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
  99         /**
 100          * Constructor
 101          * @param IContextSource $context Context to use, anything else will be ignored
 102          * @param int $old Old ID we want to show and diff with.
 103          * @param string|int $new Either revision ID or 'prev' or 'next'. Default: 0.
 104          * @param int $rcid Deprecated, no longer used!
 105          * @param bool $refreshCache If set, refreshes the diff cache
 106          * @param bool $unhide If set, allow viewing deleted revs
 107          */
 108         public function __construct( $context = null, $old = 0, $new = 0, $rcid = 0,
 109                 $refreshCache = false, $unhide = false
 110         ) {
 111                 if ( $context instanceof IContextSource ) {
 112                         $this->setContext( $context );
 113                 }
 114
 115                 wfDebug( "DifferenceEngine old '$old' new '$new' rcid '$rcid'\n" );
 116
 117                 $this->mOldid = $old;
 118                 $this->mNewid = $new;
 119                 $this->mRefreshCache = $refreshCache;
 120                 $this->unhide = $unhide;
 121         }
 122
 123         /**
 124          * @param bool $value
 125          */
 126         public function setReducedLineNumbers( $value = true ) {
 127                 $this->mReducedLineNumbers = $value;
 128         }
 129
 130         /**
 131          * @return Language
 132          */
 133         public function getDiffLang() {
 134                 if ( $this->mDiffLang === null ) {
 135                         # Default language in which the diff text is written.
 136                         $this->mDiffLang = $this->getTitle()->getPageLanguage();
 137                 }
 138
 139                 return $this->mDiffLang;
 140         }
 141
 142         /**
 143          * @return bool
 144          */
 145         public function wasCacheHit() {
 146                 return $this->mCacheHit;
 147         }
 148
 149         /**
 150          * @return int
 151          */
 152         public function getOldid() {
 153                 $this->loadRevisionIds();
 154
 155                 return $this->mOldid;
 156         }
 157
 158         /**
 159          * @return bool|int
 160          */
 161         public function getNewid() {
 162                 $this->loadRevisionIds();
 163
 164                 return $this->mNewid;
 165         }
 166
 167         /**
 168          * Look up a special:Undelete link to the given deleted revision id,
 169          * as a workaround for being unable to load deleted diffs in currently.
 170          *
 171          * @param int $id Revision ID
 172          *
 173          * @return mixed URL or false
 174          */
 175         public function deletedLink( $id ) {
 176                 if ( $this->getUser()->isAllowed( 'deletedhistory' ) ) {
 177                         $dbr = wfGetDB( DB_SLAVE );
 178                         $row = $dbr->selectRow( 'archive', '*',
 179                                 array( 'ar_rev_id' => $id ),
 180                                 __METHOD__ );
 181                         if ( $row ) {
 182                                 $rev = Revision::newFromArchiveRow( $row );
 183                                 $title = Title::makeTitleSafe( $row->ar_namespace, $row->ar_title );
 184
 185                                 return SpecialPage::getTitleFor( 'Undelete' )->getFullURL( array(
 186                                         'target' => $title->getPrefixedText(),
 187                                         'timestamp' => $rev->getTimestamp()
 188                                 ) );
 189                         }
 190                 }
 191
 192                 return false;
 193         }
 194
 195         /**
 196          * Build a wikitext link toward a deleted revision, if viewable.
