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+;;; 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