Initial revision

1 files changed, 1397 insertions, 0 deletions

diff --git a/lisp/gnus/gnus-topic.el b/lisp/gnus/gnus-topic.el
new file mode 100644
index 00000000000..c87019105f3
--- /dev/null
+++ b/lisp/gnus/gnus-topic.el
@@ -0,0 +1,1397 @@
+;;; gnus-topic.el --- a folding minor mode for Gnus group buffers
+;; Copyright (C) 1995,96,97 Free Software Foundation, Inc.
+
+;; Author: Ilja Weis <kult@uni-paderborn.de>
+;;	Lars Magne Ingebrigtsen <larsi@ifi.uio.no>
+;; Keywords: news
+
+;; 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 2, 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; see the file COPYING.  If not, write to the
+;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+;; Boston, MA 02111-1307, USA.
+
+;;; Commentary:
+
+;;; Code:
+
+(require 'gnus)
+(require 'gnus-group)
+(require 'gnus-start)
+
+(defgroup gnus-topic nil
+  "Group topics."
+  :group 'gnus-group)
+
+(defvar gnus-topic-mode nil
+  "Minor mode for Gnus group buffers.")
+
+(defcustom gnus-topic-mode-hook nil
+  "Hook run in topic mode buffers."
+  :type 'hook
+  :group 'gnus-topic)
+
+(defcustom gnus-topic-line-format "%i[ %(%{%n%}%) -- %A ]%v\n"
+  "Format of topic lines.
+It works along the same lines as a normal formatting string,
+with some simple extensions.
+
+%i  Indentation based on topic level.
+%n  Topic name.
+%v  Nothing if the topic is visible, \"...\" otherwise.
+%g  Number of groups in the topic.
+%a  Number of unread articles in the groups in the topic.
+%A  Number of unread articles in the groups in the topic and its subtopics.
+"
+  :type 'string
+  :group 'gnus-topic)
+
+(defcustom gnus-topic-indent-level 2
+  "*How much each subtopic should be indented."
+  :type 'integer
+  :group 'gnus-topic)
+
+(defcustom gnus-topic-display-empty-topics t
+  "*If non-nil, display the topic lines even of topics that have no unread articles."
+  :type 'boolean
+  :group 'gnus-topic)
+
+;; Internal variables.
+
+(defvar gnus-topic-active-topology nil)
+(defvar gnus-topic-active-alist nil)
+
+(defvar gnus-topology-checked-p nil
+  "Whether the topology has been checked in this session.")
+
+(defvar gnus-topic-killed-topics nil)
+(defvar gnus-topic-inhibit-change-level nil)
+(defvar gnus-topic-tallied-groups nil)
+
+(defconst gnus-topic-line-format-alist
+  `((?n name ?s)
+    (?v visible ?s)
+    (?i indentation ?s)
+    (?g number-of-groups ?d)
+    (?a (gnus-topic-articles-in-topic entries) ?d)
+    (?A total-number-of-articles ?d)
+    (?l level ?d)))
+
+(defvar gnus-topic-line-format-spec nil)
+
+;;; Utility functions
+
+(defun gnus-group-topic-name ()
+  "The name of the topic on the current line."
+  (let ((topic (get-text-property (gnus-point-at-bol) 'gnus-topic)))
+    (and topic (symbol-name topic))))
+
+(defun gnus-group-topic-level ()
+  "The level of the topic on the current line."
+  (get-text-property (gnus-point-at-bol) 'gnus-topic-level))
+
+(defun gnus-group-topic-unread ()
+  "The number of unread articles in topic on the current line."
+  (get-text-property (gnus-point-at-bol) 'gnus-topic-unread))
+
+(defun gnus-topic-unread (topic)
+  "Return the number of unread articles in TOPIC."
+  (or (save-excursion
+	(and (gnus-topic-goto-topic topic)
+	     (gnus-group-topic-unread)))
+      0))
+
+(defun gnus-group-topic-p ()
+  "Return non-nil if the current line is a topic."
+  (gnus-group-topic-name))
+
+(defun gnus-topic-visible-p ()
+  "Return non-nil if the current topic is visible."
+  (get-text-property (gnus-point-at-bol) 'gnus-topic-visible))
+
+(defun gnus-topic-articles-in-topic (entries)
+  (let ((total 0)
+	number)
+    (while entries
+      (when (numberp (setq number (car (pop entries))))
+	(incf total number)))
+    total))
+
+(defun gnus-group-topic (group)
+  "Return the topic GROUP is a member of."
+  (let ((alist gnus-topic-alist)
+	out)
+    (while alist
+      (when (member group (cdar alist))
+	(setq out (caar alist)
+	      alist nil))
+      (setq alist (cdr alist)))
+    out))
+
+(defun gnus-group-parent-topic (group)
+  "Return the topic GROUP is member of by looking at the group buffer."
+  (save-excursion
+    (set-buffer gnus-group-buffer)
+    (if (gnus-group-goto-group group)
+	(gnus-current-topic)
+      (gnus-group-topic group))))
+
+(defun gnus-topic-goto-topic (topic)
+  "Go to TOPIC."
+  (when topic
+    (gnus-goto-char (text-property-any (point-min) (point-max)
+				       'gnus-topic (intern topic)))))
+
+(defun gnus-current-topic ()
+  "Return the name of the current topic."
+  (let ((result
+	 (or (get-text-property (point) 'gnus-topic)
+	     (save-excursion
+	       (and (gnus-goto-char (previous-single-property-change
+				     (point) 'gnus-topic))
+		    (get-text-property (max (1- (point)) (point-min))
+				       'gnus-topic))))))
+    (when result
+      (symbol-name result))))
+
+(defun gnus-current-topics ()
+  "Return a list of all current topics, lowest in hierarchy first."
+  (let ((topic (gnus-current-topic))
+	topics)
+    (while topic
+      (push topic topics)
+      (setq topic (gnus-topic-parent-topic topic)))
+    (nreverse topics)))
+
+(defun gnus-group-active-topic-p ()
+  "Say whether the current topic comes from the active topics."
+  (save-excursion
+    (beginning-of-line)
+    (get-text-property (point) 'gnus-active)))
+
+(defun gnus-topic-find-groups (topic &optional level all)
+  "Return entries for all visible groups in TOPIC."
+  (let ((groups (cdr (assoc topic gnus-topic-alist)))
+        info clevel unread group lowest params visible-groups entry active)
+    (setq lowest (or lowest 1))
+    (setq level (or level 7))
+    ;; We go through the newsrc to look for matches.
+    (while groups
+      (when (setq group (pop groups))
+	(setq entry (gnus-gethash group gnus-newsrc-hashtb)
+	      info (nth 2 entry)
+	      params (gnus-info-params info)
+	      active (gnus-active group)
+	      unread (or (car entry)
+			 (and (not (equal group "dummy.group"))
+			      active
+			      (- (1+ (cdr active)) (car active))))
+	      clevel (or (gnus-info-level info)
+			 (if (member group gnus-zombie-list) 8 9))))
+      (and
+       unread				; nil means that the group is dead.
+       (<= clevel level)
+       (>= clevel lowest)		; Is inside the level we want.
