includes/diff/DifferenceEngine.php

   1 <?php
   2 /**
   3  * User interface for the difference engine.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup DifferenceEngine
  22  */
  23
  24 use MediaWiki\MediaWikiServices;
  25 use MediaWiki\Revision\RevisionRecord;
  26 use MediaWiki\Revision\SlotRecord;
  27 use MediaWiki\Storage\NameTableAccessException;
  28
  29 /**
  30  * DifferenceEngine is responsible for rendering the difference between two revisions as HTML.
  31  * This includes interpreting URL parameters, retrieving revision data, checking access permissions,
  32  * selecting and invoking the diff generator class for the individual slots, doing post-processing
  33  * on the generated diff, adding the rest of the HTML (such as headers) and writing the whole thing
  34  * to OutputPage.
  35  *
  36  * DifferenceEngine can be subclassed by extensions, by customizing
  37  * ContentHandler::createDifferenceEngine; the content handler will be selected based on the
  38  * content model of the main slot (of the new revision, when the two are different).
  39  * That might change after PageTypeHandler gets introduced.
  40  *
  41  * In the past, the class was also used for slot-level diff generation, and extensions might still
  42  * subclass it and add such functionality. When that is the case (sepcifically, when a
  43  * ContentHandler returns a standard SlotDiffRenderer but a nonstandard DifferenceEngine)
  44  * DifferenceEngineSlotDiffRenderer will be used to convert the old behavior into the new one.
  45  *
  46  * @ingroup DifferenceEngine
  47  *
  48  * @todo This class is huge and poorly defined. It should be split into a controller responsible
  49  * for interpreting query parameters, retrieving data and checking permissions; and a HTML renderer.
  50  */
  51 class DifferenceEngine extends ContextSource {
  52
  53         use DeprecationHelper;
  54
  55         /**
  56          * Constant to indicate diff cache compatibility.
  57          * Bump this when changing the diff formatting in a way that
  58          * fixes important bugs or such to force cached diff views to
  59          * clear.
  60          */
  61         const DIFF_VERSION = '1.12';
  62
  63         /**
  64          * Revision ID for the old revision. 0 for the revision previous to $mNewid, false
  65          * if the diff does not have an old revision (e.g. 'oldid=<first revision of page>&diff=prev'),
  66          * or the revision does not exist, null if the revision is unsaved.
  67          * @var int|false|null
  68          */
  69         protected $mOldid;
  70
  71         /**
  72          * Revision ID for the new revision. 0 for the last revision of the current page
  73          * (as defined by the request context), false if the revision does not exist, null
  74          * if it is unsaved, or an alias such as 'next'.
  75          * @var int|string|false|null
  76          */
  77         protected $mNewid;
  78
  79         /**
  80          * Old revision (left pane).
  81          * Allowed to be an unsaved revision, unlikely that's ever needed though.
  82          * False when the old revision does not exist; this can happen when using
  83          * diff=prev on the first revision. Null when the revision should exist but
  84          * doesn't (e.g. load failure); loadRevisionData() will return false in that
  85          * case. Also null until lazy-loaded. Ignored completely when isContentOverridden
  86          * is set.
  87          * Since 1.32 public access is deprecated.
  88          * @var Revision|null|false
  89          */
  90         protected $mOldRev;
  91
  92         /**
  93          * New revision (right pane).
  94          * Note that this might be an unsaved revision (e.g. for edit preview).
  95          * Null in case of load failure; diff methods will just return an error message in that case,
  96          * and loadRevisionData() will return false. Also null until lazy-loaded. Ignored completely
  97          * when isContentOverridden is set.
  98          * Since 1.32 public access is deprecated.
  99          * @var Revision|null
 100          */
 101         protected $mNewRev;
 102
 103         /**
 104          * Title of $mOldRev or null if the old revision does not exist or does not belong to a page.
 105          * Since 1.32 public access is deprecated and the property can be null.
 106          * @var Title|null
 107          */
 108         protected $mOldPage;
 109
 110         /**
 111          * Title of $mNewRev or null if the new revision does not exist or does not belong to a page.
 112          * Since 1.32 public access is deprecated and the property can be null.
 113          * @var Title|null
 114          */
 115         protected $mNewPage;
 116
 117         /**
 118          * Change tags of $mOldRev or null if it does not exist / is not saved.
 119          * @var string[]|null
 120          */
 121         private $mOldTags;
 122
 123         /**
 124          * Change tags of $mNewRev or null if it does not exist / is not saved.
 125          * @var string[]|null
 126          */
 127         private $mNewTags;
 128
 129         /**
 130          * @var Content|null
 131          * @deprecated since 1.32, content slots are now handled by the corresponding SlotDiffRenderer.
 132          *   This property is set to the content of the main slot, but not actually used for the main diff.
 133          */
 134         private $mOldContent;
 135
 136         /**
 137          * @var Content|null
 138          * @deprecated since 1.32, content slots are now handled by the corresponding SlotDiffRenderer.
 139          *   This property is set to the content of the main slot, but not actually used for the main diff.
 140          */
 141         private $mNewContent;
 142
 143         /** @var Language */
 144         protected $mDiffLang;
 145
 146         /** @var bool Have the revisions IDs been loaded */
 147         private $mRevisionsIdsLoaded = false;
 148
 149         /** @var bool Have the revisions been loaded */
 150         protected $mRevisionsLoaded = false;
 151
 152         /** @var int How many text blobs have been loaded, 0, 1 or 2? */
 153         protected $mTextLoaded = 0;
 154
 155         /**
 156          * Was the content overridden via setContent()?
 157          * If the content was overridden, most internal state (e.g. mOldid or mOldRev) should be ignored
 158          * and only mOldContent and mNewContent is reliable.
 159          * (Note that setRevisions() does not set this flag as in that case all properties are
 160          * overriden and remain consistent with each other, so no special handling is needed.)
 161          * @var bool
 162          */
 163         protected $isContentOverridden = false;
 164
 165         /** @var bool Was the diff fetched from cache? */
 166         protected $mCacheHit = false;
 167
 168         /**
 169          * Set this to true to add debug info to the HTML output.
 170          * Warning: this may cause RSS readers to spuriously mark articles as "new"
 171          * (T22601)
 172          */
 173         public $enableDebugComment = false;
 174
 175         /** @var bool If true, line X is not displayed when X is 1, for example
 176          *    to increase readability and conserve space with many small diffs.
 177          */
 178         protected $mReducedLineNumbers = false;
 179
 180         /** @var string Link to action=markpatrolled */
 181         protected $mMarkPatrolledLink = null;
 182
 183         /** @var bool Show rev_deleted content if allowed */
 184         protected $unhide = false;
 185
 186         /** @var bool Refresh the diff cache */
 187         protected $mRefreshCache = false;
 188
 189         /** @var SlotDiffRenderer[] DifferenceEngine classes for the slots, keyed by role name. */
 190         protected $slotDiffRenderers = null;
 191
 192         /**
 193          * Temporary hack for B/C while slot diff related methods of DifferenceEngine are being
 194          * deprecated. When true, we are inside a DifferenceEngineSlotDiffRenderer and
 195          * $slotDiffRenderers should not be used.
 196          * @var bool
 197          */
 198         protected $isSlotDiffRenderer = false;
 199
 200         /** #@- */
 201
 202         /**
 203          * @param IContextSource|null $context Context to use, anything else will be ignored
 204          * @param int $old Old ID we want to show and diff with.
 205          * @param string|int $new Either revision ID or 'prev' or 'next'. Default: 0.
 206          * @param int $rcid Deprecated, no longer used!
