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 = array();
  31         private $elementsToFlatten = array();
  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                         $html = mb_convert_encoding( $this->html, 'HTML-ENTITIES', 'UTF-8' );
  67
  68                         // Workaround for bug that caused spaces before references
  69                         // to disappear during processing:
  70                         // https://bugzilla.wikimedia.org/show_bug.cgi?id=53086
  71                         //
  72                         // 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 of removed DOMElements
 134          */
 135         public function filterContent() {
 136                 wfProfileIn( __METHOD__ );
 137                 $removals = $this->parseItemsToRemove();
 138
 139                 // Bail out early if nothing to do
 140                 if ( array_reduce( $removals,
 141                         function( $carry, $item ) {
 142                                 return $carry && !$item;
 143                         },
 144                         true
 145                 ) ) {
 146                         wfProfileOut( __METHOD__ );
 147                         return array();
 148                 }
 149
 150                 $doc = $this->getDoc();
 151
 152                 // Remove tags
 153
 154                 // You can't remove DOMNodes from a DOMNodeList as you're iterating
 155                 // over them in a foreach loop. It will seemingly leave the internal
 156                 // iterator on the foreach out of wack and results will be quite
 157                 // strange. Though, making a queue of items to remove seems to work.
 158                 $domElemsToRemove = array();
 159                 foreach ( $removals['TAG'] as $tagToRemove ) {
 160                         $tagToRemoveNodes = $doc->getElementsByTagName( $tagToRemove );
 161                         foreach ( $tagToRemoveNodes as $tagToRemoveNode ) {
 162                                 if ( $tagToRemoveNode ) {
 163                                         $domElemsToRemove[] = $tagToRemoveNode;
 164                                 }
 165                         }
 166                 }
 167                 $removed = $this->removeElements( $domElemsToRemove );
 168
 169                 // Elements with named IDs
 170                 $domElemsToRemove = array();
 171                 foreach ( $removals['ID'] as $itemToRemove ) {
 172                         $itemToRemoveNode = $doc->getElementById( $itemToRemove );
 173                         if ( $itemToRemoveNode ) {
 174                                 $domElemsToRemove[] = $itemToRemoveNode;
 175                         }
 176                 }
 177                 $removed = array_merge( $removed, $this->removeElements( $domElemsToRemove ) );
 178
 179                 // CSS Classes
 180                 $domElemsToRemove = array();
 181                 $xpath = new DOMXpath( $doc );
 182                 foreach ( $removals['CLASS'] as $classToRemove ) {
 183                         $elements = $xpath->query( '//*[contains(@class, "' . $classToRemove . '")]' );
 184
 185                         /** @var $element DOMElement */
 186                         foreach ( $elements as $element ) {
 187                                 $classes = $element->getAttribute( 'class' );
 188                                 if ( preg_match( "/\b$classToRemove\b/", $classes ) && $element->parentNode ) {
 189                                         $domElemsToRemove[] = $element;
 190                                 }
 191                         }
 192                 }
 193                 $removed = array_merge( $removed, $this->removeElements( $domElemsToRemove ) );
 194
 195                 // Tags with CSS Classes
 196                 foreach ( $removals['TAG_CLASS'] as $classToRemove ) {
 197                         $parts = explode( '.', $classToRemove );
 198
 199                         $elements = $xpath->query(
 200                                 '//' . $parts[0] . '[@class="' . $parts[1] . '"]'
 201                         );
 202                         $removed = array_merge( $removed, $this->removeElements( $elements ) );
 203                 }
 204
 205                 wfProfileOut( __METHOD__ );
 206                 return $removed;
 207         }
 208
 209         /**
 210          * Removes a list of elelments from DOMDocument
 211          * @param array|DOMNodeList $elements
 212          * @return array of removed elements
 213          */
 214         private function removeElements( $elements ) {
 215                 $list = $elements;
 216                 if ( $elements instanceof DOMNodeList ) {
 217                         $list = array();
 218                         foreach ( $elements as $element ) {
 219                                 $list[] = $element;
 220                         }
 221                 }
 222                 /** @var $element DOMElement */
 223                 foreach ( $list as $element ) {
 224                         if ( $element->parentNode ) {
 225                                 $element->parentNode->removeChild( $element );
 226                         }
 227                 }
 228                 return $list;
 229         }
 230
 231         /**
 232          * libxml in its usual pointlessness converts many chars to entities - this function
 233          * perfoms a reverse conversion
 234          * @param string $html
 235          * @return string
 236          */
 237         private function fixLibXML( $html ) {
 238                 wfProfileIn( __METHOD__ );
 239                 static $replacements;
 240                 if ( ! $replacements ) {
 241                         // We don't include rules like '&#34;' => '&amp;quot;' because entities had already been
 242                         // normalized by libxml. Using this function with input not sanitized by libxml is UNSAFE!
