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         /** @var bool Refresh the diff cache */
  99         protected $mRefreshCache = false;
 100
 101         /**#@-*/
 102
 103         /**
 104          * Constructor
 105          * @param IContextSource $context Context to use, anything else will be ignored
 106          * @param int $old Old ID we want to show and diff with.
 107          * @param string|int $new Either revision ID or 'prev' or 'next'. Default: 0.
 108          * @param int $rcid Deprecated, no longer used!
 109          * @param bool $refreshCache If set, refreshes the diff cache
 110          * @param bool $unhide If set, allow viewing deleted revs
 111          */
 112         public function __construct( $context = null, $old = 0, $new = 0, $rcid = 0,
 113                 $refreshCache = false, $unhide = false
 114         ) {
 115                 if ( $context instanceof IContextSource ) {
 116                         $this->setContext( $context );
 117                 }
 118
 119                 wfDebug( "DifferenceEngine old '$old' new '$new' rcid '$rcid'\n" );
 120
 121                 $this->mOldid = $old;
 122                 $this->mNewid = $new;
 123                 $this->mRefreshCache = $refreshCache;
 124                 $this->unhide = $unhide;
 125         }
 126
 127         /**
 128          * @param bool $value
 129          */
 130         public function setReducedLineNumbers( $value = true ) {
 131                 $this->mReducedLineNumbers = $value;
 132         }
 133
 134         /**
 135          * @return Language
 136          */
 137         public function getDiffLang() {
 138                 if ( $this->mDiffLang === null ) {
 139                         # Default language in which the diff text is written.
 140                         $this->mDiffLang = $this->getTitle()->getPageLanguage();
 141                 }
 142
 143                 return $this->mDiffLang;
 144         }
 145
 146         /**
 147          * @return bool
 148          */
 149         public function wasCacheHit() {
 150                 return $this->mCacheHit;
 151         }
 152
 153         /**
 154          * @return int
 155          */
 156         public function getOldid() {
 157                 $this->loadRevisionIds();
 158
 159                 return $this->mOldid;
 160         }
 161
 162         /**
 163          * @return bool|int
 164          */
 165         public function getNewid() {
 166                 $this->loadRevisionIds();
 167
 168                 return $this->mNewid;
 169         }
 170
 171         /**
 172          * Look up a special:Undelete link to the given deleted revision id,
 173          * as a workaround for being unable to load deleted diffs in currently.
 174          *
 175          * @param int $id Revision ID
 176          *
 177          * @return mixed URL or false
 178          */
 179         public function deletedLink( $id ) {
 180                 if ( $this->getUser()->isAllowed( 'deletedhistory' ) ) {
 181                         $dbr = wfGetDB( DB_SLAVE );
 182                         $row = $dbr->selectRow( 'archive', '*',
 183                                 [ 'ar_rev_id' => $id ],
 184                                 __METHOD__ );
 185                         if ( $row ) {
 186                                 $rev = Revision::newFromArchiveRow( $row );
 187                                 $title = Title::makeTitleSafe( $row->ar_namespace, $row->ar_title );
 188
 189                                 return SpecialPage::getTitleFor( 'Undelete' )->getFullURL( [
 190                                         'target' => $title->getPrefixedText(),
 191                                         'timestamp' => $rev->getTimestamp()
 192                                 ] );
 193                         }
 194                 }
 195
 196                 return false;
 197         }
 198
 199         /**
 200          * Build a wikitext link toward a deleted revision, if viewable.
 201          *
 202          * @param int $id Revision ID
 203          *
 204          * @return string Wikitext fragment
 205          */
 206         public function deletedIdMarker( $id ) {
 207                 $link = $this->deletedLink( $id );
 208                 if ( $link ) {
 209                         return "[$link $id]";
 210                 } else {
 211                         return $id;
 212                 }
 213         }
 214
 215         private function showMissingRevision() {
 216                 $out = $this->getOutput();
 217
 218                 $missing = [];
 219                 if ( $this->mOldRev === null ||
 220                         ( $this->mOldRev && $this->mOldContent === null )
 221                 ) {
 222                         $missing[] = $this->deletedIdMarker( $this->mOldid );
 223                 }
 224                 if ( $this->mNewRev === null ||
 225                         ( $this->mNewRev && $this->mNewContent === null )
 226                 ) {
 227                         $missing[] = $this->deletedIdMarker( $this->mNewid );
 228                 }
 229
 230                 $out->setPageTitle( $this->msg( 'errorpagetitle' ) );
 231                 $msg = $this->msg( 'difference-missing-revision' )
 232                         ->params( $this->getLanguage()->listToText( $missing ) )
 233                         ->numParams( count( $missing ) )
 234                         ->parseAsBlock();
 235                 $out->addHtml( $msg );
 236         }
 237
 238         public function showDiffPage( $diffOnly = false ) {
 239
 240                 # Allow frames except in certain special cases
 241                 $out = $this->getOutput();
 242                 $out->allowClickjacking();
 243                 $out->setRobotPolicy( 'noindex,nofollow' );
 244
 245                 if ( !$this->loadRevisionData() ) {
 246                         $this->showMissingRevision();
 247
 248                         return;
 249                 }
 250
 251                 $user = $this->getUser();
 252                 $permErrors = $this->mNewPage->getUserPermissionsErrors( 'read', $user );
 253                 if ( $this->mOldPage ) { # mOldPage might not be set, see below.
 254                         $permErrors = wfMergeErrorArrays( $permErrors,
 255                                 $this->mOldPage->getUserPermissionsErrors( 'read', $user ) );
 256                 }
 257                 if ( count( $permErrors ) ) {
 258                         throw new PermissionsError( 'read', $permErrors );
 259                 }
 260
 261                 $rollback = '';
 262
 263                 $query = [];
 264                 # Carry over 'diffonly' param via navigation links
 265                 if ( $diffOnly != $user->getBoolOption( 'diffonly' ) ) {
 266                         $query['diffonly'] = $diffOnly;
 267                 }
 268                 # Cascade unhide param in links for easy deletion browsing
 269                 if ( $this->unhide ) {
 270                         $query['unhide'] = 1;
 271                 }
 272
 273                 # Check if one of the revisions is deleted/suppressed
 274                 $deleted = $suppressed = false;
 275                 $allowed = $this->mNewRev->userCan( Revision::DELETED_TEXT, $user );
 276
 277                 $revisionTools = [];
 278
 279                 # mOldRev is false if the difference engine is called with a "vague" query for
 280                 # a diff between a version V and its previous version V' AND the version V
 281                 # is the first version of that article. In that case, V' does not exist.
