includes/ContentHandler.php

   1 <?php
   2
   3 /**
   4  * Exception representing a failure to serialize or unserialize a content object.
   5  */
   6 class MWContentSerializationException extends MWException {
   7
   8 }
   9
  10 /**
  11  * A content handler knows how do deal with a specific type of content on a wiki
  12  * page. Content is stored in the database in a serialized form (using a
  13  * serialization format a.k.a. MIME type) and is unserialized into its native
  14  * PHP representation (the content model), which is wrapped in an instance of
  15  * the appropriate subclass of Content.
  16  *
  17  * ContentHandler instances are stateless singletons that serve, among other
  18  * things, as a factory for Content objects. Generally, there is one subclass
  19  * of ContentHandler and one subclass of Content for every type of content model.
  20  *
  21  * Some content types have a flat model, that is, their native representation
  22  * is the same as their serialized form. Examples would be JavaScript and CSS
  23  * code. As of now, this also applies to wikitext (MediaWiki's default content
  24  * type), but wikitext content may be represented by a DOM or AST structure in
  25  * the future.
  26  *
  27  * @since 1.WD
  28  */
  29 abstract class ContentHandler {
  30
  31         /**
  32          * Convenience function for getting flat text from a Content object. This
  33          * should only be used in the context of backwards compatibility with code
  34          * that is not yet able to handle Content objects!
  35          *
  36          * If $content is null, this method returns the empty string.
  37          *
  38          * If $content is an instance of TextContent, this method returns the flat
  39          * text as returned by $content->getNativeData().
  40          *
  41          * If $content is not a TextContent object, the behavior of this method
  42          * depends on the global $wgContentHandlerTextFallback:
  43          * - If $wgContentHandlerTextFallback is 'fail' and $content is not a
  44          *   TextContent object, an MWException is thrown.
  45          * - If $wgContentHandlerTextFallback is 'serialize' and $content is not a
  46          *   TextContent object, $content->serialize() is called to get a string
  47          *   form of the content.
  48          * - If $wgContentHandlerTextFallback is 'ignore' and $content is not a
  49          *   TextContent object, this method returns null.
  50          * - otherwise, the behaviour is undefined.
  51          *
  52          * @since WD.1
  53          *
  54          * @static
  55          * @param $content Content|null
  56          * @return null|string the textual form of $content, if available
  57          * @throws MWException if $content is not an instance of TextContent and
  58          *   $wgContentHandlerTextFallback was set to 'fail'.
  59          */
  60         public static function getContentText( Content $content = null ) {
  61                 global $wgContentHandlerTextFallback;
  62
  63                 if ( is_null( $content ) ) {
  64                         return '';
  65                 }
  66
  67                 if ( $content instanceof TextContent ) {
  68                         return $content->getNativeData();
  69                 }
  70
  71                 if ( $wgContentHandlerTextFallback == 'fail' ) {
  72                         throw new MWException(
  73                                 "Attempt to get text from Content with model " .
  74                                 $content->getModel()
  75                         );
  76                 }
  77
  78                 if ( $wgContentHandlerTextFallback == 'serialize' ) {
  79                         return $content->serialize();
  80                 }
  81
  82                 return null;
  83         }
  84
  85         /**
  86          * Convenience function for creating a Content object from a given textual
  87          * representation.
  88          *
  89          * $text will be deserialized into a Content object of the model specified
  90          * by $modelId (or, if that is not given, $title->getContentModel()) using
  91          * the given format.
  92          *
  93          * @since WD.1
  94          *
  95          * @static
  96          *
  97          * @param $text string the textual representation, will be
  98          *    unserialized to create the Content object
  99          * @param $title null|Title the title of the page this text belongs to.
 100          *    Required if $modelId is not provided.
 101          * @param $modelId null|string the model to deserialize to. If not provided,
 102          *    $title->getContentModel() is used.
 103          * @param $format null|string the format to use for deserialization. If not
 104          *    given, the model's default format is used.
 105          *
 106          * @return Content a Content object representing $text
 107          *
 108          * @throw MWException if $model or $format is not supported or if $text can
 109          *    not be unserialized using $format.
 110          */
 111         public static function makeContent( $text, Title $title = null,
 112                 $modelId = null, $format = null )
 113         {
 114                 if ( is_null( $modelId ) ) {
 115                         if ( is_null( $title ) ) {
 116                                 throw new MWException( "Must provide a Title object or a content model ID." );
 117                         }
 118
 119                         $modelId = $title->getContentModel();
 120                 }
 121
 122                 $handler = ContentHandler::getForModelID( $modelId );
 123                 return $handler->unserializeContent( $text, $format );
 124         }
 125
 126         /**
 127          * Returns the name of the default content model to be used for the page
 128          * with the given title.
 129          *
 130          * Note: There should rarely be need to call this method directly.
 131          * To determine the actual content model for a given page, use
 132          * Title::getContentModel().
 133          *
 134          * Which model is to be used by default for the page is determined based
 135          * on several factors:
 136          * - The global setting $wgNamespaceContentModels specifies a content model
 137          *   per namespace.
 138          * - The hook DefaultModelFor may be used to override the page's default
 139          *   model.
