lisp/gnus/html2text.el

   1 ;;; html2text.el --- a simple html to plain text converter -*- coding: utf-8 -*-
   2
   3 ;; Copyright (C) 2002-2015 Free Software Foundation, Inc.
   4
   5 ;; Author: Joakim Hove <hove@phys.ntnu.no>
   6
   7 ;; This file is part of GNU Emacs.
   8
   9 ;; GNU Emacs is free software: you can redistribute it and/or modify
  10 ;; it under the terms of the GNU General Public License as published by
  11 ;; the Free Software Foundation, either version 3 of the License, or
  12 ;; (at your option) any later version.
  13
  14 ;; GNU Emacs is distributed in the hope that it will be useful,
  15 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  16 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17 ;; GNU General Public License for more details.
  18
  19 ;; You should have received a copy of the GNU General Public License
  20 ;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
  21
  22 ;;; Commentary:
  23
  24 ;; These functions provide a simple way to wash/clean html infected
  25 ;; mails.  Definitely do not work in all cases, but some improvement
  26 ;; in readability is generally obtained.  Formatting is only done in
  27 ;; the buffer, so the next time you enter the article it will be
  28 ;; "re-htmlized".
  29 ;;
  30 ;; The main function is `html2text'.
  31
  32 ;;; Code:
  33
  34 ;;
  35 ;; <Global variables>
  36 ;;
  37
  38 (eval-when-compile
  39   (require 'cl))
  40
  41 (defvar html2text-format-single-element-list '(("hr" . html2text-clean-hr)))
  42
  43 (defvar html2text-replace-list
  44   '(("&acute;" . "`")
  45     ("&amp;" . "&")
  46     ("&apos;" . "'")
  47     ("&brvbar;" . "|")
  48     ("&cent;" . "c")
  49     ("&circ;" . "^")
  50     ("&copy;" . "(C)")
  51     ("&curren;" . "(#)")
  52     ("&deg;" . "degree")
  53     ("&divide;" . "/")
  54     ("&euro;" . "e")
  55     ("&frac12;" . "1/2")
  56     ("&gt;" . ">")
  57     ("&iquest;" . "?")
  58     ("&laquo;" . "<<")
  59     ("&ldquo" . "\"")
  60     ("&lsaquo;" . "(")
  61     ("&lsquo;" . "`")
  62     ("&lt;" . "<")
  63     ("&mdash;" . "--")
  64     ("&nbsp;" . " ")
  65     ("&ndash;" . "-")
  66     ("&permil;" . "%%")
  67     ("&plusmn;" . "+-")
  68     ("&pound;" . "£")
  69     ("&quot;" . "\"")
  70     ("&raquo;" . ">>")
  71     ("&rdquo" . "\"")
  72     ("&reg;" . "(R)")
  73     ("&rsaquo;" . ")")
  74     ("&rsquo;" . "'")
  75     ("&sect;" . "§")
  76     ("&sup1;" . "^1")
  77     ("&sup2;" . "^2")
  78     ("&sup3;" . "^3")
  79     ("&tilde;" . "~"))
  80   "The map of entity to text.
  81
  82 This is an alist were each element is a dotted pair consisting of an
  83 old string, and a replacement string.  This replacement is done by the
  84 function `html2text-substitute' which basically performs a
  85 `replace-string' operation for every element in the list.  This is
  86 completely verbatim - without any use of REGEXP.")
  87
  88 (defvar html2text-remove-tag-list
  89   '("html" "body" "p" "img" "dir" "head" "div" "br" "font" "title" "meta")
  90   "A list of removable tags.
  91
  92 This is a list of tags which should be removed, without any
  93 formatting.  Note that tags in the list are presented *without*
  94 any \"<\" or \">\".  All occurrences of a tag appearing in this
  95 list are removed, irrespective of whether it is a closing or
  96 opening tag, or if the tag has additional attributes.  The
  97 deletion is done by the function `html2text-remove-tags'.
  98
  99 For instance the text:
 100
 101 \"Here comes something <font size\"+3\" face=\"Helvetica\"> big </font>.\"
 102
 103 will be reduced to:
 104
 105 \"Here comes something big.\"
 106
 107 If this list contains the element \"font\".")
 108
 109 (defvar html2text-format-tag-list
 110   '(("b"          . html2text-clean-bold)
 111     ("strong"     . html2text-clean-bold)
 112     ("u"          . html2text-clean-underline)
 113     ("i"          . html2text-clean-italic)
 114     ("em"         . html2text-clean-italic)
 115     ("blockquote" . html2text-clean-blockquote)
 116     ("a"          . html2text-clean-anchor)
 117     ("ul"         . html2text-clean-ul)
 118     ("ol"         . html2text-clean-ol)
 119     ("dl"         . html2text-clean-dl)
 120     ("center"     . html2text-clean-center))
 121   "An alist of tags and processing functions.
