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         /** @var int */
  38         public $mOldid;
  39
  40         /** @var int */
  41         public $mNewid;
  42
  43         private $mOldTags;
  44         private $mNewTags;
  45
  46         /** @var Content */
  47         public $mOldContent;
  48
  49         /** @var Content */
  50         public $mNewContent;
  51
  52         /** @var Language */
  53         protected $mDiffLang;
  54
  55         /** @var  Title */
  56         public $mOldPage;
  57
  58         /** @var  Title */
  59         public $mNewPage;
  60
  61         /** @var Revision */
  62         public $mOldRev;
  63
  64         /** @var  Revision */
  65         public $mNewRev;
  66
  67         /** @var bool Have the revisions IDs been loaded */
  68         private $mRevisionsIdsLoaded = false;
  69
  70         /** @var bool Have the revisions been loaded */
  71         public $mRevisionsLoaded = false;
  72
  73         /** @var int How many text blobs have been loaded, 0, 1 or 2? */
  74         public $mTextLoaded = 0;
  75
  76         /** @var bool Was the diff fetched from cache? */
  77         public $mCacheHit = false;
  78
  79         /**
  80          * Set this to true to add debug info to the HTML output.
  81          * Warning: this may cause RSS readers to spuriously mark articles as "new"
  82          * (bug 20601)
  83          */
  84         public $enableDebugComment = false;
  85
  86         /** @var bool  If true, line X is not displayed when X is 1, for example
  87          *    to increase readability and conserve space with many small diffs.
  88          */
  89         protected $mReducedLineNumbers = false;
  90
  91         /** @var string Link to action=markpatrolled  */
  92         protected $mMarkPatrolledLink = null;
  93
  94         /** @var bool Show rev_deleted content if allowed */
  95         protected $unhide = false;
  96         /**#@-*/
  97
  98         /**
  99          * Constructor
 100          * @param $context IContextSource context to use, anything else will be ignored
 101          * @param $old Integer old ID we want to show and diff with.
 102          * @param $new String|int either revision ID or 'prev' or 'next'. Default: 0.
 103          * @param $rcid Integer Deprecated, no longer used!
 104          * @param $refreshCache boolean If set, refreshes the diff cache
 105          * @param $unhide boolean If set, allow viewing deleted revs
 106          */
 107         function __construct( $context = null, $old = 0, $new = 0, $rcid = 0,
 108                 $refreshCache = false, $unhide = false
 109         ) {
 110                 if ( $context instanceof IContextSource ) {
 111                         $this->setContext( $context );
 112                 }
 113
 114                 wfDebug( "DifferenceEngine old '$old' new '$new' rcid '$rcid'\n" );
 115
 116                 $this->mOldid = $old;
 117                 $this->mNewid = $new;
 118                 $this->mRefreshCache = $refreshCache;
 119                 $this->unhide = $unhide;
 120         }
 121
 122         /**
 123          * @param $value bool
 124          */
 125         function setReducedLineNumbers( $value = true ) {
 126                 $this->mReducedLineNumbers = $value;
 127         }
 128
 129         /**
 130          * @return Language
 131          */
 132         function getDiffLang() {
 133                 if ( $this->mDiffLang === null ) {
 134                         # Default language in which the diff text is written.
 135                         $this->mDiffLang = $this->getTitle()->getPageLanguage();
 136                 }
 137
 138                 return $this->mDiffLang;
 139         }
 140
 141         /**
 142          * @return bool
 143          */
 144         function wasCacheHit() {
 145                 return $this->mCacheHit;
 146         }
 147
 148         /**
 149          * @return int
 150          */
 151         function getOldid() {
 152                 $this->loadRevisionIds();
 153
 154                 return $this->mOldid;
 155         }
 156
 157         /**
 158          * @return Bool|int
 159          */
 160         function getNewid() {
 161                 $this->loadRevisionIds();
 162
 163                 return $this->mNewid;
 164         }
 165
 166         /**
 167          * Look up a special:Undelete link to the given deleted revision id,
 168          * as a workaround for being unable to load deleted diffs in currently.
 169          *
 170          * @param int $id revision ID
 171          * @return mixed URL or false
 172          */
 173         function deletedLink( $id ) {
 174                 if ( $this->getUser()->isAllowed( 'deletedhistory' ) ) {
 175                         $dbr = wfGetDB( DB_SLAVE );
 176                         $row = $dbr->selectRow( 'archive', '*',
 177                                 array( 'ar_rev_id' => $id ),
 178                                 __METHOD__ );
 179                         if ( $row ) {
 180                                 $rev = Revision::newFromArchiveRow( $row );
 181                                 $title = Title::makeTitleSafe( $row->ar_namespace, $row->ar_title );
 182
 183                                 return SpecialPage::getTitleFor( 'Undelete' )->getFullURL( array(
 184                                         'target' => $title->getPrefixedText(),
 185                                         'timestamp' => $rev->getTimestamp()
 186                                 ) );
 187                         }
 188                 }
 189
 190                 return false;
 191         }
 192
 193         /**
 194          * Build a wikitext link toward a deleted revision, if viewable.
 195          *
 196          * @param int $id revision ID
 197          * @return string wikitext fragment
 198          */
 199         function deletedIdMarker( $id ) {
 200                 $link = $this->deletedLink( $id );
 201                 if ( $link ) {
 202                         return "[$link $id]";
 203                 } else {
 204                         return $id;
 205                 }
 206         }
 207
 208         private function showMissingRevision() {
 209                 $out = $this->getOutput();
 210
 211                 $missing = array();
 212                 if ( $this->mOldRev === null ||
 213                         ( $this->mOldRev && $this->mOldContent === null )
 214                 ) {
 215                         $missing[] = $this->deletedIdMarker( $this->mOldid );
 216                 }
 217                 if ( $this->mNewRev === null ||
 218                         ( $this->mNewRev && $this->mNewContent === null )
 219                 ) {
 220                         $missing[] = $this->deletedIdMarker( $this->mNewid );
 221                 }
 222
 223                 $out->setPageTitle( $this->msg( 'errorpagetitle' ) );
 224                 $out->addWikiMsg( 'difference-missing-revision',
 225                         $this->getLanguage()->listToText( $missing ), count( $missing ) );
 226         }
 227
 228         function showDiffPage( $diffOnly = false ) {
 229                 wfProfileIn( __METHOD__ );
 230
 231                 # Allow frames except in certain special cases
 232                 $out = $this->getOutput();
 233                 $out->allowClickjacking();
 234                 $out->setRobotPolicy( 'noindex,nofollow' );
 235
 236                 if ( !$this->loadRevisionData() ) {
 237                         $this->showMissingRevision();
 238                         wfProfileOut( __METHOD__ );
 239
 240                         return;
 241                 }
 242
 243                 $user = $this->getUser();
 244                 $permErrors = $this->mNewPage->getUserPermissionsErrors( 'read', $user );
 245                 if ( $this->mOldPage ) { # mOldPage might not be set, see below.
