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 code based on the title?
 211                 $isCodePage = NS_MEDIAWIKI == $ns && preg_match( '!\.(css|js|json)$!u', $title->getText(), $m );
 212                 if ( $isCodePage ) {
 213                         $ext = $m[1];
 214                 }
 215
 216                 // Hook can force JS/CSS
 217                 Hooks::run( 'TitleIsCssOrJsPage', array( $title, &$isCodePage ), '1.25' );
 218
 219                 // Is this a user subpage containing code?
 220                 $isCodeSubpage = NS_USER == $ns
 221                         && !$isCodePage
 222                         && preg_match( "/\\/.*\\.(js|css|json)$/", $title->getText(), $m );
 223                 if ( $isCodeSubpage ) {
 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 = $isWikitext && !$isCodePage && !$isCodeSubpage;
 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                                 case 'json':
 241                                         return CONTENT_MODEL_JSON;
 242                                 default:
 243                                         return is_null( $model ) ? CONTENT_MODEL_TEXT : $model;
 244                         }
 245                 }
 246
 247                 // We established that it must be wikitext
 248
 249                 return CONTENT_MODEL_WIKITEXT;
 250         }
 251
 252         /**
 253          * Returns the appropriate ContentHandler singleton for the given title.
 254          *
 255          * @since 1.21
 256          *
 257          * @param Title $title
 258          *
 259          * @return ContentHandler
 260          */
 261         public static function getForTitle( Title $title ) {
 262                 $modelId = $title->getContentModel();
 263
 264                 return ContentHandler::getForModelID( $modelId );
 265         }
 266
 267         /**
 268          * Returns the appropriate ContentHandler singleton for the given Content
 269          * object.
 270          *
 271          * @since 1.21
 272          *
 273          * @param Content $content
 274          *
 275          * @return ContentHandler
 276          */
 277         public static function getForContent( Content $content ) {
 278                 $modelId = $content->getModel();
 279
 280                 return ContentHandler::getForModelID( $modelId );
 281         }
 282
 283         /**
 284          * @var array A Cache of ContentHandler instances by model id
 285          */
 286         protected static $handlers;
 287
 288         /**
 289          * Returns the ContentHandler singleton for the given model ID. Use the
 290          * CONTENT_MODEL_XXX constants to identify the desired content model.
 291          *
 292          * ContentHandler singletons are taken from the global $wgContentHandlers
 293          * array. Keys in that array are model names, the values are either
 294          * ContentHandler singleton objects, or strings specifying the appropriate
 295          * subclass of ContentHandler.
 296          *
 297          * If a class name is encountered when looking up the singleton for a given
 298          * model name, the class is instantiated and the class name is replaced by
 299          * the resulting singleton in $wgContentHandlers.
 300          *
 301          * If no ContentHandler is defined for the desired $modelId, the
 302          * ContentHandler may be provided by the ContentHandlerForModelID hook.
 303          * If no ContentHandler can be determined, an MWException is raised.
 304          *
 305          * @since 1.21
 306          *
 307          * @param string $modelId The ID of the content model for which to get a
 308          *    handler. Use CONTENT_MODEL_XXX constants.
 309          *
 310          * @throws MWException If no handler is known for the model ID.
 311          * @return ContentHandler The ContentHandler singleton for handling the model given by the ID.
 312          */
 313         public static function getForModelID( $modelId ) {
 314                 global $wgContentHandlers;
 315
 316                 if ( isset( ContentHandler::$handlers[$modelId] ) ) {
 317                         return ContentHandler::$handlers[$modelId];
 318                 }
 319
 320                 if ( empty( $wgContentHandlers[$modelId] ) ) {
 321                         $handler = null;
 322
 323                         Hooks::run( 'ContentHandlerForModelID', array( $modelId, &$handler ) );
 324
 325                         if ( $handler === null ) {
 326                                 throw new MWException( "No handler for model '$modelId' registered in \$wgContentHandlers" );
 327                         }
 328
 329                         if ( !( $handler instanceof ContentHandler ) ) {
 330                                 throw new MWException( "ContentHandlerForModelID must supply a ContentHandler instance" );
 331                         }
 332                 } else {
 333                         $class = $wgContentHandlers[$modelId];
 334                         $handler = new $class( $modelId );
 335
 336                         if ( !( $handler instanceof ContentHandler ) ) {
 337                                 throw new MWException( "$class from \$wgContentHandlers is not " .
