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" data-mw="interface">[' .
 478                                         Linker::linkKnown(
 479                                                 $this->mNewPage,
 480                                                 $this->msg( 'markaspatrolleddiff' )->escaped(),
 481                                                 [],
 482                                                 [
 483                                                         'action' => 'markpatrolled',
 484                                                         'rcid' => $linkInfo['rcid'],
 485                                                         'token' => $linkInfo['token'],
 486                                                 ]
 487                                         ) . ']</span>';
 488                         }
 489                 }
 490                 return $this->mMarkPatrolledLink;
 491         }
 492
 493         /**
 494          * Returns an array of meta data needed to build a "mark as patrolled" link and
 495          * adds the mediawiki.page.patrol.ajax to the output.
 496          *
 497          * @return array|false An array of meta data for a patrol link (rcid & token)
 498          *  or false if no link is needed
 499          */
 500         protected function getMarkPatrolledLinkInfo() {
 501                 global $wgUseRCPatrol, $wgEnableAPI, $wgEnableWriteAPI;
 502
 503                 $user = $this->getUser();
 504
 505                 // Prepare a change patrol link, if applicable
 506                 if (
 507                         // Is patrolling enabled and the user allowed to?
 508                         $wgUseRCPatrol && $this->mNewPage->quickUserCan( 'patrol', $user ) &&
 509                         // Only do this if the revision isn't more than 6 hours older
 510                         // than the Max RC age (6h because the RC might not be cleaned out regularly)
 511                         RecentChange::isInRCLifespan( $this->mNewRev->getTimestamp(), 21600 )
 512                 ) {
 513                         // Look for an unpatrolled change corresponding to this diff
 514                         $db = wfGetDB( DB_SLAVE );
 515                         $change = RecentChange::newFromConds(
 516                                 [
 517                                         'rc_timestamp' => $db->timestamp( $this->mNewRev->getTimestamp() ),
 518                                         'rc_this_oldid' => $this->mNewid,
 519                                         'rc_patrolled' => 0
 520                                 ],
 521                                 __METHOD__
 522                         );
 523
 524                         if ( $change && !$change->getPerformer()->equals( $user ) ) {
 525                                 $rcid = $change->getAttribute( 'rc_id' );
 526                         } else {
 527                                 // None found or the page has been created by the current user.
 528                                 // If the user could patrol this it already would be patrolled
 529                                 $rcid = 0;
 530                         }
 531                         // Build the link
 532                         if ( $rcid ) {
 533                                 $this->getOutput()->preventClickjacking();
 534                                 if ( $wgEnableAPI && $wgEnableWriteAPI
 535                                         && $user->isAllowed( 'writeapi' )
 536                                 ) {
 537                                         $this->getOutput()->addModules( 'mediawiki.page.patrol.ajax' );
 538                                 }
 539
 540                                 $token = $user->getEditToken( $rcid );
 541                                 return [
 542                                         'rcid' => $rcid,
 543                                         'token' => $token,
 544                                 ];
 545                         }
 546                 }
 547
 548                 // No mark as patrolled link applicable
 549                 return false;
 550         }
 551
 552         /**
 553          * @param Revision $rev
 554          *
 555          * @return string
 556          */
 557         protected function revisionDeleteLink( $rev ) {
 558                 $link = Linker::getRevDeleteLink( $this->getUser(), $rev, $rev->getTitle() );
 559                 if ( $link !== '' ) {
 560                         $link = '&#160;&#160;&#160;' . $link . ' ';
 561                 }
 562
 563                 return $link;
 564         }
 565
 566         /**
 567          * Show the new revision of the page.
 568          */
 569         public function renderNewRevision() {
 570                 $out = $this->getOutput();
 571                 $revHeader = $this->getRevisionHeader( $this->mNewRev );
 572                 # Add "current version as of X" title
 573                 $out->addHTML( "<hr class='diff-hr' id='mw-oldid' />
 574                 <h2 class='diff-currentversion-title'>{$revHeader}</h2>\n" );
 575                 # Page content may be handled by a hooked call instead...
 576                 # @codingStandardsIgnoreStart Ignoring long lines.
