includes/content/ContentHandler.php

   1 <?php
   2 /**
   3  * Base class for content handling.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @since 1.21
  21  *
  22  * @file
  23  * @ingroup Content
  24  *
  25  * @author Daniel Kinzler
  26  */
  27
  28 /**
  29  * Exception representing a failure to serialize or unserialize a content object.
  30  *
  31  * @ingroup Content
  32  */
  33 class MWContentSerializationException extends MWException {
  34
  35 }
  36
  37 /**
  38  * A content handler knows how do deal with a specific type of content on a wiki
  39  * page. Content is stored in the database in a serialized form (using a
  40  * serialization format a.k.a. MIME type) and is unserialized into its native
  41  * PHP representation (the content model), which is wrapped in an instance of
  42  * the appropriate subclass of Content.
  43  *
  44  * ContentHandler instances are stateless singletons that serve, among other
  45  * things, as a factory for Content objects. Generally, there is one subclass
  46  * of ContentHandler and one subclass of Content for every type of content model.
  47  *
  48  * Some content types have a flat model, that is, their native representation
  49  * is the same as their serialized form. Examples would be JavaScript and CSS
  50  * code. As of now, this also applies to wikitext (MediaWiki's default content
  51  * type), but wikitext content may be represented by a DOM or AST structure in
  52  * the future.
  53  *
  54  * @ingroup Content
  55  */
  56 abstract class ContentHandler {
  57
  58         /**
  59          * Switch for enabling deprecation warnings. Used by ContentHandler::deprecated()
  60          * and ContentHandler::runLegacyHooks().
  61          *
  62          * Once the ContentHandler code has settled in a bit, this should be set to true to
  63          * make extensions etc. show warnings when using deprecated functions and hooks.
  64          */
  65         protected static $enableDeprecationWarnings = false;
  66
  67         /**
  68          * Convenience function for getting flat text from a Content object. This
  69          * should only be used in the context of backwards compatibility with code
  70          * that is not yet able to handle Content objects!
  71          *
  72          * If $content is null, this method returns the empty string.
  73          *
  74          * If $content is an instance of TextContent, this method returns the flat
  75          * text as returned by $content->getNativeData().
  76          *
  77          * If $content is not a TextContent object, the behavior of this method
  78          * depends on the global $wgContentHandlerTextFallback:
  79          * - If $wgContentHandlerTextFallback is 'fail' and $content is not a
  80          *   TextContent object, an MWException is thrown.
  81          * - If $wgContentHandlerTextFallback is 'serialize' and $content is not a
  82          *   TextContent object, $content->serialize() is called to get a string
  83          *   form of the content.
  84          * - If $wgContentHandlerTextFallback is 'ignore' and $content is not a
  85          *   TextContent object, this method returns null.
  86          * - otherwise, the behavior is undefined.
  87          *
  88          * @since 1.21
  89          *
  90          * @param $content Content|null
  91          * @return null|string the textual form of $content, if available
  92          * @throws MWException if $content is not an instance of TextContent and
  93          *   $wgContentHandlerTextFallback was set to 'fail'.
  94          */
  95         public static function getContentText( Content $content = null ) {
  96                 global $wgContentHandlerTextFallback;
  97
  98                 if ( is_null( $content ) ) {
  99                         return '';
 100                 }
 101
 102                 if ( $content instanceof TextContent ) {
 103                         return $content->getNativeData();
 104                 }
 105
 106                 wfDebugLog( 'ContentHandler', 'Accessing ' . $content->getModel() . ' content as text!' );
 107
 108                 if ( $wgContentHandlerTextFallback == 'fail' ) {
 109                         throw new MWException(
 110                                 "Attempt to get text from Content with model " .
 111                                 $content->getModel()
 112                         );
 113                 }
 114
 115                 if ( $wgContentHandlerTextFallback == 'serialize' ) {
 116                         return $content->serialize();
 117                 }
 118
 119                 return null;
 120         }
 121
 122         /**
 123          * Convenience function for creating a Content object from a given textual
 124          * representation.
 125          *
 126          * $text will be deserialized into a Content object of the model specified
 127          * by $modelId (or, if that is not given, $title->getContentModel()) using
 128          * the given format.
 129          *
 130          * @since 1.21
 131          *
 132          * @param string $text the textual representation, will be
 133          *    unserialized to create the Content object
 134          * @param $title null|Title the title of the page this text belongs to.
 135          *    Required if $modelId is not provided.
 136          * @param $modelId null|string the model to deserialize to. If not provided,
 137          *    $title->getContentModel() is used.
 138          * @param $format null|string the format to use for deserialization. If not
 139          *    given, the model's default format is used.
 140          *
 141          * @throws MWException
 142          * @return Content a Content object representing $text
 143          *
 144          * @throws MWException if $model or $format is not supported or if $text can
 145          *    not be unserialized using $format.
