includes/ContentHandler.php

   1 <?php
   2
   3 class MWContentSerializationException extends MWException {
   4
   5 }
   6
   7
   8 /**
   9  * A content handler knows how do deal with a specific type of content on a wiki page.
  10  * Content is stored in the database in a serialized form (using a serialization format aka mime type)
  11  * and is be unserialized into it's native PHP represenation (the content model), which is wrappe in
  12  * an instance of the appropriate subclass of Content.
  13  *
  14  * ContentHandler instances are stateless singletons that serve, among other things, as a factory for
  15  * Content objects. Generally, there is one subclass of ContentHandler and one subclass of Content
  16  * for every type of content model.
  17  *
  18  * Some content types have a flat model, that is, their native represenation is the
  19  * same as their serialized form. Examples would be JavaScript and CSS code. As of now,
  20  * this also applies to wikitext (mediawiki's default content type), but wikitext
  21  * content may be represented by a DOM or AST structure in the future.
  22  *
  23  * @since 1.WD
  24  */
  25 abstract class ContentHandler {
  26
  27         /**
  28          * Conveniance function for getting flat text from a Content object. This should only
  29          * be used in the context of backwards compatibility with code that is not yet able
  30          * to handle Content objects!
  31          *
  32          * If $content is null, this method returns the empty string.
  33          *
  34          * If $content is an instance of TextContent, this method returns the flat text as returned by $content->getNativeData().
  35          *
  36          * If $content is not a TextContent object, the bahaviour of this method depends on the global $wgContentHandlerTextFallback:
  37          * * If $wgContentHandlerTextFallback is 'fail' and $content is not a TextContent object, an MWException is thrown.
  38          * * If $wgContentHandlerTextFallback is 'serialize' and $content is not a TextContent object, $content->serialize()
  39          * is called to get a string form of the content.
  40          * * If $wgContentHandlerTextFallback is 'ignore' and $content is not a TextContent object, this method returns null.
  41          * * otherwise, the behaviour is undefined.
  42          *
  43          * @static
  44          * @param Content|null $content
  45          * @return null|string the textual form of $content, if available
  46          * @throws MWException if $content is not an instance of TextContent and $wgContentHandlerTextFallback was set to 'fail'.
  47          */
  48         public static function getContentText( Content $content = null ) {
  49                 global $wgContentHandlerTextFallback;
  50
  51                 if ( is_null( $content ) ) {
  52                         return '';
  53                 }
  54
  55                 if ( $content instanceof TextContent ) {
  56                         return $content->getNativeData();
  57                 }
  58
  59                 if ( $wgContentHandlerTextFallback == 'fail' ) {
  60                         throw new MWException( "Attempt to get text from Content with model " . $content->getModelName() );
  61                 }
  62
  63                 if ( $wgContentHandlerTextFallback == 'serialize' ) {
  64                         return $content->serialize();
  65                 }
  66
  67                 return null;
  68         }
  69
  70         /**
  71          * Conveniance function for creating a Content object from a given textual representation.
  72          *
  73          * $text will be deserialized into a Content object of the model specified by $modelName (or,
  74          * if that is not given, $title->getContentModelName()) using the given format.
  75          *
  76          * @static
  77          * @param string $text the textual represenation, will be unserialized to create the Content object
  78          * @param Title $title the title of the page this text belongs to, required as a context for deserialization
  79          * @param null|String $modelName the model to deserialize to. If not provided, $title->getContentModelName() is used.
  80          * @param null|String $format the format to use for deserialization. If not given, the model's default format is used.
  81          *
  82          * @return Content a Content object representing $text
  83          * @throw MWException if $model or $format is not supported or if $text can not be unserialized using $format.
  84          */
  85         public static function makeContent( $text, Title $title, $modelName = null, $format = null ) {
  86
  87                 if ( is_null( $modelName ) ) {
  88                         $modelName = $title->getContentModelName();
  89                 }
  90
  91                 $handler = ContentHandler::getForModelName( $modelName );
  92                 return $handler->unserializeContent( $text, $format );
  93         }
  94
  95         /**
  96          * Returns the name of the default content model to be used for the page with the given title.
  97          *
  98          * Note: There should rarely be need to call this method directly.
  99          * To determine the actual content model for a given page, use Title::getContentModelName().
