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|null $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          * Get the language of the difference engine, defaults to page content language
 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                         $arQuery = Revision::getArchiveQueryInfo();
 185                         $row = $dbr->selectRow(
 186                                 $arQuery['tables'],
 187                                 array_merge( $arQuery['fields'], [ 'ar_namespace', 'ar_title' ] ),
 188                                 [ 'ar_rev_id' => $id ],
 189                                 __METHOD__,
 190                                 [],
 191                                 $arQuery['joins']
 192                         );
 193                         if ( $row ) {
 194                                 $rev = Revision::newFromArchiveRow( $row );
 195                                 $title = Title::makeTitleSafe( $row->ar_namespace, $row->ar_title );
 196
 197                                 return SpecialPage::getTitleFor( 'Undelete' )->getFullURL( [
 198                                         'target' => $title->getPrefixedText(),
 199                                         'timestamp' => $rev->getTimestamp()
 200                                 ] );
 201                         }
 202                 }
 203
 204                 return false;
 205         }
 206
 207         /**
 208          * Build a wikitext link toward a deleted revision, if viewable.
 209          *
 210          * @param int $id Revision ID
 211          *
 212          * @return string Wikitext fragment
 213          */
 214         public function deletedIdMarker( $id ) {
 215                 $link = $this->deletedLink( $id );
 216                 if ( $link ) {
 217                         return "[$link $id]";
 218                 } else {
 219                         return (string)$id;
 220                 }
 221         }
 222
 223         private function showMissingRevision() {
 224                 $out = $this->getOutput();
 225
 226                 $missing = [];
 227                 if ( $this->mOldRev === null ||
 228                         ( $this->mOldRev && $this->mOldContent === null )
 229                 ) {
 230                         $missing[] = $this->deletedIdMarker( $this->mOldid );
 231                 }
 232                 if ( $this->mNewRev === null ||
 233                         ( $this->mNewRev && $this->mNewContent === null )
 234                 ) {
 235                         $missing[] = $this->deletedIdMarker( $this->mNewid );
 236                 }
 237
 238                 $out->setPageTitle( $this->msg( 'errorpagetitle' ) );
 239                 $msg = $this->msg( 'difference-missing-revision' )
 240                         ->params( $this->getLanguage()->listToText( $missing ) )
 241                         ->numParams( count( $missing ) )
 242                         ->parseAsBlock();
 243                 $out->addHTML( $msg );
 244         }
 245
 246         public function showDiffPage( $diffOnly = false ) {
 247                 # Allow frames except in certain special cases
 248                 $out = $this->getOutput();
 249                 $out->allowClickjacking();
 250                 $out->setRobotPolicy( 'noindex,nofollow' );
 251
 252                 // Allow extensions to add any extra output here
 253                 Hooks::run( 'DifferenceEngineShowDiffPage', [ $out ] );
 254
 255                 if ( !$this->loadRevisionData() ) {
 256                         if ( Hooks::run( 'DifferenceEngineShowDiffPageMaybeShowMissingRevision', [ $this ] ) ) {
 257                                 $this->showMissingRevision();
 258                         }
 259                         return;
 260                 }
 261
 262                 $user = $this->getUser();
 263                 $permErrors = $this->mNewPage->getUserPermissionsErrors( 'read', $user );
 264                 if ( $this->mOldPage ) { # mOldPage might not be set, see below.
 265                         $permErrors = wfMergeErrorArrays( $permErrors,
 266                                 $this->mOldPage->getUserPermissionsErrors( 'read', $user ) );
 267                 }
 268                 if ( count( $permErrors ) ) {
 269                         throw new PermissionsError( 'read', $permErrors );
 270                 }
 271
 272                 $rollback = '';
 273
 274                 $query = [];
 275                 # Carry over 'diffonly' param via navigation links
 276                 if ( $diffOnly != $user->getBoolOption( 'diffonly' ) ) {
 277                         $query['diffonly'] = $diffOnly;
 278                 }
 279                 # Cascade unhide param in links for easy deletion browsing
 280                 if ( $this->unhide ) {
 281                         $query['unhide'] = 1;
 282                 }
 283
 284                 # Check if one of the revisions is deleted/suppressed
 285                 $deleted = $suppressed = false;
 286                 $allowed = $this->mNewRev->userCan( Revision::DELETED_TEXT, $user );
 287
 288                 $revisionTools = [];
 289
 290                 # mOldRev is false if the difference engine is called with a "vague" query for
 291                 # a diff between a version V and its previous version V' AND the version V
 292                 # is the first version of that article. In that case, V' does not exist.
 293                 if ( $this->mOldRev === false ) {
 294                         $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 295                         $samePage = true;
 296                         $oldHeader = '';
 297                         // Allow extensions to change the $oldHeader variable
 298                         Hooks::run( 'DifferenceEngineOldHeaderNoOldRev', [ &$oldHeader ] );
 299                 } else {
 300                         Hooks::run( 'DiffViewHeader', [ $this, $this->mOldRev, $this->mNewRev ] );
 301
 302                         if ( $this->mNewPage->equals( $this->mOldPage ) ) {
 303                                 $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 304                                 $samePage = true;
 305                         } else {
 306                                 $out->setPageTitle( $this->msg( 'difference-title-multipage',
 307                                         $this->mOldPage->getPrefixedText(), $this->mNewPage->getPrefixedText() ) );
 308                                 $out->addSubtitle( $this->msg( 'difference-multipage' ) );
 309                                 $samePage = false;
 310                         }
 311
 312                         if ( $samePage && $this->mNewPage->quickUserCan( 'edit', $user ) ) {
 313                                 if ( $this->mNewRev->isCurrent() && $this->mNewPage->userCan( 'rollback', $user ) ) {
 314                                         $rollbackLink = Linker::generateRollback( $this->mNewRev, $this->getContext() );
 315                                         if ( $rollbackLink ) {
 316                                                 $out->preventClickjacking();
 317                                                 $rollback = "\u{00A0}\u{00A0}\u{00A0}" . $rollbackLink;
 318                                         }
 319                                 }
 320
 321                                 if ( !$this->mOldRev->isDeleted( Revision::DELETED_TEXT ) &&
 322                                         !$this->mNewRev->isDeleted( Revision::DELETED_TEXT )
 323                                 ) {
 324                                         $undoLink = Html::element( 'a', [
 325                                                         'href' => $this->mNewPage->getLocalURL( [
 326                                                                 'action' => 'edit',
 327                                                                 'undoafter' => $this->mOldid,
 328                                                                 'undo' => $this->mNewid
 329                                                         ] ),
 330                                                         'title' => Linker::titleAttrib( 'undo' ),
 331                                                 ],
 332                                                 $this->msg( 'editundo' )->text()
 333                                         );
 334                                         $revisionTools['mw-diff-undo'] = $undoLink;
 335                                 }
 336                         }
 337
 338                         # Make "previous revision link"
 339                         if ( $samePage && $this->mOldRev->getPrevious() ) {
 340                                 $prevlink = Linker::linkKnown(
 341                                         $this->mOldPage,
 342                                         $this->msg( 'previousdiff' )->escaped(),
 343                                         [ 'id' => 'differences-prevlink' ],
 344                                         [ 'diff' => 'prev', 'oldid' => $this->mOldid ] + $query
 345                                 );
 346                         } else {
 347                                 $prevlink = "\u{00A0}";
 348                         }
 349
 350                         if ( $this->mOldRev->isMinor() ) {
 351                                 $oldminor = ChangesList::flag( 'minor' );
 352                         } else {
 353                                 $oldminor = '';
 354                         }
 355
 356                         $ldel = $this->revisionDeleteLink( $this->mOldRev );
 357                         $oldRevisionHeader = $this->getRevisionHeader( $this->mOldRev, 'complete' );
 358                         $oldChangeTags = ChangeTags::formatSummaryRow( $this->mOldTags, 'diff', $this->getContext() );
 359
 360                         $oldHeader = '<div id="mw-diff-otitle1"><strong>' . $oldRevisionHeader . '</strong></div>' .
