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 use MediaWiki\Storage\RevisionRecord;
  25
  26 /**
  27  * DifferenceEngine is responsible for rendering the difference between two revisions as HTML.
  28  * This includes interpreting URL parameters, retrieving revision data, checking access permissions,
  29  * selecting and invoking the diff generator class for the individual slots, doing post-processing
  30  * on the generated diff, adding the rest of the HTML (such as headers) and writing the whole thing
  31  * to OutputPage.
  32  *
  33  * DifferenceEngine can be subclassed by extensions, by customizing
  34  * ContentHandler::createDifferenceEngine; the content handler will be selected based on the
  35  * content model of the main slot (of the new revision, when the two are different).
  36  * That might change after PageTypeHandler gets introduced.
  37  *
  38  * In the past, the class was also used for slot-level diff generation, and extensions might still
  39  * subclass it and add such functionality. When that is the case (sepcifically, when a
  40  * ContentHandler returns a standard SlotDiffRenderer but a nonstandard DifferenceEngine)
  41  * DifferenceEngineSlotDiffRenderer will be used to convert the old behavior into the new one.
  42  *
  43  * @ingroup DifferenceEngine
  44  *
  45  * @todo This class is huge and poorly defined. It should be split into a controller responsible
  46  * for interpreting query parameters, retrieving data and checking permissions; and a HTML renderer.
  47  */
  48 class DifferenceEngine extends ContextSource {
  49
  50         use DeprecationHelper;
  51
  52         /**
  53          * Constant to indicate diff cache compatibility.
  54          * Bump this when changing the diff formatting in a way that
  55          * fixes important bugs or such to force cached diff views to
  56          * clear.
  57          */
  58         const DIFF_VERSION = '1.12';
  59
  60         /**
  61          * Revision ID for the old revision. 0 for the revision previous to $mNewid, false
  62          * if the diff does not have an old revision (e.g. 'oldid=<first revision of page>&diff=prev'),
  63          * or the revision does not exist, null if the revision is unsaved.
  64          * @var int|false|null
  65          */
  66         protected $mOldid;
  67
  68         /**
  69          * Revision ID for the new revision. 0 for the last revision of the current page
  70          * (as defined by the request context), false if the revision does not exist, null
  71          * if it is unsaved, or an alias such as 'next'.
  72          * @var int|string|false|null
  73          */
  74         protected $mNewid;
  75
  76         /**
  77          * Old revision (left pane).
  78          * Allowed to be an unsaved revision, unlikely that's ever needed though.
  79          * False when the old revision does not exist; this can happen when using
  80          * diff=prev on the first revision. Null when the revision should exist but
  81          * doesn't (e.g. load failure); loadRevisionData() will return false in that
  82          * case. Also null until lazy-loaded. Ignored completely when isContentOverridden
  83          * is set.
  84          * Since 1.32 public access is deprecated.
  85          * @var Revision|null|false
  86          */
  87         protected $mOldRev;
  88
  89         /**
  90          * New revision (right pane).
  91          * Note that this might be an unsaved revision (e.g. for edit preview).
  92          * Null in case of load failure; diff methods will just return an error message in that case,
  93          * and loadRevisionData() will return false. Also null until lazy-loaded. Ignored completely
  94          * when isContentOverridden is set.
  95          * Since 1.32 public access is deprecated.
  96          * @var Revision|null
  97          */
  98         protected $mNewRev;
  99
 100         /**
 101          * Title of $mOldRev or null if the old revision does not exist or does not belong to a page.
 102          * Since 1.32 public access is deprecated and the property can be null.
 103          * @var Title|null
 104          */
 105         protected $mOldPage;
 106
 107         /**
 108          * Title of $mNewRev or null if the new revision does not exist or does not belong to a page.
 109          * Since 1.32 public access is deprecated and the property can be null.
 110          * @var Title|null
 111          */
 112         protected $mNewPage;
 113
 114         /**
 115          * Change tags of $mOldRev or null if it does not exist / is not saved.
 116          * @var string[]|null
 117          */
 118         private $mOldTags;
 119
 120         /**
 121          * Change tags of $mNewRev or null if it does not exist / is not saved.
 122          * @var string[]|null
 123          */
 124         private $mNewTags;
 125
 126         /**
 127          * @var Content|null
 128          * @deprecated since 1.32, content slots are now handled by the corresponding SlotDiffRenderer.
 129          *   This property is set to the content of the main slot, but not actually used for the main diff.
 130          */
 131         private $mOldContent;
 132
 133         /**
 134          * @var Content|null
 135          * @deprecated since 1.32, content slots are now handled by the corresponding SlotDiffRenderer.
 136          *   This property is set to the content of the main slot, but not actually used for the main diff.
 137          */
 138         private $mNewContent;
 139
 140         /** @var Language */
 141         protected $mDiffLang;
 142
 143         /** @var bool Have the revisions IDs been loaded */
 144         private $mRevisionsIdsLoaded = false;
 145
 146         /** @var bool Have the revisions been loaded */
 147         protected $mRevisionsLoaded = false;
 148
 149         /** @var int How many text blobs have been loaded, 0, 1 or 2? */
 150         protected $mTextLoaded = 0;
 151
 152         /**
 153          * Was the content overridden via setContent()?
 154          * If the content was overridden, most internal state (e.g. mOldid or mOldRev) should be ignored
 155          * and only mOldContent and mNewContent is reliable.
 156          * (Note that setRevisions() does not set this flag as in that case all properties are
 157          * overriden and remain consistent with each other, so no special handling is needed.)
 158          * @var bool
 159          */
 160         protected $isContentOverridden = false;
 161
 162         /** @var bool Was the diff fetched from cache? */
 163         protected $mCacheHit = false;
 164
 165         /**
 166          * Set this to true to add debug info to the HTML output.
 167          * Warning: this may cause RSS readers to spuriously mark articles as "new"
 168          * (T22601)
 169          */
 170         public $enableDebugComment = false;
 171
 172         /** @var bool If true, line X is not displayed when X is 1, for example
 173          *    to increase readability and conserve space with many small diffs.
 174          */
 175         protected $mReducedLineNumbers = false;
 176
 177         /** @var string Link to action=markpatrolled */
 178         protected $mMarkPatrolledLink = null;
 179
 180         /** @var bool Show rev_deleted content if allowed */
 181         protected $unhide = false;
 182
 183         /** @var bool Refresh the diff cache */
 184         protected $mRefreshCache = false;
 185
 186         /** @var SlotDiffRenderer[] DifferenceEngine classes for the slots, keyed by role name. */
 187         protected $slotDiffRenderers = null;
 188
 189         /**
 190          * Temporary hack for B/C while slot diff related methods of DifferenceEngine are being
 191          * deprecated. When true, we are inside a DifferenceEngineSlotDiffRenderer and
 192          * $slotDiffRenderers should not be used.
 193          * @var bool
 194          */
 195         protected $isSlotDiffRenderer = false;
 196
 197         /**#@-*/
 198
 199         /**
 200          * @param IContextSource|null $context Context to use, anything else will be ignored
 201          * @param int $old Old ID we want to show and diff with.
 202          * @param string|int $new Either revision ID or 'prev' or 'next'. Default: 0.
 203          * @param int $rcid Deprecated, no longer used!
 204          * @param bool $refreshCache If set, refreshes the diff cache
 205          * @param bool $unhide If set, allow viewing deleted revs
 206          */
 207         public function __construct( $context = null, $old = 0, $new = 0, $rcid = 0,
 208                 $refreshCache = false, $unhide = false
 209         ) {
 210                 $this->deprecatePublicProperty( 'mOldid', '1.32', __CLASS__ );
 211                 $this->deprecatePublicProperty( 'mNewid', '1.32', __CLASS__ );
 212                 $this->deprecatePublicProperty( 'mOldRev', '1.32', __CLASS__ );
 213                 $this->deprecatePublicProperty( 'mNewRev', '1.32', __CLASS__ );
 214                 $this->deprecatePublicProperty( 'mOldPage', '1.32', __CLASS__ );
 215                 $this->deprecatePublicProperty( 'mNewPage', '1.32', __CLASS__ );
 216                 $this->deprecatePublicProperty( 'mOldContent', '1.32', __CLASS__ );
 217                 $this->deprecatePublicProperty( 'mNewContent', '1.32', __CLASS__ );
 218                 $this->deprecatePublicProperty( 'mRevisionsLoaded', '1.32', __CLASS__ );
 219                 $this->deprecatePublicProperty( 'mTextLoaded', '1.32', __CLASS__ );
 220                 $this->deprecatePublicProperty( 'mCacheHit', '1.32', __CLASS__ );
 221
 222                 if ( $context instanceof IContextSource ) {
 223                         $this->setContext( $context );
 224                 }
 225
 226                 wfDebug( "DifferenceEngine old '$old' new '$new' rcid '$rcid'\n" );
 227
 228                 $this->mOldid = $old;
 229                 $this->mNewid = $new;
 230                 $this->mRefreshCache = $refreshCache;
 231                 $this->unhide = $unhide;
 232         }
 233
 234         /**
 235          * @return SlotDiffRenderer[] Diff renderers for each slot, keyed by role name.
 236          *   Includes slots only present in one of the revisions.
