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
  38         /** @var int */
  39         public $mOldid;
  40
  41         /** @var int */
  42         public $mNewid;
  43
  44         private $mOldTags;
  45         private $mNewTags;
  46
  47         /** @var Content */
  48         public $mOldContent;
  49
  50         /** @var Content */
  51         public $mNewContent;
  52
  53         /** @var Language */
  54         protected $mDiffLang;
  55
  56         /** @var Title */
  57         public $mOldPage;
  58
  59         /** @var Title */
  60         public $mNewPage;
  61
  62         /** @var Revision */
  63         public $mOldRev;
  64
  65         /** @var Revision */
  66         public $mNewRev;
  67
  68         /** @var bool Have the revisions IDs been loaded */
  69         private $mRevisionsIdsLoaded = false;
  70
  71         /** @var bool Have the revisions been loaded */
  72         public $mRevisionsLoaded = false;
  73
  74         /** @var int How many text blobs have been loaded, 0, 1 or 2? */
  75         public $mTextLoaded = 0;
  76
  77         /** @var bool Was the diff fetched from cache? */
  78         public $mCacheHit = false;
  79
  80         /**
  81          * Set this to true to add debug info to the HTML output.
  82          * Warning: this may cause RSS readers to spuriously mark articles as "new"
  83          * (bug 20601)
  84          */
  85         public $enableDebugComment = false;
  86
  87         /** @var bool If true, line X is not displayed when X is 1, for example
  88          *    to increase readability and conserve space with many small diffs.
  89          */
  90         protected $mReducedLineNumbers = false;
  91
  92         /** @var string Link to action=markpatrolled */
  93         protected $mMarkPatrolledLink = null;
  94
  95         /** @var bool Show rev_deleted content if allowed */
  96         protected $unhide = false;
  97         /**#@-*/
  98
  99         /**
 100          * Constructor
 101          * @param IContextSource $context Context to use, anything else will be ignored
 102          * @param int $old Old ID we want to show and diff with.
 103          * @param string|int $new Either revision ID or 'prev' or 'next'. Default: 0.
 104          * @param int $rcid Deprecated, no longer used!
 105          * @param bool $refreshCache If set, refreshes the diff cache
 106          * @param bool $unhide If set, allow viewing deleted revs
 107          */
 108         public function __construct( $context = null, $old = 0, $new = 0, $rcid = 0,
 109                 $refreshCache = false, $unhide = false
 110         ) {
 111                 if ( $context instanceof IContextSource ) {
 112                         $this->setContext( $context );
 113                 }
 114
 115                 wfDebug( "DifferenceEngine old '$old' new '$new' rcid '$rcid'\n" );
 116
 117                 $this->mOldid = $old;
 118                 $this->mNewid = $new;
 119                 $this->mRefreshCache = $refreshCache;
 120                 $this->unhide = $unhide;
 121         }
 122
 123         /**
 124          * @param bool $value
 125          */
 126         public function setReducedLineNumbers( $value = true ) {
 127                 $this->mReducedLineNumbers = $value;
 128         }
 129
 130         /**
 131          * @return Language
 132          */
 133         public function getDiffLang() {
 134                 if ( $this->mDiffLang === null ) {
 135                         # Default language in which the diff text is written.
 136                         $this->mDiffLang = $this->getTitle()->getPageLanguage();
 137                 }
 138
 139                 return $this->mDiffLang;
 140         }
 141
 142         /**
 143          * @return bool
 144          */
 145         public function wasCacheHit() {
 146                 return $this->mCacheHit;
 147         }
 148
 149         /**
 150          * @return int
 151          */
 152         public function getOldid() {
 153                 $this->loadRevisionIds();
 154
 155                 return $this->mOldid;
 156         }
 157
 158         /**
 159          * @return bool|int
 160          */
 161         public function getNewid() {
 162                 $this->loadRevisionIds();
 163
 164                 return $this->mNewid;
 165         }
 166
 167         /**
 168          * Look up a special:Undelete link to the given deleted revision id,
 169          * as a workaround for being unable to load deleted diffs in currently.
 170          *
 171          * @param int $id Revision ID
 172          *
 173          * @return mixed URL or false
 174          */
 175         public function deletedLink( $id ) {
 176                 if ( $this->getUser()->isAllowed( 'deletedhistory' ) ) {
 177                         $dbr = wfGetDB( DB_SLAVE );
 178                         $row = $dbr->selectRow( 'archive', '*',
 179                                 array( 'ar_rev_id' => $id ),
 180                                 __METHOD__ );
 181                         if ( $row ) {
 182                                 $rev = Revision::newFromArchiveRow( $row );
 183                                 $title = Title::makeTitleSafe( $row->ar_namespace, $row->ar_title );
 184
 185                                 return SpecialPage::getTitleFor( 'Undelete' )->getFullURL( array(
 186                                         'target' => $title->getPrefixedText(),
 187                                         'timestamp' => $rev->getTimestamp()
 188                                 ) );
 189                         }
 190                 }
 191
 192                 return false;
 193         }
 194
 195         /**
 196          * Build a wikitext link toward a deleted revision, if viewable.
 197          *
 198          * @param int $id Revision ID
 199          *
 200          * @return string Wikitext fragment
 201          */
 202         public function deletedIdMarker( $id ) {
 203                 $link = $this->deletedLink( $id );
 204                 if ( $link ) {
 205                         return "[$link $id]";
 206                 } else {
 207                         return $id;
 208                 }
 209         }
 210
 211         private function showMissingRevision() {
 212                 $out = $this->getOutput();
 213
 214                 $missing = array();
 215                 if ( $this->mOldRev === null ||
 216                         ( $this->mOldRev && $this->mOldContent === null )
 217                 ) {
 218                         $missing[] = $this->deletedIdMarker( $this->mOldid );
 219                 }
 220                 if ( $this->mNewRev === null ||
 221                         ( $this->mNewRev && $this->mNewContent === null )
 222                 ) {
 223                         $missing[] = $this->deletedIdMarker( $this->mNewid );
 224                 }
 225
 226                 $out->setPageTitle( $this->msg( 'errorpagetitle' ) );
 227                 $msg = $this->msg( 'difference-missing-revision' )
 228                         ->params( $this->getLanguage()->listToText( $missing ) )
 229                         ->numParams( count( $missing ) )
 230                         ->parseAsBlock();
 231                 $out->addHtml( $msg );
 232         }
 233
 234         public function showDiffPage( $diffOnly = false ) {
 235                 wfProfileIn( __METHOD__ );
 236
 237                 # Allow frames except in certain special cases
 238                 $out = $this->getOutput();
 239                 $out->allowClickjacking();
 240                 $out->setRobotPolicy( 'noindex,nofollow' );
 241
 242                 if ( !$this->loadRevisionData() ) {
 243                         $this->showMissingRevision();
 244                         wfProfileOut( __METHOD__ );
 245
 246                         return;
 247                 }
 248
 249                 $user = $this->getUser();
 250                 $permErrors = $this->mNewPage->getUserPermissionsErrors( 'read', $user );
 251                 if ( $this->mOldPage ) { # mOldPage might not be set, see below.