 246                         $permErrors = wfMergeErrorArrays( $permErrors,
 247                                 $this->mOldPage->getUserPermissionsErrors( 'read', $user ) );
 248                 }
 249                 if ( count( $permErrors ) ) {
 250                         wfProfileOut( __METHOD__ );
 251                         throw new PermissionsError( 'read', $permErrors );
 252                 }
 253
 254                 $rollback = '';
 255
 256                 $query = array();
 257                 # Carry over 'diffonly' param via navigation links
 258                 if ( $diffOnly != $user->getBoolOption( 'diffonly' ) ) {
 259                         $query['diffonly'] = $diffOnly;
 260                 }
 261                 # Cascade unhide param in links for easy deletion browsing
 262                 if ( $this->unhide ) {
 263                         $query['unhide'] = 1;
 264                 }
 265
 266                 # Check if one of the revisions is deleted/suppressed
 267                 $deleted = $suppressed = false;
 268                 $allowed = $this->mNewRev->userCan( Revision::DELETED_TEXT, $user );
 269
 270                 $revisionTools = array();
 271
 272                 # mOldRev is false if the difference engine is called with a "vague" query for
 273                 # a diff between a version V and its previous version V' AND the version V
 274                 # is the first version of that article. In that case, V' does not exist.
 275                 if ( $this->mOldRev === false ) {
 276                         $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 277                         $samePage = true;
 278                         $oldHeader = '';
 279                 } else {
 280                         wfRunHooks( 'DiffViewHeader', array( $this, $this->mOldRev, $this->mNewRev ) );
 281
 282                         if ( $this->mNewPage->equals( $this->mOldPage ) ) {
 283                                 $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 284                                 $samePage = true;
 285                         } else {
 286                                 $out->setPageTitle( $this->msg( 'difference-title-multipage',
 287                                         $this->mOldPage->getPrefixedText(), $this->mNewPage->getPrefixedText() ) );
 288                                 $out->addSubtitle( $this->msg( 'difference-multipage' ) );
 289                                 $samePage = false;
 290                         }
 291
 292                         if ( $samePage && $this->mNewPage->quickUserCan( 'edit', $user ) ) {
 293                                 if ( $this->mNewRev->isCurrent() && $this->mNewPage->userCan( 'rollback', $user ) ) {
 294                                         $rollbackLink = Linker::generateRollback( $this->mNewRev, $this->getContext() );
 295                                         if ( $rollbackLink ) {
 296                                                 $out->preventClickjacking();
 297                                                 $rollback = '&#160;&#160;&#160;' . $rollbackLink;
 298                                         }
 299                                 }
 300
 301                                 if ( !$this->mOldRev->isDeleted( Revision::DELETED_TEXT ) &&
 302                                         !$this->mNewRev->isDeleted( Revision::DELETED_TEXT )
 303                                 ) {
 304                                         $undoLink = Html::element( 'a', array(
 305                                                         'href' => $this->mNewPage->getLocalURL( array(
 306                                                                 'action' => 'edit',
 307                                                                 'undoafter' => $this->mOldid,
 308                                                                 'undo' => $this->mNewid
 309                                                         ) ),
 310                                                         'title' => Linker::titleAttrib( 'undo' )
 311                                                 ),
 312                                                 $this->msg( 'editundo' )->text()
 313                                         );
 314                                         $revisionTools[] = $undoLink;
 315                                 }
 316                         }
 317
 318                         # Make "previous revision link"
 319                         if ( $samePage && $this->mOldRev->getPrevious() ) {
 320                                 $prevlink = Linker::linkKnown(
 321                                         $this->mOldPage,
 322                                         $this->msg( 'previousdiff' )->escaped(),
 323                                         array( 'id' => 'differences-prevlink' ),
 324                                         array( 'diff' => 'prev', 'oldid' => $this->mOldid ) + $query
 325                                 );
 326                         } else {
 327                                 $prevlink = '&#160;';
 328                         }
 329
 330                         if ( $this->mOldRev->isMinor() ) {
 331                                 $oldminor = ChangesList::flag( 'minor' );
 332                         } else {
 333                                 $oldminor = '';
 334                         }
 335
 336                         $ldel = $this->revisionDeleteLink( $this->mOldRev );
 337                         $oldRevisionHeader = $this->getRevisionHeader( $this->mOldRev, 'complete' );
 338                         $oldChangeTags = ChangeTags::formatSummaryRow( $this->mOldTags, 'diff' );
 339
 340                         $oldHeader = '<div id="mw-diff-otitle1"><strong>' . $oldRevisionHeader . '</strong></div>' .
 341                                 '<div id="mw-diff-otitle2">' .
 342                                 Linker::revUserTools( $this->mOldRev, !$this->unhide ) . '</div>' .
 343                                 '<div id="mw-diff-otitle3">' . $oldminor .
 344                                 Linker::revComment( $this->mOldRev, !$diffOnly, !$this->unhide ) . $ldel . '</div>' .
 345                                 '<div id="mw-diff-otitle5">' . $oldChangeTags[0] . '</div>' .
 346                                 '<div id="mw-diff-otitle4">' . $prevlink . '</div>';
 347
 348                         if ( $this->mOldRev->isDeleted( Revision::DELETED_TEXT ) ) {
 349                                 $deleted = true; // old revisions text is hidden
 350                                 if ( $this->mOldRev->isDeleted( Revision::DELETED_RESTRICTED ) ) {
 351                                         $suppressed = true; // also suppressed
 352                                 }
 353                         }
 354
 355                         # Check if this user can see the revisions
 356                         if ( !$this->mOldRev->userCan( Revision::DELETED_TEXT, $user ) ) {
 357                                 $allowed = false;
 358                         }
 359                 }
 360
 361                 # Make "next revision link"
 362                 # Skip next link on the top revision
 363                 if ( $samePage && !$this->mNewRev->isCurrent() ) {
 364                         $nextlink = Linker::linkKnown(
 365                                 $this->mNewPage,
 366                                 $this->msg( 'nextdiff' )->escaped(),
 367                                 array( 'id' => 'differences-nextlink' ),
 368                                 array( 'diff' => 'next', 'oldid' => $this->mNewid ) + $query
 369                         );
 370                 } else {
 371                         $nextlink = '&#160;';
 372                 }
 373
 374                 if ( $this->mNewRev->isMinor() ) {
 375                         $newminor = ChangesList::flag( 'minor' );
 376                 } else {
 377                         $newminor = '';
 378                 }
 379
 380                 # Handle RevisionDelete links...
