includes/diff/DifferenceEngine.php

   1 <?php
   2 /**
   3  * User interface for the difference engine.
   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  * @file
  21  * @ingroup DifferenceEngine
  22  */
  23
  24 /**
  25  * Constant to indicate diff cache compatibility.
  26  * Bump this when changing the diff formatting in a way that
  27  * fixes important bugs or such to force cached diff views to
  28  * clear.
  29  */
  30 define( 'MW_DIFF_VERSION', '1.11a' );
  31
  32 /**
  33  * @todo document
  34  * @ingroup DifferenceEngine
  35  */
  36 class DifferenceEngine extends ContextSource {
  37         public $mOldid;
  38         public $mNewid;
  39         private $mOldTags;
  40         private $mNewTags;
  41
  42         /**
  43          * @var Content
  44          */
  45         public $mOldContent;
  46         public $mNewContent;
  47         protected $mDiffLang;
  48
  49         /**
  50          * @var Title
  51          */
  52         public $mOldPage;
  53         public $mNewPage;
  54
  55         /**
  56          * @var Revision
  57          */
  58         public $mOldRev;
  59         public $mNewRev;
  60         private $mRevisionsIdsLoaded = false; // Have the revisions IDs been loaded
  61         public $mRevisionsLoaded = false; // Have the revisions been loaded
  62         public $mTextLoaded = 0; // How many text blobs have been loaded, 0, 1 or 2?
  63         public $mCacheHit = false; // Was the diff fetched from cache?
  64
  65         /**
  66          * Set this to true to add debug info to the HTML output.
  67          * Warning: this may cause RSS readers to spuriously mark articles as "new"
  68          * (bug 20601)
  69          */
  70         public $enableDebugComment = false;
  71
  72         // If true, line X is not displayed when X is 1, for example to increase
  73         // readability and conserve space with many small diffs.
  74         protected $mReducedLineNumbers = false;
  75
  76         // Link to action=markpatrolled
  77         protected $mMarkPatrolledLink = null;
  78
  79         protected $unhide = false; # show rev_deleted content if allowed
  80         /**#@-*/
  81
  82         /**
  83          * Constructor
  84          * @param $context IContextSource context to use, anything else will be ignored
  85          * @param $old Integer old ID we want to show and diff with.
  86          * @param $new String|int either 'prev' or 'next'. Default: 0.
  87          * @param $rcid Integer Deprecated, no longer used!
  88          * @param $refreshCache boolean If set, refreshes the diff cache
  89          * @param $unhide boolean If set, allow viewing deleted revs
  90          */
  91         function __construct( $context = null, $old = 0, $new = 0, $rcid = 0,
  92                 $refreshCache = false, $unhide = false
  93         ) {
  94                 if ( $context instanceof IContextSource ) {
  95                         $this->setContext( $context );
  96                 }
  97
  98                 wfDebug( "DifferenceEngine old '$old' new '$new' rcid '$rcid'\n" );
  99
 100                 $this->mOldid = $old;
 101                 $this->mNewid = $new;
 102                 $this->mRefreshCache = $refreshCache;
 103                 $this->unhide = $unhide;
 104         }
 105
 106         /**
 107          * @param $value bool
 108          */
 109         function setReducedLineNumbers( $value = true ) {
 110                 $this->mReducedLineNumbers = $value;
 111         }
 112
 113         /**
 114          * @return Language
 115          */
 116         function getDiffLang() {
 117                 if ( $this->mDiffLang === null ) {
 118                         # Default language in which the diff text is written.
 119                         $this->mDiffLang = $this->getTitle()->getPageLanguage();
 120                 }
 121                 return $this->mDiffLang;
 122         }
 123
 124         /**
 125          * @return bool
 126          */
 127         function wasCacheHit() {
 128                 return $this->mCacheHit;
 129         }
 130
 131         /**
 132          * @return int
 133          */
 134         function getOldid() {
 135                 $this->loadRevisionIds();
 136                 return $this->mOldid;
 137         }
 138
 139         /**
 140          * @return Bool|int
 141          */
 142         function getNewid() {
 143                 $this->loadRevisionIds();
 144                 return $this->mNewid;
 145         }
 146
 147         /**
 148          * Look up a special:Undelete link to the given deleted revision id,
 149          * as a workaround for being unable to load deleted diffs in currently.
 150          *
 151          * @param int $id revision ID
 152          * @return mixed URL or false
 153          */
 154         function deletedLink( $id ) {
 155                 if ( $this->getUser()->isAllowed( 'deletedhistory' ) ) {
 156                         $dbr = wfGetDB( DB_SLAVE );
 157                         $row = $dbr->selectRow( 'archive', '*',
 158                                 array( 'ar_rev_id' => $id ),
 159                                 __METHOD__ );
 160                         if ( $row ) {
 161                                 $rev = Revision::newFromArchiveRow( $row );
 162                                 $title = Title::makeTitleSafe( $row->ar_namespace, $row->ar_title );
 163                                 return SpecialPage::getTitleFor( 'Undelete' )->getFullURL( array(
 164                                         'target' => $title->getPrefixedText(),
 165                                         'timestamp' => $rev->getTimestamp()
 166                                 ));
 167                         }
 168                 }
 169                 return false;
 170         }
 171
 172         /**
 173          * Build a wikitext link toward a deleted revision, if viewable.
 174          *
 175          * @param int $id revision ID
 176          * @return string wikitext fragment
 177          */
 178         function deletedIdMarker( $id ) {
 179                 $link = $this->deletedLink( $id );
 180                 if ( $link ) {
 181                         return "[$link $id]";
 182                 } else {
 183                         return $id;
 184                 }
 185         }
 186
 187         private function showMissingRevision() {
 188                 $out = $this->getOutput();
 189
 190                 $missing = array();
 191                 if ( $this->mOldRev === null ||
 192                         ( $this->mOldRev && $this->mOldContent === null )
 193                 ) {
 194                         $missing[] = $this->deletedIdMarker( $this->mOldid );
 195                 }
 196                 if ( $this->mNewRev === null ||
 197                         ( $this->mNewRev && $this->mNewContent === null )
 198                 ) {
 199                         $missing[] = $this->deletedIdMarker( $this->mNewid );
 200                 }
 201
 202                 $out->setPageTitle( $this->msg( 'errorpagetitle' ) );
 203                 $out->addWikiMsg( 'difference-missing-revision',
 204                         $this->getLanguage()->listToText( $missing ), count( $missing ) );
 205         }
 206
 207         function showDiffPage( $diffOnly = false ) {
 208                 wfProfileIn( __METHOD__ );
 209
 210                 # Allow frames except in certain special cases
 211                 $out = $this->getOutput();
 212                 $out->allowClickjacking();
 213                 $out->setRobotPolicy( 'noindex,nofollow' );
 214
 215                 if ( !$this->loadRevisionData() ) {
 216                         $this->showMissingRevision();
 217                         wfProfileOut( __METHOD__ );
 218                         return;
 219                 }
 220
 221                 $user = $this->getUser();
 222                 $permErrors = $this->mNewPage->getUserPermissionsErrors( 'read', $user );
 223                 if ( $this->mOldPage ) { # mOldPage might not be set, see below.