 252                         $permErrors = wfMergeErrorArrays( $permErrors,
 253                                 $this->mOldPage->getUserPermissionsErrors( 'read', $user ) );
 254                 }
 255                 if ( count( $permErrors ) ) {
 256                         wfProfileOut( __METHOD__ );
 257                         throw new PermissionsError( 'read', $permErrors );
 258                 }
 259
 260                 $rollback = '';
 261
 262                 $query = array();
 263                 # Carry over 'diffonly' param via navigation links
 264                 if ( $diffOnly != $user->getBoolOption( 'diffonly' ) ) {
 265                         $query['diffonly'] = $diffOnly;
 266                 }
 267                 # Cascade unhide param in links for easy deletion browsing
 268                 if ( $this->unhide ) {
 269                         $query['unhide'] = 1;
 270                 }
 271
 272                 # Check if one of the revisions is deleted/suppressed
 273                 $deleted = $suppressed = false;
 274                 $allowed = $this->mNewRev->userCan( Revision::DELETED_TEXT, $user );
 275
 276                 $revisionTools = array();
 277
 278                 # mOldRev is false if the difference engine is called with a "vague" query for
 279                 # a diff between a version V and its previous version V' AND the version V
 280                 # is the first version of that article. In that case, V' does not exist.
 281                 if ( $this->mOldRev === false ) {
 282                         $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 283                         $samePage = true;
 284                         $oldHeader = '';
 285                 } else {
 286                         Hooks::run( 'DiffViewHeader', array( $this, $this->mOldRev, $this->mNewRev ) );
 287
 288                         if ( $this->mNewPage->equals( $this->mOldPage ) ) {
 289                                 $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 290                                 $samePage = true;
 291                         } else {
 292                                 $out->setPageTitle( $this->msg( 'difference-title-multipage',
 293                                         $this->mOldPage->getPrefixedText(), $this->mNewPage->getPrefixedText() ) );
 294                                 $out->addSubtitle( $this->msg( 'difference-multipage' ) );
 295                                 $samePage = false;
 296                         }
 297
 298                         if ( $samePage && $this->mNewPage->quickUserCan( 'edit', $user ) ) {
 299                                 if ( $this->mNewRev->isCurrent() && $this->mNewPage->userCan( 'rollback', $user ) ) {
 300                                         $rollbackLink = Linker::generateRollback( $this->mNewRev, $this->getContext() );
 301                                         if ( $rollbackLink ) {
 302                                                 $out->preventClickjacking();
 303                                                 $rollback = '&#160;&#160;&#160;' . $rollbackLink;
 304                                         }
 305                                 }
 306
 307                                 if ( !$this->mOldRev->isDeleted( Revision::DELETED_TEXT ) &&
 308                                         !$this->mNewRev->isDeleted( Revision::DELETED_TEXT )
 309                                 ) {
 310                                         $undoLink = Html::element( 'a', array(
 311                                                         'href' => $this->mNewPage->getLocalURL( array(
 312                                                                 'action' => 'edit',
 313                                                                 'undoafter' => $this->mOldid,
 314                                                                 'undo' => $this->mNewid
 315                                                         ) ),
 316                                                         'title' => Linker::titleAttrib( 'undo' ),
 317                                                 ),
 318                                                 $this->msg( 'editundo' )->text()
 319                                         );
 320                                         $revisionTools['mw-diff-undo'] = $undoLink;
 321                                 }
 322                         }
 323
 324                         # Make "previous revision link"
 325                         if ( $samePage && $this->mOldRev->getPrevious() ) {
 326                                 $prevlink = Linker::linkKnown(
 327                                         $this->mOldPage,
 328                                         $this->msg( 'previousdiff' )->escaped(),
 329                                         array( 'id' => 'differences-prevlink' ),
 330                                         array( 'diff' => 'prev', 'oldid' => $this->mOldid ) + $query
 331                                 );
 332                         } else {
 333                                 $prevlink = '&#160;';
 334                         }
 335
 336                         if ( $this->mOldRev->isMinor() ) {
 337                                 $oldminor = ChangesList::flag( 'minor' );
 338                         } else {
 339                                 $oldminor = '';
 340                         }
 341
 342                         $ldel = $this->revisionDeleteLink( $this->mOldRev );
 343                         $oldRevisionHeader = $this->getRevisionHeader( $this->mOldRev, 'complete' );
 344                         $oldChangeTags = ChangeTags::formatSummaryRow( $this->mOldTags, 'diff' );
 345
 346                         $oldHeader = '<div id="mw-diff-otitle1"><strong>' . $oldRevisionHeader . '</strong></div>' .
 347                                 '<div id="mw-diff-otitle2">' .
 348                                 Linker::revUserTools( $this->mOldRev, !$this->unhide ) . '</div>' .
 349                                 '<div id="mw-diff-otitle3">' . $oldminor .
 350                                 Linker::revComment( $this->mOldRev, !$diffOnly, !$this->unhide ) . $ldel . '</div>' .
 351                                 '<div id="mw-diff-otitle5">' . $oldChangeTags[0] . '</div>' .
 352                                 '<div id="mw-diff-otitle4">' . $prevlink . '</div>';
 353
 354                         if ( $this->mOldRev->isDeleted( Revision::DELETED_TEXT ) ) {
 355                                 $deleted = true; // old revisions text is hidden
 356                                 if ( $this->mOldRev->isDeleted( Revision::DELETED_RESTRICTED ) ) {
 357                                         $suppressed = true; // also suppressed
 358                                 }
 359                         }
 360
 361                         # Check if this user can see the revisions
 362                         if ( !$this->mOldRev->userCan( Revision::DELETED_TEXT, $user ) ) {
 363                                 $allowed = false;
 364                         }
 365                 }
 366
 367                 # Make "next revision link"
 368                 # Skip next link on the top revision
 369                 if ( $samePage && !$this->mNewRev->isCurrent() ) {
 370                         $nextlink = Linker::linkKnown(
 371                                 $this->mNewPage,
 372                                 $this->msg( 'nextdiff' )->escaped(),
 373                                 array( 'id' => 'differences-nextlink' ),
 374                                 array( 'diff' => 'next', 'oldid' => $this->mNewid ) + $query
 375                         );
 376                 } else {
 377                         $nextlink = '&#160;';
 378                 }
 379
 380                 if ( $this->mNewRev->isMinor() ) {
 381                         $newminor = ChangesList::flag( 'minor' );
 382                 } else {
 383                         $newminor = '';
 384                 }
 385
 386                 # Handle RevisionDelete links...