 282                 if ( $this->mOldRev === false ) {
 283                         $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 284                         $samePage = true;
 285                         $oldHeader = '';
 286                 } else {
 287                         Hooks::run( 'DiffViewHeader', [ $this, $this->mOldRev, $this->mNewRev ] );
 288
 289                         if ( $this->mNewPage->equals( $this->mOldPage ) ) {
 290                                 $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 291                                 $samePage = true;
 292                         } else {
 293                                 $out->setPageTitle( $this->msg( 'difference-title-multipage',
 294                                         $this->mOldPage->getPrefixedText(), $this->mNewPage->getPrefixedText() ) );
 295                                 $out->addSubtitle( $this->msg( 'difference-multipage' ) );
 296                                 $samePage = false;
 297                         }
 298
 299                         if ( $samePage && $this->mNewPage->quickUserCan( 'edit', $user ) ) {
 300                                 if ( $this->mNewRev->isCurrent() && $this->mNewPage->userCan( 'rollback', $user ) ) {
 301                                         $rollbackLink = Linker::generateRollback( $this->mNewRev, $this->getContext() );
 302                                         if ( $rollbackLink ) {
 303                                                 $out->preventClickjacking();
 304                                                 $rollback = '&#160;&#160;&#160;' . $rollbackLink;
 305                                         }
 306                                 }
 307
 308                                 if ( !$this->mOldRev->isDeleted( Revision::DELETED_TEXT ) &&
 309                                         !$this->mNewRev->isDeleted( Revision::DELETED_TEXT )
 310                                 ) {
 311                                         $undoLink = Html::element( 'a', [
 312                                                         'href' => $this->mNewPage->getLocalURL( [
 313                                                                 'action' => 'edit',
 314                                                                 'undoafter' => $this->mOldid,
 315                                                                 'undo' => $this->mNewid
 316                                                         ] ),
 317                                                         'title' => Linker::titleAttrib( 'undo' ),
 318                                                 ],
 319                                                 $this->msg( 'editundo' )->text()
 320                                         );
 321                                         $revisionTools['mw-diff-undo'] = $undoLink;
 322                                 }
 323                         }
 324
 325                         # Make "previous revision link"
 326                         if ( $samePage && $this->mOldRev->getPrevious() ) {
 327                                 $prevlink = Linker::linkKnown(
 328                                         $this->mOldPage,
 329                                         $this->msg( 'previousdiff' )->escaped(),
 330                                         [ 'id' => 'differences-prevlink' ],
 331                                         [ 'diff' => 'prev', 'oldid' => $this->mOldid ] + $query
 332                                 );
 333                         } else {
 334                                 $prevlink = '&#160;';
 335                         }
 336
 337                         if ( $this->mOldRev->isMinor() ) {
 338                                 $oldminor = ChangesList::flag( 'minor' );
 339                         } else {
 340                                 $oldminor = '';
 341                         }
 342
 343                         $ldel = $this->revisionDeleteLink( $this->mOldRev );
 344                         $oldRevisionHeader = $this->getRevisionHeader( $this->mOldRev, 'complete' );
 345                         $oldChangeTags = ChangeTags::formatSummaryRow( $this->mOldTags, 'diff', $this->getContext() );
 346
 347                         $oldHeader = '<div id="mw-diff-otitle1"><strong>' . $oldRevisionHeader . '</strong></div>' .
 348                                 '<div id="mw-diff-otitle2">' .
 349                                 Linker::revUserTools( $this->mOldRev, !$this->unhide ) . '</div>' .
 350                                 '<div id="mw-diff-otitle3">' . $oldminor .
 351                                 Linker::revComment( $this->mOldRev, !$diffOnly, !$this->unhide ) . $ldel . '</div>' .
 352                                 '<div id="mw-diff-otitle5">' . $oldChangeTags[0] . '</div>' .
 353                                 '<div id="mw-diff-otitle4">' . $prevlink . '</div>';
 354
 355                         if ( $this->mOldRev->isDeleted( Revision::DELETED_TEXT ) ) {
 356                                 $deleted = true; // old revisions text is hidden
 357                                 if ( $this->mOldRev->isDeleted( Revision::DELETED_RESTRICTED ) ) {
 358                                         $suppressed = true; // also suppressed
 359                                 }
 360                         }
 361
 362                         # Check if this user can see the revisions
 363                         if ( !$this->mOldRev->userCan( Revision::DELETED_TEXT, $user ) ) {
 364                                 $allowed = false;
 365                         }
 366                 }
 367
 368                 # Make "next revision link"
 369                 # Skip next link on the top revision
 370                 if ( $samePage && !$this->mNewRev->isCurrent() ) {
 371                         $nextlink = Linker::linkKnown(
 372                                 $this->mNewPage,
 373                                 $this->msg( 'nextdiff' )->escaped(),
 374                                 [ 'id' => 'differences-nextlink' ],
 375                                 [ 'diff' => 'next', 'oldid' => $this->mNewid ] + $query
 376                         );
 377                 } else {
 378                         $nextlink = '&#160;';
 379                 }
 380
 381                 if ( $this->mNewRev->isMinor() ) {
 382                         $newminor = ChangesList::flag( 'minor' );
 383                 } else {
 384                         $newminor = '';
 385                 }
 386
 387                 # Handle RevisionDelete links...
 388                 $rdel = $this->revisionDeleteLink( $this->mNewRev );
 389
 390                 # Allow extensions to define their own revision tools
 391                 Hooks::run( 'DiffRevisionTools',
 392                         [ $this->mNewRev, &$revisionTools, $this->mOldRev, $user ] );
 393                 $formattedRevisionTools = [];
 394                 // Put each one in parentheses (poor man's button)
 395                 foreach ( $revisionTools as $key => $tool ) {
 396                         $toolClass = is_string( $key ) ? $key : 'mw-diff-tool';
 397                         $element = Html::rawElement(
 398                                 'span',
 399                                 [ 'class' => $toolClass ],
 400                                 $this->msg( 'parentheses' )->rawParams( $tool )->escaped()
 401                         );
 402                         $formattedRevisionTools[] = $element;
 403                 }
 404                 $newRevisionHeader = $this->getRevisionHeader( $this->mNewRev, 'complete' ) .
 405                         ' ' . implode( ' ', $formattedRevisionTools );
 406                 $newChangeTags = ChangeTags::formatSummaryRow( $this->mNewTags, 'diff', $this->getContext() );
 407
 408                 $newHeader = '<div id="mw-diff-ntitle1"><strong>' . $newRevisionHeader . '</strong></div>' .
