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|null
  89          * @return null|string the textual form of $content, if available
  90          * @throws MWException if $content is not an instance of TextContent and
  91          *   $wgContentHandlerTextFallback was set to 'fail'.
  92          */
  93         public static function getContentText( Content $content = null ) {
  94                 global $wgContentHandlerTextFallback;
  95
  96                 if ( is_null( $content ) ) {
  97                         return '';
  98                 }
  99
 100                 if ( $content instanceof TextContent ) {
 101                         return $content->getNativeData();
 102                 }
 103
 104                 wfDebugLog( 'ContentHandler', 'Accessing ' . $content->getModel() . ' content as text!' );
 105
 106                 if ( $wgContentHandlerTextFallback == 'fail' ) {
 107                         throw new MWException(
 108                                 "Attempt to get text from Content with model " .
 109                                 $content->getModel()
 110                         );
 111                 }
 112
 113                 if ( $wgContentHandlerTextFallback == 'serialize' ) {
 114                         return $content->serialize();
 115                 }
 116
 117                 return null;
 118         }
 119
 120         /**
 121          * Convenience function for creating a Content object from a given textual
 122          * representation.
 123          *
 124          * $text will be deserialized into a Content object of the model specified
 125          * by $modelId (or, if that is not given, $title->getContentModel()) using
 126          * the given format.
 127          *
 128          * @since 1.21
 129          *
 130          * @param string $text the textual representation, will be
 131          *    unserialized to create the Content object
 132          * @param $title null|Title the title of the page this text belongs to.
 133          *    Required if $modelId is not provided.
 134          * @param $modelId null|string the model to deserialize to. If not provided,
 135          *    $title->getContentModel() is used.
 136          * @param $format null|string the format to use for deserialization. If not
 137          *    given, the model's default format is used.
 138          *
 139          * @throws MWException
 140          * @return Content a Content object representing $text
 141          *
 142          * @throws MWException if $model or $format is not supported or if $text can
 143          *    not be unserialized using $format.
 144          */
 145         public static function makeContent( $text, Title $title = null,
 146                 $modelId = null, $format = null
 147         ) {
 148                 if ( is_null( $modelId ) ) {
 149                         if ( is_null( $title ) ) {
 150                                 throw new MWException( "Must provide a Title object or a content model ID." );
 151                         }
 152
 153                         $modelId = $title->getContentModel();
 154                 }
 155
 156                 $handler = ContentHandler::getForModelID( $modelId );
 157
 158                 return $handler->unserializeContent( $text, $format );
 159         }
 160
 161         /**
 162          * Returns the name of the default content model to be used for the page
 163          * with the given title.
 164          *
 165          * Note: There should rarely be need to call this method directly.
 166          * To determine the actual content model for a given page, use
 167          * Title::getContentModel().
 168          *
 169          * Which model is to be used by default for the page is determined based
 170          * on several factors:
 171          * - The global setting $wgNamespaceContentModels specifies a content model
 172          *   per namespace.
 173          * - The hook ContentHandlerDefaultModelFor may be used to override the page's default
 174          *   model.
 175          * - Pages in NS_MEDIAWIKI and NS_USER default to the CSS or JavaScript
 176          *   model if they end in .js or .css, respectively.
 177          * - Pages in NS_MEDIAWIKI default to the wikitext model otherwise.
 178          * - The hook TitleIsCssOrJsPage may be used to force a page to use the CSS
 179          *   or JavaScript model. This is a compatibility feature. The ContentHandlerDefaultModelFor
 180          *   hook should be used instead if possible.
 181          * - The hook TitleIsWikitextPage may be used to force a page to use the
 182          *   wikitext model. This is a compatibility feature. The ContentHandlerDefaultModelFor
 183          *   hook should be used instead if possible.
 184          *
 185          * If none of the above applies, the wikitext model is used.
 186          *
 187          * Note: this is used by, and may thus not use, Title::getContentModel()
 188          *
 189          * @since 1.21
 190          *
 191          * @param $title Title
 192          * @return null|string default model name for the page given by $title
 193          */
 194         public static function getDefaultModelFor( Title $title ) {
 195                 // NOTE: this method must not rely on $title->getContentModel() directly or indirectly,
 196                 //       because it is used to initialize the mContentModel member.
 197
 198                 $ns = $title->getNamespace();
 199
 200                 $ext = false;
 201                 $m = null;
 202                 $model = MWNamespace::getNamespaceContentModel( $ns );
 203
 204                 // Hook can determine default model
 205                 if ( !wfRunHooks( 'ContentHandlerDefaultModelFor', array( $title, &$model ) ) ) {
 206                         if ( !is_null( $model ) ) {
 207                                 return $model;
 208                         }
 209                 }
 210
 211                 // Could this page contain custom CSS or JavaScript, based on the title?
