;;; winner.el --- Restore old window configurations

;; Copyright (C) 1997-1998, 2001-2019 Free Software Foundation, Inc.

;; Author: Ivar Rummelhoff <ivarru@math.uio.no>
;; Created: 27 Feb 1997
;; Keywords: convenience frames

;; This file is part of GNU Emacs.

;; GNU Emacs is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.

;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.

;;; Commentary:

;; Winner mode is a global minor mode that records the changes in the
;; window configuration (i.e. how the frames are partitioned into
;; windows) so that the changes can be "undone" using the command
;; `winner-undo'.  By default this one is bound to the key sequence
;; ctrl-c left.  If you change your mind (while undoing), you can
;; press ctrl-c right (calling `winner-redo').

;;; Code:

(eval-when-compile (require 'cl-lib))

(defun winner-active-region ()
  (declare (gv-setter (lambda (store)
                        (if (featurep 'xemacs)
                            `(if ,store (zmacs-activate-region)
                               (zmacs-deactivate-region))
                          `(if ,store (activate-mark) (deactivate-mark))))))
  (region-active-p))

(defalias 'winner-edges
  (if (featurep 'xemacs) 'window-pixel-edges 'window-edges))
(defalias 'winner-window-list
  (if (featurep 'xemacs)
      (lambda () (delq (minibuffer-window) (window-list nil 0)))
    (lambda () (window-list nil 0))))

(require 'ring)

(defgroup winner nil
  "Restoring window configurations."
  :group 'windows)

(defcustom winner-dont-bind-my-keys nil
  "Non-nil means do not bind keys in Winner mode."
  :type  'boolean
  :group 'winner)

(defcustom winner-ring-size 200
  "Maximum number of stored window configurations per frame."
  :type  'integer
  :group 'winner)

(defcustom winner-boring-buffers '("*Completions*")
  "List of buffer names whose windows `winner-undo' will not restore.
You may want to include buffer names such as *Help*, *Apropos*,
*Buffer List*, *info* and *Compile-Log*."
  :type '(repeat string)
  :group 'winner)



;;;; Saving old configurations (internal variables and subroutines)


;;; Current configuration

;; List the windows according to their edges.
(defun winner-sorted-window-list ()
  (sort (winner-window-list)
        (lambda (x y)
          (cl-loop for a in (winner-edges x)
                   for b in (winner-edges y)
                   while (= a b)
                   finally return (< a b)))))

(defun winner-win-data ()
  ;; Essential properties of the windows in the selected frame.
  (cl-loop for win in (winner-sorted-window-list)
           collect (cons (winner-edges win) (window-buffer win))))

;; This variable is updated with the current window configuration
;; every time it changes.
(defvar winner-currents nil)

;; The current configuration (+ the buffers involved).
(defsubst winner-conf ()
  (cons (current-window-configuration)
        (winner-win-data)))


;; Save current configuration.
;; (Called below by `winner-save-old-configurations').
(defun winner-remember ()
  (setf (alist-get (selected-frame) winner-currents) (winner-conf)))

;; Consult `winner-currents'.
(defun winner-configuration (&optional frame)
  (or (cdr (assq (or frame (selected-frame)) winner-currents))
      (with-selected-frame frame
	(winner-conf))))



;;; Saved configurations

;; This variable contains the window configuration rings.
;; The key in this alist is the frame.
(defvar winner-ring-alist nil)

;; Find the right ring.  If it does not exist, create one.
(defsubst winner-ring (frame)
  (or (cdr (assq frame winner-ring-alist))
      (let ((ring (make-ring winner-ring-size)))
        (ring-insert ring (winner-configuration frame))
        (push (cons frame ring) winner-ring-alist)
        ring)))


;; If the same command is called several times in a row,
;; we only save one window configuration.
(defvar winner-last-command nil)

;; Frames affected by the previous command.
(defvar winner-last-frames nil)


(defsubst winner-equal (a b)
  "Check whether two Winner configurations (as produced by
`winner-conf') are equal."
  (equal (cdr a) (cdr b)))


;; Save the current window configuration, if it has changed.
;; If so return frame, otherwise return nil.
(defun winner-insert-if-new (frame)
  (unless (or (memq frame winner-last-frames)
	      (eq this-command 'winner-redo))
    (let ((conf (winner-configuration frame))
	  (ring (winner-ring frame)))
      (when (and (not (ring-empty-p ring))
		 (winner-equal conf (ring-ref ring 0)))
        ;; When the previous configuration was very similar,
        ;; keep only the latest.
	(ring-remove ring 0))
      (ring-insert ring conf)
      (push frame winner-last-frames)
      frame)))



;;; Hooks

;; Frames affected by the current command.
(defvar winner-modified-list nil)