 207          * @param bool $refreshCache If set, refreshes the diff cache
 208          * @param bool $unhide If set, allow viewing deleted revs
 209          */
 210         public function __construct( $context = null, $old = 0, $new = 0, $rcid = 0,
 211                 $refreshCache = false, $unhide = false
 212         ) {
 213                 $this->deprecatePublicProperty( 'mOldid', '1.32', __CLASS__ );
 214                 $this->deprecatePublicProperty( 'mNewid', '1.32', __CLASS__ );
 215                 $this->deprecatePublicProperty( 'mOldRev', '1.32', __CLASS__ );
 216                 $this->deprecatePublicProperty( 'mNewRev', '1.32', __CLASS__ );
 217                 $this->deprecatePublicProperty( 'mOldPage', '1.32', __CLASS__ );
 218                 $this->deprecatePublicProperty( 'mNewPage', '1.32', __CLASS__ );
 219                 $this->deprecatePublicProperty( 'mOldContent', '1.32', __CLASS__ );
 220                 $this->deprecatePublicProperty( 'mNewContent', '1.32', __CLASS__ );
 221                 $this->deprecatePublicProperty( 'mRevisionsLoaded', '1.32', __CLASS__ );
 222                 $this->deprecatePublicProperty( 'mTextLoaded', '1.32', __CLASS__ );
 223                 $this->deprecatePublicProperty( 'mCacheHit', '1.32', __CLASS__ );
 224
 225                 if ( $context instanceof IContextSource ) {
 226                         $this->setContext( $context );
 227                 }
 228
 229                 wfDebug( "DifferenceEngine old '$old' new '$new' rcid '$rcid'\n" );
 230
 231                 $this->mOldid = $old;
 232                 $this->mNewid = $new;
 233                 $this->mRefreshCache = $refreshCache;
 234                 $this->unhide = $unhide;
 235         }
 236
 237         /**
 238          * @return SlotDiffRenderer[] Diff renderers for each slot, keyed by role name.
 239          *   Includes slots only present in one of the revisions.
 240          */
 241         protected function getSlotDiffRenderers() {
 242                 if ( $this->isSlotDiffRenderer ) {
 243                         throw new LogicException( __METHOD__ . ' called in slot diff renderer mode' );
 244                 }
 245
 246                 if ( $this->slotDiffRenderers === null ) {
 247                         if ( !$this->loadRevisionData() ) {
 248                                 return [];
 249                         }
 250
 251                         $slotContents = $this->getSlotContents();
 252                         $this->slotDiffRenderers = array_map( function ( $contents ) {
 253                                 /** @var Content $content */
 254                                 $content = $contents['new'] ?: $contents['old'];
 255                                 return $content->getContentHandler()->getSlotDiffRenderer( $this->getContext() );
 256                         }, $slotContents );
 257                 }
 258                 return $this->slotDiffRenderers;
 259         }
 260
 261         /**
 262          * Mark this DifferenceEngine as a slot renderer (as opposed to a page renderer).
 263          * This is used in legacy mode when the DifferenceEngine is wrapped in a
 264          * DifferenceEngineSlotDiffRenderer.
 265          * @internal For use by DifferenceEngineSlotDiffRenderer only.
 266          */
 267         public function markAsSlotDiffRenderer() {
 268                 $this->isSlotDiffRenderer = true;
 269         }
 270
 271         /**
 272          * Get the old and new content objects for all slots.
 273          * This method does not do any permission checks.
 274          * @return array [ role => [ 'old' => SlotRecord|null, 'new' => SlotRecord|null ], ... ]
 275          */
 276         protected function getSlotContents() {
 277                 if ( $this->isContentOverridden ) {
 278                         return [
 279                                 SlotRecord::MAIN => [
 280                                         'old' => $this->mOldContent,
 281                                         'new' => $this->mNewContent,
 282                                 ]
 283                         ];
 284                 } elseif ( !$this->loadRevisionData() ) {
 285                         return [];
 286                 }
 287
 288                 $newSlots = $this->mNewRev->getRevisionRecord()->getSlots()->getSlots();
 289                 if ( $this->mOldRev ) {
 290                         $oldSlots = $this->mOldRev->getRevisionRecord()->getSlots()->getSlots();
 291                 } else {
 292                         $oldSlots = [];
 293                 }
 294                 // The order here will determine the visual order of the diff. The current logic is
 295                 // slots of the new revision first in natural order, then deleted ones. This is ad hoc
 296                 // and should not be relied on - in the future we may want the ordering to depend
 297                 // on the page type.
 298                 $roles = array_merge( array_keys( $newSlots ), array_keys( $oldSlots ) );
 299
 300                 $slots = [];
 301                 foreach ( $roles as $role ) {
 302                         $slots[$role] = [
 303                                 'old' => isset( $oldSlots[$role] ) ? $oldSlots[$role]->getContent() : null,
 304                                 'new' => isset( $newSlots[$role] ) ? $newSlots[$role]->getContent() : null,
 305                         ];
 306                 }
 307                 // move main slot to front
 308                 if ( isset( $slots[SlotRecord::MAIN] ) ) {
 309                         $slots = [ SlotRecord::MAIN => $slots[SlotRecord::MAIN] ] + $slots;
 310                 }
 311                 return $slots;
 312         }
 313
 314         public function getTitle() {
 315                 // T202454 avoid errors when there is no title
 316                 return parent::getTitle() ?: Title::makeTitle( NS_SPECIAL, 'BadTitle/DifferenceEngine' );
 317         }
 318
 319         /**
 320          * Set reduced line numbers mode.
 321          * When set, line X is not displayed when X is 1, for example to increase readability and
 322          * conserve space with many small diffs.
 323          * @param bool $value
 324          */
 325         public function setReducedLineNumbers( $value = true ) {
 326                 $this->mReducedLineNumbers = $value;
 327         }
 328
 329         /**
 330          * Get the language of the difference engine, defaults to page content language
 331          *
 332          * @return Language
 333          */
 334         public function getDiffLang() {
 335                 if ( $this->mDiffLang === null ) {
 336                         # Default language in which the diff text is written.
 337                         $this->mDiffLang = $this->getTitle()->getPageLanguage();
 338                 }
 339
 340                 return $this->mDiffLang;
 341         }
 342
 343         /**
 344          * @return bool
 345          */
 346         public function wasCacheHit() {
 347                 return $this->mCacheHit;
 348         }
 349
 350         /**
 351          * Get the ID of old revision (left pane) of the diff. 0 for the revision
 352          * previous to getNewid(), false if the old revision does not exist, null
 353          * if it's unsaved.
 354          * To get a real revision ID instead of 0, call loadRevisionData() first.
 355          * @return int|false|null
 356          */
 357         public function getOldid() {
 358                 $this->loadRevisionIds();
 359
 360                 return $this->mOldid;
 361         }
 362
 363         /**
 364          * Get the ID of new revision (right pane) of the diff. 0 for the current revision,
 365          * false if the new revision does not exist, null if it's unsaved.
 366          * To get a real revision ID instead of 0, call loadRevisionData() first.
 367          * @return int|false|null
 368          */
 369         public function getNewid() {
 370                 $this->loadRevisionIds();
 371
 372                 return $this->mNewid;
 373         }
 374
 375         /**
 376          * Get the left side of the diff.
 377          * Could be null when the first revision of the page is diffed to 'prev' (or in the case of
 378          * load failure).
 379          * @return RevisionRecord|null
 380          */
 381         public function getOldRevision() {
 382                 return $this->mOldRev ? $this->mOldRev->getRevisionRecord() : null;
 383         }
 384
 385         /**
 386          * Get the right side of the diff.
 387          * Should not be null but can still happen in the case of load failure.
 388          * @return RevisionRecord|null
 389          */
 390         public function getNewRevision() {
 391                 return $this->mNewRev ? $this->mNewRev->getRevisionRecord() : null;
 392         }
 393
 394         /**
 395          * Look up a special:Undelete link to the given deleted revision id,
 396          * as a workaround for being unable to load deleted diffs in currently.
 397          *
 398          * @param int $id Revision ID
 399          *
 400          * @return string|bool Link HTML or false
 401          */
 402         public function deletedLink( $id ) {
 403                 $permissionManager = MediaWikiServices::getInstance()->getPermissionManager();
 404                 if ( $permissionManager->userHasRight( $this->getUser(), '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->quickUserCan(
 545                                 'edit', $user, $this->mNewPage
 546                         ) ) {
 547                                 if ( $this->mNewRev->isCurrent() && $permissionManager->quickUserCan(
 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->userCanEdit( $this->mOldRev ) &&
 559                                         $this->userCanEdit( $this->mNewRev )
 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                 $permissionManager = MediaWikiServices::getInstance()->getPermissionManager();
 769
 770                 // Prepare a change patrol link, if applicable
 771                 if (
 772                         // Is patrolling enabled and the user allowed to?