 212                 $isCssOrJsPage = NS_MEDIAWIKI == $ns && preg_match( '!\.(css|js)$!u', $title->getText(), $m );
 213                 if ( $isCssOrJsPage ) {
 214                         $ext = $m[1];
 215                 }
 216
 217                 // Hook can force JS/CSS
 218                 wfRunHooks( 'TitleIsCssOrJsPage', array( $title, &$isCssOrJsPage ) );
 219
 220                 // Is this a .css subpage of a user page?
 221                 $isJsCssSubpage = NS_USER == $ns
 222                         && !$isCssOrJsPage
 223                         && preg_match( "/\\/.*\\.(js|css)$/", $title->getText(), $m );
 224                 if ( $isJsCssSubpage ) {
 225                         $ext = $m[1];
 226                 }
 227
 228                 // Is this wikitext, according to $wgNamespaceContentModels or the DefaultModelFor hook?
 229                 $isWikitext = is_null( $model ) || $model == CONTENT_MODEL_WIKITEXT;
 230                 $isWikitext = $isWikitext && !$isCssOrJsPage && !$isJsCssSubpage;
 231
 232                 // Hook can override $isWikitext
 233                 wfRunHooks( 'TitleIsWikitextPage', array( $title, &$isWikitext ) );
 234
 235                 if ( !$isWikitext ) {
 236                         switch ( $ext ) {
 237                                 case 'js':
 238                                         return CONTENT_MODEL_JAVASCRIPT;
 239                                 case 'css':
 240                                         return CONTENT_MODEL_CSS;
 241                                 default:
 242                                         return is_null( $model ) ? CONTENT_MODEL_TEXT : $model;
 243                         }
 244                 }
 245
 246                 // We established that it must be wikitext
 247
 248                 return CONTENT_MODEL_WIKITEXT;
 249         }
 250
 251         /**
 252          * Returns the appropriate ContentHandler singleton for the given title.
 253          *
 254          * @since 1.21
 255          *
 256          * @param $title Title
 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          * @return ContentHandler
 273          */
 274         public static function getForContent( Content $content ) {
 275                 $modelId = $content->getModel();
 276
 277                 return ContentHandler::getForModelID( $modelId );
 278         }
 279
 280         /**
 281          * @var array A Cache of ContentHandler instances by model id
 282          */
 283         protected static $handlers;
 284
 285         /**
 286          * Returns the ContentHandler singleton for the given model ID. Use the
 287          * CONTENT_MODEL_XXX constants to identify the desired content model.
 288          *
 289          * ContentHandler singletons are taken from the global $wgContentHandlers
 290          * array. Keys in that array are model names, the values are either
 291          * ContentHandler singleton objects, or strings specifying the appropriate
 292          * subclass of ContentHandler.
 293          *
 294          * If a class name is encountered when looking up the singleton for a given
 295          * model name, the class is instantiated and the class name is replaced by
 296          * the resulting singleton in $wgContentHandlers.
 297          *
 298          * If no ContentHandler is defined for the desired $modelId, the
 299          * ContentHandler may be provided by the ContentHandlerForModelID hook.
 300          * If no ContentHandler can be determined, an MWException is raised.
 301          *
 302          * @since 1.21
 303          *
 304          * @param string $modelId The ID of the content model for which to get a
 305          *    handler. Use CONTENT_MODEL_XXX constants.
 306          * @return ContentHandler The ContentHandler singleton for handling the
 307          *    model given by $modelId
 308          * @throws MWException if no handler is known for $modelId.
 309          */
 310         public static function getForModelID( $modelId ) {
 311                 global $wgContentHandlers;
 312
 313                 if ( isset( ContentHandler::$handlers[$modelId] ) ) {
 314                         return ContentHandler::$handlers[$modelId];
 315                 }
 316
 317                 if ( empty( $wgContentHandlers[$modelId] ) ) {
 318                         $handler = null;
 319
 320                         wfRunHooks( 'ContentHandlerForModelID', array( $modelId, &$handler ) );
 321
 322                         if ( $handler === null ) {
 323                                 throw new MWException( "No handler for model '$modelId' registered in \$wgContentHandlers" );
 324                         }
 325
 326                         if ( !( $handler instanceof ContentHandler ) ) {
 327                                 throw new MWException( "ContentHandlerForModelID must supply a ContentHandler instance" );
 328                         }
 329                 } else {
 330                         $class = $wgContentHandlers[$modelId];
 331                         $handler = new $class( $modelId );
 332
 333                         if ( !( $handler instanceof ContentHandler ) ) {
 334                                 throw new MWException( "$class from \$wgContentHandlers is not " .