 197          *
 198          * @param int $id Revision ID
 199          *
 200          * @return string Wikitext fragment
 201          */
 202         public function deletedIdMarker( $id ) {
 203                 $link = $this->deletedLink( $id );
 204                 if ( $link ) {
 205                         return "[$link $id]";
 206                 } else {
 207                         return $id;
 208                 }
 209         }
 210
 211         private function showMissingRevision() {
 212                 $out = $this->getOutput();
 213
 214                 $missing = array();
 215                 if ( $this->mOldRev === null ||
 216                         ( $this->mOldRev && $this->mOldContent === null )
 217                 ) {
 218                         $missing[] = $this->deletedIdMarker( $this->mOldid );
 219                 }
 220                 if ( $this->mNewRev === null ||
 221                         ( $this->mNewRev && $this->mNewContent === null )
 222                 ) {
 223                         $missing[] = $this->deletedIdMarker( $this->mNewid );
 224                 }
 225
 226                 $out->setPageTitle( $this->msg( 'errorpagetitle' ) );
 227                 $out->addWikiMsg( 'difference-missing-revision',
 228                         $this->getLanguage()->listToText( $missing ), count( $missing ) );
 229         }
 230
 231         public function showDiffPage( $diffOnly = false ) {
 232                 wfProfileIn( __METHOD__ );
 233
 234                 # Allow frames except in certain special cases
 235                 $out = $this->getOutput();
 236                 $out->allowClickjacking();
 237                 $out->setRobotPolicy( 'noindex,nofollow' );
 238
 239                 if ( !$this->loadRevisionData() ) {
 240                         $this->showMissingRevision();
 241                         wfProfileOut( __METHOD__ );
 242
 243                         return;
 244                 }
 245
 246                 $user = $this->getUser();
 247                 $permErrors = $this->mNewPage->getUserPermissionsErrors( 'read', $user );
 248                 if ( $this->mOldPage ) { # mOldPage might not be set, see below.
 249                         $permErrors = wfMergeErrorArrays( $permErrors,
 250                                 $this->mOldPage->getUserPermissionsErrors( 'read', $user ) );
 251                 }
 252                 if ( count( $permErrors ) ) {
 253                         wfProfileOut( __METHOD__ );
 254                         throw new PermissionsError( 'read', $permErrors );
 255                 }
 256
 257                 $rollback = '';
 258
 259                 $query = array();
 260                 # Carry over 'diffonly' param via navigation links
 261                 if ( $diffOnly != $user->getBoolOption( 'diffonly' ) ) {
 262                         $query['diffonly'] = $diffOnly;
 263                 }
 264                 # Cascade unhide param in links for easy deletion browsing
 265                 if ( $this->unhide ) {
 266                         $query['unhide'] = 1;
 267                 }
 268
 269                 # Check if one of the revisions is deleted/suppressed
 270                 $deleted = $suppressed = false;
 271                 $allowed = $this->mNewRev->userCan( Revision::DELETED_TEXT, $user );
 272
 273                 $revisionTools = array();
 274
 275                 # mOldRev is false if the difference engine is called with a "vague" query for
 276                 # a diff between a version V and its previous version V' AND the version V
 277                 # is the first version of that article. In that case, V' does not exist.
 278                 if ( $this->mOldRev === false ) {
 279                         $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 280                         $samePage = true;
 281                         $oldHeader = '';
 282                 } else {
 283                         wfRunHooks( 'DiffViewHeader', array( $this, $this->mOldRev, $this->mNewRev ) );
 284
 285                         if ( $this->mNewPage->equals( $this->mOldPage ) ) {
 286                                 $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 287                                 $samePage = true;
 288                         } else {
 289                                 $out->setPageTitle( $this->msg( 'difference-title-multipage',
 290                                         $this->mOldPage->getPrefixedText(), $this->mNewPage->getPrefixedText() ) );
 291                                 $out->addSubtitle( $this->msg( 'difference-multipage' ) );
 292                                 $samePage = false;
 293                         }
 294
 295                         if ( $samePage && $this->mNewPage->quickUserCan( 'edit', $user ) ) {
 296                                 if ( $this->mNewRev->isCurrent() && $this->mNewPage->userCan( 'rollback', $user ) ) {
 297                                         $rollbackLink = Linker::generateRollback( $this->mNewRev, $this->getContext() );
 298                                         if ( $rollbackLink ) {
