includes/diff/DifferenceEngine.php

   1 <?php
   2 /**
   3  * User interface for the difference engine.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup DifferenceEngine
  22  */
  23
  24 use MediaWiki\Storage\RevisionRecord;
  25 use MediaWiki\Storage\SlotRecord;
  26
  27 /**
  28  * DifferenceEngine is responsible for rendering the difference between two revisions as HTML.
  29  * This includes interpreting URL parameters, retrieving revision data, checking access permissions,
  30  * selecting and invoking the diff generator class for the individual slots, doing post-processing
  31  * on the generated diff, adding the rest of the HTML (such as headers) and writing the whole thing
  32  * to OutputPage.
  33  *
  34  * DifferenceEngine can be subclassed by extensions, by customizing
  35  * ContentHandler::createDifferenceEngine; the content handler will be selected based on the
  36  * content model of the main slot (of the new revision, when the two are different).
  37  * That might change after PageTypeHandler gets introduced.
  38  *
  39  * In the past, the class was also used for slot-level diff generation, and extensions might still
  40  * subclass it and add such functionality. When that is the case (sepcifically, when a
  41  * ContentHandler returns a standard SlotDiffRenderer but a nonstandard DifferenceEngine)
  42  * DifferenceEngineSlotDiffRenderer will be used to convert the old behavior into the new one.
  43  *
  44  * @ingroup DifferenceEngine
  45  *
  46  * @todo This class is huge and poorly defined. It should be split into a controller responsible
  47  * for interpreting query parameters, retrieving data and checking permissions; and a HTML renderer.
  48  */
  49 class DifferenceEngine extends ContextSource {
  50
  51         use DeprecationHelper;
  52
  53         /**
  54          * Constant to indicate diff cache compatibility.
  55          * Bump this when changing the diff formatting in a way that
  56          * fixes important bugs or such to force cached diff views to
  57          * clear.
  58          */
  59         const DIFF_VERSION = '1.12';
  60
  61         /**
  62          * Revision ID for the old revision. 0 for the revision previous to $mNewid, false
  63          * if the diff does not have an old revision (e.g. 'oldid=<first revision of page>&diff=prev'),
  64          * or the revision does not exist, null if the revision is unsaved.
  65          * @var int|false|null
  66          */
  67         protected $mOldid;
  68
  69         /**
  70          * Revision ID for the new revision. 0 for the last revision of the current page
  71          * (as defined by the request context), false if the revision does not exist, null
  72          * if it is unsaved, or an alias such as 'next'.
  73          * @var int|string|false|null
  74          */
  75         protected $mNewid;
  76
  77         /**
  78          * Old revision (left pane).
  79          * Allowed to be an unsaved revision, unlikely that's ever needed though.
  80          * False when the old revision does not exist; this can happen when using
  81          * diff=prev on the first revision. Null when the revision should exist but
  82          * doesn't (e.g. load failure); loadRevisionData() will return false in that
  83          * case. Also null until lazy-loaded. Ignored completely when isContentOverridden
  84          * is set.
  85          * Since 1.32 public access is deprecated.
  86          * @var Revision|null|false
  87          */
  88         protected $mOldRev;
  89
  90         /**
  91          * New revision (right pane).
  92          * Note that this might be an unsaved revision (e.g. for edit preview).
  93          * Null in case of load failure; diff methods will just return an error message in that case,
  94          * and loadRevisionData() will return false. Also null until lazy-loaded. Ignored completely
  95          * when isContentOverridden is set.
  96          * Since 1.32 public access is deprecated.
  97          * @var Revision|null
  98          */
  99         protected $mNewRev;
 100
 101         /**
 102          * Title of $mOldRev or null if the old revision does not exist or does not belong to a page.
 103          * Since 1.32 public access is deprecated and the property can be null.
 104          * @var Title|null
 105          */
 106         protected $mOldPage;
 107
 108         /**
 109          * Title of $mNewRev or null if the new revision does not exist or does not belong to a page.
 110          * Since 1.32 public access is deprecated and the property can be null.
 111          * @var Title|null
 112          */
 113         protected $mNewPage;
 114
 115         /**
 116          * Change tags of $mOldRev or null if it does not exist / is not saved.
 117          * @var string[]|null
 118          */
 119         private $mOldTags;
 120
 121         /**
 122          * Change tags of $mNewRev or null if it does not exist / is not saved.
 123          * @var string[]|null
 124          */
 125         private $mNewTags;
 126
 127         /**
 128          * @var Content|null
 129          * @deprecated since 1.32, content slots are now handled by the corresponding SlotDiffRenderer.
 130          *   This property is set to the content of the main slot, but not actually used for the main diff.
 131          */
 132         private $mOldContent;
 133
 134         /**
 135          * @var Content|null
 136          * @deprecated since 1.32, content slots are now handled by the corresponding SlotDiffRenderer.
 137          *   This property is set to the content of the main slot, but not actually used for the main diff.
 138          */
 139         private $mNewContent;
 140
 141         /** @var Language */
 142         protected $mDiffLang;
 143
 144         /** @var bool Have the revisions IDs been loaded */
 145         private $mRevisionsIdsLoaded = false;
 146
 147         /** @var bool Have the revisions been loaded */
 148         protected $mRevisionsLoaded = false;
 149
 150         /** @var int How many text blobs have been loaded, 0, 1 or 2? */
 151         protected $mTextLoaded = 0;
 152
 153         /**
 154          * Was the content overridden via setContent()?
 155          * If the content was overridden, most internal state (e.g. mOldid or mOldRev) should be ignored
 156          * and only mOldContent and mNewContent is reliable.
 157          * (Note that setRevisions() does not set this flag as in that case all properties are
 158          * overriden and remain consistent with each other, so no special handling is needed.)
 159          * @var bool
 160          */
 161         protected $isContentOverridden = false;
 162
 163         /** @var bool Was the diff fetched from cache? */
 164         protected $mCacheHit = false;
 165
 166         /**
 167          * Set this to true to add debug info to the HTML output.
 168          * Warning: this may cause RSS readers to spuriously mark articles as "new"
 169          * (T22601)
 170          */
 171         public $enableDebugComment = false;
 172
 173         /** @var bool If true, line X is not displayed when X is 1, for example
 174          *    to increase readability and conserve space with many small diffs.
 175          */
 176         protected $mReducedLineNumbers = false;
 177
 178         /** @var string Link to action=markpatrolled */
 179         protected $mMarkPatrolledLink = null;
 180
 181         /** @var bool Show rev_deleted content if allowed */
 182         protected $unhide = false;
 183
 184         /** @var bool Refresh the diff cache */
 185         protected $mRefreshCache = false;
 186
 187         /** @var SlotDiffRenderer[] DifferenceEngine classes for the slots, keyed by role name. */
 188         protected $slotDiffRenderers = null;
 189
 190         /**
 191          * Temporary hack for B/C while slot diff related methods of DifferenceEngine are being
 192          * deprecated. When true, we are inside a DifferenceEngineSlotDiffRenderer and
 193          * $slotDiffRenderers should not be used.
 194          * @var bool
 195          */
 196         protected $isSlotDiffRenderer = false;
 197
 198         /**#@-*/
 199
 200         /**
 201          * @param IContextSource|null $context Context to use, anything else will be ignored
 202          * @param int $old Old ID we want to show and diff with.
 203          * @param string|int $new Either revision ID or 'prev' or 'next'. Default: 0.
 204          * @param int $rcid Deprecated, no longer used!
 205          * @param bool $refreshCache If set, refreshes the diff cache
 206          * @param bool $unhide If set, allow viewing deleted revs
 207          */
 208         public function __construct( $context = null, $old = 0, $new = 0, $rcid = 0,
 209                 $refreshCache = false, $unhide = false
 210         ) {
 211                 $this->deprecatePublicProperty( 'mOldid', '1.32', __CLASS__ );
 212                 $this->deprecatePublicProperty( 'mNewid', '1.32', __CLASS__ );
 213                 $this->deprecatePublicProperty( 'mOldRev', '1.32', __CLASS__ );
 214                 $this->deprecatePublicProperty( 'mNewRev', '1.32', __CLASS__ );
 215                 $this->deprecatePublicProperty( 'mOldPage', '1.32', __CLASS__ );
 216                 $this->deprecatePublicProperty( 'mNewPage', '1.32', __CLASS__ );
 217                 $this->deprecatePublicProperty( 'mOldContent', '1.32', __CLASS__ );
 218                 $this->deprecatePublicProperty( 'mNewContent', '1.32', __CLASS__ );
 219                 $this->deprecatePublicProperty( 'mRevisionsLoaded', '1.32', __CLASS__ );
 220                 $this->deprecatePublicProperty( 'mTextLoaded', '1.32', __CLASS__ );
 221                 $this->deprecatePublicProperty( 'mCacheHit', '1.32', __CLASS__ );
 222
 223                 if ( $context instanceof IContextSource ) {
 224                         $this->setContext( $context );
 225                 }
 226
 227                 wfDebug( "DifferenceEngine old '$old' new '$new' rcid '$rcid'\n" );
 228
 229                 $this->mOldid = $old;
 230                 $this->mNewid = $new;
 231                 $this->mRefreshCache = $refreshCache;
 232                 $this->unhide = $unhide;
 233         }
 234
 235         /**
 236          * @return SlotDiffRenderer[] Diff renderers for each slot, keyed by role name.
 237          *   Includes slots only present in one of the revisions.
