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  * A content handler knows how do deal with a specific type of content on a wiki
  38  * page. Content is stored in the database in a serialized form (using a
  39  * serialization format a.k.a. MIME type) and is unserialized into its native
  40  * PHP representation (the content model), which is wrapped in an instance of
  41  * the appropriate subclass of Content.
  42  *
  43  * ContentHandler instances are stateless singletons that serve, among other
  44  * things, as a factory for Content objects. Generally, there is one subclass
  45  * of ContentHandler and one subclass of Content for every type of content model.
  46  *
  47  * Some content types have a flat model, that is, their native representation
  48  * is the same as their serialized form. Examples would be JavaScript and CSS
  49  * code. As of now, this also applies to wikitext (MediaWiki's default content
  50  * type), but wikitext content may be represented by a DOM or AST structure in
  51  * the future.
  52  *
  53  * @ingroup Content
  54  */
  55 abstract class ContentHandler {
  56         /**
  57          * Switch for enabling deprecation warnings. Used by ContentHandler::deprecated()
  58          * and ContentHandler::runLegacyHooks().
  59          *
  60          * Once the ContentHandler code has settled in a bit, this should be set to true to
  61          * make extensions etc. show warnings when using deprecated functions and hooks.
  62          */
  63         protected static $enableDeprecationWarnings = false;
  64
  65         /**
  66          * Convenience function for getting flat text from a Content object. This
  67          * should only be used in the context of backwards compatibility with code
  68          * that is not yet able to handle Content objects!
  69          *
  70          * If $content is null, this method returns the empty string.
  71          *
  72          * If $content is an instance of TextContent, this method returns the flat
  73          * text as returned by $content->getNativeData().
  74          *
  75          * If $content is not a TextContent object, the behavior of this method
  76          * depends on the global $wgContentHandlerTextFallback:
  77          * - If $wgContentHandlerTextFallback is 'fail' and $content is not a
  78          *   TextContent object, an MWException is thrown.
  79          * - If $wgContentHandlerTextFallback is 'serialize' and $content is not a
  80          *   TextContent object, $content->serialize() is called to get a string
  81          *   form of the content.
  82          * - If $wgContentHandlerTextFallback is 'ignore' and $content is not a
  83          *   TextContent object, this method returns null.
  84          * - otherwise, the behavior is undefined.
  85          *
  86          * @since 1.21
  87          *
  88          * @param Content $content
  89          *
  90          * @throws MWException If the content is not an instance of TextContent and
  91          * wgContentHandlerTextFallback was set to 'fail'.
  92          * @return string|null Textual form of the content, if available.
  93          */
  94         public static function getContentText( Content $content = null ) {
  95                 global $wgContentHandlerTextFallback;
  96
  97                 if ( is_null( $content ) ) {
  98                         return '';
  99                 }
 100
 101                 if ( $content instanceof TextContent ) {
 102                         return $content->getNativeData();
 103                 }
 104
 105                 wfDebugLog( 'ContentHandler', 'Accessing ' . $content->getModel() . ' content as text!' );
 106
 107                 if ( $wgContentHandlerTextFallback == 'fail' ) {
 108                         throw new MWException(
 109                                 "Attempt to get text from Content with model " .
 110                                 $content->getModel()
 111                         );
 112                 }
 113
 114                 if ( $wgContentHandlerTextFallback == 'serialize' ) {
 115                         return $content->serialize();
 116                 }
 117
 118                 return null;
 119         }
 120
 121         /**
 122          * Convenience function for creating a Content object from a given textual
 123          * representation.
 124          *
 125          * $text will be deserialized into a Content object of the model specified
 126          * by $modelId (or, if that is not given, $title->getContentModel()) using
 127          * the given format.
 128          *
 129          * @since 1.21
 130          *
 131          * @param string $text The textual representation, will be
 132          *    unserialized to create the Content object
 133          * @param Title $title The title of the page this text belongs to.
 134          *    Required if $modelId is not provided.
 135          * @param string $modelId The model to deserialize to. If not provided,
 136          *    $title->getContentModel() is used.
 137          * @param string $format The format to use for deserialization. If not
 138          *    given, the model's default format is used.
 139          *
 140          * @throws MWException If model ID or format is not supported or if the text can not be
 141          * unserialized using the format.
 142          * @return Content A Content object representing the text.
 143          */
 144         public static function makeContent( $text, Title $title = null,
 145                 $modelId = null, $format = null ) {
 146                 if ( is_null( $modelId ) ) {
 147                         if ( is_null( $title ) ) {
 148                                 throw new MWException( "Must provide a Title object or a content model ID." );
 149                         }
 150
 151                         $modelId = $title->getContentModel();
 152                 }
 153
 154                 $handler = ContentHandler::getForModelID( $modelId );
 155
 156                 return $handler->unserializeContent( $text, $format );
 157         }
 158
 159         /**
 160          * Returns the name of the default content model to be used for the page
 161          * with the given title.
 162          *
 163          * Note: There should rarely be need to call this method directly.
 164          * To determine the actual content model for a given page, use
 165          * Title::getContentModel().