 224                         $permErrors = wfMergeErrorArrays( $permErrors,
 225                                 $this->mOldPage->getUserPermissionsErrors( 'read', $user ) );
 226                 }
 227                 if ( count( $permErrors ) ) {
 228                         wfProfileOut( __METHOD__ );
 229                         throw new PermissionsError( 'read', $permErrors );
 230                 }
 231
 232                 $rollback = '';
 233                 $undoLink = '';
 234
 235                 $query = array();
 236                 # Carry over 'diffonly' param via navigation links
 237                 if ( $diffOnly != $user->getBoolOption( 'diffonly' ) ) {
 238                         $query['diffonly'] = $diffOnly;
 239                 }
 240                 # Cascade unhide param in links for easy deletion browsing
 241                 if ( $this->unhide ) {
 242                         $query['unhide'] = 1;
 243                 }
 244
 245                 # Check if one of the revisions is deleted/suppressed
 246                 $deleted = $suppressed = false;
 247                 $allowed = $this->mNewRev->userCan( Revision::DELETED_TEXT, $user );
 248
 249                 $revisionTools = array();
 250
 251                 # mOldRev is false if the difference engine is called with a "vague" query for
 252                 # a diff between a version V and its previous version V' AND the version V
 253                 # is the first version of that article. In that case, V' does not exist.
 254                 if ( $this->mOldRev === false ) {
 255                         $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 256                         $samePage = true;
 257                         $oldHeader = '';
 258                 } else {
 259                         wfRunHooks( 'DiffViewHeader', array( $this, $this->mOldRev, $this->mNewRev ) );
 260
 261                         if ( $this->mNewPage->equals( $this->mOldPage ) ) {
 262                                 $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 263                                 $samePage = true;
 264                         } else {
 265                                 $out->setPageTitle( $this->msg( 'difference-title-multipage',
 266                                         $this->mOldPage->getPrefixedText(), $this->mNewPage->getPrefixedText() ) );
 267                                 $out->addSubtitle( $this->msg( 'difference-multipage' ) );
 268                                 $samePage = false;
 269                         }
 270
 271                         if ( $samePage && $this->mNewPage->quickUserCan( 'edit', $user ) ) {
 272                                 if ( $this->mNewRev->isCurrent() && $this->mNewPage->userCan( 'rollback', $user ) ) {
 273                                         $rollbackLink = Linker::generateRollback( $this->mNewRev, $this->getContext() );
 274                                         if ( $rollbackLink ) {
 275                                                 $out->preventClickjacking();
 276                                                 $rollback = '&#160;&#160;&#160;' . $rollbackLink;
 277                                         }
 278                                 }
 279
 280                                 if ( !$this->mOldRev->isDeleted( Revision::DELETED_TEXT ) &&
 281                                         !$this->mNewRev->isDeleted( Revision::DELETED_TEXT )
 282                                 ) {
 283                                         $undoLink = Html::element( 'a', array(
 284                                                         'href' => $this->mNewPage->getLocalURL( array(
 285                                                                 'action' => 'edit',
 286                                                                 'undoafter' => $this->mOldid,
 287                                                                 'undo' => $this->mNewid ) ),
 288                                                         'title' => Linker::titleAttrib( 'undo' )
 289                                                 ),
 290                                                 $this->msg( 'editundo' )->text()
 291                                         );
 292                                         $revisionTools[] = $undoLink;
 293                                 }
 294                         }
 295
 296                         # Make "previous revision link"
 297                         if ( $samePage && $this->mOldRev->getPrevious() ) {
 298                                 $prevlink = Linker::linkKnown(
 299                                         $this->mOldPage,
 300                                         $this->msg( 'previousdiff' )->escaped(),
 301                                         array( 'id' => 'differences-prevlink' ),
 302                                         array( 'diff' => 'prev', 'oldid' => $this->mOldid ) + $query
 303                                 );
 304                         } else {
 305                                 $prevlink = '&#160;';
 306                         }
 307
 308                         if ( $this->mOldRev->isMinor() ) {
 309                                 $oldminor = ChangesList::flag( 'minor' );
 310                         } else {
 311                                 $oldminor = '';
 312                         }
 313
 314                         $ldel = $this->revisionDeleteLink( $this->mOldRev );
 315                         $oldRevisionHeader = $this->getRevisionHeader( $this->mOldRev, 'complete' );
 316                         $oldChangeTags = ChangeTags::formatSummaryRow( $this->mOldTags, 'diff' );
 317
 318                         $oldHeader = '<div id="mw-diff-otitle1"><strong>' . $oldRevisionHeader . '</strong></div>' .
 319                                 '<div id="mw-diff-otitle2">' .
 320                                         Linker::revUserTools( $this->mOldRev, !$this->unhide ) . '</div>' .
 321                                 '<div id="mw-diff-otitle3">' . $oldminor .
 322                                         Linker::revComment( $this->mOldRev, !$diffOnly, !$this->unhide ) . $ldel . '</div>' .
 323                                 '<div id="mw-diff-otitle5">' . $oldChangeTags[0] . '</div>' .
 324                                 '<div id="mw-diff-otitle4">' . $prevlink . '</div>';
 325
 326                         if ( $this->mOldRev->isDeleted( Revision::DELETED_TEXT ) ) {
 327                                 $deleted = true; // old revisions text is hidden
 328                                 if ( $this->mOldRev->isDeleted( Revision::DELETED_RESTRICTED ) ) {
 329                                         $suppressed = true; // also suppressed
 330                                 }
 331                         }
 332
 333                         # Check if this user can see the revisions
 334                         if ( !$this->mOldRev->userCan( Revision::DELETED_TEXT, $user ) ) {
 335                                 $allowed = false;
 336                         }
 337                 }
 338
 339                 # Make "next revision link"
 340                 # Skip next link on the top revision
 341                 if ( $samePage && !$this->mNewRev->isCurrent() ) {
 342                         $nextlink = Linker::linkKnown(
 343                                 $this->mNewPage,
 344                                 $this->msg( 'nextdiff' )->escaped(),
 345                                 array( 'id' => 'differences-nextlink' ),
 346                                 array( 'diff' => 'next', 'oldid' => $this->mNewid ) + $query
 347                         );
 348                 } else {
 349                         $nextlink = '&#160;';
 350                 }
 351
 352                 if ( $this->mNewRev->isMinor() ) {
 353                         $newminor = ChangesList::flag( 'minor' );
 354                 } else {
 355                         $newminor = '';
 356                 }
 357
 358                 # Handle RevisionDelete links...