 409                         '<div id="mw-diff-ntitle2">' . Linker::revUserTools( $this->mNewRev, !$this->unhide ) .
 410                         " $rollback</div>" .
 411                         '<div id="mw-diff-ntitle3">' . $newminor .
 412                         Linker::revComment( $this->mNewRev, !$diffOnly, !$this->unhide ) . $rdel . '</div>' .
 413                         '<div id="mw-diff-ntitle5">' . $newChangeTags[0] . '</div>' .
 414                         '<div id="mw-diff-ntitle4">' . $nextlink . $this->markPatrolledLink() . '</div>';
 415
 416                 if ( $this->mNewRev->isDeleted( Revision::DELETED_TEXT ) ) {
 417                         $deleted = true; // new revisions text is hidden
 418                         if ( $this->mNewRev->isDeleted( Revision::DELETED_RESTRICTED ) ) {
 419                                 $suppressed = true; // also suppressed
 420                         }
 421                 }
 422
 423                 # If the diff cannot be shown due to a deleted revision, then output
 424                 # the diff header and links to unhide (if available)...
 425                 if ( $deleted && ( !$this->unhide || !$allowed ) ) {
 426                         $this->showDiffStyle();
 427                         $multi = $this->getMultiNotice();
 428                         $out->addHTML( $this->addHeader( '', $oldHeader, $newHeader, $multi ) );
 429                         if ( !$allowed ) {
 430                                 $msg = $suppressed ? 'rev-suppressed-no-diff' : 'rev-deleted-no-diff';
 431                                 # Give explanation for why revision is not visible
 432                                 $out->wrapWikiMsg( "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 433                                         [ $msg ] );
 434                         } else {
 435                                 # Give explanation and add a link to view the diff...
 436                                 $query = $this->getRequest()->appendQueryValue( 'unhide', '1' );
 437                                 $link = $this->getTitle()->getFullURL( $query );
 438                                 $msg = $suppressed ? 'rev-suppressed-unhide-diff' : 'rev-deleted-unhide-diff';
 439                                 $out->wrapWikiMsg(
 440                                         "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 441                                         [ $msg, $link ]
 442                                 );
 443                         }
 444                 # Otherwise, output a regular diff...
 445                 } else {
 446                         # Add deletion notice if the user is viewing deleted content
 447                         $notice = '';
 448                         if ( $deleted ) {
 449                                 $msg = $suppressed ? 'rev-suppressed-diff-view' : 'rev-deleted-diff-view';
 450                                 $notice = "<div id='mw-$msg' class='mw-warning plainlinks'>\n" .
 451                                         $this->msg( $msg )->parse() .
 452                                         "</div>\n";
 453                         }
 454                         $this->showDiff( $oldHeader, $newHeader, $notice );
 455                         if ( !$diffOnly ) {
 456                                 $this->renderNewRevision();
 457                         }
 458                 }
 459         }
 460
 461         /**
 462          * Build a link to mark a change as patrolled.
 463          *
 464          * Returns empty string if there's either no revision to patrol or the user is not allowed to.
 465          * Side effect: When the patrol link is build, this method will call
 466          * OutputPage::preventClickjacking() and load mediawiki.page.patrol.ajax.
 467          *
 468          * @return string HTML or empty string
 469          */
 470         protected function markPatrolledLink() {
 471                 if ( $this->mMarkPatrolledLink === null ) {
 472                         $linkInfo = $this->getMarkPatrolledLinkInfo();
 473                         // If false, there is no patrol link needed/allowed
 474                         if ( !$linkInfo ) {
 475                                 $this->mMarkPatrolledLink = '';
 476                         } else {
 477                                 $this->mMarkPatrolledLink = ' <span class="patrollink">[' . Linker::linkKnown(
 478                                         $this->mNewPage,
 479                                         $this->msg( 'markaspatrolleddiff' )->escaped(),
 480                                         [],
 481                                         [
 482                                                 'action' => 'markpatrolled',
 483                                                 'rcid' => $linkInfo['rcid'],
 484                                                 'token' => $linkInfo['token'],
 485                                         ]
 486                                 ) . ']</span>';
 487                         }
 488                 }
 489                 return $this->mMarkPatrolledLink;
 490         }
 491
 492         /**
 493          * Returns an array of meta data needed to build a "mark as patrolled" link and
 494          * adds the mediawiki.page.patrol.ajax to the output.
 495          *
 496          * @return array|false An array of meta data for a patrol link (rcid & token)
 497          *  or false if no link is needed
 498          */
 499         protected function getMarkPatrolledLinkInfo() {
 500                 global $wgUseRCPatrol, $wgEnableAPI, $wgEnableWriteAPI;
 501
 502                 $user = $this->getUser();
 503
 504                 // Prepare a change patrol link, if applicable
 505                 if (
 506                         // Is patrolling enabled and the user allowed to?
 507                         $wgUseRCPatrol && $this->mNewPage->quickUserCan( 'patrol', $user ) &&
 508                         // Only do this if the revision isn't more than 6 hours older
 509                         // than the Max RC age (6h because the RC might not be cleaned out regularly)
 510                         RecentChange::isInRCLifespan( $this->mNewRev->getTimestamp(), 21600 )
 511                 ) {
 512                         // Look for an unpatrolled change corresponding to this diff
 513                         $db = wfGetDB( DB_SLAVE );
 514                         $change = RecentChange::newFromConds(
 515                                 [
 516                                         'rc_timestamp' => $db->timestamp( $this->mNewRev->getTimestamp() ),
 517                                         'rc_this_oldid' => $this->mNewid,
 518                                         'rc_patrolled' => 0
 519                                 ],
 520                                 __METHOD__
 521                         );
 522
 523                         if ( $change && !$change->getPerformer()->equals( $user ) ) {
 524                                 $rcid = $change->getAttribute( 'rc_id' );
 525                         } else {
 526                                 // None found or the page has been created by the current user.
