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 /** @deprecated use class constant instead */
  25 define( 'MW_DIFF_VERSION', '1.11a' );
  26
  27 /**
  28  * @todo document
  29  * @ingroup DifferenceEngine
  30  */
  31 class DifferenceEngine extends ContextSource {
  32         /**
  33          * Constant to indicate diff cache compatibility.
  34          * Bump this when changing the diff formatting in a way that
  35          * fixes important bugs or such to force cached diff views to
  36          * clear.
  37          */
  38         const DIFF_VERSION = MW_DIFF_VERSION;
  39
  40         /** @var int */
  41         public $mOldid;
  42
  43         /** @var int */
  44         public $mNewid;
  45
  46         private $mOldTags;
  47         private $mNewTags;
  48
  49         /** @var Content */
  50         public $mOldContent;
  51
  52         /** @var Content */
  53         public $mNewContent;
  54
  55         /** @var Language */
  56         protected $mDiffLang;
  57
  58         /** @var Title */
  59         public $mOldPage;
  60
  61         /** @var Title */
  62         public $mNewPage;
  63
  64         /** @var Revision */
  65         public $mOldRev;
  66
  67         /** @var Revision */
  68         public $mNewRev;
  69
  70         /** @var bool Have the revisions IDs been loaded */
  71         private $mRevisionsIdsLoaded = false;
  72
  73         /** @var bool Have the revisions been loaded */
  74         public $mRevisionsLoaded = false;
  75
  76         /** @var int How many text blobs have been loaded, 0, 1 or 2? */
  77         public $mTextLoaded = 0;
  78
  79         /** @var bool Was the diff fetched from cache? */
  80         public $mCacheHit = false;
  81
  82         /**
  83          * Set this to true to add debug info to the HTML output.
  84          * Warning: this may cause RSS readers to spuriously mark articles as "new"
  85          * (bug 20601)
  86          */
  87         public $enableDebugComment = false;
  88
  89         /** @var bool If true, line X is not displayed when X is 1, for example
  90          *    to increase readability and conserve space with many small diffs.
  91          */
  92         protected $mReducedLineNumbers = false;
  93
  94         /** @var string Link to action=markpatrolled */
  95         protected $mMarkPatrolledLink = null;
  96
  97         /** @var bool Show rev_deleted content if allowed */
  98         protected $unhide = false;
  99
 100         /** @var bool Refresh the diff cache */
 101         protected $mRefreshCache = false;
 102
 103         /**#@-*/
 104
 105         /**
 106          * Constructor
 107          * @param IContextSource $context Context to use, anything else will be ignored
 108          * @param int $old Old ID we want to show and diff with.
 109          * @param string|int $new Either revision ID or 'prev' or 'next'. Default: 0.
 110          * @param int $rcid Deprecated, no longer used!
 111          * @param bool $refreshCache If set, refreshes the diff cache
 112          * @param bool $unhide If set, allow viewing deleted revs
 113          */
 114         public function __construct( $context = null, $old = 0, $new = 0, $rcid = 0,
 115                 $refreshCache = false, $unhide = false
 116         ) {
 117                 if ( $context instanceof IContextSource ) {
 118                         $this->setContext( $context );
 119                 }
 120
 121                 wfDebug( "DifferenceEngine old '$old' new '$new' rcid '$rcid'\n" );
 122
 123                 $this->mOldid = $old;
 124                 $this->mNewid = $new;
 125                 $this->mRefreshCache = $refreshCache;
 126                 $this->unhide = $unhide;
 127         }
 128
 129         /**
 130          * @param bool $value
 131          */
 132         public function setReducedLineNumbers( $value = true ) {
 133                 $this->mReducedLineNumbers = $value;
 134         }
 135
 136         /**
 137          * @return Language
 138          */
 139         public function getDiffLang() {
 140                 if ( $this->mDiffLang === null ) {
 141                         # Default language in which the diff text is written.
 142                         $this->mDiffLang = $this->getTitle()->getPageLanguage();
 143                 }
 144
 145                 return $this->mDiffLang;
 146         }
 147
 148         /**
 149          * @return bool
 150          */
 151         public function wasCacheHit() {
 152                 return $this->mCacheHit;
 153         }
 154
 155         /**
 156          * @return int
 157          */
 158         public function getOldid() {
 159                 $this->loadRevisionIds();
 160
 161                 return $this->mOldid;
 162         }
 163
 164         /**
 165          * @return bool|int
 166          */
 167         public function getNewid() {
 168                 $this->loadRevisionIds();
 169
 170                 return $this->mNewid;
 171         }
 172
 173         /**
 174          * Look up a special:Undelete link to the given deleted revision id,
 175          * as a workaround for being unable to load deleted diffs in currently.
 176          *
 177          * @param int $id Revision ID
 178          *
 179          * @return string|bool Link HTML or false
 180          */
 181         public function deletedLink( $id ) {
 182                 if ( $this->getUser()->isAllowed( 'deletedhistory' ) ) {
 183                         $dbr = wfGetDB( DB_REPLICA );
 184                         $row = $dbr->selectRow( 'archive', '*',
 185                                 [ 'ar_rev_id' => $id ],
 186                                 __METHOD__ );
 187                         if ( $row ) {
 188                                 $rev = Revision::newFromArchiveRow( $row );
 189                                 $title = Title::makeTitleSafe( $row->ar_namespace, $row->ar_title );
 190
 191                                 return SpecialPage::getTitleFor( 'Undelete' )->getFullURL( [
 192                                         'target' => $title->getPrefixedText(),
 193                                         'timestamp' => $rev->getTimestamp()
 194                                 ] );
 195                         }
 196                 }
 197
 198                 return false;
 199         }
 200
 201         /**
 202          * Build a wikitext link toward a deleted revision, if viewable.
 203          *
 204          * @param int $id Revision ID
 205          *
 206          * @return string Wikitext fragment
 207          */
 208         public function deletedIdMarker( $id ) {
 209                 $link = $this->deletedLink( $id );
 210                 if ( $link ) {
 211                         return "[$link $id]";
 212                 } else {
 213                         return $id;
 214                 }
 215         }
 216
 217         private function showMissingRevision() {
 218                 $out = $this->getOutput();
 219
 220                 $missing = [];
 221                 if ( $this->mOldRev === null ||
 222                         ( $this->mOldRev && $this->mOldContent === null )
 223                 ) {
 224                         $missing[] = $this->deletedIdMarker( $this->mOldid );
 225                 }
 226                 if ( $this->mNewRev === null ||
 227                         ( $this->mNewRev && $this->mNewContent === null )
 228                 ) {
 229                         $missing[] = $this->deletedIdMarker( $this->mNewid );
 230                 }
 231
 232                 $out->setPageTitle( $this->msg( 'errorpagetitle' ) );
 233                 $msg = $this->msg( 'difference-missing-revision' )
 234                         ->params( $this->getLanguage()->listToText( $missing ) )
 235                         ->numParams( count( $missing ) )
 236                         ->parseAsBlock();
 237                 $out->addHTML( $msg );
 238         }
 239
 240         public function showDiffPage( $diffOnly = false ) {
 241                 # Allow frames except in certain special cases
 242                 $out = $this->getOutput();
 243                 $out->allowClickjacking();
 244                 $out->setRobotPolicy( 'noindex,nofollow' );
 245
 246                 // Allow extensions to add any extra output here
 247                 Hooks::run( 'DifferenceEngineShowDiffPage', [ $out ] );
 248
 249                 if ( !$this->loadRevisionData() ) {
 250                         $this->showMissingRevision();
 251
 252                         return;
 253                 }
 254
 255                 $user = $this->getUser();
 256                 $permErrors = $this->mNewPage->getUserPermissionsErrors( 'read', $user );
 257                 if ( $this->mOldPage ) { # mOldPage might not be set, see below.