 338                                         "compatible with ContentHandler" );
 339                         }
 340                 }
 341
 342                 wfDebugLog( 'ContentHandler', 'Created handler for ' . $modelId
 343                         . ': ' . get_class( $handler ) );
 344
 345                 ContentHandler::$handlers[$modelId] = $handler;
 346
 347                 return ContentHandler::$handlers[$modelId];
 348         }
 349
 350         /**
 351          * Returns the localized name for a given content model.
 352          *
 353          * Model names are localized using system messages. Message keys
 354          * have the form content-model-$name, where $name is getContentModelName( $id ).
 355          *
 356          * @param string $name The content model ID, as given by a CONTENT_MODEL_XXX
 357          *    constant or returned by Revision::getContentModel().
 358          * @param Language|null $lang The language to parse the message in (since 1.26)
 359          *
 360          * @throws MWException If the model ID isn't known.
 361          * @return string The content model's localized name.
 362          */
 363         public static function getLocalizedName( $name, Language $lang = null ) {
 364                 // Messages: content-model-wikitext, content-model-text,
 365                 // content-model-javascript, content-model-css
 366                 $key = "content-model-$name";
 367
 368                 $msg = wfMessage( $key );
 369                 if ( $lang ) {
 370                         $msg->inLanguage( $lang );
 371                 }
 372
 373                 return $msg->exists() ? $msg->plain() : $name;
 374         }
 375
 376         public static function getContentModels() {
 377                 global $wgContentHandlers;
 378
 379                 return array_keys( $wgContentHandlers );
 380         }
 381
 382         public static function getAllContentFormats() {
 383                 global $wgContentHandlers;
 384
 385                 $formats = array();
 386
 387                 foreach ( $wgContentHandlers as $model => $class ) {
 388                         $handler = ContentHandler::getForModelID( $model );
 389                         $formats = array_merge( $formats, $handler->getSupportedFormats() );
 390                 }
 391
 392                 $formats = array_unique( $formats );
 393
 394                 return $formats;
 395         }
 396
 397         // ------------------------------------------------------------------------
 398
 399         /**
 400          * @var string
 401          */
 402         protected $mModelID;
 403
 404         /**
 405          * @var string[]
 406          */
 407         protected $mSupportedFormats;
 408
 409         /**
 410          * Constructor, initializing the ContentHandler instance with its model ID
 411          * and a list of supported formats. Values for the parameters are typically
 412          * provided as literals by subclass's constructors.
 413          *
 414          * @param string $modelId (use CONTENT_MODEL_XXX constants).
 415          * @param string[] $formats List for supported serialization formats
 416          *    (typically as MIME types)
 417          */
 418         public function __construct( $modelId, $formats ) {
 419                 $this->mModelID = $modelId;
 420                 $this->mSupportedFormats = $formats;
 421
 422                 $this->mModelName = preg_replace( '/(Content)?Handler$/', '', get_class( $this ) );
 423                 $this->mModelName = preg_replace( '/[_\\\\]/', '', $this->mModelName );
 424                 $this->mModelName = strtolower( $this->mModelName );
 425         }
 426
 427         /**
 428          * Serializes a Content object of the type supported by this ContentHandler.
 429          *
 430          * @since 1.21
 431          *
 432          * @param Content $content The Content object to serialize
 433          * @param string $format The desired serialization format
 434          *
 435          * @return string Serialized form of the content
 436          */
 437         abstract public function serializeContent( Content $content, $format = null );
 438
 439         /**
 440          * Applies transformations on export (returns the blob unchanged per default).
 441          * Subclasses may override this to perform transformations such as conversion
 442          * of legacy formats or filtering of internal meta-data.
 443          *
 444          * @param string $blob The blob to be exported
 445          * @param string|null $format The blob's serialization format
 446          *
 447          * @return string
 448          */
 449         public function exportTransform( $blob, $format = null ) {
 450                 return $blob;
 451         }
 452
 453         /**
 454          * Unserializes a Content object of the type supported by this ContentHandler.
 455          *
 456          * @since 1.21
 457          *
 458          * @param string $blob Serialized form of the content
 459          * @param string $format The format used for serialization
 460          *
 461          * @return Content The Content object created by deserializing $blob
 462          */
 463         abstract public function unserializeContent( $blob, $format = null );
 464
 465         /**
 466          * Apply import transformation (per default, returns $blob unchanged).
 467          * This gives subclasses an opportunity to transform data blobs on import.
