(defun wg-update-all-base-wconfigs ()

  "Update every workgroup's base wconfig with

`wg-workgroup-update-base-wconfig'."

  (dolist (workgroup (wg-workgroup-list))

    (wg-awhen (wg-workgroup-selected-frame-wconfig workgroup)

      (setf (wg-workgroup-base-wconfig workgroup) it

            (wg-workgroup-selected-frame-wconfig workgroup) nil))))

(defun wg-update-working-wconfig-on-delete-frame (frame)

  "Update FRAME's current workgroup's working-wconfig before

FRAME is deleted, so we don't lose its state."

  (with-selected-frame frame

    (wg-update-current-workgroup-working-wconfig)))

;;; workgroup saved wconfigs

(defun wg-workgroup-saved-wconfig-names (workgroup)

  "Return a new list of the names of all WORKGROUP's saved wconfigs."

  (mapcar 'wg-wconfig-name (wg-workgroup-saved-wconfigs workgroup)))

(defun wg-workgroup-get-saved-wconfig (workgroup wconfig-or-name)

  "Return the wconfig in WORKGROUP's saved wconfigs named WCONFIG-OR-NAME.

WCONFIG-OR-NAME must be either a string or a wconfig.  If

WCONFIG-OR-NAME is a string and there is no saved wconfig with

that name, return nil.  If WCONFIG-OR-NAME is a wconfig, and it

is a member of WORKGROUP's saved wconfigs, return is as given.

Otherwise return nil."

  (let ((wconfigs (wg-workgroup-saved-wconfigs workgroup)))

    (cl-etypecase wconfig-or-name

      (wg-wconfig (car (memq wconfig-or-name wconfigs)))

      (string (cl-find wconfig-or-name wconfigs

                    :key 'wg-wconfig-name

                    :test 'string=)))))

(defun wg-workgroup-save-wconfig (workgroup wconfig)

  "Add WCONFIG to WORKGROUP's saved wconfigs.  WCONFIG must have

a name.  If there's already a wconfig with the same name in

WORKGROUP's saved wconfigs, replace it."

  (let ((name (wg-wconfig-name wconfig)))

    (unless name (error "Attempt to save a nameless wconfig"))

    (setf (wg-workgroup-modified workgroup) t)

    (wg-asetf (wg-workgroup-saved-wconfigs workgroup)

              (cons wconfig (cl-remove name it

                                       :key 'wg-wconfig-name

                                       :test 'string=)))))

(defun wg-workgroup-kill-saved-wconfig (workgroup wconfig-or-name)

  "Delete WCONFIG-OR-NAME from WORKGROUP's saved wconfigs.

WCONFIG-OR-NAME is resolved with `wg-workgroup-get-saved-wconfig'."

  (wg-when-let ((wconfig (wg-workgroup-get-saved-wconfig

                          workgroup wconfig-or-name)))

    (wg-asetf (wg-workgroup-saved-wconfigs workgroup) (remq wconfig it)

              (wg-workgroup-modified workgroup) t)))

;;; garbage collection

;; update buf list

(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 (buffer-list))))

;; gc buf uids

(defun wg-workgroup-gc-buf-uids (workgroup)

  "Remove buf uids from WORKGROUP that have no referent in `wg-buf-list'."

  (wg-asetf (wg-workgroup-strong-buf-uids workgroup)

            (cl-remove-if-not 'wg-find-buf-by-uid it)

            (wg-workgroup-weak-buf-uids workgroup)

            (cl-remove-if-not 'wg-find-buf-by-uid it)))

(defun wg-gc-buf-uids ()

  "Remove from all workgroups those buf uids that have no referent in `wg-buf-list'."

  (mapc 'wg-workgroup-gc-buf-uids (wg-workgroup-list)))

;; gc bufs

(defun wg-wtree-buf-uids (wtree)

  (wg-flatten-wtree wtree 'wg-win-buf-uid))

(defun wg-wtree-unique-buf-uids (wtree)

  (cl-remove-duplicates (wg-wtree-buf-uids wtree) :test 'string=))

(defun wg-wconfig-buf-uids (wconfig)

  "Return WCONFIG's wtree's `wg-wtree-buf-uids'."

  (wg-wtree-unique-buf-uids (wg-wconfig-wtree wconfig)))

(defun wg-workgroup-base-wconfig-buf-uids (workgroup)

  "Return a new list of all unique buf uids in WORKGROUP's working wconfig."

