lisp/gnus/html2text.el

   1 ;;; html2text.el --- a simple html to plain text converter
   2 ;; Copyright (C) 2002, 2003, 2004 Free Software Foundation, Inc.
   3
   4 ;; Author: Joakim Hove <hove@phys.ntnu.no>
   5
   6 ;; This file is part of GNU Emacs.
   7
   8 ;; GNU Emacs is free software; you can redistribute it and/or modify
   9 ;; it under the terms of the GNU General Public License as published by
  10 ;; the Free Software Foundation; either version 2, or (at your option)
  11 ;; any later version.
  12
  13 ;; GNU Emacs is distributed in the hope that it will be useful,
  14 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 ;; GNU General Public License for more details.
  17
  18 ;; You should have received a copy of the GNU General Public License
  19 ;; along with GNU Emacs; see the file COPYING.  If not, write to the
  20 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  21 ;; Boston, MA 02111-1307, USA.
  22
  23 ;;; Commentary:
  24
  25 ;; These functions provide a simple way to wash/clean html infected
  26 ;; mails.  Definitely do not work in all cases, but some improvement
  27 ;; in readability is generally obtained. Formatting is only done in
  28 ;; the buffer, so the next time you enter the article it will be
  29 ;; "re-htmlized".
  30 ;;
  31 ;; The main function is "html2text"
  32
  33 ;;; Code:
  34
  35 ;;
  36 ;; <Global variables>
  37 ;;
  38
  39 (eval-when-compile
  40   (require 'cl))
  41
  42 (defvar html2text-format-single-element-list '(("hr" . html2text-clean-hr)))
  43
  44 (defvar html2text-replace-list
  45   '(("&nbsp;" . " ") ("&gt;" . ">") ("&lt;" . "<") ("&quot;" . "\"")
  46     ("&amp;" . "&") ("&apos;" . "'"))
  47   "The map of entity to text.
  48
  49 This is an alist were each element is a dotted pair consisting of an
  50 old string, and a replacement string. This replacement is done by the
  51 function \"html2text-substitute\" which basically performs a
  52 replace-string operation for every element in the list. This is
  53 completely verbatim - without any use of REGEXP.")
  54
  55 (defvar html2text-remove-tag-list
  56   '("html" "body" "p" "img" "dir" "head" "div" "br" "font" "title" "meta")
  57   "A list of removable tags.
  58
  59 This is a list of tags which should be removed, without any
  60 formatting.  Observe that if you the tags in the list are presented
  61 *without* any \"<\" or \">\". All occurences of a tag appearing in
  62 this list are removed, irrespective of whether it is a closing or
  63 opening tag, or if the tag has additional attributes. The actual
  64 deletion is done by the function \"html2text-remove-tags\".
  65
  66 For instance the text:
  67
  68 \"Here comes something <font size\"+3\" face=\"Helvetica\"> big </font>.\"
  69
  70 will be reduced to:
  71
  72 \"Here comes something big.\"
  73
  74 If this list contains the element \"font\".")
  75
  76 (defvar html2text-format-tag-list
  77   '(("b"          . html2text-clean-bold)
  78     ("u"          . html2text-clean-underline)
  79     ("i"          . html2text-clean-italic)
  80     ("blockquote" . html2text-clean-blockquote)
  81     ("a"          . html2text-clean-anchor)
  82     ("ul"         . html2text-clean-ul)
  83     ("ol"         . html2text-clean-ol)
  84     ("dl"         . html2text-clean-dl)
  85     ("center"     . html2text-clean-center))
  86   "An alist of tags and processing functions.
  87
  88 This is an alist where each dotted pair consists of a tag, and then
  89 the name of a function to be called when this tag is found. The
  90 function is called with the arguments p1, p2, p3 and p4. These are
  91 demontrated below:
  92
  93 \"<b> This is bold text </b>\"
  94  ^   ^                 ^    ^
  95  |   |                 |    |
  96 p1  p2                p3   p4
  97
  98 Then the called function will typically format the text somewhat and
  99 remove the tags.")