 146          */
 147         public static function makeContent( $text, Title $title = null,
 148                 $modelId = null, $format = null
 149         ) {
 150                 if ( is_null( $modelId ) ) {
 151                         if ( is_null( $title ) ) {
 152                                 throw new MWException( "Must provide a Title object or a content model ID." );
 153                         }
 154
 155                         $modelId = $title->getContentModel();
 156                 }
 157
 158                 $handler = ContentHandler::getForModelID( $modelId );
 159
 160                 return $handler->unserializeContent( $text, $format );
 161         }
 162
 163         /**
 164          * Returns the name of the default content model to be used for the page
 165          * with the given title.
 166          *
 167          * Note: There should rarely be need to call this method directly.
 168          * To determine the actual content model for a given page, use
 169          * Title::getContentModel().
 170          *
 171          * Which model is to be used by default for the page is determined based
 172          * on several factors:
 173          * - The global setting $wgNamespaceContentModels specifies a content model
 174          *   per namespace.
 175          * - The hook ContentHandlerDefaultModelFor may be used to override the page's default
 176          *   model.
 177          * - Pages in NS_MEDIAWIKI and NS_USER default to the CSS or JavaScript
 178          *   model if they end in .js or .css, respectively.
 179          * - Pages in NS_MEDIAWIKI default to the wikitext model otherwise.
 180          * - The hook TitleIsCssOrJsPage may be used to force a page to use the CSS
 181          *   or JavaScript model. This is a compatibility feature. The ContentHandlerDefaultModelFor
 182          *   hook should be used instead if possible.
 183          * - The hook TitleIsWikitextPage may be used to force a page to use the
 184          *   wikitext model. This is a compatibility feature. The ContentHandlerDefaultModelFor
 185          *   hook should be used instead if possible.
 186          *
 187          * If none of the above applies, the wikitext model is used.
 188          *
 189          * Note: this is used by, and may thus not use, Title::getContentModel()
 190          *
 191          * @since 1.21
 192          *
 193          * @param $title Title
 194          * @return null|string default model name for the page given by $title
 195          */
 196         public static function getDefaultModelFor( Title $title ) {
 197                 // NOTE: this method must not rely on $title->getContentModel() directly or indirectly,
 198                 //       because it is used to initialize the mContentModel member.
 199
 200                 $ns = $title->getNamespace();
 201
 202                 $ext = false;
 203                 $m = null;
 204                 $model = MWNamespace::getNamespaceContentModel( $ns );
 205
 206                 // Hook can determine default model
 207                 if ( !wfRunHooks( 'ContentHandlerDefaultModelFor', array( $title, &$model ) ) ) {
 208                         if ( !is_null( $model ) ) {
 209                                 return $model;
 210                         }
 211                 }
 212
 213                 // Could this page contain custom CSS or JavaScript, based on the title?
 214                 $isCssOrJsPage = NS_MEDIAWIKI == $ns && preg_match( '!\.(css|js)$!u', $title->getText(), $m );
 215                 if ( $isCssOrJsPage ) {
 216                         $ext = $m[1];
 217                 }
 218
 219                 // Hook can force JS/CSS
 220                 wfRunHooks( 'TitleIsCssOrJsPage', array( $title, &$isCssOrJsPage ) );
 221
 222                 // Is this a .css subpage of a user page?
 223                 $isJsCssSubpage = NS_USER == $ns
 224                         && !$isCssOrJsPage
 225                         && preg_match( "/\\/.*\\.(js|css)$/", $title->getText(), $m );
 226                 if ( $isJsCssSubpage ) {
 227                         $ext = $m[1];
 228                 }
 229
 230                 // Is this wikitext, according to $wgNamespaceContentModels or the DefaultModelFor hook?
 231                 $isWikitext = is_null( $model ) || $model == CONTENT_MODEL_WIKITEXT;
 232                 $isWikitext = $isWikitext && !$isCssOrJsPage && !$isJsCssSubpage;
 233
 234                 // Hook can override $isWikitext
 235                 wfRunHooks( 'TitleIsWikitextPage', array( $title, &$isWikitext ) );
 236
 237                 if ( !$isWikitext ) {
 238                         switch ( $ext ) {
 239                                 case 'js':
 240                                         return CONTENT_MODEL_JAVASCRIPT;
 241                                 case 'css':
 242                                         return CONTENT_MODEL_CSS;
 243                                 default:
 244                                         return is_null( $model ) ? CONTENT_MODEL_TEXT : $model;
 245                         }
 246                 }
 247
 248                 // We established that it must be wikitext
 249
 250                 return CONTENT_MODEL_WIKITEXT;
 251         }
 252
 253         /**
 254          * Returns the appropriate ContentHandler singleton for the given title.
 255          *
 256          * @since 1.21
 257          *
 258          * @param $title Title
 259          * @return ContentHandler
 260          */
 261         public static function getForTitle( Title $title ) {
 262                 $modelId = $title->getContentModel();
 263
 264                 return ContentHandler::getForModelID( $modelId );
 265         }
 266
 267         /**
 268          * Returns the appropriate ContentHandler singleton for the given Content
 269          * object.