 299                                                 $out->preventClickjacking();
 300                                                 $rollback = '&#160;&#160;&#160;' . $rollbackLink;
 301                                         }
 302                                 }
 303
 304                                 if ( !$this->mOldRev->isDeleted( Revision::DELETED_TEXT ) &&
 305                                         !$this->mNewRev->isDeleted( Revision::DELETED_TEXT )
 306                                 ) {
 307                                         $undoLink = Html::element( 'a', array(
 308                                                         'href' => $this->mNewPage->getLocalURL( array(
 309                                                                 'action' => 'edit',
 310                                                                 'undoafter' => $this->mOldid,
 311                                                                 'undo' => $this->mNewid
 312                                                         ) ),
 313                                                         'title' => Linker::titleAttrib( 'undo' ),
 314                                                 ),
 315                                                 $this->msg( 'editundo' )->text()
 316                                         );
 317                                         $revisionTools['mw-diff-undo'] = $undoLink;
 318                                 }
 319                         }
 320
 321                         # Make "previous revision link"
 322                         if ( $samePage && $this->mOldRev->getPrevious() ) {
 323                                 $prevlink = Linker::linkKnown(
 324                                         $this->mOldPage,
 325                                         $this->msg( 'previousdiff' )->escaped(),
 326                                         array( 'id' => 'differences-prevlink' ),
 327                                         array( 'diff' => 'prev', 'oldid' => $this->mOldid ) + $query
 328                                 );
 329                         } else {
 330                                 $prevlink = '&#160;';
 331                         }
 332
 333                         if ( $this->mOldRev->isMinor() ) {
 334                                 $oldminor = ChangesList::flag( 'minor' );
 335                         } else {
 336                                 $oldminor = '';
 337                         }
 338
 339                         $ldel = $this->revisionDeleteLink( $this->mOldRev );
 340                         $oldRevisionHeader = $this->getRevisionHeader( $this->mOldRev, 'complete' );
 341                         $oldChangeTags = ChangeTags::formatSummaryRow( $this->mOldTags, 'diff' );
 342
 343                         $oldHeader = '<div id="mw-diff-otitle1"><strong>' . $oldRevisionHeader . '</strong></div>' .
 344                                 '<div id="mw-diff-otitle2">' .
 345                                 Linker::revUserTools( $this->mOldRev, !$this->unhide ) . '</div>' .
 346                                 '<div id="mw-diff-otitle3">' . $oldminor .
 347                                 Linker::revComment( $this->mOldRev, !$diffOnly, !$this->unhide ) . $ldel . '</div>' .
 348                                 '<div id="mw-diff-otitle5">' . $oldChangeTags[0] . '</div>' .
 349                                 '<div id="mw-diff-otitle4">' . $prevlink . '</div>';
 350
 351                         if ( $this->mOldRev->isDeleted( Revision::DELETED_TEXT ) ) {
 352                                 $deleted = true; // old revisions text is hidden
 353                                 if ( $this->mOldRev->isDeleted( Revision::DELETED_RESTRICTED ) ) {
 354                                         $suppressed = true; // also suppressed
 355                                 }
 356                         }
 357
 358                         # Check if this user can see the revisions
 359                         if ( !$this->mOldRev->userCan( Revision::DELETED_TEXT, $user ) ) {
 360                                 $allowed = false;
 361                         }
 362                 }
 363
 364                 # Make "next revision link"
 365                 # Skip next link on the top revision
 366                 if ( $samePage && !$this->mNewRev->isCurrent() ) {
 367                         $nextlink = Linker::linkKnown(
 368                                 $this->mNewPage,
 369                                 $this->msg( 'nextdiff' )->escaped(),
 370                                 array( 'id' => 'differences-nextlink' ),
 371                                 array( 'diff' => 'next', 'oldid' => $this->mNewid ) + $query
 372                         );
 373                 } else {
 374                         $nextlink = '&#160;';
 375                 }
 376
 377                 if ( $this->mNewRev->isMinor() ) {
 378                         $newminor = ChangesList::flag( 'minor' );
 379                 } else {
 380                         $newminor = '';
 381                 }
 382
 383                 # Handle RevisionDelete links...