 100          *
 101          * Which model is to be used per default for the page is determined based on several factors:
 102          * * The global setting $wgNamespaceContentModels specifies a content model per namespace.
 103          * * The hook DefaultModelFor may be used to override the page's default model.
 104          * * Pages in NS_MEDIAWIKI and NS_USER default to the CSS or JavaScript model if they end in .js or .css, respectively.
 105          * * Pages in NS_MEDIAWIKI default to the wikitext model otherwise.
 106          * * The hook TitleIsCssOrJsPage may be used to force a page to use the CSS or JavaScript model if they end in .js or .css, respectively.
 107          * * The hook TitleIsWikitextPage may be used to force a page to use the wikitext model.
 108          *
 109          * If none of the above applies, the wikitext model is used.
 110          *
 111          * Note: this is used by, and may thus not use, Title::getContentModelName()
 112          *
 113          * @static
 114          * @param Title $title
 115          * @return null|string default model name for the page given by $title
 116          */
 117         public static function getDefaultModelFor( Title $title ) {
 118                 global $wgNamespaceContentModels;
 119
 120                 // NOTE: this method must not rely on $title->getContentModelName() directly or indirectly,
 121                 //       because it is used to initialized the mContentModelName memebr.
 122
 123                 $ns = $title->getNamespace();
 124
 125                 $ext = false;
 126                 $m = null;
 127                 $model = null;
 128
 129                 if ( !empty( $wgNamespaceContentModels[ $ns ] ) ) {
 130                         $model = $wgNamespaceContentModels[ $ns ];
 131                 }
 132
 133                 // hook can determin default model
 134                 if ( !wfRunHooks( 'DefaultModelFor', array( $title, &$model ) ) ) { #FIXME: document new hook!
 135                         if ( !is_null( $model ) ) {
 136                                 return $model;
 137                         }
 138                 }
 139
 140                 // Could this page contain custom CSS or JavaScript, based on the title?
 141                 $isCssOrJsPage = NS_MEDIAWIKI == $ns && preg_match( '!\.(css|js)$!u', $title->getText(), $m );
 142                 if ( $isCssOrJsPage ) {
 143                         $ext = $m[1];
 144                 }
 145
 146                 // hook can force js/css
 147                 wfRunHooks( 'TitleIsCssOrJsPage', array( $title, &$isCssOrJsPage ) );
 148
 149                 // Is this a .css subpage of a user page?
 150                 $isJsCssSubpage = NS_USER == $ns && !$isCssOrJsPage && preg_match( "/\\/.*\\.(js|css)$/", $title->getText(), $m );
 151                 if ( $isJsCssSubpage ) {
 152                         $ext = $m[1];
 153                 }
 154
 155                 // is this wikitext, according to $wgNamespaceContentModels or the DefaultModelFor hook?
 156                 $isWikitext = is_null( $model ) || $model == CONTENT_MODEL_WIKITEXT;
 157                 $isWikitext = $isWikitext && !$isCssOrJsPage && !$isJsCssSubpage;
 158
 159                 // hook can override $isWikitext
 160                 wfRunHooks( 'TitleIsWikitextPage', array( $title, &$isWikitext ) );
 161
 162                 if ( !$isWikitext ) {
 163                         switch ( $ext ) {
 164                                 case 'js':
 165                                         return CONTENT_MODEL_JAVASCRIPT;
 166                                 case 'css':
 167                                         return CONTENT_MODEL_CSS;
 168                                 default:
 169                                         return is_null( $model ) ? CONTENT_MODEL_TEXT : $model;
 170                         }
 171                 }
 172
 173                 // we established that is must be wikitext
 174
 175                 return CONTENT_MODEL_WIKITEXT;
 176         }
 177
 178         /**
 179          * returns the appropriate ContentHandler singleton for the given title
 180          *
 181          * @static
 182          * @param Title $title
 183          * @return ContentHandler
 184          */
 185         public static function getForTitle( Title $title ) {
 186                 $modelName = $title->getContentModelName();
 187                 return ContentHandler::getForModelName( $modelName );
 188         }
 189
 190         /**
 191          * returns the appropriate ContentHandler singleton for the given Content object
 192          *
 193          * @static
 194          * @param Content $content
 195          * @return ContentHandler
 196          */
 197         public static function getForContent( Content $content ) {
 198                 $modelName = $content->getModelName();
 199                 return ContentHandler::getForModelName( $modelName );
 200         }
 201
 202         /**
 203          * returns the ContentHandler singleton for the given model name. Use the CONTENT_MODEL_XXX constants to
 204          * identify the desired content model.