 100
 101 (defvar html2text-remove-tag-list2  '("li" "dt" "dd" "meta")
 102   "Another list of removable tags.
 103
 104 This is a list of tags which are removed similarly to the list
 105 `html2text-remove-tag-list' - but these tags are retained for the
 106 formatting, and then moved afterward.")
 107
 108 ;;
 109 ;; </Global variables>
 110 ;;
 111
 112 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 113 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 114
 115 ;;
 116 ;; <Utility functions>
 117 ;;
 118
 119 (defun html2text-buffer-head ()
 120   (if (string= mode-name "Article")
 121       (beginning-of-buffer)
 122     (beginning-of-buffer)
 123     )
 124   )
 125
 126 (defun html2text-replace-string (from-string to-string p1 p2)
 127   (goto-char p1)
 128   (let ((delta (- (string-width to-string) (string-width from-string)))
 129         (change 0))
 130     (while (search-forward from-string p2 t)
 131       (replace-match to-string)
 132       (setq change (+ change delta))
 133       )
 134     change
 135     )
 136   )
 137
 138 ;;
 139 ;; </Utility functions>
 140 ;;
 141
 142 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 143 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 144
 145 ;;
 146 ;; <Functions related to attributes> i.e. <font size=+3>
 147 ;;
 148
 149 (defun html2text-attr-value (attr-list attr)
 150   (nth 1 (assoc attr attr-list))
 151   )
 152
 153 (defun html2text-get-attr (p1 p2 tag)
 154   (goto-char p1)
 155   (re-search-forward " +[^ ]" p2 t)
 156   (let* ((attr-string (buffer-substring-no-properties (1- (point)) (1- p2)))
 157          (tmp-list (split-string attr-string))
 158          (attr-list)
 159          (counter 0)
 160          (prev (car tmp-list))
 161          (this (nth 1 tmp-list))
 162          (next (nth 2 tmp-list))
 163          (index 1))
 164
 165     (cond
 166      ;; size=3
 167      ((string-match "[^ ]=[^ ]" prev)
 168       (let ((attr  (nth 0 (split-string prev "=")))
 169             (value (nth 1 (split-string prev "="))))
 170         (setq attr-list (cons (list attr value) attr-list))
 171         )
 172       )
 173      ;; size= 3
 174      ((string-match "[^ ]=\\'" prev)
 175       (setq attr-list (cons (list (substring prev 0 -1) this) attr-list))
 176       )
 177      )
 178
 179     (while (< index (length tmp-list))
 180       (cond
 181        ;; size=3
 182        ((string-match "[^ ]=[^ ]" this)
 183         (let ((attr  (nth 0 (split-string this "=")))
 184               (value (nth 1 (split-string this "="))))
 185           (setq attr-list (cons (list attr value) attr-list))
 186           )
 187         )
 188        ;; size =3
 189        ((string-match "\\`=[^ ]" this)
 190         (setq attr-list (cons (list prev (substring this 1)) attr-list)))
 191
 192        ;; size= 3
 193        ((string-match "[^ ]=\\'" this)
 194         (setq attr-list (cons (list (substring this 0 -1) next) attr-list))
 195         )
 196
 197        ;; size = 3
 198        ((string= "=" this)
 199         (setq attr-list (cons (list prev next) attr-list))
 200         )
 201        )
 202       (setq index (1+ index))
 203       (setq prev this)
 204       (setq this next)
 205       (setq next (nth (1+ index) tmp-list))
 206       )
 207
 208     ;;
 209     ;; Tags with no accompanying "=" i.e. value=nil
 210     ;;
 211     (setq prev (car tmp-list))
 212     (setq this (nth 1 tmp-list))
 213     (setq next (nth 2 tmp-list))
 214     (setq index 1)
 215
 216     (if (not (string-match "=" prev))
 217         (progn
 218           (if (not (string= (substring this 0 1) "="))
 219               (setq attr-list (cons (list prev nil) attr-list))
 220             )
 221           )