 577                 if ( Hooks::run( 'ArticleContentOnDiff', [ $this, $out ] ) ) {
 578                         $this->loadNewText();
 579                         $out->setRevisionId( $this->mNewid );
 580                         $out->setRevisionTimestamp( $this->mNewRev->getTimestamp() );
 581                         $out->setArticleFlag( true );
 582
 583                         // NOTE: only needed for B/C: custom rendering of JS/CSS via hook
 584                         if ( $this->mNewPage->isCssJsSubpage() || $this->mNewPage->isCssOrJsPage() ) {
 585                                 // This needs to be synchronised with Article::showCssOrJsPage(), which sucks
 586                                 // Give hooks a chance to customise the output
 587                                 // @todo standardize this crap into one function
 588                                 if ( ContentHandler::runLegacyHooks( 'ShowRawCssJs', [ $this->mNewContent, $this->mNewPage, $out ] ) ) {
 589                                         // NOTE: deprecated hook, B/C only
 590                                         // use the content object's own rendering
 591                                         $cnt = $this->mNewRev->getContent();
 592                                         $po = $cnt ? $cnt->getParserOutput( $this->mNewRev->getTitle(), $this->mNewRev->getId() ) : null;
 593                                         if ( $po ) {
 594                                                 $out->addParserOutputContent( $po );
 595                                         }
 596                                 }
 597                         } elseif ( !Hooks::run( 'ArticleContentViewCustom', [ $this->mNewContent, $this->mNewPage, $out ] ) ) {
 598                                 // Handled by extension
 599                         } elseif ( !ContentHandler::runLegacyHooks( 'ArticleViewCustom', [ $this->mNewContent, $this->mNewPage, $out ] ) ) {
 600                                 // NOTE: deprecated hook, B/C only
 601                                 // Handled by extension
 602                         } else {
 603                                 // Normal page
 604                                 if ( $this->getTitle()->equals( $this->mNewPage ) ) {
 605                                         // If the Title stored in the context is the same as the one
 606                                         // of the new revision, we can use its associated WikiPage
 607                                         // object.
 608                                         $wikiPage = $this->getWikiPage();
 609                                 } else {
 610                                         // Otherwise we need to create our own WikiPage object
 611                                         $wikiPage = WikiPage::factory( $this->mNewPage );
 612                                 }
 613
 614                                 $parserOutput = $this->getParserOutput( $wikiPage, $this->mNewRev );
 615
 616                                 # WikiPage::getParserOutput() should not return false, but just in case
 617                                 if ( $parserOutput ) {
 618                                         $out->addParserOutput( $parserOutput );
 619                                 }
 620                         }
 621                 }
 622                 # @codingStandardsIgnoreEnd
 623
 624                 # Add redundant patrol link on bottom...
 625                 $out->addHTML( $this->markPatrolledLink() );
 626
 627         }
 628
 629         protected function getParserOutput( WikiPage $page, Revision $rev ) {
 630                 $parserOptions = $page->makeParserOptions( $this->getContext() );
 631
 632                 if ( !$rev->isCurrent() || !$rev->getTitle()->quickUserCan( 'edit', $this->getUser() ) ) {
 633                         $parserOptions->setEditSection( false );
 634                 }
 635
 636                 $parserOutput = $page->getParserOutput( $parserOptions, $rev->getId() );
 637
 638                 return $parserOutput;
 639         }
 640
 641         /**
 642          * Get the diff text, send it to the OutputPage object
 643          * Returns false if the diff could not be generated, otherwise returns true
 644          *
 645          * @param string|bool $otitle Header for old text or false
 646          * @param string|bool $ntitle Header for new text or false
 647          * @param string $notice HTML between diff header and body
 648          *
 649          * @return bool
 650          */
 651         public function showDiff( $otitle, $ntitle, $notice = '' ) {
 652                 $diff = $this->getDiff( $otitle, $ntitle, $notice );
 653                 if ( $diff === false ) {
 654                         $this->showMissingRevision();
 655
 656                         return false;
 657                 } else {
 658                         $this->showDiffStyle();
 659                         $this->getOutput()->addHTML( $diff );
 660
 661                         return true;
 662                 }
 663         }
 664
 665         /**
 666          * Add style sheets and supporting JS for diff display.
 667          */
 668         public function showDiffStyle() {
 669                 $this->getOutput()->addModuleStyles( 'mediawiki.action.history.diff' );
 670         }
 671
 672         /**
 673          * Get complete diff table, including header
 674          *
 675          * @param string|bool $otitle Header for old text or false
 676          * @param string|bool $ntitle Header for new text or false
 677          * @param string $notice HTML between diff header and body
 678          *
 679          * @return mixed
 680          */
 681         public function getDiff( $otitle, $ntitle, $notice = '' ) {
 682                 $body = $this->getDiffBody();
 683                 if ( $body === false ) {
 684                         return false;
 685                 }
 686
 687                 $multi = $this->getMultiNotice();
 688                 // Display a message when the diff is empty
 689                 if ( $body === '' ) {
 690                         $notice .= '<div class="mw-diff-empty">' .
 691                                 $this->msg( 'diff-empty' )->parse() .