+       (or all
+	   (if (eq unread t)
+	       gnus-group-list-inactive-groups
+	     (> unread 0))
+	   (and gnus-list-groups-with-ticked-articles
+		(cdr (assq 'tick (gnus-info-marks info))))
+					; Has right readedness.
+	   ;; Check for permanent visibility.
+	   (and gnus-permanently-visible-groups
+		(string-match gnus-permanently-visible-groups group))
+	   (memq 'visible params)
+	   (cdr (assq 'visible params)))
+       ;; Add this group to the list of visible groups.
+       (push (or entry group) visible-groups)))
+    (nreverse visible-groups)))
+
+(defun gnus-topic-previous-topic (topic)
+  "Return the previous topic on the same level as TOPIC."
+  (let ((top (cddr (gnus-topic-find-topology
+		    (gnus-topic-parent-topic topic)))))
+    (unless (equal topic (caaar top))
+      (while (and top (not (equal (caaadr top) topic)))
+	(setq top (cdr top)))
+      (caaar top))))
+
+(defun gnus-topic-parent-topic (topic &optional topology)
+  "Return the parent of TOPIC."
+  (unless topology
+    (setq topology gnus-topic-topology))
+  (let ((parent (car (pop topology)))
+	result found)
+    (while (and topology
+		(not (setq found (equal (caaar topology) topic)))
+		(not (setq result (gnus-topic-parent-topic
+				   topic (car topology)))))
+      (setq topology (cdr topology)))
+    (or result (and found parent))))
+
+(defun gnus-topic-next-topic (topic &optional previous)
+  "Return the next sibling of TOPIC."
+  (let ((parentt (cddr (gnus-topic-find-topology
+			(gnus-topic-parent-topic topic))))
+	prev)
+    (while (and parentt
+		(not (equal (caaar parentt) topic)))
+      (setq prev (caaar parentt)
+	    parentt (cdr parentt)))
+    (if previous
+	prev
+      (caaadr parentt))))
+
+(defun gnus-topic-forward-topic (num)
+  "Go to the next topic on the same level as the current one."
+  (let* ((topic (gnus-current-topic))
+	 (way (if (< num 0) 'gnus-topic-previous-topic
+		'gnus-topic-next-topic))
+	 (num (abs num)))
+    (while (and (not (zerop num))
+		(setq topic (funcall way topic)))
+      (when (gnus-topic-goto-topic topic)
+	(decf num)))
+    (unless (zerop num)
+      (goto-char (point-max)))
+    num))
+
+(defun gnus-topic-find-topology (topic &optional topology level remove)
+  "Return the topology of TOPIC."
+  (unless topology
+    (setq topology gnus-topic-topology)
+    (setq level 0))
+  (let ((top topology)
+	result)
+    (if (equal (caar topology) topic)
+	(progn
+	  (when remove
+	    (delq topology remove))
+	  (cons level topology))
+      (setq topology (cdr topology))
+      (while (and topology
+		  (not (setq result (gnus-topic-find-topology
+				     topic (car topology) (1+ level)
+				     (and remove top)))))
+	(setq topology (cdr topology)))
+      result)))
+
+(defvar gnus-tmp-topics nil)
+(defun gnus-topic-list (&optional topology)
+  "Return a list of all topics in the topology."
+  (unless topology
+    (setq topology gnus-topic-topology
+	  gnus-tmp-topics nil))
+  (push (caar topology) gnus-tmp-topics)
+  (mapcar 'gnus-topic-list (cdr topology))
+  gnus-tmp-topics)
+
+;;; Topic parameter jazz
+
+(defun gnus-topic-parameters (topic)
+  "Return the parameters for TOPIC."
+  (let ((top (gnus-topic-find-topology topic)))
+    (when top
+      (nth 3 (cadr top)))))
+
+(defun gnus-topic-set-parameters (topic parameters)
+  "Set the topic parameters of TOPIC to PARAMETERS."
+  (let ((top (gnus-topic-find-topology topic)))
+    (unless top
+      (error "No such topic: %s" topic))
+    ;; We may have to extend if there is no parameters here
+    ;; to begin with.
+    (unless (nthcdr 2 (cadr top))
+      (nconc (cadr top) (list nil)))
+    (unless (nthcdr 3 (cadr top))
+      (nconc (cadr top) (list nil)))
+    (setcar (nthcdr 3 (cadr top)) parameters)
+    (gnus-dribble-enter
+     (format "(gnus-topic-set-parameters %S '%S)" topic parameters))))
+
+(defun gnus-group-topic-parameters (group)
+  "Compute the group parameters for GROUP taking into account inheritance from topics."
+  (let ((params-list (list (gnus-group-get-parameter group)))
+	topics params param out)
+    (save-excursion
+      (gnus-group-goto-group group)
+      (setq topics (gnus-current-topics))
+      (while topics
+	(push (gnus-topic-parameters (pop topics)) params-list))
+      ;; We probably have lots of nil elements here, so
+      ;; we remove them.  Probably faster than doing this "properly".
+      (setq params-list (delq nil params-list))
+      ;; Now we have all the parameters, so we go through them
+      ;; and do inheritance in the obvious way.
+      (while (setq params (pop params-list))
+	(while (setq param (pop params))
+	  (when (atom param)
+	    (setq param (cons param t)))
+	  ;; Override any old versions of this param.
+	  (setq out (delq (assq (car param) out) out))
+	  (push param out)))
+      ;; Return the resulting parameter list.
+      out)))
+
+;;; General utility functions
+
+(defun gnus-topic-enter-dribble ()
+  (gnus-dribble-enter
+   (format "(setq gnus-topic-topology '%S)" gnus-topic-topology)))
+
+;;; Generating group buffers
+
+(defun gnus-group-prepare-topics (level &optional all lowest regexp list-topic topic-level)
+  "List all newsgroups with unread articles of level LEVEL or lower, and
+use the `gnus-group-topics' to sort the groups.
+If ALL is non-nil, list groups that have no unread articles.
+If LOWEST is non-nil, list all newsgroups of level LOWEST or higher."
+  (set-buffer gnus-group-buffer)
+  (let ((buffer-read-only nil)
+        (lowest (or lowest 1)))
+
+    (setq gnus-topic-tallied-groups nil)
+
+    (when (or (not gnus-topic-alist)
+	      (not gnus-topology-checked-p))
+      (gnus-topic-check-topology))
+
+    (unless list-topic
+      (erase-buffer))
+
+    ;; List dead groups?
+    (when (and (>= level gnus-level-zombie) (<= lowest gnus-level-zombie))
+      (gnus-group-prepare-flat-list-dead
+       (setq gnus-zombie-list (sort gnus-zombie-list 'string<))
+       gnus-level-zombie ?Z
+       regexp))
+
+    (when (and (>= level gnus-level-killed) (<= lowest gnus-level-killed))
+      (gnus-group-prepare-flat-list-dead
+       (setq gnus-killed-list (sort gnus-killed-list 'string<))
+       gnus-level-killed ?K
+       regexp))
+
+    ;; Use topics.
