R/funr.R

In sahilseth/funr: Simple Utility Providing Terminal Access to all R Functions

#' funr: providing a simple command-line interface to R functions
#'
#' @description
#' Wraps Rscript in a easy to use manner, exposing all R functions from the terminal.
#' The \href{https://github.com/sahilseth/funr}{github page} provides more details with examples,
#' highlights and caveats.
#'
#' @aliases funr rfun cli
#'
#' @param args Should always be: \code{commandArgs(trailingOnly = TRUE)}, when used
#' inside a script. \href{https://github.com/sahilseth/funr/blob/master/inst/scripts/funr}{Example}
#' @param help_text A simple text to be displayed describing options and usage of this interface.
#' Supplying this, replaces the default text.
#' @param script_name Name of the script. This is used in the the help text. [funr]
#'
#'
#' @source https://github.com/sahilseth/funr
#'
#' @export
#' @importFrom utils head help str
#'
#' @examples
#' ## show funr help
#' ## terminal version: funr -h
#' funr()
#'
#'
#' ## show rnorm help
#' ## terminal version: funr -h rnorm
#' render_funr(funr(args=c("-h", "rnorm")))
#'
#' ## Generate a few random numbers
#' ## terminal version: funr rnorm n=10
#' render_funr(funr(args=c("rnorm", "n=10")))
#'
funr <- function(args,
                 help_text,
                 script_name = "funr"){

  ##        show help if there are no arguments
  #if(missing(help_text))

  if(missing(args)){
    message(generic_help(help_text = help_text, script_name = script_name))
    return()
  }

  if(length(args) == 0){
    message(generic_help(help_text = help_text, script_name = script_name))
    return()
  }

  # Arguments which start with - are for this script
  rm = grep("^-", args)
  script_args = args[rm]

  verbose = FALSE
  if("-v" %in% script_args)
    verbose = TRUE

  if(verbose){
    message("args:"); message(args)
    message("script_args:"); message(script_args)
  }

  # remove these from subsequent processing
  if(length(rm) > 0)
    args = args[-rm]

  if(length(args) == 0){
    message(generic_help(help_text = help_text))
    return()
  }

  #      Get name of the function
  func = args[1]
  #    all arguments to that function
  args = args[-1]

  if(verbose){
    message("\nusing func:");message(func)
    message("with final args:");message(args)
  }

  args_w_missing_eq = grep("=", args, value = TRUE, invert = TRUE)
  if(length(args_w_missing_eq) > 0){
    message("> All args must use the format variable=value!\n",
            "> Please check the followings args:",
            paste(args_w_missing_eq, collapse = "\n"),
            "\n> A valid example would be say, 'rnorm n=100'")
    generic_help()
    invisible()
  }

  #           Load the required package
  if(grepl("::", func)){
    pkg <- gsub("(.?)::.*", "\\1", func)
    cat("loading pkg:", pkg, "\n");
    library(pkg, character.only = TRUE)
    func = as.character(gsub(".*::(.*)", "\\1", func))
  }

  if( is.na(func) ){
    generic_help()
    invisible()
  }

  fn = try(get(func), silent = TRUE)
  if(class(try(fn)) == "try-error")
    stop("\nI could not find a function called '", func, "' name, please check.")

  if(is.function(fn) & "-h" %in% script_args){
    out = withVisible(help(func))
    class(out) = c("funr", "list")
    return(out)

  }else{

    params <- parse_params(func = func, paramPairs = args, verbose = verbose)
    if(verbose){
      cat("\nStarting", func, "with params\n",
          paste(names(params), unlist(params),sep=": ",
                collapse="\n"),"\n")
      #message(args)
      if(verbose) message(str(params))
    }

    if(length(args) == 0)
      message("\ntry:      ", script_name, " -h ", func, "     to get more details on this function.")

    out = try(withVisible(do.call(func, args = params)))

    if(class(out) == "try-error"){
      stop("")
    }

    class(out) = c("funr", "list")
    return(out)
  }

}