includes/content/ContentHandler.php

   1 <?php
   2
   3 /**
   4  * Exception representing a failure to serialize or unserialize a content object.
   5  */
   6 class MWContentSerializationException extends MWException {
   7
   8 }
   9
  10 /**
  11  * A content handler knows how do deal with a specific type of content on a wiki
  12  * page. Content is stored in the database in a serialized form (using a
  13  * serialization format a.k.a. MIME type) and is unserialized into its native
  14  * PHP representation (the content model), which is wrapped in an instance of
  15  * the appropriate subclass of Content.
  16  *
  17  * ContentHandler instances are stateless singletons that serve, among other
  18  * things, as a factory for Content objects. Generally, there is one subclass
  19  * of ContentHandler and one subclass of Content for every type of content model.
  20  *
  21  * Some content types have a flat model, that is, their native representation
  22  * is the same as their serialized form. Examples would be JavaScript and CSS
  23  * code. As of now, this also applies to wikitext (MediaWiki's default content
  24  * type), but wikitext content may be represented by a DOM or AST structure in
  25  * the future.
  26  *
  27  * This program is free software; you can redistribute it and/or modify
  28  * it under the terms of the GNU General Public License as published by
  29  * the Free Software Foundation; either version 2 of the License, or
  30  * (at your option) any later version.
  31  *
  32  * This program is distributed in the hope that it will be useful,
  33  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  34  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  35  * GNU General Public License for more details.
  36  *
  37  * You should have received a copy of the GNU General Public License along
  38  * with this program; if not, write to the Free Software Foundation, Inc.,
  39  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  40  * http://www.gnu.org/copyleft/gpl.html
  41  *
  42  * @since 1.21
  43  *
  44  * @file
  45  * @ingroup Content
  46  *
  47  * @author Daniel Kinzler
  48  */
  49 abstract class ContentHandler {
  50
  51         /**
  52          * Switch for enabling deprecation warnings. Used by ContentHandler::deprecated()
  53          * and ContentHandler::runLegacyHooks().
  54          *
  55          * Once the ContentHandler code has settled in a bit, this should be set to true to
  56          * make extensions etc. show warnings when using deprecated functions and hooks.
  57          */
  58         protected static $enableDeprecationWarnings = false;
  59
  60         /**
  61          * Convenience function for getting flat text from a Content object. This
  62          * should only be used in the context of backwards compatibility with code
  63          * that is not yet able to handle Content objects!
  64          *
  65          * If $content is null, this method returns the empty string.
  66          *
  67          * If $content is an instance of TextContent, this method returns the flat
  68          * text as returned by $content->getNativeData().
  69          *
  70          * If $content is not a TextContent object, the behavior of this method
  71          * depends on the global $wgContentHandlerTextFallback:
  72          * - If $wgContentHandlerTextFallback is 'fail' and $content is not a
  73          *   TextContent object, an MWException is thrown.
  74          * - If $wgContentHandlerTextFallback is 'serialize' and $content is not a
  75          *   TextContent object, $content->serialize() is called to get a string
  76          *   form of the content.
  77          * - If $wgContentHandlerTextFallback is 'ignore' and $content is not a
  78          *   TextContent object, this method returns null.
  79          * - otherwise, the behaviour is undefined.
  80          *
  81          * @since 1.21
  82          *
  83          * @param $content Content|null
  84          * @return null|string the textual form of $content, if available
  85          * @throws MWException if $content is not an instance of TextContent and
  86          *   $wgContentHandlerTextFallback was set to 'fail'.
  87          */
  88         public static function getContentText( Content $content = null ) {
  89                 global $wgContentHandlerTextFallback;
  90
  91                 if ( is_null( $content ) ) {
  92                         return '';
  93                 }
  94
  95                 if ( $content instanceof TextContent ) {
  96                         return $content->getNativeData();
  97                 }
  98
  99                 wfDebugLog( 'ContentHandler', 'Accessing ' . $content->getModel() . ' content as text!' );
 100
 101                 if ( $wgContentHandlerTextFallback == 'fail' ) {
 102                         throw new MWException(
 103                                 "Attempt to get text from Content with model " .
 104                                 $content->getModel()
 105                         );
 106                 }
 107
 108                 if ( $wgContentHandlerTextFallback == 'serialize' ) {
 109                         return $content->serialize();
 110                 }
 111
 112                 return null;
 113         }
 114
 115         /**
 116          * Convenience function for creating a Content object from a given textual
 117          * representation.
 118          *
 119          * $text will be deserialized into a Content object of the model specified
 120          * by $modelId (or, if that is not given, $title->getContentModel()) using
 121          * the given format.
 122          *
 123          * @since 1.21
 124          *
 125          * @param $text string the textual representation, will be
 126          *    unserialized to create the Content object
 127          * @param $title null|Title the title of the page this text belongs to.
