includes/diff/DifferenceEngine.php

   1 <?php
   2 /**
   3  * User interface for the difference engine.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup DifferenceEngine
  22  */
  23
  24 use MediaWiki\MediaWikiServices;
  25 use MediaWiki\Permissions\PermissionManager;
  26 use MediaWiki\Revision\RevisionRecord;
  27 use MediaWiki\Revision\SlotRecord;
  28 use MediaWiki\Storage\NameTableAccessException;
  29
  30 /**
  31  * DifferenceEngine is responsible for rendering the difference between two revisions as HTML.
  32  * This includes interpreting URL parameters, retrieving revision data, checking access permissions,
  33  * selecting and invoking the diff generator class for the individual slots, doing post-processing
  34  * on the generated diff, adding the rest of the HTML (such as headers) and writing the whole thing
  35  * to OutputPage.
  36  *
  37  * DifferenceEngine can be subclassed by extensions, by customizing
  38  * ContentHandler::createDifferenceEngine; the content handler will be selected based on the
  39  * content model of the main slot (of the new revision, when the two are different).
  40  * That might change after PageTypeHandler gets introduced.
  41  *
  42  * In the past, the class was also used for slot-level diff generation, and extensions might still
  43  * subclass it and add such functionality. When that is the case (sepcifically, when a
  44  * ContentHandler returns a standard SlotDiffRenderer but a nonstandard DifferenceEngine)
  45  * DifferenceEngineSlotDiffRenderer will be used to convert the old behavior into the new one.
  46  *
  47  * @ingroup DifferenceEngine
  48  *
  49  * @todo This class is huge and poorly defined. It should be split into a controller responsible
  50  * for interpreting query parameters, retrieving data and checking permissions; and a HTML renderer.
  51  */
  52 class DifferenceEngine extends ContextSource {
  53
  54         use DeprecationHelper;
  55
  56         /**
  57          * Constant to indicate diff cache compatibility.
  58          * Bump this when changing the diff formatting in a way that
  59          * fixes important bugs or such to force cached diff views to
  60          * clear.
  61          */
  62         const DIFF_VERSION = '1.12';
  63
  64         /**
  65          * Revision ID for the old revision. 0 for the revision previous to $mNewid, false
  66          * if the diff does not have an old revision (e.g. 'oldid=<first revision of page>&diff=prev'),
  67          * or the revision does not exist, null if the revision is unsaved.
  68          * @var int|false|null
  69          */
  70         protected $mOldid;
  71
  72         /**
  73          * Revision ID for the new revision. 0 for the last revision of the current page
  74          * (as defined by the request context), false if the revision does not exist, null
  75          * if it is unsaved, or an alias such as 'next'.
  76          * @var int|string|false|null
  77          */
  78         protected $mNewid;
  79
  80         /**
  81          * Old revision (left pane).
  82          * Allowed to be an unsaved revision, unlikely that's ever needed though.
  83          * False when the old revision does not exist; this can happen when using
  84          * diff=prev on the first revision. Null when the revision should exist but
  85          * doesn't (e.g. load failure); loadRevisionData() will return false in that
  86          * case. Also null until lazy-loaded. Ignored completely when isContentOverridden
  87          * is set.
  88          * Since 1.32 public access is deprecated.
  89          * @var Revision|null|false
  90          */
  91         protected $mOldRev;
  92
  93         /**
  94          * New revision (right pane).
  95          * Note that this might be an unsaved revision (e.g. for edit preview).
  96          * Null in case of load failure; diff methods will just return an error message in that case,
  97          * and loadRevisionData() will return false. Also null until lazy-loaded. Ignored completely
  98          * when isContentOverridden is set.
  99          * Since 1.32 public access is deprecated.
 100          * @var Revision|null
 101          */
 102         protected $mNewRev;
 103
 104         /**
 105          * Title of $mOldRev or null if the old revision does not exist or does not belong to a page.
 106          * Since 1.32 public access is deprecated and the property can be null.
 107          * @var Title|null
 108          */
 109         protected $mOldPage;
 110
 111         /**
 112          * Title of $mNewRev or null if the new revision does not exist or does not belong to a page.
 113          * Since 1.32 public access is deprecated and the property can be null.
 114          * @var Title|null
 115          */
 116         protected $mNewPage;
 117
 118         /**
 119          * Change tags of $mOldRev or null if it does not exist / is not saved.
 120          * @var string[]|null
 121          */
 122         private $mOldTags;
 123
 124         /**
 125          * Change tags of $mNewRev or null if it does not exist / is not saved.
 126          * @var string[]|null
 127          */
 128         private $mNewTags;
 129
 130         /**
 131          * @var Content|null
 132          * @deprecated since 1.32, content slots are now handled by the corresponding SlotDiffRenderer.
 133          *   This property is set to the content of the main slot, but not actually used for the main diff.
 134          */
 135         private $mOldContent;
 136
 137         /**
 138          * @var Content|null
 139          * @deprecated since 1.32, content slots are now handled by the corresponding SlotDiffRenderer.
 140          *   This property is set to the content of the main slot, but not actually used for the main diff.
 141          */
 142         private $mNewContent;
 143
 144         /** @var Language */
 145         protected $mDiffLang;
 146
 147         /** @var bool Have the revisions IDs been loaded */
 148         private $mRevisionsIdsLoaded = false;
 149
 150         /** @var bool Have the revisions been loaded */
 151         protected $mRevisionsLoaded = false;
 152
 153         /** @var int How many text blobs have been loaded, 0, 1 or 2? */
 154         protected $mTextLoaded = 0;
 155
 156         /**
 157          * Was the content overridden via setContent()?
 158          * If the content was overridden, most internal state (e.g. mOldid or mOldRev) should be ignored
 159          * and only mOldContent and mNewContent is reliable.
 160          * (Note that setRevisions() does not set this flag as in that case all properties are
 161          * overriden and remain consistent with each other, so no special handling is needed.)
 162          * @var bool
 163          */
 164         protected $isContentOverridden = false;
 165
 166         /** @var bool Was the diff fetched from cache? */
 167         protected $mCacheHit = false;
 168
 169         /**
 170          * Set this to true to add debug info to the HTML output.
 171          * Warning: this may cause RSS readers to spuriously mark articles as "new"
 172          * (T22601)
 173          */
 174         public $enableDebugComment = false;
 175
 176         /** @var bool If true, line X is not displayed when X is 1, for example
 177          *    to increase readability and conserve space with many small diffs.
 178          */
 179         protected $mReducedLineNumbers = false;
 180
 181         /** @var string Link to action=markpatrolled */
 182         protected $mMarkPatrolledLink = null;
 183
 184         /** @var bool Show rev_deleted content if allowed */
 185         protected $unhide = false;
 186
 187         /** @var bool Refresh the diff cache */
 188         protected $mRefreshCache = false;
 189
 190         /** @var SlotDiffRenderer[] DifferenceEngine classes for the slots, keyed by role name. */
 191         protected $slotDiffRenderers = null;
 192
 193         /**
 194          * Temporary hack for B/C while slot diff related methods of DifferenceEngine are being
 195          * deprecated. When true, we are inside a DifferenceEngineSlotDiffRenderer and
 196          * $slotDiffRenderers should not be used.
 197          * @var bool
 198          */
 199         protected $isSlotDiffRenderer = false;
 200
 201         /**#@-*/
 202
 203         /**
 204          * @param IContextSource|null $context Context to use, anything else will be ignored
 205          * @param int $old Old ID we want to show and diff with.
 206          * @param string|int $new Either revision ID or 'prev' or 'next'. Default: 0.
 207          * @param int $rcid Deprecated, no longer used!
 208          * @param bool $refreshCache If set, refreshes the diff cache
 209          * @param bool $unhide If set, allow viewing deleted revs
 210          */
 211         public function __construct( $context = null, $old = 0, $new = 0, $rcid = 0,
 212                 $refreshCache = false, $unhide = false
 213         ) {
 214                 $this->deprecatePublicProperty( 'mOldid', '1.32', __CLASS__ );
 215                 $this->deprecatePublicProperty( 'mNewid', '1.32', __CLASS__ );
 216                 $this->deprecatePublicProperty( 'mOldRev', '1.32', __CLASS__ );
 217                 $this->deprecatePublicProperty( 'mNewRev', '1.32', __CLASS__ );
 218                 $this->deprecatePublicProperty( 'mOldPage', '1.32', __CLASS__ );
 219                 $this->deprecatePublicProperty( 'mNewPage', '1.32', __CLASS__ );
 220                 $this->deprecatePublicProperty( 'mOldContent', '1.32', __CLASS__ );
 221                 $this->deprecatePublicProperty( 'mNewContent', '1.32', __CLASS__ );
 222                 $this->deprecatePublicProperty( 'mRevisionsLoaded', '1.32', __CLASS__ );
 223                 $this->deprecatePublicProperty( 'mTextLoaded', '1.32', __CLASS__ );
 224                 $this->deprecatePublicProperty( 'mCacheHit', '1.32', __CLASS__ );
 225
 226                 if ( $context instanceof IContextSource ) {
 227                         $this->setContext( $context );
 228                 }
 229
 230                 wfDebug( "DifferenceEngine old '$old' new '$new' rcid '$rcid'\n" );
 231
 232                 $this->mOldid = $old;
 233                 $this->mNewid = $new;
 234                 $this->mRefreshCache = $refreshCache;
 235                 $this->unhide = $unhide;
 236         }
 237
 238         /**
 239          * @return SlotDiffRenderer[] Diff renderers for each slot, keyed by role name.
 240          *   Includes slots only present in one of the revisions.
 241          */
 242         protected function getSlotDiffRenderers() {
 243                 if ( $this->isSlotDiffRenderer ) {
 244                         throw new LogicException( __METHOD__ . ' called in slot diff renderer mode' );
 245                 }
 246
 247                 if ( $this->slotDiffRenderers === null ) {
 248                         if ( !$this->loadRevisionData() ) {
 249                                 return [];
 250                         }
 251
 252                         $slotContents = $this->getSlotContents();
 253                         $this->slotDiffRenderers = array_map( function ( $contents ) {
 254                                 /** @var Content $content */
 255                                 $content = $contents['new'] ?: $contents['old'];
 256                                 return $content->getContentHandler()->getSlotDiffRenderer( $this->getContext() );
 257                         }, $slotContents );
 258                 }
 259                 return $this->slotDiffRenderers;
 260         }
 261
 262         /**
 263          * Mark this DifferenceEngine as a slot renderer (as opposed to a page renderer).