 140          * - Pages in NS_MEDIAWIKI and NS_USER default to the CSS or JavaScript
 141          *   model if they end in .js or .css, respectively.
 142          * - Pages in NS_MEDIAWIKI default to the wikitext model otherwise.
 143          * - The hook TitleIsCssOrJsPage may be used to force a page to use the CSS
 144          *   or JavaScript model if they end in .js or .css, respectively.
 145          * - The hook TitleIsWikitextPage may be used to force a page to use the
 146          *   wikitext model.
 147          *
 148          * If none of the above applies, the wikitext model is used.
 149          *
 150          * Note: this is used by, and may thus not use, Title::getContentModel()
 151          *
 152          * @since WD.1
 153          *
 154          * @static
 155          * @param $title Title
 156          * @return null|string default model name for the page given by $title
 157          */
 158         public static function getDefaultModelFor( Title $title ) {
 159                 global $wgNamespaceContentModels;
 160
 161                 // NOTE: this method must not rely on $title->getContentModel() directly or indirectly,
 162                 //       because it is used to initialize the mContentModel member.
 163
 164                 $ns = $title->getNamespace();
 165
 166                 $ext = false;
 167                 $m = null;
 168                 $model = null;
 169
 170                 if ( !empty( $wgNamespaceContentModels[ $ns ] ) ) {
 171                         $model = $wgNamespaceContentModels[ $ns ];
 172                 }
 173
 174                 // Hook can determine default model
 175                 if ( !wfRunHooks( 'ContentHandlerDefaultModelFor', array( $title, &$model ) ) ) {
 176                         if ( !is_null( $model ) ) {
 177                                 return $model;
 178                         }
 179                 }
 180
 181                 // Could this page contain custom CSS or JavaScript, based on the title?
 182                 $isCssOrJsPage = NS_MEDIAWIKI == $ns && preg_match( '!\.(css|js)$!u', $title->getText(), $m );
 183                 if ( $isCssOrJsPage ) {
 184                         $ext = $m[1];
 185                 }
 186
 187                 // Hook can force JS/CSS
 188                 wfRunHooks( 'TitleIsCssOrJsPage', array( $title, &$isCssOrJsPage ) );
 189
 190                 // Is this a .css subpage of a user page?
 191                 $isJsCssSubpage = NS_USER == $ns
 192                         && !$isCssOrJsPage
 193                         && preg_match( "/\\/.*\\.(js|css)$/", $title->getText(), $m );
 194                 if ( $isJsCssSubpage ) {
 195                         $ext = $m[1];
 196                 }
 197
 198                 // Is this wikitext, according to $wgNamespaceContentModels or the DefaultModelFor hook?
 199                 $isWikitext = is_null( $model ) || $model == CONTENT_MODEL_WIKITEXT;
 200                 $isWikitext = $isWikitext && !$isCssOrJsPage && !$isJsCssSubpage;
 201
 202                 // Hook can override $isWikitext
 203                 wfRunHooks( 'TitleIsWikitextPage', array( $title, &$isWikitext ) );
 204
 205                 if ( !$isWikitext ) {
 206                         switch ( $ext ) {
 207                                 case 'js':
 208                                         return CONTENT_MODEL_JAVASCRIPT;
 209                                 case 'css':
 210                                         return CONTENT_MODEL_CSS;
 211                                 default:
 212                                         return is_null( $model ) ? CONTENT_MODEL_TEXT : $model;
 213                         }
 214                 }
 215
 216                 // We established that it must be wikitext
 217
 218                 return CONTENT_MODEL_WIKITEXT;
 219         }
 220
 221         /**
 222          * Returns the appropriate ContentHandler singleton for the given title.
 223          *
 224          * @since WD.1
 225          *
 226          * @static
 227          * @param $title Title
 228          * @return ContentHandler
 229          */
 230         public static function getForTitle( Title $title ) {
 231                 $modelId = $title->getContentModel();
 232                 return ContentHandler::getForModelID( $modelId );
 233         }
 234
 235         /**
 236          * Returns the appropriate ContentHandler singleton for the given Content
 237          * object.
 238          *
 239          * @since WD.1
 240          *
 241          * @static
 242          * @param $content Content
 243          * @return ContentHandler
 244          */
 245         public static function getForContent( Content $content ) {
 246                 $modelId = $content->getModel();
 247                 return ContentHandler::getForModelID( $modelId );
 248         }
 249
 250         /**
 251          * @var Array A Cache of ContentHandler instances by model id
 252          */
 253         static $handlers;
 254
 255         /**
 256          * Returns the ContentHandler singleton for the given model ID. Use the
 257          * CONTENT_MODEL_XXX constants to identify the desired content model.
 258          *
 259          * ContentHandler singletons are taken from the global $wgContentHandlers
 260          * array. Keys in that array are model names, the values are either
 261          * ContentHandler singleton objects, or strings specifying the appropriate
 262          * subclass of ContentHandler.
 263          *
 264          * If a class name is encountered when looking up the singleton for a given
 265          * model name, the class is instantiated and the class name is replaced by
 266          * the resulting singleton in $wgContentHandlers.
 267          *
 268          * If no ContentHandler is defined for the desired $modelId, the
 269          * ContentHandler may be provided by the ContentHandlerForModelID hook.