 205          *
 206          * ContentHandler singletons are take from the global $wgContentHandlers array. Keys in that array are
 207          * model names, the values are either ContentHandler singleton objects, or strings specifying the appropriate
 208          * subclass of ContentHandler.
 209          *
 210          * If a class name in encountered when looking up the singleton for a given model name, the class is
 211          * instantiated and the class name is replaced by te resulting singleton in $wgContentHandlers.
 212          *
 213          * If no ContentHandler is defined for the desired $modelName, the ContentHandler may be provided by the
 214          * a ContentHandlerForModelName hook. if no Contenthandler can be determined, an MWException is raised.
 215          *
 216          * @static
 217          * @param $modelName String the name of the content model for which to get a handler. Use CONTENT_MODEL_XXX constants.
 218          * @return ContentHandler the ContentHandler singleton for handling the model given by $modelName
 219          * @throws MWException if no handler is known for $modelName.
 220          */
 221         public static function getForModelName( $modelName ) {
 222                 global $wgContentHandlers;
 223
 224                 if ( empty( $wgContentHandlers[$modelName] ) ) {
 225                         $handler = null;
 226
 227                         // FIXME: document new hook
 228                         wfRunHooks( 'ContentHandlerForModelName', array( $modelName, &$handler ) );
 229
 230                         if ( $handler ) { // NOTE: may be a string or an object, either is fine!
 231                                 $wgContentHandlers[$modelName] = $handler;
 232                         } else {
 233                                 throw new MWException( "No handler for model $modelName registered in \$wgContentHandlers" );
 234                         }
 235                 }
 236
 237                 if ( is_string( $wgContentHandlers[$modelName] ) ) {
 238                         $class = $wgContentHandlers[$modelName];
 239                         $wgContentHandlers[$modelName] = new $class( $modelName );
 240                 }
 241
 242                 return $wgContentHandlers[$modelName];
 243         }
 244
 245         // ----------------------------------------------------------------------------------------------------------
 246
 247         /**
 248          * Constructor, initializing the ContentHandler instance with it's model name and a list of supported formats.
 249          * Values for the parameters are typically provided as literals by subclasses' constructors.
 250          *
 251          * @param String $modelName (use CONTENT_MODEL_XXX constants).
 252          * @param array $formats list for supported serialization formats (typically as MIME types)
 253          */
 254         public function __construct( $modelName, $formats ) {
 255                 $this->mModelName = $modelName;
 256                 $this->mSupportedFormats = $formats;
 257         }
 258
 259
 260         /**
 261          * Serializes Content object of the type supported by this ContentHandler.
 262          *
 263          * @abstract
 264          * @param Content $content the Content object to serialize
 265          * @param null $format the desired serialization format
 266          * @return String serialized form of the content
 267          */
 268         public abstract function serializeContent( Content $content, $format = null );
 269
 270         /**
 271          * Unserializes a Content object of the type supported by this ContentHandler.
 272          *
 273          * @abstract
 274          * @param $blob String serialized form of the content
 275          * @param null $format the format used for serialization
 276          * @return Content the Content object created by deserializing $blob
 277          */
 278         public abstract function unserializeContent( $blob, $format = null );
 279
 280         /**
 281          * Creates an empty Content object of the type supported by this ContentHandler.
 282          *
 283          * @return Content
 284          */
 285         public abstract function makeEmptyContent();
 286
 287         /**
 288          * Returns the model name that identifies the content model this ContentHandler can handle.
 289          * Use with the CONTENT_MODEL_XXX constants.
 290          *
 291          * @return String the model name
 292          */
 293         public function getModelName() {
 294                 return $this->mModelName;
 295         }
 296
 297         /**
 298          * Throws an MWException if $modelName is not the content model handeled by this ContentHandler.