 270          *
 271          * @since 1.21
 272          *
 273          * @param $content Content
 274          * @return ContentHandler
 275          */
 276         public static function getForContent( Content $content ) {
 277                 $modelId = $content->getModel();
 278
 279                 return ContentHandler::getForModelID( $modelId );
 280         }
 281
 282         /**
 283          * @var Array A Cache of ContentHandler instances by model id
 284          */
 285         static $handlers;
 286
 287         /**
 288          * Returns the ContentHandler singleton for the given model ID. Use the
 289          * CONTENT_MODEL_XXX constants to identify the desired content model.
 290          *
 291          * ContentHandler singletons are taken from the global $wgContentHandlers
 292          * array. Keys in that array are model names, the values are either
 293          * ContentHandler singleton objects, or strings specifying the appropriate
 294          * subclass of ContentHandler.
 295          *
 296          * If a class name is encountered when looking up the singleton for a given
 297          * model name, the class is instantiated and the class name is replaced by
 298          * the resulting singleton in $wgContentHandlers.
 299          *
 300          * If no ContentHandler is defined for the desired $modelId, the
 301          * ContentHandler may be provided by the ContentHandlerForModelID hook.
 302          * If no ContentHandler can be determined, an MWException is raised.
 303          *
 304          * @since 1.21
 305          *
 306          * @param string $modelId The ID of the content model for which to get a
 307          *    handler. Use CONTENT_MODEL_XXX constants.
 308          * @return ContentHandler The ContentHandler singleton for handling the
 309          *    model given by $modelId
 310          * @throws MWException if no handler is known for $modelId.
 311          */
 312         public static function getForModelID( $modelId ) {
 313                 global $wgContentHandlers;
 314
 315                 if ( isset( ContentHandler::$handlers[$modelId] ) ) {
 316                         return ContentHandler::$handlers[$modelId];
 317                 }
 318
 319                 if ( empty( $wgContentHandlers[$modelId] ) ) {
 320                         $handler = null;
 321
 322                         wfRunHooks( 'ContentHandlerForModelID', array( $modelId, &$handler ) );
 323
 324                         if ( $handler === null ) {
 325                                 throw new MWException( "No handler for model '$modelId' registered in \$wgContentHandlers" );
 326                         }
 327
 328                         if ( !( $handler instanceof ContentHandler ) ) {
 329                                 throw new MWException( "ContentHandlerForModelID must supply a ContentHandler instance" );
 330                         }
 331                 } else {
 332                         $class = $wgContentHandlers[$modelId];
 333                         $handler = new $class( $modelId );
 334
 335                         if ( !( $handler instanceof ContentHandler ) ) {
 336                                 throw new MWException( "$class from \$wgContentHandlers is not compatible with ContentHandler" );
 337                         }
 338                 }
 339
 340                 wfDebugLog( 'ContentHandler', 'Created handler for ' . $modelId
 341                         . ': ' . get_class( $handler ) );
 342
 343                 ContentHandler::$handlers[$modelId] = $handler;
 344
 345                 return ContentHandler::$handlers[$modelId];
 346         }
 347
 348         /**
 349          * Returns the localized name for a given content model.
 350          *
 351          * Model names are localized using system messages. Message keys
 352          * have the form content-model-$name, where $name is getContentModelName( $id ).
 353          *
 354          * @param string $name The content model ID, as given by a CONTENT_MODEL_XXX
 355          *    constant or returned by Revision::getContentModel().
 356          *
 357          * @return string The content model's localized name.
 358          * @throws MWException if the model id isn't known.
 359          */
 360         public static function getLocalizedName( $name ) {
 361                 // Messages: content-model-wikitext, content-model-text,
 362                 // content-model-javascript, content-model-css
 363                 $key = "content-model-$name";
 364
 365                 $msg = wfMessage( $key );
 366
 367                 return $msg->exists() ? $msg->plain() : $name;
 368         }
 369
 370         public static function getContentModels() {
 371                 global $wgContentHandlers;
 372
 373                 return array_keys( $wgContentHandlers );
 374         }
 375
 376         public static function getAllContentFormats() {
 377                 global $wgContentHandlers;
 378
 379                 $formats = array();
 380
 381                 foreach ( $wgContentHandlers as $model => $class ) {
 382                         $handler = ContentHandler::getForModelID( $model );
 383                         $formats = array_merge( $formats, $handler->getSupportedFormats() );
 384                 }
 385
 386                 $formats = array_unique( $formats );
 387
 388                 return $formats;
 389         }
 390
 391         // ------------------------------------------------------------------------
 392
 393         protected $mModelID;
 394         protected $mSupportedFormats;
 395
 396         /**
 397          * Constructor, initializing the ContentHandler instance with its model ID
 398          * and a list of supported formats. Values for the parameters are typically
 399          * provided as literals by subclass's constructors.
 400          *
 401          * @param string $modelId (use CONTENT_MODEL_XXX constants).
 402          * @param array $formats List for supported serialization formats
 403          *    (typically as MIME types)
 404          */
 405         public function __construct( $modelId, $formats ) {
 406                 $this->mModelID = $modelId;
 407                 $this->mSupportedFormats = $formats;
 408
 409                 $this->mModelName = preg_replace( '/(Content)?Handler$/', '', get_class( $this ) );
 410                 $this->mModelName = preg_replace( '/[_\\\\]/', '', $this->mModelName );
 411                 $this->mModelName = strtolower( $this->mModelName );
 412         }
 413
 414         /**
 415          * Serializes a Content object of the type supported by this ContentHandler.