 166          *
 167          * Which model is to be used by default for the page is determined based
 168          * on several factors:
 169          * - The global setting $wgNamespaceContentModels specifies a content model
 170          *   per namespace.
 171          * - The hook ContentHandlerDefaultModelFor may be used to override the page's default
 172          *   model.
 173          * - Pages in NS_MEDIAWIKI and NS_USER default to the CSS or JavaScript
 174          *   model if they end in .js or .css, respectively.
 175          * - Pages in NS_MEDIAWIKI default to the wikitext model otherwise.
 176          * - The hook TitleIsCssOrJsPage may be used to force a page to use the CSS
 177          *   or JavaScript model. This is a compatibility feature. The ContentHandlerDefaultModelFor
 178          *   hook should be used instead if possible.
 179          * - The hook TitleIsWikitextPage may be used to force a page to use the
 180          *   wikitext model. This is a compatibility feature. The ContentHandlerDefaultModelFor
 181          *   hook should be used instead if possible.
 182          *
 183          * If none of the above applies, the wikitext model is used.
 184          *
 185          * Note: this is used by, and may thus not use, Title::getContentModel()
 186          *
 187          * @since 1.21
 188          *
 189          * @param Title $title
 190          *
 191          * @return string Default model name for the page given by $title
 192          */
 193         public static function getDefaultModelFor( Title $title ) {
 194                 // NOTE: this method must not rely on $title->getContentModel() directly or indirectly,
 195                 //       because it is used to initialize the mContentModel member.
 196
 197                 $ns = $title->getNamespace();
 198
 199                 $ext = false;
 200                 $m = null;
 201                 $model = MWNamespace::getNamespaceContentModel( $ns );
 202
 203                 // Hook can determine default model
 204                 if ( !Hooks::run( 'ContentHandlerDefaultModelFor', array( $title, &$model ) ) ) {
 205                         if ( !is_null( $model ) ) {
 206                                 return $model;
 207                         }
 208                 }
 209
 210                 // Could this page contain custom CSS or JavaScript, based on the title?
 211                 $isCssOrJsPage = NS_MEDIAWIKI == $ns && preg_match( '!\.(css|js)$!u', $title->getText(), $m );
 212                 if ( $isCssOrJsPage ) {
 213                         $ext = $m[1];
 214                 }
 215
 216                 // Hook can force JS/CSS
 217                 Hooks::run( 'TitleIsCssOrJsPage', array( $title, &$isCssOrJsPage ), '1.25' );
 218
 219                 // Is this a .css subpage of a user page?
 220                 $isJsCssSubpage = NS_USER == $ns
 221                         && !$isCssOrJsPage
 222                         && preg_match( "/\\/.*\\.(js|css)$/", $title->getText(), $m );
 223                 if ( $isJsCssSubpage ) {
 224                         $ext = $m[1];
 225                 }
 226
 227                 // Is this wikitext, according to $wgNamespaceContentModels or the DefaultModelFor hook?
 228                 $isWikitext = is_null( $model ) || $model == CONTENT_MODEL_WIKITEXT;
 229                 $isWikitext = $isWikitext && !$isCssOrJsPage && !$isJsCssSubpage;
 230
 231                 // Hook can override $isWikitext
 232                 Hooks::run( 'TitleIsWikitextPage', array( $title, &$isWikitext ), '1.25' );
 233
 234                 if ( !$isWikitext ) {
 235                         switch ( $ext ) {
 236                                 case 'js':
 237                                         return CONTENT_MODEL_JAVASCRIPT;
 238                                 case 'css':
 239                                         return CONTENT_MODEL_CSS;
 240                                 default:
 241                                         return is_null( $model ) ? CONTENT_MODEL_TEXT : $model;
 242                         }
 243                 }
 244
 245                 // We established that it must be wikitext
 246
 247                 return CONTENT_MODEL_WIKITEXT;
 248         }
 249
 250         /**
 251          * Returns the appropriate ContentHandler singleton for the given title.
 252          *
 253          * @since 1.21
 254          *
 255          * @param Title $title
 256          *
 257          * @return ContentHandler
 258          */
 259         public static function getForTitle( Title $title ) {
 260                 $modelId = $title->getContentModel();
 261
 262                 return ContentHandler::getForModelID( $modelId );
 263         }
 264
 265         /**
 266          * Returns the appropriate ContentHandler singleton for the given Content
 267          * object.
 268          *
 269          * @since 1.21
 270          *
 271          * @param Content $content
 272          *
 273          * @return ContentHandler
 274          */
 275         public static function getForContent( Content $content ) {
 276                 $modelId = $content->getModel();
 277
 278                 return ContentHandler::getForModelID( $modelId );
 279         }
 280
 281         /**
 282          * @var array A Cache of ContentHandler instances by model id
 283          */
 284         protected static $handlers;
 285
 286         /**
 287          * Returns the ContentHandler singleton for the given model ID. Use the
 288          * CONTENT_MODEL_XXX constants to identify the desired content model.
