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 // Deprecated, use class constant instead
  25 define( 'MW_DIFF_VERSION', '1.11a' );
  26
  27 /**
  28  * @todo document
  29  * @ingroup DifferenceEngine
  30  */
  31 class DifferenceEngine extends ContextSource {
  32         /**
  33          * Constant to indicate diff cache compatibility.
  34          * Bump this when changing the diff formatting in a way that
  35          * fixes important bugs or such to force cached diff views to
  36          * clear.
  37          */
  38         const DIFF_VERSION = MW_DIFF_VERSION;
  39
  40         /** @var int */
  41         public $mOldid;
  42
  43         /** @var int */
  44         public $mNewid;
  45
  46         private $mOldTags;
  47         private $mNewTags;
  48
  49         /** @var Content */
  50         public $mOldContent;
  51
  52         /** @var Content */
  53         public $mNewContent;
  54
  55         /** @var Language */
  56         protected $mDiffLang;
  57
  58         /** @var Title */
  59         public $mOldPage;
  60
  61         /** @var Title */
  62         public $mNewPage;
  63
  64         /** @var Revision */
  65         public $mOldRev;
  66
  67         /** @var Revision */
  68         public $mNewRev;
  69
  70         /** @var bool Have the revisions IDs been loaded */
  71         private $mRevisionsIdsLoaded = false;
  72
  73         /** @var bool Have the revisions been loaded */
  74         public $mRevisionsLoaded = false;
  75
  76         /** @var int How many text blobs have been loaded, 0, 1 or 2? */
  77         public $mTextLoaded = 0;
  78
  79         /** @var bool Was the diff fetched from cache? */
  80         public $mCacheHit = false;
  81
  82         /**
  83          * Set this to true to add debug info to the HTML output.
  84          * Warning: this may cause RSS readers to spuriously mark articles as "new"
  85          * (bug 20601)
  86          */
  87         public $enableDebugComment = false;
  88
  89         /** @var bool If true, line X is not displayed when X is 1, for example
  90          *    to increase readability and conserve space with many small diffs.
  91          */
  92         protected $mReducedLineNumbers = false;
  93
  94         /** @var string Link to action=markpatrolled */
  95         protected $mMarkPatrolledLink = null;
  96
  97         /** @var bool Show rev_deleted content if allowed */
  98         protected $unhide = false;
  99
 100         /** @var bool Refresh the diff cache */
 101         protected $mRefreshCache = false;
 102
 103         /**#@-*/
 104
 105         /**
 106          * Constructor
 107          * @param IContextSource $context Context to use, anything else will be ignored
 108          * @param int $old Old ID we want to show and diff with.
 109          * @param string|int $new Either revision ID or 'prev' or 'next'. Default: 0.
 110          * @param int $rcid Deprecated, no longer used!
 111          * @param bool $refreshCache If set, refreshes the diff cache
 112          * @param bool $unhide If set, allow viewing deleted revs
 113          */
 114         public function __construct( $context = null, $old = 0, $new = 0, $rcid = 0,
 115                 $refreshCache = false, $unhide = false
 116         ) {
 117                 if ( $context instanceof IContextSource ) {
 118                         $this->setContext( $context );
 119                 }
 120
 121                 wfDebug( "DifferenceEngine old '$old' new '$new' rcid '$rcid'\n" );
 122
 123                 $this->mOldid = $old;
 124                 $this->mNewid = $new;
 125                 $this->mRefreshCache = $refreshCache;
 126                 $this->unhide = $unhide;
 127         }
 128
 129         /**
 130          * @param bool $value
 131          */
 132         public function setReducedLineNumbers( $value = true ) {
 133                 $this->mReducedLineNumbers = $value;
 134         }
 135
 136         /**
 137          * @return Language
 138          */
 139         public function getDiffLang() {
 140                 if ( $this->mDiffLang === null ) {
 141                         # Default language in which the diff text is written.
 142                         $this->mDiffLang = $this->getTitle()->getPageLanguage();
 143                 }
 144
 145                 return $this->mDiffLang;
 146         }
 147
 148         /**
 149          * @return bool
 150          */
 151         public function wasCacheHit() {
 152                 return $this->mCacheHit;
 153         }
 154
 155         /**
 156          * @return int
 157          */
 158         public function getOldid() {
 159                 $this->loadRevisionIds();
 160
 161                 return $this->mOldid;
 162         }
 163
 164         /**
 165          * @return bool|int
 166          */
 167         public function getNewid() {
 168                 $this->loadRevisionIds();
 169
 170                 return $this->mNewid;
 171         }
 172
 173         /**
 174          * Look up a special:Undelete link to the given deleted revision id,
 175          * as a workaround for being unable to load deleted diffs in currently.
 176          *
 177          * @param int $id Revision ID
 178          *
 179          * @return mixed URL or false
 180          */
 181         public function deletedLink( $id ) {
 182                 if ( $this->getUser()->isAllowed( 'deletedhistory' ) ) {
 183                         $dbr = wfGetDB( DB_SLAVE );
 184                         $row = $dbr->selectRow( 'archive', '*',
 185                                 [ 'ar_rev_id' => $id ],
 186                                 __METHOD__ );
 187                         if ( $row ) {
 188                                 $rev = Revision::newFromArchiveRow( $row );
 189                                 $title = Title::makeTitleSafe( $row->ar_namespace, $row->ar_title );
 190
 191                                 return SpecialPage::getTitleFor( 'Undelete' )->getFullURL( [
 192                                         'target' => $title->getPrefixedText(),
 193                                         'timestamp' => $rev->getTimestamp()
 194                                 ] );
 195                         }
 196                 }
 197
 198                 return false;
 199         }
 200
 201         /**
 202          * Build a wikitext link toward a deleted revision, if viewable.
 203          *
 204          * @param int $id Revision ID
 205          *
 206          * @return string Wikitext fragment
 207          */
 208         public function deletedIdMarker( $id ) {
 209                 $link = $this->deletedLink( $id );
 210                 if ( $link ) {
 211                         return "[$link $id]";
 212                 } else {
 213                         return $id;
 214                 }
 215         }
 216
 217         private function showMissingRevision() {
 218                 $out = $this->getOutput();
 219
 220                 $missing = [];
 221                 if ( $this->mOldRev === null ||
 222                         ( $this->mOldRev && $this->mOldContent === null )
 223                 ) {
 224                         $missing[] = $this->deletedIdMarker( $this->mOldid );
 225                 }
 226                 if ( $this->mNewRev === null ||
 227                         ( $this->mNewRev && $this->mNewContent === null )
 228                 ) {
 229                         $missing[] = $this->deletedIdMarker( $this->mNewid );
 230                 }
 231
 232                 $out->setPageTitle( $this->msg( 'errorpagetitle' ) );
 233                 $msg = $this->msg( 'difference-missing-revision' )
 234                         ->params( $this->getLanguage()->listToText( $missing ) )
 235                         ->numParams( count( $missing ) )
 236                         ->parseAsBlock();
 237                 $out->addHTML( $msg );
 238         }
 239
 240         public function showDiffPage( $diffOnly = false ) {
 241
 242                 # Allow frames except in certain special cases
 243                 $out = $this->getOutput();
 244                 $out->allowClickjacking();
 245                 $out->setRobotPolicy( 'noindex,nofollow' );
 246
 247                 if ( !$this->loadRevisionData() ) {
 248                         $this->showMissingRevision();
 249
 250                         return;
 251                 }
 252
 253                 $user = $this->getUser();
 254                 $permErrors = $this->mNewPage->getUserPermissionsErrors( 'read', $user );
 255                 if ( $this->mOldPage ) { # mOldPage might not be set, see below.