 238          */
 239         protected function getSlotDiffRenderers() {
 240                 if ( $this->isSlotDiffRenderer ) {
 241                         throw new LogicException( __METHOD__ . ' called in slot diff renderer mode' );
 242                 }
 243
 244                 if ( $this->slotDiffRenderers === null ) {
 245                         if ( !$this->loadRevisionData() ) {
 246                                 return [];
 247                         }
 248
 249                         $slotContents = $this->getSlotContents();
 250                         $this->slotDiffRenderers = array_map( function ( $contents ) {
 251                                 /** @var $content Content */
 252                                 $content = $contents['new'] ?: $contents['old'];
 253                                 return $content->getContentHandler()->getSlotDiffRenderer( $this->getContext() );
 254                         }, $slotContents );
 255                 }
 256                 return $this->slotDiffRenderers;
 257         }
 258
 259         /**
 260          * Mark this DifferenceEngine as a slot renderer (as opposed to a page renderer).
 261          * This is used in legacy mode when the DifferenceEngine is wrapped in a
 262          * DifferenceEngineSlotDiffRenderer.
 263          * @internal For use by DifferenceEngineSlotDiffRenderer only.
 264          */
 265         public function markAsSlotDiffRenderer() {
 266                 $this->isSlotDiffRenderer = true;
 267         }
 268
 269         /**
 270          * Get the old and new content objects for all slots.
 271          * This method does not do any permission checks.
 272          * @return array [ role => [ 'old' => SlotRecord|null, 'new' => SlotRecord|null ], ... ]
 273          */
 274         protected function getSlotContents() {
 275                 if ( $this->isContentOverridden ) {
 276                         return [
 277                                 SlotRecord::MAIN => [
 278                                         'old' => $this->mOldContent,
 279                                         'new' => $this->mNewContent,
 280                                 ]
 281                         ];
 282                 } elseif ( !$this->loadRevisionData() ) {
 283                         return [];
 284                 }
 285
 286                 $newSlots = $this->mNewRev->getRevisionRecord()->getSlots()->getSlots();
 287                 if ( $this->mOldRev ) {
 288                         $oldSlots = $this->mOldRev->getRevisionRecord()->getSlots()->getSlots();
 289                 } else {
 290                         $oldSlots = [];
 291                 }
 292                 // The order here will determine the visual order of the diff. The current logic is
 293                 // slots of the new revision first in natural order, then deleted ones. This is ad hoc
 294                 // and should not be relied on - in the future we may want the ordering to depend
 295                 // on the page type.
 296                 $roles = array_merge( array_keys( $newSlots ), array_keys( $oldSlots ) );
 297
 298                 $slots = [];
 299                 foreach ( $roles as $role ) {
 300                         $slots[$role] = [
 301                                 'old' => isset( $oldSlots[$role] ) ? $oldSlots[$role]->getContent() : null,
 302                                 'new' => isset( $newSlots[$role] ) ? $newSlots[$role]->getContent() : null,
 303                         ];
 304                 }
 305                 // move main slot to front
 306                 if ( isset( $slots[SlotRecord::MAIN] ) ) {
 307                         $slots = [ SlotRecord::MAIN => $slots[SlotRecord::MAIN] ] + $slots;
 308                 }
 309                 return $slots;
 310         }
 311
 312         public function getTitle() {
 313                 // T202454 avoid errors when there is no title
 314                 return parent::getTitle() ?: Title::makeTitle( NS_SPECIAL, 'BadTitle/DifferenceEngine' );
 315         }
 316
 317         /**
 318          * Set reduced line numbers mode.
 319          * When set, line X is not displayed when X is 1, for example to increase readability and
 320          * conserve space with many small diffs.
 321          * @param bool $value
 322          */
 323         public function setReducedLineNumbers( $value = true ) {
 324                 $this->mReducedLineNumbers = $value;
 325         }
 326
 327         /**
 328          * Get the language of the difference engine, defaults to page content language
 329          *
 330          * @return Language
 331          */
 332         public function getDiffLang() {
 333                 if ( $this->mDiffLang === null ) {
 334                         # Default language in which the diff text is written.
 335                         $this->mDiffLang = $this->getTitle()->getPageLanguage();
 336                 }
 337
 338                 return $this->mDiffLang;
 339         }
 340
 341         /**
 342          * @return bool
 343          */
 344         public function wasCacheHit() {
 345                 return $this->mCacheHit;
 346         }
 347
 348         /**
 349          * Get the ID of old revision (left pane) of the diff. 0 for the revision
 350          * previous to getNewid(), false if the old revision does not exist, null
 351          * if it's unsaved.
 352          * To get a real revision ID instead of 0, call loadRevisionData() first.
 353          * @return int|false|null
 354          */
 355         public function getOldid() {
 356                 $this->loadRevisionIds();
 357
 358                 return $this->mOldid;
 359         }
 360
 361         /**
 362          * Get the ID of new revision (right pane) of the diff. 0 for the current revision,
 363          * false if the new revision does not exist, null if it's unsaved.
 364          * To get a real revision ID instead of 0, call loadRevisionData() first.
 365          * @return int|false|null
 366          */
 367         public function getNewid() {
 368                 $this->loadRevisionIds();
 369
 370                 return $this->mNewid;
 371         }
 372
 373         /**
 374          * Get the left side of the diff.
 375          * Could be null when the first revision of the page is diffed to 'prev' (or in the case of
 376          * load failure).
 377          * @return RevisionRecord|null
 378          */
 379         public function getOldRevision() {
 380                 return $this->mOldRev ? $this->mOldRev->getRevisionRecord() : null;
 381         }
 382
 383         /**
 384          * Get the right side of the diff.
 385          * Should not be null but can still happen in the case of load failure.
 386          * @return RevisionRecord|null
 387          */
 388         public function getNewRevision() {
 389                 return $this->mNewRev ? $this->mNewRev->getRevisionRecord() : null;
 390         }
 391
 392         /**
 393          * Look up a special:Undelete link to the given deleted revision id,
 394          * as a workaround for being unable to load deleted diffs in currently.
 395          *
 396          * @param int $id Revision ID
 397          *
 398          * @return string|bool Link HTML or false
 399          */
 400         public function deletedLink( $id ) {
 401                 if ( $this->getUser()->isAllowed( 'deletedhistory' ) ) {
 402                         $dbr = wfGetDB( DB_REPLICA );
 403                         $arQuery = Revision::getArchiveQueryInfo();
 404                         $row = $dbr->selectRow(
 405                                 $arQuery['tables'],
 406                                 array_merge( $arQuery['fields'], [ 'ar_namespace', 'ar_title' ] ),
 407                                 [ 'ar_rev_id' => $id ],
 408                                 __METHOD__,
 409                                 [],
 410                                 $arQuery['joins']
 411                         );
 412                         if ( $row ) {
 413                                 $rev = Revision::newFromArchiveRow( $row );
 414                                 $title = Title::makeTitleSafe( $row->ar_namespace, $row->ar_title );
 415
 416                                 return SpecialPage::getTitleFor( 'Undelete' )->getFullURL( [
 417                                         'target' => $title->getPrefixedText(),
 418                                         'timestamp' => $rev->getTimestamp()
 419                                 ] );
 420                         }
 421                 }
 422
 423                 return false;
 424         }
 425
 426         /**
 427          * Build a wikitext link toward a deleted revision, if viewable.
 428          *
 429          * @param int $id Revision ID
 430          *
 431          * @return string Wikitext fragment
 432          */
 433         public function deletedIdMarker( $id ) {
 434                 $link = $this->deletedLink( $id );
 435                 if ( $link ) {
 436                         return "[$link $id]";
 437                 } else {
 438                         return (string)$id;
 439                 }
 440         }
 441
 442         private function showMissingRevision() {
 443                 $out = $this->getOutput();
 444
 445                 $missing = [];
 446                 if ( $this->mOldRev === null ||
 447                         ( $this->mOldRev && $this->mOldContent === null )
 448                 ) {
 449                         $missing[] = $this->deletedIdMarker( $this->mOldid );
 450                 }
 451                 if ( $this->mNewRev === null ||
 452                         ( $this->mNewRev && $this->mNewContent === null )
 453                 ) {
 454                         $missing[] = $this->deletedIdMarker( $this->mNewid );
 455                 }
 456
 457                 $out->setPageTitle( $this->msg( 'errorpagetitle' ) );
 458                 $msg = $this->msg( 'difference-missing-revision' )
 459                         ->params( $this->getLanguage()->listToText( $missing ) )
 460                         ->numParams( count( $missing ) )
 461                         ->parseAsBlock();
 462                 $out->addHTML( $msg );
 463         }
 464
 465         public function showDiffPage( $diffOnly = false ) {
 466                 # Allow frames except in certain special cases
 467                 $out = $this->getOutput();
 468                 $out->allowClickjacking();
 469                 $out->setRobotPolicy( 'noindex,nofollow' );
 470
 471                 // Allow extensions to add any extra output here
 472                 Hooks::run( 'DifferenceEngineShowDiffPage', [ $out ] );
 473
 474                 if ( !$this->loadRevisionData() ) {
 475                         if ( Hooks::run( 'DifferenceEngineShowDiffPageMaybeShowMissingRevision', [ $this ] ) ) {
 476                                 $this->showMissingRevision();
 477                         }
 478                         return;
 479                 }
 480
 481                 $user = $this->getUser();
 482                 $permErrors = [];
 483                 if ( $this->mNewPage ) {
 484                         $permErrors = $this->mNewPage->getUserPermissionsErrors( 'read', $user );
 485                 }
 486                 if ( $this->mOldPage ) {
 487                         $permErrors = wfMergeErrorArrays( $permErrors,
 488                                 $this->mOldPage->getUserPermissionsErrors( 'read', $user ) );
 489                 }
 490                 if ( count( $permErrors ) ) {
 491                         throw new PermissionsError( 'read', $permErrors );
 492                 }
 493
 494                 $rollback = '';
 495
 496                 $query = [];
 497                 # Carry over 'diffonly' param via navigation links
 498                 if ( $diffOnly != $user->getBoolOption( 'diffonly' ) ) {
 499                         $query['diffonly'] = $diffOnly;
 500                 }
 501                 # Cascade unhide param in links for easy deletion browsing
 502                 if ( $this->unhide ) {
 503                         $query['unhide'] = 1;
 504                 }
 505
 506                 # Check if one of the revisions is deleted/suppressed
 507                 $deleted = $suppressed = false;
 508                 $allowed = $this->mNewRev->userCan( Revision::DELETED_TEXT, $user );
 509
 510                 $revisionTools = [];
 511
 512                 # mOldRev is false if the difference engine is called with a "vague" query for
 513                 # a diff between a version V and its previous version V' AND the version V
 514                 # is the first version of that article. In that case, V' does not exist.