+    (prog1
+	(when (< lowest gnus-level-zombie)
+	  (if list-topic
+	      (let ((top (gnus-topic-find-topology list-topic)))
+		(gnus-topic-prepare-topic (cdr top) (car top)
+					  (or topic-level level) all))
+	    (gnus-topic-prepare-topic gnus-topic-topology 0
+				      (or topic-level level) all)))
+
+      (gnus-group-set-mode-line)
+      (setq gnus-group-list-mode (cons level all))
+      (run-hooks 'gnus-group-prepare-hook))))
+
+(defun gnus-topic-prepare-topic (topicl level &optional list-level all silent)
+  "Insert TOPIC into the group buffer.
+If SILENT, don't insert anything.  Return the number of unread
+articles in the topic and its subtopics."
+  (let* ((type (pop topicl))
+	 (entries (gnus-topic-find-groups (car type) list-level all))
+	 (visiblep (and (eq (nth 1 type) 'visible) (not silent)))
+	 (gnus-group-indentation
+	  (make-string (* gnus-topic-indent-level level) ? ))
+	 (beg (progn (beginning-of-line) (point)))
+	 (topicl (reverse topicl))
+	 (all-entries entries)
+	 (point-max (point-max))
+	 (unread 0)
+	 (topic (car type))
+	 info entry end active tick)
+    ;; Insert any sub-topics.
+    (while topicl
+      (incf unread
+	    (gnus-topic-prepare-topic
+	     (pop topicl) (1+ level) list-level all
+	     (not visiblep))))
+    (setq end (point))
+    (goto-char beg)
+    ;; Insert all the groups that belong in this topic.
+    (while (setq entry (pop entries))
+      (when visiblep
+	(if (stringp entry)
+	    ;; Dead groups.
+	    (gnus-group-insert-group-line
+	     entry (if (member entry gnus-zombie-list) 8 9)
+	     nil (- (1+ (cdr (setq active (gnus-active entry))))
+		    (car active))
+	     nil)
+	  ;; Living groups.
+	  (when (setq info (nth 2 entry))
+	    (gnus-group-insert-group-line
+	     (gnus-info-group info)
+	     (gnus-info-level info) (gnus-info-marks info)
+	     (car entry) (gnus-info-method info)))))
+      (when (and (listp entry)
+		 (numberp (car entry))
+		 (not (member (gnus-info-group (setq info (nth 2 entry)))
+			      gnus-topic-tallied-groups)))
+	(push (gnus-info-group info) gnus-topic-tallied-groups)
+	(incf unread (car entry)))
+      (when (listp entry)
+	(setq tick t)))
+    (goto-char beg)
+    ;; Insert the topic line.
+    (when (and (not silent)
+	       (or gnus-topic-display-empty-topics ;We want empty topics
+		   (not (zerop unread))	;Non-empty
+		   tick			;Ticked articles
+		   (/= point-max (point-max)))) ;Unactivated groups
+      (gnus-extent-start-open (point))
+      (gnus-topic-insert-topic-line
+       (car type) visiblep
+       (not (eq (nth 2 type) 'hidden))
+       level all-entries unread))
+    (goto-char end)
+    unread))
+
+(defun gnus-topic-remove-topic (&optional insert total-remove hide in-level)
+  "Remove the current topic."
+  (let ((topic (gnus-group-topic-name))
+	(level (gnus-group-topic-level))
+	(beg (progn (beginning-of-line) (point)))
+	buffer-read-only)
+    (when topic
+      (while (and (zerop (forward-line 1))
+		  (> (or (gnus-group-topic-level) (1+ level)) level)))
+      (delete-region beg (point))
+      ;; Do the change in this rather odd manner because it has been
+      ;; reported that some topics share parts of some lists, for some
+      ;; reason.  I have been unable to determine why this is the
+      ;; case, but this hack seems to take care of things.
+      (let ((data (cadr (gnus-topic-find-topology topic))))
+	(setcdr data
+		(list (if insert 'visible 'invisible)
+		      (if hide 'hide nil)
+		      (cadddr data))))
+      (if total-remove
+	  (setq gnus-topic-alist
+		(delq (assoc topic gnus-topic-alist) gnus-topic-alist))
+	(gnus-topic-insert-topic topic in-level)))))
+
+(defun gnus-topic-insert-topic (topic &optional level)
+  "Insert TOPIC."
+  (gnus-group-prepare-topics
+   (car gnus-group-list-mode) (cdr gnus-group-list-mode)
+   nil nil topic level))
+
+(defun gnus-topic-fold (&optional insert)
+  "Remove/insert the current topic."
+  (let ((topic (gnus-group-topic-name)))
+    (when topic
+      (save-excursion
+	(if (not (gnus-group-active-topic-p))
+	    (gnus-topic-remove-topic
+	     (or insert (not (gnus-topic-visible-p))))
+	  (let ((gnus-topic-topology gnus-topic-active-topology)
+		(gnus-topic-alist gnus-topic-active-alist)
+		(gnus-group-list-mode (cons 5 t)))
+	    (gnus-topic-remove-topic
+	     (or insert (not (gnus-topic-visible-p))) nil nil 9)
+	    (gnus-topic-enter-dribble)))))))
+
+(defun gnus-topic-insert-topic-line (name visiblep shownp level entries
+					  &optional unread)
+  (let* ((visible (if visiblep "" "..."))
+	 (indentation (make-string (* gnus-topic-indent-level level) ? ))
+	 (total-number-of-articles unread)
+	 (number-of-groups (length entries))
+	 (active-topic (eq gnus-topic-alist gnus-topic-active-alist)))
+    (beginning-of-line)
+    ;; Insert the text.
+    (gnus-add-text-properties
+     (point)
+     (prog1 (1+ (point))
+       (eval gnus-topic-line-format-spec)
+       (gnus-topic-remove-excess-properties)1)
+     (list 'gnus-topic (intern name)
+	   'gnus-topic-level level
+	   'gnus-topic-unread unread
+	   'gnus-active active-topic
+	   'gnus-topic-visible visiblep))))
+
+(defun gnus-topic-update-topics-containing-group (group)
+  "Update all topics that have GROUP as a member."
+  (when (and (eq major-mode 'gnus-group-mode)
+	     gnus-topic-mode)
+    (save-excursion
+      (let ((alist gnus-topic-alist))
+	;; This is probably not entirely correct.  If a topic
+	;; isn't shown, then it's not updated.  But the updating
+	;; should be performed in any case, since the topic's
+	;; parent should be updated.  Pfft.
+	(while alist
+	  (when (and (member group (cdar alist))
+		     (gnus-topic-goto-topic (caar alist)))
+	    (gnus-topic-update-topic-line (caar alist)))
+	  (pop alist))))))
+
+(defun gnus-topic-update-topic ()
+  "Update all parent topics to the current group."
+  (when (and (eq major-mode 'gnus-group-mode)
+	     gnus-topic-mode)
+    (let ((group (gnus-group-group-name))
+	  (buffer-read-only nil))
+      (when (and group
+		 (gnus-get-info group)
+		 (gnus-topic-goto-topic (gnus-current-topic)))
+	(gnus-topic-update-topic-line (gnus-group-topic-name))
+	(gnus-group-goto-group group)
+	(gnus-group-position-point)))))
+
+(defun gnus-topic-goto-missing-group (group)
+  "Place point where GROUP is supposed to be inserted."