 381                 $rdel = $this->revisionDeleteLink( $this->mNewRev );
 382
 383                 # Allow extensions to define their own revision tools
 384                 wfRunHooks( 'DiffRevisionTools', array( $this->mNewRev, &$revisionTools ) );
 385                 $formattedRevisionTools = array();
 386                 // Put each one in parentheses (poor man's button)
 387                 foreach ( $revisionTools as $tool ) {
 388                         $formattedRevisionTools[] = $this->msg( 'parentheses' )->rawParams( $tool )->escaped();
 389                 }
 390                 $newRevisionHeader = $this->getRevisionHeader( $this->mNewRev, 'complete' ) .
 391                         ' ' . implode( ' ', $formattedRevisionTools );
 392                 $newChangeTags = ChangeTags::formatSummaryRow( $this->mNewTags, 'diff' );
 393
 394                 $newHeader = '<div id="mw-diff-ntitle1"><strong>' . $newRevisionHeader . '</strong></div>' .
 395                         '<div id="mw-diff-ntitle2">' . Linker::revUserTools( $this->mNewRev, !$this->unhide ) .
 396                         " $rollback</div>" .
 397                         '<div id="mw-diff-ntitle3">' . $newminor .
 398                         Linker::revComment( $this->mNewRev, !$diffOnly, !$this->unhide ) . $rdel . '</div>' .
 399                         '<div id="mw-diff-ntitle5">' . $newChangeTags[0] . '</div>' .
 400                         '<div id="mw-diff-ntitle4">' . $nextlink . $this->markPatrolledLink() . '</div>';
 401
 402                 if ( $this->mNewRev->isDeleted( Revision::DELETED_TEXT ) ) {
 403                         $deleted = true; // new revisions text is hidden
 404                         if ( $this->mNewRev->isDeleted( Revision::DELETED_RESTRICTED ) ) {
 405                                 $suppressed = true; // also suppressed
 406                         }
 407                 }
 408
 409                 # If the diff cannot be shown due to a deleted revision, then output
 410                 # the diff header and links to unhide (if available)...
 411                 if ( $deleted && ( !$this->unhide || !$allowed ) ) {
 412                         $this->showDiffStyle();
 413                         $multi = $this->getMultiNotice();
 414                         $out->addHTML( $this->addHeader( '', $oldHeader, $newHeader, $multi ) );
 415                         if ( !$allowed ) {
 416                                 $msg = $suppressed ? 'rev-suppressed-no-diff' : 'rev-deleted-no-diff';
 417                                 # Give explanation for why revision is not visible
 418                                 $out->wrapWikiMsg( "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 419                                         array( $msg ) );
 420                         } else {
 421                                 # Give explanation and add a link to view the diff...
 422                                 $query = $this->getRequest()->appendQueryValue( 'unhide', '1', true );
 423                                 $link = $this->getTitle()->getFullURL( $query );
 424                                 $msg = $suppressed ? 'rev-suppressed-unhide-diff' : 'rev-deleted-unhide-diff';
 425                                 $out->wrapWikiMsg(
 426                                         "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 427                                         array( $msg, $link )
 428                                 );
 429                         }
 430                 # Otherwise, output a regular diff...
 431                 } else {
 432                         # Add deletion notice if the user is viewing deleted content
 433                         $notice = '';
 434                         if ( $deleted ) {
 435                                 $msg = $suppressed ? 'rev-suppressed-diff-view' : 'rev-deleted-diff-view';
 436                                 $notice = "<div id='mw-$msg' class='mw-warning plainlinks'>\n" .
 437                                         $this->msg( $msg )->parse() .
 438                                         "</div>\n";
 439                         }
 440                         $this->showDiff( $oldHeader, $newHeader, $notice );
 441                         if ( !$diffOnly ) {
 442                                 $this->renderNewRevision();
 443                         }
 444                 }
 445                 wfProfileOut( __METHOD__ );
 446         }
 447
 448         /**
 449          * Get a link to mark the change as patrolled, or '' if there's either no
 450          * revision to patrol or the user is not allowed to to it.
 451          * Side effect: When the patrol link is build, this method will call
 452          * OutputPage::preventClickjacking() and load mediawiki.page.patrol.ajax.
 453          *
 454          * @return String
 455          */
 456         protected function markPatrolledLink() {
 457                 global $wgUseRCPatrol, $wgEnableAPI, $wgEnableWriteAPI;
 458                 $user = $this->getUser();
 459
 460                 if ( $this->mMarkPatrolledLink === null ) {
 461                         // Prepare a change patrol link, if applicable
 462                         if (
 463                                 // Is patrolling enabled and the user allowed to?
 464                                 $wgUseRCPatrol && $this->mNewPage->quickUserCan( 'patrol', $user ) &&
 465                                 // Only do this if the revision isn't more than 6 hours older
 466                                 // than the Max RC age (6h because the RC might not be cleaned out regularly)
 467                                 RecentChange::isInRCLifespan( $this->mNewRev->getTimestamp(), 21600 )
 468                         ) {
 469                                 // Look for an unpatrolled change corresponding to this diff
 470
 471                                 $db = wfGetDB( DB_SLAVE );
 472                                 $change = RecentChange::newFromConds(
 473                                         array(
 474                                                 'rc_timestamp' => $db->timestamp( $this->mNewRev->getTimestamp() ),
 475                                                 'rc_this_oldid' => $this->mNewid,
 476                                                 'rc_patrolled' => 0
 477                                         ),
 478                                         __METHOD__,
 479                                         array( 'USE INDEX' => 'rc_timestamp' )
 480                                 );
 481
 482                                 if ( $change && $change->getPerformer()->getName() !== $user->getName() ) {
 483                                         $rcid = $change->getAttribute( 'rc_id' );
 484                                 } else {
 485                                         // None found or the page has been created by the current user.
