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 ( !wfRunHooks( '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                 wfRunHooks( 'TitleIsCssOrJsPage', array( $title, &$isCssOrJsPage ) );
 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                 wfRunHooks( 'TitleIsWikitextPage', array( $title, &$isWikitext ) );
 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                         wfRunHooks( '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          * Unserializes a Content object of the type supported by this ContentHandler.
 435          *
 436          * @since 1.21
 437          *
 438          * @param string $blob Serialized form of the content
 439          * @param string $format The format used for serialization
 440          *
 441          * @return Content The Content object created by deserializing $blob
 442          */
 443         abstract public function unserializeContent( $blob, $format = null );
 444
 445         /**
 446          * Apply import transformation (per default, returns $blob unchanged).
 447          * This gives subclasses an opportunity to transform data blobs on import.
 448          *
 449          * @singe 1.24
 450          *
 451          * @param string $blob
 452          * @param string|null $format
 453          *
 454          * @return string
 455          */
 456         public function importTransform( $blob, $format = null ) {
 457                 return $blob;
 458         }
 459
 460         /**
 461          * Creates an empty Content object of the type supported by this
 462          * ContentHandler.
 463          *
 464          * @since 1.21
 465          *
 466          * @return Content
 467          */
 468         abstract public function makeEmptyContent();
 469
 470         /**
 471          * Creates a new Content object that acts as a redirect to the given page,
 472          * or null if redirects are not supported by this content model.
 473          *
 474          * This default implementation always returns null. Subclasses supporting redirects
 475          * must override this method.
 476          *
 477          * Note that subclasses that override this method to return a Content object
 478          * should also override supportsRedirects() to return true.
 479          *
 480          * @since 1.21
 481          *
 482          * @param Title $destination The page to redirect to.
 483          * @param string $text Text to include in the redirect, if possible.
 484          *
 485          * @return Content Always null.
 486          */
 487         public function makeRedirectContent( Title $destination, $text = '' ) {
 488                 return null;
 489         }
 490
 491         /**
 492          * Returns the model id that identifies the content model this
 493          * ContentHandler can handle. Use with the CONTENT_MODEL_XXX constants.
 494          *
 495          * @since 1.21
 496          *
 497          * @return string The model ID
 498          */
 499         public function getModelID() {
 500                 return $this->mModelID;
 501         }
 502
 503         /**
 504          * @since 1.21
 505          *
 506          * @param string $model_id The model to check
 507          *
 508          * @throws MWException If the model ID is not the ID of the content model supported by this
 509          * ContentHandler.
 510          */
 511         protected function checkModelID( $model_id ) {
 512                 if ( $model_id !== $this->mModelID ) {
 513                         throw new MWException( "Bad content model: " .
 514                                 "expected {$this->mModelID} " .
 515                                 "but got $model_id." );
 516                 }
 517         }
 518
 519         /**
 520          * Returns a list of serialization formats supported by the
 521          * serializeContent() and unserializeContent() methods of this
 522          * ContentHandler.
 523          *
 524          * @since 1.21
 525          *
 526          * @return string[] List of serialization formats as MIME type like strings
 527          */
 528         public function getSupportedFormats() {
 529                 return $this->mSupportedFormats;
 530         }
 531
 532         /**
 533          * The format used for serialization/deserialization by default by this
 534          * ContentHandler.
 535          *
 536          * This default implementation will return the first element of the array
 537          * of formats that was passed to the constructor.
 538          *
 539          * @since 1.21
 540          *
 541          * @return string The name of the default serialization format as a MIME type
 542          */
 543         public function getDefaultFormat() {
 544                 return $this->mSupportedFormats[0];
 545         }
 546
 547         /**
 548          * Returns true if $format is a serialization format supported by this
 549          * ContentHandler, and false otherwise.
 550          *
 551          * Note that if $format is null, this method always returns true, because
 552          * null means "use the default format".
 553          *
 554          * @since 1.21
 555          *
 556          * @param string $format The serialization format to check
 557          *
 558          * @return bool
 559          */
 560         public function isSupportedFormat( $format ) {
 561                 if ( !$format ) {
 562                         return true; // this means "use the default"
 563                 }
 564
 565                 return in_array( $format, $this->mSupportedFormats );
 566         }
 567
 568         /**
 569          * Convenient for checking whether a format provided as a parameter is actually supported.
