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 abstract class ContentHandler {
  24
  25     /**
  26      * Conveniance function for getting flat text from a Content object. This shleould only
  27      * be used in the context of backwards compatibility with code that is not yet able
  28      * to handle Content objects!
  29      *
  30      * If $content is equal to null or false, this method returns the empty string.
  31      *
  32      * If $content is an instance of TextContent, this method returns the flat text as returned by $content->getnativeData().
  33      *
  34      * If $content is not a TextContent object, the bahaviour of this method depends on the global $wgContentHandlerTextFallback:
  35      * If $wgContentHandlerTextFallback is 'fail' and $content is not a TextContent object, an MWException is thrown.
  36      * If $wgContentHandlerTextFallback is 'serialize' and $content is not a TextContent object, $content->serialize()
  37      * is called to get a string form of the content.
  38      * Otherwise, this method returns null.
  39      *
  40      * @static
  41      * @param Content|null $content
  42      * @return null|string the textual form of $content, if available
  43      * @throws MWException if $content is not an instance of TextContent and $wgContentHandlerTextFallback was set to 'fail'.
  44      */
  45     public static function getContentText( Content $content = null ) {
  46         global $wgContentHandlerTextFallback;
  47
  48         if ( is_null( $content ) ) {
  49                         return '';
  50                 }
  51
  52         if ( $content instanceof TextContent ) {
  53             return $content->getNativeData();
  54         }
  55
  56         if ( $wgContentHandlerTextFallback == 'fail' ) {
  57                         throw new MWException( "Attempt to get text from Content with model " . $content->getModelName() );
  58                 }
  59
  60         if ( $wgContentHandlerTextFallback == 'serialize' ) {
  61                         return $content->serialize();
  62                 }
  63
  64         return null;
  65     }
  66
  67     /**
  68      * Conveniance function for creating a Content object from a given textual representation.
  69      *
  70      * $text will be deserialized into a Content object of the model specified by $modelName (or,
  71      * if that is not given, $title->getContentModelName()) using the given format.
  72      *
  73      * @static
  74      * @param $text the textual represenation, will be unserialized to create the Content object
  75      * @param Title $title the title of the page this text belongs to, required as a context for deserialization
  76      * @param null|String $modelName the model to deserialize to. If not provided, $title->getContentModelName() is used.
  77      * @param null|String $format the format to use for deserialization. If not given, the model's default format is used.
  78      *
  79      * @return Content a Content object representing $text
  80      */
  81     public static function makeContent( $text, Title $title, $modelName = null, $format = null ) {
  82
  83         if ( is_null( $modelName ) ) {
  84             $modelName = $title->getContentModelName();
  85         }
  86
  87         $handler = ContentHandler::getForModelName( $modelName );
  88         return $handler->unserialize( $text, $format );
  89     }
  90
  91     /**
  92      * Returns the name of the default content model to be used for the page with the given title.
  93      *
  94      * Note: There should rarely be need to call this method directly.
  95      * To determine the actual content model for a given page, use Title::getContentModelName().
  96      *
  97      * Which model is to be used per default for the page is determined based on several factors:
  98      * * The global setting $wgNamespaceContentModels specifies a content model per namespace.
  99      * * The hook DefaultModelFor may be used to override the page's default model.
 100      * * Pages in NS_MEDIAWIKI and NS_USER default to the CSS or JavaScript model if they end in .js or .css, respectively.
 101      * * Pages in NS_MEDIAWIKI default to the wikitext model otherwise.
 102      * * 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.
 103      * * The hook TitleIsWikitextPage may be used to force a page to use the wikitext model.
 104      *
 105      * If none of the above applies, the wikitext model is used.
 106      *
 107      * Note: this is used by, and may thus not use, Title::getContentModelName()
 108      *
 109      * @static
 110      * @param Title $title
 111      * @return null|string default model name for the page given by $title
 112      */
 113     public static function getDefaultModelFor( Title $title ) {
 114         global $wgNamespaceContentModels;
 115
 116         // NOTE: this method must not rely on $title->getContentModelName() directly or indirectly,
 117         //       because it is used to initialized the mContentModelName memebr.
 118
 119         $ns = $title->getNamespace();
 120
 121         $ext = false;
 122         $m = null;
 123         $model = null;
 124
 125         if ( !empty( $wgNamespaceContentModels[ $ns ] ) ) {
 126             $model = $wgNamespaceContentModels[ $ns ];
 127         }
 128
 129         // hook can determin default model
 130         if ( !wfRunHooks( 'DefaultModelFor', array( $title, &$model ) ) ) { #FIXME: document new hook!