 468          *
 469          * @since 1.24
 470          *
 471          * @param string $blob
 472          * @param string|null $format
 473          *
 474          * @return string
 475          */
 476         public function importTransform( $blob, $format = null ) {
 477                 return $blob;
 478         }
 479
 480         /**
 481          * Creates an empty Content object of the type supported by this
 482          * ContentHandler.
 483          *
 484          * @since 1.21
 485          *
 486          * @return Content
 487          */
 488         abstract public function makeEmptyContent();
 489
 490         /**
 491          * Creates a new Content object that acts as a redirect to the given page,
 492          * or null if redirects are not supported by this content model.
 493          *
 494          * This default implementation always returns null. Subclasses supporting redirects
 495          * must override this method.
 496          *
 497          * Note that subclasses that override this method to return a Content object
 498          * should also override supportsRedirects() to return true.
 499          *
 500          * @since 1.21
 501          *
 502          * @param Title $destination The page to redirect to.
 503          * @param string $text Text to include in the redirect, if possible.
 504          *
 505          * @return Content Always null.
 506          */
 507         public function makeRedirectContent( Title $destination, $text = '' ) {
 508                 return null;
 509         }
 510
 511         /**
 512          * Returns the model id that identifies the content model this
 513          * ContentHandler can handle. Use with the CONTENT_MODEL_XXX constants.
 514          *
 515          * @since 1.21
 516          *
 517          * @return string The model ID
 518          */
 519         public function getModelID() {
 520                 return $this->mModelID;
 521         }
 522
 523         /**
 524          * @since 1.21
 525          *
 526          * @param string $model_id The model to check
 527          *
 528          * @throws MWException If the model ID is not the ID of the content model supported by this
 529          * ContentHandler.
 530          */
 531         protected function checkModelID( $model_id ) {
 532                 if ( $model_id !== $this->mModelID ) {
 533                         throw new MWException( "Bad content model: " .
 534                                 "expected {$this->mModelID} " .
 535                                 "but got $model_id." );
 536                 }
 537         }
 538
 539         /**
 540          * Returns a list of serialization formats supported by the
 541          * serializeContent() and unserializeContent() methods of this
 542          * ContentHandler.
 543          *
 544          * @since 1.21
 545          *
 546          * @return string[] List of serialization formats as MIME type like strings
 547          */
 548         public function getSupportedFormats() {
 549                 return $this->mSupportedFormats;
 550         }
 551
 552         /**
 553          * The format used for serialization/deserialization by default by this
 554          * ContentHandler.
 555          *
 556          * This default implementation will return the first element of the array
 557          * of formats that was passed to the constructor.
 558          *
 559          * @since 1.21
 560          *
 561          * @return string The name of the default serialization format as a MIME type
 562          */
 563         public function getDefaultFormat() {
 564                 return $this->mSupportedFormats[0];
 565         }
 566
 567         /**
 568          * Returns true if $format is a serialization format supported by this
 569          * ContentHandler, and false otherwise.
 570          *
 571          * Note that if $format is null, this method always returns true, because
 572          * null means "use the default format".
 573          *
 574          * @since 1.21
 575          *
 576          * @param string $format The serialization format to check
 577          *
 578          * @return bool
 579          */
 580         public function isSupportedFormat( $format ) {
 581                 if ( !$format ) {
 582                         return true; // this means "use the default"
 583                 }
 584
 585                 return in_array( $format, $this->mSupportedFormats );
 586         }
 587
 588         /**
 589          * Convenient for checking whether a format provided as a parameter is actually supported.
 590          *
 591          * @param string $format The serialization format to check
 592          *
 593          * @throws MWException If the format is not supported by this content handler.
 594          */
 595         protected function checkFormat( $format ) {
 596                 if ( !$this->isSupportedFormat( $format ) ) {
 597                         throw new MWException(
 598                                 "Format $format is not supported for content model "
 599                                 . $this->getModelID()
 600                         );
 601                 }
 602         }
 603
 604         /**
 605          * Returns overrides for action handlers.
 606          * Classes listed here will be used instead of the default one when
 607          * (and only when) $wgActions[$action] === true. This allows subclasses
 608          * to override the default action handlers.
 609          *
 610          * @since 1.21
 611          *
 612          * @return array Always an empty array.
 613          */
 614         public function getActionOverrides() {
 615                 return array();
 616         }
 617
 618         /**
 619          * Factory for creating an appropriate DifferenceEngine for this content model.