 361                                 '<div id="mw-diff-otitle2">' .
 362                                 Linker::revUserTools( $this->mOldRev, !$this->unhide ) . '</div>' .
 363                                 '<div id="mw-diff-otitle3">' . $oldminor .
 364                                 Linker::revComment( $this->mOldRev, !$diffOnly, !$this->unhide ) . $ldel . '</div>' .
 365                                 '<div id="mw-diff-otitle5">' . $oldChangeTags[0] . '</div>' .
 366                                 '<div id="mw-diff-otitle4">' . $prevlink . '</div>';
 367
 368                         // Allow extensions to change the $oldHeader variable
 369                         Hooks::run( 'DifferenceEngineOldHeader', [ $this, &$oldHeader, $prevlink, $oldminor,
 370                                 $diffOnly, $ldel, $this->unhide ] );
 371
 372                         if ( $this->mOldRev->isDeleted( Revision::DELETED_TEXT ) ) {
 373                                 $deleted = true; // old revisions text is hidden
 374                                 if ( $this->mOldRev->isDeleted( Revision::DELETED_RESTRICTED ) ) {
 375                                         $suppressed = true; // also suppressed
 376                                 }
 377                         }
 378
 379                         # Check if this user can see the revisions
 380                         if ( !$this->mOldRev->userCan( Revision::DELETED_TEXT, $user ) ) {
 381                                 $allowed = false;
 382                         }
 383                 }
 384
 385                 $out->addJsConfigVars( [
 386                         'wgDiffOldId' => $this->mOldid,
 387                         'wgDiffNewId' => $this->mNewid,
 388                 ] );
 389
 390                 # Make "next revision link"
 391                 # Skip next link on the top revision
 392                 if ( $samePage && !$this->mNewRev->isCurrent() ) {
 393                         $nextlink = Linker::linkKnown(
 394                                 $this->mNewPage,
 395                                 $this->msg( 'nextdiff' )->escaped(),
 396                                 [ 'id' => 'differences-nextlink' ],
 397                                 [ 'diff' => 'next', 'oldid' => $this->mNewid ] + $query
 398                         );
 399                 } else {
 400                         $nextlink = "\u{00A0}";
 401                 }
 402
 403                 if ( $this->mNewRev->isMinor() ) {
 404                         $newminor = ChangesList::flag( 'minor' );
 405                 } else {
 406                         $newminor = '';
 407                 }
 408
 409                 # Handle RevisionDelete links...
 410                 $rdel = $this->revisionDeleteLink( $this->mNewRev );
 411
 412                 # Allow extensions to define their own revision tools
 413                 Hooks::run( 'DiffRevisionTools',
 414                         [ $this->mNewRev, &$revisionTools, $this->mOldRev, $user ] );
 415                 $formattedRevisionTools = [];
 416                 // Put each one in parentheses (poor man's button)
 417                 foreach ( $revisionTools as $key => $tool ) {
 418                         $toolClass = is_string( $key ) ? $key : 'mw-diff-tool';
 419                         $element = Html::rawElement(
 420                                 'span',
 421                                 [ 'class' => $toolClass ],
 422                                 $this->msg( 'parentheses' )->rawParams( $tool )->escaped()
 423                         );
 424                         $formattedRevisionTools[] = $element;
 425                 }
 426                 $newRevisionHeader = $this->getRevisionHeader( $this->mNewRev, 'complete' ) .
 427                         ' ' . implode( ' ', $formattedRevisionTools );
 428                 $newChangeTags = ChangeTags::formatSummaryRow( $this->mNewTags, 'diff', $this->getContext() );
 429
 430                 $newHeader = '<div id="mw-diff-ntitle1"><strong>' . $newRevisionHeader . '</strong></div>' .
 431                         '<div id="mw-diff-ntitle2">' . Linker::revUserTools( $this->mNewRev, !$this->unhide ) .
 432                         " $rollback</div>" .
 433                         '<div id="mw-diff-ntitle3">' . $newminor .
 434                         Linker::revComment( $this->mNewRev, !$diffOnly, !$this->unhide ) . $rdel . '</div>' .
 435                         '<div id="mw-diff-ntitle5">' . $newChangeTags[0] . '</div>' .
 436                         '<div id="mw-diff-ntitle4">' . $nextlink . $this->markPatrolledLink() . '</div>';
 437
 438                 // Allow extensions to change the $newHeader variable
 439                 Hooks::run( 'DifferenceEngineNewHeader', [ $this, &$newHeader, $formattedRevisionTools,
 440                         $nextlink, $rollback, $newminor, $diffOnly, $rdel, $this->unhide ] );
 441
 442                 if ( $this->mNewRev->isDeleted( Revision::DELETED_TEXT ) ) {
 443                         $deleted = true; // new revisions text is hidden
 444                         if ( $this->mNewRev->isDeleted( Revision::DELETED_RESTRICTED ) ) {
 445                                 $suppressed = true; // also suppressed
 446                         }
 447                 }
 448
 449                 # If the diff cannot be shown due to a deleted revision, then output
 450                 # the diff header and links to unhide (if available)...
 451                 if ( $deleted && ( !$this->unhide || !$allowed ) ) {
 452                         $this->showDiffStyle();
 453                         $multi = $this->getMultiNotice();
 454                         $out->addHTML( $this->addHeader( '', $oldHeader, $newHeader, $multi ) );
 455                         if ( !$allowed ) {
 456                                 $msg = $suppressed ? 'rev-suppressed-no-diff' : 'rev-deleted-no-diff';
 457                                 # Give explanation for why revision is not visible
 458                                 $out->wrapWikiMsg( "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 459                                         [ $msg ] );
 460                         } else {
 461                                 # Give explanation and add a link to view the diff...
 462                                 $query = $this->getRequest()->appendQueryValue( 'unhide', '1' );
 463                                 $link = $this->getTitle()->getFullURL( $query );
 464                                 $msg = $suppressed ? 'rev-suppressed-unhide-diff' : 'rev-deleted-unhide-diff';
 465                                 $out->wrapWikiMsg(
 466                                         "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 467                                         [ $msg, $link ]
 468                                 );
 469                         }
 470                 # Otherwise, output a regular diff...