 243                         $replacements = new ReplacementArray( array(
 244                                 '&quot;' => '&amp;quot;',
 245                                 '&amp;' => '&amp;amp;',
 246                                 '&lt;' => '&amp;lt;',
 247                                 '&gt;' => '&amp;gt;',
 248                         ) );
 249                 }
 250                 $html = $replacements->replace( $html );
 251                 $html = mb_convert_encoding( $html, 'UTF-8', 'HTML-ENTITIES' );
 252                 wfProfileOut( __METHOD__ );
 253                 return $html;
 254         }
 255
 256         /**
 257          * Performs final transformations and returns resulting HTML.  Note that if you want to call this
 258          * both without an element and with an element you should call it without an element first.  If you
 259          * specify the $element in the method it'll change the underlying dom and you won't be able to get
 260          * it back.
 261          *
 262          * @param DOMElement|string|null $element ID of element to get HTML from or
 263          *   false to get it from the whole tree
 264          * @return string Processed HTML
 265          */
 266         public function getText( $element = null ) {
 267                 wfProfileIn( __METHOD__ );
 268
 269                 if ( $this->doc ) {
 270                         wfProfileIn( __METHOD__ . '-dom' );
 271                         if ( $element !== null && !( $element instanceof DOMElement ) ) {
 272                                 $element = $this->doc->getElementById( $element );
 273                         }
 274                         if ( $element ) {
 275                                 $body = $this->doc->getElementsByTagName( 'body' )->item( 0 );
 276                                 $nodesArray = array();
 277                                 foreach ( $body->childNodes as $node ) {
 278                                         $nodesArray[] = $node;
 279                                 }
 280                                 foreach ( $nodesArray as $nodeArray ) {
 281                                         $body->removeChild( $nodeArray );
 282                                 }
 283                                 $body->appendChild( $element );
 284                         }
 285                         $html = $this->doc->saveHTML();
 286                         wfProfileOut( __METHOD__ . '-dom' );
 287
 288                         wfProfileIn( __METHOD__ . '-fixes' );
 289                         $html = $this->fixLibXml( $html );
 290                         if ( wfIsWindows() ) {
 291                                 // Cleanup for CRLF misprocessing of unknown origin on Windows.
 292                                 //
 293                                 // If this error continues in the future, please track it down in the
 294                                 // XML code paths if possible and fix there.
 295                                 $html = str_replace( '&#13;', '', $html );
 296                         }
 297                         wfProfileOut( __METHOD__ . '-fixes' );
 298                 } else {
 299                         $html = $this->html;
 300                 }
 301                 // Remove stuff added by wrapHTML()
 302                 $html = preg_replace( '/<!--.*?-->|^.*?<body>|<\/body>.*$/s', '', $html );
 303                 $html = $this->onHtmlReady( $html );
 304
 305                 wfProfileIn( __METHOD__ . '-flatten' );
 306                 if ( $this->elementsToFlatten ) {
 307                         $elements = implode( '|', $this->elementsToFlatten );
 308                         $html = preg_replace( "#</?($elements)\\b[^>]*>#is", '', $html );
 309                 }
 310                 wfProfileOut( __METHOD__ . '-flatten' );
 311
 312                 wfProfileOut( __METHOD__ );
 313                 return $html;
 314         }
 315
 316         /**
 317          * @param string $selector CSS selector to parse
 318          * @param string $type
 319          * @param string $rawName
 320          * @return bool Whether the selector was successfully recognised
 321          */
 322         protected function parseSelector( $selector, &$type, &$rawName ) {
 323                 if ( strpos( $selector, '.' ) === 0 ) {
 324                         $type = 'CLASS';
 325                         $rawName = substr( $selector, 1 );
 326                 } elseif ( strpos( $selector, '#' ) === 0 ) {
 327                         $type = 'ID';
 328                         $rawName = substr( $selector, 1 );
 329                 } elseif ( strpos( $selector, '.' ) !== 0 && strpos( $selector, '.' ) !== false ) {
 330                         $type = 'TAG_CLASS';
 331                         $rawName = $selector;
 332                 } elseif ( strpos( $selector, '[' ) === false && strpos( $selector, ']' ) === false ) {
 333                         $type = 'TAG';
 334                         $rawName = $selector;
 335                 } else {
 336                         throw new MWException( __METHOD__ . "(): unrecognized selector '$selector'" );
 337                 }
 338
 339                 return true;
 340         }
 341
 342         /**
 343          * Transforms CSS selectors into an internal representation suitable for processing
 344          * @return array
 345          */
 346         protected function parseItemsToRemove() {
 347                 wfProfileIn( __METHOD__ );
 348                 $removals = array(
 349                         'ID' => array(),
 350                         'TAG' => array(),
 351                         'CLASS' => array(),
 352                         'TAG_CLASS' => array(),
 353                 );
 354
 355                 foreach ( $this->itemsToRemove as $itemToRemove ) {
 356                         $type = '';
 357                         $rawName = '';
 358                         if ( $this->parseSelector( $itemToRemove, $type, $rawName ) ) {
 359                                 $removals[$type][] = $rawName;
 360                         }
 361                 }
 362
 363                 if ( $this->removeMedia ) {
 364                         $removals['TAG'][] = 'img';
 365                         $removals['TAG'][] = 'audio';
 366                         $removals['TAG'][] = 'video';
 367                 }
 368
 369                 wfProfileOut( __METHOD__ );
 370                 return $removals;
 371         }
 372 }