 289          *
 290          * ContentHandler singletons are taken from the global $wgContentHandlers
 291          * array. Keys in that array are model names, the values are either
 292          * ContentHandler singleton objects, or strings specifying the appropriate
 293          * subclass of ContentHandler.
 294          *
 295          * If a class name is encountered when looking up the singleton for a given
 296          * model name, the class is instantiated and the class name is replaced by
 297          * the resulting singleton in $wgContentHandlers.
 298          *
 299          * If no ContentHandler is defined for the desired $modelId, the
 300          * ContentHandler may be provided by the ContentHandlerForModelID hook.
 301          * If no ContentHandler can be determined, an MWException is raised.
 302          *
 303          * @since 1.21
 304          *
 305          * @param string $modelId The ID of the content model for which to get a
 306          *    handler. Use CONTENT_MODEL_XXX constants.
 307          *
 308          * @throws MWException If no handler is known for the model ID.
 309          * @return ContentHandler The ContentHandler singleton for handling the model given by the ID.
 310          */
 311         public static function getForModelID( $modelId ) {
 312                 global $wgContentHandlers;
 313
 314                 if ( isset( ContentHandler::$handlers[$modelId] ) ) {
 315                         return ContentHandler::$handlers[$modelId];
 316                 }
 317
 318                 if ( empty( $wgContentHandlers[$modelId] ) ) {
 319                         $handler = null;
 320
 321                         Hooks::run( 'ContentHandlerForModelID', array( $modelId, &$handler ) );
 322
 323                         if ( $handler === null ) {
 324                                 throw new MWException( "No handler for model '$modelId' registered in \$wgContentHandlers" );
 325                         }
 326
 327                         if ( !( $handler instanceof ContentHandler ) ) {
 328                                 throw new MWException( "ContentHandlerForModelID must supply a ContentHandler instance" );
 329                         }
 330                 } else {
 331                         $class = $wgContentHandlers[$modelId];
 332                         $handler = new $class( $modelId );
 333
 334                         if ( !( $handler instanceof ContentHandler ) ) {
 335                                 throw new MWException( "$class from \$wgContentHandlers is not " .
 336                                         "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          * @throws MWException If the model ID isn't known.
 358          * @return string The content model's localized name.
 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         /**
 394          * @var string
 395          */
 396         protected $mModelID;
 397
 398         /**
 399          * @var string[]
 400          */
 401         protected $mSupportedFormats;
 402
 403         /**
 404          * Constructor, initializing the ContentHandler instance with its model ID
 405          * and a list of supported formats. Values for the parameters are typically
 406          * provided as literals by subclass's constructors.
 407          *
 408          * @param string $modelId (use CONTENT_MODEL_XXX constants).
 409          * @param string[] $formats List for supported serialization formats
 410          *    (typically as MIME types)
 411          */
 412         public function __construct( $modelId, $formats ) {
 413                 $this->mModelID = $modelId;
 414                 $this->mSupportedFormats = $formats;
 415
 416                 $this->mModelName = preg_replace( '/(Content)?Handler$/', '', get_class( $this ) );
 417                 $this->mModelName = preg_replace( '/[_\\\\]/', '', $this->mModelName );
 418                 $this->mModelName = strtolower( $this->mModelName );
 419         }
 420
 421         /**
 422          * Serializes a Content object of the type supported by this ContentHandler.
 423          *
 424          * @since 1.21
 425          *
 426          * @param Content $content The Content object to serialize
 427          * @param string $format The desired serialization format
 428          *
 429          * @return string Serialized form of the content
 430          */
 431         abstract public function serializeContent( Content $content, $format = null );
 432
 433         /**
 434          * Applies transformations on export (returns the blob unchanged per default).
 435          * Subclasses may override this to perform transformations such as conversion
 436          * of legacy formats or filtering of internal meta-data.
 437          *
 438          * @param string $blob The blob to be exported
 439          * @param string|null $format The blob's serialization format
 440          *
 441          * @return string
 442          */
 443         public function exportTransform( $blob, $format = null ) {
 444                 return $blob;
 445         }
 446
 447         /**
 448          * Unserializes a Content object of the type supported by this ContentHandler.
 449          *
 450          * @since 1.21
 451          *
 452          * @param string $blob Serialized form of the content
 453          * @param string $format The format used for serialization
 454          *
 455          * @return Content The Content object created by deserializing $blob
 456          */
 457         abstract public function unserializeContent( $blob, $format = null );
 458
 459         /**
 460          * Apply import transformation (per default, returns $blob unchanged).
 461          * This gives subclasses an opportunity to transform data blobs on import.
 462          *
 463          * @since 1.24
 464          *
 465          * @param string $blob
 466          * @param string|null $format
 467          *
 468          * @return string
 469          */
 470         public function importTransform( $blob, $format = null ) {
 471                 return $blob;
 472         }
 473
 474         /**
 475          * Creates an empty Content object of the type supported by this
 476          * ContentHandler.
 477          *
 478          * @since 1.21
 479          *
 480          * @return Content
 481          */
 482         abstract public function makeEmptyContent();
 483
 484         /**
 485          * Creates a new Content object that acts as a redirect to the given page,
 486          * or null if redirects are not supported by this content model.