 387                 $rdel = $this->revisionDeleteLink( $this->mNewRev );
 388
 389                 # Allow extensions to define their own revision tools
 390                 Hooks::run( 'DiffRevisionTools', array( $this->mNewRev, &$revisionTools, $this->mOldRev ) );
 391                 $formattedRevisionTools = array();
 392                 // Put each one in parentheses (poor man's button)
 393                 foreach ( $revisionTools as $key => $tool ) {
 394                         $toolClass = is_string( $key ) ? $key : 'mw-diff-tool';
 395                         $element = Html::rawElement(
 396                                 'span',
 397                                 array( 'class' => $toolClass ),
 398                                 $this->msg( 'parentheses' )->rawParams( $tool )->escaped()
 399                         );
 400                         $formattedRevisionTools[] = $element;
 401                 }
 402                 $newRevisionHeader = $this->getRevisionHeader( $this->mNewRev, 'complete' ) .
 403                         ' ' . implode( ' ', $formattedRevisionTools );
 404                 $newChangeTags = ChangeTags::formatSummaryRow( $this->mNewTags, 'diff' );
 405
 406                 $newHeader = '<div id="mw-diff-ntitle1"><strong>' . $newRevisionHeader . '</strong></div>' .
 407                         '<div id="mw-diff-ntitle2">' . Linker::revUserTools( $this->mNewRev, !$this->unhide ) .
 408                         " $rollback</div>" .
 409                         '<div id="mw-diff-ntitle3">' . $newminor .
 410                         Linker::revComment( $this->mNewRev, !$diffOnly, !$this->unhide ) . $rdel . '</div>' .
 411                         '<div id="mw-diff-ntitle5">' . $newChangeTags[0] . '</div>' .
 412                         '<div id="mw-diff-ntitle4">' . $nextlink . $this->markPatrolledLink() . '</div>';
 413
 414                 if ( $this->mNewRev->isDeleted( Revision::DELETED_TEXT ) ) {
 415                         $deleted = true; // new revisions text is hidden
 416                         if ( $this->mNewRev->isDeleted( Revision::DELETED_RESTRICTED ) ) {
 417                                 $suppressed = true; // also suppressed
 418                         }
 419                 }
 420
 421                 # If the diff cannot be shown due to a deleted revision, then output
 422                 # the diff header and links to unhide (if available)...
 423                 if ( $deleted && ( !$this->unhide || !$allowed ) ) {
 424                         $this->showDiffStyle();
 425                         $multi = $this->getMultiNotice();
 426                         $out->addHTML( $this->addHeader( '', $oldHeader, $newHeader, $multi ) );
 427                         if ( !$allowed ) {
 428                                 $msg = $suppressed ? 'rev-suppressed-no-diff' : 'rev-deleted-no-diff';
 429                                 # Give explanation for why revision is not visible
 430                                 $out->wrapWikiMsg( "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 431                                         array( $msg ) );
 432                         } else {
 433                                 # Give explanation and add a link to view the diff...
 434                                 $query = $this->getRequest()->appendQueryValue( 'unhide', '1', true );
 435                                 $link = $this->getTitle()->getFullURL( $query );
 436                                 $msg = $suppressed ? 'rev-suppressed-unhide-diff' : 'rev-deleted-unhide-diff';
 437                                 $out->wrapWikiMsg(
 438                                         "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 439                                         array( $msg, $link )
 440                                 );
 441                         }
 442                 # Otherwise, output a regular diff...
 443                 } else {
 444                         # Add deletion notice if the user is viewing deleted content
 445                         $notice = '';
 446                         if ( $deleted ) {
 447                                 $msg = $suppressed ? 'rev-suppressed-diff-view' : 'rev-deleted-diff-view';
 448                                 $notice = "<div id='mw-$msg' class='mw-warning plainlinks'>\n" .
 449                                         $this->msg( $msg )->parse() .
 450                                         "</div>\n";
 451                         }
 452                         $this->showDiff( $oldHeader, $newHeader, $notice );
 453                         if ( !$diffOnly ) {
 454                                 $this->renderNewRevision();
 455                         }
 456                 }
 457                 wfProfileOut( __METHOD__ );
 458         }
 459
 460         /**
 461          * Get a link to mark the change as patrolled, or '' if there's either no
 462          * revision to patrol or the user is not allowed to to it.
 463          * Side effect: When the patrol link is build, this method will call
 464          * OutputPage::preventClickjacking() and load mediawiki.page.patrol.ajax.
 465          *
 466          * @return string
 467          */
 468         protected function markPatrolledLink() {
 469                 global $wgUseRCPatrol, $wgEnableAPI, $wgEnableWriteAPI;
 470                 $user = $this->getUser();
 471
 472                 if ( $this->mMarkPatrolledLink === null ) {
 473                         // Prepare a change patrol link, if applicable
 474                         if (
 475                                 // Is patrolling enabled and the user allowed to?
 476                                 $wgUseRCPatrol && $this->mNewPage->quickUserCan( 'patrol', $user ) &&
 477                                 // Only do this if the revision isn't more than 6 hours older
 478                                 // than the Max RC age (6h because the RC might not be cleaned out regularly)
 479                                 RecentChange::isInRCLifespan( $this->mNewRev->getTimestamp(), 21600 )
 480                         ) {
 481                                 // Look for an unpatrolled change corresponding to this diff
 482
 483                                 $db = wfGetDB( DB_SLAVE );
 484                                 $change = RecentChange::newFromConds(
 485                                         array(
 486                                                 'rc_timestamp' => $db->timestamp( $this->mNewRev->getTimestamp() ),
 487                                                 'rc_this_oldid' => $this->mNewid,
 488                                                 'rc_patrolled' => 0
 489                                         ),
 490                                         __METHOD__,
 491                                         array( 'USE INDEX' => 'rc_timestamp' )
 492                                 );
 493
 494                                 if ( $change && $change->getPerformer()->getName() !== $user->getName() ) {
 495                                         $rcid = $change->getAttribute( 'rc_id' );
 496                                 } else {
 497                                         // None found or the page has been created by the current user.
