(defun wg-buffer-to-buf (buffer)

  "Return the serialization (a wg-buf) of Emacs buffer BUFFER."

  (with-current-buffer buffer

    (wg-make-buf

     :name           (buffer-name)

     :file-name      (buffer-file-name)

     :point          (point)

     :mark           (mark)

     :local-vars     (wg-serialize-buffer-local-variables)

     :special-data   (wg-buffer-special-data buffer))))

(defun wg-add-buffer-to-buf-list (buffer)

  "Make a buf from BUFFER, and add it to `wg-buf-list' if necessary.

If there isn't already a buf corresponding to BUFFER in

`wg-buf-list', make one and add it.  Return BUFFER's uid

in either case."

  (with-current-buffer buffer

    (setq wg-buffer-uid

          (aif (wg-find-buffer-in-buf-list buffer (wg-buf-list))

              (wg-buf-uid it)

            (let ((buf (wg-buffer-to-buf buffer)))

              (push buf (wg-buf-list))

              (wg-buf-uid buf))))))

(defun wg-buffer-uid-or-add (buffer)

  "Return BUFFER's uid.

If there isn't already a buf corresponding to BUFFER in

`wg-buf-list', make one and add it."

  (or (wg-buffer-uid buffer) (wg-add-buffer-to-buf-list buffer)))

(defun wg-bufobj-uid-or-add (bufobj)

  "If BUFOBJ is a wg-buf, return its uid.

If BUFOBJ is a buffer or a buffer name, see `wg-buffer-uid-or-add'."

  (cl-etypecase bufobj

    (wg-buf (wg-buf-uid bufobj)) ;; possibly also add to `wg-buf-list'

    (buffer (wg-buffer-uid-or-add bufobj))

    (string (wg-bufobj-uid-or-add (wg-get-buffer bufobj)))))

(defun wg-reset-buffer (buffer)

  "Return BUFFER.

Currently only sets BUFFER's `wg-buffer-uid' to nil."

  (with-current-buffer buffer (setq wg-buffer-uid nil)))

;;; buffer-list-filter commands

(defun wg-update-buffer-in-buf-list (&optional buffer)

  "Update BUFFER's corresponding buf in `wg-buf-list'.

BUFFER nil defaults to `current-buffer'."

  (let ((buffer (or buffer (current-buffer))))

    (wg-when-let ((uid (wg-buffer-uid buffer))

                  (old-buf (wg-find-buf-by-uid uid))

                  (new-buf (wg-buffer-to-buf buffer)))

      (setf (wg-buf-uid new-buf) (wg-buf-uid old-buf))

      (wg-asetf (wg-buf-list) (cons new-buf (remove old-buf it))))))

(defun wg-update-buf-list (&optional buffer-list)

  "Update all bufs in `wg-buf-list' corresponding to buffers in BUFFER-LIST."

  (mapc 'wg-update-buffer-in-buf-list (or buffer-list (wg-buffer-list-emacs))))

(defun wg-buffer-list-display (buffer-list)

  "Return the BUFFER-LIST display string."

  (wg-display-internal

   'wg-buffer-display

   (if wg-center-rotate-buffer-list-display

       (wg-center-rotate-list buffer-list) buffer-list)))

(defun wg-buffer-list-filter-display (&optional workgroup blf-id)

  "Return a buffer-list-filter display string from WORKGROUP and BLF-ID."

  (wg-fontify

    "("

    (wg-workgroup-name (wg-get-workgroup workgroup))

    ":"

    (wg-get-buffer-list-filter-val blf-id 'indicator)

    ")"))

(defun wg-buffer-list-filter-prompt (prompt &optional workgroup blf-id)

  "Return a prompt string from PROMPT indicating WORKGROUP and BLF-ID."

  (wg-fontify

    prompt " "

    (wg-buffer-list-filter-display workgroup blf-id)

    ": "))

(defun wg-buffer-command-display (&optional buffer-list)

  "Return the buffer command display string."

  (concat

   (wg-buffer-list-filter-display) ": "

   (wg-buffer-list-display (or buffer-list (wg-filtered-buffer-list)))))

(defun wg-read-buffer (prompt &optional default require-match)

The input I may be a character, or a single-letter string.