 384                 $rdel = $this->revisionDeleteLink( $this->mNewRev );
 385
 386                 # Allow extensions to define their own revision tools
 387                 wfRunHooks( 'DiffRevisionTools', array( $this->mNewRev, &$revisionTools, $this->mOldRev ) );
 388                 $formattedRevisionTools = array();
 389                 // Put each one in parentheses (poor man's button)
 390                 foreach ( $revisionTools as $key => $tool ) {
 391                         $toolClass = is_string( $key ) ? $key : 'mw-diff-tool';
 392                         $element = Html::rawElement(
 393                                 'span',
 394                                 array( 'class' => $toolClass ),
 395                                 $this->msg( 'parentheses' )->rawParams( $tool )->escaped()
 396                         );
 397                         $formattedRevisionTools[] = $element;
 398                 }
 399                 $newRevisionHeader = $this->getRevisionHeader( $this->mNewRev, 'complete' ) .
 400                         ' ' . implode( ' ', $formattedRevisionTools );
 401                 $newChangeTags = ChangeTags::formatSummaryRow( $this->mNewTags, 'diff' );
 402
 403                 $newHeader = '<div id="mw-diff-ntitle1"><strong>' . $newRevisionHeader . '</strong></div>' .
 404                         '<div id="mw-diff-ntitle2">' . Linker::revUserTools( $this->mNewRev, !$this->unhide ) .
 405                         " $rollback</div>" .
 406                         '<div id="mw-diff-ntitle3">' . $newminor .
 407                         Linker::revComment( $this->mNewRev, !$diffOnly, !$this->unhide ) . $rdel . '</div>' .
 408                         '<div id="mw-diff-ntitle5">' . $newChangeTags[0] . '</div>' .
 409                         '<div id="mw-diff-ntitle4">' . $nextlink . $this->markPatrolledLink() . '</div>';
 410
 411                 if ( $this->mNewRev->isDeleted( Revision::DELETED_TEXT ) ) {
 412                         $deleted = true; // new revisions text is hidden
 413                         if ( $this->mNewRev->isDeleted( Revision::DELETED_RESTRICTED ) ) {
 414                                 $suppressed = true; // also suppressed
 415                         }
 416                 }
 417
 418                 # If the diff cannot be shown due to a deleted revision, then output
 419                 # the diff header and links to unhide (if available)...
 420                 if ( $deleted && ( !$this->unhide || !$allowed ) ) {
 421                         $this->showDiffStyle();
 422                         $multi = $this->getMultiNotice();
 423                         $out->addHTML( $this->addHeader( '', $oldHeader, $newHeader, $multi ) );
 424                         if ( !$allowed ) {
 425                                 $msg = $suppressed ? 'rev-suppressed-no-diff' : 'rev-deleted-no-diff';
 426                                 # Give explanation for why revision is not visible
 427                                 $out->wrapWikiMsg( "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 428                                         array( $msg ) );
 429                         } else {
 430                                 # Give explanation and add a link to view the diff...
 431                                 $query = $this->getRequest()->appendQueryValue( 'unhide', '1', true );
 432                                 $link = $this->getTitle()->getFullURL( $query );
 433                                 $msg = $suppressed ? 'rev-suppressed-unhide-diff' : 'rev-deleted-unhide-diff';
 434                                 $out->wrapWikiMsg(
 435                                         "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 436                                         array( $msg, $link )
 437                                 );
 438                         }
 439                 # Otherwise, output a regular diff...
 440                 } else {
 441                         # Add deletion notice if the user is viewing deleted content
 442                         $notice = '';
 443                         if ( $deleted ) {
 444                                 $msg = $suppressed ? 'rev-suppressed-diff-view' : 'rev-deleted-diff-view';
 445                                 $notice = "<div id='mw-$msg' class='mw-warning plainlinks'>\n" .
