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 /**
  38  * A content handler knows how do deal with a specific type of content on a wiki
  39  * page. Content is stored in the database in a serialized form (using a
  40  * serialization format a.k.a. MIME type) and is unserialized into its native
  41  * PHP representation (the content model), which is wrapped in an instance of
  42  * the appropriate subclass of Content.
  43  *
  44  * ContentHandler instances are stateless singletons that serve, among other
  45  * things, as a factory for Content objects. Generally, there is one subclass
  46  * of ContentHandler and one subclass of Content for every type of content model.
  47  *
  48  * Some content types have a flat model, that is, their native representation
  49  * is the same as their serialized form. Examples would be JavaScript and CSS
  50  * code. As of now, this also applies to wikitext (MediaWiki's default content
  51  * type), but wikitext content may be represented by a DOM or AST structure in
  52  * the future.
  53  *
  54  * @ingroup Content
  55  */
  56 abstract class ContentHandler {
  57
  58         /**
  59          * Switch for enabling deprecation warnings. Used by ContentHandler::deprecated()
  60          * and ContentHandler::runLegacyHooks().
  61          *
  62          * Once the ContentHandler code has settled in a bit, this should be set to true to
  63          * make extensions etc. show warnings when using deprecated functions and hooks.
  64          */
  65         protected static $enableDeprecationWarnings = false;
  66
  67         /**
  68          * Convenience function for getting flat text from a Content object. This
  69          * should only be used in the context of backwards compatibility with code
  70          * that is not yet able to handle Content objects!
  71          *
  72          * If $content is null, this method returns the empty string.
  73          *
  74          * If $content is an instance of TextContent, this method returns the flat
  75          * text as returned by $content->getNativeData().
  76          *
  77          * If $content is not a TextContent object, the behavior of this method
  78          * depends on the global $wgContentHandlerTextFallback:
  79          * - If $wgContentHandlerTextFallback is 'fail' and $content is not a
  80          *   TextContent object, an MWException is thrown.
  81          * - If $wgContentHandlerTextFallback is 'serialize' and $content is not a
  82          *   TextContent object, $content->serialize() is called to get a string
  83          *   form of the content.
  84          * - If $wgContentHandlerTextFallback is 'ignore' and $content is not a
  85          *   TextContent object, this method returns null.
  86          * - otherwise, the behavior is undefined.
  87          *
  88          * @since 1.21
  89          *
  90          * @param $content Content|null
  91          * @return null|string the textual form of $content, if available
  92          * @throws MWException if $content is not an instance of TextContent and
  93          *   $wgContentHandlerTextFallback was set to 'fail'.
  94          */
  95         public static function getContentText( Content $content = null ) {
  96                 global $wgContentHandlerTextFallback;
  97
  98                 if ( is_null( $content ) ) {
  99                         return '';
 100                 }
 101
 102                 if ( $content instanceof TextContent ) {
 103                         return $content->getNativeData();
 104                 }
 105
 106                 wfDebugLog( 'ContentHandler', 'Accessing ' . $content->getModel() . ' content as text!' );
 107
 108                 if ( $wgContentHandlerTextFallback == 'fail' ) {
 109                         throw new MWException(
 110                                 "Attempt to get text from Content with model " .
 111                                 $content->getModel()
 112                         );
 113                 }
 114
 115                 if ( $wgContentHandlerTextFallback == 'serialize' ) {
 116                         return $content->serialize();
 117                 }
 118
 119                 return null;
 120         }
 121
 122         /**
 123          * Convenience function for creating a Content object from a given textual
 124          * representation.
 125          *
 126          * $text will be deserialized into a Content object of the model specified
 127          * by $modelId (or, if that is not given, $title->getContentModel()) using
 128          * the given format.
 129          *
 130          * @since 1.21
 131          *
 132          * @param string $text the textual representation, will be
 133          *    unserialized to create the Content object
 134          * @param $title null|Title the title of the page this text belongs to.
 135          *    Required if $modelId is not provided.
 136          * @param $modelId null|string the model to deserialize to. If not provided,
 137          *    $title->getContentModel() is used.
 138          * @param $format null|string the format to use for deserialization. If not
 139          *    given, the model's default format is used.
 140          *
 141          * @throws MWException
 142          * @return Content a Content object representing $text
 143          *
 144          * @throws MWException if $model or $format is not supported or if $text can
 145          *    not be unserialized using $format.
 146          */
 147         public static function makeContent( $text, Title $title = null,
 148                 $modelId = null, $format = null )
 149         {
 150                 if ( is_null( $modelId ) ) {
 151                         if ( is_null( $title ) ) {
 152                                 throw new MWException( "Must provide a Title object or a content model ID." );
 153                         }
 154
 155                         $modelId = $title->getContentModel();
 156                 }
 157
 158                 $handler = ContentHandler::getForModelID( $modelId );
 159                 return $handler->unserializeContent( $text, $format );
 160         }
 161
 162         /**
 163          * Returns the name of the default content model to be used for the page
 164          * with the given title.
