profilr: Profile regression models.

#' Test whether a string has been transformed.
#' @param x Character.
is_transformed <- function(x) grepl(pattern = "^.+\\(.+\\)$", x)


#' Capture a single group from a string.
#' @param x Character.
#' @param pattern Character Scalar.
#' @return Character Scalar.
#' @importFrom utils strcapture
capture <- function(x, pattern) {
  unlist(strcapture(pattern, x, proto = ""),
         use.names = FALSE)
}


#' Extract the transformation function in the variable.
#' @param x Character.
trans_function <- function(x) {
  z <- is_transformed(x)
  ifelse(z, capture(x, "^(.+)\\(.+\\)$"), "identity")
}


#' Extract the (potentially) transformed variable
#' @param x Character.
#' @return Character.
trans_variable <- function(x) {
  z <- is_transformed(x)
  ifelse(z, capture(x, "^.+\\((.+)\\)$"), x)
}


#' Return a specific value, no matter the level of x.
#'
#' This is supposed to be helpful for choosing specific values for
#' your statistic.
#' @param y Numeric value to pick.
#' @return Function with parameter x.
#' @export
at <- function(y) {
  stopifnot(length(y) == 1)
  function(x) y
}


#' Concatenate (collapse) string to a single line.
#' @param x List(k).
#' @return Character(1).
concat <- function(x, sep = "") paste(x, collapse = sep)

#' Recode values from a named lookup list.
#' List -> List
#' @param x Named List(k).
#' @param lookup Named list lookup entries.
#' @return Named List(k) that has been renamed.
#' @examples
#' concat(
#'   recode(letters[1:3],
#'          lookup = c(a = "b", b = "a", c = "z"))) # => "baz"
recode <- function(x, lookup) {
  if(is.null(names(lookup))) {
    stop("Please pass a named atomic list as a lookup.")
  }
  idx <- which(x %in% names(lookup))
  nm_look <- names(lookup)
  for(i in idx) x[i] <- lookup[x[i]]
  x
}