 486                                         // If the user could patrol this it already would be patrolled
 487                                         $rcid = 0;
 488                                 }
 489                                 // Build the link
 490                                 if ( $rcid ) {
 491                                         $this->getOutput()->preventClickjacking();
 492                                         if ( $wgEnableAPI && $wgEnableWriteAPI
 493                                                 && $user->isAllowed( 'writeapi' )
 494                                         ) {
 495                                                 $this->getOutput()->addModules( 'mediawiki.page.patrol.ajax' );
 496                                         }
 497
 498                                         $token = $user->getEditToken( $rcid );
 499                                         $this->mMarkPatrolledLink = ' <span class="patrollink">[' . Linker::linkKnown(
 500                                                 $this->mNewPage,
 501                                                 $this->msg( 'markaspatrolleddiff' )->escaped(),
 502                                                 array(),
 503                                                 array(
 504                                                         'action' => 'markpatrolled',
 505                                                         'rcid' => $rcid,
 506                                                         'token' => $token,
 507                                                 )
 508                                         ) . ']</span>';
 509                                 } else {
 510                                         $this->mMarkPatrolledLink = '';
 511                                 }
 512                         } else {
 513                                 $this->mMarkPatrolledLink = '';
 514                         }
 515                 }
 516
 517                 return $this->mMarkPatrolledLink;
 518         }
 519
 520         /**
 521          * @param $rev Revision
 522          * @return String
 523          */
 524         protected function revisionDeleteLink( $rev ) {
 525                 $link = Linker::getRevDeleteLink( $this->getUser(), $rev, $rev->getTitle() );
 526                 if ( $link !== '' ) {
 527                         $link = '&#160;&#160;&#160;' . $link . ' ';
 528                 }
 529
 530                 return $link;
 531         }
 532
 533         /**
 534          * Show the new revision of the page.
 535          */
 536         function renderNewRevision() {
 537                 wfProfileIn( __METHOD__ );
 538                 $out = $this->getOutput();
 539                 $revHeader = $this->getRevisionHeader( $this->mNewRev );
 540                 # Add "current version as of X" title
 541                 $out->addHTML( "<hr class='diff-hr' />
 542                 <h2 class='diff-currentversion-title'>{$revHeader}</h2>\n" );
 543                 # Page content may be handled by a hooked call instead...
 544                 # @codingStandardsIgnoreStart Ignoring long lines.
 545                 if ( wfRunHooks( 'ArticleContentOnDiff', array( $this, $out ) ) ) {
 546                         $this->loadNewText();
 547                         $out->setRevisionId( $this->mNewid );
 548                         $out->setRevisionTimestamp( $this->mNewRev->getTimestamp() );
 549                         $out->setArticleFlag( true );
 550
 551                         // NOTE: only needed for B/C: custom rendering of JS/CSS via hook
 552                         if ( $this->mNewPage->isCssJsSubpage() || $this->mNewPage->isCssOrJsPage() ) {
 553                                 // Stolen from Article::view --AG 2007-10-11
 554                                 // Give hooks a chance to customise the output
 555                                 // @todo standardize this crap into one function
 556                                 if ( ContentHandler::runLegacyHooks( 'ShowRawCssJs', array( $this->mNewContent, $this->mNewPage, $out ) ) ) {
 557                                         // NOTE: deprecated hook, B/C only
 558                                         // use the content object's own rendering
 559                                         $cnt = $this->mNewRev->getContent();
 560                                         $po = $cnt ? $cnt->getParserOutput( $this->mNewRev->getTitle(), $this->mNewRev->getId() ) : null;
 561                                         $txt = $po ? $po->getText() : '';
 562                                         $out->addHTML( $txt );
 563                                 }
 564                         } elseif ( !wfRunHooks( 'ArticleContentViewCustom', array( $this->mNewContent, $this->mNewPage, $out ) ) ) {
 565                                 // Handled by extension
 566                         } elseif ( !ContentHandler::runLegacyHooks( 'ArticleViewCustom', array( $this->mNewContent, $this->mNewPage, $out ) ) ) {
 567                                 // NOTE: deprecated hook, B/C only
 568                                 // Handled by extension
 569                         } else {
 570                                 // Normal page
 571                                 if ( $this->getTitle()->equals( $this->mNewPage ) ) {
 572                                         // If the Title stored in the context is the same as the one
 573                                         // of the new revision, we can use its associated WikiPage
 574                                         // object.
 575                                         $wikiPage = $this->getWikiPage();
 576                                 } else {
 577                                         // Otherwise we need to create our own WikiPage object
 578                                         $wikiPage = WikiPage::factory( $this->mNewPage );
 579                                 }
 580
 581                                 $parserOutput = $this->getParserOutput( $wikiPage, $this->mNewRev );
 582
 583                                 # Also try to load it as a redirect
 584                                 $rt = $this->mNewContent ? $this->mNewContent->getRedirectTarget() : null;
 585
 586                                 if ( $rt ) {
 587                                         $article = Article::newFromTitle( $this->mNewPage, $this->getContext() );
 588                                         $out->addHTML( $article->viewRedirect( $rt ) );
 589
 590                                         # WikiPage::getParserOutput() should not return false, but just in case
 591                                         if ( $parserOutput ) {
 592                                                 # Show categories etc.
 593                                                 $out->addParserOutputNoText( $parserOutput );
 594                                         }
 595                                 } elseif ( $parserOutput ) {
 596                                         $out->addParserOutput( $parserOutput );
 597                                 }
 598                         }
 599                 }
 600                 # @codingStandardsIgnoreEnd
 601
 602                 # Add redundant patrol link on bottom...
 603                 $out->addHTML( $this->markPatrolledLink() );
 604
 605                 wfProfileOut( __METHOD__ );
 606         }
 607
 608         protected function getParserOutput( WikiPage $page, Revision $rev ) {
 609                 $parserOptions = $page->makeParserOptions( $this->getContext() );
 610
 611                 if ( !$rev->isCurrent() || !$rev->getTitle()->quickUserCan( "edit" ) ) {
 612                         $parserOptions->setEditSection( false );
 613                 }
 614
 615                 $parserOutput = $page->getParserOutput( $parserOptions, $rev->getId() );
 616
 617                 return $parserOutput;
 618         }
 619
 620         /**
 621          * Get the diff text, send it to the OutputPage object
 622          * Returns false if the diff could not be generated, otherwise returns true
 623          *
 624          * @param string|bool $otitle Header for old text or false
 625          * @param string|bool $ntitle Header for new text or false
 626          * @param string $notice HTML between diff header and body
 627          *
 628          * @return bool
 629          */
 630         function showDiff( $otitle, $ntitle, $notice = '' ) {
 631                 $diff = $this->getDiff( $otitle, $ntitle, $notice );
 632                 if ( $diff === false ) {
 633                         $this->showMissingRevision();
 634
 635                         return false;
 636                 } else {
 637                         $this->showDiffStyle();
 638                         $this->getOutput()->addHTML( $diff );
 639
 640                         return true;
 641                 }
 642         }
 643
 644         /**
 645          * Add style sheets and supporting JS for diff display.
