includes/diff/DifferenceEngine.php

   1 <?php
   2 /**
   3  * User interface for the difference engine.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup DifferenceEngine
  22  */
  23
  24 /**
  25  * Constant to indicate diff cache compatibility.
  26  * Bump this when changing the diff formatting in a way that
  27  * fixes important bugs or such to force cached diff views to
  28  * clear.
  29  */
  30 define( 'MW_DIFF_VERSION', '1.11a' );
  31
  32 /**
  33  * @todo document
  34  * @ingroup DifferenceEngine
  35  */
  36 class DifferenceEngine extends ContextSource {
  37
  38         /** @var int */
  39         public $mOldid;
  40
  41         /** @var int */
  42         public $mNewid;
  43
  44         private $mOldTags;
  45         private $mNewTags;
  46
  47         /** @var Content */
  48         public $mOldContent;
  49
  50         /** @var Content */
  51         public $mNewContent;
  52
  53         /** @var Language */
  54         protected $mDiffLang;
  55
  56         /** @var Title */
  57         public $mOldPage;
  58
  59         /** @var Title */
  60         public $mNewPage;
  61
  62         /** @var Revision */
  63         public $mOldRev;
  64
  65         /** @var Revision */
  66         public $mNewRev;
  67
  68         /** @var bool Have the revisions IDs been loaded */
  69         private $mRevisionsIdsLoaded = false;
  70
  71         /** @var bool Have the revisions been loaded */
  72         public $mRevisionsLoaded = false;
  73
  74         /** @var int How many text blobs have been loaded, 0, 1 or 2? */
  75         public $mTextLoaded = 0;
  76
  77         /** @var bool Was the diff fetched from cache? */
  78         public $mCacheHit = false;
  79
  80         /**
  81          * Set this to true to add debug info to the HTML output.
  82          * Warning: this may cause RSS readers to spuriously mark articles as "new"
  83          * (bug 20601)
  84          */
  85         public $enableDebugComment = false;
  86
  87         /** @var bool If true, line X is not displayed when X is 1, for example
  88          *    to increase readability and conserve space with many small diffs.
  89          */
  90         protected $mReducedLineNumbers = false;
  91
  92         /** @var string Link to action=markpatrolled */
  93         protected $mMarkPatrolledLink = null;
  94
  95         /** @var bool Show rev_deleted content if allowed */
  96         protected $unhide = false;
  97
  98         /** @var bool Refresh the diff cache */
  99         protected $mRefreshCache = false;
 100
 101         /**#@-*/
 102
 103         /**
 104          * Constructor
 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 mixed URL or false
 178          */
 179         public function deletedLink( $id ) {
 180                 if ( $this->getUser()->isAllowed( 'deletedhistory' ) ) {
 181                         $dbr = wfGetDB( DB_SLAVE );
 182                         $row = $dbr->selectRow( 'archive', '*',
 183                                 [ 'ar_rev_id' => $id ],
 184                                 __METHOD__ );
 185                         if ( $row ) {
 186                                 $rev = Revision::newFromArchiveRow( $row );
 187                                 $title = Title::makeTitleSafe( $row->ar_namespace, $row->ar_title );
 188
 189                                 return SpecialPage::getTitleFor( 'Undelete' )->getFullURL( [
 190                                         'target' => $title->getPrefixedText(),
 191                                         'timestamp' => $rev->getTimestamp()
 192                                 ] );
 193                         }
 194                 }
 195
 196                 return false;
 197         }
 198
 199         /**
 200          * Build a wikitext link toward a deleted revision, if viewable.
 201          *
 202          * @param int $id Revision ID
 203          *
 204          * @return string Wikitext fragment
 205          */
 206         public function deletedIdMarker( $id ) {
 207                 $link = $this->deletedLink( $id );
 208                 if ( $link ) {
 209                         return "[$link $id]";
 210                 } else {
 211                         return $id;
 212                 }
 213         }
 214
 215         private function showMissingRevision() {
 216                 $out = $this->getOutput();
 217
 218                 $missing = [];
 219                 if ( $this->mOldRev === null ||
 220                         ( $this->mOldRev && $this->mOldContent === null )
 221                 ) {
 222                         $missing[] = $this->deletedIdMarker( $this->mOldid );
 223                 }
 224                 if ( $this->mNewRev === null ||
 225                         ( $this->mNewRev && $this->mNewContent === null )
 226                 ) {
 227                         $missing[] = $this->deletedIdMarker( $this->mNewid );
 228                 }
 229
 230                 $out->setPageTitle( $this->msg( 'errorpagetitle' ) );
 231                 $msg = $this->msg( 'difference-missing-revision' )
 232                         ->params( $this->getLanguage()->listToText( $missing ) )
 233                         ->numParams( count( $missing ) )
 234                         ->parseAsBlock();
 235                 $out->addHTML( $msg );
 236         }
 237
 238         public function showDiffPage( $diffOnly = false ) {
 239
 240                 # Allow frames except in certain special cases
 241                 $out = $this->getOutput();
 242                 $out->allowClickjacking();
 243                 $out->setRobotPolicy( 'noindex,nofollow' );
 244
 245                 if ( !$this->loadRevisionData() ) {
 246                         $this->showMissingRevision();
 247
 248                         return;
 249                 }
 250
 251                 $user = $this->getUser();
 252                 $permErrors = $this->mNewPage->getUserPermissionsErrors( 'read', $user );
 253                 if ( $this->mOldPage ) { # mOldPage might not be set, see below.
 254                         $permErrors = wfMergeErrorArrays( $permErrors,
 255                                 $this->mOldPage->getUserPermissionsErrors( 'read', $user ) );
 256                 }
 257                 if ( count( $permErrors ) ) {
 258                         throw new PermissionsError( 'read', $permErrors );
 259                 }
 260
 261                 $rollback = '';
 262
 263                 $query = [];
 264                 # Carry over 'diffonly' param via navigation links
 265                 if ( $diffOnly != $user->getBoolOption( 'diffonly' ) ) {
 266                         $query['diffonly'] = $diffOnly;
 267                 }
 268                 # Cascade unhide param in links for easy deletion browsing
 269                 if ( $this->unhide ) {
 270                         $query['unhide'] = 1;
 271                 }
 272
 273                 # Check if one of the revisions is deleted/suppressed
 274                 $deleted = $suppressed = false;
 275                 $allowed = $this->mNewRev->userCan( Revision::DELETED_TEXT, $user );
 276
 277                 $revisionTools = [];
 278
 279                 # mOldRev is false if the difference engine is called with a "vague" query for
 280                 # a diff between a version V and its previous version V' AND the version V
 281                 # is the first version of that article. In that case, V' does not exist.