+  (let* ((topic (gnus-group-topic group))
+	 (groups (cdr (assoc topic gnus-topic-alist)))
+	 (g (cdr (member group groups)))
+	 (unfound t))
+    ;; Try to jump to a visible group.
+    (while (and g (not (gnus-group-goto-group (car g) t)))
+      (pop g))
+    ;; It wasn't visible, so we try to see where to insert it.
+    (when (not g)
+      (setq g (cdr (member group (reverse groups))))
+      (while (and g unfound)
+	(when (gnus-group-goto-group (pop g) t)
+	  (forward-line 1)
+	  (setq unfound nil)))
+      (when (and unfound
+		 topic
+		 (not (gnus-topic-goto-missing-topic topic)))
+	(gnus-topic-insert-topic-line
+	 topic t t (car (gnus-topic-find-topology topic)) nil 0)))))
+
+(defun gnus-topic-goto-missing-topic (topic)
+  (if (gnus-topic-goto-topic topic)
+      (forward-line 1)
+    ;; Topic not displayed.
+    (let* ((top (gnus-topic-find-topology
+		 (gnus-topic-parent-topic topic)))
+	   (tp (reverse (cddr top))))
+      (while (not (equal (caaar tp) topic))
+	(setq tp (cdr tp)))
+      (pop tp)
+      (while (and tp
+		  (not (gnus-topic-goto-topic (caaar tp))))
+	(pop tp))
+      (if tp
+	  (gnus-topic-forward-topic 1)
+	(gnus-topic-goto-missing-topic (caadr top))))
+    nil))
+
+(defun gnus-topic-update-topic-line (topic-name &optional reads)
+  (let* ((top (gnus-topic-find-topology topic-name))
+	 (type (cadr top))
+	 (children (cddr top))
+	 (entries (gnus-topic-find-groups
+		   (car type) (car gnus-group-list-mode)
+		   (cdr gnus-group-list-mode)))
+	 (parent (gnus-topic-parent-topic topic-name))
+	 (all-entries entries)
+	 (unread 0)
+	 old-unread entry)
+    (when (gnus-topic-goto-topic (car type))
+      ;; Tally all the groups that belong in this topic.
+      (if reads
+	  (setq unread (- (gnus-group-topic-unread) reads))
+	(while children
+	  (incf unread (gnus-topic-unread (caar (pop children)))))
+	(while (setq entry (pop entries))
+	  (when (numberp (car entry))
+	    (incf unread (car entry)))))
+      (setq old-unread (gnus-group-topic-unread))
+      ;; Insert the topic line.
+      (gnus-topic-insert-topic-line
+       (car type) (gnus-topic-visible-p)
+       (not (eq (nth 2 type) 'hidden))
+       (gnus-group-topic-level) all-entries unread)
+      (gnus-delete-line))
+    (when parent
+      (forward-line -1)
+      (gnus-topic-update-topic-line
+       parent (- old-unread (gnus-group-topic-unread))))
+    unread))
+
+(defun gnus-topic-group-indentation ()
+  (make-string
+   (* gnus-topic-indent-level
+      (or (save-excursion
+	    (forward-line -1)
+	    (gnus-topic-goto-topic (gnus-current-topic))
+	    (gnus-group-topic-level))
+	  0))
+   ? ))
+
+;;; Initialization
+
+(gnus-add-shutdown 'gnus-topic-close 'gnus)
+
+(defun gnus-topic-close ()
+  (setq gnus-topic-active-topology nil
+	gnus-topic-active-alist nil
+	gnus-topic-killed-topics nil
+	gnus-topic-tallied-groups nil
+	gnus-topology-checked-p nil))
+
+(defun gnus-topic-check-topology ()
+  ;; The first time we set the topology to whatever we have
+  ;; gotten here, which can be rather random.
+  (unless gnus-topic-alist
+    (gnus-topic-init-alist))
+
+  (setq gnus-topology-checked-p t)
+  ;; Go through the topic alist and make sure that all topics
+  ;; are in the topic topology.
+  (let ((topics (gnus-topic-list))
+	(alist gnus-topic-alist)
+	changed)
+    (while alist
+      (unless (member (caar alist) topics)
+	(nconc gnus-topic-topology
+	       (list (list (list (caar alist) 'visible))))
+	(setq changed t))
+      (setq alist (cdr alist)))
+    (when changed
+      (gnus-topic-enter-dribble))
+    ;; Conversely, go through the topology and make sure that all
+    ;; topologies have alists.
+    (while topics
+      (unless (assoc (car topics) gnus-topic-alist)
+	(push (list (car topics)) gnus-topic-alist))
+      (pop topics)))
+  ;; Go through all living groups and make sure that
+  ;; they belong to some topic.
+  (let* ((tgroups (apply 'append (mapcar (lambda (entry) (cdr entry))
+					 gnus-topic-alist)))
+	 (entry (assoc (caar gnus-topic-topology) gnus-topic-alist))
+	 (newsrc (cdr gnus-newsrc-alist))
+	 group)
+    (while newsrc
+      (unless (member (setq group (gnus-info-group (pop newsrc))) tgroups)
+	(setcdr entry (cons group (cdr entry))))))
+  ;; Go through all topics and make sure they contain only living groups.
+  (let ((alist gnus-topic-alist)
+	topic)
+    (while (setq topic (pop alist))
+      (while (cdr topic)
+	(if (gnus-gethash (cadr topic) gnus-newsrc-hashtb)
+	    (setq topic (cdr topic))
+	  (setcdr topic (cddr topic)))))))
+
+(defun gnus-topic-init-alist ()
+  "Initialize the topic structures."
+  (setq gnus-topic-topology
+	(cons (list "Gnus" 'visible)
+	      (mapcar (lambda (topic)
+			(list (list (car topic) 'visible)))
+		      '(("misc")))))
+  (setq gnus-topic-alist
+	(list (cons "misc"
+		    (mapcar (lambda (info) (gnus-info-group info))
+			    (cdr gnus-newsrc-alist)))
+	      (list "Gnus")))
+  (gnus-topic-enter-dribble))
+
+;;; Maintenance
+
+(defun gnus-topic-clean-alist ()
+  "Remove bogus groups from the topic alist."
+  (let ((topic-alist gnus-topic-alist)
+	result topic)
+    (unless gnus-killed-hashtb
+      (gnus-make-hashtable-from-killed))
+    (while (setq topic (pop topic-alist))
+      (let ((topic-name (pop topic))
+	    group filtered-topic)
+	(while (setq group (pop topic))
+	  (when (and (or (gnus-gethash group gnus-active-hashtb)
+			 (gnus-info-method (gnus-get-info group)))
+		     (not (gnus-gethash group gnus-killed-hashtb)))
+	    (push group filtered-topic)))
+	(push (cons topic-name (nreverse filtered-topic)) result)))
+    (setq gnus-topic-alist (nreverse result))))
+
+(defun gnus-topic-change-level (group level oldlevel)
+  "Run when changing levels to enter/remove groups from topics."