 270          * If no ContentHandler can be determined, an MWException is raised.
 271          *
 272          * @since WD.1
 273          *
 274          * @static
 275          * @param $modelId String The ID of the content model for which to get a
 276          *    handler. Use CONTENT_MODEL_XXX constants.
 277          * @return ContentHandler The ContentHandler singleton for handling the
 278          *    model given by $modelId
 279          * @throws MWException if no handler is known for $modelId.
 280          */
 281         public static function getForModelID( $modelId ) {
 282                 global $wgContentHandlers;
 283
 284                 if ( isset( ContentHandler::$handlers[$modelId] ) ) {
 285                         return ContentHandler::$handlers[$modelId];
 286                 }
 287
 288                 if ( empty( $wgContentHandlers[$modelId] ) ) {
 289                         $handler = null;
 290
 291                         wfRunHooks( 'ContentHandlerForModelID', array( $modelId, &$handler ) );
 292
 293                         if ( $handler === null ) {
 294                                 throw new MWException( "No handler for model #$modelId registered in \$wgContentHandlers" );
 295                         }
 296
 297                         if ( !( $handler instanceof ContentHandler ) ) {
 298                                 throw new MWException( "ContentHandlerForModelID must supply a ContentHandler instance" );
 299                         }
 300                 } else {
 301                         $class = $wgContentHandlers[$modelId];
 302                         $handler = new $class( $modelId );
 303
 304                         if ( !( $handler instanceof ContentHandler ) ) {
 305                                 throw new MWException( "$class from \$wgContentHandlers is not compatible with ContentHandler" );
 306                         }
 307                 }
 308
 309                 ContentHandler::$handlers[$modelId] = $handler;
 310                 return ContentHandler::$handlers[$modelId];
 311         }
 312
 313         /**
 314          * Returns the localized name for a given content model.
 315          *
 316          * Model names are localized using system messages. Message keys
 317          * have the form content-model-$name, where $name is getContentModelName( $id ).
 318          *
 319          * @static
 320          * @param $name String The content model ID, as given by a CONTENT_MODEL_XXX
 321          *    constant or returned by Revision::getContentModel().
 322          *
 323          * @return string The content format's localized name.
 324          * @throws MWException if the model id isn't known.
 325          */
 326         public static function getLocalizedName( $name ) {
 327                 $key = "content-model-$name";
 328
 329                 if ( wfEmptyMsg( $key ) ) return $name;
 330                 else return wfMsg( $key );
 331         }
 332
 333         public static function getAllContentFormats() {
 334                 global $wgContentHandlers;
 335
 336                 $formats = array();
 337
 338                 foreach ( $wgContentHandlers as $model => $class ) {
 339                         $handler = ContentHandler::getForModelID( $model );
 340                         $formats = array_merge( $formats, $handler->getSupportedFormats() );
 341                 }
 342
 343                 $formats = array_unique( $formats );
 344                 return $formats;
 345         }
 346
 347         // ------------------------------------------------------------------------
 348
 349         protected $mModelID;
 350         protected $mSupportedFormats;
 351
 352         /**
 353          * Constructor, initializing the ContentHandler instance with its model ID
 354          * and a list of supported formats. Values for the parameters are typically
 355          * provided as literals by subclass's constructors.
 356          *
 357          * @param $modelId String (use CONTENT_MODEL_XXX constants).
 358          * @param $formats array List for supported serialization formats
 359          *    (typically as MIME types)
 360          */
 361         public function __construct( $modelId, $formats ) {
 362                 $this->mModelID = $modelId;
 363                 $this->mSupportedFormats = $formats;
 364
 365                 $this->mModelName = preg_replace( '/(Content)?Handler$/', '', get_class( $this ) );
 366                 $this->mModelName = preg_replace( '/[_\\\\]/', '', $this->mModelName );
 367                 $this->mModelName = strtolower( $this->mModelName );
 368         }
 369
 370         /**
 371          * Serializes a Content object of the type supported by this ContentHandler.
 372          *
 373          * @since WD.1
 374          *
 375          * @abstract
 376          * @param $content Content The Content object to serialize
 377          * @param $format null|String The desired serialization format
 378          * @return string Serialized form of the content
 379          */
 380         public abstract function serializeContent( Content $content, $format = null );
 381
 382         /**
 383          * Unserializes a Content object of the type supported by this ContentHandler.
 384          *
 385          * @since WD.1
 386          *
 387          * @abstract
 388          * @param $blob string serialized form of the content
 389          * @param $format null|String the format used for serialization
 390          * @return Content the Content object created by deserializing $blob
 391          */
 392         public abstract function unserializeContent( $blob, $format = null );
 393
 394         /**
 395          * Creates an empty Content object of the type supported by this
 396          * ContentHandler.
 397          *
 398          * @since WD.1
 399          *
 400          * @return Content
 401          */
 402         public abstract function makeEmptyContent();
 403
 404         /**
 405          * Returns the model id that identifies the content model this
 406          * ContentHandler can handle. Use with the CONTENT_MODEL_XXX constants.