 471                 } else {
 472                         # Add deletion notice if the user is viewing deleted content
 473                         $notice = '';
 474                         if ( $deleted ) {
 475                                 $msg = $suppressed ? 'rev-suppressed-diff-view' : 'rev-deleted-diff-view';
 476                                 $notice = "<div id='mw-$msg' class='mw-warning plainlinks'>\n" .
 477                                         $this->msg( $msg )->parse() .
 478                                         "</div>\n";
 479                         }
 480                         $this->showDiff( $oldHeader, $newHeader, $notice );
 481                         if ( !$diffOnly ) {
 482                                 $this->renderNewRevision();
 483                         }
 484                 }
 485         }
 486
 487         /**
 488          * Build a link to mark a change as patrolled.
 489          *
 490          * Returns empty string if there's either no revision to patrol or the user is not allowed to.
 491          * Side effect: When the patrol link is build, this method will call
 492          * OutputPage::preventClickjacking() and load mediawiki.page.patrol.ajax.
 493          *
 494          * @return string HTML or empty string
 495          */
 496         public function markPatrolledLink() {
 497                 if ( $this->mMarkPatrolledLink === null ) {
 498                         $linkInfo = $this->getMarkPatrolledLinkInfo();
 499                         // If false, there is no patrol link needed/allowed
 500                         if ( !$linkInfo ) {
 501                                 $this->mMarkPatrolledLink = '';
 502                         } else {
 503                                 $this->mMarkPatrolledLink = ' <span class="patrollink" data-mw="interface">[' .
 504                                         Linker::linkKnown(
 505                                                 $this->mNewPage,
 506                                                 $this->msg( 'markaspatrolleddiff' )->escaped(),
 507                                                 [],
 508                                                 [
 509                                                         'action' => 'markpatrolled',
 510                                                         'rcid' => $linkInfo['rcid'],
 511                                                 ]
 512                                         ) . ']</span>';
 513                                 // Allow extensions to change the markpatrolled link
 514                                 Hooks::run( 'DifferenceEngineMarkPatrolledLink', [ $this,
 515                                         &$this->mMarkPatrolledLink, $linkInfo['rcid'] ] );
 516                         }
 517                 }
 518                 return $this->mMarkPatrolledLink;
 519         }
 520
 521         /**
 522          * Returns an array of meta data needed to build a "mark as patrolled" link and
 523          * adds the mediawiki.page.patrol.ajax to the output.
 524          *
 525          * @return array|false An array of meta data for a patrol link (rcid only)
 526          *  or false if no link is needed
 527          */
 528         protected function getMarkPatrolledLinkInfo() {
 529                 global $wgUseRCPatrol;
 530
 531                 $user = $this->getUser();
 532
 533                 // Prepare a change patrol link, if applicable
 534                 if (
 535                         // Is patrolling enabled and the user allowed to?
 536                         $wgUseRCPatrol && $this->mNewPage->quickUserCan( 'patrol', $user ) &&
 537                         // Only do this if the revision isn't more than 6 hours older
 538                         // than the Max RC age (6h because the RC might not be cleaned out regularly)
 539                         RecentChange::isInRCLifespan( $this->mNewRev->getTimestamp(), 21600 )
 540                 ) {
 541                         // Look for an unpatrolled change corresponding to this diff
 542                         $db = wfGetDB( DB_REPLICA );
 543                         $change = RecentChange::newFromConds(
 544                                 [
 545                                         'rc_timestamp' => $db->timestamp( $this->mNewRev->getTimestamp() ),
 546                                         'rc_this_oldid' => $this->mNewid,
 547                                         'rc_patrolled' => RecentChange::PRC_UNPATROLLED
 548                                 ],
 549                                 __METHOD__
 550                         );
 551
 552                         if ( $change && !$change->getPerformer()->equals( $user ) ) {
 553                                 $rcid = $change->getAttribute( 'rc_id' );
 554                         } else {
 555                                 // None found or the page has been created by the current user.
 556                                 // If the user could patrol this it already would be patrolled
 557                                 $rcid = 0;
 558                         }
 559
 560                         // Allow extensions to possibly change the rcid here
 561                         // For example the rcid might be set to zero due to the user
 562                         // being the same as the performer of the change but an extension
 563                         // might still want to show it under certain conditions
 564                         Hooks::run( 'DifferenceEngineMarkPatrolledRCID', [ &$rcid, $this, $change, $user ] );
 565
 566                         // Build the link
 567                         if ( $rcid ) {
 568                                 $this->getOutput()->preventClickjacking();
 569                                 if ( $user->isAllowed( 'writeapi' ) ) {
 570                                         $this->getOutput()->addModules( 'mediawiki.page.patrol.ajax' );
 571                                 }
 572
 573                                 return [
 574                                         'rcid' => $rcid,
 575                                 ];
 576                         }
 577                 }
 578
 579                 // No mark as patrolled link applicable
 580                 return false;
 581         }
 582
 583         /**
 584          * @param Revision $rev
 585          *
 586          * @return string
 587          */
 588         protected function revisionDeleteLink( $rev ) {
 589                 $link = Linker::getRevDeleteLink( $this->getUser(), $rev, $rev->getTitle() );
 590                 if ( $link !== '' ) {
 591                         $link = "\u{00A0}\u{00A0}\u{00A0}" . $link . ' ';
 592                 }
 593
 594                 return $link;
 595         }
 596
 597         /**
 598          * Show the new revision of the page.
 599          */
 600         public function renderNewRevision() {
 601                 $out = $this->getOutput();
 602                 $revHeader = $this->getRevisionHeader( $this->mNewRev );
 603                 # Add "current version as of X" title
 604                 $out->addHTML( "<hr class='diff-hr' id='mw-oldid' />
 605                 <h2 class='diff-currentversion-title'>{$revHeader}</h2>\n" );
 606                 # Page content may be handled by a hooked call instead...
 607                 if ( Hooks::run( 'ArticleContentOnDiff', [ $this, $out ] ) ) {
 608                         $this->loadNewText();
 609                         $out->setRevisionId( $this->mNewid );
 610                         $out->setRevisionTimestamp( $this->mNewRev->getTimestamp() );
 611                         $out->setArticleFlag( true );
 612
 613                         if ( !Hooks::run( 'ArticleContentViewCustom',
 614                                 [ $this->mNewContent, $this->mNewPage, $out ] )
 615                         ) {
 616                                 // Handled by extension
 617                         } else {
 618                                 // Normal page
 619                                 if ( $this->getTitle()->equals( $this->mNewPage ) ) {
 620                                         // If the Title stored in the context is the same as the one
 621                                         // of the new revision, we can use its associated WikiPage
 622                                         // object.