 264          * This is used in legacy mode when the DifferenceEngine is wrapped in a
 265          * DifferenceEngineSlotDiffRenderer.
 266          * @internal For use by DifferenceEngineSlotDiffRenderer only.
 267          */
 268         public function markAsSlotDiffRenderer() {
 269                 $this->isSlotDiffRenderer = true;
 270         }
 271
 272         /**
 273          * Get the old and new content objects for all slots.
 274          * This method does not do any permission checks.
 275          * @return array [ role => [ 'old' => SlotRecord|null, 'new' => SlotRecord|null ], ... ]
 276          */
 277         protected function getSlotContents() {
 278                 if ( $this->isContentOverridden ) {
 279                         return [
 280                                 SlotRecord::MAIN => [
 281                                         'old' => $this->mOldContent,
 282                                         'new' => $this->mNewContent,
 283                                 ]
 284                         ];
 285                 } elseif ( !$this->loadRevisionData() ) {
 286                         return [];
 287                 }
 288
 289                 $newSlots = $this->mNewRev->getRevisionRecord()->getSlots()->getSlots();
 290                 if ( $this->mOldRev ) {
 291                         $oldSlots = $this->mOldRev->getRevisionRecord()->getSlots()->getSlots();
 292                 } else {
 293                         $oldSlots = [];
 294                 }
 295                 // The order here will determine the visual order of the diff. The current logic is
 296                 // slots of the new revision first in natural order, then deleted ones. This is ad hoc
 297                 // and should not be relied on - in the future we may want the ordering to depend
 298                 // on the page type.
 299                 $roles = array_merge( array_keys( $newSlots ), array_keys( $oldSlots ) );
 300
 301                 $slots = [];
 302                 foreach ( $roles as $role ) {
 303                         $slots[$role] = [
 304                                 'old' => isset( $oldSlots[$role] ) ? $oldSlots[$role]->getContent() : null,
 305                                 'new' => isset( $newSlots[$role] ) ? $newSlots[$role]->getContent() : null,
 306                         ];
 307                 }
 308                 // move main slot to front
 309                 if ( isset( $slots[SlotRecord::MAIN] ) ) {
 310                         $slots = [ SlotRecord::MAIN => $slots[SlotRecord::MAIN] ] + $slots;
 311                 }
 312                 return $slots;
 313         }
 314
 315         public function getTitle() {
 316                 // T202454 avoid errors when there is no title
 317                 return parent::getTitle() ?: Title::makeTitle( NS_SPECIAL, 'BadTitle/DifferenceEngine' );
 318         }
 319
 320         /**
 321          * Set reduced line numbers mode.
 322          * When set, line X is not displayed when X is 1, for example to increase readability and
 323          * conserve space with many small diffs.
 324          * @param bool $value
 325          */
 326         public function setReducedLineNumbers( $value = true ) {
 327                 $this->mReducedLineNumbers = $value;
 328         }
 329
 330         /**
 331          * Get the language of the difference engine, defaults to page content language
 332          *
 333          * @return Language
 334          */
 335         public function getDiffLang() {
 336                 if ( $this->mDiffLang === null ) {
 337                         # Default language in which the diff text is written.
 338                         $this->mDiffLang = $this->getTitle()->getPageLanguage();
 339                 }
 340
 341                 return $this->mDiffLang;
 342         }
 343
 344         /**
 345          * @return bool
 346          */
 347         public function wasCacheHit() {
 348                 return $this->mCacheHit;
 349         }
 350
 351         /**
 352          * Get the ID of old revision (left pane) of the diff. 0 for the revision
 353          * previous to getNewid(), false if the old revision does not exist, null
 354          * if it's unsaved.
 355          * To get a real revision ID instead of 0, call loadRevisionData() first.
 356          * @return int|false|null
 357          */
 358         public function getOldid() {
 359                 $this->loadRevisionIds();
 360
 361                 return $this->mOldid;
 362         }
 363
 364         /**
 365          * Get the ID of new revision (right pane) of the diff. 0 for the current revision,
 366          * false if the new revision does not exist, null if it's unsaved.
 367          * To get a real revision ID instead of 0, call loadRevisionData() first.
 368          * @return int|false|null
 369          */
 370         public function getNewid() {
 371                 $this->loadRevisionIds();
 372
 373                 return $this->mNewid;
 374         }
 375
 376         /**
 377          * Get the left side of the diff.
 378          * Could be null when the first revision of the page is diffed to 'prev' (or in the case of
 379          * load failure).
 380          * @return RevisionRecord|null
 381          */
 382         public function getOldRevision() {
 383                 return $this->mOldRev ? $this->mOldRev->getRevisionRecord() : null;
 384         }
 385
 386         /**
 387          * Get the right side of the diff.
 388          * Should not be null but can still happen in the case of load failure.
 389          * @return RevisionRecord|null
 390          */
 391         public function getNewRevision() {
 392                 return $this->mNewRev ? $this->mNewRev->getRevisionRecord() : null;
 393         }
 394
 395         /**
 396          * Look up a special:Undelete link to the given deleted revision id,
 397          * as a workaround for being unable to load deleted diffs in currently.
 398          *
 399          * @param int $id Revision ID
 400          *
 401          * @return string|bool Link HTML or false
 402          */
 403         public function deletedLink( $id ) {
 404                 if ( $this->getUser()->isAllowed( 'deletedhistory' ) ) {
 405                         $dbr = wfGetDB( DB_REPLICA );
 406                         $arQuery = Revision::getArchiveQueryInfo();
 407                         $row = $dbr->selectRow(
 408                                 $arQuery['tables'],
 409                                 array_merge( $arQuery['fields'], [ 'ar_namespace', 'ar_title' ] ),
 410                                 [ 'ar_rev_id' => $id ],
 411                                 __METHOD__,
 412                                 [],
 413                                 $arQuery['joins']
 414                         );
 415                         if ( $row ) {
 416                                 $rev = Revision::newFromArchiveRow( $row );
 417                                 $title = Title::makeTitleSafe( $row->ar_namespace, $row->ar_title );
 418
 419                                 return SpecialPage::getTitleFor( 'Undelete' )->getFullURL( [
 420                                         'target' => $title->getPrefixedText(),
 421                                         'timestamp' => $rev->getTimestamp()
 422                                 ] );
 423                         }
 424                 }
 425
 426                 return false;
 427         }
 428
 429         /**
 430          * Build a wikitext link toward a deleted revision, if viewable.
 431          *
 432          * @param int $id Revision ID
 433          *
 434          * @return string Wikitext fragment
 435          */
 436         public function deletedIdMarker( $id ) {
 437                 $link = $this->deletedLink( $id );
 438                 if ( $link ) {
 439                         return "[$link $id]";
 440                 } else {
 441                         return (string)$id;
 442                 }
 443         }
 444
 445         private function showMissingRevision() {
 446                 $out = $this->getOutput();
 447
 448                 $missing = [];
 449                 if ( $this->mOldRev === null ||
 450                         ( $this->mOldRev && $this->mOldContent === null )
 451                 ) {
 452                         $missing[] = $this->deletedIdMarker( $this->mOldid );
 453                 }
 454                 if ( $this->mNewRev === null ||
 455                         ( $this->mNewRev && $this->mNewContent === null )
 456                 ) {
 457                         $missing[] = $this->deletedIdMarker( $this->mNewid );
 458                 }
 459
 460                 $out->setPageTitle( $this->msg( 'errorpagetitle' ) );
 461                 $msg = $this->msg( 'difference-missing-revision' )
 462                         ->params( $this->getLanguage()->listToText( $missing ) )
 463                         ->numParams( count( $missing ) )
 464                         ->parseAsBlock();
 465                 $out->addHTML( $msg );
 466         }
 467
 468         public function showDiffPage( $diffOnly = false ) {
 469                 # Allow frames except in certain special cases
 470                 $out = $this->getOutput();
 471                 $out->allowClickjacking();
 472                 $out->setRobotPolicy( 'noindex,nofollow' );
 473
 474                 // Allow extensions to add any extra output here
 475                 Hooks::run( 'DifferenceEngineShowDiffPage', [ $out ] );
 476
 477                 if ( !$this->loadRevisionData() ) {
 478                         if ( Hooks::run( 'DifferenceEngineShowDiffPageMaybeShowMissingRevision', [ $this ] ) ) {
 479                                 $this->showMissingRevision();
 480                         }
 481                         return;
 482                 }
 483
 484                 $user = $this->getUser();
 485                 $permErrors = [];
 486                 if ( $this->mNewPage ) {
 487                         $permErrors = $this->mNewPage->getUserPermissionsErrors( 'read', $user );
 488                 }
 489                 if ( $this->mOldPage ) {
 490                         $permErrors = wfMergeErrorArrays( $permErrors,
 491                                 $this->mOldPage->getUserPermissionsErrors( 'read', $user ) );
 492                 }
 493                 if ( count( $permErrors ) ) {
 494                         throw new PermissionsError( 'read', $permErrors );
 495                 }
 496
 497                 $rollback = '';
 498
 499                 $query = [];
 500                 # Carry over 'diffonly' param via navigation links
 501                 if ( $diffOnly != $user->getBoolOption( 'diffonly' ) ) {
 502                         $query['diffonly'] = $diffOnly;
 503                 }
 504                 # Cascade unhide param in links for easy deletion browsing
 505                 if ( $this->unhide ) {
 506                         $query['unhide'] = 1;
 507                 }
 508
 509                 # Check if one of the revisions is deleted/suppressed
 510                 $deleted = $suppressed = false;
 511                 $allowed = $this->mNewRev->userCan( RevisionRecord::DELETED_TEXT, $user );
 512
 513                 $revisionTools = [];
 514
 515                 # mOldRev is false if the difference engine is called with a "vague" query for
 516                 # a diff between a version V and its previous version V' AND the version V
 517                 # is the first version of that article. In that case, V' does not exist.
