aboutsummaryrefslogtreecommitdiff
path: root/emacs/guix-history.el
diff options
context:
space:
mode:
Diffstat (limited to 'emacs/guix-history.el')
-rw-r--r--emacs/guix-history.el92
1 files changed, 92 insertions, 0 deletions
diff --git a/emacs/guix-history.el b/emacs/guix-history.el
new file mode 100644
index 0000000000..5d301a689e
--- /dev/null
+++ b/emacs/guix-history.el
@@ -0,0 +1,92 @@
+;;; guix-history.el --- History of buffer information
+
+;; Copyright © 2014 Alex Kost <alezost@gmail.com>
+
+;; This file is part of GNU Guix.
+
+;; GNU Guix 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 Guix 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 this program. If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; This file provides support for history of buffers similar to the
+;; history of a `help-mode' buffer.
+
+;;; Code:
+
+(require 'cl-macs)
+
+(defvar-local guix-history-stack-item nil
+ "Current item of the history.
+A list of the form (FUNCTION [ARGS ...]).
+The item is used by calling (apply FUNCTION ARGS).")
+(put 'guix-history-stack-item 'permanent-local t)
+
+(defvar-local guix-history-back-stack nil
+ "Stack (list) of visited items.
+Each element of the list has a form of `guix-history-stack-item'.")
+(put 'guix-history-back-stack 'permanent-local t)
+
+(defvar-local guix-history-forward-stack nil
+ "Stack (list) of items visited with `guix-history-back'.
+Each element of the list has a form of `guix-history-stack-item'.")
+(put 'guix-history-forward-stack 'permanent-local t)
+
+(defvar guix-history-size 0
+ "Maximum number of items saved in history.
+If 0, the history is disabled.")
+
+(defun guix-history-add (item)
+ "Add ITEM to history."
+ (and guix-history-stack-item
+ (push guix-history-stack-item guix-history-back-stack))
+ (setq guix-history-forward-stack nil
+ guix-history-stack-item item)
+ (when (>= (length guix-history-back-stack)
+ guix-history-size)
+ (setq guix-history-back-stack
+ (cl-loop for elt in guix-history-back-stack
+ for i from 1 to guix-history-size
+ collect elt))))
+
+(defun guix-history-replace (item)
+ "Replace current item in history with ITEM."
+ (setq guix-history-stack-item item))
+
+(defun guix-history-goto (item)
+ "Go to the ITEM of history.
+ITEM should have the form of `guix-history-stack-item'."
+ (or (listp item)
+ (error "Wrong value of history element"))
+ (setq guix-history-stack-item item)
+ (apply (car item) (cdr item)))
+
+(defun guix-history-back ()
+ "Go back to the previous element of history in the current buffer."
+ (interactive)
+ (or guix-history-back-stack
+ (user-error "No previous element in history"))
+ (push guix-history-stack-item guix-history-forward-stack)
+ (guix-history-goto (pop guix-history-back-stack)))
+
+(defun guix-history-forward ()
+ "Go forward to the next element of history in the current buffer."
+ (interactive)
+ (or guix-history-forward-stack
+ (user-error "No next element in history"))
+ (push guix-history-stack-item guix-history-back-stack)
+ (guix-history-goto (pop guix-history-forward-stack)))
+
+(provide 'guix-history)
+
+;;; guix-history.el ends here