includes/content/ContentHandler.php

   1 <?php
   2
   3 /**
   4  * Base class for content handling.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License along
  17  * with this program; if not, write to the Free Software Foundation, Inc.,
  18  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  19  * http://www.gnu.org/copyleft/gpl.html
  20  *
  21  * @since 1.21
  22  *
  23  * @file
  24  * @ingroup Content
  25  *
  26  * @author Daniel Kinzler
  27  */
  28
  29 use Wikimedia\Assert\Assert;
  30 use MediaWiki\Logger\LoggerFactory;
  31 use MediaWiki\MediaWikiServices;
  32 use MediaWiki\Revision\SlotRenderingProvider;
  33 use MediaWiki\Search\ParserOutputSearchDataExtractor;
  34
  35 /**
  36  * A content handler knows how do deal with a specific type of content on a wiki
  37  * page. Content is stored in the database in a serialized form (using a
  38  * serialization format a.k.a. MIME type) and is unserialized into its native
  39  * PHP representation (the content model), which is wrapped in an instance of
  40  * the appropriate subclass of Content.
  41  *
  42  * ContentHandler instances are stateless singletons that serve, among other
  43  * things, as a factory for Content objects. Generally, there is one subclass
  44  * of ContentHandler and one subclass of Content for every type of content model.
  45  *
  46  * Some content types have a flat model, that is, their native representation
  47  * is the same as their serialized form. Examples would be JavaScript and CSS
  48  * code. As of now, this also applies to wikitext (MediaWiki's default content
  49  * type), but wikitext content may be represented by a DOM or AST structure in
  50  * the future.
  51  *
  52  * @ingroup Content
  53  */
  54 abstract class ContentHandler {
  55         /**
  56          * Convenience function for getting flat text from a Content object. This
  57          * should only be used in the context of backwards compatibility with code
  58          * that is not yet able to handle Content objects!
  59          *
  60          * If $content is null, this method returns the empty string.
  61          *
  62          * If $content is an instance of TextContent, this method returns the flat
  63          * text as returned by $content->getText().
  64          *
  65          * If $content is not a TextContent object, the behavior of this method
  66          * depends on the global $wgContentHandlerTextFallback:
  67          * - If $wgContentHandlerTextFallback is 'fail' and $content is not a
  68          *   TextContent object, an MWException is thrown.
  69          * - If $wgContentHandlerTextFallback is 'serialize' and $content is not a
  70          *   TextContent object, $content->serialize() is called to get a string
  71          *   form of the content.
  72          * - If $wgContentHandlerTextFallback is 'ignore' and $content is not a
  73          *   TextContent object, this method returns null.
  74          * - otherwise, the behavior is undefined.
  75          *
  76          * @since 1.21
  77          *
  78          * @param Content|null $content
  79          *
  80          * @throws MWException If the content is not an instance of TextContent and
  81          * wgContentHandlerTextFallback was set to 'fail'.
  82          * @return string|null Textual form of the content, if available.
  83          */
  84         public static function getContentText( Content $content = null ) {
  85                 global $wgContentHandlerTextFallback;
  86
  87                 if ( is_null( $content ) ) {
  88                         return '';
  89                 }
  90
  91                 if ( $content instanceof TextContent ) {
  92                         return $content->getText();
  93                 }
  94
  95                 wfDebugLog( 'ContentHandler', 'Accessing ' . $content->getModel() . ' content as text!' );
  96
  97                 if ( $wgContentHandlerTextFallback == 'fail' ) {
  98                         throw new MWException(
  99                                 "Attempt to get text from Content with model " .
 100                                 $content->getModel()
 101                         );
 102                 }
 103
 104                 if ( $wgContentHandlerTextFallback == 'serialize' ) {
 105                         return $content->serialize();
 106                 }
 107
 108                 return null;
 109         }
 110
 111         /**
 112          * Convenience function for creating a Content object from a given textual
 113          * representation.
 114          *
 115          * $text will be deserialized into a Content object of the model specified
 116          * by $modelId (or, if that is not given, $title->getContentModel()) using
 117          * the given format.
 118          *
 119          * @since 1.21
 120          *
 121          * @param string $text The textual representation, will be
 122          *    unserialized to create the Content object
 123          * @param Title|null $title The title of the page this text belongs to.
 124          *    Required if $modelId is not provided.
 125          * @param string|null $modelId The model to deserialize to. If not provided,
 126          *    $title->getContentModel() is used.
 127          * @param string|null $format The format to use for deserialization. If not
 128          *    given, the model's default format is used.
 129          *
 130          * @throws MWException If model ID or format is not supported or if the text can not be
 131          * unserialized using the format.
 132          * @return Content A Content object representing the text.
 133          */
 134         public static function makeContent( $text, Title $title = null,
 135                 $modelId = null, $format = null ) {
 136                 if ( is_null( $modelId ) ) {
 137                         if ( is_null( $title ) ) {
 138                                 throw new MWException( "Must provide a Title object or a content model ID." );
 139                         }
 140
 141                         $modelId = $title->getContentModel();
 142                 }
 143
 144                 $handler = self::getForModelID( $modelId );
 145
 146                 return $handler->unserializeContent( $text, $format );
 147         }
 148
 149         /**
 150          * Returns the name of the default content model to be used for the page
 151          * with the given title.
 152          *
 153          * Note: There should rarely be need to call this method directly.
 154          * To determine the actual content model for a given page, use
 155          * Title::getContentModel().
 156          *
 157          * Which model is to be used by default for the page is determined based
 158          * on several factors:
 159          * - The global setting $wgNamespaceContentModels specifies a content model
 160          *   per namespace.
 161          * - The hook ContentHandlerDefaultModelFor may be used to override the page's default
 162          *   model.
 163          * - Pages in NS_MEDIAWIKI and NS_USER default to the CSS or JavaScript
 164          *   model if they end in .js or .css, respectively.
 165          * - Pages in NS_MEDIAWIKI default to the wikitext model otherwise.
 166          * - The hook TitleIsCssOrJsPage may be used to force a page to use the CSS
 167          *   or JavaScript model. This is a compatibility feature. The ContentHandlerDefaultModelFor
 168          *   hook should be used instead if possible.
 169          * - The hook TitleIsWikitextPage may be used to force a page to use the
 170          *   wikitext model. This is a compatibility feature. The ContentHandlerDefaultModelFor
 171          *   hook should be used instead if possible.
 172          *
 173          * If none of the above applies, the wikitext model is used.
 174          *
 175          * Note: this is used by, and may thus not use, Title::getContentModel()
 176          *
 177          * @since 1.21
 178          * @deprecated since 1.33, use SlotRoleHandler::getDefaultModel() together with
 179          * SlotRoleRegistry::getRoleHandler().