 299          *
 300          * @param String $modelName the model name to check
 301          */
 302         protected function checkModelName( $modelName ) {
 303                 if ( $modelName !== $this->mModelName ) {
 304                         throw new MWException( "Bad content model: expected " . $this->mModelName . " but got found " . $modelName );
 305                 }
 306         }
 307
 308         /**
 309          * Returns a list of serialization formats supported by the serializeContent() and unserializeContent() methods of
 310          * this ContentHandler.
 311          *
 312          * @return array of serialization formats as MIME type like strings
 313          */
 314         public function getSupportedFormats() {
 315                 return $this->mSupportedFormats;
 316         }
 317
 318         /**
 319          * The format used for serialization/deserialization per default by this ContentHandler.
 320          *
 321          * This default implementation will return the first element of the array of formats
 322          * that was passed to the constructor.
 323          *
 324          * @return String the name of the default serialiozation format as a MIME type
 325          */
 326         public function getDefaultFormat() {
 327                 return $this->mSupportedFormats[0];
 328         }
 329
 330         /**
 331          * Returns true if $format is a serialization format supported by this ContentHandler,
 332          * and false otherwise.
 333          *
 334          * Note that if $format is null, this method always returns true, because null
 335          * means "use the default format".
 336          *
 337          * @param String $format the serialization format to check
 338          * @return bool
 339          */
 340         public function isSupportedFormat( $format ) {
 341
 342                 if ( !$format ) {
 343                         return true; // this means "use the default"
 344                 }
 345
 346                 return in_array( $format, $this->mSupportedFormats );
 347         }
 348
 349         /**
 350          * Throws an MWException if isSupportedFormat( $format ) is not true. Convenient
 351          * for checking whether a format provided as a parameter is actually supported.
 352          *
 353          * @param String $format the serialization format to check
 354          */
 355         protected function checkFormat( $format ) {
 356                 if ( !$this->isSupportedFormat( $format ) ) {
 357                         throw new MWException( "Format $format is not supported for content model " . $this->getModelName() );
 358                 }
 359         }
 360
 361         /**
 362          * Returns overrides for action handlers.
 363          * Classes listed here will be used instead of the default one when
 364          * (and only when) $wgActions[$action] === true. This allows subclasses
 365          * to override the default action handlers.
 366          *
 367          * @return Array
 368          */
 369         public function getActionOverrides() {
 370                 return array();
 371         }
 372
 373         /**
 374          * Return an Article object suitable for viewing the given object
 375          *
 376          * NOTE: does *not* do special handling for Image and Category pages!
 377          *       Use Article::newFromTitle() for that!
 378          *
 379          * @param Title $title
 380          * @return Article
 381          * @todo Article is being refactored into an action class, keep track of that
 382          * @todo Article really defines the view of the content... rename this method to createViewPage ?
 383          */
 384         public function createArticle( Title $title ) {
 385                 $this->checkModelName( $title->getContentModelName() );
 386
 387                 $article = new Article($title);
 388                 return $article;
 389         }
 390
 391         /**
 392          * Return an EditPage object suitable for editing the given object
 393          *
 394          * @param Article $article
 395          * @return EditPage
 396          */
 397         public function createEditPage( Article $article ) {
 398                 $this->checkModelName( $article->getContentModelName() );
 399
 400                 $editPage = new EditPage( $article );
 401                 return $editPage;
 402         }
 403
 404         /**
 405          * Return an ExternalEdit object suitable for editing the given object
 406          *
 407          * @param IContextSource $context
 408          * @return ExternalEdit
 409          * @todo does anyone or anythign actually use the external edit facility? Can we just deprecate and ignore it?
 410          */
 411         public function createExternalEdit( IContextSource $context ) {
 412                 $this->checkModelName( $context->getTitle()->getContentModelName() );
 413
 414                 $externalEdit = new ExternalEdit( $context );
 415                 return $externalEdit;
 416         }
 417
 418         /**
 419          * Factory
 420          * @param $context IContextSource context to use, anything else will be ignored
 421          * @param $old Integer old ID we want to show and diff with.
 422          * @param $new String either 'prev' or 'next'.
 423          * @param $rcid Integer ??? FIXME (default 0)
 424          * @param $refreshCache boolean If set, refreshes the diff cache
 425          * @param $unhide boolean If set, allow viewing deleted revs
 426          *
 427          * @return DifferenceEngine
 428          */
 429         public function createDifferenceEngine( IContextSource $context, $old = 0, $new = 0, $rcid = 0, #FIMXE: use everywhere!