+  (save-excursion
+    (set-buffer gnus-group-buffer)
+    (when (and gnus-topic-mode
+	       gnus-topic-alist
+	       (not gnus-topic-inhibit-change-level))
+      ;; Remove the group from the topics.
+      (when (and (< oldlevel gnus-level-zombie)
+		 (>= level gnus-level-zombie))
+	(let (alist)
+	  (forward-line -1)
+	  (when (setq alist (assoc (gnus-current-topic) gnus-topic-alist))
+	    (setcdr alist (gnus-delete-first group (cdr alist))))))
+      ;; If the group is subscribed we enter it into the topics.
+      (when (and (< level gnus-level-zombie)
+		 (>= oldlevel gnus-level-zombie))
+	(let* ((prev (gnus-group-group-name))
+	       (gnus-topic-inhibit-change-level t)
+	       (gnus-group-indentation
+		(make-string
+		 (* gnus-topic-indent-level
+		    (or (save-excursion
+			  (gnus-topic-goto-topic (gnus-current-topic))
+			  (gnus-group-topic-level))
+			0))
+		 ? ))
+	       (yanked (list group))
+	       alist talist end)
+	  ;; Then we enter the yanked groups into the topics they belong
+	  ;; to.
+	  (when (setq alist (assoc (save-excursion
+				     (forward-line -1)
+				     (or
+				      (gnus-current-topic)
+				      (caar gnus-topic-topology)))
+				   gnus-topic-alist))
+	    (setq talist alist)
+	    (when (stringp yanked)
+	      (setq yanked (list yanked)))
+	    (if (not prev)
+		(nconc alist yanked)
+	      (if (not (cdr alist))
+		  (setcdr alist (nconc yanked (cdr alist)))
+		(while (and (not end) (cdr alist))
+		  (when (equal (cadr alist) prev)
+		    (setcdr alist (nconc yanked (cdr alist)))
+		    (setq end t))
+		  (setq alist (cdr alist)))
+		(unless end
+		  (nconc talist yanked))))))
+	(gnus-topic-update-topic)))))
+
+(defun gnus-topic-goto-next-group (group props)
+  "Go to group or the next group after group."
+  (if (not group)
+      (if (not (memq 'gnus-topic props))
+	  (goto-char (point-max))
+	(gnus-topic-goto-topic (symbol-name (cadr (memq 'gnus-topic props)))))
+    (if (gnus-group-goto-group group)
+	t
+      ;; The group is no longer visible.
+      (let* ((list (assoc (gnus-group-topic group) gnus-topic-alist))
+	     (after (cdr (member group (cdr list)))))
+	;; First try to put point on a group after the current one.
+	(while (and after
+		    (not (gnus-group-goto-group (car after))))
+	  (setq after (cdr after)))
+	;; Then try to put point on a group before point.
+	(unless after
+	  (setq after (cdr (member group (reverse (cdr list)))))
+	  (while (and after
+		      (not (gnus-group-goto-group (car after))))
+	    (setq after (cdr after))))
+	;; Finally, just put point on the topic.
+	(if (not (car list))
+	    (goto-char (point-min))
+	  (unless after
+	    (gnus-topic-goto-topic (car list))
+	    (setq after nil)))
+	t))))
+
+;;; Topic-active functions
+
+(defun gnus-topic-grok-active (&optional force)
+  "Parse all active groups and create topic structures for them."
+  ;; First we make sure that we have really read the active file.
+  (when (or force
+	    (not gnus-topic-active-alist))
+    (let (groups)
+      ;; Get a list of all groups available.
+      (mapatoms (lambda (g) (when (symbol-value g)
+			      (push (symbol-name g) groups)))
+		gnus-active-hashtb)
+      (setq groups (sort groups 'string<))
+      ;; Init the variables.
+      (setq gnus-topic-active-topology (list (list "" 'visible)))
+      (setq gnus-topic-active-alist nil)
+      ;; Descend the top-level hierarchy.
+      (gnus-topic-grok-active-1 gnus-topic-active-topology groups)
+      ;; Set the top-level topic names to something nice.
+      (setcar (car gnus-topic-active-topology) "Gnus active")
+      (setcar (car gnus-topic-active-alist) "Gnus active"))))
+
+(defun gnus-topic-grok-active-1 (topology groups)
+  (let* ((name (caar topology))
+	 (prefix (concat "^" (regexp-quote name)))
+	 tgroups ntopology group)
+    (while (and groups
+		(string-match prefix (setq group (car groups))))
+      (if (not (string-match "\\." group (match-end 0)))
+	  ;; There are no further hierarchies here, so we just
+	  ;; enter this group into the list belonging to this
+	  ;; topic.
+	  (push (pop groups) tgroups)
+	;; New sub-hierarchy, so we add it to the topology.
+	(nconc topology (list (setq ntopology
+				    (list (list (substring
+						 group 0 (match-end 0))
+						'invisible)))))
+	;; Descend the hierarchy.
+	(setq groups (gnus-topic-grok-active-1 ntopology groups))))
+    ;; We remove the trailing "." from the topic name.
+    (setq name
+	  (if (string-match "\\.$" name)
+	      (substring name 0 (match-beginning 0))
+	    name))
+    ;; Add this topic and its groups to the topic alist.
+    (push (cons name (nreverse tgroups)) gnus-topic-active-alist)
+    (setcar (car topology) name)
+    ;; We return the rest of the groups that didn't belong
+    ;; to this topic.
+    groups))
+
+;;; Topic mode, commands and keymap.
+
+(defvar gnus-topic-mode-map nil)
+(defvar gnus-group-topic-map nil)
+
+(unless gnus-topic-mode-map
+  (setq gnus-topic-mode-map (make-sparse-keymap))
+
+  ;; Override certain group mode keys.
+  (gnus-define-keys gnus-topic-mode-map
+    "=" gnus-topic-select-group
+    "\r" gnus-topic-select-group
+    " " gnus-topic-read-group
+    "\C-k" gnus-topic-kill-group
+    "\C-y" gnus-topic-yank-group
+    "\M-g" gnus-topic-get-new-news-this-topic
+    "AT" gnus-topic-list-active
+    "Gp" gnus-topic-edit-parameters
+    "#" gnus-topic-mark-topic
+    "\M-#" gnus-topic-unmark-topic
+    gnus-mouse-2 gnus-mouse-pick-topic)
+
+  ;; Define a new submap.