 416          *
 417          * @since 1.21
 418          *
 419          * @param $content Content The Content object to serialize
 420          * @param $format null|String The desired serialization format
 421          * @return string Serialized form of the content
 422          */
 423         abstract public function serializeContent( Content $content, $format = null );
 424
 425         /**
 426          * Unserializes a Content object of the type supported by this ContentHandler.
 427          *
 428          * @since 1.21
 429          *
 430          * @param string $blob serialized form of the content
 431          * @param $format null|String the format used for serialization
 432          * @return Content the Content object created by deserializing $blob
 433          */
 434         abstract public function unserializeContent( $blob, $format = null );
 435
 436         /**
 437          * Creates an empty Content object of the type supported by this
 438          * ContentHandler.
 439          *
 440          * @since 1.21
 441          *
 442          * @return Content
 443          */
 444         abstract public function makeEmptyContent();
 445
 446         /**
 447          * Creates a new Content object that acts as a redirect to the given page,
 448          * or null of redirects are not supported by this content model.
 449          *
 450          * This default implementation always returns null. Subclasses supporting redirects
 451          * must override this method.
 452          *
 453          * Note that subclasses that override this method to return a Content object
 454          * should also override supportsRedirects() to return true.
 455          *
 456          * @since 1.21
 457          *
 458          * @param Title $destination the page to redirect to.
 459          * @param string $text text to include in the redirect, if possible.
 460          *
 461          * @return Content
 462          */
 463         public function makeRedirectContent( Title $destination, $text = '' ) {
 464                 return null;
 465         }
 466
 467         /**
 468          * Returns the model id that identifies the content model this
 469          * ContentHandler can handle. Use with the CONTENT_MODEL_XXX constants.
 470          *
 471          * @since 1.21
 472          *
 473          * @return String The model ID
 474          */
 475         public function getModelID() {
 476                 return $this->mModelID;
 477         }
 478
 479         /**
 480          * Throws an MWException if $model_id is not the ID of the content model
 481          * supported by this ContentHandler.
 482          *
 483          * @since 1.21
 484          *
 485          * @param string $model_id The model to check
 486          *
 487          * @throws MWException
 488          */
 489         protected function checkModelID( $model_id ) {
 490                 if ( $model_id !== $this->mModelID ) {
 491                         throw new MWException( "Bad content model: " .
 492                                 "expected {$this->mModelID} " .
 493                                 "but got $model_id." );
 494                 }
 495         }
 496
 497         /**
 498          * Returns a list of serialization formats supported by the
 499          * serializeContent() and unserializeContent() methods of this
 500          * ContentHandler.
 501          *
 502          * @since 1.21
 503          *
 504          * @return array of serialization formats as MIME type like strings
 505          */
 506         public function getSupportedFormats() {
 507                 return $this->mSupportedFormats;
 508         }
 509
 510         /**
 511          * The format used for serialization/deserialization by default by this
 512          * ContentHandler.
 513          *
 514          * This default implementation will return the first element of the array
 515          * of formats that was passed to the constructor.
 516          *
 517          * @since 1.21
 518          *
 519          * @return string the name of the default serialization format as a MIME type
 520          */
 521         public function getDefaultFormat() {
 522                 return $this->mSupportedFormats[0];
 523         }
 524
 525         /**
 526          * Returns true if $format is a serialization format supported by this
 527          * ContentHandler, and false otherwise.
 528          *
 529          * Note that if $format is null, this method always returns true, because
 530          * null means "use the default format".
 531          *
 532          * @since 1.21
 533          *
 534          * @param string $format the serialization format to check
 535          * @return bool
 536          */
 537         public function isSupportedFormat( $format ) {
 538
 539                 if ( !$format ) {
 540                         return true; // this means "use the default"
 541                 }
 542
 543                 return in_array( $format, $this->mSupportedFormats );
 544         }
 545
 546         /**
 547          * Throws an MWException if isSupportedFormat( $format ) is not true.
 548          * Convenient for checking whether a format provided as a parameter is
 549          * actually supported.
 550          *
 551          * @param string $format the serialization format to check
 552          *
 553          * @throws MWException
 554          */
 555         protected function checkFormat( $format ) {
 556                 if ( !$this->isSupportedFormat( $format ) ) {
 557                         throw new MWException(
 558                                 "Format $format is not supported for content model "
 559                                 . $this->getModelID()
 560                         );
 561                 }
 562         }
 563
 564         /**
 565          * Returns overrides for action handlers.
 566          * Classes listed here will be used instead of the default one when
 567          * (and only when) $wgActions[$action] === true. This allows subclasses
 568          * to override the default action handlers.
 569          *
 570          * @since 1.21
 571          *
 572          * @return Array
 573          */
 574         public function getActionOverrides() {
 575                 return array();
 576         }
 577
 578         /**
 579          * Factory for creating an appropriate DifferenceEngine for this content model.