 446                                         $this->msg( $msg )->parse() .
 447                                         "</div>\n";
 448                         }
 449                         $this->showDiff( $oldHeader, $newHeader, $notice );
 450                         if ( !$diffOnly ) {
 451                                 $this->renderNewRevision();
 452                         }
 453                 }
 454                 wfProfileOut( __METHOD__ );
 455         }
 456
 457         /**
 458          * Get a link to mark the change as patrolled, or '' if there's either no
 459          * revision to patrol or the user is not allowed to to it.
 460          * Side effect: When the patrol link is build, this method will call
 461          * OutputPage::preventClickjacking() and load mediawiki.page.patrol.ajax.
 462          *
 463          * @return string
 464          */
 465         protected function markPatrolledLink() {
 466                 global $wgUseRCPatrol, $wgEnableAPI, $wgEnableWriteAPI;
 467                 $user = $this->getUser();
 468
 469                 if ( $this->mMarkPatrolledLink === null ) {
 470                         // Prepare a change patrol link, if applicable
 471                         if (
 472                                 // Is patrolling enabled and the user allowed to?
 473                                 $wgUseRCPatrol && $this->mNewPage->quickUserCan( 'patrol', $user ) &&
 474                                 // Only do this if the revision isn't more than 6 hours older
 475                                 // than the Max RC age (6h because the RC might not be cleaned out regularly)
 476                                 RecentChange::isInRCLifespan( $this->mNewRev->getTimestamp(), 21600 )
 477                         ) {
 478                                 // Look for an unpatrolled change corresponding to this diff
 479
 480                                 $db = wfGetDB( DB_SLAVE );
 481                                 $change = RecentChange::newFromConds(
 482                                         array(
 483                                                 'rc_timestamp' => $db->timestamp( $this->mNewRev->getTimestamp() ),
 484                                                 'rc_this_oldid' => $this->mNewid,
 485                                                 'rc_patrolled' => 0
 486                                         ),
 487                                         __METHOD__,
 488                                         array( 'USE INDEX' => 'rc_timestamp' )
 489                                 );
 490
 491                                 if ( $change && $change->getPerformer()->getName() !== $user->getName() ) {
 492                                         $rcid = $change->getAttribute( 'rc_id' );
 493                                 } else {
 494                                         // None found or the page has been created by the current user.
 495                                         // If the user could patrol this it already would be patrolled
 496                                         $rcid = 0;
 497                                 }
 498                                 // Build the link
 499                                 if ( $rcid ) {
 500                                         $this->getOutput()->preventClickjacking();
 501                                         if ( $wgEnableAPI && $wgEnableWriteAPI
 502                                                 && $user->isAllowed( 'writeapi' )
 503                                         ) {
 504                                                 $this->getOutput()->addModules( 'mediawiki.page.patrol.ajax' );
 505                                         }
 506
 507                                         $token = $user->getEditToken( $rcid );
 508                                         $this->mMarkPatrolledLink = ' <span class="patrollink">[' . Linker::linkKnown(
 509                                                 $this->mNewPage,
 510                                                 $this->msg( 'markaspatrolleddiff' )->escaped(),
 511                                                 array(),
 512                                                 array(
 513                                                         'action' => 'markpatrolled',
 514                                                         'rcid' => $rcid,
 515                                                         'token' => $token,
 516                                                 )
 517                                         ) . ']</span>';
 518                                 } else {
 519                                         $this->mMarkPatrolledLink = '';
 520                                 }
 521                         } else {
 522                                 $this->mMarkPatrolledLink = '';
 523                         }
 524                 }
 525
 526                 return $this->mMarkPatrolledLink;
 527         }
 528
 529         /**
 530          * @param Revision $rev
 531          *
 532          * @return string
 533          */
 534         protected function revisionDeleteLink( $rev ) {
 535                 $link = Linker::getRevDeleteLink( $this->getUser(), $rev, $rev->getTitle() );
 536                 if ( $link !== '' ) {
 537                         $link = '&#160;&#160;&#160;' . $link . ' ';
 538                 }
 539
 540                 return $link;
 541         }
 542
 543         /**
 544          * Show the new revision of the page.