 620          *
 621          * @since 1.21
 622          *
 623          * @param IContextSource $context Context to use, anything else will be ignored.
 624          * @param int $old Revision ID we want to show and diff with.
 625          * @param int|string $new Either a revision ID or one of the strings 'cur', 'prev' or 'next'.
 626          * @param int $rcid FIXME: Deprecated, no longer used. Defaults to 0.
 627          * @param bool $refreshCache If set, refreshes the diff cache. Defaults to false.
 628          * @param bool $unhide If set, allow viewing deleted revs. Defaults to false.
 629          *
 630          * @return DifferenceEngine
 631          */
 632         public function createDifferenceEngine( IContextSource $context, $old = 0, $new = 0,
 633                 $rcid = 0, //FIXME: Deprecated, no longer used
 634                 $refreshCache = false, $unhide = false ) {
 635
 636                 // hook: get difference engine
 637                 $differenceEngine = null;
 638                 if ( !Hooks::run( 'GetDifferenceEngine',
 639                         array( $context, $old, $new, $refreshCache, $unhide, &$differenceEngine )
 640                 ) ) {
 641                         return $differenceEngine;
 642                 }
 643                 $diffEngineClass = $this->getDiffEngineClass();
 644                 return new $diffEngineClass( $context, $old, $new, $rcid, $refreshCache, $unhide );
 645         }
 646
 647         /**
 648          * Get the language in which the content of the given page is written.
 649          *
 650          * This default implementation just returns $wgContLang (except for pages
 651          * in the MediaWiki namespace)
 652          *
 653          * Note that the pages language is not cacheable, since it may in some
 654          * cases depend on user settings.
 655          *
 656          * Also note that the page language may or may not depend on the actual content of the page,
 657          * that is, this method may load the content in order to determine the language.
 658          *
 659          * @since 1.21
 660          *
 661          * @param Title $title The page to determine the language for.
 662          * @param Content $content The page's content, if you have it handy, to avoid reloading it.
 663          *
 664          * @return Language The page's language
 665          */
 666         public function getPageLanguage( Title $title, Content $content = null ) {
 667                 global $wgContLang, $wgLang;
 668                 $pageLang = $wgContLang;
 669
 670                 if ( $title->getNamespace() == NS_MEDIAWIKI ) {
 671                         // Parse mediawiki messages with correct target language
 672                         list( /* $unused */, $lang ) = MessageCache::singleton()->figureMessage( $title->getText() );
 673                         $pageLang = wfGetLangObj( $lang );
 674                 }
 675
 676                 Hooks::run( 'PageContentLanguage', array( $title, &$pageLang, $wgLang ) );
 677
 678                 return wfGetLangObj( $pageLang );
 679         }
 680
 681         /**
 682          * Get the language in which the content of this page is written when
 683          * viewed by user. Defaults to $this->getPageLanguage(), but if the user
 684          * specified a preferred variant, the variant will be used.
 685          *
 686          * This default implementation just returns $this->getPageLanguage( $title, $content ) unless
 687          * the user specified a preferred variant.
 688          *
 689          * Note that the pages view language is not cacheable, since it depends on user settings.
 690          *
 691          * Also note that the page language may or may not depend on the actual content of the page,
 692          * that is, this method may load the content in order to determine the language.
 693          *
 694          * @since 1.21
 695          *
 696          * @param Title $title The page to determine the language for.
 697          * @param Content $content The page's content, if you have it handy, to avoid reloading it.
 698          *
 699          * @return Language The page's language for viewing
 700          */
 701         public function getPageViewLanguage( Title $title, Content $content = null ) {
 702                 $pageLang = $this->getPageLanguage( $title, $content );
 703
 704                 if ( $title->getNamespace() !== NS_MEDIAWIKI ) {
 705                         // If the user chooses a variant, the content is actually
 706                         // in a language whose code is the variant code.
 707                         $variant = $pageLang->getPreferredVariant();
 708                         if ( $pageLang->getCode() !== $variant ) {
 709                                 $pageLang = Language::factory( $variant );
 710                         }
 711                 }
 712
 713                 return $pageLang;
 714         }
 715
 716         /**
 717          * Determines whether the content type handled by this ContentHandler
 718          * can be used on the given page.
 719          *
 720          * This default implementation always returns true.