 222       )
 223
 224     (while (< index (1- (length tmp-list)))
 225       (if (not (string-match "=" this))
 226           (if (not (or (string= (substring next 0 1) "=")
 227                        (string= (substring prev -1) "=")))
 228               (setq attr-list (cons (list this nil) attr-list))
 229             )
 230         )
 231       (setq index (1+ index))
 232       (setq prev this)
 233       (setq this next)
 234       (setq next (nth (1+ index) tmp-list))
 235       )
 236
 237     (if this
 238         (progn
 239           (if (not (string-match "=" this))
 240               (progn
 241                 (if (not (string= (substring prev -1) "="))
 242                     (setq attr-list (cons (list this nil) attr-list))
 243                   )
 244                 )
 245             )
 246           )
 247       )
 248     attr-list ;; return - value
 249     )
 250   )
 251
 252 ;;
 253 ;; </Functions related to attributes>
 254 ;;
 255
 256 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 257 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 258
 259 ;;
 260 ;; <Functions to be called to format a tag-pair>
 261 ;;
 262 (defun html2text-clean-list-items (p1 p2 list-type)
 263   (goto-char p1)
 264   (let ((item-nr 0)
 265         (items   0))
 266     (while (re-search-forward "<li>" p2 t)
 267       (setq items (1+ items)))
 268     (goto-char p1)
 269     (while (< item-nr items)
 270       (setq item-nr (1+ item-nr))
 271       (re-search-forward "<li>" (point-max) t)
 272       (cond
 273        ((string= list-type "ul") (insert " o "))
 274        ((string= list-type "ol") (insert (format " %s: " item-nr)))
 275        (t (insert " x ")))
 276       )
 277     )
 278   )
 279
 280 (defun html2text-clean-dtdd (p1 p2)
 281   (goto-char p1)
 282   (let ((items   0)
 283         (item-nr 0))
 284     (while (re-search-forward "<dt>" p2 t)
 285       (setq items (1+ items)))
 286     (goto-char p1)
 287     (while (< item-nr items)
 288       (setq item-nr (1+ item-nr))
 289       (re-search-forward "<dt>\\([ ]*\\)" (point-max) t)
 290       (when (match-string 1)
 291         (delete-region (point) (- (point) (string-width (match-string 1)))))
 292       (let ((def-p1 (point))
 293             (def-p2 0))
 294         (re-search-forward "\\([ ]*\\)\\(</dt>\\|<dd>\\)" (point-max) t)
 295         (if (match-string 1)
 296             (progn
 297               (let* ((mw1 (string-width (match-string 1)))
 298                      (mw2 (string-width (match-string 2)))
 299                      (mw  (+ mw1 mw2)))
 300                 (goto-char (- (point) mw))
 301                 (delete-region (point) (+ (point) mw1))
 302                 (setq def-p2 (point))))
 303           (setq def-p2 (- (point) (string-width (match-string 2)))))
 304         (put-text-property def-p1 def-p2 'face 'bold)))))
 305
 306 (defun html2text-delete-tags (p1 p2 p3 p4)
 307   (delete-region p1 p2)
 308   (delete-region (- p3 (- p2 p1)) (- p4 (- p2 p1))))
 309
 310 (defun html2text-delete-single-tag (p1 p2)
 311   (delete-region p1 p2))
 312
 313 (defun html2text-clean-hr (p1 p2)
 314   (html2text-delete-single-tag p1 p2)
 315   (goto-char p1)
 316   (newline 1)
 317   (insert (make-string fill-column ?-))
 318   )
 319
 320 (defun html2text-clean-ul (p1 p2 p3 p4)
 321   (html2text-delete-tags p1 p2 p3 p4)
 322   (html2text-clean-list-items p1 (- p3 (- p1 p2)) "ul")
 323   )
 324
 325 (defun html2text-clean-ol (p1 p2 p3 p4)
 326   (html2text-delete-tags p1 p2 p3 p4)
 327   (html2text-clean-list-items p1 (- p3 (- p1 p2)) "ol")
 328   )
 329
 330 (defun html2text-clean-dl (p1 p2 p3 p4)
 331   (html2text-delete-tags p1 p2 p3 p4)