 692                                 "</div>\n";
 693                 }
 694
 695                 return $this->addHeader( $body, $otitle, $ntitle, $multi, $notice );
 696         }
 697
 698         /**
 699          * Get the diff table body, without header
 700          *
 701          * @return mixed (string/false)
 702          */
 703         public function getDiffBody() {
 704                 $this->mCacheHit = true;
 705                 // Check if the diff should be hidden from this user
 706                 if ( !$this->loadRevisionData() ) {
 707                         return false;
 708                 } elseif ( $this->mOldRev &&
 709                         !$this->mOldRev->userCan( Revision::DELETED_TEXT, $this->getUser() )
 710                 ) {
 711                         return false;
 712                 } elseif ( $this->mNewRev &&
 713                         !$this->mNewRev->userCan( Revision::DELETED_TEXT, $this->getUser() )
 714                 ) {
 715                         return false;
 716                 }
 717                 // Short-circuit
 718                 if ( $this->mOldRev === false || ( $this->mOldRev && $this->mNewRev
 719                         && $this->mOldRev->getId() == $this->mNewRev->getId() )
 720                 ) {
 721                         return '';
 722                 }
 723                 // Cacheable?
 724                 $key = false;
 725                 $cache = ObjectCache::getMainWANInstance();
 726                 if ( $this->mOldid && $this->mNewid ) {
 727                         $key = $this->getDiffBodyCacheKey();
 728
 729                         // Try cache
 730                         if ( !$this->mRefreshCache ) {
 731                                 $difftext = $cache->get( $key );
 732                                 if ( $difftext ) {
 733                                         wfIncrStats( 'diff_cache.hit' );
 734                                         $difftext = $this->localiseLineNumbers( $difftext );
 735                                         $difftext .= "\n<!-- diff cache key $key -->\n";
 736
 737                                         return $difftext;
 738                                 }
 739                         } // don't try to load but save the result
 740                 }
 741                 $this->mCacheHit = false;
 742
 743                 // Loadtext is permission safe, this just clears out the diff
 744                 if ( !$this->loadText() ) {
 745                         return false;
 746                 }
 747
 748                 $difftext = $this->generateContentDiffBody( $this->mOldContent, $this->mNewContent );
 749
 750                 // Save to cache for 7 days
 751                 if ( !Hooks::run( 'AbortDiffCache', [ &$this ] ) ) {
 752                         wfIncrStats( 'diff_cache.uncacheable' );
 753                 } elseif ( $key !== false && $difftext !== false ) {
 754                         wfIncrStats( 'diff_cache.miss' );
 755                         $cache->set( $key, $difftext, 7 * 86400 );
 756                 } else {
 757                         wfIncrStats( 'diff_cache.uncacheable' );
 758                 }
 759                 // Replace line numbers with the text in the user's language
 760                 if ( $difftext !== false ) {
 761                         $difftext = $this->localiseLineNumbers( $difftext );
 762                 }
 763
 764                 return $difftext;
 765         }
 766
 767         /**
 768          * Returns the cache key for diff body text or content.
 769          *
 770          * @since 1.23
 771          *
 772          * @throws MWException
 773          * @return string
 774          */
 775         protected function getDiffBodyCacheKey() {
 776                 if ( !$this->mOldid || !$this->mNewid ) {
 777                         throw new MWException( 'mOldid and mNewid must be set to get diff cache key.' );
 778                 }
 779
 780                 return wfMemcKey( 'diff', 'version', MW_DIFF_VERSION,
 781                         'oldid', $this->mOldid, 'newid', $this->mNewid );
 782         }
 783
 784         /**
 785          * Generate a diff, no caching.
 786          *
 787          * This implementation uses generateTextDiffBody() to generate a diff based on the default
 788          * serialization of the given Content objects. This will fail if $old or $new are not
 789          * instances of TextContent.
 790          *
 791          * Subclasses may override this to provide a different rendering for the diff,
 792          * perhaps taking advantage of the content's native form. This is required for all content
 793          * models that are not text based.
 794          *
 795          * @since 1.21
 796          *
 797          * @param Content $old Old content
 798          * @param Content $new New content
 799          *
 800          * @throws MWException If old or new content is not an instance of TextContent.
 801          * @return bool|string
 802          */
 803         public function generateContentDiffBody( Content $old, Content $new ) {
 804                 if ( !( $old instanceof TextContent ) ) {
 805                         throw new MWException( "Diff not implemented for " . get_class( $old ) . "; " .