 359                 $rdel = $this->revisionDeleteLink( $this->mNewRev );
 360
 361                 # Allow extensions to define their own revision tools
 362                 wfRunHooks( 'DiffRevisionTools', array( $this->mNewRev, &$revisionTools ) );
 363                 $formattedRevisionTools = array();
 364                 // Put each one in parentheses (poor man's button)
 365                 foreach ( $revisionTools as $tool ) {
 366                         $formattedRevisionTools[] = $this->msg( 'parentheses' )->rawParams( $tool )->escaped();
 367                 }
 368                 $newRevisionHeader = $this->getRevisionHeader( $this->mNewRev, 'complete' ) .
 369                         ' ' . implode( ' ', $formattedRevisionTools );
 370                 $newChangeTags = ChangeTags::formatSummaryRow( $this->mNewTags, 'diff' );
 371
 372                 $newHeader = '<div id="mw-diff-ntitle1"><strong>' . $newRevisionHeader . '</strong></div>' .
 373                         '<div id="mw-diff-ntitle2">' . Linker::revUserTools( $this->mNewRev, !$this->unhide ) .
 374                                 " $rollback</div>" .
 375                         '<div id="mw-diff-ntitle3">' . $newminor .
 376                                 Linker::revComment( $this->mNewRev, !$diffOnly, !$this->unhide ) . $rdel . '</div>' .
 377                         '<div id="mw-diff-ntitle5">' . $newChangeTags[0] . '</div>' .
 378                         '<div id="mw-diff-ntitle4">' . $nextlink . $this->markPatrolledLink() . '</div>';
 379
 380                 if ( $this->mNewRev->isDeleted( Revision::DELETED_TEXT ) ) {
 381                         $deleted = true; // new revisions text is hidden
 382                         if ( $this->mNewRev->isDeleted( Revision::DELETED_RESTRICTED ) ) {
 383                                 $suppressed = true; // also suppressed
 384                         }
 385                 }
 386
 387                 # If the diff cannot be shown due to a deleted revision, then output
 388                 # the diff header and links to unhide (if available)...
 389                 if ( $deleted && ( !$this->unhide || !$allowed ) ) {
 390                         $this->showDiffStyle();
 391                         $multi = $this->getMultiNotice();
 392                         $out->addHTML( $this->addHeader( '', $oldHeader, $newHeader, $multi ) );
 393                         if ( !$allowed ) {
 394                                 $msg = $suppressed ? 'rev-suppressed-no-diff' : 'rev-deleted-no-diff';
 395                                 # Give explanation for why revision is not visible
 396                                 $out->wrapWikiMsg( "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 397                                         array( $msg ) );
 398                         } else {
 399                                 # Give explanation and add a link to view the diff...
 400                                 $query = $this->getRequest()->appendQueryValue( 'unhide', '1', true );
 401                                 $link = $this->getTitle()->getFullURL( $query );
 402                                 $msg = $suppressed ? 'rev-suppressed-unhide-diff' : 'rev-deleted-unhide-diff';
 403                                 $out->wrapWikiMsg(
 404                                         "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 405                                         array( $msg, $link )
 406                                 );
 407                         }
 408                 # Otherwise, output a regular diff...
 409                 } else {
 410                         # Add deletion notice if the user is viewing deleted content
 411                         $notice = '';
 412                         if ( $deleted ) {
 413                                 $msg = $suppressed ? 'rev-suppressed-diff-view' : 'rev-deleted-diff-view';
 414                                 $notice = "<div id='mw-$msg' class='mw-warning plainlinks'>\n" .
 415                                         $this->msg( $msg )->parse() .
 416                                         "</div>\n";
 417                         }
 418                         $this->showDiff( $oldHeader, $newHeader, $notice );
 419                         if ( !$diffOnly ) {
 420                                 $this->renderNewRevision();
 421                         }
 422                 }
 423                 wfProfileOut( __METHOD__ );
 424         }
 425
 426         /**
 427          * Get a link to mark the change as patrolled, or '' if there's either no
 428          * revision to patrol or the user is not allowed to to it.
 429          * Side effect: When the patrol link is build, this method will call
 430          * OutputPage::preventClickjacking() and load mediawiki.page.patrol.ajax.
 431          *
 432          * @return String
 433          */
 434         protected function markPatrolledLink() {
 435                 global $wgUseRCPatrol, $wgEnableAPI, $wgEnableWriteAPI;
 436                 $user = $this->getUser();
 437
 438                 if ( $this->mMarkPatrolledLink === null ) {
 439                         // Prepare a change patrol link, if applicable
 440                         if (
 441                                 // Is patrolling enabled and the user allowed to?
 442                                 $wgUseRCPatrol && $this->mNewPage->quickUserCan( 'patrol', $user ) &&
 443                                 // Only do this if the revision isn't more than 6 hours older
 444                                 // than the Max RC age (6h because the RC might not be cleaned out regularly)
 445                                 RecentChange::isInRCLifespan( $this->mNewRev->getTimestamp(), 21600 )
 446                         ) {
 447                                 // Look for an unpatrolled change corresponding to this diff
 448
 449                                 $db = wfGetDB( DB_SLAVE );
 450                                 $change = RecentChange::newFromConds(
 451                                         array(
 452                                                 'rc_timestamp' => $db->timestamp( $this->mNewRev->getTimestamp() ),
 453                                                 'rc_this_oldid' => $this->mNewid,
 454                                                 'rc_patrolled' => 0
 455                                         ),
 456                                         __METHOD__,
 457                                         array( 'USE INDEX' => 'rc_timestamp' )
 458                                 );
 459
 460                                 if ( $change && $change->getPerformer()->getName() !== $user->getName() ) {
 461                                         $rcid = $change->getAttribute( 'rc_id' );
 462                                 } else {
 463                                         // None found or the page has been created by the current user.