 498                                         // If the user could patrol this it already would be patrolled
 499                                         $rcid = 0;
 500                                 }
 501                                 // Build the link
 502                                 if ( $rcid ) {
 503                                         $this->getOutput()->preventClickjacking();
 504                                         if ( $wgEnableAPI && $wgEnableWriteAPI
 505                                                 && $user->isAllowed( 'writeapi' )
 506                                         ) {
 507                                                 $this->getOutput()->addModules( 'mediawiki.page.patrol.ajax' );
 508                                         }
 509
 510                                         $token = $user->getEditToken( $rcid );
 511                                         $this->mMarkPatrolledLink = ' <span class="patrollink">[' . Linker::linkKnown(
 512                                                 $this->mNewPage,
 513                                                 $this->msg( 'markaspatrolleddiff' )->escaped(),
 514                                                 array(),
 515                                                 array(
 516                                                         'action' => 'markpatrolled',
 517                                                         'rcid' => $rcid,
 518                                                         'token' => $token,
 519                                                 )
 520                                         ) . ']</span>';
 521                                 } else {
 522                                         $this->mMarkPatrolledLink = '';
 523                                 }
 524                         } else {
 525                                 $this->mMarkPatrolledLink = '';
 526                         }
 527                 }
 528
 529                 return $this->mMarkPatrolledLink;
 530         }
 531
 532         /**
 533          * @param Revision $rev
 534          *
 535          * @return string
 536          */
 537         protected function revisionDeleteLink( $rev ) {
 538                 $link = Linker::getRevDeleteLink( $this->getUser(), $rev, $rev->getTitle() );
 539                 if ( $link !== '' ) {
 540                         $link = '&#160;&#160;&#160;' . $link . ' ';
 541                 }
 542
 543                 return $link;
 544         }
 545
 546         /**
 547          * Show the new revision of the page.
 548          */
 549         public function renderNewRevision() {
 550                 wfProfileIn( __METHOD__ );
 551                 $out = $this->getOutput();
 552                 $revHeader = $this->getRevisionHeader( $this->mNewRev );
 553                 # Add "current version as of X" title
 554                 $out->addHTML( "<hr class='diff-hr' />
 555                 <h2 class='diff-currentversion-title'>{$revHeader}</h2>\n" );
 556                 # Page content may be handled by a hooked call instead...
 557                 # @codingStandardsIgnoreStart Ignoring long lines.
 558                 if ( Hooks::run( 'ArticleContentOnDiff', array( $this, $out ) ) ) {
 559                         $this->loadNewText();
 560                         $out->setRevisionId( $this->mNewid );
 561                         $out->setRevisionTimestamp( $this->mNewRev->getTimestamp() );
 562                         $out->setArticleFlag( true );
 563
 564                         // NOTE: only needed for B/C: custom rendering of JS/CSS via hook
 565                         if ( $this->mNewPage->isCssJsSubpage() || $this->mNewPage->isCssOrJsPage() ) {
 566                                 // This needs to be synchronised with Article::showCssOrJsPage(), which sucks
 567                                 // Give hooks a chance to customise the output
 568                                 // @todo standardize this crap into one function
 569                                 if ( ContentHandler::runLegacyHooks( 'ShowRawCssJs', array( $this->mNewContent, $this->mNewPage, $out ) ) ) {
 570                                         // NOTE: deprecated hook, B/C only
 571                                         // use the content object's own rendering
 572                                         $cnt = $this->mNewRev->getContent();
 573                                         $po = $cnt ? $cnt->getParserOutput( $this->mNewRev->getTitle(), $this->mNewRev->getId() ) : null;
 574                                         if ( $po ) {
 575                                                 $out->addParserOutputContent( $po );
 576                                         }
 577                                 }
 578                         } elseif ( !Hooks::run( 'ArticleContentViewCustom', array( $this->mNewContent, $this->mNewPage, $out ) ) ) {
 579                                 // Handled by extension
 580                         } elseif ( !ContentHandler::runLegacyHooks( 'ArticleViewCustom', array( $this->mNewContent, $this->mNewPage, $out ) ) ) {
 581                                 // NOTE: deprecated hook, B/C only
 582                                 // Handled by extension
 583                         } else {
 584                                 // Normal page
 585                                 if ( $this->getTitle()->equals( $this->mNewPage ) ) {
 586                                         // If the Title stored in the context is the same as the one
 587                                         // of the new revision, we can use its associated WikiPage
 588                                         // object.
 589                                         $wikiPage = $this->getWikiPage();
 590                                 } else {
 591                                         // Otherwise we need to create our own WikiPage object
 592                                         $wikiPage = WikiPage::factory( $this->mNewPage );
 593                                 }
 594
 595                                 $parserOutput = $this->getParserOutput( $wikiPage, $this->mNewRev );
 596
 597                                 # WikiPage::getParserOutput() should not return false, but just in case
 598                                 if ( $parserOutput ) {
 599                                         $out->addParserOutput( $parserOutput );
 600                                 }
 601                         }
 602                 }
 603                 # @codingStandardsIgnoreEnd
 604
 605                 # Add redundant patrol link on bottom...
 606                 $out->addHTML( $this->markPatrolledLink() );
 607
 608                 wfProfileOut( __METHOD__ );
 609         }
 610
 611         protected function getParserOutput( WikiPage $page, Revision $rev ) {
 612                 $parserOptions = $page->makeParserOptions( $this->getContext() );
 613
 614                 if ( !$rev->isCurrent() || !$rev->getTitle()->quickUserCan( "edit" ) ) {
 615                         $parserOptions->setEditSection( false );
 616                 }
 617
 618                 $parserOutput = $page->getParserOutput( $parserOptions, $rev->getId() );
 619
 620                 return $parserOutput;
 621         }
 622
 623         /**
 624          * Get the diff text, send it to the OutputPage object
 625          * Returns false if the diff could not be generated, otherwise returns true
 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          *
 631          * @return bool
 632          */
 633         public function showDiff( $otitle, $ntitle, $notice = '' ) {
 634                 $diff = $this->getDiff( $otitle, $ntitle, $notice );
 635                 if ( $diff === false ) {
 636                         $this->showMissingRevision();
 637
 638                         return false;
 639                 } else {
 640                         $this->showDiffStyle();
 641                         $this->getOutput()->addHTML( $diff );
 642
 643                         return true;
 644                 }
 645         }
 646
 647         /**
 648          * Add style sheets and supporting JS for diff display.
 649          */
 650         public function showDiffStyle() {
 651                 $this->getOutput()->addModuleStyles( 'mediawiki.action.history.diff' );
 652         }
 653
 654         /**
 655          * Get complete diff table, including header
 656          *
 657          * @param string|bool $otitle Header for old text or false
 658          * @param string|bool $ntitle Header for new text or false
 659          * @param string $notice HTML between diff header and body
 660          *
 661          * @return mixed
 662          */
 663         public function getDiff( $otitle, $ntitle, $notice = '' ) {
 664                 $body = $this->getDiffBody();
 665                 if ( $body === false ) {
 666                         return false;
 667                 }
 668
 669                 $multi = $this->getMultiNotice();
 670                 // Display a message when the diff is empty
 671                 if ( $body === '' ) {
 672                         $notice .= '<div class="mw-diff-empty">' .
 673                                 $this->msg( 'diff-empty' )->parse() .
