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\Revision\RevisionRecord;
  26 use MediaWiki\Revision\SlotRecord;
  27 use MediaWiki\Storage\NameTableAccessException;
  28
  29 /**
  30  * DifferenceEngine is responsible for rendering the difference between two revisions as HTML.
  31  * This includes interpreting URL parameters, retrieving revision data, checking access permissions,
  32  * selecting and invoking the diff generator class for the individual slots, doing post-processing
  33  * on the generated diff, adding the rest of the HTML (such as headers) and writing the whole thing
  34  * to OutputPage.
  35  *
  36  * DifferenceEngine can be subclassed by extensions, by customizing
  37  * ContentHandler::createDifferenceEngine; the content handler will be selected based on the
  38  * content model of the main slot (of the new revision, when the two are different).
  39  * That might change after PageTypeHandler gets introduced.
  40  *
  41  * In the past, the class was also used for slot-level diff generation, and extensions might still
  42  * subclass it and add such functionality. When that is the case (sepcifically, when a
  43  * ContentHandler returns a standard SlotDiffRenderer but a nonstandard DifferenceEngine)
  44  * DifferenceEngineSlotDiffRenderer will be used to convert the old behavior into the new one.
  45  *
  46  * @ingroup DifferenceEngine
  47  *
  48  * @todo This class is huge and poorly defined. It should be split into a controller responsible
  49  * for interpreting query parameters, retrieving data and checking permissions; and a HTML renderer.
  50  */
  51 class DifferenceEngine extends ContextSource {
  52
  53         use DeprecationHelper;
  54
  55         /**
  56          * Constant to indicate diff cache compatibility.
  57          * Bump this when changing the diff formatting in a way that
  58          * fixes important bugs or such to force cached diff views to
  59          * clear.
  60          */
  61         const DIFF_VERSION = '1.12';
  62
  63         /**
  64          * Revision ID for the old revision. 0 for the revision previous to $mNewid, false
  65          * if the diff does not have an old revision (e.g. 'oldid=<first revision of page>&diff=prev'),
  66          * or the revision does not exist, null if the revision is unsaved.
  67          * @var int|false|null
  68          */
  69         protected $mOldid;
  70
  71         /**
  72          * Revision ID for the new revision. 0 for the last revision of the current page
  73          * (as defined by the request context), false if the revision does not exist, null
  74          * if it is unsaved, or an alias such as 'next'.
  75          * @var int|string|false|null
  76          */
  77         protected $mNewid;
  78
  79         /**
  80          * Old revision (left pane).
  81          * Allowed to be an unsaved revision, unlikely that's ever needed though.
  82          * False when the old revision does not exist; this can happen when using
  83          * diff=prev on the first revision. Null when the revision should exist but
  84          * doesn't (e.g. load failure); loadRevisionData() will return false in that
  85          * case. Also null until lazy-loaded. Ignored completely when isContentOverridden
  86          * is set.
  87          * Since 1.32 public access is deprecated.
  88          * @var Revision|null|false
  89          */
  90         protected $mOldRev;
  91
  92         /**
  93          * New revision (right pane).
  94          * Note that this might be an unsaved revision (e.g. for edit preview).
  95          * Null in case of load failure; diff methods will just return an error message in that case,
  96          * and loadRevisionData() will return false. Also null until lazy-loaded. Ignored completely
  97          * when isContentOverridden is set.
  98          * Since 1.32 public access is deprecated.
  99          * @var Revision|null
 100          */
 101         protected $mNewRev;
 102
 103         /**
 104          * Title of $mOldRev or null if the old revision does not exist or does not belong to a page.
 105          * Since 1.32 public access is deprecated and the property can be null.
 106          * @var Title|null
 107          */
 108         protected $mOldPage;
 109
 110         /**
 111          * Title of $mNewRev or null if the new revision does not exist or does not belong to a page.
 112          * Since 1.32 public access is deprecated and the property can be null.
 113          * @var Title|null
 114          */
 115         protected $mNewPage;
 116
 117         /**
 118          * Change tags of $mOldRev or null if it does not exist / is not saved.
 119          * @var string[]|null
 120          */
 121         private $mOldTags;
 122
 123         /**
 124          * Change tags of $mNewRev or null if it does not exist / is not saved.
 125          * @var string[]|null
 126          */
 127         private $mNewTags;
 128
 129         /**
 130          * @var Content|null
 131          * @deprecated since 1.32, content slots are now handled by the corresponding SlotDiffRenderer.
 132          *   This property is set to the content of the main slot, but not actually used for the main diff.
 133          */
 134         private $mOldContent;
 135
 136         /**
 137          * @var Content|null
 138          * @deprecated since 1.32, content slots are now handled by the corresponding SlotDiffRenderer.
 139          *   This property is set to the content of the main slot, but not actually used for the main diff.
 140          */
 141         private $mNewContent;
 142
 143         /** @var Language */
 144         protected $mDiffLang;
 145
 146         /** @var bool Have the revisions IDs been loaded */
 147         private $mRevisionsIdsLoaded = false;
 148
 149         /** @var bool Have the revisions been loaded */
 150         protected $mRevisionsLoaded = false;
 151
 152         /** @var int How many text blobs have been loaded, 0, 1 or 2? */
 153         protected $mTextLoaded = 0;
 154
 155         /**
 156          * Was the content overridden via setContent()?
 157          * If the content was overridden, most internal state (e.g. mOldid or mOldRev) should be ignored
 158          * and only mOldContent and mNewContent is reliable.
 159          * (Note that setRevisions() does not set this flag as in that case all properties are
 160          * overriden and remain consistent with each other, so no special handling is needed.)
 161          * @var bool
 162          */
 163         protected $isContentOverridden = false;
 164
 165         /** @var bool Was the diff fetched from cache? */
 166         protected $mCacheHit = false;
 167
 168         /**
 169          * Set this to true to add debug info to the HTML output.
 170          * Warning: this may cause RSS readers to spuriously mark articles as "new"
 171          * (T22601)
 172          */
 173         public $enableDebugComment = false;
 174
 175         /** @var bool If true, line X is not displayed when X is 1, for example
 176          *    to increase readability and conserve space with many small diffs.
 177          */
 178         protected $mReducedLineNumbers = false;
 179
 180         /** @var string Link to action=markpatrolled */
 181         protected $mMarkPatrolledLink = null;
 182
 183         /** @var bool Show rev_deleted content if allowed */
 184         protected $unhide = false;
 185
 186         /** @var bool Refresh the diff cache */
 187         protected $mRefreshCache = false;
 188
 189         /** @var SlotDiffRenderer[] DifferenceEngine classes for the slots, keyed by role name. */
 190         protected $slotDiffRenderers = null;
 191
 192         /**
 193          * Temporary hack for B/C while slot diff related methods of DifferenceEngine are being
 194          * deprecated. When true, we are inside a DifferenceEngineSlotDiffRenderer and
 195          * $slotDiffRenderers should not be used.
 196          * @var bool
 197          */
 198         protected $isSlotDiffRenderer = false;
 199
 200         /**#@-*/
 201
 202         /**
 203          * @param IContextSource|null $context Context to use, anything else will be ignored
 204          * @param int $old Old ID we want to show and diff with.
 205          * @param string|int $new Either revision ID or 'prev' or 'next'. Default: 0.
 206          * @param int $rcid Deprecated, no longer used!
 207          * @param bool $refreshCache If set, refreshes the diff cache
 208          * @param bool $unhide If set, allow viewing deleted revs
 209          */
 210         public function __construct( $context = null, $old = 0, $new = 0, $rcid = 0,
 211                 $refreshCache = false, $unhide = false
 212         ) {
 213                 $this->deprecatePublicProperty( 'mOldid', '1.32', __CLASS__ );
 214                 $this->deprecatePublicProperty( 'mNewid', '1.32', __CLASS__ );
 215                 $this->deprecatePublicProperty( 'mOldRev', '1.32', __CLASS__ );
 216                 $this->deprecatePublicProperty( 'mNewRev', '1.32', __CLASS__ );
 217                 $this->deprecatePublicProperty( 'mOldPage', '1.32', __CLASS__ );
 218                 $this->deprecatePublicProperty( 'mNewPage', '1.32', __CLASS__ );
 219                 $this->deprecatePublicProperty( 'mOldContent', '1.32', __CLASS__ );
 220                 $this->deprecatePublicProperty( 'mNewContent', '1.32', __CLASS__ );
 221                 $this->deprecatePublicProperty( 'mRevisionsLoaded', '1.32', __CLASS__ );
 222                 $this->deprecatePublicProperty( 'mTextLoaded', '1.32', __CLASS__ );
 223                 $this->deprecatePublicProperty( 'mCacheHit', '1.32', __CLASS__ );
 224
 225                 if ( $context instanceof IContextSource ) {
 226                         $this->setContext( $context );
 227                 }
 228
 229                 wfDebug( "DifferenceEngine old '$old' new '$new' rcid '$rcid'\n" );
 230
 231                 $this->mOldid = $old;
 232                 $this->mNewid = $new;
 233                 $this->mRefreshCache = $refreshCache;
 234                 $this->unhide = $unhide;
 235         }
 236
 237         /**
 238          * @return SlotDiffRenderer[] Diff renderers for each slot, keyed by role name.
 239          *   Includes slots only present in one of the revisions.
 240          */
 241         protected function getSlotDiffRenderers() {
 242                 if ( $this->isSlotDiffRenderer ) {
 243                         throw new LogicException( __METHOD__ . ' called in slot diff renderer mode' );
 244                 }
 245
 246                 if ( $this->slotDiffRenderers === null ) {
 247                         if ( !$this->loadRevisionData() ) {
 248                                 return [];
 249                         }
 250
 251                         $slotContents = $this->getSlotContents();
 252                         $this->slotDiffRenderers = array_map( function ( $contents ) {
 253                                 /** @var $content Content */
 254                                 $content = $contents['new'] ?: $contents['old'];
 255                                 return $content->getContentHandler()->getSlotDiffRenderer( $this->getContext() );
 256                         }, $slotContents );
 257                 }
 258                 return $this->slotDiffRenderers;
 259         }
 260
 261         /**
 262          * Mark this DifferenceEngine as a slot renderer (as opposed to a page renderer).