 180          *
 181          * @param Title $title
 182          *
 183          * @return string Default model name for the page given by $title
 184          */
 185         public static function getDefaultModelFor( Title $title ) {
 186                 $slotRoleregistry = MediaWikiServices::getInstance()->getSlotRoleRegistry();
 187                 $mainSlotHandler = $slotRoleregistry->getRoleHandler( 'main' );
 188                 return $mainSlotHandler->getDefaultModel( $title );
 189         }
 190
 191         /**
 192          * Returns the appropriate ContentHandler singleton for the given title.
 193          *
 194          * @since 1.21
 195          *
 196          * @param Title $title
 197          *
 198          * @return ContentHandler
 199          */
 200         public static function getForTitle( Title $title ) {
 201                 $modelId = $title->getContentModel();
 202
 203                 return self::getForModelID( $modelId );
 204         }
 205
 206         /**
 207          * Returns the appropriate ContentHandler singleton for the given Content
 208          * object.
 209          *
 210          * @since 1.21
 211          *
 212          * @param Content $content
 213          *
 214          * @return ContentHandler
 215          */
 216         public static function getForContent( Content $content ) {
 217                 $modelId = $content->getModel();
 218
 219                 return self::getForModelID( $modelId );
 220         }
 221
 222         /**
 223          * @var array A Cache of ContentHandler instances by model id
 224          */
 225         protected static $handlers;
 226
 227         /**
 228          * Returns the ContentHandler singleton for the given model ID. Use the
 229          * CONTENT_MODEL_XXX constants to identify the desired content model.
 230          *
 231          * ContentHandler singletons are taken from the global $wgContentHandlers
 232          * array. Keys in that array are model names, the values are either
 233          * ContentHandler singleton objects, or strings specifying the appropriate
 234          * subclass of ContentHandler.
 235          *
 236          * If a class name is encountered when looking up the singleton for a given
 237          * model name, the class is instantiated and the class name is replaced by
 238          * the resulting singleton in $wgContentHandlers.
 239          *
 240          * If no ContentHandler is defined for the desired $modelId, the
 241          * ContentHandler may be provided by the ContentHandlerForModelID hook.
 242          * If no ContentHandler can be determined, an MWException is raised.
 243          *
 244          * @since 1.21
 245          *
 246          * @param string $modelId The ID of the content model for which to get a
 247          *    handler. Use CONTENT_MODEL_XXX constants.
 248          *
 249          * @throws MWException For internal errors and problems in the configuration.
 250          * @throws MWUnknownContentModelException If no handler is known for the model ID.
 251          * @return ContentHandler The ContentHandler singleton for handling the model given by the ID.
 252          */
 253         public static function getForModelID( $modelId ) {
 254                 global $wgContentHandlers;
 255
 256                 if ( isset( self::$handlers[$modelId] ) ) {
 257                         return self::$handlers[$modelId];
 258                 }
 259
 260                 if ( empty( $wgContentHandlers[$modelId] ) ) {
 261                         $handler = null;
 262
 263                         Hooks::run( 'ContentHandlerForModelID', [ $modelId, &$handler ] );
 264
 265                         if ( $handler === null ) {
 266                                 throw new MWUnknownContentModelException( $modelId );
 267                         }
 268
 269                         if ( !( $handler instanceof ContentHandler ) ) {
 270                                 throw new MWException( "ContentHandlerForModelID must supply a ContentHandler instance" );
 271                         }
 272                 } else {
 273                         $classOrCallback = $wgContentHandlers[$modelId];
 274
 275                         if ( is_callable( $classOrCallback ) ) {
 276                                 $handler = call_user_func( $classOrCallback, $modelId );
 277                         } else {
 278                                 $handler = new $classOrCallback( $modelId );
 279                         }
 280
 281                         if ( !( $handler instanceof ContentHandler ) ) {
 282                                 throw new MWException( "$classOrCallback from \$wgContentHandlers is not " .
 283                                         "compatible with ContentHandler" );
 284                         }
 285                 }
 286
 287                 wfDebugLog( 'ContentHandler', 'Created handler for ' . $modelId
 288                         . ': ' . get_class( $handler ) );
 289
 290                 self::$handlers[$modelId] = $handler;
 291
 292                 return self::$handlers[$modelId];
 293         }
 294
 295         /**
 296          * Clean up handlers cache.
 297          */
 298         public static function cleanupHandlersCache() {
 299                 self::$handlers = [];
 300         }
 301
 302         /**
 303          * Returns the localized name for a given content model.
 304          *
 305          * Model names are localized using system messages. Message keys
 306          * have the form content-model-$name, where $name is getContentModelName( $id ).
 307          *
 308          * @param string $name The content model ID, as given by a CONTENT_MODEL_XXX
 309          *    constant or returned by Revision::getContentModel().
 310          * @param Language|null $lang The language to parse the message in (since 1.26)
 311          *
 312          * @throws MWException If the model ID isn't known.
 313          * @return string The content model's localized name.
 314          */
 315         public static function getLocalizedName( $name, Language $lang = null ) {
 316                 // Messages: content-model-wikitext, content-model-text,
 317                 // content-model-javascript, content-model-css
 318                 $key = "content-model-$name";
 319
 320                 $msg = wfMessage( $key );
 321                 if ( $lang ) {
 322                         $msg->inLanguage( $lang );
 323                 }
 324
 325                 return $msg->exists() ? $msg->plain() : $name;
 326         }
 327
 328         public static function getContentModels() {
 329                 global $wgContentHandlers;
 330
 331                 $models = array_keys( $wgContentHandlers );
 332                 Hooks::run( 'GetContentModels', [ &$models ] );
 333                 return $models;
 334         }
 335
 336         public static function getAllContentFormats() {
 337                 global $wgContentHandlers;
 338
 339                 $formats = [];
 340
 341                 foreach ( $wgContentHandlers as $model => $class ) {
 342                         $handler = self::getForModelID( $model );
 343                         $formats = array_merge( $formats, $handler->getSupportedFormats() );
 344                 }
 345
 346                 $formats = array_unique( $formats );
 347
 348                 return $formats;
 349         }
 350
 351         // ------------------------------------------------------------------------
 352
 353         /**
 354          * @var string
 355          */
 356         protected $mModelID;
 357
 358         /**
 359          * @var string[]
 360          */
 361         protected $mSupportedFormats;
 362
 363         /**
 364          * Constructor, initializing the ContentHandler instance with its model ID
 365          * and a list of supported formats. Values for the parameters are typically
 366          * provided as literals by subclass's constructors.
 367          *
 368          * @param string $modelId (use CONTENT_MODEL_XXX constants).
 369          * @param string[] $formats List for supported serialization formats
 370          *    (typically as MIME types)
 371          */
 372         public function __construct( $modelId, $formats ) {
 373                 $this->mModelID = $modelId;
 374                 $this->mSupportedFormats = $formats;
 375         }
 376
 377         /**
 378          * Serializes a Content object of the type supported by this ContentHandler.