 806                                 "override generateContentDiffBody to fix this." );
 807                 }
 808
 809                 if ( !( $new instanceof TextContent ) ) {
 810                         throw new MWException( "Diff not implemented for " . get_class( $new ) . "; "
 811                                 . "override generateContentDiffBody to fix this." );
 812                 }
 813
 814                 $otext = $old->serialize();
 815                 $ntext = $new->serialize();
 816
 817                 return $this->generateTextDiffBody( $otext, $ntext );
 818         }
 819
 820         /**
 821          * Generate a diff, no caching
 822          *
 823          * @param string $otext Old text, must be already segmented
 824          * @param string $ntext New text, must be already segmented
 825          *
 826          * @return bool|string
 827          * @deprecated since 1.21, use generateContentDiffBody() instead!
 828          */
 829         public function generateDiffBody( $otext, $ntext ) {
 830                 ContentHandler::deprecated( __METHOD__, "1.21" );
 831
 832                 return $this->generateTextDiffBody( $otext, $ntext );
 833         }
 834
 835         /**
 836          * Generate a diff, no caching
 837          *
 838          * @todo move this to TextDifferenceEngine, make DifferenceEngine abstract. At some point.
 839          *
 840          * @param string $otext Old text, must be already segmented
 841          * @param string $ntext New text, must be already segmented
 842          *
 843          * @return bool|string
 844          */
 845         public function generateTextDiffBody( $otext, $ntext ) {
 846                 $diff = function() use ( $otext, $ntext ) {
 847                         $time = microtime( true );
 848
 849                         $result = $this->textDiff( $otext, $ntext );
 850
 851                         $time = intval( ( microtime( true ) - $time ) * 1000 );
 852                         $this->getStats()->timing( 'diff_time', $time );
 853                         // Log requests slower than 99th percentile
 854                         if ( $time > 100 && $this->mOldPage && $this->mNewPage ) {
 855                                 wfDebugLog( 'diff',
 856                                         "$time ms diff: {$this->mOldid} -> {$this->mNewid} {$this->mNewPage}" );
 857                         }
 858
 859                         return $result;
 860                 };
 861
 862                 $error = function( $status ) {
 863                         throw new FatalError( $status->getWikiText() );
 864                 };
 865
 866                 // Use PoolCounter if the diff looks like it can be expensive
 867                 if ( strlen( $otext ) + strlen( $ntext ) > 20000 ) {
 868                         $work = new PoolCounterWorkViaCallback( 'diff',
 869                                 md5( $otext ) . md5( $ntext ),
 870                                 [ 'doWork' => $diff, 'error' => $error ]
 871                         );
 872                         return $work->execute();
 873                 }
 874
 875                 return $diff();
 876         }
 877
 878         /**
 879          * Generates diff, to be wrapped internally in a logging/instrumentation
 880          *
 881          * @param string $otext Old text, must be already segmented
 882          * @param string $ntext New text, must be already segmented
 883          * @return bool|string
 884          */
 885         protected function textDiff( $otext, $ntext ) {
 886                 global $wgExternalDiffEngine, $wgContLang;
 887
 888                 $otext = str_replace( "\r\n", "\n", $otext );
 889                 $ntext = str_replace( "\r\n", "\n", $ntext );
 890
 891                 if ( $wgExternalDiffEngine == 'wikidiff' || $wgExternalDiffEngine == 'wikidiff3' ) {
 892                         wfDeprecated( "\$wgExternalDiffEngine = '{$wgExternalDiffEngine}'", '1.27' );
 893                         $wgExternalDiffEngine = false;
 894                 } elseif ( $wgExternalDiffEngine == 'wikidiff2' ) {
 895                         // Same as above, but with no deprecation warnings
 896                         $wgExternalDiffEngine = false;
 897                 } elseif ( !is_string( $wgExternalDiffEngine ) && $wgExternalDiffEngine !== false ) {
 898                         // And prevent people from shooting themselves in the foot...