 527                                 // If the user could patrol this it already would be patrolled
 528                                 $rcid = 0;
 529                         }
 530                         // Build the link
 531                         if ( $rcid ) {
 532                                 $this->getOutput()->preventClickjacking();
 533                                 if ( $wgEnableAPI && $wgEnableWriteAPI
 534                                         && $user->isAllowed( 'writeapi' )
 535                                 ) {
 536                                         $this->getOutput()->addModules( 'mediawiki.page.patrol.ajax' );
 537                                 }
 538
 539                                 $token = $user->getEditToken( $rcid );
 540                                 return [
 541                                         'rcid' => $rcid,
 542                                         'token' => $token,
 543                                 ];
 544                         }
 545                 }
 546
 547                 // No mark as patrolled link applicable
 548                 return false;
 549         }
 550
 551         /**
 552          * @param Revision $rev
 553          *
 554          * @return string
 555          */
 556         protected function revisionDeleteLink( $rev ) {
 557                 $link = Linker::getRevDeleteLink( $this->getUser(), $rev, $rev->getTitle() );
 558                 if ( $link !== '' ) {
 559                         $link = '&#160;&#160;&#160;' . $link . ' ';
 560                 }
 561
 562                 return $link;
 563         }
 564
 565         /**
 566          * Show the new revision of the page.
 567          */
 568         public function renderNewRevision() {
 569                 $out = $this->getOutput();
 570                 $revHeader = $this->getRevisionHeader( $this->mNewRev );
 571                 # Add "current version as of X" title
 572                 $out->addHTML( "<hr class='diff-hr' id='mw-oldid' />
 573                 <h2 class='diff-currentversion-title'>{$revHeader}</h2>\n" );
 574                 # Page content may be handled by a hooked call instead...
 575                 # @codingStandardsIgnoreStart Ignoring long lines.
 576                 if ( Hooks::run( 'ArticleContentOnDiff', [ $this, $out ] ) ) {
 577                         $this->loadNewText();
 578                         $out->setRevisionId( $this->mNewid );
 579                         $out->setRevisionTimestamp( $this->mNewRev->getTimestamp() );
 580                         $out->setArticleFlag( true );
 581
 582                         // NOTE: only needed for B/C: custom rendering of JS/CSS via hook
 583                         if ( $this->mNewPage->isCssJsSubpage() || $this->mNewPage->isCssOrJsPage() ) {
 584                                 // This needs to be synchronised with Article::showCssOrJsPage(), which sucks
 585                                 // Give hooks a chance to customise the output
 586                                 // @todo standardize this crap into one function
 587                                 if ( ContentHandler::runLegacyHooks( 'ShowRawCssJs', [ $this->mNewContent, $this->mNewPage, $out ] ) ) {
 588                                         // NOTE: deprecated hook, B/C only
 589                                         // use the content object's own rendering
 590                                         $cnt = $this->mNewRev->getContent();
 591                                         $po = $cnt ? $cnt->getParserOutput( $this->mNewRev->getTitle(), $this->mNewRev->getId() ) : null;
 592                                         if ( $po ) {
 593                                                 $out->addParserOutputContent( $po );
 594                                         }
 595                                 }
 596                         } elseif ( !Hooks::run( 'ArticleContentViewCustom', [ $this->mNewContent, $this->mNewPage, $out ] ) ) {
 597                                 // Handled by extension
 598                         } elseif ( !ContentHandler::runLegacyHooks( 'ArticleViewCustom', [ $this->mNewContent, $this->mNewPage, $out ] ) ) {
 599                                 // NOTE: deprecated hook, B/C only
 600                                 // Handled by extension
 601                         } else {
 602                                 // Normal page
 603                                 if ( $this->getTitle()->equals( $this->mNewPage ) ) {
 604                                         // If the Title stored in the context is the same as the one
 605                                         // of the new revision, we can use its associated WikiPage
 606                                         // object.
 607                                         $wikiPage = $this->getWikiPage();
 608                                 } else {
 609                                         // Otherwise we need to create our own WikiPage object
 610                                         $wikiPage = WikiPage::factory( $this->mNewPage );
 611                                 }
 612
 613                                 $parserOutput = $this->getParserOutput( $wikiPage, $this->mNewRev );
 614
 615                                 # WikiPage::getParserOutput() should not return false, but just in case
 616                                 if ( $parserOutput ) {
 617                                         $out->addParserOutput( $parserOutput );
 618                                 }
 619                         }
 620                 }
 621                 # @codingStandardsIgnoreEnd
 622
 623                 # Add redundant patrol link on bottom...
 624                 $out->addHTML( $this->markPatrolledLink() );
 625
 626         }
 627
 628         protected function getParserOutput( WikiPage $page, Revision $rev ) {
 629                 $parserOptions = $page->makeParserOptions( $this->getContext() );
 630
 631                 if ( !$rev->isCurrent() || !$rev->getTitle()->quickUserCan( 'edit', $this->getUser() ) ) {
 632                         $parserOptions->setEditSection( false );
 633                 }
 634
 635                 $parserOutput = $page->getParserOutput( $parserOptions, $rev->getId() );
 636
 637                 return $parserOutput;
 638         }
 639
 640         /**
 641          * Get the diff text, send it to the OutputPage object
 642          * Returns false if the diff could not be generated, otherwise returns true
 643          *
 644          * @param string|bool $otitle Header for old text or false
 645          * @param string|bool $ntitle Header for new text or false
 646          * @param string $notice HTML between diff header and body
 647          *
 648          * @return bool
 649          */
 650         public function showDiff( $otitle, $ntitle, $notice = '' ) {
 651                 $diff = $this->getDiff( $otitle, $ntitle, $notice );
 652                 if ( $diff === false ) {
 653                         $this->showMissingRevision();
 654
 655                         return false;
 656                 } else {
 657                         $this->showDiffStyle();
 658                         $this->getOutput()->addHTML( $diff );
 659
 660                         return true;
 661                 }
 662         }
 663
 664         /**
 665          * Add style sheets and supporting JS for diff display.
 666          */
 667         public function showDiffStyle() {
 668                 $this->getOutput()->addModuleStyles( 'mediawiki.action.history.diff' );
 669         }
 670
 671         /**
 672          * Get complete diff table, including header
 673          *
 674          * @param string|bool $otitle Header for old text or false
 675          * @param string|bool $ntitle Header for new text or false
 676          * @param string $notice HTML between diff header and body
 677          *
 678          * @return mixed
 679          */
 680         public function getDiff( $otitle, $ntitle, $notice = '' ) {
 681                 $body = $this->getDiffBody();
 682                 if ( $body === false ) {
 683                         return false;
 684                 }
 685
 686                 $multi = $this->getMultiNotice();
 687                 // Display a message when the diff is empty
 688                 if ( $body === '' ) {
 689                         $notice .= '<div class="mw-diff-empty">' .
 690                                 $this->msg( 'diff-empty' )->parse() .