Cribbed from `org-id-b36-to-int-one-digit'."

  (and (stringp i) (setq i (string-to-char i)))

  (cond ((and (>= i ?0) (<= i ?9)) (- i ?0))

        ((and (>= i ?A) (<= i ?Z)) (+ (- i ?A) 10))

        (t (error "Invalid b36 character"))))

(defun wg-int-to-b36 (i &optional length)

  "Return a base 36 string from I."

  (let ((base 36) b36)

    (cl-labels ((add-digit () (push (wg-int-to-b36-one-digit (mod i base)) b36)

                         (setq i (/ i base))))

      (add-digit)

      (while (> i 0) (add-digit))

      (setq b36 (cl-map 'string 'identity b36))

      (if (not length) b36

        (concat (make-string (max 0 (- length (length b36))) ?0) b36)))))

(defun wg-b36-to-int (str)

  "Convert STR, a base-36 string, into the corresponding integer.

Cribbed from `org-id-b36-to-int'."

  (let ((result 0))

    (mapc (lambda (i)

            (setq result (+ (* result 36)

                            (wg-b36-to-int-one-digit i))))

          str)

    result))

;;; lists

(defmacro wg-removef-p (item seq-place &rest keys)

  "If ITEM is a `member*' of SEQ-PLACE, remove it from SEQ-PLACE and return t.

Otherwise return nil.  KEYS can be any keywords accepted by `remove*'."

  `(> (length ,seq-place)

      (length (setf ,seq-place (cl-remove ,item ,seq-place ,@keys)))))

(defmacro wg-pushnew-p (item seq-place &rest keys)

  "If ITEM is not a `member' of SEQ-PLACE, push it to SEQ-PLACE and return t.

Otherwise return nil.  KEYS can be any keyword args accepted by `pushnew'."

  `(< (length ,seq-place)

      (length (cl-pushnew ,item ,seq-place ,@keys))))

(defun wg-take (list n)

  "Return a list of the first N elts in LIST."

  (butlast list (- (length list) n)))

(defun wg-range (start end)

  "Return a list of integers from START up to but not including END."

  (let (accum)

    (dotimes (i (- end start) (nreverse accum))

      (push (+ start i) accum))))

(defun wg-rotate-list (list &optional offset)

  "Rotate LIST by OFFSET.  Positive OFFSET rotates left, negative right."

  (when list

    (let ((split (mod (or offset 1) (length list))))

      (append (nthcdr split list) (wg-take list split)))))

(defun wg-center-rotate-list (list)

  "Rotate LIST so it's first elt is in the center.  When LIST's

length is even, the first elt is left nearer the front."

  (wg-rotate-list list (- (/ (1- (length list)) 2))))

(defun wg-insert-after (elt list index)

  "Insert ELT into LIST after INDEX."

  (let ((new-list (cl-copy-list list)))

    (push elt (cdr (nthcdr index new-list)))

    new-list))

(defun wg-insert-before (elt list index)

  "Insert ELT into LIST before INDEX."

  (if (zerop index) (cons elt list)

    (wg-insert-after elt list (1- index))))

(defun wg-move-elt (elt list index &rest keys)

  "Move ELT before INDEX in LIST.

KEYS is passed to `remove*'."

  (wg-insert-before elt (apply 'cl-remove elt list keys) index))

(defun wg-cyclic-nth (list n)

  "Return the Nth element of LIST, modded by the length of list."

  (nth (mod n (length list)) list))

(defun wg-cyclic-offset-elt (elt list n)

  "Cyclically offset ELT's position in LIST by N."

  (wg-when-let ((pos (cl-position elt list)))

    (wg-move-elt elt list (mod (+ n pos) (length list)))))

(defun wg-cyclic-nth-from-elt (elt list n &rest keys)

  "Return the elt in LIST N places cyclically from ELT.

If ELT is not present is LIST, return nil.

KEYS is passed to `position'."

  (wg-when-let ((pos (apply 'cl-position elt list keys)))

    (wg-cyclic-nth list (+ pos n))))