 128          *    Required if $modelId is not provided.
 129          * @param $modelId null|string the model to deserialize to. If not provided,
 130          *    $title->getContentModel() is used.
 131          * @param $format null|string the format to use for deserialization. If not
 132          *    given, the model's default format is used.
 133          *
 134          * @return Content a Content object representing $text
 135          *
 136          * @throw MWException if $model or $format is not supported or if $text can
 137          *    not be unserialized using $format.
 138          */
 139         public static function makeContent( $text, Title $title = null,
 140                 $modelId = null, $format = null )
 141         {
 142                 if ( is_null( $modelId ) ) {
 143                         if ( is_null( $title ) ) {
 144                                 throw new MWException( "Must provide a Title object or a content model ID." );
 145                         }
 146
 147                         $modelId = $title->getContentModel();
 148                 }
 149
 150                 $handler = ContentHandler::getForModelID( $modelId );
 151                 return $handler->unserializeContent( $text, $format );
 152         }
 153
 154         /**
 155          * Returns the name of the default content model to be used for the page
 156          * with the given title.
 157          *
 158          * Note: There should rarely be need to call this method directly.
 159          * To determine the actual content model for a given page, use
 160          * Title::getContentModel().
 161          *
 162          * Which model is to be used by default for the page is determined based
 163          * on several factors:
 164          * - The global setting $wgNamespaceContentModels specifies a content model
 165          *   per namespace.
 166          * - The hook ContentHandlerDefaultModelFor may be used to override the page's default
 167          *   model.
 168          * - Pages in NS_MEDIAWIKI and NS_USER default to the CSS or JavaScript
 169          *   model if they end in .js or .css, respectively.
 170          * - Pages in NS_MEDIAWIKI default to the wikitext model otherwise.
 171          * - The hook TitleIsCssOrJsPage may be used to force a page to use the CSS
 172          *   or JavaScript model. This is a compatibility feature. The ContentHandlerDefaultModelFor
 173          *   hook should be used instead if possible.
 174          * - The hook TitleIsWikitextPage may be used to force a page to use the
 175          *   wikitext model. This is a compatibility feature. The ContentHandlerDefaultModelFor
 176          *   hook should be used instead if possible.
 177          *
 178          * If none of the above applies, the wikitext model is used.
 179          *
 180          * Note: this is used by, and may thus not use, Title::getContentModel()
 181          *
 182          * @since 1.21
 183          *
 184          * @param $title Title
 185          * @return null|string default model name for the page given by $title
 186          */
 187         public static function getDefaultModelFor( Title $title ) {
 188                 global $wgNamespaceContentModels;
 189
 190                 // NOTE: this method must not rely on $title->getContentModel() directly or indirectly,
 191                 //       because it is used to initialize the mContentModel member.
 192
 193                 $ns = $title->getNamespace();
 194
 195                 $ext = false;
 196                 $m = null;
 197                 $model = null;
 198
 199                 if ( !empty( $wgNamespaceContentModels[ $ns ] ) ) {
 200                         $model = $wgNamespaceContentModels[ $ns ];
 201                 }
 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          * @return ContentHandler
 257          */
 258         public static function getForTitle( Title $title ) {
 259                 $modelId = $title->getContentModel();
 260                 return ContentHandler::getForModelID( $modelId );
 261         }
 262
 263         /**
 264          * Returns the appropriate ContentHandler singleton for the given Content
 265          * object.
 266          *
 267          * @since 1.21
 268          *
 269          * @param $content Content
 270          * @return ContentHandler
 271          */
 272         public static function getForContent( Content $content ) {
 273                 $modelId = $content->getModel();
 274                 return ContentHandler::getForModelID( $modelId );
 275         }
 276
 277         /**
 278          * @var Array A Cache of ContentHandler instances by model id
 279          */
 280         static $handlers;
 281
 282         /**
 283          * Returns the ContentHandler singleton for the given model ID. Use the
 284          * CONTENT_MODEL_XXX constants to identify the desired content model.
 285          *
 286          * ContentHandler singletons are taken from the global $wgContentHandlers
 287          * array. Keys in that array are model names, the values are either
 288          * ContentHandler singleton objects, or strings specifying the appropriate
 289          * subclass of ContentHandler.
 290          *
 291          * If a class name is encountered when looking up the singleton for a given
 292          * model name, the class is instantiated and the class name is replaced by
 293          * the resulting singleton in $wgContentHandlers.
 294          *
 295          * If no ContentHandler is defined for the desired $modelId, the
 296          * ContentHandler may be provided by the ContentHandlerForModelID hook.
 297          * If no ContentHandler can be determined, an MWException is raised.