 487          *
 488          * This default implementation always returns null. Subclasses supporting redirects
 489          * must override this method.
 490          *
 491          * Note that subclasses that override this method to return a Content object
 492          * should also override supportsRedirects() to return true.
 493          *
 494          * @since 1.21
 495          *
 496          * @param Title $destination The page to redirect to.
 497          * @param string $text Text to include in the redirect, if possible.
 498          *
 499          * @return Content Always null.
 500          */
 501         public function makeRedirectContent( Title $destination, $text = '' ) {
 502                 return null;
 503         }
 504
 505         /**
 506          * Returns the model id that identifies the content model this
 507          * ContentHandler can handle. Use with the CONTENT_MODEL_XXX constants.
 508          *
 509          * @since 1.21
 510          *
 511          * @return string The model ID
 512          */
 513         public function getModelID() {
 514                 return $this->mModelID;
 515         }
 516
 517         /**
 518          * @since 1.21
 519          *
 520          * @param string $model_id The model to check
 521          *
 522          * @throws MWException If the model ID is not the ID of the content model supported by this
 523          * ContentHandler.
 524          */
 525         protected function checkModelID( $model_id ) {
 526                 if ( $model_id !== $this->mModelID ) {
 527                         throw new MWException( "Bad content model: " .
 528                                 "expected {$this->mModelID} " .
 529                                 "but got $model_id." );
 530                 }
 531         }
 532
 533         /**
 534          * Returns a list of serialization formats supported by the
 535          * serializeContent() and unserializeContent() methods of this
 536          * ContentHandler.
 537          *
 538          * @since 1.21
 539          *
 540          * @return string[] List of serialization formats as MIME type like strings
 541          */
 542         public function getSupportedFormats() {
 543                 return $this->mSupportedFormats;
 544         }
 545
 546         /**
 547          * The format used for serialization/deserialization by default by this
 548          * ContentHandler.
 549          *
 550          * This default implementation will return the first element of the array
 551          * of formats that was passed to the constructor.
 552          *
 553          * @since 1.21
 554          *
 555          * @return string The name of the default serialization format as a MIME type
 556          */
 557         public function getDefaultFormat() {
 558                 return $this->mSupportedFormats[0];
 559         }
 560
 561         /**
 562          * Returns true if $format is a serialization format supported by this
 563          * ContentHandler, and false otherwise.
 564          *
 565          * Note that if $format is null, this method always returns true, because
 566          * null means "use the default format".
 567          *
 568          * @since 1.21
 569          *
 570          * @param string $format The serialization format to check
 571          *
 572          * @return bool
 573          */
 574         public function isSupportedFormat( $format ) {
 575                 if ( !$format ) {
 576                         return true; // this means "use the default"
 577                 }
 578
 579                 return in_array( $format, $this->mSupportedFormats );
 580         }
 581
 582         /**
 583          * Convenient for checking whether a format provided as a parameter is actually supported.
 584          *
 585          * @param string $format The serialization format to check
 586          *
 587          * @throws MWException If the format is not supported by this content handler.
 588          */
 589         protected function checkFormat( $format ) {
 590                 if ( !$this->isSupportedFormat( $format ) ) {
 591                         throw new MWException(
 592                                 "Format $format is not supported for content model "
 593                                 . $this->getModelID()
 594                         );
 595                 }
 596         }
 597
 598         /**
 599          * Returns overrides for action handlers.
 600          * Classes listed here will be used instead of the default one when
 601          * (and only when) $wgActions[$action] === true. This allows subclasses
 602          * to override the default action handlers.
 603          *
 604          * @since 1.21
 605          *
 606          * @return array Always an empty array.
 607          */
 608         public function getActionOverrides() {
 609                 return array();
 610         }
 611
 612         /**
 613          * Factory for creating an appropriate DifferenceEngine for this content model.
 614          *
 615          * @since 1.21
 616          *
 617          * @param IContextSource $context Context to use, anything else will be ignored.
 618          * @param int $old Revision ID we want to show and diff with.
 619          * @param int|string $new Either a revision ID or one of the strings 'cur', 'prev' or 'next'.
 620          * @param int $rcid FIXME: Deprecated, no longer used. Defaults to 0.
 621          * @param bool $refreshCache If set, refreshes the diff cache. Defaults to false.
 622          * @param bool $unhide If set, allow viewing deleted revs. Defaults to false.
 623          *
 624          * @return DifferenceEngine
 625          */
 626         public function createDifferenceEngine( IContextSource $context, $old = 0, $new = 0,
 627                 $rcid = 0, //FIXME: Deprecated, no longer used
 628                 $refreshCache = false, $unhide = false ) {
 629
 630                 // hook: get difference engine
 631                 $differenceEngine = null;
 632                 if ( !wfRunHooks( 'GetDifferenceEngine',
 633                         array( $context, $old, $new, $refreshCache, $unhide, &$differenceEngine )
 634                 ) ) {
 635                         return $differenceEngine;
 636                 }
 637                 $diffEngineClass = $this->getDiffEngineClass();
 638                 return new $diffEngineClass( $context, $old, $new, $rcid, $refreshCache, $unhide );
 639         }
 640
 641         /**
 642          * Get the language in which the content of the given page is written.