 570          *
 571          * @param string $format The serialization format to check
 572          *
 573          * @throws MWException If the format is not supported by this content handler.
 574          */
 575         protected function checkFormat( $format ) {
 576                 if ( !$this->isSupportedFormat( $format ) ) {
 577                         throw new MWException(
 578                                 "Format $format is not supported for content model "
 579                                 . $this->getModelID()
 580                         );
 581                 }
 582         }
 583
 584         /**
 585          * Returns overrides for action handlers.
 586          * Classes listed here will be used instead of the default one when
 587          * (and only when) $wgActions[$action] === true. This allows subclasses
 588          * to override the default action handlers.
 589          *
 590          * @since 1.21
 591          *
 592          * @return array Always an empty array.
 593          */
 594         public function getActionOverrides() {
 595                 return array();
 596         }
 597
 598         /**
 599          * Factory for creating an appropriate DifferenceEngine for this content model.
 600          *
 601          * @since 1.21
 602          *
 603          * @param IContextSource $context Context to use, anything else will be ignored.
 604          * @param int $old Revision ID we want to show and diff with.
 605          * @param int|string $new Either a revision ID or one of the strings 'cur', 'prev' or 'next'.
 606          * @param int $rcid FIXME: Deprecated, no longer used. Defaults to 0.
 607          * @param bool $refreshCache If set, refreshes the diff cache. Defaults to false.
 608          * @param bool $unhide If set, allow viewing deleted revs. Defaults to false.
 609          *
 610          * @return DifferenceEngine
 611          */
 612         public function createDifferenceEngine( IContextSource $context, $old = 0, $new = 0,
 613                 $rcid = 0, //FIXME: Deprecated, no longer used
 614                 $refreshCache = false, $unhide = false ) {
 615                 $diffEngineClass = $this->getDiffEngineClass();
 616
 617                 return new $diffEngineClass( $context, $old, $new, $rcid, $refreshCache, $unhide );
 618         }
 619
 620         /**
 621          * Get the language in which the content of the given page is written.
 622          *
 623          * This default implementation just returns $wgContLang (except for pages
 624          * in the MediaWiki namespace)
 625          *
 626          * Note that the pages language is not cacheable, since it may in some
 627          * cases depend on user settings.
 628          *
 629          * Also note that the page language may or may not depend on the actual content of the page,
 630          * that is, this method may load the content in order to determine the language.
 631          *
 632          * @since 1.21
 633          *
 634          * @param Title $title The page to determine the language for.
 635          * @param Content $content The page's content, if you have it handy, to avoid reloading it.
 636          *
 637          * @return Language The page's language
 638          */
 639         public function getPageLanguage( Title $title, Content $content = null ) {
 640                 global $wgContLang, $wgLang;
 641                 $pageLang = $wgContLang;
 642
 643                 if ( $title->getNamespace() == NS_MEDIAWIKI ) {
 644                         // Parse mediawiki messages with correct target language
 645                         list( /* $unused */, $lang ) = MessageCache::singleton()->figureMessage( $title->getText() );
 646                         $pageLang = wfGetLangObj( $lang );
 647                 }
 648
 649                 wfRunHooks( 'PageContentLanguage', array( $title, &$pageLang, $wgLang ) );
 650
 651                 return wfGetLangObj( $pageLang );
 652         }
 653
 654         /**
 655          * Get the language in which the content of this page is written when
 656          * viewed by user. Defaults to $this->getPageLanguage(), but if the user
 657          * specified a preferred variant, the variant will be used.
 658          *
 659          * This default implementation just returns $this->getPageLanguage( $title, $content ) unless
 660          * the user specified a preferred variant.
 661          *
 662          * Note that the pages view language is not cacheable, since it depends on user settings.
 663          *
 664          * Also note that the page language may or may not depend on the actual content of the page,
 665          * that is, this method may load the content in order to determine the language.
 666          *
 667          * @since 1.21
 668          *
 669          * @param Title $title The page to determine the language for.
 670          * @param Content $content The page's content, if you have it handy, to avoid reloading it.
 671          *
 672          * @return Language The page's language for viewing
 673          */
 674         public function getPageViewLanguage( Title $title, Content $content = null ) {
 675                 $pageLang = $this->getPageLanguage( $title, $content );
 676
 677                 if ( $title->getNamespace() !== NS_MEDIAWIKI ) {
 678                         // If the user chooses a variant, the content is actually
 679                         // in a language whose code is the variant code.