 518                 if ( $this->mOldRev === false ) {
 519                         if ( $this->mNewPage ) {
 520                                 $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 521                         }
 522                         $samePage = true;
 523                         $oldHeader = '';
 524                         // Allow extensions to change the $oldHeader variable
 525                         Hooks::run( 'DifferenceEngineOldHeaderNoOldRev', [ &$oldHeader ] );
 526                 } else {
 527                         Hooks::run( 'DiffViewHeader', [ $this, $this->mOldRev, $this->mNewRev ] );
 528
 529                         if ( !$this->mOldPage || !$this->mNewPage ) {
 530                                 // XXX say something to the user?
 531                                 $samePage = false;
 532                         } elseif ( $this->mNewPage->equals( $this->mOldPage ) ) {
 533                                 $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 534                                 $samePage = true;
 535                         } else {
 536                                 $out->setPageTitle( $this->msg( 'difference-title-multipage',
 537                                         $this->mOldPage->getPrefixedText(), $this->mNewPage->getPrefixedText() ) );
 538                                 $out->addSubtitle( $this->msg( 'difference-multipage' ) );
 539                                 $samePage = false;
 540                         }
 541
 542                         $permissionManager = MediaWikiServices::getInstance()->getPermissionManager();
 543
 544                         if ( $samePage && $this->mNewPage && $permissionManager->userCan(
 545                                 'edit', $user, $this->mNewPage, PermissionManager::RIGOR_QUICK
 546                         ) ) {
 547                                 if ( $this->mNewRev->isCurrent() && $permissionManager->userCan(
 548                                         'rollback', $user, $this->mNewPage
 549                                 ) ) {
 550                                         $rollbackLink = Linker::generateRollback( $this->mNewRev, $this->getContext(),
 551                                                 [ 'noBrackets' ] );
 552                                         if ( $rollbackLink ) {
 553                                                 $out->preventClickjacking();
 554                                                 $rollback = "\u{00A0}\u{00A0}\u{00A0}" . $rollbackLink;
 555                                         }
 556                                 }
 557
 558                                 if ( !$this->mOldRev->isDeleted( RevisionRecord::DELETED_TEXT ) &&
 559                                         !$this->mNewRev->isDeleted( RevisionRecord::DELETED_TEXT )
 560                                 ) {
 561                                         $undoLink = Html::element( 'a', [
 562                                                         'href' => $this->mNewPage->getLocalURL( [
 563                                                                 'action' => 'edit',
 564                                                                 'undoafter' => $this->mOldid,
 565                                                                 'undo' => $this->mNewid
 566                                                         ] ),
 567                                                         'title' => Linker::titleAttrib( 'undo' ),
 568                                                 ],
 569                                                 $this->msg( 'editundo' )->text()
 570                                         );
 571                                         $revisionTools['mw-diff-undo'] = $undoLink;
 572                                 }
 573                         }
 574
 575                         # Make "previous revision link"
 576                         if ( $samePage && $this->mOldPage && $this->mOldRev->getPrevious() ) {
 577                                 $prevlink = Linker::linkKnown(
 578                                         $this->mOldPage,
 579                                         $this->msg( 'previousdiff' )->escaped(),
 580                                         [ 'id' => 'differences-prevlink' ],
 581                                         [ 'diff' => 'prev', 'oldid' => $this->mOldid ] + $query
 582                                 );
 583                         } else {
 584                                 $prevlink = "\u{00A0}";
 585                         }
 586
 587                         if ( $this->mOldRev->isMinor() ) {
 588                                 $oldminor = ChangesList::flag( 'minor' );
 589                         } else {
 590                                 $oldminor = '';
 591                         }
 592
 593                         $ldel = $this->revisionDeleteLink( $this->mOldRev );
 594                         $oldRevisionHeader = $this->getRevisionHeader( $this->mOldRev, 'complete' );
 595                         $oldChangeTags = ChangeTags::formatSummaryRow( $this->mOldTags, 'diff', $this->getContext() );
 596
 597                         $oldHeader = '<div id="mw-diff-otitle1"><strong>' . $oldRevisionHeader . '</strong></div>' .
 598                                 '<div id="mw-diff-otitle2">' .
 599                                 Linker::revUserTools( $this->mOldRev, !$this->unhide ) . '</div>' .
 600                                 '<div id="mw-diff-otitle3">' . $oldminor .
 601                                 Linker::revComment( $this->mOldRev, !$diffOnly, !$this->unhide ) . $ldel . '</div>' .
 602                                 '<div id="mw-diff-otitle5">' . $oldChangeTags[0] . '</div>' .
 603                                 '<div id="mw-diff-otitle4">' . $prevlink . '</div>';
 604
 605                         // Allow extensions to change the $oldHeader variable
 606                         Hooks::run( 'DifferenceEngineOldHeader', [ $this, &$oldHeader, $prevlink, $oldminor,
 607                                 $diffOnly, $ldel, $this->unhide ] );
 608
 609                         if ( $this->mOldRev->isDeleted( RevisionRecord::DELETED_TEXT ) ) {
 610                                 $deleted = true; // old revisions text is hidden
 611                                 if ( $this->mOldRev->isDeleted( RevisionRecord::DELETED_RESTRICTED ) ) {
 612                                         $suppressed = true; // also suppressed
 613                                 }
 614                         }
 615
 616                         # Check if this user can see the revisions
 617                         if ( !$this->mOldRev->userCan( RevisionRecord::DELETED_TEXT, $user ) ) {
 618                                 $allowed = false;
 619                         }
 620                 }
 621
 622                 $out->addJsConfigVars( [
 623                         'wgDiffOldId' => $this->mOldid,
 624                         'wgDiffNewId' => $this->mNewid,
 625                 ] );
 626
 627                 # Make "next revision link"
 628                 # Skip next link on the top revision
 629                 if ( $samePage && $this->mNewPage && !$this->mNewRev->isCurrent() ) {
 630                         $nextlink = Linker::linkKnown(
 631                                 $this->mNewPage,
 632                                 $this->msg( 'nextdiff' )->escaped(),
 633                                 [ 'id' => 'differences-nextlink' ],
 634                                 [ 'diff' => 'next', 'oldid' => $this->mNewid ] + $query
 635                         );
 636                 } else {
 637                         $nextlink = "\u{00A0}";
 638                 }
 639
 640                 if ( $this->mNewRev->isMinor() ) {
 641                         $newminor = ChangesList::flag( 'minor' );
 642                 } else {
 643                         $newminor = '';
 644                 }
 645
 646                 # Handle RevisionDelete links...
 647                 $rdel = $this->revisionDeleteLink( $this->mNewRev );
 648
 649                 # Allow extensions to define their own revision tools
 650                 Hooks::run( 'DiffRevisionTools',
 651                         [ $this->mNewRev, &$revisionTools, $this->mOldRev, $user ] );
 652                 $formattedRevisionTools = [];
 653                 // Put each one in parentheses (poor man's button)
 654                 foreach ( $revisionTools as $key => $tool ) {
 655                         $toolClass = is_string( $key ) ? $key : 'mw-diff-tool';
 656                         $element = Html::rawElement(
 657                                 'span',
 658                                 [ 'class' => $toolClass ],
 659                                 $this->msg( 'parentheses' )->rawParams( $tool )->escaped()
 660                         );
 661                         $formattedRevisionTools[] = $element;
 662                 }
 663                 $newRevisionHeader = $this->getRevisionHeader( $this->mNewRev, 'complete' ) .
 664                         ' ' . implode( ' ', $formattedRevisionTools );
 665                 $newChangeTags = ChangeTags::formatSummaryRow( $this->mNewTags, 'diff', $this->getContext() );
 666
 667                 $newHeader = '<div id="mw-diff-ntitle1"><strong>' . $newRevisionHeader . '</strong></div>' .
 668                         '<div id="mw-diff-ntitle2">' . Linker::revUserTools( $this->mNewRev, !$this->unhide ) .
 669                         " $rollback</div>" .
 670                         '<div id="mw-diff-ntitle3">' . $newminor .
 671                         Linker::revComment( $this->mNewRev, !$diffOnly, !$this->unhide ) . $rdel . '</div>' .
 672                         '<div id="mw-diff-ntitle5">' . $newChangeTags[0] . '</div>' .
 673                         '<div id="mw-diff-ntitle4">' . $nextlink . $this->markPatrolledLink() . '</div>';
 674
 675                 // Allow extensions to change the $newHeader variable
 676                 Hooks::run( 'DifferenceEngineNewHeader', [ $this, &$newHeader, $formattedRevisionTools,
 677                         $nextlink, $rollback, $newminor, $diffOnly, $rdel, $this->unhide ] );
 678
 679                 if ( $this->mNewRev->isDeleted( RevisionRecord::DELETED_TEXT ) ) {
 680                         $deleted = true; // new revisions text is hidden
 681                         if ( $this->mNewRev->isDeleted( RevisionRecord::DELETED_RESTRICTED ) ) {
 682                                 $suppressed = true; // also suppressed
 683                         }
 684                 }
 685
 686                 # If the diff cannot be shown due to a deleted revision, then output
 687                 # the diff header and links to unhide (if available)...
 688                 if ( $deleted && ( !$this->unhide || !$allowed ) ) {
 689                         $this->showDiffStyle();
 690                         $multi = $this->getMultiNotice();
 691                         $out->addHTML( $this->addHeader( '', $oldHeader, $newHeader, $multi ) );
 692                         if ( !$allowed ) {
 693                                 $msg = $suppressed ? 'rev-suppressed-no-diff' : 'rev-deleted-no-diff';
 694                                 # Give explanation for why revision is not visible
 695                                 $out->wrapWikiMsg( "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 696                                         [ $msg ] );
 697                         } else {
 698                                 # Give explanation and add a link to view the diff...