 263          * This is used in legacy mode when the DifferenceEngine is wrapped in a
 264          * DifferenceEngineSlotDiffRenderer.
 265          * @internal For use by DifferenceEngineSlotDiffRenderer only.
 266          */
 267         public function markAsSlotDiffRenderer() {
 268                 $this->isSlotDiffRenderer = true;
 269         }
 270
 271         /**
 272          * Get the old and new content objects for all slots.
 273          * This method does not do any permission checks.
 274          * @return array [ role => [ 'old' => SlotRecord|null, 'new' => SlotRecord|null ], ... ]
 275          */
 276         protected function getSlotContents() {
 277                 if ( $this->isContentOverridden ) {
 278                         return [
 279                                 SlotRecord::MAIN => [
 280                                         'old' => $this->mOldContent,
 281                                         'new' => $this->mNewContent,
 282                                 ]
 283                         ];
 284                 } elseif ( !$this->loadRevisionData() ) {
 285                         return [];
 286                 }
 287
 288                 $newSlots = $this->mNewRev->getRevisionRecord()->getSlots()->getSlots();
 289                 if ( $this->mOldRev ) {
 290                         $oldSlots = $this->mOldRev->getRevisionRecord()->getSlots()->getSlots();
 291                 } else {
 292                         $oldSlots = [];
 293                 }
 294                 // The order here will determine the visual order of the diff. The current logic is
 295                 // slots of the new revision first in natural order, then deleted ones. This is ad hoc
 296                 // and should not be relied on - in the future we may want the ordering to depend
 297                 // on the page type.
 298                 $roles = array_merge( array_keys( $newSlots ), array_keys( $oldSlots ) );
 299
 300                 $slots = [];
 301                 foreach ( $roles as $role ) {
 302                         $slots[$role] = [
 303                                 'old' => isset( $oldSlots[$role] ) ? $oldSlots[$role]->getContent() : null,
 304                                 'new' => isset( $newSlots[$role] ) ? $newSlots[$role]->getContent() : null,
 305                         ];
 306                 }
 307                 // move main slot to front
 308                 if ( isset( $slots[SlotRecord::MAIN] ) ) {
 309                         $slots = [ SlotRecord::MAIN => $slots[SlotRecord::MAIN] ] + $slots;
 310                 }
 311                 return $slots;
 312         }
 313
 314         public function getTitle() {
 315                 // T202454 avoid errors when there is no title
 316                 return parent::getTitle() ?: Title::makeTitle( NS_SPECIAL, 'BadTitle/DifferenceEngine' );
 317         }
 318
 319         /**
 320          * Set reduced line numbers mode.
 321          * When set, line X is not displayed when X is 1, for example to increase readability and
 322          * conserve space with many small diffs.
 323          * @param bool $value
 324          */
 325         public function setReducedLineNumbers( $value = true ) {
 326                 $this->mReducedLineNumbers = $value;
 327         }
 328
 329         /**
 330          * Get the language of the difference engine, defaults to page content language
 331          *
 332          * @return Language
 333          */
 334         public function getDiffLang() {
 335                 if ( $this->mDiffLang === null ) {
 336                         # Default language in which the diff text is written.
 337                         $this->mDiffLang = $this->getTitle()->getPageLanguage();
 338                 }
 339
 340                 return $this->mDiffLang;
 341         }
 342
 343         /**
 344          * @return bool
 345          */
 346         public function wasCacheHit() {
 347                 return $this->mCacheHit;
 348         }
 349
 350         /**
 351          * Get the ID of old revision (left pane) of the diff. 0 for the revision
 352          * previous to getNewid(), false if the old revision does not exist, null
 353          * if it's unsaved.
 354          * To get a real revision ID instead of 0, call loadRevisionData() first.
 355          * @return int|false|null
 356          */
 357         public function getOldid() {
 358                 $this->loadRevisionIds();
 359
 360                 return $this->mOldid;
 361         }
 362
 363         /**
 364          * Get the ID of new revision (right pane) of the diff. 0 for the current revision,
 365          * false if the new revision does not exist, null if it's unsaved.
 366          * To get a real revision ID instead of 0, call loadRevisionData() first.
 367          * @return int|false|null
 368          */
 369         public function getNewid() {
 370                 $this->loadRevisionIds();
 371
 372                 return $this->mNewid;
 373         }
 374
 375         /**
 376          * Get the left side of the diff.
 377          * Could be null when the first revision of the page is diffed to 'prev' (or in the case of
 378          * load failure).
 379          * @return RevisionRecord|null
 380          */
 381         public function getOldRevision() {
 382                 return $this->mOldRev ? $this->mOldRev->getRevisionRecord() : null;
 383         }
 384
 385         /**
 386          * Get the right side of the diff.
 387          * Should not be null but can still happen in the case of load failure.
 388          * @return RevisionRecord|null
 389          */
 390         public function getNewRevision() {
 391                 return $this->mNewRev ? $this->mNewRev->getRevisionRecord() : null;
 392         }
 393
 394         /**
 395          * Look up a special:Undelete link to the given deleted revision id,
 396          * as a workaround for being unable to load deleted diffs in currently.
 397          *
 398          * @param int $id Revision ID
 399          *
 400          * @return string|bool Link HTML or false
 401          */
 402         public function deletedLink( $id ) {
 403                 if ( $this->getUser()->isAllowed( 'deletedhistory' ) ) {
 404                         $dbr = wfGetDB( DB_REPLICA );
 405                         $arQuery = Revision::getArchiveQueryInfo();
 406                         $row = $dbr->selectRow(
 407                                 $arQuery['tables'],
 408                                 array_merge( $arQuery['fields'], [ 'ar_namespace', 'ar_title' ] ),
 409                                 [ 'ar_rev_id' => $id ],
 410                                 __METHOD__,
 411                                 [],
 412                                 $arQuery['joins']
 413                         );
 414                         if ( $row ) {
 415                                 $rev = Revision::newFromArchiveRow( $row );
 416                                 $title = Title::makeTitleSafe( $row->ar_namespace, $row->ar_title );
 417
 418                                 return SpecialPage::getTitleFor( 'Undelete' )->getFullURL( [
 419                                         'target' => $title->getPrefixedText(),
 420                                         'timestamp' => $rev->getTimestamp()
 421                                 ] );
 422                         }
 423                 }
 424
 425                 return false;
 426         }
 427
 428         /**
 429          * Build a wikitext link toward a deleted revision, if viewable.
 430          *
 431          * @param int $id Revision ID
 432          *
 433          * @return string Wikitext fragment
 434          */
 435         public function deletedIdMarker( $id ) {
 436                 $link = $this->deletedLink( $id );
 437                 if ( $link ) {
 438                         return "[$link $id]";
 439                 } else {
 440                         return (string)$id;
 441                 }
 442         }
 443
 444         private function showMissingRevision() {
 445                 $out = $this->getOutput();
 446
 447                 $missing = [];
 448                 if ( $this->mOldRev === null ||
 449                         ( $this->mOldRev && $this->mOldContent === null )
 450                 ) {
 451                         $missing[] = $this->deletedIdMarker( $this->mOldid );
 452                 }
 453                 if ( $this->mNewRev === null ||
 454                         ( $this->mNewRev && $this->mNewContent === null )
 455                 ) {
 456                         $missing[] = $this->deletedIdMarker( $this->mNewid );
 457                 }
 458
 459                 $out->setPageTitle( $this->msg( 'errorpagetitle' ) );
 460                 $msg = $this->msg( 'difference-missing-revision' )
 461                         ->params( $this->getLanguage()->listToText( $missing ) )
 462                         ->numParams( count( $missing ) )
 463                         ->parseAsBlock();
 464                 $out->addHTML( $msg );
 465         }
 466
 467         public function showDiffPage( $diffOnly = false ) {
 468                 # Allow frames except in certain special cases
 469                 $out = $this->getOutput();
 470                 $out->allowClickjacking();
 471                 $out->setRobotPolicy( 'noindex,nofollow' );
 472
 473                 // Allow extensions to add any extra output here
 474                 Hooks::run( 'DifferenceEngineShowDiffPage', [ $out ] );
 475
 476                 if ( !$this->loadRevisionData() ) {
 477                         if ( Hooks::run( 'DifferenceEngineShowDiffPageMaybeShowMissingRevision', [ $this ] ) ) {
 478                                 $this->showMissingRevision();
 479                         }
 480                         return;
 481                 }
 482
 483                 $user = $this->getUser();
 484                 $permErrors = [];
 485                 if ( $this->mNewPage ) {
 486                         $permErrors = $this->mNewPage->getUserPermissionsErrors( 'read', $user );
 487                 }
 488                 if ( $this->mOldPage ) {
 489                         $permErrors = wfMergeErrorArrays( $permErrors,
 490                                 $this->mOldPage->getUserPermissionsErrors( 'read', $user ) );
 491                 }
 492                 if ( count( $permErrors ) ) {
 493                         throw new PermissionsError( 'read', $permErrors );
 494                 }
 495
 496                 $rollback = '';
 497
 498                 $query = [];
 499                 # Carry over 'diffonly' param via navigation links
 500                 if ( $diffOnly != $user->getBoolOption( 'diffonly' ) ) {
 501                         $query['diffonly'] = $diffOnly;
 502                 }
 503                 # Cascade unhide param in links for easy deletion browsing
 504                 if ( $this->unhide ) {
 505                         $query['unhide'] = 1;
 506                 }
 507
 508                 # Check if one of the revisions is deleted/suppressed
 509                 $deleted = $suppressed = false;
 510                 $allowed = $this->mNewRev->userCan( Revision::DELETED_TEXT, $user );
 511
 512                 $revisionTools = [];
 513
 514                 # mOldRev is false if the difference engine is called with a "vague" query for
 515                 # a diff between a version V and its previous version V' AND the version V
 516                 # is the first version of that article. In that case, V' does not exist.