 131             if ( !is_null( $model ) ) {
 132                                 return $model;
 133                         }
 134         }
 135
 136         // Could this page contain custom CSS or JavaScript, based on the title?
 137         $isCssOrJsPage = NS_MEDIAWIKI == $ns && preg_match( '!\.(css|js)$!u', $title->getText(), $m );
 138         if ( $isCssOrJsPage ) {
 139                         $ext = $m[1];
 140                 }
 141
 142         // hook can force js/css
 143         wfRunHooks( 'TitleIsCssOrJsPage', array( $title, &$isCssOrJsPage ) );
 144
 145         // Is this a .css subpage of a user page?
 146         $isJsCssSubpage = NS_USER == $ns && !$isCssOrJsPage && preg_match( "/\\/.*\\.(js|css)$/", $title->getText(), $m );
 147         if ( $isJsCssSubpage ) {
 148                         $ext = $m[1];
 149                 }
 150
 151         // is this wikitext, according to $wgNamespaceContentModels or the DefaultModelFor hook?
 152         $isWikitext = is_null( $model ) || $model == CONTENT_MODEL_WIKITEXT;
 153         $isWikitext = $isWikitext && !$isCssOrJsPage && !$isJsCssSubpage;
 154
 155         // hook can override $isWikitext
 156         wfRunHooks( 'TitleIsWikitextPage', array( $title, &$isWikitext ) );
 157
 158         if ( !$isWikitext ) {
 159                         switch ( $ext ) {
 160                                 case 'js':
 161                                         return CONTENT_MODEL_JAVASCRIPT;
 162                                 case 'css':
 163                                         return CONTENT_MODEL_CSS;
 164                                 default:
 165                                         return is_null( $model ) ? CONTENT_MODEL_TEXT : $model;
 166                         }
 167         }
 168
 169         // we established that is must be wikitext
 170
 171         return CONTENT_MODEL_WIKITEXT;
 172     }
 173
 174     /**
 175      * returns the appropriate ContentHandler singleton for the given title
 176      *
 177      * @static
 178      * @param Title $title
 179      * @return ContentHandler
 180      */
 181     public static function getForTitle( Title $title ) {
 182         $modelName = $title->getContentModelName();
 183         return ContentHandler::getForModelName( $modelName );
 184     }
 185
 186     /**
 187      * returns the appropriate ContentHandler singleton for the given Content object
 188      *
 189      * @static
 190      * @param Content $content
 191      * @return ContentHandler
 192      */
 193     public static function getForContent( Content $content ) {
 194         $modelName = $content->getModelName();
 195         return ContentHandler::getForModelName( $modelName );
 196     }
 197
 198     /**
 199      * returns the ContentHandler singleton for the given model name. Use the CONTENT_MODEL_XXX constants to
 200      * identify the desired content model.
 201      *
 202      * ContentHandler singletons are take from the global $wgContentHandlers array. Keys in that array are
 203      * model names, the values are either ContentHandler singleton objects, or strings specifying the appropriate
 204      * subclass of ContentHandler.
 205      *
 206      * If a class name in encountered when looking up the singleton for a given model name, the class is
 207      * instantiated and the class name is replaced by te resulting singleton in $wgContentHandlers.
 208      *
 209      * If no ContentHandler is defined for the desired $modelName, the ContentHandler may be provided by the
 210      * a ContentHandlerForModelName hook. if no Contenthandler can be determined, an MWException is raised.
 211      *
 212      * @static
 213      * @param $modelName String the name of the content model for which to get a handler. Use CONTENT_MODEL_XXX constants.
 214      * @return ContentHandler the ContentHandler singleton for handling the model given by $modelName
 215      * @throws MWException if no handler is known for $modelName.
 216      */
 217     public static function getForModelName( $modelName ) {
 218         global $wgContentHandlers;
 219
 220         if ( empty( $wgContentHandlers[$modelName] ) ) {
 221             $handler = null;
 222
 223                         // TODO: document new hook
 224             wfRunHooks( 'ContentHandlerForModelName', array( $modelName, &$handler ) );
 225
 226             if ( $handler ) { // NOTE: may be a string or an object, either is fine!