 699                                 $query = $this->getRequest()->appendQueryValue( 'unhide', '1' );
 700                                 $link = $this->getTitle()->getFullURL( $query );
 701                                 $msg = $suppressed ? 'rev-suppressed-unhide-diff' : 'rev-deleted-unhide-diff';
 702                                 $out->wrapWikiMsg(
 703                                         "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 704                                         [ $msg, $link ]
 705                                 );
 706                         }
 707                 # Otherwise, output a regular diff...
 708                 } else {
 709                         # Add deletion notice if the user is viewing deleted content
 710                         $notice = '';
 711                         if ( $deleted ) {
 712                                 $msg = $suppressed ? 'rev-suppressed-diff-view' : 'rev-deleted-diff-view';
 713                                 $notice = "<div id='mw-$msg' class='mw-warning plainlinks'>\n" .
 714                                         $this->msg( $msg )->parse() .
 715                                         "</div>\n";
 716                         }
 717                         $this->showDiff( $oldHeader, $newHeader, $notice );
 718                         if ( !$diffOnly ) {
 719                                 $this->renderNewRevision();
 720                         }
 721                 }
 722         }
 723
 724         /**
 725          * Build a link to mark a change as patrolled.
 726          *
 727          * Returns empty string if there's either no revision to patrol or the user is not allowed to.
 728          * Side effect: When the patrol link is build, this method will call
 729          * OutputPage::preventClickjacking() and load mediawiki.page.patrol.ajax.
 730          *
 731          * @return string HTML or empty string
 732          */
 733         public function markPatrolledLink() {
 734                 if ( $this->mMarkPatrolledLink === null ) {
 735                         $linkInfo = $this->getMarkPatrolledLinkInfo();
 736                         // If false, there is no patrol link needed/allowed
 737                         if ( !$linkInfo || !$this->mNewPage ) {
 738                                 $this->mMarkPatrolledLink = '';
 739                         } else {
 740                                 $this->mMarkPatrolledLink = ' <span class="patrollink" data-mw="interface">[' .
 741                                         Linker::linkKnown(
 742                                                 $this->mNewPage,
 743                                                 $this->msg( 'markaspatrolleddiff' )->escaped(),
 744                                                 [],
 745                                                 [
 746                                                         'action' => 'markpatrolled',
 747                                                         'rcid' => $linkInfo['rcid'],
 748                                                 ]
 749                                         ) . ']</span>';
 750                                 // Allow extensions to change the markpatrolled link
 751                                 Hooks::run( 'DifferenceEngineMarkPatrolledLink', [ $this,
 752                                         &$this->mMarkPatrolledLink, $linkInfo['rcid'] ] );
 753                         }
 754                 }
 755                 return $this->mMarkPatrolledLink;
 756         }
 757
 758         /**
 759          * Returns an array of meta data needed to build a "mark as patrolled" link and
 760          * adds the mediawiki.page.patrol.ajax to the output.
 761          *
 762          * @return array|false An array of meta data for a patrol link (rcid only)
 763          *  or false if no link is needed
 764          */
 765         protected function getMarkPatrolledLinkInfo() {
 766                 $user = $this->getUser();
 767                 $config = $this->getConfig();
 768
 769                 // Prepare a change patrol link, if applicable
 770                 if (
 771                         // Is patrolling enabled and the user allowed to?
 772                         $config->get( 'UseRCPatrol' ) &&
 773                         $this->mNewPage && $this->mNewPage->quickUserCan( 'patrol', $user ) &&
 774                         // Only do this if the revision isn't more than 6 hours older
 775                         // than the Max RC age (6h because the RC might not be cleaned out regularly)
 776                         RecentChange::isInRCLifespan( $this->mNewRev->getTimestamp(), 21600 )
 777                 ) {
 778                         // Look for an unpatrolled change corresponding to this diff
 779                         $db = wfGetDB( DB_REPLICA );
 780                         $change = RecentChange::newFromConds(
 781                                 [
 782                                         'rc_timestamp' => $db->timestamp( $this->mNewRev->getTimestamp() ),
 783                                         'rc_this_oldid' => $this->mNewid,
 784                                         'rc_patrolled' => RecentChange::PRC_UNPATROLLED
 785                                 ],
 786                                 __METHOD__
 787                         );
 788
 789                         if ( $change && !$change->getPerformer()->equals( $user ) ) {
 790                                 $rcid = $change->getAttribute( 'rc_id' );
 791                         } else {
 792                                 // None found or the page has been created by the current user.
 793                                 // If the user could patrol this it already would be patrolled
 794                                 $rcid = 0;
 795                         }
 796
 797                         // Allow extensions to possibly change the rcid here
 798                         // For example the rcid might be set to zero due to the user
 799                         // being the same as the performer of the change but an extension
 800                         // might still want to show it under certain conditions
 801                         Hooks::run( 'DifferenceEngineMarkPatrolledRCID', [ &$rcid, $this, $change, $user ] );
 802
 803                         // Build the link
 804                         if ( $rcid ) {
 805                                 $this->getOutput()->preventClickjacking();
 806                                 if ( $user->isAllowed( 'writeapi' ) ) {
 807                                         $this->getOutput()->addModules( 'mediawiki.page.patrol.ajax' );
 808                                 }
 809
 810                                 return [
 811                                         'rcid' => $rcid,
 812                                 ];
 813                         }
 814                 }
 815
 816                 // No mark as patrolled link applicable
 817                 return false;
 818         }
 819
 820         /**
 821          * @param Revision $rev
 822          *
 823          * @return string
 824          */
 825         protected function revisionDeleteLink( $rev ) {
 826                 $link = Linker::getRevDeleteLink( $this->getUser(), $rev, $rev->getTitle() );
 827                 if ( $link !== '' ) {
 828                         $link = "\u{00A0}\u{00A0}\u{00A0}" . $link . ' ';
 829                 }
 830
 831                 return $link;
 832         }
 833
 834         /**
 835          * Show the new revision of the page.
 836          *
 837          * @note Not supported after calling setContent().
 838          */
 839         public function renderNewRevision() {
 840                 if ( $this->isContentOverridden ) {
 841                         // The code below only works with a Revision object. We could construct a fake revision
 842                         // (here or in setContent), but since this does not seem needed at the moment,
 843                         // we'll just fail for now.
 844                         throw new LogicException(
 845                                 __METHOD__
 846                                 . ' is not supported after calling setContent(). Use setRevisions() instead.'
 847                         );
 848                 }
 849
 850                 $out = $this->getOutput();
 851                 $revHeader = $this->getRevisionHeader( $this->mNewRev );
 852                 # Add "current version as of X" title
 853                 $out->addHTML( "<hr class='diff-hr' id='mw-oldid' />
 854                 <h2 class='diff-currentversion-title'>{$revHeader}</h2>\n" );
 855                 # Page content may be handled by a hooked call instead...
 856                 if ( Hooks::run( 'ArticleContentOnDiff', [ $this, $out ] ) ) {
 857                         $this->loadNewText();
 858                         if ( !$this->mNewPage ) {
 859                                 // New revision is unsaved; bail out.
 860                                 // TODO in theory rendering the new revision is a meaningful thing to do
 861                                 // even if it's unsaved, but a lot of untangling is required to do it safely.
 862                                 return;
 863                         }
 864
 865                         $out->setRevisionId( $this->mNewid );
 866                         $out->setRevisionTimestamp( $this->mNewRev->getTimestamp() );
 867                         $out->setArticleFlag( true );
 868
 869                         if ( !Hooks::run( 'ArticleRevisionViewCustom',
 870                                 [ $this->mNewRev->getRevisionRecord(), $this->mNewPage, $out ] )
 871                         ) {
 872                                 // Handled by extension
 873                                 // NOTE: sync with hooks called in Article::view()
 874                         } elseif ( !Hooks::run( 'ArticleContentViewCustom',
 875                                 [ $this->mNewContent, $this->mNewPage, $out ], '1.32' )
 876                         ) {
 877                                 // Handled by extension
 878                                 // NOTE: sync with hooks called in Article::view()
 879                         } else {
 880                                 // Normal page
 881                                 if ( $this->getTitle()->equals( $this->mNewPage ) ) {
 882                                         // If the Title stored in the context is the same as the one
 883                                         // of the new revision, we can use its associated WikiPage
 884                                         // object.
 885                                         $wikiPage = $this->getWikiPage();
 886                                 } else {
 887                                         // Otherwise we need to create our own WikiPage object
 888                                         $wikiPage = WikiPage::factory( $this->mNewPage );
 889                                 }
 890
 891                                 $parserOutput = $this->getParserOutput( $wikiPage, $this->mNewRev );
 892
 893                                 # WikiPage::getParserOutput() should not return false, but just in case
 894                                 if ( $parserOutput ) {
 895                                         // Allow extensions to change parser output here
 896                                         if ( Hooks::run( 'DifferenceEngineRenderRevisionAddParserOutput',
 897                                                 [ $this, $out, $parserOutput, $wikiPage ] )
 898                                         ) {
 899                                                 $out->addParserOutput( $parserOutput, [
 900                                                         'enableSectionEditLinks' => $this->mNewRev->isCurrent()
 901                                                                 && $this->mNewRev->getTitle()->quickUserCan( 'edit', $this->getUser() ),
 902                                                 ] );
 903                                         }
 904                                 }
 905                         }
 906                 }
 907
 908                 // Allow extensions to optionally not show the final patrolled link
 909                 if ( Hooks::run( 'DifferenceEngineRenderRevisionShowFinalPatrolLink' ) ) {
 910                         # Add redundant patrol link on bottom...
 911                         $out->addHTML( $this->markPatrolledLink() );
 912                 }
 913         }
 914
 915         /**
 916          * @param WikiPage $page
 917          * @param Revision $rev
 918          *
 919          * @return ParserOutput|bool False if the revision was not found
 920          */
 921         protected function getParserOutput( WikiPage $page, Revision $rev ) {
 922                 if ( !$rev->getId() ) {
 923                         // WikiPage::getParserOutput wants a revision ID. Passing 0 will incorrectly show
 924                         // the current revision, so fail instead. If need be, WikiPage::getParserOutput
 925                         // could be made to accept a Revision or RevisionRecord instead of the id.