 464                                         // If the user could patrol this it already would be patrolled
 465                                         $rcid = 0;
 466                                 }
 467                                 // Build the link
 468                                 if ( $rcid ) {
 469                                         $this->getOutput()->preventClickjacking();
 470                                         if ( $wgEnableAPI && $wgEnableWriteAPI
 471                                                 && $user->isAllowed( 'writeapi' )
 472                                         ) {
 473                                                 $this->getOutput()->addModules( 'mediawiki.page.patrol.ajax' );
 474                                         }
 475
 476                                         $token = $user->getEditToken( $rcid );
 477                                         $this->mMarkPatrolledLink = ' <span class="patrollink">[' . Linker::linkKnown(
 478                                                 $this->mNewPage,
 479                                                 $this->msg( 'markaspatrolleddiff' )->escaped(),
 480                                                 array(),
 481                                                 array(
 482                                                         'action' => 'markpatrolled',
 483                                                         'rcid' => $rcid,
 484                                                         'token' => $token,
 485                                                 )
 486                                         ) . ']</span>';
 487                                 } else {
 488                                         $this->mMarkPatrolledLink = '';
 489                                 }
 490                         } else {
 491                                 $this->mMarkPatrolledLink = '';
 492                         }
 493                 }
 494
 495                 return $this->mMarkPatrolledLink;
 496         }
 497
 498         /**
 499          * @param $rev Revision
 500          * @return String
 501          */
 502         protected function revisionDeleteLink( $rev ) {
 503                 $link = Linker::getRevDeleteLink( $this->getUser(), $rev, $rev->getTitle() );
 504                 if ( $link !== '' ) {
 505                         $link = '&#160;&#160;&#160;' . $link . ' ';
 506                 }
 507                 return $link;
 508         }
 509
 510         /**
 511          * Show the new revision of the page.
 512          */
 513         function renderNewRevision() {
 514                 wfProfileIn( __METHOD__ );
 515                 $out = $this->getOutput();
 516                 $revHeader = $this->getRevisionHeader( $this->mNewRev );
 517                 # Add "current version as of X" title
 518                 $out->addHTML( "<hr class='diff-hr' />
 519                 <h2 class='diff-currentversion-title'>{$revHeader}</h2>\n" );
 520                 # Page content may be handled by a hooked call instead...
 521                 # @codingStandardsIgnoreStart Ignoring long lines.
 522                 if ( wfRunHooks( 'ArticleContentOnDiff', array( $this, $out ) ) ) {
 523                         $this->loadNewText();
 524                         $out->setRevisionId( $this->mNewid );
 525                         $out->setRevisionTimestamp( $this->mNewRev->getTimestamp() );
 526                         $out->setArticleFlag( true );
 527
 528                         // NOTE: only needed for B/C: custom rendering of JS/CSS via hook
 529                         if ( $this->mNewPage->isCssJsSubpage() || $this->mNewPage->isCssOrJsPage() ) {
 530                                 // Stolen from Article::view --AG 2007-10-11
 531                                 // Give hooks a chance to customise the output
 532                                 // @todo standardize this crap into one function
 533                                 if ( ContentHandler::runLegacyHooks( 'ShowRawCssJs', array( $this->mNewContent, $this->mNewPage, $out ) ) ) {
 534                                         // NOTE: deprecated hook, B/C only
 535                                         // use the content object's own rendering
 536                                         $cnt = $this->mNewRev->getContent();
 537                                         $po = $cnt ? $cnt->getParserOutput( $this->mNewRev->getTitle(), $this->mNewRev->getId() ) : null;
 538                                         $txt = $po ? $po->getText() : '';
 539                                         $out->addHTML( $txt );
 540                                 }
 541                         } elseif ( !wfRunHooks( 'ArticleContentViewCustom', array( $this->mNewContent, $this->mNewPage, $out ) ) ) {
 542                                 // Handled by extension
 543                         } elseif ( !ContentHandler::runLegacyHooks( 'ArticleViewCustom', array( $this->mNewContent, $this->mNewPage, $out ) ) ) {
 544                                 // NOTE: deprecated hook, B/C only
 545                                 // Handled by extension
 546                         } else {
 547                                 // Normal page
 548                                 if ( $this->getTitle()->equals( $this->mNewPage ) ) {
 549                                         // If the Title stored in the context is the same as the one
 550                                         // of the new revision, we can use its associated WikiPage
 551                                         // object.
 552                                         $wikiPage = $this->getWikiPage();
 553                                 } else {
 554                                         // Otherwise we need to create our own WikiPage object
 555                                         $wikiPage = WikiPage::factory( $this->mNewPage );
 556                                 }
 557
 558                                 $parserOutput = $this->getParserOutput( $wikiPage, $this->mNewRev );
 559
 560                                 # Also try to load it as a redirect
 561                                 $rt = $this->mNewContent ? $this->mNewContent->getRedirectTarget() : null;
 562
 563                                 if ( $rt ) {
 564                                         $article = Article::newFromTitle( $this->mNewPage, $this->getContext() );
 565                                         $out->addHTML( $article->viewRedirect( $rt ) );
 566
 567                                         # WikiPage::getParserOutput() should not return false, but just in case
 568                                         if ( $parserOutput ) {
 569                                                 # Show categories etc.
 570                                                 $out->addParserOutputNoText( $parserOutput );
 571                                         }
 572                                 } elseif ( $parserOutput ) {
 573                                         $out->addParserOutput( $parserOutput );
 574                                 }
 575                         }
 576                 }
 577                 # @codingStandardsIgnoreEnd
 578
 579                 # Add redundant patrol link on bottom...
 580                 $out->addHTML( $this->markPatrolledLink() );
 581
 582                 wfProfileOut( __METHOD__ );
 583         }
 584
 585         protected function getParserOutput( WikiPage $page, Revision $rev ) {
 586                 $parserOptions = $page->makeParserOptions( $this->getContext() );
 587
 588                 if ( !$rev->isCurrent() || !$rev->getTitle()->quickUserCan( "edit" ) ) {
 589                         $parserOptions->setEditSection( false );
 590                 }
 591
 592                 $parserOutput = $page->getParserOutput( $parserOptions, $rev->getId() );
 593                 return $parserOutput;
 594         }
 595
 596         /**
 597          * Get the diff text, send it to the OutputPage object
 598          * Returns false if the diff could not be generated, otherwise returns true
 599          *
 600          * @param string|bool $otitle Header for old text or false
 601          * @param string|bool $ntitle Header for new text or false
 602          * @param string $notice
 603          * @return bool
 604          */
 605         function showDiff( $otitle, $ntitle, $notice = '' ) {
 606                 $diff = $this->getDiff( $otitle, $ntitle, $notice );
 607                 if ( $diff === false ) {
 608                         $this->showMissingRevision();
 609                         return false;
 610                 } else {
 611                         $this->showDiffStyle();
 612                         $this->getOutput()->addHTML( $diff );
 613                         return true;
 614                 }
 615         }
 616
 617         /**
 618          * Add style sheets and supporting JS for diff display.