;; Called whenever the window configuration changes
;; (a `window-configuration-change-hook').
(defun winner-change-fun ()

  ;; Cull dead frames.
  (setq winner-modified-list
        (cl-loop for frame in winner-modified-list
             if (frame-live-p frame) collect frame))

  (unless (or (memq (selected-frame) winner-modified-list)
              (/= 0 (minibuffer-depth)))
    (push (selected-frame) winner-modified-list)))

;; A `post-command-hook' for emacsen with
;; `window-configuration-change-hook'.
(defun winner-save-old-configurations ()
  (when (zerop (minibuffer-depth))
    (unless (eq this-command winner-last-command)
      (setq winner-last-frames nil)
      (setq winner-last-command this-command))
    (dolist (frame winner-modified-list)
      (winner-insert-if-new frame))
    (setq winner-modified-list nil)
    (winner-remember)))

;; A `minibuffer-setup-hook'.
(defun winner-save-unconditionally ()
  (unless (eq this-command winner-last-command)
    (setq winner-last-frames nil)
    (setq winner-last-command this-command))
  (winner-insert-if-new (selected-frame))
  (winner-remember))

;; A `post-command-hook' for other emacsen.
;; Also called by `winner-undo' before "undoing".
(defun winner-save-conditionally ()
  (when (zerop (minibuffer-depth))
    (winner-save-unconditionally)))




;;;; Restoring configurations

;; Works almost as `set-window-configuration',
;; but does not change the contents or the size of the minibuffer,
;; and tries to preserve the selected window.
(defun winner-set-conf (winconf)
  (let* ((miniwin  (minibuffer-window))
         (chosen   (selected-window))
         (minisize (window-height miniwin)))
    (cl-letf (((window-buffer miniwin))
              ((window-point  miniwin)))
      (set-window-configuration winconf))
    (cond
     ((window-live-p chosen) (select-window chosen))
     ((window-minibuffer-p) (other-window 1)))
    (when (/= minisize (window-height miniwin))
      (with-selected-window miniwin
        (setf (window-height) minisize)))))



(defvar winner-point-alist nil)
;; `set-window-configuration' restores old points and marks.  This is
;; not what we want, so we make a list of the "real" (i.e. new) points
;; and marks before undoing window configurations.
;;
;; Format of entries: (buffer (mark . mark-active) (window . point) ..)

(defun winner-make-point-alist ()
  (save-current-buffer
    (cl-loop with alist
             for win in (winner-window-list)
             for entry =
             (or (assq (window-buffer win) alist)
                 (car (push (list (set-buffer (window-buffer win))
                                  (cons (mark t) (winner-active-region)))
                            alist)))
             do (push (cons win (window-point win))
                      (cddr entry))
             finally return alist)))

(defun winner-get-point (buf win)
  ;; Consult (and possibly extend) `winner-point-alist'.
  ;; Returns nil if buf no longer exists.
  (when (buffer-name buf)
    (let ((entry (assq buf winner-point-alist)))
      (cond
       (entry
	(or (cdr (assq win (cddr entry)))
	    (cdr (assq nil (cddr entry)))
	    (with-current-buffer buf
	      (push (cons nil (point)) (cddr entry))
	      (point))))
       (t (with-current-buffer buf
	    (push (list buf
			(cons (mark t) (winner-active-region))
			(cons nil (point)))
		  winner-point-alist)
	    (point)))))))


;; Make sure point does not end up in the minibuffer and delete
;; windows displaying dead or boring buffers
;; (c.f. `winner-boring-buffers').  Return nil if all the windows
;; should be deleted.  Preserve correct points and marks.
(defun winner-set (conf)
  ;; For the format of `conf', see `winner-conf'.
  (let* ((buffers nil)
	 (alive
          ;; Possibly update `winner-point-alist'
	  (cl-loop for buf in (mapcar 'cdr (cdr conf))
                   for pos = (winner-get-point buf nil)
                   if (and pos (not (memq buf buffers)))
                   do (push buf buffers)
                   collect pos)))
    (winner-set-conf (car conf))
    (let (xwins)                        ; to be deleted

      ;; Restore points
      (dolist (win (winner-sorted-window-list))
        (unless (and (pop alive)
                     (setf (window-point win)
                           (winner-get-point (window-buffer win) win))
                     (not (member (buffer-name (window-buffer win))
                                  winner-boring-buffers)))
          (push win xwins)))            ; delete this window

      ;; Restore marks
      ;; `winner-undo' shouldn't update the selection (Bug#28631) when
      ;; select-enable-primary is non-nil.
      (unless select-enable-primary
        (save-current-buffer
	  (cl-loop for buf in buffers
                   for entry = (cadr (assq buf winner-point-alist))
                   do (progn (set-buffer buf)
                             (set-mark (car entry))
                             (setf (winner-active-region) (cdr entry))))))
      ;; Delete windows, whose buffers are dead or boring.
      ;; Return t if this is still a possible configuration.
      (or (null xwins)
	  (progn
            (mapc 'delete-window (cdr xwins)) ; delete all but one
            (unless (one-window-p t)
              (delete-window (car xwins))
              t))))))