 691                                 "</div>\n";
 692                 }
 693
 694                 return $this->addHeader( $body, $otitle, $ntitle, $multi, $notice );
 695         }
 696
 697         /**
 698          * Get the diff table body, without header
 699          *
 700          * @return mixed (string/false)
 701          */
 702         public function getDiffBody() {
 703                 $this->mCacheHit = true;
 704                 // Check if the diff should be hidden from this user
 705                 if ( !$this->loadRevisionData() ) {
 706                         return false;
 707                 } elseif ( $this->mOldRev &&
 708                         !$this->mOldRev->userCan( Revision::DELETED_TEXT, $this->getUser() )
 709                 ) {
 710                         return false;
 711                 } elseif ( $this->mNewRev &&
 712                         !$this->mNewRev->userCan( Revision::DELETED_TEXT, $this->getUser() )
 713                 ) {
 714                         return false;
 715                 }
 716                 // Short-circuit
 717                 if ( $this->mOldRev === false || ( $this->mOldRev && $this->mNewRev
 718                         && $this->mOldRev->getID() == $this->mNewRev->getID() )
 719                 ) {
 720                         return '';
 721                 }
 722                 // Cacheable?
 723                 $key = false;
 724                 $cache = ObjectCache::getMainWANInstance();
 725                 if ( $this->mOldid && $this->mNewid ) {
 726                         $key = $this->getDiffBodyCacheKey();
 727
 728                         // Try cache
 729                         if ( !$this->mRefreshCache ) {
 730                                 $difftext = $cache->get( $key );
 731                                 if ( $difftext ) {
 732                                         wfIncrStats( 'diff_cache.hit' );
 733                                         $difftext = $this->localiseLineNumbers( $difftext );
 734                                         $difftext .= "\n<!-- diff cache key $key -->\n";
 735
 736                                         return $difftext;
 737                                 }
 738                         } // don't try to load but save the result
 739                 }
 740                 $this->mCacheHit = false;
 741
 742                 // Loadtext is permission safe, this just clears out the diff
 743                 if ( !$this->loadText() ) {
 744                         return false;
 745                 }
 746
 747                 $difftext = $this->generateContentDiffBody( $this->mOldContent, $this->mNewContent );
 748
 749                 // Save to cache for 7 days
 750                 if ( !Hooks::run( 'AbortDiffCache', [ &$this ] ) ) {
 751                         wfIncrStats( 'diff_cache.uncacheable' );
 752                 } elseif ( $key !== false && $difftext !== false ) {
 753                         wfIncrStats( 'diff_cache.miss' );
 754                         $cache->set( $key, $difftext, 7 * 86400 );
 755                 } else {
 756                         wfIncrStats( 'diff_cache.uncacheable' );
 757                 }
 758                 // Replace line numbers with the text in the user's language
 759                 if ( $difftext !== false ) {
 760                         $difftext = $this->localiseLineNumbers( $difftext );
 761                 }
 762
 763                 return $difftext;
 764         }
 765
 766         /**
 767          * Returns the cache key for diff body text or content.
 768          *
 769          * @since 1.23
 770          *
 771          * @throws MWException
 772          * @return string
 773          */
 774         protected function getDiffBodyCacheKey() {
 775                 if ( !$this->mOldid || !$this->mNewid ) {
 776                         throw new MWException( 'mOldid and mNewid must be set to get diff cache key.' );
 777                 }
 778
 779                 return wfMemcKey( 'diff', 'version', MW_DIFF_VERSION,
 780                         'oldid', $this->mOldid, 'newid', $this->mNewid );
 781         }
 782
 783         /**
 784          * Generate a diff, no caching.
 785          *
 786          * This implementation uses generateTextDiffBody() to generate a diff based on the default
 787          * serialization of the given Content objects. This will fail if $old or $new are not
 788          * instances of TextContent.
 789          *
 790          * Subclasses may override this to provide a different rendering for the diff,
 791          * perhaps taking advantage of the content's native form. This is required for all content
 792          * models that are not text based.
 793          *
 794          * @since 1.21
 795          *
 796          * @param Content $old Old content
 797          * @param Content $new New content
 798          *
 799          * @throws MWException If old or new content is not an instance of TextContent.
 800          * @return bool|string
 801          */
 802         public function generateContentDiffBody( Content $old, Content $new ) {
 803                 if ( !( $old instanceof TextContent ) ) {
 804                         throw new MWException( "Diff not implemented for " . get_class( $old ) . "; " .
 805                                 "override generateContentDiffBody to fix this." );
 806                 }
 807
 808                 if ( !( $new instanceof TextContent ) ) {
 809                         throw new MWException( "Diff not implemented for " . get_class( $new ) . "; "
 810                                 . "override generateContentDiffBody to fix this." );
 811                 }
 812
 813                 $otext = $old->serialize();
 814                 $ntext = $new->serialize();
 815
 816                 return $this->generateTextDiffBody( $otext, $ntext );
 817         }
 818
 819         /**
 820          * Generate a diff, no caching
 821          *
 822          * @param string $otext Old text, must be already segmented
 823          * @param string $ntext New text, must be already segmented
 824          *
 825          * @return bool|string
 826          * @deprecated since 1.21, use generateContentDiffBody() instead!
 827          */
 828         public function generateDiffBody( $otext, $ntext ) {
 829                 ContentHandler::deprecated( __METHOD__, "1.21" );
 830
 831                 return $this->generateTextDiffBody( $otext, $ntext );
 832         }
 833
 834         /**
 835          * Generate a diff, no caching
 836          *
 837          * @todo move this to TextDifferenceEngine, make DifferenceEngine abstract. At some point.