 165          *
 166          * Note: There should rarely be need to call this method directly.
 167          * To determine the actual content model for a given page, use
 168          * Title::getContentModel().
 169          *
 170          * Which model is to be used by default for the page is determined based
 171          * on several factors:
 172          * - The global setting $wgNamespaceContentModels specifies a content model
 173          *   per namespace.
 174          * - The hook ContentHandlerDefaultModelFor may be used to override the page's default
 175          *   model.
 176          * - Pages in NS_MEDIAWIKI and NS_USER default to the CSS or JavaScript
 177          *   model if they end in .js or .css, respectively.
 178          * - Pages in NS_MEDIAWIKI default to the wikitext model otherwise.
 179          * - The hook TitleIsCssOrJsPage may be used to force a page to use the CSS
 180          *   or JavaScript model. This is a compatibility feature. The ContentHandlerDefaultModelFor
 181          *   hook should be used instead if possible.
 182          * - The hook TitleIsWikitextPage may be used to force a page to use the
 183          *   wikitext model. This is a compatibility feature. The ContentHandlerDefaultModelFor
 184          *   hook should be used instead if possible.
 185          *
 186          * If none of the above applies, the wikitext model is used.
 187          *
 188          * Note: this is used by, and may thus not use, Title::getContentModel()
 189          *
 190          * @since 1.21
 191          *
 192          * @param $title Title
 193          * @return null|string default model name for the page given by $title
 194          */
 195         public static function getDefaultModelFor( Title $title ) {
 196                 // NOTE: this method must not rely on $title->getContentModel() directly or indirectly,
 197                 //       because it is used to initialize the mContentModel member.
 198
 199                 $ns = $title->getNamespace();
 200
 201                 $ext = false;
 202                 $m = null;
 203                 $model = MWNamespace::getNamespaceContentModel( $ns );
 204
 205                 // Hook can determine default model
 206                 if ( !wfRunHooks( 'ContentHandlerDefaultModelFor', array( $title, &$model ) ) ) {
 207                         if ( !is_null( $model ) ) {
 208                                 return $model;
 209                         }
 210                 }
 211
 212                 // Could this page contain custom CSS or JavaScript, based on the title?
 213                 $isCssOrJsPage = NS_MEDIAWIKI == $ns && preg_match( '!\.(css|js)$!u', $title->getText(), $m );
 214                 if ( $isCssOrJsPage ) {
 215                         $ext = $m[1];
 216                 }
 217
 218                 // Hook can force JS/CSS
 219                 wfRunHooks( 'TitleIsCssOrJsPage', array( $title, &$isCssOrJsPage ) );
 220
 221                 // Is this a .css subpage of a user page?
 222                 $isJsCssSubpage = NS_USER == $ns
 223                         && !$isCssOrJsPage
 224                         && preg_match( "/\\/.*\\.(js|css)$/", $title->getText(), $m );
 225                 if ( $isJsCssSubpage ) {
 226                         $ext = $m[1];
 227                 }
 228
 229                 // Is this wikitext, according to $wgNamespaceContentModels or the DefaultModelFor hook?
 230                 $isWikitext = is_null( $model ) || $model == CONTENT_MODEL_WIKITEXT;
 231                 $isWikitext = $isWikitext && !$isCssOrJsPage && !$isJsCssSubpage;
 232
 233                 // Hook can override $isWikitext
 234                 wfRunHooks( 'TitleIsWikitextPage', array( $title, &$isWikitext ) );
 235
 236                 if ( !$isWikitext ) {
 237                         switch ( $ext ) {
 238                                 case 'js':
 239                                         return CONTENT_MODEL_JAVASCRIPT;
 240                                 case 'css':
 241                                         return CONTENT_MODEL_CSS;
 242                                 default:
 243                                         return is_null( $model ) ? CONTENT_MODEL_TEXT : $model;
 244                         }
 245                 }
 246
 247                 // We established that it must be wikitext
 248
 249                 return CONTENT_MODEL_WIKITEXT;
 250         }
 251
 252         /**
 253          * Returns the appropriate ContentHandler singleton for the given title.
 254          *
 255          * @since 1.21
 256          *
 257          * @param $title Title
 258          * @return ContentHandler
 259          */
 260         public static function getForTitle( Title $title ) {
 261                 $modelId = $title->getContentModel();
 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                 return ContentHandler::getForModelID( $modelId );
 277         }
 278
 279         /**
 280          * @var Array A Cache of ContentHandler instances by model id
 281          */
 282         static $handlers;
 283
 284         /**
 285          * Returns the ContentHandler singleton for the given model ID. Use the
 286          * CONTENT_MODEL_XXX constants to identify the desired content model.
 287          *
 288          * ContentHandler singletons are taken from the global $wgContentHandlers
 289          * array. Keys in that array are model names, the values are either
 290          * ContentHandler singleton objects, or strings specifying the appropriate
 291          * subclass of ContentHandler.