 430                                                                                  $refreshCache = false, $unhide = false ) {
 431
 432                 $this->checkModelName( $context->getTitle()->getContentModelName() );
 433
 434                 $diffEngineClass = $this->getDiffEngineClass();
 435
 436                 return new $diffEngineClass( $context, $old, $new, $rcid, $refreshCache, $unhide );
 437         }
 438
 439         /**
 440          * Returns the name of the diff engine to use.
 441          *
 442          * @since 0.1
 443          *
 444          * @return string
 445          */
 446         protected function getDiffEngineClass() {
 447                 return 'DifferenceEngine';
 448         }
 449
 450         /**
 451          * attempts to merge differences between three versions.
 452          * Returns a new Content object for a clean merge and false for failure or a conflict.
 453          *
 454          * This default implementation always returns false.
 455          *
 456          * @param $oldContent String
 457          * @param $myContent String
 458          * @param $yourContent String
 459          * @return Content|Bool
 460          */
 461         public function merge3( Content $oldContent, Content $myContent, Content $yourContent ) {
 462                 return false;
 463         }
 464
 465         /**
 466          * Return an applicable autosummary if one exists for the given edit.
 467          *
 468          * @param $oldContent Content|null: the previous text of the page.
 469          * @param $newContent Content|null: The submitted text of the page.
 470          * @param $flags Int bitmask: a bitmask of flags submitted for the edit.
 471          *
 472          * @return string An appropriate autosummary, or an empty string.
 473          */
 474         public function getAutosummary( Content $oldContent = null, Content $newContent = null, $flags ) {
 475                 global $wgContLang;
 476
 477                 // Decide what kind of autosummary is needed.
 478
 479                 // Redirect autosummaries
 480
 481                 /**
 482                  * @var $ot Title
 483                  * @var $rt Title
 484                  */
 485
 486                 $ot = !is_null( $oldContent ) ? $oldContent->getRedirectTarget() : null;
 487                 $rt = !is_null( $newContent ) ? $newContent->getRedirectTarget() : null;
 488
 489                 if ( is_object( $rt ) && ( !is_object( $ot ) || !$rt->equals( $ot ) || $ot->getFragment() != $rt->getFragment() ) ) {
 490
 491                         $truncatedtext = $newContent->getTextForSummary(
 492                                 250
 493                                         - strlen( wfMsgForContent( 'autoredircomment' ) )
 494                                         - strlen( $rt->getFullText() ) );
 495
 496                         return wfMsgForContent( 'autoredircomment', $rt->getFullText(), $truncatedtext );
 497                 }
 498
 499                 // New page autosummaries
 500                 if ( $flags & EDIT_NEW && $newContent->getSize() > 0 ) {
 501                         // If they're making a new article, give its text, truncated, in the summary.
 502
 503                         $truncatedtext = $newContent->getTextForSummary(
 504                                 200 - strlen( wfMsgForContent( 'autosumm-new' ) ) );
 505
 506                         return wfMsgForContent( 'autosumm-new', $truncatedtext );
 507                 }
 508
 509                 // Blanking autosummaries
 510                 if ( !empty( $oldContent ) && $oldContent->getSize() > 0 && $newContent->getSize() == 0 ) {
 511                         return wfMsgForContent( 'autosumm-blank' );
 512                 } elseif ( !empty( $oldContent ) && $oldContent->getSize() > 10 * $newContent->getSize() && $newContent->getSize() < 500 ) {
 513                         // Removing more than 90% of the article
 514
 515                         $truncatedtext = $newContent->getTextForSummary(
 516                                 200 - strlen( wfMsgForContent( 'autosumm-replace' ) ) );
 517
 518                         return wfMsgForContent( 'autosumm-replace', $truncatedtext );
 519                 }
 520
 521                 // If we reach this point, there's no applicable autosummary for our case, so our
 522                 // autosummary is empty.