 298          *
 299          * @since 1.21
 300          *
 301          * @param $modelId String The ID of the content model for which to get a
 302          *    handler. Use CONTENT_MODEL_XXX constants.
 303          * @return ContentHandler The ContentHandler singleton for handling the
 304          *    model given by $modelId
 305          * @throws MWException if no handler is known for $modelId.
 306          */
 307         public static function getForModelID( $modelId ) {
 308                 global $wgContentHandlers;
 309
 310                 if ( isset( ContentHandler::$handlers[$modelId] ) ) {
 311                         return ContentHandler::$handlers[$modelId];
 312                 }
 313
 314                 if ( empty( $wgContentHandlers[$modelId] ) ) {
 315                         $handler = null;
 316
 317                         wfRunHooks( 'ContentHandlerForModelID', array( $modelId, &$handler ) );
 318
 319                         if ( $handler === null ) {
 320                                 throw new MWException( "No handler for model '$modelId'' registered in \$wgContentHandlers" );
 321                         }
 322
 323                         if ( !( $handler instanceof ContentHandler ) ) {
 324                                 throw new MWException( "ContentHandlerForModelID must supply a ContentHandler instance" );
 325                         }
 326                 } else {
 327                         $class = $wgContentHandlers[$modelId];
 328                         $handler = new $class( $modelId );
 329
 330                         if ( !( $handler instanceof ContentHandler ) ) {
 331                                 throw new MWException( "$class from \$wgContentHandlers is not compatible with ContentHandler" );
 332                         }
 333                 }
 334
 335                 wfDebugLog( 'ContentHandler', 'Created handler for ' . $modelId
 336                                         . ': ' . get_class( $handler ) );
 337
 338                 ContentHandler::$handlers[$modelId] = $handler;
 339                 return ContentHandler::$handlers[$modelId];
 340         }
 341
 342         /**
 343          * Returns the localized name for a given content model.
 344          *
 345          * Model names are localized using system messages. Message keys
 346          * have the form content-model-$name, where $name is getContentModelName( $id ).
 347          *
 348          * @param $name String The content model ID, as given by a CONTENT_MODEL_XXX
 349          *    constant or returned by Revision::getContentModel().
 350          *
 351          * @return string The content format's localized name.
 352          * @throws MWException if the model id isn't known.
 353          */
 354         public static function getLocalizedName( $name ) {
 355                 $key = "content-model-$name";
 356
 357                 $msg = wfMessage( $key );
 358
 359                 return $msg->exists() ? $msg->plain() : $name;
 360         }
 361
 362         public static function getContentModels() {
 363                 global $wgContentHandlers;
 364
 365                 return array_keys( $wgContentHandlers );
 366         }
 367
 368         public static function getAllContentFormats() {
 369                 global $wgContentHandlers;
 370
 371                 $formats = array();
 372
 373                 foreach ( $wgContentHandlers as $model => $class ) {
 374                         $handler = ContentHandler::getForModelID( $model );
 375                         $formats = array_merge( $formats, $handler->getSupportedFormats() );
 376                 }
 377
 378                 $formats = array_unique( $formats );
 379                 return $formats;
 380         }
 381
 382         // ------------------------------------------------------------------------
 383
 384         protected $mModelID;
 385         protected $mSupportedFormats;
 386
 387         /**
 388          * Constructor, initializing the ContentHandler instance with its model ID
 389          * and a list of supported formats. Values for the parameters are typically
 390          * provided as literals by subclass's constructors.
 391          *
 392          * @param $modelId String (use CONTENT_MODEL_XXX constants).
 393          * @param $formats array List for supported serialization formats
 394          *    (typically as MIME types)
 395          */
 396         public function __construct( $modelId, $formats ) {
 397                 $this->mModelID = $modelId;
 398                 $this->mSupportedFormats = $formats;
 399
 400                 $this->mModelName = preg_replace( '/(Content)?Handler$/', '', get_class( $this ) );
 401                 $this->mModelName = preg_replace( '/[_\\\\]/', '', $this->mModelName );
 402                 $this->mModelName = strtolower( $this->mModelName );
 403         }
 404
 405         /**
 406          * Serializes a Content object of the type supported by this ContentHandler.
 407          *
 408          * @since 1.21
 409          *
 410          * @param $content Content The Content object to serialize
 411          * @param $format null|String The desired serialization format
 412          * @return string Serialized form of the content
 413          */
 414         public abstract function serializeContent( Content $content, $format = null );
 415
 416         /**
 417          * Unserializes a Content object of the type supported by this ContentHandler.
 418          *
 419          * @since 1.21
 420          *
 421          * @param $blob string serialized form of the content
 422          * @param $format null|String the format used for serialization
 423          * @return Content the Content object created by deserializing $blob
 424          */
 425         public abstract function unserializeContent( $blob, $format = null );
 426
 427         /**
 428          * Creates an empty Content object of the type supported by this
 429          * ContentHandler.