 292          *
 293          * If a class name is encountered when looking up the singleton for a given
 294          * model name, the class is instantiated and the class name is replaced by
 295          * the resulting singleton in $wgContentHandlers.
 296          *
 297          * If no ContentHandler is defined for the desired $modelId, the
 298          * ContentHandler may be provided by the ContentHandlerForModelID hook.
 299          * If no ContentHandler can be determined, an MWException is raised.
 300          *
 301          * @since 1.21
 302          *
 303          * @param string $modelId The ID of the content model for which to get a
 304          *    handler. Use CONTENT_MODEL_XXX constants.
 305          * @return ContentHandler The ContentHandler singleton for handling the
 306          *    model given by $modelId
 307          * @throws MWException if no handler is known for $modelId.
 308          */
 309         public static function getForModelID( $modelId ) {
 310                 global $wgContentHandlers;
 311
 312                 if ( isset( ContentHandler::$handlers[$modelId] ) ) {
 313                         return ContentHandler::$handlers[$modelId];
 314                 }
 315
 316                 if ( empty( $wgContentHandlers[$modelId] ) ) {
 317                         $handler = null;
 318
 319                         wfRunHooks( 'ContentHandlerForModelID', array( $modelId, &$handler ) );
 320
 321                         if ( $handler === null ) {
 322                                 throw new MWException( "No handler for model '$modelId' registered in \$wgContentHandlers" );
 323                         }
 324
 325                         if ( !( $handler instanceof ContentHandler ) ) {
 326                                 throw new MWException( "ContentHandlerForModelID must supply a ContentHandler instance" );
 327                         }
 328                 } else {
 329                         $class = $wgContentHandlers[$modelId];
 330                         $handler = new $class( $modelId );
 331
 332                         if ( !( $handler instanceof ContentHandler ) ) {
 333                                 throw new MWException( "$class from \$wgContentHandlers is not compatible with ContentHandler" );
 334                         }
 335                 }
 336
 337                 wfDebugLog( 'ContentHandler', 'Created handler for ' . $modelId
 338                                         . ': ' . get_class( $handler ) );
 339
 340                 ContentHandler::$handlers[$modelId] = $handler;
 341                 return ContentHandler::$handlers[$modelId];
 342         }
 343
 344         /**
 345          * Returns the localized name for a given content model.
 346          *
 347          * Model names are localized using system messages. Message keys
 348          * have the form content-model-$name, where $name is getContentModelName( $id ).
 349          *
 350          * @param string $name The content model ID, as given by a CONTENT_MODEL_XXX
 351          *    constant or returned by Revision::getContentModel().
 352          *
 353          * @return string The content format's localized name.
 354          * @throws MWException if the model id isn't known.
 355          */
 356         public static function getLocalizedName( $name ) {
 357                 $key = "content-model-$name";
 358
 359                 $msg = wfMessage( $key );
 360
 361                 return $msg->exists() ? $msg->plain() : $name;
 362         }
 363
 364         public static function getContentModels() {
 365                 global $wgContentHandlers;
 366
 367                 return array_keys( $wgContentHandlers );
 368         }
 369
 370         public static function getAllContentFormats() {
 371                 global $wgContentHandlers;
 372
 373                 $formats = array();
 374
 375                 foreach ( $wgContentHandlers as $model => $class ) {
 376                         $handler = ContentHandler::getForModelID( $model );
 377                         $formats = array_merge( $formats, $handler->getSupportedFormats() );
 378                 }
 379
 380                 $formats = array_unique( $formats );
 381                 return $formats;
 382         }
 383
 384         // ------------------------------------------------------------------------
 385
 386         protected $mModelID;
 387         protected $mSupportedFormats;
 388
 389         /**
 390          * Constructor, initializing the ContentHandler instance with its model ID
 391          * and a list of supported formats. Values for the parameters are typically
 392          * provided as literals by subclass's constructors.
 393          *
 394          * @param string $modelId (use CONTENT_MODEL_XXX constants).
 395          * @param array $formats List for supported serialization formats
 396          *    (typically as MIME types)
 397          */
 398         public function __construct( $modelId, $formats ) {
 399                 $this->mModelID = $modelId;
 400                 $this->mSupportedFormats = $formats;
 401
 402                 $this->mModelName = preg_replace( '/(Content)?Handler$/', '', get_class( $this ) );
 403                 $this->mModelName = preg_replace( '/[_\\\\]/', '', $this->mModelName );
 404                 $this->mModelName = strtolower( $this->mModelName );
 405         }
 406
 407         /**
 408          * Serializes a Content object of the type supported by this ContentHandler.
 409          *
 410          * @since 1.21
 411          *
 412          * @param $content Content The Content object to serialize
 413          * @param $format null|String The desired serialization format
 414          * @return string Serialized form of the content
 415          */
 416         abstract public function serializeContent( Content $content, $format = null );
 417
 418         /**
 419          * Unserializes a Content object of the type supported by this ContentHandler.