 545          */
 546         public function renderNewRevision() {
 547                 wfProfileIn( __METHOD__ );
 548                 $out = $this->getOutput();
 549                 $revHeader = $this->getRevisionHeader( $this->mNewRev );
 550                 # Add "current version as of X" title
 551                 $out->addHTML( "<hr class='diff-hr' />
 552                 <h2 class='diff-currentversion-title'>{$revHeader}</h2>\n" );
 553                 # Page content may be handled by a hooked call instead...
 554                 # @codingStandardsIgnoreStart Ignoring long lines.
 555                 if ( wfRunHooks( 'ArticleContentOnDiff', array( $this, $out ) ) ) {
 556                         $this->loadNewText();
 557                         $out->setRevisionId( $this->mNewid );
 558                         $out->setRevisionTimestamp( $this->mNewRev->getTimestamp() );
 559                         $out->setArticleFlag( true );
 560
 561                         // NOTE: only needed for B/C: custom rendering of JS/CSS via hook
 562                         if ( $this->mNewPage->isCssJsSubpage() || $this->mNewPage->isCssOrJsPage() ) {
 563                                 // This needs to be synchronised with Article::showCssOrJsPage(), which sucks
 564                                 // Give hooks a chance to customise the output
 565                                 // @todo standardize this crap into one function
 566                                 if ( ContentHandler::runLegacyHooks( 'ShowRawCssJs', array( $this->mNewContent, $this->mNewPage, $out ) ) ) {
 567                                         // NOTE: deprecated hook, B/C only
 568                                         // use the content object's own rendering
 569                                         $cnt = $this->mNewRev->getContent();
 570                                         $po = $cnt ? $cnt->getParserOutput( $this->mNewRev->getTitle(), $this->mNewRev->getId() ) : null;
 571                                         if ( $po ) {
 572                                                 $out->addParserOutputContent( $po );
 573                                         }
 574                                 }
 575                         } elseif ( !wfRunHooks( 'ArticleContentViewCustom', array( $this->mNewContent, $this->mNewPage, $out ) ) ) {
 576                                 // Handled by extension
 577                         } elseif ( !ContentHandler::runLegacyHooks( 'ArticleViewCustom', array( $this->mNewContent, $this->mNewPage, $out ) ) ) {
 578                                 // NOTE: deprecated hook, B/C only
 579                                 // Handled by extension
 580                         } else {
 581                                 // Normal page
 582                                 if ( $this->getTitle()->equals( $this->mNewPage ) ) {
 583                                         // If the Title stored in the context is the same as the one
 584                                         // of the new revision, we can use its associated WikiPage
 585                                         // object.
 586                                         $wikiPage = $this->getWikiPage();
 587                                 } else {
 588                                         // Otherwise we need to create our own WikiPage object
 589                                         $wikiPage = WikiPage::factory( $this->mNewPage );
 590                                 }
 591
 592                                 $parserOutput = $this->getParserOutput( $wikiPage, $this->mNewRev );
 593
 594                                 # WikiPage::getParserOutput() should not return false, but just in case
 595                                 if ( $parserOutput ) {
 596                                         $out->addParserOutput( $parserOutput );
 597                                 }
 598                         }
 599                 }
 600                 # @codingStandardsIgnoreEnd
 601
 602                 # Add redundant patrol link on bottom...