 227                 $wgContentHandlers[$modelName] = $handler;
 228             } else {
 229                 throw new MWException( "No handler for model $modelName registered in \$wgContentHandlers" );
 230             }
 231         }
 232
 233         if ( is_string( $wgContentHandlers[$modelName] ) ) {
 234             $class = $wgContentHandlers[$modelName];
 235             $wgContentHandlers[$modelName] = new $class( $modelName );
 236         }
 237
 238         return $wgContentHandlers[$modelName];
 239     }
 240
 241     // ----------------------------------------------------------------------------------------------------------
 242
 243     /**
 244      * Constructor, initializing the ContentHandler instance with it's model name and a list of supported formats.
 245      * Values for the parameters are typically provided as literals by subclasses' constructors.
 246      *
 247      * @param String $modelName (use CONTENT_MODEL_XXX constants).
 248      * @param array $formats list for supported serialization formats (typically as MIME types)
 249      */
 250     public function __construct( $modelName, $formats ) {
 251         $this->mModelName = $modelName;
 252         $this->mSupportedFormats = $formats;
 253     }
 254
 255
 256     /**
 257      * Serializes Content object of the type supported by this ContentHandler.
 258      *
 259      * @FIXME: bad method name: suggests it serializes a ContentHandler, while in fact it serializes a Content object
 260      *
 261      * @abstract
 262      * @param Content $content the Content object to serialize
 263      * @param null $format the desired serialization format
 264      * @return String serialized form of the content
 265      */
 266     public abstract function serialize( Content $content, $format = null );
 267
 268     /**
 269      * Unserializes a Content object of the type supported by this ContentHandler.
 270      *
 271      * @FIXME: bad method name: suggests it unserializes a ContentHandler, while in fact it unserializes a Content object
 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 unserialize( $blob, $format = null );
 279
 280     /**
 281      * Creates an empty Content object of the type supported by this ContentHandler.
 282      *
 283      * @FIXME: bad method name: suggests it empties the content of an instance rather then creating a new empty one
 284      */
 285     public abstract function emptyContent();
 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 $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 serialize() and unserialize() 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 $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 $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 actiuon 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()->getModelName() );
 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      * @todo rename to createDifferenceEngine for consistency.
 429      */
 430     public function getDifferenceEngine( IContextSource $context, $old = 0, $new = 0, $rcid = 0, #FIMXE: use everywhere!
 431                                          $refreshCache = false, $unhide = false ) {
 432
 433         $this->checkModelName( $context->getTitle()->getModelName() );
 434
 435                 $diffEngineClass = $this->getDiffEngineClass();
 436
 437         return new $diffEngineClass( $context, $old, $new, $rcid, $refreshCache, $unhide );
 438     }
 439
 440         /**
 441          * Returns the name of the diff engine to use.
 442          *
 443          * @since 0.1
 444          *
 445          * @return string
 446          */
 447         protected function getDiffEngineClass() {
 448                 return 'DifferenceEngine';
 449         }
 450
 451     /**
 452      * attempts to merge differences between three versions.
 453      * Returns a new Content object for a clean merge and false for failure or a conflict.
 454      *
 455      * This default implementation always returns false.
 456      *
 457      * @param $oldContent String
 458      * @param $myContent String
 459      * @param $yourContent String
 460      * @return Content|Bool
 461      */
 462     public function merge3( Content $oldContent, Content $myContent, Content $yourContent ) {
 463         return false;
 464     }
 465
 466     /**
 467      * Return an applicable autosummary if one exists for the given edit.
 468      *
 469      * @param $oldContent Content|null: the previous text of the page.
 470      * @param $newContent Content|null: The submitted text of the page.
 471      * @param $flags Int bitmask: a bitmask of flags submitted for the edit.
 472      *
 473      * @return string An appropriate autosummary, or an empty string.
 474      */
 475     public function getAutosummary( Content $oldContent = null, Content $newContent = null, $flags ) {
 476         global $wgContLang;
 477
 478         // Decide what kind of autosummary is needed.
 479
 480         // Redirect autosummaries
 481
 482         $ot = !empty( $ot ) ? $oldContent->getRedirectTarget() : false;
 483         $rt = !empty( $rt ) ? $newContent->getRedirectTarget() : false;
 484
 485         if ( is_object( $rt ) && ( !is_object( $ot ) || !$rt->equals( $ot ) || $ot->getFragment() != $rt->getFragment() ) ) {
 486
 487             $truncatedtext = $newContent->getTextForSummary(
 488                 250
 489                     - strlen( wfMsgForContent( 'autoredircomment' ) )
 490                     - strlen( $rt->getFullText() ) );
 491
 492             return wfMsgForContent( 'autoredircomment', $rt->getFullText(), $truncatedtext );
 493         }
 494
 495         // New page autosummaries
 496         if ( $flags & EDIT_NEW && $newContent->getSize() > 0 ) {
 497             // If they're making a new article, give its text, truncated, in the summary.