  (wg-wconfig-buf-uids (wg-workgroup-base-wconfig workgroup)))

(defun wg-workgroup-saved-wconfigs-buf-uids (workgroup)

  "Return a new list of all unique buf uids in WORKGROUP's base wconfig."

  (cl-reduce 'wg-string-list-union

          (wg-workgroup-saved-wconfigs workgroup)

          :key 'wg-wconfig-buf-uids))

(defun wg-workgroup-all-wconfig-buf-uids (workgroup)

  "Return a new list of all unique buf uids in WORKGROUP's wconfigs."

  (cl-union (wg-workgroup-base-wconfig-buf-uids workgroup)

         (wg-workgroup-saved-wconfigs-buf-uids workgroup)

         :test 'string=))

(defun wg-workgroup-all-buf-uids (workgroup)

  "Return a new list of all unique buf uids in WORKGROUP."

  (cl-reduce 'wg-string-list-union

          (list (wg-workgroup-base-wconfig-buf-uids workgroup)

                (wg-workgroup-saved-wconfigs-buf-uids workgroup)

                (if wg-restore-associated-buffers

                    (wg-workgroup-associated-buf-uids workgroup))

                )))

(defun wg-session-all-buf-uids (&optional session)

  "Return a new list of all unique buf uids in SESSION.

SESSION nil defaults to `wg-current-session'."

  (cl-reduce 'wg-string-list-union

          (wg-session-workgroup-list (or session (wg-current-session)))

          :key 'wg-workgroup-all-buf-uids))

(defun wg-buffer-list-all-uids (&optional buffer-list)

  "Return a list of the uids of all buffers in BUFFER-LIST in

which `wg-buffer-uid' is locally bound.

BUFFER-LIST nil defaults to `buffer-list'."

  (delq nil (mapcar 'wg-buffer-uid (or buffer-list (buffer-list)))))

(defun wg-all-buf-uids (&optional session buffer-list)

  "Return the union of `wg-session-all-buf-uids' and `wg-buffer-list-all-uids'."

  (cl-union (wg-session-all-buf-uids session)

         (wg-buffer-list-all-uids buffer-list)

         :test 'string=))

(defun wg-gc-bufs ()

  "gc bufs from `wg-buf-list' that are no longer needed."

  (let ((all-buf-uids (wg-all-buf-uids)))

    (wg-asetf (wg-buf-list)

              (cl-remove-if-not (lambda (uid) (member uid all-buf-uids)) it

                                :key 'wg-buf-uid))))

;; FIXME: Duplicate buf names probably shouldn't be allowed.  An unrelated error

;; causes two *scratch* buffers to be present, triggering the "uids don't match"

;; error.  Write something to remove bufs with duplicate names.

(defun wg-perform-session-maintenance ()

  "Perform various maintenance operations on the current Workgroups session."

  (wg-update-current-workgroup-working-wconfig)

  (wg-update-all-base-wconfigs)

  (wg-gc-bufs)

  (wg-gc-buf-uids)

  (wg-update-buf-list))

;; session consistency testing

(defun wg-session-uids-consistent-p ()

  "Return t if there are no duplicate bufs or buf uids in the wrong places,

nil otherwise."

  (and (cl-every (lambda (wg)

                (not (wg-dups-p (wg-workgroup-associated-buf-uids wg)

                                :test 'string=)))

              (wg-workgroup-list))

       (not (wg-dups-p (wg-buf-list) :key 'wg-buf-uid :test 'string=))

       (not (wg-dups-p (wg-workgroup-list) :key 'wg-workgroup-uid :test 'string=))))

;;; workgroup restoration

(defun wg-restore-workgroup-associated-buffers-internal (workgroup)

  "Restore all the buffers associated with WORKGROUP that can be restored."

  (save-window-excursion

    (delete nil (mapcar 'wg-restore-buffer

                        (wg-workgroup-associated-bufs workgroup)))))

(defun wg-restore-workgroup (workgroup)

  "Restore WORKGROUP in `selected-frame'."

  (when wg-restore-associated-buffers

    (wg-restore-workgroup-associated-buffers-internal workgroup))

  (let (wg-flag-modified)

    (wg-restore-wconfig-undoably