 420          *
 421          * @since 1.21
 422          *
 423          * @param string $blob serialized form of the content
 424          * @param $format null|String the format used for serialization
 425          * @return Content the Content object created by deserializing $blob
 426          */
 427         abstract public function unserializeContent( $blob, $format = null );
 428
 429         /**
 430          * Creates an empty Content object of the type supported by this
 431          * ContentHandler.
 432          *
 433          * @since 1.21
 434          *
 435          * @return Content
 436          */
 437         abstract public function makeEmptyContent();
 438
 439         /**
 440          * Creates a new Content object that acts as a redirect to the given page,
 441          * or null of redirects are not supported by this content model.
 442          *
 443          * This default implementation always returns null. Subclasses supporting redirects
 444          * must override this method.
 445          *
 446          * Note that subclasses that override this method to return a Content object
 447          * should also override supportsRedirects() to return true.
 448          *
 449          * @since 1.21
 450          *
 451          * @param Title $destination the page to redirect to.
 452          * @param string $text text to include in the redirect, if possible.
 453          *
 454          * @return Content
 455          */
 456         public function makeRedirectContent( Title $destination, $text = '' ) {
 457                 return null;
 458         }
 459
 460         /**
 461          * Returns the model id that identifies the content model this
 462          * ContentHandler can handle. Use with the CONTENT_MODEL_XXX constants.
 463          *
 464          * @since 1.21
 465          *
 466          * @return String The model ID
 467          */
 468         public function getModelID() {
 469                 return $this->mModelID;
 470         }
 471
 472         /**
 473          * Throws an MWException if $model_id is not the ID of the content model
 474          * supported by this ContentHandler.
 475          *
 476          * @since 1.21
 477          *
 478          * @param string $model_id The model to check
 479          *
 480          * @throws MWException
 481          */
 482         protected function checkModelID( $model_id ) {
 483                 if ( $model_id !== $this->mModelID ) {
 484                         throw new MWException( "Bad content model: " .
 485                                 "expected {$this->mModelID} " .
 486                                 "but got $model_id." );
 487                 }
 488         }
 489
 490         /**
 491          * Returns a list of serialization formats supported by the
 492          * serializeContent() and unserializeContent() methods of this
 493          * ContentHandler.
 494          *
 495          * @since 1.21
 496          *
 497          * @return array of serialization formats as MIME type like strings
 498          */
 499         public function getSupportedFormats() {
 500                 return $this->mSupportedFormats;
 501         }
 502
 503         /**
 504          * The format used for serialization/deserialization by default by this
 505          * ContentHandler.
 506          *
 507          * This default implementation will return the first element of the array
 508          * of formats that was passed to the constructor.
 509          *
 510          * @since 1.21
 511          *
 512          * @return string the name of the default serialization format as a MIME type
 513          */
 514         public function getDefaultFormat() {
 515                 return $this->mSupportedFormats[0];
 516         }
 517
 518         /**
 519          * Returns true if $format is a serialization format supported by this
 520          * ContentHandler, and false otherwise.
 521          *
 522          * Note that if $format is null, this method always returns true, because
 523          * null means "use the default format".
 524          *
 525          * @since 1.21
 526          *
 527          * @param string $format the serialization format to check
 528          * @return bool
 529          */
 530         public function isSupportedFormat( $format ) {
 531
 532                 if ( !$format ) {
 533                         return true; // this means "use the default"
 534                 }
 535
 536                 return in_array( $format, $this->mSupportedFormats );
 537         }
 538
 539         /**
 540          * Throws an MWException if isSupportedFormat( $format ) is not true.
 541          * Convenient for checking whether a format provided as a parameter is
 542          * actually supported.
 543          *
 544          * @param string $format the serialization format to check
 545          *
 546          * @throws MWException
 547          */
 548         protected function checkFormat( $format ) {
 549                 if ( !$this->isSupportedFormat( $format ) ) {
 550                         throw new MWException(
 551                                 "Format $format is not supported for content model "
 552                                 . $this->getModelID()
 553                         );
 554                 }
 555         }
 556
 557         /**
 558          * Returns overrides for action handlers.
 559          * Classes listed here will be used instead of the default one when
 560          * (and only when) $wgActions[$action] === true. This allows subclasses
 561          * to override the default action handlers.
 562          *
 563          * @since 1.21
 564          *
 565          * @return Array
 566          */
 567         public function getActionOverrides() {
 568                 return array();
 569         }
 570
 571         /**
 572          * Factory for creating an appropriate DifferenceEngine for this content model.
 573          *
 574          * @since 1.21
 575          *
 576          * @param $context IContextSource context to use, anything else will be
 577          *    ignored
 578          * @param $old Integer Old ID we want to show and diff with.
 579          * @param int|string $new String either 'prev' or 'next'.