 282                 if ( $this->mOldRev === false ) {
 283                         $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 284                         $samePage = true;
 285                         $oldHeader = '';
 286                 } else {
 287                         Hooks::run( 'DiffViewHeader', [ $this, $this->mOldRev, $this->mNewRev ] );
 288
 289                         if ( $this->mNewPage->equals( $this->mOldPage ) ) {
 290                                 $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 291                                 $samePage = true;
 292                         } else {
 293                                 $out->setPageTitle( $this->msg( 'difference-title-multipage',
 294                                         $this->mOldPage->getPrefixedText(), $this->mNewPage->getPrefixedText() ) );
 295                                 $out->addSubtitle( $this->msg( 'difference-multipage' ) );
 296                                 $samePage = false;
 297                         }
 298
 299                         if ( $samePage && $this->mNewPage->quickUserCan( 'edit', $user ) ) {
 300                                 if ( $this->mNewRev->isCurrent() && $this->mNewPage->userCan( 'rollback', $user ) ) {
 301                                         $rollbackLink = Linker::generateRollback( $this->mNewRev, $this->getContext() );
 302                                         if ( $rollbackLink ) {
 303                                                 $out->preventClickjacking();
 304                                                 $rollback = '&#160;&#160;&#160;' . $rollbackLink;
 305                                         }
 306                                 }
 307
 308                                 if ( !$this->mOldRev->isDeleted( Revision::DELETED_TEXT ) &&
 309                                         !$this->mNewRev->isDeleted( Revision::DELETED_TEXT )
 310                                 ) {
 311                                         $undoLink = Html::element( 'a', [
 312                                                         'href' => $this->mNewPage->getLocalURL( [
 313                                                                 'action' => 'edit',
 314                                                                 'undoafter' => $this->mOldid,
 315                                                                 'undo' => $this->mNewid
 316                                                         ] ),
 317                                                         'title' => Linker::titleAttrib( 'undo' ),
 318                                                 ],
 319                                                 $this->msg( 'editundo' )->text()
 320                                         );
 321                                         $revisionTools['mw-diff-undo'] = $undoLink;
 322                                 }
 323                         }
 324
 325                         # Make "previous revision link"
 326                         if ( $samePage && $this->mOldRev->getPrevious() ) {
 327                                 $prevlink = Linker::linkKnown(
 328                                         $this->mOldPage,
 329                                         $this->msg( 'previousdiff' )->escaped(),
 330                                         [ 'id' => 'differences-prevlink' ],
 331                                         [ 'diff' => 'prev', 'oldid' => $this->mOldid ] + $query
 332                                 );
 333                         } else {
 334                                 $prevlink = '&#160;';
 335                         }
 336
 337                         if ( $this->mOldRev->isMinor() ) {
 338                                 $oldminor = ChangesList::flag( 'minor' );
 339                         } else {
 340                                 $oldminor = '';
 341                         }
 342
 343                         $ldel = $this->revisionDeleteLink( $this->mOldRev );
 344                         $oldRevisionHeader = $this->getRevisionHeader( $this->mOldRev, 'complete' );
 345                         $oldChangeTags = ChangeTags::formatSummaryRow( $this->mOldTags, 'diff', $this->getContext() );
 346
 347                         $oldHeader = '<div id="mw-diff-otitle1"><strong>' . $oldRevisionHeader . '</strong></div>' .
 348                                 '<div id="mw-diff-otitle2">' .
 349                                 Linker::revUserTools( $this->mOldRev, !$this->unhide ) . '</div>' .
 350                                 '<div id="mw-diff-otitle3">' . $oldminor .
 351                                 Linker::revComment( $this->mOldRev, !$diffOnly, !$this->unhide ) . $ldel . '</div>' .
 352                                 '<div id="mw-diff-otitle5">' . $oldChangeTags[0] . '</div>' .
 353                                 '<div id="mw-diff-otitle4">' . $prevlink . '</div>';
 354
 355                         if ( $this->mOldRev->isDeleted( Revision::DELETED_TEXT ) ) {
 356                                 $deleted = true; // old revisions text is hidden
 357                                 if ( $this->mOldRev->isDeleted( Revision::DELETED_RESTRICTED ) ) {
 358                                         $suppressed = true; // also suppressed
 359                                 }
 360                         }
 361
 362                         # Check if this user can see the revisions
 363                         if ( !$this->mOldRev->userCan( Revision::DELETED_TEXT, $user ) ) {
 364                                 $allowed = false;
 365                         }
 366                 }
 367
 368                 # Make "next revision link"
 369                 # Skip next link on the top revision
 370                 if ( $samePage && !$this->mNewRev->isCurrent() ) {
 371                         $nextlink = Linker::linkKnown(
 372                                 $this->mNewPage,
 373                                 $this->msg( 'nextdiff' )->escaped(),
 374                                 [ 'id' => 'differences-nextlink' ],
 375                                 [ 'diff' => 'next', 'oldid' => $this->mNewid ] + $query
 376                         );
 377                 } else {
 378                         $nextlink = '&#160;';
 379                 }
 380
 381                 if ( $this->mNewRev->isMinor() ) {
 382                         $newminor = ChangesList::flag( 'minor' );
 383                 } else {
 384                         $newminor = '';
 385                 }
 386
 387                 # Handle RevisionDelete links...
 388                 $rdel = $this->revisionDeleteLink( $this->mNewRev );
 389
 390                 # Allow extensions to define their own revision tools
 391                 Hooks::run( 'DiffRevisionTools',
 392                         [ $this->mNewRev, &$revisionTools, $this->mOldRev, $user ] );
 393                 $formattedRevisionTools = [];
 394                 // Put each one in parentheses (poor man's button)
 395                 foreach ( $revisionTools as $key => $tool ) {
 396                         $toolClass = is_string( $key ) ? $key : 'mw-diff-tool';
 397                         $element = Html::rawElement(
 398                                 'span',
 399                                 [ 'class' => $toolClass ],
 400                                 $this->msg( 'parentheses' )->rawParams( $tool )->escaped()
 401                         );
 402                         $formattedRevisionTools[] = $element;
 403                 }
 404                 $newRevisionHeader = $this->getRevisionHeader( $this->mNewRev, 'complete' ) .
 405                         ' ' . implode( ' ', $formattedRevisionTools );
 406                 $newChangeTags = ChangeTags::formatSummaryRow( $this->mNewTags, 'diff', $this->getContext() );
 407
 408                 $newHeader = '<div id="mw-diff-ntitle1"><strong>' . $newRevisionHeader . '</strong></div>' .
