R/templateFiller.R

In tkonopka/Rpipelines: Writing pipelines in R

##
## object TemplateFiller and associated functions
##
## The point of this object is to hold template strings
## The templates can then be used with values in a script
##




##' Read template objects from files
##'
##' This function scans a directory for .txt files and loads each of them
##' into a list of strings
##' 
##' @param dirname character string, name of directory holding templates
##' @export
read.templates = function(dirname) {

  if (!file.exists(dirname)) {
    stop("Directory does not exist\n");
  }

  ## get all the file names that end with .txt
  templfiles = list.files(dirname, pattern=".txt$", recursive=T, full.names=T);

  ans = list();
  for (nowfile in templfiles) {

    ## cut out the .txt from the filename
    nowname = substring(basename(nowfile), 1, nchar(basename(nowfile))-4);

    ## read from the file
    fcon = file(nowfile, open="r");
    fconread = readLines(fcon, n=4096);
    ans[[nowfile]] = c();
    while (length(fconread)>0) {
      ans[[nowname]] = c(ans[[nowfile]], fconread);
      fconread = readLines(fcon, n=4096);
    }    
    close(fcon);
    
    ans[[nowname]] = paste(ans[[nowname]] , collapse="\n");
        
  }

  class(ans)="templates";
  
  return (ans);
}





##' Fill-in a template with specific key-value pairs
##' 
##' @param templs list of templates
##' @param templatename character string, name of template to use
##' @param keys vector of character strings, elements in the template to replace
##' @param values vector of character strings, matched with keys, these values
##'  will be used to replace generic keys within the template
##' 
##' @export
fill.templates = function(templs, templatename, keys = c(), values=c()) {

    if (length(keys)<length(values)) {
        stop("keys and/or values are misspecified\n");
    }
    
    ## check that the templatename exists among the templates templs
    if (!(templatename %in% names(templs))) {
        stop(paste("template ",templatename," does not exist\n"));
    }
    
    ## replace all the keys with the corresponding values
    ans = templs[[templatename]];
    if (length(keys)>0) {
        for (i in 1:length(keys)) {
            ans = gsub(keys[i], values[i], ans);
        }
    }
    
    return (ans);
}