;;; mst-point.el --- bullet points in text mode.

;; Author: Mark Triggs <mst@dishevelled.net>

;; This file 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.

;; This file 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:

;; *Disgusting* code for inserting and manipulating bullet points.
;; M-x mst-point inserts a dot point if there isn't one already.  If there is
;; already a dot point, it cycles through different possible indentations.
;; Obviously `mst-point' should be bound to a key.

;;; Code:


(defun mst-point-indent-to-level (level)
  (let ((mark (point-marker)))
    (unless (and (looking-at "$") (looking-back "[*-] "))
      (destructuring-bind (start end) (mst-point-find-bounds)
        (unless (and start end)
          (error "Couldn't find the bounds of this point"))
        (replace-regexp "\\(\n\\|^ +\\)" "" nil start end)))
    (beginning-of-line)
    (delete-horizontal-space)
    (let ((indent (* (1- (* 2 level)) 2)))
      (insert (make-string indent ?\ ))
      (delete-char 1)
      (if (oddp level)
          (insert "*")
        (insert "-")))
    (let ((old-prefix fill-prefix))
      (fill-region (line-beginning-position)
                   (line-end-position))
      (setq fill-prefix old-prefix))
    (goto-char (marker-position mark))))

(defun mst-last-level ()
  (or (save-excursion
        (let ((start (car (mst-point-find-bounds))))
          (and start
               (goto-char start)
               (progn (back-to-indentation)
                      (mst-point-spaces-to-level (current-column))))))
      (mst-point-parent-level)
      2))

(defun mst-point-find-bounds ()
  (let ((start nil)
        (end nil))
    (save-excursion
      (back-to-indentation)
      (while (and (not (looking-at "[*-]"))
                  (not (bobp))
                  (not (zerop (current-column))))
        (previous-line 1)
        (back-to-indentation))
      (when (looking-at "[*-]")
        (setq start (line-beginning-position)))

      (when start
        ;; Find the end
        (forward-char 2)
        (let ((goal (current-column)))
          (while (and (not (save-excursion (end-of-line) (eobp)))
                      (= (current-column) goal)
                      (looking-back "[ *-]+"))
            (next-line 1)
            (back-to-indentation))
          (if (and (save-excursion (end-of-line) (eobp))
                   (= (current-column) goal)
                   (looking-back "[ *-]+"))
              (setq end (point-max))
            (previous-line 1)
            (end-of-line)
            (setq end (point))))
        (while (or (looking-back " ")
                   (looking-back "^"))
          (setq end (1- end))
          (goto-char end)))
      (list start end))))


(defun mst-point ()
  (interactive)
  (cond ((let ((bounds (mst-point-find-bounds)))
           (and (every 'identity bounds)
                (<= (car bounds) (point))
                (<= (point) (1+ (cadr bounds)))))
         (let ((parent (mst-point-parent-level)))
           (cond ((not parent) nil)
                 ((> (mst-last-level) 1)
                  (mst-point-indent-to-level (1- (mst-last-level))))
                 ((= (mst-last-level) 1)
                  (mst-point-indent-to-level (1+ parent))))
           (when (and (looking-back "[-*]")
                      (looking-at "$"))
             (insert " "))))
        (t (unless (save-excursion
                     (beginning-of-line)
                     (looking-at "^ *$"))
             (end-of-line)
             (newline))
           (delete-horizontal-space)
           (insert "* ")
           (let ((parent (mst-point-parent-level)))
             (if parent
                 (mst-point-indent-to-level parent)
               (mst-point-indent-to-level 1))
             (insert " ")))))


(defun mst-point-spaces-to-level (spaces)
  (/ (1+ (/ spaces 2)) 2))


(defun mst-point-parent-level ()
  (save-excursion
    (destructuring-bind (start end) (mst-point-find-bounds)
      (cond (start
             (goto-char start)
             (next-line -1)
             (catch 'finished
               (while (not (bobp))
                 (save-excursion
                   (beginning-of-line)
                   (cond ((looking-at "^\\( +\\)[*-]")
                          (throw 'finished (mst-point-spaces-to-level
                                            (length (match-string 1)))))
                         ((and (not (looking-at "^$"))
                               (looking-at "^[^ ]"))
                          (throw 'finished nil))
                         (t nil)))
                 (next-line -1))))
            (t (next-line -1)
               (catch 'finished
                 (while (not (bobp))
                   (back-to-indentation)
                   (cond ((zerop (current-column))
                          (throw 'finished nil))
                         ((every 'identity (mst-point-find-bounds))
                          (mst-point-parent-level))
                         (t (next-line -1))))))))))

(provide 'mst-point)
;;; mst-point.el ends here