 430          *
 431          * @since 1.21
 432          *
 433          * @return Content
 434          */
 435         public abstract function makeEmptyContent();
 436
 437         /**
 438          * Creates a new Content object that acts as a redirect to the given page,
 439          * or null of redirects are not supported by this content model.
 440          *
 441          * This default implementation always returns null. Subclasses supporting redirects
 442          * must override this method.
 443          *
 444          * @since 1.21
 445          *
 446          * @param Title $destination the page to redirect to.
 447          *
 448          * @return Content
 449          */
 450         public function makeRedirectContent( Title $destination ) {
 451                 return null;
 452         }
 453
 454         /**
 455          * Returns the model id that identifies the content model this
 456          * ContentHandler can handle. Use with the CONTENT_MODEL_XXX constants.
 457          *
 458          * @since 1.21
 459          *
 460          * @return String The model ID
 461          */
 462         public function getModelID() {
 463                 return $this->mModelID;
 464         }
 465
 466         /**
 467          * Throws an MWException if $model_id is not the ID of the content model
 468          * supported by this ContentHandler.
 469          *
 470          * @since 1.21
 471          *
 472          * @param String $model_id The model to check
 473          *
 474          * @throws MWException
 475          */
 476         protected function checkModelID( $model_id ) {
 477                 if ( $model_id !== $this->mModelID ) {
 478                         throw new MWException( "Bad content model: " .
 479                                 "expected {$this->mModelID} " .
 480                                 "but got $model_id." );
 481                 }
 482         }
 483
 484         /**
 485          * Returns a list of serialization formats supported by the
 486          * serializeContent() and unserializeContent() methods of this
 487          * ContentHandler.
 488          *
 489          * @since 1.21
 490          *
 491          * @return array of serialization formats as MIME type like strings
 492          */
 493         public function getSupportedFormats() {
 494                 return $this->mSupportedFormats;
 495         }
 496
 497         /**
 498          * The format used for serialization/deserialization by default by this
 499          * ContentHandler.
 500          *
 501          * This default implementation will return the first element of the array
 502          * of formats that was passed to the constructor.
 503          *
 504          * @since 1.21
 505          *
 506          * @return string the name of the default serialization format as a MIME type
 507          */
 508         public function getDefaultFormat() {
 509                 return $this->mSupportedFormats[0];
 510         }
 511
 512         /**
 513          * Returns true if $format is a serialization format supported by this
 514          * ContentHandler, and false otherwise.
 515          *
 516          * Note that if $format is null, this method always returns true, because
 517          * null means "use the default format".
 518          *
 519          * @since 1.21
 520          *
 521          * @param $format string the serialization format to check
 522          * @return bool
 523          */
 524         public function isSupportedFormat( $format ) {
 525
 526                 if ( !$format ) {
 527                         return true; // this means "use the default"
 528                 }
 529
 530                 return in_array( $format, $this->mSupportedFormats );
 531         }
 532
 533         /**
 534          * Throws an MWException if isSupportedFormat( $format ) is not true.
 535          * Convenient for checking whether a format provided as a parameter is
 536          * actually supported.
 537          *
 538          * @param $format string the serialization format to check
 539          *
 540          * @throws MWException
 541          */
 542         protected function checkFormat( $format ) {
 543                 if ( !$this->isSupportedFormat( $format ) ) {
 544                         throw new MWException(
 545                                 "Format $format is not supported for content model "
 546                                 . $this->getModelID()
 547                         );
 548                 }
 549         }
 550
 551         /**
 552          * Returns overrides for action handlers.
 553          * Classes listed here will be used instead of the default one when
 554          * (and only when) $wgActions[$action] === true. This allows subclasses
 555          * to override the default action handlers.
 556          *
 557          * @since 1.21
 558          *
 559          * @return Array
 560          */
 561         public function getActionOverrides() {
 562                 return array();
 563         }
 564
 565         /**
 566          * Factory for creating an appropriate DifferenceEngine for this content model.
 567          *
 568          * @since 1.21
 569          *
 570          * @param $context IContextSource context to use, anything else will be
 571          *    ignored
 572          * @param $old Integer Old ID we want to show and diff with.
 573          * @param $new int|string String either 'prev' or 'next'.
 574          * @param $rcid Integer ??? FIXME (default 0)
 575          * @param $refreshCache boolean If set, refreshes the diff cache
 576          * @param $unhide boolean If set, allow viewing deleted revs
 577          *
 578          * @return DifferenceEngine
 579          */
 580         public function createDifferenceEngine( IContextSource $context,
 581                 $old = 0, $new = 0,
 582                 $rcid = 0, # FIXME: use everywhere!