 515                 if ( $this->mOldRev === false ) {
 516                         if ( $this->mNewPage ) {
 517                                 $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 518                         }
 519                         $samePage = true;
 520                         $oldHeader = '';
 521                         // Allow extensions to change the $oldHeader variable
 522                         Hooks::run( 'DifferenceEngineOldHeaderNoOldRev', [ &$oldHeader ] );
 523                 } else {
 524                         Hooks::run( 'DiffViewHeader', [ $this, $this->mOldRev, $this->mNewRev ] );
 525
 526                         if ( !$this->mOldPage || !$this->mNewPage ) {
 527                                 // XXX say something to the user?
 528                                 $samePage = false;
 529                         } elseif ( $this->mNewPage->equals( $this->mOldPage ) ) {
 530                                 $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 531                                 $samePage = true;
 532                         } else {
 533                                 $out->setPageTitle( $this->msg( 'difference-title-multipage',
 534                                         $this->mOldPage->getPrefixedText(), $this->mNewPage->getPrefixedText() ) );
 535                                 $out->addSubtitle( $this->msg( 'difference-multipage' ) );
 536                                 $samePage = false;
 537                         }
 538
 539                         if ( $samePage && $this->mNewPage && $this->mNewPage->quickUserCan( 'edit', $user ) ) {
 540                                 if ( $this->mNewRev->isCurrent() && $this->mNewPage->userCan( 'rollback', $user ) ) {
 541                                         $rollbackLink = Linker::generateRollback( $this->mNewRev, $this->getContext() );
 542                                         if ( $rollbackLink ) {
 543                                                 $out->preventClickjacking();
 544                                                 $rollback = "\u{00A0}\u{00A0}\u{00A0}" . $rollbackLink;
 545                                         }
 546                                 }
 547
 548                                 if ( !$this->mOldRev->isDeleted( Revision::DELETED_TEXT ) &&
 549                                         !$this->mNewRev->isDeleted( Revision::DELETED_TEXT )
 550                                 ) {
 551                                         $undoLink = Html::element( 'a', [
 552                                                         'href' => $this->mNewPage->getLocalURL( [
 553                                                                 'action' => 'edit',
 554                                                                 'undoafter' => $this->mOldid,
 555                                                                 'undo' => $this->mNewid
 556                                                         ] ),
 557                                                         'title' => Linker::titleAttrib( 'undo' ),
 558                                                 ],
 559                                                 $this->msg( 'editundo' )->text()
 560                                         );
 561                                         $revisionTools['mw-diff-undo'] = $undoLink;
 562                                 }
 563                         }
 564
 565                         # Make "previous revision link"
 566                         if ( $samePage && $this->mOldPage && $this->mOldRev->getPrevious() ) {
 567                                 $prevlink = Linker::linkKnown(
 568                                         $this->mOldPage,
 569                                         $this->msg( 'previousdiff' )->escaped(),
 570                                         [ 'id' => 'differences-prevlink' ],
 571                                         [ 'diff' => 'prev', 'oldid' => $this->mOldid ] + $query
 572                                 );
 573                         } else {
 574                                 $prevlink = "\u{00A0}";
 575                         }
 576
 577                         if ( $this->mOldRev->isMinor() ) {
 578                                 $oldminor = ChangesList::flag( 'minor' );
 579                         } else {
 580                                 $oldminor = '';
 581                         }
 582
 583                         $ldel = $this->revisionDeleteLink( $this->mOldRev );
 584                         $oldRevisionHeader = $this->getRevisionHeader( $this->mOldRev, 'complete' );
 585                         $oldChangeTags = ChangeTags::formatSummaryRow( $this->mOldTags, 'diff', $this->getContext() );
 586
 587                         $oldHeader = '<div id="mw-diff-otitle1"><strong>' . $oldRevisionHeader . '</strong></div>' .
 588                                 '<div id="mw-diff-otitle2">' .
 589                                 Linker::revUserTools( $this->mOldRev, !$this->unhide ) . '</div>' .
 590                                 '<div id="mw-diff-otitle3">' . $oldminor .
 591                                 Linker::revComment( $this->mOldRev, !$diffOnly, !$this->unhide ) . $ldel . '</div>' .
 592                                 '<div id="mw-diff-otitle5">' . $oldChangeTags[0] . '</div>' .
 593                                 '<div id="mw-diff-otitle4">' . $prevlink . '</div>';
 594
 595                         // Allow extensions to change the $oldHeader variable
 596                         Hooks::run( 'DifferenceEngineOldHeader', [ $this, &$oldHeader, $prevlink, $oldminor,
 597                                 $diffOnly, $ldel, $this->unhide ] );
 598
 599                         if ( $this->mOldRev->isDeleted( Revision::DELETED_TEXT ) ) {
 600                                 $deleted = true; // old revisions text is hidden
 601                                 if ( $this->mOldRev->isDeleted( Revision::DELETED_RESTRICTED ) ) {
 602                                         $suppressed = true; // also suppressed
 603                                 }
 604                         }
 605
 606                         # Check if this user can see the revisions
 607                         if ( !$this->mOldRev->userCan( Revision::DELETED_TEXT, $user ) ) {
 608                                 $allowed = false;
 609                         }
 610                 }
 611
 612                 $out->addJsConfigVars( [
 613                         'wgDiffOldId' => $this->mOldid,
 614                         'wgDiffNewId' => $this->mNewid,
 615                 ] );
 616
 617                 # Make "next revision link"
 618                 # Skip next link on the top revision
 619                 if ( $samePage && $this->mNewPage && !$this->mNewRev->isCurrent() ) {
 620                         $nextlink = Linker::linkKnown(
 621                                 $this->mNewPage,
 622                                 $this->msg( 'nextdiff' )->escaped(),
 623                                 [ 'id' => 'differences-nextlink' ],
 624                                 [ 'diff' => 'next', 'oldid' => $this->mNewid ] + $query
 625                         );
 626                 } else {
 627                         $nextlink = "\u{00A0}";
 628                 }
 629
 630                 if ( $this->mNewRev->isMinor() ) {
 631                         $newminor = ChangesList::flag( 'minor' );
 632                 } else {
 633                         $newminor = '';
 634                 }
 635
 636                 # Handle RevisionDelete links...
 637                 $rdel = $this->revisionDeleteLink( $this->mNewRev );
 638
 639                 # Allow extensions to define their own revision tools
 640                 Hooks::run( 'DiffRevisionTools',
 641                         [ $this->mNewRev, &$revisionTools, $this->mOldRev, $user ] );
 642                 $formattedRevisionTools = [];
 643                 // Put each one in parentheses (poor man's button)
 644                 foreach ( $revisionTools as $key => $tool ) {
 645                         $toolClass = is_string( $key ) ? $key : 'mw-diff-tool';
 646                         $element = Html::rawElement(
 647                                 'span',
 648                                 [ 'class' => $toolClass ],
 649                                 $this->msg( 'parentheses' )->rawParams( $tool )->escaped()
 650                         );
 651                         $formattedRevisionTools[] = $element;
 652                 }
 653                 $newRevisionHeader = $this->getRevisionHeader( $this->mNewRev, 'complete' ) .
 654                         ' ' . implode( ' ', $formattedRevisionTools );
 655                 $newChangeTags = ChangeTags::formatSummaryRow( $this->mNewTags, 'diff', $this->getContext() );
 656
 657                 $newHeader = '<div id="mw-diff-ntitle1"><strong>' . $newRevisionHeader . '</strong></div>' .
 658                         '<div id="mw-diff-ntitle2">' . Linker::revUserTools( $this->mNewRev, !$this->unhide ) .
 659                         " $rollback</div>" .
 660                         '<div id="mw-diff-ntitle3">' . $newminor .
 661                         Linker::revComment( $this->mNewRev, !$diffOnly, !$this->unhide ) . $rdel . '</div>' .
 662                         '<div id="mw-diff-ntitle5">' . $newChangeTags[0] . '</div>' .
 663                         '<div id="mw-diff-ntitle4">' . $nextlink . $this->markPatrolledLink() . '</div>';
 664
 665                 // Allow extensions to change the $newHeader variable
 666                 Hooks::run( 'DifferenceEngineNewHeader', [ $this, &$newHeader, $formattedRevisionTools,
 667                         $nextlink, $rollback, $newminor, $diffOnly, $rdel, $this->unhide ] );
 668
 669                 if ( $this->mNewRev->isDeleted( Revision::DELETED_TEXT ) ) {
 670                         $deleted = true; // new revisions text is hidden
 671                         if ( $this->mNewRev->isDeleted( Revision::DELETED_RESTRICTED ) ) {
 672                                 $suppressed = true; // also suppressed
 673                         }
 674                 }
 675
 676                 # If the diff cannot be shown due to a deleted revision, then output
 677                 # the diff header and links to unhide (if available)...
 678                 if ( $deleted && ( !$this->unhide || !$allowed ) ) {
 679                         $this->showDiffStyle();
 680                         $multi = $this->getMultiNotice();
 681                         $out->addHTML( $this->addHeader( '', $oldHeader, $newHeader, $multi ) );
 682                         if ( !$allowed ) {
 683                                 $msg = $suppressed ? 'rev-suppressed-no-diff' : 'rev-deleted-no-diff';
 684                                 # Give explanation for why revision is not visible
 685                                 $out->wrapWikiMsg( "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 686                                         [ $msg ] );
 687                         } else {
 688                                 # Give explanation and add a link to view the diff...
