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
 132          */
 133         public function filterContent() {
 134                 wfProfileIn( __METHOD__ );
 135                 $removals = $this->parseItemsToRemove();
 136
 137                 if ( !$removals ) {
 138                         wfProfileOut( __METHOD__ );
 139                         return;
 140                 }
 141
 142                 $doc = $this->getDoc();
 143
 144                 // Remove tags
 145
 146                 // You can't remove DOMNodes from a DOMNodeList as you're iterating
 147                 // over them in a foreach loop. It will seemingly leave the internal
 148                 // iterator on the foreach out of wack and results will be quite
 149                 // strange. Though, making a queue of items to remove seems to work.
 150                 $domElemsToRemove = array();
 151                 foreach ( $removals['TAG'] as $tagToRemove ) {
 152                         $tagToRemoveNodes = $doc->getElementsByTagName( $tagToRemove );
 153                         foreach ( $tagToRemoveNodes as $tagToRemoveNode ) {
 154                                 if ( $tagToRemoveNode ) {
 155                                         $domElemsToRemove[] = $tagToRemoveNode;
 156                                 }
 157                         }
 158                 }
 159
 160                 $this->removeElements( $domElemsToRemove );
 161
 162                 // Elements with named IDs
 163                 $domElemsToRemove = array();
 164                 foreach ( $removals['ID'] as $itemToRemove ) {
 165                         $itemToRemoveNode = $doc->getElementById( $itemToRemove );
 166                         if ( $itemToRemoveNode ) {
 167                                 $domElemsToRemove[] = $itemToRemoveNode;
 168                         }
 169                 }
 170                 $this->removeElements( $domElemsToRemove );
 171
 172                 // CSS Classes
 173                 $domElemsToRemove = array();
 174                 $xpath = new DOMXpath( $doc );
 175                 foreach ( $removals['CLASS'] as $classToRemove ) {
 176                         $elements = $xpath->query( '//*[contains(@class, "' . $classToRemove . '")]' );
 177
 178                         /** @var $element DOMElement */
 179                         foreach ( $elements as $element ) {
 180                                 $classes = $element->getAttribute( 'class' );
 181                                 if ( preg_match( "/\b$classToRemove\b/", $classes ) && $element->parentNode ) {
 182                                         $domElemsToRemove[] = $element;
 183                                 }
 184                         }
 185                 }
 186                 $this->removeElements( $domElemsToRemove );
 187
 188                 // Tags with CSS Classes
 189                 foreach ( $removals['TAG_CLASS'] as $classToRemove ) {
 190                         $parts = explode( '.', $classToRemove );
 191
 192                         $elements = $xpath->query(
 193                                 '//' . $parts[0] . '[@class="' . $parts[1] . '"]'
 194                         );
 195
 196                         $this->removeElements( $elements );
 197                 }
 198
 199                 wfProfileOut( __METHOD__ );
 200         }
 201
 202         /**
 203          * Removes a list of elelments from DOMDocument
 204          * @param array|DOMNodeList $elements
 205          */
 206         private function removeElements( $elements ) {
 207                 $list = $elements;
 208                 if ( $elements instanceof DOMNodeList ) {
 209                         $list = array();
 210                         foreach ( $elements as $element ) {
 211                                 $list[] = $element;
 212                         }
 213                 }
 214                 /** @var $element DOMElement */
 215                 foreach ( $list as $element ) {
 216                         if ( $element->parentNode ) {
 217                                 $element->parentNode->removeChild( $element );
 218                         }
 219                 }
 220         }
 221
 222         /**
 223          * libxml in its usual pointlessness converts many chars to entities - this function
 224          * perfoms a reverse conversion
 225          * @param string $html
 226          * @return string
 227          */
 228         private function fixLibXML( $html ) {
 229                 wfProfileIn( __METHOD__ );
 230                 static $replacements;
 231                 if ( ! $replacements ) {
 232                         // We don't include rules like '&#34;' => '&amp;quot;' because entities had already been
 233                         // normalized by libxml. Using this function with input not sanitized by libxml is UNSAFE!