 619          */
 620         function showDiffStyle() {
 621                 $this->getOutput()->addModuleStyles( 'mediawiki.action.history.diff' );
 622         }
 623
 624         /**
 625          * Get complete diff table, including header
 626          *
 627          * @param string|bool $otitle Header for old text or false
 628          * @param string|bool $ntitle Header for new text or false
 629          * @param string $notice HTML between diff header and body
 630          * @return mixed
 631          */
 632         function getDiff( $otitle, $ntitle, $notice = '' ) {
 633                 $body = $this->getDiffBody();
 634                 if ( $body === false ) {
 635                         return false;
 636                 }
 637
 638                 $multi = $this->getMultiNotice();
 639                 // Display a message when the diff is empty
 640                 if ( $body === '' ) {
 641                         $notice .= '<div class="mw-diff-empty">' .
 642                                 $this->msg( 'diff-empty' )->parse() .
 643                                 "</div>\n";
 644                 }
 645
 646                 return $this->addHeader( $body, $otitle, $ntitle, $multi, $notice );
 647         }
 648
 649         /**
 650          * Get the diff table body, without header
 651          *
 652          * @return mixed (string/false)
 653          */
 654         public function getDiffBody() {
 655                 global $wgMemc;
 656                 wfProfileIn( __METHOD__ );
 657                 $this->mCacheHit = true;
 658                 // Check if the diff should be hidden from this user
 659                 if ( !$this->loadRevisionData() ) {
 660                         wfProfileOut( __METHOD__ );
 661                         return false;
 662                 } elseif ( $this->mOldRev &&
 663                         !$this->mOldRev->userCan( Revision::DELETED_TEXT, $this->getUser() )
 664                 ) {
 665                         wfProfileOut( __METHOD__ );
 666                         return false;
 667                 } elseif ( $this->mNewRev &&
 668                         !$this->mNewRev->userCan( Revision::DELETED_TEXT, $this->getUser() )
 669                 ) {
 670                         wfProfileOut( __METHOD__ );
 671                         return false;
 672                 }
 673                 // Short-circuit
 674                 if ( $this->mOldRev === false || ( $this->mOldRev && $this->mNewRev
 675                         && $this->mOldRev->getID() == $this->mNewRev->getID() ) )
 676                 {
 677                         wfProfileOut( __METHOD__ );
 678                         return '';
 679                 }
 680                 // Cacheable?
 681                 $key = false;
 682                 if ( $this->mOldid && $this->mNewid ) {
 683                         $key = $this->getDiffBodyCacheKey();
 684
 685                         // Try cache
 686                         if ( !$this->mRefreshCache ) {
 687                                 $difftext = $wgMemc->get( $key );
 688                                 if ( $difftext ) {
 689                                         wfIncrStats( 'diff_cache_hit' );
 690                                         $difftext = $this->localiseLineNumbers( $difftext );
 691                                         $difftext .= "\n<!-- diff cache key $key -->\n";
 692                                         wfProfileOut( __METHOD__ );
 693                                         return $difftext;
 694                                 }
 695                         } // don't try to load but save the result
 696                 }
 697                 $this->mCacheHit = false;
 698
 699                 // Loadtext is permission safe, this just clears out the diff
 700                 if ( !$this->loadText() ) {
 701                         wfProfileOut( __METHOD__ );
 702                         return false;
 703                 }
 704
 705                 $difftext = $this->generateContentDiffBody( $this->mOldContent, $this->mNewContent );
 706
 707                 // Save to cache for 7 days
 708                 if ( !wfRunHooks( 'AbortDiffCache', array( &$this ) ) ) {
 709                         wfIncrStats( 'diff_uncacheable' );
 710                 } elseif ( $key !== false && $difftext !== false ) {
 711                         wfIncrStats( 'diff_cache_miss' );
 712                         $wgMemc->set( $key, $difftext, 7 * 86400 );
 713                 } else {
 714                         wfIncrStats( 'diff_uncacheable' );
 715                 }
 716                 // Replace line numbers with the text in the user's language
 717                 if ( $difftext !== false ) {
 718                         $difftext = $this->localiseLineNumbers( $difftext );
 719                 }
 720                 wfProfileOut( __METHOD__ );
 721                 return $difftext;
 722         }
 723
 724         /**
 725          * Returns the cache key for diff body text or content.
 726          *
 727          * @return string
 728          * @since 1.23
 729          * @throws MWException
 730          */
 731         protected function getDiffBodyCacheKey() {
 732                 if ( !$this->mOldid || !$this->mNewid ) {
 733                         throw new MWException( 'mOldid and mNewid must be set to get diff cache key.' );
 734                 }
 735
 736                 return wfMemcKey( 'diff', 'version', MW_DIFF_VERSION,
 737                         'oldid', $this->mOldid, 'newid', $this->mNewid );
 738         }
 739
 740         /**
 741          * Generate a diff, no caching.
 742          *
 743          * This implementation uses generateTextDiffBody() to generate a diff based on the default
 744          * serialization of the given Content objects. This will fail if $old or $new are not
 745          * instances of TextContent.
 746          *
 747          * Subclasses may override this to provide a different rendering for the diff,
 748          * perhaps taking advantage of the content's native form. This is required for all content
 749          * models that are not text based.
 750          *
 751          * @param $old Content: old content
 752          * @param $new Content: new content
 753          *
 754          * @return bool|string
 755          * @since 1.21
 756          * @throws MWException if $old or $new are not instances of TextContent.
 757          */
 758         function generateContentDiffBody( Content $old, Content $new ) {
 759                 if ( !( $old instanceof TextContent ) ) {
 760                         throw new MWException( "Diff not implemented for " . get_class( $old ) . "; "
 761                                         . "override generateContentDiffBody to fix this." );
 762                 }
 763
 764                 if ( !( $new instanceof TextContent ) ) {
 765                         throw new MWException( "Diff not implemented for " . get_class( $new ) . "; "
 766                                 . "override generateContentDiffBody to fix this." );
 767                 }
 768
 769                 $otext = $old->serialize();
 770                 $ntext = $new->serialize();
 771
 772                 return $this->generateTextDiffBody( $otext, $ntext );
 773         }
 774
 775         /**
 776          * Generate a diff, no caching
 777          *
 778          * @param string $otext old text, must be already segmented
 779          * @param string $ntext new text, must be already segmented
 780          * @return bool|string
 781          * @deprecated since 1.21, use generateContentDiffBody() instead!