 643          *
 644          * This default implementation just returns $wgContLang (except for pages
 645          * in the MediaWiki namespace)
 646          *
 647          * Note that the pages language is not cacheable, since it may in some
 648          * cases depend on user settings.
 649          *
 650          * Also note that the page language may or may not depend on the actual content of the page,
 651          * that is, this method may load the content in order to determine the language.
 652          *
 653          * @since 1.21
 654          *
 655          * @param Title $title The page to determine the language for.
 656          * @param Content $content The page's content, if you have it handy, to avoid reloading it.
 657          *
 658          * @return Language The page's language
 659          */
 660         public function getPageLanguage( Title $title, Content $content = null ) {
 661                 global $wgContLang, $wgLang;
 662                 $pageLang = $wgContLang;
 663
 664                 if ( $title->getNamespace() == NS_MEDIAWIKI ) {
 665                         // Parse mediawiki messages with correct target language
 666                         list( /* $unused */, $lang ) = MessageCache::singleton()->figureMessage( $title->getText() );
 667                         $pageLang = wfGetLangObj( $lang );
 668                 }
 669
 670                 Hooks::run( 'PageContentLanguage', array( $title, &$pageLang, $wgLang ) );
 671
 672                 return wfGetLangObj( $pageLang );
 673         }
 674
 675         /**
 676          * Get the language in which the content of this page is written when
 677          * viewed by user. Defaults to $this->getPageLanguage(), but if the user
 678          * specified a preferred variant, the variant will be used.
 679          *
 680          * This default implementation just returns $this->getPageLanguage( $title, $content ) unless
 681          * the user specified a preferred variant.
 682          *
 683          * Note that the pages view language is not cacheable, since it depends on user settings.
 684          *
 685          * Also note that the page language may or may not depend on the actual content of the page,
 686          * that is, this method may load the content in order to determine the language.
 687          *
 688          * @since 1.21
 689          *
 690          * @param Title $title The page to determine the language for.
 691          * @param Content $content The page's content, if you have it handy, to avoid reloading it.
 692          *
 693          * @return Language The page's language for viewing
 694          */
 695         public function getPageViewLanguage( Title $title, Content $content = null ) {
 696                 $pageLang = $this->getPageLanguage( $title, $content );
 697
 698                 if ( $title->getNamespace() !== NS_MEDIAWIKI ) {
 699                         // If the user chooses a variant, the content is actually
 700                         // in a language whose code is the variant code.
 701                         $variant = $pageLang->getPreferredVariant();
 702                         if ( $pageLang->getCode() !== $variant ) {
 703                                 $pageLang = Language::factory( $variant );
 704                         }
 705                 }
 706
 707                 return $pageLang;
 708         }
 709
 710         /**
 711          * Determines whether the content type handled by this ContentHandler
 712          * can be used on the given page.
 713          *
 714          * This default implementation always returns true.
 715          * Subclasses may override this to restrict the use of this content model to specific locations,
 716          * typically based on the namespace or some other aspect of the title, such as a special suffix
 717          * (e.g. ".svg" for SVG content).
 718          *
 719          * @note this calls the ContentHandlerCanBeUsedOn hook which may be used to override which
 720          * content model can be used where.
 721          *
 722          * @param Title $title The page's title.
 723          *
 724          * @return bool True if content of this kind can be used on the given page, false otherwise.
 725          */
 726         public function canBeUsedOn( Title $title ) {
 727                 $ok = true;
 728
 729                 Hooks::run( 'ContentModelCanBeUsedOn', array( $this->getModelID(), $title, &$ok ) );
 730
 731                 return $ok;
 732         }
 733
 734         /**
 735          * Returns the name of the diff engine to use.
 736          *
 737          * @since 1.21
 738          *
 739          * @return string
 740          */
 741         protected function getDiffEngineClass() {
 742                 return 'DifferenceEngine';
 743         }
 744
 745         /**
 746          * Attempts to merge differences between three versions. Returns a new
 747          * Content object for a clean merge and false for failure or a conflict.
 748          *
 749          * This default implementation always returns false.
 750          *
 751          * @since 1.21
 752          *
 753          * @param Content $oldContent The page's previous content.
 754          * @param Content $myContent One of the page's conflicting contents.
 755          * @param Content $yourContent One of the page's conflicting contents.
 756          *
 757          * @return Content|bool Always false.
 758          */
 759         public function merge3( Content $oldContent, Content $myContent, Content $yourContent ) {
 760                 return false;
 761         }
 762
 763         /**
 764          * Return an applicable auto-summary if one exists for the given edit.
 765          *
 766          * @since 1.21
 767          *
 768          * @param Content $oldContent The previous text of the page.
 769          * @param Content $newContent The submitted text of the page.
 770          * @param int $flags Bit mask: a bit mask of flags submitted for the edit.