 256                         $permErrors = wfMergeErrorArrays( $permErrors,
 257                                 $this->mOldPage->getUserPermissionsErrors( 'read', $user ) );
 258                 }
 259                 if ( count( $permErrors ) ) {
 260                         throw new PermissionsError( 'read', $permErrors );
 261                 }
 262
 263                 $rollback = '';
 264
 265                 $query = [];
 266                 # Carry over 'diffonly' param via navigation links
 267                 if ( $diffOnly != $user->getBoolOption( 'diffonly' ) ) {
 268                         $query['diffonly'] = $diffOnly;
 269                 }
 270                 # Cascade unhide param in links for easy deletion browsing
 271                 if ( $this->unhide ) {
 272                         $query['unhide'] = 1;
 273                 }
 274
 275                 # Check if one of the revisions is deleted/suppressed
 276                 $deleted = $suppressed = false;
 277                 $allowed = $this->mNewRev->userCan( Revision::DELETED_TEXT, $user );
 278
 279                 $revisionTools = [];
 280
 281                 # mOldRev is false if the difference engine is called with a "vague" query for
 282                 # a diff between a version V and its previous version V' AND the version V
 283                 # is the first version of that article. In that case, V' does not exist.
 284                 if ( $this->mOldRev === false ) {
 285                         $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 286                         $samePage = true;
 287                         $oldHeader = '';
 288                 } else {
 289                         Hooks::run( 'DiffViewHeader', [ $this, $this->mOldRev, $this->mNewRev ] );
 290
 291                         if ( $this->mNewPage->equals( $this->mOldPage ) ) {
 292                                 $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 293                                 $samePage = true;
 294                         } else {
 295                                 $out->setPageTitle( $this->msg( 'difference-title-multipage',
 296                                         $this->mOldPage->getPrefixedText(), $this->mNewPage->getPrefixedText() ) );
 297                                 $out->addSubtitle( $this->msg( 'difference-multipage' ) );
 298                                 $samePage = false;
 299                         }
 300
 301                         if ( $samePage && $this->mNewPage->quickUserCan( 'edit', $user ) ) {
 302                                 if ( $this->mNewRev->isCurrent() && $this->mNewPage->userCan( 'rollback', $user ) ) {
 303                                         $rollbackLink = Linker::generateRollback( $this->mNewRev, $this->getContext() );
 304                                         if ( $rollbackLink ) {
 305                                                 $out->preventClickjacking();
 306                                                 $rollback = '&#160;&#160;&#160;' . $rollbackLink;
 307                                         }
 308                                 }
 309
 310                                 if ( !$this->mOldRev->isDeleted( Revision::DELETED_TEXT ) &&
 311                                         !$this->mNewRev->isDeleted( Revision::DELETED_TEXT )
 312                                 ) {
 313                                         $undoLink = Html::element( 'a', [
 314                                                         'href' => $this->mNewPage->getLocalURL( [
 315                                                                 'action' => 'edit',
 316                                                                 'undoafter' => $this->mOldid,
 317                                                                 'undo' => $this->mNewid
 318                                                         ] ),
 319                                                         'title' => Linker::titleAttrib( 'undo' ),
 320                                                 ],
 321                                                 $this->msg( 'editundo' )->text()
 322                                         );
 323                                         $revisionTools['mw-diff-undo'] = $undoLink;
 324                                 }
 325                         }
 326
 327                         # Make "previous revision link"
 328                         if ( $samePage && $this->mOldRev->getPrevious() ) {
 329                                 $prevlink = Linker::linkKnown(
 330                                         $this->mOldPage,
 331                                         $this->msg( 'previousdiff' )->escaped(),
 332                                         [ 'id' => 'differences-prevlink' ],
 333                                         [ 'diff' => 'prev', 'oldid' => $this->mOldid ] + $query
 334                                 );
 335                         } else {
 336                                 $prevlink = '&#160;';
 337                         }
 338
 339                         if ( $this->mOldRev->isMinor() ) {
 340                                 $oldminor = ChangesList::flag( 'minor' );
 341                         } else {
 342                                 $oldminor = '';
 343                         }
 344
 345                         $ldel = $this->revisionDeleteLink( $this->mOldRev );
 346                         $oldRevisionHeader = $this->getRevisionHeader( $this->mOldRev, 'complete' );
 347                         $oldChangeTags = ChangeTags::formatSummaryRow( $this->mOldTags, 'diff', $this->getContext() );
 348
 349                         $oldHeader = '<div id="mw-diff-otitle1"><strong>' . $oldRevisionHeader . '</strong></div>' .
 350                                 '<div id="mw-diff-otitle2">' .
 351                                 Linker::revUserTools( $this->mOldRev, !$this->unhide ) . '</div>' .
 352                                 '<div id="mw-diff-otitle3">' . $oldminor .
 353                                 Linker::revComment( $this->mOldRev, !$diffOnly, !$this->unhide ) . $ldel . '</div>' .
 354                                 '<div id="mw-diff-otitle5">' . $oldChangeTags[0] . '</div>' .
 355                                 '<div id="mw-diff-otitle4">' . $prevlink . '</div>';
 356
 357                         if ( $this->mOldRev->isDeleted( Revision::DELETED_TEXT ) ) {
 358                                 $deleted = true; // old revisions text is hidden
 359                                 if ( $this->mOldRev->isDeleted( Revision::DELETED_RESTRICTED ) ) {
 360                                         $suppressed = true; // also suppressed
 361                                 }
 362                         }
 363
 364                         # Check if this user can see the revisions
 365                         if ( !$this->mOldRev->userCan( Revision::DELETED_TEXT, $user ) ) {
 366                                 $allowed = false;
 367                         }
 368                 }
 369
 370                 # Make "next revision link"
 371                 # Skip next link on the top revision
 372                 if ( $samePage && !$this->mNewRev->isCurrent() ) {
 373                         $nextlink = Linker::linkKnown(
 374                                 $this->mNewPage,
 375                                 $this->msg( 'nextdiff' )->escaped(),
 376                                 [ 'id' => 'differences-nextlink' ],
 377                                 [ 'diff' => 'next', 'oldid' => $this->mNewid ] + $query
 378                         );
 379                 } else {
 380                         $nextlink = '&#160;';
 381                 }
 382
 383                 if ( $this->mNewRev->isMinor() ) {
 384                         $newminor = ChangesList::flag( 'minor' );
 385                 } else {
 386                         $newminor = '';
 387                 }
 388
 389                 # Handle RevisionDelete links...