 674                                 "</div>\n";
 675                 }
 676
 677                 return $this->addHeader( $body, $otitle, $ntitle, $multi, $notice );
 678         }
 679
 680         /**
 681          * Get the diff table body, without header
 682          *
 683          * @return mixed (string/false)
 684          */
 685         public function getDiffBody() {
 686                 global $wgMemc;
 687                 wfProfileIn( __METHOD__ );
 688                 $this->mCacheHit = true;
 689                 // Check if the diff should be hidden from this user
 690                 if ( !$this->loadRevisionData() ) {
 691                         wfProfileOut( __METHOD__ );
 692
 693                         return false;
 694                 } elseif ( $this->mOldRev &&
 695                         !$this->mOldRev->userCan( Revision::DELETED_TEXT, $this->getUser() )
 696                 ) {
 697                         wfProfileOut( __METHOD__ );
 698
 699                         return false;
 700                 } elseif ( $this->mNewRev &&
 701                         !$this->mNewRev->userCan( Revision::DELETED_TEXT, $this->getUser() )
 702                 ) {
 703                         wfProfileOut( __METHOD__ );
 704
 705                         return false;
 706                 }
 707                 // Short-circuit
 708                 if ( $this->mOldRev === false || ( $this->mOldRev && $this->mNewRev
 709                         && $this->mOldRev->getID() == $this->mNewRev->getID() )
 710                 ) {
 711                         wfProfileOut( __METHOD__ );
 712
 713                         return '';
 714                 }
 715                 // Cacheable?
 716                 $key = false;
 717                 if ( $this->mOldid && $this->mNewid ) {
 718                         $key = $this->getDiffBodyCacheKey();
 719
 720                         // Try cache
 721                         if ( !$this->mRefreshCache ) {
 722                                 $difftext = $wgMemc->get( $key );
 723                                 if ( $difftext ) {
 724                                         wfIncrStats( 'diff_cache_hit' );
 725                                         $difftext = $this->localiseLineNumbers( $difftext );
 726                                         $difftext .= "\n<!-- diff cache key $key -->\n";
 727                                         wfProfileOut( __METHOD__ );
 728
 729                                         return $difftext;
 730                                 }
 731                         } // don't try to load but save the result
 732                 }
 733                 $this->mCacheHit = false;
 734
 735                 // Loadtext is permission safe, this just clears out the diff
 736                 if ( !$this->loadText() ) {
 737                         wfProfileOut( __METHOD__ );
 738
 739                         return false;
 740                 }
 741
 742                 $difftext = $this->generateContentDiffBody( $this->mOldContent, $this->mNewContent );
 743
 744                 // Save to cache for 7 days
 745                 if ( !Hooks::run( 'AbortDiffCache', array( &$this ) ) ) {
 746                         wfIncrStats( 'diff_uncacheable' );
 747                 } elseif ( $key !== false && $difftext !== false ) {
 748                         wfIncrStats( 'diff_cache_miss' );
 749                         $wgMemc->set( $key, $difftext, 7 * 86400 );
 750                 } else {
 751                         wfIncrStats( 'diff_uncacheable' );
 752                 }
 753                 // Replace line numbers with the text in the user's language
 754                 if ( $difftext !== false ) {
 755                         $difftext = $this->localiseLineNumbers( $difftext );
 756                 }
 757                 wfProfileOut( __METHOD__ );
 758
 759                 return $difftext;
 760         }
 761
 762         /**
 763          * Returns the cache key for diff body text or content.
 764          *
 765          * @since 1.23
 766          *
 767          * @throws MWException
 768          * @return string
 769          */
 770         protected function getDiffBodyCacheKey() {
 771                 if ( !$this->mOldid || !$this->mNewid ) {
 772                         throw new MWException( 'mOldid and mNewid must be set to get diff cache key.' );
 773                 }
 774
 775                 return wfMemcKey( 'diff', 'version', MW_DIFF_VERSION,
 776                         'oldid', $this->mOldid, 'newid', $this->mNewid );
 777         }
 778
 779         /**
 780          * Generate a diff, no caching.
 781          *
 782          * This implementation uses generateTextDiffBody() to generate a diff based on the default
 783          * serialization of the given Content objects. This will fail if $old or $new are not
 784          * instances of TextContent.
 785          *
 786          * Subclasses may override this to provide a different rendering for the diff,
 787          * perhaps taking advantage of the content's native form. This is required for all content
 788          * models that are not text based.
 789          *
 790          * @since 1.21
 791          *
 792          * @param Content $old Old content
 793          * @param Content $new New content
 794          *
 795          * @throws MWException If old or new content is not an instance of TextContent.
 796          * @return bool|string
 797          */
 798         public function generateContentDiffBody( Content $old, Content $new ) {
 799                 if ( !( $old instanceof TextContent ) ) {
 800                         throw new MWException( "Diff not implemented for " . get_class( $old ) . "; " .
 801                                 "override generateContentDiffBody to fix this." );
 802                 }
 803
 804                 if ( !( $new instanceof TextContent ) ) {
 805                         throw new MWException( "Diff not implemented for " . get_class( $new ) . "; "
 806                                 . "override generateContentDiffBody to fix this." );
 807                 }
 808
 809                 $otext = $old->serialize();
 810                 $ntext = $new->serialize();
 811
 812                 return $this->generateTextDiffBody( $otext, $ntext );
 813         }
 814
 815         /**
 816          * Generate a diff, no caching
 817          *
 818          * @param string $otext Old text, must be already segmented
 819          * @param string $ntext New text, must be already segmented
 820          *
 821          * @return bool|string
 822          * @deprecated since 1.21, use generateContentDiffBody() instead!
 823          */
 824         public function generateDiffBody( $otext, $ntext ) {
 825                 ContentHandler::deprecated( __METHOD__, "1.21" );
 826
 827                 return $this->generateTextDiffBody( $otext, $ntext );
 828         }
 829
 830         /**
 831          * Generate a diff, no caching
 832          *
 833          * @todo move this to TextDifferenceEngine, make DifferenceEngine abstract. At some point.
 834          *
 835          * @param string $otext Old text, must be already segmented
 836          * @param string $ntext New text, must be already segmented
 837          *
 838          * @return bool|string
 839          */
 840         public function generateTextDiffBody( $otext, $ntext ) {
 841                 global $wgExternalDiffEngine, $wgContLang;
 842
 843                 wfProfileIn( __METHOD__ );
 844
 845                 $otext = str_replace( "\r\n", "\n", $otext );
 846                 $ntext = str_replace( "\r\n", "\n", $ntext );
 847
 848                 if ( $wgExternalDiffEngine == 'wikidiff' && function_exists( 'wikidiff_do_diff' ) ) {
 849                         # For historical reasons, external diff engine expects
 850                         # input text to be HTML-escaped already
 851                         $otext = htmlspecialchars( $wgContLang->segmentForDiff( $otext ) );
 852                         $ntext = htmlspecialchars( $wgContLang->segmentForDiff( $ntext ) );
 853                         wfProfileOut( __METHOD__ );
 854
 855                         return $wgContLang->unsegmentForDiff( wikidiff_do_diff( $otext, $ntext, 2 ) ) .