+  (gnus-define-keys (gnus-group-topic-map "T" gnus-group-mode-map)
+    "#" gnus-topic-mark-topic
+    "\M-#" gnus-topic-unmark-topic
+    "n" gnus-topic-create-topic
+    "m" gnus-topic-move-group
+    "D" gnus-topic-remove-group
+    "c" gnus-topic-copy-group
+    "h" gnus-topic-hide-topic
+    "s" gnus-topic-show-topic
+    "M" gnus-topic-move-matching
+    "C" gnus-topic-copy-matching
+    "\C-i" gnus-topic-indent
+    [tab] gnus-topic-indent
+    "r" gnus-topic-rename
+    "\177" gnus-topic-delete)
+
+  (gnus-define-keys (gnus-topic-sort-map "S" gnus-group-topic-map)
+    "s" gnus-topic-sort-groups
+    "a" gnus-topic-sort-groups-by-alphabet
+    "u" gnus-topic-sort-groups-by-unread
+    "l" gnus-topic-sort-groups-by-level
+    "v" gnus-topic-sort-groups-by-score
+    "r" gnus-topic-sort-groups-by-rank
+    "m" gnus-topic-sort-groups-by-method))
+
+(defun gnus-topic-make-menu-bar ()
+  (unless (boundp 'gnus-topic-menu)
+    (easy-menu-define
+     gnus-topic-menu gnus-topic-mode-map ""
+     '("Topics"
+       ["Toggle topics" gnus-topic-mode t]
+       ("Groups"
+	["Copy" gnus-topic-copy-group t]
+	["Move" gnus-topic-move-group t]
+	["Remove" gnus-topic-remove-group t]
+	["Copy matching" gnus-topic-copy-matching t]
+	["Move matching" gnus-topic-move-matching t])
+       ("Topics"
+	["Show" gnus-topic-show-topic t]
+	["Hide" gnus-topic-hide-topic t]
+	["Delete" gnus-topic-delete t]
+	["Rename" gnus-topic-rename t]
+	["Create" gnus-topic-create-topic t]
+	["Mark" gnus-topic-mark-topic t]
+	["Indent" gnus-topic-indent t])
+       ["List active" gnus-topic-list-active t]))))
+
+(defun gnus-topic-mode (&optional arg redisplay)
+  "Minor mode for topicsifying Gnus group buffers."
+  (interactive (list current-prefix-arg t))
+  (when (eq major-mode 'gnus-group-mode)
+    (make-local-variable 'gnus-topic-mode)
+    (setq gnus-topic-mode
+	  (if (null arg) (not gnus-topic-mode)
+	    (> (prefix-numeric-value arg) 0)))
+    ;; Infest Gnus with topics.
+    (when gnus-topic-mode
+      (when (gnus-visual-p 'topic-menu 'menu)
+	(gnus-topic-make-menu-bar))
+      (setq gnus-topic-line-format-spec
+	    (gnus-parse-format gnus-topic-line-format
+			       gnus-topic-line-format-alist t))
+      (unless (assq 'gnus-topic-mode minor-mode-alist)
+	(push '(gnus-topic-mode " Topic") minor-mode-alist))
+      (unless (assq 'gnus-topic-mode minor-mode-map-alist)
+	(push (cons 'gnus-topic-mode gnus-topic-mode-map)
+	      minor-mode-map-alist))
+      (add-hook 'gnus-summary-exit-hook 'gnus-topic-update-topic)
+      (add-hook 'gnus-group-catchup-group-hook 'gnus-topic-update-topic)
+      (set (make-local-variable 'gnus-group-prepare-function)
+	   'gnus-group-prepare-topics)
+      (set (make-local-variable 'gnus-group-get-parameter-function)
+	   'gnus-group-topic-parameters)
+      (set (make-local-variable 'gnus-group-goto-next-group-function)
+	   'gnus-topic-goto-next-group)
+      (set (make-local-variable 'gnus-group-indentation-function)
+	   'gnus-topic-group-indentation)
+      (set (make-local-variable 'gnus-group-update-group-function)
+	   'gnus-topic-update-topics-containing-group)
+      (set (make-local-variable 'gnus-group-sort-alist-function)
+	   'gnus-group-sort-topic)
+      (setq gnus-group-change-level-function 'gnus-topic-change-level)
+      (setq gnus-goto-missing-group-function 'gnus-topic-goto-missing-group)
+      (make-local-hook 'gnus-check-bogus-groups-hook)
+      (add-hook 'gnus-check-bogus-groups-hook 'gnus-topic-clean-alist)
+      (setq gnus-topology-checked-p nil)
+      ;; We check the topology.
+      (when gnus-newsrc-alist
+	(gnus-topic-check-topology))
+      (run-hooks 'gnus-topic-mode-hook))
+    ;; Remove topic infestation.
+    (unless gnus-topic-mode
+      (remove-hook 'gnus-summary-exit-hook 'gnus-topic-update-topic)
+      (remove-hook 'gnus-group-change-level-function
+		   'gnus-topic-change-level)
+      (remove-hook 'gnus-check-bogus-groups-hook 'gnus-topic-clean-alist)
+      (setq gnus-group-prepare-function 'gnus-group-prepare-flat)
+      (setq gnus-group-sort-alist-function 'gnus-group-sort-flat))
+    (when redisplay
+      (gnus-group-list-groups))))
+
+(defun gnus-topic-select-group (&optional all)
+  "Select this newsgroup.
+No article is selected automatically.
+If ALL is non-nil, already read articles become readable.
+If ALL is a number, fetch this number of articles.
+
+If performed over a topic line, toggle folding the topic."
+  (interactive "P")
+  (if (gnus-group-topic-p)
+      (let ((gnus-group-list-mode
+	     (if all (cons (if (numberp all) all 7) t) gnus-group-list-mode)))
+	(gnus-topic-fold all))
+    (gnus-group-select-group all)))
+
+(defun gnus-mouse-pick-topic (e)
+  "Select the group or topic under the mouse pointer."
+  (interactive "e")
+  (mouse-set-point e)
+  (gnus-topic-read-group nil))
+
+(defun gnus-topic-read-group (&optional all no-article group)
+  "Read news in this newsgroup.
+If the prefix argument ALL is non-nil, already read articles become
+readable.  IF ALL is a number, fetch this number of articles.  If the
+optional argument NO-ARTICLE is non-nil, no article will be
+auto-selected upon group entry.  If GROUP is non-nil, fetch that
+group.
+
+If performed over a topic line, toggle folding the topic."
+  (interactive "P")
+  (if (gnus-group-topic-p)
+      (let ((gnus-group-list-mode
+	     (if all (cons (if (numberp all) all 7) t) gnus-group-list-mode)))
+	(gnus-topic-fold all))
+    (gnus-group-read-group all no-article group)))
+
+(defun gnus-topic-create-topic (topic parent &optional previous full-topic)
+  (interactive
+   (list
+    (read-string "New topic: ")
+    (gnus-current-topic)))
+  ;; Check whether this topic already exists.
+  (when (gnus-topic-find-topology topic)
+    (error "Topic already exists"))
+  (unless parent
+    (setq parent (caar gnus-topic-topology)))
+  (let ((top (cdr (gnus-topic-find-topology parent)))
+	(full-topic (or full-topic `((,topic visible)))))
+    (unless top
+      (error "No such parent topic: %s" parent))
+    (if previous
+	(progn
+	  (while (and (cdr top)
+		      (not (equal (caaadr top) previous)))
+	    (setq top (cdr top)))
+	  (setcdr top (cons full-topic (cdr top))))
+      (nconc top (list full-topic)))
+    (unless (assoc topic gnus-topic-alist)
+      (push (list topic) gnus-topic-alist)))
+  (gnus-topic-enter-dribble)
+  (gnus-group-list-groups)
+  (gnus-topic-goto-topic topic))
+
+(defun gnus-topic-move-group (n topic &optional copyp)
+  "Move the next N groups to TOPIC.
