;;; deuglify.el --- deuglify broken Outlook (Express) articles

;; Copyright (C) 2001-2019 Free Software Foundation, Inc.

;; Author: Raymond Scholz <rscholz@zonix.de>
;;         Thomas Steffen
;; (unwrapping algorithm, based on an idea of Stefan Monnier)
;; Keywords: mail, 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 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 <https://www.gnu.org/licenses/>.

;;; Commentary:

;; This file enables Gnus to repair broken citations produced by
;; common user agents like MS Outlook (Express).  It may repair
;; articles of other user agents too.
;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;;
;; Outlook sometimes wraps cited lines before sending a message as
;; seen in this example:
;;
;; Example #1
;; ----------
;;
;; John Doe wrote:
;;
;; > This sentence no verb.  This sentence no verb.  This sentence
;; no
;; > verb.  This sentence no verb.  This sentence no verb.  This
;; > sentence no verb.
;;
;; The function `gnus-article-outlook-unwrap-lines' tries to recognize those
;; erroneously wrapped lines and will unwrap them.  I.e. putting the
;; wrapped parts ("no" in this example) back where they belong (at the
;; end of the cited line above).
;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;; Note that some people not only use broken user agents but also
;; practice a bad citation style by omitting blank lines between the
;; cited text and their own text.
;:
;; Example #2
;; ----------
;;
;; John Doe wrote:
;;
;; > This sentence no verb.  This sentence no verb.  This sentence no
;; You forgot in all your sentences.
;; > verb.  This sentence no verb.  This sentence no verb.  This
;; > sentence no verb.
;;
;; Unwrapping "You forgot in all your sentences." would be invalid as
;; this part wasn't intended to be cited text.
;; `gnus-article-outlook-unwrap-lines' will only unwrap lines if the resulting
;; citation line will be of a certain maximum length.  You can control
;; this by adjusting `gnus-outlook-deuglify-unwrap-max'.  Also
;; unwrapping will only be done if the line above the (possibly)
;; wrapped line has a minimum length of `gnus-outlook-deuglify-unwrap-min'.
;;
;; Furthermore no unwrapping will be undertaken if the last character
;; is one of the chars specified in
;; `gnus-outlook-deuglify-unwrap-stop-chars'.  Setting this to ".?!"
;; inhibits unwrapping if the cited line ends with a full stop,
;; question mark or exclamation mark.  Note that this variable
;; defaults to nil, triggering a few false positives but generally
;; giving you better results.
;;
;; Unwrapping works on every level of citation.  Thus you will be able
;; repair broken citations of broken user agents citing broken
;; citations of broken user agents citing broken citations...
;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;; Citations are commonly introduced with an attribution line
;; indicating who wrote the cited text.  Outlook adds superfluous
;; information that can be found in the header of the message to this
;; line and often wraps it.
;;
;; If that weren't enough, lots of people write their own text above
;; the cited text and cite the complete original article below.
;;
;; Example #3
;; ----------
;;
;; Hey, John.  There's no in all your sentences!
;;
;; John Doe <john.doe@some.domain> wrote in message
;; news:a87usw8$dklsssa$2@some.news.server...
;; > This sentence no verb.  This sentence no verb.  This sentence
;; no
;; > verb.  This sentence no verb.  This sentence no verb.  This
;; > sentence no verb.
;; >
;; > Bye, John
;;
;; Repairing the attribution line will be done by function
;; `gnus-article-outlook-repair-attribution' which calls other function that
;; try to recognize and repair broken attribution lines.  See variable
;; `gnus-outlook-deuglify-attrib-cut-regexp' for stuff that should be
;; cut off from the beginning of an attribution line and variable
;; `gnus-outlook-deuglify-attrib-verb-regexp' for the verbs that are
;; required to be found in an attribution line.  These function return
;; the point where the repaired attribution line starts.
;;
;; Rearranging the article so that the cited text appears above the
;; new text will be done by function
;; `gnus-article-outlook-rearrange-citation'.  This function calls
;; `gnus-article-outlook-repair-attribution' to find and repair an attribution
;; line.
;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;; Well, and that's what the message will look like after applying
;; deuglification:
;;
;; Example #3 (deuglified)
;; -----------------------
;;
;; John Doe <john.doe@some.domain> wrote:
;;
;; > This sentence no verb.  This sentence no verb.  This sentence no
;; > verb.  This sentence no verb.  This sentence no verb.  This
;; > sentence no verb.
;; >
;; > Bye, John
;;
;; Hey, John.  There's no in all your sentences!
;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;; Usage
;; -----
;;
;; Press `W k' in the Summary Buffer.
;;
;; Non recommended usage :-)
;; ---------------------
;;
;; To automatically invoke deuglification on every article you read,
;; put something like that in your .gnus:
;;
;; (add-hook 'gnus-article-decode-hook 'gnus-article-outlook-unwrap-lines)
;;
;; or _one_ of the following lines:
;;
;; ;; repair broken attribution lines
;; (add-hook 'gnus-article-decode-hook 'gnus-article-outlook-repair-attribution)
;;
;; ;; repair broken attribution lines and citations
;; (add-hook 'gnus-article-decode-hook 'gnus-article-outlook-rearrange-citation)
;;
;; Note that there always may be some false positives, so I suggest
;; using the manual invocation.  After deuglification you may want to
;; refill the whole article using `W w'.
;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;; Limitations
;; -----------
;;
;; As I said before there may (or will) be a few false positives on
;; unwrapping cited lines with `gnus-article-outlook-unwrap-lines'.
;;
;; `gnus-article-outlook-repair-attribution' will only fix the first
;; attribution line found in the article.  Furthermore it fixed to
;; certain kinds of attributions.  And there may be horribly many
;; false positives, vanishing lines and so on -- so don't trust your
;; eyes.  Again I recommend manual invocation.
;;
;; `gnus-article-outlook-rearrange-citation' carries all the limitations of
;; `gnus-article-outlook-repair-attribution'.
;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;; See commit log for other changes.
;;
;; Revision 1.5  2002/01/27 14:39:17  rscholz
;; * New variable `gnus-outlook-deuglify-no-wrap-chars' to inhibit
;;   unwrapping if one these chars is first in the possibly wrapped line.
;; * Improved rearranging of the article.
;; * New function `gnus-outlook-repair-attribution-block' for repairing
;;   those big "Original Message (following some headers)" attributions.
;;
;; Revision 1.4  2002/01/03 14:05:00  rscholz
;; Renamed `gnus-outlook-deuglify-article' to
;; `gnus-article-outlook-deuglify-article'.
;; Made it easier to deuglify the article while being in Gnus' Article
;; Edit Mode.  (suggested by Phil Nitschke)
;;
;;
;; Revision 1.3  2002/01/02 23:35:54  rscholz
;; Fix a bug that caused succeeding long attribution lines to be
;; unwrapped.  Minor doc fixes and regular expression tuning.
;;
;; Revision 1.2  2001/12/30 20:14:34  rscholz
;; Clean up source.
;;
;; Revision 1.1  2001/12/30 20:13:32  rscholz
;; Initial revision
;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;;; Code:

(require 'gnus-art)
(require 'gnus-sum)

(defconst gnus-outlook-deuglify-version "1.5 Gnus version"
  "Version of gnus-outlook-deuglify.")

;;; User Customizable Variables:

(defgroup gnus-outlook-deuglify nil
  "Deuglify articles generated by broken user agents like MS Outlook (Express)."
  :version "22.1"
  :group 'gnus)

(defcustom gnus-outlook-deuglify-unwrap-min 45
  "Minimum length of the cited line above the (possibly) wrapped line."
  :version "22.1"
  :type 'integer
  :group 'gnus-outlook-deuglify)

(defcustom gnus-outlook-deuglify-unwrap-max 95
  "Maximum length of the cited line after unwrapping."
  :version "22.1"
  :type 'integer
  :group 'gnus-outlook-deuglify)

(defcustom gnus-outlook-deuglify-cite-marks ">|#%"
  "Characters that indicate cited lines."
  :version "22.1"
  :type 'string
  :group 'gnus-outlook-deuglify)

(defcustom gnus-outlook-deuglify-unwrap-stop-chars nil ;; ".?!" or nil
  "Characters that inhibit unwrapping if they are the last one on the cited line above the possible wrapped line."
  :version "22.1"
  :type '(radio (const :format "None  " nil)
		(string :value ".?!"))
  :group 'gnus-outlook-deuglify)

(defcustom gnus-outlook-deuglify-no-wrap-chars "`"
  "Characters that inhibit unwrapping if they are the first one in the possibly wrapped line."
  :version "22.1"
  :type 'string
  :group 'gnus-outlook-deuglify)

(defcustom  gnus-outlook-deuglify-attrib-cut-regexp
  "\\(On \\|Am \\)?\\(Mon\\|Tue\\|Wed\\|Thu\\|Fri\\|Sat\\|Sun\\),[^,]+, "
  "Regular expression matching the beginning of an attribution line that should be cut off."
  :version "22.1"
  :type 'regexp
  :group 'gnus-outlook-deuglify)