 838          *
 839          * @param string $otext Old text, must be already segmented
 840          * @param string $ntext New text, must be already segmented
 841          *
 842          * @return bool|string
 843          */
 844         public function generateTextDiffBody( $otext, $ntext ) {
 845                 $time = microtime( true );
 846
 847                 $result = $this->textDiff( $otext, $ntext );
 848
 849                 $time = microtime( true ) - $time;
 850                 $this->getStats()->timing( 'diff_time', $time * 1000 );
 851
 852                 return $result;
 853         }
 854
 855         /**
 856          * Generates diff, to be wrapped internally in a logging/instrumentation
 857          *
 858          * @param string $otext Old text, must be already segmented
 859          * @param string $ntext New text, must be already segmented
 860          * @return bool|string
 861          */
 862         protected function textDiff( $otext, $ntext ) {
 863                 global $wgExternalDiffEngine, $wgContLang;
 864
 865                 $otext = str_replace( "\r\n", "\n", $otext );
 866                 $ntext = str_replace( "\r\n", "\n", $ntext );
 867
 868                 if ( $wgExternalDiffEngine == 'wikidiff' ) {
 869                         wfDeprecated( 'wikidiff support', '1.27' );
 870                         $wgExternalDiffEngine = false;
 871                 }
 872
 873                 if ( $wgExternalDiffEngine == 'wikidiff2' ) {
 874                         if ( function_exists( 'wikidiff2_do_diff' ) ) {
 875                                 # Better external diff engine, the 2 may some day be dropped
 876                                 # This one does the escaping and segmenting itself
 877                                 $text = wikidiff2_do_diff( $otext, $ntext, 2 );
 878                                 $text .= $this->debug( 'wikidiff2' );
 879
 880                                 return $text;
 881                         }
 882                 } elseif ( $wgExternalDiffEngine != 'wikidiff3' && $wgExternalDiffEngine !== false ) {
 883                         # Diff via the shell
 884                         $tmpDir = wfTempDir();
 885                         $tempName1 = tempnam( $tmpDir, 'diff_' );
 886                         $tempName2 = tempnam( $tmpDir, 'diff_' );
 887
 888                         $tempFile1 = fopen( $tempName1, "w" );
 889                         if ( !$tempFile1 ) {
 890                                 return false;
 891                         }
 892                         $tempFile2 = fopen( $tempName2, "w" );
 893                         if ( !$tempFile2 ) {
 894                                 return false;
 895                         }
 896                         fwrite( $tempFile1, $otext );
 897                         fwrite( $tempFile2, $ntext );
 898                         fclose( $tempFile1 );
 899                         fclose( $tempFile2 );
 900                         $cmd = wfEscapeShellArg( $wgExternalDiffEngine, $tempName1, $tempName2 );
 901                         $difftext = wfShellExec( $cmd );
 902                         $difftext .= $this->debug( "external $wgExternalDiffEngine" );
 903                         unlink( $tempName1 );
 904                         unlink( $tempName2 );
 905
 906                         return $difftext;
 907                 }
 908
 909                 # Native PHP diff
 910                 $ota = explode( "\n", $wgContLang->segmentForDiff( $otext ) );
 911                 $nta = explode( "\n", $wgContLang->segmentForDiff( $ntext ) );
 912                 $diffs = new Diff( $ota, $nta );
 913                 $formatter = new TableDiffFormatter();
 914                 $difftext = $wgContLang->unsegmentForDiff( $formatter->format( $diffs ) );
 915
 916                 return $difftext;
 917         }
 918
 919         /**
 920          * Generate a debug comment indicating diff generating time,
 921          * server node, and generator backend.
 922          *
 923          * @param string $generator : What diff engine was used
 924          *
 925          * @return string
 926          */
 927         protected function debug( $generator = "internal" ) {
 928                 global $wgShowHostnames;
 929                 if ( !$this->enableDebugComment ) {
 930                         return '';
 931                 }
 932                 $data = [ $generator ];
 933                 if ( $wgShowHostnames ) {
 934                         $data[] = wfHostname();
 935                 }
 936                 $data[] = wfTimestamp( TS_DB );
 937
 938                 return "<!-- diff generator: " .
 939                         implode( " ", array_map( "htmlspecialchars", $data ) ) .
 940                         " -->\n";
 941         }
 942
 943         /**
 944          * Replace line numbers with the text in the user's language
 945          *
 946          * @param string $text
 947          *
 948          * @return mixed
 949          */
 950         public function localiseLineNumbers( $text ) {
 951                 return preg_replace_callback(
 952                         '/<!--LINE (\d+)-->/',
 953                         [ &$this, 'localiseLineNumbersCb' ],
 954                         $text
 955                 );
 956         }
 957
 958         public function localiseLineNumbersCb( $matches ) {
 959                 if ( $matches[1] === '1' && $this->mReducedLineNumbers ) {
 960                         return '';
 961                 }
 962
 963                 return $this->msg( 'lineno' )->numParams( $matches[1] )->escaped();
 964         }
 965
 966         /**
 967          * If there are revisions between the ones being compared, return a note saying so.
 968          *
 969          * @return string
 970          */
 971         public function getMultiNotice() {
 972                 if ( !is_object( $this->mOldRev ) || !is_object( $this->mNewRev ) ) {
 973                         return '';
 974                 } elseif ( !$this->mOldPage->equals( $this->mNewPage ) ) {
 975                         // Comparing two different pages? Count would be meaningless.
 976                         return '';
 977                 }
 978
 979                 if ( $this->mOldRev->getTimestamp() > $this->mNewRev->getTimestamp() ) {
 980                         $oldRev = $this->mNewRev; // flip
 981                         $newRev = $this->mOldRev; // flip
 982                 } else { // normal case
 983                         $oldRev = $this->mOldRev;
 984                         $newRev = $this->mNewRev;
 985                 }
 986
 987                 // Sanity: don't show the notice if too many rows must be scanned
 988                 // @todo show some special message for that case
 989                 $nEdits = $this->mNewPage->countRevisionsBetween( $oldRev, $newRev, 1000 );
 990                 if ( $nEdits > 0 && $nEdits <= 1000 ) {
 991                         $limit = 100; // use diff-multi-manyusers if too many users
 992                         $users = $this->mNewPage->getAuthorsBetween( $oldRev, $newRev, $limit );
 993                         $numUsers = count( $users );
 994
 995                         if ( $numUsers == 1 && $users[0] == $newRev->getUserText( Revision::RAW ) ) {
 996                                 $numUsers = 0; // special case to say "by the same user" instead of "by one other user"
 997                         }
 998
 999                         return self::intermediateEditsMsg( $nEdits, $numUsers, $limit );
1000                 }
1001
1002                 return ''; // nothing
1003         }
1004
1005         /**
1006          * Get a notice about how many intermediate edits and users there are
1007          *
1008          * @param int $numEdits
1009          * @param int $numUsers
1010          * @param int $limit
1011          *
1012          * @return string
1013          */
1014         public static function intermediateEditsMsg( $numEdits, $numUsers, $limit ) {
1015                 if ( $numUsers === 0 ) {
1016                         $msg = 'diff-multi-sameuser';
1017                 } elseif ( $numUsers > $limit ) {
1018                         $msg = 'diff-multi-manyusers';
1019                         $numUsers = $limit;
1020                 } else {
1021                         $msg = 'diff-multi-otherusers';
1022                 }
1023
1024                 return wfMessage( $msg )->numParams( $numEdits, $numUsers )->parse();
1025         }
1026
1027         /**
1028          * Get a header for a specified revision.
1029          *
1030          * @param Revision $rev
1031          * @param string $complete 'complete' to get the header wrapped depending
1032          *        the visibility of the revision and a link to edit the page.