 237          */
 238         protected function getSlotDiffRenderers() {
 239                 if ( $this->isSlotDiffRenderer ) {
 240                         throw new LogicException( __METHOD__ . ' called in slot diff renderer mode' );
 241                 }
 242
 243                 if ( $this->slotDiffRenderers === null ) {
 244                         if ( !$this->loadRevisionData() ) {
 245                                 return [];
 246                         }
 247
 248                         $slotContents = $this->getSlotContents();
 249                         $this->slotDiffRenderers = array_map( function ( $contents ) {
 250                                 /** @var $content Content */
 251                                 $content = $contents['new'] ?: $contents['old'];
 252                                 return $content->getContentHandler()->getSlotDiffRenderer( $this->getContext() );
 253                         }, $slotContents );
 254                 }
 255                 return $this->slotDiffRenderers;
 256         }
 257
 258         /**
 259          * Mark this DifferenceEngine as a slot renderer (as opposed to a page renderer).
 260          * This is used in legacy mode when the DifferenceEngine is wrapped in a
 261          * DifferenceEngineSlotDiffRenderer.
 262          * @internal For use by DifferenceEngineSlotDiffRenderer only.
 263          */
 264         public function markAsSlotDiffRenderer() {
 265                 $this->isSlotDiffRenderer = true;
 266         }
 267
 268         /**
 269          * Get the old and new content objects for all slots.
 270          * This method does not do any permission checks.
 271          * @return array [ role => [ 'old' => SlotRecord|null, 'new' => SlotRecord|null ], ... ]
 272          */
 273         protected function getSlotContents() {
 274                 if ( $this->isContentOverridden ) {
 275                         return [
 276                                 'main' => [
 277                                         'old' => $this->mOldContent,
 278                                         'new' => $this->mNewContent,
 279                                 ]
 280                         ];
 281                 } elseif ( !$this->loadRevisionData() ) {
 282                         return [];
 283                 }
 284
 285                 $newSlots = $this->mNewRev->getRevisionRecord()->getSlots()->getSlots();
 286                 if ( $this->mOldRev ) {
 287                         $oldSlots = $this->mOldRev->getRevisionRecord()->getSlots()->getSlots();
 288                 } else {
 289                         $oldSlots = [];
 290                 }
 291                 // The order here will determine the visual order of the diff. The current logic is
 292                 // slots of the new revision first in natural order, then deleted ones. This is ad hoc
 293                 // and should not be relied on - in the future we may want the ordering to depend
 294                 // on the page type.
 295                 $roles = array_merge( array_keys( $newSlots ), array_keys( $oldSlots ) );
 296
 297                 $slots = [];
 298                 foreach ( $roles as $role ) {
 299                         $slots[$role] = [
 300                                 'old' => isset( $oldSlots[$role] ) ? $oldSlots[$role]->getContent() : null,
 301                                 'new' => isset( $newSlots[$role] ) ? $newSlots[$role]->getContent() : null,
 302                         ];
 303                 }
 304                 // move main slot to front
 305                 if ( isset( $slots['main'] ) ) {
 306                         $slots = [ 'main' => $slots['main'] ] + $slots;
 307                 }
 308                 return $slots;
 309         }
 310
 311         /**
 312          * Set reduced line numbers mode.
 313          * When set, line X is not displayed when X is 1, for example to increase readability and
 314          * conserve space with many small diffs.
 315          * @param bool $value
 316          */
 317         public function setReducedLineNumbers( $value = true ) {
 318                 $this->mReducedLineNumbers = $value;
 319         }
 320
 321         /**
 322          * Get the language of the difference engine, defaults to page content language
 323          *
 324          * @return Language
 325          */
 326         public function getDiffLang() {
 327                 if ( $this->mDiffLang === null ) {
 328                         # Default language in which the diff text is written.
 329                         $this->mDiffLang = $this->getTitle()->getPageLanguage();
 330                 }
 331
 332                 return $this->mDiffLang;
 333         }
 334
 335         /**
 336          * @return bool
 337          */
 338         public function wasCacheHit() {
 339                 return $this->mCacheHit;
 340         }
 341
 342         /**
 343          * Get the ID of old revision (left pane) of the diff. 0 for the revision
 344          * previous to getNewid(), false if the old revision does not exist, null
 345          * if it's unsaved.
 346          * To get a real revision ID instead of 0, call loadRevisionData() first.
 347          * @return int|false|null
 348          */
 349         public function getOldid() {
 350                 $this->loadRevisionIds();
 351
 352                 return $this->mOldid;
 353         }
 354
 355         /**
 356          * Get the ID of new revision (right pane) of the diff. 0 for the current revision,
 357          * false if the new revision does not exist, null if it's unsaved.
 358          * To get a real revision ID instead of 0, call loadRevisionData() first.
 359          * @return int|false|null
 360          */
 361         public function getNewid() {
 362                 $this->loadRevisionIds();
 363
 364                 return $this->mNewid;
 365         }
 366
 367         /**
 368          * Get the left side of the diff.
 369          * Could be null when the first revision of the page is diffed to 'prev' (or in the case of
 370          * load failure).
 371          * @return RevisionRecord|null
 372          */
 373         public function getOldRevision() {
 374                 return $this->mOldRev ? $this->mOldRev->getRevisionRecord() : null;
 375         }
 376
 377         /**
 378          * Get the right side of the diff.
 379          * Should not be null but can still happen in the case of load failure.
 380          * @return RevisionRecord|null
 381          */
 382         public function getNewRevision() {
 383                 return $this->mNewRev ? $this->mNewRev->getRevisionRecord() : null;
 384         }
 385
 386         /**
 387          * Look up a special:Undelete link to the given deleted revision id,
 388          * as a workaround for being unable to load deleted diffs in currently.
 389          *
 390          * @param int $id Revision ID
 391          *
 392          * @return string|bool Link HTML or false
 393          */
 394         public function deletedLink( $id ) {
 395                 if ( $this->getUser()->isAllowed( 'deletedhistory' ) ) {
 396                         $dbr = wfGetDB( DB_REPLICA );
 397                         $arQuery = Revision::getArchiveQueryInfo();
 398                         $row = $dbr->selectRow(
 399                                 $arQuery['tables'],
 400                                 array_merge( $arQuery['fields'], [ 'ar_namespace', 'ar_title' ] ),
 401                                 [ 'ar_rev_id' => $id ],
 402                                 __METHOD__,
 403                                 [],
 404                                 $arQuery['joins']
 405                         );
 406                         if ( $row ) {
 407                                 $rev = Revision::newFromArchiveRow( $row );
 408                                 $title = Title::makeTitleSafe( $row->ar_namespace, $row->ar_title );
 409
 410                                 return SpecialPage::getTitleFor( 'Undelete' )->getFullURL( [
 411                                         'target' => $title->getPrefixedText(),
 412                                         'timestamp' => $rev->getTimestamp()
 413                                 ] );
 414                         }
 415                 }
 416
 417                 return false;
 418         }
 419
 420         /**
 421          * Build a wikitext link toward a deleted revision, if viewable.
 422          *
 423          * @param int $id Revision ID
 424          *
 425          * @return string Wikitext fragment
 426          */
 427         public function deletedIdMarker( $id ) {
 428                 $link = $this->deletedLink( $id );
 429                 if ( $link ) {
 430                         return "[$link $id]";
 431                 } else {
 432                         return (string)$id;
 433                 }
 434         }
 435
 436         private function showMissingRevision() {
 437                 $out = $this->getOutput();
 438
 439                 $missing = [];
 440                 if ( $this->mOldRev === null ||
 441                         ( $this->mOldRev && $this->mOldContent === null )
 442                 ) {
 443                         $missing[] = $this->deletedIdMarker( $this->mOldid );
 444                 }
 445                 if ( $this->mNewRev === null ||
 446                         ( $this->mNewRev && $this->mNewContent === null )
 447                 ) {
 448                         $missing[] = $this->deletedIdMarker( $this->mNewid );
 449                 }
 450
 451                 $out->setPageTitle( $this->msg( 'errorpagetitle' ) );
 452                 $msg = $this->msg( 'difference-missing-revision' )
 453                         ->params( $this->getLanguage()->listToText( $missing ) )
 454                         ->numParams( count( $missing ) )
 455                         ->parseAsBlock();
 456                 $out->addHTML( $msg );
 457         }
 458
 459         public function showDiffPage( $diffOnly = false ) {
 460                 # Allow frames except in certain special cases
 461                 $out = $this->getOutput();
 462                 $out->allowClickjacking();
 463                 $out->setRobotPolicy( 'noindex,nofollow' );
 464
 465                 // Allow extensions to add any extra output here
 466                 Hooks::run( 'DifferenceEngineShowDiffPage', [ $out ] );
 467
 468                 if ( !$this->loadRevisionData() ) {
 469                         if ( Hooks::run( 'DifferenceEngineShowDiffPageMaybeShowMissingRevision', [ $this ] ) ) {
 470                                 $this->showMissingRevision();
 471                         }
 472                         return;
 473                 }
 474
 475                 $user = $this->getUser();
 476                 $permErrors = [];
 477                 if ( $this->mNewPage ) {
 478                         $permErrors = $this->mNewPage->getUserPermissionsErrors( 'read', $user );
 479                 }
 480                 if ( $this->mOldPage ) {
 481                         $permErrors = wfMergeErrorArrays( $permErrors,
 482                                 $this->mOldPage->getUserPermissionsErrors( 'read', $user ) );
 483                 }
 484                 if ( count( $permErrors ) ) {
 485                         throw new PermissionsError( 'read', $permErrors );
 486                 }
 487
 488                 $rollback = '';
 489
 490                 $query = [];
 491                 # Carry over 'diffonly' param via navigation links
 492                 if ( $diffOnly != $user->getBoolOption( 'diffonly' ) ) {
 493                         $query['diffonly'] = $diffOnly;
 494                 }
 495                 # Cascade unhide param in links for easy deletion browsing
 496                 if ( $this->unhide ) {
 497                         $query['unhide'] = 1;
 498                 }
 499
 500                 # Check if one of the revisions is deleted/suppressed
 501                 $deleted = $suppressed = false;
 502                 $allowed = $this->mNewRev->userCan( Revision::DELETED_TEXT, $user );
 503
 504                 $revisionTools = [];
 505
 506                 # mOldRev is false if the difference engine is called with a "vague" query for
 507                 # a diff between a version V and its previous version V' AND the version V
 508                 # is the first version of that article. In that case, V' does not exist.