 721          * Subclasses may override this to restrict the use of this content model to specific locations,
 722          * typically based on the namespace or some other aspect of the title, such as a special suffix
 723          * (e.g. ".svg" for SVG content).
 724          *
 725          * @note this calls the ContentHandlerCanBeUsedOn hook which may be used to override which
 726          * content model can be used where.
 727          *
 728          * @param Title $title The page's title.
 729          *
 730          * @return bool True if content of this kind can be used on the given page, false otherwise.
 731          */
 732         public function canBeUsedOn( Title $title ) {
 733                 $ok = true;
 734
 735                 Hooks::run( 'ContentModelCanBeUsedOn', array( $this->getModelID(), $title, &$ok ) );
 736
 737                 return $ok;
 738         }
 739
 740         /**
 741          * Returns the name of the diff engine to use.
 742          *
 743          * @since 1.21
 744          *
 745          * @return string
 746          */
 747         protected function getDiffEngineClass() {
 748                 return 'DifferenceEngine';
 749         }
 750
 751         /**
 752          * Attempts to merge differences between three versions. Returns a new
 753          * Content object for a clean merge and false for failure or a conflict.
 754          *
 755          * This default implementation always returns false.
 756          *
 757          * @since 1.21
 758          *
 759          * @param Content $oldContent The page's previous content.
 760          * @param Content $myContent One of the page's conflicting contents.
 761          * @param Content $yourContent One of the page's conflicting contents.
 762          *
 763          * @return Content|bool Always false.
 764          */
 765         public function merge3( Content $oldContent, Content $myContent, Content $yourContent ) {
 766                 return false;
 767         }
 768
 769         /**
 770          * Return an applicable auto-summary if one exists for the given edit.
 771          *
 772          * @since 1.21
 773          *
 774          * @param Content $oldContent The previous text of the page.
 775          * @param Content $newContent The submitted text of the page.
 776          * @param int $flags Bit mask: a bit mask of flags submitted for the edit.
 777          *
 778          * @return string An appropriate auto-summary, or an empty string.
 779          */
 780         public function getAutosummary( Content $oldContent = null, Content $newContent = null,
 781                 $flags ) {
 782                 // Decide what kind of auto-summary is needed.
 783
 784                 // Redirect auto-summaries
 785
 786                 /**
 787                  * @var $ot Title
 788                  * @var $rt Title
 789                  */
 790
 791                 $ot = !is_null( $oldContent ) ? $oldContent->getRedirectTarget() : null;
 792                 $rt = !is_null( $newContent ) ? $newContent->getRedirectTarget() : null;
 793
 794                 if ( is_object( $rt ) ) {
 795                         if ( !is_object( $ot )
 796                                 || !$rt->equals( $ot )
 797                                 || $ot->getFragment() != $rt->getFragment()
 798                         ) {
 799                                 $truncatedtext = $newContent->getTextForSummary(
 800                                         250
 801                                         - strlen( wfMessage( 'autoredircomment' )->inContentLanguage()->text() )
 802                                         - strlen( $rt->getFullText() ) );
 803
 804                                 return wfMessage( 'autoredircomment', $rt->getFullText() )
 805                                         ->rawParams( $truncatedtext )->inContentLanguage()->text();
 806                         }
 807                 }
 808
 809                 // New page auto-summaries
 810                 if ( $flags & EDIT_NEW && $newContent->getSize() > 0 ) {
 811                         // If they're making a new article, give its text, truncated, in
 812                         // the summary.
 813
 814                         $truncatedtext = $newContent->getTextForSummary(
 815                                 200 - strlen( wfMessage( 'autosumm-new' )->inContentLanguage()->text() ) );
 816
 817                         return wfMessage( 'autosumm-new' )->rawParams( $truncatedtext )
 818                                 ->inContentLanguage()->text();
 819                 }
 820
 821                 // Blanking auto-summaries
 822                 if ( !empty( $oldContent ) && $oldContent->getSize() > 0 && $newContent->getSize() == 0 ) {
 823                         return wfMessage( 'autosumm-blank' )->inContentLanguage()->text();
 824                 } elseif ( !empty( $oldContent )
 825                         && $oldContent->getSize() > 10 * $newContent->getSize()
 826                         && $newContent->getSize() < 500
 827                 ) {
 828                         // Removing more than 90% of the article
 829
 830                         $truncatedtext = $newContent->getTextForSummary(
 831                                 200 - strlen( wfMessage( 'autosumm-replace' )->inContentLanguage()->text() ) );
 832
 833                         return wfMessage( 'autosumm-replace' )->rawParams( $truncatedtext )
 834                                 ->inContentLanguage()->text();
 835                 }
 836
 837                 // New blank article auto-summary
 838                 if ( $flags & EDIT_NEW && $newContent->isEmpty() ) {
 839                         return wfMessage( 'autosumm-newblank' )->inContentLanguage()->text();
 840                 }
 841
 842                 // If we reach this point, there's no applicable auto-summary for our
 843                 // case, so our auto-summary is empty.