 335                                         "compatible with ContentHandler" );
 336                         }
 337                 }
 338
 339                 wfDebugLog( 'ContentHandler', 'Created handler for ' . $modelId
 340                         . ': ' . get_class( $handler ) );
 341
 342                 ContentHandler::$handlers[$modelId] = $handler;
 343
 344                 return ContentHandler::$handlers[$modelId];
 345         }
 346
 347         /**
 348          * Returns the localized name for a given content model.
 349          *
 350          * Model names are localized using system messages. Message keys
 351          * have the form content-model-$name, where $name is getContentModelName( $id ).
 352          *
 353          * @param string $name The content model ID, as given by a CONTENT_MODEL_XXX
 354          *    constant or returned by Revision::getContentModel().
 355          *
 356          * @return string The content model's localized name.
 357          * @throws MWException if the model id isn't known.
 358          */
 359         public static function getLocalizedName( $name ) {
 360                 // Messages: content-model-wikitext, content-model-text,
 361                 // content-model-javascript, content-model-css
 362                 $key = "content-model-$name";
 363
 364                 $msg = wfMessage( $key );
 365
 366                 return $msg->exists() ? $msg->plain() : $name;
 367         }
 368
 369         public static function getContentModels() {
 370                 global $wgContentHandlers;
 371
 372                 return array_keys( $wgContentHandlers );
 373         }
 374
 375         public static function getAllContentFormats() {
 376                 global $wgContentHandlers;
 377
 378                 $formats = array();
 379
 380                 foreach ( $wgContentHandlers as $model => $class ) {
 381                         $handler = ContentHandler::getForModelID( $model );
 382                         $formats = array_merge( $formats, $handler->getSupportedFormats() );
 383                 }
 384
 385                 $formats = array_unique( $formats );
 386
 387                 return $formats;
 388         }
 389
 390         // ------------------------------------------------------------------------
 391
 392         protected $mModelID;
 393         protected $mSupportedFormats;
 394
 395         /**
 396          * Constructor, initializing the ContentHandler instance with its model ID
 397          * and a list of supported formats. Values for the parameters are typically
 398          * provided as literals by subclass's constructors.
 399          *
 400          * @param string $modelId (use CONTENT_MODEL_XXX constants).
 401          * @param array $formats List for supported serialization formats
 402          *    (typically as MIME types)
 403          */
 404         public function __construct( $modelId, $formats ) {
 405                 $this->mModelID = $modelId;
 406                 $this->mSupportedFormats = $formats;
 407
 408                 $this->mModelName = preg_replace( '/(Content)?Handler$/', '', get_class( $this ) );
 409                 $this->mModelName = preg_replace( '/[_\\\\]/', '', $this->mModelName );
 410                 $this->mModelName = strtolower( $this->mModelName );
 411         }
 412
 413         /**
 414          * Serializes a Content object of the type supported by this ContentHandler.
 415          *
 416          * @since 1.21
 417          *
 418          * @param $content Content The Content object to serialize
 419          * @param $format null|String The desired serialization format
 420          * @return string Serialized form of the content
 421          */
 422         abstract public function serializeContent( Content $content, $format = null );
 423
 424         /**
 425          * Unserializes a Content object of the type supported by this ContentHandler.
 426          *
 427          * @since 1.21
 428          *
 429          * @param string $blob serialized form of the content
 430          * @param $format null|String the format used for serialization
 431          * @return Content the Content object created by deserializing $blob
 432          */
 433         abstract public function unserializeContent( $blob, $format = null );
 434
 435         /**
 436          * Creates an empty Content object of the type supported by this
 437          * ContentHandler.
 438          *
 439          * @since 1.21
 440          *
 441          * @return Content
 442          */
 443         abstract public function makeEmptyContent();
 444
 445         /**
 446          * Creates a new Content object that acts as a redirect to the given page,
 447          * or null of redirects are not supported by this content model.
 448          *
 449          * This default implementation always returns null. Subclasses supporting redirects
 450          * must override this method.
 451          *
 452          * Note that subclasses that override this method to return a Content object
 453          * should also override supportsRedirects() to return true.
 454          *
 455          * @since 1.21
 456          *
 457          * @param Title $destination the page to redirect to.
 458          * @param string $text text to include in the redirect, if possible.
 459          *
 460          * @return Content
 461          */
 462         public function makeRedirectContent( Title $destination, $text = '' ) {
 463                 return null;
 464         }
 465
 466         /**
 467          * Returns the model id that identifies the content model this
 468          * ContentHandler can handle. Use with the CONTENT_MODEL_XXX constants.