 689                                 $query = $this->getRequest()->appendQueryValue( 'unhide', '1' );
 690                                 $link = $this->getTitle()->getFullURL( $query );
 691                                 $msg = $suppressed ? 'rev-suppressed-unhide-diff' : 'rev-deleted-unhide-diff';
 692                                 $out->wrapWikiMsg(
 693                                         "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 694                                         [ $msg, $link ]
 695                                 );
 696                         }
 697                 # Otherwise, output a regular diff...
 698                 } else {
 699                         # Add deletion notice if the user is viewing deleted content
 700                         $notice = '';
 701                         if ( $deleted ) {
 702                                 $msg = $suppressed ? 'rev-suppressed-diff-view' : 'rev-deleted-diff-view';
 703                                 $notice = "<div id='mw-$msg' class='mw-warning plainlinks'>\n" .
 704                                         $this->msg( $msg )->parse() .
 705                                         "</div>\n";
 706                         }
 707                         $this->showDiff( $oldHeader, $newHeader, $notice );
 708                         if ( !$diffOnly ) {
 709                                 $this->renderNewRevision();
 710                         }
 711                 }
 712         }
 713
 714         /**
 715          * Build a link to mark a change as patrolled.
 716          *
 717          * Returns empty string if there's either no revision to patrol or the user is not allowed to.
 718          * Side effect: When the patrol link is build, this method will call
 719          * OutputPage::preventClickjacking() and load mediawiki.page.patrol.ajax.
 720          *
 721          * @return string HTML or empty string
 722          */
 723         public function markPatrolledLink() {
 724                 if ( $this->mMarkPatrolledLink === null ) {
 725                         $linkInfo = $this->getMarkPatrolledLinkInfo();
 726                         // If false, there is no patrol link needed/allowed
 727                         if ( !$linkInfo || !$this->mNewPage ) {
 728                                 $this->mMarkPatrolledLink = '';
 729                         } else {
 730                                 $this->mMarkPatrolledLink = ' <span class="patrollink" data-mw="interface">[' .
 731                                         Linker::linkKnown(
 732                                                 $this->mNewPage,
 733                                                 $this->msg( 'markaspatrolleddiff' )->escaped(),
 734                                                 [],
 735                                                 [
 736                                                         'action' => 'markpatrolled',
 737                                                         'rcid' => $linkInfo['rcid'],
 738                                                 ]
 739                                         ) . ']</span>';
 740                                 // Allow extensions to change the markpatrolled link
 741                                 Hooks::run( 'DifferenceEngineMarkPatrolledLink', [ $this,
 742                                         &$this->mMarkPatrolledLink, $linkInfo['rcid'] ] );
 743                         }
 744                 }
 745                 return $this->mMarkPatrolledLink;
 746         }
 747
 748         /**
 749          * Returns an array of meta data needed to build a "mark as patrolled" link and
 750          * adds the mediawiki.page.patrol.ajax to the output.
 751          *
 752          * @return array|false An array of meta data for a patrol link (rcid only)
 753          *  or false if no link is needed
 754          */
 755         protected function getMarkPatrolledLinkInfo() {
 756                 global $wgUseRCPatrol;
 757
 758                 $user = $this->getUser();
 759
 760                 // Prepare a change patrol link, if applicable
 761                 if (
 762                         // Is patrolling enabled and the user allowed to?
 763                         $wgUseRCPatrol && $this->mNewPage && $this->mNewPage->quickUserCan( 'patrol', $user ) &&
 764                         // Only do this if the revision isn't more than 6 hours older
 765                         // than the Max RC age (6h because the RC might not be cleaned out regularly)
 766                         RecentChange::isInRCLifespan( $this->mNewRev->getTimestamp(), 21600 )
 767                 ) {
 768                         // Look for an unpatrolled change corresponding to this diff
 769                         $db = wfGetDB( DB_REPLICA );
 770                         $change = RecentChange::newFromConds(
 771                                 [
 772                                         'rc_timestamp' => $db->timestamp( $this->mNewRev->getTimestamp() ),
 773                                         'rc_this_oldid' => $this->mNewid,
 774                                         'rc_patrolled' => RecentChange::PRC_UNPATROLLED
 775                                 ],
 776                                 __METHOD__
 777                         );
 778
 779                         if ( $change && !$change->getPerformer()->equals( $user ) ) {
 780                                 $rcid = $change->getAttribute( 'rc_id' );
 781                         } else {
 782                                 // None found or the page has been created by the current user.
 783                                 // If the user could patrol this it already would be patrolled
 784                                 $rcid = 0;
 785                         }
 786
 787                         // Allow extensions to possibly change the rcid here
 788                         // For example the rcid might be set to zero due to the user
 789                         // being the same as the performer of the change but an extension
 790                         // might still want to show it under certain conditions
 791                         Hooks::run( 'DifferenceEngineMarkPatrolledRCID', [ &$rcid, $this, $change, $user ] );
 792
 793                         // Build the link
 794                         if ( $rcid ) {
 795                                 $this->getOutput()->preventClickjacking();
 796                                 if ( $user->isAllowed( 'writeapi' ) ) {
 797                                         $this->getOutput()->addModules( 'mediawiki.page.patrol.ajax' );
 798                                 }
 799
 800                                 return [
 801                                         'rcid' => $rcid,
 802                                 ];
 803                         }
 804                 }
 805
 806                 // No mark as patrolled link applicable
 807                 return false;
 808         }
 809
 810         /**
 811          * @param Revision $rev
 812          *
 813          * @return string
 814          */
 815         protected function revisionDeleteLink( $rev ) {
 816                 $link = Linker::getRevDeleteLink( $this->getUser(), $rev, $rev->getTitle() );
 817                 if ( $link !== '' ) {
 818                         $link = "\u{00A0}\u{00A0}\u{00A0}" . $link . ' ';
 819                 }
 820
 821                 return $link;
 822         }
 823
 824         /**
 825          * Show the new revision of the page.
 826          *
 827          * @note Not supported after calling setContent().
 828          */
 829         public function renderNewRevision() {
 830                 if ( $this->isContentOverridden ) {
 831                         // The code below only works with a Revision object. We could construct a fake revision
 832                         // (here or in setContent), but since this does not seem needed at the moment,
 833                         // we'll just fail for now.
 834                         throw new LogicException(
 835                                 __METHOD__
 836                                 . ' is not supported after calling setContent(). Use setRevisions() instead.'
 837                         );
 838                 }
 839
 840                 $out = $this->getOutput();
 841                 $revHeader = $this->getRevisionHeader( $this->mNewRev );
 842                 # Add "current version as of X" title
 843                 $out->addHTML( "<hr class='diff-hr' id='mw-oldid' />
 844                 <h2 class='diff-currentversion-title'>{$revHeader}</h2>\n" );
 845                 # Page content may be handled by a hooked call instead...
 846                 if ( Hooks::run( 'ArticleContentOnDiff', [ $this, $out ] ) ) {
 847                         $this->loadNewText();
 848                         if ( !$this->mNewPage ) {
 849                                 // New revision is unsaved; bail out.
 850                                 // TODO in theory rendering the new revision is a meaningful thing to do
 851                                 // even if it's unsaved, but a lot of untangling is required to do it safely.
 852                                 return;
 853                         }
 854
 855                         $out->setRevisionId( $this->mNewid );
 856                         $out->setRevisionTimestamp( $this->mNewRev->getTimestamp() );
 857                         $out->setArticleFlag( true );
 858
 859                         if ( !Hooks::run( 'ArticleRevisionViewCustom',
 860                                 [ $this->mNewRev->getRevisionRecord(), $this->mNewPage, $out ] )
 861                         ) {
 862                                 // Handled by extension
 863                                 // NOTE: sync with hooks called in Article::view()
 864                         } elseif ( !Hooks::run( 'ArticleContentViewCustom',
 865                                 [ $this->mNewContent, $this->mNewPage, $out ], '1.32' )
 866                         ) {
 867                                 // Handled by extension
 868                                 // NOTE: sync with hooks called in Article::view()
 869                         } else {
 870                                 // Normal page
 871                                 if ( $this->getTitle()->equals( $this->mNewPage ) ) {
 872                                         // If the Title stored in the context is the same as the one
 873                                         // of the new revision, we can use its associated WikiPage
 874                                         // object.
 875                                         $wikiPage = $this->getWikiPage();
 876                                 } else {
 877                                         // Otherwise we need to create our own WikiPage object
 878                                         $wikiPage = WikiPage::factory( $this->mNewPage );
 879                                 }
 880
 881                                 $parserOutput = $this->getParserOutput( $wikiPage, $this->mNewRev );
 882
 883                                 # WikiPage::getParserOutput() should not return false, but just in case
 884                                 if ( $parserOutput ) {
 885                                         // Allow extensions to change parser output here
 886                                         if ( Hooks::run( 'DifferenceEngineRenderRevisionAddParserOutput',
 887                                                 [ $this, $out, $parserOutput, $wikiPage ] )
 888                                         ) {
 889                                                 $out->addParserOutput( $parserOutput, [
 890                                                         'enableSectionEditLinks' => $this->mNewRev->isCurrent()
 891                                                                 && $this->mNewRev->getTitle()->quickUserCan( 'edit', $this->getUser() ),
 892                                                 ] );
 893                                         }
 894                                 }
 895                         }
 896                 }
 897
 898                 // Allow extensions to optionally not show the final patrolled link
 899                 if ( Hooks::run( 'DifferenceEngineRenderRevisionShowFinalPatrolLink' ) ) {
 900                         # Add redundant patrol link on bottom...