 583                 $refreshCache = false, $unhide = false
 584         ) {
 585                 $diffEngineClass = $this->getDiffEngineClass();
 586
 587                 return new $diffEngineClass( $context, $old, $new, $rcid, $refreshCache, $unhide );
 588         }
 589
 590         /**
 591          * Get the language in which the content of the given page is written.
 592          *
 593          * This default implementation just returns $wgContLang (except for pages in the MediaWiki namespace)
 594          *
 595          * Note that the pages language is not cacheable, since it may in some cases depend on user settings.
 596          *
 597          * Also note that the page language may or may not depend on the actual content of the page,
 598          * that is, this method may load the content in order to determine the language.
 599          *
 600          * @since 1.21
 601          *
 602          * @param Title        $title the page to determine the language for.
 603          * @param Content|null $content the page's content, if you have it handy, to avoid reloading it.
 604          *
 605          * @return Language the page's language
 606          */
 607         public function getPageLanguage( Title $title, Content $content = null ) {
 608                 global $wgContLang, $wgLang;
 609                 $pageLang = $wgContLang;
 610
 611                 if ( $title->getNamespace() == NS_MEDIAWIKI ) {
 612                         // Parse mediawiki messages with correct target language
 613                         list( /* $unused */, $lang ) = MessageCache::singleton()->figureMessage( $title->getText() );
 614                         $pageLang = wfGetLangObj( $lang );
 615                 }
 616
 617                 wfRunHooks( 'PageContentLanguage', array( $title, &$pageLang, $wgLang ) );
 618                 return wfGetLangObj( $pageLang );
 619         }
 620
 621         /**
 622          * Get the language in which the content of this page is written when
 623          * viewed by user. Defaults to $this->getPageLanguage(), but if the user
 624          * specified a preferred variant, the variant will be used.
 625          *
 626          * This default implementation just returns $this->getPageLanguage( $title, $content ) unless
 627          * the user specified a preferred variant.
 628          *
 629          * Note that the pages view language is not cacheable, since it depends on user settings.
 630          *
 631          * Also note that the page language may or may not depend on the actual content of the page,
 632          * that is, this method may load the content in order to determine the language.
 633          *
 634          * @since 1.21
 635          *
 636          * @param Title        $title the page to determine the language for.
 637          * @param Content|null $content the page's content, if you have it handy, to avoid reloading it.
 638          *
 639          * @return Language the page's language for viewing
 640          */
 641         public function getPageViewLanguage( Title $title, Content $content = null ) {
 642                 $pageLang = $this->getPageLanguage( $title, $content );
 643
 644                 if ( $title->getNamespace() !== NS_MEDIAWIKI ) {
 645                         // If the user chooses a variant, the content is actually
 646                         // in a language whose code is the variant code.
 647                         $variant = $pageLang->getPreferredVariant();
 648                         if ( $pageLang->getCode() !== $variant ) {
 649                                 $pageLang = Language::factory( $variant );
 650                         }
 651                 }
 652
 653                 return $pageLang;
 654         }
 655
 656         /**
 657          * Determines whether the content type handled by this ContentHandler
 658          * can be used on the given page.
 659          *
 660          * This default implementation always returns true.
 661          * Subclasses may override this to restrict the use of this content model to specific locations,
 662          * typically based on the namespace or some other aspect of the title, such as a special suffix
 663          * (e.g. ".svg" for SVG content).
 664          *
 665          * @param Title $title the page's title.
 666          *
 667          * @return bool true if content of this kind can be used on the given page, false otherwise.
 668          */
 669         public function canBeUsedOn( Title $title ) {
 670                 return true;
 671         }
 672
 673         /**
 674          * Returns the name of the diff engine to use.
 675          *
 676          * @since 1.21
 677          *
 678          * @return string
 679          */
 680         protected function getDiffEngineClass() {
 681                 return 'DifferenceEngine';
 682         }
 683
 684         /**
 685          * Attempts to merge differences between three versions.
 686          * Returns a new Content object for a clean merge and false for failure or
 687          * a conflict.
 688          *
 689          * This default implementation always returns false.
 690          *
 691          * @since 1.21
 692          *
 693          * @param $oldContent Content|string  String
 694          * @param $myContent Content|string   String
 695          * @param $yourContent Content|string String
 696          *
 697          * @return Content|Bool
 698          */
 699         public function merge3( Content $oldContent, Content $myContent, Content $yourContent ) {
 700                 return false;
 701         }
 702
 703         /**
 704          * Return an applicable auto-summary if one exists for the given edit.
 705          *
 706          * @since 1.21
 707          *
 708          * @param $oldContent Content|null: the previous text of the page.
 709          * @param $newContent Content|null: The submitted text of the page.
 710          * @param $flags int Bit mask: a bit mask of flags submitted for the edit.
 711          *
 712          * @return string An appropriate auto-summary, or an empty string.