 580          * @param $rcid Integer ??? FIXME (default 0)
 581          * @param $refreshCache boolean If set, refreshes the diff cache
 582          * @param $unhide boolean If set, allow viewing deleted revs
 583          *
 584          * @return DifferenceEngine
 585          */
 586         public function createDifferenceEngine( IContextSource $context,
 587                 $old = 0, $new = 0,
 588                 $rcid = 0, # FIXME: use everywhere!
 589                 $refreshCache = false, $unhide = false
 590         ) {
 591                 $diffEngineClass = $this->getDiffEngineClass();
 592
 593                 return new $diffEngineClass( $context, $old, $new, $rcid, $refreshCache, $unhide );
 594         }
 595
 596         /**
 597          * Get the language in which the content of the given page is written.
 598          *
 599          * This default implementation just returns $wgContLang (except for pages in the MediaWiki namespace)
 600          *
 601          * Note that the pages language is not cacheable, since it may in some cases depend on user settings.
 602          *
 603          * Also note that the page language may or may not depend on the actual content of the page,
 604          * that is, this method may load the content in order to determine the language.
 605          *
 606          * @since 1.21
 607          *
 608          * @param Title        $title the page to determine the language for.
 609          * @param Content|null $content the page's content, if you have it handy, to avoid reloading it.
 610          *
 611          * @return Language the page's language
 612          */
 613         public function getPageLanguage( Title $title, Content $content = null ) {
 614                 global $wgContLang, $wgLang;
 615                 $pageLang = $wgContLang;
 616
 617                 if ( $title->getNamespace() == NS_MEDIAWIKI ) {
 618                         // Parse mediawiki messages with correct target language
 619                         list( /* $unused */, $lang ) = MessageCache::singleton()->figureMessage( $title->getText() );
 620                         $pageLang = wfGetLangObj( $lang );
 621                 }
 622
 623                 wfRunHooks( 'PageContentLanguage', array( $title, &$pageLang, $wgLang ) );
 624                 return wfGetLangObj( $pageLang );
 625         }
 626
 627         /**
 628          * Get the language in which the content of this page is written when
 629          * viewed by user. Defaults to $this->getPageLanguage(), but if the user
 630          * specified a preferred variant, the variant will be used.
 631          *
 632          * This default implementation just returns $this->getPageLanguage( $title, $content ) unless
 633          * the user specified a preferred variant.
 634          *
 635          * Note that the pages view language is not cacheable, since it depends on user settings.
 636          *
 637          * Also note that the page language may or may not depend on the actual content of the page,
 638          * that is, this method may load the content in order to determine the language.
 639          *
 640          * @since 1.21
 641          *
 642          * @param Title        $title the page to determine the language for.
 643          * @param Content|null $content the page's content, if you have it handy, to avoid reloading it.
 644          *
 645          * @return Language the page's language for viewing
 646          */
 647         public function getPageViewLanguage( Title $title, Content $content = null ) {
 648                 $pageLang = $this->getPageLanguage( $title, $content );
 649
 650                 if ( $title->getNamespace() !== NS_MEDIAWIKI ) {
 651                         // If the user chooses a variant, the content is actually
 652                         // in a language whose code is the variant code.
 653                         $variant = $pageLang->getPreferredVariant();
 654                         if ( $pageLang->getCode() !== $variant ) {
 655                                 $pageLang = Language::factory( $variant );
 656                         }
 657                 }
 658
 659                 return $pageLang;
 660         }
 661
 662         /**
 663          * Determines whether the content type handled by this ContentHandler
 664          * can be used on the given page.
 665          *
 666          * This default implementation always returns true.
 667          * Subclasses may override this to restrict the use of this content model to specific locations,
 668          * typically based on the namespace or some other aspect of the title, such as a special suffix
 669          * (e.g. ".svg" for SVG content).
 670          *
 671          * @param Title $title the page's title.
 672          *
 673          * @return bool true if content of this kind can be used on the given page, false otherwise.
 674          */
 675         public function canBeUsedOn( Title $title ) {
 676                 return true;
 677         }
 678
 679         /**
 680          * Returns the name of the diff engine to use.
 681          *
 682          * @since 1.21
 683          *
 684          * @return string
 685          */
 686         protected function getDiffEngineClass() {
 687                 return 'DifferenceEngine';
 688         }
 689
 690         /**
 691          * Attempts to merge differences between three versions.
 692          * Returns a new Content object for a clean merge and false for failure or
 693          * a conflict.
 694          *
 695          * This default implementation always returns false.
 696          *
 697          * @since 1.21
 698          *
 699          * @param $oldContent Content|string  String
 700          * @param $myContent Content|string   String
 701          * @param $yourContent Content|string String
 702          *
 703          * @return Content|Bool
 704          */
 705         public function merge3( Content $oldContent, Content $myContent, Content $yourContent ) {
 706                 return false;
 707         }
 708
 709         /**
 710          * Return an applicable auto-summary if one exists for the given edit.
 711          *
 712          * @since 1.21
 713          *
 714          * @param $oldContent Content|null: the previous text of the page.
 715          * @param $newContent Content|null: The submitted text of the page.