 379          *
 380          * @since 1.21
 381          *
 382          * @param Content $content The Content object to serialize
 383          * @param string|null $format The desired serialization format
 384          *
 385          * @return string Serialized form of the content
 386          */
 387         abstract public function serializeContent( Content $content, $format = null );
 388
 389         /**
 390          * Applies transformations on export (returns the blob unchanged per default).
 391          * Subclasses may override this to perform transformations such as conversion
 392          * of legacy formats or filtering of internal meta-data.
 393          *
 394          * @param string $blob The blob to be exported
 395          * @param string|null $format The blob's serialization format
 396          *
 397          * @return string
 398          */
 399         public function exportTransform( $blob, $format = null ) {
 400                 return $blob;
 401         }
 402
 403         /**
 404          * Unserializes a Content object of the type supported by this ContentHandler.
 405          *
 406          * @since 1.21
 407          *
 408          * @param string $blob Serialized form of the content
 409          * @param string|null $format The format used for serialization
 410          *
 411          * @return Content The Content object created by deserializing $blob
 412          */
 413         abstract public function unserializeContent( $blob, $format = null );
 414
 415         /**
 416          * Apply import transformation (per default, returns $blob unchanged).
 417          * This gives subclasses an opportunity to transform data blobs on import.
 418          *
 419          * @since 1.24
 420          *
 421          * @param string $blob
 422          * @param string|null $format
 423          *
 424          * @return string
 425          */
 426         public function importTransform( $blob, $format = null ) {
 427                 return $blob;
 428         }
 429
 430         /**
 431          * Creates an empty Content object of the type supported by this
 432          * ContentHandler.
 433          *
 434          * @since 1.21
 435          *
 436          * @return Content
 437          */
 438         abstract public function makeEmptyContent();
 439
 440         /**
 441          * Creates a new Content object that acts as a redirect to the given page,
 442          * or null if redirects are not supported by this content model.
 443          *
 444          * This default implementation always returns null. Subclasses supporting redirects
 445          * must override this method.
 446          *
 447          * Note that subclasses that override this method to return a Content object
 448          * should also override supportsRedirects() to return true.
 449          *
 450          * @since 1.21
 451          *
 452          * @param Title $destination The page to redirect to.
 453          * @param string $text Text to include in the redirect, if possible.
 454          *
 455          * @return Content Always null.
 456          */
 457         public function makeRedirectContent( Title $destination, $text = '' ) {
 458                 return null;
 459         }
 460
 461         /**
 462          * Returns the model id that identifies the content model this
 463          * ContentHandler can handle. Use with the CONTENT_MODEL_XXX constants.
 464          *
 465          * @since 1.21
 466          *
 467          * @return string The model ID
 468          */
 469         public function getModelID() {
 470                 return $this->mModelID;
 471         }
 472
 473         /**
 474          * @since 1.21
 475          *
 476          * @param string $model_id The model to check
 477          *
 478          * @throws MWException If the model ID is not the ID of the content model supported by this
 479          * ContentHandler.
 480          */
 481         protected function checkModelID( $model_id ) {
 482                 if ( $model_id !== $this->mModelID ) {
 483                         throw new MWException( "Bad content model: " .
 484                                 "expected {$this->mModelID} " .
 485                                 "but got $model_id." );
 486                 }
 487         }
 488
 489         /**
 490          * Returns a list of serialization formats supported by the
 491          * serializeContent() and unserializeContent() methods of this
 492          * ContentHandler.
 493          *
 494          * @since 1.21
 495          *
 496          * @return string[] List of serialization formats as MIME type like strings
 497          */
 498         public function getSupportedFormats() {
 499                 return $this->mSupportedFormats;
 500         }
 501
 502         /**
 503          * The format used for serialization/deserialization by default by this
 504          * ContentHandler.
 505          *
 506          * This default implementation will return the first element of the array
 507          * of formats that was passed to the constructor.
 508          *
 509          * @since 1.21
 510          *
 511          * @return string The name of the default serialization format as a MIME type
 512          */
 513         public function getDefaultFormat() {
 514                 return $this->mSupportedFormats[0];
 515         }
 516
 517         /**
 518          * Returns true if $format is a serialization format supported by this
 519          * ContentHandler, and false otherwise.
 520          *
 521          * Note that if $format is null, this method always returns true, because
 522          * null means "use the default format".
 523          *
 524          * @since 1.21
 525          *
 526          * @param string $format The serialization format to check
 527          *
 528          * @return bool
 529          */
 530         public function isSupportedFormat( $format ) {
 531                 if ( !$format ) {
 532                         return true; // this means "use the default"
 533                 }
 534
 535                 return in_array( $format, $this->mSupportedFormats );
 536         }
 537
 538         /**
 539          * Convenient for checking whether a format provided as a parameter is actually supported.
 540          *
 541          * @param string $format The serialization format to check
 542          *
 543          * @throws MWException If the format is not supported by this content handler.
 544          */
 545         protected function checkFormat( $format ) {
 546                 if ( !$this->isSupportedFormat( $format ) ) {
 547                         throw new MWException(
 548                                 "Format $format is not supported for content model "
 549                                 . $this->getModelID()
 550                         );
 551                 }
 552         }
 553
 554         /**
 555          * Returns overrides for action handlers.
 556          * Classes listed here will be used instead of the default one when
 557          * (and only when) $wgActions[$action] === true. This allows subclasses
 558          * to override the default action handlers.
 559          *
 560          * @since 1.21
 561          *
 562          * @return array An array mapping action names (typically "view", "edit", "history" etc.) to
 563          *  either the full qualified class name of an Action class, a callable taking ( Page $page,
 564          *  IContextSource $context = null ) as parameters and returning an Action object, or an actual
 565          *  Action object. An empty array in this default implementation.
 566          *
 567          * @see Action::factory
 568          */
 569         public function getActionOverrides() {
 570                 return [];
 571         }
 572
 573         /**
 574          * Factory for creating an appropriate DifferenceEngine for this content model.
 575          * Since 1.32, this is only used for page-level diffs; to diff two content objects,
 576          * use getSlotDiffRenderer.
 577          *
 578          * The DifferenceEngine subclass to use is selected in getDiffEngineClass(). The
 579          * GetDifferenceEngine hook will receive the DifferenceEngine object and can replace or
 580          * wrap it.
 581          * (Note that in older versions of MediaWiki the hook documentation instructed extensions
 582          * to return false from the hook; you should not rely on always being able to decorate
 583          * the DifferenceEngine instance from the hook. If the owner of the content type wants to
 584          * decorare the instance, overriding this method is a safer approach.)
 585          *
 586          * @todo This is page-level functionality so it should not belong to ContentHandler.
 587          *   Move it to a better place once one exists (e.g. PageTypeHandler).
 588          *
 589          * @since 1.21
 590          *
 591          * @param IContextSource $context Context to use, anything else will be ignored.
 592          * @param int $old Revision ID we want to show and diff with.
 593          * @param int|string $new Either a revision ID or one of the strings 'cur', 'prev' or 'next'.