 844                 return '';
 845         }
 846
 847         /**
 848          * Auto-generates a deletion reason
 849          *
 850          * @since 1.21
 851          *
 852          * @param Title $title The page's title
 853          * @param bool &$hasHistory Whether the page has a history
 854          *
 855          * @return mixed String containing deletion reason or empty string, or
 856          *    boolean false if no revision occurred
 857          *
 858          * @todo &$hasHistory is extremely ugly, it's here because
 859          * WikiPage::getAutoDeleteReason() and Article::generateReason()
 860          * have it / want it.
 861          */
 862         public function getAutoDeleteReason( Title $title, &$hasHistory ) {
 863                 $dbw = wfGetDB( DB_MASTER );
 864
 865                 // Get the last revision
 866                 $rev = Revision::newFromTitle( $title );
 867
 868                 if ( is_null( $rev ) ) {
 869                         return false;
 870                 }
 871
 872                 // Get the article's contents
 873                 $content = $rev->getContent();
 874                 $blank = false;
 875
 876                 // If the page is blank, use the text from the previous revision,
 877                 // which can only be blank if there's a move/import/protect dummy
 878                 // revision involved
 879                 if ( !$content || $content->isEmpty() ) {
 880                         $prev = $rev->getPrevious();
 881
 882                         if ( $prev ) {
 883                                 $rev = $prev;
 884                                 $content = $rev->getContent();
 885                                 $blank = true;
 886                         }
 887                 }
 888
 889                 $this->checkModelID( $rev->getContentModel() );
 890
 891                 // Find out if there was only one contributor
 892                 // Only scan the last 20 revisions
 893                 $res = $dbw->select( 'revision', 'rev_user_text',
 894                         array(
 895                                 'rev_page' => $title->getArticleID(),
 896                                 $dbw->bitAnd( 'rev_deleted', Revision::DELETED_USER ) . ' = 0'
 897                         ),
 898                         __METHOD__,
 899                         array( 'LIMIT' => 20 )
 900                 );
 901
 902                 if ( $res === false ) {
 903                         // This page has no revisions, which is very weird
 904                         return false;
 905                 }
 906
 907                 $hasHistory = ( $res->numRows() > 1 );
 908                 $row = $dbw->fetchObject( $res );
 909
 910                 if ( $row ) { // $row is false if the only contributor is hidden
 911                         $onlyAuthor = $row->rev_user_text;
 912                         // Try to find a second contributor
 913                         foreach ( $res as $row ) {
 914                                 if ( $row->rev_user_text != $onlyAuthor ) { // Bug 22999
 915                                         $onlyAuthor = false;
 916                                         break;
 917                                 }
 918                         }
 919                 } else {
 920                         $onlyAuthor = false;
 921                 }
 922
 923                 // Generate the summary with a '$1' placeholder
 924                 if ( $blank ) {
 925                         // The current revision is blank and the one before is also
 926                         // blank. It's just not our lucky day
 927                         $reason = wfMessage( 'exbeforeblank', '$1' )->inContentLanguage()->text();
 928                 } else {
 929                         if ( $onlyAuthor ) {
 930                                 $reason = wfMessage(
 931                                         'excontentauthor',
 932                                         '$1',
 933                                         $onlyAuthor
 934                                 )->inContentLanguage()->text();
 935                         } else {
 936                                 $reason = wfMessage( 'excontent', '$1' )->inContentLanguage()->text();
 937                         }
 938                 }
 939
 940                 if ( $reason == '-' ) {
 941                         // Allow these UI messages to be blanked out cleanly
 942                         return '';
 943                 }
 944
 945                 // Max content length = max comment length - length of the comment (excl. $1)
 946                 $text = $content ? $content->getTextForSummary( 255 - ( strlen( $reason ) - 2 ) ) : '';
 947
 948                 // Now replace the '$1' placeholder
 949                 $reason = str_replace( '$1', $text, $reason );
 950
 951                 return $reason;
 952         }
 953
 954         /**
 955          * Get the Content object that needs to be saved in order to undo all revisions
 956          * between $undo and $undoafter. Revisions must belong to the same page,
 957          * must exist and must not be deleted.
