emacs: Add more functions to clean up text/plain parts

Add:
- notmuch-wash-wrap-long-lines: Wrap lines longer than the width of
  the current window whilst maintaining any citation prefix.
- notmuch-wash-tidy-citations: Tidy up citations by:
  - compress repeated otherwise blank citation lines,
  - remove otherwise blank citation lines at the head and tail of a
    citation,
- notmuch-wash-elide-blank-lines: Compress repeated blank lines and
  remove leading and trailing blank lines.

None of these is enabled by default - add them to
`notmuch-show-insert-text/plain-hook' to use.

Reviewed-by: Carl Worth <cworth@cworth.org>: I previously committed a
stale version of this patch.

1 files changed, 145 insertions, 0 deletions

diff --git a/emacs/coolj.el b/emacs/coolj.el
new file mode 100644
index 00000000..60af60af
--- /dev/null
+++ b/emacs/coolj.el
@@ -0,0 +1,145 @@
+;;; coolj.el --- automatically wrap long lines  -*- coding:utf-8 -*-
+
+;; Copyright (C) 2000, 2001, 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
+
+;; Authors:    Kai Grossjohann <Kai.Grossjohann@CS.Uni-Dortmund.DE>
+;;             Alex Schroeder <alex@gnu.org>
+;;             Chong Yidong <cyd@stupidchicken.com>
+;; Maintainer: David Edmondson <dme@dme.org>
+;; Keywords: convenience, wp
+
+;; This file is not 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 3 of the License, 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.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;;; This is a simple derivative of some functionality from
+;;; `longlines.el'. The key difference is that this version will
+;;; insert a prefix at the head of each wrapped line. The prefix is
+;;; calculated from the originating long line.
+
+;;; No minor-mode is provided, the caller is expected to call
+;;; `coolj-wrap-region' to wrap the region of interest.
+
+;;; Code:
+
+(defgroup coolj nil
+  "Wrapping of long lines with prefix."
+  :group 'fill)
+
+(defcustom coolj-wrap-follows-window-size t
+  "Non-nil means wrap text to the window size.
+Otherwise respect `fill-column'."
+  :group 'coolj
+  :type 'boolean)
+
+(defcustom coolj-line-prefix-regexp "^\\(>+ \\)*"
+  "Regular expression that matches line prefixes."
+  :group 'coolj
+  :type 'regexp)
+
+(defvar coolj-wrap-point nil)
+
+(make-variable-buffer-local 'coolj-wrap-point)
+
+(defun coolj-determine-prefix ()
+  "Determine the prefix for the current line."
+  (save-excursion
+    (beginning-of-line)
+    (if (re-search-forward coolj-line-prefix-regexp nil t)
+	(buffer-substring (match-beginning 0) (match-end 0))
+      "")))
+
+(defun coolj-wrap-buffer ()
+  "Wrap the current buffer."
+  (coolj-wrap-region (point-min) (point-max)))
+
+(defun coolj-wrap-region (beg end)
+  "Wrap each successive line, starting with the line before BEG.
+Stop when we reach lines after END that don't need wrapping, or the
+end of the buffer."
+  (setq fill-column (if coolj-wrap-follows-window-size
+			(window-width)
+		      fill-column))
+  (let ((mod (buffer-modified-p)))
+    (setq coolj-wrap-point (point))
+    (goto-char beg)
+    (forward-line -1)
+    ;; Two successful coolj-wrap-line's in a row mean successive
+    ;; lines don't need wrapping.
+    (while (null (and (coolj-wrap-line)
+		      (or (eobp)
+			  (and (>= (point) end)
+			       (coolj-wrap-line))))))
+    (goto-char coolj-wrap-point)
+    (set-buffer-modified-p mod)))
+
+(defun coolj-wrap-line ()
+  "If the current line needs to be wrapped, wrap it and return nil.
+If wrapping is performed, point remains on the line.  If the line does
+not need to be wrapped, move point to the next line and return t."
+  (let ((prefix (coolj-determine-prefix)))
+    (if (coolj-set-breakpoint prefix)
+	(progn
+	  (insert-before-markers ?\n)
+	  (backward-char 1)
+	  (delete-char -1)
+	  (forward-char 1)
+	  (insert-before-markers prefix)
+	  nil)
+      (forward-line 1)
+      t)))
+
+(defun coolj-set-breakpoint (prefix)
+  "Place point where we should break the current line, and return t.
+If the line should not be broken, return nil; point remains on the
+line."
+  (move-to-column fill-column)
+  (if (and (re-search-forward "[^ ]" (line-end-position) 1)
+           (> (current-column) fill-column))
+      ;; This line is too long.  Can we break it?
+      (or (coolj-find-break-backward prefix)
+          (progn (move-to-column fill-column)
+                 (coolj-find-break-forward)))))
+
+(defun coolj-find-break-backward (prefix)
+  "Move point backward to the first available breakpoint and return t.
+If no breakpoint is found, return nil."
+  (let ((end-of-prefix (+ (line-beginning-position) (length prefix))))
+    (and (search-backward " " end-of-prefix 1)
+	 (save-excursion
+	   (skip-chars-backward " " end-of-prefix)
+	   (null (bolp)))
+	 (progn (forward-char 1)
+		(if (and fill-nobreak-predicate
+			 (run-hook-with-args-until-success
+			  'fill-nobreak-predicate))
+		    (progn (skip-chars-backward " " end-of-prefix)
+			   (coolj-find-break-backward prefix))
+		  t)))))
+
+(defun coolj-find-break-forward ()
+  "Move point forward to the first available breakpoint and return t.
+If no break point is found, return nil."
+  (and (search-forward " " (line-end-position) 1)
+       (progn (skip-chars-forward " " (line-end-position))
+              (null (eolp)))
+       (if (and fill-nobreak-predicate
+                (run-hook-with-args-until-success
+                 'fill-nobreak-predicate))
+           (coolj-find-break-forward)
+         t)))
+
+(provide 'coolj)