 469          *
 470          * @since 1.21
 471          *
 472          * @return String The model ID
 473          */
 474         public function getModelID() {
 475                 return $this->mModelID;
 476         }
 477
 478         /**
 479          * Throws an MWException if $model_id is not the ID of the content model
 480          * supported by this ContentHandler.
 481          *
 482          * @since 1.21
 483          *
 484          * @param string $model_id The model to check
 485          *
 486          * @throws MWException
 487          */
 488         protected function checkModelID( $model_id ) {
 489                 if ( $model_id !== $this->mModelID ) {
 490                         throw new MWException( "Bad content model: " .
 491                                 "expected {$this->mModelID} " .
 492                                 "but got $model_id." );
 493                 }
 494         }
 495
 496         /**
 497          * Returns a list of serialization formats supported by the
 498          * serializeContent() and unserializeContent() methods of this
 499          * ContentHandler.
 500          *
 501          * @since 1.21
 502          *
 503          * @return array of serialization formats as MIME type like strings
 504          */
 505         public function getSupportedFormats() {
 506                 return $this->mSupportedFormats;
 507         }
 508
 509         /**
 510          * The format used for serialization/deserialization by default by this
 511          * ContentHandler.
 512          *
 513          * This default implementation will return the first element of the array
 514          * of formats that was passed to the constructor.
 515          *
 516          * @since 1.21
 517          *
 518          * @return string the name of the default serialization format as a MIME type
 519          */
 520         public function getDefaultFormat() {
 521                 return $this->mSupportedFormats[0];
 522         }
 523
 524         /**
 525          * Returns true if $format is a serialization format supported by this
 526          * ContentHandler, and false otherwise.
 527          *
 528          * Note that if $format is null, this method always returns true, because
 529          * null means "use the default format".
 530          *
 531          * @since 1.21
 532          *
 533          * @param string $format the serialization format to check
 534          * @return bool
 535          */
 536         public function isSupportedFormat( $format ) {
 537
 538                 if ( !$format ) {
 539                         return true; // this means "use the default"
 540                 }
 541
 542                 return in_array( $format, $this->mSupportedFormats );
 543         }
 544
 545         /**
 546          * Throws an MWException if isSupportedFormat( $format ) is not true.
 547          * Convenient for checking whether a format provided as a parameter is
 548          * actually supported.
 549          *
 550          * @param string $format the serialization format to check
 551          *
 552          * @throws MWException
 553          */
 554         protected function checkFormat( $format ) {
 555                 if ( !$this->isSupportedFormat( $format ) ) {
 556                         throw new MWException(
 557                                 "Format $format is not supported for content model "
 558                                 . $this->getModelID()
 559                         );
 560                 }
 561         }
 562
 563         /**
 564          * Returns overrides for action handlers.
 565          * Classes listed here will be used instead of the default one when
 566          * (and only when) $wgActions[$action] === true. This allows subclasses
 567          * to override the default action handlers.
 568          *
 569          * @since 1.21
 570          *
 571          * @return Array
 572          */
 573         public function getActionOverrides() {
 574                 return array();
 575         }
 576
 577         /**
 578          * Factory for creating an appropriate DifferenceEngine for this content model.
 579          *
 580          * @since 1.21
 581          *
 582          * @param $context IContextSource context to use, anything else will be
 583          *    ignored
 584          * @param $old Integer Old ID we want to show and diff with.
 585          * @param int|string $new String either 'prev' or 'next'.
 586          * @param $rcid Integer ??? FIXME (default 0)
 587          * @param $refreshCache boolean If set, refreshes the diff cache
 588          * @param $unhide boolean If set, allow viewing deleted revs
 589          *
 590          * @return DifferenceEngine
 591          */
 592         public function createDifferenceEngine( IContextSource $context,
 593                 $old = 0, $new = 0,
 594                 $rcid = 0, # FIXME: use everywhere!
 595                 $refreshCache = false, $unhide = false
 596         ) {
 597                 $diffEngineClass = $this->getDiffEngineClass();
 598
 599                 return new $diffEngineClass( $context, $old, $new, $rcid, $refreshCache, $unhide );
 600         }
 601
 602         /**
 603          * Get the language in which the content of the given page is written.
 604          *
 605          * This default implementation just returns $wgContLang (except for pages
 606          * in the MediaWiki namespace)
 607          *
 608          * Note that the pages language is not cacheable, since it may in some
 609          * cases depend on user settings.
 610          *
 611          * Also note that the page language may or may not depend on the actual content of the page,
 612          * that is, this method may load the content in order to determine the language.
 613          *
 614          * @since 1.21
 615          *
 616          * @param Title $title the page to determine the language for.
 617          * @param Content|null $content the page's content, if you have it handy, to avoid reloading it.
