includes/HtmlFormatter.php

   1 <?php
   2 /**
   3  * Performs transformations of HTML by wrapping around libxml2 and working
   4  * around its countless bugs.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License along
  17  * with this program; if not, write to the Free Software Foundation, Inc.,
  18  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  19  * http://www.gnu.org/copyleft/gpl.html
  20  *
  21  * @file
  22  */
  23 class HtmlFormatter {
  24         /**
  25          * @var DOMDocument
  26          */
  27         private $doc;
  28
  29         private $html;
  30         private $itemsToRemove = [];
  31         private $elementsToFlatten = [];
  32         protected $removeMedia = false;
  33
  34         /**
  35          * Constructor
  36          *
  37          * @param string $html Text to process
  38          */
  39         public function __construct( $html ) {
  40                 $this->html = $html;
  41         }
  42
  43         /**
  44          * Turns a chunk of HTML into a proper document
  45          * @param string $html
  46          * @return string
  47          */
  48         public static function wrapHTML( $html ) {
  49                 return '<!doctype html><html><head></head><body>' . $html . '</body></html>';
  50         }
  51
  52         /**
  53          * Override this in descendant class to modify HTML after it has been converted from DOM tree
  54          * @param string $html HTML to process
  55          * @return string Processed HTML
  56          */
  57         protected function onHtmlReady( $html ) {
  58                 return $html;
  59         }
  60
  61         /**
  62          * @return DOMDocument DOM to manipulate
  63          */
  64         public function getDoc() {
  65                 if ( !$this->doc ) {
  66                         // DOMDocument::loadHTML isn't very good with encodings, so
  67                         // convert input to ASCII by encoding everything above 128 as entities.
  68                         $html = mb_convert_encoding( $this->html, 'HTML-ENTITIES', 'UTF-8' );
  69
  70                         // Workaround for bug that caused spaces before references
  71                         // to disappear during processing: https://phabricator.wikimedia.org/T55086
  72                         // TODO: Please replace with a better fix if one can be found.
  73                         $html = str_replace( ' <', '&#32;<', $html );
  74
  75                         libxml_use_internal_errors( true );
  76                         $loader = libxml_disable_entity_loader();
  77                         $this->doc = new DOMDocument();
  78                         $this->doc->strictErrorChecking = false;
  79                         $this->doc->loadHTML( $html );
  80                         libxml_disable_entity_loader( $loader );
  81                         libxml_use_internal_errors( false );
  82                         $this->doc->encoding = 'UTF-8';
  83                 }
  84                 return $this->doc;
  85         }
  86
  87         /**
  88          * Sets whether images/videos/sounds should be removed from output
  89          * @param bool $flag
  90          */
  91         public function setRemoveMedia( $flag = true ) {
  92                 $this->removeMedia = $flag;
  93         }
  94
  95         /**
  96          * Adds one or more selector of content to remove. A subset of CSS selector
  97          * syntax is supported:
  98          *
  99          *   <tag>
 100          *   <tag>.class
 101          *   .<class>
 102          *   #<id>
 103          *
 104          * @param array|string $selectors Selector(s) of stuff to remove
 105          */
 106         public function remove( $selectors ) {
 107                 $this->itemsToRemove = array_merge( $this->itemsToRemove, (array)$selectors );
 108         }
 109
 110         /**
 111          * Adds one or more element name to the list to flatten (remove tag, but not its content)
 112          * Can accept undelimited regexes
 113          *
 114          * Note this interface may fail in surprising unexpected ways due to usage of regexes,
 115          * so should not be relied on for HTML markup security measures.
 116          *
 117          * @param array|string $elements Name(s) of tag(s) to flatten
 118          */
 119         public function flatten( $elements ) {
 120                 $this->elementsToFlatten = array_merge( $this->elementsToFlatten, (array)$elements );
 121         }
 122
 123         /**
 124          * Instructs the formatter to flatten all tags
 125          */
 126         public function flattenAllTags() {
 127                 $this->flatten( '[?!]?[a-z0-9]+' );
 128         }
 129
 130         /**
 131          * Removes content we've chosen to remove.  The text of the removed elements can be
 132          * extracted with the getText method.
 133          * @return array Array of removed DOMElements
 134          */
 135         public function filterContent() {
 136                 $removals = $this->parseItemsToRemove();
 137
 138                 // Bail out early if nothing to do
 139                 if ( array_reduce( $removals,
 140                         function ( $carry, $item ) {
 141                                 return $carry && !$item;
 142                         },
 143                         true
 144                 ) ) {
 145                         return [];
 146                 }
 147
 148                 $doc = $this->getDoc();
 149
 150                 // Remove tags
 151
 152                 // You can't remove DOMNodes from a DOMNodeList as you're iterating
 153                 // over them in a foreach loop. It will seemingly leave the internal
 154                 // iterator on the foreach out of wack and results will be quite
 155                 // strange. Though, making a queue of items to remove seems to work.