 390                 $rdel = $this->revisionDeleteLink( $this->mNewRev );
 391
 392                 # Allow extensions to define their own revision tools
 393                 Hooks::run( 'DiffRevisionTools',
 394                         [ $this->mNewRev, &$revisionTools, $this->mOldRev, $user ] );
 395                 $formattedRevisionTools = [];
 396                 // Put each one in parentheses (poor man's button)
 397                 foreach ( $revisionTools as $key => $tool ) {
 398                         $toolClass = is_string( $key ) ? $key : 'mw-diff-tool';
 399                         $element = Html::rawElement(
 400                                 'span',
 401                                 [ 'class' => $toolClass ],
 402                                 $this->msg( 'parentheses' )->rawParams( $tool )->escaped()
 403                         );
 404                         $formattedRevisionTools[] = $element;
 405                 }
 406                 $newRevisionHeader = $this->getRevisionHeader( $this->mNewRev, 'complete' ) .
 407                         ' ' . implode( ' ', $formattedRevisionTools );
 408                 $newChangeTags = ChangeTags::formatSummaryRow( $this->mNewTags, 'diff', $this->getContext() );
 409
 410                 $newHeader = '<div id="mw-diff-ntitle1"><strong>' . $newRevisionHeader . '</strong></div>' .
 411                         '<div id="mw-diff-ntitle2">' . Linker::revUserTools( $this->mNewRev, !$this->unhide ) .
 412                         " $rollback</div>" .
 413                         '<div id="mw-diff-ntitle3">' . $newminor .
 414                         Linker::revComment( $this->mNewRev, !$diffOnly, !$this->unhide ) . $rdel . '</div>' .
 415                         '<div id="mw-diff-ntitle5">' . $newChangeTags[0] . '</div>' .
 416                         '<div id="mw-diff-ntitle4">' . $nextlink . $this->markPatrolledLink() . '</div>';
 417
 418                 if ( $this->mNewRev->isDeleted( Revision::DELETED_TEXT ) ) {
 419                         $deleted = true; // new revisions text is hidden
 420                         if ( $this->mNewRev->isDeleted( Revision::DELETED_RESTRICTED ) ) {
 421                                 $suppressed = true; // also suppressed
 422                         }
 423                 }
 424
 425                 # If the diff cannot be shown due to a deleted revision, then output
 426                 # the diff header and links to unhide (if available)...
 427                 if ( $deleted && ( !$this->unhide || !$allowed ) ) {
 428                         $this->showDiffStyle();
 429                         $multi = $this->getMultiNotice();
 430                         $out->addHTML( $this->addHeader( '', $oldHeader, $newHeader, $multi ) );
 431                         if ( !$allowed ) {
 432                                 $msg = $suppressed ? 'rev-suppressed-no-diff' : 'rev-deleted-no-diff';
 433                                 # Give explanation for why revision is not visible
 434                                 $out->wrapWikiMsg( "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 435                                         [ $msg ] );
 436                         } else {
 437                                 # Give explanation and add a link to view the diff...
 438                                 $query = $this->getRequest()->appendQueryValue( 'unhide', '1' );
 439                                 $link = $this->getTitle()->getFullURL( $query );
 440                                 $msg = $suppressed ? 'rev-suppressed-unhide-diff' : 'rev-deleted-unhide-diff';
 441                                 $out->wrapWikiMsg(
 442                                         "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 443                                         [ $msg, $link ]
 444                                 );
 445                         }
 446                 # Otherwise, output a regular diff...
 447                 } else {
 448                         # Add deletion notice if the user is viewing deleted content
 449                         $notice = '';
 450                         if ( $deleted ) {
 451                                 $msg = $suppressed ? 'rev-suppressed-diff-view' : 'rev-deleted-diff-view';
 452                                 $notice = "<div id='mw-$msg' class='mw-warning plainlinks'>\n" .
 453                                         $this->msg( $msg )->parse() .
 454                                         "</div>\n";
 455                         }
 456                         $this->showDiff( $oldHeader, $newHeader, $notice );
 457                         if ( !$diffOnly ) {
 458                                 $this->renderNewRevision();
 459                         }
 460                 }
 461         }
 462
 463         /**
 464          * Build a link to mark a change as patrolled.
 465          *
 466          * Returns empty string if there's either no revision to patrol or the user is not allowed to.
 467          * Side effect: When the patrol link is build, this method will call
 468          * OutputPage::preventClickjacking() and load mediawiki.page.patrol.ajax.
 469          *
 470          * @return string HTML or empty string
 471          */
 472         protected function markPatrolledLink() {
 473                 if ( $this->mMarkPatrolledLink === null ) {
 474                         $linkInfo = $this->getMarkPatrolledLinkInfo();
 475                         // If false, there is no patrol link needed/allowed
 476                         if ( !$linkInfo ) {
 477                                 $this->mMarkPatrolledLink = '';
 478                         } else {
 479                                 $this->mMarkPatrolledLink = ' <span class="patrollink" data-mw="interface">[' .
 480                                         Linker::linkKnown(
 481                                                 $this->mNewPage,
 482                                                 $this->msg( 'markaspatrolleddiff' )->escaped(),
 483                                                 [],
 484                                                 [
 485                                                         'action' => 'markpatrolled',
 486                                                         'rcid' => $linkInfo['rcid'],
 487                                                         'token' => $linkInfo['token'],
 488                                                 ]
 489                                         ) . ']</span>';
 490                         }
 491                 }
 492                 return $this->mMarkPatrolledLink;
 493         }
 494
 495         /**
 496          * Returns an array of meta data needed to build a "mark as patrolled" link and
 497          * adds the mediawiki.page.patrol.ajax to the output.
 498          *
 499          * @return array|false An array of meta data for a patrol link (rcid & token)
 500          *  or false if no link is needed
 501          */
 502         protected function getMarkPatrolledLinkInfo() {
 503                 global $wgUseRCPatrol, $wgEnableAPI, $wgEnableWriteAPI;
 504
 505                 $user = $this->getUser();
 506
 507                 // Prepare a change patrol link, if applicable
 508                 if (
 509                         // Is patrolling enabled and the user allowed to?