 899                         wfWarn( '$wgExternalDiffEngine is set to a non-string value, forcing it to false' );
 900                         $wgExternalDiffEngine = false;
 901                 }
 902
 903                 if ( function_exists( 'wikidiff2_do_diff' ) && $wgExternalDiffEngine === false ) {
 904                         # Better external diff engine, the 2 may some day be dropped
 905                         # This one does the escaping and segmenting itself
 906                         $text = wikidiff2_do_diff( $otext, $ntext, 2 );
 907                         $text .= $this->debug( 'wikidiff2' );
 908
 909                         return $text;
 910                 } elseif ( $wgExternalDiffEngine !== false && is_executable( $wgExternalDiffEngine ) ) {
 911                         # Diff via the shell
 912                         $tmpDir = wfTempDir();
 913                         $tempName1 = tempnam( $tmpDir, 'diff_' );
 914                         $tempName2 = tempnam( $tmpDir, 'diff_' );
 915
 916                         $tempFile1 = fopen( $tempName1, "w" );
 917                         if ( !$tempFile1 ) {
 918                                 return false;
 919                         }
 920                         $tempFile2 = fopen( $tempName2, "w" );
 921                         if ( !$tempFile2 ) {
 922                                 return false;
 923                         }
 924                         fwrite( $tempFile1, $otext );
 925                         fwrite( $tempFile2, $ntext );
 926                         fclose( $tempFile1 );
 927                         fclose( $tempFile2 );
 928                         $cmd = wfEscapeShellArg( $wgExternalDiffEngine, $tempName1, $tempName2 );
 929                         $difftext = wfShellExec( $cmd );
 930                         $difftext .= $this->debug( "external $wgExternalDiffEngine" );
 931                         unlink( $tempName1 );
 932                         unlink( $tempName2 );
 933
 934                         return $difftext;
 935                 }
 936
 937                 # Native PHP diff
 938                 $ota = explode( "\n", $wgContLang->segmentForDiff( $otext ) );
 939                 $nta = explode( "\n", $wgContLang->segmentForDiff( $ntext ) );
 940                 $diffs = new Diff( $ota, $nta );
 941                 $formatter = new TableDiffFormatter();
 942                 $difftext = $wgContLang->unsegmentForDiff( $formatter->format( $diffs ) );
 943
 944                 return $difftext;
 945         }
 946
 947         /**
 948          * Generate a debug comment indicating diff generating time,
 949          * server node, and generator backend.
 950          *
 951          * @param string $generator : What diff engine was used
 952          *
 953          * @return string
 954          */
 955         protected function debug( $generator = "internal" ) {
 956                 global $wgShowHostnames;
 957                 if ( !$this->enableDebugComment ) {
 958                         return '';
 959                 }
 960                 $data = [ $generator ];
 961                 if ( $wgShowHostnames ) {
 962                         $data[] = wfHostname();
 963                 }
 964                 $data[] = wfTimestamp( TS_DB );
 965
 966                 return "<!-- diff generator: " .
 967                         implode( " ", array_map( "htmlspecialchars", $data ) ) .
 968                         " -->\n";
 969         }
 970
 971         /**
 972          * Replace line numbers with the text in the user's language
 973          *
 974          * @param string $text
 975          *
 976          * @return mixed
 977          */
 978         public function localiseLineNumbers( $text ) {
 979                 return preg_replace_callback(
 980                         '/<!--LINE (\d+)-->/',
 981                         [ &$this, 'localiseLineNumbersCb' ],
 982                         $text
 983                 );
 984         }
 985
 986         public function localiseLineNumbersCb( $matches ) {
 987                 if ( $matches[1] === '1' && $this->mReducedLineNumbers ) {
 988                         return '';
 989                 }
 990
 991                 return $this->msg( 'lineno' )->numParams( $matches[1] )->escaped();
 992         }
 993
 994         /**
 995          * If there are revisions between the ones being compared, return a note saying so.
 996          *
 997          * @return string
 998          */
 999         public function getMultiNotice() {
1000                 if ( !is_object( $this->mOldRev ) || !is_object( $this->mNewRev ) ) {
1001                         return '';
1002                 } elseif ( !$this->mOldPage->equals( $this->mNewPage ) ) {
1003                         // Comparing two different pages? Count would be meaningless.
1004                         return '';
1005                 }
1006
1007                 if ( $this->mOldRev->getTimestamp() > $this->mNewRev->getTimestamp() ) {
1008                         $oldRev = $this->mNewRev; // flip
1009                         $newRev = $this->mOldRev; // flip
1010                 } else { // normal case
1011                         $oldRev = $this->mOldRev;
1012                         $newRev = $this->mNewRev;
1013                 }
1014
1015                 // Sanity: don't show the notice if too many rows must be scanned
1016                 // @todo show some special message for that case
1017                 $nEdits = $this->mNewPage->countRevisionsBetween( $oldRev, $newRev, 1000 );
1018                 if ( $nEdits > 0 && $nEdits <= 1000 ) {
1019                         $limit = 100; // use diff-multi-manyusers if too many users
1020                         $users = $this->mNewPage->getAuthorsBetween( $oldRev, $newRev, $limit );
1021                         $numUsers = count( $users );
1022
1023                         if ( $numUsers == 1 && $users[0] == $newRev->getUserText( Revision::RAW ) ) {
1024                                 $numUsers = 0; // special case to say "by the same user" instead of "by one other user"
1025                         }
1026
1027                         return self::intermediateEditsMsg( $nEdits, $numUsers, $limit );
1028                 }
1029
1030                 return ''; // nothing
1031         }
1032
1033         /**
1034          * Get a notice about how many intermediate edits and users there are
1035          *
1036          * @param int $numEdits
1037          * @param int $numUsers
1038          * @param int $limit
1039          *
1040          * @return string
1041          */
1042         public static function intermediateEditsMsg( $numEdits, $numUsers, $limit ) {
1043                 if ( $numUsers === 0 ) {
1044                         $msg = 'diff-multi-sameuser';
1045                 } elseif ( $numUsers > $limit ) {
1046                         $msg = 'diff-multi-manyusers';
1047                         $numUsers = $limit;
1048                 } else {
1049                         $msg = 'diff-multi-otherusers';
1050                 }
1051
1052                 return wfMessage( $msg )->numParams( $numEdits, $numUsers )->parse();
1053         }
1054
1055         /**
1056          * Get a header for a specified revision.