 498
 499             $truncatedtext = $newContent->getTextForSummary(
 500                 200 - strlen( wfMsgForContent( 'autosumm-new' ) ) );
 501
 502             return wfMsgForContent( 'autosumm-new', $truncatedtext );
 503         }
 504
 505         // Blanking autosummaries
 506         if ( $oldContent->getSize() > 0 && $newContent->getSize() == 0 ) {
 507             return wfMsgForContent( 'autosumm-blank' );
 508         } elseif ( $oldContent->getSize() > 10 * $newContent->getSize() && $newContent->getSize() < 500 ) {
 509             // Removing more than 90% of the article
 510
 511             $truncatedtext = $newContent->getTextForSummary(
 512                 200 - strlen( wfMsgForContent( 'autosumm-replace' ) ) );
 513
 514             return wfMsgForContent( 'autosumm-replace', $truncatedtext );
 515         }
 516
 517         // If we reach this point, there's no applicable autosummary for our case, so our
 518         // autosummary is empty.
 519
 520         return '';
 521     }
 522
 523     /**
 524      * Auto-generates a deletion reason
 525      *
 526      * @param $title Title: the page's title
 527      * @param &$hasHistory Boolean: whether the page has a history
 528      * @return mixed String containing deletion reason or empty string, or boolean false
 529      *    if no revision occurred
 530      *
 531      * @todo &$hasHistory is extremely ugly, it's here because WikiPage::getAutoDeleteReason() and Article::getReason() have it / want it.
 532      */
 533     public function getAutoDeleteReason( Title $title, &$hasHistory ) {
 534         $dbw = wfGetDB( DB_MASTER );
 535
 536         // Get the last revision
 537         $rev = Revision::newFromTitle( $title );
 538
 539         if ( is_null( $rev ) ) {
 540             return false;
 541         }
 542
 543         // Get the article's contents
 544         $content = $rev->getContent();
 545         $blank = false;
 546
 547         // If the page is blank, use the text from the previous revision,
 548         // which can only be blank if there's a move/import/protect dummy revision involved
 549         if ( $content->getSize() == 0 ) {
 550             $prev = $rev->getPrevious();
 551
 552             if ( $prev )        {
 553                 $content = $rev->getContent();
 554                 $blank = true;
 555             }
 556         }
 557
 558         // Find out if there was only one contributor
 559         // Only scan the last 20 revisions
 560         $res = $dbw->select( 'revision', 'rev_user_text',
 561             array( 'rev_page' => $title->getArticleID(), $dbw->bitAnd( 'rev_deleted', Revision::DELETED_USER ) . ' = 0' ),
 562             __METHOD__,
 563             array( 'LIMIT' => 20 )
 564         );
 565
 566         if ( $res === false ) {
 567             // This page has no revisions, which is very weird
 568             return false;
 569         }
 570
 571         $hasHistory = ( $res->numRows() > 1 );
 572         $row = $dbw->fetchObject( $res );
 573
 574         if ( $row ) { // $row is false if the only contributor is hidden
 575             $onlyAuthor = $row->rev_user_text;
 576             // Try to find a second contributor
 577             foreach ( $res as $row ) {
 578                 if ( $row->rev_user_text != $onlyAuthor ) { // Bug 22999
 579                     $onlyAuthor = false;
 580                     break;
 581                 }
 582             }
 583         } else {
 584             $onlyAuthor = false;
 585         }
 586
 587         // Generate the summary with a '$1' placeholder
 588         if ( $blank ) {
 589             // The current revision is blank and the one before is also
 590             // blank. It's just not our lucky day
 591             $reason = wfMsgForContent( 'exbeforeblank', '$1' );
 592         } else {
 593             if ( $onlyAuthor ) {
 594                 $reason = wfMsgForContent( 'excontentauthor', '$1', $onlyAuthor );
 595             } else {
 596                 $reason = wfMsgForContent( 'excontent', '$1' );
 597             }
 598         }
 599
 600         if ( $reason == '-' ) {
 601             // Allow these UI messages to be blanked out cleanly
 602             return '';
 603         }
 604
 605         // Max content length = max comment length - length of the comment (excl. $1)
 606         $text = $content->getTextForSummary( 255 - ( strlen( $reason ) - 2 ) );
 607
 608         // Now replace the '$1' placeholder
 609         $reason = str_replace( '$1', $text, $reason );
 610
 611         return $reason;
 612     }
 613
 614     /**
 615      * Get the Content object that needs to be saved in order to undo all revisions
 616      * between $undo and $undoafter. Revisions must belong to the same page,
 617      * must exist and must not be deleted
 618      * @param $undo Revision
 619      * @param $undoafter null|Revision Must be an earlier revision than $undo
 620      * @return mixed string on success, false on failure
 621      */
 622     public function getUndoContent( Revision $current, Revision $undo, Revision $undoafter = null ) {
 623         $cur_content = $current->getContent();
 624
 625         if ( empty( $cur_content ) ) {
 626             return false; // no page
 627         }
 628
 629         $undo_content = $undo->getContent();
 630         $undoafter_content = $undoafter->getContent();
 631
 632         if ( $cur_content->equals( $undo_content ) ) {
 633             // No use doing a merge if it's just a straight revert.