 409                         '<div id="mw-diff-ntitle2">' . Linker::revUserTools( $this->mNewRev, !$this->unhide ) .
 410                         " $rollback</div>" .
 411                         '<div id="mw-diff-ntitle3">' . $newminor .
 412                         Linker::revComment( $this->mNewRev, !$diffOnly, !$this->unhide ) . $rdel . '</div>' .
 413                         '<div id="mw-diff-ntitle5">' . $newChangeTags[0] . '</div>' .
 414                         '<div id="mw-diff-ntitle4">' . $nextlink . $this->markPatrolledLink() . '</div>';
 415
 416                 if ( $this->mNewRev->isDeleted( Revision::DELETED_TEXT ) ) {
 417                         $deleted = true; // new revisions text is hidden
 418                         if ( $this->mNewRev->isDeleted( Revision::DELETED_RESTRICTED ) ) {
 419                                 $suppressed = true; // also suppressed
 420                         }
 421                 }
 422
 423                 # If the diff cannot be shown due to a deleted revision, then output
 424                 # the diff header and links to unhide (if available)...
 425                 if ( $deleted && ( !$this->unhide || !$allowed ) ) {
 426                         $this->showDiffStyle();
 427                         $multi = $this->getMultiNotice();
 428                         $out->addHTML( $this->addHeader( '', $oldHeader, $newHeader, $multi ) );
 429                         if ( !$allowed ) {
 430                                 $msg = $suppressed ? 'rev-suppressed-no-diff' : 'rev-deleted-no-diff';
 431                                 # Give explanation for why revision is not visible
 432                                 $out->wrapWikiMsg( "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 433                                         [ $msg ] );
 434                         } else {
 435                                 # Give explanation and add a link to view the diff...
 436                                 $query = $this->getRequest()->appendQueryValue( 'unhide', '1' );
 437                                 $link = $this->getTitle()->getFullURL( $query );
 438                                 $msg = $suppressed ? 'rev-suppressed-unhide-diff' : 'rev-deleted-unhide-diff';
 439                                 $out->wrapWikiMsg(
 440                                         "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 441                                         [ $msg, $link ]
 442                                 );
 443                         }
 444                 # Otherwise, output a regular diff...
 445                 } else {
 446                         # Add deletion notice if the user is viewing deleted content
 447                         $notice = '';
 448                         if ( $deleted ) {
 449                                 $msg = $suppressed ? 'rev-suppressed-diff-view' : 'rev-deleted-diff-view';
 450                                 $notice = "<div id='mw-$msg' class='mw-warning plainlinks'>\n" .
 451                                         $this->msg( $msg )->parse() .
 452                                         "</div>\n";
 453                         }
 454                         $this->showDiff( $oldHeader, $newHeader, $notice );
 455                         if ( !$diffOnly ) {
 456                                 $this->renderNewRevision();
 457                         }
 458                 }
 459         }
 460
 461         /**
 462          * Build a link to mark a change as patrolled.
 463          *
 464          * Returns empty string if there's either no revision to patrol or the user is not allowed to.
 465          * Side effect: When the patrol link is build, this method will call
 466          * OutputPage::preventClickjacking() and load mediawiki.page.patrol.ajax.
 467          *
 468          * @return string HTML or empty string
 469          */
 470         protected function markPatrolledLink() {
 471                 if ( $this->mMarkPatrolledLink === null ) {
 472                         $linkInfo = $this->getMarkPatrolledLinkInfo();
 473                         // If false, there is no patrol link needed/allowed
 474                         if ( !$linkInfo ) {
 475                                 $this->mMarkPatrolledLink = '';
 476                         } else {
 477                                 $this->mMarkPatrolledLink = ' <span class="patrollink" data-mw="interface">[' .
 478                                         Linker::linkKnown(
 479                                                 $this->mNewPage,
 480                                                 $this->msg( 'markaspatrolleddiff' )->escaped(),
 481                                                 [],
 482                                                 [
 483                                                         'action' => 'markpatrolled',
 484                                                         'rcid' => $linkInfo['rcid'],
 485                                                         'token' => $linkInfo['token'],
 486                                                 ]
 487                                         ) . ']</span>';
 488                         }
 489                 }
 490                 return $this->mMarkPatrolledLink;
 491         }
 492
 493         /**
 494          * Returns an array of meta data needed to build a "mark as patrolled" link and
 495          * adds the mediawiki.page.patrol.ajax to the output.
 496          *
 497          * @return array|false An array of meta data for a patrol link (rcid & token)
 498          *  or false if no link is needed
 499          */
 500         protected function getMarkPatrolledLinkInfo() {
 501                 global $wgUseRCPatrol, $wgEnableAPI, $wgEnableWriteAPI;
 502
 503                 $user = $this->getUser();
 504
 505                 // Prepare a change patrol link, if applicable
 506                 if (
 507                         // Is patrolling enabled and the user allowed to?
 508                         $wgUseRCPatrol && $this->mNewPage->quickUserCan( 'patrol', $user ) &&
 509                         // Only do this if the revision isn't more than 6 hours older
 510                         // than the Max RC age (6h because the RC might not be cleaned out regularly)
 511                         RecentChange::isInRCLifespan( $this->mNewRev->getTimestamp(), 21600 )
 512                 ) {
 513                         // Look for an unpatrolled change corresponding to this diff
 514                         $db = wfGetDB( DB_SLAVE );
 515                         $change = RecentChange::newFromConds(
 516                                 [
 517                                         'rc_timestamp' => $db->timestamp( $this->mNewRev->getTimestamp() ),
 518                                         'rc_this_oldid' => $this->mNewid,
 519                                         'rc_patrolled' => 0
 520                                 ],
 521                                 __METHOD__
 522                         );
 523
 524                         if ( $change && !$change->getPerformer()->equals( $user ) ) {
 525                                 $rcid = $change->getAttribute( 'rc_id' );
 526                         } else {
 527                                 // None found or the page has been created by the current user.
 528                                 // If the user could patrol this it already would be patrolled
 529                                 $rcid = 0;
 530                         }
 531                         // Build the link
 532                         if ( $rcid ) {
 533                                 $this->getOutput()->preventClickjacking();
 534                                 if ( $wgEnableAPI && $wgEnableWriteAPI
 535                                         && $user->isAllowed( 'writeapi' )
 536                                 ) {
 537                                         $this->getOutput()->addModules( 'mediawiki.page.patrol.ajax' );
 538                                 }
 539
 540                                 $token = $user->getEditToken( $rcid );
 541                                 return [
 542                                         'rcid' => $rcid,
 543                                         'token' => $token,
 544                                 ];
 545                         }
 546                 }
 547
 548                 // No mark as patrolled link applicable
 549                 return false;
 550         }
 551
 552         /**
 553          * @param Revision $rev
 554          *
 555          * @return string
 556          */
 557         protected function revisionDeleteLink( $rev ) {
 558                 $link = Linker::getRevDeleteLink( $this->getUser(), $rev, $rev->getTitle() );
 559                 if ( $link !== '' ) {
 560                         $link = '&#160;&#160;&#160;' . $link . ' ';
 561                 }
 562
 563                 return $link;
 564         }
 565
 566         /**
 567          * Show the new revision of the page.