1057          *
1058          * @param Revision $rev
1059          * @param string $complete 'complete' to get the header wrapped depending
1060          *        the visibility of the revision and a link to edit the page.
1061          *
1062          * @return string HTML fragment
1063          */
1064         protected function getRevisionHeader( Revision $rev, $complete = '' ) {
1065                 $lang = $this->getLanguage();
1066                 $user = $this->getUser();
1067                 $revtimestamp = $rev->getTimestamp();
1068                 $timestamp = $lang->userTimeAndDate( $revtimestamp, $user );
1069                 $dateofrev = $lang->userDate( $revtimestamp, $user );
1070                 $timeofrev = $lang->userTime( $revtimestamp, $user );
1071
1072                 $header = $this->msg(
1073                         $rev->isCurrent() ? 'currentrev-asof' : 'revisionasof',
1074                         $timestamp,
1075                         $dateofrev,
1076                         $timeofrev
1077                 )->escaped();
1078
1079                 if ( $complete !== 'complete' ) {
1080                         return $header;
1081                 }
1082
1083                 $title = $rev->getTitle();
1084
1085                 $header = Linker::linkKnown( $title, $header, [],
1086                         [ 'oldid' => $rev->getId() ] );
1087
1088                 if ( $rev->userCan( Revision::DELETED_TEXT, $user ) ) {
1089                         $editQuery = [ 'action' => 'edit' ];
1090                         if ( !$rev->isCurrent() ) {
1091                                 $editQuery['oldid'] = $rev->getId();
1092                         }
1093
1094                         $key = $title->quickUserCan( 'edit', $user ) ? 'editold' : 'viewsourceold';
1095                         $msg = $this->msg( $key )->escaped();
1096                         $editLink = $this->msg( 'parentheses' )->rawParams(
1097                                 Linker::linkKnown( $title, $msg, [], $editQuery ) )->escaped();
1098                         $header .= ' ' . Html::rawElement(
1099                                 'span',
1100                                 [ 'class' => 'mw-diff-edit' ],
1101                                 $editLink
1102                         );
1103                         if ( $rev->isDeleted( Revision::DELETED_TEXT ) ) {
1104                                 $header = Html::rawElement(
1105                                         'span',
1106                                         [ 'class' => 'history-deleted' ],
1107                                         $header
1108                                 );
1109                         }
1110                 } else {
1111                         $header = Html::rawElement( 'span', [ 'class' => 'history-deleted' ], $header );
1112                 }
1113
1114                 return $header;
1115         }
1116
1117         /**
1118          * Add the header to a diff body
1119          *
1120          * @param string $diff Diff body
1121          * @param string $otitle Old revision header
1122          * @param string $ntitle New revision header
1123          * @param string $multi Notice telling user that there are intermediate
1124          *   revisions between the ones being compared
1125          * @param string $notice Other notices, e.g. that user is viewing deleted content
1126          *
1127          * @return string
1128          */
1129         public function addHeader( $diff, $otitle, $ntitle, $multi = '', $notice = '' ) {
1130                 // shared.css sets diff in interface language/dir, but the actual content
1131                 // is often in a different language, mostly the page content language/dir
1132                 $header = Html::openElement( 'table', [
1133                         'class' => [ 'diff', 'diff-contentalign-' . $this->getDiffLang()->alignStart() ],
1134                         'data-mw' => 'interface',
1135                 ] );
1136                 $userLang = htmlspecialchars( $this->getLanguage()->getHtmlCode() );
1137
1138                 if ( !$diff && !$otitle ) {
1139                         $header .= "
1140                         <tr style='vertical-align: top;' lang='{$userLang}'>
1141                         <td class='diff-ntitle'>{$ntitle}</td>
1142                         </tr>";
1143                         $multiColspan = 1;
1144                 } else {
1145                         if ( $diff ) { // Safari/Chrome show broken output if cols not used
1146                                 $header .= "
1147                                 <col class='diff-marker' />
1148                                 <col class='diff-content' />
1149                                 <col class='diff-marker' />
1150                                 <col class='diff-content' />";
1151                                 $colspan = 2;
1152                                 $multiColspan = 4;
1153                         } else {
1154                                 $colspan = 1;
1155                                 $multiColspan = 2;
1156                         }
1157                         if ( $otitle || $ntitle ) {
1158                                 $header .= "
1159                                 <tr style='vertical-align: top;' lang='{$userLang}'>
1160                                 <td colspan='$colspan' class='diff-otitle'>{$otitle}</td>
1161                                 <td colspan='$colspan' class='diff-ntitle'>{$ntitle}</td>
1162                                 </tr>";
1163                         }
1164                 }
1165
1166                 if ( $multi != '' ) {
1167                         $header .= "<tr><td colspan='{$multiColspan}' style='text-align: center;' " .