 634             return $undoafter_content;
 635         }
 636
 637         $undone_content = $this->merge3( $undo_content, $undoafter_content, $cur_content );
 638
 639         return $undone_content;
 640     }
 641 }
 642
 643
 644 abstract class TextContentHandler extends ContentHandler {
 645
 646     public function __construct( $modelName, $formats ) {
 647         parent::__construct( $modelName, $formats );
 648     }
 649
 650     public function serialize( Content $content, $format = null ) {
 651         $this->checkFormat( $format );
 652         return $content->getNativeData();
 653     }
 654
 655     /**
 656      * attempts to merge differences between three versions.
 657      * Returns a new Content object for a clean merge and false for failure or a conflict.
 658      *
 659      * This text-based implementation uses wfMerge().
 660      *
 661      * @param $oldContent String
 662      * @param $myContent String
 663      * @param $yourContent String
 664      * @return Content|Bool
 665      */
 666     public function merge3( Content $oldContent, Content $myContent, Content $yourContent ) {
 667         $this->checkModelName( $oldContent->getModelName() );
 668         #TODO: check that all Content objects have the same content model! #XXX: what to do if they don't?
 669
 670         $format = $this->getDefaultFormat();
 671
 672         $old = $this->serialize( $oldContent, $format );
 673         $mine = $this->serialize( $myContent, $format );
 674         $yours = $this->serialize( $yourContent, $format );
 675
 676         $ok = wfMerge( $old, $mine, $yours, $result );
 677
 678         if ( !$ok ) {
 679                         return false;
 680                 }
 681
 682         if ( !$result ) {
 683                         return $this->emptyContent();
 684                 }
 685
 686         $mergedContent = $this->unserialize( $result, $format );
 687         return $mergedContent;
 688     }
 689
 690
 691 }
 692 class WikitextContentHandler extends TextContentHandler {
 693
 694     public function __construct( $modelName = CONTENT_MODEL_WIKITEXT ) {
 695         parent::__construct( $modelName, array( 'application/x-wikitext' ) ); #FIXME: mime
 696     }
 697
 698     public function unserialize( $text, $format = null ) {
 699         $this->checkFormat( $format );
 700
 701         return new WikitextContent( $text );
 702     }
 703
 704     public function emptyContent() {
 705         return new WikitextContent( '' );
 706     }
 707
 708
 709 }
 710
 711 #TODO: make ScriptContentHandler base class with plugin interface for syntax highlighting!
 712
 713 class JavaScriptContentHandler extends TextContentHandler {
 714
 715     public function __construct( $modelName = CONTENT_MODEL_WIKITEXT ) {
 716         parent::__construct( $modelName, array( 'text/javascript' ) ); #XXX: or use $wgJsMimeType? this is for internal storage, not HTTP...
 717     }
 718
 719     public function unserialize( $text, $format = null ) {
 720         return new JavaScriptContent( $text );
 721     }
 722
 723     public function emptyContent() {
 724         return new JavaScriptContent( '' );
 725     }
 726 }
 727
 728 class CssContentHandler extends TextContentHandler {
 729
 730     public function __construct( $modelName = CONTENT_MODEL_WIKITEXT ) {
 731         parent::__construct( $modelName, array( 'text/css' ) );
 732     }
 733
 734     public function unserialize( $text, $format = null ) {
 735         return new CssContent( $text );
 736     }
 737
 738     public function emptyContent() {
 739         return new CssContent( '' );
 740     }
 741
 742 }