 856                         $this->debug( 'wikidiff1' );
 857                 }
 858
 859                 if ( $wgExternalDiffEngine == 'wikidiff2' && function_exists( 'wikidiff2_do_diff' ) ) {
 860                         # Better external diff engine, the 2 may some day be dropped
 861                         # This one does the escaping and segmenting itself
 862                         wfProfileIn( 'wikidiff2_do_diff' );
 863                         $text = wikidiff2_do_diff( $otext, $ntext, 2 );
 864                         $text .= $this->debug( 'wikidiff2' );
 865                         wfProfileOut( 'wikidiff2_do_diff' );
 866                         wfProfileOut( __METHOD__ );
 867
 868                         return $text;
 869                 }
 870                 if ( $wgExternalDiffEngine != 'wikidiff3' && $wgExternalDiffEngine !== false ) {
 871                         # Diff via the shell
 872                         $tmpDir = wfTempDir();
 873                         $tempName1 = tempnam( $tmpDir, 'diff_' );
 874                         $tempName2 = tempnam( $tmpDir, 'diff_' );
 875
 876                         $tempFile1 = fopen( $tempName1, "w" );
 877                         if ( !$tempFile1 ) {
 878                                 wfProfileOut( __METHOD__ );
 879
 880                                 return false;
 881                         }
 882                         $tempFile2 = fopen( $tempName2, "w" );
 883                         if ( !$tempFile2 ) {
 884                                 wfProfileOut( __METHOD__ );
 885
 886                                 return false;
 887                         }
 888                         fwrite( $tempFile1, $otext );
 889                         fwrite( $tempFile2, $ntext );
 890                         fclose( $tempFile1 );
 891                         fclose( $tempFile2 );
 892                         $cmd = wfEscapeShellArg( $wgExternalDiffEngine, $tempName1, $tempName2 );
 893                         wfProfileIn( __METHOD__ . "-shellexec" );
 894                         $difftext = wfShellExec( $cmd );
 895                         $difftext .= $this->debug( "external $wgExternalDiffEngine" );
 896                         wfProfileOut( __METHOD__ . "-shellexec" );
 897                         unlink( $tempName1 );
 898                         unlink( $tempName2 );
 899                         wfProfileOut( __METHOD__ );
 900
 901                         return $difftext;
 902                 }
 903
 904                 # Native PHP diff
 905                 $ota = explode( "\n", $wgContLang->segmentForDiff( $otext ) );
 906                 $nta = explode( "\n", $wgContLang->segmentForDiff( $ntext ) );
 907                 $diffs = new Diff( $ota, $nta );
 908                 $formatter = new TableDiffFormatter();
 909                 $difftext = $wgContLang->unsegmentForDiff( $formatter->format( $diffs ) ) .
 910                         wfProfileOut( __METHOD__ );
 911
 912                 return $difftext;
 913         }
 914
 915         /**
 916          * Generate a debug comment indicating diff generating time,
 917          * server node, and generator backend.
 918          *
 919          * @param string $generator : What diff engine was used
 920          *
 921          * @return string
 922          */
 923         protected function debug( $generator = "internal" ) {
 924                 global $wgShowHostnames;
 925                 if ( !$this->enableDebugComment ) {
 926                         return '';
 927                 }
 928                 $data = array( $generator );
 929                 if ( $wgShowHostnames ) {
 930                         $data[] = wfHostname();
 931                 }
 932                 $data[] = wfTimestamp( TS_DB );
 933
 934                 return "<!-- diff generator: " .
 935                         implode( " ", array_map( "htmlspecialchars", $data ) ) .
 936                         " -->\n";
 937         }
 938
 939         /**
 940          * Replace line numbers with the text in the user's language
 941          *
 942          * @param string $text
 943          *
 944          * @return mixed
 945          */
 946         public function localiseLineNumbers( $text ) {
 947                 return preg_replace_callback(
 948                         '/<!--LINE (\d+)-->/',
 949                         array( &$this, 'localiseLineNumbersCb' ),
 950                         $text
 951                 );
 952         }
 953
 954         public function localiseLineNumbersCb( $matches ) {
 955                 if ( $matches[1] === '1' && $this->mReducedLineNumbers ) {
 956                         return '';
 957                 }
 958
 959                 return $this->msg( 'lineno' )->numParams( $matches[1] )->escaped();
 960         }
 961
 962         /**
 963          * If there are revisions between the ones being compared, return a note saying so.
 964          *
 965          * @return string
 966          */
 967         public function getMultiNotice() {
 968                 if ( !is_object( $this->mOldRev ) || !is_object( $this->mNewRev ) ) {
 969                         return '';
 970                 } elseif ( !$this->mOldPage->equals( $this->mNewPage ) ) {
 971                         // Comparing two different pages? Count would be meaningless.
 972                         return '';
 973                 }
 974
 975                 if ( $this->mOldRev->getTimestamp() > $this->mNewRev->getTimestamp() ) {
 976                         $oldRev = $this->mNewRev; // flip
 977                         $newRev = $this->mOldRev; // flip
 978                 } else { // normal case
 979                         $oldRev = $this->mOldRev;
 980                         $newRev = $this->mNewRev;
 981                 }
 982
 983                 // Sanity: don't show the notice if too many rows must be scanned
 984                 // @todo show some special message for that case
 985                 $nEdits = $this->mNewPage->countRevisionsBetween( $oldRev, $newRev, 1000 );
 986                 if ( $nEdits > 0 && $nEdits <= 1000 ) {
 987                         $limit = 100; // use diff-multi-manyusers if too many users
 988                         $users = $this->mNewPage->getAuthorsBetween( $oldRev, $newRev, $limit );
 989                         $numUsers = count( $users );
 990
 991                         if ( $numUsers == 1 && $users[0] == $newRev->getRawUserText() ) {
 992                                 $numUsers = 0; // special case to say "by the same user" instead of "by one other user"
 993                         }
 994
 995                         return self::intermediateEditsMsg( $nEdits, $numUsers, $limit );
 996                 }
 997
 998                 return ''; // nothing
 999         }
1000
1001         /**
1002          * Get a notice about how many intermediate edits and users there are
1003          *
1004          * @param int $numEdits
1005          * @param int $numUsers
1006          * @param int $limit
1007          *
1008          * @return string
1009          */
1010         public static function intermediateEditsMsg( $numEdits, $numUsers, $limit ) {
1011                 if ( $numUsers === 0 ) {
1012                         $msg = 'diff-multi-sameuser';
1013                 } elseif ( $numUsers > $limit ) {
1014                         $msg = 'diff-multi-manyusers';
1015                         $numUsers = $limit;
1016                 } else {
1017                         $msg = 'diff-multi-otherusers';
1018                 }
1019
1020                 return wfMessage( $msg )->numParams( $numEdits, $numUsers )->parse();
1021         }
1022
1023         /**
1024          * Get a header for a specified revision.