 771          *
 772          * @return string An appropriate auto-summary, or an empty string.
 773          */
 774         public function getAutosummary( Content $oldContent = null, Content $newContent = null,
 775                 $flags ) {
 776                 // Decide what kind of auto-summary is needed.
 777
 778                 // Redirect auto-summaries
 779
 780                 /**
 781                  * @var $ot Title
 782                  * @var $rt Title
 783                  */
 784
 785                 $ot = !is_null( $oldContent ) ? $oldContent->getRedirectTarget() : null;
 786                 $rt = !is_null( $newContent ) ? $newContent->getRedirectTarget() : null;
 787
 788                 if ( is_object( $rt ) ) {
 789                         if ( !is_object( $ot )
 790                                 || !$rt->equals( $ot )
 791                                 || $ot->getFragment() != $rt->getFragment()
 792                         ) {
 793                                 $truncatedtext = $newContent->getTextForSummary(
 794                                         250
 795                                         - strlen( wfMessage( 'autoredircomment' )->inContentLanguage()->text() )
 796                                         - strlen( $rt->getFullText() ) );
 797
 798                                 return wfMessage( 'autoredircomment', $rt->getFullText() )
 799                                         ->rawParams( $truncatedtext )->inContentLanguage()->text();
 800                         }
 801                 }
 802
 803                 // New page auto-summaries
 804                 if ( $flags & EDIT_NEW && $newContent->getSize() > 0 ) {
 805                         // If they're making a new article, give its text, truncated, in
 806                         // the summary.
 807
 808                         $truncatedtext = $newContent->getTextForSummary(
 809                                 200 - strlen( wfMessage( 'autosumm-new' )->inContentLanguage()->text() ) );
 810
 811                         return wfMessage( 'autosumm-new' )->rawParams( $truncatedtext )
 812                                 ->inContentLanguage()->text();
 813                 }
 814
 815                 // Blanking auto-summaries
 816                 if ( !empty( $oldContent ) && $oldContent->getSize() > 0 && $newContent->getSize() == 0 ) {
 817                         return wfMessage( 'autosumm-blank' )->inContentLanguage()->text();
 818                 } elseif ( !empty( $oldContent )
 819                         && $oldContent->getSize() > 10 * $newContent->getSize()
 820                         && $newContent->getSize() < 500
 821                 ) {
 822                         // Removing more than 90% of the article
 823
 824                         $truncatedtext = $newContent->getTextForSummary(
 825                                 200 - strlen( wfMessage( 'autosumm-replace' )->inContentLanguage()->text() ) );
 826
 827                         return wfMessage( 'autosumm-replace' )->rawParams( $truncatedtext )
 828                                 ->inContentLanguage()->text();
 829                 }
 830
 831                 // New blank article auto-summary
 832                 if ( $flags & EDIT_NEW && $newContent->isEmpty() ) {
 833                         return wfMessage( 'autosumm-newblank' )->inContentLanguage()->text();
 834                 }
 835
 836                 // If we reach this point, there's no applicable auto-summary for our
 837                 // case, so our auto-summary is empty.
 838                 return '';
 839         }
 840
 841         /**
 842          * Auto-generates a deletion reason
 843          *
 844          * @since 1.21
 845          *
 846          * @param Title $title The page's title
 847          * @param bool &$hasHistory Whether the page has a history
 848          *
 849          * @return mixed String containing deletion reason or empty string, or
 850          *    boolean false if no revision occurred
 851          *
 852          * @todo &$hasHistory is extremely ugly, it's here because
 853          * WikiPage::getAutoDeleteReason() and Article::generateReason()
 854          * have it / want it.
