(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 (wg-buffer-list-emacs)))))

(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)

  ;; 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)))

  (wg-gc-bufs)

  (wg-gc-buf-uids)

  (wg-update-buf-list))

;; session consistency testing

(defun wg-modified-p ()

  "Return t when the current session or any of its workgroups are modified."

  (or (wg-session-modified (wg-current-session))

      (cl-some 'wg-workgroup-modified (wg-workgroup-list))))

(defun wg-mark-everything-unmodified ()

  "Mark the session and all workgroups as unmodified."

  (setf (wg-session-modified (wg-current-session)) nil)

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

    (setf (wg-workgroup-modified workgroup) nil)))

(defun wg-workgroup-names (&optional noerror)

  "Return a list of workgroup names or scream unless NOERROR."

  (mapcar 'wg-workgroup-name (wg-workgroup-list-or-error noerror)))

;;; session parameters

(defun wg-session-parameter (session parameter &optional default)

  "Return SESSION's value for PARAMETER.

If PARAMETER is not found, return DEFAULT which defaults to nil.

SESSION nil defaults to the current session."

  (wg-aget (wg-session-parameters (or session (wg-current-session)))

           parameter default))

(defun wg-set-session-parameter (session parameter value)

  "Set SESSION's value of PARAMETER to VALUE.

SESSION nil means use the current session.

Return value."

  (let ((session (or session (wg-current-session))))

    (wg-set-parameter (wg-session-parameters session) parameter value)

    (setf (wg-session-modified session) t)

    value))

(defun wg-remove-session-parameter (session parameter)

  "Remove parameter PARAMETER from SESSION's parameters."

  (let ((session (or session (wg-current-session))))

    (wg-asetf (wg-session-parameters session) (wg-aremove it parameter))

    (setf (wg-session-modified session) t)))

(defun wg-session-local-value (variable &optional session)

  "Return the value of VARIABLE in SESSION.

SESSION nil defaults to the current session.  If VARIABLE does

not have a session-local binding in SESSION, the value is

resolved by Emacs."

  (let* ((undefined (cl-gensym))

         (value (wg-session-parameter session variable undefined)))

    (if (not (eq value undefined)) value

      (symbol-value variable))))

(defun wg-reset-frame (frame)

  (set-frame-parameter frame 'wg-workgroup-state-table nil)

  (set-frame-parameter frame 'wg-current-workgroup-uid nil)

  (set-frame-parameter frame 'wg-previous-workgroup-uid nil))

(defun wg-save-session-on-exit (behavior)

  "Perform session-saving operations based on BEHAVIOR."

  (cl-case behavior

    (ask (wg-query-and-save-if-modified))

    (save

     (if (wg-determine-session-save-file-name)

         (wg-save-session)

       (wg-query-and-save-if-modified)))))

(defun wg-save-frames ()

  "Save opened frames as a session parameter.

Exclude `selected-frame' and daemon one (if any).

http://stackoverflow.com/questions/21151992/why-emacs-as-daemon-gives-1-more-frame-than-is-opened"

  (interactive)

  (let ((fl (frame-list)))

    (mapc (lambda (frame)

            (if (string-equal "initial_terminal" (terminal-name frame))

                (delete frame fl))) fl)

    (setq fl (delete (selected-frame) fl))

    (if (wg-current-session t)

        (wg-set-session-parameter (wg-current-session t)

                                  'frame-list

                                  (mapcar 'wg-frame-to-wconfig fl)))))

(defun wg-reload-session ()

  "Reload current workgroups session."

  (interactive)

  (let ((file (or (wg-determine-session-save-file-name)

                  wg-session-file)))

    (when (file-exists-p file)

      (condition-case err

          (wg-open-session wg-session-file)

        (progn

          (wg-create-first-wg)

          (error (message "Error finding session-file: %s" err)))))

    (wg-create-first-wg)))

(defun wg-save-session-on-emacs-exit ()

  "Call `wg-save-session-on-exit' with `wg-emacs-exit-save-behavior'.

Added to `kill-emacs-query-functions'."

  (wg-save-session-on-exit wg-emacs-exit-save-behavior) t)

(defun wg-save-session-on-workgroups-mode-exit ()

  "Call `wg-save-session-on-exit' with `wg-workgroups-mode-exit-save-behavior'.

Called when `workgroups-mode' is turned off."

  (wg-save-session-on-exit wg-workgroups-mode-exit-save-behavior) t)

(defun wg-pickel-all-session-parameters (session)

  "Return a copy of SESSION after pickeling its

parameters and the parameters of all its workgroups."

  (let ((copy (wg-copy-session session)))

    (when (wg-session-parameters copy)

      (wg-asetf (wg-session-parameters copy) (wg-pickel it)))

    (wg-asetf (wg-session-workgroup-list copy)

              (cl-mapcar 'wg-pickel-workgroup-parameters it))

    copy))

(defun wg-unpickel-session-parameters (session)

  "Return a copy of SESSION after unpickeling its

parameters and the parameters of all its workgroups."

  (let ((copy (wg-copy-session session)))

    (when (wg-session-parameters copy)

      (wg-asetf (wg-session-parameters copy) (wg-unpickel it)))

    (wg-asetf (wg-session-workgroup-list copy)

              (cl-mapcar 'wg-unpickel-workgroup-parameters it))

    copy))

(provide 'workgroups-session)

;;; workgroups-session.el ends here