 510                         $wgUseRCPatrol && $this->mNewPage->quickUserCan( 'patrol', $user ) &&
 511                         // Only do this if the revision isn't more than 6 hours older
 512                         // than the Max RC age (6h because the RC might not be cleaned out regularly)
 513                         RecentChange::isInRCLifespan( $this->mNewRev->getTimestamp(), 21600 )
 514                 ) {
 515                         // Look for an unpatrolled change corresponding to this diff
 516                         $db = wfGetDB( DB_SLAVE );
 517                         $change = RecentChange::newFromConds(
 518                                 [
 519                                         'rc_timestamp' => $db->timestamp( $this->mNewRev->getTimestamp() ),
 520                                         'rc_this_oldid' => $this->mNewid,
 521                                         'rc_patrolled' => 0
 522                                 ],
 523                                 __METHOD__
 524                         );
 525
 526                         if ( $change && !$change->getPerformer()->equals( $user ) ) {
 527                                 $rcid = $change->getAttribute( 'rc_id' );
 528                         } else {
 529                                 // None found or the page has been created by the current user.
 530                                 // If the user could patrol this it already would be patrolled
 531                                 $rcid = 0;
 532                         }
 533                         // Build the link
 534                         if ( $rcid ) {
 535                                 $this->getOutput()->preventClickjacking();
 536                                 $this->getOutput()->addModuleStyles( 'mediawiki.page.patrol' );
 537                                 if ( $wgEnableAPI && $wgEnableWriteAPI
 538                                         && $user->isAllowed( 'writeapi' )
 539                                 ) {
 540                                         $this->getOutput()->addModules( 'mediawiki.page.patrol.ajax' );
 541                                 }
 542
 543                                 $token = $user->getEditToken( $rcid );
 544                                 return [
 545                                         'rcid' => $rcid,
 546                                         'token' => $token,
 547                                 ];
 548                         }
 549                 }
 550
 551                 // No mark as patrolled link applicable
 552                 return false;
 553         }
 554
 555         /**
 556          * @param Revision $rev
 557          *
 558          * @return string
 559          */
 560         protected function revisionDeleteLink( $rev ) {
 561                 $link = Linker::getRevDeleteLink( $this->getUser(), $rev, $rev->getTitle() );
 562                 if ( $link !== '' ) {
 563                         $link = '&#160;&#160;&#160;' . $link . ' ';
 564                 }
 565
 566                 return $link;
 567         }
 568
 569         /**
 570          * Show the new revision of the page.
 571          */
 572         public function renderNewRevision() {
 573                 $out = $this->getOutput();
 574                 $revHeader = $this->getRevisionHeader( $this->mNewRev );
 575                 # Add "current version as of X" title
 576                 $out->addHTML( "<hr class='diff-hr' id='mw-oldid' />
 577                 <h2 class='diff-currentversion-title'>{$revHeader}</h2>\n" );
 578                 # Page content may be handled by a hooked call instead...
 579                 # @codingStandardsIgnoreStart Ignoring long lines.
 580                 if ( Hooks::run( 'ArticleContentOnDiff', [ $this, $out ] ) ) {
 581                         $this->loadNewText();
 582                         $out->setRevisionId( $this->mNewid );
 583                         $out->setRevisionTimestamp( $this->mNewRev->getTimestamp() );
 584                         $out->setArticleFlag( true );
 585
 586                         // NOTE: only needed for B/C: custom rendering of JS/CSS via hook
 587                         if ( $this->mNewPage->isCssJsSubpage() || $this->mNewPage->isCssOrJsPage() ) {
 588                                 // This needs to be synchronised with Article::showCssOrJsPage(), which sucks
 589                                 // Give hooks a chance to customise the output
 590                                 // @todo standardize this crap into one function
 591                                 if ( ContentHandler::runLegacyHooks( 'ShowRawCssJs', [ $this->mNewContent, $this->mNewPage, $out ] ) ) {
 592                                         // NOTE: deprecated hook, B/C only
 593                                         // use the content object's own rendering
 594                                         $cnt = $this->mNewRev->getContent();
 595                                         $po = $cnt ? $cnt->getParserOutput( $this->mNewRev->getTitle(), $this->mNewRev->getId() ) : null;
 596                                         if ( $po ) {
 597                                                 $out->addParserOutputContent( $po );
 598                                         }
 599                                 }
 600                         } elseif ( !Hooks::run( 'ArticleContentViewCustom', [ $this->mNewContent, $this->mNewPage, $out ] ) ) {
 601                                 // Handled by extension
 602                         } elseif ( !ContentHandler::runLegacyHooks( 'ArticleViewCustom', [ $this->mNewContent, $this->mNewPage, $out ] ) ) {
 603                                 // NOTE: deprecated hook, B/C only
 604                                 // Handled by extension
 605                         } else {
 606                                 // Normal page
 607                                 if ( $this->getTitle()->equals( $this->mNewPage ) ) {
 608                                         // If the Title stored in the context is the same as the one
 609                                         // of the new revision, we can use its associated WikiPage
 610                                         // object.
 611                                         $wikiPage = $this->getWikiPage();
 612                                 } else {
 613                                         // Otherwise we need to create our own WikiPage object
 614                                         $wikiPage = WikiPage::factory( $this->mNewPage );
 615                                 }
 616
 617                                 $parserOutput = $this->getParserOutput( $wikiPage, $this->mNewRev );
 618
 619                                 # WikiPage::getParserOutput() should not return false, but just in case
 620                                 if ( $parserOutput ) {
 621                                         $out->addParserOutput( $parserOutput );
 622                                 }
 623                         }
 624                 }
 625                 # @codingStandardsIgnoreEnd
 626
 627                 # Add redundant patrol link on bottom...
 628                 $out->addHTML( $this->markPatrolledLink() );
 629
 630         }
 631
 632         protected function getParserOutput( WikiPage $page, Revision $rev ) {
 633                 $parserOptions = $page->makeParserOptions( $this->getContext() );
 634
 635                 if ( !$rev->isCurrent() || !$rev->getTitle()->quickUserCan( 'edit', $this->getUser() ) ) {
 636                         $parserOptions->setEditSection( false );
 637                 }
 638
 639                 $parserOutput = $page->getParserOutput( $parserOptions, $rev->getId() );
 640
 641                 return $parserOutput;
 642         }
 643
 644         /**
 645          * Get the diff text, send it to the OutputPage object
 646          * Returns false if the diff could not be generated, otherwise returns true
 647          *
 648          * @param string|bool $otitle Header for old text or false
 649          * @param string|bool $ntitle Header for new text or false
 650          * @param string $notice HTML between diff header and body
 651          *
 652          * @return bool
 653          */
 654         public function showDiff( $otitle, $ntitle, $notice = '' ) {
 655                 $diff = $this->getDiff( $otitle, $ntitle, $notice );
 656                 if ( $diff === false ) {
 657                         $this->showMissingRevision();
 658
 659                         return false;
 660                 } else {
 661                         $this->showDiffStyle();
 662                         $this->getOutput()->addHTML( $diff );
 663
 664                         return true;
 665                 }
 666         }
 667
 668         /**
 669          * Add style sheets and supporting JS for diff display.