1168                                 "class='diff-multi' lang='{$userLang}'>{$multi}</td></tr>";
1169                 }
1170                 if ( $notice != '' ) {
1171                         $header .= "<tr><td colspan='{$multiColspan}' style='text-align: center;' " .
1172                                 "lang='{$userLang}'>{$notice}</td></tr>";
1173                 }
1174
1175                 return $header . $diff . "</table>";
1176         }
1177
1178         /**
1179          * Use specified text instead of loading from the database
1180          * @param Content $oldContent
1181          * @param Content $newContent
1182          * @since 1.21
1183          */
1184         public function setContent( Content $oldContent, Content $newContent ) {
1185                 $this->mOldContent = $oldContent;
1186                 $this->mNewContent = $newContent;
1187
1188                 $this->mTextLoaded = 2;
1189                 $this->mRevisionsLoaded = true;
1190         }
1191
1192         /**
1193          * Set the language in which the diff text is written
1194          * (Defaults to page content language).
1195          * @param Language|string $lang
1196          * @since 1.19
1197          */
1198         public function setTextLanguage( $lang ) {
1199                 $this->mDiffLang = wfGetLangObj( $lang );
1200         }
1201
1202         /**
1203          * Maps a revision pair definition as accepted by DifferenceEngine constructor
1204          * to a pair of actual integers representing revision ids.
1205          *
1206          * @param int $old Revision id, e.g. from URL parameter 'oldid'
1207          * @param int|string $new Revision id or strings 'next' or 'prev', e.g. from URL parameter 'diff'
1208          *
1209          * @return int[] List of two revision ids, older first, later second.
1210          *     Zero signifies invalid argument passed.
1211          *     false signifies that there is no previous/next revision ($old is the oldest/newest one).
1212          */
1213         public function mapDiffPrevNext( $old, $new ) {
1214                 if ( $new === 'prev' ) {
1215                         // Show diff between revision $old and the previous one. Get previous one from DB.
1216                         $newid = intval( $old );
1217                         $oldid = $this->getTitle()->getPreviousRevisionID( $newid );
1218                 } elseif ( $new === 'next' ) {
1219                         // Show diff between revision $old and the next one. Get next one from DB.
1220                         $oldid = intval( $old );
1221                         $newid = $this->getTitle()->getNextRevisionID( $oldid );
1222                 } else {
1223                         $oldid = intval( $old );
1224                         $newid = intval( $new );
1225                 }
1226
1227                 return [ $oldid, $newid ];
1228         }
1229
1230         /**
1231          * Load revision IDs
1232          */
1233         private function loadRevisionIds() {
1234                 if ( $this->mRevisionsIdsLoaded ) {
1235                         return;
1236                 }
1237
1238                 $this->mRevisionsIdsLoaded = true;
1239
1240                 $old = $this->mOldid;
1241                 $new = $this->mNewid;
1242
1243                 list( $this->mOldid, $this->mNewid ) = self::mapDiffPrevNext( $old, $new );
1244                 if ( $new === 'next' && $this->mNewid === false ) {
1245                         # if no result, NewId points to the newest old revision. The only newer
1246                         # revision is cur, which is "0".
1247                         $this->mNewid = 0;
1248                 }
1249
1250                 Hooks::run(
1251                         'NewDifferenceEngine',
1252                         [ $this->getTitle(), &$this->mOldid, &$this->mNewid, $old, $new ]
1253                 );
1254         }
1255
1256         /**
1257          * Load revision metadata for the specified articles. If newid is 0, then compare
1258          * the old article in oldid to the current article; if oldid is 0, then
1259          * compare the current article to the immediately previous one (ignoring the
1260          * value of newid).