1033          *
1034          * @return string HTML fragment
1035          */
1036         protected function getRevisionHeader( Revision $rev, $complete = '' ) {
1037                 $lang = $this->getLanguage();
1038                 $user = $this->getUser();
1039                 $revtimestamp = $rev->getTimestamp();
1040                 $timestamp = $lang->userTimeAndDate( $revtimestamp, $user );
1041                 $dateofrev = $lang->userDate( $revtimestamp, $user );
1042                 $timeofrev = $lang->userTime( $revtimestamp, $user );
1043
1044                 $header = $this->msg(
1045                         $rev->isCurrent() ? 'currentrev-asof' : 'revisionasof',
1046                         $timestamp,
1047                         $dateofrev,
1048                         $timeofrev
1049                 )->escaped();
1050
1051                 if ( $complete !== 'complete' ) {
1052                         return $header;
1053                 }
1054
1055                 $title = $rev->getTitle();
1056
1057                 $header = Linker::linkKnown( $title, $header, [],
1058                         [ 'oldid' => $rev->getID() ] );
1059
1060                 if ( $rev->userCan( Revision::DELETED_TEXT, $user ) ) {
1061                         $editQuery = [ 'action' => 'edit' ];
1062                         if ( !$rev->isCurrent() ) {
1063                                 $editQuery['oldid'] = $rev->getID();
1064                         }
1065
1066                         $key = $title->quickUserCan( 'edit', $user ) ? 'editold' : 'viewsourceold';
1067                         $msg = $this->msg( $key )->escaped();
1068                         $editLink = $this->msg( 'parentheses' )->rawParams(
1069                                 Linker::linkKnown( $title, $msg, [], $editQuery ) )->escaped();
1070                         $header .= ' ' . Html::rawElement(
1071                                 'span',
1072                                 [ 'class' => 'mw-diff-edit' ],
1073                                 $editLink
1074                         );
1075                         if ( $rev->isDeleted( Revision::DELETED_TEXT ) ) {
1076                                 $header = Html::rawElement(
1077                                         'span',
1078                                         [ 'class' => 'history-deleted' ],
1079                                         $header
1080                                 );
1081                         }
1082                 } else {
1083                         $header = Html::rawElement( 'span', [ 'class' => 'history-deleted' ], $header );
1084                 }
1085
1086                 return $header;
1087         }
1088
1089         /**
1090          * Add the header to a diff body
1091          *
1092          * @param string $diff Diff body
1093          * @param string $otitle Old revision header
1094          * @param string $ntitle New revision header
1095          * @param string $multi Notice telling user that there are intermediate
1096          *   revisions between the ones being compared
1097          * @param string $notice Other notices, e.g. that user is viewing deleted content
1098          *
1099          * @return string
1100          */
1101         public function addHeader( $diff, $otitle, $ntitle, $multi = '', $notice = '' ) {
1102                 // shared.css sets diff in interface language/dir, but the actual content
1103                 // is often in a different language, mostly the page content language/dir
1104                 $header = Html::openElement( 'table', [
1105                         'class' => [ 'diff', 'diff-contentalign-' . $this->getDiffLang()->alignStart() ],
1106                         'data-mw' => 'interface',
1107                 ] );
1108                 $userLang = htmlspecialchars( $this->getLanguage()->getHtmlCode() );
1109
1110                 if ( !$diff && !$otitle ) {
1111                         $header .= "
1112                         <tr style='vertical-align: top;' lang='{$userLang}'>
1113                         <td class='diff-ntitle'>{$ntitle}</td>
1114                         </tr>";
1115                         $multiColspan = 1;
1116                 } else {
1117                         if ( $diff ) { // Safari/Chrome show broken output if cols not used
1118                                 $header .= "
1119                                 <col class='diff-marker' />
1120                                 <col class='diff-content' />
1121                                 <col class='diff-marker' />
1122                                 <col class='diff-content' />";
1123                                 $colspan = 2;
1124                                 $multiColspan = 4;
1125                         } else {
1126                                 $colspan = 1;
1127                                 $multiColspan = 2;
1128                         }
1129                         if ( $otitle || $ntitle ) {
1130                                 $header .= "
1131                                 <tr style='vertical-align: top;' lang='{$userLang}'>
1132                                 <td colspan='$colspan' class='diff-otitle'>{$otitle}</td>
1133                                 <td colspan='$colspan' class='diff-ntitle'>{$ntitle}</td>
1134                                 </tr>";
1135                         }
1136                 }
1137
1138                 if ( $multi != '' ) {
1139                         $header .= "<tr><td colspan='{$multiColspan}' style='text-align: center;' " .
1140                                 "class='diff-multi' lang='{$userLang}'>{$multi}</td></tr>";
1141                 }
1142                 if ( $notice != '' ) {
1143                         $header .= "<tr><td colspan='{$multiColspan}' style='text-align: center;' " .
1144                                 "lang='{$userLang}'>{$notice}</td></tr>";
1145                 }
1146
1147                 return $header . $diff . "</table>";
1148         }
1149
1150         /**
1151          * Use specified text instead of loading from the database
1152          * @deprecated since 1.21, use setContent() instead.
1153          */
1154         public function setText( $oldText, $newText ) {
1155                 ContentHandler::deprecated( __METHOD__, "1.21" );
1156
1157                 $oldContent = ContentHandler::makeContent( $oldText, $this->getTitle() );
1158                 $newContent = ContentHandler::makeContent( $newText, $this->getTitle() );
1159
1160                 $this->setContent( $oldContent, $newContent );
1161         }
1162
1163         /**
1164          * Use specified text instead of loading from the database
1165          * @param Content $oldContent
1166          * @param Content $newContent
1167          * @since 1.21
1168          */
1169         public function setContent( Content $oldContent, Content $newContent ) {
1170                 $this->mOldContent = $oldContent;
1171                 $this->mNewContent = $newContent;
1172
1173                 $this->mTextLoaded = 2;
1174                 $this->mRevisionsLoaded = true;
1175         }
1176
1177         /**
1178          * Set the language in which the diff text is written
1179          * (Defaults to page content language).
1180          * @param Language|string $lang
1181          * @since 1.19
1182          */
1183         public function setTextLanguage( $lang ) {
1184                 $this->mDiffLang = wfGetLangObj( $lang );
1185         }
1186
1187         /**
1188          * Maps a revision pair definition as accepted by DifferenceEngine constructor
1189          * to a pair of actual integers representing revision ids.