 332   (html2text-clean-dtdd p1 (- p3 (- p1 p2)))
 333   )
 334
 335 (defun html2text-clean-center (p1 p2 p3 p4)
 336   (html2text-delete-tags p1 p2 p3 p4)
 337   (center-region p1 (- p3 (- p2 p1)))
 338   )
 339
 340 (defun html2text-clean-bold (p1 p2 p3 p4)
 341   (put-text-property p2 p3 'face 'bold)
 342   (html2text-delete-tags p1 p2 p3 p4)
 343   )
 344
 345 (defun html2text-clean-title (p1 p2 p3 p4)
 346   (put-text-property p2 p3 'face 'bold)
 347   (html2text-delete-tags p1 p2 p3 p4)
 348   )
 349
 350 (defun html2text-clean-underline (p1 p2 p3 p4)
 351   (put-text-property p2 p3 'face 'underline)
 352   (html2text-delete-tags p1 p2 p3 p4)
 353   )
 354
 355 (defun html2text-clean-italic (p1 p2 p3 p4)
 356   (put-text-property p2 p3 'face 'italic)
 357   (html2text-delete-tags p1 p2 p3 p4)
 358   )
 359
 360 (defun html2text-clean-font (p1 p2 p3 p4)
 361   (html2text-delete-tags p1 p2 p3 p4)
 362   )
 363
 364 (defun html2text-clean-blockquote (p1 p2 p3 p4)
 365   (html2text-delete-tags p1 p2 p3 p4)
 366   )
 367
 368 (defun html2text-clean-anchor (p1 p2 p3 p4)
 369   ;; If someone can explain how to make the URL clickable I will
 370   ;; surely improve upon this.
 371   (let* ((attr-list (html2text-get-attr p1 p2 "a"))
 372          (href (html2text-attr-value attr-list "href")))
 373     (delete-region p1 p4)
 374     (when href
 375       (goto-char p1)
 376       (insert (substring href 1 -1 ))
 377       (put-text-property p1 (point) 'face 'bold))))
 378
 379 ;;
 380 ;; </Functions to be called to format a tag-pair>
 381 ;;
 382
 383 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 384 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 385
 386 ;;
 387 ;; <Functions to be called to fix up paragraphs>
 388 ;;
 389
 390 (defun html2text-fix-paragraph (p1 p2)
 391   (goto-char p1)
 392   (let ((has-br-line)
 393         (refill-start)
 394         (refill-stop))
 395     (if (re-search-forward "<br>$" p2 t)
 396         (setq has-br-line t)
 397       )
 398     (if has-br-line
 399         (progn
 400           (goto-char p1)
 401           (if (re-search-forward ".+[^<][^b][^r][^>]$" p2 t)
 402               (progn
 403                 (beginning-of-line)
 404                 (setq refill-start (point))
 405                 (goto-char p2)
 406                 (re-search-backward ".+[^<][^b][^r][^>]$" refill-start t)
 407                 (next-line 1)
 408                 (end-of-line)
 409                 ;; refill-stop should ideally be adjusted to
 410                 ;; accomodate the "<br>" strings which are removed
 411                 ;; between refill-start and refill-stop.  Can simply
 412                 ;; be returned from my-replace-string
 413                 (setq refill-stop (+ (point)
 414                                      (html2text-replace-string
 415                                       "<br>" ""
 416                                       refill-start (point))))
 417                 ;; (message "Point = %s  refill-stop = %s" (point) refill-stop)
 418                 ;; (sleep-for 4)
 419                 (fill-region refill-start refill-stop)
 420                 )
 421             )
 422           )
 423       )
 424     )
 425   (html2text-replace-string "<br>" "" p1 p2)
 426   )
 427
 428 ;;
 429 ;; This one is interactive ...
 430 ;;
 431 (defun html2text-fix-paragraphs ()
 432   "This _tries_ to fix up the paragraphs - this is done in quite a ad-hook
 433 fashion, quite close to pure guess-work. It does work in some cases though."
 434   (interactive)
 435   (html2text-buffer-head)
 436   (replace-regexp "^<br>$" "")
 437   ;; Removing lonely <br> on a single line, if they are left intact we
 438   ;; dont have any paragraphs at all.