 509                 if ( $this->mOldRev === false ) {
 510                         if ( $this->mNewPage ) {
 511                                 $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 512                         }
 513                         $samePage = true;
 514                         $oldHeader = '';
 515                         // Allow extensions to change the $oldHeader variable
 516                         Hooks::run( 'DifferenceEngineOldHeaderNoOldRev', [ &$oldHeader ] );
 517                 } else {
 518                         Hooks::run( 'DiffViewHeader', [ $this, $this->mOldRev, $this->mNewRev ] );
 519
 520                         if ( !$this->mOldPage || !$this->mNewPage ) {
 521                                 // XXX say something to the user?
 522                                 $samePage = false;
 523                         } elseif ( $this->mNewPage->equals( $this->mOldPage ) ) {
 524                                 $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 525                                 $samePage = true;
 526                         } else {
 527                                 $out->setPageTitle( $this->msg( 'difference-title-multipage',
 528                                         $this->mOldPage->getPrefixedText(), $this->mNewPage->getPrefixedText() ) );
 529                                 $out->addSubtitle( $this->msg( 'difference-multipage' ) );
 530                                 $samePage = false;
 531                         }
 532
 533                         if ( $samePage && $this->mNewPage && $this->mNewPage->quickUserCan( 'edit', $user ) ) {
 534                                 if ( $this->mNewRev->isCurrent() && $this->mNewPage->userCan( 'rollback', $user ) ) {
 535                                         $rollbackLink = Linker::generateRollback( $this->mNewRev, $this->getContext() );
 536                                         if ( $rollbackLink ) {
 537                                                 $out->preventClickjacking();
 538                                                 $rollback = "\u{00A0}\u{00A0}\u{00A0}" . $rollbackLink;
 539                                         }
 540                                 }
 541
 542                                 if ( !$this->mOldRev->isDeleted( Revision::DELETED_TEXT ) &&
 543                                         !$this->mNewRev->isDeleted( Revision::DELETED_TEXT )
 544                                 ) {
 545                                         $undoLink = Html::element( 'a', [
 546                                                         'href' => $this->mNewPage->getLocalURL( [
 547                                                                 'action' => 'edit',
 548                                                                 'undoafter' => $this->mOldid,
 549                                                                 'undo' => $this->mNewid
 550                                                         ] ),
 551                                                         'title' => Linker::titleAttrib( 'undo' ),
 552                                                 ],
 553                                                 $this->msg( 'editundo' )->text()
 554                                         );
 555                                         $revisionTools['mw-diff-undo'] = $undoLink;
 556                                 }
 557                         }
 558
 559                         # Make "previous revision link"
 560                         if ( $samePage && $this->mOldPage && $this->mOldRev->getPrevious() ) {
 561                                 $prevlink = Linker::linkKnown(
 562                                         $this->mOldPage,
 563                                         $this->msg( 'previousdiff' )->escaped(),
 564                                         [ 'id' => 'differences-prevlink' ],
 565                                         [ 'diff' => 'prev', 'oldid' => $this->mOldid ] + $query
 566                                 );
 567                         } else {
 568                                 $prevlink = "\u{00A0}";
 569                         }
 570
 571                         if ( $this->mOldRev->isMinor() ) {
 572                                 $oldminor = ChangesList::flag( 'minor' );
 573                         } else {
 574                                 $oldminor = '';
 575                         }
 576
 577                         $ldel = $this->revisionDeleteLink( $this->mOldRev );
 578                         $oldRevisionHeader = $this->getRevisionHeader( $this->mOldRev, 'complete' );
 579                         $oldChangeTags = ChangeTags::formatSummaryRow( $this->mOldTags, 'diff', $this->getContext() );
 580
 581                         $oldHeader = '<div id="mw-diff-otitle1"><strong>' . $oldRevisionHeader . '</strong></div>' .
 582                                 '<div id="mw-diff-otitle2">' .
 583                                 Linker::revUserTools( $this->mOldRev, !$this->unhide ) . '</div>' .
 584                                 '<div id="mw-diff-otitle3">' . $oldminor .
 585                                 Linker::revComment( $this->mOldRev, !$diffOnly, !$this->unhide ) . $ldel . '</div>' .
 586                                 '<div id="mw-diff-otitle5">' . $oldChangeTags[0] . '</div>' .
 587                                 '<div id="mw-diff-otitle4">' . $prevlink . '</div>';
 588
 589                         // Allow extensions to change the $oldHeader variable
 590                         Hooks::run( 'DifferenceEngineOldHeader', [ $this, &$oldHeader, $prevlink, $oldminor,
 591                                 $diffOnly, $ldel, $this->unhide ] );
 592
 593                         if ( $this->mOldRev->isDeleted( Revision::DELETED_TEXT ) ) {
 594                                 $deleted = true; // old revisions text is hidden
 595                                 if ( $this->mOldRev->isDeleted( Revision::DELETED_RESTRICTED ) ) {
 596                                         $suppressed = true; // also suppressed
 597                                 }
 598                         }
 599
 600                         # Check if this user can see the revisions
 601                         if ( !$this->mOldRev->userCan( Revision::DELETED_TEXT, $user ) ) {
 602                                 $allowed = false;
 603                         }
 604                 }
 605
 606                 $out->addJsConfigVars( [
 607                         'wgDiffOldId' => $this->mOldid,
 608                         'wgDiffNewId' => $this->mNewid,
 609                 ] );
 610
 611                 # Make "next revision link"
 612                 # Skip next link on the top revision
 613                 if ( $samePage && $this->mNewPage && !$this->mNewRev->isCurrent() ) {
 614                         $nextlink = Linker::linkKnown(
 615                                 $this->mNewPage,
 616                                 $this->msg( 'nextdiff' )->escaped(),
 617                                 [ 'id' => 'differences-nextlink' ],
 618                                 [ 'diff' => 'next', 'oldid' => $this->mNewid ] + $query
 619                         );
 620                 } else {
 621                         $nextlink = "\u{00A0}";
 622                 }
 623
 624                 if ( $this->mNewRev->isMinor() ) {
 625                         $newminor = ChangesList::flag( 'minor' );
 626                 } else {
 627                         $newminor = '';
 628                 }
 629
 630                 # Handle RevisionDelete links...
 631                 $rdel = $this->revisionDeleteLink( $this->mNewRev );
 632
 633                 # Allow extensions to define their own revision tools
 634                 Hooks::run( 'DiffRevisionTools',
 635                         [ $this->mNewRev, &$revisionTools, $this->mOldRev, $user ] );
 636                 $formattedRevisionTools = [];
 637                 // Put each one in parentheses (poor man's button)
 638                 foreach ( $revisionTools as $key => $tool ) {
 639                         $toolClass = is_string( $key ) ? $key : 'mw-diff-tool';
 640                         $element = Html::rawElement(
 641                                 'span',
 642                                 [ 'class' => $toolClass ],
 643                                 $this->msg( 'parentheses' )->rawParams( $tool )->escaped()
 644                         );
 645                         $formattedRevisionTools[] = $element;
 646                 }
 647                 $newRevisionHeader = $this->getRevisionHeader( $this->mNewRev, 'complete' ) .
 648                         ' ' . implode( ' ', $formattedRevisionTools );
 649                 $newChangeTags = ChangeTags::formatSummaryRow( $this->mNewTags, 'diff', $this->getContext() );
 650
 651                 $newHeader = '<div id="mw-diff-ntitle1"><strong>' . $newRevisionHeader . '</strong></div>' .
 652                         '<div id="mw-diff-ntitle2">' . Linker::revUserTools( $this->mNewRev, !$this->unhide ) .
 653                         " $rollback</div>" .
 654                         '<div id="mw-diff-ntitle3">' . $newminor .
 655                         Linker::revComment( $this->mNewRev, !$diffOnly, !$this->unhide ) . $rdel . '</div>' .
 656                         '<div id="mw-diff-ntitle5">' . $newChangeTags[0] . '</div>' .
 657                         '<div id="mw-diff-ntitle4">' . $nextlink . $this->markPatrolledLink() . '</div>';
 658
 659                 // Allow extensions to change the $newHeader variable
 660                 Hooks::run( 'DifferenceEngineNewHeader', [ $this, &$newHeader, $formattedRevisionTools,
 661                         $nextlink, $rollback, $newminor, $diffOnly, $rdel, $this->unhide ] );
 662
 663                 if ( $this->mNewRev->isDeleted( Revision::DELETED_TEXT ) ) {
 664                         $deleted = true; // new revisions text is hidden
 665                         if ( $this->mNewRev->isDeleted( Revision::DELETED_RESTRICTED ) ) {
 666                                 $suppressed = true; // also suppressed
 667                         }
 668                 }
 669
 670                 # If the diff cannot be shown due to a deleted revision, then output
 671                 # the diff header and links to unhide (if available)...
 672                 if ( $deleted && ( !$this->unhide || !$allowed ) ) {
 673                         $this->showDiffStyle();
 674                         $multi = $this->getMultiNotice();
 675                         $out->addHTML( $this->addHeader( '', $oldHeader, $newHeader, $multi ) );
 676                         if ( !$allowed ) {
 677                                 $msg = $suppressed ? 'rev-suppressed-no-diff' : 'rev-deleted-no-diff';
 678                                 # Give explanation for why revision is not visible
 679                                 $out->wrapWikiMsg( "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 680                                         [ $msg ] );
 681                         } else {
 682                                 # Give explanation and add a link to view the diff...
 683                                 $query = $this->getRequest()->appendQueryValue( 'unhide', '1' );
 684                                 $link = $this->getTitle()->getFullURL( $query );
 685                                 $msg = $suppressed ? 'rev-suppressed-unhide-diff' : 'rev-deleted-unhide-diff';
 686                                 $out->wrapWikiMsg(
 687                                         "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 688                                         [ $msg, $link ]
 689                                 );
 690                         }
 691                 # Otherwise, output a regular diff...
 692                 } else {
 693                         # Add deletion notice if the user is viewing deleted content
 694                         $notice = '';
 695                         if ( $deleted ) {
 696                                 $msg = $suppressed ? 'rev-suppressed-diff-view' : 'rev-deleted-diff-view';
 697                                 $notice = "<div id='mw-$msg' class='mw-warning plainlinks'>\n" .
 698                                         $this->msg( $msg )->parse() .
 699                                         "</div>\n";
 700                         }
 701                         $this->showDiff( $oldHeader, $newHeader, $notice );
 702                         if ( !$diffOnly ) {
 703                                 $this->renderNewRevision();
 704                         }
 705                 }
 706         }
 707
 708         /**
 709          * Build a link to mark a change as patrolled.
 710          *
 711          * Returns empty string if there's either no revision to patrol or the user is not allowed to.
 712          * Side effect: When the patrol link is build, this method will call
 713          * OutputPage::preventClickjacking() and load mediawiki.page.patrol.ajax.
 714          *
 715          * @return string HTML or empty string
 716          */
 717         public function markPatrolledLink() {
 718                 if ( $this->mMarkPatrolledLink === null ) {
 719                         $linkInfo = $this->getMarkPatrolledLinkInfo();
 720                         // If false, there is no patrol link needed/allowed
 721                         if ( !$linkInfo || !$this->mNewPage ) {
 722                                 $this->mMarkPatrolledLink = '';
 723                         } else {
 724                                 $this->mMarkPatrolledLink = ' <span class="patrollink" data-mw="interface">[' .
 725                                         Linker::linkKnown(
 726                                                 $this->mNewPage,
 727                                                 $this->msg( 'markaspatrolleddiff' )->escaped(),
 728                                                 [],
 729                                                 [
 730                                                         'action' => 'markpatrolled',
 731                                                         'rcid' => $linkInfo['rcid'],
 732                                                 ]
 733                                         ) . ']</span>';
 734                                 // Allow extensions to change the markpatrolled link
 735                                 Hooks::run( 'DifferenceEngineMarkPatrolledLink', [ $this,
 736                                         &$this->mMarkPatrolledLink, $linkInfo['rcid'] ] );
 737                         }
 738                 }
 739                 return $this->mMarkPatrolledLink;
 740         }
 741
 742         /**
 743          * Returns an array of meta data needed to build a "mark as patrolled" link and
 744          * adds the mediawiki.page.patrol.ajax to the output.
 745          *
 746          * @return array|false An array of meta data for a patrol link (rcid only)
 747          *  or false if no link is needed
 748          */
 749         protected function getMarkPatrolledLinkInfo() {
 750                 global $wgUseRCPatrol;
 751
 752                 $user = $this->getUser();
 753
 754                 // Prepare a change patrol link, if applicable
 755                 if (
 756                         // Is patrolling enabled and the user allowed to?
 757                         $wgUseRCPatrol && $this->mNewPage && $this->mNewPage->quickUserCan( 'patrol', $user ) &&
 758                         // Only do this if the revision isn't more than 6 hours older
 759                         // than the Max RC age (6h because the RC might not be cleaned out regularly)
 760                         RecentChange::isInRCLifespan( $this->mNewRev->getTimestamp(), 21600 )
 761                 ) {
 762                         // Look for an unpatrolled change corresponding to this diff
 763                         $db = wfGetDB( DB_REPLICA );
 764                         $change = RecentChange::newFromConds(
 765                                 [
 766                                         'rc_timestamp' => $db->timestamp( $this->mNewRev->getTimestamp() ),
 767                                         'rc_this_oldid' => $this->mNewid,
 768                                         'rc_patrolled' => RecentChange::PRC_UNPATROLLED
 769                                 ],
 770                                 __METHOD__
 771                         );
 772
 773                         if ( $change && !$change->getPerformer()->equals( $user ) ) {
 774                                 $rcid = $change->getAttribute( 'rc_id' );
 775                         } else {
 776                                 // None found or the page has been created by the current user.
 777                                 // If the user could patrol this it already would be patrolled
 778                                 $rcid = 0;
 779                         }
 780
 781                         // Allow extensions to possibly change the rcid here
 782                         // For example the rcid might be set to zero due to the user
 783                         // being the same as the performer of the change but an extension
 784                         // might still want to show it under certain conditions
 785                         Hooks::run( 'DifferenceEngineMarkPatrolledRCID', [ &$rcid, $this, $change, $user ] );
 786
 787                         // Build the link
 788                         if ( $rcid ) {
 789                                 $this->getOutput()->preventClickjacking();
 790                                 if ( $user->isAllowed( 'writeapi' ) ) {
 791                                         $this->getOutput()->addModules( 'mediawiki.page.patrol.ajax' );
 792                                 }
 793
 794                                 return [
 795                                         'rcid' => $rcid,
 796                                 ];
 797                         }
 798                 }
 799
 800                 // No mark as patrolled link applicable
 801                 return false;
 802         }
 803
 804         /**
 805          * @param Revision $rev
 806          *
 807          * @return string
 808          */
 809         protected function revisionDeleteLink( $rev ) {
 810                 $link = Linker::getRevDeleteLink( $this->getUser(), $rev, $rev->getTitle() );
 811                 if ( $link !== '' ) {
 812                         $link = "\u{00A0}\u{00A0}\u{00A0}" . $link . ' ';
 813                 }
 814
 815                 return $link;
 816         }
 817
 818         /**
 819          * Show the new revision of the page.
 820          */
 821         public function renderNewRevision() {
 822                 $out = $this->getOutput();
 823                 $revHeader = $this->getRevisionHeader( $this->mNewRev );
 824                 # Add "current version as of X" title
 825                 $out->addHTML( "<hr class='diff-hr' id='mw-oldid' />
 826                 <h2 class='diff-currentversion-title'>{$revHeader}</h2>\n" );
 827                 # Page content may be handled by a hooked call instead...
 828                 if ( Hooks::run( 'ArticleContentOnDiff', [ $this, $out ] ) ) {
 829                         $this->loadNewText();
 830                         if ( !$this->mNewPage ) {
 831                                 // New revision is unsaved; bail out.
 832                                 // TODO in theory rendering the new revision is a meaningful thing to do
 833                                 // even if it's unsaved, but a lot of untangling is required to do it safely.
 834                         }
 835
 836                         $out->setRevisionId( $this->mNewid );
 837                         $out->setRevisionTimestamp( $this->mNewRev->getTimestamp() );
 838                         $out->setArticleFlag( true );
 839
 840                         if ( !Hooks::run( 'ArticleContentViewCustom',
 841                                 [ $this->mNewContent, $this->mNewPage, $out ] )
 842                         ) {
 843                                 // Handled by extension
 844                         } else {
 845                                 // Normal page
 846                                 if ( $this->getTitle()->equals( $this->mNewPage ) ) {
 847                                         // If the Title stored in the context is the same as the one
 848                                         // of the new revision, we can use its associated WikiPage
 849                                         // object.
 850                                         $wikiPage = $this->getWikiPage();
 851                                 } else {
 852                                         // Otherwise we need to create our own WikiPage object
 853                                         $wikiPage = WikiPage::factory( $this->mNewPage );
 854                                 }
 855
 856                                 $parserOutput = $this->getParserOutput( $wikiPage, $this->mNewRev );
 857
 858                                 # WikiPage::getParserOutput() should not return false, but just in case
 859                                 if ( $parserOutput ) {
 860                                         // Allow extensions to change parser output here
 861                                         if ( Hooks::run( 'DifferenceEngineRenderRevisionAddParserOutput',
 862                                                 [ $this, $out, $parserOutput, $wikiPage ] )
 863                                         ) {
 864                                                 $out->addParserOutput( $parserOutput, [
 865                                                         'enableSectionEditLinks' => $this->mNewRev->isCurrent()
 866                                                                 && $this->mNewRev->getTitle()->quickUserCan( 'edit', $this->getUser() ),
 867                                                 ] );
 868                                         }
 869                                 }
 870                         }
 871                 }
 872
 873                 // Allow extensions to optionally not show the final patrolled link
 874                 if ( Hooks::run( 'DifferenceEngineRenderRevisionShowFinalPatrolLink' ) ) {
 875                         # Add redundant patrol link on bottom...