1025          *
1026          * @param Revision $rev
1027          * @param string $complete 'complete' to get the header wrapped depending
1028          *        the visibility of the revision and a link to edit the page.
1029          *
1030          * @return string HTML fragment
1031          */
1032         protected function getRevisionHeader( Revision $rev, $complete = '' ) {
1033                 $lang = $this->getLanguage();
1034                 $user = $this->getUser();
1035                 $revtimestamp = $rev->getTimestamp();
1036                 $timestamp = $lang->userTimeAndDate( $revtimestamp, $user );
1037                 $dateofrev = $lang->userDate( $revtimestamp, $user );
1038                 $timeofrev = $lang->userTime( $revtimestamp, $user );
1039
1040                 $header = $this->msg(
1041                         $rev->isCurrent() ? 'currentrev-asof' : 'revisionasof',
1042                         $timestamp,
1043                         $dateofrev,
1044                         $timeofrev
1045                 )->escaped();
1046
1047                 if ( $complete !== 'complete' ) {
1048                         return $header;
1049                 }
1050
1051                 $title = $rev->getTitle();
1052
1053                 $header = Linker::linkKnown( $title, $header, array(),
1054                         array( 'oldid' => $rev->getID() ) );
1055
1056                 if ( $rev->userCan( Revision::DELETED_TEXT, $user ) ) {
1057                         $editQuery = array( 'action' => 'edit' );
1058                         if ( !$rev->isCurrent() ) {
1059                                 $editQuery['oldid'] = $rev->getID();
1060                         }
1061
1062                         $key = $title->quickUserCan( 'edit', $user ) ? 'editold' : 'viewsourceold';
1063                         $msg = $this->msg( $key )->escaped();
1064                         $editLink = $this->msg( 'parentheses' )->rawParams(
1065                                 Linker::linkKnown( $title, $msg, array( ), $editQuery ) )->escaped();
1066                         $header .= ' ' . Html::rawElement(
1067                                 'span',
1068                                 array( 'class' => 'mw-diff-edit' ),
1069                                 $editLink
1070                         );
1071                         if ( $rev->isDeleted( Revision::DELETED_TEXT ) ) {
1072                                 $header = Html::rawElement(
1073                                         'span',
1074                                         array( 'class' => 'history-deleted' ),
1075                                         $header
1076                                 );
1077                         }
1078                 } else {
1079                         $header = Html::rawElement( 'span', array( 'class' => 'history-deleted' ), $header );
1080                 }
1081
1082                 return $header;
1083         }
1084
1085         /**
1086          * Add the header to a diff body
1087          *
1088          * @param string $diff Diff body
1089          * @param string $otitle Old revision header
1090          * @param string $ntitle New revision header
1091          * @param string $multi Notice telling user that there are intermediate
1092          *   revisions between the ones being compared
1093          * @param string $notice Other notices, e.g. that user is viewing deleted content
1094          *
1095          * @return string
1096          */
1097         public function addHeader( $diff, $otitle, $ntitle, $multi = '', $notice = '' ) {
1098                 // shared.css sets diff in interface language/dir, but the actual content
1099                 // is often in a different language, mostly the page content language/dir
1100                 $tableClass = 'diff diff-contentalign-' . htmlspecialchars( $this->getDiffLang()->alignStart() );
1101                 $header = "<table class='$tableClass'>";
1102
1103                 if ( !$diff && !$otitle ) {
1104                         $header .= "
1105                         <tr style='vertical-align: top;'>
1106                         <td class='diff-ntitle'>{$ntitle}</td>
1107                         </tr>";
1108                         $multiColspan = 1;
1109                 } else {
1110                         if ( $diff ) { // Safari/Chrome show broken output if cols not used
1111                                 $header .= "
1112                                 <col class='diff-marker' />
1113                                 <col class='diff-content' />
1114                                 <col class='diff-marker' />
1115                                 <col class='diff-content' />";
1116                                 $colspan = 2;
1117                                 $multiColspan = 4;
1118                         } else {
1119                                 $colspan = 1;
1120                                 $multiColspan = 2;
1121                         }
1122                         if ( $otitle || $ntitle ) {
1123                                 $header .= "
1124                                 <tr style='vertical-align: top;'>
1125                                 <td colspan='$colspan' class='diff-otitle'>{$otitle}</td>
1126                                 <td colspan='$colspan' class='diff-ntitle'>{$ntitle}</td>
1127                                 </tr>";
1128                         }
1129                 }
1130
1131                 if ( $multi != '' ) {
1132                         $header .= "<tr><td colspan='{$multiColspan}' style='text-align: center;' " .
1133                                 "class='diff-multi'>{$multi}</td></tr>";
1134                 }
1135                 if ( $notice != '' ) {
1136                         $header .= "<tr><td colspan='{$multiColspan}' style='text-align: center;'>{$notice}</td></tr>";
1137                 }
1138
1139                 return $header . $diff . "</table>";
1140         }
1141
1142         /**
1143          * Use specified text instead of loading from the database
1144          * @deprecated since 1.21, use setContent() instead.
1145          */
1146         public function setText( $oldText, $newText ) {
1147                 ContentHandler::deprecated( __METHOD__, "1.21" );
1148
1149                 $oldContent = ContentHandler::makeContent( $oldText, $this->getTitle() );
1150                 $newContent = ContentHandler::makeContent( $newText, $this->getTitle() );
1151
1152                 $this->setContent( $oldContent, $newContent );
1153         }
1154
1155         /**
1156          * Use specified text instead of loading from the database
1157          * @param Content $oldContent
1158          * @param Content $newContent
1159          * @since 1.21
1160          */
1161         public function setContent( Content $oldContent, Content $newContent ) {
1162                 $this->mOldContent = $oldContent;
1163                 $this->mNewContent = $newContent;
1164
1165                 $this->mTextLoaded = 2;
1166                 $this->mRevisionsLoaded = true;
1167         }
1168
1169         /**
1170          * Set the language in which the diff text is written
1171          * (Defaults to page content language).
1172          * @param Language|string $lang
1173          * @since 1.19
1174          */
1175         public function setTextLanguage( $lang ) {
1176                 $this->mDiffLang = wfGetLangObj( $lang );
1177         }
1178
1179         /**
1180          * Maps a revision pair definition as accepted by DifferenceEngine constructor
1181          * to a pair of actual integers representing revision ids.
