = FALSE
      )
    }
  }

  footer_text <- "Brought to you by the *blastula* R package"

  # Compose the email test message
  compose_email(
    body = md(test_message_text),
    footer = md(footer_text)
  )

  # nocov end
}