 670          */
 671         public function showDiffStyle() {
 672                 $this->getOutput()->addModuleStyles( 'mediawiki.action.history.diff' );
 673         }
 674
 675         /**
 676          * Get complete diff table, including header
 677          *
 678          * @param string|bool $otitle Header for old text or false
 679          * @param string|bool $ntitle Header for new text or false
 680          * @param string $notice HTML between diff header and body
 681          *
 682          * @return mixed
 683          */
 684         public function getDiff( $otitle, $ntitle, $notice = '' ) {
 685                 $body = $this->getDiffBody();
 686                 if ( $body === false ) {
 687                         return false;
 688                 }
 689
 690                 $multi = $this->getMultiNotice();
 691                 // Display a message when the diff is empty
 692                 if ( $body === '' ) {
 693                         $notice .= '<div class="mw-diff-empty">' .
 694                                 $this->msg( 'diff-empty' )->parse() .
 695                                 "</div>\n";
 696                 }
 697
 698                 return $this->addHeader( $body, $otitle, $ntitle, $multi, $notice );
 699         }
 700
 701         /**
 702          * Get the diff table body, without header
 703          *
 704          * @return mixed (string/false)
 705          */
 706         public function getDiffBody() {
 707                 $this->mCacheHit = true;
 708                 // Check if the diff should be hidden from this user
 709                 if ( !$this->loadRevisionData() ) {
 710                         return false;
 711                 } elseif ( $this->mOldRev &&
 712                         !$this->mOldRev->userCan( Revision::DELETED_TEXT, $this->getUser() )
 713                 ) {
 714                         return false;
 715                 } elseif ( $this->mNewRev &&
 716                         !$this->mNewRev->userCan( Revision::DELETED_TEXT, $this->getUser() )
 717                 ) {
 718                         return false;
 719                 }
 720                 // Short-circuit
 721                 if ( $this->mOldRev === false || ( $this->mOldRev && $this->mNewRev
 722                         && $this->mOldRev->getId() == $this->mNewRev->getId() )
 723                 ) {
 724                         return '';
 725                 }
 726                 // Cacheable?
 727                 $key = false;
 728                 $cache = ObjectCache::getMainWANInstance();
 729                 if ( $this->mOldid && $this->mNewid ) {
 730                         $key = $this->getDiffBodyCacheKey();
 731
 732                         // Try cache
 733                         if ( !$this->mRefreshCache ) {
 734                                 $difftext = $cache->get( $key );
 735                                 if ( $difftext ) {
 736                                         wfIncrStats( 'diff_cache.hit' );
 737                                         $difftext = $this->localiseLineNumbers( $difftext );
 738                                         $difftext .= "\n<!-- diff cache key $key -->\n";
 739
 740                                         return $difftext;
 741                                 }
 742                         } // don't try to load but save the result
 743                 }
 744                 $this->mCacheHit = false;
 745
 746                 // Loadtext is permission safe, this just clears out the diff
 747                 if ( !$this->loadText() ) {
 748                         return false;
 749                 }
 750
 751                 $difftext = $this->generateContentDiffBody( $this->mOldContent, $this->mNewContent );
 752
 753                 // Save to cache for 7 days
 754                 if ( !Hooks::run( 'AbortDiffCache', [ &$this ] ) ) {
 755                         wfIncrStats( 'diff_cache.uncacheable' );
 756                 } elseif ( $key !== false && $difftext !== false ) {
 757                         wfIncrStats( 'diff_cache.miss' );
 758                         $cache->set( $key, $difftext, 7 * 86400 );
 759                 } else {
 760                         wfIncrStats( 'diff_cache.uncacheable' );
 761                 }
 762                 // Replace line numbers with the text in the user's language
 763                 if ( $difftext !== false ) {
 764                         $difftext = $this->localiseLineNumbers( $difftext );
 765                 }
 766
 767                 return $difftext;
 768         }
 769
 770         /**
 771          * Returns the cache key for diff body text or content.
 772          *
 773          * @since 1.23
 774          *
 775          * @throws MWException
 776          * @return string
 777          */
 778         protected function getDiffBodyCacheKey() {
 779                 if ( !$this->mOldid || !$this->mNewid ) {
 780                         throw new MWException( 'mOldid and mNewid must be set to get diff cache key.' );
 781                 }
 782
 783                 return wfMemcKey( 'diff', 'version', self::DIFF_VERSION,
 784                         'oldid', $this->mOldid, 'newid', $this->mNewid );
 785         }
 786
 787         /**
 788          * Generate a diff, no caching.
 789          *
 790          * This implementation uses generateTextDiffBody() to generate a diff based on the default
 791          * serialization of the given Content objects. This will fail if $old or $new are not
 792          * instances of TextContent.
 793          *
 794          * Subclasses may override this to provide a different rendering for the diff,
 795          * perhaps taking advantage of the content's native form. This is required for all content
 796          * models that are not text based.
 797          *
 798          * @since 1.21
 799          *
 800          * @param Content $old Old content
 801          * @param Content $new New content
 802          *
 803          * @throws MWException If old or new content is not an instance of TextContent.
 804          * @return bool|string
 805          */
 806         public function generateContentDiffBody( Content $old, Content $new ) {
 807                 if ( !( $old instanceof TextContent ) ) {
 808                         throw new MWException( "Diff not implemented for " . get_class( $old ) . "; " .
 809                                 "override generateContentDiffBody to fix this." );
 810                 }
 811
 812                 if ( !( $new instanceof TextContent ) ) {
 813                         throw new MWException( "Diff not implemented for " . get_class( $new ) . "; "
 814                                 . "override generateContentDiffBody to fix this." );
 815                 }
 816
 817                 $otext = $old->serialize();
 818                 $ntext = $new->serialize();
 819
 820                 return $this->generateTextDiffBody( $otext, $ntext );
 821         }
 822
 823         /**
 824          * Generate a diff, no caching
 825          *
 826          * @todo move this to TextDifferenceEngine, make DifferenceEngine abstract. At some point.