 646          */
 647         function showDiffStyle() {
 648                 $this->getOutput()->addModuleStyles( 'mediawiki.action.history.diff' );
 649         }
 650
 651         /**
 652          * Get complete diff table, including header
 653          *
 654          * @param string|bool $otitle Header for old text or false
 655          * @param string|bool $ntitle Header for new text or false
 656          * @param string $notice HTML between diff header and body
 657          * @return mixed
 658          */
 659         function getDiff( $otitle, $ntitle, $notice = '' ) {
 660                 $body = $this->getDiffBody();
 661                 if ( $body === false ) {
 662                         return false;
 663                 }
 664
 665                 $multi = $this->getMultiNotice();
 666                 // Display a message when the diff is empty
 667                 if ( $body === '' ) {
 668                         $notice .= '<div class="mw-diff-empty">' .
 669                                 $this->msg( 'diff-empty' )->parse() .
 670                                 "</div>\n";
 671                 }
 672
 673                 return $this->addHeader( $body, $otitle, $ntitle, $multi, $notice );
 674         }
 675
 676         /**
 677          * Get the diff table body, without header
 678          *
 679          * @return mixed (string/false)
 680          */
 681         public function getDiffBody() {
 682                 global $wgMemc;
 683                 wfProfileIn( __METHOD__ );
 684                 $this->mCacheHit = true;
 685                 // Check if the diff should be hidden from this user
 686                 if ( !$this->loadRevisionData() ) {
 687                         wfProfileOut( __METHOD__ );
 688
 689                         return false;
 690                 } elseif ( $this->mOldRev &&
 691                         !$this->mOldRev->userCan( Revision::DELETED_TEXT, $this->getUser() )
 692                 ) {
 693                         wfProfileOut( __METHOD__ );
 694
 695                         return false;
 696                 } elseif ( $this->mNewRev &&
 697                         !$this->mNewRev->userCan( Revision::DELETED_TEXT, $this->getUser() )
 698                 ) {
 699                         wfProfileOut( __METHOD__ );
 700
 701                         return false;
 702                 }
 703                 // Short-circuit
 704                 if ( $this->mOldRev === false || ( $this->mOldRev && $this->mNewRev
 705                         && $this->mOldRev->getID() == $this->mNewRev->getID() )
 706                 ) {
 707                         wfProfileOut( __METHOD__ );
 708
 709                         return '';
 710                 }
 711                 // Cacheable?
 712                 $key = false;
 713                 if ( $this->mOldid && $this->mNewid ) {
 714                         $key = $this->getDiffBodyCacheKey();
 715
 716                         // Try cache
 717                         if ( !$this->mRefreshCache ) {
 718                                 $difftext = $wgMemc->get( $key );
 719                                 if ( $difftext ) {
 720                                         wfIncrStats( 'diff_cache_hit' );
 721                                         $difftext = $this->localiseLineNumbers( $difftext );
 722                                         $difftext .= "\n<!-- diff cache key $key -->\n";
 723                                         wfProfileOut( __METHOD__ );
 724
 725                                         return $difftext;
 726                                 }
 727                         } // don't try to load but save the result
 728                 }
 729                 $this->mCacheHit = false;
 730
 731                 // Loadtext is permission safe, this just clears out the diff
 732                 if ( !$this->loadText() ) {
 733                         wfProfileOut( __METHOD__ );
 734
 735                         return false;
 736                 }
 737
 738                 $difftext = $this->generateContentDiffBody( $this->mOldContent, $this->mNewContent );
 739
 740                 // Save to cache for 7 days
 741                 if ( !wfRunHooks( 'AbortDiffCache', array( &$this ) ) ) {
 742                         wfIncrStats( 'diff_uncacheable' );
 743                 } elseif ( $key !== false && $difftext !== false ) {
 744                         wfIncrStats( 'diff_cache_miss' );
 745                         $wgMemc->set( $key, $difftext, 7 * 86400 );
 746                 } else {
 747                         wfIncrStats( 'diff_uncacheable' );
 748                 }
 749                 // Replace line numbers with the text in the user's language
 750                 if ( $difftext !== false ) {
 751                         $difftext = $this->localiseLineNumbers( $difftext );
 752                 }
 753                 wfProfileOut( __METHOD__ );
 754
 755                 return $difftext;
 756         }
 757
 758         /**
 759          * Returns the cache key for diff body text or content.
 760          *
 761          * @return string
 762          * @since 1.23
 763          * @throws MWException
 764          */
 765         protected function getDiffBodyCacheKey() {
 766                 if ( !$this->mOldid || !$this->mNewid ) {
 767                         throw new MWException( 'mOldid and mNewid must be set to get diff cache key.' );
 768                 }
 769
 770                 return wfMemcKey( 'diff', 'version', MW_DIFF_VERSION,
 771                         'oldid', $this->mOldid, 'newid', $this->mNewid );
 772         }
 773
 774         /**
 775          * Generate a diff, no caching.
 776          *
 777          * This implementation uses generateTextDiffBody() to generate a diff based on the default
 778          * serialization of the given Content objects. This will fail if $old or $new are not
 779          * instances of TextContent.
 780          *
 781          * Subclasses may override this to provide a different rendering for the diff,
 782          * perhaps taking advantage of the content's native form. This is required for all content
 783          * models that are not text based.
 784          *
 785          * @param $old Content: old content
 786          * @param $new Content: new content
 787          *
 788          * @return bool|string
 789          * @since 1.21
 790          * @throws MWException if $old or $new are not instances of TextContent.
 791          */
 792         function generateContentDiffBody( Content $old, Content $new ) {
 793                 if ( !( $old instanceof TextContent ) ) {
 794                         throw new MWException( "Diff not implemented for " . get_class( $old ) . "; " .
 795                                 "override generateContentDiffBody to fix this." );
 796                 }
 797
 798                 if ( !( $new instanceof TextContent ) ) {
 799                         throw new MWException( "Diff not implemented for " . get_class( $new ) . "; "
 800                                 . "override generateContentDiffBody to fix this." );
 801                 }
 802
 803                 $otext = $old->serialize();
 804                 $ntext = $new->serialize();
 805
 806                 return $this->generateTextDiffBody( $otext, $ntext );
 807         }
 808
 809         /**
 810          * Generate a diff, no caching
 811          *
 812          * @param string $otext old text, must be already segmented
 813          * @param string $ntext new text, must be already segmented
 814          * @return bool|string
 815          * @deprecated since 1.21, use generateContentDiffBody() instead!
 816          */
 817         function generateDiffBody( $otext, $ntext ) {
 818                 ContentHandler::deprecated( __METHOD__, "1.21" );
 819
 820                 return $this->generateTextDiffBody( $otext, $ntext );
 821         }
 822
 823         /**
 824          * Generate a diff, no caching
 825          *
 826          * @todo move this to TextDifferenceEngine, make DifferenceEngine abstract. At some point.