 594          * @param int $rcid FIXME: Deprecated, no longer used. Defaults to 0.
 595          * @param bool $refreshCache If set, refreshes the diff cache. Defaults to false.
 596          * @param bool $unhide If set, allow viewing deleted revs. Defaults to false.
 597          *
 598          * @return DifferenceEngine
 599          */
 600         public function createDifferenceEngine( IContextSource $context, $old = 0, $new = 0,
 601                 $rcid = 0, // FIXME: Deprecated, no longer used
 602                 $refreshCache = false, $unhide = false
 603         ) {
 604                 $diffEngineClass = $this->getDiffEngineClass();
 605                 $differenceEngine = new $diffEngineClass( $context, $old, $new, $rcid, $refreshCache, $unhide );
 606                 Hooks::run( 'GetDifferenceEngine', [ $context, $old, $new, $refreshCache, $unhide,
 607                         &$differenceEngine ] );
 608                 return $differenceEngine;
 609         }
 610
 611         /**
 612          * Get an appropriate SlotDiffRenderer for this content model.
 613          * @since 1.32
 614          * @param IContextSource $context
 615          * @return SlotDiffRenderer
 616          */
 617         final public function getSlotDiffRenderer( IContextSource $context ) {
 618                 $slotDiffRenderer = $this->getSlotDiffRendererInternal( $context );
 619                 if ( get_class( $slotDiffRenderer ) === TextSlotDiffRenderer::class ) {
 620                         //  To keep B/C, when SlotDiffRenderer is not overridden for a given content type
 621                         // but DifferenceEngine is, use that instead.
 622                         $differenceEngine = $this->createDifferenceEngine( $context );
 623                         if ( get_class( $differenceEngine ) !== DifferenceEngine::class ) {
 624                                 // TODO turn this into a deprecation warning in a later release
 625                                 LoggerFactory::getInstance( 'diff' )->info(
 626                                         'Falling back to DifferenceEngineSlotDiffRenderer', [
 627                                                 'modelID' => $this->getModelID(),
 628                                                 'DifferenceEngine' => get_class( $differenceEngine ),
 629                                         ] );
 630                                 $slotDiffRenderer = new DifferenceEngineSlotDiffRenderer( $differenceEngine );
 631                         }
 632                 }
 633                 Hooks::run( 'GetSlotDiffRenderer', [ $this, &$slotDiffRenderer, $context ] );
 634                 return $slotDiffRenderer;
 635         }
 636
 637         /**
 638          * Return the SlotDiffRenderer appropriate for this content handler.
 639          * @param IContextSource $context
 640          * @return SlotDiffRenderer
 641          */
 642         protected function getSlotDiffRendererInternal( IContextSource $context ) {
 643                 $contentLanguage = MediaWikiServices::getInstance()->getContentLanguage();
 644                 $statsdDataFactory = MediaWikiServices::getInstance()->getStatsdDataFactory();
 645                 $slotDiffRenderer = new TextSlotDiffRenderer();
 646                 $slotDiffRenderer->setStatsdDataFactory( $statsdDataFactory );
 647                 // XXX using the page language would be better, but it's unclear how that should be injected
 648                 $slotDiffRenderer->setLanguage( $contentLanguage );
 649
 650                 $engine = DifferenceEngine::getEngine();
 651                 if ( $engine === false ) {
 652                         $slotDiffRenderer->setEngine( TextSlotDiffRenderer::ENGINE_PHP );
 653                 } elseif ( $engine === 'wikidiff2' ) {
 654                         $slotDiffRenderer->setEngine( TextSlotDiffRenderer::ENGINE_WIKIDIFF2 );
 655                 } else {
 656                         $slotDiffRenderer->setEngine( TextSlotDiffRenderer::ENGINE_EXTERNAL, $engine );
 657                 }
 658
 659                 return $slotDiffRenderer;
 660         }
 661
 662         /**
 663          * Get the language in which the content of the given page is written.
 664          *
 665          * This default implementation just returns the content language (except for pages
 666          * in the MediaWiki namespace)
 667          *
 668          * Note that the page's language is not cacheable, since it may in some
 669          * cases depend on user settings.
 670          *
 671          * Also note that the page language may or may not depend on the actual content of the page,
 672          * that is, this method may load the content in order to determine the language.
 673          *
 674          * @since 1.21
 675          *
 676          * @param Title $title The page to determine the language for.
 677          * @param Content|null $content The page's content, if you have it handy, to avoid reloading it.
 678          *
 679          * @return Language The page's language
 680          */
 681         public function getPageLanguage( Title $title, Content $content = null ) {
 682                 global $wgLang;
 683                 $pageLang = MediaWikiServices::getInstance()->getContentLanguage();
 684
 685                 if ( $title->inNamespace( NS_MEDIAWIKI ) ) {
 686                         // Parse mediawiki messages with correct target language
 687                         list( /* $unused */, $lang ) = MessageCache::singleton()->figureMessage( $title->getText() );
 688                         $pageLang = Language::factory( $lang );
 689                 }
 690
 691                 // Simplify hook handlers by only passing objects of one type, in case nothing
 692                 // else has unstubbed the StubUserLang object by now.
 693                 StubObject::unstub( $wgLang );
 694
 695                 Hooks::run( 'PageContentLanguage', [ $title, &$pageLang, $wgLang ] );
 696
 697                 return wfGetLangObj( $pageLang );
 698         }
 699
 700         /**
 701          * Get the language in which the content of this page is written when
 702          * viewed by user. Defaults to $this->getPageLanguage(), but if the user
 703          * specified a preferred variant, the variant will be used.
 704          *
 705          * This default implementation just returns $this->getPageLanguage( $title, $content ) unless
 706          * the user specified a preferred variant.
 707          *
 708          * Note that the pages view language is not cacheable, since it depends on user settings.
 709          *
 710          * Also note that the page language may or may not depend on the actual content of the page,
 711          * that is, this method may load the content in order to determine the language.
 712          *
 713          * @since 1.21
 714          *
 715          * @param Title $title The page to determine the language for.
 716          * @param Content|null $content The page's content, if you have it handy, to avoid reloading it.
 717          *
 718          * @return Language The page's language for viewing
 719          */
 720         public function getPageViewLanguage( Title $title, Content $content = null ) {
 721                 $pageLang = $this->getPageLanguage( $title, $content );
 722
 723                 if ( $title->getNamespace() !== NS_MEDIAWIKI ) {
 724                         // If the user chooses a variant, the content is actually
 725                         // in a language whose code is the variant code.
 726                         $variant = $pageLang->getPreferredVariant();
 727                         if ( $pageLang->getCode() !== $variant ) {
 728                                 $pageLang = Language::factory( $variant );
 729                         }
 730                 }
 731
 732                 return $pageLang;
 733         }
 734
 735         /**
 736          * Determines whether the content type handled by this ContentHandler
 737          * can be used for the main slot of the given page.