 855          */
 856         public function getAutoDeleteReason( Title $title, &$hasHistory ) {
 857                 $dbw = wfGetDB( DB_MASTER );
 858
 859                 // Get the last revision
 860                 $rev = Revision::newFromTitle( $title );
 861
 862                 if ( is_null( $rev ) ) {
 863                         return false;
 864                 }
 865
 866                 // Get the article's contents
 867                 $content = $rev->getContent();
 868                 $blank = false;
 869
 870                 // If the page is blank, use the text from the previous revision,
 871                 // which can only be blank if there's a move/import/protect dummy
 872                 // revision involved
 873                 if ( !$content || $content->isEmpty() ) {
 874                         $prev = $rev->getPrevious();
 875
 876                         if ( $prev ) {
 877                                 $rev = $prev;
 878                                 $content = $rev->getContent();
 879                                 $blank = true;
 880                         }
 881                 }
 882
 883                 $this->checkModelID( $rev->getContentModel() );
 884
 885                 // Find out if there was only one contributor
 886                 // Only scan the last 20 revisions
 887                 $res = $dbw->select( 'revision', 'rev_user_text',
 888                         array(
 889                                 'rev_page' => $title->getArticleID(),
 890                                 $dbw->bitAnd( 'rev_deleted', Revision::DELETED_USER ) . ' = 0'
 891                         ),
 892                         __METHOD__,
 893                         array( 'LIMIT' => 20 )
 894                 );
 895
 896                 if ( $res === false ) {
 897                         // This page has no revisions, which is very weird
 898                         return false;
 899                 }
 900
 901                 $hasHistory = ( $res->numRows() > 1 );
 902                 $row = $dbw->fetchObject( $res );
 903
 904                 if ( $row ) { // $row is false if the only contributor is hidden
 905                         $onlyAuthor = $row->rev_user_text;
 906                         // Try to find a second contributor
 907                         foreach ( $res as $row ) {
 908                                 if ( $row->rev_user_text != $onlyAuthor ) { // Bug 22999
 909                                         $onlyAuthor = false;
 910                                         break;
 911                                 }
 912                         }
 913                 } else {
 914                         $onlyAuthor = false;
 915                 }
 916
 917                 // Generate the summary with a '$1' placeholder
 918                 if ( $blank ) {
 919                         // The current revision is blank and the one before is also
 920                         // blank. It's just not our lucky day
 921                         $reason = wfMessage( 'exbeforeblank', '$1' )->inContentLanguage()->text();
 922                 } else {
 923                         if ( $onlyAuthor ) {
 924                                 $reason = wfMessage(
 925                                         'excontentauthor',
 926                                         '$1',
 927                                         $onlyAuthor
 928                                 )->inContentLanguage()->text();
 929                         } else {
 930                                 $reason = wfMessage( 'excontent', '$1' )->inContentLanguage()->text();
 931                         }
 932                 }
 933
 934                 if ( $reason == '-' ) {
 935                         // Allow these UI messages to be blanked out cleanly
 936                         return '';
 937                 }
 938
 939                 // Max content length = max comment length - length of the comment (excl. $1)
 940                 $text = $content ? $content->getTextForSummary( 255 - ( strlen( $reason ) - 2 ) ) : '';
 941
 942                 // Now replace the '$1' placeholder
 943                 $reason = str_replace( '$1', $text, $reason );
 944
 945                 return $reason;
 946         }
 947
 948         /**
 949          * Get the Content object that needs to be saved in order to undo all revisions
 950          * between $undo and $undoafter. Revisions must belong to the same page,
 951          * must exist and must not be deleted.
 952          *
 953          * @since 1.21
 954          *
 955          * @param Revision $current The current text
 956          * @param Revision $undo The revision to undo
 957          * @param Revision $undoafter Must be an earlier revision than $undo
 958          *
 959          * @return mixed String on success, false on failure
 960          */
 961         public function getUndoContent( Revision $current, Revision $undo, Revision $undoafter ) {
 962                 $cur_content = $current->getContent();
 963
 964                 if ( empty( $cur_content ) ) {
 965                         return false; // no page
 966                 }
 967
 968                 $undo_content = $undo->getContent();
 969                 $undoafter_content = $undoafter->getContent();
 970
 971                 if ( !$undo_content || !$undoafter_content ) {
 972                         return false; // no content to undo
 973                 }
 974
 975                 $this->checkModelID( $cur_content->getModel() );
 976                 $this->checkModelID( $undo_content->getModel() );
 977                 $this->checkModelID( $undoafter_content->getModel() );
 978
 979                 if ( $cur_content->equals( $undo_content ) ) {
 980                         // No use doing a merge if it's just a straight revert.
 981                         return $undoafter_content;
 982                 }
 983
 984                 $undone_content = $this->merge3( $undo_content, $undoafter_content, $cur_content );
 985
 986                 return $undone_content;
 987         }
 988
 989         /**
 990          * Get parser options suitable for rendering and caching the article
 991          *
 992          * @param IContextSource|User|string $context One of the following:
 993          *        - IContextSource: Use the User and the Language of the provided
 994          *                                            context
 995          *        - User: Use the provided User object and $wgLang for the language,
 996          *                                            so use an IContextSource object if possible.
 997          *        - 'canonical': Canonical options (anonymous user with default
 998          *                                            preferences and content language).
 999          *
1000          * @throws MWException
1001          * @return ParserOptions
1002          */
1003         public function makeParserOptions( $context ) {
1004                 global $wgContLang, $wgEnableParserLimitReporting;
1005
1006                 if ( $context instanceof IContextSource ) {
1007                         $options = ParserOptions::newFromContext( $context );
1008                 } elseif ( $context instanceof User ) { // settings per user (even anons)
1009                         $options = ParserOptions::newFromUser( $context );
1010                 } elseif ( $context === 'canonical' ) { // canonical settings
1011                         $options = ParserOptions::newFromUserAndLang( new User, $wgContLang );
1012                 } else {
1013                         throw new MWException( "Bad context for parser options: $context" );
1014                 }
1015
1016                 $options->enableLimitReport( $wgEnableParserLimitReporting ); // show inclusion/loop reports
1017                 $options->setTidy( true ); // fix bad HTML
1018
1019                 return $options;
1020         }
1021
1022         /**
1023          * Returns true for content models that support caching using the
1024          * ParserCache mechanism. See WikiPage::isParserCacheUsed().
1025          *
1026          * @since 1.21
1027          *
1028          * @return bool Always false.