1182          *
1183          * @param int $old Revision id, e.g. from URL parameter 'oldid'
1184          * @param int|string $new Revision id or strings 'next' or 'prev', e.g. from URL parameter 'diff'
1185          *
1186          * @return int[] List of two revision ids, older first, later second.
1187          *     Zero signifies invalid argument passed.
1188          *     false signifies that there is no previous/next revision ($old is the oldest/newest one).
1189          */
1190         public function mapDiffPrevNext( $old, $new ) {
1191                 if ( $new === 'prev' ) {
1192                         // Show diff between revision $old and the previous one. Get previous one from DB.
1193                         $newid = intval( $old );
1194                         $oldid = $this->getTitle()->getPreviousRevisionID( $newid );
1195                 } elseif ( $new === 'next' ) {
1196                         // Show diff between revision $old and the next one. Get next one from DB.
1197                         $oldid = intval( $old );
1198                         $newid = $this->getTitle()->getNextRevisionID( $oldid );
1199                 } else {
1200                         $oldid = intval( $old );
1201                         $newid = intval( $new );
1202                 }
1203
1204                 return array( $oldid, $newid );
1205         }
1206
1207         /**
1208          * Load revision IDs
1209          */
1210         private function loadRevisionIds() {
1211                 if ( $this->mRevisionsIdsLoaded ) {
1212                         return;
1213                 }
1214
1215                 $this->mRevisionsIdsLoaded = true;
1216
1217                 $old = $this->mOldid;
1218                 $new = $this->mNewid;
1219
1220                 list( $this->mOldid, $this->mNewid ) = self::mapDiffPrevNext( $old, $new );
1221                 if ( $new === 'next' && $this->mNewid === false ) {
1222                         # if no result, NewId points to the newest old revision. The only newer
1223                         # revision is cur, which is "0".
1224                         $this->mNewid = 0;
1225                 }
1226
1227                 Hooks::run(
1228                         'NewDifferenceEngine',
1229                         array( $this->getTitle(), &$this->mOldid, &$this->mNewid, $old, $new )
1230                 );
1231         }
1232
1233         /**
1234          * Load revision metadata for the specified articles. If newid is 0, then compare
1235          * the old article in oldid to the current article; if oldid is 0, then
1236          * compare the current article to the immediately previous one (ignoring the
1237          * value of newid).
1238          *
1239          * If oldid is false, leave the corresponding revision object set
1240          * to false. This is impossible via ordinary user input, and is provided for
1241          * API convenience.
1242          *
1243          * @return bool
1244          */
1245         public function loadRevisionData() {
1246                 if ( $this->mRevisionsLoaded ) {
1247                         return true;
1248                 }
1249
1250                 // Whether it succeeds or fails, we don't want to try again
1251                 $this->mRevisionsLoaded = true;
1252
1253                 $this->loadRevisionIds();
1254
1255                 // Load the new revision object
1256                 if ( $this->mNewid ) {
1257                         $this->mNewRev = Revision::newFromId( $this->mNewid );
1258                 } else {
1259                         $this->mNewRev = Revision::newFromTitle(
1260                                 $this->getTitle(),
1261                                 false,
1262                                 Revision::READ_NORMAL
1263                         );
1264                 }
1265
1266                 if ( !$this->mNewRev instanceof Revision ) {
1267                         return false;
1268                 }
1269
1270                 // Update the new revision ID in case it was 0 (makes life easier doing UI stuff)
1271                 $this->mNewid = $this->mNewRev->getId();
1272                 $this->mNewPage = $this->mNewRev->getTitle();
1273
1274                 // Load the old revision object
1275                 $this->mOldRev = false;
1276                 if ( $this->mOldid ) {
1277                         $this->mOldRev = Revision::newFromId( $this->mOldid );
1278                 } elseif ( $this->mOldid === 0 ) {
1279                         $rev = $this->mNewRev->getPrevious();
1280                         if ( $rev ) {
1281                                 $this->mOldid = $rev->getId();
1282                                 $this->mOldRev = $rev;
1283                         } else {
1284                                 // No previous revision; mark to show as first-version only.
1285                                 $this->mOldid = false;
1286                                 $this->mOldRev = false;
1287                         }
1288                 } /* elseif ( $this->mOldid === false ) leave mOldRev false; */
1289
1290                 if ( is_null( $this->mOldRev ) ) {
1291                         return false;
1292                 }
1293
1294                 if ( $this->mOldRev ) {
1295                         $this->mOldPage = $this->mOldRev->getTitle();
1296                 }
1297
1298                 // Load tags information for both revisions
1299                 $dbr = wfGetDB( DB_SLAVE );
1300                 if ( $this->mOldid !== false ) {
1301                         $this->mOldTags = $dbr->selectField(
1302                                 'tag_summary',
1303                                 'ts_tags',
1304                                 array( 'ts_rev_id' => $this->mOldid ),
1305                                 __METHOD__
1306                         );
1307                 } else {
1308                         $this->mOldTags = false;
1309                 }
1310                 $this->mNewTags = $dbr->selectField(
1311                         'tag_summary',
1312                         'ts_tags',
1313                         array( 'ts_rev_id' => $this->mNewid ),
1314                         __METHOD__
1315                 );
1316
1317                 return true;
1318         }
1319
1320         /**
1321          * Load the text of the revisions, as well as revision data.
1322          *
1323          * @return bool
1324          */
1325         public function loadText() {
1326                 if ( $this->mTextLoaded == 2 ) {
1327                         return true;
1328                 }
1329
1330                 // Whether it succeeds or fails, we don't want to try again
1331                 $this->mTextLoaded = 2;
1332
1333                 if ( !$this->loadRevisionData() ) {
1334                         return false;
1335                 }
1336
1337                 if ( $this->mOldRev ) {
1338                         $this->mOldContent = $this->mOldRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1339                         if ( $this->mOldContent === null ) {
1340                                 return false;
1341                         }
1342                 }
1343
1344                 if ( $this->mNewRev ) {
1345                         $this->mNewContent = $this->mNewRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1346                         if ( $this->mNewContent === null ) {
1347                                 return false;
1348                         }
1349                 }
1350
1351                 return true;
1352         }
1353
1354         /**
1355          * Load the text of the new revision, not the old one
1356          *
1357          * @return bool
1358          */
1359         public function loadNewText() {
1360                 if ( $this->mTextLoaded >= 1 ) {
1361                         return true;
1362                 }
1363
1364                 $this->mTextLoaded = 1;
1365
1366                 if ( !$this->loadRevisionData() ) {
1367                         return false;
1368                 }
1369
1370                 $this->mNewContent = $this->mNewRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1371
1372                 return true;
1373         }
1374
1375 }