R/options.R

In diffmatchpatch: String Diff, Match, and Patch Utilities

#' @title diffmatchpatch settings
#' 
#' @description Allows for examining or setting options that affect the behavior of the 
#' diff, match, and patch related functions in this package.
#' 
#' @return When getting options returns a named list of options and their current values, 
#' when setting options returns a named list of the previous value(s).
#' 
#' @param ... No arguments returns all current options and their values. Character values retrieve a subset 
#' of options and the current values. Options can be set, using name = value. However, only the options named 
#' below are used. Options can also be passed by giving a single unnamed argument which is a named list.
#'
#' @details ## Available options
#' 
#' * `diff_timeout` (float) - Number of seconds to map a diff before giving up (0 for infinity).
#'
#' * `diff_edit_cost` (int) - Cost of an empty edit operation in terms of edit characters.
#' 
#' * `match_threshold` (float) - At what point is no match declared (0.0 = perfection, 1.0 = very loose).
#'
#' * `match_distance` (int) - How far to search for a match (0 = exact location, 1000+ = broad match).
#'   A match this many characters away from the expected location will add
#'   1.0 to the score (0.0 is a perfect match).
#'
#' * `patch_delete_threshold` (float) - When deleting a large block of text (over ~64 characters), how close does
#'   the contents have to match the expected contents. (0.0 = perfection,
#'   1.0 = very loose).  Note that Match_Threshold controls how closely the
#'   end points of a delete need to match.
#'
#' * `patch_margin` (int) - Chunk size for context length.
#'
#' * `match_max_bits` (int) - The number of bits in an int.
#' 
#' @examples 
#' dmp_options()
#' 
#' dmp_options("diff_timeout")
#' 
#' prev = dmp_options(diff_timeout = 5)
#' prev
#' 
#' @export
dmp_options = function(...) {
  opts = list(...)
  
  if (length(opts) == 1 && is.list(opts[[1]]))
    opts = opts[[1]]
    
  if (length(opts) == 0) {
    get_options()
  } else if (is.null(names(opts))) {
    opts = unlist(opts)
    if (!is.character(opts))
      stop("Invalid argument - expected Character got ", class(opts), call. = FALSE)
    
    get_options()[opts]
  } else {
    prev = get_options()[names(opts)]
    set_options(opts)
    
    invisible(prev)
  }
}