render_metadata.R

#' Render a metadata statement to EML
#' 
#' Basically an expanded version of [rmarkdown::render]/[quarto::quarto_render]
#' to convert a metadata statement to EML. Note that this process ignores
#' the `output` section of the supplied `yaml`, though that should still be
#' supplied for rendering via other packages. Internally this function wraps
#' [read_md()] and [write_eml()] in that order; see those functions for details.
#' @param input A file to be rendered to EML
#' @param output_file The name of the output file
#' @param output_dir The output directory for the rendered `output_file`
#' @param overwrite (logical) Should any existing file be overwritten? Defaults
#' to `TRUE`.
#' @param quiet (logical) Should messages be suppressed? Defaults to `FALSE`.
#' @returns Does not return an object; called for the side-effect of rendering
#' a file to EML.
#' @examples \dontrun{
#' use_metadata("example.Rmd") 
#' # assume the user edits the file, then calls:
#' render_metadata("example.Rmd", output_file = "example.xml")
#' }
#' @export
render_metadata <- function(input,
                            output_file = NULL,
                            output_dir = NULL,
                            overwrite = TRUE,
                            quiet = FALSE){
  if(missing(input)){
    c("No `input` provided",
      i = "Please provide a metadata file",
      i = "You can call`use_metadata()` to create one") |>
      cli::cli_abort()
  }

  # create file name
  # NOTE: This is too basic at present, as either could be NULL
  if(is.null(output_file)){
    output_file <- "meta.xml"  
  }
  
  # create file string, including path
  if(is.null(output_dir)){
    output_string <- output_file
  }else{
    output_string <- glue::glue("{output_dir}/{output_file}")  
  }

  # write or not, depending on `overwrite`
  if(file.exists(output_string)){
    if(overwrite){
      if(!quiet){
        c(glue::glue("file `{output_string}` has been overwritten"),
          i = "set `overwrite = FALSE` to change this behaviour") |>
        cli::cli_inform()
      }
      read_md(input) |> 
        write_eml(file = output_string) 
    }else{
      if(!quiet){
        c(glue::glue("file `{output_string}` already exists and has not been overwritten"),
          i = "set `overwrite = TRUE` to change this behaviour") |>
        cli::cli_inform()
      }
    }
  }else{
    if(!quiet){
      glue::glue("Writing to file `{output_string}`") |>
        cli::cli_inform()
    }
    read_md(input) |> 
      write_eml(file = output_string)
  }
}