 901                         $out->addHTML( $this->markPatrolledLink() );
 902                 }
 903         }
 904
 905         /**
 906          * @param WikiPage $page
 907          * @param Revision $rev
 908          *
 909          * @return ParserOutput|bool False if the revision was not found
 910          */
 911         protected function getParserOutput( WikiPage $page, Revision $rev ) {
 912                 if ( !$rev->getId() ) {
 913                         // WikiPage::getParserOutput wants a revision ID. Passing 0 will incorrectly show
 914                         // the current revision, so fail instead. If need be, WikiPage::getParserOutput
 915                         // could be made to accept a Revision or RevisionRecord instead of the id.
 916                         return false;
 917                 }
 918
 919                 $parserOptions = $page->makeParserOptions( $this->getContext() );
 920                 $parserOutput = $page->getParserOutput( $parserOptions, $rev->getId() );
 921
 922                 return $parserOutput;
 923         }
 924
 925         /**
 926          * Get the diff text, send it to the OutputPage object
 927          * Returns false if the diff could not be generated, otherwise returns true
 928          *
 929          * @param string|bool $otitle Header for old text or false
 930          * @param string|bool $ntitle Header for new text or false
 931          * @param string $notice HTML between diff header and body
 932          *
 933          * @return bool
 934          */
 935         public function showDiff( $otitle, $ntitle, $notice = '' ) {
 936                 // Allow extensions to affect the output here
 937                 Hooks::run( 'DifferenceEngineShowDiff', [ $this ] );
 938
 939                 $diff = $this->getDiff( $otitle, $ntitle, $notice );
 940                 if ( $diff === false ) {
 941                         $this->showMissingRevision();
 942
 943                         return false;
 944                 } else {
 945                         $this->showDiffStyle();
 946                         $this->getOutput()->addHTML( $diff );
 947
 948                         return true;
 949                 }
 950         }
 951
 952         /**
 953          * Add style sheets for diff display.
 954          */
 955         public function showDiffStyle() {
 956                 if ( !$this->isSlotDiffRenderer ) {
 957                         $this->getOutput()->addModuleStyles( 'mediawiki.diff.styles' );
 958                         foreach ( $this->getSlotDiffRenderers() as $slotDiffRenderer ) {
 959                                 $slotDiffRenderer->addModules( $this->getOutput() );
 960                         }
 961                 }
 962         }
 963
 964         /**
 965          * Get complete diff table, including header
 966          *
 967          * @param string|bool $otitle Header for old text or false
 968          * @param string|bool $ntitle Header for new text or false
 969          * @param string $notice HTML between diff header and body
 970          *
 971          * @return mixed
 972          */
 973         public function getDiff( $otitle, $ntitle, $notice = '' ) {
 974                 $body = $this->getDiffBody();
 975                 if ( $body === false ) {
 976                         return false;
 977                 }
 978
 979                 $multi = $this->getMultiNotice();
 980                 // Display a message when the diff is empty
 981                 if ( $body === '' ) {
 982                         $notice .= '<div class="mw-diff-empty">' .
 983                                 $this->msg( 'diff-empty' )->parse() .
 984                                 "</div>\n";
 985                 }
 986
 987                 return $this->addHeader( $body, $otitle, $ntitle, $multi, $notice );
 988         }
 989
 990         /**
 991          * Get the diff table body, without header
 992          *
 993          * @return mixed (string/false)
 994          */
 995         public function getDiffBody() {
 996                 $this->mCacheHit = true;
 997                 // Check if the diff should be hidden from this user
 998                 if ( !$this->isContentOverridden ) {
 999                         if ( !$this->loadRevisionData() ) {
1000                                 return false;
1001                         } elseif ( $this->mOldRev &&
1002                                 !$this->mOldRev->userCan( Revision::DELETED_TEXT, $this->getUser() )
1003                         ) {
1004                                 return false;
1005                         } elseif ( $this->mNewRev &&
1006                                 !$this->mNewRev->userCan( Revision::DELETED_TEXT, $this->getUser() )
1007                         ) {
1008                                 return false;
1009                         }
1010                         // Short-circuit
1011                         if ( $this->mOldRev === false || ( $this->mOldRev && $this->mNewRev &&
1012                                 $this->mOldRev->getId() && $this->mOldRev->getId() == $this->mNewRev->getId() )
1013                         ) {
1014                                 if ( Hooks::run( 'DifferenceEngineShowEmptyOldContent', [ $this ] ) ) {
1015                                         return '';
1016                                 }
1017                         }
1018                 }
1019
1020                 // Cacheable?
1021                 $key = false;
1022                 $cache = ObjectCache::getMainWANInstance();
1023                 if ( $this->mOldid && $this->mNewid ) {
1024                         // Check if subclass is still using the old way
1025                         // for backwards-compatibility
1026                         $key = $this->getDiffBodyCacheKey();
1027                         if ( $key === null ) {
1028                                 $key = $cache->makeKey( ...$this->getDiffBodyCacheKeyParams() );
1029                         }
1030
1031                         // Try cache
1032                         if ( !$this->mRefreshCache ) {
1033                                 $difftext = $cache->get( $key );
1034                                 if ( $difftext ) {
1035                                         wfIncrStats( 'diff_cache.hit' );
1036                                         $difftext = $this->localiseDiff( $difftext );
1037                                         $difftext .= "\n<!-- diff cache key $key -->\n";
1038
1039                                         return $difftext;
1040                                 }
1041                         } // don't try to load but save the result
1042                 }
1043                 $this->mCacheHit = false;
1044
1045                 // Loadtext is permission safe, this just clears out the diff
1046                 if ( !$this->loadText() ) {
1047                         return false;
1048                 }
1049
1050                 $difftext = '';
1051                 // We've checked for revdelete at the beginning of this method; it's OK to ignore
1052                 // read permissions here.
1053                 $slotContents = $this->getSlotContents();
1054                 foreach ( $this->getSlotDiffRenderers() as $role => $slotDiffRenderer ) {
1055                         $slotDiff = $slotDiffRenderer->getDiff( $slotContents[$role]['old'],
1056                                 $slotContents[$role]['new'] );
1057                         if ( $slotDiff && $role !== SlotRecord::MAIN ) {
1058                                 // TODO use human-readable role name at least
1059                                 $slotTitle = $role;
1060                                 $difftext .= $this->getSlotHeader( $slotTitle );
1061                         }
1062                         $difftext .= $slotDiff;
1063                 }
1064
1065                 // Avoid PHP 7.1 warning from passing $this by reference
1066                 $diffEngine = $this;
1067
1068                 // Save to cache for 7 days
1069                 if ( !Hooks::run( 'AbortDiffCache', [ &$diffEngine ] ) ) {
1070                         wfIncrStats( 'diff_cache.uncacheable' );
1071                 } elseif ( $key !== false && $difftext !== false ) {
1072                         wfIncrStats( 'diff_cache.miss' );
1073                         $cache->set( $key, $difftext, 7 * 86400 );
1074                 } else {
1075                         wfIncrStats( 'diff_cache.uncacheable' );
1076                 }
1077                 // localise line numbers and title attribute text
1078                 if ( $difftext !== false ) {
1079                         $difftext = $this->localiseDiff( $difftext );
1080                 }
1081
1082                 return $difftext;
1083         }
1084
1085         /**
1086          * Get the diff table body for one slot, without header
1087          *
1088          * @param string $role
1089          * @return string|false
1090          */
1091         public function getDiffBodyForRole( $role ) {
1092                 $diffRenderers = $this->getSlotDiffRenderers();
1093                 if ( !isset( $diffRenderers[$role] ) ) {
1094                         return false;
1095                 }
1096
1097                 $slotContents = $this->getSlotContents();
1098                 $slotDiff = $diffRenderers[$role]->getDiff( $slotContents[$role]['old'],
1099                         $slotContents[$role]['new'] );
1100                 if ( !$slotDiff ) {
1101                         return false;
1102                 }
1103
1104                 if ( $role !== SlotRecord::MAIN ) {
1105                         // TODO use human-readable role name at least
1106                         $slotTitle = $role;
1107                         $slotDiff = $this->getSlotHeader( $slotTitle ) . $slotDiff;
1108                 }
1109
1110                 return $this->localiseDiff( $slotDiff );
1111         }
1112
1113         /**
1114          * Get a slot header for inclusion in a diff body (as a table row).
1115          *
1116          * @param string $headerText The text of the header
1117          * @return string
1118          *
1119          */
1120         protected function getSlotHeader( $headerText ) {
1121                 // The old revision is missing on oldid=<first>&diff=prev; only 2 columns in that case.
1122                 $columnCount = $this->mOldRev ? 4 : 2;
1123                 $userLang = $this->getLanguage()->getHtmlCode();
1124                 return Html::rawElement( 'tr', [ 'class' => 'mw-diff-slot-header', 'lang' => $userLang ],
1125                         Html::element( 'th', [ 'colspan' => $columnCount ], $headerText ) );
1126         }
1127
1128         /**
1129          * Returns the cache key for diff body text or content.
1130          *
1131          * @deprecated since 1.31, use getDiffBodyCacheKeyParams() instead
1132          * @since 1.23
1133          *
1134          * @throws MWException
1135          * @return string|null
1136          */
1137         protected function getDiffBodyCacheKey() {
1138                 return null;
1139         }
1140
1141         /**
1142          * Get the cache key parameters
1143          *
1144          * Subclasses can replace the first element in the array to something
1145          * more specific to the type of diff (e.g. "inline-diff"), or append
1146          * if the cache should vary on more things. Overriding entirely should
1147          * be avoided.
