;; Find occurrences of regexp and pick one from a menu.
;; Copyright (C) 1985 Richard M. Stallman.
;;  based loosely on mocklisp original by Jeff Shrager and Duane Williams: CMU.

;; This file is part of GNU Emacs.

;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY.  No author or distributor
;; accepts responsibility to anyone for the consequences of using it
;; or for whether it serves any particular purpose or works at all,
;; unless he says so in writing.  Refer to the GNU Emacs General Public
;; License for full details.

;; Everyone is granted permission to copy, modify and redistribute
;; GNU Emacs, but only under the conditions described in the
;; GNU Emacs General Public License.   A copy of this license is
;; supposed to have been given to you along with GNU Emacs so you
;; can know your rights and responsibilities.  It should be in a
;; file named COPYING.  Among other things, the copyright notice
;; and this notice must be preserved on all copies.


(defun occur-menu (string)
  "Show menu of lines containing match for REGEXP.
Enters recursive edit on text showing an entry for each matching line.
User can move to an entry and then exit with \\[exit-recursive-edit] to
move to the line in the original buffer described by the selected entry.
Abort with \\[abort-recursive-edit] to avoid moving in the original buffer.

If REGEXP is empty then THE EXACT SAME menu is presented again,
with cursor initially at the next successive entry.
This is useful for stepping through located lines rapidly in order."
  (interactive "sOccur menu (regexp): ")
  (let (ln track-eol
	(accumbuf (get-buffer-create " *Occur menu*"))
	(databuf (current-buffer))
	(prev (point-min))
	(rebuild-summary (not (string-equal string ""))))
    (if rebuild-summary
	(progn
	  (save-excursion		; setup temp buffer
	    (set-buffer accumbuf)
	    (erase-buffer))
	  (save-excursion
	    (goto-char (point-min))
	    (setq ln 1)			; init accumulator
	    (while (re-search-forward string nil t)
	      (beginning-of-line)
	      (setq ln (+ ln (count-lines prev (point))))
	      (setq beg (point))
	      (setq prev (point))
	      (end-of-line)		; to pick up entire line
	      (setq end (point))
	      (save-excursion
		(set-buffer accumbuf)
		(insert (int-to-string ln) ". ")
		(insert-buffer-substring databuf beg end)
		(newline))
	      (forward-line 1))
	    (set-buffer accumbuf)
	    (set-buffer-modified-p nil))))
    (goto-line
     (save-window-excursion
       (switch-to-buffer accumbuf)
       (delete-other-windows)
       (if rebuild-summary
	   (goto-char (point-min))
	 (forward-line 1))
       (if (= (point-max) 1)
	   (error "No occurrences found."))
       (message (substitute-command-keys "Use \\[exit-recursive-edit] to select line, \\[abort-recursive-edit] to abort."))
       (let ((buffer-read-only t))
	 (recursive-edit))
       (beginning-of-line)
       (read accumbuf)))))