 568          */
 569         public function renderNewRevision() {
 570                 $out = $this->getOutput();
 571                 $revHeader = $this->getRevisionHeader( $this->mNewRev );
 572                 # Add "current version as of X" title
 573                 $out->addHTML( "<hr class='diff-hr' id='mw-oldid' />
 574                 <h2 class='diff-currentversion-title'>{$revHeader}</h2>\n" );
 575                 # Page content may be handled by a hooked call instead...
 576                 # @codingStandardsIgnoreStart Ignoring long lines.
 577                 if ( Hooks::run( 'ArticleContentOnDiff', [ $this, $out ] ) ) {
 578                         $this->loadNewText();
 579                         $out->setRevisionId( $this->mNewid );
 580                         $out->setRevisionTimestamp( $this->mNewRev->getTimestamp() );
 581                         $out->setArticleFlag( true );
 582
 583                         // NOTE: only needed for B/C: custom rendering of JS/CSS via hook
 584                         if ( $this->mNewPage->isCssJsSubpage() || $this->mNewPage->isCssOrJsPage() ) {
 585                                 // This needs to be synchronised with Article::showCssOrJsPage(), which sucks
 586                                 // Give hooks a chance to customise the output
 587                                 // @todo standardize this crap into one function
 588                                 if ( ContentHandler::runLegacyHooks( 'ShowRawCssJs', [ $this->mNewContent, $this->mNewPage, $out ] ) ) {
 589                                         // NOTE: deprecated hook, B/C only
 590                                         // use the content object's own rendering
 591                                         $cnt = $this->mNewRev->getContent();
 592                                         $po = $cnt ? $cnt->getParserOutput( $this->mNewRev->getTitle(), $this->mNewRev->getId() ) : null;
 593                                         if ( $po ) {
 594                                                 $out->addParserOutputContent( $po );
 595                                         }
 596                                 }
 597                         } elseif ( !Hooks::run( 'ArticleContentViewCustom', [ $this->mNewContent, $this->mNewPage, $out ] ) ) {
 598                                 // Handled by extension
 599                         } elseif ( !ContentHandler::runLegacyHooks( 'ArticleViewCustom', [ $this->mNewContent, $this->mNewPage, $out ] ) ) {
 600                                 // NOTE: deprecated hook, B/C only
 601                                 // Handled by extension
 602                         } else {
 603                                 // Normal page
 604                                 if ( $this->getTitle()->equals( $this->mNewPage ) ) {
 605                                         // If the Title stored in the context is the same as the one
 606                                         // of the new revision, we can use its associated WikiPage
 607                                         // object.
 608                                         $wikiPage = $this->getWikiPage();
 609                                 } else {
 610                                         // Otherwise we need to create our own WikiPage object
 611                                         $wikiPage = WikiPage::factory( $this->mNewPage );
 612                                 }
 613
 614                                 $parserOutput = $this->getParserOutput( $wikiPage, $this->mNewRev );
 615
 616                                 # WikiPage::getParserOutput() should not return false, but just in case
 617                                 if ( $parserOutput ) {
 618                                         $out->addParserOutput( $parserOutput );
 619                                 }
 620                         }
 621                 }
 622                 # @codingStandardsIgnoreEnd
 623
 624                 # Add redundant patrol link on bottom...
 625                 $out->addHTML( $this->markPatrolledLink() );
 626
 627         }
 628
 629         protected function getParserOutput( WikiPage $page, Revision $rev ) {
 630                 $parserOptions = $page->makeParserOptions( $this->getContext() );
 631
 632                 if ( !$rev->isCurrent() || !$rev->getTitle()->quickUserCan( 'edit', $this->getUser() ) ) {
 633                         $parserOptions->setEditSection( false );
 634                 }
 635
 636                 $parserOutput = $page->getParserOutput( $parserOptions, $rev->getId() );
 637
 638                 return $parserOutput;
 639         }
 640
 641         /**
 642          * Get the diff text, send it to the OutputPage object
 643          * Returns false if the diff could not be generated, otherwise returns true
 644          *
 645          * @param string|bool $otitle Header for old text or false
 646          * @param string|bool $ntitle Header for new text or false
 647          * @param string $notice HTML between diff header and body
 648          *
 649          * @return bool
 650          */
 651         public function showDiff( $otitle, $ntitle, $notice = '' ) {
 652                 $diff = $this->getDiff( $otitle, $ntitle, $notice );
 653                 if ( $diff === false ) {
 654                         $this->showMissingRevision();
 655
 656                         return false;
 657                 } else {
 658                         $this->showDiffStyle();
 659                         $this->getOutput()->addHTML( $diff );
 660
 661                         return true;
 662                 }
 663         }
 664
 665         /**
 666          * Add style sheets and supporting JS for diff display.
 667          */
 668         public function showDiffStyle() {
 669                 $this->getOutput()->addModuleStyles( 'mediawiki.action.history.diff' );
 670         }
 671
 672         /**
 673          * Get complete diff table, including header
 674          *
 675          * @param string|bool $otitle Header for old text or false
 676          * @param string|bool $ntitle Header for new text or false
 677          * @param string $notice HTML between diff header and body
 678          *
 679          * @return mixed
 680          */
 681         public function getDiff( $otitle, $ntitle, $notice = '' ) {
 682                 $body = $this->getDiffBody();
 683                 if ( $body === false ) {
 684                         return false;
 685                 }
 686
 687                 $multi = $this->getMultiNotice();
 688                 // Display a message when the diff is empty
 689                 if ( $body === '' ) {
 690                         $notice .= '<div class="mw-diff-empty">' .
 691                                 $this->msg( 'diff-empty' )->parse() .