 580          *
 581          * @since 1.21
 582          *
 583          * @param $context IContextSource context to use, anything else will be
 584          *    ignored
 585          * @param $old Integer Old ID we want to show and diff with.
 586          * @param int|string $new String either 'prev' or 'next'.
 587          * @param $rcid Integer ??? FIXME (default 0)
 588          * @param $refreshCache boolean If set, refreshes the diff cache
 589          * @param $unhide boolean If set, allow viewing deleted revs
 590          *
 591          * @return DifferenceEngine
 592          */
 593         public function createDifferenceEngine( IContextSource $context,
 594                 $old = 0, $new = 0,
 595                 $rcid = 0, # FIXME: use everywhere!
 596                 $refreshCache = false, $unhide = false
 597         ) {
 598                 $diffEngineClass = $this->getDiffEngineClass();
 599
 600                 return new $diffEngineClass( $context, $old, $new, $rcid, $refreshCache, $unhide );
 601         }
 602
 603         /**
 604          * Get the language in which the content of the given page is written.
 605          *
 606          * This default implementation just returns $wgContLang (except for pages in the MediaWiki namespace)
 607          *
 608          * Note that the pages language is not cacheable, since it may in some cases depend on user settings.
 609          *
 610          * Also note that the page language may or may not depend on the actual content of the page,
 611          * that is, this method may load the content in order to determine the language.
 612          *
 613          * @since 1.21
 614          *
 615          * @param Title $title the page to determine the language for.
 616          * @param Content|null $content the page's content, if you have it handy, to avoid reloading it.
 617          *
 618          * @return Language the page's language
 619          */
 620         public function getPageLanguage( Title $title, Content $content = null ) {
 621                 global $wgContLang, $wgLang;
 622                 $pageLang = $wgContLang;
 623
 624                 if ( $title->getNamespace() == NS_MEDIAWIKI ) {
 625                         // Parse mediawiki messages with correct target language
 626                         list( /* $unused */, $lang ) = MessageCache::singleton()->figureMessage( $title->getText() );
 627                         $pageLang = wfGetLangObj( $lang );
 628                 }
 629
 630                 wfRunHooks( 'PageContentLanguage', array( $title, &$pageLang, $wgLang ) );
 631
 632                 return wfGetLangObj( $pageLang );
 633         }
 634
 635         /**
 636          * Get the language in which the content of this page is written when
 637          * viewed by user. Defaults to $this->getPageLanguage(), but if the user
 638          * specified a preferred variant, the variant will be used.
 639          *
 640          * This default implementation just returns $this->getPageLanguage( $title, $content ) unless
 641          * the user specified a preferred variant.
 642          *
 643          * Note that the pages view language is not cacheable, since it depends on user settings.
 644          *
 645          * Also note that the page language may or may not depend on the actual content of the page,
 646          * that is, this method may load the content in order to determine the language.
 647          *
 648          * @since 1.21
 649          *
 650          * @param Title $title the page to determine the language for.
 651          * @param Content|null $content the page's content, if you have it handy, to avoid reloading it.
 652          *
 653          * @return Language the page's language for viewing
 654          */
 655         public function getPageViewLanguage( Title $title, Content $content = null ) {
 656                 $pageLang = $this->getPageLanguage( $title, $content );
 657
 658                 if ( $title->getNamespace() !== NS_MEDIAWIKI ) {
 659                         // If the user chooses a variant, the content is actually
 660                         // in a language whose code is the variant code.
 661                         $variant = $pageLang->getPreferredVariant();
 662                         if ( $pageLang->getCode() !== $variant ) {
 663                                 $pageLang = Language::factory( $variant );
 664                         }
 665                 }
 666
 667                 return $pageLang;
 668         }
 669
 670         /**
 671          * Determines whether the content type handled by this ContentHandler
 672          * can be used on the given page.
 673          *
 674          * This default implementation always returns true.
 675          * Subclasses may override this to restrict the use of this content model to specific locations,
 676          * typically based on the namespace or some other aspect of the title, such as a special suffix
 677          * (e.g. ".svg" for SVG content).
 678          *
 679          * @param Title $title the page's title.
 680          *
 681          * @return bool true if content of this kind can be used on the given page, false otherwise.
 682          */
 683         public function canBeUsedOn( Title $title ) {
 684                 return true;
 685         }
 686
 687         /**
 688          * Returns the name of the diff engine to use.
 689          *
 690          * @since 1.21
 691          *
 692          * @return string
 693          */
 694         protected function getDiffEngineClass() {
 695                 return 'DifferenceEngine';
 696         }
 697
 698         /**
 699          * Attempts to merge differences between three versions.
 700          * Returns a new Content object for a clean merge and false for failure or
 701          * a conflict.
 702          *
 703          * This default implementation always returns false.
 704          *
 705          * @since 1.21
 706          *
 707          * @param $oldContent Content|string  String
 708          * @param $myContent Content|string   String
 709          * @param $yourContent Content|string String
 710          *
 711          * @return Content|Bool
 712          */
 713         public function merge3( Content $oldContent, Content $myContent, Content $yourContent ) {
 714                 return false;
 715         }
 716
 717         /**
 718          * Return an applicable auto-summary if one exists for the given edit.