 523
 524                 return '';
 525         }
 526
 527         /**
 528          * Auto-generates a deletion reason
 529          *
 530          * @param $title Title: the page's title
 531          * @param &$hasHistory Boolean: whether the page has a history
 532          * @return mixed String containing deletion reason or empty string, or boolean false
 533          *    if no revision occurred
 534          *
 535          * @XXX &$hasHistory is extremely ugly, it's here because WikiPage::getAutoDeleteReason() and Article::getReason() have it / want it.
 536          */
 537         public function getAutoDeleteReason( Title $title, &$hasHistory ) {
 538                 $dbw = wfGetDB( DB_MASTER );
 539
 540                 // Get the last revision
 541                 $rev = Revision::newFromTitle( $title );
 542
 543                 if ( is_null( $rev ) ) {
 544                         return false;
 545                 }
 546
 547                 // Get the article's contents
 548                 $content = $rev->getContent();
 549                 $blank = false;
 550
 551                 // If the page is blank, use the text from the previous revision,
 552                 // which can only be blank if there's a move/import/protect dummy revision involved
 553                 if ( $content->getSize() == 0 ) {
 554                         $prev = $rev->getPrevious();
 555
 556                         if ( $prev )    {
 557                                 $content = $rev->getContent();
 558                                 $blank = true;
 559                         }
 560                 }
 561
 562                 // Find out if there was only one contributor
 563                 // Only scan the last 20 revisions
 564                 $res = $dbw->select( 'revision', 'rev_user_text',
 565                         array( 'rev_page' => $title->getArticleID(), $dbw->bitAnd( 'rev_deleted', Revision::DELETED_USER ) . ' = 0' ),
 566                         __METHOD__,
 567                         array( 'LIMIT' => 20 )
 568                 );
 569
 570                 if ( $res === false ) {
 571                         // This page has no revisions, which is very weird
 572                         return false;
 573                 }
 574
 575                 $hasHistory = ( $res->numRows() > 1 );
 576                 $row = $dbw->fetchObject( $res );
 577
 578                 if ( $row ) { // $row is false if the only contributor is hidden
 579                         $onlyAuthor = $row->rev_user_text;
 580                         // Try to find a second contributor
 581                         foreach ( $res as $row ) {
 582                                 if ( $row->rev_user_text != $onlyAuthor ) { // Bug 22999
 583                                         $onlyAuthor = false;
 584                                         break;
 585                                 }
 586                         }
 587                 } else {
 588                         $onlyAuthor = false;
 589                 }
 590
 591                 // Generate the summary with a '$1' placeholder
 592                 if ( $blank ) {
 593                         // The current revision is blank and the one before is also
 594                         // blank. It's just not our lucky day
 595                         $reason = wfMsgForContent( 'exbeforeblank', '$1' );
 596                 } else {
 597                         if ( $onlyAuthor ) {
 598                                 $reason = wfMsgForContent( 'excontentauthor', '$1', $onlyAuthor );
 599                         } else {
 600                                 $reason = wfMsgForContent( 'excontent', '$1' );
 601                         }
 602                 }
 603
 604                 if ( $reason == '-' ) {
 605                         // Allow these UI messages to be blanked out cleanly
 606                         return '';
 607                 }
 608
 609                 // Max content length = max comment length - length of the comment (excl. $1)
 610                 $text = $content->getTextForSummary( 255 - ( strlen( $reason ) - 2 ) );
 611
 612                 // Now replace the '$1' placeholder
 613                 $reason = str_replace( '$1', $text, $reason );
 614
 615                 return $reason;
 616         }
 617
 618         #@TODO: getSecondaryUpdatesForDeletion( Content ) returns an array of SecondaryDataUpdate objects
 619         #... or do that in the Content class?
 620
 621         /**
 622          * Get the Content object that needs to be saved in order to undo all revisions
 623          * between $undo and $undoafter. Revisions must belong to the same page,
 624          * must exist and must not be deleted
 625          * @param $current Revision the current text
 626          * @param $undo Revision the revision to undo
 627          * @param $undoafter Revision Must be an earlier revision than $undo
 628          * @return mixed string on success, false on failure
 629          */
 630         public function getUndoContent( Revision $current, Revision $undo, Revision $undoafter ) {
 631                 $cur_content = $current->getContent();
 632
 633                 if ( empty( $cur_content ) ) {
 634                         return false; // no page
 635                 }
 636
 637                 $undo_content = $undo->getContent();
 638                 $undoafter_content = $undoafter->getContent();
 639
 640                 if ( $cur_content->equals( $undo_content ) ) {
 641                         // No use doing a merge if it's just a straight revert.