1029          */
1030         public function isParserCacheSupported() {
1031                 return false;
1032         }
1033
1034         /**
1035          * Returns true if this content model supports sections.
1036          * This default implementation returns false.
1037          *
1038          * Content models that return true here should also implement
1039          * Content::getSection, Content::replaceSection, etc. to handle sections..
1040          *
1041          * @return bool Always false.
1042          */
1043         public function supportsSections() {
1044                 return false;
1045         }
1046
1047         /**
1048          * Returns true if this content model supports redirects.
1049          * This default implementation returns false.
1050          *
1051          * Content models that return true here should also implement
1052          * ContentHandler::makeRedirectContent to return a Content object.
1053          *
1054          * @return bool Always false.
1055          */
1056         public function supportsRedirects() {
1057                 return false;
1058         }
1059
1060         /**
1061          * Logs a deprecation warning, visible if $wgDevelopmentWarnings, but only if
1062          * self::$enableDeprecationWarnings is set to true.
1063          *
1064          * @param string $func The name of the deprecated function
1065          * @param string $version The version since the method is deprecated. Usually 1.21
1066          *   for ContentHandler related stuff.
1067          * @param string|bool $component : Component to which the function belongs.
1068          *   If false, it is assumed the function is in MediaWiki core.
1069          *
1070          * @see ContentHandler::$enableDeprecationWarnings
1071          * @see wfDeprecated
1072          */
1073         public static function deprecated( $func, $version, $component = false ) {
1074                 if ( self::$enableDeprecationWarnings ) {
1075                         wfDeprecated( $func, $version, $component, 3 );
1076                 }
1077         }
1078
1079         /**
1080          * Call a legacy hook that uses text instead of Content objects.
1081          * Will log a warning when a matching hook function is registered.
1082          * If the textual representation of the content is changed by the
1083          * hook function, a new Content object is constructed from the new
1084          * text.
1085          *
1086          * @param string $event Event name
1087          * @param array $args Parameters passed to hook functions
1088          * @param bool $warn Whether to log a warning.
1089          *                    Default to self::$enableDeprecationWarnings.
1090          *                    May be set to false for testing.
1091          *
1092          * @return bool True if no handler aborted the hook
1093          *
1094          * @see ContentHandler::$enableDeprecationWarnings
1095          */
1096         public static function runLegacyHooks( $event, $args = array(),
1097                 $warn = null
1098         ) {
1099
1100                 if ( $warn === null ) {
1101                         $warn = self::$enableDeprecationWarnings;
1102                 }
1103
1104                 if ( !Hooks::isRegistered( $event ) ) {
1105                         return true; // nothing to do here
1106                 }
1107
1108                 if ( $warn ) {
1109                         // Log information about which handlers are registered for the legacy hook,
1110                         // so we can find and fix them.
1111
1112                         $handlers = Hooks::getHandlers( $event );
1113                         $handlerInfo = array();
1114
1115                         wfSuppressWarnings();
1116
1117                         foreach ( $handlers as $handler ) {
1118                                 if ( is_array( $handler ) ) {
1119                                         if ( is_object( $handler[0] ) ) {
1120                                                 $info = get_class( $handler[0] );
1121                                         } else {
1122                                                 $info = $handler[0];
1123                                         }
1124
1125                                         if ( isset( $handler[1] ) ) {
1126                                                 $info .= '::' . $handler[1];
1127                                         }
1128                                 } elseif ( is_object( $handler ) ) {
1129                                         $info = get_class( $handler[0] );
1130                                         $info .= '::on' . $event;
1131                                 } else {
1132                                         $info = $handler;
1133                                 }
1134
1135                                 $handlerInfo[] = $info;
1136                         }
1137
1138                         wfRestoreWarnings();
1139
1140                         wfWarn( "Using obsolete hook $event via ContentHandler::runLegacyHooks()! Handlers: " .
1141                                 implode( ', ', $handlerInfo ), 2 );
1142                 }
1143
1144                 // convert Content objects to text
1145                 $contentObjects = array();
1146                 $contentTexts = array();
1147
1148                 foreach ( $args as $k => $v ) {
1149                         if ( $v instanceof Content ) {
1150                                 /* @var Content $v */
1151
1152                                 $contentObjects[$k] = $v;
1153
1154                                 $v = $v->serialize();
1155                                 $contentTexts[$k] = $v;
1156                                 $args[$k] = $v;
1157                         }
1158                 }
1159
1160                 // call the hook functions
1161                 $ok = Hooks::run( $event, $args );
1162
1163                 // see if the hook changed the text
1164                 foreach ( $contentTexts as $k => $orig ) {
1165                         /* @var Content $content */
1166
1167                         $modified = $args[$k];
1168                         $content = $contentObjects[$k];
1169
1170                         if ( $modified !== $orig ) {
1171                                 // text was changed, create updated Content object
1172                                 $content = $content->getContentHandler()->unserializeContent( $modified );
1173                         }
1174
1175                         $args[$k] = $content;
1176                 }
1177
1178                 return $ok;
1179         }
1180 }