 156                 $domElemsToRemove = [];
 157                 foreach ( $removals['TAG'] as $tagToRemove ) {
 158                         $tagToRemoveNodes = $doc->getElementsByTagName( $tagToRemove );
 159                         foreach ( $tagToRemoveNodes as $tagToRemoveNode ) {
 160                                 if ( $tagToRemoveNode ) {
 161                                         $domElemsToRemove[] = $tagToRemoveNode;
 162                                 }
 163                         }
 164                 }
 165                 $removed = $this->removeElements( $domElemsToRemove );
 166
 167                 // Elements with named IDs
 168                 $domElemsToRemove = [];
 169                 foreach ( $removals['ID'] as $itemToRemove ) {
 170                         $itemToRemoveNode = $doc->getElementById( $itemToRemove );
 171                         if ( $itemToRemoveNode ) {
 172                                 $domElemsToRemove[] = $itemToRemoveNode;
 173                         }
 174                 }
 175                 $removed = array_merge( $removed, $this->removeElements( $domElemsToRemove ) );
 176
 177                 // CSS Classes
 178                 $domElemsToRemove = [];
 179                 $xpath = new DOMXPath( $doc );
 180                 foreach ( $removals['CLASS'] as $classToRemove ) {
 181                         $elements = $xpath->query( '//*[contains(@class, "' . $classToRemove . '")]' );
 182
 183                         /** @var $element DOMElement */
 184                         foreach ( $elements as $element ) {
 185                                 $classes = $element->getAttribute( 'class' );
 186                                 if ( preg_match( "/\b$classToRemove\b/", $classes ) && $element->parentNode ) {
 187                                         $domElemsToRemove[] = $element;
 188                                 }
 189                         }
 190                 }
 191                 $removed = array_merge( $removed, $this->removeElements( $domElemsToRemove ) );
 192
 193                 // Tags with CSS Classes
 194                 foreach ( $removals['TAG_CLASS'] as $classToRemove ) {
 195                         $parts = explode( '.', $classToRemove );
 196
 197                         $elements = $xpath->query(
 198                                 '//' . $parts[0] . '[@class="' . $parts[1] . '"]'
 199                         );
 200                         $removed = array_merge( $removed, $this->removeElements( $elements ) );
 201                 }
 202
 203                 return $removed;
 204         }
 205
 206         /**
 207          * Removes a list of elelments from DOMDocument
 208          * @param array|DOMNodeList $elements
 209          * @return array Array of removed elements
 210          */
 211         private function removeElements( $elements ) {
 212                 $list = $elements;
 213                 if ( $elements instanceof DOMNodeList ) {
 214                         $list = [];
 215                         foreach ( $elements as $element ) {
 216                                 $list[] = $element;
 217                         }
 218                 }
 219                 /** @var $element DOMElement */
 220                 foreach ( $list as $element ) {
 221                         if ( $element->parentNode ) {
 222                                 $element->parentNode->removeChild( $element );
 223                         }
 224                 }
 225                 return $list;
 226         }
 227
 228         /**
 229          * libxml in its usual pointlessness converts many chars to entities - this function
 230          * perfoms a reverse conversion
 231          * @param string $html
 232          * @return string
 233          */
 234         private function fixLibXML( $html ) {
 235                 static $replacements;
 236                 if ( !$replacements ) {
 237                         // We don't include rules like '&#34;' => '&amp;quot;' because entities had already been
 238                         // normalized by libxml. Using this function with input not sanitized by libxml is UNSAFE!
 239                         $replacements = new ReplacementArray( [
 240                                 '&quot;' => '&amp;quot;',
 241                                 '&amp;' => '&amp;amp;',
 242                                 '&lt;' => '&amp;lt;',
 243                                 '&gt;' => '&amp;gt;',
 244                         ] );
 245                 }
 246                 $html = $replacements->replace( $html );
 247
 248                 // Just in case the conversion in getDoc() above used named
 249                 // entities that aren't known to html_entity_decode().
 250                 $html = mb_convert_encoding( $html, 'UTF-8', 'HTML-ENTITIES' );
 251
 252                 return $html;
 253         }
 254
 255         /**
 256          * Performs final transformations and returns resulting HTML.  Note that if you want to call this
 257          * both without an element and with an element you should call it without an element first.  If you
 258          * specify the $element in the method it'll change the underlying dom and you won't be able to get
 259          * it back.