 773                         $config->get( 'UseRCPatrol' ) &&
 774                         $this->mNewPage &&
 775                         $permissionManager->quickUserCan( 'patrol', $user, $this->mNewPage ) &&
 776                         // Only do this if the revision isn't more than 6 hours older
 777                         // than the Max RC age (6h because the RC might not be cleaned out regularly)
 778                         RecentChange::isInRCLifespan( $this->mNewRev->getTimestamp(), 21600 )
 779                 ) {
 780                         // Look for an unpatrolled change corresponding to this diff
 781                         $db = wfGetDB( DB_REPLICA );
 782                         $change = RecentChange::newFromConds(
 783                                 [
 784                                         'rc_timestamp' => $db->timestamp( $this->mNewRev->getTimestamp() ),
 785                                         'rc_this_oldid' => $this->mNewid,
 786                                         'rc_patrolled' => RecentChange::PRC_UNPATROLLED
 787                                 ],
 788                                 __METHOD__
 789                         );
 790
 791                         if ( $change && !$change->getPerformer()->equals( $user ) ) {
 792                                 $rcid = $change->getAttribute( 'rc_id' );
 793                         } else {
 794                                 // None found or the page has been created by the current user.
 795                                 // If the user could patrol this it already would be patrolled
 796                                 $rcid = 0;
 797                         }
 798
 799                         // Allow extensions to possibly change the rcid here
 800                         // For example the rcid might be set to zero due to the user
 801                         // being the same as the performer of the change but an extension
 802                         // might still want to show it under certain conditions
 803                         Hooks::run( 'DifferenceEngineMarkPatrolledRCID', [ &$rcid, $this, $change, $user ] );
 804
 805                         // Build the link
 806                         if ( $rcid ) {
 807                                 $this->getOutput()->preventClickjacking();
 808                                 if ( $permissionManager->userHasRight( $user, 'writeapi' ) ) {
 809                                         $this->getOutput()->addModules( 'mediawiki.page.patrol.ajax' );
 810                                 }
 811
 812                                 return [
 813                                         'rcid' => $rcid,
 814                                 ];
 815                         }
 816                 }
 817
 818                 // No mark as patrolled link applicable
 819                 return false;
 820         }
 821
 822         /**
 823          * @param Revision $rev
 824          *
 825          * @return string
 826          */
 827         protected function revisionDeleteLink( $rev ) {
 828                 $link = Linker::getRevDeleteLink( $this->getUser(), $rev, $rev->getTitle() );
 829                 if ( $link !== '' ) {
 830                         $link = "\u{00A0}\u{00A0}\u{00A0}" . $link . ' ';
 831                 }
 832
 833                 return $link;
 834         }
 835
 836         /**
 837          * Show the new revision of the page.
 838          *
 839          * @note Not supported after calling setContent().
 840          */
 841         public function renderNewRevision() {
 842                 if ( $this->isContentOverridden ) {
 843                         // The code below only works with a Revision object. We could construct a fake revision
 844                         // (here or in setContent), but since this does not seem needed at the moment,
 845                         // we'll just fail for now.
 846                         throw new LogicException(
 847                                 __METHOD__
 848                                 . ' is not supported after calling setContent(). Use setRevisions() instead.'
 849                         );
 850                 }
 851
 852                 $out = $this->getOutput();
 853                 $revHeader = $this->getRevisionHeader( $this->mNewRev );
 854                 # Add "current version as of X" title
 855                 $out->addHTML( "<hr class='diff-hr' id='mw-oldid' />
 856                 <h2 class='diff-currentversion-title'>{$revHeader}</h2>\n" );
 857                 # Page content may be handled by a hooked call instead...
 858                 if ( Hooks::run( 'ArticleContentOnDiff', [ $this, $out ] ) ) {
 859                         $this->loadNewText();
 860                         if ( !$this->mNewPage ) {
 861                                 // New revision is unsaved; bail out.
 862                                 // TODO in theory rendering the new revision is a meaningful thing to do
 863                                 // even if it's unsaved, but a lot of untangling is required to do it safely.
 864                                 return;
 865                         }
 866
 867                         $out->setRevisionId( $this->mNewid );
 868                         $out->setRevisionTimestamp( $this->mNewRev->getTimestamp() );
 869                         $out->setArticleFlag( true );
 870
 871                         if ( !Hooks::run( 'ArticleRevisionViewCustom',
 872                                 [ $this->mNewRev->getRevisionRecord(), $this->mNewPage, $out ] )
 873                         ) {
 874                                 // Handled by extension
 875                                 // NOTE: sync with hooks called in Article::view()
 876                         } elseif ( !Hooks::run( 'ArticleContentViewCustom',
 877                                 [ $this->mNewContent, $this->mNewPage, $out ], '1.32' )
 878                         ) {
 879                                 // Handled by extension
 880                                 // NOTE: sync with hooks called in Article::view()
 881                         } else {
 882                                 // Normal page
 883                                 if ( $this->getTitle()->equals( $this->mNewPage ) ) {
 884                                         // If the Title stored in the context is the same as the one
 885                                         // of the new revision, we can use its associated WikiPage
 886                                         // object.
 887                                         $wikiPage = $this->getWikiPage();
 888                                 } else {
 889                                         // Otherwise we need to create our own WikiPage object
 890                                         $wikiPage = WikiPage::factory( $this->mNewPage );
 891                                 }
 892
 893                                 $parserOutput = $this->getParserOutput( $wikiPage, $this->mNewRev );
 894
 895                                 # WikiPage::getParserOutput() should not return false, but just in case
 896                                 if ( $parserOutput ) {
 897                                         // Allow extensions to change parser output here
 898                                         if ( Hooks::run( 'DifferenceEngineRenderRevisionAddParserOutput',
 899                                                 [ $this, $out, $parserOutput, $wikiPage ] )
 900                                         ) {
 901                                                 $out->addParserOutput( $parserOutput, [
 902                                                         'enableSectionEditLinks' => $this->mNewRev->isCurrent()
 903                                                                 && MediaWikiServices::getInstance()->getPermissionManager()->quickUserCan(
 904                                                                         'edit',
 905                                                                         $this->getUser(),
 906                                                                         $this->mNewRev->getTitle()
 907                                                                 )
 908                                                 ] );
 909                                         }
 910                                 }
 911                         }
 912                 }
 913
 914                 // Allow extensions to optionally not show the final patrolled link
 915                 if ( Hooks::run( 'DifferenceEngineRenderRevisionShowFinalPatrolLink' ) ) {
 916                         # Add redundant patrol link on bottom...
 917                         $out->addHTML( $this->markPatrolledLink() );
 918                 }
 919         }
 920
 921         /**
 922          * @param WikiPage $page
 923          * @param Revision $rev
 924          *
 925          * @return ParserOutput|bool False if the revision was not found
 926          */
 927         protected function getParserOutput( WikiPage $page, Revision $rev ) {
 928                 if ( !$rev->getId() ) {
 929                         // WikiPage::getParserOutput wants a revision ID. Passing 0 will incorrectly show
 930                         // the current revision, so fail instead. If need be, WikiPage::getParserOutput
 931                         // could be made to accept a Revision or RevisionRecord instead of the id.
 932                         return false;
 933                 }
 934
 935                 $parserOptions = $page->makeParserOptions( $this->getContext() );
 936                 $parserOutput = $page->getParserOutput( $parserOptions, $rev->getId() );
 937
 938                 return $parserOutput;
 939         }
 940
 941         /**
 942          * Get the diff text, send it to the OutputPage object
 943          * Returns false if the diff could not be generated, otherwise returns true
 944          *
 945          * @param string|bool $otitle Header for old text or false
 946          * @param string|bool $ntitle Header for new text or false
 947          * @param string $notice HTML between diff header and body
 948          *
 949          * @return bool
 950          */
 951         public function showDiff( $otitle, $ntitle, $notice = '' ) {
 952                 // Allow extensions to affect the output here
 953                 Hooks::run( 'DifferenceEngineShowDiff', [ $this ] );
 954
 955                 $diff = $this->getDiff( $otitle, $ntitle, $notice );
 956                 if ( $diff === false ) {
 957                         $this->showMissingRevision();
 958
 959                         return false;
 960                 } else {
 961                         $this->showDiffStyle();
 962                         $this->getOutput()->addHTML( $diff );
 963
 964                         return true;
 965                 }
 966         }
 967
 968         /**
 969          * Add style sheets for diff display.
 970          */
 971         public function showDiffStyle() {
 972                 if ( !$this->isSlotDiffRenderer ) {
 973                         $this->getOutput()->addModuleStyles( [
 974                                 'mediawiki.interface.helpers.styles',
 975                                 'mediawiki.diff.styles'
 976                         ] );
 977                         foreach ( $this->getSlotDiffRenderers() as $slotDiffRenderer ) {
 978                                 $slotDiffRenderer->addModules( $this->getOutput() );
 979                         }
 980                 }
 981         }
 982
 983         /**
 984          * Get complete diff table, including header
 985          *
 986          * @param string|bool $otitle Header for old text or false
 987          * @param string|bool $ntitle Header for new text or false
 988          * @param string $notice HTML between diff header and body
 989          *
 990          * @return mixed
 991          */
 992         public function getDiff( $otitle, $ntitle, $notice = '' ) {
 993                 $body = $this->getDiffBody();
 994                 if ( $body === false ) {
 995                         return false;
 996                 }
 997
 998                 $multi = $this->getMultiNotice();
 999                 // Display a message when the diff is empty
1000                 if ( $body === '' ) {
1001                         $notice .= '<div class="mw-diff-empty">' .
1002                                 $this->msg( 'diff-empty' )->parse() .
1003                                 "</div>\n";
1004                 }
1005
1006                 return $this->addHeader( $body, $otitle, $ntitle, $multi, $notice );
1007         }
1008
1009         /**
1010          * Get the diff table body, without header
1011          *
1012          * @return mixed (string/false)
1013          */
1014         public function getDiffBody() {
1015                 $this->mCacheHit = true;
1016                 // Check if the diff should be hidden from this user
1017                 if ( !$this->isContentOverridden ) {
1018                         if ( !$this->loadRevisionData() ) {
1019                                 return false;
1020                         } elseif ( $this->mOldRev &&
1021                                 !$this->mOldRev->userCan( RevisionRecord::DELETED_TEXT, $this->getUser() )
1022                         ) {
1023                                 return false;
1024                         } elseif ( $this->mNewRev &&
1025                                 !$this->mNewRev->userCan( RevisionRecord::DELETED_TEXT, $this->getUser() )
1026                         ) {
1027                                 return false;
1028                         }
1029                         // Short-circuit
1030                         if ( $this->mOldRev === false || ( $this->mOldRev && $this->mNewRev &&
1031                                 $this->mOldRev->getId() && $this->mOldRev->getId() == $this->mNewRev->getId() )
1032                         ) {
1033                                 if ( Hooks::run( 'DifferenceEngineShowEmptyOldContent', [ $this ] ) ) {
1034                                         return '';
1035                                 }
1036                         }
1037                 }
1038
1039                 // Cacheable?
1040                 $key = false;
1041                 $cache = MediaWikiServices::getInstance()->getMainWANObjectCache();
1042                 if ( $this->mOldid && $this->mNewid ) {
1043                         // Check if subclass is still using the old way
1044                         // for backwards-compatibility
1045                         $key = $this->getDiffBodyCacheKey();
1046                         if ( $key === null ) {
1047                                 $key = $cache->makeKey( ...$this->getDiffBodyCacheKeyParams() );
1048                         }
1049
1050                         // Try cache
1051                         if ( !$this->mRefreshCache ) {
1052                                 $difftext = $cache->get( $key );
1053                                 if ( is_string( $difftext ) ) {
1054                                         wfIncrStats( 'diff_cache.hit' );
1055                                         $difftext = $this->localiseDiff( $difftext );
1056                                         $difftext .= "\n<!-- diff cache key $key -->\n";
1057
1058                                         return $difftext;
1059                                 }
1060                         } // don't try to load but save the result
1061                 }
1062                 $this->mCacheHit = false;
1063
1064                 // Loadtext is permission safe, this just clears out the diff
1065                 if ( !$this->loadText() ) {
1066                         return false;
1067                 }
1068
1069                 $difftext = '';
1070                 // We've checked for revdelete at the beginning of this method; it's OK to ignore
1071                 // read permissions here.
1072                 $slotContents = $this->getSlotContents();
1073                 foreach ( $this->getSlotDiffRenderers() as $role => $slotDiffRenderer ) {
1074                         $slotDiff = $slotDiffRenderer->getDiff( $slotContents[$role]['old'],
1075                                 $slotContents[$role]['new'] );
1076                         if ( $slotDiff && $role !== SlotRecord::MAIN ) {
1077                                 // FIXME: ask SlotRoleHandler::getSlotNameMessage
1078                                 $slotTitle = $role;
1079                                 $difftext .= $this->getSlotHeader( $slotTitle );
1080                         }
1081                         $difftext .= $slotDiff;
1082                 }
1083
1084                 // Avoid PHP 7.1 warning from passing $this by reference
1085                 $diffEngine = $this;
1086
1087                 // Save to cache for 7 days
1088                 if ( !Hooks::run( 'AbortDiffCache', [ &$diffEngine ] ) ) {
1089                         wfIncrStats( 'diff_cache.uncacheable' );
1090                 } elseif ( $key !== false && $difftext !== false ) {
1091                         wfIncrStats( 'diff_cache.miss' );
1092                         $cache->set( $key, $difftext, 7 * 86400 );
1093                 } else {
1094                         wfIncrStats( 'diff_cache.uncacheable' );
1095                 }
1096                 // localise line numbers and title attribute text
1097                 if ( $difftext !== false ) {
1098                         $difftext = $this->localiseDiff( $difftext );
1099                 }
1100
1101                 return $difftext;
1102         }
1103
1104         /**
1105          * Get the diff table body for one slot, without header
1106          *
1107          * @param string $role
1108          * @return string|false
1109          */
1110         public function getDiffBodyForRole( $role ) {
1111                 $diffRenderers = $this->getSlotDiffRenderers();
1112                 if ( !isset( $diffRenderers[$role] ) ) {
1113                         return false;
1114                 }
1115
1116                 $slotContents = $this->getSlotContents();
1117                 $slotDiff = $diffRenderers[$role]->getDiff( $slotContents[$role]['old'],
1118                         $slotContents[$role]['new'] );
1119                 if ( !$slotDiff ) {
1120                         return false;
1121                 }
1122
1123                 if ( $role !== SlotRecord::MAIN ) {
1124                         // TODO use human-readable role name at least
1125                         $slotTitle = $role;
1126                         $slotDiff = $this->getSlotHeader( $slotTitle ) . $slotDiff;
1127                 }
1128
1129                 return $this->localiseDiff( $slotDiff );
1130         }
1131
1132         /**
1133          * Get a slot header for inclusion in a diff body (as a table row).
1134          *
1135          * @param string $headerText The text of the header
1136          * @return string
1137          *
1138          */
1139         protected function getSlotHeader( $headerText ) {
1140                 // The old revision is missing on oldid=<first>&diff=prev; only 2 columns in that case.
1141                 $columnCount = $this->mOldRev ? 4 : 2;
1142                 $userLang = $this->getLanguage()->getHtmlCode();
1143                 return Html::rawElement( 'tr', [ 'class' => 'mw-diff-slot-header', 'lang' => $userLang ],
1144                         Html::element( 'th', [ 'colspan' => $columnCount ], $headerText ) );
1145         }
1146
1147         /**
1148          * Returns the cache key for diff body text or content.
1149          *
1150          * @deprecated since 1.31, use getDiffBodyCacheKeyParams() instead
1151          * @since 1.23
1152          *
1153          * @throws MWException
1154          * @return string|null
1155          */
1156         protected function getDiffBodyCacheKey() {
1157                 return null;
1158         }
1159
1160         /**
1161          * Get the cache key parameters
1162          *
1163          * Subclasses can replace the first element in the array to something
1164          * more specific to the type of diff (e.g. "inline-diff"), or append
1165          * if the cache should vary on more things. Overriding entirely should
1166          * be avoided.
1167          *
1168          * @since 1.31
1169          *
1170          * @return array
1171          * @throws MWException
1172          */
1173         protected function getDiffBodyCacheKeyParams() {
1174                 if ( !$this->mOldid || !$this->mNewid ) {
1175                         throw new MWException( 'mOldid and mNewid must be set to get diff cache key.' );
1176                 }
1177
1178                 $engine = $this->getEngine();
1179                 $params = [
1180                         'diff',
1181                         $engine,
1182                         self::DIFF_VERSION,
1183                         "old-{$this->mOldid}",
1184                         "rev-{$this->mNewid}"
1185                 ];
1186
1187                 if ( $engine === 'wikidiff2' ) {
1188                         $params[] = phpversion( 'wikidiff2' );
1189                 }
1190
1191                 if ( !$this->isSlotDiffRenderer ) {
1192                         foreach ( $this->getSlotDiffRenderers() as $slotDiffRenderer ) {
1193                                 $params = array_merge( $params, $slotDiffRenderer->getExtraCacheKeys() );
1194                         }
1195                 }
1196
1197                 return $params;
1198         }
1199
1200         /**
1201          * Implements DifferenceEngineSlotDiffRenderer::getExtraCacheKeys(). Only used when
1202          * DifferenceEngine is wrapped in DifferenceEngineSlotDiffRenderer.
1203          * @return array
1204          * @internal for use by DifferenceEngineSlotDiffRenderer only
1205          * @deprecated
1206          */
1207         public function getExtraCacheKeys() {
1208                 // This method is called when the DifferenceEngine is used for a slot diff. We only care
1209                 // about special things, not the revision IDs, which are added to the cache key by the
1210                 // page-level DifferenceEngine, and which might not have a valid value for this object.
1211                 $this->mOldid = 123456789;
1212                 $this->mNewid = 987654321;
1213
1214                 // This will repeat a bunch of unnecessary key fields for each slot. Not nice but harmless.
1215                 $cacheString = $this->getDiffBodyCacheKey();
1216                 if ( $cacheString ) {
1217                         return [ $cacheString ];
1218                 }
1219
1220                 $params = $this->getDiffBodyCacheKeyParams();
1221
1222                 // Try to get rid of the standard keys to keep the cache key human-readable:
1223                 // call the getDiffBodyCacheKeyParams implementation of the base class, and if
1224                 // the child class includes the same keys, drop them.
1225                 // Uses an obscure PHP feature where static calls to non-static methods are allowed
1226                 // as long as we are already in a non-static method of the same class, and the call context
1227                 // ($this) will be inherited.
1228                 // phpcs:ignore Squiz.Classes.SelfMemberReference.NotUsed
1229                 $standardParams = DifferenceEngine::getDiffBodyCacheKeyParams();
1230                 if ( array_slice( $params, 0, count( $standardParams ) ) === $standardParams ) {
1231                         $params = array_slice( $params, count( $standardParams ) );
1232                 }
1233
1234                 return $params;
1235         }
1236
1237         /**
1238          * Generate a diff, no caching.
1239          *
1240          * @since 1.21
1241          *
1242          * @param Content $old Old content
1243          * @param Content $new New content
1244          *
1245          * @throws Exception If old or new content is not an instance of TextContent.
1246          * @return bool|string
1247          *
1248          * @deprecated since 1.32, use a SlotDiffRenderer instead.
1249          */
1250         public function generateContentDiffBody( Content $old, Content $new ) {
1251                 $slotDiffRenderer = $new->getContentHandler()->getSlotDiffRenderer( $this->getContext() );
1252                 if (
1253                         $slotDiffRenderer instanceof DifferenceEngineSlotDiffRenderer
1254                         && $this->isSlotDiffRenderer
1255                 ) {
1256                         // Oops, we are just about to enter an infinite loop (the slot-level DifferenceEngine
1257                         // called a DifferenceEngineSlotDiffRenderer that wraps the same DifferenceEngine class).
1258                         // This will happen when a content model has no custom slot diff renderer, it does have
1259                         // a custom difference engine, but that does not override this method.
1260                         throw new Exception( get_class( $this ) . ': could not maintain backwards compatibility. '
1261                                 . 'Please use a SlotDiffRenderer.' );
1262                 }
1263                 return $slotDiffRenderer->getDiff( $old, $new ) . $this->getDebugString();
1264         }
1265
1266         /**
1267          * Generate a diff, no caching
1268          *
1269          * @param string $otext Old text, must be already segmented
1270          * @param string $ntext New text, must be already segmented
1271          *
1272          * @throws Exception If content handling for text content is configured in a way
1273          *   that makes maintaining B/C hard.
1274          * @return bool|string
1275          *
1276          * @deprecated since 1.32, use a TextSlotDiffRenderer instead.
1277          */
1278         public function generateTextDiffBody( $otext, $ntext ) {
1279                 $slotDiffRenderer = ContentHandler::getForModelID( CONTENT_MODEL_TEXT )
1280                         ->getSlotDiffRenderer( $this->getContext() );
1281                 if ( !( $slotDiffRenderer instanceof TextSlotDiffRenderer ) ) {
1282                         // Someone used the GetSlotDiffRenderer hook to replace the renderer.
1283                         // This is too unlikely to happen to bother handling properly.
1284                         throw new Exception( 'The slot diff renderer for text content should be a '
1285                                 . 'TextSlotDiffRenderer subclass' );
1286                 }
1287                 return $slotDiffRenderer->getTextDiff( $otext, $ntext ) . $this->getDebugString();
1288         }
1289
1290         /**
1291          * Process $wgExternalDiffEngine and get a sane, usable engine
1292          *
1293          * @return bool|string 'wikidiff2', path to an executable, or false
1294          * @internal For use by this class and TextSlotDiffRenderer only.
1295          */
1296         public static function getEngine() {
1297                 global $wgExternalDiffEngine;
1298                 // We use the global here instead of Config because we write to the value,
1299                 // and Config is not mutable.
1300                 if ( $wgExternalDiffEngine == 'wikidiff' || $wgExternalDiffEngine == 'wikidiff3' ) {
1301                         wfDeprecated( "\$wgExternalDiffEngine = '{$wgExternalDiffEngine}'", '1.27' );
1302                         $wgExternalDiffEngine = false;
1303                 } elseif ( $wgExternalDiffEngine == 'wikidiff2' ) {
1304                         wfDeprecated( "\$wgExternalDiffEngine = '{$wgExternalDiffEngine}'", '1.32' );
1305                         $wgExternalDiffEngine = false;
1306                 } elseif ( !is_string( $wgExternalDiffEngine ) && $wgExternalDiffEngine !== false ) {
1307                         // And prevent people from shooting themselves in the foot...
1308                         wfWarn( '$wgExternalDiffEngine is set to a non-string value, forcing it to false' );
1309                         $wgExternalDiffEngine = false;
1310                 }
1311
1312                 if ( is_string( $wgExternalDiffEngine ) && is_executable( $wgExternalDiffEngine ) ) {
1313                         return $wgExternalDiffEngine;
1314                 } elseif ( $wgExternalDiffEngine === false && function_exists( 'wikidiff2_do_diff' ) ) {
1315                         return 'wikidiff2';
1316                 } else {
1317                         // Native PHP
1318                         return false;
1319                 }
1320         }
1321
1322         /**
1323          * Generates diff, to be wrapped internally in a logging/instrumentation
1324          *
1325          * @param string $otext Old text, must be already segmented
1326          * @param string $ntext New text, must be already segmented
1327          *
1328          * @throws Exception If content handling for text content is configured in a way
1329          *   that makes maintaining B/C hard.
1330          * @return bool|string
1331          *
1332          * @deprecated since 1.32, use a TextSlotDiffRenderer instead.
1333          */
1334         protected function textDiff( $otext, $ntext ) {
1335                 $slotDiffRenderer = ContentHandler::getForModelID( CONTENT_MODEL_TEXT )
1336                         ->getSlotDiffRenderer( $this->getContext() );
1337                 if ( !( $slotDiffRenderer instanceof TextSlotDiffRenderer ) ) {
1338                         // Someone used the GetSlotDiffRenderer hook to replace the renderer.
1339                         // This is too unlikely to happen to bother handling properly.
1340                         throw new Exception( 'The slot diff renderer for text content should be a '
1341                                 . 'TextSlotDiffRenderer subclass' );
1342                 }
1343                 return $slotDiffRenderer->getTextDiff( $otext, $ntext ) . $this->getDebugString();
1344         }
1345
1346         /**
1347          * Generate a debug comment indicating diff generating time,
1348          * server node, and generator backend.
1349          *
1350          * @param string $generator : What diff engine was used
1351          *
1352          * @return string
1353          */
1354         protected function debug( $generator = "internal" ) {
1355                 if ( !$this->enableDebugComment ) {
1356                         return '';
1357                 }
1358                 $data = [ $generator ];
1359                 if ( $this->getConfig()->get( 'ShowHostnames' ) ) {
1360                         $data[] = wfHostname();
1361                 }
1362                 $data[] = wfTimestamp( TS_DB );
1363
1364                 return "<!-- diff generator: " .
1365                         implode( " ", array_map( "htmlspecialchars", $data ) ) .
1366                         " -->\n";
1367         }
1368
1369         private function getDebugString() {
1370                 $engine = self::getEngine();
1371                 if ( $engine === 'wikidiff2' ) {
1372                         return $this->debug( 'wikidiff2' );
1373                 } elseif ( $engine === false ) {
1374                         return $this->debug( 'native PHP' );
1375                 } else {
1376                         return $this->debug( "external $engine" );
1377                 }
1378         }
1379
1380         /**
1381          * Localise diff output
1382          *
1383          * @param string $text
1384          * @return string
1385          */
1386         private function localiseDiff( $text ) {
1387                 $text = $this->localiseLineNumbers( $text );
1388                 if ( $this->getEngine() === 'wikidiff2' &&
1389                         version_compare( phpversion( 'wikidiff2' ), '1.5.1', '>=' )
1390                 ) {
1391                         $text = $this->addLocalisedTitleTooltips( $text );
1392                 }
1393                 return $text;
1394         }
1395
1396         /**
1397          * Replace line numbers with the text in the user's language
1398          *
1399          * @param string $text
1400          *
1401          * @return mixed
1402          */
1403         public function localiseLineNumbers( $text ) {
1404                 return preg_replace_callback(
1405                         '/<!--LINE (\d+)-->/',
1406                         [ $this, 'localiseLineNumbersCb' ],
1407                         $text
1408                 );
1409         }
1410
1411         public function localiseLineNumbersCb( $matches ) {
1412                 if ( $matches[1] === '1' && $this->mReducedLineNumbers ) {
1413                         return '';
1414                 }
1415
1416                 return $this->msg( 'lineno' )->numParams( $matches[1] )->escaped();
1417         }
1418
1419         /**
1420          * Add title attributes for tooltips on moved paragraph indicators
1421          *
1422          * @param string $text
1423          * @return string
1424          */
1425         private function addLocalisedTitleTooltips( $text ) {
1426                 return preg_replace_callback(
1427                         '/class="mw-diff-movedpara-(left|right)"/',
1428                         [ $this, 'addLocalisedTitleTooltipsCb' ],
1429                         $text
1430                 );
1431         }
1432
1433         /**
1434          * @param array $matches
1435          * @return string
1436          */
1437         private function addLocalisedTitleTooltipsCb( array $matches ) {
1438                 $key = $matches[1] === 'right' ?
1439                         'diff-paragraph-moved-toold' :
1440                         'diff-paragraph-moved-tonew';
1441                 return $matches[0] . ' title="' . $this->msg( $key )->escaped() . '"';
1442         }
1443
1444         /**
1445          * If there are revisions between the ones being compared, return a note saying so.
1446          *
1447          * @return string
1448          */
1449         public function getMultiNotice() {
1450                 // The notice only make sense if we are diffing two saved revisions of the same page.
1451                 if (
1452                         !$this->mOldRev || !$this->mNewRev
1453                         || !$this->mOldPage || !$this->mNewPage
1454                         || !$this->mOldPage->equals( $this->mNewPage )
1455                 ) {
1456                         return '';
1457                 }
1458
1459                 if ( $this->mOldRev->getTimestamp() > $this->mNewRev->getTimestamp() ) {
1460                         $oldRev = $this->mNewRev; // flip
1461                         $newRev = $this->mOldRev; // flip
1462                 } else { // normal case
1463                         $oldRev = $this->mOldRev;
1464                         $newRev = $this->mNewRev;
1465                 }
1466
1467                 // Sanity: don't show the notice if too many rows must be scanned
1468                 // @todo show some special message for that case
1469                 $nEdits = $this->mNewPage->countRevisionsBetween( $oldRev, $newRev, 1000 );
1470                 if ( $nEdits > 0 && $nEdits <= 1000 ) {
1471                         $limit = 100; // use diff-multi-manyusers if too many users
1472                         $users = $this->mNewPage->getAuthorsBetween( $oldRev, $newRev, $limit );
1473                         $numUsers = count( $users );
1474
1475                         if ( $numUsers == 1 && $users[0] == $newRev->getUserText( RevisionRecord::RAW ) ) {
1476                                 $numUsers = 0; // special case to say "by the same user" instead of "by one other user"
1477                         }
1478
1479                         return self::intermediateEditsMsg( $nEdits, $numUsers, $limit );
1480                 }
1481
1482                 return '';
1483         }
1484
1485         /**
1486          * Get a notice about how many intermediate edits and users there are
1487          *
1488          * @param int $numEdits
1489          * @param int $numUsers
1490          * @param int $limit
1491          *
1492          * @return string
1493          */
1494         public static function intermediateEditsMsg( $numEdits, $numUsers, $limit ) {
1495                 if ( $numUsers === 0 ) {
1496                         $msg = 'diff-multi-sameuser';
1497                 } elseif ( $numUsers > $limit ) {
1498                         $msg = 'diff-multi-manyusers';
1499                         $numUsers = $limit;
1500                 } else {
1501                         $msg = 'diff-multi-otherusers';
1502                 }
1503
1504                 return wfMessage( $msg )->numParams( $numEdits, $numUsers )->parse();
1505         }
1506
1507         /**
1508          * @param Revision $rev
1509          * @return bool whether the user can see and edit the revision.
1510          */
1511         private function userCanEdit( Revision $rev ) {
1512                 $user = $this->getUser();
1513
1514                 if ( !$rev->userCan( RevisionRecord::DELETED_TEXT, $user ) ) {
1515                         return false;
1516                 }
1517
1518                 return true;
1519         }
1520
1521         /**
1522          * Get a header for a specified revision.
1523          *
1524          * @param Revision $rev
1525          * @param string $complete 'complete' to get the header wrapped depending
1526          *        the visibility of the revision and a link to edit the page.
1527          *
1528          * @return string HTML fragment
1529          */
1530         public function getRevisionHeader( Revision $rev, $complete = '' ) {
1531                 $lang = $this->getLanguage();
1532                 $user = $this->getUser();
1533                 $revtimestamp = $rev->getTimestamp();
1534                 $timestamp = $lang->userTimeAndDate( $revtimestamp, $user );
1535                 $dateofrev = $lang->userDate( $revtimestamp, $user );
1536                 $timeofrev = $lang->userTime( $revtimestamp, $user );
1537
1538                 $header = $this->msg(
1539                         $rev->isCurrent() ? 'currentrev-asof' : 'revisionasof',
1540                         $timestamp,
1541                         $dateofrev,
1542                         $timeofrev
1543                 )->escaped();
1544
1545                 if ( $complete !== 'complete' ) {
1546                         return $header;
1547                 }
1548
1549                 $title = $rev->getTitle();
1550
1551                 $header = Linker::linkKnown( $title, $header, [],
1552                         [ 'oldid' => $rev->getId() ] );
1553
1554                 if ( $this->userCanEdit( $rev ) ) {
1555                         $editQuery = [ 'action' => 'edit' ];
1556                         if ( !$rev->isCurrent() ) {
1557                                 $editQuery['oldid'] = $rev->getId();
1558                         }
1559
1560                         $key = MediaWikiServices::getInstance()->getPermissionManager()
1561                                 ->quickUserCan( 'edit', $user, $title ) ? 'editold' : 'viewsourceold';
1562                         $msg = $this->msg( $key )->escaped();
1563                         $editLink = $this->msg( 'parentheses' )->rawParams(
1564                                 Linker::linkKnown( $title, $msg, [], $editQuery ) )->escaped();
1565                         $header .= ' ' . Html::rawElement(
1566                                 'span',
1567                                 [ 'class' => 'mw-diff-edit' ],
1568                                 $editLink
1569                         );
1570                         if ( $rev->isDeleted( RevisionRecord::DELETED_TEXT ) ) {
1571                                 $header = Html::rawElement(
1572                                         'span',
1573                                         [ 'class' => 'history-deleted' ],
1574                                         $header
1575                                 );
1576                         }
1577                 } else {
1578                         $header = Html::rawElement( 'span', [ 'class' => 'history-deleted' ], $header );
1579                 }
1580
1581                 return $header;
1582         }
1583
1584         /**
1585          * Add the header to a diff body
1586          *
1587          * @param string $diff Diff body
1588          * @param string $otitle Old revision header
1589          * @param string $ntitle New revision header
1590          * @param string $multi Notice telling user that there are intermediate
1591          *   revisions between the ones being compared
1592          * @param string $notice Other notices, e.g. that user is viewing deleted content
1593          *
1594          * @return string
1595          */
1596         public function addHeader( $diff, $otitle, $ntitle, $multi = '', $notice = '' ) {
1597                 // shared.css sets diff in interface language/dir, but the actual content
1598                 // is often in a different language, mostly the page content language/dir
1599                 $header = Html::openElement( 'table', [
1600                         'class' => [ 'diff', 'diff-contentalign-' . $this->getDiffLang()->alignStart() ],
1601                         'data-mw' => 'interface',
1602                 ] );
1603                 $userLang = htmlspecialchars( $this->getLanguage()->getHtmlCode() );
1604
1605                 if ( !$diff && !$otitle ) {
1606                         $header .= "
1607                         <tr class=\"diff-title\" lang=\"{$userLang}\">
1608                         <td class=\"diff-ntitle\">{$ntitle}</td>
1609                         </tr>";
1610                         $multiColspan = 1;
1611                 } else {
1612                         if ( $diff ) { // Safari/Chrome show broken output if cols not used
1613                                 $header .= "
1614                                 <col class=\"diff-marker\" />
1615                                 <col class=\"diff-content\" />
1616                                 <col class=\"diff-marker\" />
1617                                 <col class=\"diff-content\" />";
1618                                 $colspan = 2;
1619                                 $multiColspan = 4;
1620                         } else {
1621                                 $colspan = 1;
1622                                 $multiColspan = 2;
1623                         }
1624                         if ( $otitle || $ntitle ) {
1625                                 $header .= "
1626                                 <tr class=\"diff-title\" lang=\"{$userLang}\">
1627                                 <td colspan=\"$colspan\" class=\"diff-otitle\">{$otitle}</td>
1628                                 <td colspan=\"$colspan\" class=\"diff-ntitle\">{$ntitle}</td>
1629                                 </tr>";
1630                         }
1631                 }
1632
1633                 if ( $multi != '' ) {
1634                         $header .= "<tr><td colspan=\"{$multiColspan}\" " .
1635                                 "class=\"diff-multi\" lang=\"{$userLang}\">{$multi}</td></tr>";
1636                 }
1637                 if ( $notice != '' ) {
1638                         $header .= "<tr><td colspan=\"{$multiColspan}\" " .
1639                                 "class=\"diff-notice\" lang=\"{$userLang}\">{$notice}</td></tr>";
1640                 }
1641
1642                 return $header . $diff . "</table>";
1643         }
1644
1645         /**
1646          * Use specified text instead of loading from the database
1647          * @param Content $oldContent
1648          * @param Content $newContent
1649          * @since 1.21
1650          * @deprecated since 1.32, use setRevisions or ContentHandler::getSlotDiffRenderer.
1651          */
1652         public function setContent( Content $oldContent, Content $newContent ) {
1653                 $this->mOldContent = $oldContent;
1654                 $this->mNewContent = $newContent;
1655
1656                 $this->mTextLoaded = 2;
1657                 $this->mRevisionsLoaded = true;
1658                 $this->isContentOverridden = true;
1659                 $this->slotDiffRenderers = null;
1660         }
1661
1662         /**
1663          * Use specified text instead of loading from the database.
1664          * @param RevisionRecord|null $oldRevision
1665          * @param RevisionRecord $newRevision
1666          */
1667         public function setRevisions(
1668                 RevisionRecord $oldRevision = null, RevisionRecord $newRevision
1669         ) {
1670                 if ( $oldRevision ) {
1671                         $this->mOldRev = new Revision( $oldRevision );
1672                         $this->mOldid = $oldRevision->getId();
1673                         $this->mOldPage = Title::newFromLinkTarget( $oldRevision->getPageAsLinkTarget() );
1674                         // This method is meant for edit diffs and such so there is no reason to provide a
1675                         // revision that's not readable to the user, but check it just in case.
1676                         $this->mOldContent = $oldRevision->getContent( SlotRecord::MAIN,
1677                                 RevisionRecord::FOR_THIS_USER, $this->getUser() );
1678                 } else {
1679                         $this->mOldPage = null;
1680                         $this->mOldRev = $this->mOldid = false;
1681                 }
1682                 $this->mNewRev = new Revision( $newRevision );
1683                 $this->mNewid = $newRevision->getId();
1684                 $this->mNewPage = Title::newFromLinkTarget( $newRevision->getPageAsLinkTarget() );
1685                 $this->mNewContent = $newRevision->getContent( SlotRecord::MAIN,
1686                         RevisionRecord::FOR_THIS_USER, $this->getUser() );
1687
1688                 $this->mRevisionsIdsLoaded = $this->mRevisionsLoaded = true;
1689                 $this->mTextLoaded = $oldRevision ? 2 : 1;
1690                 $this->isContentOverridden = false;
1691                 $this->slotDiffRenderers = null;
1692         }
1693
1694         /**
1695          * Set the language in which the diff text is written
1696          *
1697          * @param Language $lang
1698          * @since 1.19
1699          */
1700         public function setTextLanguage( Language $lang ) {
1701                 $this->mDiffLang = $lang;
1702         }
1703
1704         /**
1705          * Maps a revision pair definition as accepted by DifferenceEngine constructor
1706          * to a pair of actual integers representing revision ids.
1707          *
1708          * @param int $old Revision id, e.g. from URL parameter 'oldid'
1709          * @param int|string $new Revision id or strings 'next' or 'prev', e.g. from URL parameter 'diff'
1710          *
1711          * @return array List of two revision ids, older first, later second.
1712          *     Zero signifies invalid argument passed.
1713          *     false signifies that there is no previous/next revision ($old is the oldest/newest one).
1714          */
1715         public function mapDiffPrevNext( $old, $new ) {
1716                 $rl = MediaWikiServices::getInstance()->getRevisionLookup();
1717                 if ( $new === 'prev' ) {
1718                         // Show diff between revision $old and the previous one. Get previous one from DB.
1719                         $newid = intval( $old );
1720                         $oldid = false;
1721                         $newRev = $rl->getRevisionById( $newid );
1722                         if ( $newRev ) {
1723                                 $oldRev = $rl->getPreviousRevision( $newRev );
1724                                 if ( $oldRev ) {
1725                                         $oldid = $oldRev->getId();
1726                                 }
1727                         }
1728                 } elseif ( $new === 'next' ) {
1729                         // Show diff between revision $old and the next one. Get next one from DB.