 738          *
 739          * This default implementation always returns true.
 740          * Subclasses may override this to restrict the use of this content model to specific locations,
 741          * typically based on the namespace or some other aspect of the title, such as a special suffix
 742          * (e.g. ".svg" for SVG content).
 743          *
 744          * @note this calls the ContentHandlerCanBeUsedOn hook which may be used to override which
 745          * content model can be used where.
 746          *
 747          * @see SlotRoleHandler::isAllowedModel
 748          *
 749          * @param Title $title The page's title.
 750          *
 751          * @return bool True if content of this kind can be used on the given page, false otherwise.
 752          */
 753         public function canBeUsedOn( Title $title ) {
 754                 $ok = true;
 755
 756                 Hooks::run( 'ContentModelCanBeUsedOn', [ $this->getModelID(), $title, &$ok ] );
 757
 758                 return $ok;
 759         }
 760
 761         /**
 762          * Returns the name of the diff engine to use.
 763          *
 764          * @since 1.21
 765          *
 766          * @return string
 767          */
 768         protected function getDiffEngineClass() {
 769                 return DifferenceEngine::class;
 770         }
 771
 772         /**
 773          * Attempts to merge differences between three versions. Returns a new
 774          * Content object for a clean merge and false for failure or a conflict.
 775          *
 776          * This default implementation always returns false.
 777          *
 778          * @since 1.21
 779          *
 780          * @param Content $oldContent The page's previous content.
 781          * @param Content $myContent One of the page's conflicting contents.
 782          * @param Content $yourContent One of the page's conflicting contents.
 783          *
 784          * @return Content|bool Always false.
 785          */
 786         public function merge3( Content $oldContent, Content $myContent, Content $yourContent ) {
 787                 return false;
 788         }
 789
 790         /**
 791          * Return type of change if one exists for the given edit.
 792          *
 793          * @since 1.31
 794          *
 795          * @param Content|null $oldContent The previous text of the page.
 796          * @param Content|null $newContent The submitted text of the page.
 797          * @param int $flags Bit mask: a bit mask of flags submitted for the edit.
 798          *
 799          * @return string|null String key representing type of change, or null.
 800          */
 801         private function getChangeType(
 802                 Content $oldContent = null,
 803                 Content $newContent = null,
 804                 $flags = 0
 805         ) {
 806                 $oldTarget = $oldContent !== null ? $oldContent->getRedirectTarget() : null;
 807                 $newTarget = $newContent !== null ? $newContent->getRedirectTarget() : null;
 808
 809                 // We check for the type of change in the given edit, and return string key accordingly
 810
 811                 // Blanking of a page
 812                 if ( $oldContent && $oldContent->getSize() > 0 &&
 813                         $newContent && $newContent->getSize() === 0
 814                 ) {
 815                         return 'blank';
 816                 }
 817
 818                 // Redirects
 819                 if ( $newTarget ) {
 820                         if ( !$oldTarget ) {
 821                                 // New redirect page (by creating new page or by changing content page)
 822                                 return 'new-redirect';
 823                         } elseif ( !$newTarget->equals( $oldTarget ) ||
 824                                 $oldTarget->getFragment() !== $newTarget->getFragment()
 825                         ) {
 826                                 // Redirect target changed
 827                                 return 'changed-redirect-target';
 828                         }
 829                 } elseif ( $oldTarget ) {
 830                         // Changing an existing redirect into a non-redirect
 831                         return 'removed-redirect';
 832                 }
 833
 834                 // New page created
 835                 if ( $flags & EDIT_NEW && $newContent ) {
 836                         if ( $newContent->getSize() === 0 ) {
 837                                 // New blank page
 838                                 return 'newblank';
 839                         } else {
 840                                 return 'newpage';
 841                         }
 842                 }
 843
 844                 // Removing more than 90% of the page
 845                 if ( $oldContent && $newContent && $oldContent->getSize() > 10 * $newContent->getSize() ) {
 846                         return 'replace';
 847                 }
 848
 849                 // Content model changed
 850                 if ( $oldContent && $newContent && $oldContent->getModel() !== $newContent->getModel() ) {
 851                         return 'contentmodelchange';
 852                 }
 853
 854                 return null;
 855         }
 856
 857         /**
 858          * Return an applicable auto-summary if one exists for the given edit.
 859          *
 860          * @since 1.21
 861          *
 862          * @param Content|null $oldContent The previous text of the page.
 863          * @param Content|null $newContent The submitted text of the page.
 864          * @param int $flags Bit mask: a bit mask of flags submitted for the edit.
 865          *
 866          * @return string An appropriate auto-summary, or an empty string.
 867          */
 868         public function getAutosummary(
 869                 Content $oldContent = null,
 870                 Content $newContent = null,
 871                 $flags = 0
 872         ) {
 873                 $changeType = $this->getChangeType( $oldContent, $newContent, $flags );
 874
 875                 // There's no applicable auto-summary for our case, so our auto-summary is empty.
 876                 if ( !$changeType ) {
 877                         return '';
 878                 }
 879
 880                 // Decide what kind of auto-summary is needed.
 881                 switch ( $changeType ) {
 882                         case 'new-redirect':
 883                                 $newTarget = $newContent->getRedirectTarget();
 884                                 $truncatedtext = $newContent->getTextForSummary(
 885                                         250
 886                                         - strlen( wfMessage( 'autoredircomment' )->inContentLanguage()->text() )
 887                                         - strlen( $newTarget->getFullText() )
 888                                 );
 889
 890                                 return wfMessage( 'autoredircomment', $newTarget->getFullText() )
 891                                         ->plaintextParams( $truncatedtext )->inContentLanguage()->text();
 892                         case 'changed-redirect-target':
 893                                 $oldTarget = $oldContent->getRedirectTarget();
 894                                 $newTarget = $newContent->getRedirectTarget();
 895
 896                                 $truncatedtext = $newContent->getTextForSummary(
 897                                         250
 898                                         - strlen( wfMessage( 'autosumm-changed-redirect-target' )
 899                                                 ->inContentLanguage()->text() )
 900                                         - strlen( $oldTarget->getFullText() )
 901                                         - strlen( $newTarget->getFullText() )
 902                                 );
 903
 904                                 return wfMessage( 'autosumm-changed-redirect-target',
 905                                                 $oldTarget->getFullText(),
 906                                                 $newTarget->getFullText() )
 907                                         ->rawParams( $truncatedtext )->inContentLanguage()->text();
 908                         case 'removed-redirect':
 909                                 $oldTarget = $oldContent->getRedirectTarget();
 910                                 $truncatedtext = $newContent->getTextForSummary(
 911                                         250
 912                                         - strlen( wfMessage( 'autosumm-removed-redirect' )
 913                                                 ->inContentLanguage()->text() )
 914                                         - strlen( $oldTarget->getFullText() ) );
 915
 916                                 return wfMessage( 'autosumm-removed-redirect', $oldTarget->getFullText() )
 917                                         ->rawParams( $truncatedtext )->inContentLanguage()->text();
 918                         case 'newpage':
 919                                 // If they're making a new article, give its text, truncated, in the summary.