 603                 $out->addHTML( $this->markPatrolledLink() );
 604
 605                 wfProfileOut( __METHOD__ );
 606         }
 607
 608         protected function getParserOutput( WikiPage $page, Revision $rev ) {
 609                 $parserOptions = $page->makeParserOptions( $this->getContext() );
 610
 611                 if ( !$rev->isCurrent() || !$rev->getTitle()->quickUserCan( "edit" ) ) {
 612                         $parserOptions->setEditSection( false );
 613                 }
 614
 615                 $parserOutput = $page->getParserOutput( $parserOptions, $rev->getId() );
 616
 617                 return $parserOutput;
 618         }
 619
 620         /**
 621          * Get the diff text, send it to the OutputPage object
 622          * Returns false if the diff could not be generated, otherwise returns true
 623          *
 624          * @param string|bool $otitle Header for old text or false
 625          * @param string|bool $ntitle Header for new text or false
 626          * @param string $notice HTML between diff header and body
 627          *
 628          * @return bool
 629          */
 630         public function showDiff( $otitle, $ntitle, $notice = '' ) {
 631                 $diff = $this->getDiff( $otitle, $ntitle, $notice );
 632                 if ( $diff === false ) {
 633                         $this->showMissingRevision();
 634
 635                         return false;
 636                 } else {
 637                         $this->showDiffStyle();
 638                         $this->getOutput()->addHTML( $diff );
 639
 640                         return true;
 641                 }
 642         }
 643
 644         /**
 645          * Add style sheets and supporting JS for diff display.
 646          */
 647         public function showDiffStyle() {
 648                 $this->getOutput()->addModuleStyles( 'mediawiki.action.history.diff' );
 649         }
 650
 651         /**
 652          * Get complete diff table, including header
 653          *
 654          * @param string|bool $otitle Header for old text or false
 655          * @param string|bool $ntitle Header for new text or false
 656          * @param string $notice HTML between diff header and body
 657          *
 658          * @return mixed
 659          */
 660         public function getDiff( $otitle, $ntitle, $notice = '' ) {
 661                 $body = $this->getDiffBody();
 662                 if ( $body === false ) {
 663                         return false;
 664                 }
 665
 666                 $multi = $this->getMultiNotice();
 667                 // Display a message when the diff is empty
 668                 if ( $body === '' ) {
 669                         $notice .= '<div class="mw-diff-empty">' .
 670                                 $this->msg( 'diff-empty' )->parse() .
 671                                 "</div>\n";
 672                 }
 673
 674                 return $this->addHeader( $body, $otitle, $ntitle, $multi, $notice );
 675         }
 676
 677         /**
 678          * Get the diff table body, without header
 679          *
 680          * @return mixed (string/false)
 681          */
 682         public function getDiffBody() {
 683                 global $wgMemc;
 684                 wfProfileIn( __METHOD__ );
 685                 $this->mCacheHit = true;
 686                 // Check if the diff should be hidden from this user
 687                 if ( !$this->loadRevisionData() ) {
 688                         wfProfileOut( __METHOD__ );
 689
 690                         return false;
 691                 } elseif ( $this->mOldRev &&
 692                         !$this->mOldRev->userCan( Revision::DELETED_TEXT, $this->getUser() )
 693                 ) {
 694                         wfProfileOut( __METHOD__ );
 695
 696                         return false;
 697                 } elseif ( $this->mNewRev &&
 698                         !$this->mNewRev->userCan( Revision::DELETED_TEXT, $this->getUser() )
 699                 ) {
 700                         wfProfileOut( __METHOD__ );
 701
 702                         return false;
 703                 }
 704                 // Short-circuit
 705                 if ( $this->mOldRev === false || ( $this->mOldRev && $this->mNewRev
 706                         && $this->mOldRev->getID() == $this->mNewRev->getID() )
 707                 ) {
 708                         wfProfileOut( __METHOD__ );
 709
 710                         return '';
 711                 }
 712                 // Cacheable?