 623                                         $wikiPage = $this->getWikiPage();
 624                                 } else {
 625                                         // Otherwise we need to create our own WikiPage object
 626                                         $wikiPage = WikiPage::factory( $this->mNewPage );
 627                                 }
 628
 629                                 $parserOutput = $this->getParserOutput( $wikiPage, $this->mNewRev );
 630
 631                                 # WikiPage::getParserOutput() should not return false, but just in case
 632                                 if ( $parserOutput ) {
 633                                         // Allow extensions to change parser output here
 634                                         if ( Hooks::run( 'DifferenceEngineRenderRevisionAddParserOutput',
 635                                                 [ $this, $out, $parserOutput, $wikiPage ] )
 636                                         ) {
 637                                                 $out->addParserOutput( $parserOutput, [
 638                                                         'enableSectionEditLinks' => $this->mNewRev->isCurrent()
 639                                                                 && $this->mNewRev->getTitle()->quickUserCan( 'edit', $this->getUser() ),
 640                                                 ] );
 641                                         }
 642                                 }
 643                         }
 644                 }
 645
 646                 // Allow extensions to optionally not show the final patrolled link
 647                 if ( Hooks::run( 'DifferenceEngineRenderRevisionShowFinalPatrolLink' ) ) {
 648                         # Add redundant patrol link on bottom...
 649                         $out->addHTML( $this->markPatrolledLink() );
 650                 }
 651         }
 652
 653         /**
 654          * @param WikiPage $page
 655          * @param Revision $rev
 656          *
 657          * @return ParserOutput|bool False if the revision was not found
 658          */
 659         protected function getParserOutput( WikiPage $page, Revision $rev ) {
 660                 $parserOptions = $page->makeParserOptions( $this->getContext() );
 661                 $parserOutput = $page->getParserOutput( $parserOptions, $rev->getId() );
 662
 663                 return $parserOutput;
 664         }
 665
 666         /**
 667          * Get the diff text, send it to the OutputPage object
 668          * Returns false if the diff could not be generated, otherwise returns true
 669          *
 670          * @param string|bool $otitle Header for old text or false
 671          * @param string|bool $ntitle Header for new text or false
 672          * @param string $notice HTML between diff header and body
 673          *
 674          * @return bool
 675          */
 676         public function showDiff( $otitle, $ntitle, $notice = '' ) {
 677                 // Allow extensions to affect the output here
 678                 Hooks::run( 'DifferenceEngineShowDiff', [ $this ] );
 679
 680                 $diff = $this->getDiff( $otitle, $ntitle, $notice );
 681                 if ( $diff === false ) {
 682                         $this->showMissingRevision();
 683
 684                         return false;
 685                 } else {
 686                         $this->showDiffStyle();
 687                         $this->getOutput()->addHTML( $diff );
 688
 689                         return true;
 690                 }
 691         }
 692
 693         /**
 694          * Add style sheets for diff display.
 695          */
 696         public function showDiffStyle() {
 697                 $this->getOutput()->addModuleStyles( 'mediawiki.diff.styles' );
 698         }
 699
 700         /**
 701          * Get complete diff table, including header
 702          *
 703          * @param string|bool $otitle Header for old text or false
 704          * @param string|bool $ntitle Header for new text or false
 705          * @param string $notice HTML between diff header and body
 706          *
 707          * @return mixed
 708          */
 709         public function getDiff( $otitle, $ntitle, $notice = '' ) {
 710                 $body = $this->getDiffBody();
 711                 if ( $body === false ) {
 712                         return false;
 713                 }
 714
 715                 $multi = $this->getMultiNotice();
 716                 // Display a message when the diff is empty
 717                 if ( $body === '' ) {
 718                         $notice .= '<div class="mw-diff-empty">' .
 719                                 $this->msg( 'diff-empty' )->parse() .
 720                                 "</div>\n";
 721                 }
 722
 723                 return $this->addHeader( $body, $otitle, $ntitle, $multi, $notice );
 724         }
 725
 726         /**
 727          * Get the diff table body, without header
 728          *
 729          * @return mixed (string/false)
 730          */
 731         public function getDiffBody() {
 732                 $this->mCacheHit = true;
 733                 // Check if the diff should be hidden from this user
 734                 if ( !$this->loadRevisionData() ) {
 735                         return false;
 736                 } elseif ( $this->mOldRev &&
 737                         !$this->mOldRev->userCan( Revision::DELETED_TEXT, $this->getUser() )
 738                 ) {
 739                         return false;
 740                 } elseif ( $this->mNewRev &&
 741                         !$this->mNewRev->userCan( Revision::DELETED_TEXT, $this->getUser() )
 742                 ) {
 743                         return false;
 744                 }
 745                 // Short-circuit
 746                 if ( $this->mOldRev === false || ( $this->mOldRev && $this->mNewRev
 747                         && $this->mOldRev->getId() == $this->mNewRev->getId() )
 748                 ) {
 749                         if ( Hooks::run( 'DifferenceEngineShowEmptyOldContent', [ $this ] ) ) {
 750                                 return '';
 751                         }
 752                 }
 753                 // Cacheable?
 754                 $key = false;
 755                 $cache = ObjectCache::getMainWANInstance();
 756                 if ( $this->mOldid && $this->mNewid ) {
 757                         // Check if subclass is still using the old way
 758                         // for backwards-compatibility
 759                         $key = $this->getDiffBodyCacheKey();
 760                         if ( $key === null ) {
 761                                 $key = $cache->makeKey( ...$this->getDiffBodyCacheKeyParams() );
 762                         }
 763
 764                         // Try cache
 765                         if ( !$this->mRefreshCache ) {
 766                                 $difftext = $cache->get( $key );
 767                                 if ( $difftext ) {
 768                                         wfIncrStats( 'diff_cache.hit' );
 769                                         $difftext = $this->localiseDiff( $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                 // Avoid PHP 7.1 warning from passing $this by reference
 786                 $diffEngine = $this;
 787
 788                 // Save to cache for 7 days
 789                 if ( !Hooks::run( 'AbortDiffCache', [ &$diffEngine ] ) ) {
 790                         wfIncrStats( 'diff_cache.uncacheable' );
 791                 } elseif ( $key !== false && $difftext !== false ) {
 792                         wfIncrStats( 'diff_cache.miss' );
 793                         $cache->set( $key, $difftext, 7 * 86400 );
 794                 } else {
 795                         wfIncrStats( 'diff_cache.uncacheable' );
 796                 }
 797                 // localise line numbers and title attribute text
 798                 if ( $difftext !== false ) {
 799                         $difftext = $this->localiseDiff( $difftext );
 800                 }
 801
 802                 return $difftext;
 803         }
 804
 805         /**
 806          * Returns the cache key for diff body text or content.
 807          *
 808          * @deprecated since 1.31, use getDiffBodyCacheKeyParams() instead
 809          * @since 1.23
 810          *
 811          * @throws MWException
 812          * @return string|null
 813          */
 814         protected function getDiffBodyCacheKey() {
 815                 return null;
 816         }
 817
 818         /**
 819          * Get the cache key parameters
 820          *
 821          * Subclasses can replace the first element in the array to something
 822          * more specific to the type of diff (e.g. "inline-diff"), or append
 823          * if the cache should vary on more things. Overriding entirely should
 824          * be avoided.