 407          *
 408          * @since WD.1
 409          *
 410          * @return String The model ID
 411          */
 412         public function getModelID() {
 413                 return $this->mModelID;
 414         }
 415
 416         /**
 417          * Throws an MWException if $model_id is not the ID of the content model
 418          * supported by this ContentHandler.
 419          *
 420          * @since WD.1
 421          *
 422          * @param String $model_id The model to check
 423          *
 424          * @throws MWException
 425          */
 426         protected function checkModelID( $model_id ) {
 427                 if ( $model_id !== $this->mModelID ) {
 428                         throw new MWException( "Bad content model: " .
 429                                 "expected {$this->mModelID} " .
 430                                 "but got $model_id." );
 431                 }
 432         }
 433
 434         /**
 435          * Returns a list of serialization formats supported by the
 436          * serializeContent() and unserializeContent() methods of this
 437          * ContentHandler.
 438          *
 439          * @since WD.1
 440          *
 441          * @return array of serialization formats as MIME type like strings
 442          */
 443         public function getSupportedFormats() {
 444                 return $this->mSupportedFormats;
 445         }
 446
 447         /**
 448          * The format used for serialization/deserialization by default by this
 449          * ContentHandler.
 450          *
 451          * This default implementation will return the first element of the array
 452          * of formats that was passed to the constructor.
 453          *
 454          * @since WD.1
 455          *
 456          * @return string the name of the default serialization format as a MIME type
 457          */
 458         public function getDefaultFormat() {
 459                 return $this->mSupportedFormats[0];
 460         }
 461
 462         /**
 463          * Returns true if $format is a serialization format supported by this
 464          * ContentHandler, and false otherwise.
 465          *
 466          * Note that if $format is null, this method always returns true, because
 467          * null means "use the default format".
 468          *
 469          * @since WD.1
 470          *
 471          * @param $format string the serialization format to check
 472          * @return bool
 473          */
 474         public function isSupportedFormat( $format ) {
 475
 476                 if ( !$format ) {
 477                         return true; // this means "use the default"
 478                 }
 479
 480                 return in_array( $format, $this->mSupportedFormats );
 481         }
 482
 483         /**
 484          * Throws an MWException if isSupportedFormat( $format ) is not true.
 485          * Convenient for checking whether a format provided as a parameter is
 486          * actually supported.
 487          *
 488          * @param $format string the serialization format to check
 489          *
 490          * @throws MWException
 491          */
 492         protected function checkFormat( $format ) {
 493                 if ( !$this->isSupportedFormat( $format ) ) {
 494                         throw new MWException(
 495                                 "Format $format is not supported for content model "
 496                                 . $this->getModelID()
 497                         );
 498                 }
 499         }
 500
 501         /**
 502          * Returns true if the content is consistent with the database, that is if
 503          * saving it to the database would not violate any global constraints.
 504          *
 505          * Content needs to be valid using this method before it can be saved.
 506          *
 507          * This default implementation always returns true.
 508          *
 509          * @since WD.1
 510          *
 511          * @param $content \Content
 512          *
 513          * @return boolean
 514          */
 515         public function isConsistentWithDatabase( Content $content ) {
 516                 return true;
 517         }
 518
 519         /**
 520          * Returns overrides for action handlers.
 521          * Classes listed here will be used instead of the default one when
 522          * (and only when) $wgActions[$action] === true. This allows subclasses
 523          * to override the default action handlers.
 524          *
 525          * @since WD.1
 526          *
 527          * @return Array
 528          */
 529         public function getActionOverrides() {
 530                 return array();
 531         }
 532
 533         /**
 534          * Factory for creating an appropriate DifferenceEngine for this content model.
 535          *
 536          * @since WD.1
 537          *
 538          * @param $context IContextSource context to use, anything else will be
 539          *    ignored
 540          * @param $old Integer Old ID we want to show and diff with.
 541          * @param $new int|string String either 'prev' or 'next'.
 542          * @param $rcid Integer ??? FIXME (default 0)
 543          * @param $refreshCache boolean If set, refreshes the diff cache
 544          * @param $unhide boolean If set, allow viewing deleted revs
 545          *
 546          * @return DifferenceEngine
 547          */
 548         public function createDifferenceEngine( IContextSource $context,
 549                 $old = 0, $new = 0,
 550                 $rcid = 0, # FIXME: use everywhere!
 551                 $refreshCache = false, $unhide = false
 552         ) {
 553                 $this->checkModelID( $context->getTitle()->getContentModel() );
 554
 555                 $diffEngineClass = $this->getDiffEngineClass();
 556
 557                 return new $diffEngineClass( $context, $old, $new, $rcid, $refreshCache, $unhide );
 558         }
 559
 560         /**
 561          * Returns the name of the diff engine to use.
 562          *
 563          * @since WD.1
 564          *
 565          * @return string
 566          */
 567         protected function getDiffEngineClass() {
 568                 return 'DifferenceEngine';
 569         }
 570
 571         /**
 572          * Attempts to merge differences between three versions.
 573          * Returns a new Content object for a clean merge and false for failure or
 574          * a conflict.
 575          *
 576          * This default implementation always returns false.