 827          *
 828          * @param string $otext old text, must be already segmented
 829          * @param string $ntext new text, must be already segmented
 830          * @return bool|string
 831          */
 832         function generateTextDiffBody( $otext, $ntext ) {
 833                 global $wgExternalDiffEngine, $wgContLang;
 834
 835                 wfProfileIn( __METHOD__ );
 836
 837                 $otext = str_replace( "\r\n", "\n", $otext );
 838                 $ntext = str_replace( "\r\n", "\n", $ntext );
 839
 840                 if ( $wgExternalDiffEngine == 'wikidiff' && function_exists( 'wikidiff_do_diff' ) ) {
 841                         # For historical reasons, external diff engine expects
 842                         # input text to be HTML-escaped already
 843                         $otext = htmlspecialchars( $wgContLang->segmentForDiff( $otext ) );
 844                         $ntext = htmlspecialchars( $wgContLang->segmentForDiff( $ntext ) );
 845                         wfProfileOut( __METHOD__ );
 846
 847                         return $wgContLang->unsegmentForDiff( wikidiff_do_diff( $otext, $ntext, 2 ) ) .
 848                         $this->debug( 'wikidiff1' );
 849                 }
 850
 851                 if ( $wgExternalDiffEngine == 'wikidiff2' && function_exists( 'wikidiff2_do_diff' ) ) {
 852                         # Better external diff engine, the 2 may some day be dropped
 853                         # This one does the escaping and segmenting itself
 854                         wfProfileIn( 'wikidiff2_do_diff' );
 855                         $text = wikidiff2_do_diff( $otext, $ntext, 2 );
 856                         $text .= $this->debug( 'wikidiff2' );
 857                         wfProfileOut( 'wikidiff2_do_diff' );
 858                         wfProfileOut( __METHOD__ );
 859
 860                         return $text;
 861                 }
 862                 if ( $wgExternalDiffEngine != 'wikidiff3' && $wgExternalDiffEngine !== false ) {
 863                         # Diff via the shell
 864                         $tmpDir = wfTempDir();
 865                         $tempName1 = tempnam( $tmpDir, 'diff_' );
 866                         $tempName2 = tempnam( $tmpDir, 'diff_' );
 867
 868                         $tempFile1 = fopen( $tempName1, "w" );
 869                         if ( !$tempFile1 ) {
 870                                 wfProfileOut( __METHOD__ );
 871
 872                                 return false;
 873                         }
 874                         $tempFile2 = fopen( $tempName2, "w" );
 875                         if ( !$tempFile2 ) {
 876                                 wfProfileOut( __METHOD__ );
 877
 878                                 return false;
 879                         }
 880                         fwrite( $tempFile1, $otext );
 881                         fwrite( $tempFile2, $ntext );
 882                         fclose( $tempFile1 );
 883                         fclose( $tempFile2 );
 884                         $cmd = wfEscapeShellArg( $wgExternalDiffEngine, $tempName1, $tempName2 );
 885                         wfProfileIn( __METHOD__ . "-shellexec" );
 886                         $difftext = wfShellExec( $cmd );
 887                         $difftext .= $this->debug( "external $wgExternalDiffEngine" );
 888                         wfProfileOut( __METHOD__ . "-shellexec" );
 889                         unlink( $tempName1 );
 890                         unlink( $tempName2 );
 891                         wfProfileOut( __METHOD__ );
 892
 893                         return $difftext;
 894                 }
 895
 896                 # Native PHP diff
 897                 $ota = explode( "\n", $wgContLang->segmentForDiff( $otext ) );
 898                 $nta = explode( "\n", $wgContLang->segmentForDiff( $ntext ) );
 899                 $diffs = new Diff( $ota, $nta );
 900                 $formatter = new TableDiffFormatter();
 901                 $difftext = $wgContLang->unsegmentForDiff( $formatter->format( $diffs ) ) .
 902                         wfProfileOut( __METHOD__ );
 903
 904                 return $difftext;
 905         }
 906
 907         /**
 908          * Generate a debug comment indicating diff generating time,
 909          * server node, and generator backend.
 910          *
 911          * @param String $generator : What diff engine was used
 912          *
 913          * @return string
 914          */
 915         protected function debug( $generator = "internal" ) {
 916                 global $wgShowHostnames;
 917                 if ( !$this->enableDebugComment ) {
 918                         return '';
 919                 }
 920                 $data = array( $generator );
 921                 if ( $wgShowHostnames ) {
 922                         $data[] = wfHostname();
 923                 }
 924                 $data[] = wfTimestamp( TS_DB );
 925
 926                 return "<!-- diff generator: " .
 927                         implode( " ", array_map( "htmlspecialchars", $data ) ) .
 928                         " -->\n";
 929         }
 930
 931         /**
 932          * Replace line numbers with the text in the user's language
 933          *
 934          * @param String $text
 935          *
 936          * @return mixed
 937          */
 938         function localiseLineNumbers( $text ) {
 939                 return preg_replace_callback(
 940                         '/<!--LINE (\d+)-->/',
 941                         array( &$this, 'localiseLineNumbersCb' ),
 942                         $text
 943                 );
 944         }
 945
 946         function localiseLineNumbersCb( $matches ) {
 947                 if ( $matches[1] === '1' && $this->mReducedLineNumbers ) {
 948                         return '';
 949                 }
 950
 951                 return $this->msg( 'lineno' )->numParams( $matches[1] )->escaped();
 952         }
 953
 954         /**
 955          * If there are revisions between the ones being compared, return a note saying so.
 956          * @return string
 957          */
 958         function getMultiNotice() {
 959                 if ( !is_object( $this->mOldRev ) || !is_object( $this->mNewRev ) ) {
 960                         return '';
 961                 } elseif ( !$this->mOldPage->equals( $this->mNewPage ) ) {
 962                         // Comparing two different pages? Count would be meaningless.
 963                         return '';
 964                 }
 965
 966                 if ( $this->mOldRev->getTimestamp() > $this->mNewRev->getTimestamp() ) {
 967                         $oldRev = $this->mNewRev; // flip
 968                         $newRev = $this->mOldRev; // flip
 969                 } else { // normal case
 970                         $oldRev = $this->mOldRev;
 971                         $newRev = $this->mNewRev;
 972                 }
 973
 974                 $nEdits = $this->mNewPage->countRevisionsBetween( $oldRev, $newRev );
 975                 if ( $nEdits > 0 ) {
 976                         $limit = 100; // use diff-multi-manyusers if too many users
 977                         $numUsers = $this->mNewPage->countAuthorsBetween( $oldRev, $newRev, $limit );
 978
 979                         return self::intermediateEditsMsg( $nEdits, $numUsers, $limit );
 980                 }
 981
 982                 return ''; // nothing
 983         }
 984
 985         /**
 986          * Get a notice about how many intermediate edits and users there are
 987          * @param $numEdits int
 988          * @param $numUsers int
 989          * @param $limit int
 990          * @return string
 991          */
 992         public static function intermediateEditsMsg( $numEdits, $numUsers, $limit ) {
 993                 if ( $numUsers > $limit ) {
 994                         $msg = 'diff-multi-manyusers';
 995                         $numUsers = $limit;
 996                 } else {
 997                         $msg = 'diff-multi';
 998                 }
 999
1000                 return wfMessage( $msg )->numParams( $numEdits, $numUsers )->parse();
1001         }
1002
1003         /**
1004          * Get a header for a specified revision.