 517                 if ( $this->mOldRev === false ) {
 518                         if ( $this->mNewPage ) {
 519                                 $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 520                         }
 521                         $samePage = true;
 522                         $oldHeader = '';
 523                         // Allow extensions to change the $oldHeader variable
 524                         Hooks::run( 'DifferenceEngineOldHeaderNoOldRev', [ &$oldHeader ] );
 525                 } else {
 526                         Hooks::run( 'DiffViewHeader', [ $this, $this->mOldRev, $this->mNewRev ] );
 527
 528                         if ( !$this->mOldPage || !$this->mNewPage ) {
 529                                 // XXX say something to the user?
 530                                 $samePage = false;
 531                         } elseif ( $this->mNewPage->equals( $this->mOldPage ) ) {
 532                                 $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 533                                 $samePage = true;
 534                         } else {
 535                                 $out->setPageTitle( $this->msg( 'difference-title-multipage',
 536                                         $this->mOldPage->getPrefixedText(), $this->mNewPage->getPrefixedText() ) );
 537                                 $out->addSubtitle( $this->msg( 'difference-multipage' ) );
 538                                 $samePage = false;
 539                         }
 540
 541                         if ( $samePage && $this->mNewPage && $this->mNewPage->quickUserCan( 'edit', $user ) ) {
 542                                 if ( $this->mNewRev->isCurrent() && $this->mNewPage->userCan( 'rollback', $user ) ) {
 543                                         $rollbackLink = Linker::generateRollback( $this->mNewRev, $this->getContext() );
 544                                         if ( $rollbackLink ) {
 545                                                 $out->preventClickjacking();
 546                                                 $rollback = "\u{00A0}\u{00A0}\u{00A0}" . $rollbackLink;
 547                                         }
 548                                 }
 549
 550                                 if ( !$this->mOldRev->isDeleted( Revision::DELETED_TEXT ) &&
 551                                         !$this->mNewRev->isDeleted( Revision::DELETED_TEXT )
 552                                 ) {
 553                                         $undoLink = Html::element( 'a', [
 554                                                         'href' => $this->mNewPage->getLocalURL( [
 555                                                                 'action' => 'edit',
 556                                                                 'undoafter' => $this->mOldid,
 557                                                                 'undo' => $this->mNewid
 558                                                         ] ),
 559                                                         'title' => Linker::titleAttrib( 'undo' ),
 560                                                 ],
 561                                                 $this->msg( 'editundo' )->text()
 562                                         );
 563                                         $revisionTools['mw-diff-undo'] = $undoLink;
 564                                 }
 565                         }
 566
 567                         # Make "previous revision link"
 568                         if ( $samePage && $this->mOldPage && $this->mOldRev->getPrevious() ) {
 569                                 $prevlink = Linker::linkKnown(
 570                                         $this->mOldPage,
 571                                         $this->msg( 'previousdiff' )->escaped(),
 572                                         [ 'id' => 'differences-prevlink' ],
 573                                         [ 'diff' => 'prev', 'oldid' => $this->mOldid ] + $query
 574                                 );
 575                         } else {
 576                                 $prevlink = "\u{00A0}";
 577                         }
 578
 579                         if ( $this->mOldRev->isMinor() ) {
 580                                 $oldminor = ChangesList::flag( 'minor' );
 581                         } else {
 582                                 $oldminor = '';
 583                         }
 584
 585                         $ldel = $this->revisionDeleteLink( $this->mOldRev );
 586                         $oldRevisionHeader = $this->getRevisionHeader( $this->mOldRev, 'complete' );
 587                         $oldChangeTags = ChangeTags::formatSummaryRow( $this->mOldTags, 'diff', $this->getContext() );
 588
 589                         $oldHeader = '<div id="mw-diff-otitle1"><strong>' . $oldRevisionHeader . '</strong></div>' .
 590                                 '<div id="mw-diff-otitle2">' .
 591                                 Linker::revUserTools( $this->mOldRev, !$this->unhide ) . '</div>' .
 592                                 '<div id="mw-diff-otitle3">' . $oldminor .
 593                                 Linker::revComment( $this->mOldRev, !$diffOnly, !$this->unhide ) . $ldel . '</div>' .
 594                                 '<div id="mw-diff-otitle5">' . $oldChangeTags[0] . '</div>' .
 595                                 '<div id="mw-diff-otitle4">' . $prevlink . '</div>';
 596
 597                         // Allow extensions to change the $oldHeader variable
 598                         Hooks::run( 'DifferenceEngineOldHeader', [ $this, &$oldHeader, $prevlink, $oldminor,
 599                                 $diffOnly, $ldel, $this->unhide ] );
 600
 601                         if ( $this->mOldRev->isDeleted( Revision::DELETED_TEXT ) ) {
 602                                 $deleted = true; // old revisions text is hidden
 603                                 if ( $this->mOldRev->isDeleted( Revision::DELETED_RESTRICTED ) ) {
 604                                         $suppressed = true; // also suppressed
 605                                 }
 606                         }
 607
 608                         # Check if this user can see the revisions
 609                         if ( !$this->mOldRev->userCan( Revision::DELETED_TEXT, $user ) ) {
 610                                 $allowed = false;
 611                         }
 612                 }
 613
 614                 $out->addJsConfigVars( [
 615                         'wgDiffOldId' => $this->mOldid,
 616                         'wgDiffNewId' => $this->mNewid,
 617                 ] );
 618
 619                 # Make "next revision link"
 620                 # Skip next link on the top revision
 621                 if ( $samePage && $this->mNewPage && !$this->mNewRev->isCurrent() ) {
 622                         $nextlink = Linker::linkKnown(
 623                                 $this->mNewPage,
 624                                 $this->msg( 'nextdiff' )->escaped(),
 625                                 [ 'id' => 'differences-nextlink' ],
 626                                 [ 'diff' => 'next', 'oldid' => $this->mNewid ] + $query
 627                         );
 628                 } else {
 629                         $nextlink = "\u{00A0}";
 630                 }
 631
 632                 if ( $this->mNewRev->isMinor() ) {
 633                         $newminor = ChangesList::flag( 'minor' );
 634                 } else {
 635                         $newminor = '';
 636                 }
 637
 638                 # Handle RevisionDelete links...
 639                 $rdel = $this->revisionDeleteLink( $this->mNewRev );
 640
 641                 # Allow extensions to define their own revision tools
 642                 Hooks::run( 'DiffRevisionTools',
 643                         [ $this->mNewRev, &$revisionTools, $this->mOldRev, $user ] );
 644                 $formattedRevisionTools = [];
 645                 // Put each one in parentheses (poor man's button)
 646                 foreach ( $revisionTools as $key => $tool ) {
 647                         $toolClass = is_string( $key ) ? $key : 'mw-diff-tool';
 648                         $element = Html::rawElement(
 649                                 'span',
 650                                 [ 'class' => $toolClass ],
 651                                 $this->msg( 'parentheses' )->rawParams( $tool )->escaped()
 652                         );
 653                         $formattedRevisionTools[] = $element;
 654                 }
 655                 $newRevisionHeader = $this->getRevisionHeader( $this->mNewRev, 'complete' ) .
 656                         ' ' . implode( ' ', $formattedRevisionTools );
 657                 $newChangeTags = ChangeTags::formatSummaryRow( $this->mNewTags, 'diff', $this->getContext() );
 658
 659                 $newHeader = '<div id="mw-diff-ntitle1"><strong>' . $newRevisionHeader . '</strong></div>' .
 660                         '<div id="mw-diff-ntitle2">' . Linker::revUserTools( $this->mNewRev, !$this->unhide ) .
 661                         " $rollback</div>" .
 662                         '<div id="mw-diff-ntitle3">' . $newminor .
 663                         Linker::revComment( $this->mNewRev, !$diffOnly, !$this->unhide ) . $rdel . '</div>' .
 664                         '<div id="mw-diff-ntitle5">' . $newChangeTags[0] . '</div>' .
 665                         '<div id="mw-diff-ntitle4">' . $nextlink . $this->markPatrolledLink() . '</div>';
 666
 667                 // Allow extensions to change the $newHeader variable
 668                 Hooks::run( 'DifferenceEngineNewHeader', [ $this, &$newHeader, $formattedRevisionTools,
 669                         $nextlink, $rollback, $newminor, $diffOnly, $rdel, $this->unhide ] );
 670
 671                 if ( $this->mNewRev->isDeleted( Revision::DELETED_TEXT ) ) {
 672                         $deleted = true; // new revisions text is hidden
 673                         if ( $this->mNewRev->isDeleted( Revision::DELETED_RESTRICTED ) ) {
 674                                 $suppressed = true; // also suppressed
 675                         }
 676                 }
 677
 678                 # If the diff cannot be shown due to a deleted revision, then output
 679                 # the diff header and links to unhide (if available)...
 680                 if ( $deleted && ( !$this->unhide || !$allowed ) ) {
 681                         $this->showDiffStyle();
 682                         $multi = $this->getMultiNotice();
 683                         $out->addHTML( $this->addHeader( '', $oldHeader, $newHeader, $multi ) );
 684                         if ( !$allowed ) {
 685                                 $msg = $suppressed ? 'rev-suppressed-no-diff' : 'rev-deleted-no-diff';
 686                                 # Give explanation for why revision is not visible
 687                                 $out->wrapWikiMsg( "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 688                                         [ $msg ] );
 689                         } else {
 690                                 # Give explanation and add a link to view the diff...
 691                                 $query = $this->getRequest()->appendQueryValue( 'unhide', '1' );
 692                                 $link = $this->getTitle()->getFullURL( $query );
 693                                 $msg = $suppressed ? 'rev-suppressed-unhide-diff' : 'rev-deleted-unhide-diff';
 694                                 $out->wrapWikiMsg(
 695                                         "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 696                                         [ $msg, $link ]
 697                                 );
 698                         }
 699                 # Otherwise, output a regular diff...