 825          *
 826          * @since 1.31
 827          *
 828          * @return array
 829          * @throws MWException
 830          */
 831         protected function getDiffBodyCacheKeyParams() {
 832                 if ( !$this->mOldid || !$this->mNewid ) {
 833                         throw new MWException( 'mOldid and mNewid must be set to get diff cache key.' );
 834                 }
 835
 836                 $engine = $this->getEngine();
 837                 $params = [
 838                         'diff',
 839                         $engine,
 840                         self::DIFF_VERSION,
 841                         "old-{$this->mOldid}",
 842                         "rev-{$this->mNewid}"
 843                 ];
 844
 845                 if ( $engine === 'wikidiff2' ) {
 846                         $params[] = phpversion( 'wikidiff2' );
 847                         $params[] = $this->getConfig()->get( 'WikiDiff2MovedParagraphDetectionCutoff' );
 848                 }
 849
 850                 return $params;
 851         }
 852
 853         /**
 854          * Generate a diff, no caching.
 855          *
 856          * This implementation uses generateTextDiffBody() to generate a diff based on the default
 857          * serialization of the given Content objects. This will fail if $old or $new are not
 858          * instances of TextContent.
 859          *
 860          * Subclasses may override this to provide a different rendering for the diff,
 861          * perhaps taking advantage of the content's native form. This is required for all content
 862          * models that are not text based.
 863          *
 864          * @since 1.21
 865          *
 866          * @param Content $old Old content
 867          * @param Content $new New content
 868          *
 869          * @throws MWException If old or new content is not an instance of TextContent.
 870          * @return bool|string
 871          */
 872         public function generateContentDiffBody( Content $old, Content $new ) {
 873                 if ( !( $old instanceof TextContent ) ) {
 874                         throw new MWException( "Diff not implemented for " . get_class( $old ) . "; " .
 875                                 "override generateContentDiffBody to fix this." );
 876                 }
 877
 878                 if ( !( $new instanceof TextContent ) ) {
 879                         throw new MWException( "Diff not implemented for " . get_class( $new ) . "; "
 880                                 . "override generateContentDiffBody to fix this." );
 881                 }
 882
 883                 $otext = $old->serialize();
 884                 $ntext = $new->serialize();
 885
 886                 return $this->generateTextDiffBody( $otext, $ntext );
 887         }
 888
 889         /**
 890          * Generate a diff, no caching
 891          *
 892          * @todo move this to TextDifferenceEngine, make DifferenceEngine abstract. At some point.
 893          *
 894          * @param string $otext Old text, must be already segmented
 895          * @param string $ntext New text, must be already segmented
 896          *
 897          * @return bool|string
 898          */
 899         public function generateTextDiffBody( $otext, $ntext ) {
 900                 $diff = function () use ( $otext, $ntext ) {
 901                         $time = microtime( true );
 902
 903                         $result = $this->textDiff( $otext, $ntext );
 904
 905                         $time = intval( ( microtime( true ) - $time ) * 1000 );
 906                         MediaWikiServices::getInstance()->getStatsdDataFactory()->timing( 'diff_time', $time );
 907                         // Log requests slower than 99th percentile
 908                         if ( $time > 100 && $this->mOldPage && $this->mNewPage ) {
 909                                 wfDebugLog( 'diff',
 910                                         "$time ms diff: {$this->mOldid} -> {$this->mNewid} {$this->mNewPage}" );
 911                         }
 912
 913                         return $result;
 914                 };
 915
 916                 /**
 917                  * @param Status $status
 918                  * @throws FatalError
 919                  */
 920                 $error = function ( $status ) {
 921                         throw new FatalError( $status->getWikiText() );
 922                 };
 923
 924                 // Use PoolCounter if the diff looks like it can be expensive
 925                 if ( strlen( $otext ) + strlen( $ntext ) > 20000 ) {
 926                         $work = new PoolCounterWorkViaCallback( 'diff',
 927                                 md5( $otext ) . md5( $ntext ),
 928                                 [ 'doWork' => $diff, 'error' => $error ]
 929                         );
 930                         return $work->execute();
 931                 }
 932
 933                 return $diff();
 934         }
 935
 936         /**
 937          * Process $wgExternalDiffEngine and get a sane, usable engine
 938          *
 939          * @return bool|string 'wikidiff2', path to an executable, or false
 940          */
 941         private function getEngine() {
 942                 global $wgExternalDiffEngine;
 943                 // We use the global here instead of Config because we write to the value,
 944                 // and Config is not mutable.
 945                 if ( $wgExternalDiffEngine == 'wikidiff' || $wgExternalDiffEngine == 'wikidiff3' ) {
 946                         wfDeprecated( "\$wgExternalDiffEngine = '{$wgExternalDiffEngine}'", '1.27' );
 947                         $wgExternalDiffEngine = false;
 948                 } elseif ( $wgExternalDiffEngine == 'wikidiff2' ) {
 949                         // Same as above, but with no deprecation warnings
 950                         $wgExternalDiffEngine = false;
 951                 } elseif ( !is_string( $wgExternalDiffEngine ) && $wgExternalDiffEngine !== false ) {
 952                         // And prevent people from shooting themselves in the foot...