 618          *
 619          * @return Language the page's language
 620          */
 621         public function getPageLanguage( Title $title, Content $content = null ) {
 622                 global $wgContLang, $wgLang;
 623                 $pageLang = $wgContLang;
 624
 625                 if ( $title->getNamespace() == NS_MEDIAWIKI ) {
 626                         // Parse mediawiki messages with correct target language
 627                         list( /* $unused */, $lang ) = MessageCache::singleton()->figureMessage( $title->getText() );
 628                         $pageLang = wfGetLangObj( $lang );
 629                 }
 630
 631                 wfRunHooks( 'PageContentLanguage', array( $title, &$pageLang, $wgLang ) );
 632
 633                 return wfGetLangObj( $pageLang );
 634         }
 635
 636         /**
 637          * Get the language in which the content of this page is written when
 638          * viewed by user. Defaults to $this->getPageLanguage(), but if the user
 639          * specified a preferred variant, the variant will be used.
 640          *
 641          * This default implementation just returns $this->getPageLanguage( $title, $content ) unless
 642          * the user specified a preferred variant.
 643          *
 644          * Note that the pages view language is not cacheable, since it depends on user settings.
 645          *
 646          * Also note that the page language may or may not depend on the actual content of the page,
 647          * that is, this method may load the content in order to determine the language.
 648          *
 649          * @since 1.21
 650          *
 651          * @param Title $title the page to determine the language for.
 652          * @param Content|null $content the page's content, if you have it handy, to avoid reloading it.
 653          *
 654          * @return Language the page's language for viewing
 655          */
 656         public function getPageViewLanguage( Title $title, Content $content = null ) {
 657                 $pageLang = $this->getPageLanguage( $title, $content );
 658
 659                 if ( $title->getNamespace() !== NS_MEDIAWIKI ) {
 660                         // If the user chooses a variant, the content is actually
 661                         // in a language whose code is the variant code.
 662                         $variant = $pageLang->getPreferredVariant();
 663                         if ( $pageLang->getCode() !== $variant ) {
 664                                 $pageLang = Language::factory( $variant );
 665                         }
 666                 }
 667
 668                 return $pageLang;
 669         }
 670
 671         /**
 672          * Determines whether the content type handled by this ContentHandler
 673          * can be used on the given page.
 674          *
 675          * This default implementation always returns true.
 676          * Subclasses may override this to restrict the use of this content model to specific locations,
 677          * typically based on the namespace or some other aspect of the title, such as a special suffix
 678          * (e.g. ".svg" for SVG content).
 679          *
 680          * @param Title $title the page's title.
 681          *
 682          * @return bool true if content of this kind can be used on the given page, false otherwise.
 683          */
 684         public function canBeUsedOn( Title $title ) {
 685                 return true;
 686         }
 687
 688         /**
 689          * Returns the name of the diff engine to use.
 690          *
 691          * @since 1.21
 692          *
 693          * @return string
 694          */
 695         protected function getDiffEngineClass() {
 696                 return 'DifferenceEngine';
 697         }
 698
 699         /**
 700          * Attempts to merge differences between three versions.
 701          * Returns a new Content object for a clean merge and false for failure or
 702          * a conflict.
 703          *
 704          * This default implementation always returns false.
 705          *
 706          * @since 1.21
 707          *
 708          * @param $oldContent Content|string  String
 709          * @param $myContent Content|string   String
 710          * @param $yourContent Content|string String
 711          *
 712          * @return Content|Bool
 713          */
 714         public function merge3( Content $oldContent, Content $myContent, Content $yourContent ) {
 715                 return false;
 716         }
 717
 718         /**
 719          * Return an applicable auto-summary if one exists for the given edit.
 720          *
 721          * @since 1.21
 722          *
 723          * @param $oldContent Content|null: the previous text of the page.
 724          * @param $newContent Content|null: The submitted text of the page.
 725          * @param int $flags Bit mask: a bit mask of flags submitted for the edit.
 726          *
 727          * @return string An appropriate auto-summary, or an empty string.
 728          */
 729         public function getAutosummary( Content $oldContent = null, Content $newContent = null, $flags ) {
 730                 // Decide what kind of auto-summary is needed.
 731
 732                 // Redirect auto-summaries
 733
 734                 /**
 735                  * @var $ot Title
 736                  * @var $rt Title
 737                  */
 738
 739                 $ot = !is_null( $oldContent ) ? $oldContent->getRedirectTarget() : null;
 740                 $rt = !is_null( $newContent ) ? $newContent->getRedirectTarget() : null;
 741
 742                 if ( is_object( $rt ) ) {
 743                         if ( !is_object( $ot )
 744                                 || !$rt->equals( $ot )
 745                                 || $ot->getFragment() != $rt->getFragment()
 746                         ) {
 747                                 $truncatedtext = $newContent->getTextForSummary(
 748                                         250
 749                                         - strlen( wfMessage( 'autoredircomment' )->inContentLanguage()->text() )
 750                                         - strlen( $rt->getFullText() ) );
 751
 752                                 return wfMessage( 'autoredircomment', $rt->getFullText() )
 753                                         ->rawParams( $truncatedtext )->inContentLanguage()->text();
 754                         }
 755                 }
 756
 757                 // New page auto-summaries
 758                 if ( $flags & EDIT_NEW && $newContent->getSize() > 0 ) {
 759                         // If they're making a new article, give its text, truncated, in
 760                         // the summary.