 920                                 $truncatedtext = $newContent->getTextForSummary(
 921                                         200 - strlen( wfMessage( 'autosumm-new' )->inContentLanguage()->text() ) );
 922
 923                                 return wfMessage( 'autosumm-new' )->rawParams( $truncatedtext )
 924                                         ->inContentLanguage()->text();
 925                         case 'blank':
 926                                 return wfMessage( 'autosumm-blank' )->inContentLanguage()->text();
 927                         case 'replace':
 928                                 $truncatedtext = $newContent->getTextForSummary(
 929                                         200 - strlen( wfMessage( 'autosumm-replace' )->inContentLanguage()->text() ) );
 930
 931                                 return wfMessage( 'autosumm-replace' )->rawParams( $truncatedtext )
 932                                         ->inContentLanguage()->text();
 933                         case 'newblank':
 934                                 return wfMessage( 'autosumm-newblank' )->inContentLanguage()->text();
 935                         default:
 936                                 return '';
 937                 }
 938         }
 939
 940         /**
 941          * Return an applicable tag if one exists for the given edit or return null.
 942          *
 943          * @since 1.31
 944          *
 945          * @param Content|null $oldContent The previous text of the page.
 946          * @param Content|null $newContent The submitted text of the page.
 947          * @param int $flags Bit mask: a bit mask of flags submitted for the edit.
 948          *
 949          * @return string|null An appropriate tag, or null.
 950          */
 951         public function getChangeTag(
 952                 Content $oldContent = null,
 953                 Content $newContent = null,
 954                 $flags = 0
 955         ) {
 956                 $changeType = $this->getChangeType( $oldContent, $newContent, $flags );
 957
 958                 // There's no applicable tag for this change.
 959                 if ( !$changeType ) {
 960                         return null;
 961                 }
 962
 963                 // Core tags use the same keys as ones returned from $this->getChangeType()
 964                 // but prefixed with pseudo namespace 'mw-', so we add the prefix before checking
 965                 // if this type of change should be tagged
 966                 $tag = 'mw-' . $changeType;
 967
 968                 // Not all change types are tagged, so we check against the list of defined tags.
 969                 if ( in_array( $tag, ChangeTags::getSoftwareTags() ) ) {
 970                         return $tag;
 971                 }
 972
 973                 return null;
 974         }
 975
 976         /**
 977          * Auto-generates a deletion reason
 978          *
 979          * @since 1.21
 980          *
 981          * @param Title $title The page's title
 982          * @param bool &$hasHistory Whether the page has a history
 983          *
 984          * @return mixed String containing deletion reason or empty string, or
 985          *    boolean false if no revision occurred
 986          *
 987          * @todo &$hasHistory is extremely ugly, it's here because
 988          * WikiPage::getAutoDeleteReason() and Article::generateReason()
 989          * have it / want it.
 990          */
 991         public function getAutoDeleteReason( Title $title, &$hasHistory ) {
 992                 $dbr = wfGetDB( DB_REPLICA );
 993
 994                 // Get the last revision
 995                 $rev = Revision::newFromTitle( $title );
 996
 997                 if ( is_null( $rev ) ) {
 998                         return false;
 999                 }
1000
1001                 // Get the article's contents
1002                 $content = $rev->getContent();
1003                 $blank = false;
1004
1005                 // If the page is blank, use the text from the previous revision,
1006                 // which can only be blank if there's a move/import/protect dummy
1007                 // revision involved
1008                 if ( !$content || $content->isEmpty() ) {
1009                         $prev = $rev->getPrevious();
1010
1011                         if ( $prev ) {
1012                                 $rev = $prev;
1013                                 $content = $rev->getContent();
1014                                 $blank = true;
1015                         }
1016                 }
1017
1018                 $this->checkModelID( $rev->getContentModel() );
1019
1020                 // Find out if there was only one contributor
1021                 // Only scan the last 20 revisions
1022                 $revQuery = Revision::getQueryInfo();
1023                 $res = $dbr->select(
1024                         $revQuery['tables'],
1025                         [ 'rev_user_text' => $revQuery['fields']['rev_user_text'] ],
1026                         [
1027                                 'rev_page' => $title->getArticleID(),
1028                                 $dbr->bitAnd( 'rev_deleted', Revision::DELETED_USER ) . ' = 0'
1029                         ],
1030                         __METHOD__,
1031                         [ 'LIMIT' => 20 ],
1032                         $revQuery['joins']
1033                 );
1034
1035                 if ( $res === false ) {
1036                         // This page has no revisions, which is very weird
1037                         return false;
1038                 }
1039
1040                 $hasHistory = ( $res->numRows() > 1 );
1041                 $row = $dbr->fetchObject( $res );
1042
1043                 if ( $row ) { // $row is false if the only contributor is hidden
1044                         $onlyAuthor = $row->rev_user_text;
1045                         // Try to find a second contributor
1046                         foreach ( $res as $row ) {
1047                                 if ( $row->rev_user_text != $onlyAuthor ) { // T24999
1048                                         $onlyAuthor = false;
1049                                         break;
1050                                 }
1051                         }
1052                 } else {
1053                         $onlyAuthor = false;
1054                 }
1055
1056                 // Generate the summary with a '$1' placeholder
1057                 if ( $blank ) {
1058                         // The current revision is blank and the one before is also
1059                         // blank. It's just not our lucky day
1060                         $reason = wfMessage( 'exbeforeblank', '$1' )->inContentLanguage()->text();
1061                 } else {
1062                         if ( $onlyAuthor ) {
1063                                 $reason = wfMessage(
1064                                         'excontentauthor',
1065                                         '$1',
1066                                         $onlyAuthor
1067                                 )->inContentLanguage()->text();
1068                         } else {
1069                                 $reason = wfMessage( 'excontent', '$1' )->inContentLanguage()->text();
1070                         }
1071                 }
1072
1073                 if ( $reason == '-' ) {
1074                         // Allow these UI messages to be blanked out cleanly
1075                         return '';
1076                 }
1077
1078                 // Max content length = max comment length - length of the comment (excl. $1)
1079                 $text = $content ? $content->getTextForSummary( 255 - ( strlen( $reason ) - 2 ) ) : '';
1080
1081                 // Now replace the '$1' placeholder
1082                 $reason = str_replace( '$1', $text, $reason );
1083
1084                 return $reason;
1085         }
1086
1087         /**
1088          * Get the Content object that needs to be saved in order to undo all revisions
1089          * between $undo and $undoafter. Revisions must belong to the same page,
1090          * must exist and must not be deleted.
1091          *
1092          * @since 1.21
1093          * @since 1.32 accepts Content objects for all parameters instead of Revision objects.