 716          * @param int $flags Bit mask: a bit mask of flags submitted for the edit.
 717          *
 718          * @return string An appropriate auto-summary, or an empty string.
 719          */
 720         public function getAutosummary( Content $oldContent = null, Content $newContent = null, $flags ) {
 721                 // Decide what kind of auto-summary is needed.
 722
 723                 // Redirect auto-summaries
 724
 725                 /**
 726                  * @var $ot Title
 727                  * @var $rt Title
 728                  */
 729
 730                 $ot = !is_null( $oldContent ) ? $oldContent->getRedirectTarget() : null;
 731                 $rt = !is_null( $newContent ) ? $newContent->getRedirectTarget() : null;
 732
 733                 if ( is_object( $rt ) ) {
 734                         if ( !is_object( $ot )
 735                                 || !$rt->equals( $ot )
 736                                 || $ot->getFragment() != $rt->getFragment() )
 737                         {
 738                                 $truncatedtext = $newContent->getTextForSummary(
 739                                         250
 740                                                 - strlen( wfMessage( 'autoredircomment' )->inContentLanguage()->text() )
 741                                                 - strlen( $rt->getFullText() ) );
 742
 743                                 return wfMessage( 'autoredircomment', $rt->getFullText() )
 744                                                 ->rawParams( $truncatedtext )->inContentLanguage()->text();
 745                         }
 746                 }
 747
 748                 // New page auto-summaries
 749                 if ( $flags & EDIT_NEW && $newContent->getSize() > 0 ) {
 750                         // If they're making a new article, give its text, truncated, in
 751                         // the summary.
 752
 753                         $truncatedtext = $newContent->getTextForSummary(
 754                                 200 - strlen( wfMessage( 'autosumm-new' )->inContentLanguage()->text() ) );
 755
 756                         return wfMessage( 'autosumm-new' )->rawParams( $truncatedtext )
 757                                         ->inContentLanguage()->text();
 758                 }
 759
 760                 // Blanking auto-summaries
 761                 if ( !empty( $oldContent ) && $oldContent->getSize() > 0 && $newContent->getSize() == 0 ) {
 762                         return wfMessage( 'autosumm-blank' )->inContentLanguage()->text();
 763                 } elseif ( !empty( $oldContent )
 764                         && $oldContent->getSize() > 10 * $newContent->getSize()
 765                         && $newContent->getSize() < 500 )
 766                 {
 767                         // Removing more than 90% of the article
 768
 769                         $truncatedtext = $newContent->getTextForSummary(
 770                                 200 - strlen( wfMessage( 'autosumm-replace' )->inContentLanguage()->text() ) );
 771
 772                         return wfMessage( 'autosumm-replace' )->rawParams( $truncatedtext )
 773                                         ->inContentLanguage()->text();
 774                 }
 775
 776                 // If we reach this point, there's no applicable auto-summary for our
 777                 // case, so our auto-summary is empty.
 778                 return '';
 779         }
 780
 781         /**
 782          * Auto-generates a deletion reason
 783          *
 784          * @since 1.21
 785          *
 786          * @param $title Title: the page's title
 787          * @param &$hasHistory Boolean: whether the page has a history
 788          * @return mixed String containing deletion reason or empty string, or
 789          *    boolean false if no revision occurred
 790          *
 791          * @XXX &$hasHistory is extremely ugly, it's here because
 792          * WikiPage::getAutoDeleteReason() and Article::generateReason()
 793          * have it / want it.
 794          */
 795         public function getAutoDeleteReason( Title $title, &$hasHistory ) {
 796                 $dbw = wfGetDB( DB_MASTER );
 797
 798                 // Get the last revision
 799                 $rev = Revision::newFromTitle( $title );
 800
 801                 if ( is_null( $rev ) ) {
 802                         return false;
 803                 }
 804
 805                 // Get the article's contents
 806                 $content = $rev->getContent();
 807                 $blank = false;
 808
 809                 // If the page is blank, use the text from the previous revision,
 810                 // which can only be blank if there's a move/import/protect dummy
 811                 // revision involved
 812                 if ( !$content || $content->isEmpty() ) {
 813                         $prev = $rev->getPrevious();
 814
 815                         if ( $prev ) {
 816                                 $rev = $prev;
 817                                 $content = $rev->getContent();
 818                                 $blank = true;
 819                         }
 820                 }
 821
 822                 $this->checkModelID( $rev->getContentModel() );
 823
 824                 // Find out if there was only one contributor
 825                 // Only scan the last 20 revisions
 826                 $res = $dbw->select( 'revision', 'rev_user_text',
 827                         array(
 828                                 'rev_page' => $title->getArticleID(),
 829                                 $dbw->bitAnd( 'rev_deleted', Revision::DELETED_USER ) . ' = 0'
 830                         ),
 831                         __METHOD__,
 832                         array( 'LIMIT' => 20 )
 833                 );
 834
 835                 if ( $res === false ) {
 836                         // This page has no revisions, which is very weird
 837                         return false;
 838                 }
 839
 840                 $hasHistory = ( $res->numRows() > 1 );
 841                 $row = $dbw->fetchObject( $res );
 842