 258                         $permErrors = wfMergeErrorArrays( $permErrors,
 259                                 $this->mOldPage->getUserPermissionsErrors( 'read', $user ) );
 260                 }
 261                 if ( count( $permErrors ) ) {
 262                         throw new PermissionsError( 'read', $permErrors );
 263                 }
 264
 265                 $rollback = '';
 266
 267                 $query = [];
 268                 # Carry over 'diffonly' param via navigation links
 269                 if ( $diffOnly != $user->getBoolOption( 'diffonly' ) ) {
 270                         $query['diffonly'] = $diffOnly;
 271                 }
 272                 # Cascade unhide param in links for easy deletion browsing
 273                 if ( $this->unhide ) {
 274                         $query['unhide'] = 1;
 275                 }
 276
 277                 # Check if one of the revisions is deleted/suppressed
 278                 $deleted = $suppressed = false;
 279                 $allowed = $this->mNewRev->userCan( Revision::DELETED_TEXT, $user );
 280
 281                 $revisionTools = [];
 282
 283                 # mOldRev is false if the difference engine is called with a "vague" query for
 284                 # a diff between a version V and its previous version V' AND the version V
 285                 # is the first version of that article. In that case, V' does not exist.
 286                 if ( $this->mOldRev === false ) {
 287                         $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 288                         $samePage = true;
 289                         $oldHeader = '';
 290                         // Allow extensions to change the $oldHeader variable
 291                         Hooks::run( 'DifferenceEngineOldHeaderNoOldRev', [ &$oldHeader ] );
 292                 } else {
 293                         Hooks::run( 'DiffViewHeader', [ $this, $this->mOldRev, $this->mNewRev ] );
 294
 295                         if ( $this->mNewPage->equals( $this->mOldPage ) ) {
 296                                 $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 297                                 $samePage = true;
 298                         } else {
 299                                 $out->setPageTitle( $this->msg( 'difference-title-multipage',
 300                                         $this->mOldPage->getPrefixedText(), $this->mNewPage->getPrefixedText() ) );
 301                                 $out->addSubtitle( $this->msg( 'difference-multipage' ) );
 302                                 $samePage = false;
 303                         }
 304
 305                         if ( $samePage && $this->mNewPage->quickUserCan( 'edit', $user ) ) {
 306                                 if ( $this->mNewRev->isCurrent() && $this->mNewPage->userCan( 'rollback', $user ) ) {
 307                                         $rollbackLink = Linker::generateRollback( $this->mNewRev, $this->getContext() );
 308                                         if ( $rollbackLink ) {
 309                                                 $out->preventClickjacking();
 310                                                 $rollback = '&#160;&#160;&#160;' . $rollbackLink;
 311                                         }
 312                                 }
 313
 314                                 if ( !$this->mOldRev->isDeleted( Revision::DELETED_TEXT ) &&
 315                                         !$this->mNewRev->isDeleted( Revision::DELETED_TEXT )
 316                                 ) {
 317                                         $undoLink = Html::element( 'a', [
 318                                                         'href' => $this->mNewPage->getLocalURL( [
 319                                                                 'action' => 'edit',
 320                                                                 'undoafter' => $this->mOldid,
 321                                                                 'undo' => $this->mNewid
 322                                                         ] ),
 323                                                         'title' => Linker::titleAttrib( 'undo' ),
 324                                                 ],
 325                                                 $this->msg( 'editundo' )->text()
 326                                         );
 327                                         $revisionTools['mw-diff-undo'] = $undoLink;
 328                                 }
 329                         }
 330
 331                         # Make "previous revision link"
 332                         if ( $samePage && $this->mOldRev->getPrevious() ) {
 333                                 $prevlink = Linker::linkKnown(
 334                                         $this->mOldPage,
 335                                         $this->msg( 'previousdiff' )->escaped(),
 336                                         [ 'id' => 'differences-prevlink' ],
 337                                         [ 'diff' => 'prev', 'oldid' => $this->mOldid ] + $query
 338                                 );
 339                         } else {
 340                                 $prevlink = '&#160;';
 341                         }
 342
 343                         if ( $this->mOldRev->isMinor() ) {
 344                                 $oldminor = ChangesList::flag( 'minor' );
 345                         } else {
 346                                 $oldminor = '';
 347                         }
 348
 349                         $ldel = $this->revisionDeleteLink( $this->mOldRev );
 350                         $oldRevisionHeader = $this->getRevisionHeader( $this->mOldRev, 'complete' );
 351                         $oldChangeTags = ChangeTags::formatSummaryRow( $this->mOldTags, 'diff', $this->getContext() );
 352
 353                         $oldHeader = '<div id="mw-diff-otitle1"><strong>' . $oldRevisionHeader . '</strong></div>' .
 354                                 '<div id="mw-diff-otitle2">' .
 355                                 Linker::revUserTools( $this->mOldRev, !$this->unhide ) . '</div>' .
 356                                 '<div id="mw-diff-otitle3">' . $oldminor .
 357                                 Linker::revComment( $this->mOldRev, !$diffOnly, !$this->unhide ) . $ldel . '</div>' .
 358                                 '<div id="mw-diff-otitle5">' . $oldChangeTags[0] . '</div>' .
 359                                 '<div id="mw-diff-otitle4">' . $prevlink . '</div>';
 360
 361                         // Allow extensions to change the $oldHeader variable
 362                         Hooks::run( 'DifferenceEngineOldHeader', [ $this, &$oldHeader, $prevlink, $oldminor,
 363                                 $diffOnly, $ldel, $this->unhide ] );
 364
 365                         if ( $this->mOldRev->isDeleted( Revision::DELETED_TEXT ) ) {
 366                                 $deleted = true; // old revisions text is hidden
 367                                 if ( $this->mOldRev->isDeleted( Revision::DELETED_RESTRICTED ) ) {
 368                                         $suppressed = true; // also suppressed
 369                                 }
 370                         }
 371
 372                         # Check if this user can see the revisions
 373                         if ( !$this->mOldRev->userCan( Revision::DELETED_TEXT, $user ) ) {
 374                                 $allowed = false;
 375                         }
 376                 }
 377
 378                 # Make "next revision link"
 379                 # Skip next link on the top revision
 380                 if ( $samePage && !$this->mNewRev->isCurrent() ) {
 381                         $nextlink = Linker::linkKnown(
 382                                 $this->mNewPage,
 383                                 $this->msg( 'nextdiff' )->escaped(),
 384                                 [ 'id' => 'differences-nextlink' ],
 385                                 [ 'diff' => 'next', 'oldid' => $this->mNewid ] + $query
 386                         );
 387                 } else {
 388                         $nextlink = '&#160;';
 389                 }
 390
 391                 if ( $this->mNewRev->isMinor() ) {
 392                         $newminor = ChangesList::flag( 'minor' );
 393                 } else {
 394                         $newminor = '';
 395                 }
 396
 397                 # Handle RevisionDelete links...