1005          *
1006          * @param $rev Revision
1007          * @param string $complete 'complete' to get the header wrapped depending
1008          *        the visibility of the revision and a link to edit the page.
1009          * @return String HTML fragment
1010          */
1011         protected function getRevisionHeader( Revision $rev, $complete = '' ) {
1012                 $lang = $this->getLanguage();
1013                 $user = $this->getUser();
1014                 $revtimestamp = $rev->getTimestamp();
1015                 $timestamp = $lang->userTimeAndDate( $revtimestamp, $user );
1016                 $dateofrev = $lang->userDate( $revtimestamp, $user );
1017                 $timeofrev = $lang->userTime( $revtimestamp, $user );
1018
1019                 $header = $this->msg(
1020                         $rev->isCurrent() ? 'currentrev-asof' : 'revisionasof',
1021                         $timestamp,
1022                         $dateofrev,
1023                         $timeofrev
1024                 )->escaped();
1025
1026                 if ( $complete !== 'complete' ) {
1027                         return $header;
1028                 }
1029
1030                 $title = $rev->getTitle();
1031
1032                 $header = Linker::linkKnown( $title, $header, array(),
1033                         array( 'oldid' => $rev->getID() ) );
1034
1035                 if ( $rev->userCan( Revision::DELETED_TEXT, $user ) ) {
1036                         $editQuery = array( 'action' => 'edit' );
1037                         if ( !$rev->isCurrent() ) {
1038                                 $editQuery['oldid'] = $rev->getID();
1039                         }
1040
1041                         $key = $title->quickUserCan( 'edit', $user ) ? 'editold' : 'viewsourceold';
1042                         $msg = $this->msg( $key )->escaped();
1043                         $header .= ' ' . $this->msg( 'parentheses' )->rawParams(
1044                                 Linker::linkKnown( $title, $msg, array(), $editQuery ) )->plain();
1045                         if ( $rev->isDeleted( Revision::DELETED_TEXT ) ) {
1046                                 $header = Html::rawElement(
1047                                         'span',
1048                                         array( 'class' => 'history-deleted' ),
1049                                         $header
1050                                 );
1051                         }
1052                 } else {
1053                         $header = Html::rawElement( 'span', array( 'class' => 'history-deleted' ), $header );
1054                 }
1055
1056                 return $header;
1057         }
1058
1059         /**
1060          * Add the header to a diff body
1061          *
1062          * @param string $diff Diff body
1063          * @param string $otitle Old revision header
1064          * @param string $ntitle New revision header
1065          * @param string $multi Notice telling user that there are intermediate
1066          *   revisions between the ones being compared
1067          * @param string $notice Other notices, e.g. that user is viewing deleted content
1068          *
1069          * @return string
1070          */
1071         function addHeader( $diff, $otitle, $ntitle, $multi = '', $notice = '' ) {
1072                 // shared.css sets diff in interface language/dir, but the actual content
1073                 // is often in a different language, mostly the page content language/dir
1074                 $tableClass = 'diff diff-contentalign-' . htmlspecialchars( $this->getDiffLang()->alignStart() );
1075                 $header = "<table class='$tableClass'>";
1076
1077                 if ( !$diff && !$otitle ) {
1078                         $header .= "
1079                         <tr style='vertical-align: top;'>
1080                         <td class='diff-ntitle'>{$ntitle}</td>
1081                         </tr>";
1082                         $multiColspan = 1;
1083                 } else {
1084                         if ( $diff ) { // Safari/Chrome show broken output if cols not used
1085                                 $header .= "
1086                                 <col class='diff-marker' />
1087                                 <col class='diff-content' />
1088                                 <col class='diff-marker' />
1089                                 <col class='diff-content' />";
1090                                 $colspan = 2;
1091                                 $multiColspan = 4;
1092                         } else {
1093                                 $colspan = 1;
1094                                 $multiColspan = 2;
1095                         }
1096                         if ( $otitle || $ntitle ) {
1097                                 $header .= "
1098                                 <tr style='vertical-align: top;'>
1099                                 <td colspan='$colspan' class='diff-otitle'>{$otitle}</td>
1100                                 <td colspan='$colspan' class='diff-ntitle'>{$ntitle}</td>
1101                                 </tr>";
1102                         }
1103                 }
1104
1105                 if ( $multi != '' ) {
1106                         $header .= "<tr><td colspan='{$multiColspan}' style='text-align: center;' " .
1107                                 "class='diff-multi'>{$multi}</td></tr>";
1108                 }
1109                 if ( $notice != '' ) {
1110                         $header .= "<tr><td colspan='{$multiColspan}' style='text-align: center;'>{$notice}</td></tr>";
1111                 }
1112
1113                 return $header . $diff . "</table>";
1114         }
1115
1116         /**
1117          * Use specified text instead of loading from the database
1118          * @deprecated since 1.21, use setContent() instead.
1119          */
1120         function setText( $oldText, $newText ) {
1121                 ContentHandler::deprecated( __METHOD__, "1.21" );
1122
1123                 $oldContent = ContentHandler::makeContent( $oldText, $this->getTitle() );
1124                 $newContent = ContentHandler::makeContent( $newText, $this->getTitle() );
1125
1126                 $this->setContent( $oldContent, $newContent );
1127         }
1128
1129         /**
1130          * Use specified text instead of loading from the database
1131          * @since 1.21
1132          */
1133         function setContent( Content $oldContent, Content $newContent ) {
1134                 $this->mOldContent = $oldContent;
1135                 $this->mNewContent = $newContent;
1136
1137                 $this->mTextLoaded = 2;
1138                 $this->mRevisionsLoaded = true;
1139         }
1140
1141         /**
1142          * Set the language in which the diff text is written
1143          * (Defaults to page content language).
1144          * @since 1.19
1145          */
1146         function setTextLanguage( $lang ) {
1147                 $this->mDiffLang = wfGetLangObj( $lang );
1148         }
1149
1150         /**
1151          * Maps a revision pair definition as accepted by DifferenceEngine constructor
1152          * to a pair of actual integers representing revision ids.