1730                         $oldid = intval( $old );
1731                         $newid = false;
1732                         $oldRev = $rl->getRevisionById( $oldid );
1733                         if ( $oldRev ) {
1734                                 $newRev = $rl->getNextRevision( $oldRev );
1735                                 if ( $newRev ) {
1736                                         $newid = $newRev->getId();
1737                                 }
1738                         }
1739                 } else {
1740                         $oldid = intval( $old );
1741                         $newid = intval( $new );
1742                 }
1743
1744                 return [ $oldid, $newid ];
1745         }
1746
1747         /**
1748          * Load revision IDs
1749          */
1750         private function loadRevisionIds() {
1751                 if ( $this->mRevisionsIdsLoaded ) {
1752                         return;
1753                 }
1754
1755                 $this->mRevisionsIdsLoaded = true;
1756
1757                 $old = $this->mOldid;
1758                 $new = $this->mNewid;
1759
1760                 list( $this->mOldid, $this->mNewid ) = self::mapDiffPrevNext( $old, $new );
1761                 if ( $new === 'next' && $this->mNewid === false ) {
1762                         # if no result, NewId points to the newest old revision. The only newer
1763                         # revision is cur, which is "0".
1764                         $this->mNewid = 0;
1765                 }
1766
1767                 Hooks::run(
1768                         'NewDifferenceEngine',
1769                         [ $this->getTitle(), &$this->mOldid, &$this->mNewid, $old, $new ]
1770                 );
1771         }
1772
1773         /**
1774          * Load revision metadata for the specified revisions. If newid is 0, then compare
1775          * the old revision in oldid to the current revision of the current page (as defined
1776          * by the request context); if oldid is 0, then compare the revision in newid to the
1777          * immediately previous one.
1778          *
1779          * If oldid is false, leave the corresponding revision object set to false. This can
1780          * happen with 'diff=prev' pointing to a non-existent revision, and is also used directly
1781          * by the API.
1782          *
1783          * @return bool Whether both revisions were loaded successfully. Setting mOldRev
1784          *   to false counts as successful loading.
1785          */
1786         public function loadRevisionData() {
1787                 if ( $this->mRevisionsLoaded ) {
1788                         return $this->isContentOverridden || ( $this->mOldRev !== null && $this->mNewRev !== null );
1789                 }
1790
1791                 // Whether it succeeds or fails, we don't want to try again
1792                 $this->mRevisionsLoaded = true;
1793
1794                 $this->loadRevisionIds();
1795
1796                 // Load the new revision object
1797                 if ( $this->mNewid ) {
1798                         $this->mNewRev = Revision::newFromId( $this->mNewid );
1799                 } else {
1800                         $this->mNewRev = Revision::newFromTitle(
1801                                 $this->getTitle(),
1802                                 false,
1803                                 Revision::READ_NORMAL
1804                         );
1805                 }
1806
1807                 if ( !$this->mNewRev instanceof Revision ) {
1808                         return false;
1809                 }
1810
1811                 // Update the new revision ID in case it was 0 (makes life easier doing UI stuff)
1812                 $this->mNewid = $this->mNewRev->getId();
1813                 if ( $this->mNewid ) {
1814                         $this->mNewPage = $this->mNewRev->getTitle();
1815                 } else {
1816                         $this->mNewPage = null;
1817                 }
1818
1819                 // Load the old revision object
1820                 $this->mOldRev = false;
1821                 if ( $this->mOldid ) {
1822                         $this->mOldRev = Revision::newFromId( $this->mOldid );
1823                 } elseif ( $this->mOldid === 0 ) {
1824                         $rev = $this->mNewRev->getPrevious();
1825                         if ( $rev ) {
1826                                 $this->mOldid = $rev->getId();
1827                                 $this->mOldRev = $rev;
1828                         } else {
1829                                 // No previous revision; mark to show as first-version only.
1830                                 $this->mOldid = false;
1831                                 $this->mOldRev = false;
1832                         }
1833                 } /* elseif ( $this->mOldid === false ) leave mOldRev false; */
1834
1835                 if ( is_null( $this->mOldRev ) ) {
1836                         return false;
1837                 }
1838
1839                 if ( $this->mOldRev && $this->mOldRev->getId() ) {
1840                         $this->mOldPage = $this->mOldRev->getTitle();
1841                 } else {
1842                         $this->mOldPage = null;
1843                 }
1844
1845                 // Load tags information for both revisions
1846                 $dbr = wfGetDB( DB_REPLICA );
1847                 $changeTagDefStore = MediaWikiServices::getInstance()->getChangeTagDefStore();
1848                 if ( $this->mOldid !== false ) {
1849                         $tagIds = $dbr->selectFieldValues(
1850                                 'change_tag',
1851                                 'ct_tag_id',
1852                                 [ 'ct_rev_id' => $this->mOldid ],
1853                                 __METHOD__
1854                         );
1855                         $tags = [];
1856                         foreach ( $tagIds as $tagId ) {
1857                                 try {
1858                                         $tags[] = $changeTagDefStore->getName( (int)$tagId );
1859                                 } catch ( NameTableAccessException $exception ) {
1860                                         continue;
1861                                 }
1862                         }
1863                         $this->mOldTags = implode( ',', $tags );
1864                 } else {
1865                         $this->mOldTags = false;
1866                 }
1867
1868                 $tagIds = $dbr->selectFieldValues(
1869                         'change_tag',
1870                         'ct_tag_id',
1871                         [ 'ct_rev_id' => $this->mNewid ],
1872                         __METHOD__
1873                 );
1874                 $tags = [];
1875                 foreach ( $tagIds as $tagId ) {
1876                         try {
1877                                 $tags[] = $changeTagDefStore->getName( (int)$tagId );
1878                         } catch ( NameTableAccessException $exception ) {
1879                                 continue;
1880                         }
1881                 }
1882                 $this->mNewTags = implode( ',', $tags );
1883
1884                 return true;
1885         }
1886
1887         /**
1888          * Load the text of the revisions, as well as revision data.
1889          * When the old revision is missing (mOldRev is false), loading mOldContent is not attempted.
1890          *
1891          * @return bool Whether the content of both revisions could be loaded successfully.
1892          *   (When mOldRev is false, that still counts as a success.)
1893          *
1894          */
1895         public function loadText() {
1896                 if ( $this->mTextLoaded == 2 ) {
1897                         return $this->loadRevisionData() && ( $this->mOldRev === false || $this->mOldContent )
1898                                 && $this->mNewContent;
1899                 }
1900
1901                 // Whether it succeeds or fails, we don't want to try again
1902                 $this->mTextLoaded = 2;
1903
1904                 if ( !$this->loadRevisionData() ) {
1905                         return false;
1906                 }
1907
1908                 if ( $this->mOldRev ) {
1909                         $this->mOldContent = $this->mOldRev->getContent(
1910                                 RevisionRecord::FOR_THIS_USER, $this->getUser()
1911                         );
1912                         if ( $this->mOldContent === null ) {
1913                                 return false;
1914                         }
1915                 }
1916
1917                 $this->mNewContent = $this->mNewRev->getContent(
1918                         RevisionRecord::FOR_THIS_USER, $this->getUser()
1919                 );
1920                 Hooks::run( 'DifferenceEngineLoadTextAfterNewContentIsLoaded', [ $this ] );
1921                 if ( $this->mNewContent === null ) {
1922                         return false;
1923                 }
1924
1925                 return true;
1926         }
1927
1928         /**
1929          * Load the text of the new revision, not the old one
1930          *
1931          * @return bool Whether the content of the new revision could be loaded successfully.
1932          */
1933         public function loadNewText() {
1934                 if ( $this->mTextLoaded >= 1 ) {
1935                         return $this->loadRevisionData();
1936                 }
1937
1938                 $this->mTextLoaded = 1;
1939
1940                 if ( !$this->loadRevisionData() ) {
1941                         return false;
1942                 }
1943
1944                 $this->mNewContent = $this->mNewRev->getContent(
1945                         RevisionRecord::FOR_THIS_USER, $this->getUser()
1946                 );
1947
1948                 Hooks::run( 'DifferenceEngineAfterLoadNewText', [ $this ] );
1949
1950                 return true;
1951         }
1952
1953 }