 398                 $rdel = $this->revisionDeleteLink( $this->mNewRev );
 399
 400                 # Allow extensions to define their own revision tools
 401                 Hooks::run( 'DiffRevisionTools',
 402                         [ $this->mNewRev, &$revisionTools, $this->mOldRev, $user ] );
 403                 $formattedRevisionTools = [];
 404                 // Put each one in parentheses (poor man's button)
 405                 foreach ( $revisionTools as $key => $tool ) {
 406                         $toolClass = is_string( $key ) ? $key : 'mw-diff-tool';
 407                         $element = Html::rawElement(
 408                                 'span',
 409                                 [ 'class' => $toolClass ],
 410                                 $this->msg( 'parentheses' )->rawParams( $tool )->escaped()
 411                         );
 412                         $formattedRevisionTools[] = $element;
 413                 }
 414                 $newRevisionHeader = $this->getRevisionHeader( $this->mNewRev, 'complete' ) .
 415                         ' ' . implode( ' ', $formattedRevisionTools );
 416                 $newChangeTags = ChangeTags::formatSummaryRow( $this->mNewTags, 'diff', $this->getContext() );
 417
 418                 $newHeader = '<div id="mw-diff-ntitle1"><strong>' . $newRevisionHeader . '</strong></div>' .
 419                         '<div id="mw-diff-ntitle2">' . Linker::revUserTools( $this->mNewRev, !$this->unhide ) .
 420                         " $rollback</div>" .
 421                         '<div id="mw-diff-ntitle3">' . $newminor .
 422                         Linker::revComment( $this->mNewRev, !$diffOnly, !$this->unhide ) . $rdel . '</div>' .
 423                         '<div id="mw-diff-ntitle5">' . $newChangeTags[0] . '</div>' .
 424                         '<div id="mw-diff-ntitle4">' . $nextlink . $this->markPatrolledLink() . '</div>';
 425
 426                 // Allow extensions to change the $newHeader variable
 427                 Hooks::run( 'DifferenceEngineNewHeader', [ $this, &$newHeader, $formattedRevisionTools,
 428                         $nextlink, $rollback, $newminor, $diffOnly, $rdel, $this->unhide ] );
 429
 430                 if ( $this->mNewRev->isDeleted( Revision::DELETED_TEXT ) ) {
 431                         $deleted = true; // new revisions text is hidden
 432                         if ( $this->mNewRev->isDeleted( Revision::DELETED_RESTRICTED ) ) {
 433                                 $suppressed = true; // also suppressed
 434                         }
 435                 }
 436
 437                 # If the diff cannot be shown due to a deleted revision, then output
 438                 # the diff header and links to unhide (if available)...
 439                 if ( $deleted && ( !$this->unhide || !$allowed ) ) {
 440                         $this->showDiffStyle();
 441                         $multi = $this->getMultiNotice();
 442                         $out->addHTML( $this->addHeader( '', $oldHeader, $newHeader, $multi ) );
 443                         if ( !$allowed ) {
 444                                 $msg = $suppressed ? 'rev-suppressed-no-diff' : 'rev-deleted-no-diff';
 445                                 # Give explanation for why revision is not visible
 446                                 $out->wrapWikiMsg( "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 447                                         [ $msg ] );
 448                         } else {
 449                                 # Give explanation and add a link to view the diff...
 450                                 $query = $this->getRequest()->appendQueryValue( 'unhide', '1' );
 451                                 $link = $this->getTitle()->getFullURL( $query );
 452                                 $msg = $suppressed ? 'rev-suppressed-unhide-diff' : 'rev-deleted-unhide-diff';
 453                                 $out->wrapWikiMsg(
 454                                         "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 455                                         [ $msg, $link ]
 456                                 );
 457                         }
 458                 # Otherwise, output a regular diff...
 459                 } else {
 460                         # Add deletion notice if the user is viewing deleted content
 461                         $notice = '';
 462                         if ( $deleted ) {
 463                                 $msg = $suppressed ? 'rev-suppressed-diff-view' : 'rev-deleted-diff-view';
 464                                 $notice = "<div id='mw-$msg' class='mw-warning plainlinks'>\n" .
 465                                         $this->msg( $msg )->parse() .
 466                                         "</div>\n";
 467                         }
 468                         $this->showDiff( $oldHeader, $newHeader, $notice );
 469                         if ( !$diffOnly ) {
 470                                 $this->renderNewRevision();
 471                         }
 472                 }
 473         }
 474
 475         /**
 476          * Build a link to mark a change as patrolled.
 477          *
 478          * Returns empty string if there's either no revision to patrol or the user is not allowed to.
 479          * Side effect: When the patrol link is build, this method will call
 480          * OutputPage::preventClickjacking() and load mediawiki.page.patrol.ajax.
 481          *
 482          * @return string HTML or empty string
 483          */
 484         protected function markPatrolledLink() {
 485                 if ( $this->mMarkPatrolledLink === null ) {
 486                         $linkInfo = $this->getMarkPatrolledLinkInfo();
 487                         // If false, there is no patrol link needed/allowed
 488                         if ( !$linkInfo ) {
 489                                 $this->mMarkPatrolledLink = '';
 490                         } else {
 491                                 $this->mMarkPatrolledLink = ' <span class="patrollink" data-mw="interface">[' .
 492                                         Linker::linkKnown(
 493                                                 $this->mNewPage,
 494                                                 $this->msg( 'markaspatrolleddiff' )->escaped(),
 495                                                 [],
 496                                                 [
 497                                                         'action' => 'markpatrolled',
 498                                                         'rcid' => $linkInfo['rcid'],
 499                                                 ]
 500                                         ) . ']</span>';
 501                                 // Allow extensions to change the markpatrolled link
 502                                 Hooks::run( 'DifferenceEngineMarkPatrolledLink', [ $this,
 503                                         &$this->mMarkPatrolledLink, $linkInfo['rcid'] ] );
 504                         }
 505                 }
 506                 return $this->mMarkPatrolledLink;
 507         }
 508
 509         /**
 510          * Returns an array of meta data needed to build a "mark as patrolled" link and
 511          * adds the mediawiki.page.patrol.ajax to the output.
 512          *
 513          * @return array|false An array of meta data for a patrol link (rcid only)
 514          *  or false if no link is needed
 515          */
 516         protected function getMarkPatrolledLinkInfo() {
 517                 global $wgUseRCPatrol, $wgEnableAPI, $wgEnableWriteAPI;
 518
 519                 $user = $this->getUser();
 520
 521                 // Prepare a change patrol link, if applicable
 522                 if (
 523                         // Is patrolling enabled and the user allowed to?