 719          *
 720          * @since 1.21
 721          *
 722          * @param $oldContent Content|null: the previous text of the page.
 723          * @param $newContent Content|null: The submitted text of the page.
 724          * @param int $flags Bit mask: a bit mask of flags submitted for the edit.
 725          *
 726          * @return string An appropriate auto-summary, or an empty string.
 727          */
 728         public function getAutosummary( Content $oldContent = null, Content $newContent = null, $flags ) {
 729                 // Decide what kind of auto-summary is needed.
 730
 731                 // Redirect auto-summaries
 732
 733                 /**
 734                  * @var $ot Title
 735                  * @var $rt Title
 736                  */
 737
 738                 $ot = !is_null( $oldContent ) ? $oldContent->getRedirectTarget() : null;
 739                 $rt = !is_null( $newContent ) ? $newContent->getRedirectTarget() : null;
 740
 741                 if ( is_object( $rt ) ) {
 742                         if ( !is_object( $ot )
 743                                 || !$rt->equals( $ot )
 744                                 || $ot->getFragment() != $rt->getFragment()
 745                         ) {
 746                                 $truncatedtext = $newContent->getTextForSummary(
 747                                         250
 748                                         - strlen( wfMessage( 'autoredircomment' )->inContentLanguage()->text() )
 749                                         - strlen( $rt->getFullText() ) );
 750
 751                                 return wfMessage( 'autoredircomment', $rt->getFullText() )
 752                                         ->rawParams( $truncatedtext )->inContentLanguage()->text();
 753                         }
 754                 }
 755
 756                 // New page auto-summaries
 757                 if ( $flags & EDIT_NEW && $newContent->getSize() > 0 ) {
 758                         // If they're making a new article, give its text, truncated, in
 759                         // the summary.
 760
 761                         $truncatedtext = $newContent->getTextForSummary(
 762                                 200 - strlen( wfMessage( 'autosumm-new' )->inContentLanguage()->text() ) );
 763
 764                         return wfMessage( 'autosumm-new' )->rawParams( $truncatedtext )
 765                                 ->inContentLanguage()->text();
 766                 }
 767
 768                 // Blanking auto-summaries
 769                 if ( !empty( $oldContent ) && $oldContent->getSize() > 0 && $newContent->getSize() == 0 ) {
 770                         return wfMessage( 'autosumm-blank' )->inContentLanguage()->text();
 771                 } elseif ( !empty( $oldContent )
 772                         && $oldContent->getSize() > 10 * $newContent->getSize()
 773                         && $newContent->getSize() < 500
 774                 ) {
 775                         // Removing more than 90% of the article
 776
 777                         $truncatedtext = $newContent->getTextForSummary(
 778                                 200 - strlen( wfMessage( 'autosumm-replace' )->inContentLanguage()->text() ) );
 779
 780                         return wfMessage( 'autosumm-replace' )->rawParams( $truncatedtext )
 781                                 ->inContentLanguage()->text();
 782                 }
 783
 784                 // If we reach this point, there's no applicable auto-summary for our
 785                 // case, so our auto-summary is empty.
 786                 return '';
 787         }
 788
 789         /**
 790          * Auto-generates a deletion reason
 791          *
 792          * @since 1.21
 793          *
 794          * @param $title Title: the page's title
 795          * @param &$hasHistory Boolean: whether the page has a history
 796          * @return mixed String containing deletion reason or empty string, or
 797          *    boolean false if no revision occurred
 798          *
 799          * @XXX &$hasHistory is extremely ugly, it's here because
 800          * WikiPage::getAutoDeleteReason() and Article::generateReason()
 801          * have it / want it.