 782          */
 783         function generateDiffBody( $otext, $ntext ) {
 784                 ContentHandler::deprecated( __METHOD__, "1.21" );
 785
 786                 return $this->generateTextDiffBody( $otext, $ntext );
 787         }
 788
 789         /**
 790          * Generate a diff, no caching
 791          *
 792          * @todo move this to TextDifferenceEngine, make DifferenceEngine abstract. At some point.
 793          *
 794          * @param string $otext old text, must be already segmented
 795          * @param string $ntext new text, must be already segmented
 796          * @return bool|string
 797          */
 798         function generateTextDiffBody( $otext, $ntext ) {
 799                 global $wgExternalDiffEngine, $wgContLang;
 800
 801                 wfProfileIn( __METHOD__ );
 802
 803                 $otext = str_replace( "\r\n", "\n", $otext );
 804                 $ntext = str_replace( "\r\n", "\n", $ntext );
 805
 806                 if ( $wgExternalDiffEngine == 'wikidiff' && function_exists( 'wikidiff_do_diff' ) ) {
 807                         # For historical reasons, external diff engine expects
 808                         # input text to be HTML-escaped already
 809                         $otext = htmlspecialchars ( $wgContLang->segmentForDiff( $otext ) );
 810                         $ntext = htmlspecialchars ( $wgContLang->segmentForDiff( $ntext ) );
 811                         wfProfileOut( __METHOD__ );
 812                         return $wgContLang->unsegmentForDiff( wikidiff_do_diff( $otext, $ntext, 2 ) ) .
 813                         $this->debug( 'wikidiff1' );
 814                 }
 815
 816                 if ( $wgExternalDiffEngine == 'wikidiff2' && function_exists( 'wikidiff2_do_diff' ) ) {
 817                         # Better external diff engine, the 2 may some day be dropped
 818                         # This one does the escaping and segmenting itself
 819                         wfProfileIn( 'wikidiff2_do_diff' );
 820                         $text = wikidiff2_do_diff( $otext, $ntext, 2 );
 821                         $text .= $this->debug( 'wikidiff2' );
 822                         wfProfileOut( 'wikidiff2_do_diff' );
 823                         wfProfileOut( __METHOD__ );
 824                         return $text;
 825                 }
 826                 if ( $wgExternalDiffEngine != 'wikidiff3' && $wgExternalDiffEngine !== false ) {
 827                         # Diff via the shell
 828                         $tmpDir = wfTempDir();
 829                         $tempName1 = tempnam( $tmpDir, 'diff_' );
 830                         $tempName2 = tempnam( $tmpDir, 'diff_' );
 831
 832                         $tempFile1 = fopen( $tempName1, "w" );
 833                         if ( !$tempFile1 ) {
 834                                 wfProfileOut( __METHOD__ );
 835                                 return false;
 836                         }
 837                         $tempFile2 = fopen( $tempName2, "w" );
 838                         if ( !$tempFile2 ) {
 839                                 wfProfileOut( __METHOD__ );
 840                                 return false;
 841                         }
 842                         fwrite( $tempFile1, $otext );
 843                         fwrite( $tempFile2, $ntext );
 844                         fclose( $tempFile1 );
 845                         fclose( $tempFile2 );
 846                         $cmd = wfEscapeShellArg( $wgExternalDiffEngine, $tempName1, $tempName2 );
 847                         wfProfileIn( __METHOD__ . "-shellexec" );
 848                         $difftext = wfShellExec( $cmd );
 849                         $difftext .= $this->debug( "external $wgExternalDiffEngine" );
 850                         wfProfileOut( __METHOD__ . "-shellexec" );
 851                         unlink( $tempName1 );
 852                         unlink( $tempName2 );
 853                         wfProfileOut( __METHOD__ );
 854                         return $difftext;
 855                 }
 856
 857                 # Native PHP diff
 858                 $ota = explode( "\n", $wgContLang->segmentForDiff( $otext ) );
 859                 $nta = explode( "\n", $wgContLang->segmentForDiff( $ntext ) );
 860                 $diffs = new Diff( $ota, $nta );
 861                 $formatter = new TableDiffFormatter();
 862                 $difftext = $wgContLang->unsegmentForDiff( $formatter->format( $diffs ) ) .
 863                 wfProfileOut( __METHOD__ );
 864                 return $difftext;
 865         }
 866
 867         /**
 868          * Generate a debug comment indicating diff generating time,
 869          * server node, and generator backend.
 870          * @return string
 871          */
 872         protected function debug( $generator = "internal" ) {
 873                 global $wgShowHostnames;
 874                 if ( !$this->enableDebugComment ) {
 875                         return '';
 876                 }
 877                 $data = array( $generator );
 878                 if ( $wgShowHostnames ) {
 879                         $data[] = wfHostname();
 880                 }
 881                 $data[] = wfTimestamp( TS_DB );
 882                 return "<!-- diff generator: " .
 883                 implode( " ",
 884                 array_map(
 885                                         "htmlspecialchars",
 886                 $data ) ) .
 887                         " -->\n";
 888         }
 889
 890         /**
 891          * Replace line numbers with the text in the user's language
 892          * @return mixed
 893          */
 894         function localiseLineNumbers( $text ) {
 895                 return preg_replace_callback( '/<!--LINE (\d+)-->/',
 896                 array( &$this, 'localiseLineNumbersCb' ), $text );
 897         }
 898
 899         function localiseLineNumbersCb( $matches ) {
 900                 if ( $matches[1] === '1' && $this->mReducedLineNumbers ) {
 901                         return '';
 902                 }
 903                 return $this->msg( 'lineno' )->numParams( $matches[1] )->escaped();
 904         }
 905
 906         /**
 907          * If there are revisions between the ones being compared, return a note saying so.
 908          * @return string
 909          */
 910         function getMultiNotice() {
 911                 if ( !is_object( $this->mOldRev ) || !is_object( $this->mNewRev ) ) {
 912                         return '';
 913                 } elseif ( !$this->mOldPage->equals( $this->mNewPage ) ) {
 914                         // Comparing two different pages? Count would be meaningless.