 761
 762                         $truncatedtext = $newContent->getTextForSummary(
 763                                 200 - strlen( wfMessage( 'autosumm-new' )->inContentLanguage()->text() ) );
 764
 765                         return wfMessage( 'autosumm-new' )->rawParams( $truncatedtext )
 766                                 ->inContentLanguage()->text();
 767                 }
 768
 769                 // Blanking auto-summaries
 770                 if ( !empty( $oldContent ) && $oldContent->getSize() > 0 && $newContent->getSize() == 0 ) {
 771                         return wfMessage( 'autosumm-blank' )->inContentLanguage()->text();
 772                 } elseif ( !empty( $oldContent )
 773                         && $oldContent->getSize() > 10 * $newContent->getSize()
 774                         && $newContent->getSize() < 500
 775                 ) {
 776                         // Removing more than 90% of the article
 777
 778                         $truncatedtext = $newContent->getTextForSummary(
 779                                 200 - strlen( wfMessage( 'autosumm-replace' )->inContentLanguage()->text() ) );
 780
 781                         return wfMessage( 'autosumm-replace' )->rawParams( $truncatedtext )
 782                                 ->inContentLanguage()->text();
 783                 }
 784
 785                 // If we reach this point, there's no applicable auto-summary for our
 786                 // case, so our auto-summary is empty.
 787                 return '';
 788         }
 789
 790         /**
 791          * Auto-generates a deletion reason
 792          *
 793          * @since 1.21
 794          *
 795          * @param $title Title: the page's title
 796          * @param &$hasHistory Boolean: whether the page has a history
 797          * @return mixed String containing deletion reason or empty string, or
 798          *    boolean false if no revision occurred
 799          *
 800          * @XXX &$hasHistory is extremely ugly, it's here because
 801          * WikiPage::getAutoDeleteReason() and Article::generateReason()
 802          * have it / want it.
 803          */
 804         public function getAutoDeleteReason( Title $title, &$hasHistory ) {
 805                 $dbw = wfGetDB( DB_MASTER );
 806
 807                 // Get the last revision
 808                 $rev = Revision::newFromTitle( $title );
 809
 810                 if ( is_null( $rev ) ) {
 811                         return false;
 812                 }
 813
 814                 // Get the article's contents
 815                 $content = $rev->getContent();
 816                 $blank = false;
 817
 818                 // If the page is blank, use the text from the previous revision,
 819                 // which can only be blank if there's a move/import/protect dummy
 820                 // revision involved
 821                 if ( !$content || $content->isEmpty() ) {
 822                         $prev = $rev->getPrevious();
 823
 824                         if ( $prev ) {
 825                                 $rev = $prev;
 826                                 $content = $rev->getContent();
 827                                 $blank = true;
 828                         }
 829                 }
 830
 831                 $this->checkModelID( $rev->getContentModel() );
 832
 833                 // Find out if there was only one contributor
 834                 // Only scan the last 20 revisions
 835                 $res = $dbw->select( 'revision', 'rev_user_text',
 836                         array(
 837                                 'rev_page' => $title->getArticleID(),
 838                                 $dbw->bitAnd( 'rev_deleted', Revision::DELETED_USER ) . ' = 0'
 839                         ),
 840                         __METHOD__,
 841                         array( 'LIMIT' => 20 )
 842                 );
 843
 844                 if ( $res === false ) {
 845                         // This page has no revisions, which is very weird
 846                         return false;
 847                 }
 848
 849                 $hasHistory = ( $res->numRows() > 1 );
 850                 $row = $dbw->fetchObject( $res );
 851
 852                 if ( $row ) { // $row is false if the only contributor is hidden
 853                         $onlyAuthor = $row->rev_user_text;
 854                         // Try to find a second contributor
 855                         foreach ( $res as $row ) {
 856                                 if ( $row->rev_user_text != $onlyAuthor ) { // Bug 22999
 857                                         $onlyAuthor = false;
 858                                         break;
 859                                 }
 860                         }
 861                 } else {
 862                         $onlyAuthor = false;
 863                 }
 864
 865                 // Generate the summary with a '$1' placeholder
 866                 if ( $blank ) {
 867                         // The current revision is blank and the one before is also
 868                         // blank. It's just not our lucky day
 869                         $reason = wfMessage( 'exbeforeblank', '$1' )->inContentLanguage()->text();
 870                 } else {
 871                         if ( $onlyAuthor ) {
 872                                 $reason = wfMessage(
 873                                         'excontentauthor',
 874                                         '$1',
 875                                         $onlyAuthor
 876                                 )->inContentLanguage()->text();
 877                         } else {
 878                                 $reason = wfMessage( 'excontent', '$1' )->inContentLanguage()->text();
 879                         }
 880                 }
 881
 882                 if ( $reason == '-' ) {
 883                         // Allow these UI messages to be blanked out cleanly
 884                         return '';
 885                 }
 886
 887                 // Max content length = max comment length - length of the comment (excl. $1)
 888                 $text = $content ? $content->getTextForSummary( 255 - ( strlen( $reason ) - 2 ) ) : '';
 889
 890                 // Now replace the '$1' placeholder
 891                 $reason = str_replace( '$1', $text, $reason );
 892
 893                 return $reason;
 894         }
 895
 896         /**
 897          * Get the Content object that needs to be saved in order to undo all revisions
 898          * between $undo and $undoafter. Revisions must belong to the same page,
 899          * must exist and must not be deleted.