 122
 123 This is an alist where each dotted pair consists of a tag, and then
 124 the name of a function to be called when this tag is found.  The
 125 function is called with the arguments p1, p2, p3 and p4. These are
 126 demonstrated below:
 127
 128 \"<b> This is bold text </b>\"
 129  ^   ^                 ^    ^
 130  |   |                 |    |
 131 p1  p2                p3   p4
 132
 133 Then the called function will typically format the text somewhat and
 134 remove the tags.")
 135
 136 (defvar html2text-remove-tag-list2  '("li" "dt" "dd" "meta")
 137   "Another list of removable tags.
 138
 139 This is a list of tags which are removed similarly to the list
 140 `html2text-remove-tag-list' - but these tags are retained for the
 141 formatting, and then moved afterward.")
 142
 143 ;;
 144 ;; </Global variables>
 145 ;;
 146
 147 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 148 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 149
 150 ;;
 151 ;; <Utility functions>
 152 ;;
 153
 154
 155 (defun html2text-replace-string (from-string to-string min max)
 156   "Replace FROM-STRING with TO-STRING in region from MIN to MAX."
 157   (goto-char min)
 158   (let ((delta (- (string-width to-string) (string-width from-string)))
 159         (change 0))
 160     (while (search-forward from-string max t)
 161       (replace-match to-string)
 162       (setq change (+ change delta)))
 163     change))
 164
 165 ;;
 166 ;; </Utility functions>
 167 ;;
 168
 169 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 170 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 171
 172 ;;
 173 ;; <Functions related to attributes> i.e. <font size=+3>
 174 ;;
 175
 176 (defun html2text-attr-value (list attribute)
 177   "Get value of ATTRIBUTE from LIST."
 178   (nth 1 (assoc attribute list)))
 179
 180 (defun html2text-get-attr (p1 p2)
 181   (goto-char p1)
 182   (re-search-forward "\\s-+" p2 t)
 183   (let (attr-list)
 184     (while (re-search-forward "[-a-z0-9._]+" p2 t)
 185       (setq attr-list
 186             (cons
 187              (list (match-string 0)
 188                    (when (looking-at "\\s-*=")
 189                      (goto-char (match-end 0))
 190                      (skip-chars-forward "[:space:]")
 191                      (when (or (looking-at "\"[^\"]*\"\\|'[^']*'")
 192                                (looking-at "[-a-z0-9._:]+"))
 193                        (goto-char (match-end 0))
 194                        (match-string 0))))
 195              attr-list)))
 196     attr-list))
 197
 198 ;;
 199 ;; </Functions related to attributes>
 200 ;;
 201
 202 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 203 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 204
 205 ;;
 206 ;; <Functions to be called to format a tag-pair>
 207 ;;
 208 (defun html2text-clean-list-items (p1 p2 list-type)
 209   (goto-char p1)
 210   (let ((item-nr 0)
 211         (items   0))
 212     (while (search-forward "<li>" p2 t)
 213       (setq items (1+ items)))
 214     (goto-char p1)
 215     (while (< item-nr items)
 216       (setq item-nr (1+ item-nr))
 217       (search-forward "<li>" (point-max) t)
 218       (cond
 219        ((string= list-type "ul") (insert " o "))
 220        ((string= list-type "ol") (insert (format " %s: " item-nr)))
 221        (t (insert " x "))))))
 222
 223 (defun html2text-clean-dtdd (p1 p2)
 224   (goto-char p1)
 225   (let ((items   0)
 226         (item-nr 0))
 227     (while (search-forward "<dt>" p2 t)
 228       (setq items (1+ items)))
 229     (goto-char p1)
 230     (while (< item-nr items)
 231       (setq item-nr (1+ item-nr))
 232       (re-search-forward "<dt>\\([ ]*\\)" (point-max) t)
 233       (when (match-string 1)
 234         (delete-region (point) (- (point) (string-width (match-string 1)))))
 235       (let ((def-p1 (point))
 236             (def-p2 0))
 237         (re-search-forward "\\([ ]*\\)\\(</dt>\\|<dd>\\)" (point-max) t)
 238         (if (match-string 1)
 239             (progn
 240               (let* ((mw1 (string-width (match-string 1)))
 241                      (mw2 (string-width (match-string 2)))