1190          *
1191          * @param int $old Revision id, e.g. from URL parameter 'oldid'
1192          * @param int|string $new Revision id or strings 'next' or 'prev', e.g. from URL parameter 'diff'
1193          *
1194          * @return int[] List of two revision ids, older first, later second.
1195          *     Zero signifies invalid argument passed.
1196          *     false signifies that there is no previous/next revision ($old is the oldest/newest one).
1197          */
1198         public function mapDiffPrevNext( $old, $new ) {
1199                 if ( $new === 'prev' ) {
1200                         // Show diff between revision $old and the previous one. Get previous one from DB.
1201                         $newid = intval( $old );
1202                         $oldid = $this->getTitle()->getPreviousRevisionID( $newid );
1203                 } elseif ( $new === 'next' ) {
1204                         // Show diff between revision $old and the next one. Get next one from DB.
1205                         $oldid = intval( $old );
1206                         $newid = $this->getTitle()->getNextRevisionID( $oldid );
1207                 } else {
1208                         $oldid = intval( $old );
1209                         $newid = intval( $new );
1210                 }
1211
1212                 return [ $oldid, $newid ];
1213         }
1214
1215         /**
1216          * Load revision IDs
1217          */
1218         private function loadRevisionIds() {
1219                 if ( $this->mRevisionsIdsLoaded ) {
1220                         return;
1221                 }
1222
1223                 $this->mRevisionsIdsLoaded = true;
1224
1225                 $old = $this->mOldid;
1226                 $new = $this->mNewid;
1227
1228                 list( $this->mOldid, $this->mNewid ) = self::mapDiffPrevNext( $old, $new );
1229                 if ( $new === 'next' && $this->mNewid === false ) {
1230                         # if no result, NewId points to the newest old revision. The only newer
1231                         # revision is cur, which is "0".
1232                         $this->mNewid = 0;
1233                 }
1234
1235                 Hooks::run(
1236                         'NewDifferenceEngine',
1237                         [ $this->getTitle(), &$this->mOldid, &$this->mNewid, $old, $new ]
1238                 );
1239         }
1240
1241         /**
1242          * Load revision metadata for the specified articles. If newid is 0, then compare
1243          * the old article in oldid to the current article; if oldid is 0, then
1244          * compare the current article to the immediately previous one (ignoring the
1245          * value of newid).
1246          *
1247          * If oldid is false, leave the corresponding revision object set
1248          * to false. This is impossible via ordinary user input, and is provided for
1249          * API convenience.
1250          *
1251          * @return bool
1252          */
1253         public function loadRevisionData() {
1254                 if ( $this->mRevisionsLoaded ) {
1255                         return true;
1256                 }
1257
1258                 // Whether it succeeds or fails, we don't want to try again
1259                 $this->mRevisionsLoaded = true;
1260
1261                 $this->loadRevisionIds();
1262
1263                 // Load the new revision object
1264                 if ( $this->mNewid ) {
1265                         $this->mNewRev = Revision::newFromId( $this->mNewid );
1266                 } else {
1267                         $this->mNewRev = Revision::newFromTitle(
1268                                 $this->getTitle(),
1269                                 false,
1270                                 Revision::READ_NORMAL
1271                         );
1272                 }
1273
1274                 if ( !$this->mNewRev instanceof Revision ) {
1275                         return false;
1276                 }
1277
1278                 // Update the new revision ID in case it was 0 (makes life easier doing UI stuff)
1279                 $this->mNewid = $this->mNewRev->getId();
1280                 $this->mNewPage = $this->mNewRev->getTitle();
1281
1282                 // Load the old revision object
1283                 $this->mOldRev = false;
1284                 if ( $this->mOldid ) {
1285                         $this->mOldRev = Revision::newFromId( $this->mOldid );
1286                 } elseif ( $this->mOldid === 0 ) {
1287                         $rev = $this->mNewRev->getPrevious();
1288                         if ( $rev ) {
1289                                 $this->mOldid = $rev->getId();
1290                                 $this->mOldRev = $rev;
1291                         } else {
1292                                 // No previous revision; mark to show as first-version only.
1293                                 $this->mOldid = false;
1294                                 $this->mOldRev = false;
1295                         }
1296                 } /* elseif ( $this->mOldid === false ) leave mOldRev false; */
1297
1298                 if ( is_null( $this->mOldRev ) ) {
1299                         return false;
1300                 }
1301
1302                 if ( $this->mOldRev ) {
1303                         $this->mOldPage = $this->mOldRev->getTitle();
1304                 }
1305
1306                 // Load tags information for both revisions
1307                 $dbr = wfGetDB( DB_SLAVE );
1308                 if ( $this->mOldid !== false ) {
1309                         $this->mOldTags = $dbr->selectField(
1310                                 'tag_summary',
1311                                 'ts_tags',
1312                                 [ 'ts_rev_id' => $this->mOldid ],
1313                                 __METHOD__
1314                         );
1315                 } else {
1316                         $this->mOldTags = false;
1317                 }
1318                 $this->mNewTags = $dbr->selectField(
1319                         'tag_summary',
1320                         'ts_tags',
1321                         [ 'ts_rev_id' => $this->mNewid ],
1322                         __METHOD__
1323                 );
1324
1325                 return true;
1326         }
1327
1328         /**
1329          * Load the text of the revisions, as well as revision data.
1330          *
1331          * @return bool
1332          */
1333         public function loadText() {
1334                 if ( $this->mTextLoaded == 2 ) {
1335                         return true;
1336                 }
1337
1338                 // Whether it succeeds or fails, we don't want to try again
1339                 $this->mTextLoaded = 2;
1340
1341                 if ( !$this->loadRevisionData() ) {
1342                         return false;
1343                 }
1344
1345                 if ( $this->mOldRev ) {
1346                         $this->mOldContent = $this->mOldRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1347                         if ( $this->mOldContent === null ) {
1348                                 return false;
1349                         }
1350                 }
1351
1352                 if ( $this->mNewRev ) {
1353                         $this->mNewContent = $this->mNewRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1354                         if ( $this->mNewContent === null ) {
1355                                 return false;
1356                         }
1357                 }
1358
1359                 return true;
1360         }
1361
1362         /**
1363          * Load the text of the new revision, not the old one
1364          *
1365          * @return bool
1366          */
1367         public function loadNewText() {
1368                 if ( $this->mTextLoaded >= 1 ) {
1369                         return true;
1370                 }
1371
1372                 $this->mTextLoaded = 1;
1373
1374                 if ( !$this->loadRevisionData() ) {
1375                         return false;
1376                 }
1377
1378                 $this->mNewContent = $this->mNewRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1379
1380                 return true;
1381         }
1382
1383 }