 680                         $variant = $pageLang->getPreferredVariant();
 681                         if ( $pageLang->getCode() !== $variant ) {
 682                                 $pageLang = Language::factory( $variant );
 683                         }
 684                 }
 685
 686                 return $pageLang;
 687         }
 688
 689         /**
 690          * Determines whether the content type handled by this ContentHandler
 691          * can be used on the given page.
 692          *
 693          * This default implementation always returns true.
 694          * Subclasses may override this to restrict the use of this content model to specific locations,
 695          * typically based on the namespace or some other aspect of the title, such as a special suffix
 696          * (e.g. ".svg" for SVG content).
 697          *
 698          * @note: this calls the ContentHandlerCanBeUsedOn hook which may be used to override which
 699          * content model can be used where.
 700          *
 701          * @param Title $title The page's title.
 702          *
 703          * @return bool True if content of this kind can be used on the given page, false otherwise.
 704          */
 705         public function canBeUsedOn( Title $title ) {
 706                 $ok = true;
 707
 708                 wfRunHooks( 'ContentModelCanBeUsedOn', array( $this->getModelID(), $title, &$ok ) );
 709
 710                 return $ok;
 711         }
 712
 713         /**
 714          * Returns the name of the diff engine to use.
 715          *
 716          * @since 1.21
 717          *
 718          * @return string
 719          */
 720         protected function getDiffEngineClass() {
 721                 return 'DifferenceEngine';
 722         }
 723
 724         /**
 725          * Attempts to merge differences between three versions. Returns a new
 726          * Content object for a clean merge and false for failure or a conflict.
 727          *
 728          * This default implementation always returns false.
 729          *
 730          * @since 1.21
 731          *
 732          * @param Content|string $oldContent The page's previous content.
 733          * @param Content|string $myContent One of the page's conflicting contents.
 734          * @param Content|string $yourContent One of the page's conflicting contents.
 735          *
 736          * @return Content|bool Always false.
 737          */
 738         public function merge3( Content $oldContent, Content $myContent, Content $yourContent ) {
 739                 return false;
 740         }
 741
 742         /**
 743          * Return an applicable auto-summary if one exists for the given edit.
 744          *
 745          * @since 1.21
 746          *
 747          * @param Content $oldContent The previous text of the page.
 748          * @param Content $newContent The submitted text of the page.
 749          * @param int $flags Bit mask: a bit mask of flags submitted for the edit.
 750          *
 751          * @return string An appropriate auto-summary, or an empty string.
 752          */
 753         public function getAutosummary( Content $oldContent = null, Content $newContent = null,
 754                 $flags ) {
 755                 // Decide what kind of auto-summary is needed.
 756
 757                 // Redirect auto-summaries
 758
 759                 /**
 760                  * @var $ot Title
 761                  * @var $rt Title
 762                  */
 763
 764                 $ot = !is_null( $oldContent ) ? $oldContent->getRedirectTarget() : null;
 765                 $rt = !is_null( $newContent ) ? $newContent->getRedirectTarget() : null;
 766
 767                 if ( is_object( $rt ) ) {
 768                         if ( !is_object( $ot )
 769                                 || !$rt->equals( $ot )
 770                                 || $ot->getFragment() != $rt->getFragment()
 771                         ) {
 772                                 $truncatedtext = $newContent->getTextForSummary(
 773                                         250
 774                                         - strlen( wfMessage( 'autoredircomment' )->inContentLanguage()->text() )
 775                                         - strlen( $rt->getFullText() ) );
 776
 777                                 return wfMessage( 'autoredircomment', $rt->getFullText() )
 778                                         ->rawParams( $truncatedtext )->inContentLanguage()->text();
 779                         }
 780                 }
 781
 782                 // New page auto-summaries
 783                 if ( $flags & EDIT_NEW && $newContent->getSize() > 0 ) {
 784                         // If they're making a new article, give its text, truncated, in
 785                         // the summary.
 786
 787                         $truncatedtext = $newContent->getTextForSummary(
 788                                 200 - strlen( wfMessage( 'autosumm-new' )->inContentLanguage()->text() ) );
 789
 790                         return wfMessage( 'autosumm-new' )->rawParams( $truncatedtext )
 791                                 ->inContentLanguage()->text();
 792                 }
 793
 794                 // Blanking auto-summaries
 795                 if ( !empty( $oldContent ) && $oldContent->getSize() > 0 && $newContent->getSize() == 0 ) {
 796                         return wfMessage( 'autosumm-blank' )->inContentLanguage()->text();
 797                 } elseif ( !empty( $oldContent )
 798                         && $oldContent->getSize() > 10 * $newContent->getSize()
 799                         && $newContent->getSize() < 500
 800                 ) {
 801                         // Removing more than 90% of the article
 802
 803                         $truncatedtext = $newContent->getTextForSummary(
 804                                 200 - strlen( wfMessage( 'autosumm-replace' )->inContentLanguage()->text() ) );
 805
 806                         return wfMessage( 'autosumm-replace' )->rawParams( $truncatedtext )
 807                                 ->inContentLanguage()->text();
 808                 }
 809
 810                 // If we reach this point, there's no applicable auto-summary for our
 811                 // case, so our auto-summary is empty.
 812                 return '';
 813         }
 814
 815         /**
 816          * Auto-generates a deletion reason
 817          *
 818          * @since 1.21
 819          *
 820          * @param Title $title The page's title
 821          * @param bool &$hasHistory Whether the page has a history
 822          *
 823          * @return mixed String containing deletion reason or empty string, or
 824          *    boolean false if no revision occurred
 825          *
 826          * @XXX &$hasHistory is extremely ugly, it's here because
 827          * WikiPage::getAutoDeleteReason() and Article::generateReason()
 828          * have it / want it.
 829          */
 830         public function getAutoDeleteReason( Title $title, &$hasHistory ) {
 831                 $dbw = wfGetDB( DB_MASTER );
 832
 833                 // Get the last revision
 834                 $rev = Revision::newFromTitle( $title );
 835
 836                 if ( is_null( $rev ) ) {
 837                         return false;
 838                 }
 839
 840                 // Get the article's contents
 841                 $content = $rev->getContent();
 842                 $blank = false;
 843
 844                 // If the page is blank, use the text from the previous revision,
 845                 // which can only be blank if there's a move/import/protect dummy
 846                 // revision involved
 847                 if ( !$content || $content->isEmpty() ) {
 848                         $prev = $rev->getPrevious();
 849
 850                         if ( $prev ) {
 851                                 $rev = $prev;
 852                                 $content = $rev->getContent();
 853                                 $blank = true;
 854                         }
 855                 }
 856
 857                 $this->checkModelID( $rev->getContentModel() );
 858
 859                 // Find out if there was only one contributor
 860                 // Only scan the last 20 revisions
 861                 $res = $dbw->select( 'revision', 'rev_user_text',
 862                         array(
 863                                 'rev_page' => $title->getArticleID(),
 864                                 $dbw->bitAnd( 'rev_deleted', Revision::DELETED_USER ) . ' = 0'
 865                         ),
 866                         __METHOD__,
 867                         array( 'LIMIT' => 20 )
 868                 );
 869
 870                 if ( $res === false ) {
 871                         // This page has no revisions, which is very weird
 872                         return false;
 873                 }
 874
 875                 $hasHistory = ( $res->numRows() > 1 );
 876                 $row = $dbw->fetchObject( $res );
 877
 878                 if ( $row ) { // $row is false if the only contributor is hidden
 879                         $onlyAuthor = $row->rev_user_text;
 880                         // Try to find a second contributor
 881                         foreach ( $res as $row ) {
 882                                 if ( $row->rev_user_text != $onlyAuthor ) { // Bug 22999
 883                                         $onlyAuthor = false;
 884                                         break;
 885                                 }
 886                         }
 887                 } else {
 888                         $onlyAuthor = false;
 889                 }
 890
 891                 // Generate the summary with a '$1' placeholder
 892                 if ( $blank ) {
 893                         // The current revision is blank and the one before is also
 894                         // blank. It's just not our lucky day
 895                         $reason = wfMessage( 'exbeforeblank', '$1' )->inContentLanguage()->text();
 896                 } else {
 897                         if ( $onlyAuthor ) {
 898                                 $reason = wfMessage(
 899                                         'excontentauthor',
 900                                         '$1',
 901                                         $onlyAuthor
 902                                 )->inContentLanguage()->text();
 903                         } else {
 904                                 $reason = wfMessage( 'excontent', '$1' )->inContentLanguage()->text();
 905                         }
 906                 }
 907
 908                 if ( $reason == '-' ) {
 909                         // Allow these UI messages to be blanked out cleanly
 910                         return '';
 911                 }
 912
 913                 // Max content length = max comment length - length of the comment (excl. $1)
 914                 $text = $content ? $content->getTextForSummary( 255 - ( strlen( $reason ) - 2 ) ) : '';
 915
 916                 // Now replace the '$1' placeholder
 917                 $reason = str_replace( '$1', $text, $reason );
 918
 919                 return $reason;
 920         }
 921
 922         /**
 923          * Get the Content object that needs to be saved in order to undo all revisions
 924          * between $undo and $undoafter. Revisions must belong to the same page,
 925          * must exist and must not be deleted.
 926          *
 927          * @since 1.21
 928          *
 929          * @param Revision $current The current text
 930          * @param Revision $undo The revision to undo
 931          * @param Revision $undoafter Must be an earlier revision than $undo
 932          *
 933          * @return mixed String on success, false on failure
 934          */
 935         public function getUndoContent( Revision $current, Revision $undo, Revision $undoafter ) {
 936                 $cur_content = $current->getContent();
 937
 938                 if ( empty( $cur_content ) ) {
 939                         return false; // no page
 940                 }
 941
 942                 $undo_content = $undo->getContent();
 943                 $undoafter_content = $undoafter->getContent();
 944
 945                 if ( !$undo_content || !$undoafter_content ) {
 946                         return false; // no content to undo
 947                 }
 948
 949                 $this->checkModelID( $cur_content->getModel() );
 950                 $this->checkModelID( $undo_content->getModel() );
 951                 $this->checkModelID( $undoafter_content->getModel() );
 952
 953                 if ( $cur_content->equals( $undo_content ) ) {
 954                         // No use doing a merge if it's just a straight revert.
 955                         return $undoafter_content;
 956                 }
 957
 958                 $undone_content = $this->merge3( $undo_content, $undoafter_content, $cur_content );
 959
 960                 return $undone_content;
 961         }
 962
 963         /**
 964          * Get parser options suitable for rendering and caching the article
 965          *
 966          * @param IContextSource|User|string $context One of the following:
 967          *        - IContextSource: Use the User and the Language of the provided
 968          *                                            context
 969          *        - User: Use the provided User object and $wgLang for the language,
 970          *                                            so use an IContextSource object if possible.
 971          *        - 'canonical': Canonical options (anonymous user with default
 972          *                                            preferences and content language).
 973          *
 974          * @throws MWException
 975          * @return ParserOptions
 976          */
 977         public function makeParserOptions( $context ) {
 978                 global $wgContLang, $wgEnableParserLimitReporting;
 979
 980                 if ( $context instanceof IContextSource ) {
 981                         $options = ParserOptions::newFromContext( $context );
 982                 } elseif ( $context instanceof User ) { // settings per user (even anons)
 983                         $options = ParserOptions::newFromUser( $context );
 984                 } elseif ( $context === 'canonical' ) { // canonical settings
 985                         $options = ParserOptions::newFromUserAndLang( new User, $wgContLang );
 986                 } else {
 987                         throw new MWException( "Bad context for parser options: $context" );
 988                 }
 989
 990                 $options->enableLimitReport( $wgEnableParserLimitReporting ); // show inclusion/loop reports
 991                 $options->setTidy( true ); // fix bad HTML
 992
 993                 return $options;
 994         }
 995
 996         /**
 997          * Returns true for content models that support caching using the
 998          * ParserCache mechanism. See WikiPage::isParserCacheUsed().
 999          *
1000          * @since 1.21
1001          *
1002          * @return bool Always false.
1003          */
1004         public function isParserCacheSupported() {
1005                 return false;
1006         }
1007
1008         /**
1009          * Returns true if this content model supports sections.
1010          * This default implementation returns false.
1011          *
1012          * Content models that return true here should also implement
1013          * Content::getSection, Content::replaceSection, etc. to handle sections..
1014          *
1015          * @return bool Always false.
1016          */
1017         public function supportsSections() {
1018                 return false;
1019         }
1020
1021         /**
1022          * Returns true if this content model supports redirects.
1023          * This default implementation returns false.
1024          *
1025          * Content models that return true here should also implement
1026          * ContentHandler::makeRedirectContent to return a Content object.
1027          *
1028          * @return bool Always false.