 713          */
 714         public function getAutosummary( Content $oldContent = null, Content $newContent = null, $flags ) {
 715                 // Decide what kind of auto-summary is needed.
 716
 717                 // Redirect auto-summaries
 718
 719                 /**
 720                  * @var $ot Title
 721                  * @var $rt Title
 722                  */
 723
 724                 $ot = !is_null( $oldContent ) ? $oldContent->getRedirectTarget() : null;
 725                 $rt = !is_null( $newContent ) ? $newContent->getRedirectTarget() : null;
 726
 727                 if ( is_object( $rt ) ) {
 728                         if ( !is_object( $ot )
 729                                 || !$rt->equals( $ot )
 730                                 || $ot->getFragment() != $rt->getFragment() )
 731                         {
 732                                 $truncatedtext = $newContent->getTextForSummary(
 733                                         250
 734                                                 - strlen( wfMessage( 'autoredircomment' )->inContentLanguage()->text() )
 735                                                 - strlen( $rt->getFullText() ) );
 736
 737                                 return wfMessage( 'autoredircomment', $rt->getFullText() )
 738                                                 ->rawParams( $truncatedtext )->inContentLanguage()->text();
 739                         }
 740                 }
 741
 742                 // New page auto-summaries
 743                 if ( $flags & EDIT_NEW && $newContent->getSize() > 0 ) {
 744                         // If they're making a new article, give its text, truncated, in
 745                         // the summary.
 746
 747                         $truncatedtext = $newContent->getTextForSummary(
 748                                 200 - strlen( wfMessage( 'autosumm-new' )->inContentLanguage()->text() ) );
 749
 750                         return wfMessage( 'autosumm-new' )->rawParams( $truncatedtext )
 751                                         ->inContentLanguage()->text();
 752                 }
 753
 754                 // Blanking auto-summaries
 755                 if ( !empty( $oldContent ) && $oldContent->getSize() > 0 && $newContent->getSize() == 0 ) {
 756                         return wfMessage( 'autosumm-blank' )->inContentLanguage()->text();
 757                 } elseif ( !empty( $oldContent )
 758                         && $oldContent->getSize() > 10 * $newContent->getSize()
 759                         && $newContent->getSize() < 500 )
 760                 {
 761                         // Removing more than 90% of the article
 762
 763                         $truncatedtext = $newContent->getTextForSummary(
 764                                 200 - strlen( wfMessage( 'autosumm-replace' )->inContentLanguage()->text() ) );
 765
 766                         return wfMessage( 'autosumm-replace' )->rawParams( $truncatedtext )
 767                                         ->inContentLanguage()->text();
 768                 }
 769
 770                 // If we reach this point, there's no applicable auto-summary for our
 771                 // case, so our auto-summary is empty.
 772                 return '';
 773         }
 774
 775         /**
 776          * Auto-generates a deletion reason
 777          *
 778          * @since 1.21
 779          *
 780          * @param $title Title: the page's title
 781          * @param &$hasHistory Boolean: whether the page has a history
 782          * @return mixed String containing deletion reason or empty string, or
 783          *    boolean false if no revision occurred
 784          *
 785          * @XXX &$hasHistory is extremely ugly, it's here because
 786          * WikiPage::getAutoDeleteReason() and Article::getReason()
 787          * have it / want it.
 788          */
 789         public function getAutoDeleteReason( Title $title, &$hasHistory ) {
 790                 $dbw = wfGetDB( DB_MASTER );
 791
 792                 // Get the last revision
 793                 $rev = Revision::newFromTitle( $title );
 794
 795                 if ( is_null( $rev ) ) {
 796                         return false;
 797                 }
 798
 799                 // Get the article's contents
 800                 $content = $rev->getContent();
 801                 $blank = false;
 802
 803                 // If the page is blank, use the text from the previous revision,
 804                 // which can only be blank if there's a move/import/protect dummy
 805                 // revision involved
 806                 if ( !$content || $content->isEmpty() ) {
 807                         $prev = $rev->getPrevious();
 808
 809                         if ( $prev ) {
 810                                 $rev = $prev;
 811                                 $content = $rev->getContent();
 812                                 $blank = true;
 813                         }
 814                 }
 815
 816                 $this->checkModelID( $rev->getContentModel() );
 817
 818                 // Find out if there was only one contributor
 819                 // Only scan the last 20 revisions
 820                 $res = $dbw->select( 'revision', 'rev_user_text',
 821                         array(
 822                                 'rev_page' => $title->getArticleID(),
 823                                 $dbw->bitAnd( 'rev_deleted', Revision::DELETED_USER ) . ' = 0'
 824                         ),
 825                         __METHOD__,
 826                         array( 'LIMIT' => 20 )
 827                 );
 828
 829                 if ( $res === false ) {
 830                         // This page has no revisions, which is very weird
 831                         return false;
 832                 }
 833
 834                 $hasHistory = ( $res->numRows() > 1 );
 835                 $row = $dbw->fetchObject( $res );
