R/preprocessor.R

In thomasWeise/bookbuildeR: An R Package for Building Books or Documents using pandoc

#' @title Pre-Process a Document File
#' @description Pre-process the root file of a hierarchically structured
#'   document to a single monolithic output.
#' @param sourceFile the source file
#' @param destName the name of the destination file (to be created in the same
#'   folder as the source file)
#' @return a list \code{list(path=path, meta=meta)} with the canonical path \code{path} to the destination file and the yaml metadata \code{meta}
#' @include logger.R
#' @include preprocessorInput.R
#' @include preprocessorPlain.R
#' @include preprocessorTextblock.R
#' @include preprocessorCommand.R
#' @include preprocessorRepo.R
#' @export preprocess.doc
preprocess.doc <- function(sourceFile, destName) {
  # get the canonical path of the source file
  sourceFile <- .check.file(sourceFile);
  sourceDir <- .check.dir(dirname(sourceFile));

  # create dest file
  destFile <- normalizePath(file.path(sourceDir, destName), mustWork = FALSE);
  if(file.exists(destFile)) {
    .exit("Destination file '", destFile, "' already exists.");
  }

  # load the text
  text <- preprocess.input(sourceFile);
  
  .logger("Now preprocessing the ",
          nchar(text), " characters loaded from '",
          sourceFile, "'.");
  
  # do the pre-processing
  text <- preprocess.plain(text);
  text <- preprocess.textblocks(text);

  # get the yaml metadata
  meta <- metadata.get(text);
    
  # if a repository is specified, download the repository, load the code, delete the repository
  text <- preprocess.repo(text, meta);
  
  # transform text back to lines
  text <- unname(unlist(strsplit(
              text, split="\n", fixed = TRUE)));
  
  .logger("Obtained ", length(text),
          " lines of text from preprocessing '",
          sourceFile, "', now writing to '",
          destFile, "'.");
  
  output <- file(destFile, open="wt");
  writeLines(text=text, con=output);
  
  close(output);
  destFile <- .check.file(destFile);

  .logger("Finished pre-processing contents from main source file '",
         sourceFile,
         "' to output file '",
         destFile,
         "'.");
  return(list(path=destFile, meta=meta));
}