 577          *
 578          * @since WD.1
 579          *
 580          * @param $oldContent Content|string  String
 581          * @param $myContent Content|string   String
 582          * @param $yourContent Content|string String
 583          *
 584          * @return Content|Bool
 585          */
 586         public function merge3( Content $oldContent, Content $myContent, Content $yourContent ) {
 587                 return false;
 588         }
 589
 590         /**
 591          * Return an applicable auto-summary if one exists for the given edit.
 592          *
 593          * @since WD.1
 594          *
 595          * @param $oldContent Content|null: the previous text of the page.
 596          * @param $newContent Content|null: The submitted text of the page.
 597          * @param $flags int Bit mask: a bit mask of flags submitted for the edit.
 598          *
 599          * @return string An appropriate auto-summary, or an empty string.
 600          */
 601         public function getAutosummary( Content $oldContent = null, Content $newContent = null, $flags ) {
 602                 global $wgContLang;
 603
 604                 // Decide what kind of auto-summary is needed.
 605
 606                 // Redirect auto-summaries
 607
 608                 /**
 609                  * @var $ot Title
 610                  * @var $rt Title
 611                  */
 612
 613                 $ot = !is_null( $oldContent ) ? $oldContent->getRedirectTarget() : null;
 614                 $rt = !is_null( $newContent ) ? $newContent->getRedirectTarget() : null;
 615
 616                 if ( is_object( $rt ) ) {
 617                         if ( !is_object( $ot )
 618                                 || !$rt->equals( $ot )
 619                                 || $ot->getFragment() != $rt->getFragment() )
 620                         {
 621                                 $truncatedtext = $newContent->getTextForSummary(
 622                                         250
 623                                                 - strlen( wfMsgForContent( 'autoredircomment' ) )
 624                                                 - strlen( $rt->getFullText() ) );
 625
 626                                 return wfMsgForContent( 'autoredircomment', $rt->getFullText(), $truncatedtext );
 627                         }
 628                 }
 629
 630                 // New page auto-summaries
 631                 if ( $flags & EDIT_NEW && $newContent->getSize() > 0 ) {
 632                         // If they're making a new article, give its text, truncated, in
 633                         // the summary.
 634
 635                         $truncatedtext = $newContent->getTextForSummary(
 636                                 200 - strlen( wfMsgForContent( 'autosumm-new' ) ) );
 637
 638                         return wfMsgForContent( 'autosumm-new', $truncatedtext );
 639                 }
 640
 641                 // Blanking auto-summaries
 642                 if ( !empty( $oldContent ) && $oldContent->getSize() > 0 && $newContent->getSize() == 0 ) {
 643                         return wfMsgForContent( 'autosumm-blank' );
 644                 } elseif ( !empty( $oldContent )
 645                         && $oldContent->getSize() > 10 * $newContent->getSize()
 646                         && $newContent->getSize() < 500 )
 647                 {
 648                         // Removing more than 90% of the article
 649
 650                         $truncatedtext = $newContent->getTextForSummary(
 651                                 200 - strlen( wfMsgForContent( 'autosumm-replace' ) ) );
 652
 653                         return wfMsgForContent( 'autosumm-replace', $truncatedtext );
 654                 }
 655
 656                 // If we reach this point, there's no applicable auto-summary for our
 657                 // case, so our auto-summary is empty.
 658
 659                 return '';
 660         }
 661
 662         /**
 663          * Auto-generates a deletion reason
 664          *
 665          * @since WD.1
 666          *
 667          * @param $title Title: the page's title
 668          * @param &$hasHistory Boolean: whether the page has a history
 669          * @return mixed String containing deletion reason or empty string, or
 670          *    boolean false if no revision occurred
 671          *
 672          * @XXX &$hasHistory is extremely ugly, it's here because
 673          * WikiPage::getAutoDeleteReason() and Article::getReason()
 674          * have it / want it.