1153          *
1154          * @param int $old Revision id, e.g. from URL parameter 'oldid'
1155          * @param int|string $new Revision id or strings 'next' or 'prev', e.g. from URL parameter 'diff'
1156          * @return array Array of two revision ids, older first, later second.
1157          *     Zero signifies invalid argument passed.
1158          *     false signifies that there is no previous/next revision ($old is the oldest/newest one).
1159          */
1160         public function mapDiffPrevNext( $old, $new ) {
1161                 if ( $new === 'prev' ) {
1162                         // Show diff between revision $old and the previous one. Get previous one from DB.
1163                         $newid = intval( $old );
1164                         $oldid = $this->getTitle()->getPreviousRevisionID( $newid );
1165                 } elseif ( $new === 'next' ) {
1166                         // Show diff between revision $old and the next one. Get next one from DB.
1167                         $oldid = intval( $old );
1168                         $newid = $this->getTitle()->getNextRevisionID( $oldid );
1169                 } else {
1170                         $oldid = intval( $old );
1171                         $newid = intval( $new );
1172                 }
1173
1174                 return array( $oldid, $newid );
1175         }
1176
1177         /**
1178          * Load revision IDs
1179          */
1180         private function loadRevisionIds() {
1181                 if ( $this->mRevisionsIdsLoaded ) {
1182                         return;
1183                 }
1184
1185                 $this->mRevisionsIdsLoaded = true;
1186
1187                 $old = $this->mOldid;
1188                 $new = $this->mNewid;
1189
1190                 list( $this->mOldid, $this->mNewid ) = self::mapDiffPrevNext( $old, $new );
1191                 if ( $new === 'next' && $this->mNewid === false ) {
1192                         # if no result, NewId points to the newest old revision. The only newer
1193                         # revision is cur, which is "0".
1194                         $this->mNewid = 0;
1195                 }
1196
1197                 wfRunHooks(
1198                         'NewDifferenceEngine',
1199                         array( $this->getTitle(), &$this->mOldid, &$this->mNewid, $old, $new )
1200                 );
1201         }
1202
1203         /**
1204          * Load revision metadata for the specified articles. If newid is 0, then compare
1205          * the old article in oldid to the current article; if oldid is 0, then
1206          * compare the current article to the immediately previous one (ignoring the
1207          * value of newid).
1208          *
1209          * If oldid is false, leave the corresponding revision object set
1210          * to false. This is impossible via ordinary user input, and is provided for
1211          * API convenience.
1212          *
1213          * @return bool
1214          */
1215         function loadRevisionData() {
1216                 if ( $this->mRevisionsLoaded ) {
1217                         return true;
1218                 }
1219
1220                 // Whether it succeeds or fails, we don't want to try again
1221                 $this->mRevisionsLoaded = true;
1222
1223                 $this->loadRevisionIds();
1224
1225                 // Load the new revision object
1226                 if ( $this->mNewid ) {
1227                         $this->mNewRev = Revision::newFromId( $this->mNewid );
1228                 } else {
1229                         $this->mNewRev = Revision::newFromTitle(
1230                                 $this->getTitle(),
1231                                 false,
1232                                 Revision::READ_NORMAL
1233                         );
1234                 }
1235
1236                 if ( !$this->mNewRev instanceof Revision ) {
1237                         return false;
1238                 }
1239
1240                 // Update the new revision ID in case it was 0 (makes life easier doing UI stuff)
1241                 $this->mNewid = $this->mNewRev->getId();
1242                 $this->mNewPage = $this->mNewRev->getTitle();
1243
1244                 // Load the old revision object
1245                 $this->mOldRev = false;
1246                 if ( $this->mOldid ) {
1247                         $this->mOldRev = Revision::newFromId( $this->mOldid );
1248                 } elseif ( $this->mOldid === 0 ) {
1249                         $rev = $this->mNewRev->getPrevious();
1250                         if ( $rev ) {
1251                                 $this->mOldid = $rev->getId();
1252                                 $this->mOldRev = $rev;
1253                         } else {
1254                                 // No previous revision; mark to show as first-version only.
1255                                 $this->mOldid = false;
1256                                 $this->mOldRev = false;
1257                         }
1258                 } /* elseif ( $this->mOldid === false ) leave mOldRev false; */
1259
1260                 if ( is_null( $this->mOldRev ) ) {
1261                         return false;
1262                 }
1263
1264                 if ( $this->mOldRev ) {
1265                         $this->mOldPage = $this->mOldRev->getTitle();
1266                 }
1267
1268                 // Load tags information for both revisions
1269                 $dbr = wfGetDB( DB_SLAVE );
1270                 if ( $this->mOldid !== false ) {
1271                         $this->mOldTags = $dbr->selectField(
1272                                 'tag_summary',
1273                                 'ts_tags',
1274                                 array( 'ts_rev_id' => $this->mOldid ),
1275                                 __METHOD__
1276                         );
1277                 } else {
1278                         $this->mOldTags = false;
1279                 }
1280                 $this->mNewTags = $dbr->selectField(
1281                         'tag_summary',
1282                         'ts_tags',
1283                         array( 'ts_rev_id' => $this->mNewid ),
1284                         __METHOD__
1285                 );
1286
1287                 return true;
1288         }
1289
1290         /**
1291          * Load the text of the revisions, as well as revision data.
1292          *
1293          * @return bool
1294          */
1295         function loadText() {
1296                 if ( $this->mTextLoaded == 2 ) {
1297                         return true;
1298                 }
1299
1300                 // Whether it succeeds or fails, we don't want to try again
1301                 $this->mTextLoaded = 2;
1302
1303                 if ( !$this->loadRevisionData() ) {
1304                         return false;
1305                 }
1306
1307                 if ( $this->mOldRev ) {
1308                         $this->mOldContent = $this->mOldRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1309                         if ( $this->mOldContent === null ) {
1310                                 return false;
1311                         }
1312                 }
1313
1314                 if ( $this->mNewRev ) {
1315                         $this->mNewContent = $this->mNewRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1316                         if ( $this->mNewContent === null ) {
1317                                 return false;
1318                         }
1319                 }
1320
1321                 return true;
1322         }
1323
1324         /**
1325          * Load the text of the new revision, not the old one
1326          *
1327          * @return bool
1328          */
1329         function loadNewText() {
1330                 if ( $this->mTextLoaded >= 1 ) {
1331                         return true;
1332                 }
1333
1334                 $this->mTextLoaded = 1;
1335
1336                 if ( !$this->loadRevisionData() ) {
1337                         return false;
1338                 }
1339
1340                 $this->mNewContent = $this->mNewRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1341
1342                 return true;
1343         }
1344 }