 915                         return '';
 916                 }
 917
 918                 if ( $this->mOldRev->getTimestamp() > $this->mNewRev->getTimestamp() ) {
 919                         $oldRev = $this->mNewRev; // flip
 920                         $newRev = $this->mOldRev; // flip
 921                 } else { // normal case
 922                         $oldRev = $this->mOldRev;
 923                         $newRev = $this->mNewRev;
 924                 }
 925
 926                 $nEdits = $this->mNewPage->countRevisionsBetween( $oldRev, $newRev );
 927                 if ( $nEdits > 0 ) {
 928                         $limit = 100; // use diff-multi-manyusers if too many users
 929                         $numUsers = $this->mNewPage->countAuthorsBetween( $oldRev, $newRev, $limit );
 930                         return self::intermediateEditsMsg( $nEdits, $numUsers, $limit );
 931                 }
 932                 return ''; // nothing
 933         }
 934
 935         /**
 936          * Get a notice about how many intermediate edits and users there are
 937          * @param $numEdits int
 938          * @param $numUsers int
 939          * @param $limit int
 940          * @return string
 941          */
 942         public static function intermediateEditsMsg( $numEdits, $numUsers, $limit ) {
 943                 if ( $numUsers > $limit ) {
 944                         $msg = 'diff-multi-manyusers';
 945                         $numUsers = $limit;
 946                 } else {
 947                         $msg = 'diff-multi';
 948                 }
 949                 return wfMessage( $msg )->numParams( $numEdits, $numUsers )->parse();
 950         }
 951
 952         /**
 953          * Get a header for a specified revision.
 954          *
 955          * @param $rev Revision
 956          * @param string $complete 'complete' to get the header wrapped depending
 957          *        the visibility of the revision and a link to edit the page.
 958          * @return String HTML fragment
 959          */
 960         protected function getRevisionHeader( Revision $rev, $complete = '' ) {
 961                 $lang = $this->getLanguage();
 962                 $user = $this->getUser();
 963                 $revtimestamp = $rev->getTimestamp();
 964                 $timestamp = $lang->userTimeAndDate( $revtimestamp, $user );
 965                 $dateofrev = $lang->userDate( $revtimestamp, $user );
 966                 $timeofrev = $lang->userTime( $revtimestamp, $user );
 967
 968                 $header = $this->msg(
 969                         $rev->isCurrent() ? 'currentrev-asof' : 'revisionasof',
 970                         $timestamp,
 971                         $dateofrev,
 972                         $timeofrev
 973                 )->escaped();
 974
 975                 if ( $complete !== 'complete' ) {
 976                         return $header;
 977                 }
 978
 979                 $title = $rev->getTitle();
 980
 981                 $header = Linker::linkKnown( $title, $header, array(),
 982                         array( 'oldid' => $rev->getID() ) );
 983
 984                 if ( $rev->userCan( Revision::DELETED_TEXT, $user ) ) {
 985                         $editQuery = array( 'action' => 'edit' );
 986                         if ( !$rev->isCurrent() ) {
 987                                 $editQuery['oldid'] = $rev->getID();
 988                         }
 989
 990                         $key = $title->quickUserCan( 'edit', $user ) ? 'editold' : 'viewsourceold';
 991                         $msg = $this->msg( $key )->escaped();
 992                         $header .= ' ' . $this->msg( 'parentheses' )->rawParams(
 993                                 Linker::linkKnown( $title, $msg, array(), $editQuery ) )->plain();
 994                         if ( $rev->isDeleted( Revision::DELETED_TEXT ) ) {
 995                                 $header = Html::rawElement(
 996                                         'span',
 997                                         array( 'class' => 'history-deleted' ),
 998                                         $header
 999                                 );
1000                         }
1001                 } else {
1002                         $header = Html::rawElement( 'span', array( 'class' => 'history-deleted' ), $header );
1003                 }
1004
1005                 return $header;
1006         }
1007
1008         /**
1009          * Add the header to a diff body
1010          *
1011          * @return string
1012          */
1013         function addHeader( $diff, $otitle, $ntitle, $multi = '', $notice = '' ) {
1014                 // shared.css sets diff in interface language/dir, but the actual content
1015                 // is often in a different language, mostly the page content language/dir
1016                 $tableClass = 'diff diff-contentalign-' . htmlspecialchars( $this->getDiffLang()->alignStart() );
1017                 $header = "<table class='$tableClass'>";
1018
1019                 if ( !$diff && !$otitle ) {
1020                         $header .= "
1021                         <tr style='vertical-align: top;'>
1022                         <td class='diff-ntitle'>{$ntitle}</td>
1023                         </tr>";
1024                         $multiColspan = 1;
1025                 } else {
1026                         if ( $diff ) { // Safari/Chrome show broken output if cols not used
1027                                 $header .= "
1028                                 <col class='diff-marker' />
1029                                 <col class='diff-content' />
1030                                 <col class='diff-marker' />
1031                                 <col class='diff-content' />";
1032                                 $colspan = 2;
1033                                 $multiColspan = 4;
1034                         } else {
1035                                 $colspan = 1;
1036                                 $multiColspan = 2;
1037                         }
1038                         if ( $otitle || $ntitle ) {
1039                                 $header .= "
1040                                 <tr style='vertical-align: top;'>
1041                                 <td colspan='$colspan' class='diff-otitle'>{$otitle}</td>
1042                                 <td colspan='$colspan' class='diff-ntitle'>{$ntitle}</td>
1043                                 </tr>";
1044                         }
1045                 }
1046
1047                 if ( $multi != '' ) {
1048                         $header .= "<tr><td colspan='{$multiColspan}' style='text-align: center;' " .
1049                                 "class='diff-multi'>{$multi}</td></tr>";
1050                 }
1051                 if ( $notice != '' ) {
1052                         $header .= "<tr><td colspan='{$multiColspan}' style='text-align: center;'>{$notice}</td></tr>";
1053                 }
1054
1055                 return $header . $diff . "</table>";
1056         }
1057
1058         /**
1059          * Use specified text instead of loading from the database
1060          * @deprecated since 1.21, use setContent() instead.
1061          */
1062         function setText( $oldText, $newText ) {
1063                 ContentHandler::deprecated( __METHOD__, "1.21" );
1064
1065                 $oldContent = ContentHandler::makeContent( $oldText, $this->getTitle() );
1066                 $newContent = ContentHandler::makeContent( $newText, $this->getTitle() );
1067
1068                 $this->setContent( $oldContent, $newContent );
1069         }
1070
1071         /**
1072          * Use specified text instead of loading from the database
1073          * @since 1.21
1074          */
1075         function setContent( Content $oldContent, Content $newContent ) {
1076                 $this->mOldContent = $oldContent;
1077                 $this->mNewContent = $newContent;
1078
1079                 $this->mTextLoaded = 2;
1080                 $this->mRevisionsLoaded = true;
1081         }
1082
1083         /**
1084          * Set the language in which the diff text is written
1085          * (Defaults to page content language).
1086          * @since 1.19
1087          */
1088         function setTextLanguage( $lang ) {
1089                 $this->mDiffLang = wfGetLangObj( $lang );
1090         }
1091
1092         /**
1093          * Maps a revision pair definition as accepted by DifferenceEngine constructor
1094          * to a pair of actual integers representing revision ids.
