format_slides.R

"Post-processing of R Markdown generated markdown file slides for Ines Montani open course framework.

Usage: format_slides.R --input=<input> [--output=<output>]
  
Options:
  --input=<input>       Path (including filename) to input markdown file to be pre-processed
  [--output=<output>]   Optional path (including filename) to output file (if not used then input path/filename is used)
" -> doc

library(docopt)
library(readr)
library(stringr)
library(rmarkdown)

opt <- docopt(doc)

main <- function(input) {
  
  # render the rmd and give variable to created md path
  render(input) 
  str_input <- gsub(input, pattern=".rmd$|.Rmd$", replacement="")
  md_input = paste(str_input, ".md", sep = "")
  text <- read_file(md_input)
  
  # replace global enviromnent with relative  
  text <- str_replace_all( text, "/Users/.+/static", "" )
  text <- str_replace_all( text, "../../../../static", "" )
  
  # replace Altair json output
  text <- str_replace_all( text, "\n\n    ## alt.Chart\\(..\\.\\)\n", "" )
  
  # replace latex formatting
  #text <- str_replace( text, "\\(", "$" )
  #text <- str_replace( text, "\\)", "$" )

  # replace \n-----\n with \n---\n to denote slide breaks
  text <- str_replace_all(string = text, 
                          pattern = "\n-----.*\n",
                          replacement = "\n---\n")
  
  # fix title slide
  text <- str_replace(string = text, 
                      pattern = "type: slides\n", 
                      replacement = "---\ntype: slides\n---\n")
  
  # add backtick code fence and out to beginning of output code chunks
  text <- str_replace_all(string = text, 
                          pattern = "\n\n    ##",
                          replacement = "\n\n```out\n    ##")
  
  # add backtick code fence to end of output code chunks
  text <- str_replace_all(text, "(?<=    ## .{0,2000})\n\n", "\n```\n\n")
  
  # remove comment blocks and indentation from output code chunks
  text <- str_replace_all(string = text, 
                          pattern = "    ## ",
                          replacement = "")
  
  # remove doctype text before svg plots, otherwise this string shows up above the plot
  text <- str_replace_all(string = text, 
                          pattern = '&lt;!DOCTYPE svg PUBLIC “-//W3C//DTD SVG 1.1//EN”\n“<http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd>”&gt;',
                          replacement = "")

  if (!is.null(opt[["--output"]])) {
    write_file(text, opt[["--output"]])
  } else {
    write_file(text, md_input)
  }
}


main(opt[["--input"]])