 242                      (mw  (+ mw1 mw2)))
 243                 (goto-char (- (point) mw))
 244                 (delete-region (point) (+ (point) mw1))
 245                 (setq def-p2 (point))))
 246           (setq def-p2 (- (point) (string-width (match-string 2)))))
 247         (put-text-property def-p1 def-p2 'face 'bold)))))
 248
 249 (defun html2text-delete-tags (p1 p2 p3 p4)
 250   (delete-region p1 p2)
 251   (delete-region (- p3 (- p2 p1)) (- p4 (- p2 p1))))
 252
 253 (defun html2text-delete-single-tag (p1 p2)
 254   (delete-region p1 p2))
 255
 256 (defun html2text-clean-hr (p1 p2)
 257   (html2text-delete-single-tag p1 p2)
 258   (goto-char p1)
 259   (newline 1)
 260   (insert (make-string fill-column ?-)))
 261
 262 (defun html2text-clean-ul (p1 p2 p3 p4)
 263   (html2text-delete-tags p1 p2 p3 p4)
 264   (html2text-clean-list-items p1 (- p3 (- p1 p2)) "ul"))
 265
 266 (defun html2text-clean-ol (p1 p2 p3 p4)
 267   (html2text-delete-tags p1 p2 p3 p4)
 268   (html2text-clean-list-items p1 (- p3 (- p1 p2)) "ol"))
 269
 270 (defun html2text-clean-dl (p1 p2 p3 p4)
 271   (html2text-delete-tags p1 p2 p3 p4)
 272   (html2text-clean-dtdd p1 (- p3 (- p1 p2))))
 273
 274 (defun html2text-clean-center (p1 p2 p3 p4)
 275   (html2text-delete-tags p1 p2 p3 p4)
 276   (center-region p1 (- p3 (- p2 p1))))
 277
 278 (defun html2text-clean-bold (p1 p2 p3 p4)
 279   (put-text-property p2 p3 'face 'bold)
 280   (html2text-delete-tags p1 p2 p3 p4))
 281
 282 (defun html2text-clean-title (p1 p2 p3 p4)
 283   (put-text-property p2 p3 'face 'bold)
 284   (html2text-delete-tags p1 p2 p3 p4))
 285
 286 (defun html2text-clean-underline (p1 p2 p3 p4)
 287   (put-text-property p2 p3 'face 'underline)
 288   (html2text-delete-tags p1 p2 p3 p4))
 289
 290 (defun html2text-clean-italic (p1 p2 p3 p4)
 291   (put-text-property p2 p3 'face 'italic)
 292   (html2text-delete-tags p1 p2 p3 p4))
 293
 294 (defun html2text-clean-font (p1 p2 p3 p4)
 295   (html2text-delete-tags p1 p2 p3 p4))
 296
 297 (defun html2text-clean-blockquote (p1 p2 p3 p4)
 298   (html2text-delete-tags p1 p2 p3 p4))
 299
 300 (defun html2text-clean-anchor (p1 p2 p3 p4)
 301   ;; If someone can explain how to make the URL clickable I will surely
 302   ;; improve upon this.
 303   ;; Maybe `goto-addr.el' can be used here.
 304   (let* ((attr-list (html2text-get-attr p1 p2))
 305          (href (html2text-attr-value attr-list "href")))
 306     (delete-region p1 p4)
 307     (when href
 308       (goto-char p1)
 309       (insert (if (string-match "\\`['\"].*['\"]\\'" href)
 310                   (substring href 1 -1) href))
 311       (put-text-property p1 (point) 'face 'bold))))
 312
 313 ;;
 314 ;; </Functions to be called to format a tag-pair>
 315 ;;
 316
 317 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 318 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 319
 320 ;;
 321 ;; <Functions to be called to fix up paragraphs>
 322 ;;
 323
 324 (defun html2text-fix-paragraph (p1 p2)
 325   (goto-char p1)
 326   (let ((refill-start)
 327         (refill-stop))
 328     (when (re-search-forward "<br>$" p2 t)
 329       (goto-char p1)
 330       (when (re-search-forward ".+[^<][^b][^r][^>]$" p2 t)
 331         (beginning-of-line)
 332         (setq refill-start (point))
 333         (goto-char p2)
 334         (re-search-backward ".+[^<][^b][^r][^>]$" refill-start t)
 335         (forward-line 1)
 336         (end-of-line)
 337         ;; refill-stop should ideally be adjusted to
 338         ;; accommodate the "<br>" strings which are removed
 339         ;; between refill-start and refill-stop.  Can simply
 340         ;; be returned from my-replace-string
 341         (setq refill-stop (+ (point)
 342                              (html2text-replace-string
 343                               "<br>" ""
 344                               refill-start (point))))
 345         ;; (message "Point = %s  refill-stop = %s" (point) refill-stop)
 346         ;; (sleep-for 4)
 347         (fill-region refill-start refill-stop))))
 348   (html2text-replace-string "<br>" "" p1 p2))
 349
 350 ;;
 351 ;; This one is interactive ...
