includes/diff/DifferenceEngine.php

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