;;;; Winner mode  (a minor mode)

(defcustom winner-mode-hook nil
  "Functions to run whenever Winner mode is turned on or off."
  :type 'hook
  :group 'winner)

(define-obsolete-variable-alias 'winner-mode-leave-hook
  'winner-mode-off-hook "24.3")

(defcustom winner-mode-off-hook nil
  "Functions to run whenever Winner mode is turned off."
  :type 'hook
  :group 'winner)

(defvar winner-mode-map
  (let ((map (make-sparse-keymap)))
    (unless winner-dont-bind-my-keys
      (define-key map [(control c) left] 'winner-undo)
      (define-key map [(control c) right] 'winner-redo))
    map)
  "Keymap for Winner mode.")


;;;###autoload
(define-minor-mode winner-mode
  "Toggle Winner mode on or off.
With a prefix argument ARG, enable Winner mode if ARG is
positive, and disable it otherwise.  If called from Lisp, enable
the mode if ARG is omitted or nil, and toggle it if ARG is `toggle'.

Winner mode is a global minor mode that records the changes in
the window configuration (i.e. how the frames are partitioned
into windows) so that the changes can be \"undone\" using the
command `winner-undo'.  By default this one is bound to the key
sequence `C-c <left>'.  If you change your mind (while undoing),
you can press `C-c <right>' (calling `winner-redo')."
  :global t
  (if winner-mode
      (progn
        (add-hook 'window-configuration-change-hook 'winner-change-fun)
        (add-hook 'post-command-hook 'winner-save-old-configurations)
        (add-hook 'minibuffer-setup-hook 'winner-save-unconditionally)
        (setq winner-modified-list (frame-list))
        (winner-save-old-configurations))
    (remove-hook 'window-configuration-change-hook 'winner-change-fun)
    (remove-hook 'post-command-hook 'winner-save-old-configurations)
    (remove-hook 'minibuffer-setup-hook 'winner-save-unconditionally)))

;; Inspired by undo (simple.el)

(defvar winner-undo-frame nil)

(defvar winner-pending-undo-ring nil
  "The ring currently used by `winner-undo'.")
(defvar winner-undo-counter nil)
(defvar winner-undone-data  nil) ; There confs have been passed.

(defun winner-undo ()
  "Switch back to an earlier window configuration saved by Winner mode.
In other words, \"undo\" changes in window configuration."
  (interactive)
  (cond
   ((not winner-mode) (error "Winner mode is turned off"))
   (t (unless (and (eq last-command 'winner-undo)
 		   (eq winner-undo-frame (selected-frame)))
	(winner-save-conditionally)     ; current configuration->stack
 	(setq winner-undo-frame (selected-frame))
 	(setq winner-point-alist (winner-make-point-alist))
 	(setq winner-pending-undo-ring (winner-ring (selected-frame)))
 	(setq winner-undo-counter 0)
 	(setq winner-undone-data (list (winner-win-data))))
      (cl-incf winner-undo-counter)	; starting at 1
      (when (and (winner-undo-this)
 		 (not (window-minibuffer-p)))
 	(message "Winner undo (%d / %d)"
 		 winner-undo-counter
 		 (1- (ring-length winner-pending-undo-ring)))))))




(defun winner-undo-this ()		; The heart of winner undo.
  (cl-loop
   (cond
    ((>= winner-undo-counter (ring-length winner-pending-undo-ring))
     (message "No further window configuration undo information")
     (cl-return nil))

    ((and				; If possible configuration
      (winner-set (ring-ref winner-pending-undo-ring
 			    winner-undo-counter))
                                        ; .. and new configuration
      (let ((data (winner-win-data)))
 	(and (not (member data winner-undone-data))
 	     (push data winner-undone-data))))
     (cl-return t))			; .. then everything is fine.
    (t ;; Otherwise, discharge it (and try the next one).
     (ring-remove winner-pending-undo-ring winner-undo-counter)))))


(defun winner-redo ()			; If you change your mind.
  "Restore a more recent window configuration saved by Winner mode."
  (interactive)
  (cond
   ((eq last-command 'winner-undo)
    (winner-set
     (if (zerop (minibuffer-depth))
         (ring-remove winner-pending-undo-ring 0)
       (ring-ref winner-pending-undo-ring 0)))
    (unless (eq (selected-window) (minibuffer-window))
      (message "Winner undid undo")))
   (t (user-error "Previous command was not a `winner-undo'"))))

(provide 'winner)
;;; winner.el ends here