 675          */
 676         public function getAutoDeleteReason( Title $title, &$hasHistory ) {
 677                 $dbw = wfGetDB( DB_MASTER );
 678
 679                 // Get the last revision
 680                 $rev = Revision::newFromTitle( $title );
 681
 682                 if ( is_null( $rev ) ) {
 683                         return false;
 684                 }
 685
 686                 // Get the article's contents
 687                 $content = $rev->getContent();
 688                 $blank = false;
 689
 690                 $this->checkModelID( $content->getModel() );
 691
 692                 // If the page is blank, use the text from the previous revision,
 693                 // which can only be blank if there's a move/import/protect dummy
 694                 // revision involved
 695                 if ( $content->getSize() == 0 ) {
 696                         $prev = $rev->getPrevious();
 697
 698                         if ( $prev )    {
 699                                 $content = $prev->getContent();
 700                                 $blank = true;
 701                         }
 702                 }
 703
 704                 // Find out if there was only one contributor
 705                 // Only scan the last 20 revisions
 706                 $res = $dbw->select( 'revision', 'rev_user_text',
 707                         array(
 708                                 'rev_page' => $title->getArticleID(),
 709                                 $dbw->bitAnd( 'rev_deleted', Revision::DELETED_USER ) . ' = 0'
 710                         ),
 711                         __METHOD__,
 712                         array( 'LIMIT' => 20 )
 713                 );
 714
 715                 if ( $res === false ) {
 716                         // This page has no revisions, which is very weird
 717                         return false;
 718                 }
 719
 720                 $hasHistory = ( $res->numRows() > 1 );
 721                 $row = $dbw->fetchObject( $res );
 722
 723                 if ( $row ) { // $row is false if the only contributor is hidden
 724                         $onlyAuthor = $row->rev_user_text;
 725                         // Try to find a second contributor
 726                         foreach ( $res as $row ) {
 727                                 if ( $row->rev_user_text != $onlyAuthor ) { // Bug 22999
 728                                         $onlyAuthor = false;
 729                                         break;
 730                                 }
 731                         }
 732                 } else {
 733                         $onlyAuthor = false;
 734                 }
 735
 736                 // Generate the summary with a '$1' placeholder
 737                 if ( $blank ) {
 738                         // The current revision is blank and the one before is also
 739                         // blank. It's just not our lucky day
 740                         $reason = wfMsgForContent( 'exbeforeblank', '$1' );
 741                 } else {
 742                         if ( $onlyAuthor ) {
 743                                 $reason = wfMsgForContent( 'excontentauthor', '$1', $onlyAuthor );
 744                         } else {
 745                                 $reason = wfMsgForContent( 'excontent', '$1' );
 746                         }
 747                 }
 748
 749                 if ( $reason == '-' ) {
 750                         // Allow these UI messages to be blanked out cleanly
 751                         return '';
 752                 }
 753
 754                 // Max content length = max comment length - length of the comment (excl. $1)
 755                 $text = $content->getTextForSummary( 255 - ( strlen( $reason ) - 2 ) );
 756
 757                 // Now replace the '$1' placeholder
 758                 $reason = str_replace( '$1', $text, $reason );
 759
 760                 return $reason;
 761         }
 762
 763         /**
 764          * Parse the Content object and generate a ParserOutput from the result.
 765          * $result->getText() can be used to obtain the generated HTML. If no HTML
 766          * is needed, $generateHtml can be set to false; in that case,
 767          * $result->getText() may return null.
 768          *
 769          * @param $content Content the content to render
 770          * @param $title Title The page title to use as a context for rendering
 771          * @param $revId null|int The revision being rendered (optional)
 772          * @param $options null|ParserOptions Any parser options
 773          * @param $generateHtml Boolean Whether to generate HTML (default: true). If false,
 774          *        the result of calling getText() on the ParserOutput object returned by
 775          *        this method is undefined.
 776          *
 777          * @since WD.1
 778          *
 779          * @return ParserOutput
 780          */
 781         public abstract function getParserOutput( Content $content, Title $title,
 782                 $revId = null,
 783                 ParserOptions $options = null, $generateHtml = true );
 784         # TODO: make RenderOutput and RenderOptions base classes
 785
 786         /**
 787          * Returns a list of DataUpdate objects for recording information about this
 788          * Content in some secondary data store. If the optional second argument,
 789          * $old, is given, the updates may model only the changes that need to be
 790          * made to replace information about the old content with information about
 791          * the new content.
 792          *
 793          * This default implementation calls
 794          * $this->getParserOutput( $content, $title, null, null, false ),
 795          * and then calls getSecondaryDataUpdates( $title, $recursive ) on the
 796          * resulting ParserOutput object.
 797          *
 798          * Subclasses may implement this to determine the necessary updates more
 799          * efficiently, or make use of information about the old content.
 800          *
 801          * @param $content Content The content for determining the necessary updates
 802          * @param $title Title The context for determining the necessary updates
 803          * @param $old Content|null An optional Content object representing the
 804          *    previous content, i.e. the content being replaced by this Content
 805          *    object.
 806          * @param $recursive boolean Whether to include recursive updates (default:
 807          *    false).
 808          * @param $parserOutput ParserOutput|null Optional ParserOutput object.
 809          *    Provide if you have one handy, to avoid re-parsing of the content.
 810          *
 811          * @return Array. A list of DataUpdate objects for putting information
 812          *    about this content object somewhere.
 813          *
 814          * @since WD.1
 815          */
 816         public function getSecondaryDataUpdates( Content $content, Title $title,
 817                 Content $old = null,
 818                 $recursive = true, ParserOutput $parserOutput = null
 819         ) {
 820                 if ( !$parserOutput ) {
 821                         $parserOutput = $this->getParserOutput( $content, $title, null, null, false );
 822                 }
 823
 824                 return $parserOutput->getSecondaryDataUpdates( $title, $recursive );
 825         }
 826
 827
 828         /**
 829          * Get the Content object that needs to be saved in order to undo all revisions
 830          * between $undo and $undoafter. Revisions must belong to the same page,
 831          * must exist and must not be deleted.
