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