 827          *
 828          * @param string $otext Old text, must be already segmented
 829          * @param string $ntext New text, must be already segmented
 830          *
 831          * @return bool|string
 832          */
 833         public function generateTextDiffBody( $otext, $ntext ) {
 834                 $diff = function() use ( $otext, $ntext ) {
 835                         $time = microtime( true );
 836
 837                         $result = $this->textDiff( $otext, $ntext );
 838
 839                         $time = intval( ( microtime( true ) - $time ) * 1000 );
 840                         $this->getStats()->timing( 'diff_time', $time );
 841                         // Log requests slower than 99th percentile
 842                         if ( $time > 100 && $this->mOldPage && $this->mNewPage ) {
 843                                 wfDebugLog( 'diff',
 844                                         "$time ms diff: {$this->mOldid} -> {$this->mNewid} {$this->mNewPage}" );
 845                         }
 846
 847                         return $result;
 848                 };
 849
 850                 $error = function( $status ) {
 851                         throw new FatalError( $status->getWikiText() );
 852                 };
 853
 854                 // Use PoolCounter if the diff looks like it can be expensive
 855                 if ( strlen( $otext ) + strlen( $ntext ) > 20000 ) {
 856                         $work = new PoolCounterWorkViaCallback( 'diff',
 857                                 md5( $otext ) . md5( $ntext ),
 858                                 [ 'doWork' => $diff, 'error' => $error ]
 859                         );
 860                         return $work->execute();
 861                 }
 862
 863                 return $diff();
 864         }
 865
 866         /**
 867          * Generates diff, to be wrapped internally in a logging/instrumentation
 868          *
 869          * @param string $otext Old text, must be already segmented
 870          * @param string $ntext New text, must be already segmented
 871          * @return bool|string
 872          */
 873         protected function textDiff( $otext, $ntext ) {
 874                 global $wgExternalDiffEngine, $wgContLang;
 875
 876                 $otext = str_replace( "\r\n", "\n", $otext );
 877                 $ntext = str_replace( "\r\n", "\n", $ntext );
 878
 879                 if ( $wgExternalDiffEngine == 'wikidiff' || $wgExternalDiffEngine == 'wikidiff3' ) {
 880                         wfDeprecated( "\$wgExternalDiffEngine = '{$wgExternalDiffEngine}'", '1.27' );
 881                         $wgExternalDiffEngine = false;
 882                 } elseif ( $wgExternalDiffEngine == 'wikidiff2' ) {
 883                         // Same as above, but with no deprecation warnings
 884                         $wgExternalDiffEngine = false;
 885                 } elseif ( !is_string( $wgExternalDiffEngine ) && $wgExternalDiffEngine !== false ) {
 886                         // And prevent people from shooting themselves in the foot...
 887                         wfWarn( '$wgExternalDiffEngine is set to a non-string value, forcing it to false' );
 888                         $wgExternalDiffEngine = false;
 889                 }
 890
 891                 if ( function_exists( 'wikidiff2_do_diff' ) && $wgExternalDiffEngine === false ) {
 892                         # Better external diff engine, the 2 may some day be dropped
 893                         # This one does the escaping and segmenting itself
 894                         $text = wikidiff2_do_diff( $otext, $ntext, 2 );
 895                         $text .= $this->debug( 'wikidiff2' );
 896
 897                         return $text;
 898                 } elseif ( $wgExternalDiffEngine !== false && is_executable( $wgExternalDiffEngine ) ) {
 899                         # Diff via the shell
 900                         $tmpDir = wfTempDir();
 901                         $tempName1 = tempnam( $tmpDir, 'diff_' );
 902                         $tempName2 = tempnam( $tmpDir, 'diff_' );
 903
 904                         $tempFile1 = fopen( $tempName1, "w" );
 905                         if ( !$tempFile1 ) {
 906                                 return false;
 907                         }
 908                         $tempFile2 = fopen( $tempName2, "w" );
 909                         if ( !$tempFile2 ) {
 910                                 return false;
 911                         }
 912                         fwrite( $tempFile1, $otext );
 913                         fwrite( $tempFile2, $ntext );
 914                         fclose( $tempFile1 );
 915                         fclose( $tempFile2 );
 916                         $cmd = wfEscapeShellArg( $wgExternalDiffEngine, $tempName1, $tempName2 );
 917                         $difftext = wfShellExec( $cmd );
 918                         $difftext .= $this->debug( "external $wgExternalDiffEngine" );
 919                         unlink( $tempName1 );
 920                         unlink( $tempName2 );
 921
 922                         return $difftext;
 923                 }
 924
 925                 # Native PHP diff
 926                 $ota = explode( "\n", $wgContLang->segmentForDiff( $otext ) );
 927                 $nta = explode( "\n", $wgContLang->segmentForDiff( $ntext ) );
 928                 $diffs = new Diff( $ota, $nta );
 929                 $formatter = new TableDiffFormatter();
 930                 $difftext = $wgContLang->unsegmentForDiff( $formatter->format( $diffs ) );
 931
 932                 return $difftext;
 933         }
 934
 935         /**
 936          * Generate a debug comment indicating diff generating time,
 937          * server node, and generator backend.
 938          *
 939          * @param string $generator : What diff engine was used
 940          *
 941          * @return string
 942          */
 943         protected function debug( $generator = "internal" ) {
 944                 global $wgShowHostnames;
 945                 if ( !$this->enableDebugComment ) {
 946                         return '';
 947                 }
 948                 $data = [ $generator ];
 949                 if ( $wgShowHostnames ) {
 950                         $data[] = wfHostname();
 951                 }
 952                 $data[] = wfTimestamp( TS_DB );
 953
 954                 return "<!-- diff generator: " .
 955                         implode( " ", array_map( "htmlspecialchars", $data ) ) .
 956                         " -->\n";
 957         }
 958
 959         /**
 960          * Replace line numbers with the text in the user's language
 961          *
 962          * @param string $text
 963          *
 964          * @return mixed
 965          */
 966         public function localiseLineNumbers( $text ) {
 967                 return preg_replace_callback(
 968                         '/<!--LINE (\d+)-->/',
 969                         [ &$this, 'localiseLineNumbersCb' ],
 970                         $text
 971                 );
 972         }
 973
 974         public function localiseLineNumbersCb( $matches ) {
 975                 if ( $matches[1] === '1' && $this->mReducedLineNumbers ) {
 976                         return '';
 977                 }
 978
 979                 return $this->msg( 'lineno' )->numParams( $matches[1] )->escaped();
 980         }
 981
 982         /**
 983          * If there are revisions between the ones being compared, return a note saying so.
 984          *
 985          * @return string
 986          */
 987         public function getMultiNotice() {
 988                 if ( !is_object( $this->mOldRev ) || !is_object( $this->mNewRev ) ) {
 989                         return '';
 990                 } elseif ( !$this->mOldPage->equals( $this->mNewPage ) ) {
 991                         // Comparing two different pages? Count would be meaningless.