 352 ;;
 353 (defun html2text-fix-paragraphs ()
 354   "This _tries_ to fix up the paragraphs - this is done in quite a ad-hook
 355 fashion, quite close to pure guess-work. It does work in some cases though."
 356   (interactive)
 357   (goto-char (point-min))
 358   (while (re-search-forward "^<br>$" nil t)
 359     (delete-region (match-beginning 0) (match-end 0)))
 360   ;; Removing lonely <br> on a single line, if they are left intact we
 361   ;; don't have any paragraphs at all.
 362   (goto-char (point-min))
 363   (while (not (eobp))
 364     (let ((p1 (point)))
 365       (forward-paragraph 1)
 366       ;;(message "Kaller fix med p1=%s  p2=%s " p1 (1- (point))) (sleep-for 5)
 367       (html2text-fix-paragraph p1 (1- (point)))
 368       (goto-char p1)
 369       (when (not (eobp))
 370         (forward-paragraph 1)))))
 371
 372 ;;
 373 ;; </Functions to be called to fix up paragraphs>
 374 ;;
 375
 376 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 377 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 378
 379 ;;
 380 ;; <Interactive functions>
 381 ;;
 382
 383 (defun html2text-remove-tags (tag-list)
 384   "Removes the tags listed in the list `html2text-remove-tag-list'.
 385 See the documentation for that variable."
 386   (interactive)
 387   (dolist (tag tag-list)
 388     (goto-char (point-min))
 389     (while (re-search-forward (format "\\(</?%s[^>]*>\\)" tag) (point-max) t)
 390       (delete-region (match-beginning 0) (match-end 0)))))
 391
 392 (defun html2text-format-tags ()
 393   "See the variable `html2text-format-tag-list' for documentation."
 394   (interactive)
 395   (dolist (tag-and-function html2text-format-tag-list)
 396     (let ((tag      (car tag-and-function))
 397           (function (cdr tag-and-function)))
 398       (goto-char (point-min))
 399       (while (re-search-forward (format "\\(<%s\\( [^>]*\\)?>\\)" tag)
 400                                 (point-max) t)
 401         (let ((p1)
 402               (p2 (point))
 403               (p3) (p4))
 404           (search-backward "<" (point-min) t)
 405           (setq p1 (point))
 406           (unless (search-forward (format "</%s>" tag) (point-max) t)
 407             (goto-char p2)
 408             (insert (format "</%s>" tag)))
 409           (setq p4 (point))
 410           (search-backward "</" (point-min) t)
 411           (setq p3 (point))
 412           (funcall function p1 p2 p3 p4)
 413           (goto-char p1))))))
 414
 415 (defun html2text-substitute ()
 416   "See the variable `html2text-replace-list' for documentation."
 417   (interactive)
 418   (dolist (e html2text-replace-list)
 419     (goto-char (point-min))
 420     (let ((old-string (car e))
 421           (new-string (cdr e)))
 422       (html2text-replace-string old-string new-string (point-min) (point-max)))))
 423
 424 (defun html2text-format-single-elements ()
 425   (interactive)
 426   (dolist (tag-and-function html2text-format-single-element-list)
 427     (let ((tag      (car tag-and-function))
 428           (function (cdr tag-and-function)))
 429       (goto-char (point-min))
 430       (while (re-search-forward (format "\\(<%s\\( [^>]*\\)?>\\)" tag)
 431                                 (point-max) t)
 432         (let ((p1)
 433               (p2 (point)))
 434           (search-backward "<" (point-min) t)
 435           (setq p1 (point))
 436           (funcall function p1 p2))))))
 437
 438 ;;
 439 ;; Main function
 440 ;;
 441
 442 ;;;###autoload
 443 (defun html2text ()
 444   "Convert HTML to plain text in the current buffer."
 445   (interactive)
 446   (save-excursion
 447     (let ((case-fold-search t)
 448           (buffer-read-only))
 449       (html2text-remove-tags html2text-remove-tag-list)
 450       (html2text-format-tags)
 451       (html2text-remove-tags html2text-remove-tag-list2)
 452       (html2text-substitute)
 453       (html2text-format-single-elements)
 454       (html2text-fix-paragraphs))))
 455
 456 ;;
 457 ;; </Interactive functions>
 458 ;;
 459 (provide 'html2text)
 460
 461 ;;; html2text.el ends here