 802          */
 803         public function getAutoDeleteReason( Title $title, &$hasHistory ) {
 804                 $dbw = wfGetDB( DB_MASTER );
 805
 806                 // Get the last revision
 807                 $rev = Revision::newFromTitle( $title );
 808
 809                 if ( is_null( $rev ) ) {
 810                         return false;
 811                 }
 812
 813                 // Get the article's contents
 814                 $content = $rev->getContent();
 815                 $blank = false;
 816
 817                 // If the page is blank, use the text from the previous revision,
 818                 // which can only be blank if there's a move/import/protect dummy
 819                 // revision involved
 820                 if ( !$content || $content->isEmpty() ) {
 821                         $prev = $rev->getPrevious();
 822
 823                         if ( $prev ) {
 824                                 $rev = $prev;
 825                                 $content = $rev->getContent();
 826                                 $blank = true;
 827                         }
 828                 }
 829
 830                 $this->checkModelID( $rev->getContentModel() );
 831
 832                 // Find out if there was only one contributor
 833                 // Only scan the last 20 revisions
 834                 $res = $dbw->select( 'revision', 'rev_user_text',
 835                         array(
 836                                 'rev_page' => $title->getArticleID(),
 837                                 $dbw->bitAnd( 'rev_deleted', Revision::DELETED_USER ) . ' = 0'
 838                         ),
 839                         __METHOD__,
 840                         array( 'LIMIT' => 20 )
 841                 );
 842
 843                 if ( $res === false ) {
 844                         // This page has no revisions, which is very weird
 845                         return false;
 846                 }
 847
 848                 $hasHistory = ( $res->numRows() > 1 );
 849                 $row = $dbw->fetchObject( $res );
 850
 851                 if ( $row ) { // $row is false if the only contributor is hidden
 852                         $onlyAuthor = $row->rev_user_text;
 853                         // Try to find a second contributor
 854                         foreach ( $res as $row ) {
 855                                 if ( $row->rev_user_text != $onlyAuthor ) { // Bug 22999
 856                                         $onlyAuthor = false;
 857                                         break;
 858                                 }
 859                         }
 860                 } else {
 861                         $onlyAuthor = false;
 862                 }
 863
 864                 // Generate the summary with a '$1' placeholder
 865                 if ( $blank ) {
 866                         // The current revision is blank and the one before is also
 867                         // blank. It's just not our lucky day
 868                         $reason = wfMessage( 'exbeforeblank', '$1' )->inContentLanguage()->text();
 869                 } else {
 870                         if ( $onlyAuthor ) {
 871                                 $reason = wfMessage(
 872                                         'excontentauthor',
 873                                         '$1',
 874                                         $onlyAuthor
 875                                 )->inContentLanguage()->text();
 876                         } else {
 877                                 $reason = wfMessage( 'excontent', '$1' )->inContentLanguage()->text();
 878                         }
 879                 }
 880
 881                 if ( $reason == '-' ) {
 882                         // Allow these UI messages to be blanked out cleanly
 883                         return '';
 884                 }
 885
 886                 // Max content length = max comment length - length of the comment (excl. $1)
 887                 $text = $content ? $content->getTextForSummary( 255 - ( strlen( $reason ) - 2 ) ) : '';
 888
 889                 // Now replace the '$1' placeholder
 890                 $reason = str_replace( '$1', $text, $reason );
 891
 892                 return $reason;
 893         }
 894
 895         /**
 896          * Get the Content object that needs to be saved in order to undo all revisions
 897          * between $undo and $undoafter. Revisions must belong to the same page,
 898          * must exist and must not be deleted.
 899          *
 900          * @since 1.21
 901          *
 902          * @param $current Revision The current text
 903          * @param $undo Revision The revision to undo
 904          * @param $undoafter Revision Must be an earlier revision than $undo
 905          *
 906          * @return mixed String on success, false on failure
 907          */
 908         public function getUndoContent( Revision $current, Revision $undo, Revision $undoafter ) {
 909                 $cur_content = $current->getContent();
 910
 911                 if ( empty( $cur_content ) ) {
 912                         return false; // no page
 913                 }
 914
 915                 $undo_content = $undo->getContent();
 916                 $undoafter_content = $undoafter->getContent();
 917
 918                 if ( !$undo_content || !$undoafter_content ) {
 919                         return false; // no content to undo
 920                 }
 921
 922                 $this->checkModelID( $cur_content->getModel() );
 923                 $this->checkModelID( $undo_content->getModel() );
 924                 $this->checkModelID( $undoafter_content->getModel() );
 925
 926                 if ( $cur_content->equals( $undo_content ) ) {
 927                         // No use doing a merge if it's just a straight revert.
 928                         return $undoafter_content;
 929                 }
 930
 931                 $undone_content = $this->merge3( $undo_content, $undoafter_content, $cur_content );
 932
 933                 return $undone_content;
 934         }
 935
 936         /**
 937          * Get parser options suitable for rendering the primary article wikitext
 938          *
 939          * @param IContextSource|User|string $context One of the following:
 940          *        - IContextSource: Use the User and the Language of the provided
 941          *                                            context
 942          *        - User: Use the provided User object and $wgLang for the language,
 943          *                                            so use an IContextSource object if possible.
 944          *        - 'canonical': Canonical options (anonymous user with default
 945          *                                            preferences and content language).
 946          *
 947          * @param IContextSource|User|string $context
 948          *
 949          * @throws MWException
 950          * @return ParserOptions
 951          */
 952         public function makeParserOptions( $context ) {
 953                 global $wgContLang, $wgEnableParserLimitReporting;
 954
 955                 if ( $context instanceof IContextSource ) {
 956                         $options = ParserOptions::newFromContext( $context );
 957                 } elseif ( $context instanceof User ) { // settings per user (even anons)
 958                         $options = ParserOptions::newFromUser( $context );
 959                 } elseif ( $context === 'canonical' ) { // canonical settings
 960                         $options = ParserOptions::newFromUserAndLang( new User, $wgContLang );
 961                 } else {
 962                         throw new MWException( "Bad context for parser options: $context" );
 963                 }
 964
 965                 $options->enableLimitReport( $wgEnableParserLimitReporting ); // show inclusion/loop reports
 966                 $options->setTidy( true ); // fix bad HTML
 967
 968                 return $options;
 969         }
 970
 971         /**
 972          * Returns true for content models that support caching using the
 973          * ParserCache mechanism. See WikiPage::isParserCacheUsed().
