controlLabel <- function(controlName, label) {
  label %AND% tags$label(class = "control-label", `for` = controlName, label)
}

# This function takes in either a list or vector for `choices` (and
# `choiceNames` and `choiceValues` are passed in as NULL) OR it takes
# in a list or vector for both `choiceNames` and `choiceValues` (and
# `choices` is passed as NULL) and returns a list of two elements:
#    - `choiceNames` is a vector or list that holds the options names
#      (each element can be arbitrary UI, or simple text)
#    - `choiceValues` is a vector or list that holds the options values
#       (each element must be simple text)
normalizeChoicesArgs <- function(choices, choiceNames, choiceValues,
  mustExist = TRUE) {
  # if-else to check that either choices OR (choiceNames + choiceValues)
  # were correctly provided
  if (is.null(choices)) {
    if (is.null(choiceNames) || is.null(choiceValues)) {
      if (mustExist) {
        stop("Please specify a non-empty vector for `choices` (or, ",
             "alternatively, for both `choiceNames` AND `choiceValues`).")
      } else {
        if (is.null(choiceNames) && is.null(choiceValues)) {
          # this is useful when we call this function from `updateInputOptions()`
          # in which case, all three `choices`, `choiceNames` and `choiceValues`
          # may legitimately be NULL
          return(list(choiceNames = NULL, choiceValues = NULL))
        } else {
          stop("One of `choiceNames` or `choiceValues` was set to ",
               "NULL, but either both or none should be NULL.")
        }
      }
    }
    if (length(choiceNames) != length(choiceValues)) {
      stop("`choiceNames` and `choiceValues` must have the same length.")
    }
    if (anyNamed(choiceNames) || anyNamed(choiceValues)) {
      stop("`choiceNames` and `choiceValues` must not be named.")
    }
  } else {
    if (!is.null(choiceNames) || !is.null(choiceValues)) {
      warning("Using `choices` argument; ignoring `choiceNames` and `choiceValues`.")
    }
    choices <- choicesWithNames(choices) # resolve names if not specified
    choiceNames <- names(choices)
    choiceValues <- unname(choices)
  }

  return(list(choiceNames = as.list(choiceNames),
              choiceValues = as.list(as.character(choiceValues))))
}

# generate options for radio buttons and checkbox groups (type = 'checkbox' or
# 'radio')
generateOptions <- function(inputId, selected, inline, type = 'checkbox',
                            choiceNames, choiceValues,
                            session = getDefaultReactiveDomain()) {
  # generate a list of <input type=? [checked] />
  options <- mapply(
    choiceValues, choiceNames,
    FUN = function(value, name) {
      inputTag <- tags$input(
        type = type, name = inputId, value = value
      )
      if (value %in% selected)
        inputTag$attribs$checked <- "checked"

      # in case, the options include UI code other than text
      # (arbitrary HTML using the tags() function or equivalent)
      pd <- processDeps(name, session)

      # If inline, there's no wrapper div, and the label needs a class like
      # checkbox-inline.
      if (inline) {
        tags$label(class = paste0(type, "-inline"), inputTag,
                   tags$span(pd$html, pd$deps))
      } else {
        tags$div(class = type, tags$label(inputTag,
                 tags$span(pd$html, pd$deps)))
      }
    },
    SIMPLIFY = FALSE, USE.NAMES = FALSE
  )

  div(class = "shiny-options-group", options)
}


# Takes a vector or list, and adds names (same as the value) to any entries
# without names. Coerces all leaf nodes to `character`.
choicesWithNames <- function(choices) {
  # Take a vector or list, and convert to list. Also, if any children are
  # vectors with length > 1, convert those to list. If the list is unnamed,
  # convert it to a named list with blank names.
  listify <- function(obj) {
    # If a list/vector is unnamed, give it blank names
    makeNamed <- function(x) {
      if (is.null(names(x))) names(x) <- character(length(x))
      x
    }

    res <- lapply(obj, function(val) {
      if (is.list(val))
        listify(val)
      else if (length(val) == 1 && is.null(names(val)))
        as.character(val)
      else
        makeNamed(as.list(val))
    })

    makeNamed(res)
  }

  choices <- listify(choices)
  if (length(choices) == 0) return(choices)

  # Recurse into any subgroups
  choices <- mapply(choices, names(choices), FUN = function(choice, name) {
    if (!is.list(choice)) return(choice)
    if (name == "") stop('All sub-lists in "choices" must be named.')
    choicesWithNames(choice)
  }, SIMPLIFY = FALSE)

  # default missing names to choice values
  missing <- names(choices) == ""
  names(choices)[missing] <- as.character(choices)[missing]

  choices
}