 836
 837                 if ( $row ) { // $row is false if the only contributor is hidden
 838                         $onlyAuthor = $row->rev_user_text;
 839                         // Try to find a second contributor
 840                         foreach ( $res as $row ) {
 841                                 if ( $row->rev_user_text != $onlyAuthor ) { // Bug 22999
 842                                         $onlyAuthor = false;
 843                                         break;
 844                                 }
 845                         }
 846                 } else {
 847                         $onlyAuthor = false;
 848                 }
 849
 850                 // Generate the summary with a '$1' placeholder
 851                 if ( $blank ) {
 852                         // The current revision is blank and the one before is also
 853                         // blank. It's just not our lucky day
 854                         $reason = wfMessage( 'exbeforeblank', '$1' )->inContentLanguage()->text();
 855                 } else {
 856                         if ( $onlyAuthor ) {
 857                                 $reason = wfMessage(
 858                                         'excontentauthor',
 859                                         '$1',
 860                                         $onlyAuthor
 861                                 )->inContentLanguage()->text();
 862                         } else {
 863                                 $reason = wfMessage( 'excontent', '$1' )->inContentLanguage()->text();
 864                         }
 865                 }
 866
 867                 if ( $reason == '-' ) {
 868                         // Allow these UI messages to be blanked out cleanly
 869                         return '';
 870                 }
 871
 872                 // Max content length = max comment length - length of the comment (excl. $1)
 873                 $text = $content ? $content->getTextForSummary( 255 - ( strlen( $reason ) - 2 ) ) : '';
 874
 875                 // Now replace the '$1' placeholder
 876                 $reason = str_replace( '$1', $text, $reason );
 877
 878                 return $reason;
 879         }
 880
 881         /**
 882          * Get the Content object that needs to be saved in order to undo all revisions
 883          * between $undo and $undoafter. Revisions must belong to the same page,
 884          * must exist and must not be deleted.
 885          *
 886          * @since 1.21
 887          *
 888          * @param $current Revision The current text
 889          * @param $undo Revision The revision to undo
 890          * @param $undoafter Revision Must be an earlier revision than $undo
 891          *
 892          * @return mixed String on success, false on failure
 893          */
 894         public function getUndoContent( Revision $current, Revision $undo, Revision $undoafter ) {
 895                 $cur_content = $current->getContent();
 896
 897                 if ( empty( $cur_content ) ) {
 898                         return false; // no page
 899                 }
 900
 901                 $undo_content = $undo->getContent();
 902                 $undoafter_content = $undoafter->getContent();
 903
 904                 $this->checkModelID( $cur_content->getModel() );
 905                 $this->checkModelID( $undo_content->getModel() );
 906                 $this->checkModelID( $undoafter_content->getModel() );
 907
 908                 if ( $cur_content->equals( $undo_content ) ) {
 909                         // No use doing a merge if it's just a straight revert.
 910                         return $undoafter_content;
 911                 }
 912
 913                 $undone_content = $this->merge3( $undo_content, $undoafter_content, $cur_content );
 914
 915                 return $undone_content;
 916         }
 917
 918         /**
 919          * Get parser options suitable for rendering the primary article wikitext
 920          *
 921          * @param IContextSource|User|string $context One of the following:
 922          *        - IContextSource: Use the User and the Language of the provided
 923          *                                            context
 924          *        - User: Use the provided User object and $wgLang for the language,
 925          *                                            so use an IContextSource object if possible.
 926          *        - 'canonical': Canonical options (anonymous user with default
 927          *                                            preferences and content language).
 928          *
 929          * @param IContextSource|User|string $context
 930          *
 931          * @throws MWException
 932          * @return ParserOptions
 933          */
 934         public function makeParserOptions( $context ) {
 935                 global $wgContLang;
 936
 937                 if ( $context instanceof IContextSource ) {
 938                         $options = ParserOptions::newFromContext( $context );
 939                 } elseif ( $context instanceof User ) { // settings per user (even anons)
 940                         $options = ParserOptions::newFromUser( $context );
 941                 } elseif ( $context === 'canonical' ) { // canonical settings
 942                         $options = ParserOptions::newFromUserAndLang( new User, $wgContLang );
 943                 } else {
 944                         throw new MWException( "Bad context for parser options: $context" );
 945                 }
 946
 947                 $options->enableLimitReport(); // show inclusion/loop reports
 948                 $options->setTidy( true ); // fix bad HTML
 949
 950                 return $options;
 951         }
 952
 953         /**
 954          * Returns true for content models that support caching using the
 955          * ParserCache mechanism. See WikiPage::isParserCacheUsed().