 700                 } else {
 701                         # Add deletion notice if the user is viewing deleted content
 702                         $notice = '';
 703                         if ( $deleted ) {
 704                                 $msg = $suppressed ? 'rev-suppressed-diff-view' : 'rev-deleted-diff-view';
 705                                 $notice = "<div id='mw-$msg' class='mw-warning plainlinks'>\n" .
 706                                         $this->msg( $msg )->parse() .
 707                                         "</div>\n";
 708                         }
 709                         $this->showDiff( $oldHeader, $newHeader, $notice );
 710                         if ( !$diffOnly ) {
 711                                 $this->renderNewRevision();
 712                         }
 713                 }
 714         }
 715
 716         /**
 717          * Build a link to mark a change as patrolled.
 718          *
 719          * Returns empty string if there's either no revision to patrol or the user is not allowed to.
 720          * Side effect: When the patrol link is build, this method will call
 721          * OutputPage::preventClickjacking() and load mediawiki.page.patrol.ajax.
 722          *
 723          * @return string HTML or empty string
 724          */
 725         public function markPatrolledLink() {
 726                 if ( $this->mMarkPatrolledLink === null ) {
 727                         $linkInfo = $this->getMarkPatrolledLinkInfo();
 728                         // If false, there is no patrol link needed/allowed
 729                         if ( !$linkInfo || !$this->mNewPage ) {
 730                                 $this->mMarkPatrolledLink = '';
 731                         } else {
 732                                 $this->mMarkPatrolledLink = ' <span class="patrollink" data-mw="interface">[' .
 733                                         Linker::linkKnown(
 734                                                 $this->mNewPage,
 735                                                 $this->msg( 'markaspatrolleddiff' )->escaped(),
 736                                                 [],
 737                                                 [
 738                                                         'action' => 'markpatrolled',
 739                                                         'rcid' => $linkInfo['rcid'],
 740                                                 ]
 741                                         ) . ']</span>';
 742                                 // Allow extensions to change the markpatrolled link
 743                                 Hooks::run( 'DifferenceEngineMarkPatrolledLink', [ $this,
 744                                         &$this->mMarkPatrolledLink, $linkInfo['rcid'] ] );
 745                         }
 746                 }
 747                 return $this->mMarkPatrolledLink;
 748         }
 749
 750         /**
 751          * Returns an array of meta data needed to build a "mark as patrolled" link and
 752          * adds the mediawiki.page.patrol.ajax to the output.
 753          *
 754          * @return array|false An array of meta data for a patrol link (rcid only)
 755          *  or false if no link is needed
 756          */
 757         protected function getMarkPatrolledLinkInfo() {
 758                 $user = $this->getUser();
 759                 $config = $this->getConfig();
 760
 761                 // Prepare a change patrol link, if applicable
 762                 if (
 763                         // Is patrolling enabled and the user allowed to?
 764                         $config->get( 'UseRCPatrol' ) &&
 765                         $this->mNewPage && $this->mNewPage->quickUserCan( 'patrol', $user ) &&
 766                         // Only do this if the revision isn't more than 6 hours older
 767                         // than the Max RC age (6h because the RC might not be cleaned out regularly)
 768                         RecentChange::isInRCLifespan( $this->mNewRev->getTimestamp(), 21600 )
 769                 ) {
 770                         // Look for an unpatrolled change corresponding to this diff
 771                         $db = wfGetDB( DB_REPLICA );
 772                         $change = RecentChange::newFromConds(
 773                                 [
 774                                         'rc_timestamp' => $db->timestamp( $this->mNewRev->getTimestamp() ),
 775                                         'rc_this_oldid' => $this->mNewid,
 776                                         'rc_patrolled' => RecentChange::PRC_UNPATROLLED
 777                                 ],
 778                                 __METHOD__
 779                         );
 780
 781                         if ( $change && !$change->getPerformer()->equals( $user ) ) {
 782                                 $rcid = $change->getAttribute( 'rc_id' );
 783                         } else {
 784                                 // None found or the page has been created by the current user.
 785                                 // If the user could patrol this it already would be patrolled
 786                                 $rcid = 0;
 787                         }
 788
 789                         // Allow extensions to possibly change the rcid here
 790                         // For example the rcid might be set to zero due to the user
 791                         // being the same as the performer of the change but an extension
 792                         // might still want to show it under certain conditions
 793                         Hooks::run( 'DifferenceEngineMarkPatrolledRCID', [ &$rcid, $this, $change, $user ] );
 794
 795                         // Build the link
 796                         if ( $rcid ) {
 797                                 $this->getOutput()->preventClickjacking();
 798                                 if ( $user->isAllowed( 'writeapi' ) ) {
 799                                         $this->getOutput()->addModules( 'mediawiki.page.patrol.ajax' );
 800                                 }
 801
 802                                 return [
 803                                         'rcid' => $rcid,
 804                                 ];
 805                         }
 806                 }
 807
 808                 // No mark as patrolled link applicable
 809                 return false;
 810         }
 811
 812         /**
 813          * @param Revision $rev
 814          *
 815          * @return string
 816          */
 817         protected function revisionDeleteLink( $rev ) {
 818                 $link = Linker::getRevDeleteLink( $this->getUser(), $rev, $rev->getTitle() );
 819                 if ( $link !== '' ) {
 820                         $link = "\u{00A0}\u{00A0}\u{00A0}" . $link . ' ';
 821                 }
 822
 823                 return $link;
 824         }
 825
 826         /**
 827          * Show the new revision of the page.
 828          *
 829          * @note Not supported after calling setContent().
 830          */
 831         public function renderNewRevision() {
 832                 if ( $this->isContentOverridden ) {
 833                         // The code below only works with a Revision object. We could construct a fake revision
 834                         // (here or in setContent), but since this does not seem needed at the moment,
 835                         // we'll just fail for now.
 836                         throw new LogicException(
 837                                 __METHOD__
 838                                 . ' is not supported after calling setContent(). Use setRevisions() instead.'
 839                         );
 840                 }
 841
 842                 $out = $this->getOutput();
 843                 $revHeader = $this->getRevisionHeader( $this->mNewRev );
 844                 # Add "current version as of X" title
 845                 $out->addHTML( "<hr class='diff-hr' id='mw-oldid' />
 846                 <h2 class='diff-currentversion-title'>{$revHeader}</h2>\n" );
 847                 # Page content may be handled by a hooked call instead...
 848                 if ( Hooks::run( 'ArticleContentOnDiff', [ $this, $out ] ) ) {
 849                         $this->loadNewText();
 850                         if ( !$this->mNewPage ) {
 851                                 // New revision is unsaved; bail out.
 852                                 // TODO in theory rendering the new revision is a meaningful thing to do
 853                                 // even if it's unsaved, but a lot of untangling is required to do it safely.
 854                                 return;
 855                         }
 856
 857                         $out->setRevisionId( $this->mNewid );
 858                         $out->setRevisionTimestamp( $this->mNewRev->getTimestamp() );
 859                         $out->setArticleFlag( true );
 860
 861                         if ( !Hooks::run( 'ArticleRevisionViewCustom',
 862                                 [ $this->mNewRev->getRevisionRecord(), $this->mNewPage, $out ] )
 863                         ) {
 864                                 // Handled by extension
 865                                 // NOTE: sync with hooks called in Article::view()
 866                         } elseif ( !Hooks::run( 'ArticleContentViewCustom',
 867                                 [ $this->mNewContent, $this->mNewPage, $out ], '1.32' )
 868                         ) {
 869                                 // Handled by extension
 870                                 // NOTE: sync with hooks called in Article::view()
 871                         } else {
 872                                 // Normal page
 873                                 if ( $this->getTitle()->equals( $this->mNewPage ) ) {
 874                                         // If the Title stored in the context is the same as the one
 875                                         // of the new revision, we can use its associated WikiPage
 876                                         // object.
 877                                         $wikiPage = $this->getWikiPage();
 878                                 } else {
 879                                         // Otherwise we need to create our own WikiPage object
 880                                         $wikiPage = WikiPage::factory( $this->mNewPage );
 881                                 }
 882
 883                                 $parserOutput = $this->getParserOutput( $wikiPage, $this->mNewRev );
 884
 885                                 # WikiPage::getParserOutput() should not return false, but just in case
 886                                 if ( $parserOutput ) {
 887                                         // Allow extensions to change parser output here
 888                                         if ( Hooks::run( 'DifferenceEngineRenderRevisionAddParserOutput',
 889                                                 [ $this, $out, $parserOutput, $wikiPage ] )
 890                                         ) {
 891                                                 $out->addParserOutput( $parserOutput, [
 892                                                         'enableSectionEditLinks' => $this->mNewRev->isCurrent()
 893                                                                 && $this->mNewRev->getTitle()->quickUserCan( 'edit', $this->getUser() ),
 894                                                 ] );
 895                                         }
 896                                 }
 897                         }
 898                 }
 899
 900                 // Allow extensions to optionally not show the final patrolled link
 901                 if ( Hooks::run( 'DifferenceEngineRenderRevisionShowFinalPatrolLink' ) ) {
 902                         # Add redundant patrol link on bottom...
 903                         $out->addHTML( $this->markPatrolledLink() );
 904                 }
 905         }
 906
 907         /**
 908          * @param WikiPage $page
 909          * @param Revision $rev
 910          *
 911          * @return ParserOutput|bool False if the revision was not found
 912          */
 913         protected function getParserOutput( WikiPage $page, Revision $rev ) {
 914                 if ( !$rev->getId() ) {
 915                         // WikiPage::getParserOutput wants a revision ID. Passing 0 will incorrectly show
 916                         // the current revision, so fail instead. If need be, WikiPage::getParserOutput
 917                         // could be made to accept a Revision or RevisionRecord instead of the id.