 832          *
 833          * @since WD.1
 834          *
 835          * @param $current Revision The current text
 836          * @param $undo Revision The revision to undo
 837          * @param $undoafter Revision Must be an earlier revision than $undo
 838          *
 839          * @return mixed String on success, false on failure
 840          */
 841         public function getUndoContent( Revision $current, Revision $undo, Revision $undoafter ) {
 842                 $cur_content = $current->getContent();
 843
 844                 if ( empty( $cur_content ) ) {
 845                         return false; // no page
 846                 }
 847
 848                 $undo_content = $undo->getContent();
 849                 $undoafter_content = $undoafter->getContent();
 850
 851                 $this->checkModelID( $cur_content->getModel() );
 852                 $this->checkModelID( $undo_content->getModel() );
 853                 $this->checkModelID( $undoafter_content->getModel() );
 854
 855                 if ( $cur_content->equals( $undo_content ) ) {
 856                         // No use doing a merge if it's just a straight revert.
 857                         return $undoafter_content;
 858                 }
 859
 860                 $undone_content = $this->merge3( $undo_content, $undoafter_content, $cur_content );
 861
 862                 return $undone_content;
 863         }
 864
 865         /**
 866          * Returns true for content models that support caching using the
 867          * ParserCache mechanism. See WikiPage::isParserCacheUser().
 868          *
 869          * @since WD.1
 870          *
 871          * @return bool
 872          */
 873         public function isParserCacheSupported() {
 874                 return true;
 875         }
 876
 877         /**
 878          * Returns a list of updates to perform when the given content is deleted.
 879          * The necessary updates may be taken from the Content object, or depend on
 880          * the current state of the database.
 881          *
 882          * @since WD.1
 883          *
 884          * @param $content \Content the Content object for deletion
 885          * @param $title \Title the title of the deleted page
 886          * @param $parserOutput null|\ParserOutput optional parser output object
 887          *    for efficient access to meta-information about the content object.
 888          *    Provide if you have one handy.
 889          *
 890          * @return array A list of DataUpdate instances that will clean up the
 891          *    database after deletion.
 892          */
 893         public function getDeletionUpdates( Content $content, Title $title,
 894                 ParserOutput $parserOutput = null )
 895         {
 896                 return array(
 897                         new LinksDeletionUpdate( $title ),
 898                 );
 899         }
 900
 901         /**
 902          * Returns true if this content model supports sections.
 903          *
 904          * This default implementation returns false.
 905          *
 906          * @return boolean whether sections are supported.
 907          */
 908         public function supportsSections() {
 909                 return false;
 910         }
 911 }
 912
 913 /**
 914  * @since WD.1
 915  */
 916 abstract class TextContentHandler extends ContentHandler {
 917
 918         public function __construct( $modelId, $formats ) {
 919                 parent::__construct( $modelId, $formats );
 920         }
 921
 922         /**
 923          * Returns the content's text as-is.
 924          *
 925          * @param $content Content
 926          * @param $format string|null
 927          * @return mixed
 928          */
 929         public function serializeContent( Content $content, $format = null ) {
 930                 $this->checkFormat( $format );
 931                 return $content->getNativeData();
 932         }
 933
 934         /**
 935          * Attempts to merge differences between three versions. Returns a new
 936          * Content object for a clean merge and false for failure or a conflict.
 937          *
 938          * All three Content objects passed as parameters must have the same
 939          * content model.
 940          *
 941          * This text-based implementation uses wfMerge().
 942          *
 943          * @param $oldContent \Content|string  String
 944          * @param $myContent \Content|string   String
 945          * @param $yourContent \Content|string String
 946          *
 947          * @return Content|Bool
 948          */
 949         public function merge3( Content $oldContent, Content $myContent, Content $yourContent ) {
 950                 $this->checkModelID( $oldContent->getModel() );
 951                 $this->checkModelID( $myContent->getModel() );
 952                 $this->checkModelID( $yourContent->getModel() );
 953
 954                 $format = $this->getDefaultFormat();
 955
 956                 $old = $this->serializeContent( $oldContent, $format );
 957                 $mine = $this->serializeContent( $myContent, $format );
 958                 $yours = $this->serializeContent( $yourContent, $format );
 959
 960                 $ok = wfMerge( $old, $mine, $yours, $result );
 961
 962                 if ( !$ok ) {
 963                         return false;
 964                 }
 965
 966                 if ( !$result ) {
 967                         return $this->makeEmptyContent();
 968                 }
 969
 970                 $mergedContent = $this->unserializeContent( $result, $format );
 971                 return $mergedContent;
 972         }
 973
 974         /**
 975          * Returns a generic ParserOutput object, wrapping the HTML returned by
 976          * getHtml().
 977          *
 978          * @param $content Content The content to render
 979          * @param $title Title Context title for parsing
 980          * @param $revId int|null Revision ID (for {{REVISIONID}})
 981          * @param $options ParserOptions|null Parser options
 982          * @param $generateHtml bool Whether or not to generate HTML
 983          *
 984          * @return ParserOutput representing the HTML form of the text
 985          */
 986         public function getParserOutput( Content $content, Title $title,
 987                 $revId = null,
 988                 ParserOptions $options = null, $generateHtml = true
 989         ) {
 990                 $this->checkModelID( $content->getModel() );
 991
 992                 # Generic implementation, relying on $this->getHtml()
 993
 994                 if ( $generateHtml ) {
 995                         $html = $this->getHtml( $content );
 996                 } else {
 997                         $html = '';
 998                 }
 999
1000                 $po = new ParserOutput( $html );
1001                 return $po;
1002         }
1003
1004         /**
1005          * Generates an HTML version of the content, for display. Used by
1006          * getParserOutput() to construct a ParserOutput object.