1029          */
1030         public function supportsRedirects() {
1031                 return false;
1032         }
1033
1034         /**
1035          * Logs a deprecation warning, visible if $wgDevelopmentWarnings, but only if
1036          * self::$enableDeprecationWarnings is set to true.
1037          *
1038          * @param string $func The name of the deprecated function
1039          * @param string $version The version since the method is deprecated. Usually 1.21
1040          *   for ContentHandler related stuff.
1041          * @param string|bool $component : Component to which the function belongs.
1042          *   If false, it is assumed the function is in MediaWiki core.
1043          *
1044          * @see ContentHandler::$enableDeprecationWarnings
1045          * @see wfDeprecated
1046          */
1047         public static function deprecated( $func, $version, $component = false ) {
1048                 if ( self::$enableDeprecationWarnings ) {
1049                         wfDeprecated( $func, $version, $component, 3 );
1050                 }
1051         }
1052
1053         /**
1054          * Call a legacy hook that uses text instead of Content objects.
1055          * Will log a warning when a matching hook function is registered.
1056          * If the textual representation of the content is changed by the
1057          * hook function, a new Content object is constructed from the new
1058          * text.
1059          *
1060          * @param string $event Event name
1061          * @param array $args Parameters passed to hook functions
1062          * @param bool $warn Whether to log a warning.
1063          *                    Default to self::$enableDeprecationWarnings.
1064          *                    May be set to false for testing.
1065          *
1066          * @return bool True if no handler aborted the hook
1067          *
1068          * @see ContentHandler::$enableDeprecationWarnings
1069          */
1070         public static function runLegacyHooks( $event, $args = array(),
1071                 $warn = null
1072         ) {
1073
1074                 if ( $warn === null ) {
1075                         $warn = self::$enableDeprecationWarnings;
1076                 }
1077
1078                 if ( !Hooks::isRegistered( $event ) ) {
1079                         return true; // nothing to do here
1080                 }
1081
1082                 if ( $warn ) {
1083                         // Log information about which handlers are registered for the legacy hook,
1084                         // so we can find and fix them.
1085
1086                         $handlers = Hooks::getHandlers( $event );
1087                         $handlerInfo = array();
1088
1089                         wfSuppressWarnings();
1090
1091                         foreach ( $handlers as $handler ) {
1092                                 if ( is_array( $handler ) ) {
1093                                         if ( is_object( $handler[0] ) ) {
1094                                                 $info = get_class( $handler[0] );
1095                                         } else {
1096                                                 $info = $handler[0];
1097                                         }
1098
1099                                         if ( isset( $handler[1] ) ) {
1100                                                 $info .= '::' . $handler[1];
1101                                         }
1102                                 } elseif ( is_object( $handler ) ) {
1103                                         $info = get_class( $handler[0] );
1104                                         $info .= '::on' . $event;
1105                                 } else {
1106                                         $info = $handler;
1107                                 }
1108
1109                                 $handlerInfo[] = $info;
1110                         }
1111
1112                         wfRestoreWarnings();
1113
1114                         wfWarn( "Using obsolete hook $event via ContentHandler::runLegacyHooks()! Handlers: " .
1115                                 implode( ', ', $handlerInfo ), 2 );
1116                 }
1117
1118                 // convert Content objects to text
1119                 $contentObjects = array();
1120                 $contentTexts = array();
1121
1122                 foreach ( $args as $k => $v ) {
1123                         if ( $v instanceof Content ) {
1124                                 /* @var Content $v */
1125
1126                                 $contentObjects[$k] = $v;
1127
1128                                 $v = $v->serialize();
1129                                 $contentTexts[$k] = $v;
1130                                 $args[$k] = $v;
1131                         }
1132                 }
1133
1134                 // call the hook functions
1135                 $ok = wfRunHooks( $event, $args );
1136
1137                 // see if the hook changed the text
1138                 foreach ( $contentTexts as $k => $orig ) {
1139                         /* @var Content $content */
1140
1141                         $modified = $args[$k];
1142                         $content = $contentObjects[$k];
1143
1144                         if ( $modified !== $orig ) {
1145                                 // text was changed, create updated Content object
1146                                 $content = $content->getContentHandler()->unserializeContent( $modified );
1147                         }
1148
1149                         $args[$k] = $content;
1150                 }
1151
1152                 return $ok;
1153         }
1154 }