 958          *
 959          * @since 1.21
 960          *
 961          * @param Revision $current The current text
 962          * @param Revision $undo The revision to undo
 963          * @param Revision $undoafter Must be an earlier revision than $undo
 964          *
 965          * @return mixed String on success, false on failure
 966          */
 967         public function getUndoContent( Revision $current, Revision $undo, Revision $undoafter ) {
 968                 $cur_content = $current->getContent();
 969
 970                 if ( empty( $cur_content ) ) {
 971                         return false; // no page
 972                 }
 973
 974                 $undo_content = $undo->getContent();
 975                 $undoafter_content = $undoafter->getContent();
 976
 977                 if ( !$undo_content || !$undoafter_content ) {
 978                         return false; // no content to undo
 979                 }
 980
 981                 $this->checkModelID( $cur_content->getModel() );
 982                 $this->checkModelID( $undo_content->getModel() );
 983                 $this->checkModelID( $undoafter_content->getModel() );
 984
 985                 if ( $cur_content->equals( $undo_content ) ) {
 986                         // No use doing a merge if it's just a straight revert.
 987                         return $undoafter_content;
 988                 }
 989
 990                 $undone_content = $this->merge3( $undo_content, $undoafter_content, $cur_content );
 991
 992                 return $undone_content;
 993         }
 994
 995         /**
 996          * Get parser options suitable for rendering and caching the article
 997          *
 998          * @param IContextSource|User|string $context One of the following:
 999          *        - IContextSource: Use the User and the Language of the provided
1000          *                                            context
1001          *        - User: Use the provided User object and $wgLang for the language,
1002          *                                            so use an IContextSource object if possible.
1003          *        - 'canonical': Canonical options (anonymous user with default
1004          *                                            preferences and content language).
1005          *
1006          * @throws MWException
1007          * @return ParserOptions
1008          */
1009         public function makeParserOptions( $context ) {
1010                 global $wgContLang, $wgEnableParserLimitReporting;
1011
1012                 if ( $context instanceof IContextSource ) {
1013                         $options = ParserOptions::newFromContext( $context );
1014                 } elseif ( $context instanceof User ) { // settings per user (even anons)
1015                         $options = ParserOptions::newFromUser( $context );
1016                 } elseif ( $context === 'canonical' ) { // canonical settings
1017                         $options = ParserOptions::newFromUserAndLang( new User, $wgContLang );
1018                 } else {
1019                         throw new MWException( "Bad context for parser options: $context" );
1020                 }
1021
1022                 $options->enableLimitReport( $wgEnableParserLimitReporting ); // show inclusion/loop reports
1023                 $options->setTidy( true ); // fix bad HTML
1024
1025                 return $options;
1026         }
1027
1028         /**
1029          * Returns true for content models that support caching using the
1030          * ParserCache mechanism. See WikiPage::shouldCheckParserCache().
1031          *
1032          * @since 1.21
1033          *
1034          * @return bool Always false.
1035          */
1036         public function isParserCacheSupported() {
1037                 return false;
1038         }
1039
1040         /**
1041          * Returns true if this content model supports sections.
1042          * This default implementation returns false.
1043          *
1044          * Content models that return true here should also implement
1045          * Content::getSection, Content::replaceSection, etc. to handle sections..
1046          *
1047          * @return bool Always false.
1048          */
1049         public function supportsSections() {
1050                 return false;
1051         }
1052
1053         /**
1054          * Returns true if this content model supports redirects.
1055          * This default implementation returns false.
1056          *
1057          * Content models that return true here should also implement
1058          * ContentHandler::makeRedirectContent to return a Content object.
1059          *
1060          * @return bool Always false.
1061          */
1062         public function supportsRedirects() {
1063                 return false;
1064         }
1065
1066         /**
1067          * Return true if this content model supports direct editing, such as via EditPage.
1068          *
1069          * @return bool Default is false, and true for TextContent and it's derivatives.
1070          */
1071         public function supportsDirectEditing() {
1072                 return false;
1073         }
1074
1075         /**
1076          * Whether or not this content model supports direct editing via ApiEditPage
1077          *
1078          * @return bool Default is false, and true for TextContent and derivatives.