 524                         $wgUseRCPatrol && $this->mNewPage->quickUserCan( 'patrol', $user ) &&
 525                         // Only do this if the revision isn't more than 6 hours older
 526                         // than the Max RC age (6h because the RC might not be cleaned out regularly)
 527                         RecentChange::isInRCLifespan( $this->mNewRev->getTimestamp(), 21600 )
 528                 ) {
 529                         // Look for an unpatrolled change corresponding to this diff
 530                         $db = wfGetDB( DB_REPLICA );
 531                         $change = RecentChange::newFromConds(
 532                                 [
 533                                         'rc_timestamp' => $db->timestamp( $this->mNewRev->getTimestamp() ),
 534                                         'rc_this_oldid' => $this->mNewid,
 535                                         'rc_patrolled' => 0
 536                                 ],
 537                                 __METHOD__
 538                         );
 539
 540                         if ( $change && !$change->getPerformer()->equals( $user ) ) {
 541                                 $rcid = $change->getAttribute( 'rc_id' );
 542                         } else {
 543                                 // None found or the page has been created by the current user.
 544                                 // If the user could patrol this it already would be patrolled
 545                                 $rcid = 0;
 546                         }
 547
 548                         // Allow extensions to possibly change the rcid here
 549                         // For example the rcid might be set to zero due to the user
 550                         // being the same as the performer of the change but an extension
 551                         // might still want to show it under certain conditions
 552                         Hooks::run( 'DifferenceEngineMarkPatrolledRCID', [ &$rcid, $this, $change, $user ] );
 553
 554                         // Build the link
 555                         if ( $rcid ) {
 556                                 $this->getOutput()->preventClickjacking();
 557                                 if ( $wgEnableAPI && $wgEnableWriteAPI
 558                                         && $user->isAllowed( 'writeapi' )
 559                                 ) {
 560                                         $this->getOutput()->addModules( 'mediawiki.page.patrol.ajax' );
 561                                 }
 562
 563                                 return [
 564                                         'rcid' => $rcid,
 565                                 ];
 566                         }
 567                 }
 568
 569                 // No mark as patrolled link applicable
 570                 return false;
 571         }
 572
 573         /**
 574          * @param Revision $rev
 575          *
 576          * @return string
 577          */
 578         protected function revisionDeleteLink( $rev ) {
 579                 $link = Linker::getRevDeleteLink( $this->getUser(), $rev, $rev->getTitle() );
 580                 if ( $link !== '' ) {
 581                         $link = '&#160;&#160;&#160;' . $link . ' ';
 582                 }
 583
 584                 return $link;
 585         }
 586
 587         /**
 588          * Show the new revision of the page.
 589          */
 590         public function renderNewRevision() {
 591                 $out = $this->getOutput();
 592                 $revHeader = $this->getRevisionHeader( $this->mNewRev );
 593                 # Add "current version as of X" title
 594                 $out->addHTML( "<hr class='diff-hr' id='mw-oldid' />
 595                 <h2 class='diff-currentversion-title'>{$revHeader}</h2>\n" );
 596                 # Page content may be handled by a hooked call instead...
 597                 # @codingStandardsIgnoreStart Ignoring long lines.
 598                 if ( Hooks::run( 'ArticleContentOnDiff', [ $this, $out ] ) ) {
 599                         $this->loadNewText();
 600                         $out->setRevisionId( $this->mNewid );
 601                         $out->setRevisionTimestamp( $this->mNewRev->getTimestamp() );
 602                         $out->setArticleFlag( true );
 603
 604                         // NOTE: only needed for B/C: custom rendering of JS/CSS via hook
 605                         if ( $this->mNewPage->isCssJsSubpage() || $this->mNewPage->isCssOrJsPage() ) {
 606                                 // This needs to be synchronised with Article::showCssOrJsPage(), which sucks
 607                                 // Give hooks a chance to customise the output
 608                                 // @todo standardize this crap into one function
 609                                 if ( ContentHandler::runLegacyHooks( 'ShowRawCssJs', [ $this->mNewContent, $this->mNewPage, $out ], '1.24' ) ) {
 610                                         // NOTE: deprecated hook, B/C only
 611                                         // use the content object's own rendering
 612                                         $cnt = $this->mNewRev->getContent();
 613                                         $po = $cnt ? $cnt->getParserOutput( $this->mNewRev->getTitle(), $this->mNewRev->getId() ) : null;
 614                                         if ( $po ) {
 615                                                 $out->addParserOutputContent( $po );
 616                                         }
 617                                 }
 618                         } elseif ( !Hooks::run( 'ArticleContentViewCustom', [ $this->mNewContent, $this->mNewPage, $out ] ) ) {
 619                                 // Handled by extension
 620                         } elseif ( !ContentHandler::runLegacyHooks(
 621                                 'ArticleViewCustom',
 622                                 [ $this->mNewContent, $this->mNewPage, $out ],
 623                                 '1.21'
 624                         ) ) {
 625                                 // NOTE: deprecated hook, B/C only
 626                                 // Handled by extension
 627                         } else {
 628                                 // Normal page
 629                                 if ( $this->getTitle()->equals( $this->mNewPage ) ) {
 630                                         // If the Title stored in the context is the same as the one
 631                                         // of the new revision, we can use its associated WikiPage
 632                                         // object.
 633                                         $wikiPage = $this->getWikiPage();
 634                                 } else {
 635                                         // Otherwise we need to create our own WikiPage object
 636                                         $wikiPage = WikiPage::factory( $this->mNewPage );
 637                                 }
 638
 639                                 $parserOutput = $this->getParserOutput( $wikiPage, $this->mNewRev );
 640
 641                                 # WikiPage::getParserOutput() should not return false, but just in case
 642                                 if ( $parserOutput ) {
 643                                         // Allow extensions to change parser output here
 644                                         if ( Hooks::run( 'DifferenceEngineRenderRevisionAddParserOutput', [ $this, $out, $parserOutput, $wikiPage ] ) ) {
 645                                                 $out->addParserOutput( $parserOutput );
 646                                         }
 647                                 }
 648                         }
 649                 }
 650                 # @codingStandardsIgnoreEnd
 651
 652                 // Allow extensions to optionally not show the final patrolled link
 653                 if ( Hooks::run( 'DifferenceEngineRenderRevisionShowFinalPatrolLink' ) ) {
 654                         # Add redundant patrol link on bottom...
 655                         $out->addHTML( $this->markPatrolledLink() );
 656                 }
 657         }
 658
 659         protected function getParserOutput( WikiPage $page, Revision $rev ) {
 660                 $parserOptions = $page->makeParserOptions( $this->getContext() );
 661
 662                 if ( !$rev->isCurrent() || !$rev->getTitle()->quickUserCan( 'edit', $this->getUser() ) ) {
 663                         $parserOptions->setEditSection( false );
 664                 }
 665
 666                 $parserOutput = $page->getParserOutput( $parserOptions, $rev->getId() );
 667
 668                 return $parserOutput;
 669         }
 670
 671         /**
 672          * Get the diff text, send it to the OutputPage object
 673          * Returns false if the diff could not be generated, otherwise returns true
 674          *
 675          * @param string|bool $otitle Header for old text or false
 676          * @param string|bool $ntitle Header for new text or false
 677          * @param string $notice HTML between diff header and body
 678          *
 679          * @return bool
 680          */
 681         public function showDiff( $otitle, $ntitle, $notice = '' ) {
 682                 // Allow extensions to affect the output here
 683                 Hooks::run( 'DifferenceEngineShowDiff', [ $this ] );
 684
 685                 $diff = $this->getDiff( $otitle, $ntitle, $notice );
 686                 if ( $diff === false ) {
 687                         $this->showMissingRevision();
 688
 689                         return false;
 690                 } else {
 691                         $this->showDiffStyle();
 692                         $this->getOutput()->addHTML( $diff );
 693
 694                         return true;
 695                 }
 696         }
 697
 698         /**
 699          * Add style sheets for diff display.