1261          *
1262          * If oldid is false, leave the corresponding revision object set
1263          * to false. This is impossible via ordinary user input, and is provided for
1264          * API convenience.
1265          *
1266          * @return bool
1267          */
1268         public function loadRevisionData() {
1269                 if ( $this->mRevisionsLoaded ) {
1270                         return true;
1271                 }
1272
1273                 // Whether it succeeds or fails, we don't want to try again
1274                 $this->mRevisionsLoaded = true;
1275
1276                 $this->loadRevisionIds();
1277
1278                 // Load the new revision object
1279                 if ( $this->mNewid ) {
1280                         $this->mNewRev = Revision::newFromId( $this->mNewid );
1281                 } else {
1282                         $this->mNewRev = Revision::newFromTitle(
1283                                 $this->getTitle(),
1284                                 false,
1285                                 Revision::READ_NORMAL
1286                         );
1287                 }
1288
1289                 if ( !$this->mNewRev instanceof Revision ) {
1290                         return false;
1291                 }
1292
1293                 // Update the new revision ID in case it was 0 (makes life easier doing UI stuff)
1294                 $this->mNewid = $this->mNewRev->getId();
1295                 $this->mNewPage = $this->mNewRev->getTitle();
1296
1297                 // Load the old revision object
1298                 $this->mOldRev = false;
1299                 if ( $this->mOldid ) {
1300                         $this->mOldRev = Revision::newFromId( $this->mOldid );
1301                 } elseif ( $this->mOldid === 0 ) {
1302                         $rev = $this->mNewRev->getPrevious();
1303                         if ( $rev ) {
1304                                 $this->mOldid = $rev->getId();
1305                                 $this->mOldRev = $rev;
1306                         } else {
1307                                 // No previous revision; mark to show as first-version only.
1308                                 $this->mOldid = false;
1309                                 $this->mOldRev = false;
1310                         }
1311                 } /* elseif ( $this->mOldid === false ) leave mOldRev false; */
1312
1313                 if ( is_null( $this->mOldRev ) ) {
1314                         return false;
1315                 }
1316
1317                 if ( $this->mOldRev ) {
1318                         $this->mOldPage = $this->mOldRev->getTitle();
1319                 }
1320
1321                 // Load tags information for both revisions
1322                 $dbr = wfGetDB( DB_SLAVE );
1323                 if ( $this->mOldid !== false ) {
1324                         $this->mOldTags = $dbr->selectField(
1325                                 'tag_summary',
1326                                 'ts_tags',
1327                                 [ 'ts_rev_id' => $this->mOldid ],
1328                                 __METHOD__
1329                         );
1330                 } else {
1331                         $this->mOldTags = false;
1332                 }
1333                 $this->mNewTags = $dbr->selectField(
1334                         'tag_summary',
1335                         'ts_tags',
1336                         [ 'ts_rev_id' => $this->mNewid ],
1337                         __METHOD__
1338                 );
1339
1340                 return true;
1341         }
1342
1343         /**
1344          * Load the text of the revisions, as well as revision data.
1345          *
1346          * @return bool
1347          */
1348         public function loadText() {
1349                 if ( $this->mTextLoaded == 2 ) {
1350                         return true;
1351                 }
1352
1353                 // Whether it succeeds or fails, we don't want to try again
1354                 $this->mTextLoaded = 2;
1355
1356                 if ( !$this->loadRevisionData() ) {
1357                         return false;
1358                 }
1359
1360                 if ( $this->mOldRev ) {
1361                         $this->mOldContent = $this->mOldRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1362                         if ( $this->mOldContent === null ) {
1363                                 return false;
1364                         }
1365                 }
1366
1367                 if ( $this->mNewRev ) {
1368                         $this->mNewContent = $this->mNewRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1369                         if ( $this->mNewContent === null ) {
1370                                 return false;
1371                         }
1372                 }
1373
1374                 return true;
1375         }
1376
1377         /**
1378          * Load the text of the new revision, not the old one
1379          *
1380          * @return bool
1381          */
1382         public function loadNewText() {
1383                 if ( $this->mTextLoaded >= 1 ) {
1384                         return true;
1385                 }
1386
1387                 $this->mTextLoaded = 1;
1388
1389                 if ( !$this->loadRevisionData() ) {
1390                         return false;
1391                 }
1392
1393                 $this->mNewContent = $this->mNewRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1394
1395                 return true;
1396         }
1397
1398 }