 956          *
 957          * @since 1.21
 958          *
 959          * @return bool
 960          */
 961         public function isParserCacheSupported() {
 962                 return false;
 963         }
 964
 965         /**
 966          * Returns true if this content model supports sections.
 967          *
 968          * This default implementation returns false.
 969          *
 970          * @return boolean whether sections are supported.
 971          */
 972         public function supportsSections() {
 973                 return false;
 974         }
 975
 976         /**
 977          * Logs a deprecation warning, visible if $wgDevelopmentWarnings, but only if
 978          * self::$enableDeprecationWarnings is set to true.
 979          *
 980          * @param String      $func The name of the deprecated function
 981          * @param string      $version The version since the method is deprecated. Usually 1.21
 982          *                    for ContentHandler related stuff.
 983          * @param String|bool $component: Component to which the function belongs.
 984          *                                If false, it is assumed the function is in MediaWiki core.
 985          *
 986          * @see ContentHandler::$enableDeprecationWarnings
 987          * @see wfDeprecated
 988          */
 989         public static function deprecated( $func, $version, $component = false ) {
 990                 if ( self::$enableDeprecationWarnings ) {
 991                         wfDeprecated( $func, $version, $component, 3 );
 992                 }
 993         }
 994
 995         /**
 996          * Call a legacy hook that uses text instead of Content objects.
 997          * Will log a warning when a matching hook function is registered.
 998          * If the textual representation of the content is changed by the
 999          * hook function, a new Content object is constructed from the new
1000          * text.
1001          *
1002          * @param $event String: event name
1003          * @param $args Array: parameters passed to hook functions
1004          * @param $warn bool: whether to log a warning.
1005          *                    Default to self::$enableDeprecationWarnings.
1006          *                    May be set to false for testing.
1007          *
1008          * @return Boolean True if no handler aborted the hook
1009          *
1010          * @see ContentHandler::$enableDeprecationWarnings
1011          */
1012         public static function runLegacyHooks( $event, $args = array(),
1013                         $warn = null ) {
1014
1015                 if ( $warn === null ) {
1016                         $warn = self::$enableDeprecationWarnings;
1017                 }
1018
1019                 if ( !Hooks::isRegistered( $event ) ) {
1020                         return true; // nothing to do here
1021                 }
1022
1023                 if ( $warn ) {
1024                         // Log information about which handlers are registered for the legacy hook,
1025                         // so we can find and fix them.
1026
1027                         $handlers = Hooks::getHandlers( $event );
1028                         $handlerInfo = array();
1029
1030                         wfSuppressWarnings();
1031
1032                         foreach ( $handlers as $handler ) {
1033                                 $info = '';
1034
1035                                 if ( is_array( $handler ) ) {
1036                                         if ( is_object( $handler[0] ) ) {
1037                                                 $info = get_class( $handler[0] );
1038                                         } else {
1039                                                 $info = $handler[0];
1040                                         }
1041
1042                                         if ( isset( $handler[1] ) ) {
1043                                                 $info .= '::' . $handler[1];
1044                                         }
1045                                 } else if ( is_object( $handler ) ) {
1046                                         $info = get_class( $handler[0] );
1047                                         $info .= '::on' . $event;
1048                                 } else {
1049                                         $info = $handler;
1050                                 }
1051
1052                                 $handlerInfo[] = $info;
1053                         }
1054
1055                         wfRestoreWarnings();
1056
1057                         wfWarn( "Using obsolete hook $event via ContentHandler::runLegacyHooks()! Handlers: " . implode(', ', $handlerInfo), 2 );
1058                 }
1059
1060                 // convert Content objects to text
1061                 $contentObjects = array();
1062                 $contentTexts = array();
1063
1064                 foreach ( $args as $k => $v ) {
1065                         if ( $v instanceof Content ) {
1066                                 /* @var Content $v */
1067
1068                                 $contentObjects[$k] = $v;
1069
1070                                 $v = $v->serialize();
1071                                 $contentTexts[ $k ] = $v;
1072                                 $args[ $k ] = $v;
1073                         }
1074                 }
1075
1076                 // call the hook functions
1077                 $ok = wfRunHooks( $event, $args );
1078
1079                 // see if the hook changed the text
1080                 foreach ( $contentTexts as $k => $orig ) {
1081                         /* @var Content $content */
1082
1083                         $modified = $args[ $k ];
1084                         $content = $contentObjects[$k];
1085
1086                         if ( $modified !== $orig ) {
1087                                 // text was changed, create updated Content object
1088                                 $content = $content->getContentHandler()->unserializeContent( $modified );
1089                         }
1090
1091                         $args[ $k ] = $content;
1092                 }
1093
1094                 return $ok;
1095         }
1096 }
1097