 992                         return '';
 993                 }
 994
 995                 if ( $this->mOldRev->getTimestamp() > $this->mNewRev->getTimestamp() ) {
 996                         $oldRev = $this->mNewRev; // flip
 997                         $newRev = $this->mOldRev; // flip
 998                 } else { // normal case
 999                         $oldRev = $this->mOldRev;
1000                         $newRev = $this->mNewRev;
1001                 }
1002
1003                 // Sanity: don't show the notice if too many rows must be scanned
1004                 // @todo show some special message for that case
1005                 $nEdits = $this->mNewPage->countRevisionsBetween( $oldRev, $newRev, 1000 );
1006                 if ( $nEdits > 0 && $nEdits <= 1000 ) {
1007                         $limit = 100; // use diff-multi-manyusers if too many users
1008                         $users = $this->mNewPage->getAuthorsBetween( $oldRev, $newRev, $limit );
1009                         $numUsers = count( $users );
1010
1011                         if ( $numUsers == 1 && $users[0] == $newRev->getUserText( Revision::RAW ) ) {
1012                                 $numUsers = 0; // special case to say "by the same user" instead of "by one other user"
1013                         }
1014
1015                         return self::intermediateEditsMsg( $nEdits, $numUsers, $limit );
1016                 }
1017
1018                 return ''; // nothing
1019         }
1020
1021         /**
1022          * Get a notice about how many intermediate edits and users there are
1023          *
1024          * @param int $numEdits
1025          * @param int $numUsers
1026          * @param int $limit
1027          *
1028          * @return string
1029          */
1030         public static function intermediateEditsMsg( $numEdits, $numUsers, $limit ) {
1031                 if ( $numUsers === 0 ) {
1032                         $msg = 'diff-multi-sameuser';
1033                 } elseif ( $numUsers > $limit ) {
1034                         $msg = 'diff-multi-manyusers';
1035                         $numUsers = $limit;
1036                 } else {
1037                         $msg = 'diff-multi-otherusers';
1038                 }
1039
1040                 return wfMessage( $msg )->numParams( $numEdits, $numUsers )->parse();
1041         }
1042
1043         /**
1044          * Get a header for a specified revision.
1045          *
1046          * @param Revision $rev
1047          * @param string $complete 'complete' to get the header wrapped depending
1048          *        the visibility of the revision and a link to edit the page.
1049          *
1050          * @return string HTML fragment
1051          */
1052         protected function getRevisionHeader( Revision $rev, $complete = '' ) {
1053                 $lang = $this->getLanguage();
1054                 $user = $this->getUser();
1055                 $revtimestamp = $rev->getTimestamp();
1056                 $timestamp = $lang->userTimeAndDate( $revtimestamp, $user );
1057                 $dateofrev = $lang->userDate( $revtimestamp, $user );
1058                 $timeofrev = $lang->userTime( $revtimestamp, $user );
1059
1060                 $header = $this->msg(
1061                         $rev->isCurrent() ? 'currentrev-asof' : 'revisionasof',
1062                         $timestamp,
1063                         $dateofrev,
1064                         $timeofrev
1065                 )->escaped();
1066
1067                 if ( $complete !== 'complete' ) {
1068                         return $header;
1069                 }
1070
1071                 $title = $rev->getTitle();
1072
1073                 $header = Linker::linkKnown( $title, $header, [],
1074                         [ 'oldid' => $rev->getId() ] );
1075
1076                 if ( $rev->userCan( Revision::DELETED_TEXT, $user ) ) {
1077                         $editQuery = [ 'action' => 'edit' ];
1078                         if ( !$rev->isCurrent() ) {
1079                                 $editQuery['oldid'] = $rev->getId();
1080                         }
1081
1082                         $key = $title->quickUserCan( 'edit', $user ) ? 'editold' : 'viewsourceold';
1083                         $msg = $this->msg( $key )->escaped();
1084                         $editLink = $this->msg( 'parentheses' )->rawParams(
1085                                 Linker::linkKnown( $title, $msg, [], $editQuery ) )->escaped();
1086                         $header .= ' ' . Html::rawElement(
1087                                 'span',
1088                                 [ 'class' => 'mw-diff-edit' ],
1089                                 $editLink
1090                         );
1091                         if ( $rev->isDeleted( Revision::DELETED_TEXT ) ) {
1092                                 $header = Html::rawElement(
1093                                         'span',
1094                                         [ 'class' => 'history-deleted' ],
1095                                         $header
1096                                 );
1097                         }
1098                 } else {
1099                         $header = Html::rawElement( 'span', [ 'class' => 'history-deleted' ], $header );
1100                 }
1101
1102                 return $header;
1103         }
1104
1105         /**
1106          * Add the header to a diff body
1107          *
1108          * @param string $diff Diff body
1109          * @param string $otitle Old revision header
1110          * @param string $ntitle New revision header
1111          * @param string $multi Notice telling user that there are intermediate
1112          *   revisions between the ones being compared
1113          * @param string $notice Other notices, e.g. that user is viewing deleted content
1114          *
1115          * @return string
1116          */
1117         public function addHeader( $diff, $otitle, $ntitle, $multi = '', $notice = '' ) {
1118                 // shared.css sets diff in interface language/dir, but the actual content
1119                 // is often in a different language, mostly the page content language/dir
1120                 $header = Html::openElement( 'table', [
1121                         'class' => [ 'diff', 'diff-contentalign-' . $this->getDiffLang()->alignStart() ],
1122                         'data-mw' => 'interface',
1123                 ] );
1124                 $userLang = htmlspecialchars( $this->getLanguage()->getHtmlCode() );
1125
1126                 if ( !$diff && !$otitle ) {
1127                         $header .= "
1128                         <tr style='vertical-align: top;' lang='{$userLang}'>
1129                         <td class='diff-ntitle'>{$ntitle}</td>
1130                         </tr>";
1131                         $multiColspan = 1;
1132                 } else {
1133                         if ( $diff ) { // Safari/Chrome show broken output if cols not used
1134                                 $header .= "
1135                                 <col class='diff-marker' />
1136                                 <col class='diff-content' />
1137                                 <col class='diff-marker' />
1138                                 <col class='diff-content' />";
1139                                 $colspan = 2;
1140                                 $multiColspan = 4;
1141                         } else {
1142                                 $colspan = 1;
1143                                 $multiColspan = 2;
1144                         }
1145                         if ( $otitle || $ntitle ) {
1146                                 $header .= "
1147                                 <tr style='vertical-align: top;' lang='{$userLang}'>
1148                                 <td colspan='$colspan' class='diff-otitle'>{$otitle}</td>
1149                                 <td colspan='$colspan' class='diff-ntitle'>{$ntitle}</td>
1150                                 </tr>";
1151                         }
1152                 }
1153
1154                 if ( $multi != '' ) {
1155                         $header .= "<tr><td colspan='{$multiColspan}' style='text-align: center;' " .
1156                                 "class='diff-multi' lang='{$userLang}'>{$multi}</td></tr>";
1157                 }
1158                 if ( $notice != '' ) {
1159                         $header .= "<tr><td colspan='{$multiColspan}' style='text-align: center;' " .
1160                                 "lang='{$userLang}'>{$notice}</td></tr>";
1161                 }
1162
1163                 return $header . $diff . "</table>";
1164         }
1165
1166         /**
1167          * Use specified text instead of loading from the database
1168          * @param Content $oldContent
1169          * @param Content $newContent
1170          * @since 1.21
1171          */
1172         public function setContent( Content $oldContent, Content $newContent ) {
1173                 $this->mOldContent = $oldContent;
1174                 $this->mNewContent = $newContent;
1175
1176                 $this->mTextLoaded = 2;
1177                 $this->mRevisionsLoaded = true;
1178         }
1179
1180         /**
1181          * Set the language in which the diff text is written
1182          * (Defaults to page content language).