1079          */
1080         public function supportsDirectApiEditing() {
1081                 return $this->supportsDirectEditing();
1082         }
1083
1084         /**
1085          * Logs a deprecation warning, visible if $wgDevelopmentWarnings, but only if
1086          * self::$enableDeprecationWarnings is set to true.
1087          *
1088          * @param string $func The name of the deprecated function
1089          * @param string $version The version since the method is deprecated. Usually 1.21
1090          *   for ContentHandler related stuff.
1091          * @param string|bool $component : Component to which the function belongs.
1092          *   If false, it is assumed the function is in MediaWiki core.
1093          *
1094          * @see ContentHandler::$enableDeprecationWarnings
1095          * @see wfDeprecated
1096          */
1097         public static function deprecated( $func, $version, $component = false ) {
1098                 if ( self::$enableDeprecationWarnings ) {
1099                         wfDeprecated( $func, $version, $component, 3 );
1100                 }
1101         }
1102
1103         /**
1104          * Call a legacy hook that uses text instead of Content objects.
1105          * Will log a warning when a matching hook function is registered.
1106          * If the textual representation of the content is changed by the
1107          * hook function, a new Content object is constructed from the new
1108          * text.
1109          *
1110          * @param string $event Event name
1111          * @param array $args Parameters passed to hook functions
1112          * @param bool $warn Whether to log a warning.
1113          *                    Default to self::$enableDeprecationWarnings.
1114          *                    May be set to false for testing.
1115          *
1116          * @return bool True if no handler aborted the hook
1117          *
1118          * @see ContentHandler::$enableDeprecationWarnings
1119          */
1120         public static function runLegacyHooks( $event, $args = array(),
1121                 $warn = null
1122         ) {
1123
1124                 if ( $warn === null ) {
1125                         $warn = self::$enableDeprecationWarnings;
1126                 }
1127
1128                 if ( !Hooks::isRegistered( $event ) ) {
1129                         return true; // nothing to do here
1130                 }
1131
1132                 if ( $warn ) {
1133                         // Log information about which handlers are registered for the legacy hook,
1134                         // so we can find and fix them.
1135
1136                         $handlers = Hooks::getHandlers( $event );
1137                         $handlerInfo = array();
1138
1139                         MediaWiki\suppressWarnings();
1140
1141                         foreach ( $handlers as $handler ) {
1142                                 if ( is_array( $handler ) ) {
1143                                         if ( is_object( $handler[0] ) ) {
1144                                                 $info = get_class( $handler[0] );
1145                                         } else {
1146                                                 $info = $handler[0];
1147                                         }
1148
1149                                         if ( isset( $handler[1] ) ) {
1150                                                 $info .= '::' . $handler[1];
1151                                         }
1152                                 } elseif ( is_object( $handler ) ) {
1153                                         $info = get_class( $handler[0] );
1154                                         $info .= '::on' . $event;
1155                                 } else {
1156                                         $info = $handler;
1157                                 }
1158
1159                                 $handlerInfo[] = $info;
1160                         }
1161
1162                         MediaWiki\restoreWarnings();
1163
1164                         wfWarn( "Using obsolete hook $event via ContentHandler::runLegacyHooks()! Handlers: " .
1165                                 implode( ', ', $handlerInfo ), 2 );
1166                 }
1167
1168                 // convert Content objects to text
1169                 $contentObjects = array();
1170                 $contentTexts = array();
1171
1172                 foreach ( $args as $k => $v ) {
1173                         if ( $v instanceof Content ) {
1174                                 /* @var Content $v */
1175
1176                                 $contentObjects[$k] = $v;
1177
1178                                 $v = $v->serialize();
1179                                 $contentTexts[$k] = $v;
1180                                 $args[$k] = $v;
1181                         }
1182                 }
1183
1184                 // call the hook functions
1185                 $ok = Hooks::run( $event, $args );
1186
1187                 // see if the hook changed the text
1188                 foreach ( $contentTexts as $k => $orig ) {
1189                         /* @var Content $content */
1190
1191                         $modified = $args[$k];
1192                         $content = $contentObjects[$k];
1193
1194                         if ( $modified !== $orig ) {
1195                                 // text was changed, create updated Content object
1196                                 $content = $content->getContentHandler()->unserializeContent( $modified );
1197                         }
1198
1199                         $args[$k] = $content;
1200                 }
1201
1202                 return $ok;
1203         }
1204 }