R/knit_to_html.R

In polymathematic/Longform: A framework for generating dynamic longform HTML in R

#' Knit a document to an HTML character string
#'
#' \code{knit_to_html()} creates properly formatted HTML and metadata from an R markdown file.
#'
#' @param input Path to the input R markdown file.
#' @param params Parameters to pass to rmarkdown::render().
#' @param self_contained Should the output HTML reference external assets or should they be compiled?
#' @return Returns properly formatted HTML derived from an R Markdown file.
#' @export

knit_to_html <- function(input, parameters = list(), self_contained = FALSE){

  #Declare output
  output_html <- character()

  #Determine how the filesystem formats paths
  if(Sys.info()["sysname"] == "Linux"){
    path_sep = "/"
  } else {
    path_sep = "\\"
  }

  #Format HTML
  temp_dir <- tempdir() #tempdir(check = TRUE)
  temp_file <- unlist(strsplit(tempfile(pattern = "temp",
                                        tmpdir = temp_dir,
                                        fileext = ".html"),
                               sprintf("[%s]", path_sep)))
  temp_file <- temp_file[length(temp_file)]
  rmarkdown::render(input,
                    output_file = temp_file,
                    output_dir = temp_dir,
                    output_options = list(self_contained = self_contained),
                    params = parameters)
  output_html <- readr::read_file(paste0(temp_dir, path_sep, temp_file))

  #Clean up HTML
  output_html <- stringr::str_replace_all(output_html, "\"(?=[^<]*>)" , "'")
  output_html <- stringr::str_replace_all(output_html, "[\r\n]" , "")

  #Delete temp file
  unlink(paste0(temp_dir, path_sep, temp_file))

  #Return output
  return(output_html)

}