 974          *
 975          * @since 1.21
 976          *
 977          * @return bool
 978          */
 979         public function isParserCacheSupported() {
 980                 return false;
 981         }
 982
 983         /**
 984          * Returns true if this content model supports sections.
 985          * This default implementation returns false.
 986          *
 987          * Content models that return true here should also implement
 988          * Content::getSection, Content::replaceSection, etc. to handle sections..
 989          *
 990          * @return boolean whether sections are supported.
 991          */
 992         public function supportsSections() {
 993                 return false;
 994         }
 995
 996         /**
 997          * Returns true if this content model supports redirects.
 998          * This default implementation returns false.
 999          *
1000          * Content models that return true here should also implement
1001          * ContentHandler::makeRedirectContent to return a Content object.
1002          *
1003          * @return boolean whether redirects are supported.
1004          */
1005         public function supportsRedirects() {
1006                 return false;
1007         }
1008
1009         /**
1010          * Logs a deprecation warning, visible if $wgDevelopmentWarnings, but only if
1011          * self::$enableDeprecationWarnings is set to true.
1012          *
1013          * @param string $func The name of the deprecated function
1014          * @param string $version The version since the method is deprecated. Usually 1.21
1015          *   for ContentHandler related stuff.
1016          * @param string|bool $component : Component to which the function belongs.
1017          *   If false, it is assumed the function is in MediaWiki core.
1018          *
1019          * @see ContentHandler::$enableDeprecationWarnings
1020          * @see wfDeprecated
1021          */
1022         public static function deprecated( $func, $version, $component = false ) {
1023                 if ( self::$enableDeprecationWarnings ) {
1024                         wfDeprecated( $func, $version, $component, 3 );
1025                 }
1026         }
1027
1028         /**
1029          * Call a legacy hook that uses text instead of Content objects.
1030          * Will log a warning when a matching hook function is registered.
1031          * If the textual representation of the content is changed by the
1032          * hook function, a new Content object is constructed from the new
1033          * text.
1034          *
1035          * @param string $event event name
1036          * @param array $args parameters passed to hook functions
1037          * @param bool $warn whether to log a warning.
1038          *                    Default to self::$enableDeprecationWarnings.
1039          *                    May be set to false for testing.
1040          *
1041          * @return Boolean True if no handler aborted the hook
1042          *
1043          * @see ContentHandler::$enableDeprecationWarnings
1044          */
1045         public static function runLegacyHooks( $event, $args = array(),
1046                 $warn = null
1047         ) {
1048
1049                 if ( $warn === null ) {
1050                         $warn = self::$enableDeprecationWarnings;
1051                 }
1052
1053                 if ( !Hooks::isRegistered( $event ) ) {
1054                         return true; // nothing to do here
1055                 }
1056
1057                 if ( $warn ) {
1058                         // Log information about which handlers are registered for the legacy hook,
1059                         // so we can find and fix them.
1060
1061                         $handlers = Hooks::getHandlers( $event );
1062                         $handlerInfo = array();
1063
1064                         wfSuppressWarnings();
1065
1066                         foreach ( $handlers as $handler ) {
1067                                 if ( is_array( $handler ) ) {
1068                                         if ( is_object( $handler[0] ) ) {
1069                                                 $info = get_class( $handler[0] );
1070                                         } else {
1071                                                 $info = $handler[0];
1072                                         }
1073
1074                                         if ( isset( $handler[1] ) ) {
1075                                                 $info .= '::' . $handler[1];
1076                                         }
1077                                 } elseif ( is_object( $handler ) ) {
1078                                         $info = get_class( $handler[0] );
1079                                         $info .= '::on' . $event;
1080                                 } else {
1081                                         $info = $handler;
1082                                 }
1083
1084                                 $handlerInfo[] = $info;
1085                         }
1086
1087                         wfRestoreWarnings();
1088
1089                         wfWarn( "Using obsolete hook $event via ContentHandler::runLegacyHooks()! Handlers: " . implode( ', ', $handlerInfo ), 2 );
1090                 }
1091
1092                 // convert Content objects to text
1093                 $contentObjects = array();
1094                 $contentTexts = array();
1095
1096                 foreach ( $args as $k => $v ) {
1097                         if ( $v instanceof Content ) {
1098                                 /* @var Content $v */
1099
1100                                 $contentObjects[$k] = $v;
1101
1102                                 $v = $v->serialize();
1103                                 $contentTexts[$k] = $v;
1104                                 $args[$k] = $v;
1105                         }
1106                 }
1107
1108                 // call the hook functions
1109                 $ok = wfRunHooks( $event, $args );
1110
1111                 // see if the hook changed the text
1112                 foreach ( $contentTexts as $k => $orig ) {
1113                         /* @var Content $content */
1114
1115                         $modified = $args[$k];
1116                         $content = $contentObjects[$k];
1117
1118                         if ( $modified !== $orig ) {
1119                                 // text was changed, create updated Content object
1120                                 $content = $content->getContentHandler()->unserializeContent( $modified );
1121                         }
1122
1123                         $args[$k] = $content;
1124                 }
1125
1126                 return $ok;
1127         }
1128 }