 953                         wfWarn( '$wgExternalDiffEngine is set to a non-string value, forcing it to false' );
 954                         $wgExternalDiffEngine = false;
 955                 }
 956
 957                 if ( is_string( $wgExternalDiffEngine ) && is_executable( $wgExternalDiffEngine ) ) {
 958                         return $wgExternalDiffEngine;
 959                 } elseif ( $wgExternalDiffEngine === false && function_exists( 'wikidiff2_do_diff' ) ) {
 960                         return 'wikidiff2';
 961                 } else {
 962                         // Native PHP
 963                         return false;
 964                 }
 965         }
 966
 967         /**
 968          * Generates diff, to be wrapped internally in a logging/instrumentation
 969          *
 970          * @param string $otext Old text, must be already segmented
 971          * @param string $ntext New text, must be already segmented
 972          * @return bool|string
 973          */
 974         protected function textDiff( $otext, $ntext ) {
 975                 global $wgContLang;
 976
 977                 $otext = str_replace( "\r\n", "\n", $otext );
 978                 $ntext = str_replace( "\r\n", "\n", $ntext );
 979
 980                 $engine = $this->getEngine();
 981
 982                 // Better external diff engine, the 2 may some day be dropped
 983                 // This one does the escaping and segmenting itself
 984                 if ( $engine === 'wikidiff2' ) {
 985                         $wikidiff2Version = phpversion( 'wikidiff2' );
 986                         if (
 987                                 $wikidiff2Version !== false &&
 988                                 version_compare( $wikidiff2Version, '1.5.0', '>=' )
 989                         ) {
 990                                 $text = wikidiff2_do_diff(
 991                                         $otext,
 992                                         $ntext,
 993                                         2,
 994                                         $this->getConfig()->get( 'WikiDiff2MovedParagraphDetectionCutoff' )
 995                                 );
 996                         } else {
 997                                 // Don't pass the 4th parameter for compatibility with older versions of wikidiff2
 998                                 $text = wikidiff2_do_diff(
 999                                         $otext,
1000                                         $ntext,
1001                                         2
1002                                 );
1003
1004                                 // Log a warning in case the configuration value is set to not silently ignore it
1005                                 if ( $this->getConfig()->get( 'WikiDiff2MovedParagraphDetectionCutoff' ) > 0 ) {
1006                                         wfLogWarning( '$wgWikiDiff2MovedParagraphDetectionCutoff is set but has no
1007                                                 effect since the used version of WikiDiff2 does not support it.' );
1008                                 }
1009                         }
1010
1011                         $text .= $this->debug( 'wikidiff2' );
1012
1013                         return $text;
1014                 } elseif ( $engine !== false ) {
1015                         # Diff via the shell
1016                         $tmpDir = wfTempDir();
1017                         $tempName1 = tempnam( $tmpDir, 'diff_' );
1018                         $tempName2 = tempnam( $tmpDir, 'diff_' );
1019
1020                         $tempFile1 = fopen( $tempName1, "w" );
1021                         if ( !$tempFile1 ) {
1022                                 return false;
1023                         }
1024                         $tempFile2 = fopen( $tempName2, "w" );
1025                         if ( !$tempFile2 ) {
1026                                 return false;
1027                         }
1028                         fwrite( $tempFile1, $otext );
1029                         fwrite( $tempFile2, $ntext );
1030                         fclose( $tempFile1 );
1031                         fclose( $tempFile2 );
1032                         $cmd = [ $engine, $tempName1, $tempName2 ];
1033                         $result = Shell::command( $cmd )
1034                                 ->execute();
1035                         $exitCode = $result->getExitCode();
1036                         if ( $exitCode !== 0 ) {
1037                                 throw new Exception( "External diff command returned code {$exitCode}. Stderr: "
1038                                         . wfEscapeWikiText( $result->getStderr() )
1039                                 );
1040                         }
1041                         $difftext = $result->getStdout();
1042                         $difftext .= $this->debug( "external $engine" );
1043                         unlink( $tempName1 );
1044                         unlink( $tempName2 );
1045
1046                         return $difftext;
1047                 }
1048
1049                 # Native PHP diff
1050                 $ota = explode( "\n", $wgContLang->segmentForDiff( $otext ) );
1051                 $nta = explode( "\n", $wgContLang->segmentForDiff( $ntext ) );
1052                 $diffs = new Diff( $ota, $nta );
1053                 $formatter = new TableDiffFormatter();
1054                 $difftext = $wgContLang->unsegmentForDiff( $formatter->format( $diffs ) );
1055                 $difftext .= $this->debug( 'native PHP' );
1056
1057                 return $difftext;
1058         }
1059
1060         /**
1061          * Generate a debug comment indicating diff generating time,
1062          * server node, and generator backend.
1063          *
1064          * @param string $generator : What diff engine was used
1065          *
1066          * @return string
1067          */
1068         protected function debug( $generator = "internal" ) {
1069                 global $wgShowHostnames;
1070                 if ( !$this->enableDebugComment ) {
1071                         return '';
1072                 }
1073                 $data = [ $generator ];
1074                 if ( $wgShowHostnames ) {
1075                         $data[] = wfHostname();
1076                 }
1077                 $data[] = wfTimestamp( TS_DB );
1078
1079                 return "<!-- diff generator: " .
1080                         implode( " ", array_map( "htmlspecialchars", $data ) ) .
1081                         " -->\n";
1082         }
1083
1084         /**
1085          * Localise diff output
1086          *
1087          * @param string $text
1088          * @return string
1089          */
1090         private function localiseDiff( $text ) {
1091                 $text = $this->localiseLineNumbers( $text );
1092                 if ( $this->getEngine() === 'wikidiff2' &&
1093                         version_compare( phpversion( 'wikidiff2' ), '1.5.1', '>=' )
1094                 ) {
1095                         $text = $this->addLocalisedTitleTooltips( $text );
1096                 }
1097                 return $text;
1098         }
1099
1100         /**
1101          * Replace line numbers with the text in the user's language
1102          *
1103          * @param string $text
1104          *
1105          * @return mixed
1106          */
1107         public function localiseLineNumbers( $text ) {
1108                 return preg_replace_callback(
1109                         '/<!--LINE (\d+)-->/',
1110                         [ $this, 'localiseLineNumbersCb' ],
1111                         $text
1112                 );
1113         }
1114
1115         public function localiseLineNumbersCb( $matches ) {
1116                 if ( $matches[1] === '1' && $this->mReducedLineNumbers ) {
1117                         return '';
1118                 }
1119
1120                 return $this->msg( 'lineno' )->numParams( $matches[1] )->escaped();
1121         }
1122
1123         /**
1124          * Add title attributes for tooltips on moved paragraph indicators
1125          *
1126          * @param string $text
1127          * @return string
1128          */
1129         private function addLocalisedTitleTooltips( $text ) {
1130                 return preg_replace_callback(
1131                         '/class="mw-diff-movedpara-(left|right)"/',
1132                         [ $this, 'addLocalisedTitleTooltipsCb' ],
1133                         $text
1134                 );
1135         }
1136
1137         /**
1138          * @param array $matches
1139          * @return string
1140          */
1141         private function addLocalisedTitleTooltipsCb( array $matches ) {
1142                 $key = $matches[1] === 'right' ?
1143                         'diff-paragraph-moved-toold' :
1144                         'diff-paragraph-moved-tonew';
1145                 return $matches[0] . ' title="' . $this->msg( $key )->escaped() . '"';
1146         }
1147
1148         /**
1149          * If there are revisions between the ones being compared, return a note saying so.
1150          *
1151          * @return string
1152          */
1153         public function getMultiNotice() {
1154                 if ( !is_object( $this->mOldRev ) || !is_object( $this->mNewRev ) ) {
1155                         return '';
1156                 } elseif ( !$this->mOldPage->equals( $this->mNewPage ) ) {
1157                         // Comparing two different pages? Count would be meaningless.
1158                         return '';
1159                 }
1160
1161                 if ( $this->mOldRev->getTimestamp() > $this->mNewRev->getTimestamp() ) {
1162                         $oldRev = $this->mNewRev; // flip
1163                         $newRev = $this->mOldRev; // flip
1164                 } else { // normal case
1165                         $oldRev = $this->mOldRev;
1166                         $newRev = $this->mNewRev;
1167                 }
1168
1169                 // Sanity: don't show the notice if too many rows must be scanned
1170                 // @todo show some special message for that case
1171                 $nEdits = $this->mNewPage->countRevisionsBetween( $oldRev, $newRev, 1000 );
1172                 if ( $nEdits > 0 && $nEdits <= 1000 ) {
1173                         $limit = 100; // use diff-multi-manyusers if too many users
1174                         $users = $this->mNewPage->getAuthorsBetween( $oldRev, $newRev, $limit );
1175                         $numUsers = count( $users );
1176
1177                         if ( $numUsers == 1 && $users[0] == $newRev->getUserText( Revision::RAW ) ) {
1178                                 $numUsers = 0; // special case to say "by the same user" instead of "by one other user"
1179                         }
1180
1181                         return self::intermediateEditsMsg( $nEdits, $numUsers, $limit );
1182                 }
1183
1184                 return ''; // nothing
1185         }
1186
1187         /**
1188          * Get a notice about how many intermediate edits and users there are
1189          *
1190          * @param int $numEdits
1191          * @param int $numUsers
1192          * @param int $limit
1193          *
1194          * @return string
1195          */
1196         public static function intermediateEditsMsg( $numEdits, $numUsers, $limit ) {
1197                 if ( $numUsers === 0 ) {
1198                         $msg = 'diff-multi-sameuser';
1199                 } elseif ( $numUsers > $limit ) {
1200                         $msg = 'diff-multi-manyusers';
1201                         $numUsers = $limit;
1202                 } else {
1203                         $msg = 'diff-multi-otherusers';
1204                 }
1205
1206                 return wfMessage( $msg )->numParams( $numEdits, $numUsers )->parse();
1207         }
1208
1209         /**
1210          * Get a header for a specified revision.
1211          *
1212          * @param Revision $rev
1213          * @param string $complete 'complete' to get the header wrapped depending
1214          *        the visibility of the revision and a link to edit the page.
1215          *
1216          * @return string HTML fragment
1217          */
1218         public function getRevisionHeader( Revision $rev, $complete = '' ) {
1219                 $lang = $this->getLanguage();
1220                 $user = $this->getUser();
1221                 $revtimestamp = $rev->getTimestamp();
1222                 $timestamp = $lang->userTimeAndDate( $revtimestamp, $user );
1223                 $dateofrev = $lang->userDate( $revtimestamp, $user );
1224                 $timeofrev = $lang->userTime( $revtimestamp, $user );
1225
1226                 $header = $this->msg(
1227                         $rev->isCurrent() ? 'currentrev-asof' : 'revisionasof',
1228                         $timestamp,
1229                         $dateofrev,
1230                         $timeofrev
1231                 )->escaped();
1232
1233                 if ( $complete !== 'complete' ) {
1234                         return $header;
1235                 }
1236
1237                 $title = $rev->getTitle();
1238
1239                 $header = Linker::linkKnown( $title, $header, [],
1240                         [ 'oldid' => $rev->getId() ] );
1241
1242                 if ( $rev->userCan( Revision::DELETED_TEXT, $user ) ) {
1243                         $editQuery = [ 'action' => 'edit' ];
1244                         if ( !$rev->isCurrent() ) {
1245                                 $editQuery['oldid'] = $rev->getId();
1246                         }
1247
1248                         $key = $title->quickUserCan( 'edit', $user ) ? 'editold' : 'viewsourceold';
1249                         $msg = $this->msg( $key )->escaped();
1250                         $editLink = $this->msg( 'parentheses' )->rawParams(
1251                                 Linker::linkKnown( $title, $msg, [], $editQuery ) )->escaped();
1252                         $header .= ' ' . Html::rawElement(
1253                                 'span',
1254                                 [ 'class' => 'mw-diff-edit' ],
1255                                 $editLink
1256                         );
1257                         if ( $rev->isDeleted( Revision::DELETED_TEXT ) ) {
1258                                 $header = Html::rawElement(
1259                                         'span',
1260                                         [ 'class' => 'history-deleted' ],
1261                                         $header
1262                                 );
1263                         }
1264                 } else {
1265                         $header = Html::rawElement( 'span', [ 'class' => 'history-deleted' ], $header );
1266                 }
1267
1268                 return $header;
1269         }
1270
1271         /**
1272          * Add the header to a diff body
1273          *
1274          * @param string $diff Diff body
1275          * @param string $otitle Old revision header
1276          * @param string $ntitle New revision header
1277          * @param string $multi Notice telling user that there are intermediate
1278          *   revisions between the ones being compared
1279          * @param string $notice Other notices, e.g. that user is viewing deleted content
1280          *
1281          * @return string
1282          */
1283         public function addHeader( $diff, $otitle, $ntitle, $multi = '', $notice = '' ) {
1284                 // shared.css sets diff in interface language/dir, but the actual content
1285                 // is often in a different language, mostly the page content language/dir
1286                 $header = Html::openElement( 'table', [
1287                         'class' => [ 'diff', 'diff-contentalign-' . $this->getDiffLang()->alignStart() ],
1288                         'data-mw' => 'interface',
1289                 ] );
1290                 $userLang = htmlspecialchars( $this->getLanguage()->getHtmlCode() );
1291
1292                 if ( !$diff && !$otitle ) {
1293                         $header .= "
1294                         <tr class=\"diff-title\" lang=\"{$userLang}\">
1295                         <td class=\"diff-ntitle\">{$ntitle}</td>
1296                         </tr>";
1297                         $multiColspan = 1;
1298                 } else {
1299                         if ( $diff ) { // Safari/Chrome show broken output if cols not used
1300                                 $header .= "
1301                                 <col class=\"diff-marker\" />
1302                                 <col class=\"diff-content\" />
1303                                 <col class=\"diff-marker\" />
1304                                 <col class=\"diff-content\" />";
1305                                 $colspan = 2;
1306                                 $multiColspan = 4;
1307                         } else {
1308                                 $colspan = 1;
1309                                 $multiColspan = 2;
1310                         }
1311                         if ( $otitle || $ntitle ) {
1312                                 $header .= "
1313                                 <tr class=\"diff-title\" lang=\"{$userLang}\">
1314                                 <td colspan=\"$colspan\" class=\"diff-otitle\">{$otitle}</td>
1315                                 <td colspan=\"$colspan\" class=\"diff-ntitle\">{$ntitle}</td>
1316                                 </tr>";
1317                         }
1318                 }
1319
1320                 if ( $multi != '' ) {
1321                         $header .= "<tr><td colspan=\"{$multiColspan}\" " .
1322                                 "class=\"diff-multi\" lang=\"{$userLang}\">{$multi}</td></tr>";
1323                 }
1324                 if ( $notice != '' ) {
1325                         $header .= "<tr><td colspan=\"{$multiColspan}\" " .
1326                                 "class=\"diff-notice\" lang=\"{$userLang}\">{$notice}</td></tr>";
1327                 }
1328
1329                 return $header . $diff . "</table>";
1330         }
1331
1332         /**
1333          * Use specified text instead of loading from the database
1334          * @param Content $oldContent
1335          * @param Content $newContent
1336          * @since 1.21
1337          */
1338         public function setContent( Content $oldContent, Content $newContent ) {
1339                 $this->mOldContent = $oldContent;
1340                 $this->mNewContent = $newContent;
1341
1342                 $this->mTextLoaded = 2;
1343                 $this->mRevisionsLoaded = true;
1344         }
1345
1346         /**
1347          * Set the language in which the diff text is written
1348          *
1349          * @param Language $lang
1350          * @since 1.19
1351          */
1352         public function setTextLanguage( $lang ) {
1353                 if ( !$lang instanceof Language ) {
1354                         wfDeprecated( __METHOD__ . ' with other type than Language for $lang', '1.32' );
1355                 }
1356                 $this->mDiffLang = wfGetLangObj( $lang );
1357         }
1358
1359         /**
1360          * Maps a revision pair definition as accepted by DifferenceEngine constructor
1361          * to a pair of actual integers representing revision ids.
1362          *
1363          * @param int $old Revision id, e.g. from URL parameter 'oldid'
1364          * @param int|string $new Revision id or strings 'next' or 'prev', e.g. from URL parameter 'diff'
1365          *
1366          * @return int[] List of two revision ids, older first, later second.
1367          *     Zero signifies invalid argument passed.
1368          *     false signifies that there is no previous/next revision ($old is the oldest/newest one).
1369          */
1370         public function mapDiffPrevNext( $old, $new ) {
1371                 if ( $new === 'prev' ) {
1372                         // Show diff between revision $old and the previous one. Get previous one from DB.
1373                         $newid = intval( $old );
1374                         $oldid = $this->getTitle()->getPreviousRevisionID( $newid );
1375                 } elseif ( $new === 'next' ) {
1376                         // Show diff between revision $old and the next one. Get next one from DB.
1377                         $oldid = intval( $old );
1378                         $newid = $this->getTitle()->getNextRevisionID( $oldid );
1379                 } else {
1380                         $oldid = intval( $old );
1381                         $newid = intval( $new );
1382                 }
1383
1384                 return [ $oldid, $newid ];
1385         }
1386
1387         /**
1388          * Load revision IDs
1389          */
1390         private function loadRevisionIds() {
1391                 if ( $this->mRevisionsIdsLoaded ) {
1392                         return;
1393                 }
1394
1395                 $this->mRevisionsIdsLoaded = true;
1396
1397                 $old = $this->mOldid;
1398                 $new = $this->mNewid;
1399
1400                 list( $this->mOldid, $this->mNewid ) = self::mapDiffPrevNext( $old, $new );
1401                 if ( $new === 'next' && $this->mNewid === false ) {
1402                         # if no result, NewId points to the newest old revision. The only newer
1403                         # revision is cur, which is "0".
1404                         $this->mNewid = 0;
1405                 }
1406
1407                 Hooks::run(
1408                         'NewDifferenceEngine',
1409                         [ $this->getTitle(), &$this->mOldid, &$this->mNewid, $old, $new ]
1410                 );
1411         }
1412
1413         /**
1414          * Load revision metadata for the specified articles. If newid is 0, then compare
1415          * the old article in oldid to the current article; if oldid is 0, then
1416          * compare the current article to the immediately previous one (ignoring the
1417          * value of newid).
1418          *
1419          * If oldid is false, leave the corresponding revision object set
1420          * to false. This is impossible via ordinary user input, and is provided for
1421          * API convenience.
1422          *
1423          * @return bool
1424          */
1425         public function loadRevisionData() {
1426                 if ( $this->mRevisionsLoaded ) {
1427                         return true;
1428                 }
1429
1430                 // Whether it succeeds or fails, we don't want to try again
1431                 $this->mRevisionsLoaded = true;
1432
1433                 $this->loadRevisionIds();
1434
1435                 // Load the new revision object
1436                 if ( $this->mNewid ) {
1437                         $this->mNewRev = Revision::newFromId( $this->mNewid );
1438                 } else {
1439                         $this->mNewRev = Revision::newFromTitle(
1440                                 $this->getTitle(),
1441                                 false,
1442                                 Revision::READ_NORMAL
1443                         );
1444                 }
1445
1446                 if ( !$this->mNewRev instanceof Revision ) {
1447                         return false;
1448                 }
1449
1450                 // Update the new revision ID in case it was 0 (makes life easier doing UI stuff)
1451                 $this->mNewid = $this->mNewRev->getId();
1452                 $this->mNewPage = $this->mNewRev->getTitle();
1453
1454                 // Load the old revision object
1455                 $this->mOldRev = false;
1456                 if ( $this->mOldid ) {
1457                         $this->mOldRev = Revision::newFromId( $this->mOldid );
1458                 } elseif ( $this->mOldid === 0 ) {
1459                         $rev = $this->mNewRev->getPrevious();
1460                         if ( $rev ) {
1461                                 $this->mOldid = $rev->getId();
1462                                 $this->mOldRev = $rev;
1463                         } else {
1464                                 // No previous revision; mark to show as first-version only.
1465                                 $this->mOldid = false;
1466                                 $this->mOldRev = false;
1467                         }
1468                 } /* elseif ( $this->mOldid === false ) leave mOldRev false; */
1469
1470                 if ( is_null( $this->mOldRev ) ) {
1471                         return false;
1472                 }
1473
1474                 if ( $this->mOldRev ) {
1475                         $this->mOldPage = $this->mOldRev->getTitle();
1476                 }
1477
1478                 // Load tags information for both revisions
1479                 $dbr = wfGetDB( DB_REPLICA );
1480                 if ( $this->mOldid !== false ) {
1481                         $this->mOldTags = $dbr->selectField(
1482                                 'tag_summary',
1483                                 'ts_tags',
1484                                 [ 'ts_rev_id' => $this->mOldid ],
1485                                 __METHOD__
1486                         );
1487                 } else {
1488                         $this->mOldTags = false;
1489                 }
1490                 $this->mNewTags = $dbr->selectField(
1491                         'tag_summary',
1492                         'ts_tags',
1493                         [ 'ts_rev_id' => $this->mNewid ],
1494                         __METHOD__
1495                 );
1496
1497                 return true;
1498         }
1499
1500         /**
1501          * Load the text of the revisions, as well as revision data.
1502          *
1503          * @return bool
1504          */
1505         public function loadText() {
1506                 if ( $this->mTextLoaded == 2 ) {
1507                         return true;
1508                 }
1509
1510                 // Whether it succeeds or fails, we don't want to try again
1511                 $this->mTextLoaded = 2;
1512
1513                 if ( !$this->loadRevisionData() ) {
1514                         return false;
1515                 }
1516
1517                 if ( $this->mOldRev ) {
1518                         $this->mOldContent = $this->mOldRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1519                         if ( $this->mOldContent === null ) {
1520                                 return false;
1521                         }
1522                 }
1523
1524                 if ( $this->mNewRev ) {
1525                         $this->mNewContent = $this->mNewRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1526                         Hooks::run( 'DifferenceEngineLoadTextAfterNewContentIsLoaded', [ $this ] );
1527                         if ( $this->mNewContent === null ) {
1528                                 return false;
1529                         }
1530                 }
1531
1532                 return true;
1533         }
1534
1535         /**
1536          * Load the text of the new revision, not the old one
1537          *
1538          * @return bool
1539          */
1540         public function loadNewText() {
1541                 if ( $this->mTextLoaded >= 1 ) {
1542                         return true;
1543                 }
1544
1545                 $this->mTextLoaded = 1;
1546
1547                 if ( !$this->loadRevisionData() ) {
1548                         return false;
1549                 }
1550
1551                 $this->mNewContent = $this->mNewRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1552
1553                 Hooks::run( 'DifferenceEngineAfterLoadNewText', [ $this ] );
1554
1555                 return true;
1556         }
1557
1558 }