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 use MediaWiki\MediaWikiServices;
  24 use MediaWiki\Shell\Shell;
  25
  26 /**
  27  * @todo document
  28  * @ingroup DifferenceEngine
  29  */
  30 class DifferenceEngine extends ContextSource {
  31         /**
  32          * Constant to indicate diff cache compatibility.
  33          * Bump this when changing the diff formatting in a way that
  34          * fixes important bugs or such to force cached diff views to
  35          * clear.
  36          */
  37         const DIFF_VERSION = '1.12';
  38
  39         /** @var int */
  40         public $mOldid;
  41
  42         /** @var int */
  43         public $mNewid;
  44
  45         private $mOldTags;
  46         private $mNewTags;
  47
  48         /** @var Content */
  49         public $mOldContent;
  50
  51         /** @var Content */
  52         public $mNewContent;
  53
  54         /** @var Language */
  55         protected $mDiffLang;
  56
  57         /** @var Title */
  58         public $mOldPage;
  59
  60         /** @var Title */
  61         public $mNewPage;
  62
  63         /** @var Revision */
  64         public $mOldRev;
  65
  66         /** @var Revision */
  67         public $mNewRev;
  68
  69         /** @var bool Have the revisions IDs been loaded */
  70         private $mRevisionsIdsLoaded = false;
  71
  72         /** @var bool Have the revisions been loaded */
  73         public $mRevisionsLoaded = false;
  74
  75         /** @var int How many text blobs have been loaded, 0, 1 or 2? */
  76         public $mTextLoaded = 0;
  77
  78         /** @var bool Was the diff fetched from cache? */
  79         public $mCacheHit = false;
  80
  81         /**
  82          * Set this to true to add debug info to the HTML output.
  83          * Warning: this may cause RSS readers to spuriously mark articles as "new"
  84          * (T22601)
  85          */
  86         public $enableDebugComment = false;
  87
  88         /** @var bool If true, line X is not displayed when X is 1, for example
  89          *    to increase readability and conserve space with many small diffs.
  90          */
  91         protected $mReducedLineNumbers = false;
  92
  93         /** @var string Link to action=markpatrolled */
  94         protected $mMarkPatrolledLink = null;
  95
  96         /** @var bool Show rev_deleted content if allowed */
  97         protected $unhide = false;
  98
  99         /** @var bool Refresh the diff cache */
 100         protected $mRefreshCache = false;
 101
 102         /**#@-*/
 103
 104         /**
 105          * @param IContextSource $context Context to use, anything else will be ignored
 106          * @param int $old Old ID we want to show and diff with.
 107          * @param string|int $new Either revision ID or 'prev' or 'next'. Default: 0.
 108          * @param int $rcid Deprecated, no longer used!
 109          * @param bool $refreshCache If set, refreshes the diff cache
 110          * @param bool $unhide If set, allow viewing deleted revs
 111          */
 112         public function __construct( $context = null, $old = 0, $new = 0, $rcid = 0,
 113                 $refreshCache = false, $unhide = false
 114         ) {
 115                 if ( $context instanceof IContextSource ) {
 116                         $this->setContext( $context );
 117                 }
 118
 119                 wfDebug( "DifferenceEngine old '$old' new '$new' rcid '$rcid'\n" );
 120
 121                 $this->mOldid = $old;
 122                 $this->mNewid = $new;
 123                 $this->mRefreshCache = $refreshCache;
 124                 $this->unhide = $unhide;
 125         }
 126
 127         /**
 128          * @param bool $value
 129          */
 130         public function setReducedLineNumbers( $value = true ) {
 131                 $this->mReducedLineNumbers = $value;
 132         }
 133
 134         /**
 135          * @return Language
 136          */
 137         public function getDiffLang() {
 138                 if ( $this->mDiffLang === null ) {
 139                         # Default language in which the diff text is written.
 140                         $this->mDiffLang = $this->getTitle()->getPageLanguage();
 141                 }
 142
 143                 return $this->mDiffLang;
 144         }
 145
 146         /**
 147          * @return bool
 148          */
 149         public function wasCacheHit() {
 150                 return $this->mCacheHit;
 151         }
 152
 153         /**
 154          * @return int
 155          */
 156         public function getOldid() {
 157                 $this->loadRevisionIds();
 158
 159                 return $this->mOldid;
 160         }
 161
 162         /**
 163          * @return bool|int
 164          */
 165         public function getNewid() {
 166                 $this->loadRevisionIds();
 167
 168                 return $this->mNewid;
 169         }
 170
 171         /**
 172          * Look up a special:Undelete link to the given deleted revision id,
 173          * as a workaround for being unable to load deleted diffs in currently.
 174          *
 175          * @param int $id Revision ID
 176          *
 177          * @return string|bool Link HTML or false
 178          */
 179         public function deletedLink( $id ) {
 180                 if ( $this->getUser()->isAllowed( 'deletedhistory' ) ) {
 181                         $dbr = wfGetDB( DB_REPLICA );
 182                         $arQuery = Revision::getArchiveQueryInfo();
 183                         $row = $dbr->selectRow(
 184                                 $arQuery['tables'],
 185                                 array_merge( $arQuery['fields'], [ 'ar_namespace', 'ar_title' ] ),
 186                                 [ 'ar_rev_id' => $id ],
 187                                 __METHOD__,
 188                                 [],
 189                                 $arQuery['joins']
 190                         );
 191                         if ( $row ) {
 192                                 $rev = Revision::newFromArchiveRow( $row );
 193                                 $title = Title::makeTitleSafe( $row->ar_namespace, $row->ar_title );
 194
 195                                 return SpecialPage::getTitleFor( 'Undelete' )->getFullURL( [
 196                                         'target' => $title->getPrefixedText(),
 197                                         'timestamp' => $rev->getTimestamp()
 198                                 ] );
 199                         }
 200                 }
 201
 202                 return false;
 203         }
 204
 205         /**
 206          * Build a wikitext link toward a deleted revision, if viewable.
 207          *
 208          * @param int $id Revision ID
 209          *
 210          * @return string Wikitext fragment
 211          */
 212         public function deletedIdMarker( $id ) {
 213                 $link = $this->deletedLink( $id );
 214                 if ( $link ) {
 215                         return "[$link $id]";
 216                 } else {
 217                         return (string)$id;
 218                 }
 219         }
 220
 221         private function showMissingRevision() {
 222                 $out = $this->getOutput();
 223
 224                 $missing = [];
 225                 if ( $this->mOldRev === null ||
 226                         ( $this->mOldRev && $this->mOldContent === null )
 227                 ) {
 228                         $missing[] = $this->deletedIdMarker( $this->mOldid );
 229                 }
 230                 if ( $this->mNewRev === null ||
 231                         ( $this->mNewRev && $this->mNewContent === null )
 232                 ) {
 233                         $missing[] = $this->deletedIdMarker( $this->mNewid );
 234                 }
 235
 236                 $out->setPageTitle( $this->msg( 'errorpagetitle' ) );
 237                 $msg = $this->msg( 'difference-missing-revision' )
 238                         ->params( $this->getLanguage()->listToText( $missing ) )
 239                         ->numParams( count( $missing ) )
 240                         ->parseAsBlock();
 241                 $out->addHTML( $msg );
 242         }
 243
 244         public function showDiffPage( $diffOnly = false ) {
 245                 # Allow frames except in certain special cases
 246                 $out = $this->getOutput();
 247                 $out->allowClickjacking();
 248                 $out->setRobotPolicy( 'noindex,nofollow' );
 249
 250                 // Allow extensions to add any extra output here
 251                 Hooks::run( 'DifferenceEngineShowDiffPage', [ $out ] );
 252
 253                 if ( !$this->loadRevisionData() ) {
 254                         if ( Hooks::run( 'DifferenceEngineShowDiffPageMaybeShowMissingRevision', [ $this ] ) ) {
 255                                 $this->showMissingRevision();
 256                         }
 257                         return;
 258                 }
 259
 260                 $user = $this->getUser();
 261                 $permErrors = $this->mNewPage->getUserPermissionsErrors( 'read', $user );
 262                 if ( $this->mOldPage ) { # mOldPage might not be set, see below.
 263                         $permErrors = wfMergeErrorArrays( $permErrors,
 264                                 $this->mOldPage->getUserPermissionsErrors( 'read', $user ) );
 265                 }
 266                 if ( count( $permErrors ) ) {
 267                         throw new PermissionsError( 'read', $permErrors );
 268                 }
 269
 270                 $rollback = '';
 271
 272                 $query = [];
 273                 # Carry over 'diffonly' param via navigation links
 274                 if ( $diffOnly != $user->getBoolOption( 'diffonly' ) ) {
 275                         $query['diffonly'] = $diffOnly;
 276                 }
 277                 # Cascade unhide param in links for easy deletion browsing
 278                 if ( $this->unhide ) {
 279                         $query['unhide'] = 1;
 280                 }
 281
 282                 # Check if one of the revisions is deleted/suppressed
 283                 $deleted = $suppressed = false;
 284                 $allowed = $this->mNewRev->userCan( Revision::DELETED_TEXT, $user );
 285
 286                 $revisionTools = [];
 287
 288                 # mOldRev is false if the difference engine is called with a "vague" query for
 289                 # a diff between a version V and its previous version V' AND the version V
 290                 # is the first version of that article. In that case, V' does not exist.
 291                 if ( $this->mOldRev === false ) {
 292                         $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 293                         $samePage = true;
 294                         $oldHeader = '';
 295                         // Allow extensions to change the $oldHeader variable
 296                         Hooks::run( 'DifferenceEngineOldHeaderNoOldRev', [ &$oldHeader ] );
 297                 } else {
 298                         Hooks::run( 'DiffViewHeader', [ $this, $this->mOldRev, $this->mNewRev ] );
 299
 300                         if ( $this->mNewPage->equals( $this->mOldPage ) ) {
 301                                 $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 302                                 $samePage = true;
 303                         } else {
 304                                 $out->setPageTitle( $this->msg( 'difference-title-multipage',
 305                                         $this->mOldPage->getPrefixedText(), $this->mNewPage->getPrefixedText() ) );
 306                                 $out->addSubtitle( $this->msg( 'difference-multipage' ) );
 307                                 $samePage = false;
 308                         }
 309
 310                         if ( $samePage && $this->mNewPage->quickUserCan( 'edit', $user ) ) {
 311                                 if ( $this->mNewRev->isCurrent() && $this->mNewPage->userCan( 'rollback', $user ) ) {
 312                                         $rollbackLink = Linker::generateRollback( $this->mNewRev, $this->getContext() );
 313                                         if ( $rollbackLink ) {
 314                                                 $out->preventClickjacking();
 315                                                 $rollback = "\u{00A0}\u{00A0}\u{00A0}" . $rollbackLink;
 316                                         }
 317                                 }
 318
 319                                 if ( !$this->mOldRev->isDeleted( Revision::DELETED_TEXT ) &&
 320                                         !$this->mNewRev->isDeleted( Revision::DELETED_TEXT )
 321                                 ) {
 322                                         $undoLink = Html::element( 'a', [
 323                                                         'href' => $this->mNewPage->getLocalURL( [
 324                                                                 'action' => 'edit',
 325                                                                 'undoafter' => $this->mOldid,
 326                                                                 'undo' => $this->mNewid
 327                                                         ] ),
 328                                                         'title' => Linker::titleAttrib( 'undo' ),
 329                                                 ],
 330                                                 $this->msg( 'editundo' )->text()
 331                                         );
 332                                         $revisionTools['mw-diff-undo'] = $undoLink;
 333                                 }
 334                         }
 335
 336                         # Make "previous revision link"
 337                         if ( $samePage && $this->mOldRev->getPrevious() ) {
 338                                 $prevlink = Linker::linkKnown(
 339                                         $this->mOldPage,
 340                                         $this->msg( 'previousdiff' )->escaped(),
 341                                         [ 'id' => 'differences-prevlink' ],
 342                                         [ 'diff' => 'prev', 'oldid' => $this->mOldid ] + $query
 343                                 );
 344                         } else {
 345                                 $prevlink = "\u{00A0}";
 346                         }
 347
 348                         if ( $this->mOldRev->isMinor() ) {
 349                                 $oldminor = ChangesList::flag( 'minor' );
 350                         } else {
 351                                 $oldminor = '';
 352                         }
 353
 354                         $ldel = $this->revisionDeleteLink( $this->mOldRev );
 355                         $oldRevisionHeader = $this->getRevisionHeader( $this->mOldRev, 'complete' );
 356                         $oldChangeTags = ChangeTags::formatSummaryRow( $this->mOldTags, 'diff', $this->getContext() );
 357
 358                         $oldHeader = '<div id="mw-diff-otitle1"><strong>' . $oldRevisionHeader . '</strong></div>' .
 359                                 '<div id="mw-diff-otitle2">' .
 360                                 Linker::revUserTools( $this->mOldRev, !$this->unhide ) . '</div>' .
 361                                 '<div id="mw-diff-otitle3">' . $oldminor .
 362                                 Linker::revComment( $this->mOldRev, !$diffOnly, !$this->unhide ) . $ldel . '</div>' .
 363                                 '<div id="mw-diff-otitle5">' . $oldChangeTags[0] . '</div>' .
 364                                 '<div id="mw-diff-otitle4">' . $prevlink . '</div>';
 365
 366                         // Allow extensions to change the $oldHeader variable
 367                         Hooks::run( 'DifferenceEngineOldHeader', [ $this, &$oldHeader, $prevlink, $oldminor,
 368                                 $diffOnly, $ldel, $this->unhide ] );
 369
 370                         if ( $this->mOldRev->isDeleted( Revision::DELETED_TEXT ) ) {
 371                                 $deleted = true; // old revisions text is hidden
 372                                 if ( $this->mOldRev->isDeleted( Revision::DELETED_RESTRICTED ) ) {
 373                                         $suppressed = true; // also suppressed
 374                                 }
 375                         }
 376
 377                         # Check if this user can see the revisions
 378                         if ( !$this->mOldRev->userCan( Revision::DELETED_TEXT, $user ) ) {
 379                                 $allowed = false;
 380                         }
 381                 }
 382
 383                 $out->addJsConfigVars( [
 384                         'wgDiffOldId' => $this->mOldid,
 385                         'wgDiffNewId' => $this->mNewid,
 386                 ] );
 387
 388                 # Make "next revision link"
 389                 # Skip next link on the top revision
 390                 if ( $samePage && !$this->mNewRev->isCurrent() ) {
 391                         $nextlink = Linker::linkKnown(
 392                                 $this->mNewPage,
 393                                 $this->msg( 'nextdiff' )->escaped(),
 394                                 [ 'id' => 'differences-nextlink' ],
 395                                 [ 'diff' => 'next', 'oldid' => $this->mNewid ] + $query
 396                         );
 397                 } else {
 398                         $nextlink = "\u{00A0}";
 399                 }
 400
 401                 if ( $this->mNewRev->isMinor() ) {
 402                         $newminor = ChangesList::flag( 'minor' );
 403                 } else {
 404                         $newminor = '';
 405                 }
 406
 407                 # Handle RevisionDelete links...
 408                 $rdel = $this->revisionDeleteLink( $this->mNewRev );
 409
 410                 # Allow extensions to define their own revision tools
 411                 Hooks::run( 'DiffRevisionTools',
 412                         [ $this->mNewRev, &$revisionTools, $this->mOldRev, $user ] );
 413                 $formattedRevisionTools = [];
 414                 // Put each one in parentheses (poor man's button)
 415                 foreach ( $revisionTools as $key => $tool ) {
 416                         $toolClass = is_string( $key ) ? $key : 'mw-diff-tool';
 417                         $element = Html::rawElement(
 418                                 'span',
 419                                 [ 'class' => $toolClass ],
 420                                 $this->msg( 'parentheses' )->rawParams( $tool )->escaped()
 421                         );
 422                         $formattedRevisionTools[] = $element;
 423                 }
 424                 $newRevisionHeader = $this->getRevisionHeader( $this->mNewRev, 'complete' ) .
 425                         ' ' . implode( ' ', $formattedRevisionTools );
 426                 $newChangeTags = ChangeTags::formatSummaryRow( $this->mNewTags, 'diff', $this->getContext() );
 427
 428                 $newHeader = '<div id="mw-diff-ntitle1"><strong>' . $newRevisionHeader . '</strong></div>' .
 429                         '<div id="mw-diff-ntitle2">' . Linker::revUserTools( $this->mNewRev, !$this->unhide ) .
 430                         " $rollback</div>" .
 431                         '<div id="mw-diff-ntitle3">' . $newminor .
 432                         Linker::revComment( $this->mNewRev, !$diffOnly, !$this->unhide ) . $rdel . '</div>' .
 433                         '<div id="mw-diff-ntitle5">' . $newChangeTags[0] . '</div>' .
 434                         '<div id="mw-diff-ntitle4">' . $nextlink . $this->markPatrolledLink() . '</div>';
 435
 436                 // Allow extensions to change the $newHeader variable
 437                 Hooks::run( 'DifferenceEngineNewHeader', [ $this, &$newHeader, $formattedRevisionTools,
 438                         $nextlink, $rollback, $newminor, $diffOnly, $rdel, $this->unhide ] );
 439
 440                 if ( $this->mNewRev->isDeleted( Revision::DELETED_TEXT ) ) {
 441                         $deleted = true; // new revisions text is hidden
 442                         if ( $this->mNewRev->isDeleted( Revision::DELETED_RESTRICTED ) ) {
 443                                 $suppressed = true; // also suppressed
 444                         }
 445                 }
 446
 447                 # If the diff cannot be shown due to a deleted revision, then output
 448                 # the diff header and links to unhide (if available)...
 449                 if ( $deleted && ( !$this->unhide || !$allowed ) ) {
 450                         $this->showDiffStyle();
 451                         $multi = $this->getMultiNotice();
 452                         $out->addHTML( $this->addHeader( '', $oldHeader, $newHeader, $multi ) );
 453                         if ( !$allowed ) {
 454                                 $msg = $suppressed ? 'rev-suppressed-no-diff' : 'rev-deleted-no-diff';
 455                                 # Give explanation for why revision is not visible
 456                                 $out->wrapWikiMsg( "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 457                                         [ $msg ] );
 458                         } else {
 459                                 # Give explanation and add a link to view the diff...
 460                                 $query = $this->getRequest()->appendQueryValue( 'unhide', '1' );
 461                                 $link = $this->getTitle()->getFullURL( $query );
 462                                 $msg = $suppressed ? 'rev-suppressed-unhide-diff' : 'rev-deleted-unhide-diff';
 463                                 $out->wrapWikiMsg(
 464                                         "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 465                                         [ $msg, $link ]
 466                                 );
 467                         }
 468                 # Otherwise, output a regular diff...
 469                 } else {
 470                         # Add deletion notice if the user is viewing deleted content
 471                         $notice = '';
 472                         if ( $deleted ) {
 473                                 $msg = $suppressed ? 'rev-suppressed-diff-view' : 'rev-deleted-diff-view';
 474                                 $notice = "<div id='mw-$msg' class='mw-warning plainlinks'>\n" .
 475                                         $this->msg( $msg )->parse() .
 476                                         "</div>\n";
 477                         }
 478                         $this->showDiff( $oldHeader, $newHeader, $notice );
 479                         if ( !$diffOnly ) {
 480                                 $this->renderNewRevision();
 481                         }
 482                 }
 483         }
 484
 485         /**
 486          * Build a link to mark a change as patrolled.
 487          *
 488          * Returns empty string if there's either no revision to patrol or the user is not allowed to.
 489          * Side effect: When the patrol link is build, this method will call
 490          * OutputPage::preventClickjacking() and load mediawiki.page.patrol.ajax.
 491          *
 492          * @return string HTML or empty string
 493          */
 494         public function markPatrolledLink() {
 495                 if ( $this->mMarkPatrolledLink === null ) {
 496                         $linkInfo = $this->getMarkPatrolledLinkInfo();
 497                         // If false, there is no patrol link needed/allowed
 498                         if ( !$linkInfo ) {
 499                                 $this->mMarkPatrolledLink = '';
 500                         } else {
 501                                 $this->mMarkPatrolledLink = ' <span class="patrollink" data-mw="interface">[' .
 502                                         Linker::linkKnown(
 503                                                 $this->mNewPage,
 504                                                 $this->msg( 'markaspatrolleddiff' )->escaped(),
 505                                                 [],
 506                                                 [
 507                                                         'action' => 'markpatrolled',
 508                                                         'rcid' => $linkInfo['rcid'],
 509                                                 ]
 510                                         ) . ']</span>';
 511                                 // Allow extensions to change the markpatrolled link
 512                                 Hooks::run( 'DifferenceEngineMarkPatrolledLink', [ $this,
 513                                         &$this->mMarkPatrolledLink, $linkInfo['rcid'] ] );
 514                         }
 515                 }
 516                 return $this->mMarkPatrolledLink;
 517         }
 518
 519         /**
 520          * Returns an array of meta data needed to build a "mark as patrolled" link and
 521          * adds the mediawiki.page.patrol.ajax to the output.
 522          *
 523          * @return array|false An array of meta data for a patrol link (rcid only)
 524          *  or false if no link is needed
 525          */
 526         protected function getMarkPatrolledLinkInfo() {
 527                 global $wgUseRCPatrol;
 528
 529                 $user = $this->getUser();
 530
 531                 // Prepare a change patrol link, if applicable
 532                 if (
 533                         // Is patrolling enabled and the user allowed to?
 534                         $wgUseRCPatrol && $this->mNewPage->quickUserCan( 'patrol', $user ) &&
 535                         // Only do this if the revision isn't more than 6 hours older
 536                         // than the Max RC age (6h because the RC might not be cleaned out regularly)
 537                         RecentChange::isInRCLifespan( $this->mNewRev->getTimestamp(), 21600 )
 538                 ) {
 539                         // Look for an unpatrolled change corresponding to this diff
 540                         $db = wfGetDB( DB_REPLICA );
 541                         $change = RecentChange::newFromConds(
 542                                 [
 543                                         'rc_timestamp' => $db->timestamp( $this->mNewRev->getTimestamp() ),
 544                                         'rc_this_oldid' => $this->mNewid,
 545                                         'rc_patrolled' => RecentChange::PRC_UNPATROLLED
 546                                 ],
 547                                 __METHOD__
 548                         );
 549
 550                         if ( $change && !$change->getPerformer()->equals( $user ) ) {
 551                                 $rcid = $change->getAttribute( 'rc_id' );
 552                         } else {
 553                                 // None found or the page has been created by the current user.
 554                                 // If the user could patrol this it already would be patrolled
 555                                 $rcid = 0;
 556                         }
 557
 558                         // Allow extensions to possibly change the rcid here
 559                         // For example the rcid might be set to zero due to the user
 560                         // being the same as the performer of the change but an extension
 561                         // might still want to show it under certain conditions
 562                         Hooks::run( 'DifferenceEngineMarkPatrolledRCID', [ &$rcid, $this, $change, $user ] );
 563
 564                         // Build the link
 565                         if ( $rcid ) {
 566                                 $this->getOutput()->preventClickjacking();
 567                                 if ( $user->isAllowed( 'writeapi' ) ) {
 568                                         $this->getOutput()->addModules( 'mediawiki.page.patrol.ajax' );
 569                                 }
 570
 571                                 return [
 572                                         'rcid' => $rcid,
 573                                 ];
 574                         }
 575                 }
 576
 577                 // No mark as patrolled link applicable
 578                 return false;
 579         }
 580
 581         /**
 582          * @param Revision $rev
 583          *
 584          * @return string
 585          */
 586         protected function revisionDeleteLink( $rev ) {
 587                 $link = Linker::getRevDeleteLink( $this->getUser(), $rev, $rev->getTitle() );
 588                 if ( $link !== '' ) {
 589                         $link = "\u{00A0}\u{00A0}\u{00A0}" . $link . ' ';
 590                 }
 591
 592                 return $link;
 593         }
 594
 595         /**
 596          * Show the new revision of the page.
 597          */
 598         public function renderNewRevision() {
 599                 $out = $this->getOutput();
 600                 $revHeader = $this->getRevisionHeader( $this->mNewRev );
 601                 # Add "current version as of X" title
 602                 $out->addHTML( "<hr class='diff-hr' id='mw-oldid' />
 603                 <h2 class='diff-currentversion-title'>{$revHeader}</h2>\n" );
 604                 # Page content may be handled by a hooked call instead...
 605                 if ( Hooks::run( 'ArticleContentOnDiff', [ $this, $out ] ) ) {
 606                         $this->loadNewText();
 607                         $out->setRevisionId( $this->mNewid );
 608                         $out->setRevisionTimestamp( $this->mNewRev->getTimestamp() );
 609                         $out->setArticleFlag( true );
 610
 611                         if ( !Hooks::run( 'ArticleContentViewCustom',
 612                                 [ $this->mNewContent, $this->mNewPage, $out ] )
 613                         ) {
 614                                 // Handled by extension
 615                         } else {
 616                                 // Normal page
 617                                 if ( $this->getTitle()->equals( $this->mNewPage ) ) {
 618                                         // If the Title stored in the context is the same as the one
 619                                         // of the new revision, we can use its associated WikiPage
 620                                         // object.
 621                                         $wikiPage = $this->getWikiPage();
 622                                 } else {
 623                                         // Otherwise we need to create our own WikiPage object
 624                                         $wikiPage = WikiPage::factory( $this->mNewPage );
 625                                 }
 626
 627                                 $parserOutput = $this->getParserOutput( $wikiPage, $this->mNewRev );
 628
 629                                 # WikiPage::getParserOutput() should not return false, but just in case
 630                                 if ( $parserOutput ) {
 631                                         // Allow extensions to change parser output here
 632                                         if ( Hooks::run( 'DifferenceEngineRenderRevisionAddParserOutput',
 633                                                 [ $this, $out, $parserOutput, $wikiPage ] )
 634                                         ) {
 635                                                 $out->addParserOutput( $parserOutput, [
 636                                                         'enableSectionEditLinks' => $this->mNewRev->isCurrent()
 637                                                                 && $this->mNewRev->getTitle()->quickUserCan( 'edit', $this->getUser() ),
 638                                                 ] );
 639                                         }
 640                                 }
 641                         }
 642                 }
 643
 644                 // Allow extensions to optionally not show the final patrolled link
 645                 if ( Hooks::run( 'DifferenceEngineRenderRevisionShowFinalPatrolLink' ) ) {
 646                         # Add redundant patrol link on bottom...
 647                         $out->addHTML( $this->markPatrolledLink() );
 648                 }
 649         }
 650
 651         /**
 652          * @param WikiPage $page
 653          * @param Revision $rev
 654          *
 655          * @return ParserOutput|bool False if the revision was not found
 656          */
 657         protected function getParserOutput( WikiPage $page, Revision $rev ) {
 658                 $parserOptions = $page->makeParserOptions( $this->getContext() );
 659                 $parserOutput = $page->getParserOutput( $parserOptions, $rev->getId() );
 660
 661                 return $parserOutput;
 662         }
 663
 664         /**
 665          * Get the diff text, send it to the OutputPage object
 666          * Returns false if the diff could not be generated, otherwise returns true
 667          *
 668          * @param string|bool $otitle Header for old text or false
 669          * @param string|bool $ntitle Header for new text or false
 670          * @param string $notice HTML between diff header and body
 671          *
 672          * @return bool
 673          */
 674         public function showDiff( $otitle, $ntitle, $notice = '' ) {
 675                 // Allow extensions to affect the output here
 676                 Hooks::run( 'DifferenceEngineShowDiff', [ $this ] );
 677
 678                 $diff = $this->getDiff( $otitle, $ntitle, $notice );
 679                 if ( $diff === false ) {
 680                         $this->showMissingRevision();
 681
 682                         return false;
 683                 } else {
 684                         $this->showDiffStyle();
 685                         $this->getOutput()->addHTML( $diff );
 686
 687                         return true;
 688                 }
 689         }
 690
 691         /**
 692          * Add style sheets for diff display.
 693          */
 694         public function showDiffStyle() {
 695                 $this->getOutput()->addModuleStyles( 'mediawiki.diff.styles' );
 696         }
 697
 698         /**
 699          * Get complete diff table, including header
 700          *
 701          * @param string|bool $otitle Header for old text or false
 702          * @param string|bool $ntitle Header for new text or false
 703          * @param string $notice HTML between diff header and body
 704          *
 705          * @return mixed
 706          */
 707         public function getDiff( $otitle, $ntitle, $notice = '' ) {
 708                 $body = $this->getDiffBody();
 709                 if ( $body === false ) {
 710                         return false;
 711                 }
 712
 713                 $multi = $this->getMultiNotice();
 714                 // Display a message when the diff is empty
 715                 if ( $body === '' ) {
 716                         $notice .= '<div class="mw-diff-empty">' .
 717                                 $this->msg( 'diff-empty' )->parse() .
 718                                 "</div>\n";
 719                 }
 720
 721                 return $this->addHeader( $body, $otitle, $ntitle, $multi, $notice );
 722         }
 723
 724         /**
 725          * Get the diff table body, without header
 726          *
 727          * @return mixed (string/false)
 728          */
 729         public function getDiffBody() {
 730                 $this->mCacheHit = true;
 731                 // Check if the diff should be hidden from this user
 732                 if ( !$this->loadRevisionData() ) {
 733                         return false;
 734                 } elseif ( $this->mOldRev &&
 735                         !$this->mOldRev->userCan( Revision::DELETED_TEXT, $this->getUser() )
 736                 ) {
 737                         return false;
 738                 } elseif ( $this->mNewRev &&
 739                         !$this->mNewRev->userCan( Revision::DELETED_TEXT, $this->getUser() )
 740                 ) {
 741                         return false;
 742                 }
 743                 // Short-circuit
 744                 if ( $this->mOldRev === false || ( $this->mOldRev && $this->mNewRev
 745                         && $this->mOldRev->getId() == $this->mNewRev->getId() )
 746                 ) {
 747                         if ( Hooks::run( 'DifferenceEngineShowEmptyOldContent', [ $this ] ) ) {
 748                                 return '';
 749                         }
 750                 }
 751                 // Cacheable?
 752                 $key = false;
 753                 $cache = ObjectCache::getMainWANInstance();
 754                 if ( $this->mOldid && $this->mNewid ) {
 755                         // Check if subclass is still using the old way
 756                         // for backwards-compatibility
 757                         $key = $this->getDiffBodyCacheKey();
 758                         if ( $key === null ) {
 759                                 $key = $cache->makeKey( ...$this->getDiffBodyCacheKeyParams() );
 760                         }
 761
 762                         // Try cache
 763                         if ( !$this->mRefreshCache ) {
 764                                 $difftext = $cache->get( $key );
 765                                 if ( $difftext ) {
 766                                         wfIncrStats( 'diff_cache.hit' );
 767                                         $difftext = $this->localiseDiff( $difftext );
 768                                         $difftext .= "\n<!-- diff cache key $key -->\n";
 769
 770                                         return $difftext;
 771                                 }
 772                         } // don't try to load but save the result
 773                 }
 774                 $this->mCacheHit = false;
 775
 776                 // Loadtext is permission safe, this just clears out the diff
 777                 if ( !$this->loadText() ) {
 778                         return false;
 779                 }
 780
 781                 $difftext = $this->generateContentDiffBody( $this->mOldContent, $this->mNewContent );
 782
 783                 // Avoid PHP 7.1 warning from passing $this by reference
 784                 $diffEngine = $this;
 785
 786                 // Save to cache for 7 days
 787                 if ( !Hooks::run( 'AbortDiffCache', [ &$diffEngine ] ) ) {
 788                         wfIncrStats( 'diff_cache.uncacheable' );
 789                 } elseif ( $key !== false && $difftext !== false ) {
 790                         wfIncrStats( 'diff_cache.miss' );
 791                         $cache->set( $key, $difftext, 7 * 86400 );
 792                 } else {
 793                         wfIncrStats( 'diff_cache.uncacheable' );
 794                 }
 795                 // localise line numbers and title attribute text
 796                 if ( $difftext !== false ) {
 797                         $difftext = $this->localiseDiff( $difftext );
 798                 }
 799
 800                 return $difftext;
 801         }
 802
 803         /**
 804          * Returns the cache key for diff body text or content.
 805          *
 806          * @deprecated since 1.31, use getDiffBodyCacheKeyParams() instead
 807          * @since 1.23
 808          *
 809          * @throws MWException
 810          * @return string|null
 811          */
 812         protected function getDiffBodyCacheKey() {
 813                 return null;
 814         }
 815
 816         /**
 817          * Get the cache key parameters
 818          *
 819          * Subclasses can replace the first element in the array to something
 820          * more specific to the type of diff (e.g. "inline-diff"), or append
 821          * if the cache should vary on more things. Overriding entirely should
 822          * be avoided.
 823          *
 824          * @since 1.31
 825          *
 826          * @return array
 827          * @throws MWException
 828          */
 829         protected function getDiffBodyCacheKeyParams() {
 830                 if ( !$this->mOldid || !$this->mNewid ) {
 831                         throw new MWException( 'mOldid and mNewid must be set to get diff cache key.' );
 832                 }
 833
 834                 $engine = $this->getEngine();
 835                 $params = [
 836                         'diff',
 837                         $engine,
 838                         self::DIFF_VERSION,
 839                         "old-{$this->mOldid}",
 840                         "rev-{$this->mNewid}"
 841                 ];
 842
 843                 if ( $engine === 'wikidiff2' ) {
 844                         $params[] = phpversion( 'wikidiff2' );
 845                         $params[] = $this->getConfig()->get( 'WikiDiff2MovedParagraphDetectionCutoff' );
 846                 }
 847
 848                 return $params;
 849         }
 850
 851         /**
 852          * Generate a diff, no caching.
 853          *
 854          * This implementation uses generateTextDiffBody() to generate a diff based on the default
 855          * serialization of the given Content objects. This will fail if $old or $new are not
 856          * instances of TextContent.
 857          *
 858          * Subclasses may override this to provide a different rendering for the diff,
 859          * perhaps taking advantage of the content's native form. This is required for all content
 860          * models that are not text based.
 861          *
 862          * @since 1.21
 863          *
 864          * @param Content $old Old content
 865          * @param Content $new New content
 866          *
 867          * @throws MWException If old or new content is not an instance of TextContent.
 868          * @return bool|string
 869          */
 870         public function generateContentDiffBody( Content $old, Content $new ) {
 871                 if ( !( $old instanceof TextContent ) ) {
 872                         throw new MWException( "Diff not implemented for " . get_class( $old ) . "; " .
 873                                 "override generateContentDiffBody to fix this." );
 874                 }
 875
 876                 if ( !( $new instanceof TextContent ) ) {
 877                         throw new MWException( "Diff not implemented for " . get_class( $new ) . "; "
 878                                 . "override generateContentDiffBody to fix this." );
 879                 }
 880
 881                 $otext = $old->serialize();
 882                 $ntext = $new->serialize();
 883
 884                 return $this->generateTextDiffBody( $otext, $ntext );
 885         }
 886
 887         /**
 888          * Generate a diff, no caching
 889          *
 890          * @todo move this to TextDifferenceEngine, make DifferenceEngine abstract. At some point.
 891          *
 892          * @param string $otext Old text, must be already segmented
 893          * @param string $ntext New text, must be already segmented
 894          *
 895          * @return bool|string
 896          */
 897         public function generateTextDiffBody( $otext, $ntext ) {
 898                 $diff = function () use ( $otext, $ntext ) {
 899                         $time = microtime( true );
 900
 901                         $result = $this->textDiff( $otext, $ntext );
 902
 903                         $time = intval( ( microtime( true ) - $time ) * 1000 );
 904                         MediaWikiServices::getInstance()->getStatsdDataFactory()->timing( 'diff_time', $time );
 905                         // Log requests slower than 99th percentile
 906                         if ( $time > 100 && $this->mOldPage && $this->mNewPage ) {
 907                                 wfDebugLog( 'diff',
 908                                         "$time ms diff: {$this->mOldid} -> {$this->mNewid} {$this->mNewPage}" );
 909                         }
 910
 911                         return $result;
 912                 };
 913
 914                 /**
 915                  * @param Status $status
 916                  * @throws FatalError
 917                  */
 918                 $error = function ( $status ) {
 919                         throw new FatalError( $status->getWikiText() );
 920                 };
 921
 922                 // Use PoolCounter if the diff looks like it can be expensive
 923                 if ( strlen( $otext ) + strlen( $ntext ) > 20000 ) {
 924                         $work = new PoolCounterWorkViaCallback( 'diff',
 925                                 md5( $otext ) . md5( $ntext ),
 926                                 [ 'doWork' => $diff, 'error' => $error ]
 927                         );
 928                         return $work->execute();
 929                 }
 930
 931                 return $diff();
 932         }
 933
 934         /**
 935          * Process $wgExternalDiffEngine and get a sane, usable engine
 936          *
 937          * @return bool|string 'wikidiff2', path to an executable, or false
 938          */
 939         private function getEngine() {
 940                 global $wgExternalDiffEngine;
 941                 // We use the global here instead of Config because we write to the value,
 942                 // and Config is not mutable.
 943                 if ( $wgExternalDiffEngine == 'wikidiff' || $wgExternalDiffEngine == 'wikidiff3' ) {
 944                         wfDeprecated( "\$wgExternalDiffEngine = '{$wgExternalDiffEngine}'", '1.27' );
 945                         $wgExternalDiffEngine = false;
 946                 } elseif ( $wgExternalDiffEngine == 'wikidiff2' ) {
 947                         // Same as above, but with no deprecation warnings
 948                         $wgExternalDiffEngine = false;
 949                 } elseif ( !is_string( $wgExternalDiffEngine ) && $wgExternalDiffEngine !== false ) {
 950                         // And prevent people from shooting themselves in the foot...
 951                         wfWarn( '$wgExternalDiffEngine is set to a non-string value, forcing it to false' );
 952                         $wgExternalDiffEngine = false;
 953                 }
 954
 955                 if ( is_string( $wgExternalDiffEngine ) && is_executable( $wgExternalDiffEngine ) ) {
 956                         return $wgExternalDiffEngine;
 957                 } elseif ( $wgExternalDiffEngine === false && function_exists( 'wikidiff2_do_diff' ) ) {
 958                         return 'wikidiff2';
 959                 } else {
 960                         // Native PHP
 961                         return false;
 962                 }
 963         }
 964
 965         /**
 966          * Generates diff, to be wrapped internally in a logging/instrumentation
 967          *
 968          * @param string $otext Old text, must be already segmented
 969          * @param string $ntext New text, must be already segmented
 970          * @return bool|string
 971          */
 972         protected function textDiff( $otext, $ntext ) {
 973                 global $wgContLang;
 974
 975                 $otext = str_replace( "\r\n", "\n", $otext );
 976                 $ntext = str_replace( "\r\n", "\n", $ntext );
 977
 978                 $engine = $this->getEngine();
 979
 980                 // Better external diff engine, the 2 may some day be dropped
 981                 // This one does the escaping and segmenting itself
 982                 if ( $engine === 'wikidiff2' ) {
 983                         $wikidiff2Version = phpversion( 'wikidiff2' );
 984                         if (
 985                                 $wikidiff2Version !== false &&
 986                                 version_compare( $wikidiff2Version, '1.5.0', '>=' )
 987                         ) {
 988                                 $text = wikidiff2_do_diff(
 989                                         $otext,
 990                                         $ntext,
 991                                         2,
 992                                         $this->getConfig()->get( 'WikiDiff2MovedParagraphDetectionCutoff' )
 993                                 );
 994                         } else {
 995                                 // Don't pass the 4th parameter for compatibility with older versions of wikidiff2
 996                                 $text = wikidiff2_do_diff(
 997                                         $otext,
 998                                         $ntext,
 999                                         2
1000                                 );
1001
1002                                 // Log a warning in case the configuration value is set to not silently ignore it
1003                                 if ( $this->getConfig()->get( 'WikiDiff2MovedParagraphDetectionCutoff' ) > 0 ) {
1004                                         wfLogWarning( '$wgWikiDiff2MovedParagraphDetectionCutoff is set but has no
1005                                                 effect since the used version of WikiDiff2 does not support it.' );
1006                                 }
1007                         }
1008
1009                         $text .= $this->debug( 'wikidiff2' );
1010
1011                         return $text;
1012                 } elseif ( $engine !== false ) {
1013                         # Diff via the shell
1014                         $tmpDir = wfTempDir();
1015                         $tempName1 = tempnam( $tmpDir, 'diff_' );
1016                         $tempName2 = tempnam( $tmpDir, 'diff_' );
1017
1018                         $tempFile1 = fopen( $tempName1, "w" );
1019                         if ( !$tempFile1 ) {
1020                                 return false;
1021                         }
1022                         $tempFile2 = fopen( $tempName2, "w" );
1023                         if ( !$tempFile2 ) {
1024                                 return false;
1025                         }
1026                         fwrite( $tempFile1, $otext );
1027                         fwrite( $tempFile2, $ntext );
1028                         fclose( $tempFile1 );
1029                         fclose( $tempFile2 );
1030                         $cmd = [ $engine, $tempName1, $tempName2 ];
1031                         $result = Shell::command( $cmd )
1032                                 ->execute();
1033                         $exitCode = $result->getExitCode();
1034                         if ( $exitCode !== 0 ) {
1035                                 throw new Exception( "External diff command returned code {$exitCode}. Stderr: "
1036                                         . wfEscapeWikiText( $result->getStderr() )
1037                                 );
1038                         }
1039                         $difftext = $result->getStdout();
1040                         $difftext .= $this->debug( "external $engine" );
1041                         unlink( $tempName1 );
1042                         unlink( $tempName2 );
1043
1044                         return $difftext;
1045                 }
1046
1047                 # Native PHP diff
1048                 $ota = explode( "\n", $wgContLang->segmentForDiff( $otext ) );
1049                 $nta = explode( "\n", $wgContLang->segmentForDiff( $ntext ) );
1050                 $diffs = new Diff( $ota, $nta );
1051                 $formatter = new TableDiffFormatter();
1052                 $difftext = $wgContLang->unsegmentForDiff( $formatter->format( $diffs ) );
1053                 $difftext .= $this->debug( 'native PHP' );
1054
1055                 return $difftext;
1056         }
1057
1058         /**
1059          * Generate a debug comment indicating diff generating time,
1060          * server node, and generator backend.
1061          *
1062          * @param string $generator : What diff engine was used
1063          *
1064          * @return string
1065          */
1066         protected function debug( $generator = "internal" ) {
1067                 global $wgShowHostnames;
1068                 if ( !$this->enableDebugComment ) {
1069                         return '';
1070                 }
1071                 $data = [ $generator ];
1072                 if ( $wgShowHostnames ) {
1073                         $data[] = wfHostname();
1074                 }
1075                 $data[] = wfTimestamp( TS_DB );
1076
1077                 return "<!-- diff generator: " .
1078                         implode( " ", array_map( "htmlspecialchars", $data ) ) .
1079                         " -->\n";
1080         }
1081
1082         /**
1083          * Localise diff output
1084          *
1085          * @param string $text
1086          * @return string
1087          */
1088         private function localiseDiff( $text ) {
1089                 $text = $this->localiseLineNumbers( $text );
1090                 if ( $this->getEngine() === 'wikidiff2' &&
1091                         version_compare( phpversion( 'wikidiff2' ), '1.5.1', '>=' )
1092                 ) {
1093                         $text = $this->addLocalisedTitleTooltips( $text );
1094                 }
1095                 return $text;
1096         }
1097
1098         /**
1099          * Replace line numbers with the text in the user's language
1100          *
1101          * @param string $text
1102          *
1103          * @return mixed
1104          */
1105         public function localiseLineNumbers( $text ) {
1106                 return preg_replace_callback(
1107                         '/<!--LINE (\d+)-->/',
1108                         [ $this, 'localiseLineNumbersCb' ],
1109                         $text
1110                 );
1111         }
1112
1113         public function localiseLineNumbersCb( $matches ) {
1114                 if ( $matches[1] === '1' && $this->mReducedLineNumbers ) {
1115                         return '';
1116                 }
1117
1118                 return $this->msg( 'lineno' )->numParams( $matches[1] )->escaped();
1119         }
1120
1121         /**
1122          * Add title attributes for tooltips on moved paragraph indicators
1123          *
1124          * @param string $text
1125          * @return string
1126          */
1127         private function addLocalisedTitleTooltips( $text ) {
1128                 return preg_replace_callback(
1129                         '/class="mw-diff-movedpara-(left|right)"/',
1130                         [ $this, 'addLocalisedTitleTooltipsCb' ],
1131                         $text
1132                 );
1133         }
1134
1135         /**
1136          * @param array $matches
1137          * @return string
1138          */
1139         private function addLocalisedTitleTooltipsCb( array $matches ) {
1140                 $key = $matches[1] === 'right' ?
1141                         'diff-paragraph-moved-toold' :
1142                         'diff-paragraph-moved-tonew';
1143                 return $matches[0] . ' title="' . $this->msg( $key )->escaped() . '"';
1144         }
1145
1146         /**
1147          * If there are revisions between the ones being compared, return a note saying so.
1148          *
1149          * @return string
1150          */
1151         public function getMultiNotice() {
1152                 if ( !is_object( $this->mOldRev ) || !is_object( $this->mNewRev ) ) {
1153                         return '';
1154                 } elseif ( !$this->mOldPage->equals( $this->mNewPage ) ) {
1155                         // Comparing two different pages? Count would be meaningless.
1156                         return '';
1157                 }
1158
1159                 if ( $this->mOldRev->getTimestamp() > $this->mNewRev->getTimestamp() ) {
1160                         $oldRev = $this->mNewRev; // flip
1161                         $newRev = $this->mOldRev; // flip
1162                 } else { // normal case
1163                         $oldRev = $this->mOldRev;
1164                         $newRev = $this->mNewRev;
1165                 }
1166
1167                 // Sanity: don't show the notice if too many rows must be scanned
1168                 // @todo show some special message for that case
1169                 $nEdits = $this->mNewPage->countRevisionsBetween( $oldRev, $newRev, 1000 );
1170                 if ( $nEdits > 0 && $nEdits <= 1000 ) {
1171                         $limit = 100; // use diff-multi-manyusers if too many users
1172                         $users = $this->mNewPage->getAuthorsBetween( $oldRev, $newRev, $limit );
1173                         $numUsers = count( $users );
1174
1175                         if ( $numUsers == 1 && $users[0] == $newRev->getUserText( Revision::RAW ) ) {
1176                                 $numUsers = 0; // special case to say "by the same user" instead of "by one other user"
1177                         }
1178
1179                         return self::intermediateEditsMsg( $nEdits, $numUsers, $limit );
1180                 }
1181
1182                 return ''; // nothing
1183         }
1184
1185         /**
1186          * Get a notice about how many intermediate edits and users there are
1187          *
1188          * @param int $numEdits
1189          * @param int $numUsers
1190          * @param int $limit
1191          *
1192          * @return string
1193          */
1194         public static function intermediateEditsMsg( $numEdits, $numUsers, $limit ) {
1195                 if ( $numUsers === 0 ) {
1196                         $msg = 'diff-multi-sameuser';
1197                 } elseif ( $numUsers > $limit ) {
1198                         $msg = 'diff-multi-manyusers';
1199                         $numUsers = $limit;
1200                 } else {
1201                         $msg = 'diff-multi-otherusers';
1202                 }
1203
1204                 return wfMessage( $msg )->numParams( $numEdits, $numUsers )->parse();
1205         }
1206
1207         /**
1208          * Get a header for a specified revision.
1209          *
1210          * @param Revision $rev
1211          * @param string $complete 'complete' to get the header wrapped depending
1212          *        the visibility of the revision and a link to edit the page.
1213          *
1214          * @return string HTML fragment
1215          */
1216         public function getRevisionHeader( Revision $rev, $complete = '' ) {
1217                 $lang = $this->getLanguage();
1218                 $user = $this->getUser();
1219                 $revtimestamp = $rev->getTimestamp();
1220                 $timestamp = $lang->userTimeAndDate( $revtimestamp, $user );
1221                 $dateofrev = $lang->userDate( $revtimestamp, $user );
1222                 $timeofrev = $lang->userTime( $revtimestamp, $user );
1223
1224                 $header = $this->msg(
1225                         $rev->isCurrent() ? 'currentrev-asof' : 'revisionasof',
1226                         $timestamp,
1227                         $dateofrev,
1228                         $timeofrev
1229                 )->escaped();
1230
1231                 if ( $complete !== 'complete' ) {
1232                         return $header;
1233                 }
1234
1235                 $title = $rev->getTitle();
1236
1237                 $header = Linker::linkKnown( $title, $header, [],
1238                         [ 'oldid' => $rev->getId() ] );
1239
1240                 if ( $rev->userCan( Revision::DELETED_TEXT, $user ) ) {
1241                         $editQuery = [ 'action' => 'edit' ];
1242                         if ( !$rev->isCurrent() ) {
1243                                 $editQuery['oldid'] = $rev->getId();
1244                         }
1245
1246                         $key = $title->quickUserCan( 'edit', $user ) ? 'editold' : 'viewsourceold';
1247                         $msg = $this->msg( $key )->escaped();
1248                         $editLink = $this->msg( 'parentheses' )->rawParams(
1249                                 Linker::linkKnown( $title, $msg, [], $editQuery ) )->escaped();
1250                         $header .= ' ' . Html::rawElement(
1251                                 'span',
1252                                 [ 'class' => 'mw-diff-edit' ],
1253                                 $editLink
1254                         );
1255                         if ( $rev->isDeleted( Revision::DELETED_TEXT ) ) {
1256                                 $header = Html::rawElement(
1257                                         'span',
1258                                         [ 'class' => 'history-deleted' ],
1259                                         $header
1260                                 );
1261                         }
1262                 } else {
1263                         $header = Html::rawElement( 'span', [ 'class' => 'history-deleted' ], $header );
1264                 }
1265
1266                 return $header;
1267         }
1268
1269         /**
1270          * Add the header to a diff body
1271          *
1272          * @param string $diff Diff body
1273          * @param string $otitle Old revision header
1274          * @param string $ntitle New revision header
1275          * @param string $multi Notice telling user that there are intermediate
1276          *   revisions between the ones being compared
1277          * @param string $notice Other notices, e.g. that user is viewing deleted content
1278          *
1279          * @return string
1280          */
1281         public function addHeader( $diff, $otitle, $ntitle, $multi = '', $notice = '' ) {
1282                 // shared.css sets diff in interface language/dir, but the actual content
1283                 // is often in a different language, mostly the page content language/dir
1284                 $header = Html::openElement( 'table', [
1285                         'class' => [ 'diff', 'diff-contentalign-' . $this->getDiffLang()->alignStart() ],
1286                         'data-mw' => 'interface',
1287                 ] );
1288                 $userLang = htmlspecialchars( $this->getLanguage()->getHtmlCode() );
1289
1290                 if ( !$diff && !$otitle ) {
1291                         $header .= "
1292                         <tr class=\"diff-title\" lang=\"{$userLang}\">
1293                         <td class=\"diff-ntitle\">{$ntitle}</td>
1294                         </tr>";
1295                         $multiColspan = 1;
1296                 } else {
1297                         if ( $diff ) { // Safari/Chrome show broken output if cols not used
1298                                 $header .= "
1299                                 <col class=\"diff-marker\" />
1300                                 <col class=\"diff-content\" />
1301                                 <col class=\"diff-marker\" />
1302                                 <col class=\"diff-content\" />";
1303                                 $colspan = 2;
1304                                 $multiColspan = 4;
1305                         } else {
1306                                 $colspan = 1;
1307                                 $multiColspan = 2;
1308                         }
1309                         if ( $otitle || $ntitle ) {
1310                                 $header .= "
1311                                 <tr class=\"diff-title\" lang=\"{$userLang}\">
1312                                 <td colspan=\"$colspan\" class=\"diff-otitle\">{$otitle}</td>
1313                                 <td colspan=\"$colspan\" class=\"diff-ntitle\">{$ntitle}</td>
1314                                 </tr>";
1315                         }
1316                 }
1317
1318                 if ( $multi != '' ) {
1319                         $header .= "<tr><td colspan=\"{$multiColspan}\" " .
1320                                 "class=\"diff-multi\" lang=\"{$userLang}\">{$multi}</td></tr>";
1321                 }
1322                 if ( $notice != '' ) {
1323                         $header .= "<tr><td colspan=\"{$multiColspan}\" " .
1324                                 "class=\"diff-notice\" lang=\"{$userLang}\">{$notice}</td></tr>";
1325                 }
1326
1327                 return $header . $diff . "</table>";
1328         }
1329
1330         /**
1331          * Use specified text instead of loading from the database
1332          * @param Content $oldContent
1333          * @param Content $newContent
1334          * @since 1.21
1335          */
1336         public function setContent( Content $oldContent, Content $newContent ) {
1337                 $this->mOldContent = $oldContent;
1338                 $this->mNewContent = $newContent;
1339
1340                 $this->mTextLoaded = 2;
1341                 $this->mRevisionsLoaded = true;
1342         }
1343
1344         /**
1345          * Set the language in which the diff text is written
1346          * (Defaults to page content language).
1347          * @param Language|string $lang
1348          * @since 1.19
1349          */
1350         public function setTextLanguage( $lang ) {
1351                 $this->mDiffLang = wfGetLangObj( $lang );
1352         }
1353
1354         /**
1355          * Maps a revision pair definition as accepted by DifferenceEngine constructor
1356          * to a pair of actual integers representing revision ids.
1357          *
1358          * @param int $old Revision id, e.g. from URL parameter 'oldid'
1359          * @param int|string $new Revision id or strings 'next' or 'prev', e.g. from URL parameter 'diff'
1360          *
1361          * @return int[] List of two revision ids, older first, later second.
1362          *     Zero signifies invalid argument passed.
1363          *     false signifies that there is no previous/next revision ($old is the oldest/newest one).
1364          */
1365         public function mapDiffPrevNext( $old, $new ) {
1366                 if ( $new === 'prev' ) {
1367                         // Show diff between revision $old and the previous one. Get previous one from DB.
1368                         $newid = intval( $old );
1369                         $oldid = $this->getTitle()->getPreviousRevisionID( $newid );
1370                 } elseif ( $new === 'next' ) {
1371                         // Show diff between revision $old and the next one. Get next one from DB.
1372                         $oldid = intval( $old );
1373                         $newid = $this->getTitle()->getNextRevisionID( $oldid );
1374                 } else {
1375                         $oldid = intval( $old );
1376                         $newid = intval( $new );
1377                 }
1378
1379                 return [ $oldid, $newid ];
1380         }
1381
1382         /**
1383          * Load revision IDs
1384          */
1385         private function loadRevisionIds() {
1386                 if ( $this->mRevisionsIdsLoaded ) {
1387                         return;
1388                 }
1389
1390                 $this->mRevisionsIdsLoaded = true;
1391
1392                 $old = $this->mOldid;
1393                 $new = $this->mNewid;
1394
1395                 list( $this->mOldid, $this->mNewid ) = self::mapDiffPrevNext( $old, $new );
1396                 if ( $new === 'next' && $this->mNewid === false ) {
1397                         # if no result, NewId points to the newest old revision. The only newer
1398                         # revision is cur, which is "0".
1399                         $this->mNewid = 0;
1400                 }
1401
1402                 Hooks::run(
1403                         'NewDifferenceEngine',
1404                         [ $this->getTitle(), &$this->mOldid, &$this->mNewid, $old, $new ]
1405                 );
1406         }
1407
1408         /**
1409          * Load revision metadata for the specified articles. If newid is 0, then compare
1410          * the old article in oldid to the current article; if oldid is 0, then
1411          * compare the current article to the immediately previous one (ignoring the
1412          * value of newid).
1413          *
1414          * If oldid is false, leave the corresponding revision object set
1415          * to false. This is impossible via ordinary user input, and is provided for
1416          * API convenience.
1417          *
1418          * @return bool
1419          */
1420         public function loadRevisionData() {
1421                 if ( $this->mRevisionsLoaded ) {
1422                         return true;
1423                 }
1424
1425                 // Whether it succeeds or fails, we don't want to try again
1426                 $this->mRevisionsLoaded = true;
1427
1428                 $this->loadRevisionIds();
1429
1430                 // Load the new revision object
1431                 if ( $this->mNewid ) {
1432                         $this->mNewRev = Revision::newFromId( $this->mNewid );
1433                 } else {
1434                         $this->mNewRev = Revision::newFromTitle(
1435                                 $this->getTitle(),
1436                                 false,
1437                                 Revision::READ_NORMAL
1438                         );
1439                 }
1440
1441                 if ( !$this->mNewRev instanceof Revision ) {
1442                         return false;
1443                 }
1444
1445                 // Update the new revision ID in case it was 0 (makes life easier doing UI stuff)
1446                 $this->mNewid = $this->mNewRev->getId();
1447                 $this->mNewPage = $this->mNewRev->getTitle();
1448
1449                 // Load the old revision object
1450                 $this->mOldRev = false;
1451                 if ( $this->mOldid ) {
1452                         $this->mOldRev = Revision::newFromId( $this->mOldid );
1453                 } elseif ( $this->mOldid === 0 ) {
1454                         $rev = $this->mNewRev->getPrevious();
1455                         if ( $rev ) {
1456                                 $this->mOldid = $rev->getId();
1457                                 $this->mOldRev = $rev;
1458                         } else {
1459                                 // No previous revision; mark to show as first-version only.
1460                                 $this->mOldid = false;
1461                                 $this->mOldRev = false;
1462                         }
1463                 } /* elseif ( $this->mOldid === false ) leave mOldRev false; */
1464
1465                 if ( is_null( $this->mOldRev ) ) {
1466                         return false;
1467                 }
1468
1469                 if ( $this->mOldRev ) {
1470                         $this->mOldPage = $this->mOldRev->getTitle();
1471                 }
1472
1473                 // Load tags information for both revisions
1474                 $dbr = wfGetDB( DB_REPLICA );
1475                 if ( $this->mOldid !== false ) {
1476                         $this->mOldTags = $dbr->selectField(
1477                                 'tag_summary',
1478                                 'ts_tags',
1479                                 [ 'ts_rev_id' => $this->mOldid ],
1480                                 __METHOD__
1481                         );
1482                 } else {
1483                         $this->mOldTags = false;
1484                 }
1485                 $this->mNewTags = $dbr->selectField(
1486                         'tag_summary',
1487                         'ts_tags',
1488                         [ 'ts_rev_id' => $this->mNewid ],
1489                         __METHOD__
1490                 );
1491
1492                 return true;
1493         }
1494
1495         /**
1496          * Load the text of the revisions, as well as revision data.
1497          *
1498          * @return bool
1499          */
1500         public function loadText() {
1501                 if ( $this->mTextLoaded == 2 ) {
1502                         return true;
1503                 }
1504
1505                 // Whether it succeeds or fails, we don't want to try again
1506                 $this->mTextLoaded = 2;
1507
1508                 if ( !$this->loadRevisionData() ) {
1509                         return false;
1510                 }
1511
1512                 if ( $this->mOldRev ) {
1513                         $this->mOldContent = $this->mOldRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1514                         if ( $this->mOldContent === null ) {
1515                                 return false;
1516                         }
1517                 }
1518
1519                 if ( $this->mNewRev ) {
1520                         $this->mNewContent = $this->mNewRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1521                         Hooks::run( 'DifferenceEngineLoadTextAfterNewContentIsLoaded', [ $this ] );
1522                         if ( $this->mNewContent === null ) {
1523                                 return false;
1524                         }
1525                 }
1526
1527                 return true;
1528         }
1529
1530         /**
1531          * Load the text of the new revision, not the old one
1532          *
1533          * @return bool
1534          */
1535         public function loadNewText() {
1536                 if ( $this->mTextLoaded >= 1 ) {
1537                         return true;
1538                 }
1539
1540                 $this->mTextLoaded = 1;
1541
1542                 if ( !$this->loadRevisionData() ) {
1543                         return false;
1544                 }
1545
1546                 $this->mNewContent = $this->mNewRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1547
1548                 Hooks::run( 'DifferenceEngineAfterLoadNewText', [ $this ] );
1549
1550                 return true;
1551         }
1552
1553 }