 439   (html2text-buffer-head)
 440   (while (not (eobp))
 441     (let ((p1 (point)))
 442       (forward-paragraph 1)
 443       ;;(message "Kaller fix med p1=%s  p2=%s " p1 (1- (point))) (sleep-for 5)
 444       (html2text-fix-paragraph p1 (1- (point)))
 445       (goto-char p1)
 446       (when (not (eobp))
 447         (forward-paragraph 1)))))
 448
 449 ;;
 450 ;; </Functions to be called to fix up paragraphs>
 451 ;;
 452
 453 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 454 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 455
 456 ;;
 457 ;; <Interactive functions>
 458 ;;
 459
 460 (defun html2text-remove-tags (tag-list)
 461   "Removes the tags listed in the list \"html2text-remove-tag-list\".
 462 See the documentation for that variable."
 463   (interactive)
 464   (dolist (tag tag-list)
 465     (html2text-buffer-head)
 466     (while (re-search-forward (format "\\(</?%s[^>]*>\\)" tag) (point-max) t)
 467       (delete-region (match-beginning 0) (match-end 0)))))
 468
 469 (defun html2text-format-tags ()
 470   "See the variable \"html2text-format-tag-list\" for documentation"
 471   (interactive)
 472   (dolist (tag-and-function html2text-format-tag-list)
 473     (let ((tag      (car tag-and-function))
 474           (function (cdr tag-and-function)))
 475       (html2text-buffer-head)
 476       (while (re-search-forward (format "\\(<%s\\( [^>]*\\)?>\\)" tag)
 477                                 (point-max) t)
 478         (let ((p1)
 479               (p2 (point))
 480               (p3) (p4)
 481               (attr (match-string 1)))
 482           (search-backward "<" (point-min) t)
 483           (setq p1 (point))
 484           (re-search-forward (format "</%s>" tag) (point-max) t)
 485           (setq p4 (point))
 486           (search-backward "</" (point-min) t)
 487           (setq p3 (point))
 488           (funcall function p1 p2 p3 p4)
 489           (goto-char p1)
 490           )
 491         )
 492       )
 493     )
 494   )
 495
 496 (defun html2text-substitute ()
 497   "See the variable \"html2text-replace-list\" for documentation"
 498   (interactive)
 499   (dolist (e html2text-replace-list)
 500     (html2text-buffer-head)
 501     (let ((old-string (car e))
 502           (new-string (cdr e)))
 503       (html2text-replace-string old-string new-string (point-min) (point-max))
 504       )
 505     )
 506   )
 507
 508 (defun html2text-format-single-elements ()
 509   ""
 510   (interactive)
 511   (dolist (tag-and-function html2text-format-single-element-list)
 512     (let ((tag      (car tag-and-function))
 513           (function (cdr tag-and-function)))
 514       (html2text-buffer-head)
 515       (while (re-search-forward (format "\\(<%s\\( [^>]*\\)?>\\)" tag)
 516                                 (point-max) t)
 517         (let ((p1)
 518               (p2 (point)))
 519           (search-backward "<" (point-min) t)
 520           (setq p1 (point))
 521           (funcall function p1 p2)
 522           )
 523         )
 524       )
 525     )
 526   )
 527
 528 ;;
 529 ;; Main function
 530 ;;
 531
 532 ;;;###autoload
 533 (defun html2text ()
 534   "Convert HTML to plain text in the current buffer."
 535   (interactive)
 536   (save-excursion
 537     (let ((case-fold-search t)
 538           (buffer-read-only))
 539       (html2text-remove-tags html2text-remove-tag-list)
 540       (html2text-format-tags)
 541       (html2text-remove-tags html2text-remove-tag-list2)
 542       (html2text-substitute)
 543       (html2text-format-single-elements)
 544       (html2text-fix-paragraphs))))
 545
 546 ;;
 547 ;; </Interactive functions>
 548 ;;
 549
 550 ;;; arch-tag: e9e57b79-35d4-4de1-a647-e7e01fe56d1e
 551 ;;; html2text.el ends here