+If COPYP, copy the groups instead."
+  (interactive
+   (list current-prefix-arg
+	 (completing-read "Move to topic: " gnus-topic-alist nil t)))
+  (let ((groups (gnus-group-process-prefix n))
+	(topicl (assoc topic gnus-topic-alist))
+	(start-group (progn (forward-line 1) (gnus-group-group-name)))
+	(start-topic (gnus-group-topic-name))
+	entry)
+    (mapcar
+     (lambda (g)
+       (gnus-group-remove-mark g)
+       (when (and
+	      (setq entry (assoc (gnus-current-topic) gnus-topic-alist))
+	      (not copyp))
+	 (setcdr entry (gnus-delete-first g (cdr entry))))
+       (nconc topicl (list g)))
+     groups)
+    (gnus-topic-enter-dribble)
+    (if start-group
+	(gnus-group-goto-group start-group)
+      (gnus-topic-goto-topic start-topic))
+    (gnus-group-list-groups)))
+
+(defun gnus-topic-remove-group (&optional arg)
+  "Remove the current group from the topic."
+  (interactive "P")
+  (gnus-group-iterate arg
+    (lambda (group)
+      (let ((topicl (assoc (gnus-current-topic) gnus-topic-alist))
+	    (buffer-read-only nil))
+	(when (and topicl group)
+	  (gnus-delete-line)
+	  (gnus-delete-first group topicl))
+	(gnus-topic-update-topic)
+	(gnus-group-position-point)))))
+
+(defun gnus-topic-copy-group (n topic)
+  "Copy the current group to a topic."
+  (interactive
+   (list current-prefix-arg
+	 (completing-read "Copy to topic: " gnus-topic-alist nil t)))
+  (gnus-topic-move-group n topic t))
+
+(defun gnus-topic-kill-group (&optional n discard)
+  "Kill the next N groups."
+  (interactive "P")
+  (if (gnus-group-topic-p)
+      (let ((topic (gnus-group-topic-name)))
+	(push (cons
+	       (gnus-topic-find-topology topic)
+	       (assoc topic gnus-topic-alist))
+	      gnus-topic-killed-topics)
+	(gnus-topic-remove-topic nil t)
+	(gnus-topic-find-topology topic nil nil gnus-topic-topology)
+	(gnus-topic-enter-dribble))
+    (gnus-group-kill-group n discard)
+    (gnus-topic-update-topic)))
+
+(defun gnus-topic-yank-group (&optional arg)
+  "Yank the last topic."
+  (interactive "p")
+  (if gnus-topic-killed-topics
+      (let* ((previous
+	      (or (gnus-group-topic-name)
+		  (gnus-topic-next-topic (gnus-current-topic))))
+	     (data (pop gnus-topic-killed-topics))
+	     (alist (cdr data))
+	     (item (cdar data)))
+	(push alist gnus-topic-alist)
+	(gnus-topic-create-topic
+	 (caar item) (gnus-topic-parent-topic previous) previous
+	 item)
+	(gnus-topic-enter-dribble)
+	(gnus-topic-goto-topic (caar item)))
+    (let* ((prev (gnus-group-group-name))
+	   (gnus-topic-inhibit-change-level t)
+	   (gnus-group-indentation
+	    (make-string
+	     (* gnus-topic-indent-level
+		(or (save-excursion
+		      (gnus-topic-goto-topic (gnus-current-topic))
+		      (gnus-group-topic-level))
+		    0))
+	     ? ))
+	   yanked alist)
+      ;; We first yank the groups the normal way...
+      (setq yanked (gnus-group-yank-group arg))
+      ;; Then we enter the yanked groups into the topics they belong
+      ;; to.
+      (setq alist (assoc (save-excursion
+			   (forward-line -1)
+			   (gnus-current-topic))
+			 gnus-topic-alist))
+      (when (stringp yanked)
+	(setq yanked (list yanked)))
+      (if (not prev)
+	  (nconc alist yanked)
+	(if (not (cdr alist))
+	    (setcdr alist (nconc yanked (cdr alist)))
+	  (while (cdr alist)
+	    (when (equal (cadr alist) prev)
+	      (setcdr alist (nconc yanked (cdr alist)))
+	      (setq alist nil))
+	    (setq alist (cdr alist))))))
+    (gnus-topic-update-topic)))
+
+(defun gnus-topic-hide-topic ()
+  "Hide the current topic."
+  (interactive)
+  (when (gnus-current-topic)
+    (gnus-topic-goto-topic (gnus-current-topic))
+    (gnus-topic-remove-topic nil nil 'hidden)))
+
+(defun gnus-topic-show-topic ()
+  "Show the hidden topic."
+  (interactive)
+  (when (gnus-group-topic-p)
+    (gnus-topic-remove-topic t nil 'shown)))
+
+(defun gnus-topic-mark-topic (topic &optional unmark)
+  "Mark all groups in the topic with the process mark."
+  (interactive (list (gnus-group-topic-name)))
+  (if (not topic)
+      (call-interactively 'gnus-group-mark-group)
+    (save-excursion
+      (let ((groups (gnus-topic-find-groups topic 9 t)))
+	(while groups
+	  (funcall (if unmark 'gnus-group-remove-mark 'gnus-group-set-mark)
+		   (gnus-info-group (nth 2 (pop groups)))))))))
+
+(defun gnus-topic-unmark-topic (topic &optional unmark)
+  "Remove the process mark from all groups in the topic."
+  (interactive (list (gnus-group-topic-name)))
+  (if (not topic)
+      (call-interactively 'gnus-group-unmark-group)
+    (gnus-topic-mark-topic topic t)))
+
+(defun gnus-topic-get-new-news-this-topic (&optional n)
+  "Check for new news in the current topic."
+  (interactive "P")
+  (if (not (gnus-group-topic-p))
+      (gnus-group-get-new-news-this-group n)
+    (gnus-topic-mark-topic (gnus-group-topic-name))
+    (gnus-group-get-new-news-this-group)))
+
+(defun gnus-topic-move-matching (regexp topic &optional copyp)
+  "Move all groups that match REGEXP to some topic."
+  (interactive
+   (let (topic)
+     (nreverse
+      (list
+       (setq topic (completing-read "Move to topic: " gnus-topic-alist nil t))
+       (read-string (format "Move to %s (regexp): " topic))))))
+  (gnus-group-mark-regexp regexp)
+  (gnus-topic-move-group nil topic copyp))
+
+(defun gnus-topic-copy-matching (regexp topic &optional copyp)
+  "Copy all groups that match REGEXP to some topic."
+  (interactive
+   (let (topic)
+     (nreverse
+      (list
+       (setq topic (completing-read "Copy to topic: " gnus-topic-alist nil t))
+       (read-string (format "Copy to %s (regexp): " topic))))))
+  (gnus-topic-move-matching regexp topic t))
+
+(defun gnus-topic-delete (topic)
+  "Delete a topic."
+  (interactive (list (gnus-group-topic-name)))
+  (unless topic
+    (error "No topic to be deleted"))
+  (let ((entry (assoc topic gnus-topic-alist))
+	(buffer-read-only nil))
+    (when (cdr entry)
+      (error "Topic not empty"))
+    ;; Delete if visible.