 926                         return false;
 927                 }
 928
 929                 $parserOptions = $page->makeParserOptions( $this->getContext() );
 930                 $parserOutput = $page->getParserOutput( $parserOptions, $rev->getId() );
 931
 932                 return $parserOutput;
 933         }
 934
 935         /**
 936          * Get the diff text, send it to the OutputPage object
 937          * Returns false if the diff could not be generated, otherwise returns true
 938          *
 939          * @param string|bool $otitle Header for old text or false
 940          * @param string|bool $ntitle Header for new text or false
 941          * @param string $notice HTML between diff header and body
 942          *
 943          * @return bool
 944          */
 945         public function showDiff( $otitle, $ntitle, $notice = '' ) {
 946                 // Allow extensions to affect the output here
 947                 Hooks::run( 'DifferenceEngineShowDiff', [ $this ] );
 948
 949                 $diff = $this->getDiff( $otitle, $ntitle, $notice );
 950                 if ( $diff === false ) {
 951                         $this->showMissingRevision();
 952
 953                         return false;
 954                 } else {
 955                         $this->showDiffStyle();
 956                         $this->getOutput()->addHTML( $diff );
 957
 958                         return true;
 959                 }
 960         }
 961
 962         /**
 963          * Add style sheets for diff display.
 964          */
 965         public function showDiffStyle() {
 966                 if ( !$this->isSlotDiffRenderer ) {
 967                         $this->getOutput()->addModuleStyles( [
 968                                 'mediawiki.interface.helpers.styles',
 969                                 'mediawiki.diff.styles'
 970                         ] );
 971                         foreach ( $this->getSlotDiffRenderers() as $slotDiffRenderer ) {
 972                                 $slotDiffRenderer->addModules( $this->getOutput() );
 973                         }
 974                 }
 975         }
 976
 977         /**
 978          * Get complete diff table, including header
 979          *
 980          * @param string|bool $otitle Header for old text or false
 981          * @param string|bool $ntitle Header for new text or false
 982          * @param string $notice HTML between diff header and body
 983          *
 984          * @return mixed
 985          */
 986         public function getDiff( $otitle, $ntitle, $notice = '' ) {
 987                 $body = $this->getDiffBody();
 988                 if ( $body === false ) {
 989                         return false;
 990                 }
 991
 992                 $multi = $this->getMultiNotice();
 993                 // Display a message when the diff is empty
 994                 if ( $body === '' ) {
 995                         $notice .= '<div class="mw-diff-empty">' .
 996                                 $this->msg( 'diff-empty' )->parse() .
 997                                 "</div>\n";
 998                 }
 999
1000                 return $this->addHeader( $body, $otitle, $ntitle, $multi, $notice );
1001         }
1002
1003         /**
1004          * Get the diff table body, without header
1005          *
1006          * @return mixed (string/false)
1007          */
1008         public function getDiffBody() {
1009                 $this->mCacheHit = true;
1010                 // Check if the diff should be hidden from this user
1011                 if ( !$this->isContentOverridden ) {
1012                         if ( !$this->loadRevisionData() ) {
1013                                 return false;
1014                         } elseif ( $this->mOldRev &&
1015                                 !$this->mOldRev->userCan( RevisionRecord::DELETED_TEXT, $this->getUser() )
1016                         ) {
1017                                 return false;
1018                         } elseif ( $this->mNewRev &&
1019                                 !$this->mNewRev->userCan( RevisionRecord::DELETED_TEXT, $this->getUser() )
1020                         ) {
1021                                 return false;
1022                         }
1023                         // Short-circuit
1024                         if ( $this->mOldRev === false || ( $this->mOldRev && $this->mNewRev &&
1025                                 $this->mOldRev->getId() && $this->mOldRev->getId() == $this->mNewRev->getId() )
1026                         ) {
1027                                 if ( Hooks::run( 'DifferenceEngineShowEmptyOldContent', [ $this ] ) ) {
1028                                         return '';
1029                                 }
1030                         }
1031                 }
1032
1033                 // Cacheable?
1034                 $key = false;
1035                 $cache = MediaWikiServices::getInstance()->getMainWANObjectCache();
1036                 if ( $this->mOldid && $this->mNewid ) {
1037                         // Check if subclass is still using the old way
1038                         // for backwards-compatibility
1039                         $key = $this->getDiffBodyCacheKey();
1040                         if ( $key === null ) {
1041                                 $key = $cache->makeKey( ...$this->getDiffBodyCacheKeyParams() );
1042                         }
1043
1044                         // Try cache
1045                         if ( !$this->mRefreshCache ) {
1046                                 $difftext = $cache->get( $key );
1047                                 if ( is_string( $difftext ) ) {
1048                                         wfIncrStats( 'diff_cache.hit' );
1049                                         $difftext = $this->localiseDiff( $difftext );
1050                                         $difftext .= "\n<!-- diff cache key $key -->\n";
1051
1052                                         return $difftext;
1053                                 }
1054                         } // don't try to load but save the result
1055                 }
1056                 $this->mCacheHit = false;
1057
1058                 // Loadtext is permission safe, this just clears out the diff
1059                 if ( !$this->loadText() ) {
1060                         return false;
1061                 }
1062
1063                 $difftext = '';
1064                 // We've checked for revdelete at the beginning of this method; it's OK to ignore
1065                 // read permissions here.
1066                 $slotContents = $this->getSlotContents();
1067                 foreach ( $this->getSlotDiffRenderers() as $role => $slotDiffRenderer ) {
1068                         $slotDiff = $slotDiffRenderer->getDiff( $slotContents[$role]['old'],
1069                                 $slotContents[$role]['new'] );
1070                         if ( $slotDiff && $role !== SlotRecord::MAIN ) {
1071                                 // FIXME: ask SlotRoleHandler::getSlotNameMessage
1072                                 $slotTitle = $role;
1073                                 $difftext .= $this->getSlotHeader( $slotTitle );
1074                         }
1075                         $difftext .= $slotDiff;
1076                 }
1077
1078                 // Avoid PHP 7.1 warning from passing $this by reference
1079                 $diffEngine = $this;
1080
1081                 // Save to cache for 7 days
1082                 if ( !Hooks::run( 'AbortDiffCache', [ &$diffEngine ] ) ) {
1083                         wfIncrStats( 'diff_cache.uncacheable' );
1084                 } elseif ( $key !== false && $difftext !== false ) {
1085                         wfIncrStats( 'diff_cache.miss' );
1086                         $cache->set( $key, $difftext, 7 * 86400 );
1087                 } else {
1088                         wfIncrStats( 'diff_cache.uncacheable' );
1089                 }
1090                 // localise line numbers and title attribute text
1091                 if ( $difftext !== false ) {
1092                         $difftext = $this->localiseDiff( $difftext );
1093                 }
1094
1095                 return $difftext;
1096         }
1097
1098         /**
1099          * Get the diff table body for one slot, without header
1100          *
1101          * @param string $role
1102          * @return string|false
1103          */
1104         public function getDiffBodyForRole( $role ) {
1105                 $diffRenderers = $this->getSlotDiffRenderers();
1106                 if ( !isset( $diffRenderers[$role] ) ) {
1107                         return false;
1108                 }
1109
1110                 $slotContents = $this->getSlotContents();
1111                 $slotDiff = $diffRenderers[$role]->getDiff( $slotContents[$role]['old'],
1112                         $slotContents[$role]['new'] );
1113                 if ( !$slotDiff ) {
1114                         return false;
1115                 }
1116
1117                 if ( $role !== SlotRecord::MAIN ) {
1118                         // TODO use human-readable role name at least
1119                         $slotTitle = $role;
1120                         $slotDiff = $this->getSlotHeader( $slotTitle ) . $slotDiff;
1121                 }
1122
1123                 return $this->localiseDiff( $slotDiff );
1124         }
1125
1126         /**
1127          * Get a slot header for inclusion in a diff body (as a table row).
1128          *
1129          * @param string $headerText The text of the header
1130          * @return string
1131          *
1132          */
1133         protected function getSlotHeader( $headerText ) {
1134                 // The old revision is missing on oldid=<first>&diff=prev; only 2 columns in that case.
1135                 $columnCount = $this->mOldRev ? 4 : 2;
1136                 $userLang = $this->getLanguage()->getHtmlCode();
1137                 return Html::rawElement( 'tr', [ 'class' => 'mw-diff-slot-header', 'lang' => $userLang ],
1138                         Html::element( 'th', [ 'colspan' => $columnCount ], $headerText ) );
1139         }
1140
1141         /**
1142          * Returns the cache key for diff body text or content.
1143          *
1144          * @deprecated since 1.31, use getDiffBodyCacheKeyParams() instead
1145          * @since 1.23
1146          *
1147          * @throws MWException
1148          * @return string|null
1149          */
1150         protected function getDiffBodyCacheKey() {
1151                 return null;
1152         }
1153
1154         /**
1155          * Get the cache key parameters
1156          *
1157          * Subclasses can replace the first element in the array to something
1158          * more specific to the type of diff (e.g. "inline-diff"), or append
1159          * if the cache should vary on more things. Overriding entirely should
1160          * be avoided.
1161          *
1162          * @since 1.31
1163          *
1164          * @return array
1165          * @throws MWException
1166          */
1167         protected function getDiffBodyCacheKeyParams() {
1168                 if ( !$this->mOldid || !$this->mNewid ) {
1169                         throw new MWException( 'mOldid and mNewid must be set to get diff cache key.' );
1170                 }
1171
1172                 $engine = $this->getEngine();
1173                 $params = [
1174                         'diff',
1175                         $engine,
1176                         self::DIFF_VERSION,
1177                         "old-{$this->mOldid}",
1178                         "rev-{$this->mNewid}"
1179                 ];
1180
1181                 if ( $engine === 'wikidiff2' ) {
1182                         $params[] = phpversion( 'wikidiff2' );
1183                 }
1184
1185                 if ( !$this->isSlotDiffRenderer ) {
1186                         foreach ( $this->getSlotDiffRenderers() as $slotDiffRenderer ) {
1187                                 $params = array_merge( $params, $slotDiffRenderer->getExtraCacheKeys() );
1188                         }
1189                 }
1190
1191                 return $params;
1192         }
1193
1194         /**
1195          * Implements DifferenceEngineSlotDiffRenderer::getExtraCacheKeys(). Only used when
1196          * DifferenceEngine is wrapped in DifferenceEngineSlotDiffRenderer.
1197          * @return array
1198          * @internal for use by DifferenceEngineSlotDiffRenderer only
1199          * @deprecated
1200          */
1201         public function getExtraCacheKeys() {
1202                 // This method is called when the DifferenceEngine is used for a slot diff. We only care
1203                 // about special things, not the revision IDs, which are added to the cache key by the
1204                 // page-level DifferenceEngine, and which might not have a valid value for this object.
1205                 $this->mOldid = 123456789;
1206                 $this->mNewid = 987654321;
1207
1208                 // This will repeat a bunch of unnecessary key fields for each slot. Not nice but harmless.
1209                 $cacheString = $this->getDiffBodyCacheKey();
1210                 if ( $cacheString ) {
1211                         return [ $cacheString ];
1212                 }
1213
1214                 $params = $this->getDiffBodyCacheKeyParams();
1215
1216                 // Try to get rid of the standard keys to keep the cache key human-readable:
1217                 // call the getDiffBodyCacheKeyParams implementation of the base class, and if
1218                 // the child class includes the same keys, drop them.
1219                 // Uses an obscure PHP feature where static calls to non-static methods are allowed
1220                 // as long as we are already in a non-static method of the same class, and the call context
1221                 // ($this) will be inherited.
1222                 // phpcs:ignore Squiz.Classes.SelfMemberReference.NotUsed
1223                 $standardParams = DifferenceEngine::getDiffBodyCacheKeyParams();
1224                 if ( array_slice( $params, 0, count( $standardParams ) ) === $standardParams ) {
1225                         $params = array_slice( $params, count( $standardParams ) );
1226                 }
1227
1228                 return $params;
1229         }
1230
1231         /**
1232          * Generate a diff, no caching.
1233          *
1234          * @since 1.21
1235          *
1236          * @param Content $old Old content
1237          * @param Content $new New content
1238          *
1239          * @throws Exception If old or new content is not an instance of TextContent.
1240          * @return bool|string
1241          *
1242          * @deprecated since 1.32, use a SlotDiffRenderer instead.
1243          */
1244         public function generateContentDiffBody( Content $old, Content $new ) {
1245                 $slotDiffRenderer = $new->getContentHandler()->getSlotDiffRenderer( $this->getContext() );
1246                 if (
1247                         $slotDiffRenderer instanceof DifferenceEngineSlotDiffRenderer
1248                         && $this->isSlotDiffRenderer
1249                 ) {
1250                         // Oops, we are just about to enter an infinite loop (the slot-level DifferenceEngine
1251                         // called a DifferenceEngineSlotDiffRenderer that wraps the same DifferenceEngine class).
1252                         // This will happen when a content model has no custom slot diff renderer, it does have
1253                         // a custom difference engine, but that does not override this method.
1254                         throw new Exception( get_class( $this ) . ': could not maintain backwards compatibility. '
1255                                 . 'Please use a SlotDiffRenderer.' );
1256                 }
1257                 return $slotDiffRenderer->getDiff( $old, $new ) . $this->getDebugString();
1258         }
1259
1260         /**
1261          * Generate a diff, no caching
1262          *
1263          * @param string $otext Old text, must be already segmented
1264          * @param string $ntext New text, must be already segmented
1265          *
1266          * @throws Exception If content handling for text content is configured in a way
1267          *   that makes maintaining B/C hard.
1268          * @return bool|string
1269          *
1270          * @deprecated since 1.32, use a TextSlotDiffRenderer instead.
1271          */
1272         public function generateTextDiffBody( $otext, $ntext ) {
1273                 $slotDiffRenderer = ContentHandler::getForModelID( CONTENT_MODEL_TEXT )
1274                         ->getSlotDiffRenderer( $this->getContext() );
1275                 if ( !( $slotDiffRenderer instanceof TextSlotDiffRenderer ) ) {
1276                         // Someone used the GetSlotDiffRenderer hook to replace the renderer.
1277                         // This is too unlikely to happen to bother handling properly.
1278                         throw new Exception( 'The slot diff renderer for text content should be a '
1279                                 . 'TextSlotDiffRenderer subclass' );
1280                 }
1281                 return $slotDiffRenderer->getTextDiff( $otext, $ntext ) . $this->getDebugString();
1282         }
1283
1284         /**
1285          * Process $wgExternalDiffEngine and get a sane, usable engine
1286          *
1287          * @return bool|string 'wikidiff2', path to an executable, or false
1288          * @internal For use by this class and TextSlotDiffRenderer only.
1289          */
1290         public static function getEngine() {
1291                 global $wgExternalDiffEngine;
1292                 // We use the global here instead of Config because we write to the value,
1293                 // and Config is not mutable.
1294                 if ( $wgExternalDiffEngine == 'wikidiff' || $wgExternalDiffEngine == 'wikidiff3' ) {
1295                         wfDeprecated( "\$wgExternalDiffEngine = '{$wgExternalDiffEngine}'", '1.27' );
1296                         $wgExternalDiffEngine = false;
1297                 } elseif ( $wgExternalDiffEngine == 'wikidiff2' ) {
1298                         wfDeprecated( "\$wgExternalDiffEngine = '{$wgExternalDiffEngine}'", '1.32' );
1299                         $wgExternalDiffEngine = false;
1300                 } elseif ( !is_string( $wgExternalDiffEngine ) && $wgExternalDiffEngine !== false ) {
1301                         // And prevent people from shooting themselves in the foot...
1302                         wfWarn( '$wgExternalDiffEngine is set to a non-string value, forcing it to false' );
1303                         $wgExternalDiffEngine = false;
1304                 }
1305
1306                 if ( is_string( $wgExternalDiffEngine ) && is_executable( $wgExternalDiffEngine ) ) {
1307                         return $wgExternalDiffEngine;
1308                 } elseif ( $wgExternalDiffEngine === false && function_exists( 'wikidiff2_do_diff' ) ) {
1309                         return 'wikidiff2';
1310                 } else {
1311                         // Native PHP
1312                         return false;
1313                 }
1314         }
1315
1316         /**
1317          * Generates diff, to be wrapped internally in a logging/instrumentation
1318          *
1319          * @param string $otext Old text, must be already segmented
1320          * @param string $ntext New text, must be already segmented
1321          *
1322          * @throws Exception If content handling for text content is configured in a way
1323          *   that makes maintaining B/C hard.
1324          * @return bool|string
1325          *
1326          * @deprecated since 1.32, use a TextSlotDiffRenderer instead.
1327          */
1328         protected function textDiff( $otext, $ntext ) {
1329                 $slotDiffRenderer = ContentHandler::getForModelID( CONTENT_MODEL_TEXT )
1330                         ->getSlotDiffRenderer( $this->getContext() );
1331                 if ( !( $slotDiffRenderer instanceof TextSlotDiffRenderer ) ) {
1332                         // Someone used the GetSlotDiffRenderer hook to replace the renderer.
1333                         // This is too unlikely to happen to bother handling properly.
1334                         throw new Exception( 'The slot diff renderer for text content should be a '
1335                                 . 'TextSlotDiffRenderer subclass' );
1336                 }
1337                 return $slotDiffRenderer->getTextDiff( $otext, $ntext ) . $this->getDebugString();
1338         }
1339
1340         /**
1341          * Generate a debug comment indicating diff generating time,
1342          * server node, and generator backend.
1343          *
1344          * @param string $generator : What diff engine was used
1345          *
1346          * @return string
1347          */
1348         protected function debug( $generator = "internal" ) {
1349                 if ( !$this->enableDebugComment ) {
1350                         return '';
1351                 }
1352                 $data = [ $generator ];
1353                 if ( $this->getConfig()->get( 'ShowHostnames' ) ) {
1354                         $data[] = wfHostname();
1355                 }
1356                 $data[] = wfTimestamp( TS_DB );
1357
1358                 return "<!-- diff generator: " .
1359                         implode( " ", array_map( "htmlspecialchars", $data ) ) .
1360                         " -->\n";
1361         }
1362
1363         private function getDebugString() {
1364                 $engine = self::getEngine();
1365                 if ( $engine === 'wikidiff2' ) {
1366                         return $this->debug( 'wikidiff2' );
1367                 } elseif ( $engine === false ) {
1368                         return $this->debug( 'native PHP' );
1369                 } else {
1370                         return $this->debug( "external $engine" );
1371                 }
1372         }
1373
1374         /**
1375          * Localise diff output
1376          *
1377          * @param string $text
1378          * @return string
1379          */
1380         private function localiseDiff( $text ) {
1381                 $text = $this->localiseLineNumbers( $text );
1382                 if ( $this->getEngine() === 'wikidiff2' &&
1383                         version_compare( phpversion( 'wikidiff2' ), '1.5.1', '>=' )
1384                 ) {
1385                         $text = $this->addLocalisedTitleTooltips( $text );
1386                 }
1387                 return $text;
1388         }
1389
1390         /**
1391          * Replace line numbers with the text in the user's language
1392          *
1393          * @param string $text
1394          *
1395          * @return mixed
1396          */
1397         public function localiseLineNumbers( $text ) {
1398                 return preg_replace_callback(
1399                         '/<!--LINE (\d+)-->/',
1400                         [ $this, 'localiseLineNumbersCb' ],
1401                         $text
1402                 );
1403         }
1404
1405         public function localiseLineNumbersCb( $matches ) {
1406                 if ( $matches[1] === '1' && $this->mReducedLineNumbers ) {
1407                         return '';
1408                 }
1409
1410                 return $this->msg( 'lineno' )->numParams( $matches[1] )->escaped();
1411         }
1412
1413         /**
1414          * Add title attributes for tooltips on moved paragraph indicators
1415          *
1416          * @param string $text
1417          * @return string
1418          */
1419         private function addLocalisedTitleTooltips( $text ) {
1420                 return preg_replace_callback(
1421                         '/class="mw-diff-movedpara-(left|right)"/',
1422                         [ $this, 'addLocalisedTitleTooltipsCb' ],
1423                         $text
1424                 );
1425         }
1426
1427         /**
1428          * @param array $matches
1429          * @return string
1430          */
1431         private function addLocalisedTitleTooltipsCb( array $matches ) {
1432                 $key = $matches[1] === 'right' ?
1433                         'diff-paragraph-moved-toold' :
1434                         'diff-paragraph-moved-tonew';
1435                 return $matches[0] . ' title="' . $this->msg( $key )->escaped() . '"';
1436         }
1437
1438         /**
1439          * If there are revisions between the ones being compared, return a note saying so.
1440          *
1441          * @return string
1442          */
1443         public function getMultiNotice() {
1444                 // The notice only make sense if we are diffing two saved revisions of the same page.
1445                 if (
1446                         !$this->mOldRev || !$this->mNewRev
1447                         || !$this->mOldPage || !$this->mNewPage
1448                         || !$this->mOldPage->equals( $this->mNewPage )
1449                 ) {
1450                         return '';
1451                 }
1452
1453                 if ( $this->mOldRev->getTimestamp() > $this->mNewRev->getTimestamp() ) {
1454                         $oldRev = $this->mNewRev; // flip
1455                         $newRev = $this->mOldRev; // flip
1456                 } else { // normal case
1457                         $oldRev = $this->mOldRev;
1458                         $newRev = $this->mNewRev;
1459                 }
1460
1461                 // Sanity: don't show the notice if too many rows must be scanned
1462                 // @todo show some special message for that case
1463                 $nEdits = $this->mNewPage->countRevisionsBetween( $oldRev, $newRev, 1000 );
1464                 if ( $nEdits > 0 && $nEdits <= 1000 ) {
1465                         $limit = 100; // use diff-multi-manyusers if too many users
1466                         $users = $this->mNewPage->getAuthorsBetween( $oldRev, $newRev, $limit );
1467                         $numUsers = count( $users );
1468
1469                         if ( $numUsers == 1 && $users[0] == $newRev->getUserText( RevisionRecord::RAW ) ) {
1470                                 $numUsers = 0; // special case to say "by the same user" instead of "by one other user"
1471                         }
1472
1473                         return self::intermediateEditsMsg( $nEdits, $numUsers, $limit );
1474                 }
1475
1476                 return '';
1477         }
1478
1479         /**
1480          * Get a notice about how many intermediate edits and users there are
1481          *
1482          * @param int $numEdits
1483          * @param int $numUsers
1484          * @param int $limit
1485          *
1486          * @return string
1487          */
1488         public static function intermediateEditsMsg( $numEdits, $numUsers, $limit ) {
1489                 if ( $numUsers === 0 ) {
1490                         $msg = 'diff-multi-sameuser';
1491                 } elseif ( $numUsers > $limit ) {
1492                         $msg = 'diff-multi-manyusers';
1493                         $numUsers = $limit;
1494                 } else {
1495                         $msg = 'diff-multi-otherusers';
1496                 }
1497
1498                 return wfMessage( $msg )->numParams( $numEdits, $numUsers )->parse();
1499         }
1500
1501         /**
1502          * Get a header for a specified revision.
1503          *
1504          * @param Revision $rev
1505          * @param string $complete 'complete' to get the header wrapped depending
1506          *        the visibility of the revision and a link to edit the page.
1507          *
1508          * @return string HTML fragment
1509          */
1510         public function getRevisionHeader( Revision $rev, $complete = '' ) {
1511                 $lang = $this->getLanguage();
1512                 $user = $this->getUser();
1513                 $revtimestamp = $rev->getTimestamp();
1514                 $timestamp = $lang->userTimeAndDate( $revtimestamp, $user );
1515                 $dateofrev = $lang->userDate( $revtimestamp, $user );
1516                 $timeofrev = $lang->userTime( $revtimestamp, $user );
1517
1518                 $header = $this->msg(
1519                         $rev->isCurrent() ? 'currentrev-asof' : 'revisionasof',
1520                         $timestamp,
1521                         $dateofrev,
1522                         $timeofrev
1523                 )->escaped();
1524
1525                 if ( $complete !== 'complete' ) {
1526                         return $header;
1527                 }
1528
1529                 $title = $rev->getTitle();
1530
1531                 $header = Linker::linkKnown( $title, $header, [],
1532                         [ 'oldid' => $rev->getId() ] );
1533
1534                 if ( $rev->userCan( RevisionRecord::DELETED_TEXT, $user ) ) {
1535                         $editQuery = [ 'action' => 'edit' ];
1536                         if ( !$rev->isCurrent() ) {
1537                                 $editQuery['oldid'] = $rev->getId();
1538                         }
1539
1540                         $key = $title->quickUserCan( 'edit', $user ) ? 'editold' : 'viewsourceold';
1541                         $msg = $this->msg( $key )->escaped();
1542                         $editLink = $this->msg( 'parentheses' )->rawParams(
1543                                 Linker::linkKnown( $title, $msg, [], $editQuery ) )->escaped();
1544                         $header .= ' ' . Html::rawElement(
1545                                 'span',
1546                                 [ 'class' => 'mw-diff-edit' ],
1547                                 $editLink
1548                         );
1549                         if ( $rev->isDeleted( RevisionRecord::DELETED_TEXT ) ) {
1550                                 $header = Html::rawElement(
1551                                         'span',
1552                                         [ 'class' => 'history-deleted' ],
1553                                         $header
1554                                 );
1555                         }
1556                 } else {
1557                         $header = Html::rawElement( 'span', [ 'class' => 'history-deleted' ], $header );
1558                 }
1559
1560                 return $header;
1561         }
1562
1563         /**
1564          * Add the header to a diff body
1565          *
1566          * @param string $diff Diff body
1567          * @param string $otitle Old revision header
1568          * @param string $ntitle New revision header
1569          * @param string $multi Notice telling user that there are intermediate
1570          *   revisions between the ones being compared
1571          * @param string $notice Other notices, e.g. that user is viewing deleted content
1572          *
1573          * @return string
1574          */
1575         public function addHeader( $diff, $otitle, $ntitle, $multi = '', $notice = '' ) {
1576                 // shared.css sets diff in interface language/dir, but the actual content
1577                 // is often in a different language, mostly the page content language/dir
1578                 $header = Html::openElement( 'table', [
1579                         'class' => [ 'diff', 'diff-contentalign-' . $this->getDiffLang()->alignStart() ],
1580                         'data-mw' => 'interface',
1581                 ] );
1582                 $userLang = htmlspecialchars( $this->getLanguage()->getHtmlCode() );
1583
1584                 if ( !$diff && !$otitle ) {
1585                         $header .= "
1586                         <tr class=\"diff-title\" lang=\"{$userLang}\">
1587                         <td class=\"diff-ntitle\">{$ntitle}</td>
1588                         </tr>";
1589                         $multiColspan = 1;
1590                 } else {
1591                         if ( $diff ) { // Safari/Chrome show broken output if cols not used
1592                                 $header .= "
1593                                 <col class=\"diff-marker\" />
1594                                 <col class=\"diff-content\" />
1595                                 <col class=\"diff-marker\" />
1596                                 <col class=\"diff-content\" />";
1597                                 $colspan = 2;
1598                                 $multiColspan = 4;
1599                         } else {
1600                                 $colspan = 1;
1601                                 $multiColspan = 2;
1602                         }
1603                         if ( $otitle || $ntitle ) {
1604                                 $header .= "
1605                                 <tr class=\"diff-title\" lang=\"{$userLang}\">
1606                                 <td colspan=\"$colspan\" class=\"diff-otitle\">{$otitle}</td>
1607                                 <td colspan=\"$colspan\" class=\"diff-ntitle\">{$ntitle}</td>
1608                                 </tr>";
1609                         }
1610                 }
1611
1612                 if ( $multi != '' ) {
1613                         $header .= "<tr><td colspan=\"{$multiColspan}\" " .
1614                                 "class=\"diff-multi\" lang=\"{$userLang}\">{$multi}</td></tr>";
1615                 }
1616                 if ( $notice != '' ) {
1617                         $header .= "<tr><td colspan=\"{$multiColspan}\" " .
1618                                 "class=\"diff-notice\" lang=\"{$userLang}\">{$notice}</td></tr>";
1619                 }
1620
1621                 return $header . $diff . "</table>";
1622         }
1623
1624         /**
1625          * Use specified text instead of loading from the database
1626          * @param Content $oldContent
1627          * @param Content $newContent
1628          * @since 1.21
1629          * @deprecated since 1.32, use setRevisions or ContentHandler::getSlotDiffRenderer.
1630          */
1631         public function setContent( Content $oldContent, Content $newContent ) {
1632                 $this->mOldContent = $oldContent;
1633                 $this->mNewContent = $newContent;
1634
1635                 $this->mTextLoaded = 2;
1636                 $this->mRevisionsLoaded = true;
1637                 $this->isContentOverridden = true;
1638                 $this->slotDiffRenderers = null;
1639         }
1640
1641         /**
1642          * Use specified text instead of loading from the database.
1643          * @param RevisionRecord|null $oldRevision
1644          * @param RevisionRecord $newRevision
1645          */
1646         public function setRevisions(
1647                 RevisionRecord $oldRevision = null, RevisionRecord $newRevision
1648         ) {
1649                 if ( $oldRevision ) {
1650                         $this->mOldRev = new Revision( $oldRevision );
1651                         $this->mOldid = $oldRevision->getId();
1652                         $this->mOldPage = Title::newFromLinkTarget( $oldRevision->getPageAsLinkTarget() );
1653                         // This method is meant for edit diffs and such so there is no reason to provide a
1654                         // revision that's not readable to the user, but check it just in case.
1655                         $this->mOldContent = $oldRevision->getContent( SlotRecord::MAIN,
1656                                 RevisionRecord::FOR_THIS_USER, $this->getUser() );
1657                 } else {
1658                         $this->mOldPage = null;
1659                         $this->mOldRev = $this->mOldid = false;
1660                 }
1661                 $this->mNewRev = new Revision( $newRevision );
1662                 $this->mNewid = $newRevision->getId();
1663                 $this->mNewPage = Title::newFromLinkTarget( $newRevision->getPageAsLinkTarget() );
1664                 $this->mNewContent = $newRevision->getContent( SlotRecord::MAIN,
1665                         RevisionRecord::FOR_THIS_USER, $this->getUser() );
1666
1667                 $this->mRevisionsIdsLoaded = $this->mRevisionsLoaded = true;
1668                 $this->mTextLoaded = $oldRevision ? 2 : 1;
1669                 $this->isContentOverridden = false;
1670                 $this->slotDiffRenderers = null;
1671         }
1672
1673         /**
1674          * Set the language in which the diff text is written
1675          *
1676          * @param Language $lang
1677          * @since 1.19
1678          */
1679         public function setTextLanguage( Language $lang ) {
1680                 $this->mDiffLang = $lang;
1681         }
1682
1683         /**
1684          * Maps a revision pair definition as accepted by DifferenceEngine constructor
1685          * to a pair of actual integers representing revision ids.
1686          *
1687          * @param int $old Revision id, e.g. from URL parameter 'oldid'
1688          * @param int|string $new Revision id or strings 'next' or 'prev', e.g. from URL parameter 'diff'
1689          *
1690          * @return array List of two revision ids, older first, later second.
1691          *     Zero signifies invalid argument passed.
1692          *     false signifies that there is no previous/next revision ($old is the oldest/newest one).
1693          */
1694         public function mapDiffPrevNext( $old, $new ) {
1695                 if ( $new === 'prev' ) {
1696                         // Show diff between revision $old and the previous one. Get previous one from DB.
1697                         $newid = intval( $old );
1698                         $oldid = $this->getTitle()->getPreviousRevisionID( $newid );
1699                 } elseif ( $new === 'next' ) {
1700                         // Show diff between revision $old and the next one. Get next one from DB.
1701                         $oldid = intval( $old );
1702                         $newid = $this->getTitle()->getNextRevisionID( $oldid );
1703                 } else {
1704                         $oldid = intval( $old );
1705                         $newid = intval( $new );
1706                 }
1707
1708                 return [ $oldid, $newid ];
1709         }
1710
1711         /**
1712          * Load revision IDs
1713          */
1714         private function loadRevisionIds() {
1715                 if ( $this->mRevisionsIdsLoaded ) {
1716                         return;
1717                 }
1718
1719                 $this->mRevisionsIdsLoaded = true;
1720
1721                 $old = $this->mOldid;
1722                 $new = $this->mNewid;
1723
1724                 list( $this->mOldid, $this->mNewid ) = self::mapDiffPrevNext( $old, $new );
1725                 if ( $new === 'next' && $this->mNewid === false ) {
1726                         # if no result, NewId points to the newest old revision. The only newer
1727                         # revision is cur, which is "0".
1728                         $this->mNewid = 0;
1729                 }
1730
1731                 Hooks::run(
1732                         'NewDifferenceEngine',
1733                         [ $this->getTitle(), &$this->mOldid, &$this->mNewid, $old, $new ]
1734                 );
1735         }
1736
1737         /**
1738          * Load revision metadata for the specified revisions. If newid is 0, then compare
1739          * the old revision in oldid to the current revision of the current page (as defined
1740          * by the request context); if oldid is 0, then compare the revision in newid to the
1741          * immediately previous one.
1742          *
1743          * If oldid is false, leave the corresponding revision object set to false. This can
1744          * happen with 'diff=prev' pointing to a non-existent revision, and is also used directly
1745          * by the API.
1746          *
1747          * @return bool Whether both revisions were loaded successfully. Setting mOldRev
1748          *   to false counts as successful loading.
1749          */
1750         public function loadRevisionData() {
1751                 if ( $this->mRevisionsLoaded ) {
1752                         return $this->isContentOverridden || ( $this->mOldRev !== null && $this->mNewRev !== null );
1753                 }
1754
1755                 // Whether it succeeds or fails, we don't want to try again
1756                 $this->mRevisionsLoaded = true;
1757
1758                 $this->loadRevisionIds();
1759
1760                 // Load the new revision object
1761                 if ( $this->mNewid ) {
1762                         $this->mNewRev = Revision::newFromId( $this->mNewid );
1763                 } else {
1764                         $this->mNewRev = Revision::newFromTitle(
1765                                 $this->getTitle(),
1766                                 false,
1767                                 Revision::READ_NORMAL
1768                         );
1769                 }
1770
1771                 if ( !$this->mNewRev instanceof Revision ) {
1772                         return false;
1773                 }
1774
1775                 // Update the new revision ID in case it was 0 (makes life easier doing UI stuff)
1776                 $this->mNewid = $this->mNewRev->getId();
1777                 if ( $this->mNewid ) {
1778                         $this->mNewPage = $this->mNewRev->getTitle();
1779                 } else {
1780                         $this->mNewPage = null;
1781                 }
1782
1783                 // Load the old revision object
1784                 $this->mOldRev = false;
1785                 if ( $this->mOldid ) {
1786                         $this->mOldRev = Revision::newFromId( $this->mOldid );
1787                 } elseif ( $this->mOldid === 0 ) {
1788                         $rev = $this->mNewRev->getPrevious();
1789                         if ( $rev ) {
1790                                 $this->mOldid = $rev->getId();
1791                                 $this->mOldRev = $rev;
1792                         } else {
1793                                 // No previous revision; mark to show as first-version only.
1794                                 $this->mOldid = false;
1795                                 $this->mOldRev = false;
1796                         }
1797                 } /* elseif ( $this->mOldid === false ) leave mOldRev false; */
1798
1799                 if ( is_null( $this->mOldRev ) ) {
1800                         return false;
1801                 }
1802
1803                 if ( $this->mOldRev && $this->mOldRev->getId() ) {
1804                         $this->mOldPage = $this->mOldRev->getTitle();
1805                 } else {
1806                         $this->mOldPage = null;
1807                 }
1808
1809                 // Load tags information for both revisions
1810                 $dbr = wfGetDB( DB_REPLICA );
1811                 $changeTagDefStore = MediaWikiServices::getInstance()->getChangeTagDefStore();
1812                 if ( $this->mOldid !== false ) {
1813                         $tagIds = $dbr->selectFieldValues(
1814                                 'change_tag',
1815                                 'ct_tag_id',
1816                                 [ 'ct_rev_id' => $this->mOldid ],
1817                                 __METHOD__
1818                         );
1819                         $tags = [];
1820                         foreach ( $tagIds as $tagId ) {
1821                                 try {
1822                                         $tags[] = $changeTagDefStore->getName( (int)$tagId );
1823                                 } catch ( NameTableAccessException $exception ) {
1824                                         continue;
1825                                 }
1826                         }
1827                         $this->mOldTags = implode( ',', $tags );
1828                 } else {
1829                         $this->mOldTags = false;
1830                 }
1831
1832                 $tagIds = $dbr->selectFieldValues(
1833                         'change_tag',
1834                         'ct_tag_id',
1835                         [ 'ct_rev_id' => $this->mNewid ],
1836                         __METHOD__
1837                 );
1838                 $tags = [];
1839                 foreach ( $tagIds as $tagId ) {
1840                         try {
1841                                 $tags[] = $changeTagDefStore->getName( (int)$tagId );
1842                         } catch ( NameTableAccessException $exception ) {
1843                                 continue;
1844                         }
1845                 }
1846                 $this->mNewTags = implode( ',', $tags );
1847
1848                 return true;
1849         }
1850
1851         /**
1852          * Load the text of the revisions, as well as revision data.
1853          * When the old revision is missing (mOldRev is false), loading mOldContent is not attempted.
1854          *
1855          * @return bool Whether the content of both revisions could be loaded successfully.
1856          *   (When mOldRev is false, that still counts as a success.)
1857          *
1858          */
1859         public function loadText() {
1860                 if ( $this->mTextLoaded == 2 ) {
1861                         return $this->loadRevisionData() && ( $this->mOldRev === false || $this->mOldContent )
1862                                 && $this->mNewContent;
1863                 }
1864
1865                 // Whether it succeeds or fails, we don't want to try again
1866                 $this->mTextLoaded = 2;
1867
1868                 if ( !$this->loadRevisionData() ) {
1869                         return false;
1870                 }
1871
1872                 if ( $this->mOldRev ) {
1873                         $this->mOldContent = $this->mOldRev->getContent(
1874                                 RevisionRecord::FOR_THIS_USER, $this->getUser()
1875                         );
1876                         if ( $this->mOldContent === null ) {
1877                                 return false;
1878                         }
1879                 }
1880
1881                 $this->mNewContent = $this->mNewRev->getContent(
1882                         RevisionRecord::FOR_THIS_USER, $this->getUser()
1883                 );
1884                 Hooks::run( 'DifferenceEngineLoadTextAfterNewContentIsLoaded', [ $this ] );
1885                 if ( $this->mNewContent === null ) {
1886                         return false;
1887                 }
1888
1889                 return true;
1890         }
1891
1892         /**
1893          * Load the text of the new revision, not the old one
1894          *
1895          * @return bool Whether the content of the new revision could be loaded successfully.
1896          */
1897         public function loadNewText() {
1898                 if ( $this->mTextLoaded >= 1 ) {
1899                         return $this->loadRevisionData();
1900                 }
1901
1902                 $this->mTextLoaded = 1;
1903
1904                 if ( !$this->loadRevisionData() ) {
1905                         return false;
1906                 }
1907
1908                 $this->mNewContent = $this->mNewRev->getContent(
1909                         RevisionRecord::FOR_THIS_USER, $this->getUser()
1910                 );
1911
1912                 Hooks::run( 'DifferenceEngineAfterLoadNewText', [ $this ] );
1913
1914                 return true;
1915         }
1916
1917 }