1007          *
1008          * This default implementation just calls getHighlightHtml(). Content
1009          * models that have another mapping to HTML (as is the case for markup
1010          * languages like wikitext) should override this method to generate the
1011          * appropriate HTML.
1012          *
1013          * @param $content Content The content to render
1014          *
1015          * @return string An HTML representation of the content
1016          */
1017         protected function getHtml( Content $content ) {
1018                 $this->checkModelID( $content->getModel() );
1019
1020                 return $this->getHighlightHtml( $content );
1021         }
1022
1023         /**
1024          * Generates a syntax-highlighted version the content, as HTML.
1025          * Used by the default implementation of getHtml().
1026          *
1027          * @param $content Content the content to render
1028          *
1029          * @return string an HTML representation of the content's markup
1030          */
1031         protected function getHighlightHtml( Content $content ) {
1032                 $this->checkModelID( $content->getModel() );
1033
1034                 # TODO: make Highlighter interface, use highlighter here, if available
1035                 return htmlspecialchars( $content->getNativeData() );
1036         }
1037
1038
1039 }
1040
1041 /**
1042  * @since WD.1
1043  */
1044 class WikitextContentHandler extends TextContentHandler {
1045
1046         public function __construct( $modelId = CONTENT_MODEL_WIKITEXT ) {
1047                 parent::__construct( $modelId, array( CONTENT_FORMAT_WIKITEXT ) );
1048         }
1049
1050         public function unserializeContent( $text, $format = null ) {
1051                 $this->checkFormat( $format );
1052
1053                 return new WikitextContent( $text );
1054         }
1055
1056         public function makeEmptyContent() {
1057                 return new WikitextContent( '' );
1058         }
1059
1060         /**
1061          * Returns a ParserOutput object resulting from parsing the content's text
1062          * using $wgParser.
1063          *
1064          * @since    WD.1
1065          *
1066          * @param $content Content the content to render
1067          * @param $title \Title
1068          * @param $revId null
1069          * @param $options null|ParserOptions
1070          * @param $generateHtml bool
1071          *
1072          * @internal param \IContextSource|null $context
1073          * @return ParserOutput representing the HTML form of the text
1074          */
1075         public function getParserOutput( Content $content, Title $title,
1076                 $revId = null,
1077                 ParserOptions $options = null, $generateHtml = true
1078         ) {
1079                 global $wgParser;
1080
1081                 $this->checkModelID( $content->getModel() );
1082
1083                 if ( !$options ) {
1084                         $options = new ParserOptions();
1085                 }
1086
1087                 $po = $wgParser->parse( $content->getNativeData(), $title, $options, true, true, $revId );
1088                 return $po;
1089         }
1090
1091         protected function getHtml( Content $content ) {
1092                 throw new MWException(
1093                         "getHtml() not implemented for wikitext. "
1094                         . "Use getParserOutput()->getText()."
1095                 );
1096         }
1097
1098         /**
1099          * Returns true because wikitext supports sections.
1100          *
1101          * @return boolean whether sections are supported.
1102          */
1103         public function supportsSections() {
1104                 return true;
1105         }
1106 }
1107
1108 # XXX: make ScriptContentHandler base class, do highlighting stuff there?
1109
1110 /**
1111  * @since WD.1
1112  */
1113 class JavaScriptContentHandler extends TextContentHandler {
1114
1115         public function __construct( $modelId = CONTENT_MODEL_JAVASCRIPT ) {
1116                 parent::__construct( $modelId, array( CONTENT_FORMAT_JAVASCRIPT ) );
1117         }
1118
1119         public function unserializeContent( $text, $format = null ) {
1120                 $this->checkFormat( $format );
1121
1122                 return new JavaScriptContent( $text );
1123         }
1124
1125         public function makeEmptyContent() {
1126                 return new JavaScriptContent( '' );
1127         }
1128
1129         protected function getHtml( Content $content ) {
1130                 $html = "";
1131                 $html .= "<pre class=\"mw-code mw-js\" dir=\"ltr\">\n";
1132                 $html .= $this->getHighlightHtml( $content );
1133                 $html .= "\n</pre>\n";
1134
1135                 return $html;
1136         }
1137 }
1138
1139 /**
1140  * @since WD.1
1141  */
1142 class CssContentHandler extends TextContentHandler {
1143
1144         public function __construct( $modelId = CONTENT_MODEL_CSS ) {
1145                 parent::__construct( $modelId, array( CONTENT_FORMAT_CSS ) );
1146         }
1147
1148         public function unserializeContent( $text, $format = null ) {
1149                 $this->checkFormat( $format );
1150
1151                 return new CssContent( $text );
1152         }
1153
1154         public function makeEmptyContent() {
1155                 return new CssContent( '' );
1156         }
1157
1158
1159         protected function getHtml( Content $content ) {
1160                 $html = "";
1161                 $html .= "<pre class=\"mw-code mw-css\" dir=\"ltr\">\n";
1162                 $html .= $this->getHighlightHtml( $content );
1163                 $html .= "\n</pre>\n";
1164
1165                 return $html;
1166         }
1167 }