(defcustom gnus-outlook-deuglify-attrib-verb-regexp
  "wrote\\|writes\\|says\\|schrieb\\|schreibt\\|meinte\\|skrev\\|a écrit\\|schreef\\|escribió"
  "Regular expression matching the verb used in an attribution line."
  :version "22.1"
  :type 'regexp
  :group 'gnus-outlook-deuglify)

(defcustom  gnus-outlook-deuglify-attrib-end-regexp
  ": *\\|\\.\\.\\."
  "Regular expression matching the end of an attribution line."
  :version "22.1"
  :type 'regexp
  :group 'gnus-outlook-deuglify)

(defcustom gnus-outlook-display-hook nil
  "A hook called after a deuglified article has been prepared.
It is run after `gnus-article-prepare-hook'."
  :version "22.1"
  :type 'hook
  :group 'gnus-outlook-deuglify)

;; Functions

(defun gnus-outlook-display-article-buffer ()
  "Redisplay current buffer or article buffer."
  (with-current-buffer (or gnus-article-buffer (current-buffer))
    ;; "Emulate" `gnus-article-prepare-display' without calling
    ;; it. Calling `gnus-article-prepare-display' on an already
    ;; prepared article removes all MIME parts.  I'm unsure whether
    ;; this is a bug or not.
    (save-excursion
      (save-restriction
	(widen)
	(article-goto-body)
	(narrow-to-region (point) (point-max))
	(gnus-treat-article nil)))
    (gnus-run-hooks 'gnus-article-prepare-hook
		    'gnus-outlook-display-hook)))

;;;###autoload
(defun gnus-article-outlook-unwrap-lines (&optional nodisplay)
  "Unwrap lines that appear to be wrapped citation lines.
You can control what lines will be unwrapped by frobbing
`gnus-outlook-deuglify-unwrap-min' and `gnus-outlook-deuglify-unwrap-max',
indicating the minimum and maximum length of an unwrapped citation line.  If
NODISPLAY is non-nil, don't redisplay the article buffer."
  (interactive "P")
  (let ((case-fold-search nil)
	(inhibit-read-only t)
	(cite-marks gnus-outlook-deuglify-cite-marks)
	(no-wrap gnus-outlook-deuglify-no-wrap-chars)
	(stop-chars gnus-outlook-deuglify-unwrap-stop-chars))
    (gnus-with-article-buffer
      (article-goto-body)
      (while (re-search-forward
	      (concat
	       "^\\([ \t" cite-marks "]*\\)"
	       "\\([" cite-marks "].*[^\n " stop-chars "]\\)[ \t]?\n"
	       "\\1\\([^\n " cite-marks no-wrap "]+.*\\)$")
              nil t)
	(let ((len12 (- (match-end 2) (match-beginning 1)))
	      (len3 (- (match-end 3) (match-beginning 3))))
	  (when (and (> len12 gnus-outlook-deuglify-unwrap-min)
		     (< (+ len12 len3) gnus-outlook-deuglify-unwrap-max))
	    (replace-match "\\1\\2 \\3")
	    (goto-char (match-beginning 0)))))))
  (unless nodisplay (gnus-outlook-display-article-buffer)))

(defun gnus-outlook-rearrange-article (attr-start)
  "Put the text from ATTR-START to the end of buffer at the top of the article buffer."
  ;; FIXME: 1.  (*) text/plain          ( ) text/html
  (let ((inhibit-read-only t)
	(cite-marks gnus-outlook-deuglify-cite-marks))
    (gnus-with-article-buffer
      (article-goto-body)
      ;; article does not start with attribution
      (unless (= (point) attr-start)
	(gnus-kill-all-overlays)
	(let ((cur (point))
	      ;; before signature or end of buffer
	      (to (if (gnus-article-search-signature)
		      (point)
		    (point-max))))
	  ;; handle the case where the full quote is below the
	  ;; signature
	  (when (< to attr-start)
	    (setq to (point-max)))
	  (save-excursion
	    (narrow-to-region attr-start to)
	    (goto-char attr-start)
	    (forward-line)
	    (unless (looking-at ">")
	      (message-indent-citation (point) (point-max) 'yank-only)
	      (goto-char (point-max))
	      (newline)
	      (setq to (point-max)))
	    (widen))
	  (transpose-regions cur attr-start attr-start to))))))

;; John Doe <john.doe@some.domain> wrote in message
;; news:a87usw8$dklsssa$2@some.news.server...