 692                                 "</div>\n";
 693                 }
 694
 695                 return $this->addHeader( $body, $otitle, $ntitle, $multi, $notice );
 696         }
 697
 698         /**
 699          * Get the diff table body, without header
 700          *
 701          * @return mixed (string/false)
 702          */
 703         public function getDiffBody() {
 704                 $this->mCacheHit = true;
 705                 // Check if the diff should be hidden from this user
 706                 if ( !$this->loadRevisionData() ) {
 707                         return false;
 708                 } elseif ( $this->mOldRev &&
 709                         !$this->mOldRev->userCan( Revision::DELETED_TEXT, $this->getUser() )
 710                 ) {
 711                         return false;
 712                 } elseif ( $this->mNewRev &&
 713                         !$this->mNewRev->userCan( Revision::DELETED_TEXT, $this->getUser() )
 714                 ) {
 715                         return false;
 716                 }
 717                 // Short-circuit
 718                 if ( $this->mOldRev === false || ( $this->mOldRev && $this->mNewRev
 719                         && $this->mOldRev->getId() == $this->mNewRev->getId() )
 720                 ) {
 721                         return '';
 722                 }
 723                 // Cacheable?
 724                 $key = false;
 725                 $cache = ObjectCache::getMainWANInstance();
 726                 if ( $this->mOldid && $this->mNewid ) {
 727                         $key = $this->getDiffBodyCacheKey();
 728
 729                         // Try cache
 730                         if ( !$this->mRefreshCache ) {
 731                                 $difftext = $cache->get( $key );
 732                                 if ( $difftext ) {
 733                                         wfIncrStats( 'diff_cache.hit' );
 734                                         $difftext = $this->localiseLineNumbers( $difftext );
 735                                         $difftext .= "\n<!-- diff cache key $key -->\n";
 736
 737                                         return $difftext;
 738                                 }
 739                         } // don't try to load but save the result
 740                 }
 741                 $this->mCacheHit = false;
 742
 743                 // Loadtext is permission safe, this just clears out the diff
 744                 if ( !$this->loadText() ) {
 745                         return false;
 746                 }
 747
 748                 $difftext = $this->generateContentDiffBody( $this->mOldContent, $this->mNewContent );
 749
 750                 // Save to cache for 7 days
 751                 if ( !Hooks::run( 'AbortDiffCache', [ &$this ] ) ) {
 752                         wfIncrStats( 'diff_cache.uncacheable' );
 753                 } elseif ( $key !== false && $difftext !== false ) {
 754                         wfIncrStats( 'diff_cache.miss' );
 755                         $cache->set( $key, $difftext, 7 * 86400 );
 756                 } else {
 757                         wfIncrStats( 'diff_cache.uncacheable' );
 758                 }
 759                 // Replace line numbers with the text in the user's language
 760                 if ( $difftext !== false ) {
 761                         $difftext = $this->localiseLineNumbers( $difftext );
 762                 }
 763
 764                 return $difftext;
 765         }
 766
 767         /**
 768          * Returns the cache key for diff body text or content.
 769          *
 770          * @since 1.23
 771          *
 772          * @throws MWException
 773          * @return string
 774          */
 775         protected function getDiffBodyCacheKey() {
 776                 if ( !$this->mOldid || !$this->mNewid ) {
 777                         throw new MWException( 'mOldid and mNewid must be set to get diff cache key.' );
 778                 }
 779
 780                 return wfMemcKey( 'diff', 'version', MW_DIFF_VERSION,
 781                         'oldid', $this->mOldid, 'newid', $this->mNewid );
 782         }
 783
 784         /**
 785          * Generate a diff, no caching.
 786          *
 787          * This implementation uses generateTextDiffBody() to generate a diff based on the default
 788          * serialization of the given Content objects. This will fail if $old or $new are not
 789          * instances of TextContent.
 790          *
 791          * Subclasses may override this to provide a different rendering for the diff,
 792          * perhaps taking advantage of the content's native form. This is required for all content
 793          * models that are not text based.
 794          *
 795          * @since 1.21
 796          *
 797          * @param Content $old Old content
 798          * @param Content $new New content
 799          *
 800          * @throws MWException If old or new content is not an instance of TextContent.
 801          * @return bool|string
 802          */
 803         public function generateContentDiffBody( Content $old, Content $new ) {
 804                 if ( !( $old instanceof TextContent ) ) {
 805                         throw new MWException( "Diff not implemented for " . get_class( $old ) . "; " .
 806                                 "override generateContentDiffBody to fix this." );
 807                 }
 808
 809                 if ( !( $new instanceof TextContent ) ) {
 810                         throw new MWException( "Diff not implemented for " . get_class( $new ) . "; "
 811                                 . "override generateContentDiffBody to fix this." );
 812                 }
 813
 814                 $otext = $old->serialize();
 815                 $ntext = $new->serialize();
 816
 817                 return $this->generateTextDiffBody( $otext, $ntext );
 818         }
 819
 820         /**
 821          * Generate a diff, no caching
 822          *
 823          * @param string $otext Old text, must be already segmented
 824          * @param string $ntext New text, must be already segmented
 825          *
 826          * @return bool|string
 827          * @deprecated since 1.21, use generateContentDiffBody() instead!
 828          */
 829         public function generateDiffBody( $otext, $ntext ) {
 830                 ContentHandler::deprecated( __METHOD__, "1.21" );
 831
 832                 return $this->generateTextDiffBody( $otext, $ntext );
 833         }
 834
 835         /**
 836          * Generate a diff, no caching
 837          *
 838          * @todo move this to TextDifferenceEngine, make DifferenceEngine abstract. At some point.
 839          *
 840          * @param string $otext Old text, must be already segmented
 841          * @param string $ntext New text, must be already segmented
 842          *
 843          * @return bool|string
 844          */
 845         public function generateTextDiffBody( $otext, $ntext ) {
 846                 $diff = function() use ( $otext, $ntext ) {
 847                         $time = microtime( true );
 848
 849                         $result = $this->textDiff( $otext, $ntext );
 850
 851                         $time = intval( ( microtime( true ) - $time ) * 1000 );
 852                         $this->getStats()->timing( 'diff_time', $time );
 853                         // Log requests slower than 99th percentile
 854                         if ( $time > 100 && $this->mOldPage && $this->mNewPage ) {
 855                                 wfDebugLog( 'diff',
 856                                         "$time ms diff: {$this->mOldid} -> {$this->mNewid} {$this->mNewPage}" );
 857                         }
 858
 859                         return $result;
 860                 };
 861
 862                 $error = function( $status ) {
 863                         throw new FatalError( $status->getWikiText() );
 864                 };
 865
 866                 // Use PoolCounter if the diff looks like it can be expensive
 867                 if ( strlen( $otext ) + strlen( $ntext ) > 20000 ) {
 868                         $work = new PoolCounterWorkViaCallback( 'diff',
 869                                 md5( $otext ) . md5( $ntext ),
 870                                 [ 'doWork' => $diff, 'error' => $error ]
 871                         );
 872                         return $work->execute();
 873                 }
 874
 875                 return $diff();
 876         }
 877
 878         /**
 879          * Generates diff, to be wrapped internally in a logging/instrumentation
 880          *
 881          * @param string $otext Old text, must be already segmented
 882          * @param string $ntext New text, must be already segmented
 883          * @return bool|string
 884          */
 885         protected function textDiff( $otext, $ntext ) {
 886                 global $wgExternalDiffEngine, $wgContLang;
 887
 888                 $otext = str_replace( "\r\n", "\n", $otext );
 889                 $ntext = str_replace( "\r\n", "\n", $ntext );
 890
 891                 if ( $wgExternalDiffEngine == 'wikidiff' || $wgExternalDiffEngine == 'wikidiff3' ) {
 892                         wfDeprecated( "\$wgExternalDiffEngine = '{$wgExternalDiffEngine}'", '1.27' );
 893                         $wgExternalDiffEngine = false;
 894                 }
 895
 896                 if ( $wgExternalDiffEngine == 'wikidiff2' ) {
 897                         if ( function_exists( 'wikidiff2_do_diff' ) ) {
 898                                 # Better external diff engine, the 2 may some day be dropped
 899                                 # This one does the escaping and segmenting itself
 900                                 $text = wikidiff2_do_diff( $otext, $ntext, 2 );
 901                                 $text .= $this->debug( 'wikidiff2' );
 902
 903                                 return $text;
 904                         }
 905                 } elseif ( $wgExternalDiffEngine !== false ) {
 906                         # Diff via the shell
 907                         $tmpDir = wfTempDir();
 908                         $tempName1 = tempnam( $tmpDir, 'diff_' );
 909                         $tempName2 = tempnam( $tmpDir, 'diff_' );
 910
 911                         $tempFile1 = fopen( $tempName1, "w" );
 912                         if ( !$tempFile1 ) {
 913                                 return false;
 914                         }
 915                         $tempFile2 = fopen( $tempName2, "w" );
 916                         if ( !$tempFile2 ) {
 917                                 return false;
 918                         }
 919                         fwrite( $tempFile1, $otext );
 920                         fwrite( $tempFile2, $ntext );
 921                         fclose( $tempFile1 );
 922                         fclose( $tempFile2 );
 923                         $cmd = wfEscapeShellArg( $wgExternalDiffEngine, $tempName1, $tempName2 );
 924                         $difftext = wfShellExec( $cmd );
 925                         $difftext .= $this->debug( "external $wgExternalDiffEngine" );
 926                         unlink( $tempName1 );
 927                         unlink( $tempName2 );
 928
 929                         return $difftext;
 930                 }
 931
 932                 # Native PHP diff
 933                 $ota = explode( "\n", $wgContLang->segmentForDiff( $otext ) );
 934                 $nta = explode( "\n", $wgContLang->segmentForDiff( $ntext ) );
 935                 $diffs = new Diff( $ota, $nta );
 936                 $formatter = new TableDiffFormatter();
 937                 $difftext = $wgContLang->unsegmentForDiff( $formatter->format( $diffs ) );
 938
 939                 return $difftext;
 940         }
 941
 942         /**
 943          * Generate a debug comment indicating diff generating time,
 944          * server node, and generator backend.
 945          *
 946          * @param string $generator : What diff engine was used
 947          *
 948          * @return string
 949          */
 950         protected function debug( $generator = "internal" ) {
 951                 global $wgShowHostnames;
 952                 if ( !$this->enableDebugComment ) {
 953                         return '';
 954                 }
 955                 $data = [ $generator ];
 956                 if ( $wgShowHostnames ) {
 957                         $data[] = wfHostname();
 958                 }
 959                 $data[] = wfTimestamp( TS_DB );
 960
 961                 return "<!-- diff generator: " .
 962                         implode( " ", array_map( "htmlspecialchars", $data ) ) .
 963                         " -->\n";
 964         }
 965
 966         /**
 967          * Replace line numbers with the text in the user's language
 968          *
 969          * @param string $text
 970          *
 971          * @return mixed
 972          */
 973         public function localiseLineNumbers( $text ) {
 974                 return preg_replace_callback(
 975                         '/<!--LINE (\d+)-->/',
 976                         [ &$this, 'localiseLineNumbersCb' ],
 977                         $text
 978                 );
 979         }
 980
 981         public function localiseLineNumbersCb( $matches ) {
 982                 if ( $matches[1] === '1' && $this->mReducedLineNumbers ) {
 983                         return '';
 984                 }
 985
 986                 return $this->msg( 'lineno' )->numParams( $matches[1] )->escaped();
 987         }
 988
 989         /**
 990          * If there are revisions between the ones being compared, return a note saying so.
 991          *
 992          * @return string
 993          */
 994         public function getMultiNotice() {
 995                 if ( !is_object( $this->mOldRev ) || !is_object( $this->mNewRev ) ) {
 996                         return '';
 997                 } elseif ( !$this->mOldPage->equals( $this->mNewPage ) ) {
 998                         // Comparing two different pages? Count would be meaningless.
 999                         return '';
1000                 }
1001
1002                 if ( $this->mOldRev->getTimestamp() > $this->mNewRev->getTimestamp() ) {
1003                         $oldRev = $this->mNewRev; // flip
1004                         $newRev = $this->mOldRev; // flip
1005                 } else { // normal case
1006                         $oldRev = $this->mOldRev;
1007                         $newRev = $this->mNewRev;
1008                 }
1009
1010                 // Sanity: don't show the notice if too many rows must be scanned
1011                 // @todo show some special message for that case
1012                 $nEdits = $this->mNewPage->countRevisionsBetween( $oldRev, $newRev, 1000 );
1013                 if ( $nEdits > 0 && $nEdits <= 1000 ) {
1014                         $limit = 100; // use diff-multi-manyusers if too many users
1015                         $users = $this->mNewPage->getAuthorsBetween( $oldRev, $newRev, $limit );
1016                         $numUsers = count( $users );
1017
1018                         if ( $numUsers == 1 && $users[0] == $newRev->getUserText( Revision::RAW ) ) {
1019                                 $numUsers = 0; // special case to say "by the same user" instead of "by one other user"
1020                         }
1021
1022                         return self::intermediateEditsMsg( $nEdits, $numUsers, $limit );
1023                 }
1024
1025                 return ''; // nothing
1026         }
1027
1028         /**
1029          * Get a notice about how many intermediate edits and users there are
1030          *
1031          * @param int $numEdits
1032          * @param int $numUsers
1033          * @param int $limit
1034          *
1035          * @return string
1036          */
1037         public static function intermediateEditsMsg( $numEdits, $numUsers, $limit ) {
1038                 if ( $numUsers === 0 ) {
1039                         $msg = 'diff-multi-sameuser';
1040                 } elseif ( $numUsers > $limit ) {
1041                         $msg = 'diff-multi-manyusers';
1042                         $numUsers = $limit;
1043                 } else {
1044                         $msg = 'diff-multi-otherusers';
1045                 }
1046
1047                 return wfMessage( $msg )->numParams( $numEdits, $numUsers )->parse();
1048         }
1049
1050         /**
1051          * Get a header for a specified revision.
1052          *
1053          * @param Revision $rev
1054          * @param string $complete 'complete' to get the header wrapped depending
1055          *        the visibility of the revision and a link to edit the page.
1056          *
1057          * @return string HTML fragment
1058          */
1059         protected function getRevisionHeader( Revision $rev, $complete = '' ) {
1060                 $lang = $this->getLanguage();
1061                 $user = $this->getUser();
1062                 $revtimestamp = $rev->getTimestamp();
1063                 $timestamp = $lang->userTimeAndDate( $revtimestamp, $user );
1064                 $dateofrev = $lang->userDate( $revtimestamp, $user );
1065                 $timeofrev = $lang->userTime( $revtimestamp, $user );
1066
1067                 $header = $this->msg(
1068                         $rev->isCurrent() ? 'currentrev-asof' : 'revisionasof',
1069                         $timestamp,
1070                         $dateofrev,
1071                         $timeofrev
1072                 )->escaped();
1073
1074                 if ( $complete !== 'complete' ) {
1075                         return $header;
1076                 }
1077
1078                 $title = $rev->getTitle();
1079
1080                 $header = Linker::linkKnown( $title, $header, [],
1081                         [ 'oldid' => $rev->getId() ] );
1082
1083                 if ( $rev->userCan( Revision::DELETED_TEXT, $user ) ) {
1084                         $editQuery = [ 'action' => 'edit' ];
1085                         if ( !$rev->isCurrent() ) {
1086                                 $editQuery['oldid'] = $rev->getId();
1087                         }
1088
1089                         $key = $title->quickUserCan( 'edit', $user ) ? 'editold' : 'viewsourceold';
1090                         $msg = $this->msg( $key )->escaped();
1091                         $editLink = $this->msg( 'parentheses' )->rawParams(
1092                                 Linker::linkKnown( $title, $msg, [], $editQuery ) )->escaped();
1093                         $header .= ' ' . Html::rawElement(
1094                                 'span',
1095                                 [ 'class' => 'mw-diff-edit' ],
1096                                 $editLink
1097                         );
1098                         if ( $rev->isDeleted( Revision::DELETED_TEXT ) ) {
1099                                 $header = Html::rawElement(
1100                                         'span',
1101                                         [ 'class' => 'history-deleted' ],
1102                                         $header
1103                                 );
1104                         }
1105                 } else {
1106                         $header = Html::rawElement( 'span', [ 'class' => 'history-deleted' ], $header );
1107                 }
1108
1109                 return $header;
1110         }
1111
1112         /**
1113          * Add the header to a diff body
1114          *
1115          * @param string $diff Diff body
1116          * @param string $otitle Old revision header
1117          * @param string $ntitle New revision header
1118          * @param string $multi Notice telling user that there are intermediate
1119          *   revisions between the ones being compared
1120          * @param string $notice Other notices, e.g. that user is viewing deleted content
1121          *
1122          * @return string
1123          */
1124         public function addHeader( $diff, $otitle, $ntitle, $multi = '', $notice = '' ) {
1125                 // shared.css sets diff in interface language/dir, but the actual content
1126                 // is often in a different language, mostly the page content language/dir
1127                 $header = Html::openElement( 'table', [
1128                         'class' => [ 'diff', 'diff-contentalign-' . $this->getDiffLang()->alignStart() ],
1129                         'data-mw' => 'interface',
1130                 ] );
1131                 $userLang = htmlspecialchars( $this->getLanguage()->getHtmlCode() );
1132
1133                 if ( !$diff && !$otitle ) {
1134                         $header .= "
1135                         <tr style='vertical-align: top;' lang='{$userLang}'>
1136                         <td class='diff-ntitle'>{$ntitle}</td>
1137                         </tr>";
1138                         $multiColspan = 1;
1139                 } else {
1140                         if ( $diff ) { // Safari/Chrome show broken output if cols not used
1141                                 $header .= "
1142                                 <col class='diff-marker' />
1143                                 <col class='diff-content' />
1144                                 <col class='diff-marker' />
1145                                 <col class='diff-content' />";
1146                                 $colspan = 2;
1147                                 $multiColspan = 4;
1148                         } else {
1149                                 $colspan = 1;
1150                                 $multiColspan = 2;
1151                         }
1152                         if ( $otitle || $ntitle ) {
1153                                 $header .= "
1154                                 <tr style='vertical-align: top;' lang='{$userLang}'>
1155                                 <td colspan='$colspan' class='diff-otitle'>{$otitle}</td>
1156                                 <td colspan='$colspan' class='diff-ntitle'>{$ntitle}</td>
1157                                 </tr>";
1158                         }
1159                 }
1160
1161                 if ( $multi != '' ) {
1162                         $header .= "<tr><td colspan='{$multiColspan}' style='text-align: center;' " .
1163                                 "class='diff-multi' lang='{$userLang}'>{$multi}</td></tr>";
1164                 }
1165                 if ( $notice != '' ) {
1166                         $header .= "<tr><td colspan='{$multiColspan}' style='text-align: center;' " .
1167                                 "lang='{$userLang}'>{$notice}</td></tr>";
1168                 }
1169
1170                 return $header . $diff . "</table>";
1171         }
1172
1173         /**
1174          * Use specified text instead of loading from the database
1175          * @param Content $oldContent
1176          * @param Content $newContent
1177          * @since 1.21
1178          */
1179         public function setContent( Content $oldContent, Content $newContent ) {
1180                 $this->mOldContent = $oldContent;
1181                 $this->mNewContent = $newContent;
1182
1183                 $this->mTextLoaded = 2;
1184                 $this->mRevisionsLoaded = true;
1185         }
1186
1187         /**
1188          * Set the language in which the diff text is written
1189          * (Defaults to page content language).
1190          * @param Language|string $lang
1191          * @since 1.19
1192          */
1193         public function setTextLanguage( $lang ) {
1194                 $this->mDiffLang = wfGetLangObj( $lang );
1195         }
1196
1197         /**
1198          * Maps a revision pair definition as accepted by DifferenceEngine constructor
1199          * to a pair of actual integers representing revision ids.