 918                         return false;
 919                 }
 920
 921                 $parserOptions = $page->makeParserOptions( $this->getContext() );
 922                 $parserOutput = $page->getParserOutput( $parserOptions, $rev->getId() );
 923
 924                 return $parserOutput;
 925         }
 926
 927         /**
 928          * Get the diff text, send it to the OutputPage object
 929          * Returns false if the diff could not be generated, otherwise returns true
 930          *
 931          * @param string|bool $otitle Header for old text or false
 932          * @param string|bool $ntitle Header for new text or false
 933          * @param string $notice HTML between diff header and body
 934          *
 935          * @return bool
 936          */
 937         public function showDiff( $otitle, $ntitle, $notice = '' ) {
 938                 // Allow extensions to affect the output here
 939                 Hooks::run( 'DifferenceEngineShowDiff', [ $this ] );
 940
 941                 $diff = $this->getDiff( $otitle, $ntitle, $notice );
 942                 if ( $diff === false ) {
 943                         $this->showMissingRevision();
 944
 945                         return false;
 946                 } else {
 947                         $this->showDiffStyle();
 948                         $this->getOutput()->addHTML( $diff );
 949
 950                         return true;
 951                 }
 952         }
 953
 954         /**
 955          * Add style sheets for diff display.
 956          */
 957         public function showDiffStyle() {
 958                 if ( !$this->isSlotDiffRenderer ) {
 959                         $this->getOutput()->addModuleStyles( 'mediawiki.diff.styles' );
 960                         foreach ( $this->getSlotDiffRenderers() as $slotDiffRenderer ) {
 961                                 $slotDiffRenderer->addModules( $this->getOutput() );
 962                         }
 963                 }
 964         }
 965
 966         /**
 967          * Get complete diff table, including header
 968          *
 969          * @param string|bool $otitle Header for old text or false
 970          * @param string|bool $ntitle Header for new text or false
 971          * @param string $notice HTML between diff header and body
 972          *
 973          * @return mixed
 974          */
 975         public function getDiff( $otitle, $ntitle, $notice = '' ) {
 976                 $body = $this->getDiffBody();
 977                 if ( $body === false ) {
 978                         return false;
 979                 }
 980
 981                 $multi = $this->getMultiNotice();
 982                 // Display a message when the diff is empty
 983                 if ( $body === '' ) {
 984                         $notice .= '<div class="mw-diff-empty">' .
 985                                 $this->msg( 'diff-empty' )->parse() .
 986                                 "</div>\n";
 987                 }
 988
 989                 return $this->addHeader( $body, $otitle, $ntitle, $multi, $notice );
 990         }
 991
 992         /**
 993          * Get the diff table body, without header
 994          *
 995          * @return mixed (string/false)
 996          */
 997         public function getDiffBody() {
 998                 $this->mCacheHit = true;
 999                 // Check if the diff should be hidden from this user
1000                 if ( !$this->isContentOverridden ) {
1001                         if ( !$this->loadRevisionData() ) {
1002                                 return false;
1003                         } elseif ( $this->mOldRev &&
1004                                 !$this->mOldRev->userCan( Revision::DELETED_TEXT, $this->getUser() )
1005                         ) {
1006                                 return false;
1007                         } elseif ( $this->mNewRev &&
1008                                 !$this->mNewRev->userCan( Revision::DELETED_TEXT, $this->getUser() )
1009                         ) {
1010                                 return false;
1011                         }
1012                         // Short-circuit
1013                         if ( $this->mOldRev === false || ( $this->mOldRev && $this->mNewRev &&
1014                                 $this->mOldRev->getId() && $this->mOldRev->getId() == $this->mNewRev->getId() )
1015                         ) {
1016                                 if ( Hooks::run( 'DifferenceEngineShowEmptyOldContent', [ $this ] ) ) {
1017                                         return '';
1018                                 }
1019                         }
1020                 }
1021
1022                 // Cacheable?
1023                 $key = false;
1024                 $cache = ObjectCache::getMainWANInstance();
1025                 if ( $this->mOldid && $this->mNewid ) {
1026                         // Check if subclass is still using the old way
1027                         // for backwards-compatibility
1028                         $key = $this->getDiffBodyCacheKey();
1029                         if ( $key === null ) {
1030                                 $key = $cache->makeKey( ...$this->getDiffBodyCacheKeyParams() );
1031                         }
1032
1033                         // Try cache
1034                         if ( !$this->mRefreshCache ) {
1035                                 $difftext = $cache->get( $key );
1036                                 if ( $difftext ) {
1037                                         wfIncrStats( 'diff_cache.hit' );
1038                                         $difftext = $this->localiseDiff( $difftext );
1039                                         $difftext .= "\n<!-- diff cache key $key -->\n";
1040
1041                                         return $difftext;
1042                                 }
1043                         } // don't try to load but save the result
1044                 }
1045                 $this->mCacheHit = false;
1046
1047                 // Loadtext is permission safe, this just clears out the diff
1048                 if ( !$this->loadText() ) {
1049                         return false;
1050                 }
1051
1052                 $difftext = '';
1053                 // We've checked for revdelete at the beginning of this method; it's OK to ignore
1054                 // read permissions here.
1055                 $slotContents = $this->getSlotContents();
1056                 foreach ( $this->getSlotDiffRenderers() as $role => $slotDiffRenderer ) {
1057                         $slotDiff = $slotDiffRenderer->getDiff( $slotContents[$role]['old'],
1058                                 $slotContents[$role]['new'] );
1059                         if ( $slotDiff && $role !== SlotRecord::MAIN ) {
1060                                 // FIXME: ask SlotRoleHandler::getSlotNameMessage
1061                                 $slotTitle = $role;
1062                                 $difftext .= $this->getSlotHeader( $slotTitle );
1063                         }
1064                         $difftext .= $slotDiff;
1065                 }
1066
1067                 // Avoid PHP 7.1 warning from passing $this by reference
1068                 $diffEngine = $this;
1069
1070                 // Save to cache for 7 days
1071                 if ( !Hooks::run( 'AbortDiffCache', [ &$diffEngine ] ) ) {
1072                         wfIncrStats( 'diff_cache.uncacheable' );
1073                 } elseif ( $key !== false && $difftext !== false ) {
1074                         wfIncrStats( 'diff_cache.miss' );
1075                         $cache->set( $key, $difftext, 7 * 86400 );
1076                 } else {
1077                         wfIncrStats( 'diff_cache.uncacheable' );
1078                 }
1079                 // localise line numbers and title attribute text
1080                 if ( $difftext !== false ) {
1081                         $difftext = $this->localiseDiff( $difftext );
1082                 }
1083
1084                 return $difftext;
1085         }
1086
1087         /**
1088          * Get the diff table body for one slot, without header
1089          *
1090          * @param string $role
1091          * @return string|false
1092          */
1093         public function getDiffBodyForRole( $role ) {
1094                 $diffRenderers = $this->getSlotDiffRenderers();
1095                 if ( !isset( $diffRenderers[$role] ) ) {
1096                         return false;
1097                 }
1098
1099                 $slotContents = $this->getSlotContents();
1100                 $slotDiff = $diffRenderers[$role]->getDiff( $slotContents[$role]['old'],
1101                         $slotContents[$role]['new'] );
1102                 if ( !$slotDiff ) {
1103                         return false;
1104                 }
1105
1106                 if ( $role !== SlotRecord::MAIN ) {
1107                         // TODO use human-readable role name at least
1108                         $slotTitle = $role;
1109                         $slotDiff = $this->getSlotHeader( $slotTitle ) . $slotDiff;
1110                 }
1111
1112                 return $this->localiseDiff( $slotDiff );
1113         }
1114
1115         /**
1116          * Get a slot header for inclusion in a diff body (as a table row).
1117          *
1118          * @param string $headerText The text of the header
1119          * @return string
1120          *
1121          */
1122         protected function getSlotHeader( $headerText ) {
1123                 // The old revision is missing on oldid=<first>&diff=prev; only 2 columns in that case.
1124                 $columnCount = $this->mOldRev ? 4 : 2;
1125                 $userLang = $this->getLanguage()->getHtmlCode();
1126                 return Html::rawElement( 'tr', [ 'class' => 'mw-diff-slot-header', 'lang' => $userLang ],
1127                         Html::element( 'th', [ 'colspan' => $columnCount ], $headerText ) );
1128         }
1129
1130         /**
1131          * Returns the cache key for diff body text or content.
1132          *
1133          * @deprecated since 1.31, use getDiffBodyCacheKeyParams() instead
1134          * @since 1.23
1135          *
1136          * @throws MWException
1137          * @return string|null
1138          */
1139         protected function getDiffBodyCacheKey() {
1140                 return null;
1141         }
1142
1143         /**
1144          * Get the cache key parameters
1145          *
1146          * Subclasses can replace the first element in the array to something
1147          * more specific to the type of diff (e.g. "inline-diff"), or append
1148          * if the cache should vary on more things. Overriding entirely should
1149          * be avoided.
1150          *
1151          * @since 1.31
1152          *
1153          * @return array
1154          * @throws MWException
1155          */
1156         protected function getDiffBodyCacheKeyParams() {
1157                 if ( !$this->mOldid || !$this->mNewid ) {
1158                         throw new MWException( 'mOldid and mNewid must be set to get diff cache key.' );
1159                 }
1160
1161                 $engine = $this->getEngine();
1162                 $params = [
1163                         'diff',
1164                         $engine,
1165                         self::DIFF_VERSION,
1166                         "old-{$this->mOldid}",
1167                         "rev-{$this->mNewid}"
1168                 ];
1169
1170                 if ( $engine === 'wikidiff2' ) {
1171                         $params[] = phpversion( 'wikidiff2' );
1172                         $params[] = $this->getConfig()->get( 'WikiDiff2MovedParagraphDetectionCutoff' );
1173                 }
1174
1175                 if ( !$this->isSlotDiffRenderer ) {
1176                         foreach ( $this->getSlotDiffRenderers() as $slotDiffRenderer ) {
1177                                 $params = array_merge( $params, $slotDiffRenderer->getExtraCacheKeys() );
1178                         }
1179                 }
1180
1181                 return $params;
1182         }
1183
1184         /**
1185          * Implements DifferenceEngineSlotDiffRenderer::getExtraCacheKeys(). Only used when
1186          * DifferenceEngine is wrapped in DifferenceEngineSlotDiffRenderer.
1187          * @return array
1188          * @internal for use by DifferenceEngineSlotDiffRenderer only
1189          * @deprecated
1190          */
1191         public function getExtraCacheKeys() {
1192                 // This method is called when the DifferenceEngine is used for a slot diff. We only care
1193                 // about special things, not the revision IDs, which are added to the cache key by the
1194                 // page-level DifferenceEngine, and which might not have a valid value for this object.
1195                 $this->mOldid = 123456789;
1196                 $this->mNewid = 987654321;
1197
1198                 // This will repeat a bunch of unnecessary key fields for each slot. Not nice but harmless.
1199                 $cacheString = $this->getDiffBodyCacheKey();
1200                 if ( $cacheString ) {
1201                         return [ $cacheString ];
1202                 }
1203
1204                 $params = $this->getDiffBodyCacheKeyParams();
1205
1206                 // Try to get rid of the standard keys to keep the cache key human-readable:
1207                 // call the getDiffBodyCacheKeyParams implementation of the base class, and if
1208                 // the child class includes the same keys, drop them.
1209                 // Uses an obscure PHP feature where static calls to non-static methods are allowed
1210                 // as long as we are already in a non-static method of the same class, and the call context
1211                 // ($this) will be inherited.
1212                 // phpcs:ignore Squiz.Classes.SelfMemberReference.NotUsed
1213                 $standardParams = DifferenceEngine::getDiffBodyCacheKeyParams();
1214                 if ( array_slice( $params, 0, count( $standardParams ) ) === $standardParams ) {
1215                         $params = array_slice( $params, count( $standardParams ) );
1216                 }
1217
1218                 return $params;
1219         }
1220
1221         /**
1222          * Generate a diff, no caching.
1223          *
1224          * @since 1.21
1225          *
1226          * @param Content $old Old content
1227          * @param Content $new New content
1228          *
1229          * @throws Exception If old or new content is not an instance of TextContent.
1230          * @return bool|string
1231          *
1232          * @deprecated since 1.32, use a SlotDiffRenderer instead.
1233          */
1234         public function generateContentDiffBody( Content $old, Content $new ) {
1235                 $slotDiffRenderer = $new->getContentHandler()->getSlotDiffRenderer( $this->getContext() );
1236                 if (
1237                         $slotDiffRenderer instanceof DifferenceEngineSlotDiffRenderer
1238                         && $this->isSlotDiffRenderer
1239                 ) {
1240                         // Oops, we are just about to enter an infinite loop (the slot-level DifferenceEngine
1241                         // called a DifferenceEngineSlotDiffRenderer that wraps the same DifferenceEngine class).
1242                         // This will happen when a content model has no custom slot diff renderer, it does have
1243                         // a custom difference engine, but that does not override this method.
1244                         throw new Exception( get_class( $this ) . ': could not maintain backwards compatibility. '
1245                                 . 'Please use a SlotDiffRenderer.' );
1246                 }
1247                 return $slotDiffRenderer->getDiff( $old, $new ) . $this->getDebugString();
1248         }
1249
1250         /**
1251          * Generate a diff, no caching
1252          *
1253          * @param string $otext Old text, must be already segmented
1254          * @param string $ntext New text, must be already segmented
1255          *
1256          * @throws Exception If content handling for text content is configured in a way
1257          *   that makes maintaining B/C hard.
1258          * @return bool|string
1259          *
1260          * @deprecated since 1.32, use a TextSlotDiffRenderer instead.
1261          */
1262         public function generateTextDiffBody( $otext, $ntext ) {
1263                 $slotDiffRenderer = ContentHandler::getForModelID( CONTENT_MODEL_TEXT )
1264                         ->getSlotDiffRenderer( $this->getContext() );
1265                 if ( !( $slotDiffRenderer instanceof TextSlotDiffRenderer ) ) {
1266                         // Someone used the GetSlotDiffRenderer hook to replace the renderer.
1267                         // This is too unlikely to happen to bother handling properly.
1268                         throw new Exception( 'The slot diff renderer for text content should be a '
1269                                 . 'TextSlotDiffRenderer subclass' );
1270                 }
1271                 return $slotDiffRenderer->getTextDiff( $otext, $ntext ) . $this->getDebugString();
1272         }
1273
1274         /**
1275          * Process $wgExternalDiffEngine and get a sane, usable engine
1276          *
1277          * @return bool|string 'wikidiff2', path to an executable, or false
1278          * @internal For use by this class and TextSlotDiffRenderer only.
1279          */
1280         public static function getEngine() {
1281                 global $wgExternalDiffEngine;
1282                 // We use the global here instead of Config because we write to the value,
1283                 // and Config is not mutable.
1284                 if ( $wgExternalDiffEngine == 'wikidiff' || $wgExternalDiffEngine == 'wikidiff3' ) {
1285                         wfDeprecated( "\$wgExternalDiffEngine = '{$wgExternalDiffEngine}'", '1.27' );
1286                         $wgExternalDiffEngine = false;
1287                 } elseif ( $wgExternalDiffEngine == 'wikidiff2' ) {
1288                         wfDeprecated( "\$wgExternalDiffEngine = '{$wgExternalDiffEngine}'", '1.32' );
1289                         $wgExternalDiffEngine = false;
1290                 } elseif ( !is_string( $wgExternalDiffEngine ) && $wgExternalDiffEngine !== false ) {
1291                         // And prevent people from shooting themselves in the foot...
1292                         wfWarn( '$wgExternalDiffEngine is set to a non-string value, forcing it to false' );
1293                         $wgExternalDiffEngine = false;
1294                 }
1295
1296                 if ( is_string( $wgExternalDiffEngine ) && is_executable( $wgExternalDiffEngine ) ) {
1297                         return $wgExternalDiffEngine;
1298                 } elseif ( $wgExternalDiffEngine === false && function_exists( 'wikidiff2_do_diff' ) ) {
1299                         return 'wikidiff2';
1300                 } else {
1301                         // Native PHP
1302                         return false;
1303                 }
1304         }
1305
1306         /**
1307          * Generates diff, to be wrapped internally in a logging/instrumentation
1308          *
1309          * @param string $otext Old text, must be already segmented
1310          * @param string $ntext New text, must be already segmented
1311          *
1312          * @throws Exception If content handling for text content is configured in a way
1313          *   that makes maintaining B/C hard.
1314          * @return bool|string
1315          *
1316          * @deprecated since 1.32, use a TextSlotDiffRenderer instead.
1317          */
1318         protected function textDiff( $otext, $ntext ) {
1319                 $slotDiffRenderer = ContentHandler::getForModelID( CONTENT_MODEL_TEXT )
1320                         ->getSlotDiffRenderer( $this->getContext() );
1321                 if ( !( $slotDiffRenderer instanceof TextSlotDiffRenderer ) ) {
1322                         // Someone used the GetSlotDiffRenderer hook to replace the renderer.
1323                         // This is too unlikely to happen to bother handling properly.
1324                         throw new Exception( 'The slot diff renderer for text content should be a '
1325                                 . 'TextSlotDiffRenderer subclass' );
1326                 }
1327                 return $slotDiffRenderer->getTextDiff( $otext, $ntext ) . $this->getDebugString();
1328         }
1329
1330         /**
1331          * Generate a debug comment indicating diff generating time,
1332          * server node, and generator backend.
1333          *
1334          * @param string $generator : What diff engine was used
1335          *
1336          * @return string
1337          */
1338         protected function debug( $generator = "internal" ) {
1339                 if ( !$this->enableDebugComment ) {
1340                         return '';
1341                 }
1342                 $data = [ $generator ];
1343                 if ( $this->getConfig()->get( 'ShowHostnames' ) ) {
1344                         $data[] = wfHostname();
1345                 }
1346                 $data[] = wfTimestamp( TS_DB );
1347
1348                 return "<!-- diff generator: " .
1349                         implode( " ", array_map( "htmlspecialchars", $data ) ) .
1350                         " -->\n";
1351         }
1352
1353         private function getDebugString() {
1354                 $engine = self::getEngine();
1355                 if ( $engine === 'wikidiff2' ) {
1356                         return $this->debug( 'wikidiff2' );
1357                 } elseif ( $engine === false ) {
1358                         return $this->debug( 'native PHP' );
1359                 } else {
1360                         return $this->debug( "external $engine" );
1361                 }
1362         }
1363
1364         /**
1365          * Localise diff output
1366          *
1367          * @param string $text
1368          * @return string
1369          */
1370         private function localiseDiff( $text ) {
1371                 $text = $this->localiseLineNumbers( $text );
1372                 if ( $this->getEngine() === 'wikidiff2' &&
1373                         version_compare( phpversion( 'wikidiff2' ), '1.5.1', '>=' )
1374                 ) {
1375                         $text = $this->addLocalisedTitleTooltips( $text );
1376                 }
1377                 return $text;
1378         }
1379
1380         /**
1381          * Replace line numbers with the text in the user's language
1382          *
1383          * @param string $text
1384          *
1385          * @return mixed
1386          */
1387         public function localiseLineNumbers( $text ) {
1388                 return preg_replace_callback(
1389                         '/<!--LINE (\d+)-->/',
1390                         [ $this, 'localiseLineNumbersCb' ],
1391                         $text
1392                 );
1393         }
1394
1395         public function localiseLineNumbersCb( $matches ) {
1396                 if ( $matches[1] === '1' && $this->mReducedLineNumbers ) {
1397                         return '';
1398                 }
1399
1400                 return $this->msg( 'lineno' )->numParams( $matches[1] )->escaped();
1401         }
1402
1403         /**
1404          * Add title attributes for tooltips on moved paragraph indicators
1405          *
1406          * @param string $text
1407          * @return string
1408          */
1409         private function addLocalisedTitleTooltips( $text ) {
1410                 return preg_replace_callback(
1411                         '/class="mw-diff-movedpara-(left|right)"/',
1412                         [ $this, 'addLocalisedTitleTooltipsCb' ],
1413                         $text
1414                 );
1415         }
1416
1417         /**
1418          * @param array $matches
1419          * @return string
1420          */
1421         private function addLocalisedTitleTooltipsCb( array $matches ) {
1422                 $key = $matches[1] === 'right' ?
1423                         'diff-paragraph-moved-toold' :
1424                         'diff-paragraph-moved-tonew';
1425                 return $matches[0] . ' title="' . $this->msg( $key )->escaped() . '"';
1426         }
1427
1428         /**
1429          * If there are revisions between the ones being compared, return a note saying so.
1430          *
1431          * @return string
1432          */
1433         public function getMultiNotice() {
1434                 // The notice only make sense if we are diffing two saved revisions of the same page.
1435                 if (
1436                         !$this->mOldRev || !$this->mNewRev
1437                         || !$this->mOldPage || !$this->mNewPage
1438                         || !$this->mOldPage->equals( $this->mNewPage )
1439                 ) {
1440                         return '';
1441                 }
1442
1443                 if ( $this->mOldRev->getTimestamp() > $this->mNewRev->getTimestamp() ) {
1444                         $oldRev = $this->mNewRev; // flip
1445                         $newRev = $this->mOldRev; // flip
1446                 } else { // normal case
1447                         $oldRev = $this->mOldRev;
1448                         $newRev = $this->mNewRev;
1449                 }
1450
1451                 // Sanity: don't show the notice if too many rows must be scanned
1452                 // @todo show some special message for that case
1453                 $nEdits = $this->mNewPage->countRevisionsBetween( $oldRev, $newRev, 1000 );
1454                 if ( $nEdits > 0 && $nEdits <= 1000 ) {
1455                         $limit = 100; // use diff-multi-manyusers if too many users
1456                         $users = $this->mNewPage->getAuthorsBetween( $oldRev, $newRev, $limit );
1457                         $numUsers = count( $users );
1458
1459                         if ( $numUsers == 1 && $users[0] == $newRev->getUserText( Revision::RAW ) ) {
1460                                 $numUsers = 0; // special case to say "by the same user" instead of "by one other user"
1461                         }
1462
1463                         return self::intermediateEditsMsg( $nEdits, $numUsers, $limit );
1464                 }
1465
1466                 return '';
1467         }
1468
1469         /**
1470          * Get a notice about how many intermediate edits and users there are
1471          *
1472          * @param int $numEdits
1473          * @param int $numUsers
1474          * @param int $limit
1475          *
1476          * @return string
1477          */
1478         public static function intermediateEditsMsg( $numEdits, $numUsers, $limit ) {
1479                 if ( $numUsers === 0 ) {
1480                         $msg = 'diff-multi-sameuser';
1481                 } elseif ( $numUsers > $limit ) {
1482                         $msg = 'diff-multi-manyusers';
1483                         $numUsers = $limit;
1484                 } else {
1485                         $msg = 'diff-multi-otherusers';
1486                 }
1487
1488                 return wfMessage( $msg )->numParams( $numEdits, $numUsers )->parse();
1489         }
1490
1491         /**
1492          * Get a header for a specified revision.
1493          *
1494          * @param Revision $rev
1495          * @param string $complete 'complete' to get the header wrapped depending
1496          *        the visibility of the revision and a link to edit the page.
1497          *
1498          * @return string HTML fragment
1499          */
1500         public function getRevisionHeader( Revision $rev, $complete = '' ) {
1501                 $lang = $this->getLanguage();
1502                 $user = $this->getUser();
1503                 $revtimestamp = $rev->getTimestamp();
1504                 $timestamp = $lang->userTimeAndDate( $revtimestamp, $user );
1505                 $dateofrev = $lang->userDate( $revtimestamp, $user );
1506                 $timeofrev = $lang->userTime( $revtimestamp, $user );
1507
1508                 $header = $this->msg(
1509                         $rev->isCurrent() ? 'currentrev-asof' : 'revisionasof',
1510                         $timestamp,
1511                         $dateofrev,
1512                         $timeofrev
1513                 )->escaped();
1514
1515                 if ( $complete !== 'complete' ) {
1516                         return $header;
1517                 }
1518
1519                 $title = $rev->getTitle();
1520
1521                 $header = Linker::linkKnown( $title, $header, [],
1522                         [ 'oldid' => $rev->getId() ] );
1523
1524                 if ( $rev->userCan( Revision::DELETED_TEXT, $user ) ) {
1525                         $editQuery = [ 'action' => 'edit' ];
1526                         if ( !$rev->isCurrent() ) {
1527                                 $editQuery['oldid'] = $rev->getId();
1528                         }
1529
1530                         $key = $title->quickUserCan( 'edit', $user ) ? 'editold' : 'viewsourceold';
1531                         $msg = $this->msg( $key )->escaped();
1532                         $editLink = $this->msg( 'parentheses' )->rawParams(
1533                                 Linker::linkKnown( $title, $msg, [], $editQuery ) )->escaped();
1534                         $header .= ' ' . Html::rawElement(
1535                                 'span',
1536                                 [ 'class' => 'mw-diff-edit' ],
1537                                 $editLink
1538                         );
1539                         if ( $rev->isDeleted( Revision::DELETED_TEXT ) ) {
1540                                 $header = Html::rawElement(
1541                                         'span',
1542                                         [ 'class' => 'history-deleted' ],
1543                                         $header
1544                                 );
1545                         }
1546                 } else {
1547                         $header = Html::rawElement( 'span', [ 'class' => 'history-deleted' ], $header );
1548                 }
1549
1550                 return $header;
1551         }
1552
1553         /**
1554          * Add the header to a diff body
1555          *
1556          * @param string $diff Diff body
1557          * @param string $otitle Old revision header
1558          * @param string $ntitle New revision header
1559          * @param string $multi Notice telling user that there are intermediate
1560          *   revisions between the ones being compared
1561          * @param string $notice Other notices, e.g. that user is viewing deleted content
1562          *
1563          * @return string
1564          */
1565         public function addHeader( $diff, $otitle, $ntitle, $multi = '', $notice = '' ) {
1566                 // shared.css sets diff in interface language/dir, but the actual content
1567                 // is often in a different language, mostly the page content language/dir
1568                 $header = Html::openElement( 'table', [
1569                         'class' => [ 'diff', 'diff-contentalign-' . $this->getDiffLang()->alignStart() ],
1570                         'data-mw' => 'interface',
1571                 ] );
1572                 $userLang = htmlspecialchars( $this->getLanguage()->getHtmlCode() );
1573
1574                 if ( !$diff && !$otitle ) {
1575                         $header .= "
1576                         <tr class=\"diff-title\" lang=\"{$userLang}\">
1577                         <td class=\"diff-ntitle\">{$ntitle}</td>
1578                         </tr>";
1579                         $multiColspan = 1;
1580                 } else {
1581                         if ( $diff ) { // Safari/Chrome show broken output if cols not used
1582                                 $header .= "
1583                                 <col class=\"diff-marker\" />
1584                                 <col class=\"diff-content\" />
1585                                 <col class=\"diff-marker\" />
1586                                 <col class=\"diff-content\" />";
1587                                 $colspan = 2;
1588                                 $multiColspan = 4;
1589                         } else {
1590                                 $colspan = 1;
1591                                 $multiColspan = 2;
1592                         }
1593                         if ( $otitle || $ntitle ) {
1594                                 $header .= "
1595                                 <tr class=\"diff-title\" lang=\"{$userLang}\">
1596                                 <td colspan=\"$colspan\" class=\"diff-otitle\">{$otitle}</td>
1597                                 <td colspan=\"$colspan\" class=\"diff-ntitle\">{$ntitle}</td>
1598                                 </tr>";
1599                         }
1600                 }
1601
1602                 if ( $multi != '' ) {
1603                         $header .= "<tr><td colspan=\"{$multiColspan}\" " .
1604                                 "class=\"diff-multi\" lang=\"{$userLang}\">{$multi}</td></tr>";
1605                 }
1606                 if ( $notice != '' ) {
1607                         $header .= "<tr><td colspan=\"{$multiColspan}\" " .
1608                                 "class=\"diff-notice\" lang=\"{$userLang}\">{$notice}</td></tr>";
1609                 }
1610
1611                 return $header . $diff . "</table>";
1612         }
1613
1614         /**
1615          * Use specified text instead of loading from the database
1616          * @param Content $oldContent
1617          * @param Content $newContent
1618          * @since 1.21
1619          * @deprecated since 1.32, use setRevisions or ContentHandler::getSlotDiffRenderer.
1620          */
1621         public function setContent( Content $oldContent, Content $newContent ) {
1622                 $this->mOldContent = $oldContent;
1623                 $this->mNewContent = $newContent;
1624
1625                 $this->mTextLoaded = 2;
1626                 $this->mRevisionsLoaded = true;
1627                 $this->isContentOverridden = true;
1628                 $this->slotDiffRenderers = null;
1629         }
1630
1631         /**
1632          * Use specified text instead of loading from the database.
1633          * @param RevisionRecord|null $oldRevision
1634          * @param RevisionRecord $newRevision
1635          */
1636         public function setRevisions(
1637                 RevisionRecord $oldRevision = null, RevisionRecord $newRevision
1638         ) {
1639                 if ( $oldRevision ) {
1640                         $this->mOldRev = new Revision( $oldRevision );
1641                         $this->mOldid = $oldRevision->getId();
1642                         $this->mOldPage = Title::newFromLinkTarget( $oldRevision->getPageAsLinkTarget() );
1643                         // This method is meant for edit diffs and such so there is no reason to provide a
1644                         // revision that's not readable to the user, but check it just in case.
1645                         $this->mOldContent = $oldRevision->getContent( SlotRecord::MAIN,
1646                                 RevisionRecord::FOR_THIS_USER, $this->getUser() );
1647                 } else {
1648                         $this->mOldPage = null;
1649                         $this->mOldRev = $this->mOldid = false;
1650                 }
1651                 $this->mNewRev = new Revision( $newRevision );
1652                 $this->mNewid = $newRevision->getId();
1653                 $this->mNewPage = Title::newFromLinkTarget( $newRevision->getPageAsLinkTarget() );
1654                 $this->mNewContent = $newRevision->getContent( SlotRecord::MAIN,
1655                         RevisionRecord::FOR_THIS_USER, $this->getUser() );
1656
1657                 $this->mRevisionsIdsLoaded = $this->mRevisionsLoaded = true;
1658                 $this->mTextLoaded = $oldRevision ? 2 : 1;
1659                 $this->isContentOverridden = false;
1660                 $this->slotDiffRenderers = null;
1661         }
1662
1663         /**
1664          * Set the language in which the diff text is written
1665          *
1666          * @param Language $lang
1667          * @since 1.19
1668          */
1669         public function setTextLanguage( Language $lang ) {
1670                 $this->mDiffLang = $lang;
1671         }
1672
1673         /**
1674          * Maps a revision pair definition as accepted by DifferenceEngine constructor
1675          * to a pair of actual integers representing revision ids.
1676          *
1677          * @param int $old Revision id, e.g. from URL parameter 'oldid'
1678          * @param int|string $new Revision id or strings 'next' or 'prev', e.g. from URL parameter 'diff'
1679          *
1680          * @return array List of two revision ids, older first, later second.
1681          *     Zero signifies invalid argument passed.
1682          *     false signifies that there is no previous/next revision ($old is the oldest/newest one).
1683          */
1684         public function mapDiffPrevNext( $old, $new ) {
1685                 if ( $new === 'prev' ) {
1686                         // Show diff between revision $old and the previous one. Get previous one from DB.
1687                         $newid = intval( $old );
1688                         $oldid = $this->getTitle()->getPreviousRevisionID( $newid );
1689                 } elseif ( $new === 'next' ) {
1690                         // Show diff between revision $old and the next one. Get next one from DB.
1691                         $oldid = intval( $old );
1692                         $newid = $this->getTitle()->getNextRevisionID( $oldid );
1693                 } else {
1694                         $oldid = intval( $old );
1695                         $newid = intval( $new );
1696                 }
1697
1698                 return [ $oldid, $newid ];
1699         }
1700
1701         /**
1702          * Load revision IDs
1703          */
1704         private function loadRevisionIds() {
1705                 if ( $this->mRevisionsIdsLoaded ) {
1706                         return;
1707                 }
1708
1709                 $this->mRevisionsIdsLoaded = true;
1710
1711                 $old = $this->mOldid;
1712                 $new = $this->mNewid;
1713
1714                 list( $this->mOldid, $this->mNewid ) = self::mapDiffPrevNext( $old, $new );
1715                 if ( $new === 'next' && $this->mNewid === false ) {
1716                         # if no result, NewId points to the newest old revision. The only newer
1717                         # revision is cur, which is "0".
1718                         $this->mNewid = 0;
1719                 }
1720
1721                 Hooks::run(
1722                         'NewDifferenceEngine',
1723                         [ $this->getTitle(), &$this->mOldid, &$this->mNewid, $old, $new ]
1724                 );
1725         }
1726
1727         /**
1728          * Load revision metadata for the specified revisions. If newid is 0, then compare
1729          * the old revision in oldid to the current revision of the current page (as defined
1730          * by the request context); if oldid is 0, then compare the revision in newid to the
1731          * immediately previous one.
1732          *
1733          * If oldid is false, leave the corresponding revision object set
1734          * to false. This can happen with 'diff=prev' pointing to a non-existent revision,
1735          * and is also used directly by the API.
1736          *
1737          * @return bool Whether both revisions were loaded successfully. Setting mOldRev
1738          *   to false counts as successful loading.
1739          */
1740         public function loadRevisionData() {
1741                 if ( $this->mRevisionsLoaded ) {
1742                         return $this->isContentOverridden || $this->mNewRev && !is_null( $this->mOldRev );
1743                 }
1744
1745                 // Whether it succeeds or fails, we don't want to try again
1746                 $this->mRevisionsLoaded = true;
1747
1748                 $this->loadRevisionIds();
1749
1750                 // Load the new revision object
1751                 if ( $this->mNewid ) {
1752                         $this->mNewRev = Revision::newFromId( $this->mNewid );
1753                 } else {
1754                         $this->mNewRev = Revision::newFromTitle(
1755                                 $this->getTitle(),
1756                                 false,
1757                                 Revision::READ_NORMAL
1758                         );
1759                 }
1760
1761                 if ( !$this->mNewRev instanceof Revision ) {
1762                         return false;
1763                 }
1764
1765                 // Update the new revision ID in case it was 0 (makes life easier doing UI stuff)
1766                 $this->mNewid = $this->mNewRev->getId();
1767                 if ( $this->mNewid ) {
1768                         $this->mNewPage = $this->mNewRev->getTitle();
1769                 } else {
1770                         $this->mNewPage = null;
1771                 }
1772
1773                 // Load the old revision object
1774                 $this->mOldRev = false;
1775                 if ( $this->mOldid ) {
1776                         $this->mOldRev = Revision::newFromId( $this->mOldid );
1777                 } elseif ( $this->mOldid === 0 ) {
1778                         $rev = $this->mNewRev->getPrevious();
1779                         if ( $rev ) {
1780                                 $this->mOldid = $rev->getId();
1781                                 $this->mOldRev = $rev;
1782                         } else {
1783                                 // No previous revision; mark to show as first-version only.
1784                                 $this->mOldid = false;
1785                                 $this->mOldRev = false;
1786                         }
1787                 } /* elseif ( $this->mOldid === false ) leave mOldRev false; */
1788
1789                 if ( is_null( $this->mOldRev ) ) {
1790                         return false;
1791                 }
1792
1793                 if ( $this->mOldRev && $this->mOldRev->getId() ) {
1794                         $this->mOldPage = $this->mOldRev->getTitle();
1795                 } else {
1796                         $this->mOldPage = null;
1797                 }
1798
1799                 // Load tags information for both revisions
1800                 $dbr = wfGetDB( DB_REPLICA );
1801                 $changeTagDefStore = MediaWikiServices::getInstance()->getChangeTagDefStore();
1802                 if ( $this->mOldid !== false ) {
1803                         $tagIds = $dbr->selectFieldValues(
1804                                 'change_tag',
1805                                 'ct_tag_id',
1806                                 [ 'ct_rev_id' => $this->mOldid ],
1807                                 __METHOD__
1808                         );
1809                         $tags = [];
1810                         foreach ( $tagIds as $tagId ) {
1811                                 try {
1812                                         $tags[] = $changeTagDefStore->getName( (int)$tagId );
1813                                 } catch ( NameTableAccessException $exception ) {
1814                                         continue;
1815                                 }
1816                         }
1817                         $this->mOldTags = implode( ',', $tags );
1818                 } else {
1819                         $this->mOldTags = false;
1820                 }
1821
1822                 $tagIds = $dbr->selectFieldValues(
1823                         'change_tag',
1824                         'ct_tag_id',
1825                         [ 'ct_rev_id' => $this->mNewid ],
1826                         __METHOD__
1827                 );
1828                 $tags = [];
1829                 foreach ( $tagIds as $tagId ) {
1830                         try {
1831                                 $tags[] = $changeTagDefStore->getName( (int)$tagId );
1832                         } catch ( NameTableAccessException $exception ) {
1833                                 continue;
1834                         }
1835                 }
1836                 $this->mNewTags = implode( ',', $tags );
1837
1838                 return true;
1839         }
1840
1841         /**
1842          * Load the text of the revisions, as well as revision data.
1843          * When the old revision is missing (mOldRev is false), loading mOldContent is not attempted.
1844          *
1845          * @return bool Whether the content of both revisions could be loaded successfully.
1846          *   (When mOldRev is false, that still counts as a success.)
1847          *
1848          */
1849         public function loadText() {
1850                 if ( $this->mTextLoaded == 2 ) {
1851                         return $this->loadRevisionData() && ( $this->mOldRev === false || $this->mOldContent )
1852                                 && $this->mNewContent;
1853                 }
1854
1855                 // Whether it succeeds or fails, we don't want to try again
1856                 $this->mTextLoaded = 2;
1857
1858                 if ( !$this->loadRevisionData() ) {
1859                         return false;
1860                 }
1861
1862                 if ( $this->mOldRev ) {
1863                         $this->mOldContent = $this->mOldRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1864                         if ( $this->mOldContent === null ) {
1865                                 return false;
1866                         }
1867                 }
1868
1869                 $this->mNewContent = $this->mNewRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1870                 Hooks::run( 'DifferenceEngineLoadTextAfterNewContentIsLoaded', [ $this ] );
1871                 if ( $this->mNewContent === null ) {
1872                         return false;
1873                 }
1874
1875                 return true;
1876         }
1877
1878         /**
1879          * Load the text of the new revision, not the old one
1880          *
1881          * @return bool Whether the content of the new revision could be loaded successfully.
1882          */
1883         public function loadNewText() {
1884                 if ( $this->mTextLoaded >= 1 ) {
1885                         return $this->loadRevisionData();
1886                 }
1887
1888                 $this->mTextLoaded = 1;
1889
1890                 if ( !$this->loadRevisionData() ) {
1891                         return false;
1892                 }
1893
1894                 $this->mNewContent = $this->mNewRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1895
1896                 Hooks::run( 'DifferenceEngineAfterLoadNewText', [ $this ] );
1897
1898                 return true;
1899         }
1900
1901 }