 843                 if ( $row ) { // $row is false if the only contributor is hidden
 844                         $onlyAuthor = $row->rev_user_text;
 845                         // Try to find a second contributor
 846                         foreach ( $res as $row ) {
 847                                 if ( $row->rev_user_text != $onlyAuthor ) { // Bug 22999
 848                                         $onlyAuthor = false;
 849                                         break;
 850                                 }
 851                         }
 852                 } else {
 853                         $onlyAuthor = false;
 854                 }
 855
 856                 // Generate the summary with a '$1' placeholder
 857                 if ( $blank ) {
 858                         // The current revision is blank and the one before is also
 859                         // blank. It's just not our lucky day
 860                         $reason = wfMessage( 'exbeforeblank', '$1' )->inContentLanguage()->text();
 861                 } else {
 862                         if ( $onlyAuthor ) {
 863                                 $reason = wfMessage(
 864                                         'excontentauthor',
 865                                         '$1',
 866                                         $onlyAuthor
 867                                 )->inContentLanguage()->text();
 868                         } else {
 869                                 $reason = wfMessage( 'excontent', '$1' )->inContentLanguage()->text();
 870                         }
 871                 }
 872
 873                 if ( $reason == '-' ) {
 874                         // Allow these UI messages to be blanked out cleanly
 875                         return '';
 876                 }
 877
 878                 // Max content length = max comment length - length of the comment (excl. $1)
 879                 $text = $content ? $content->getTextForSummary( 255 - ( strlen( $reason ) - 2 ) ) : '';
 880
 881                 // Now replace the '$1' placeholder
 882                 $reason = str_replace( '$1', $text, $reason );
 883
 884                 return $reason;
 885         }
 886
 887         /**
 888          * Get the Content object that needs to be saved in order to undo all revisions
 889          * between $undo and $undoafter. Revisions must belong to the same page,
 890          * must exist and must not be deleted.
 891          *
 892          * @since 1.21
 893          *
 894          * @param $current Revision The current text
 895          * @param $undo Revision The revision to undo
 896          * @param $undoafter Revision Must be an earlier revision than $undo
 897          *
 898          * @return mixed String on success, false on failure
 899          */
 900         public function getUndoContent( Revision $current, Revision $undo, Revision $undoafter ) {
 901                 $cur_content = $current->getContent();
 902
 903                 if ( empty( $cur_content ) ) {
 904                         return false; // no page
 905                 }
 906
 907                 $undo_content = $undo->getContent();
 908                 $undoafter_content = $undoafter->getContent();
 909
 910                 $this->checkModelID( $cur_content->getModel() );
 911                 $this->checkModelID( $undo_content->getModel() );
 912                 $this->checkModelID( $undoafter_content->getModel() );
 913
 914                 if ( $cur_content->equals( $undo_content ) ) {
 915                         // No use doing a merge if it's just a straight revert.
 916                         return $undoafter_content;
 917                 }
 918
 919                 $undone_content = $this->merge3( $undo_content, $undoafter_content, $cur_content );
 920
 921                 return $undone_content;
 922         }
 923
 924         /**
 925          * Get parser options suitable for rendering the primary article wikitext
 926          *
 927          * @param IContextSource|User|string $context One of the following:
 928          *        - IContextSource: Use the User and the Language of the provided
 929          *                                            context
 930          *        - User: Use the provided User object and $wgLang for the language,
 931          *                                            so use an IContextSource object if possible.
 932          *        - 'canonical': Canonical options (anonymous user with default
 933          *                                            preferences and content language).
 934          *
 935          * @param IContextSource|User|string $context
 936          *
 937          * @throws MWException
 938          * @return ParserOptions
 939          */
 940         public function makeParserOptions( $context ) {
 941                 global $wgContLang;
 942
 943                 if ( $context instanceof IContextSource ) {
 944                         $options = ParserOptions::newFromContext( $context );
 945                 } elseif ( $context instanceof User ) { // settings per user (even anons)
 946                         $options = ParserOptions::newFromUser( $context );
 947                 } elseif ( $context === 'canonical' ) { // canonical settings
 948                         $options = ParserOptions::newFromUserAndLang( new User, $wgContLang );
 949                 } else {
 950                         throw new MWException( "Bad context for parser options: $context" );
 951                 }
 952
 953                 $options->enableLimitReport(); // show inclusion/loop reports
 954                 $options->setTidy( true ); // fix bad HTML
 955
 956                 return $options;
 957         }
 958
 959         /**
 960          * Returns true for content models that support caching using the
 961          * ParserCache mechanism. See WikiPage::isParserCacheUsed().
 962          *
 963          * @since 1.21
 964          *
 965          * @return bool
 966          */
 967         public function isParserCacheSupported() {
 968                 return false;
 969         }
 970
 971         /**
 972          * Returns true if this content model supports sections.