1200          *
1201          * @param int $old Revision id, e.g. from URL parameter 'oldid'
1202          * @param int|string $new Revision id or strings 'next' or 'prev', e.g. from URL parameter 'diff'
1203          *
1204          * @return int[] List of two revision ids, older first, later second.
1205          *     Zero signifies invalid argument passed.
1206          *     false signifies that there is no previous/next revision ($old is the oldest/newest one).
1207          */
1208         public function mapDiffPrevNext( $old, $new ) {
1209                 if ( $new === 'prev' ) {
1210                         // Show diff between revision $old and the previous one. Get previous one from DB.
1211                         $newid = intval( $old );
1212                         $oldid = $this->getTitle()->getPreviousRevisionID( $newid );
1213                 } elseif ( $new === 'next' ) {
1214                         // Show diff between revision $old and the next one. Get next one from DB.
1215                         $oldid = intval( $old );
1216                         $newid = $this->getTitle()->getNextRevisionID( $oldid );
1217                 } else {
1218                         $oldid = intval( $old );
1219                         $newid = intval( $new );
1220                 }
1221
1222                 return [ $oldid, $newid ];
1223         }
1224
1225         /**
1226          * Load revision IDs
1227          */
1228         private function loadRevisionIds() {
1229                 if ( $this->mRevisionsIdsLoaded ) {
1230                         return;
1231                 }
1232
1233                 $this->mRevisionsIdsLoaded = true;
1234
1235                 $old = $this->mOldid;
1236                 $new = $this->mNewid;
1237
1238                 list( $this->mOldid, $this->mNewid ) = self::mapDiffPrevNext( $old, $new );
1239                 if ( $new === 'next' && $this->mNewid === false ) {
1240                         # if no result, NewId points to the newest old revision. The only newer
1241                         # revision is cur, which is "0".
1242                         $this->mNewid = 0;
1243                 }
1244
1245                 Hooks::run(
1246                         'NewDifferenceEngine',
1247                         [ $this->getTitle(), &$this->mOldid, &$this->mNewid, $old, $new ]
1248                 );
1249         }
1250
1251         /**
1252          * Load revision metadata for the specified articles. If newid is 0, then compare
1253          * the old article in oldid to the current article; if oldid is 0, then
1254          * compare the current article to the immediately previous one (ignoring the
1255          * value of newid).
1256          *
1257          * If oldid is false, leave the corresponding revision object set
1258          * to false. This is impossible via ordinary user input, and is provided for
1259          * API convenience.
1260          *
1261          * @return bool
1262          */
1263         public function loadRevisionData() {
1264                 if ( $this->mRevisionsLoaded ) {
1265                         return true;
1266                 }
1267
1268                 // Whether it succeeds or fails, we don't want to try again
1269                 $this->mRevisionsLoaded = true;
1270
1271                 $this->loadRevisionIds();
1272
1273                 // Load the new revision object
1274                 if ( $this->mNewid ) {
1275                         $this->mNewRev = Revision::newFromId( $this->mNewid );
1276                 } else {
1277                         $this->mNewRev = Revision::newFromTitle(
1278                                 $this->getTitle(),
1279                                 false,
1280                                 Revision::READ_NORMAL
1281                         );
1282                 }
1283
1284                 if ( !$this->mNewRev instanceof Revision ) {
1285                         return false;
1286                 }
1287
1288                 // Update the new revision ID in case it was 0 (makes life easier doing UI stuff)
1289                 $this->mNewid = $this->mNewRev->getId();
1290                 $this->mNewPage = $this->mNewRev->getTitle();
1291
1292                 // Load the old revision object
1293                 $this->mOldRev = false;
1294                 if ( $this->mOldid ) {
1295                         $this->mOldRev = Revision::newFromId( $this->mOldid );
1296                 } elseif ( $this->mOldid === 0 ) {
1297                         $rev = $this->mNewRev->getPrevious();
1298                         if ( $rev ) {
1299                                 $this->mOldid = $rev->getId();
1300                                 $this->mOldRev = $rev;
1301                         } else {
1302                                 // No previous revision; mark to show as first-version only.
1303                                 $this->mOldid = false;
1304                                 $this->mOldRev = false;
1305                         }
1306                 } /* elseif ( $this->mOldid === false ) leave mOldRev false; */
1307
1308                 if ( is_null( $this->mOldRev ) ) {
1309                         return false;
1310                 }
1311
1312                 if ( $this->mOldRev ) {
1313                         $this->mOldPage = $this->mOldRev->getTitle();
1314                 }
1315
1316                 // Load tags information for both revisions
1317                 $dbr = wfGetDB( DB_SLAVE );
1318                 if ( $this->mOldid !== false ) {
1319                         $this->mOldTags = $dbr->selectField(
1320                                 'tag_summary',
1321                                 'ts_tags',
1322                                 [ 'ts_rev_id' => $this->mOldid ],
1323                                 __METHOD__
1324                         );
1325                 } else {
1326                         $this->mOldTags = false;
1327                 }
1328                 $this->mNewTags = $dbr->selectField(
1329                         'tag_summary',
1330                         'ts_tags',
1331                         [ 'ts_rev_id' => $this->mNewid ],
1332                         __METHOD__
1333                 );
1334
1335                 return true;
1336         }
1337
1338         /**
1339          * Load the text of the revisions, as well as revision data.
1340          *
1341          * @return bool
1342          */
1343         public function loadText() {
1344                 if ( $this->mTextLoaded == 2 ) {
1345                         return true;
1346                 }
1347
1348                 // Whether it succeeds or fails, we don't want to try again
1349                 $this->mTextLoaded = 2;
1350
1351                 if ( !$this->loadRevisionData() ) {
1352                         return false;
1353                 }
1354
1355                 if ( $this->mOldRev ) {
1356                         $this->mOldContent = $this->mOldRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1357                         if ( $this->mOldContent === null ) {
1358                                 return false;
1359                         }
1360                 }
1361
1362                 if ( $this->mNewRev ) {
1363                         $this->mNewContent = $this->mNewRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1364                         if ( $this->mNewContent === null ) {
1365                                 return false;
1366                         }
1367                 }
1368
1369                 return true;
1370         }
1371
1372         /**
1373          * Load the text of the new revision, not the old one
1374          *
1375          * @return bool
1376          */
1377         public function loadNewText() {
1378                 if ( $this->mTextLoaded >= 1 ) {
1379                         return true;
1380                 }
1381
1382                 $this->mTextLoaded = 1;
1383
1384                 if ( !$this->loadRevisionData() ) {
1385                         return false;
1386                 }
1387
1388                 $this->mNewContent = $this->mNewRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1389
1390                 return true;
1391         }
1392
1393 }