1094          *  Passing Revision objects is deprecated.
1095          *
1096          * @param Revision|Content $current The current text
1097          * @param Revision|Content $undo The content of the revision to undo
1098          * @param Revision|Content $undoafter Must be from an earlier revision than $undo
1099          * @param bool $undoIsLatest Set true if $undo is from the current revision (since 1.32)
1100          *
1101          * @return mixed Content on success, false on failure
1102          */
1103         public function getUndoContent( $current, $undo, $undoafter, $undoIsLatest = false ) {
1104                 Assert::parameterType( Revision::class . '|' . Content::class, $current, '$current' );
1105                 if ( $current instanceof Content ) {
1106                         Assert::parameter( $undo instanceof Content, '$undo',
1107                                 'Must be Content when $current is Content' );
1108                         Assert::parameter( $undoafter instanceof Content, '$undoafter',
1109                                 'Must be Content when $current is Content' );
1110                         $cur_content = $current;
1111                         $undo_content = $undo;
1112                         $undoafter_content = $undoafter;
1113                 } else {
1114                         Assert::parameter( $undo instanceof Revision, '$undo',
1115                                 'Must be Revision when $current is Revision' );
1116                         Assert::parameter( $undoafter instanceof Revision, '$undoafter',
1117                                 'Must be Revision when $current is Revision' );
1118
1119                         $cur_content = $current->getContent();
1120
1121                         if ( empty( $cur_content ) ) {
1122                                 return false; // no page
1123                         }
1124
1125                         $undo_content = $undo->getContent();
1126                         $undoafter_content = $undoafter->getContent();
1127
1128                         if ( !$undo_content || !$undoafter_content ) {
1129                                 return false; // no content to undo
1130                         }
1131
1132                         $undoIsLatest = $current->getId() === $undo->getId();
1133                 }
1134
1135                 try {
1136                         $this->checkModelID( $cur_content->getModel() );
1137                         $this->checkModelID( $undo_content->getModel() );
1138                         if ( !$undoIsLatest ) {
1139                                 // If we are undoing the most recent revision,
1140                                 // its ok to revert content model changes. However
1141                                 // if we are undoing a revision in the middle, then
1142                                 // doing that will be confusing.
1143                                 $this->checkModelID( $undoafter_content->getModel() );
1144                         }
1145                 } catch ( MWException $e ) {
1146                         // If the revisions have different content models
1147                         // just return false
1148                         return false;
1149                 }
1150
1151                 if ( $cur_content->equals( $undo_content ) ) {
1152                         // No use doing a merge if it's just a straight revert.
1153                         return $undoafter_content;
1154                 }
1155
1156                 $undone_content = $this->merge3( $undo_content, $undoafter_content, $cur_content );
1157
1158                 return $undone_content;
1159         }
1160
1161         /**
1162          * Get parser options suitable for rendering and caching the article
1163          *
1164          * @deprecated since 1.32, use WikiPage::makeParserOptions() or
1165          *  ParserOptions::newCanonical() instead.
1166          * @param IContextSource|User|string $context One of the following:
1167          *        - IContextSource: Use the User and the Language of the provided
1168          *                                            context
1169          *        - User: Use the provided User object and $wgLang for the language,
1170          *                                            so use an IContextSource object if possible.
1171          *        - 'canonical': Canonical options (anonymous user with default
1172          *                                            preferences and content language).
1173          *
1174          * @throws MWException
1175          * @return ParserOptions
1176          */
1177         public function makeParserOptions( $context ) {
1178                 wfDeprecated( __METHOD__, '1.32' );
1179                 return ParserOptions::newCanonical( $context );
1180         }
1181
1182         /**
1183          * Returns true for content models that support caching using the
1184          * ParserCache mechanism. See WikiPage::shouldCheckParserCache().
1185          *
1186          * @since 1.21
1187          *
1188          * @return bool Always false.
1189          */
1190         public function isParserCacheSupported() {
1191                 return false;
1192         }
1193
1194         /**
1195          * Returns true if this content model supports sections.
1196          * This default implementation returns false.
1197          *
1198          * Content models that return true here should also implement
1199          * Content::getSection, Content::replaceSection, etc. to handle sections..
1200          *
1201          * @return bool Always false.
1202          */
1203         public function supportsSections() {
1204                 return false;
1205         }
1206
1207         /**
1208          * Returns true if this content model supports categories.
1209          * The default implementation returns true.
1210          *
1211          * @return bool Always true.
1212          */
1213         public function supportsCategories() {
1214                 return true;
1215         }
1216
1217         /**
1218          * Returns true if this content model supports redirects.
1219          * This default implementation returns false.
1220          *
1221          * Content models that return true here should also implement
1222          * ContentHandler::makeRedirectContent to return a Content object.
1223          *
1224          * @return bool Always false.
1225          */
1226         public function supportsRedirects() {
1227                 return false;
1228         }
1229
1230         /**
1231          * Return true if this content model supports direct editing, such as via EditPage.
1232          *
1233          * @return bool Default is false, and true for TextContent and it's derivatives.
1234          */
1235         public function supportsDirectEditing() {
1236                 return false;
1237         }
1238
1239         /**
1240          * Whether or not this content model supports direct editing via ApiEditPage
1241          *
1242          * @return bool Default is false, and true for TextContent and derivatives.
1243          */
1244         public function supportsDirectApiEditing() {
1245                 return $this->supportsDirectEditing();
1246         }
1247
1248         /**
1249          * Get fields definition for search index
1250          *
1251          * @todo Expose title, redirect, namespace, text, source_text, text_bytes
1252          *       field mappings here. (see T142670 and T143409)
1253          *
1254          * @param SearchEngine $engine
1255          * @return SearchIndexField[] List of fields this content handler can provide.
1256          * @since 1.28
1257          */
1258         public function getFieldsForSearchIndex( SearchEngine $engine ) {
1259                 $fields['category'] = $engine->makeSearchFieldMapping(
1260                         'category',
1261                         SearchIndexField::INDEX_TYPE_TEXT
1262                 );
1263                 $fields['category']->setFlag( SearchIndexField::FLAG_CASEFOLD );
1264
1265                 $fields['external_link'] = $engine->makeSearchFieldMapping(
1266                         'external_link',
1267                         SearchIndexField::INDEX_TYPE_KEYWORD
1268                 );
1269
1270                 $fields['outgoing_link'] = $engine->makeSearchFieldMapping(
1271                         'outgoing_link',
1272                         SearchIndexField::INDEX_TYPE_KEYWORD
1273                 );
1274
1275                 $fields['template'] = $engine->makeSearchFieldMapping(
1276                         'template',
1277                         SearchIndexField::INDEX_TYPE_KEYWORD
1278                 );
1279                 $fields['template']->setFlag( SearchIndexField::FLAG_CASEFOLD );
1280
1281                 $fields['content_model'] = $engine->makeSearchFieldMapping(
1282                         'content_model',
1283                         SearchIndexField::INDEX_TYPE_KEYWORD
1284                 );
1285
1286                 return $fields;
1287         }
1288
1289         /**
1290          * Add new field definition to array.