 713                 $key = false;
 714                 if ( $this->mOldid && $this->mNewid ) {
 715                         $key = $this->getDiffBodyCacheKey();
 716
 717                         // Try cache
 718                         if ( !$this->mRefreshCache ) {
 719                                 $difftext = $wgMemc->get( $key );
 720                                 if ( $difftext ) {
 721                                         wfIncrStats( 'diff_cache_hit' );
 722                                         $difftext = $this->localiseLineNumbers( $difftext );
 723                                         $difftext .= "\n<!-- diff cache key $key -->\n";
 724                                         wfProfileOut( __METHOD__ );
 725
 726                                         return $difftext;
 727                                 }
 728                         } // don't try to load but save the result
 729                 }
 730                 $this->mCacheHit = false;
 731
 732                 // Loadtext is permission safe, this just clears out the diff
 733                 if ( !$this->loadText() ) {
 734                         wfProfileOut( __METHOD__ );
 735
 736                         return false;
 737                 }
 738
 739                 $difftext = $this->generateContentDiffBody( $this->mOldContent, $this->mNewContent );
 740
 741                 // Save to cache for 7 days
 742                 if ( !wfRunHooks( 'AbortDiffCache', array( &$this ) ) ) {
 743                         wfIncrStats( 'diff_uncacheable' );
 744                 } elseif ( $key !== false && $difftext !== false ) {
 745                         wfIncrStats( 'diff_cache_miss' );
 746                         $wgMemc->set( $key, $difftext, 7 * 86400 );
 747                 } else {
 748                         wfIncrStats( 'diff_uncacheable' );
 749                 }
 750                 // Replace line numbers with the text in the user's language
 751                 if ( $difftext !== false ) {
 752                         $difftext = $this->localiseLineNumbers( $difftext );
 753                 }
 754                 wfProfileOut( __METHOD__ );
 755
 756                 return $difftext;
 757         }
 758
 759         /**
 760          * Returns the cache key for diff body text or content.
 761          *
 762          * @since 1.23
 763          *
 764          * @throws MWException
 765          * @return string
 766          */
 767         protected function getDiffBodyCacheKey() {
 768                 if ( !$this->mOldid || !$this->mNewid ) {
 769                         throw new MWException( 'mOldid and mNewid must be set to get diff cache key.' );
 770                 }
 771
 772                 return wfMemcKey( 'diff', 'version', MW_DIFF_VERSION,
 773                         'oldid', $this->mOldid, 'newid', $this->mNewid );
 774         }
 775
 776         /**
 777          * Generate a diff, no caching.
 778          *
 779          * This implementation uses generateTextDiffBody() to generate a diff based on the default
 780          * serialization of the given Content objects. This will fail if $old or $new are not
 781          * instances of TextContent.
 782          *
 783          * Subclasses may override this to provide a different rendering for the diff,
 784          * perhaps taking advantage of the content's native form. This is required for all content
 785          * models that are not text based.
 786          *
 787          * @since 1.21
 788          *
 789          * @param Content $old Old content
 790          * @param Content $new New content
 791          *
 792          * @throws MWException If old or new content is not an instance of TextContent.
 793          * @return bool|string
 794          */
 795         public function generateContentDiffBody( Content $old, Content $new ) {
 796                 if ( !( $old instanceof TextContent ) ) {
 797                         throw new MWException( "Diff not implemented for " . get_class( $old ) . "; " .
 798                                 "override generateContentDiffBody to fix this." );
 799                 }
 800
 801                 if ( !( $new instanceof TextContent ) ) {
 802                         throw new MWException( "Diff not implemented for " . get_class( $new ) . "; "
 803                                 . "override generateContentDiffBody to fix this." );
 804                 }
 805
 806                 $otext = $old->serialize();
 807                 $ntext = $new->serialize();
 808
 809                 return $this->generateTextDiffBody( $otext, $ntext );
 810         }
 811
 812         /**
 813          * