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\MediaWikiServices;
  25 use MediaWiki\Permissions\PermissionManager;
  26 use MediaWiki\Revision\RevisionRecord;
  27 use MediaWiki\Revision\SlotRecord;
  28 use MediaWiki\Storage\NameTableAccessException;
  29
  30 /**
  31  * DifferenceEngine is responsible for rendering the difference between two revisions as HTML.
  32  * This includes interpreting URL parameters, retrieving revision data, checking access permissions,
  33  * selecting and invoking the diff generator class for the individual slots, doing post-processing
  34  * on the generated diff, adding the rest of the HTML (such as headers) and writing the whole thing
  35  * to OutputPage.
  36  *
  37  * DifferenceEngine can be subclassed by extensions, by customizing
  38  * ContentHandler::createDifferenceEngine; the content handler will be selected based on the
  39  * content model of the main slot (of the new revision, when the two are different).
  40  * That might change after PageTypeHandler gets introduced.
  41  *
  42  * In the past, the class was also used for slot-level diff generation, and extensions might still
  43  * subclass it and add such functionality. When that is the case (sepcifically, when a
  44  * ContentHandler returns a standard SlotDiffRenderer but a nonstandard DifferenceEngine)
  45  * DifferenceEngineSlotDiffRenderer will be used to convert the old behavior into the new one.
  46  *
  47  * @ingroup DifferenceEngine
  48  *
  49  * @todo This class is huge and poorly defined. It should be split into a controller responsible
  50  * for interpreting query parameters, retrieving data and checking permissions; and a HTML renderer.
  51  */
  52 class DifferenceEngine extends ContextSource {
  53
  54         use DeprecationHelper;
  55
  56         /**
  57          * Constant to indicate diff cache compatibility.
  58          * Bump this when changing the diff formatting in a way that
  59          * fixes important bugs or such to force cached diff views to
  60          * clear.
  61          */
  62         const DIFF_VERSION = '1.12';
  63
  64         /**
  65          * Revision ID for the old revision. 0 for the revision previous to $mNewid, false
  66          * if the diff does not have an old revision (e.g. 'oldid=<first revision of page>&diff=prev'),
  67          * or the revision does not exist, null if the revision is unsaved.
  68          * @var int|false|null
  69          */
  70         protected $mOldid;
  71
  72         /**
  73          * Revision ID for the new revision. 0 for the last revision of the current page
  74          * (as defined by the request context), false if the revision does not exist, null
  75          * if it is unsaved, or an alias such as 'next'.
  76          * @var int|string|false|null
  77          */
  78         protected $mNewid;
  79
  80         /**
  81          * Old revision (left pane).
  82          * Allowed to be an unsaved revision, unlikely that's ever needed though.
  83          * False when the old revision does not exist; this can happen when using
  84          * diff=prev on the first revision. Null when the revision should exist but
  85          * doesn't (e.g. load failure); loadRevisionData() will return false in that
  86          * case. Also null until lazy-loaded. Ignored completely when isContentOverridden
  87          * is set.
  88          * Since 1.32 public access is deprecated.
  89          * @var Revision|null|false
  90          */
  91         protected $mOldRev;
  92
  93         /**
  94          * New revision (right pane).
  95          * Note that this might be an unsaved revision (e.g. for edit preview).
  96          * Null in case of load failure; diff methods will just return an error message in that case,
  97          * and loadRevisionData() will return false. Also null until lazy-loaded. Ignored completely
  98          * when isContentOverridden is set.
  99          * Since 1.32 public access is deprecated.
 100          * @var Revision|null
 101          */
 102         protected $mNewRev;
 103
 104         /**
 105          * Title of $mOldRev or null if the old revision does not exist or does not belong to a page.
 106          * Since 1.32 public access is deprecated and the property can be null.
 107          * @var Title|null
 108          */
 109         protected $mOldPage;
 110
 111         /**
 112          * Title of $mNewRev or null if the new revision does not exist or does not belong to a page.
 113          * Since 1.32 public access is deprecated and the property can be null.
 114          * @var Title|null
 115          */
 116         protected $mNewPage;
 117
 118         /**
 119          * Change tags of $mOldRev or null if it does not exist / is not saved.
 120          * @var string[]|null
 121          */
 122         private $mOldTags;
 123
 124         /**
 125          * Change tags of $mNewRev or null if it does not exist / is not saved.
 126          * @var string[]|null
 127          */
 128         private $mNewTags;
 129
 130         /**
 131          * @var Content|null
 132          * @deprecated since 1.32, content slots are now handled by the corresponding SlotDiffRenderer.
 133          *   This property is set to the content of the main slot, but not actually used for the main diff.
 134          */
 135         private $mOldContent;
 136
 137         /**
 138          * @var Content|null
 139          * @deprecated since 1.32, content slots are now handled by the corresponding SlotDiffRenderer.
 140          *   This property is set to the content of the main slot, but not actually used for the main diff.
 141          */
 142         private $mNewContent;
 143
 144         /** @var Language */
 145         protected $mDiffLang;
 146
 147         /** @var bool Have the revisions IDs been loaded */
 148         private $mRevisionsIdsLoaded = false;
 149
 150         /** @var bool Have the revisions been loaded */
 151         protected $mRevisionsLoaded = false;
 152
 153         /** @var int How many text blobs have been loaded, 0, 1 or 2? */
 154         protected $mTextLoaded = 0;
 155
 156         /**
 157          * Was the content overridden via setContent()?
 158          * If the content was overridden, most internal state (e.g. mOldid or mOldRev) should be ignored
 159          * and only mOldContent and mNewContent is reliable.
 160          * (Note that setRevisions() does not set this flag as in that case all properties are
 161          * overriden and remain consistent with each other, so no special handling is needed.)
 162          * @var bool
 163          */
 164         protected $isContentOverridden = false;
 165
 166         /** @var bool Was the diff fetched from cache? */
 167         protected $mCacheHit = false;
 168
 169         /**
 170          * Set this to true to add debug info to the HTML output.
 171          * Warning: this may cause RSS readers to spuriously mark articles as "new"
 172          * (T22601)
 173          */
 174         public $enableDebugComment = false;
 175
 176         /** @var bool If true, line X is not displayed when X is 1, for example
 177          *    to increase readability and conserve space with many small diffs.
 178          */
 179         protected $mReducedLineNumbers = false;
 180
 181         /** @var string Link to action=markpatrolled */
 182         protected $mMarkPatrolledLink = null;
 183
 184         /** @var bool Show rev_deleted content if allowed */
 185         protected $unhide = false;
 186
 187         /** @var bool Refresh the diff cache */
 188         protected $mRefreshCache = false;
 189
 190         /** @var SlotDiffRenderer[] DifferenceEngine classes for the slots, keyed by role name. */
 191         protected $slotDiffRenderers = null;
 192
 193         /**
 194          * Temporary hack for B/C while slot diff related methods of DifferenceEngine are being
 195          * deprecated. When true, we are inside a DifferenceEngineSlotDiffRenderer and
 196          * $slotDiffRenderers should not be used.
 197          * @var bool
 198          */
 199         protected $isSlotDiffRenderer = false;
 200
 201         /** #@- */
 202
 203         /**
 204          * @param IContextSource|null $context Context to use, anything else will be ignored
 205          * @param int $old Old ID we want to show and diff with.
 206          * @param string|int $new Either revision ID or 'prev' or 'next'. Default: 0.
 207          * @param int $rcid Deprecated, no longer used!
 208          * @param bool $refreshCache If set, refreshes the diff cache
 209          * @param bool $unhide If set, allow viewing deleted revs
 210          */
 211         public function __construct( $context = null, $old = 0, $new = 0, $rcid = 0,
 212                 $refreshCache = false, $unhide = false
 213         ) {
 214                 $this->deprecatePublicProperty( 'mOldid', '1.32', __CLASS__ );
 215                 $this->deprecatePublicProperty( 'mNewid', '1.32', __CLASS__ );
 216                 $this->deprecatePublicProperty( 'mOldRev', '1.32', __CLASS__ );
 217                 $this->deprecatePublicProperty( 'mNewRev', '1.32', __CLASS__ );
 218                 $this->deprecatePublicProperty( 'mOldPage', '1.32', __CLASS__ );
 219                 $this->deprecatePublicProperty( 'mNewPage', '1.32', __CLASS__ );
 220                 $this->deprecatePublicProperty( 'mOldContent', '1.32', __CLASS__ );
 221                 $this->deprecatePublicProperty( 'mNewContent', '1.32', __CLASS__ );
 222                 $this->deprecatePublicProperty( 'mRevisionsLoaded', '1.32', __CLASS__ );
 223                 $this->deprecatePublicProperty( 'mTextLoaded', '1.32', __CLASS__ );
 224                 $this->deprecatePublicProperty( 'mCacheHit', '1.32', __CLASS__ );
 225
 226                 if ( $context instanceof IContextSource ) {
 227                         $this->setContext( $context );
 228                 }
 229
 230                 wfDebug( "DifferenceEngine old '$old' new '$new' rcid '$rcid'\n" );
 231
 232                 $this->mOldid = $old;
 233                 $this->mNewid = $new;
 234                 $this->mRefreshCache = $refreshCache;
 235                 $this->unhide = $unhide;
 236         }
 237
 238         /**
 239          * @return SlotDiffRenderer[] Diff renderers for each slot, keyed by role name.
 240          *   Includes slots only present in one of the revisions.
 241          */
 242         protected function getSlotDiffRenderers() {
 243                 if ( $this->isSlotDiffRenderer ) {
 244                         throw new LogicException( __METHOD__ . ' called in slot diff renderer mode' );
 245                 }
 246
 247                 if ( $this->slotDiffRenderers === null ) {
 248                         if ( !$this->loadRevisionData() ) {
 249                                 return [];
 250                         }
 251
 252                         $slotContents = $this->getSlotContents();
 253                         $this->slotDiffRenderers = array_map( function ( $contents ) {
 254                                 /** @var Content $content */
 255                                 $content = $contents['new'] ?: $contents['old'];
 256                                 return $content->getContentHandler()->getSlotDiffRenderer( $this->getContext() );
 257                         }, $slotContents );
 258                 }
 259                 return $this->slotDiffRenderers;
 260         }
 261
 262         /**
 263          * Mark this DifferenceEngine as a slot renderer (as opposed to a page renderer).
 264          * This is used in legacy mode when the DifferenceEngine is wrapped in a
 265          * DifferenceEngineSlotDiffRenderer.
 266          * @internal For use by DifferenceEngineSlotDiffRenderer only.
 267          */
 268         public function markAsSlotDiffRenderer() {
 269                 $this->isSlotDiffRenderer = true;
 270         }
 271
 272         /**
 273          * Get the old and new content objects for all slots.
 274          * This method does not do any permission checks.
 275          * @return array [ role => [ 'old' => SlotRecord|null, 'new' => SlotRecord|null ], ... ]
 276          */
 277         protected function getSlotContents() {
 278                 if ( $this->isContentOverridden ) {
 279                         return [
 280                                 SlotRecord::MAIN => [
 281                                         'old' => $this->mOldContent,
 282                                         'new' => $this->mNewContent,
 283                                 ]
 284                         ];
 285                 } elseif ( !$this->loadRevisionData() ) {
 286                         return [];
 287                 }
 288
 289                 $newSlots = $this->mNewRev->getRevisionRecord()->getSlots()->getSlots();
 290                 if ( $this->mOldRev ) {
 291                         $oldSlots = $this->mOldRev->getRevisionRecord()->getSlots()->getSlots();
 292                 } else {
 293                         $oldSlots = [];
 294                 }
 295                 // The order here will determine the visual order of the diff. The current logic is
 296                 // slots of the new revision first in natural order, then deleted ones. This is ad hoc
 297                 // and should not be relied on - in the future we may want the ordering to depend
 298                 // on the page type.
 299                 $roles = array_merge( array_keys( $newSlots ), array_keys( $oldSlots ) );
 300
 301                 $slots = [];
 302                 foreach ( $roles as $role ) {
 303                         $slots[$role] = [
 304                                 'old' => isset( $oldSlots[$role] ) ? $oldSlots[$role]->getContent() : null,
 305                                 'new' => isset( $newSlots[$role] ) ? $newSlots[$role]->getContent() : null,
 306                         ];
 307                 }
 308                 // move main slot to front
 309                 if ( isset( $slots[SlotRecord::MAIN] ) ) {
 310                         $slots = [ SlotRecord::MAIN => $slots[SlotRecord::MAIN] ] + $slots;
 311                 }
 312                 return $slots;
 313         }
 314
 315         public function getTitle() {
 316                 // T202454 avoid errors when there is no title
 317                 return parent::getTitle() ?: Title::makeTitle( NS_SPECIAL, 'BadTitle/DifferenceEngine' );
 318         }
 319
 320         /**
 321          * Set reduced line numbers mode.
 322          * When set, line X is not displayed when X is 1, for example to increase readability and
 323          * conserve space with many small diffs.
 324          * @param bool $value
 325          */
 326         public function setReducedLineNumbers( $value = true ) {
 327                 $this->mReducedLineNumbers = $value;
 328         }
 329
 330         /**
 331          * Get the language of the difference engine, defaults to page content language
 332          *
 333          * @return Language
 334          */
 335         public function getDiffLang() {
 336                 if ( $this->mDiffLang === null ) {
 337                         # Default language in which the diff text is written.
 338                         $this->mDiffLang = $this->getTitle()->getPageLanguage();
 339                 }
 340
 341                 return $this->mDiffLang;
 342         }
 343
 344         /**
 345          * @return bool
 346          */
 347         public function wasCacheHit() {
 348                 return $this->mCacheHit;
 349         }
 350
 351         /**
 352          * Get the ID of old revision (left pane) of the diff. 0 for the revision
 353          * previous to getNewid(), false if the old revision does not exist, null
 354          * if it's unsaved.
 355          * To get a real revision ID instead of 0, call loadRevisionData() first.
 356          * @return int|false|null
 357          */
 358         public function getOldid() {
 359                 $this->loadRevisionIds();
 360
 361                 return $this->mOldid;
 362         }
 363
 364         /**
 365          * Get the ID of new revision (right pane) of the diff. 0 for the current revision,
 366          * false if the new revision does not exist, null if it's unsaved.
 367          * To get a real revision ID instead of 0, call loadRevisionData() first.
 368          * @return int|false|null
 369          */
 370         public function getNewid() {
 371                 $this->loadRevisionIds();
 372
 373                 return $this->mNewid;
 374         }
 375
 376         /**
 377          * Get the left side of the diff.
 378          * Could be null when the first revision of the page is diffed to 'prev' (or in the case of
 379          * load failure).
 380          * @return RevisionRecord|null
 381          */
 382         public function getOldRevision() {
 383                 return $this->mOldRev ? $this->mOldRev->getRevisionRecord() : null;
 384         }
 385
 386         /**
 387          * Get the right side of the diff.
 388          * Should not be null but can still happen in the case of load failure.
 389          * @return RevisionRecord|null
 390          */
 391         public function getNewRevision() {
 392                 return $this->mNewRev ? $this->mNewRev->getRevisionRecord() : null;
 393         }
 394
 395         /**
 396          * Look up a special:Undelete link to the given deleted revision id,
 397          * as a workaround for being unable to load deleted diffs in currently.
 398          *
 399          * @param int $id Revision ID
 400          *
 401          * @return string|bool Link HTML or false
 402          */
 403         public function deletedLink( $id ) {
 404                 $permissionManager = MediaWikiServices::getInstance()->getPermissionManager();
 405                 if ( $permissionManager->userHasRight( $this->getUser(), 'deletedhistory' ) ) {
 406                         $dbr = wfGetDB( DB_REPLICA );
 407                         $arQuery = Revision::getArchiveQueryInfo();
 408                         $row = $dbr->selectRow(
 409                                 $arQuery['tables'],
 410                                 array_merge( $arQuery['fields'], [ 'ar_namespace', 'ar_title' ] ),
 411                                 [ 'ar_rev_id' => $id ],
 412                                 __METHOD__,
 413                                 [],
 414                                 $arQuery['joins']
 415                         );
 416                         if ( $row ) {
 417                                 $rev = Revision::newFromArchiveRow( $row );
 418                                 $title = Title::makeTitleSafe( $row->ar_namespace, $row->ar_title );
 419
 420                                 return SpecialPage::getTitleFor( 'Undelete' )->getFullURL( [
 421                                         'target' => $title->getPrefixedText(),
 422                                         'timestamp' => $rev->getTimestamp()
 423                                 ] );
 424                         }
 425                 }
 426
 427                 return false;
 428         }
 429
 430         /**
 431          * Build a wikitext link toward a deleted revision, if viewable.
 432          *
 433          * @param int $id Revision ID
 434          *
 435          * @return string Wikitext fragment
 436          */
 437         public function deletedIdMarker( $id ) {
 438                 $link = $this->deletedLink( $id );
 439                 if ( $link ) {
 440                         return "[$link $id]";
 441                 } else {
 442                         return (string)$id;
 443                 }
 444         }
 445
 446         private function showMissingRevision() {
 447                 $out = $this->getOutput();
 448
 449                 $missing = [];
 450                 if ( $this->mOldRev === null ||
 451                         ( $this->mOldRev && $this->mOldContent === null )
 452                 ) {
 453                         $missing[] = $this->deletedIdMarker( $this->mOldid );
 454                 }
 455                 if ( $this->mNewRev === null ||
 456                         ( $this->mNewRev && $this->mNewContent === null )
 457                 ) {
 458                         $missing[] = $this->deletedIdMarker( $this->mNewid );
 459                 }
 460
 461                 $out->setPageTitle( $this->msg( 'errorpagetitle' ) );
 462                 $msg = $this->msg( 'difference-missing-revision' )
 463                         ->params( $this->getLanguage()->listToText( $missing ) )
 464                         ->numParams( count( $missing ) )
 465                         ->parseAsBlock();
 466                 $out->addHTML( $msg );
 467         }
 468
 469         public function showDiffPage( $diffOnly = false ) {
 470                 # Allow frames except in certain special cases
 471                 $out = $this->getOutput();
 472                 $out->allowClickjacking();
 473                 $out->setRobotPolicy( 'noindex,nofollow' );
 474
 475                 // Allow extensions to add any extra output here
 476                 Hooks::run( 'DifferenceEngineShowDiffPage', [ $out ] );
 477
 478                 if ( !$this->loadRevisionData() ) {
 479                         if ( Hooks::run( 'DifferenceEngineShowDiffPageMaybeShowMissingRevision', [ $this ] ) ) {
 480                                 $this->showMissingRevision();
 481                         }
 482                         return;
 483                 }
 484
 485                 $user = $this->getUser();
 486                 $permErrors = [];
 487                 if ( $this->mNewPage ) {
 488                         $permErrors = $this->mNewPage->getUserPermissionsErrors( 'read', $user );
 489                 }
 490                 if ( $this->mOldPage ) {
 491                         $permErrors = wfMergeErrorArrays( $permErrors,
 492                                 $this->mOldPage->getUserPermissionsErrors( 'read', $user ) );
 493                 }
 494                 if ( count( $permErrors ) ) {
 495                         throw new PermissionsError( 'read', $permErrors );
 496                 }
 497
 498                 $rollback = '';
 499
 500                 $query = [];
 501                 # Carry over 'diffonly' param via navigation links
 502                 if ( $diffOnly != $user->getBoolOption( 'diffonly' ) ) {
 503                         $query['diffonly'] = $diffOnly;
 504                 }
 505                 # Cascade unhide param in links for easy deletion browsing
 506                 if ( $this->unhide ) {
 507                         $query['unhide'] = 1;
 508                 }
 509
 510                 # Check if one of the revisions is deleted/suppressed
 511                 $deleted = $suppressed = false;
 512                 $allowed = $this->mNewRev->userCan( RevisionRecord::DELETED_TEXT, $user );
 513
 514                 $revisionTools = [];
 515
 516                 # mOldRev is false if the difference engine is called with a "vague" query for
 517                 # a diff between a version V and its previous version V' AND the version V
 518                 # is the first version of that article. In that case, V' does not exist.
 519                 if ( $this->mOldRev === false ) {
 520                         if ( $this->mNewPage ) {
 521                                 $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 522                         }
 523                         $samePage = true;
 524                         $oldHeader = '';
 525                         // Allow extensions to change the $oldHeader variable
 526                         Hooks::run( 'DifferenceEngineOldHeaderNoOldRev', [ &$oldHeader ] );
 527                 } else {
 528                         Hooks::run( 'DiffViewHeader', [ $this, $this->mOldRev, $this->mNewRev ] );
 529
 530                         if ( !$this->mOldPage || !$this->mNewPage ) {
 531                                 // XXX say something to the user?
 532                                 $samePage = false;
 533                         } elseif ( $this->mNewPage->equals( $this->mOldPage ) ) {
 534                                 $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 535                                 $samePage = true;
 536                         } else {
 537                                 $out->setPageTitle( $this->msg( 'difference-title-multipage',
 538                                         $this->mOldPage->getPrefixedText(), $this->mNewPage->getPrefixedText() ) );
 539                                 $out->addSubtitle( $this->msg( 'difference-multipage' ) );
 540                                 $samePage = false;
 541                         }
 542
 543                         $permissionManager = MediaWikiServices::getInstance()->getPermissionManager();
 544
 545                         if ( $samePage && $this->mNewPage && $permissionManager->userCan(
 546                                 'edit', $user, $this->mNewPage, PermissionManager::RIGOR_QUICK
 547                         ) ) {
 548                                 if ( $this->mNewRev->isCurrent() && $permissionManager->userCan(
 549                                         'rollback', $user, $this->mNewPage
 550                                 ) ) {
 551                                         $rollbackLink = Linker::generateRollback( $this->mNewRev, $this->getContext(),
 552                                                 [ 'noBrackets' ] );
 553                                         if ( $rollbackLink ) {
 554                                                 $out->preventClickjacking();
 555                                                 $rollback = "\u{00A0}\u{00A0}\u{00A0}" . $rollbackLink;
 556                                         }
 557                                 }
 558
 559                                 if ( !$this->mOldRev->isDeleted( RevisionRecord::DELETED_TEXT ) &&
 560                                         !$this->mNewRev->isDeleted( RevisionRecord::DELETED_TEXT )
 561                                 ) {
 562                                         $undoLink = Html::element( 'a', [
 563                                                         'href' => $this->mNewPage->getLocalURL( [
 564                                                                 'action' => 'edit',
 565                                                                 'undoafter' => $this->mOldid,
 566                                                                 'undo' => $this->mNewid
 567                                                         ] ),
 568                                                         'title' => Linker::titleAttrib( 'undo' ),
 569                                                 ],
 570                                                 $this->msg( 'editundo' )->text()
 571                                         );
 572                                         $revisionTools['mw-diff-undo'] = $undoLink;
 573                                 }
 574                         }
 575
 576                         # Make "previous revision link"
 577                         if ( $samePage && $this->mOldPage && $this->mOldRev->getPrevious() ) {
 578                                 $prevlink = Linker::linkKnown(
 579                                         $this->mOldPage,
 580                                         $this->msg( 'previousdiff' )->escaped(),
 581                                         [ 'id' => 'differences-prevlink' ],
 582                                         [ 'diff' => 'prev', 'oldid' => $this->mOldid ] + $query
 583                                 );
 584                         } else {
 585                                 $prevlink = "\u{00A0}";
 586                         }
 587
 588                         if ( $this->mOldRev->isMinor() ) {
 589                                 $oldminor = ChangesList::flag( 'minor' );
 590                         } else {
 591                                 $oldminor = '';
 592                         }
 593
 594                         $ldel = $this->revisionDeleteLink( $this->mOldRev );
 595                         $oldRevisionHeader = $this->getRevisionHeader( $this->mOldRev, 'complete' );
 596                         $oldChangeTags = ChangeTags::formatSummaryRow( $this->mOldTags, 'diff', $this->getContext() );
 597
 598                         $oldHeader = '<div id="mw-diff-otitle1"><strong>' . $oldRevisionHeader . '</strong></div>' .
 599                                 '<div id="mw-diff-otitle2">' .
 600                                 Linker::revUserTools( $this->mOldRev, !$this->unhide ) . '</div>' .
 601                                 '<div id="mw-diff-otitle3">' . $oldminor .
 602                                 Linker::revComment( $this->mOldRev, !$diffOnly, !$this->unhide ) . $ldel . '</div>' .
 603                                 '<div id="mw-diff-otitle5">' . $oldChangeTags[0] . '</div>' .
 604                                 '<div id="mw-diff-otitle4">' . $prevlink . '</div>';
 605
 606                         // Allow extensions to change the $oldHeader variable
 607                         Hooks::run( 'DifferenceEngineOldHeader', [ $this, &$oldHeader, $prevlink, $oldminor,
 608                                 $diffOnly, $ldel, $this->unhide ] );
 609
 610                         if ( $this->mOldRev->isDeleted( RevisionRecord::DELETED_TEXT ) ) {
 611                                 $deleted = true; // old revisions text is hidden
 612                                 if ( $this->mOldRev->isDeleted( RevisionRecord::DELETED_RESTRICTED ) ) {
 613                                         $suppressed = true; // also suppressed
 614                                 }
 615                         }
 616
 617                         # Check if this user can see the revisions
 618                         if ( !$this->mOldRev->userCan( RevisionRecord::DELETED_TEXT, $user ) ) {
 619                                 $allowed = false;
 620                         }
 621                 }
 622
 623                 $out->addJsConfigVars( [
 624                         'wgDiffOldId' => $this->mOldid,
 625                         'wgDiffNewId' => $this->mNewid,
 626                 ] );
 627
 628                 # Make "next revision link"
 629                 # Skip next link on the top revision
 630                 if ( $samePage && $this->mNewPage && !$this->mNewRev->isCurrent() ) {
 631                         $nextlink = Linker::linkKnown(
 632                                 $this->mNewPage,
 633                                 $this->msg( 'nextdiff' )->escaped(),
 634                                 [ 'id' => 'differences-nextlink' ],
 635                                 [ 'diff' => 'next', 'oldid' => $this->mNewid ] + $query
 636                         );
 637                 } else {
 638                         $nextlink = "\u{00A0}";
 639                 }
 640
 641                 if ( $this->mNewRev->isMinor() ) {
 642                         $newminor = ChangesList::flag( 'minor' );
 643                 } else {
 644                         $newminor = '';
 645                 }
 646
 647                 # Handle RevisionDelete links...
 648                 $rdel = $this->revisionDeleteLink( $this->mNewRev );
 649
 650                 # Allow extensions to define their own revision tools
 651                 Hooks::run( 'DiffRevisionTools',
 652                         [ $this->mNewRev, &$revisionTools, $this->mOldRev, $user ] );
 653                 $formattedRevisionTools = [];
 654                 // Put each one in parentheses (poor man's button)
 655                 foreach ( $revisionTools as $key => $tool ) {
 656                         $toolClass = is_string( $key ) ? $key : 'mw-diff-tool';
 657                         $element = Html::rawElement(
 658                                 'span',
 659                                 [ 'class' => $toolClass ],
 660                                 $this->msg( 'parentheses' )->rawParams( $tool )->escaped()
 661                         );
 662                         $formattedRevisionTools[] = $element;
 663                 }
 664                 $newRevisionHeader = $this->getRevisionHeader( $this->mNewRev, 'complete' ) .
 665                         ' ' . implode( ' ', $formattedRevisionTools );
 666                 $newChangeTags = ChangeTags::formatSummaryRow( $this->mNewTags, 'diff', $this->getContext() );
 667
 668                 $newHeader = '<div id="mw-diff-ntitle1"><strong>' . $newRevisionHeader . '</strong></div>' .
 669                         '<div id="mw-diff-ntitle2">' . Linker::revUserTools( $this->mNewRev, !$this->unhide ) .
 670                         " $rollback</div>" .
 671                         '<div id="mw-diff-ntitle3">' . $newminor .
 672                         Linker::revComment( $this->mNewRev, !$diffOnly, !$this->unhide ) . $rdel . '</div>' .
 673                         '<div id="mw-diff-ntitle5">' . $newChangeTags[0] . '</div>' .
 674                         '<div id="mw-diff-ntitle4">' . $nextlink . $this->markPatrolledLink() . '</div>';
 675
 676                 // Allow extensions to change the $newHeader variable
 677                 Hooks::run( 'DifferenceEngineNewHeader', [ $this, &$newHeader, $formattedRevisionTools,
 678                         $nextlink, $rollback, $newminor, $diffOnly, $rdel, $this->unhide ] );
 679
 680                 if ( $this->mNewRev->isDeleted( RevisionRecord::DELETED_TEXT ) ) {
 681                         $deleted = true; // new revisions text is hidden
 682                         if ( $this->mNewRev->isDeleted( RevisionRecord::DELETED_RESTRICTED ) ) {
 683                                 $suppressed = true; // also suppressed
 684                         }
 685                 }
 686
 687                 # If the diff cannot be shown due to a deleted revision, then output
 688                 # the diff header and links to unhide (if available)...
 689                 if ( $deleted && ( !$this->unhide || !$allowed ) ) {
 690                         $this->showDiffStyle();
 691                         $multi = $this->getMultiNotice();
 692                         $out->addHTML( $this->addHeader( '', $oldHeader, $newHeader, $multi ) );
 693                         if ( !$allowed ) {
 694                                 $msg = $suppressed ? 'rev-suppressed-no-diff' : 'rev-deleted-no-diff';
 695                                 # Give explanation for why revision is not visible
 696                                 $out->wrapWikiMsg( "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 697                                         [ $msg ] );
 698                         } else {
 699                                 # Give explanation and add a link to view the diff...
 700                                 $query = $this->getRequest()->appendQueryValue( 'unhide', '1' );
 701                                 $link = $this->getTitle()->getFullURL( $query );
 702                                 $msg = $suppressed ? 'rev-suppressed-unhide-diff' : 'rev-deleted-unhide-diff';
 703                                 $out->wrapWikiMsg(
 704                                         "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 705                                         [ $msg, $link ]
 706                                 );
 707                         }
 708                 # Otherwise, output a regular diff...
 709                 } else {
 710                         # Add deletion notice if the user is viewing deleted content
 711                         $notice = '';
 712                         if ( $deleted ) {
 713                                 $msg = $suppressed ? 'rev-suppressed-diff-view' : 'rev-deleted-diff-view';
 714                                 $notice = "<div id='mw-$msg' class='mw-warning plainlinks'>\n" .
 715                                         $this->msg( $msg )->parse() .
 716                                         "</div>\n";
 717                         }
 718                         $this->showDiff( $oldHeader, $newHeader, $notice );
 719                         if ( !$diffOnly ) {
 720                                 $this->renderNewRevision();
 721                         }
 722                 }
 723         }
 724
 725         /**
 726          * Build a link to mark a change as patrolled.
 727          *
 728          * Returns empty string if there's either no revision to patrol or the user is not allowed to.
 729          * Side effect: When the patrol link is build, this method will call
 730          * OutputPage::preventClickjacking() and load mediawiki.page.patrol.ajax.
 731          *
 732          * @return string HTML or empty string
 733          */
 734         public function markPatrolledLink() {
 735                 if ( $this->mMarkPatrolledLink === null ) {
 736                         $linkInfo = $this->getMarkPatrolledLinkInfo();
 737                         // If false, there is no patrol link needed/allowed
 738                         if ( !$linkInfo || !$this->mNewPage ) {
 739                                 $this->mMarkPatrolledLink = '';
 740                         } else {
 741                                 $this->mMarkPatrolledLink = ' <span class="patrollink" data-mw="interface">[' .
 742                                         Linker::linkKnown(
 743                                                 $this->mNewPage,
 744                                                 $this->msg( 'markaspatrolleddiff' )->escaped(),
 745                                                 [],
 746                                                 [
 747                                                         'action' => 'markpatrolled',
 748                                                         'rcid' => $linkInfo['rcid'],
 749                                                 ]
 750                                         ) . ']</span>';
 751                                 // Allow extensions to change the markpatrolled link
 752                                 Hooks::run( 'DifferenceEngineMarkPatrolledLink', [ $this,
 753                                         &$this->mMarkPatrolledLink, $linkInfo['rcid'] ] );
 754                         }
 755                 }
 756                 return $this->mMarkPatrolledLink;
 757         }
 758
 759         /**
 760          * Returns an array of meta data needed to build a "mark as patrolled" link and
 761          * adds the mediawiki.page.patrol.ajax to the output.
 762          *
 763          * @return array|false An array of meta data for a patrol link (rcid only)
 764          *  or false if no link is needed
 765          */
 766         protected function getMarkPatrolledLinkInfo() {
 767                 $user = $this->getUser();
 768                 $config = $this->getConfig();
 769
 770                 // Prepare a change patrol link, if applicable
 771                 if (
 772                         // Is patrolling enabled and the user allowed to?
 773                         $config->get( 'UseRCPatrol' ) &&
 774                         $this->mNewPage && $this->mNewPage->quickUserCan( 'patrol', $user ) &&
 775                         // Only do this if the revision isn't more than 6 hours older
 776                         // than the Max RC age (6h because the RC might not be cleaned out regularly)
 777                         RecentChange::isInRCLifespan( $this->mNewRev->getTimestamp(), 21600 )
 778                 ) {
 779                         // Look for an unpatrolled change corresponding to this diff
 780                         $db = wfGetDB( DB_REPLICA );
 781                         $change = RecentChange::newFromConds(
 782                                 [
 783                                         'rc_timestamp' => $db->timestamp( $this->mNewRev->getTimestamp() ),
 784                                         'rc_this_oldid' => $this->mNewid,
 785                                         'rc_patrolled' => RecentChange::PRC_UNPATROLLED
 786                                 ],
 787                                 __METHOD__
 788                         );
 789
 790                         if ( $change && !$change->getPerformer()->equals( $user ) ) {
 791                                 $rcid = $change->getAttribute( 'rc_id' );
 792                         } else {
 793                                 // None found or the page has been created by the current user.
 794                                 // If the user could patrol this it already would be patrolled
 795                                 $rcid = 0;
 796                         }
 797
 798                         // Allow extensions to possibly change the rcid here
 799                         // For example the rcid might be set to zero due to the user
 800                         // being the same as the performer of the change but an extension
 801                         // might still want to show it under certain conditions
 802                         Hooks::run( 'DifferenceEngineMarkPatrolledRCID', [ &$rcid, $this, $change, $user ] );
 803
 804                         // Build the link
 805                         if ( $rcid ) {
 806                                 $this->getOutput()->preventClickjacking();
 807                                 if ( MediaWikiServices::getInstance()->getPermissionManager()
 808                                                 ->userHasRight( $user, 'writeapi' ) ) {
 809                                         $this->getOutput()->addModules( 'mediawiki.page.patrol.ajax' );
 810                                 }
 811
 812                                 return [
 813                                         'rcid' => $rcid,
 814                                 ];
 815                         }
 816                 }
 817
 818                 // No mark as patrolled link applicable
 819                 return false;
 820         }
 821
 822         /**
 823          * @param Revision $rev
 824          *
 825          * @return string
 826          */
 827         protected function revisionDeleteLink( $rev ) {
 828                 $link = Linker::getRevDeleteLink( $this->getUser(), $rev, $rev->getTitle() );
 829                 if ( $link !== '' ) {
 830                         $link = "\u{00A0}\u{00A0}\u{00A0}" . $link . ' ';
 831                 }
 832
 833                 return $link;
 834         }
 835
 836         /**
 837          * Show the new revision of the page.
 838          *
 839          * @note Not supported after calling setContent().
 840          */
 841         public function renderNewRevision() {
 842                 if ( $this->isContentOverridden ) {
 843                         // The code below only works with a Revision object. We could construct a fake revision
 844                         // (here or in setContent), but since this does not seem needed at the moment,
 845                         // we'll just fail for now.
 846                         throw new LogicException(
 847                                 __METHOD__
 848                                 . ' is not supported after calling setContent(). Use setRevisions() instead.'
 849                         );
 850                 }
 851
 852                 $out = $this->getOutput();
 853                 $revHeader = $this->getRevisionHeader( $this->mNewRev );
 854                 # Add "current version as of X" title
 855                 $out->addHTML( "<hr class='diff-hr' id='mw-oldid' />
 856                 <h2 class='diff-currentversion-title'>{$revHeader}</h2>\n" );
 857                 # Page content may be handled by a hooked call instead...
 858                 if ( Hooks::run( 'ArticleContentOnDiff', [ $this, $out ] ) ) {
 859                         $this->loadNewText();
 860                         if ( !$this->mNewPage ) {
 861                                 // New revision is unsaved; bail out.
 862                                 // TODO in theory rendering the new revision is a meaningful thing to do
 863                                 // even if it's unsaved, but a lot of untangling is required to do it safely.
 864                                 return;
 865                         }
 866
 867                         $out->setRevisionId( $this->mNewid );
 868                         $out->setRevisionTimestamp( $this->mNewRev->getTimestamp() );
 869                         $out->setArticleFlag( true );
 870
 871                         if ( !Hooks::run( 'ArticleRevisionViewCustom',
 872                                 [ $this->mNewRev->getRevisionRecord(), $this->mNewPage, $out ] )
 873                         ) {
 874                                 // Handled by extension
 875                                 // NOTE: sync with hooks called in Article::view()
 876                         } elseif ( !Hooks::run( 'ArticleContentViewCustom',
 877                                 [ $this->mNewContent, $this->mNewPage, $out ], '1.32' )
 878                         ) {
 879                                 // Handled by extension
 880                                 // NOTE: sync with hooks called in Article::view()
 881                         } else {
 882                                 // Normal page
 883                                 if ( $this->getTitle()->equals( $this->mNewPage ) ) {
 884                                         // If the Title stored in the context is the same as the one
 885                                         // of the new revision, we can use its associated WikiPage
 886                                         // object.
 887                                         $wikiPage = $this->getWikiPage();
 888                                 } else {
 889                                         // Otherwise we need to create our own WikiPage object
 890                                         $wikiPage = WikiPage::factory( $this->mNewPage );
 891                                 }
 892
 893                                 $parserOutput = $this->getParserOutput( $wikiPage, $this->mNewRev );
 894
 895                                 # WikiPage::getParserOutput() should not return false, but just in case
 896                                 if ( $parserOutput ) {
 897                                         // Allow extensions to change parser output here
 898                                         if ( Hooks::run( 'DifferenceEngineRenderRevisionAddParserOutput',
 899                                                 [ $this, $out, $parserOutput, $wikiPage ] )
 900                                         ) {
 901                                                 $out->addParserOutput( $parserOutput, [
 902                                                         'enableSectionEditLinks' => $this->mNewRev->isCurrent()
 903                                                                 && $this->mNewRev->getTitle()->quickUserCan( 'edit', $this->getUser() ),
 904                                                 ] );
 905                                         }
 906                                 }
 907                         }
 908                 }
 909
 910                 // Allow extensions to optionally not show the final patrolled link
 911                 if ( Hooks::run( 'DifferenceEngineRenderRevisionShowFinalPatrolLink' ) ) {
 912                         # Add redundant patrol link on bottom...
 913                         $out->addHTML( $this->markPatrolledLink() );
 914                 }
 915         }
 916
 917         /**
 918          * @param WikiPage $page
 919          * @param Revision $rev
 920          *
 921          * @return ParserOutput|bool False if the revision was not found
 922          */
 923         protected function getParserOutput( WikiPage $page, Revision $rev ) {
 924                 if ( !$rev->getId() ) {
 925                         // WikiPage::getParserOutput wants a revision ID. Passing 0 will incorrectly show
 926                         // the current revision, so fail instead. If need be, WikiPage::getParserOutput
 927                         // could be made to accept a Revision or RevisionRecord instead of the id.
 928                         return false;
 929                 }
 930
 931                 $parserOptions = $page->makeParserOptions( $this->getContext() );
 932                 $parserOutput = $page->getParserOutput( $parserOptions, $rev->getId() );
 933
 934                 return $parserOutput;
 935         }
 936
 937         /**
 938          * Get the diff text, send it to the OutputPage object
 939          * Returns false if the diff could not be generated, otherwise returns true
 940          *
 941          * @param string|bool $otitle Header for old text or false
 942          * @param string|bool $ntitle Header for new text or false
 943          * @param string $notice HTML between diff header and body
 944          *
 945          * @return bool
 946          */
 947         public function showDiff( $otitle, $ntitle, $notice = '' ) {
 948                 // Allow extensions to affect the output here
 949                 Hooks::run( 'DifferenceEngineShowDiff', [ $this ] );
 950
 951                 $diff = $this->getDiff( $otitle, $ntitle, $notice );
 952                 if ( $diff === false ) {
 953                         $this->showMissingRevision();
 954
 955                         return false;
 956                 } else {
 957                         $this->showDiffStyle();
 958                         $this->getOutput()->addHTML( $diff );
 959
 960                         return true;
 961                 }
 962         }
 963
 964         /**
 965          * Add style sheets for diff display.
 966          */
 967         public function showDiffStyle() {
 968                 if ( !$this->isSlotDiffRenderer ) {
 969                         $this->getOutput()->addModuleStyles( [
 970                                 'mediawiki.interface.helpers.styles',
 971                                 'mediawiki.diff.styles'
 972                         ] );
 973                         foreach ( $this->getSlotDiffRenderers() as $slotDiffRenderer ) {
 974                                 $slotDiffRenderer->addModules( $this->getOutput() );
 975                         }
 976                 }
 977         }
 978
 979         /**
 980          * Get complete diff table, including header
 981          *
 982          * @param string|bool $otitle Header for old text or false
 983          * @param string|bool $ntitle Header for new text or false
 984          * @param string $notice HTML between diff header and body
 985          *
 986          * @return mixed
 987          */
 988         public function getDiff( $otitle, $ntitle, $notice = '' ) {
 989                 $body = $this->getDiffBody();
 990                 if ( $body === false ) {
 991                         return false;
 992                 }
 993
 994                 $multi = $this->getMultiNotice();
 995                 // Display a message when the diff is empty
 996                 if ( $body === '' ) {
 997                         $notice .= '<div class="mw-diff-empty">' .
 998                                 $this->msg( 'diff-empty' )->parse() .
 999                                 "</div>\n";
1000                 }
1001
1002                 return $this->addHeader( $body, $otitle, $ntitle, $multi, $notice );
1003         }
1004
1005         /**
1006          * Get the diff table body, without header
1007          *
1008          * @return mixed (string/false)
1009          */
1010         public function getDiffBody() {
1011                 $this->mCacheHit = true;
1012                 // Check if the diff should be hidden from this user
1013                 if ( !$this->isContentOverridden ) {
1014                         if ( !$this->loadRevisionData() ) {
1015                                 return false;
1016                         } elseif ( $this->mOldRev &&
1017                                 !$this->mOldRev->userCan( RevisionRecord::DELETED_TEXT, $this->getUser() )
1018                         ) {
1019                                 return false;
1020                         } elseif ( $this->mNewRev &&
1021                                 !$this->mNewRev->userCan( RevisionRecord::DELETED_TEXT, $this->getUser() )
1022                         ) {
1023                                 return false;
1024                         }
1025                         // Short-circuit
1026                         if ( $this->mOldRev === false || ( $this->mOldRev && $this->mNewRev &&
1027                                 $this->mOldRev->getId() && $this->mOldRev->getId() == $this->mNewRev->getId() )
1028                         ) {
1029                                 if ( Hooks::run( 'DifferenceEngineShowEmptyOldContent', [ $this ] ) ) {
1030                                         return '';
1031                                 }
1032                         }
1033                 }
1034
1035                 // Cacheable?
1036                 $key = false;
1037                 $cache = MediaWikiServices::getInstance()->getMainWANObjectCache();
1038                 if ( $this->mOldid && $this->mNewid ) {
1039                         // Check if subclass is still using the old way
1040                         // for backwards-compatibility
1041                         $key = $this->getDiffBodyCacheKey();
1042                         if ( $key === null ) {
1043                                 $key = $cache->makeKey( ...$this->getDiffBodyCacheKeyParams() );
1044                         }
1045
1046                         // Try cache
1047                         if ( !$this->mRefreshCache ) {
1048                                 $difftext = $cache->get( $key );
1049                                 if ( is_string( $difftext ) ) {
1050                                         wfIncrStats( 'diff_cache.hit' );
1051                                         $difftext = $this->localiseDiff( $difftext );
1052                                         $difftext .= "\n<!-- diff cache key $key -->\n";
1053
1054                                         return $difftext;
1055                                 }
1056                         } // don't try to load but save the result
1057                 }
1058                 $this->mCacheHit = false;
1059
1060                 // Loadtext is permission safe, this just clears out the diff
1061                 if ( !$this->loadText() ) {
1062                         return false;
1063                 }
1064
1065                 $difftext = '';
1066                 // We've checked for revdelete at the beginning of this method; it's OK to ignore
1067                 // read permissions here.
1068                 $slotContents = $this->getSlotContents();
1069                 foreach ( $this->getSlotDiffRenderers() as $role => $slotDiffRenderer ) {
1070                         $slotDiff = $slotDiffRenderer->getDiff( $slotContents[$role]['old'],
1071                                 $slotContents[$role]['new'] );
1072                         if ( $slotDiff && $role !== SlotRecord::MAIN ) {
1073                                 // FIXME: ask SlotRoleHandler::getSlotNameMessage
1074                                 $slotTitle = $role;
1075                                 $difftext .= $this->getSlotHeader( $slotTitle );
1076                         }
1077                         $difftext .= $slotDiff;
1078                 }
1079
1080                 // Avoid PHP 7.1 warning from passing $this by reference
1081                 $diffEngine = $this;
1082
1083                 // Save to cache for 7 days
1084                 if ( !Hooks::run( 'AbortDiffCache', [ &$diffEngine ] ) ) {
1085                         wfIncrStats( 'diff_cache.uncacheable' );
1086                 } elseif ( $key !== false && $difftext !== false ) {
1087                         wfIncrStats( 'diff_cache.miss' );
1088                         $cache->set( $key, $difftext, 7 * 86400 );
1089                 } else {
1090                         wfIncrStats( 'diff_cache.uncacheable' );
1091                 }
1092                 // localise line numbers and title attribute text
1093                 if ( $difftext !== false ) {
1094                         $difftext = $this->localiseDiff( $difftext );
1095                 }
1096
1097                 return $difftext;
1098         }
1099
1100         /**
1101          * Get the diff table body for one slot, without header
1102          *
1103          * @param string $role
1104          * @return string|false
1105          */
1106         public function getDiffBodyForRole( $role ) {
1107                 $diffRenderers = $this->getSlotDiffRenderers();
1108                 if ( !isset( $diffRenderers[$role] ) ) {
1109                         return false;
1110                 }
1111
1112                 $slotContents = $this->getSlotContents();
1113                 $slotDiff = $diffRenderers[$role]->getDiff( $slotContents[$role]['old'],
1114                         $slotContents[$role]['new'] );
1115                 if ( !$slotDiff ) {
1116                         return false;
1117                 }
1118
1119                 if ( $role !== SlotRecord::MAIN ) {
1120                         // TODO use human-readable role name at least
1121                         $slotTitle = $role;
1122                         $slotDiff = $this->getSlotHeader( $slotTitle ) . $slotDiff;
1123                 }
1124
1125                 return $this->localiseDiff( $slotDiff );
1126         }
1127
1128         /**
1129          * Get a slot header for inclusion in a diff body (as a table row).
1130          *
1131          * @param string $headerText The text of the header
1132          * @return string
1133          *
1134          */
1135         protected function getSlotHeader( $headerText ) {
1136                 // The old revision is missing on oldid=<first>&diff=prev; only 2 columns in that case.
1137                 $columnCount = $this->mOldRev ? 4 : 2;
1138                 $userLang = $this->getLanguage()->getHtmlCode();
1139                 return Html::rawElement( 'tr', [ 'class' => 'mw-diff-slot-header', 'lang' => $userLang ],
1140                         Html::element( 'th', [ 'colspan' => $columnCount ], $headerText ) );
1141         }
1142
1143         /**
1144          * Returns the cache key for diff body text or content.
1145          *
1146          * @deprecated since 1.31, use getDiffBodyCacheKeyParams() instead
1147          * @since 1.23
1148          *
1149          * @throws MWException
1150          * @return string|null
1151          */
1152         protected function getDiffBodyCacheKey() {
1153                 return null;
1154         }
1155
1156         /**
1157          * Get the cache key parameters
1158          *
1159          * Subclasses can replace the first element in the array to something
1160          * more specific to the type of diff (e.g. "inline-diff"), or append
1161          * if the cache should vary on more things. Overriding entirely should
1162          * be avoided.
1163          *
1164          * @since 1.31
1165          *
1166          * @return array
1167          * @throws MWException
1168          */
1169         protected function getDiffBodyCacheKeyParams() {
1170                 if ( !$this->mOldid || !$this->mNewid ) {
1171                         throw new MWException( 'mOldid and mNewid must be set to get diff cache key.' );
1172                 }
1173
1174                 $engine = $this->getEngine();
1175                 $params = [
1176                         'diff',
1177                         $engine,
1178                         self::DIFF_VERSION,
1179                         "old-{$this->mOldid}",
1180                         "rev-{$this->mNewid}"
1181                 ];
1182
1183                 if ( $engine === 'wikidiff2' ) {
1184                         $params[] = phpversion( 'wikidiff2' );
1185                 }
1186
1187                 if ( !$this->isSlotDiffRenderer ) {
1188                         foreach ( $this->getSlotDiffRenderers() as $slotDiffRenderer ) {
1189                                 $params = array_merge( $params, $slotDiffRenderer->getExtraCacheKeys() );
1190                         }
1191                 }
1192
1193                 return $params;
1194         }
1195
1196         /**
1197          * Implements DifferenceEngineSlotDiffRenderer::getExtraCacheKeys(). Only used when
1198          * DifferenceEngine is wrapped in DifferenceEngineSlotDiffRenderer.
1199          * @return array
1200          * @internal for use by DifferenceEngineSlotDiffRenderer only
1201          * @deprecated
1202          */
1203         public function getExtraCacheKeys() {
1204                 // This method is called when the DifferenceEngine is used for a slot diff. We only care
1205                 // about special things, not the revision IDs, which are added to the cache key by the
1206                 // page-level DifferenceEngine, and which might not have a valid value for this object.
1207                 $this->mOldid = 123456789;
1208                 $this->mNewid = 987654321;
1209
1210                 // This will repeat a bunch of unnecessary key fields for each slot. Not nice but harmless.
1211                 $cacheString = $this->getDiffBodyCacheKey();
1212                 if ( $cacheString ) {
1213                         return [ $cacheString ];
1214                 }
1215
1216                 $params = $this->getDiffBodyCacheKeyParams();
1217
1218                 // Try to get rid of the standard keys to keep the cache key human-readable:
1219                 // call the getDiffBodyCacheKeyParams implementation of the base class, and if
1220                 // the child class includes the same keys, drop them.
1221                 // Uses an obscure PHP feature where static calls to non-static methods are allowed
1222                 // as long as we are already in a non-static method of the same class, and the call context
1223                 // ($this) will be inherited.
1224                 // phpcs:ignore Squiz.Classes.SelfMemberReference.NotUsed
1225                 $standardParams = DifferenceEngine::getDiffBodyCacheKeyParams();
1226                 if ( array_slice( $params, 0, count( $standardParams ) ) === $standardParams ) {
1227                         $params = array_slice( $params, count( $standardParams ) );
1228                 }
1229
1230                 return $params;
1231         }
1232
1233         /**
1234          * Generate a diff, no caching.
1235          *
1236          * @since 1.21
1237          *
1238          * @param Content $old Old content
1239          * @param Content $new New content
1240          *
1241          * @throws Exception If old or new content is not an instance of TextContent.
1242          * @return bool|string
1243          *
1244          * @deprecated since 1.32, use a SlotDiffRenderer instead.
1245          */
1246         public function generateContentDiffBody( Content $old, Content $new ) {
1247                 $slotDiffRenderer = $new->getContentHandler()->getSlotDiffRenderer( $this->getContext() );
1248                 if (
1249                         $slotDiffRenderer instanceof DifferenceEngineSlotDiffRenderer
1250                         && $this->isSlotDiffRenderer
1251                 ) {
1252                         // Oops, we are just about to enter an infinite loop (the slot-level DifferenceEngine
1253                         // called a DifferenceEngineSlotDiffRenderer that wraps the same DifferenceEngine class).
1254                         // This will happen when a content model has no custom slot diff renderer, it does have
1255                         // a custom difference engine, but that does not override this method.
1256                         throw new Exception( get_class( $this ) . ': could not maintain backwards compatibility. '
1257                                 . 'Please use a SlotDiffRenderer.' );
1258                 }
1259                 return $slotDiffRenderer->getDiff( $old, $new ) . $this->getDebugString();
1260         }
1261
1262         /**
1263          * Generate a diff, no caching
1264          *
1265          * @param string $otext Old text, must be already segmented
1266          * @param string $ntext New text, must be already segmented
1267          *
1268          * @throws Exception If content handling for text content is configured in a way
1269          *   that makes maintaining B/C hard.
1270          * @return bool|string
1271          *
1272          * @deprecated since 1.32, use a TextSlotDiffRenderer instead.
1273          */
1274         public function generateTextDiffBody( $otext, $ntext ) {
1275                 $slotDiffRenderer = ContentHandler::getForModelID( CONTENT_MODEL_TEXT )
1276                         ->getSlotDiffRenderer( $this->getContext() );
1277                 if ( !( $slotDiffRenderer instanceof TextSlotDiffRenderer ) ) {
1278                         // Someone used the GetSlotDiffRenderer hook to replace the renderer.
1279                         // This is too unlikely to happen to bother handling properly.
1280                         throw new Exception( 'The slot diff renderer for text content should be a '
1281                                 . 'TextSlotDiffRenderer subclass' );
1282                 }
1283                 return $slotDiffRenderer->getTextDiff( $otext, $ntext ) . $this->getDebugString();
1284         }
1285
1286         /**
1287          * Process $wgExternalDiffEngine and get a sane, usable engine
1288          *
1289          * @return bool|string 'wikidiff2', path to an executable, or false
1290          * @internal For use by this class and TextSlotDiffRenderer only.
1291          */
1292         public static function getEngine() {
1293                 global $wgExternalDiffEngine;
1294                 // We use the global here instead of Config because we write to the value,
1295                 // and Config is not mutable.
1296                 if ( $wgExternalDiffEngine == 'wikidiff' || $wgExternalDiffEngine == 'wikidiff3' ) {
1297                         wfDeprecated( "\$wgExternalDiffEngine = '{$wgExternalDiffEngine}'", '1.27' );
1298                         $wgExternalDiffEngine = false;
1299                 } elseif ( $wgExternalDiffEngine == 'wikidiff2' ) {
1300                         wfDeprecated( "\$wgExternalDiffEngine = '{$wgExternalDiffEngine}'", '1.32' );
1301                         $wgExternalDiffEngine = false;
1302                 } elseif ( !is_string( $wgExternalDiffEngine ) && $wgExternalDiffEngine !== false ) {
1303                         // And prevent people from shooting themselves in the foot...
1304                         wfWarn( '$wgExternalDiffEngine is set to a non-string value, forcing it to false' );
1305                         $wgExternalDiffEngine = false;
1306                 }
1307
1308                 if ( is_string( $wgExternalDiffEngine ) && is_executable( $wgExternalDiffEngine ) ) {
1309                         return $wgExternalDiffEngine;
1310                 } elseif ( $wgExternalDiffEngine === false && function_exists( 'wikidiff2_do_diff' ) ) {
1311                         return 'wikidiff2';
1312                 } else {
1313                         // Native PHP
1314                         return false;
1315                 }
1316         }
1317
1318         /**
1319          * Generates diff, to be wrapped internally in a logging/instrumentation
1320          *
1321          * @param string $otext Old text, must be already segmented
1322          * @param string $ntext New text, must be already segmented
1323          *
1324          * @throws Exception If content handling for text content is configured in a way
1325          *   that makes maintaining B/C hard.
1326          * @return bool|string
1327          *
1328          * @deprecated since 1.32, use a TextSlotDiffRenderer instead.
1329          */
1330         protected function textDiff( $otext, $ntext ) {
1331                 $slotDiffRenderer = ContentHandler::getForModelID( CONTENT_MODEL_TEXT )
1332                         ->getSlotDiffRenderer( $this->getContext() );
1333                 if ( !( $slotDiffRenderer instanceof TextSlotDiffRenderer ) ) {
1334                         // Someone used the GetSlotDiffRenderer hook to replace the renderer.
1335                         // This is too unlikely to happen to bother handling properly.
1336                         throw new Exception( 'The slot diff renderer for text content should be a '
1337                                 . 'TextSlotDiffRenderer subclass' );
1338                 }
1339                 return $slotDiffRenderer->getTextDiff( $otext, $ntext ) . $this->getDebugString();
1340         }
1341
1342         /**
1343          * Generate a debug comment indicating diff generating time,
1344          * server node, and generator backend.
1345          *
1346          * @param string $generator : What diff engine was used
1347          *
1348          * @return string
1349          */
1350         protected function debug( $generator = "internal" ) {
1351                 if ( !$this->enableDebugComment ) {
1352                         return '';
1353                 }
1354                 $data = [ $generator ];
1355                 if ( $this->getConfig()->get( 'ShowHostnames' ) ) {
1356                         $data[] = wfHostname();
1357                 }
1358                 $data[] = wfTimestamp( TS_DB );
1359
1360                 return "<!-- diff generator: " .
1361                         implode( " ", array_map( "htmlspecialchars", $data ) ) .
1362                         " -->\n";
1363         }
1364
1365         private function getDebugString() {
1366                 $engine = self::getEngine();
1367                 if ( $engine === 'wikidiff2' ) {
1368                         return $this->debug( 'wikidiff2' );
1369                 } elseif ( $engine === false ) {
1370                         return $this->debug( 'native PHP' );
1371                 } else {
1372                         return $this->debug( "external $engine" );
1373                 }
1374         }
1375
1376         /**
1377          * Localise diff output
1378          *
1379          * @param string $text
1380          * @return string
1381          */
1382         private function localiseDiff( $text ) {
1383                 $text = $this->localiseLineNumbers( $text );
1384                 if ( $this->getEngine() === 'wikidiff2' &&
1385                         version_compare( phpversion( 'wikidiff2' ), '1.5.1', '>=' )
1386                 ) {
1387                         $text = $this->addLocalisedTitleTooltips( $text );
1388                 }
1389                 return $text;
1390         }
1391
1392         /**
1393          * Replace line numbers with the text in the user's language
1394          *
1395          * @param string $text
1396          *
1397          * @return mixed
1398          */
1399         public function localiseLineNumbers( $text ) {
1400                 return preg_replace_callback(
1401                         '/<!--LINE (\d+)-->/',
1402                         [ $this, 'localiseLineNumbersCb' ],
1403                         $text
1404                 );
1405         }
1406
1407         public function localiseLineNumbersCb( $matches ) {
1408                 if ( $matches[1] === '1' && $this->mReducedLineNumbers ) {
1409                         return '';
1410                 }
1411
1412                 return $this->msg( 'lineno' )->numParams( $matches[1] )->escaped();
1413         }
1414
1415         /**
1416          * Add title attributes for tooltips on moved paragraph indicators
1417          *
1418          * @param string $text
1419          * @return string
1420          */
1421         private function addLocalisedTitleTooltips( $text ) {
1422                 return preg_replace_callback(
1423                         '/class="mw-diff-movedpara-(left|right)"/',
1424                         [ $this, 'addLocalisedTitleTooltipsCb' ],
1425                         $text
1426                 );
1427         }
1428
1429         /**
1430          * @param array $matches
1431          * @return string
1432          */
1433         private function addLocalisedTitleTooltipsCb( array $matches ) {
1434                 $key = $matches[1] === 'right' ?
1435                         'diff-paragraph-moved-toold' :
1436                         'diff-paragraph-moved-tonew';
1437                 return $matches[0] . ' title="' . $this->msg( $key )->escaped() . '"';
1438         }
1439
1440         /**
1441          * If there are revisions between the ones being compared, return a note saying so.
1442          *
1443          * @return string
1444          */
1445         public function getMultiNotice() {
1446                 // The notice only make sense if we are diffing two saved revisions of the same page.
1447                 if (
1448                         !$this->mOldRev || !$this->mNewRev
1449                         || !$this->mOldPage || !$this->mNewPage
1450                         || !$this->mOldPage->equals( $this->mNewPage )
1451                 ) {
1452                         return '';
1453                 }
1454
1455                 if ( $this->mOldRev->getTimestamp() > $this->mNewRev->getTimestamp() ) {
1456                         $oldRev = $this->mNewRev; // flip
1457                         $newRev = $this->mOldRev; // flip
1458                 } else { // normal case
1459                         $oldRev = $this->mOldRev;
1460                         $newRev = $this->mNewRev;
1461                 }
1462
1463                 // Sanity: don't show the notice if too many rows must be scanned
1464                 // @todo show some special message for that case
1465                 $nEdits = $this->mNewPage->countRevisionsBetween( $oldRev, $newRev, 1000 );
1466                 if ( $nEdits > 0 && $nEdits <= 1000 ) {
1467                         $limit = 100; // use diff-multi-manyusers if too many users
1468                         $users = $this->mNewPage->getAuthorsBetween( $oldRev, $newRev, $limit );
1469                         $numUsers = count( $users );
1470
1471                         if ( $numUsers == 1 && $users[0] == $newRev->getUserText( RevisionRecord::RAW ) ) {
1472                                 $numUsers = 0; // special case to say "by the same user" instead of "by one other user"
1473                         }
1474
1475                         return self::intermediateEditsMsg( $nEdits, $numUsers, $limit );
1476                 }
1477
1478                 return '';
1479         }
1480
1481         /**
1482          * Get a notice about how many intermediate edits and users there are
1483          *
1484          * @param int $numEdits
1485          * @param int $numUsers
1486          * @param int $limit
1487          *
1488          * @return string
1489          */
1490         public static function intermediateEditsMsg( $numEdits, $numUsers, $limit ) {
1491                 if ( $numUsers === 0 ) {
1492                         $msg = 'diff-multi-sameuser';
1493                 } elseif ( $numUsers > $limit ) {
1494                         $msg = 'diff-multi-manyusers';
1495                         $numUsers = $limit;
1496                 } else {
1497                         $msg = 'diff-multi-otherusers';
1498                 }
1499
1500                 return wfMessage( $msg )->numParams( $numEdits, $numUsers )->parse();
1501         }
1502
1503         /**
1504          * Get a header for a specified revision.
1505          *
1506          * @param Revision $rev
1507          * @param string $complete 'complete' to get the header wrapped depending
1508          *        the visibility of the revision and a link to edit the page.
1509          *
1510          * @return string HTML fragment
1511          */
1512         public function getRevisionHeader( Revision $rev, $complete = '' ) {
1513                 $lang = $this->getLanguage();
1514                 $user = $this->getUser();
1515                 $revtimestamp = $rev->getTimestamp();
1516                 $timestamp = $lang->userTimeAndDate( $revtimestamp, $user );
1517                 $dateofrev = $lang->userDate( $revtimestamp, $user );
1518                 $timeofrev = $lang->userTime( $revtimestamp, $user );
1519
1520                 $header = $this->msg(
1521                         $rev->isCurrent() ? 'currentrev-asof' : 'revisionasof',
1522                         $timestamp,
1523                         $dateofrev,
1524                         $timeofrev
1525                 )->escaped();
1526
1527                 if ( $complete !== 'complete' ) {
1528                         return $header;
1529                 }
1530
1531                 $title = $rev->getTitle();
1532
1533                 $header = Linker::linkKnown( $title, $header, [],
1534                         [ 'oldid' => $rev->getId() ] );
1535
1536                 if ( $rev->userCan( RevisionRecord::DELETED_TEXT, $user ) ) {
1537                         $editQuery = [ 'action' => 'edit' ];
1538                         if ( !$rev->isCurrent() ) {
1539                                 $editQuery['oldid'] = $rev->getId();
1540                         }
1541
1542                         $key = $title->quickUserCan( 'edit', $user ) ? 'editold' : 'viewsourceold';
1543                         $msg = $this->msg( $key )->escaped();
1544                         $editLink = $this->msg( 'parentheses' )->rawParams(
1545                                 Linker::linkKnown( $title, $msg, [], $editQuery ) )->escaped();
1546                         $header .= ' ' . Html::rawElement(
1547                                 'span',
1548                                 [ 'class' => 'mw-diff-edit' ],
1549                                 $editLink
1550                         );
1551                         if ( $rev->isDeleted( RevisionRecord::DELETED_TEXT ) ) {
1552                                 $header = Html::rawElement(
1553                                         'span',
1554                                         [ 'class' => 'history-deleted' ],
1555                                         $header
1556                                 );
1557                         }
1558                 } else {
1559                         $header = Html::rawElement( 'span', [ 'class' => 'history-deleted' ], $header );
1560                 }
1561
1562                 return $header;
1563         }
1564
1565         /**
1566          * Add the header to a diff body
1567          *
1568          * @param string $diff Diff body
1569          * @param string $otitle Old revision header
1570          * @param string $ntitle New revision header
1571          * @param string $multi Notice telling user that there are intermediate
1572          *   revisions between the ones being compared
1573          * @param string $notice Other notices, e.g. that user is viewing deleted content
1574          *
1575          * @return string
1576          */
1577         public function addHeader( $diff, $otitle, $ntitle, $multi = '', $notice = '' ) {
1578                 // shared.css sets diff in interface language/dir, but the actual content
1579                 // is often in a different language, mostly the page content language/dir
1580                 $header = Html::openElement( 'table', [
1581                         'class' => [ 'diff', 'diff-contentalign-' . $this->getDiffLang()->alignStart() ],
1582                         'data-mw' => 'interface',
1583                 ] );
1584                 $userLang = htmlspecialchars( $this->getLanguage()->getHtmlCode() );
1585
1586                 if ( !$diff && !$otitle ) {
1587                         $header .= "
1588                         <tr class=\"diff-title\" lang=\"{$userLang}\">
1589                         <td class=\"diff-ntitle\">{$ntitle}</td>
1590                         </tr>";
1591                         $multiColspan = 1;
1592                 } else {
1593                         if ( $diff ) { // Safari/Chrome show broken output if cols not used
1594                                 $header .= "
1595                                 <col class=\"diff-marker\" />
1596                                 <col class=\"diff-content\" />
1597                                 <col class=\"diff-marker\" />
1598                                 <col class=\"diff-content\" />";
1599                                 $colspan = 2;
1600                                 $multiColspan = 4;
1601                         } else {
1602                                 $colspan = 1;
1603                                 $multiColspan = 2;
1604                         }
1605                         if ( $otitle || $ntitle ) {
1606                                 $header .= "
1607                                 <tr class=\"diff-title\" lang=\"{$userLang}\">
1608                                 <td colspan=\"$colspan\" class=\"diff-otitle\">{$otitle}</td>
1609                                 <td colspan=\"$colspan\" class=\"diff-ntitle\">{$ntitle}</td>
1610                                 </tr>";
1611                         }
1612                 }
1613
1614                 if ( $multi != '' ) {
1615                         $header .= "<tr><td colspan=\"{$multiColspan}\" " .
1616                                 "class=\"diff-multi\" lang=\"{$userLang}\">{$multi}</td></tr>";
1617                 }
1618                 if ( $notice != '' ) {
1619                         $header .= "<tr><td colspan=\"{$multiColspan}\" " .
1620                                 "class=\"diff-notice\" lang=\"{$userLang}\">{$notice}</td></tr>";
1621                 }
1622
1623                 return $header . $diff . "</table>";
1624         }
1625
1626         /**
1627          * Use specified text instead of loading from the database
1628          * @param Content $oldContent
1629          * @param Content $newContent
1630          * @since 1.21
1631          * @deprecated since 1.32, use setRevisions or ContentHandler::getSlotDiffRenderer.
1632          */
1633         public function setContent( Content $oldContent, Content $newContent ) {
1634                 $this->mOldContent = $oldContent;
1635                 $this->mNewContent = $newContent;
1636
1637                 $this->mTextLoaded = 2;
1638                 $this->mRevisionsLoaded = true;
1639                 $this->isContentOverridden = true;
1640                 $this->slotDiffRenderers = null;
1641         }
1642
1643         /**
1644          * Use specified text instead of loading from the database.
1645          * @param RevisionRecord|null $oldRevision
1646          * @param RevisionRecord $newRevision
1647          */
1648         public function setRevisions(
1649                 RevisionRecord $oldRevision = null, RevisionRecord $newRevision
1650         ) {
1651                 if ( $oldRevision ) {
1652                         $this->mOldRev = new Revision( $oldRevision );
1653                         $this->mOldid = $oldRevision->getId();
1654                         $this->mOldPage = Title::newFromLinkTarget( $oldRevision->getPageAsLinkTarget() );
1655                         // This method is meant for edit diffs and such so there is no reason to provide a
1656                         // revision that's not readable to the user, but check it just in case.
1657                         $this->mOldContent = $oldRevision->getContent( SlotRecord::MAIN,
1658                                 RevisionRecord::FOR_THIS_USER, $this->getUser() );
1659                 } else {
1660                         $this->mOldPage = null;
1661                         $this->mOldRev = $this->mOldid = false;
1662                 }
1663                 $this->mNewRev = new Revision( $newRevision );
1664                 $this->mNewid = $newRevision->getId();
1665                 $this->mNewPage = Title::newFromLinkTarget( $newRevision->getPageAsLinkTarget() );
1666                 $this->mNewContent = $newRevision->getContent( SlotRecord::MAIN,
1667                         RevisionRecord::FOR_THIS_USER, $this->getUser() );
1668
1669                 $this->mRevisionsIdsLoaded = $this->mRevisionsLoaded = true;
1670                 $this->mTextLoaded = $oldRevision ? 2 : 1;
1671                 $this->isContentOverridden = false;
1672                 $this->slotDiffRenderers = null;
1673         }
1674
1675         /**
1676          * Set the language in which the diff text is written
1677          *
1678          * @param Language $lang
1679          * @since 1.19
1680          */
1681         public function setTextLanguage( Language $lang ) {
1682                 $this->mDiffLang = $lang;
1683         }
1684
1685         /**
1686          * Maps a revision pair definition as accepted by DifferenceEngine constructor
1687          * to a pair of actual integers representing revision ids.
1688          *
1689          * @param int $old Revision id, e.g. from URL parameter 'oldid'
1690          * @param int|string $new Revision id or strings 'next' or 'prev', e.g. from URL parameter 'diff'
1691          *
1692          * @return array List of two revision ids, older first, later second.
1693          *     Zero signifies invalid argument passed.
1694          *     false signifies that there is no previous/next revision ($old is the oldest/newest one).
1695          */
1696         public function mapDiffPrevNext( $old, $new ) {
1697                 if ( $new === 'prev' ) {
1698                         // Show diff between revision $old and the previous one. Get previous one from DB.
1699                         $newid = intval( $old );
1700                         $oldid = $this->getTitle()->getPreviousRevisionID( $newid );
1701                 } elseif ( $new === 'next' ) {
1702                         // Show diff between revision $old and the next one. Get next one from DB.
1703                         $oldid = intval( $old );
1704                         $newid = $this->getTitle()->getNextRevisionID( $oldid );
1705                 } else {
1706                         $oldid = intval( $old );
1707                         $newid = intval( $new );
1708                 }
1709
1710                 return [ $oldid, $newid ];
1711         }
1712
1713         /**
1714          * Load revision IDs
1715          */
1716         private function loadRevisionIds() {
1717                 if ( $this->mRevisionsIdsLoaded ) {
1718                         return;
1719                 }
1720
1721                 $this->mRevisionsIdsLoaded = true;
1722
1723                 $old = $this->mOldid;
1724                 $new = $this->mNewid;
1725
1726                 list( $this->mOldid, $this->mNewid ) = self::mapDiffPrevNext( $old, $new );
1727                 if ( $new === 'next' && $this->mNewid === false ) {
1728                         # if no result, NewId points to the newest old revision. The only newer
1729                         # revision is cur, which is "0".
1730                         $this->mNewid = 0;
1731                 }
1732
1733                 Hooks::run(
1734                         'NewDifferenceEngine',
1735                         [ $this->getTitle(), &$this->mOldid, &$this->mNewid, $old, $new ]
1736                 );
1737         }
1738
1739         /**
1740          * Load revision metadata for the specified revisions. If newid is 0, then compare
1741          * the old revision in oldid to the current revision of the current page (as defined
1742          * by the request context); if oldid is 0, then compare the revision in newid to the
1743          * immediately previous one.
1744          *
1745          * If oldid is false, leave the corresponding revision object set to false. This can
1746          * happen with 'diff=prev' pointing to a non-existent revision, and is also used directly
1747          * by the API.
1748          *
1749          * @return bool Whether both revisions were loaded successfully. Setting mOldRev
1750          *   to false counts as successful loading.
1751          */
1752         public function loadRevisionData() {
1753                 if ( $this->mRevisionsLoaded ) {
1754                         return $this->isContentOverridden || ( $this->mOldRev !== null && $this->mNewRev !== null );
1755                 }
1756
1757                 // Whether it succeeds or fails, we don't want to try again
1758                 $this->mRevisionsLoaded = true;
1759
1760                 $this->loadRevisionIds();
1761
1762                 // Load the new revision object
1763                 if ( $this->mNewid ) {
1764                         $this->mNewRev = Revision::newFromId( $this->mNewid );
1765                 } else {
1766                         $this->mNewRev = Revision::newFromTitle(
1767                                 $this->getTitle(),
1768                                 false,
1769                                 Revision::READ_NORMAL
1770                         );
1771                 }
1772
1773                 if ( !$this->mNewRev instanceof Revision ) {
1774                         return false;
1775                 }
1776
1777                 // Update the new revision ID in case it was 0 (makes life easier doing UI stuff)
1778                 $this->mNewid = $this->mNewRev->getId();
1779                 if ( $this->mNewid ) {
1780                         $this->mNewPage = $this->mNewRev->getTitle();
1781                 } else {
1782                         $this->mNewPage = null;
1783                 }
1784
1785                 // Load the old revision object
1786                 $this->mOldRev = false;
1787                 if ( $this->mOldid ) {
1788                         $this->mOldRev = Revision::newFromId( $this->mOldid );
1789                 } elseif ( $this->mOldid === 0 ) {
1790                         $rev = $this->mNewRev->getPrevious();
1791                         if ( $rev ) {
1792                                 $this->mOldid = $rev->getId();
1793                                 $this->mOldRev = $rev;
1794                         } else {
1795                                 // No previous revision; mark to show as first-version only.
1796                                 $this->mOldid = false;
1797                                 $this->mOldRev = false;
1798                         }
1799                 } /* elseif ( $this->mOldid === false ) leave mOldRev false; */
1800
1801                 if ( is_null( $this->mOldRev ) ) {
1802                         return false;
1803                 }
1804
1805                 if ( $this->mOldRev && $this->mOldRev->getId() ) {
1806                         $this->mOldPage = $this->mOldRev->getTitle();
1807                 } else {
1808                         $this->mOldPage = null;
1809                 }
1810
1811                 // Load tags information for both revisions
1812                 $dbr = wfGetDB( DB_REPLICA );
1813                 $changeTagDefStore = MediaWikiServices::getInstance()->getChangeTagDefStore();
1814                 if ( $this->mOldid !== false ) {
1815                         $tagIds = $dbr->selectFieldValues(
1816                                 'change_tag',
1817                                 'ct_tag_id',
1818                                 [ 'ct_rev_id' => $this->mOldid ],
1819                                 __METHOD__
1820                         );
1821                         $tags = [];
1822                         foreach ( $tagIds as $tagId ) {
1823                                 try {
1824                                         $tags[] = $changeTagDefStore->getName( (int)$tagId );
1825                                 } catch ( NameTableAccessException $exception ) {
1826                                         continue;
1827                                 }
1828                         }
1829                         $this->mOldTags = implode( ',', $tags );
1830                 } else {
1831                         $this->mOldTags = false;
1832                 }
1833
1834                 $tagIds = $dbr->selectFieldValues(
1835                         'change_tag',
1836                         'ct_tag_id',
1837                         [ 'ct_rev_id' => $this->mNewid ],
1838                         __METHOD__
1839                 );
1840                 $tags = [];
1841                 foreach ( $tagIds as $tagId ) {
1842                         try {
1843                                 $tags[] = $changeTagDefStore->getName( (int)$tagId );
1844                         } catch ( NameTableAccessException $exception ) {
1845                                 continue;
1846                         }
1847                 }
1848                 $this->mNewTags = implode( ',', $tags );
1849
1850                 return true;
1851         }
1852
1853         /**
1854          * Load the text of the revisions, as well as revision data.
1855          * When the old revision is missing (mOldRev is false), loading mOldContent is not attempted.
1856          *
1857          * @return bool Whether the content of both revisions could be loaded successfully.
1858          *   (When mOldRev is false, that still counts as a success.)
1859          *
1860          */
1861         public function loadText() {
1862                 if ( $this->mTextLoaded == 2 ) {
1863                         return $this->loadRevisionData() && ( $this->mOldRev === false || $this->mOldContent )
1864                                 && $this->mNewContent;
1865                 }
1866
1867                 // Whether it succeeds or fails, we don't want to try again
1868                 $this->mTextLoaded = 2;
1869
1870                 if ( !$this->loadRevisionData() ) {
1871                         return false;
1872                 }
1873
1874                 if ( $this->mOldRev ) {
1875                         $this->mOldContent = $this->mOldRev->getContent(
1876                                 RevisionRecord::FOR_THIS_USER, $this->getUser()
1877                         );
1878                         if ( $this->mOldContent === null ) {
1879                                 return false;
1880                         }
1881                 }
1882
1883                 $this->mNewContent = $this->mNewRev->getContent(
1884                         RevisionRecord::FOR_THIS_USER, $this->getUser()
1885                 );
1886                 Hooks::run( 'DifferenceEngineLoadTextAfterNewContentIsLoaded', [ $this ] );
1887                 if ( $this->mNewContent === null ) {
1888                         return false;
1889                 }
1890
1891                 return true;
1892         }
1893
1894         /**
1895          * Load the text of the new revision, not the old one
1896          *
1897          * @return bool Whether the content of the new revision could be loaded successfully.
1898          */
1899         public function loadNewText() {
1900                 if ( $this->mTextLoaded >= 1 ) {
1901                         return $this->loadRevisionData();
1902                 }
1903
1904                 $this->mTextLoaded = 1;
1905
1906                 if ( !$this->loadRevisionData() ) {
1907                         return false;
1908                 }
1909
1910                 $this->mNewContent = $this->mNewRev->getContent(
1911                         RevisionRecord::FOR_THIS_USER, $this->getUser()
1912                 );
1913
1914                 Hooks::run( 'DifferenceEngineAfterLoadNewText', [ $this ] );
1915
1916                 return true;
1917         }
1918
1919 }