 876                         $out->addHTML( $this->markPatrolledLink() );
 877                 }
 878         }
 879
 880         /**
 881          * @param WikiPage $page
 882          * @param Revision $rev
 883          *
 884          * @return ParserOutput|bool False if the revision was not found
 885          */
 886         protected function getParserOutput( WikiPage $page, Revision $rev ) {
 887                 $parserOptions = $page->makeParserOptions( $this->getContext() );
 888                 $parserOutput = $page->getParserOutput( $parserOptions, $rev->getId() );
 889
 890                 return $parserOutput;
 891         }
 892
 893         /**
 894          * Get the diff text, send it to the OutputPage object
 895          * Returns false if the diff could not be generated, otherwise returns true
 896          *
 897          * @param string|bool $otitle Header for old text or false
 898          * @param string|bool $ntitle Header for new text or false
 899          * @param string $notice HTML between diff header and body
 900          *
 901          * @return bool
 902          */
 903         public function showDiff( $otitle, $ntitle, $notice = '' ) {
 904                 // Allow extensions to affect the output here
 905                 Hooks::run( 'DifferenceEngineShowDiff', [ $this ] );
 906
 907                 $diff = $this->getDiff( $otitle, $ntitle, $notice );
 908                 if ( $diff === false ) {
 909                         $this->showMissingRevision();
 910
 911                         return false;
 912                 } else {
 913                         $this->showDiffStyle();
 914                         $this->getOutput()->addHTML( $diff );
 915
 916                         return true;
 917                 }
 918         }
 919
 920         /**
 921          * Add style sheets for diff display.
 922          */
 923         public function showDiffStyle() {
 924                 if ( !$this->isSlotDiffRenderer ) {
 925                         $this->getOutput()->addModuleStyles( 'mediawiki.diff.styles' );
 926                         foreach ( $this->getSlotDiffRenderers() as $slotDiffRenderer ) {
 927                                 $slotDiffRenderer->addModules( $this->getOutput() );
 928                         }
 929                 }
 930         }
 931
 932         /**
 933          * Get complete diff table, including header
 934          *
 935          * @param string|bool $otitle Header for old text or false
 936          * @param string|bool $ntitle Header for new text or false
 937          * @param string $notice HTML between diff header and body
 938          *
 939          * @return mixed
 940          */
 941         public function getDiff( $otitle, $ntitle, $notice = '' ) {
 942                 $body = $this->getDiffBody();
 943                 if ( $body === false ) {
 944                         return false;
 945                 }
 946
 947                 $multi = $this->getMultiNotice();
 948                 // Display a message when the diff is empty
 949                 if ( $body === '' ) {
 950                         $notice .= '<div class="mw-diff-empty">' .
 951                                 $this->msg( 'diff-empty' )->parse() .
 952                                 "</div>\n";
 953                 }
 954
 955                 return $this->addHeader( $body, $otitle, $ntitle, $multi, $notice );
 956         }
 957
 958         /**
 959          * Get the diff table body, without header
 960          *
 961          * @return mixed (string/false)
 962          */
 963         public function getDiffBody() {
 964                 $this->mCacheHit = true;
 965                 // Check if the diff should be hidden from this user
 966                 if ( !$this->isContentOverridden ) {
 967                         if ( !$this->loadRevisionData() ) {
 968                                 return false;
 969                         } elseif ( $this->mOldRev &&
 970                                 !$this->mOldRev->userCan( Revision::DELETED_TEXT, $this->getUser() )
 971                         ) {
 972                                 return false;
 973                         } elseif ( $this->mNewRev &&
 974                                 !$this->mNewRev->userCan( Revision::DELETED_TEXT, $this->getUser() )
 975                         ) {
 976                                 return false;
 977                         }
 978                         // Short-circuit
 979                         if ( $this->mOldRev === false || ( $this->mOldRev && $this->mNewRev &&
 980                                 $this->mOldRev->getId() && $this->mOldRev->getId() == $this->mNewRev->getId() )
 981                         ) {
 982                                 if ( Hooks::run( 'DifferenceEngineShowEmptyOldContent', [ $this ] ) ) {
 983                                         return '';
 984                                 }
 985                         }
 986                 }
 987
 988                 // Cacheable?
 989                 $key = false;
 990                 $cache = ObjectCache::getMainWANInstance();
 991                 if ( $this->mOldid && $this->mNewid ) {
 992                         // Check if subclass is still using the old way
 993                         // for backwards-compatibility
 994                         $key = $this->getDiffBodyCacheKey();
 995                         if ( $key === null ) {
 996                                 $key = $cache->makeKey( ...$this->getDiffBodyCacheKeyParams() );
 997                         }
 998
 999                         // Try cache
1000                         if ( !$this->mRefreshCache ) {
1001                                 $difftext = $cache->get( $key );
1002                                 if ( $difftext ) {
1003                                         wfIncrStats( 'diff_cache.hit' );
1004                                         $difftext = $this->localiseDiff( $difftext );
1005                                         $difftext .= "\n<!-- diff cache key $key -->\n";
1006
1007                                         return $difftext;
1008                                 }
1009                         } // don't try to load but save the result
1010                 }
1011                 $this->mCacheHit = false;
1012
1013                 // Loadtext is permission safe, this just clears out the diff
1014                 if ( !$this->loadText() ) {
1015                         return false;
1016                 }
1017
1018                 $difftext = '';
1019                 // We've checked for revdelete at the beginning of this method; it's OK to ignore
1020                 // read permissions here.
1021                 $slotContents = $this->getSlotContents();
1022                 foreach ( $this->getSlotDiffRenderers() as $role => $slotDiffRenderer ) {
1023                         $slotDiff = $slotDiffRenderer->getDiff( $slotContents[$role]['old'],
1024                                 $slotContents[$role]['new'] );
1025                         if ( $slotDiff && $role !== 'main' ) {
1026                                 // TODO use human-readable role name at least
1027                                 $slotTitle = $role;
1028                                 $difftext .= $this->getSlotHeader( $slotTitle );
1029                         }
1030                         $difftext .= $slotDiff;
1031                 }
1032
1033                 // Avoid PHP 7.1 warning from passing $this by reference
1034                 $diffEngine = $this;
1035
1036                 // Save to cache for 7 days
1037                 if ( !Hooks::run( 'AbortDiffCache', [ &$diffEngine ] ) ) {
1038                         wfIncrStats( 'diff_cache.uncacheable' );
1039                 } elseif ( $key !== false && $difftext !== false ) {
1040                         wfIncrStats( 'diff_cache.miss' );
1041                         $cache->set( $key, $difftext, 7 * 86400 );
1042                 } else {
1043                         wfIncrStats( 'diff_cache.uncacheable' );
1044                 }
1045                 // localise line numbers and title attribute text
1046                 if ( $difftext !== false ) {
1047                         $difftext = $this->localiseDiff( $difftext );
1048                 }
1049
1050                 return $difftext;
1051         }
1052
1053         /**
1054          * Get the diff table body for one slot, without header
1055          *
1056          * @param string $role
1057          * @return string|false
1058          */
1059         public function getDiffBodyForRole( $role ) {
1060                 $diffRenderers = $this->getSlotDiffRenderers();
1061                 if ( !isset( $diffRenderers[$role] ) ) {
1062                         return false;
1063                 }
1064
1065                 $slotContents = $this->getSlotContents();
1066                 $slotDiff = $diffRenderers[$role]->getDiff( $slotContents[$role]['old'],
1067                         $slotContents[$role]['new'] );
1068                 if ( !$slotDiff ) {
1069                         return false;
1070                 }
1071
1072                 if ( $role !== 'main' ) {
1073                         // TODO use human-readable role name at least
1074                         $slotTitle = $role;
1075                         $slotDiff = $this->getSlotHeader( $slotTitle ) . $slotDiff;
1076                 }
1077
1078                 return $this->localiseDiff( $slotDiff );
1079         }
1080
1081         /**
1082          * Get a slot header for inclusion in a diff body (as a table row).
1083          *
1084          * @param string $headerText The text of the header
1085          * @return string
1086          *
1087          */
1088         protected function getSlotHeader( $headerText ) {
1089                 // The old revision is missing on oldid=<first>&diff=prev; only 2 columns in that case.
1090                 $columnCount = $this->mOldRev ? 4 : 2;
1091                 $userLang = $this->getLanguage()->getHtmlCode();
1092                 return Html::rawElement( 'tr', [ 'class' => 'mw-diff-slot-header', 'lang' => $userLang ],
1093                         Html::element( 'th', [ 'colspan' => $columnCount ], $headerText ) );
1094         }
1095
1096         /**
1097          * Returns the cache key for diff body text or content.
1098          *
1099          * @deprecated since 1.31, use getDiffBodyCacheKeyParams() instead
1100          * @since 1.23
1101          *
1102          * @throws MWException
1103          * @return string|null
1104          */
1105         protected function getDiffBodyCacheKey() {
1106                 return null;
1107         }
1108
1109         /**
1110          * Get the cache key parameters
1111          *
1112          * Subclasses can replace the first element in the array to something
1113          * more specific to the type of diff (e.g. "inline-diff"), or append
1114          * if the cache should vary on more things. Overriding entirely should
1115          * be avoided.
1116          *
1117          * @since 1.31
1118          *
1119          * @return array
1120          * @throws MWException
1121          */
1122         protected function getDiffBodyCacheKeyParams() {
1123                 if ( !$this->mOldid || !$this->mNewid ) {
1124                         throw new MWException( 'mOldid and mNewid must be set to get diff cache key.' );
1125                 }
1126
1127                 $engine = $this->getEngine();
1128                 $params = [
1129                         'diff',
1130                         $engine,
1131                         self::DIFF_VERSION,
1132                         "old-{$this->mOldid}",
1133                         "rev-{$this->mNewid}"
1134                 ];
1135
1136                 if ( $engine === 'wikidiff2' ) {
1137                         $params[] = phpversion( 'wikidiff2' );
1138                         $params[] = $this->getConfig()->get( 'WikiDiff2MovedParagraphDetectionCutoff' );
1139                 }
1140
1141                 if ( !$this->isSlotDiffRenderer ) {
1142                         foreach ( $this->getSlotDiffRenderers() as $slotDiffRenderer ) {
1143                                 $params = array_merge( $params, $slotDiffRenderer->getExtraCacheKeys() );
1144                         }
1145                 }
1146
1147                 return $params;
1148         }
1149
1150         /**
1151          * Implements DifferenceEngineSlotDiffRenderer::getExtraCacheKeys(). Only used when
1152          * DifferenceEngine is wrapped in DifferenceEngineSlotDiffRenderer.