1148          *
1149          * @since 1.31
1150          *
1151          * @return array
1152          * @throws MWException
1153          */
1154         protected function getDiffBodyCacheKeyParams() {
1155                 if ( !$this->mOldid || !$this->mNewid ) {
1156                         throw new MWException( 'mOldid and mNewid must be set to get diff cache key.' );
1157                 }
1158
1159                 $engine = $this->getEngine();
1160                 $params = [
1161                         'diff',
1162                         $engine,
1163                         self::DIFF_VERSION,
1164                         "old-{$this->mOldid}",
1165                         "rev-{$this->mNewid}"
1166                 ];
1167
1168                 if ( $engine === 'wikidiff2' ) {
1169                         $params[] = phpversion( 'wikidiff2' );
1170                         $params[] = $this->getConfig()->get( 'WikiDiff2MovedParagraphDetectionCutoff' );
1171                 }
1172
1173                 if ( !$this->isSlotDiffRenderer ) {
1174                         foreach ( $this->getSlotDiffRenderers() as $slotDiffRenderer ) {
1175                                 $params = array_merge( $params, $slotDiffRenderer->getExtraCacheKeys() );
1176                         }
1177                 }
1178
1179                 return $params;
1180         }
1181
1182         /**
1183          * Implements DifferenceEngineSlotDiffRenderer::getExtraCacheKeys(). Only used when
1184          * DifferenceEngine is wrapped in DifferenceEngineSlotDiffRenderer.
1185          * @return array
1186          * @internal for use by DifferenceEngineSlotDiffRenderer only
1187          * @deprecated
1188          */
1189         public function getExtraCacheKeys() {
1190                 // This method is called when the DifferenceEngine is used for a slot diff. We only care
1191                 // about special things, not the revision IDs, which are added to the cache key by the
1192                 // page-level DifferenceEngine, and which might not have a valid value for this object.
1193                 $this->mOldid = 123456789;
1194                 $this->mNewid = 987654321;
1195
1196                 // This will repeat a bunch of unnecessary key fields for each slot. Not nice but harmless.
1197                 $cacheString = $this->getDiffBodyCacheKey();
1198                 if ( $cacheString ) {
1199                         return [ $cacheString ];
1200                 }
1201
1202                 $params = $this->getDiffBodyCacheKeyParams();
1203
1204                 // Try to get rid of the standard keys to keep the cache key human-readable:
1205                 // call the getDiffBodyCacheKeyParams implementation of the base class, and if
1206                 // the child class includes the same keys, drop them.
1207                 // Uses an obscure PHP feature where static calls to non-static methods are allowed
1208                 // as long as we are already in a non-static method of the same class, and the call context
1209                 // ($this) will be inherited.
1210                 // phpcs:ignore Squiz.Classes.SelfMemberReference.NotUsed
1211                 $standardParams = DifferenceEngine::getDiffBodyCacheKeyParams();
1212                 if ( array_slice( $params, 0, count( $standardParams ) ) === $standardParams ) {
1213                         $params = array_slice( $params, count( $standardParams ) );
1214                 }
1215
1216                 return $params;
1217         }
1218
1219         /**
1220          * Generate a diff, no caching.
1221          *
1222          * @since 1.21
1223          *
1224          * @param Content $old Old content
1225          * @param Content $new New content
1226          *
1227          * @throws Exception If old or new content is not an instance of TextContent.
1228          * @return bool|string
1229          *
1230          * @deprecated since 1.32, use a SlotDiffRenderer instead.
1231          */
1232         public function generateContentDiffBody( Content $old, Content $new ) {
1233                 $slotDiffRenderer = $new->getContentHandler()->getSlotDiffRenderer( $this->getContext() );
1234                 if (
1235                         $slotDiffRenderer instanceof DifferenceEngineSlotDiffRenderer
1236                         && $this->isSlotDiffRenderer
1237                 ) {
1238                         // Oops, we are just about to enter an infinite loop (the slot-level DifferenceEngine
1239                         // called a DifferenceEngineSlotDiffRenderer that wraps the same DifferenceEngine class).
1240                         // This will happen when a content model has no custom slot diff renderer, it does have
1241                         // a custom difference engine, but that does not override this method.
1242                         throw new Exception( get_class( $this ) . ': could not maintain backwards compatibility. '
1243                                 . 'Please use a SlotDiffRenderer.' );
1244                 }
1245                 return $slotDiffRenderer->getDiff( $old, $new ) . $this->getDebugString();
1246         }
1247
1248         /**
1249          * Generate a diff, no caching
1250          *
1251          * @param string $otext Old text, must be already segmented
1252          * @param string $ntext New text, must be already segmented
1253          *
1254          * @throws Exception If content handling for text content is configured in a way
1255          *   that makes maintaining B/C hard.
1256          * @return bool|string
1257          *
1258          * @deprecated since 1.32, use a TextSlotDiffRenderer instead.
1259          */
1260         public function generateTextDiffBody( $otext, $ntext ) {
1261                 $slotDiffRenderer = ContentHandler::getForModelID( CONTENT_MODEL_TEXT )
1262                         ->getSlotDiffRenderer( $this->getContext() );
1263                 if ( !( $slotDiffRenderer instanceof TextSlotDiffRenderer ) ) {
1264                         // Someone used the GetSlotDiffRenderer hook to replace the renderer.
1265                         // This is too unlikely to happen to bother handling properly.
1266                         throw new Exception( 'The slot diff renderer for text content should be a '
1267                                 . 'TextSlotDiffRenderer subclass' );
1268                 }
1269                 return $slotDiffRenderer->getTextDiff( $otext, $ntext ) . $this->getDebugString();
1270         }
1271
1272         /**
1273          * Process $wgExternalDiffEngine and get a sane, usable engine
1274          *
1275          * @return bool|string 'wikidiff2', path to an executable, or false
1276          * @internal For use by this class and TextSlotDiffRenderer only.
1277          */
1278         public static function getEngine() {
1279                 global $wgExternalDiffEngine;
1280                 // We use the global here instead of Config because we write to the value,
1281                 // and Config is not mutable.
1282                 if ( $wgExternalDiffEngine == 'wikidiff' || $wgExternalDiffEngine == 'wikidiff3' ) {
1283                         wfDeprecated( "\$wgExternalDiffEngine = '{$wgExternalDiffEngine}'", '1.27' );
1284                         $wgExternalDiffEngine = false;
1285                 } elseif ( $wgExternalDiffEngine == 'wikidiff2' ) {
1286                         wfDeprecated( "\$wgExternalDiffEngine = '{$wgExternalDiffEngine}'", '1.32' );
1287                         $wgExternalDiffEngine = false;
1288                 } elseif ( !is_string( $wgExternalDiffEngine ) && $wgExternalDiffEngine !== false ) {
1289                         // And prevent people from shooting themselves in the foot...
1290                         wfWarn( '$wgExternalDiffEngine is set to a non-string value, forcing it to false' );
1291                         $wgExternalDiffEngine = false;
1292                 }
1293
1294                 if ( is_string( $wgExternalDiffEngine ) && is_executable( $wgExternalDiffEngine ) ) {
1295                         return $wgExternalDiffEngine;
1296                 } elseif ( $wgExternalDiffEngine === false && function_exists( 'wikidiff2_do_diff' ) ) {
1297                         return 'wikidiff2';
1298                 } else {
1299                         // Native PHP
1300                         return false;
1301                 }
1302         }
1303
1304         /**
1305          * Generates diff, to be wrapped internally in a logging/instrumentation
1306          *
1307          * @param string $otext Old text, must be already segmented
1308          * @param string $ntext New text, must be already segmented
1309          *
1310          * @throws Exception If content handling for text content is configured in a way
1311          *   that makes maintaining B/C hard.
1312          * @return bool|string
1313          *
1314          * @deprecated since 1.32, use a TextSlotDiffRenderer instead.
1315          */
1316         protected function textDiff( $otext, $ntext ) {
1317                 $slotDiffRenderer = ContentHandler::getForModelID( CONTENT_MODEL_TEXT )
1318                         ->getSlotDiffRenderer( $this->getContext() );
1319                 if ( !( $slotDiffRenderer instanceof TextSlotDiffRenderer ) ) {
1320                         // Someone used the GetSlotDiffRenderer hook to replace the renderer.
1321                         // This is too unlikely to happen to bother handling properly.
1322                         throw new Exception( 'The slot diff renderer for text content should be a '
1323                                 . 'TextSlotDiffRenderer subclass' );
1324                 }
1325                 return $slotDiffRenderer->getTextDiff( $otext, $ntext ) . $this->getDebugString();
1326         }
1327
1328         /**
1329          * Generate a debug comment indicating diff generating time,
1330          * server node, and generator backend.
1331          *
1332          * @param string $generator : What diff engine was used
1333          *
1334          * @return string
1335          */
1336         protected function debug( $generator = "internal" ) {
1337                 global $wgShowHostnames;
1338                 if ( !$this->enableDebugComment ) {
1339                         return '';
1340                 }
1341                 $data = [ $generator ];
1342                 if ( $wgShowHostnames ) {
1343                         $data[] = wfHostname();
1344                 }
1345                 $data[] = wfTimestamp( TS_DB );
1346
1347                 return "<!-- diff generator: " .
1348                         implode( " ", array_map( "htmlspecialchars", $data ) ) .
1349                         " -->\n";
1350         }
1351
1352         private function getDebugString() {
1353                 $engine = self::getEngine();
1354                 if ( $engine === 'wikidiff2' ) {
1355                         return $this->debug( 'wikidiff2' );
1356                 } elseif ( $engine === false ) {
1357                         return $this->debug( 'native PHP' );
1358                 } else {
1359                         return $this->debug( "external $engine" );
1360                 }
1361         }
1362
1363         /**
1364          * Localise diff output
1365          *
1366          * @param string $text
1367          * @return string
1368          */
1369         private function localiseDiff( $text ) {
1370                 $text = $this->localiseLineNumbers( $text );
1371                 if ( $this->getEngine() === 'wikidiff2' &&
1372                         version_compare( phpversion( 'wikidiff2' ), '1.5.1', '>=' )
1373                 ) {
1374                         $text = $this->addLocalisedTitleTooltips( $text );
1375                 }
1376                 return $text;
1377         }
1378
1379         /**
1380          * Replace line numbers with the text in the user's language
1381          *
1382          * @param string $text
1383          *
1384          * @return mixed
1385          */
1386         public function localiseLineNumbers( $text ) {
1387                 return preg_replace_callback(
1388                         '/<!--LINE (\d+)-->/',
1389                         [ $this, 'localiseLineNumbersCb' ],
1390                         $text
1391                 );
1392         }
1393
1394         public function localiseLineNumbersCb( $matches ) {
1395                 if ( $matches[1] === '1' && $this->mReducedLineNumbers ) {
1396                         return '';
1397                 }
1398
1399                 return $this->msg( 'lineno' )->numParams( $matches[1] )->escaped();
1400         }
1401
1402         /**
1403          * Add title attributes for tooltips on moved paragraph indicators
1404          *
1405          * @param string $text
1406          * @return string
1407          */
1408         private function addLocalisedTitleTooltips( $text ) {
1409                 return preg_replace_callback(
1410                         '/class="mw-diff-movedpara-(left|right)"/',
1411                         [ $this, 'addLocalisedTitleTooltipsCb' ],
1412                         $text
1413                 );
1414         }
1415
1416         /**
1417          * @param array $matches
1418          * @return string
1419          */
1420         private function addLocalisedTitleTooltipsCb( array $matches ) {
1421                 $key = $matches[1] === 'right' ?