 642                         return $undoafter_content;
 643                 }
 644
 645                 $undone_content = $this->merge3( $undo_content, $undoafter_content, $cur_content );
 646
 647                 return $undone_content;
 648         }
 649
 650         /**
 651          * Returns true for content models that support caching using the ParserCache mechanism.
 652          * See WikiPage::isParserCacheUser().
 653          *
 654          * @return bool
 655          */
 656         public function isParserCacheSupported() {
 657                 return true;
 658         }
 659 }
 660
 661
 662 abstract class TextContentHandler extends ContentHandler {
 663
 664         public function __construct( $modelName, $formats ) {
 665                 parent::__construct( $modelName, $formats );
 666         }
 667
 668         public function serializeContent( Content $content, $format = null ) {
 669                 $this->checkFormat( $format );
 670                 return $content->getNativeData();
 671         }
 672
 673         /**
 674          * attempts to merge differences between three versions.
 675          * Returns a new Content object for a clean merge and false for failure or a conflict.
 676          *
 677          * All three Content objects passed as parameters must have the same content model.
 678          *
 679          * This text-based implementation uses wfMerge().
 680          *
 681          * @param $oldContent String
 682          * @param $myContent String
 683          * @param $yourContent String
 684          * @return Content|Bool
 685          */
 686         public function merge3( Content $oldContent, Content $myContent, Content $yourContent ) {
 687                 $this->checkModelName( $oldContent->getModelName() );
 688                 $this->checkModelName( $myContent->getModelName() );
 689                 $this->checkModelName( $yourContent->getModelName() );
 690
 691                 $format = $this->getDefaultFormat();
 692
 693                 $old = $this->serializeContent( $oldContent, $format );
 694                 $mine = $this->serializeContent( $myContent, $format );
 695                 $yours = $this->serializeContent( $yourContent, $format );
 696
 697                 $ok = wfMerge( $old, $mine, $yours, $result );
 698
 699                 if ( !$ok ) {
 700                         return false;
 701                 }
 702
 703                 if ( !$result ) {
 704                         return $this->makeEmptyContent();
 705                 }
 706
 707                 $mergedContent = $this->unserializeContent( $result, $format );
 708                 return $mergedContent;
 709         }
 710
 711
 712 }
 713 class WikitextContentHandler extends TextContentHandler {
 714
 715         public function __construct( $modelName = CONTENT_MODEL_WIKITEXT ) {
 716                 parent::__construct( $modelName, array( 'text/x-wiki' ) );
 717         }
 718
 719         public function unserializeContent( $text, $format = null ) {
 720                 $this->checkFormat( $format );
 721
 722                 return new WikitextContent( $text );
 723         }
 724
 725         public function makeEmptyContent() {
 726                 return new WikitextContent( '' );
 727         }
 728
 729
 730 }
 731
 732 #XXX: make ScriptContentHandler base class with plugin interface for syntax highlighting?
 733
 734 class JavaScriptContentHandler extends TextContentHandler {
 735
 736         public function __construct( $modelName = CONTENT_MODEL_WIKITEXT ) {
 737                 parent::__construct( $modelName, array( 'text/javascript' ) ); #XXX: or use $wgJsMimeType? this is for internal storage, not HTTP...
 738         }
 739
 740         public function unserializeContent( $text, $format = null ) {
 741                 $this->checkFormat( $format );
 742
 743                 return new JavaScriptContent( $text );
 744         }
 745
 746         public function makeEmptyContent() {
 747                 return new JavaScriptContent( '' );
 748         }
 749 }
 750
 751 class CssContentHandler extends TextContentHandler {
 752
 753         public function __construct( $modelName = CONTENT_MODEL_WIKITEXT ) {
 754                 parent::__construct( $modelName, array( 'text/css' ) );
 755         }
 756
 757         public function unserializeContent( $text, $format = null ) {
 758                 $this->checkFormat( $format );
 759
 760                 return new CssContent( $text );
 761         }
 762
 763         public function makeEmptyContent() {
 764                 return new CssContent( '' );
 765         }
 766
 767 }