Clean up passwords and tokens for use in documentation

clean-token.el

;; Turns a password like "qWXNNXb6m(TM77WiVtC87c*" into "aABCDEb0c(FG12HdIeJ34f*"
;;
;; Use the clean-token function by marking a region you want to be "cleaned" and then running M-x clean-token
(defun token-cleaner (token)
  "Given a TOKEN as a string, return a string where the letters in TOKEN have been replaced with letters from the same type"
  (defun next-letter (letter smallest-letter largest-letter)
    "Given LETTER, return the next letter in the sequence between SMALLEST-LETTER and LARGEST-LETTER"
    (let ((proposed-letter (char-to-string (1+ (string-to-char letter)))))
      (if (string> proposed-letter largest-letter)
	  smallest-letter
	proposed-letter)))
  (defun char-type-equal-p (char expected-type)
    "Check if CHAR is EXPECTED-TYPE"
    (equal (get-char-code-property (string-to-char char) 'general-category) expected-type))
  (defun char-type-replace (char)
    "Replace letter CHAR with the next letter in the sequence"
    (cond ((char-type-equal-p char 'Ll)
	   (setq letter-lowercase (next-letter letter-lowercase "a" "z")))
	  ((char-type-equal-p char 'Lu)
	   (setq letter-uppercase (next-letter letter-uppercase "A" "Z")))
	  ((char-type-equal-p char 'Nd)
	   (setq numeric-digit (next-letter numeric-digit "0" "9")))
	  (t char)))
  (let ((letter-lowercase "z") (letter-uppercase "Z") (numeric-digit "9"))
    (mapconcat 'identity (mapcar 'char-type-replace (mapcar 'string token)) "")))

(defun clean-token (beg end)
  "message region or \"empty string\" if none highlighted"
    (interactive (if (use-region-p)
		     (list (region-beginning) (region-end))
		   (list nil nil)))
    (let ((region-contents))
      (setf region-contents (buffer-substring-no-properties beg end))
      (delete-region beg end)
      (insert (token-cleaner region-contents))))