1422                         'diff-paragraph-moved-toold' :
1423                         'diff-paragraph-moved-tonew';
1424                 return $matches[0] . ' title="' . $this->msg( $key )->escaped() . '"';
1425         }
1426
1427         /**
1428          * If there are revisions between the ones being compared, return a note saying so.
1429          *
1430          * @return string
1431          */
1432         public function getMultiNotice() {
1433                 // The notice only make sense if we are diffing two saved revisions of the same page.
1434                 if (
1435                         !$this->mOldRev || !$this->mNewRev
1436                         || !$this->mOldPage || !$this->mNewPage
1437                         || !$this->mOldPage->equals( $this->mNewPage )
1438                 ) {
1439                         return '';
1440                 }
1441
1442                 if ( $this->mOldRev->getTimestamp() > $this->mNewRev->getTimestamp() ) {
1443                         $oldRev = $this->mNewRev; // flip
1444                         $newRev = $this->mOldRev; // flip
1445                 } else { // normal case
1446                         $oldRev = $this->mOldRev;
1447                         $newRev = $this->mNewRev;
1448                 }
1449
1450                 // Sanity: don't show the notice if too many rows must be scanned
1451                 // @todo show some special message for that case
1452                 $nEdits = $this->mNewPage->countRevisionsBetween( $oldRev, $newRev, 1000 );
1453                 if ( $nEdits > 0 && $nEdits <= 1000 ) {
1454                         $limit = 100; // use diff-multi-manyusers if too many users
1455                         $users = $this->mNewPage->getAuthorsBetween( $oldRev, $newRev, $limit );
1456                         $numUsers = count( $users );
1457
1458                         if ( $numUsers == 1 && $users[0] == $newRev->getUserText( Revision::RAW ) ) {
1459                                 $numUsers = 0; // special case to say "by the same user" instead of "by one other user"
1460                         }
1461
1462                         return self::intermediateEditsMsg( $nEdits, $numUsers, $limit );
1463                 }
1464
1465                 return ''; // nothing
1466         }
1467
1468         /**
1469          * Get a notice about how many intermediate edits and users there are
1470          *
1471          * @param int $numEdits
1472          * @param int $numUsers
1473          * @param int $limit
1474          *
1475          * @return string
1476          */
1477         public static function intermediateEditsMsg( $numEdits, $numUsers, $limit ) {
1478                 if ( $numUsers === 0 ) {
1479                         $msg = 'diff-multi-sameuser';
1480                 } elseif ( $numUsers > $limit ) {
1481                         $msg = 'diff-multi-manyusers';
1482                         $numUsers = $limit;
1483                 } else {
1484                         $msg = 'diff-multi-otherusers';
1485                 }
1486
1487                 return wfMessage( $msg )->numParams( $numEdits, $numUsers )->parse();
1488         }
1489
1490         /**
1491          * Get a header for a specified revision.
1492          *
1493          * @param Revision $rev
1494          * @param string $complete 'complete' to get the header wrapped depending
1495          *        the visibility of the revision and a link to edit the page.
1496          *
1497          * @return string HTML fragment
1498          */
1499         public function getRevisionHeader( Revision $rev, $complete = '' ) {
1500                 $lang = $this->getLanguage();
1501                 $user = $this->getUser();
1502                 $revtimestamp = $rev->getTimestamp();
1503                 $timestamp = $lang->userTimeAndDate( $revtimestamp, $user );
1504                 $dateofrev = $lang->userDate( $revtimestamp, $user );
1505                 $timeofrev = $lang->userTime( $revtimestamp, $user );
1506
1507                 $header = $this->msg(
1508                         $rev->isCurrent() ? 'currentrev-asof' : 'revisionasof',
1509                         $timestamp,
1510                         $dateofrev,
1511                         $timeofrev
1512                 )->escaped();
1513
1514                 if ( $complete !== 'complete' ) {
1515                         return $header;
1516                 }
1517
1518                 $title = $rev->getTitle();
1519
1520                 $header = Linker::linkKnown( $title, $header, [],
1521                         [ 'oldid' => $rev->getId() ] );
1522
1523                 if ( $rev->userCan( Revision::DELETED_TEXT, $user ) ) {
1524                         $editQuery = [ 'action' => 'edit' ];
1525                         if ( !$rev->isCurrent() ) {
1526                                 $editQuery['oldid'] = $rev->getId();
1527                         }
1528
1529                         $key = $title->quickUserCan( 'edit', $user ) ? 'editold' : 'viewsourceold';
1530                         $msg = $this->msg( $key )->escaped();
1531                         $editLink = $this->msg( 'parentheses' )->rawParams(
1532                                 Linker::linkKnown( $title, $msg, [], $editQuery ) )->escaped();
1533                         $header .= ' ' . Html::rawElement(
1534                                 'span',
1535                                 [ 'class' => 'mw-diff-edit' ],
1536                                 $editLink
1537                         );
1538                         if ( $rev->isDeleted( Revision::DELETED_TEXT ) ) {
1539                                 $header = Html::rawElement(
1540                                         'span',
1541                                         [ 'class' => 'history-deleted' ],
1542                                         $header
1543                                 );
1544                         }
1545                 } else {
1546                         $header = Html::rawElement( 'span', [ 'class' => 'history-deleted' ], $header );
1547                 }
1548
1549                 return $header;
1550         }
1551
1552         /**
1553          * Add the header to a diff body
1554          *
1555          * @param string $diff Diff body
1556          * @param string $otitle Old revision header
1557          * @param string $ntitle New revision header
1558          * @param string $multi Notice telling user that there are intermediate
1559          *   revisions between the ones being compared
1560          * @param string $notice Other notices, e.g. that user is viewing deleted content
1561          *
1562          * @return string
1563          */
1564         public function addHeader( $diff, $otitle, $ntitle, $multi = '', $notice = '' ) {
1565                 // shared.css sets diff in interface language/dir, but the actual content
1566                 // is often in a different language, mostly the page content language/dir
1567                 $header = Html::openElement( 'table', [
1568                         'class' => [ 'diff', 'diff-contentalign-' . $this->getDiffLang()->alignStart() ],
1569                         'data-mw' => 'interface',
1570                 ] );
1571                 $userLang = htmlspecialchars( $this->getLanguage()->getHtmlCode() );
1572
1573                 if ( !$diff && !$otitle ) {
1574                         $header .= "
1575                         <tr class=\"diff-title\" lang=\"{$userLang}\">
1576                         <td class=\"diff-ntitle\">{$ntitle}</td>
1577                         </tr>";
1578                         $multiColspan = 1;
1579                 } else {
1580                         if ( $diff ) { // Safari/Chrome show broken output if cols not used
1581                                 $header .= "
1582                                 <col class=\"diff-marker\" />
1583                                 <col class=\"diff-content\" />
1584                                 <col class=\"diff-marker\" />
1585                                 <col class=\"diff-content\" />";
1586                                 $colspan = 2;
1587                                 $multiColspan = 4;
1588                         } else {
1589                                 $colspan = 1;
1590                                 $multiColspan = 2;
1591                         }
1592                         if ( $otitle || $ntitle ) {
1593                                 $header .= "
1594                                 <tr class=\"diff-title\" lang=\"{$userLang}\">
1595                                 <td colspan=\"$colspan\" class=\"diff-otitle\">{$otitle}</td>
1596                                 <td colspan=\"$colspan\" class=\"diff-ntitle\">{$ntitle}</td>
1597                                 </tr>";
1598                         }
1599                 }
1600
1601                 if ( $multi != '' ) {
1602                         $header .= "<tr><td colspan=\"{$multiColspan}\" " .
1603                                 "class=\"diff-multi\" lang=\"{$userLang}\">{$multi}</td></tr>";
1604                 }
1605                 if ( $notice != '' ) {
1606                         $header .= "<tr><td colspan=\"{$multiColspan}\" " .
1607                                 "class=\"diff-notice\" lang=\"{$userLang}\">{$notice}</td></tr>";
1608                 }
1609
1610                 return $header . $diff . "</table>";
1611         }
1612
1613         /**
1614          * Use specified text instead of loading from the database
1615          * @param Content $oldContent
1616          * @param Content $newContent
1617          * @since 1.21
1618          * @deprecated since 1.32, use setRevisions or ContentHandler::getSlotDiffRenderer.
1619          */
1620         public function setContent( Content $oldContent, Content $newContent ) {
1621                 $this->mOldContent = $oldContent;
1622                 $this->mNewContent = $newContent;
1623
1624                 $this->mTextLoaded = 2;
1625                 $this->mRevisionsLoaded = true;
1626                 $this->isContentOverridden = true;
1627                 $this->slotDiffRenderers = null;
1628         }
1629
1630         /**
1631          * Use specified text instead of loading from the database.
