;;; deuglify.el --- deuglify broken Outlook (Express) articles  -*- lexical-binding: t; -*-

;; Copyright (C) 2001-2021 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)

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

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

(defcustom gnus-outlook-deuglify-unwrap-stop-chars nil ;; ".?!" or nil
  "Characters that, when at end of cited line, inhibit unwrapping.
When one of these characters is the last one on the cited line
above the possibly wrapped line, it disallows unwrapping."
  :version "22.1"
  :type '(radio (const :format "None  " nil)
		(string :value ".?!")))

(defcustom gnus-outlook-deuglify-no-wrap-chars "`"
  "Characters that, when at beginning of line, inhibit unwrapping.
When one of these characters is the first one in the possibly
wrapped line, it disallows unwrapping."
  :version "22.1"
  :type 'string)

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

(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)

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

(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)

;; 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" gnus-article-mode gnus-summary-mode)
  (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 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:]+:[^\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" gnus-article-mode gnus-summary-mode)
  (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" gnus-article-mode gnus-summary-mode)
  (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" gnus-article-mode gnus-summary-mode)
  ;; 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 nil gnus-article-mode gnus-summary-mode)
  (gnus-outlook-deuglify-article nil))

(provide 'deuglify)

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

;;; deuglify.el ends here