(defun gnus-outlook-repair-attribution-outlook ()
  "Repair a broken attribution line (Outlook)."
  (let ((case-fold-search nil)
	(inhibit-read-only t)
	(cite-marks gnus-outlook-deuglify-cite-marks))
    (gnus-with-article-buffer
      (article-goto-body)
      (when (re-search-forward
	     (concat "^\\([^" cite-marks "].+\\)"
		     "\\(" gnus-outlook-deuglify-attrib-verb-regexp "\\)"
		     "\\(.*\n?[^\n" cite-marks "].*\\)?"
		     "\\(" gnus-outlook-deuglify-attrib-end-regexp "\\)$")
	     nil t)
	(gnus-kill-all-overlays)
	(replace-match "\\1\\2\\4")
	(match-beginning 0)))))


;; ----- Original Message -----
;; From: "John Doe" <john.doe@some.domain>
;; To: "Doe Foundation" <info@doefnd.org>
;; Sent: Monday, November 19, 2001 12:13 PM
;; Subject: More Doenuts

(defun gnus-outlook-repair-attribution-block ()
  "Repair a big broken attribution block."
  (let ((case-fold-search nil)
	(inhibit-read-only t)
	(cite-marks gnus-outlook-deuglify-cite-marks))
    (gnus-with-article-buffer
      (article-goto-body)
      (when (re-search-forward
	     (concat "^[" cite-marks " \t]*--* ?[^-]+ [^-]+ ?--*\\s *\n"
		     "[^\n:]+:[ \t]*\\([^\n]+\\)\n"
		     "\\([^\n:]+:[ \t]*[^\n]+\n\\)+")
	     nil t)
	(gnus-kill-all-overlays)
	(replace-match "\\1 wrote:\n")
	(match-beginning 0)))))

;; On Wed, 16 Jan 2002 23:23:30 +0100, John Doe <john.doe@some.domain> wrote:

(defun gnus-outlook-repair-attribution-other ()
  "Repair a broken attribution line (other user agents than Outlook)."
  (let ((case-fold-search nil)
	(inhibit-read-only t)
	(cite-marks gnus-outlook-deuglify-cite-marks))
    (gnus-with-article-buffer
      (article-goto-body)
      (when (re-search-forward
	     (concat "^\\("gnus-outlook-deuglify-attrib-cut-regexp"\\)?"
		     "\\([^" cite-marks "].+\\)\n\\([^\n" cite-marks "].*\\)?"
		     "\\(" gnus-outlook-deuglify-attrib-verb-regexp "\\).*"
		     "\\(" gnus-outlook-deuglify-attrib-end-regexp "\\)$")
	     nil t)
	(gnus-kill-all-overlays)
	(replace-match "\\4 \\5\\6\\7")
	(match-beginning 0)))))

;;;###autoload
(defun gnus-article-outlook-repair-attribution (&optional nodisplay)
  "Repair a broken attribution line.
If NODISPLAY is non-nil, don't redisplay the article buffer."
  (interactive "P")
  (let ((attrib-start
	 (or
	  (gnus-outlook-repair-attribution-other)
	  (gnus-outlook-repair-attribution-block)
	  (gnus-outlook-repair-attribution-outlook))))
    (unless nodisplay (gnus-outlook-display-article-buffer))
    attrib-start))

(defun gnus-article-outlook-rearrange-citation (&optional nodisplay)
  "Repair broken citations.
If NODISPLAY is non-nil, don't redisplay the article buffer."
  (interactive "P")
  (let ((attrib-start (gnus-article-outlook-repair-attribution 'nodisplay)))
    ;; rearrange citations if an attribution line has been recognized
    (if attrib-start
	(gnus-outlook-rearrange-article attrib-start)))
  (unless nodisplay (gnus-outlook-display-article-buffer)))

;;;###autoload
(defun gnus-outlook-deuglify-article (&optional nodisplay)
  "Full deuglify of broken Outlook (Express) articles.
Treat \"smartquotes\", unwrap lines, repair attribution and
rearrange citation.  If NODISPLAY is non-nil, don't redisplay the
article buffer."
  (interactive "P")
  ;; apply treatment of dumb quotes
  (gnus-article-treat-smartquotes)
  ;; repair wrapped cited lines
  (gnus-article-outlook-unwrap-lines 'nodisplay)
  ;; repair attribution line and rearrange citation.
  (gnus-article-outlook-rearrange-citation 'nodisplay)
  (unless nodisplay (gnus-outlook-display-article-buffer)))

;;;###autoload
(defun gnus-article-outlook-deuglify-article ()
  "Deuglify broken Outlook (Express) articles and redisplay."
  (interactive)
  (gnus-outlook-deuglify-article nil))

(provide 'deuglify)

;; Local Variables:
;; coding: utf-8
;; End:

;;; deuglify.el ends here