1632          * @param RevisionRecord|null $oldRevision
1633          * @param RevisionRecord $newRevision
1634          */
1635         public function setRevisions(
1636                 RevisionRecord $oldRevision = null, RevisionRecord $newRevision
1637         ) {
1638                 if ( $oldRevision ) {
1639                         $this->mOldRev = new Revision( $oldRevision );
1640                         $this->mOldid = $oldRevision->getId();
1641                         $this->mOldPage = Title::newFromLinkTarget( $oldRevision->getPageAsLinkTarget() );
1642                         // This method is meant for edit diffs and such so there is no reason to provide a
1643                         // revision that's not readable to the user, but check it just in case.
1644                         $this->mOldContent = $oldRevision ? $oldRevision->getContent( SlotRecord::MAIN,
1645                                 RevisionRecord::FOR_THIS_USER, $this->getUser() ) : null;
1646                 } else {
1647                         $this->mOldPage = null;
1648                         $this->mOldRev = $this->mOldid = false;
1649                 }
1650                 $this->mNewRev = new Revision( $newRevision );
1651                 $this->mNewid = $newRevision->getId();
1652                 $this->mNewPage = Title::newFromLinkTarget( $newRevision->getPageAsLinkTarget() );
1653                 $this->mNewContent = $newRevision->getContent( SlotRecord::MAIN,
1654                         RevisionRecord::FOR_THIS_USER, $this->getUser() );
1655
1656                 $this->mRevisionsIdsLoaded = $this->mRevisionsLoaded = true;
1657                 $this->mTextLoaded = !!$oldRevision + 1;
1658                 $this->isContentOverridden = false;
1659                 $this->slotDiffRenderers = null;
1660         }
1661
1662         /**
1663          * Set the language in which the diff text is written
1664          *
1665          * @param Language $lang
1666          * @since 1.19
1667          */
1668         public function setTextLanguage( $lang ) {
1669                 if ( !$lang instanceof Language ) {
1670                         wfDeprecated( __METHOD__ . ' with other type than Language for $lang', '1.32' );
1671                 }
1672                 $this->mDiffLang = wfGetLangObj( $lang );
1673         }
1674
1675         /**
1676          * Maps a revision pair definition as accepted by DifferenceEngine constructor
1677          * to a pair of actual integers representing revision ids.
1678          *
1679          * @param int $old Revision id, e.g. from URL parameter 'oldid'
1680          * @param int|string $new Revision id or strings 'next' or 'prev', e.g. from URL parameter 'diff'
1681          *
1682          * @return array List of two revision ids, older first, later second.
1683          *     Zero signifies invalid argument passed.
1684          *     false signifies that there is no previous/next revision ($old is the oldest/newest one).
1685          */
1686         public function mapDiffPrevNext( $old, $new ) {
1687                 if ( $new === 'prev' ) {
1688                         // Show diff between revision $old and the previous one. Get previous one from DB.
1689                         $newid = intval( $old );
1690                         $oldid = $this->getTitle()->getPreviousRevisionID( $newid );
1691                 } elseif ( $new === 'next' ) {
1692                         // Show diff between revision $old and the next one. Get next one from DB.
1693                         $oldid = intval( $old );
1694                         $newid = $this->getTitle()->getNextRevisionID( $oldid );
1695                 } else {
1696                         $oldid = intval( $old );
1697                         $newid = intval( $new );
1698                 }
1699
1700                 return [ $oldid, $newid ];
1701         }
1702
1703         /**
1704          * Load revision IDs
1705          */
1706         private function loadRevisionIds() {
1707                 if ( $this->mRevisionsIdsLoaded ) {
1708                         return;
1709                 }
1710
1711                 $this->mRevisionsIdsLoaded = true;
1712
1713                 $old = $this->mOldid;
1714                 $new = $this->mNewid;
1715
1716                 list( $this->mOldid, $this->mNewid ) = self::mapDiffPrevNext( $old, $new );
1717                 if ( $new === 'next' && $this->mNewid === false ) {
1718                         # if no result, NewId points to the newest old revision. The only newer
1719                         # revision is cur, which is "0".
1720                         $this->mNewid = 0;
1721                 }
1722
1723                 Hooks::run(
1724                         'NewDifferenceEngine',
1725                         [ $this->getTitle(), &$this->mOldid, &$this->mNewid, $old, $new ]
1726                 );
1727         }
1728
1729         /**
1730          * Load revision metadata for the specified revisions. If newid is 0, then compare
1731          * the old revision in oldid to the current revision of the current page (as defined
1732          * by the request context); if oldid is 0, then compare the revision in newid to the
1733          * immediately previous one.
1734          *
1735          * If oldid is false, leave the corresponding revision object set
1736          * to false. This can happen with 'diff=prev' pointing to a non-existent revision,
1737          * and is also used directly by the API.
1738          *
1739          * @return bool Whether both revisions were loaded successfully. Setting mOldRev
1740          *   to false counts as successful loading.
1741          */
1742         public function loadRevisionData() {
1743                 if ( $this->mRevisionsLoaded ) {
1744                         return $this->isContentOverridden || $this->mNewRev && !is_null( $this->mOldRev );
1745                 }
1746
1747                 // Whether it succeeds or fails, we don't want to try again
1748                 $this->mRevisionsLoaded = true;
1749
1750                 $this->loadRevisionIds();
1751
1752                 // Load the new revision object
1753                 if ( $this->mNewid ) {
1754                         $this->mNewRev = Revision::newFromId( $this->mNewid );
1755                 } else {
1756                         $this->mNewRev = Revision::newFromTitle(
1757                                 $this->getTitle(),
1758                                 false,
1759                                 Revision::READ_NORMAL
1760                         );
1761                 }
1762
1763                 if ( !$this->mNewRev instanceof Revision ) {
1764                         return false;
1765                 }
1766
1767                 // Update the new revision ID in case it was 0 (makes life easier doing UI stuff)
1768                 $this->mNewid = $this->mNewRev->getId();
1769                 if ( $this->mNewid ) {
1770                         $this->mNewPage = $this->mNewRev->getTitle();
1771                 } else {
1772                         $this->mNewPage = null;
1773                 }
1774
1775                 // Load the old revision object
1776                 $this->mOldRev = false;
1777                 if ( $this->mOldid ) {
1778                         $this->mOldRev = Revision::newFromId( $this->mOldid );
1779                 } elseif ( $this->mOldid === 0 ) {
1780                         $rev = $this->mNewRev->getPrevious();
1781                         if ( $rev ) {
1782                                 $this->mOldid = $rev->getId();
1783                                 $this->mOldRev = $rev;
1784                         } else {
1785                                 // No previous revision; mark to show as first-version only.
1786                                 $this->mOldid = false;
1787                                 $this->mOldRev = false;
1788                         }
1789                 } /* elseif ( $this->mOldid === false ) leave mOldRev false; */
1790
1791                 if ( is_null( $this->mOldRev ) ) {
1792                         return false;
1793                 }
1794
1795                 if ( $this->mOldRev && $this->mOldRev->getId() ) {
1796                         $this->mOldPage = $this->mOldRev->getTitle();
1797                 } else {
1798                         $this->mOldPage = null;
1799                 }
1800
1801                 // Load tags information for both revisions
1802                 $dbr = wfGetDB( DB_REPLICA );
1803                 if ( $this->mOldid !== false ) {
1804                         $this->mOldTags = $dbr->selectField(
1805                                 'tag_summary',
1806                                 'ts_tags',
1807                                 [ 'ts_rev_id' => $this->mOldid ],
1808                                 __METHOD__
1809                         );
1810                 } else {
1811                         $this->mOldTags = false;
1812                 }
1813                 $this->mNewTags = $dbr->selectField(
1814                         'tag_summary',
1815                         'ts_tags',
1816                         [ 'ts_rev_id' => $this->mNewid ],
1817                         __METHOD__
1818                 );
1819
1820                 return true;
1821         }
1822
1823         /**
1824          * Load the text of the revisions, as well as revision data.
1825          * When the old revision is missing (mOldRev is false), loading mOldContent is not attempted.
1826          *
1827          * @return bool Whether the content of both revisions could be loaded successfully.
1828          *   (When mOldRev is false, that still counts as a success.)
1829          *
1830          */
1831         public function loadText() {
1832                 if ( $this->mTextLoaded == 2 ) {
1833                         return $this->loadRevisionData() && ( $this->mOldRev === false || $this->mOldContent )
1834                                 && $this->mNewContent;
1835                 }
1836
1837                 // Whether it succeeds or fails, we don't want to try again
1838                 $this->mTextLoaded = 2;
1839
1840                 if ( !$this->loadRevisionData() ) {
1841                         return false;
1842                 }
1843
1844                 if ( $this->mOldRev ) {
1845                         $this->mOldContent = $this->mOldRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1846                         if ( $this->mOldContent === null ) {
1847                                 return false;
1848                         }
1849                 }
1850
1851                 $this->mNewContent = $this->mNewRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1852                 Hooks::run( 'DifferenceEngineLoadTextAfterNewContentIsLoaded', [ $this ] );
1853                 if ( $this->mNewContent === null ) {
1854                         return false;
1855                 }
1856
1857                 return true;
1858         }
1859
1860         /**
1861          * Load the text of the new revision, not the old one
1862          *
1863          * @return bool Whether the content of the new revision could be loaded successfully.
1864          */
1865         public function loadNewText() {
1866                 if ( $this->mTextLoaded >= 1 ) {
1867                         return $this->loadRevisionData();
1868                 }
1869
1870                 $this->mTextLoaded = 1;
1871
1872                 if ( !$this->loadRevisionData() ) {
1873                         return false;
1874                 }
1875
1876                 $this->mNewContent = $this->mNewRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1877
1878                 Hooks::run( 'DifferenceEngineAfterLoadNewText', [ $this ] );
1879
1880                 return true;
1881         }
1882
1883 }