1183          * @param Language|string $lang
1184          * @since 1.19
1185          */
1186         public function setTextLanguage( $lang ) {
1187                 $this->mDiffLang = wfGetLangObj( $lang );
1188         }
1189
1190         /**
1191          * Maps a revision pair definition as accepted by DifferenceEngine constructor
1192          * to a pair of actual integers representing revision ids.
1193          *
1194          * @param int $old Revision id, e.g. from URL parameter 'oldid'
1195          * @param int|string $new Revision id or strings 'next' or 'prev', e.g. from URL parameter 'diff'
1196          *
1197          * @return int[] List of two revision ids, older first, later second.
1198          *     Zero signifies invalid argument passed.
1199          *     false signifies that there is no previous/next revision ($old is the oldest/newest one).
1200          */
1201         public function mapDiffPrevNext( $old, $new ) {
1202                 if ( $new === 'prev' ) {
1203                         // Show diff between revision $old and the previous one. Get previous one from DB.
1204                         $newid = intval( $old );
1205                         $oldid = $this->getTitle()->getPreviousRevisionID( $newid );
1206                 } elseif ( $new === 'next' ) {
1207                         // Show diff between revision $old and the next one. Get next one from DB.
1208                         $oldid = intval( $old );
1209                         $newid = $this->getTitle()->getNextRevisionID( $oldid );
1210                 } else {
1211                         $oldid = intval( $old );
1212                         $newid = intval( $new );
1213                 }
1214
1215                 return [ $oldid, $newid ];
1216         }
1217
1218         /**
1219          * Load revision IDs
1220          */
1221         private function loadRevisionIds() {
1222                 if ( $this->mRevisionsIdsLoaded ) {
1223                         return;
1224                 }
1225
1226                 $this->mRevisionsIdsLoaded = true;
1227
1228                 $old = $this->mOldid;
1229                 $new = $this->mNewid;
1230
1231                 list( $this->mOldid, $this->mNewid ) = self::mapDiffPrevNext( $old, $new );
1232                 if ( $new === 'next' && $this->mNewid === false ) {
1233                         # if no result, NewId points to the newest old revision. The only newer
1234                         # revision is cur, which is "0".
1235                         $this->mNewid = 0;
1236                 }
1237
1238                 Hooks::run(
1239                         'NewDifferenceEngine',
1240                         [ $this->getTitle(), &$this->mOldid, &$this->mNewid, $old, $new ]
1241                 );
1242         }
1243
1244         /**
1245          * Load revision metadata for the specified articles. If newid is 0, then compare
1246          * the old article in oldid to the current article; if oldid is 0, then
1247          * compare the current article to the immediately previous one (ignoring the
1248          * value of newid).
1249          *
1250          * If oldid is false, leave the corresponding revision object set
1251          * to false. This is impossible via ordinary user input, and is provided for
1252          * API convenience.
1253          *
1254          * @return bool
1255          */
1256         public function loadRevisionData() {
1257                 if ( $this->mRevisionsLoaded ) {
1258                         return true;
1259                 }
1260
1261                 // Whether it succeeds or fails, we don't want to try again
1262                 $this->mRevisionsLoaded = true;
1263
1264                 $this->loadRevisionIds();
1265
1266                 // Load the new revision object
1267                 if ( $this->mNewid ) {
1268                         $this->mNewRev = Revision::newFromId( $this->mNewid );
1269                 } else {
1270                         $this->mNewRev = Revision::newFromTitle(
1271                                 $this->getTitle(),
1272                                 false,
1273                                 Revision::READ_NORMAL
1274                         );
1275                 }
1276
1277                 if ( !$this->mNewRev instanceof Revision ) {
1278                         return false;
1279                 }
1280
1281                 // Update the new revision ID in case it was 0 (makes life easier doing UI stuff)
1282                 $this->mNewid = $this->mNewRev->getId();
1283                 $this->mNewPage = $this->mNewRev->getTitle();
1284
1285                 // Load the old revision object
1286                 $this->mOldRev = false;
1287                 if ( $this->mOldid ) {
1288                         $this->mOldRev = Revision::newFromId( $this->mOldid );
1289                 } elseif ( $this->mOldid === 0 ) {
1290                         $rev = $this->mNewRev->getPrevious();
1291                         if ( $rev ) {
1292                                 $this->mOldid = $rev->getId();
1293                                 $this->mOldRev = $rev;
1294                         } else {
1295                                 // No previous revision; mark to show as first-version only.
1296                                 $this->mOldid = false;
1297                                 $this->mOldRev = false;
1298                         }
1299                 } /* elseif ( $this->mOldid === false ) leave mOldRev false; */
1300
1301                 if ( is_null( $this->mOldRev ) ) {
1302                         return false;
1303                 }
1304
1305                 if ( $this->mOldRev ) {
1306                         $this->mOldPage = $this->mOldRev->getTitle();
1307                 }
1308
1309                 // Load tags information for both revisions
1310                 $dbr = wfGetDB( DB_SLAVE );
1311                 if ( $this->mOldid !== false ) {
1312                         $this->mOldTags = $dbr->selectField(
1313                                 'tag_summary',
1314                                 'ts_tags',
1315                                 [ 'ts_rev_id' => $this->mOldid ],
1316                                 __METHOD__
1317                         );
1318                 } else {
1319                         $this->mOldTags = false;
1320                 }
1321                 $this->mNewTags = $dbr->selectField(
1322                         'tag_summary',
1323                         'ts_tags',
1324                         [ 'ts_rev_id' => $this->mNewid ],
1325                         __METHOD__
1326                 );
1327
1328                 return true;
1329         }
1330
1331         /**
1332          * Load the text of the revisions, as well as revision data.
1333          *
1334          * @return bool
1335          */
1336         public function loadText() {
1337                 if ( $this->mTextLoaded == 2 ) {
1338                         return true;
1339                 }
1340
1341                 // Whether it succeeds or fails, we don't want to try again
1342                 $this->mTextLoaded = 2;
1343
1344                 if ( !$this->loadRevisionData() ) {
1345                         return false;
1346                 }
1347
1348                 if ( $this->mOldRev ) {
1349                         $this->mOldContent = $this->mOldRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1350                         if ( $this->mOldContent === null ) {
1351                                 return false;
1352                         }
1353                 }
1354
1355                 if ( $this->mNewRev ) {
1356                         $this->mNewContent = $this->mNewRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1357                         if ( $this->mNewContent === null ) {
1358                                 return false;
1359                         }
1360                 }
1361
1362                 return true;
1363         }
1364
1365         /**
1366          * Load the text of the new revision, not the old one
1367          *
1368          * @return bool
1369          */
1370         public function loadNewText() {
1371                 if ( $this->mTextLoaded >= 1 ) {
1372                         return true;
1373                 }
1374
1375                 $this->mTextLoaded = 1;
1376
1377                 if ( !$this->loadRevisionData() ) {
1378                         return false;
1379                 }
1380
1381                 $this->mNewContent = $this->mNewRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1382
1383                 return true;
1384         }
1385
1386 }