 700          */
 701         public function showDiffStyle() {
 702                 $this->getOutput()->addModuleStyles( 'mediawiki.diff.styles' );
 703         }
 704
 705         /**
 706          * Get complete diff table, including header
 707          *
 708          * @param string|bool $otitle Header for old text or false
 709          * @param string|bool $ntitle Header for new text or false
 710          * @param string $notice HTML between diff header and body
 711          *
 712          * @return mixed
 713          */
 714         public function getDiff( $otitle, $ntitle, $notice = '' ) {
 715                 $body = $this->getDiffBody();
 716                 if ( $body === false ) {
 717                         return false;
 718                 }
 719
 720                 $multi = $this->getMultiNotice();
 721                 // Display a message when the diff is empty
 722                 if ( $body === '' ) {
 723                         $notice .= '<div class="mw-diff-empty">' .
 724                                 $this->msg( 'diff-empty' )->parse() .
 725                                 "</div>\n";
 726                 }
 727
 728                 return $this->addHeader( $body, $otitle, $ntitle, $multi, $notice );
 729         }
 730
 731         /**
 732          * Get the diff table body, without header
 733          *
 734          * @return mixed (string/false)
 735          */
 736         public function getDiffBody() {
 737                 $this->mCacheHit = true;
 738                 // Check if the diff should be hidden from this user
 739                 if ( !$this->loadRevisionData() ) {
 740                         return false;
 741                 } elseif ( $this->mOldRev &&
 742                         !$this->mOldRev->userCan( Revision::DELETED_TEXT, $this->getUser() )
 743                 ) {
 744                         return false;
 745                 } elseif ( $this->mNewRev &&
 746                         !$this->mNewRev->userCan( Revision::DELETED_TEXT, $this->getUser() )
 747                 ) {
 748                         return false;
 749                 }
 750                 // Short-circuit
 751                 if ( $this->mOldRev === false || ( $this->mOldRev && $this->mNewRev
 752                         && $this->mOldRev->getId() == $this->mNewRev->getId() )
 753                 ) {
 754                         if ( Hooks::run( 'DifferenceEngineShowEmptyOldContent', [ $this ] ) ) {
 755                                 return '';
 756                         }
 757                 }
 758                 // Cacheable?
 759                 $key = false;
 760                 $cache = ObjectCache::getMainWANInstance();
 761                 if ( $this->mOldid && $this->mNewid ) {
 762                         $key = $this->getDiffBodyCacheKey();
 763
 764                         // Try cache
 765                         if ( !$this->mRefreshCache ) {
 766                                 $difftext = $cache->get( $key );
 767                                 if ( $difftext ) {
 768                                         wfIncrStats( 'diff_cache.hit' );
 769                                         $difftext = $this->localiseLineNumbers( $difftext );
 770                                         $difftext .= "\n<!-- diff cache key $key -->\n";
 771
 772                                         return $difftext;
 773                                 }
 774                         } // don't try to load but save the result
 775                 }
 776                 $this->mCacheHit = false;
 777
 778                 // Loadtext is permission safe, this just clears out the diff
 779                 if ( !$this->loadText() ) {
 780                         return false;
 781                 }
 782
 783                 $difftext = $this->generateContentDiffBody( $this->mOldContent, $this->mNewContent );
 784
 785                 // Save to cache for 7 days
 786                 if ( !Hooks::run( 'AbortDiffCache', [ &$this ] ) ) {
 787                         wfIncrStats( 'diff_cache.uncacheable' );
 788                 } elseif ( $key !== false && $difftext !== false ) {
 789                         wfIncrStats( 'diff_cache.miss' );
 790                         $cache->set( $key, $difftext, 7 * 86400 );
 791                 } else {
 792                         wfIncrStats( 'diff_cache.uncacheable' );
 793                 }
 794                 // Replace line numbers with the text in the user's language
 795                 if ( $difftext !== false ) {
 796                         $difftext = $this->localiseLineNumbers( $difftext );
 797                 }
 798
 799                 return $difftext;
 800         }
 801
 802         /**
 803          * Returns the cache key for diff body text or content.
 804          *
 805          * @since 1.23
 806          *
 807          * @throws MWException
 808          * @return string
 809          */
 810         protected function getDiffBodyCacheKey() {
 811                 if ( !$this->mOldid || !$this->mNewid ) {
 812                         throw new MWException( 'mOldid and mNewid must be set to get diff cache key.' );
 813                 }
 814
 815                 return wfMemcKey( 'diff', 'version', self::DIFF_VERSION,
 816                         'oldid', $this->mOldid, 'newid', $this->mNewid );
 817         }
 818
 819         /**
 820          * Generate a diff, no caching.
 821          *
 822          * This implementation uses generateTextDiffBody() to generate a diff based on the default
 823          * serialization of the given Content objects. This will fail if $old or $new are not
 824          * instances of TextContent.
 825          *
 826          * Subclasses may override this to provide a different rendering for the diff,
 827          * perhaps taking advantage of the content's native form. This is required for all content
 828          * models that are not text based.
 829          *
 830          * @since 1.21
 831          *
 832          * @param Content $old Old content
 833          * @param Content $new New content
 834          *
 835          * @throws MWException If old or new content is not an instance of TextContent.
 836          * @return bool|string
 837          */
 838         public function generateContentDiffBody( Content $old, Content $new ) {
 839                 if ( !( $old instanceof TextContent ) ) {
 840                         throw new MWException( "Diff not implemented for " . get_class( $old ) . "; " .
 841                                 "override generateContentDiffBody to fix this." );
 842                 }
 843
 844                 if ( !( $new instanceof TextContent ) ) {
 845                         throw new MWException( "Diff not implemented for " . get_class( $new ) . "; "
 846                                 . "override generateContentDiffBody to fix this." );
 847                 }
 848
 849                 $otext = $old->serialize();
 850                 $ntext = $new->serialize();
 851
 852                 return $this->generateTextDiffBody( $otext, $ntext );
 853         }
 854
 855         /**
 856          * Generate a diff, no caching
 857          *
 858          * @todo move this to TextDifferenceEngine, make DifferenceEngine abstract. At some point.
 859          *
 860          * @param string $otext Old text, must be already segmented
 861          * @param string $ntext New text, must be already segmented
 862          *
 863          * @return bool|string
 864          */
 865         public function generateTextDiffBody( $otext, $ntext ) {
 866                 $diff = function() use ( $otext, $ntext ) {
 867                         $time = microtime( true );
 868
 869                         $result = $this->textDiff( $otext, $ntext );
 870
 871                         $time = intval( ( microtime( true ) - $time ) * 1000 );
 872                         $this->getStats()->timing( 'diff_time', $time );
 873                         // Log requests slower than 99th percentile
 874                         if ( $time > 100 && $this->mOldPage && $this->mNewPage ) {
 875                                 wfDebugLog( 'diff',
 876                                         "$time ms diff: {$this->mOldid} -> {$this->mNewid} {$this->mNewPage}" );
 877                         }
 878
 879                         return $result;
 880                 };
 881
 882                 /**
 883                  * @param Status $status
 884                  * @throws FatalError
 885                  */
 886                 $error = function( $status ) {
 887                         throw new FatalError( $status->getWikiText() );
 888                 };
 889
 890                 // Use PoolCounter if the diff looks like it can be expensive
 891                 if ( strlen( $otext ) + strlen( $ntext ) > 20000 ) {
 892                         $work = new PoolCounterWorkViaCallback( 'diff',
 893                                 md5( $otext ) . md5( $ntext ),
 894                                 [ 'doWork' => $diff, 'error' => $error ]
 895                         );
 896                         return $work->execute();
 897                 }
 898
 899                 return $diff();
 900         }
 901
 902         /**
 903          * Generates diff, to be wrapped internally in a logging/instrumentation
 904          *
 905          * @param string $otext Old text, must be already segmented
 906          * @param string $ntext New text, must be already segmented
 907          * @return bool|string
 908          */
 909         protected function textDiff( $otext, $ntext ) {
 910                 global $wgExternalDiffEngine, $wgContLang;
 911
 912                 $otext = str_replace( "\r\n", "\n", $otext );
 913                 $ntext = str_replace( "\r\n", "\n", $ntext );
 914
 915                 if ( $wgExternalDiffEngine == 'wikidiff' || $wgExternalDiffEngine == 'wikidiff3' ) {
 916                         wfDeprecated( "\$wgExternalDiffEngine = '{$wgExternalDiffEngine}'", '1.27' );
 917                         $wgExternalDiffEngine = false;
 918                 } elseif ( $wgExternalDiffEngine == 'wikidiff2' ) {
 919                         // Same as above, but with no deprecation warnings
 920                         $wgExternalDiffEngine = false;
 921                 } elseif ( !is_string( $wgExternalDiffEngine ) && $wgExternalDiffEngine !== false ) {
 922                         // And prevent people from shooting themselves in the foot...
 923                         wfWarn( '$wgExternalDiffEngine is set to a non-string value, forcing it to false' );
 924                         $wgExternalDiffEngine = false;
 925                 }
 926
 927                 if ( function_exists( 'wikidiff2_do_diff' ) && $wgExternalDiffEngine === false ) {
 928                         # Better external diff engine, the 2 may some day be dropped
 929                         # This one does the escaping and segmenting itself
 930                         $text = wikidiff2_do_diff( $otext, $ntext, 2 );
 931                         $text .= $this->debug( 'wikidiff2' );
 932
 933                         return $text;
 934                 } elseif ( $wgExternalDiffEngine !== false && is_executable( $wgExternalDiffEngine ) ) {
 935                         # Diff via the shell
 936                         $tmpDir = wfTempDir();
 937                         $tempName1 = tempnam( $tmpDir, 'diff_' );
 938                         $tempName2 = tempnam( $tmpDir, 'diff_' );
 939
 940                         $tempFile1 = fopen( $tempName1, "w" );
 941                         if ( !$tempFile1 ) {
 942                                 return false;
 943                         }
 944                         $tempFile2 = fopen( $tempName2, "w" );
 945                         if ( !$tempFile2 ) {
 946                                 return false;
 947                         }
 948                         fwrite( $tempFile1, $otext );
 949                         fwrite( $tempFile2, $ntext );
 950                         fclose( $tempFile1 );
 951                         fclose( $tempFile2 );
 952                         $cmd = wfEscapeShellArg( $wgExternalDiffEngine, $tempName1, $tempName2 );
 953                         $difftext = wfShellExec( $cmd );
 954                         $difftext .= $this->debug( "external $wgExternalDiffEngine" );
 955                         unlink( $tempName1 );
 956                         unlink( $tempName2 );
 957
 958                         return $difftext;
 959                 }
 960
 961                 # Native PHP diff
 962                 $ota = explode( "\n", $wgContLang->segmentForDiff( $otext ) );
 963                 $nta = explode( "\n", $wgContLang->segmentForDiff( $ntext ) );
 964                 $diffs = new Diff( $ota, $nta );
 965                 $formatter = new TableDiffFormatter();
 966                 $difftext = $wgContLang->unsegmentForDiff( $formatter->format( $diffs ) );
 967
 968                 return $difftext;
 969         }
 970
 971         /**
 972          * Generate a debug comment indicating diff generating time,
 973          * server node, and generator backend.
 974          *
 975          * @param string $generator : What diff engine was used
 976          *
 977          * @return string
 978          */
 979         protected function debug( $generator = "internal" ) {
 980                 global $wgShowHostnames;
 981                 if ( !$this->enableDebugComment ) {
 982                         return '';
 983                 }
 984                 $data = [ $generator ];
 985                 if ( $wgShowHostnames ) {
 986                         $data[] = wfHostname();
 987                 }
 988                 $data[] = wfTimestamp( TS_DB );
 989
 990                 return "<!-- diff generator: " .
 991                         implode( " ", array_map( "htmlspecialchars", $data ) ) .
 992                         " -->\n";
 993         }
 994
 995         /**
 996          * Replace line numbers with the text in the user's language
 997          *
 998          * @param string $text
 999          *
1000          * @return mixed
1001          */
1002         public function localiseLineNumbers( $text ) {
1003                 return preg_replace_callback(
1004                         '/<!--LINE (\d+)-->/',
1005                         [ &$this, 'localiseLineNumbersCb' ],
1006                         $text
1007                 );
1008         }
1009
1010         public function localiseLineNumbersCb( $matches ) {
1011                 if ( $matches[1] === '1' && $this->mReducedLineNumbers ) {
1012                         return '';
1013                 }
1014
1015                 return $this->msg( 'lineno' )->numParams( $matches[1] )->escaped();
1016         }
1017
1018         /**
1019          * If there are revisions between the ones being compared, return a note saying so.
1020          *
1021          * @return string
1022          */
1023         public function getMultiNotice() {
1024                 if ( !is_object( $this->mOldRev ) || !is_object( $this->mNewRev ) ) {
1025                         return '';
1026                 } elseif ( !$this->mOldPage->equals( $this->mNewPage ) ) {
1027                         // Comparing two different pages? Count would be meaningless.
1028                         return '';
1029                 }
1030
1031                 if ( $this->mOldRev->getTimestamp() > $this->mNewRev->getTimestamp() ) {
1032                         $oldRev = $this->mNewRev; // flip
1033                         $newRev = $this->mOldRev; // flip
1034                 } else { // normal case
1035                         $oldRev = $this->mOldRev;
1036                         $newRev = $this->mNewRev;
1037                 }
1038
1039                 // Sanity: don't show the notice if too many rows must be scanned
1040                 // @todo show some special message for that case
1041                 $nEdits = $this->mNewPage->countRevisionsBetween( $oldRev, $newRev, 1000 );
1042                 if ( $nEdits > 0 && $nEdits <= 1000 ) {
1043                         $limit = 100; // use diff-multi-manyusers if too many users
1044                         $users = $this->mNewPage->getAuthorsBetween( $oldRev, $newRev, $limit );
1045                         $numUsers = count( $users );
1046
1047                         if ( $numUsers == 1 && $users[0] == $newRev->getUserText( Revision::RAW ) ) {
1048                                 $numUsers = 0; // special case to say "by the same user" instead of "by one other user"
1049                         }
1050
1051                         return self::intermediateEditsMsg( $nEdits, $numUsers, $limit );
1052                 }
1053
1054                 return ''; // nothing
1055         }
1056
1057         /**
1058          * Get a notice about how many intermediate edits and users there are
1059          *
1060          * @param int $numEdits
1061          * @param int $numUsers
1062          * @param int $limit
1063          *
1064          * @return string
1065          */
1066         public static function intermediateEditsMsg( $numEdits, $numUsers, $limit ) {
1067                 if ( $numUsers === 0 ) {
1068                         $msg = 'diff-multi-sameuser';
1069                 } elseif ( $numUsers > $limit ) {
1070                         $msg = 'diff-multi-manyusers';
1071                         $numUsers = $limit;
1072                 } else {
1073                         $msg = 'diff-multi-otherusers';
1074                 }
1075
1076                 return wfMessage( $msg )->numParams( $numEdits, $numUsers )->parse();
1077         }
1078
1079         /**
1080          * Get a header for a specified revision.
1081          *
1082          * @param Revision $rev
1083          * @param string $complete 'complete' to get the header wrapped depending
1084          *        the visibility of the revision and a link to edit the page.
1085          *
1086          * @return string HTML fragment
1087          */
1088         protected function getRevisionHeader( Revision $rev, $complete = '' ) {
1089                 $lang = $this->getLanguage();
1090                 $user = $this->getUser();
1091                 $revtimestamp = $rev->getTimestamp();
1092                 $timestamp = $lang->userTimeAndDate( $revtimestamp, $user );
1093                 $dateofrev = $lang->userDate( $revtimestamp, $user );
1094                 $timeofrev = $lang->userTime( $revtimestamp, $user );
1095
1096                 $header = $this->msg(
1097                         $rev->isCurrent() ? 'currentrev-asof' : 'revisionasof',
1098                         $timestamp,
1099                         $dateofrev,
1100                         $timeofrev
1101                 )->escaped();
1102
1103                 if ( $complete !== 'complete' ) {
1104                         return $header;
1105                 }
1106
1107                 $title = $rev->getTitle();
1108
1109                 $header = Linker::linkKnown( $title, $header, [],
1110                         [ 'oldid' => $rev->getId() ] );
1111
1112                 if ( $rev->userCan( Revision::DELETED_TEXT, $user ) ) {
1113                         $editQuery = [ 'action' => 'edit' ];
1114                         if ( !$rev->isCurrent() ) {
1115                                 $editQuery['oldid'] = $rev->getId();
1116                         }
1117
1118                         $key = $title->quickUserCan( 'edit', $user ) ? 'editold' : 'viewsourceold';
1119                         $msg = $this->msg( $key )->escaped();
1120                         $editLink = $this->msg( 'parentheses' )->rawParams(
1121                                 Linker::linkKnown( $title, $msg, [], $editQuery ) )->escaped();
1122                         $header .= ' ' . Html::rawElement(
1123                                 'span',
1124                                 [ 'class' => 'mw-diff-edit' ],
1125                                 $editLink
1126                         );
1127                         if ( $rev->isDeleted( Revision::DELETED_TEXT ) ) {
1128                                 $header = Html::rawElement(
1129                                         'span',
1130                                         [ 'class' => 'history-deleted' ],
1131                                         $header
1132                                 );
1133                         }
1134                 } else {
1135                         $header = Html::rawElement( 'span', [ 'class' => 'history-deleted' ], $header );
1136                 }
1137
1138                 return $header;
1139         }
1140
1141         /**
1142          * Add the header to a diff body
1143          *
1144          * @param string $diff Diff body
1145          * @param string $otitle Old revision header
1146          * @param string $ntitle New revision header
1147          * @param string $multi Notice telling user that there are intermediate
1148          *   revisions between the ones being compared
1149          * @param string $notice Other notices, e.g. that user is viewing deleted content
1150          *
1151          * @return string
1152          */
1153         public function addHeader( $diff, $otitle, $ntitle, $multi = '', $notice = '' ) {
1154                 // shared.css sets diff in interface language/dir, but the actual content
1155                 // is often in a different language, mostly the page content language/dir
1156                 $header = Html::openElement( 'table', [
1157                         'class' => [ 'diff', 'diff-contentalign-' . $this->getDiffLang()->alignStart() ],
1158                         'data-mw' => 'interface',
1159                 ] );
1160                 $userLang = htmlspecialchars( $this->getLanguage()->getHtmlCode() );
1161
1162                 if ( !$diff && !$otitle ) {
1163                         $header .= "
1164                         <tr style='vertical-align: top;' lang='{$userLang}'>
1165                         <td class='diff-ntitle'>{$ntitle}</td>
1166                         </tr>";
1167                         $multiColspan = 1;
1168                 } else {
1169                         if ( $diff ) { // Safari/Chrome show broken output if cols not used
1170                                 $header .= "
1171                                 <col class='diff-marker' />
1172                                 <col class='diff-content' />
1173                                 <col class='diff-marker' />
1174                                 <col class='diff-content' />";
1175                                 $colspan = 2;
1176                                 $multiColspan = 4;
1177                         } else {
1178                                 $colspan = 1;
1179                                 $multiColspan = 2;
1180                         }
1181                         if ( $otitle || $ntitle ) {
1182                                 $header .= "
1183                                 <tr style='vertical-align: top;' lang='{$userLang}'>
1184                                 <td colspan='$colspan' class='diff-otitle'>{$otitle}</td>
1185                                 <td colspan='$colspan' class='diff-ntitle'>{$ntitle}</td>
1186                                 </tr>";
1187                         }
1188                 }
1189
1190                 if ( $multi != '' ) {
1191                         $header .= "<tr><td colspan='{$multiColspan}' style='text-align: center;' " .
1192                                 "class='diff-multi' lang='{$userLang}'>{$multi}</td></tr>";
1193                 }
1194                 if ( $notice != '' ) {
1195                         $header .= "<tr><td colspan='{$multiColspan}' style='text-align: center;' " .
1196                                 "lang='{$userLang}'>{$notice}</td></tr>";
1197                 }
1198
1199                 return $header . $diff . "</table>";
1200         }
1201
1202         /**
1203          * Use specified text instead of loading from the database
1204          * @param Content $oldContent
1205          * @param Content $newContent
1206          * @since 1.21
1207          */
1208         public function setContent( Content $oldContent, Content $newContent ) {
1209                 $this->mOldContent = $oldContent;
1210                 $this->mNewContent = $newContent;
1211
1212                 $this->mTextLoaded = 2;
1213                 $this->mRevisionsLoaded = true;
1214         }
1215
1216         /**
1217          * Set the language in which the diff text is written
1218          * (Defaults to page content language).
1219          * @param Language|string $lang
1220          * @since 1.19
1221          */
1222         public function setTextLanguage( $lang ) {
1223                 $this->mDiffLang = wfGetLangObj( $lang );
1224         }
1225
1226         /**
1227          * Maps a revision pair definition as accepted by DifferenceEngine constructor
1228          * to a pair of actual integers representing revision ids.
1229          *
1230          * @param int $old Revision id, e.g. from URL parameter 'oldid'
1231          * @param int|string $new Revision id or strings 'next' or 'prev', e.g. from URL parameter 'diff'
1232          *
1233          * @return int[] List of two revision ids, older first, later second.
1234          *     Zero signifies invalid argument passed.
1235          *     false signifies that there is no previous/next revision ($old is the oldest/newest one).
1236          */
1237         public function mapDiffPrevNext( $old, $new ) {
1238                 if ( $new === 'prev' ) {
1239                         // Show diff between revision $old and the previous one. Get previous one from DB.
1240                         $newid = intval( $old );
1241                         $oldid = $this->getTitle()->getPreviousRevisionID( $newid );
1242                 } elseif ( $new === 'next' ) {
1243                         // Show diff between revision $old and the next one. Get next one from DB.
1244                         $oldid = intval( $old );
1245                         $newid = $this->getTitle()->getNextRevisionID( $oldid );
1246                 } else {
1247                         $oldid = intval( $old );
1248                         $newid = intval( $new );
1249                 }
1250
1251                 return [ $oldid, $newid ];
1252         }
1253
1254         /**
1255          * Load revision IDs
1256          */
1257         private function loadRevisionIds() {
1258                 if ( $this->mRevisionsIdsLoaded ) {
1259                         return;
1260                 }
1261
1262                 $this->mRevisionsIdsLoaded = true;
1263
1264                 $old = $this->mOldid;
1265                 $new = $this->mNewid;
1266
1267                 list( $this->mOldid, $this->mNewid ) = self::mapDiffPrevNext( $old, $new );
1268                 if ( $new === 'next' && $this->mNewid === false ) {
1269                         # if no result, NewId points to the newest old revision. The only newer
1270                         # revision is cur, which is "0".
1271                         $this->mNewid = 0;
1272                 }
1273
1274                 Hooks::run(
1275                         'NewDifferenceEngine',
1276                         [ $this->getTitle(), &$this->mOldid, &$this->mNewid, $old, $new ]
1277                 );
1278         }
1279
1280         /**
1281          * Load revision metadata for the specified articles. If newid is 0, then compare
1282          * the old article in oldid to the current article; if oldid is 0, then
1283          * compare the current article to the immediately previous one (ignoring the
1284          * value of newid).
1285          *
1286          * If oldid is false, leave the corresponding revision object set
1287          * to false. This is impossible via ordinary user input, and is provided for
1288          * API convenience.
1289          *
1290          * @return bool
1291          */
1292         public function loadRevisionData() {
1293                 if ( $this->mRevisionsLoaded ) {
1294                         return true;
1295                 }
1296
1297                 // Whether it succeeds or fails, we don't want to try again
1298                 $this->mRevisionsLoaded = true;
1299
1300                 $this->loadRevisionIds();
1301
1302                 // Load the new revision object
1303                 if ( $this->mNewid ) {
1304                         $this->mNewRev = Revision::newFromId( $this->mNewid );
1305                 } else {
1306                         $this->mNewRev = Revision::newFromTitle(
1307                                 $this->getTitle(),
1308                                 false,
1309                                 Revision::READ_NORMAL
1310                         );
1311                 }
1312
1313                 if ( !$this->mNewRev instanceof Revision ) {
1314                         return false;
1315                 }
1316
1317                 // Update the new revision ID in case it was 0 (makes life easier doing UI stuff)
1318                 $this->mNewid = $this->mNewRev->getId();
1319                 $this->mNewPage = $this->mNewRev->getTitle();
1320
1321                 // Load the old revision object
1322                 $this->mOldRev = false;
1323                 if ( $this->mOldid ) {
1324                         $this->mOldRev = Revision::newFromId( $this->mOldid );
1325                 } elseif ( $this->mOldid === 0 ) {
1326                         $rev = $this->mNewRev->getPrevious();
1327                         if ( $rev ) {
1328                                 $this->mOldid = $rev->getId();
1329                                 $this->mOldRev = $rev;
1330                         } else {
1331                                 // No previous revision; mark to show as first-version only.
1332                                 $this->mOldid = false;
1333                                 $this->mOldRev = false;
1334                         }
1335                 } /* elseif ( $this->mOldid === false ) leave mOldRev false; */
1336
1337                 if ( is_null( $this->mOldRev ) ) {
1338                         return false;
1339                 }
1340
1341                 if ( $this->mOldRev ) {
1342                         $this->mOldPage = $this->mOldRev->getTitle();
1343                 }
1344
1345                 // Load tags information for both revisions
1346                 $dbr = wfGetDB( DB_REPLICA );
1347                 if ( $this->mOldid !== false ) {
1348                         $this->mOldTags = $dbr->selectField(
1349                                 'tag_summary',
1350                                 'ts_tags',
1351                                 [ 'ts_rev_id' => $this->mOldid ],
1352                                 __METHOD__
1353                         );
1354                 } else {
1355                         $this->mOldTags = false;
1356                 }
1357                 $this->mNewTags = $dbr->selectField(
1358                         'tag_summary',
1359                         'ts_tags',
1360                         [ 'ts_rev_id' => $this->mNewid ],
1361                         __METHOD__
1362                 );
1363
1364                 return true;
1365         }
1366
1367         /**
1368          * Load the text of the revisions, as well as revision data.
1369          *
1370          * @return bool
1371          */
1372         public function loadText() {
1373                 if ( $this->mTextLoaded == 2 ) {
1374                         return true;
1375                 }
1376
1377                 // Whether it succeeds or fails, we don't want to try again
1378                 $this->mTextLoaded = 2;
1379
1380                 if ( !$this->loadRevisionData() ) {
1381                         return false;
1382                 }
1383
1384                 if ( $this->mOldRev ) {
1385                         $this->mOldContent = $this->mOldRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1386                         if ( $this->mOldContent === null ) {
1387                                 return false;
1388                         }
1389                 }
1390
1391                 if ( $this->mNewRev ) {
1392                         $this->mNewContent = $this->mNewRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1393                         if ( $this->mNewContent === null ) {
1394                                 return false;
1395                         }
1396                 }
1397
1398                 return true;
1399         }
1400
1401         /**
1402          * Load the text of the new revision, not the old one
1403          *
1404          * @return bool
1405          */
1406         public function loadNewText() {
1407                 if ( $this->mTextLoaded >= 1 ) {
1408                         return true;
1409                 }
1410
1411                 $this->mTextLoaded = 1;
1412
1413                 if ( !$this->loadRevisionData() ) {
1414                         return false;
1415                 }
1416
1417                 $this->mNewContent = $this->mNewRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1418
1419                 return true;
1420         }
1421
1422 }