 234                         $replacements = new ReplacementArray( array(
 235                                 '&quot;' => '&amp;quot;',
 236                                 '&amp;' => '&amp;amp;',
 237                                 '&lt;' => '&amp;lt;',
 238                                 '&gt;' => '&amp;gt;',
 239                         ) );
 240                 }
 241                 $html = $replacements->replace( $html );
 242                 $html = mb_convert_encoding( $html, 'UTF-8', 'HTML-ENTITIES' );
 243                 wfProfileOut( __METHOD__ );
 244                 return $html;
 245         }
 246
 247         /**
 248          * Performs final transformations and returns resulting HTML
 249          *
 250          * @param DOMElement|string|null $element: ID of element to get HTML from or false to get it from the whole tree
 251          * @return string: Processed HTML
 252          */
 253         public function getText( $element = null ) {
 254                 wfProfileIn( __METHOD__ );
 255
 256                 if ( $this->doc ) {
 257                         if ( $element !== null && !( $element instanceof DOMElement ) ) {
 258                                 $element = $this->doc->getElementById( $element );
 259                         }
 260                         if ( $element ) {
 261                                 $body = $this->doc->getElementsByTagName( 'body' )->item( 0 );
 262                                 $nodesArray = array();
 263                                 foreach ( $body->childNodes as $node ) {
 264                                         $nodesArray[] = $node;
 265                                 }
 266                                 foreach ( $nodesArray as $nodeArray ) {
 267                                         $body->removeChild( $nodeArray );
 268                                 }
 269                                 $body->appendChild( $element );
 270                         }
 271                         $html = $this->doc->saveHTML();
 272                         $html = $this->fixLibXml( $html );
 273                 } else {
 274                         $html = $this->html;
 275                 }
 276                 if ( wfIsWindows() ) {
 277                         // Appears to be cleanup for CRLF misprocessing of unknown origin
 278                         // when running server on Windows platform.
 279                         //
 280                         // If this error continues in the future, please track it down in the
 281                         // XML code paths if possible and fix there.
 282                         $html = str_replace( '&#13;', '', $html );
 283                 }
 284                 $html = preg_replace( '/<!--.*?-->|^.*?<body>|<\/body>.*$/s', '', $html );
 285                 $html = $this->onHtmlReady( $html );
 286
 287                 if ( $this->elementsToFlatten ) {
 288                         $elements = implode( '|', $this->elementsToFlatten );
 289                         $html = preg_replace( "#</?($elements)\\b[^>]*>#is", '', $html );
 290                 }
 291
 292                 wfProfileOut( __METHOD__ );
 293                 return $html;
 294         }
 295
 296         /**
 297          * @param $selector: CSS selector to parse
 298          * @param $type
 299          * @param $rawName
 300          * @return bool: Whether the selector was successfully recognised
 301          */
 302         protected function parseSelector( $selector, &$type, &$rawName ) {
 303                 if ( strpos( $selector, '.' ) === 0 ) {
 304                         $type = 'CLASS';
 305                         $rawName = substr( $selector, 1 );
 306                 } elseif ( strpos( $selector, '#' ) === 0 ) {
 307                         $type = 'ID';
 308                         $rawName = substr( $selector, 1 );
 309                 } elseif ( strpos( $selector, '.' ) !== 0 &&
 310                         strpos( $selector, '.' ) !== false )
 311                 {
 312                         $type = 'TAG_CLASS';
 313                         $rawName = $selector;
 314                 } elseif ( strpos( $selector, '[' ) === false
 315                         && strpos( $selector, ']' ) === false )
 316                 {
 317                         $type = 'TAG';
 318                         $rawName = $selector;
 319                 } else {
 320                         throw new MWException( __METHOD__ . "(): unrecognized selector '$selector'" );
 321                 }
 322
 323                 return true;
 324         }
 325
 326         /**
 327          * Transforms CSS selectors into an internal representation suitable for processing
 328          * @return array
 329          */
 330         protected function parseItemsToRemove() {
 331                 wfProfileIn( __METHOD__ );
 332                 $removals = array(
 333                         'ID' => array(),
 334                         'TAG' => array(),
 335                         'CLASS' => array(),
 336                         'TAG_CLASS' => array(),
 337                 );
 338
 339                 foreach ( $this->itemsToRemove as $itemToRemove ) {
 340                         $type = '';
 341                         $rawName = '';
 342                         if ( $this->parseSelector( $itemToRemove, $type, $rawName ) ) {
 343                                 $removals[$type][] = $rawName;
 344                         }
 345                 }
 346
 347                 if ( $this->removeMedia ) {
 348                         $removals['TAG'][] = 'img';
 349                         $removals['TAG'][] = 'audio';
 350                         $removals['TAG'][] = 'video';
 351                 }
 352
 353                 wfProfileOut( __METHOD__ );
 354                 return $removals;
 355         }
 356 }