1095          *
1096          * @param int $old Revision id, e.g. from URL parameter 'oldid'
1097          * @param int|string $new Revision id or strings 'next' or 'prev', e.g. from URL parameter 'diff'
1098          * @return array Array of two revision ids, older first, later second.
1099          *     Zero signifies invalid argument passed.
1100          *     false signifies that there is no previous/next revision ($old is the oldest/newest one).
1101          */
1102         public function mapDiffPrevNext( $old, $new ) {
1103                 if ( $new === 'prev' ) {
1104                         // Show diff between revision $old and the previous one. Get previous one from DB.
1105                         $newid = intval( $old );
1106                         $oldid = $this->getTitle()->getPreviousRevisionID( $newid );
1107                 } elseif ( $new === 'next' ) {
1108                         // Show diff between revision $old and the next one. Get next one from DB.
1109                         $oldid = intval( $old );
1110                         $newid = $this->getTitle()->getNextRevisionID( $oldid );
1111                 } else {
1112                         $oldid = intval( $old );
1113                         $newid = intval( $new );
1114                 }
1115
1116                 return array( $oldid, $newid );
1117         }
1118
1119         /**
1120          * Load revision IDs
1121          */
1122         private function loadRevisionIds() {
1123                 if ( $this->mRevisionsIdsLoaded ) {
1124                         return;
1125                 }
1126
1127                 $this->mRevisionsIdsLoaded = true;
1128
1129                 $old = $this->mOldid;
1130                 $new = $this->mNewid;
1131
1132                 list( $this->mOldid, $this->mNewid ) = self::mapDiffPrevNext( $old, $new );
1133                 if ( $new === 'next' && $this->mNewid === false ) {
1134                         # if no result, NewId points to the newest old revision. The only newer
1135                         # revision is cur, which is "0".
1136                         $this->mNewid = 0;
1137                 }
1138
1139                 wfRunHooks( 'NewDifferenceEngine', array( $this->getTitle(), &$this->mOldid, &$this->mNewid, $old, $new ) );
1140         }
1141
1142         /**
1143          * Load revision metadata for the specified articles. If newid is 0, then compare
1144          * the old article in oldid to the current article; if oldid is 0, then
1145          * compare the current article to the immediately previous one (ignoring the
1146          * value of newid).
1147          *
1148          * If oldid is false, leave the corresponding revision object set
1149          * to false. This is impossible via ordinary user input, and is provided for
1150          * API convenience.
1151          *
1152          * @return bool
1153          */
1154         function loadRevisionData() {
1155                 if ( $this->mRevisionsLoaded ) {
1156                         return true;
1157                 }
1158
1159                 // Whether it succeeds or fails, we don't want to try again
1160                 $this->mRevisionsLoaded = true;
1161
1162                 $this->loadRevisionIds();
1163
1164                 // Load the new revision object
1165                 if ( $this->mNewid ) {
1166                         $this->mNewRev = Revision::newFromId( $this->mNewid );
1167                 } else {
1168                         $this->mNewRev = Revision::newFromTitle(
1169                                 $this->getTitle(),
1170                                 false,
1171                                 Revision::READ_NORMAL
1172                         );
1173                 }
1174
1175                 if ( !$this->mNewRev instanceof Revision ) {
1176                         return false;
1177                 }
1178
1179                 // Update the new revision ID in case it was 0 (makes life easier doing UI stuff)
1180                 $this->mNewid = $this->mNewRev->getId();
1181                 $this->mNewPage = $this->mNewRev->getTitle();
1182
1183                 // Load the old revision object
1184                 $this->mOldRev = false;
1185                 if ( $this->mOldid ) {
1186                         $this->mOldRev = Revision::newFromId( $this->mOldid );
1187                 } elseif ( $this->mOldid === 0 ) {
1188                         $rev = $this->mNewRev->getPrevious();
1189                         if ( $rev ) {
1190                                 $this->mOldid = $rev->getId();
1191                                 $this->mOldRev = $rev;
1192                         } else {
1193                                 // No previous revision; mark to show as first-version only.
1194                                 $this->mOldid = false;
1195                                 $this->mOldRev = false;
1196                         }
1197                 } /* elseif ( $this->mOldid === false ) leave mOldRev false; */
1198
1199                 if ( is_null( $this->mOldRev ) ) {
1200                         return false;
1201                 }
1202
1203                 if ( $this->mOldRev ) {
1204                         $this->mOldPage = $this->mOldRev->getTitle();
1205                 }
1206
1207                 // Load tags information for both revisions
1208                 $dbr = wfGetDB( DB_SLAVE );
1209                 if ( $this->mOldid !== false ) {
1210                         $this->mOldTags = $dbr->selectField(
1211                                 'tag_summary',
1212                                 'ts_tags',
1213                                 array( 'ts_rev_id' => $this->mOldid ),
1214                                 __METHOD__
1215                         );
1216                 } else {
1217                         $this->mOldTags = false;
1218                 }
1219                 $this->mNewTags = $dbr->selectField(
1220                         'tag_summary',
1221                         'ts_tags',
1222                         array( 'ts_rev_id' => $this->mNewid ),
1223                         __METHOD__
1224                 );
1225
1226                 return true;
1227         }
1228
1229         /**
1230          * Load the text of the revisions, as well as revision data.
1231          *
1232          * @return bool
1233          */
1234         function loadText() {
1235                 if ( $this->mTextLoaded == 2 ) {
1236                         return true;
1237                 }
1238
1239                 // Whether it succeeds or fails, we don't want to try again
1240                 $this->mTextLoaded = 2;
1241
1242                 if ( !$this->loadRevisionData() ) {
1243                         return false;
1244                 }
1245
1246                 if ( $this->mOldRev ) {
1247                         $this->mOldContent = $this->mOldRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1248                         if ( $this->mOldContent === null ) {
1249                                 return false;
1250                         }
1251                 }
1252
1253                 if ( $this->mNewRev ) {
1254                         $this->mNewContent = $this->mNewRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1255                         if ( $this->mNewContent === null ) {
1256                                 return false;
1257                         }
1258                 }
1259
1260                 return true;
1261         }
1262
1263         /**
1264          * Load the text of the new revision, not the old one
1265          *
1266          * @return bool
1267          */
1268         function loadNewText() {
1269                 if ( $this->mTextLoaded >= 1 ) {
1270                         return true;
1271                 }
1272
1273                 $this->mTextLoaded = 1;
1274
1275                 if ( !$this->loadRevisionData() ) {
1276                         return false;
1277                 }
1278
1279                 $this->mNewContent = $this->mNewRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1280
1281                 return true;
1282         }
1283 }