1153          * @return array
1154          * @internal for use by DifferenceEngineSlotDiffRenderer only
1155          * @deprecated
1156          */
1157         public function getExtraCacheKeys() {
1158                 // This method is called when the DifferenceEngine is used for a slot diff. We only care
1159                 // about special things, not the revision IDs, which are added to the cache key by the
1160                 // page-level DifferenceEngine, and which might not have a valid value for this object.
1161                 $this->mOldid = 123456789;
1162                 $this->mNewid = 987654321;
1163
1164                 // This will repeat a bunch of unnecessary key fields for each slot. Not nice but harmless.
1165                 $cacheString = $this->getDiffBodyCacheKey();
1166                 if ( $cacheString ) {
1167                         return [ $cacheString ];
1168                 }
1169
1170                 $params = $this->getDiffBodyCacheKeyParams();
1171
1172                 // Try to get rid of the standard keys to keep the cache key human-readable:
1173                 // call the getDiffBodyCacheKeyParams implementation of the base class, and if
1174                 // the child class includes the same keys, drop them.
1175                 // Uses an obscure PHP feature where static calls to non-static methods are allowed
1176                 // as long as we are already in a non-static method of the same class, and the call context
1177                 // ($this) will be inherited.
1178                 // phpcs:ignore Squiz.Classes.SelfMemberReference.NotUsed
1179                 $standardParams = DifferenceEngine::getDiffBodyCacheKeyParams();
1180                 if ( array_slice( $params, 0, count( $standardParams ) ) === $standardParams ) {
1181                         $params = array_slice( $params, count( $standardParams ) );
1182                 }
1183
1184                 return $params;
1185         }
1186
1187         /**
1188          * Generate a diff, no caching.
1189          *
1190          * @since 1.21
1191          *
1192          * @param Content $old Old content
1193          * @param Content $new New content
1194          *
1195          * @throws Exception If old or new content is not an instance of TextContent.
1196          * @return bool|string
1197          *
1198          * @deprecated since 1.32, use a SlotDiffRenderer instead.
1199          */
1200         public function generateContentDiffBody( Content $old, Content $new ) {
1201                 $slotDiffRenderer = $new->getContentHandler()->getSlotDiffRenderer( $this->getContext() );
1202                 if (
1203                         $slotDiffRenderer instanceof DifferenceEngineSlotDiffRenderer
1204                         && $this->isSlotDiffRenderer
1205                 ) {
1206                         // Oops, we are just about to enter an infinite loop (the slot-level DifferenceEngine
1207                         // called a DifferenceEngineSlotDiffRenderer that wraps the same DifferenceEngine class).
1208                         // This will happen when a content model has no custom slot diff renderer, it does have
1209                         // a custom difference engine, but that does not override this method.
1210                         throw new Exception( get_class( $this ) . ': could not maintain backwards compatibility. '
1211                                 . 'Please use a SlotDiffRenderer.' );
1212                 }
1213                 return $slotDiffRenderer->getDiff( $old, $new ) . $this->getDebugString();
1214         }
1215
1216         /**
1217          * Generate a diff, no caching
1218          *
1219          * @param string $otext Old text, must be already segmented
1220          * @param string $ntext New text, must be already segmented
1221          *
1222          * @throws Exception If content handling for text content is configured in a way
1223          *   that makes maintaining B/C hard.
1224          * @return bool|string
1225          *
1226          * @deprecated since 1.32, use a TextSlotDiffRenderer instead.
1227          */
1228         public function generateTextDiffBody( $otext, $ntext ) {
1229                 $slotDiffRenderer = ContentHandler::getForModelID( CONTENT_MODEL_TEXT )
1230                         ->getSlotDiffRenderer( $this->getContext() );
1231                 if ( !( $slotDiffRenderer instanceof TextSlotDiffRenderer ) ) {
1232                         // Someone used the GetSlotDiffRenderer hook to replace the renderer.
1233                         // This is too unlikely to happen to bother handling properly.
1234                         throw new Exception( 'The slot diff renderer for text content should be a '
1235                                 . 'TextSlotDiffRenderer subclass' );
1236                 }
1237                 return $slotDiffRenderer->getTextDiff( $otext, $ntext ) . $this->getDebugString();
1238         }
1239
1240         /**
1241          * Process $wgExternalDiffEngine and get a sane, usable engine
1242          *
1243          * @return bool|string 'wikidiff2', path to an executable, or false
1244          * @internal For use by this class and TextSlotDiffRenderer only.
1245          */
1246         public static function getEngine() {
1247                 global $wgExternalDiffEngine;
1248                 // We use the global here instead of Config because we write to the value,
1249                 // and Config is not mutable.
1250                 if ( $wgExternalDiffEngine == 'wikidiff' || $wgExternalDiffEngine == 'wikidiff3' ) {
1251                         wfDeprecated( "\$wgExternalDiffEngine = '{$wgExternalDiffEngine}'", '1.27' );
1252                         $wgExternalDiffEngine = false;
1253                 } elseif ( $wgExternalDiffEngine == 'wikidiff2' ) {
1254                         wfDeprecated( "\$wgExternalDiffEngine = '{$wgExternalDiffEngine}'", '1.32' );
1255                         $wgExternalDiffEngine = false;
1256                 } elseif ( !is_string( $wgExternalDiffEngine ) && $wgExternalDiffEngine !== false ) {
1257                         // And prevent people from shooting themselves in the foot...
1258                         wfWarn( '$wgExternalDiffEngine is set to a non-string value, forcing it to false' );
1259                         $wgExternalDiffEngine = false;
1260                 }
1261
1262                 if ( is_string( $wgExternalDiffEngine ) && is_executable( $wgExternalDiffEngine ) ) {
1263                         return $wgExternalDiffEngine;
1264                 } elseif ( $wgExternalDiffEngine === false && function_exists( 'wikidiff2_do_diff' ) ) {
1265                         return 'wikidiff2';
1266                 } else {
1267                         // Native PHP
1268                         return false;
1269                 }
1270         }
1271
1272         /**
1273          * Generates diff, to be wrapped internally in a logging/instrumentation
1274          *
1275          * @param string $otext Old text, must be already segmented
1276          * @param string $ntext New text, must be already segmented
1277          *
1278          * @throws Exception If content handling for text content is configured in a way
1279          *   that makes maintaining B/C hard.
1280          * @return bool|string
1281          *
1282          * @deprecated since 1.32, use a TextSlotDiffRenderer instead.
1283          */
1284         protected function textDiff( $otext, $ntext ) {
1285                 $slotDiffRenderer = ContentHandler::getForModelID( CONTENT_MODEL_TEXT )
1286                         ->getSlotDiffRenderer( $this->getContext() );
1287                 if ( !( $slotDiffRenderer instanceof TextSlotDiffRenderer ) ) {
1288                         // Someone used the GetSlotDiffRenderer hook to replace the renderer.
1289                         // This is too unlikely to happen to bother handling properly.
1290                         throw new Exception( 'The slot diff renderer for text content should be a '
1291                                 . 'TextSlotDiffRenderer subclass' );
1292                 }
1293                 return $slotDiffRenderer->getTextDiff( $otext, $ntext ) . $this->getDebugString();
1294         }
1295
1296         /**
1297          * Generate a debug comment indicating diff generating time,
1298          * server node, and generator backend.
1299          *
1300          * @param string $generator : What diff engine was used
1301          *
1302          * @return string
1303          */
1304         protected function debug( $generator = "internal" ) {
1305                 global $wgShowHostnames;
1306                 if ( !$this->enableDebugComment ) {
1307                         return '';
1308                 }
1309                 $data = [ $generator ];
1310                 if ( $wgShowHostnames ) {
1311                         $data[] = wfHostname();
1312                 }
1313                 $data[] = wfTimestamp( TS_DB );
1314
1315                 return "<!-- diff generator: " .
1316                         implode( " ", array_map( "htmlspecialchars", $data ) ) .
1317                         " -->\n";
1318         }
1319
1320         private function getDebugString() {
1321                 $engine = self::getEngine();
1322                 if ( $engine === 'wikidiff2' ) {
1323                         return $this->debug( 'wikidiff2' );
1324                 } elseif ( $engine === false ) {
1325                         return $this->debug( 'native PHP' );
1326                 } else {
1327                         return $this->debug( "external $engine" );
1328                 }
1329         }
1330
1331         /**
1332          * Localise diff output
1333          *
1334          * @param string $text
1335          * @return string
1336          */
1337         private function localiseDiff( $text ) {
1338                 $text = $this->localiseLineNumbers( $text );
1339                 if ( $this->getEngine() === 'wikidiff2' &&
1340                         version_compare( phpversion( 'wikidiff2' ), '1.5.1', '>=' )
1341                 ) {
1342                         $text = $this->addLocalisedTitleTooltips( $text );
1343                 }
1344                 return $text;
1345         }
1346
1347         /**
1348          * Replace line numbers with the text in the user's language
1349          *
1350          * @param string $text
1351          *
1352          * @return mixed
1353          */
1354         public function localiseLineNumbers( $text ) {
1355                 return preg_replace_callback(
1356                         '/<!--LINE (\d+)-->/',
1357                         [ $this, 'localiseLineNumbersCb' ],
1358                         $text
1359                 );
1360         }
1361
1362         public function localiseLineNumbersCb( $matches ) {
1363                 if ( $matches[1] === '1' && $this->mReducedLineNumbers ) {
1364                         return '';
1365                 }
1366
1367                 return $this->msg( 'lineno' )->numParams( $matches[1] )->escaped();
1368         }
1369
1370         /**
1371          * Add title attributes for tooltips on moved paragraph indicators
1372          *
1373          * @param string $text
1374          * @return string
1375          */
1376         private function addLocalisedTitleTooltips( $text ) {
1377                 return preg_replace_callback(
1378                         '/class="mw-diff-movedpara-(left|right)"/',
1379                         [ $this, 'addLocalisedTitleTooltipsCb' ],
1380                         $text
1381                 );
1382         }
1383
1384         /**
1385          * @param array $matches
1386          * @return string
1387          */
1388         private function addLocalisedTitleTooltipsCb( array $matches ) {
1389                 $key = $matches[1] === 'right' ?
1390                         'diff-paragraph-moved-toold' :
1391                         'diff-paragraph-moved-tonew';
1392                 return $matches[0] . ' title="' . $this->msg( $key )->escaped() . '"';
1393         }
1394
1395         /**
1396          * If there are revisions between the ones being compared, return a note saying so.
1397          *
1398          * @return string
1399          */
1400         public function getMultiNotice() {
1401                 // The notice only make sense if we are diffing two saved revisions of the same page.
1402                 if (
1403                         !$this->mOldRev || !$this->mNewRev
1404                         || !$this->mOldPage || !$this->mNewPage
1405                         || !$this->mOldPage->equals( $this->mNewPage )
1406                 ) {
1407                         return '';
1408                 }
1409
1410                 if ( $this->mOldRev->getTimestamp() > $this->mNewRev->getTimestamp() ) {
1411                         $oldRev = $this->mNewRev; // flip
1412                         $newRev = $this->mOldRev; // flip
1413                 } else { // normal case
1414                         $oldRev = $this->mOldRev;
1415                         $newRev = $this->mNewRev;
1416                 }
1417
1418                 // Sanity: don't show the notice if too many rows must be scanned
1419                 // @todo show some special message for that case
1420                 $nEdits = $this->mNewPage->countRevisionsBetween( $oldRev, $newRev, 1000 );
1421                 if ( $nEdits > 0 && $nEdits <= 1000 ) {
1422                         $limit = 100; // use diff-multi-manyusers if too many users
1423                         $users = $this->mNewPage->getAuthorsBetween( $oldRev, $newRev, $limit );
1424                         $numUsers = count( $users );
1425
1426                         if ( $numUsers == 1 && $users[0] == $newRev->getUserText( Revision::RAW ) ) {
1427                                 $numUsers = 0; // special case to say "by the same user" instead of "by one other user"
1428                         }
1429
1430                         return self::intermediateEditsMsg( $nEdits, $numUsers, $limit );
1431                 }
1432
1433                 return ''; // nothing
1434         }
1435
1436         /**
1437          * Get a notice about how many intermediate edits and users there are
1438          *
1439          * @param int $numEdits
1440          * @param int $numUsers
1441          * @param int $limit
1442          *
1443          * @return string
1444          */
1445         public static function intermediateEditsMsg( $numEdits, $numUsers, $limit ) {
1446                 if ( $numUsers === 0 ) {
1447                         $msg = 'diff-multi-sameuser';
1448                 } elseif ( $numUsers > $limit ) {
1449                         $msg = 'diff-multi-manyusers';
1450                         $numUsers = $limit;
1451                 } else {
1452                         $msg = 'diff-multi-otherusers';
1453                 }
1454
1455                 return wfMessage( $msg )->numParams( $numEdits, $numUsers )->parse();
1456         }
1457
1458         /**
1459          * Get a header for a specified revision.
1460          *
1461          * @param Revision $rev
1462          * @param string $complete 'complete' to get the header wrapped depending
1463          *        the visibility of the revision and a link to edit the page.
1464          *
1465          * @return string HTML fragment
1466          */
1467         public function getRevisionHeader( Revision $rev, $complete = '' ) {
1468                 $lang = $this->getLanguage();
1469                 $user = $this->getUser();
1470                 $revtimestamp = $rev->getTimestamp();
1471                 $timestamp = $lang->userTimeAndDate( $revtimestamp, $user );
1472                 $dateofrev = $lang->userDate( $revtimestamp, $user );
1473                 $timeofrev = $lang->userTime( $revtimestamp, $user );
1474
1475                 $header = $this->msg(
1476                         $rev->isCurrent() ? 'currentrev-asof' : 'revisionasof',
1477                         $timestamp,
1478                         $dateofrev,
1479                         $timeofrev
1480                 )->escaped();
1481
1482                 if ( $complete !== 'complete' ) {
1483                         return $header;
1484                 }
1485
1486                 $title = $rev->getTitle();
1487
1488                 $header = Linker::linkKnown( $title, $header, [],
1489                         [ 'oldid' => $rev->getId() ] );
1490
1491                 if ( $rev->userCan( Revision::DELETED_TEXT, $user ) ) {
1492                         $editQuery = [ 'action' => 'edit' ];
1493                         if ( !$rev->isCurrent() ) {
1494                                 $editQuery['oldid'] = $rev->getId();
1495                         }
1496
1497                         $key = $title->quickUserCan( 'edit', $user ) ? 'editold' : 'viewsourceold';
1498                         $msg = $this->msg( $key )->escaped();
1499                         $editLink = $this->msg( 'parentheses' )->rawParams(
1500                                 Linker::linkKnown( $title, $msg, [], $editQuery ) )->escaped();
1501                         $header .= ' ' . Html::rawElement(
1502                                 'span',
1503                                 [ 'class' => 'mw-diff-edit' ],
1504                                 $editLink
1505                         );
1506                         if ( $rev->isDeleted( Revision::DELETED_TEXT ) ) {
1507                                 $header = Html::rawElement(
1508                                         'span',
1509                                         [ 'class' => 'history-deleted' ],
1510                                         $header
1511                                 );
1512                         }
1513                 } else {
1514                         $header = Html::rawElement( 'span', [ 'class' => 'history-deleted' ], $header );
1515                 }
1516
1517                 return $header;
1518         }
1519
1520         /**
1521          * Add the header to a diff body
1522          *
1523          * @param string $diff Diff body
1524          * @param string $otitle Old revision header
1525          * @param string $ntitle New revision header
1526          * @param string $multi Notice telling user that there are intermediate
1527          *   revisions between the ones being compared
1528          * @param string $notice Other notices, e.g. that user is viewing deleted content
1529          *
1530          * @return string
1531          */
1532         public function addHeader( $diff, $otitle, $ntitle, $multi = '', $notice = '' ) {
1533                 // shared.css sets diff in interface language/dir, but the actual content
1534                 // is often in a different language, mostly the page content language/dir
1535                 $header = Html::openElement( 'table', [
1536                         'class' => [ 'diff', 'diff-contentalign-' . $this->getDiffLang()->alignStart() ],
1537                         'data-mw' => 'interface',
1538                 ] );
1539                 $userLang = htmlspecialchars( $this->getLanguage()->getHtmlCode() );
1540
1541                 if ( !$diff && !$otitle ) {
1542                         $header .= "
1543                         <tr class=\"diff-title\" lang=\"{$userLang}\">
1544                         <td class=\"diff-ntitle\">{$ntitle}</td>
1545                         </tr>";
1546                         $multiColspan = 1;
1547                 } else {
1548                         if ( $diff ) { // Safari/Chrome show broken output if cols not used
1549                                 $header .= "
1550                                 <col class=\"diff-marker\" />
1551                                 <col class=\"diff-content\" />
1552                                 <col class=\"diff-marker\" />
1553                                 <col class=\"diff-content\" />";
1554                                 $colspan = 2;
1555                                 $multiColspan = 4;
1556                         } else {
1557                                 $colspan = 1;
1558                                 $multiColspan = 2;
1559                         }
1560                         if ( $otitle || $ntitle ) {
1561                                 $header .= "
1562                                 <tr class=\"diff-title\" lang=\"{$userLang}\">
1563                                 <td colspan=\"$colspan\" class=\"diff-otitle\">{$otitle}</td>
1564                                 <td colspan=\"$colspan\" class=\"diff-ntitle\">{$ntitle}</td>
1565                                 </tr>";
1566                         }
1567                 }
1568
1569                 if ( $multi != '' ) {
1570                         $header .= "<tr><td colspan=\"{$multiColspan}\" " .
1571                                 "class=\"diff-multi\" lang=\"{$userLang}\">{$multi}</td></tr>";
1572                 }
1573                 if ( $notice != '' ) {
1574                         $header .= "<tr><td colspan=\"{$multiColspan}\" " .
1575                                 "class=\"diff-notice\" lang=\"{$userLang}\">{$notice}</td></tr>";
1576                 }
1577
1578                 return $header . $diff . "</table>";
1579         }
1580
1581         /**
1582          * Use specified text instead of loading from the database
1583          * @param Content $oldContent
1584          * @param Content $newContent
1585          * @since 1.21
1586          * @deprecated since 1.32, use setRevisions or ContentHandler::getSlotDiffRenderer.
1587          */
1588         public function setContent( Content $oldContent, Content $newContent ) {
1589                 $this->mOldContent = $oldContent;
1590                 $this->mNewContent = $newContent;
1591
1592                 $this->mTextLoaded = 2;
1593                 $this->mRevisionsLoaded = true;
1594                 $this->isContentOverridden = true;
1595                 $this->slotDiffRenderers = null;
1596         }
1597
1598         /**
1599          * Use specified text instead of loading from the database.
1600          * @param RevisionRecord|null $oldRevision
1601          * @param RevisionRecord $newRevision
1602          */
1603         public function setRevisions(
1604                 RevisionRecord $oldRevision = null, RevisionRecord $newRevision
1605         ) {
1606                 if ( $oldRevision ) {
1607                         $this->mOldRev = new Revision( $oldRevision );
1608                         $this->mOldid = $oldRevision->getId();
1609                         $this->mOldPage = Title::newFromLinkTarget( $oldRevision->getPageAsLinkTarget() );
1610                         // This method is meant for edit diffs and such so there is no reason to provide a
1611                         // revision that's not readable to the user, but check it just in case.
1612                         $this->mOldContent = $oldRevision ? $oldRevision->getContent( 'main',
1613                                 RevisionRecord::FOR_THIS_USER, $this->getUser() ) : null;
1614                 } else {
1615                         $this->mOldPage = null;
1616                         $this->mOldRev = $this->mOldid = false;
1617                 }
1618                 $this->mNewRev = new Revision( $newRevision );
1619                 $this->mNewid = $newRevision->getId();
1620                 $this->mNewPage = Title::newFromLinkTarget( $newRevision->getPageAsLinkTarget() );
1621                 $this->mNewContent = $newRevision->getContent( 'main',
1622                         RevisionRecord::FOR_THIS_USER, $this->getUser() );
1623
1624                 $this->mRevisionsIdsLoaded = $this->mRevisionsLoaded = true;
1625                 $this->mTextLoaded = !!$oldRevision + 1;
1626                 $this->isContentOverridden = false;
1627                 $this->slotDiffRenderers = null;
1628         }
1629
1630         /**
1631          * Set the language in which the diff text is written
1632          *
1633          * @param Language $lang
1634          * @since 1.19
1635          */
1636         public function setTextLanguage( $lang ) {
1637                 if ( !$lang instanceof Language ) {
1638                         wfDeprecated( __METHOD__ . ' with other type than Language for $lang', '1.32' );
1639                 }
1640                 $this->mDiffLang = wfGetLangObj( $lang );
1641         }
1642
1643         /**
1644          * Maps a revision pair definition as accepted by DifferenceEngine constructor
1645          * to a pair of actual integers representing revision ids.
1646          *
1647          * @param int $old Revision id, e.g. from URL parameter 'oldid'
1648          * @param int|string $new Revision id or strings 'next' or 'prev', e.g. from URL parameter 'diff'
1649          *
1650          * @return array List of two revision ids, older first, later second.
1651          *     Zero signifies invalid argument passed.
1652          *     false signifies that there is no previous/next revision ($old is the oldest/newest one).
1653          */
1654         public function mapDiffPrevNext( $old, $new ) {
1655                 if ( $new === 'prev' ) {
1656                         // Show diff between revision $old and the previous one. Get previous one from DB.
1657                         $newid = intval( $old );
1658                         $oldid = $this->getTitle()->getPreviousRevisionID( $newid );
1659                 } elseif ( $new === 'next' ) {
1660                         // Show diff between revision $old and the next one. Get next one from DB.
1661                         $oldid = intval( $old );
1662                         $newid = $this->getTitle()->getNextRevisionID( $oldid );
1663                 } else {
1664                         $oldid = intval( $old );
1665                         $newid = intval( $new );
1666                 }
1667
1668                 return [ $oldid, $newid ];
1669         }
1670
1671         /**
1672          * Load revision IDs
1673          */
1674         private function loadRevisionIds() {
1675                 if ( $this->mRevisionsIdsLoaded ) {
1676                         return;
1677                 }
1678
1679                 $this->mRevisionsIdsLoaded = true;
1680
1681                 $old = $this->mOldid;
1682                 $new = $this->mNewid;
1683
1684                 list( $this->mOldid, $this->mNewid ) = self::mapDiffPrevNext( $old, $new );
1685                 if ( $new === 'next' && $this->mNewid === false ) {
1686                         # if no result, NewId points to the newest old revision. The only newer
1687                         # revision is cur, which is "0".
1688                         $this->mNewid = 0;
1689                 }
1690
1691                 Hooks::run(
1692                         'NewDifferenceEngine',
1693                         [ $this->getTitle(), &$this->mOldid, &$this->mNewid, $old, $new ]
1694                 );
1695         }
1696
1697         /**
1698          * Load revision metadata for the specified revisions. If newid is 0, then compare
1699          * the old revision in oldid to the current revision of the current page (as defined
1700          * by the request context); if oldid is 0, then compare the revision in newid to the
1701          * immediately previous one.
1702          *
1703          * If oldid is false, leave the corresponding revision object set
1704          * to false. This can happen with 'diff=prev' pointing to a non-existent revision,
1705          * and is also used directly by the API.
1706          *
1707          * @return bool Whether both revisions were loaded successfully. Setting mOldRev
1708          *   to false counts as successful loading.
1709          */
1710         public function loadRevisionData() {
1711                 if ( $this->mRevisionsLoaded ) {
1712                         return $this->isContentOverridden || $this->mNewRev && !is_null( $this->mOldRev );
1713                 }
1714
1715                 // Whether it succeeds or fails, we don't want to try again
1716                 $this->mRevisionsLoaded = true;
1717
1718                 $this->loadRevisionIds();
1719
1720                 // Load the new revision object
1721                 if ( $this->mNewid ) {
1722                         $this->mNewRev = Revision::newFromId( $this->mNewid );
1723                 } else {
1724                         $this->mNewRev = Revision::newFromTitle(
1725                                 $this->getTitle(),
1726                                 false,
1727                                 Revision::READ_NORMAL
1728                         );
1729                 }
1730
1731                 if ( !$this->mNewRev instanceof Revision ) {
1732                         return false;
1733                 }
1734
1735                 // Update the new revision ID in case it was 0 (makes life easier doing UI stuff)
1736                 $this->mNewid = $this->mNewRev->getId();
1737                 if ( $this->mNewid ) {
1738                         $this->mNewPage = $this->mNewRev->getTitle();
1739                 } else {
1740                         $this->mNewPage = null;
1741                 }
1742
1743                 // Load the old revision object
1744                 $this->mOldRev = false;
1745                 if ( $this->mOldid ) {
1746                         $this->mOldRev = Revision::newFromId( $this->mOldid );
1747                 } elseif ( $this->mOldid === 0 ) {
1748                         $rev = $this->mNewRev->getPrevious();
1749                         if ( $rev ) {
1750                                 $this->mOldid = $rev->getId();
1751                                 $this->mOldRev = $rev;
1752                         } else {
1753                                 // No previous revision; mark to show as first-version only.
1754                                 $this->mOldid = false;
1755                                 $this->mOldRev = false;
1756                         }
1757                 } /* elseif ( $this->mOldid === false ) leave mOldRev false; */
1758
1759                 if ( is_null( $this->mOldRev ) ) {
1760                         return false;
1761                 }
1762
1763                 if ( $this->mOldRev && $this->mOldRev->getId() ) {
1764                         $this->mOldPage = $this->mOldRev->getTitle();
1765                 } else {
1766                         $this->mOldPage = null;
1767                 }
1768
1769                 // Load tags information for both revisions
1770                 $dbr = wfGetDB( DB_REPLICA );
1771                 if ( $this->mOldid !== false ) {
1772                         $this->mOldTags = $dbr->selectField(
1773                                 'tag_summary',
1774                                 'ts_tags',
1775                                 [ 'ts_rev_id' => $this->mOldid ],
1776                                 __METHOD__
1777                         );
1778                 } else {
1779                         $this->mOldTags = false;
1780                 }
1781                 $this->mNewTags = $dbr->selectField(
1782                         'tag_summary',
1783                         'ts_tags',
1784                         [ 'ts_rev_id' => $this->mNewid ],
1785                         __METHOD__
1786                 );
1787
1788                 return true;
1789         }
1790
1791         /**
1792          * Load the text of the revisions, as well as revision data.
1793          * When the old revision is missing (mOldRev is false), loading mOldContent is not attempted.
1794          *
1795          * @return bool Whether the content of both revisions could be loaded successfully.
1796          *   (When mOldRev is false, that still counts as a success.)
1797          *
1798          */
1799         public function loadText() {
1800                 if ( $this->mTextLoaded == 2 ) {
1801                         return $this->loadRevisionData() && ( $this->mOldRev === false || $this->mOldContent )
1802                                 && $this->mNewContent;
1803                 }
1804
1805                 // Whether it succeeds or fails, we don't want to try again
1806                 $this->mTextLoaded = 2;
1807
1808                 if ( !$this->loadRevisionData() ) {
1809                         return false;
1810                 }
1811
1812                 if ( $this->mOldRev ) {
1813                         $this->mOldContent = $this->mOldRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1814                         if ( $this->mOldContent === null ) {
1815                                 return false;
1816                         }
1817                 }
1818
1819                 $this->mNewContent = $this->mNewRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1820                 Hooks::run( 'DifferenceEngineLoadTextAfterNewContentIsLoaded', [ $this ] );
1821                 if ( $this->mNewContent === null ) {
1822                         return false;
1823                 }
1824
1825                 return true;
1826         }
1827
1828         /**
1829          * Load the text of the new revision, not the old one
1830          *
1831          * @return bool Whether the content of the new revision could be loaded successfully.
1832          */
1833         public function loadNewText() {
1834                 if ( $this->mTextLoaded >= 1 ) {
1835                         return $this->loadRevisionData();
1836                 }
1837
1838                 $this->mTextLoaded = 1;
1839
1840                 if ( !$this->loadRevisionData() ) {
1841                         return false;
1842                 }
1843
1844                 $this->mNewContent = $this->mNewRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1845
1846                 Hooks::run( 'DifferenceEngineAfterLoadNewText', [ $this ] );
1847
1848                 return true;
1849         }
1850
1851 }