1291          * @param SearchIndexField[] &$fields
1292          * @param SearchEngine $engine
1293          * @param string $name
1294          * @param int $type
1295          * @return SearchIndexField[] new field defs
1296          * @since 1.28
1297          */
1298         protected function addSearchField( &$fields, SearchEngine $engine, $name, $type ) {
1299                 $fields[$name] = $engine->makeSearchFieldMapping( $name, $type );
1300                 return $fields;
1301         }
1302
1303         /**
1304          * Return fields to be indexed by search engine
1305          * as representation of this document.
1306          * Overriding class should call parent function or take care of calling
1307          * the SearchDataForIndex hook.
1308          * @param WikiPage $page Page to index
1309          * @param ParserOutput $output
1310          * @param SearchEngine $engine Search engine for which we are indexing
1311          * @return array Map of name=>value for fields
1312          * @since 1.28
1313          */
1314         public function getDataForSearchIndex(
1315                 WikiPage $page,
1316                 ParserOutput $output,
1317                 SearchEngine $engine
1318         ) {
1319                 $fieldData = [];
1320                 $content = $page->getContent();
1321
1322                 if ( $content ) {
1323                         $searchDataExtractor = new ParserOutputSearchDataExtractor();
1324
1325                         $fieldData['category'] = $searchDataExtractor->getCategories( $output );
1326                         $fieldData['external_link'] = $searchDataExtractor->getExternalLinks( $output );
1327                         $fieldData['outgoing_link'] = $searchDataExtractor->getOutgoingLinks( $output );
1328                         $fieldData['template'] = $searchDataExtractor->getTemplates( $output );
1329
1330                         $text = $content->getTextForSearchIndex();
1331
1332                         $fieldData['text'] = $text;
1333                         $fieldData['source_text'] = $text;
1334                         $fieldData['text_bytes'] = $content->getSize();
1335                         $fieldData['content_model'] = $content->getModel();
1336                 }
1337
1338                 Hooks::run( 'SearchDataForIndex', [ &$fieldData, $this, $page, $output, $engine ] );
1339                 return $fieldData;
1340         }
1341
1342         /**
1343          * Produce page output suitable for indexing.
1344          *
1345          * Specific content handlers may override it if they need different content handling.
1346          *
1347          * @param WikiPage $page
1348          * @param ParserCache|null $cache
1349          * @return ParserOutput
1350          */
1351         public function getParserOutputForIndexing( WikiPage $page, ParserCache $cache = null ) {
1352                 // TODO: MCR: ContentHandler should be called per slot, not for the whole page.
1353                 // See T190066.
1354                 $parserOptions = $page->makeParserOptions( 'canonical' );
1355                 if ( $cache ) {
1356                         $parserOutput = $cache->get( $page, $parserOptions );
1357                 }
1358
1359                 if ( empty( $parserOutput ) ) {
1360                         $renderer = MediaWikiServices::getInstance()->getRevisionRenderer();
1361                         $parserOutput =
1362                                 $renderer->getRenderedRevision(
1363                                         $page->getRevision()->getRevisionRecord(),
1364                                         $parserOptions
1365                                 )->getRevisionParserOutput();
1366                         if ( $cache ) {
1367                                 $cache->save( $parserOutput, $page, $parserOptions );
1368                         }
1369                 }
1370                 return $parserOutput;
1371         }
1372
1373         /**
1374          * Returns a list of DeferrableUpdate objects for recording information about the
1375          * given Content in some secondary data store.
1376          *
1377          * Application logic should not call this method directly. Instead, it should call
1378          * DerivedPageDataUpdater::getSecondaryDataUpdates().
1379          *
1380          * @note Implementations must not return a LinksUpdate instance. Instead, a LinksUpdate
1381          * is created by the calling code in DerivedPageDataUpdater, on the combined ParserOutput
1382          * of all slots, not for each slot individually. This is in contrast to the old
1383          * getSecondaryDataUpdates method defined by AbstractContent, which returned a LinksUpdate.
1384          *
1385          * @note Implementations should not call $content->getParserOutput, they should call
1386          * $slotOutput->getSlotRendering( $role, false ) instead if they need to access a ParserOutput
1387          * of $content. This allows existing ParserOutput objects to be re-used, while avoiding
1388          * creating a ParserOutput when none is needed.
1389          *
1390          * @param Title $title The title of the page to supply the updates for
1391          * @param Content $content The content to generate data updates for.
1392          * @param string $role The role (slot) in which the content is being used. Which updates
1393          *        are performed should generally not depend on the role the content has, but the
1394          *        DeferrableUpdates themselves may need to know the role, to track to which slot the
1395          *        data refers, and to avoid overwriting data of the same kind from another slot.
1396          * @param SlotRenderingProvider $slotOutput A provider that can be used to gain access to
1397          *        a ParserOutput of $content by calling $slotOutput->getSlotParserOutput( $role, false ).
1398          * @return DeferrableUpdate[] A list of DeferrableUpdate objects for putting information
1399          *        about this content object somewhere. The default implementation returns an empty
1400          *        array.
1401          * @since 1.32
1402          */
1403         public function getSecondaryDataUpdates(
1404                 Title $title,
1405                 Content $content,
1406                 $role,
1407                 SlotRenderingProvider $slotOutput
1408         ) {
1409                 return [];
1410         }
1411
1412         /**
1413          * Returns a list of DeferrableUpdate objects for removing information about content
1414          * in some secondary data store. This is used when a page is deleted, and also when
1415          * a slot is removed from a page.
1416          *
1417          * Application logic should not call this method directly. Instead, it should call
1418          * WikiPage::getSecondaryDataUpdates().
1419          *
1420          * @note Implementations must not return a LinksDeletionUpdate instance. Instead, a
1421          * LinksDeletionUpdate is created by the calling code in WikiPage.
1422          * This is in contrast to the old getDeletionUpdates method defined by AbstractContent,
1423          * which returned a LinksUpdate.
1424          *
1425          * @note Implementations should not rely on the page's current content, but rather the current
1426          * state of the secondary data store.
1427          *
1428          * @param Title $title The title of the page to supply the updates for
1429          * @param string $role The role (slot) in which the content is being used. Which updates
1430          *        are performed should generally not depend on the role the content has, but the
1431          *        DeferrableUpdates themselves may need to know the role, to track to which slot the
1432          *        data refers, and to avoid overwriting data of the same kind from another slot.
1433          *
1434          * @return DeferrableUpdate[] A list of DeferrableUpdate objects for putting information
1435          *        about this content object somewhere. The default implementation returns an empty
1436          *        array.
1437          *
1438          * @since 1.32
1439          */
1440         public function getDeletionUpdates( Title $title, $role ) {
1441                 return [];
1442         }
1443
1444 }