 973          * This default implementation returns false.
 974          *
 975          * Content models that return true here should also implement
 976          * Content::getSection, Content::replaceSection, etc. to handle sections..
 977          *
 978          * @return boolean whether sections are supported.
 979          */
 980         public function supportsSections() {
 981                 return false;
 982         }
 983
 984         /**
 985          * Returns true if this content model supports redirects.
 986          * This default implementation returns false.
 987          *
 988          * Content models that return true here should also implement
 989          * ContentHandler::makeRedirectContent to return a Content object.
 990          *
 991          * @return boolean whether redirects are supported.
 992          */
 993         public function supportsRedirects() {
 994                 return false;
 995         }
 996
 997         /**
 998          * Logs a deprecation warning, visible if $wgDevelopmentWarnings, but only if
 999          * self::$enableDeprecationWarnings is set to true.
1000          *
1001          * @param string      $func The name of the deprecated function
1002          * @param string      $version The version since the method is deprecated. Usually 1.21
1003          *                    for ContentHandler related stuff.
1004          * @param string|bool $component: Component to which the function belongs.
1005          *                                If false, it is assumed the function is in MediaWiki core.
1006          *
1007          * @see ContentHandler::$enableDeprecationWarnings
1008          * @see wfDeprecated
1009          */
1010         public static function deprecated( $func, $version, $component = false ) {
1011                 if ( self::$enableDeprecationWarnings ) {
1012                         wfDeprecated( $func, $version, $component, 3 );
1013                 }
1014         }
1015
1016         /**
1017          * Call a legacy hook that uses text instead of Content objects.
1018          * Will log a warning when a matching hook function is registered.
1019          * If the textual representation of the content is changed by the
1020          * hook function, a new Content object is constructed from the new
1021          * text.
1022          *
1023          * @param string $event event name
1024          * @param array $args parameters passed to hook functions
1025          * @param bool $warn whether to log a warning.
1026          *                    Default to self::$enableDeprecationWarnings.
1027          *                    May be set to false for testing.
1028          *
1029          * @return Boolean True if no handler aborted the hook
1030          *
1031          * @see ContentHandler::$enableDeprecationWarnings
1032          */
1033         public static function runLegacyHooks( $event, $args = array(),
1034                         $warn = null ) {
1035
1036                 if ( $warn === null ) {
1037                         $warn = self::$enableDeprecationWarnings;
1038                 }
1039
1040                 if ( !Hooks::isRegistered( $event ) ) {
1041                         return true; // nothing to do here
1042                 }
1043
1044                 if ( $warn ) {
1045                         // Log information about which handlers are registered for the legacy hook,
1046                         // so we can find and fix them.
1047
1048                         $handlers = Hooks::getHandlers( $event );
1049                         $handlerInfo = array();
1050
1051                         wfSuppressWarnings();
1052
1053                         foreach ( $handlers as $handler ) {
1054                                 if ( is_array( $handler ) ) {
1055                                         if ( is_object( $handler[0] ) ) {
1056                                                 $info = get_class( $handler[0] );
1057                                         } else {
1058                                                 $info = $handler[0];
1059                                         }
1060
1061                                         if ( isset( $handler[1] ) ) {
1062                                                 $info .= '::' . $handler[1];
1063                                         }
1064                                 } elseif ( is_object( $handler ) ) {
1065                                         $info = get_class( $handler[0] );
1066                                         $info .= '::on' . $event;
1067                                 } else {
1068                                         $info = $handler;
1069                                 }
1070
1071                                 $handlerInfo[] = $info;
1072                         }
1073
1074                         wfRestoreWarnings();
1075
1076                         wfWarn( "Using obsolete hook $event via ContentHandler::runLegacyHooks()! Handlers: " . implode( ', ', $handlerInfo ), 2 );
1077                 }
1078
1079                 // convert Content objects to text
1080                 $contentObjects = array();
1081                 $contentTexts = array();
1082
1083                 foreach ( $args as $k => $v ) {
1084                         if ( $v instanceof Content ) {
1085                                 /* @var Content $v */
1086
1087                                 $contentObjects[$k] = $v;
1088
1089                                 $v = $v->serialize();
1090                                 $contentTexts[$k] = $v;
1091                                 $args[$k] = $v;
1092                         }
1093                 }
1094
1095                 // call the hook functions
1096                 $ok = wfRunHooks( $event, $args );
1097
1098                 // see if the hook changed the text
1099                 foreach ( $contentTexts as $k => $orig ) {
1100                         /* @var Content $content */
1101
1102                         $modified = $args[$k];
1103                         $content = $contentObjects[$k];
1104
1105                         if ( $modified !== $orig ) {
1106                                 // text was changed, create updated Content object
1107                                 $content = $content->getContentHandler()->unserializeContent( $modified );
1108                         }
1109
1110                         $args[$k] = $content;
1111                 }
1112
1113                 return $ok;
1114         }
1115 }