 900          *
 901          * @since 1.21
 902          *
 903          * @param $current Revision The current text
 904          * @param $undo Revision The revision to undo
 905          * @param $undoafter Revision Must be an earlier revision than $undo
 906          *
 907          * @return mixed String on success, false on failure
 908          */
 909         public function getUndoContent( Revision $current, Revision $undo, Revision $undoafter ) {
 910                 $cur_content = $current->getContent();
 911
 912                 if ( empty( $cur_content ) ) {
 913                         return false; // no page
 914                 }
 915
 916                 $undo_content = $undo->getContent();
 917                 $undoafter_content = $undoafter->getContent();
 918
 919                 if ( !$undo_content || !$undoafter_content ) {
 920                         return false; // no content to undo
 921                 }
 922
 923                 $this->checkModelID( $cur_content->getModel() );
 924                 $this->checkModelID( $undo_content->getModel() );
 925                 $this->checkModelID( $undoafter_content->getModel() );
 926
 927                 if ( $cur_content->equals( $undo_content ) ) {
 928                         // No use doing a merge if it's just a straight revert.
 929                         return $undoafter_content;
 930                 }
 931
 932                 $undone_content = $this->merge3( $undo_content, $undoafter_content, $cur_content );
 933
 934                 return $undone_content;
 935         }
 936
 937         /**
 938          * Get parser options suitable for rendering the primary article wikitext
 939          *
 940          * @param IContextSource|User|string $context One of the following:
 941          *        - IContextSource: Use the User and the Language of the provided
 942          *                                            context
 943          *        - User: Use the provided User object and $wgLang for the language,
 944          *                                            so use an IContextSource object if possible.
 945          *        - 'canonical': Canonical options (anonymous user with default
 946          *                                            preferences and content language).
 947          *
 948          * @param IContextSource|User|string $context
 949          *
 950          * @throws MWException
 951          * @return ParserOptions
 952          */
 953         public function makeParserOptions( $context ) {
 954                 global $wgContLang, $wgEnableParserLimitReporting;
 955
 956                 if ( $context instanceof IContextSource ) {
 957                         $options = ParserOptions::newFromContext( $context );
 958                 } elseif ( $context instanceof User ) { // settings per user (even anons)
 959                         $options = ParserOptions::newFromUser( $context );
 960                 } elseif ( $context === 'canonical' ) { // canonical settings
 961                         $options = ParserOptions::newFromUserAndLang( new User, $wgContLang );
 962                 } else {
 963                         throw new MWException( "Bad context for parser options: $context" );
 964                 }
 965
 966                 $options->enableLimitReport( $wgEnableParserLimitReporting ); // show inclusion/loop reports
 967                 $options->setTidy( true ); // fix bad HTML
 968
 969                 return $options;
 970         }
 971
 972         /**
 973          * Returns true for content models that support caching using the
 974          * ParserCache mechanism. See WikiPage::isParserCacheUsed().
 975          *
 976          * @since 1.21
 977          *
 978          * @return bool
 979          */
 980         public function isParserCacheSupported() {
 981                 return false;
 982         }
 983
 984         /**
 985          * Returns true if this content model supports sections.
 986          * This default implementation returns false.
 987          *
 988          * Content models that return true here should also implement
 989          * Content::getSection, Content::replaceSection, etc. to handle sections..
 990          *
 991          * @return boolean whether sections are supported.