+    (when (gnus-topic-goto-topic topic)
+      (gnus-delete-line))
+    ;; Remove from alist.
+    (setq gnus-topic-alist (delq entry gnus-topic-alist))
+    ;; Remove from topology.
+    (gnus-topic-find-topology topic nil nil 'delete)))
+
+(defun gnus-topic-rename (old-name new-name)
+  "Rename a topic."
+  (interactive
+   (let ((topic (gnus-current-topic)))
+     (list topic
+	   (read-string (format "Rename %s to: " topic)))))
+  (let ((top (gnus-topic-find-topology old-name))
+	(entry (assoc old-name gnus-topic-alist)))
+    (when top
+      (setcar (cadr top) new-name))
+    (when entry
+      (setcar entry new-name))
+    (forward-line -1)
+    (gnus-dribble-touch)
+    (gnus-group-list-groups)))
+
+(defun gnus-topic-indent (&optional unindent)
+  "Indent a topic -- make it a sub-topic of the previous topic.
+If UNINDENT, remove an indentation."
+  (interactive "P")
+  (if unindent
+      (gnus-topic-unindent)
+    (let* ((topic (gnus-current-topic))
+	   (parent (gnus-topic-previous-topic topic))
+	   (buffer-read-only nil))
+      (unless parent
+	(error "Nothing to indent %s into" topic))
+      (when topic
+	(gnus-topic-goto-topic topic)
+	(gnus-topic-kill-group)
+	(push (cdar gnus-topic-killed-topics) gnus-topic-alist)
+	(gnus-topic-create-topic
+	 topic parent nil (cdaar gnus-topic-killed-topics))
+	(pop gnus-topic-killed-topics)
+	(or (gnus-topic-goto-topic topic)
+	    (gnus-topic-goto-topic parent))))))
+
+(defun gnus-topic-unindent ()
+  "Unindent a topic."
+  (interactive)
+  (let* ((topic (gnus-current-topic))
+	 (parent (gnus-topic-parent-topic topic))
+	 (grandparent (gnus-topic-parent-topic parent)))
+    (unless grandparent
+      (error "Nothing to indent %s into" topic))
+    (when topic
+      (gnus-topic-goto-topic topic)
+      (gnus-topic-kill-group)
+      (push (cdar gnus-topic-killed-topics) gnus-topic-alist)
+      (gnus-topic-create-topic
+       topic grandparent (gnus-topic-next-topic parent)
+       (cdaar gnus-topic-killed-topics))
+      (pop gnus-topic-killed-topics)
+      (gnus-topic-goto-topic topic))))
+
+(defun gnus-topic-list-active (&optional force)
+  "List all groups that Gnus knows about in a topicsified fashion.
+If FORCE, always re-read the active file."
+  (interactive "P")
+  (when force
+    (gnus-get-killed-groups))
+  (gnus-topic-grok-active force)
+  (let ((gnus-topic-topology gnus-topic-active-topology)
+	(gnus-topic-alist gnus-topic-active-alist)
+	gnus-killed-list gnus-zombie-list)
+    (gnus-group-list-groups 9 nil 1)))
+
+;;; Topic sorting functions
+
+(defun gnus-topic-edit-parameters (group)
+  "Edit the group parameters of GROUP.
+If performed on a topic, edit the topic parameters instead."
+  (interactive (list (gnus-group-group-name)))
+  (if group
+      (gnus-group-edit-group-parameters group)
+    (if (not (gnus-group-topic-p))
+	(error "Nothing to edit on the current line.")
+      (let ((topic (gnus-group-topic-name)))
+	(gnus-edit-form
+	 (gnus-topic-parameters topic)
+	 (format "Editing the topic parameters for `%s'."
+		 (or group topic))
+	 `(lambda (form)
+	    (gnus-topic-set-parameters ,topic form)))))))
+
+(defun gnus-group-sort-topic (func reverse)
+  "Sort groups in the topics according to FUNC and REVERSE."
+  (let ((alist gnus-topic-alist))
+    (while alist
+      ;; !!!Sometimes nil elements sneak into the alist,
+      ;; for some reason or other.
+      (setcar alist (delq nil (car alist)))
+      (setcar alist (delete "dummy.group" (car alist)))
+      (gnus-topic-sort-topic (pop alist) func reverse))))
+
+(defun gnus-topic-sort-topic (topic func reverse)
+  ;; Each topic only lists the name of the group, while
+  ;; the sort predicates expect group infos as inputs.
+  ;; So we first transform the group names into infos,
+  ;; then sort, and then transform back into group names.
+  (setcdr
+   topic
+   (mapcar
+    (lambda (info) (gnus-info-group info))
+    (sort
+     (mapcar
+      (lambda (group) (gnus-get-info group))
+      (cdr topic))
+     func)))
+  ;; Do the reversal, if necessary.
+  (when reverse
+    (setcdr topic (nreverse (cdr topic)))))
+
+(defun gnus-topic-sort-groups (func &optional reverse)
+  "Sort the current topic according to FUNC.
+If REVERSE, reverse the sorting order."
+  (interactive (list gnus-group-sort-function current-prefix-arg))
+  (let ((topic (assoc (gnus-current-topic) gnus-topic-alist)))
+    (gnus-topic-sort-topic
+     topic (gnus-make-sort-function func) reverse)
+    (gnus-group-list-groups)))
+
+(defun gnus-topic-sort-groups-by-alphabet (&optional reverse)
+  "Sort the current topic alphabetically by group name.
+If REVERSE, sort in reverse order."
+  (interactive "P")
+  (gnus-topic-sort-groups 'gnus-group-sort-by-alphabet reverse))
+
+(defun gnus-topic-sort-groups-by-unread (&optional reverse)
+  "Sort the current topic by number of unread articles.
+If REVERSE, sort in reverse order."
+  (interactive "P")
+  (gnus-topic-sort-groups 'gnus-group-sort-by-unread reverse))
+
+(defun gnus-topic-sort-groups-by-level (&optional reverse)
+  "Sort the current topic by group level.
+If REVERSE, sort in reverse order."
+  (interactive "P")
+  (gnus-topic-sort-groups 'gnus-group-sort-by-level reverse))
+
+(defun gnus-topic-sort-groups-by-score (&optional reverse)
+  "Sort the current topic by group score.
+If REVERSE, sort in reverse order."
+  (interactive "P")
+  (gnus-topic-sort-groups 'gnus-group-sort-by-score reverse))
+
+(defun gnus-topic-sort-groups-by-rank (&optional reverse)
+  "Sort the current topic by group rank.
+If REVERSE, sort in reverse order."
+  (interactive "P")
+  (gnus-topic-sort-groups 'gnus-group-sort-by-rank reverse))
+
+(defun gnus-topic-sort-groups-by-method (&optional reverse)
+  "Sort the current topic alphabetically by backend name.
+If REVERSE, sort in reverse order."
+  (interactive "P")
+  (gnus-topic-sort-groups 'gnus-group-sort-by-method reverse))
+
+(provide 'gnus-topic)
+
+;;; gnus-topic.el ends here