 260          *
 261          * @param DOMElement|string|null $element ID of element to get HTML from or
 262          *   false to get it from the whole tree
 263          * @return string Processed HTML
 264          */
 265         public function getText( $element = null ) {
 266
 267                 if ( $this->doc ) {
 268                         if ( $element !== null && !( $element instanceof DOMElement ) ) {
 269                                 $element = $this->doc->getElementById( $element );
 270                         }
 271                         if ( $element ) {
 272                                 $body = $this->doc->getElementsByTagName( 'body' )->item( 0 );
 273                                 $nodesArray = [];
 274                                 foreach ( $body->childNodes as $node ) {
 275                                         $nodesArray[] = $node;
 276                                 }
 277                                 foreach ( $nodesArray as $nodeArray ) {
 278                                         $body->removeChild( $nodeArray );
 279                                 }
 280                                 $body->appendChild( $element );
 281                         }
 282                         $html = $this->doc->saveHTML();
 283
 284                         $html = $this->fixLibXML( $html );
 285                         if ( wfIsWindows() ) {
 286                                 // Cleanup for CRLF misprocessing of unknown origin on Windows.
 287                                 // If this error continues in the future, please track it down in the
 288                                 // XML code paths if possible and fix there.
 289                                 $html = str_replace( '&#13;', '', $html );
 290                         }
 291                 } else {
 292                         $html = $this->html;
 293                 }
 294                 // Remove stuff added by wrapHTML()
 295                 $html = preg_replace( '/<!--.*?-->|^.*?<body>|<\/body>.*$/s', '', $html );
 296                 $html = $this->onHtmlReady( $html );
 297
 298                 if ( $this->elementsToFlatten ) {
 299                         $elements = implode( '|', $this->elementsToFlatten );
 300                         $html = preg_replace( "#</?($elements)\\b[^>]*>#is", '', $html );
 301                 }
 302
 303                 return $html;
 304         }
 305
 306         /**
 307          * Helper function for parseItemsToRemove(). This function extracts the selector type
 308          * and the raw name of a selector from a CSS-style selector string and assigns those
 309          * values to parameters passed by reference. For example, if given '#toc' as the
 310          * $selector parameter, it will assign 'ID' as the $type and 'toc' as the $rawName.
 311          * @param string $selector CSS selector to parse
 312          * @param string $type The type of selector (ID, CLASS, TAG_CLASS, or TAG)
 313          * @param string $rawName The raw name of the selector
 314          * @return bool Whether the selector was successfully recognised
 315          * @throws MWException
 316          */
 317         protected function parseSelector( $selector, &$type, &$rawName ) {
 318                 if ( strpos( $selector, '.' ) === 0 ) {
 319                         $type = 'CLASS';
 320                         $rawName = substr( $selector, 1 );
 321                 } elseif ( strpos( $selector, '#' ) === 0 ) {
 322                         $type = 'ID';
 323                         $rawName = substr( $selector, 1 );
 324                 } elseif ( strpos( $selector, '.' ) !== 0 && strpos( $selector, '.' ) !== false ) {
 325                         $type = 'TAG_CLASS';
 326                         $rawName = $selector;
 327                 } elseif ( strpos( $selector, '[' ) === false && strpos( $selector, ']' ) === false ) {
 328                         $type = 'TAG';
 329                         $rawName = $selector;
 330                 } else {
 331                         throw new MWException( __METHOD__ . "(): unrecognized selector '$selector'" );
 332                 }
 333
 334                 return true;
 335         }
 336
 337         /**
 338          * Transforms CSS-style selectors into an internal representation suitable for
 339          * processing by filterContent()
 340          * @return array
 341          */
 342         protected function parseItemsToRemove() {
 343                 $removals = [
 344                         'ID' => [],
 345                         'TAG' => [],
 346                         'CLASS' => [],
 347                         'TAG_CLASS' => [],
 348                 ];
 349
 350                 foreach ( $this->itemsToRemove as $itemToRemove ) {
 351                         $type = '';
 352                         $rawName = '';
 353                         if ( $this->parseSelector( $itemToRemove, $type, $rawName ) ) {
 354                                 $removals[$type][] = $rawName;
 355                         }
 356                 }
 357
 358                 if ( $this->removeMedia ) {
 359                         $removals['TAG'][] = 'img';
 360                         $removals['TAG'][] = 'audio';
 361                         $removals['TAG'][] = 'video';
 362                 }
 363
 364                 return $removals;
 365         }
 366 }