 992          */
 993         public function supportsSections() {
 994                 return false;
 995         }
 996
 997         /**
 998          * Returns true if this content model supports redirects.
 999          * This default implementation returns false.
1000          *
1001          * Content models that return true here should also implement
1002          * ContentHandler::makeRedirectContent to return a Content object.
1003          *
1004          * @return boolean whether redirects are supported.
1005          */
1006         public function supportsRedirects() {
1007                 return false;
1008         }
1009
1010         /**
1011          * Logs a deprecation warning, visible if $wgDevelopmentWarnings, but only if
1012          * self::$enableDeprecationWarnings is set to true.
1013          *
1014          * @param string $func The name of the deprecated function
1015          * @param string $version The version since the method is deprecated. Usually 1.21
1016          *   for ContentHandler related stuff.
1017          * @param string|bool $component : Component to which the function belongs.
1018          *   If false, it is assumed the function is in MediaWiki core.
1019          *
1020          * @see ContentHandler::$enableDeprecationWarnings
1021          * @see wfDeprecated
1022          */
1023         public static function deprecated( $func, $version, $component = false ) {
1024                 if ( self::$enableDeprecationWarnings ) {
1025                         wfDeprecated( $func, $version, $component, 3 );
1026                 }
1027         }
1028
1029         /**
1030          * Call a legacy hook that uses text instead of Content objects.
1031          * Will log a warning when a matching hook function is registered.
1032          * If the textual representation of the content is changed by the
1033          * hook function, a new Content object is constructed from the new
1034          * text.
1035          *
1036          * @param string $event event name
1037          * @param array $args parameters passed to hook functions
1038          * @param bool $warn whether to log a warning.
1039          *                    Default to self::$enableDeprecationWarnings.
1040          *                    May be set to false for testing.
1041          *
1042          * @return Boolean True if no handler aborted the hook
1043          *
1044          * @see ContentHandler::$enableDeprecationWarnings
1045          */
1046         public static function runLegacyHooks( $event, $args = array(),
1047                 $warn = null
1048         ) {
1049
1050                 if ( $warn === null ) {
1051                         $warn = self::$enableDeprecationWarnings;
1052                 }
1053
1054                 if ( !Hooks::isRegistered( $event ) ) {
1055                         return true; // nothing to do here
1056                 }
1057
1058                 if ( $warn ) {
1059                         // Log information about which handlers are registered for the legacy hook,
1060                         // so we can find and fix them.
1061
1062                         $handlers = Hooks::getHandlers( $event );
1063                         $handlerInfo = array();
1064
1065                         wfSuppressWarnings();
1066
1067                         foreach ( $handlers as $handler ) {
1068                                 if ( is_array( $handler ) ) {
1069                                         if ( is_object( $handler[0] ) ) {
1070                                                 $info = get_class( $handler[0] );
1071                                         } else {
1072                                                 $info = $handler[0];
1073                                         }
1074
1075                                         if ( isset( $handler[1] ) ) {
1076                                                 $info .= '::' . $handler[1];
1077                                         }
1078                                 } elseif ( is_object( $handler ) ) {
1079                                         $info = get_class( $handler[0] );
1080                                         $info .= '::on' . $event;
1081                                 } else {
1082                                         $info = $handler;
1083                                 }
1084
1085                                 $handlerInfo[] = $info;
1086                         }
1087
1088                         wfRestoreWarnings();
1089
1090                         wfWarn( "Using obsolete hook $event via ContentHandler::runLegacyHooks()! Handlers: " .
1091                                 implode( ', ', $handlerInfo ), 2 );
1092                 }
1093
1094                 // convert Content objects to text
1095                 $contentObjects = array();
1096                 $contentTexts = array();
1097
1098                 foreach ( $args as $k => $v ) {
1099                         if ( $v instanceof Content ) {
1100                                 /* @var Content $v */
1101
1102                                 $contentObjects[$k] = $v;
1103
1104                                 $v = $v->serialize();
1105                                 $contentTexts[$k] = $v;
1106                                 $args[$k] = $v;
1107                         }
1108                 }
1109
1110                 // call the hook functions
1111                 $ok = wfRunHooks( $event, $args );
1112
1113                 // see if the hook changed the text
1114                 foreach ( $contentTexts as $k => $orig ) {
1115                         /* @var Content $content */
1116
1117                         $modified = $args[$k];
1118                         $content = $contentObjects[$k];
1119
1120                         if ( $modified !== $orig ) {
1121                                 // text was changed, create updated Content object
1122                                 $content = $content->getContentHandler()->unserializeContent( $modified );
1123                         }
1124
1125                         $args[$k] = $content;
1126                 }
1127
1128                 return $ok;
1129         }
1130 }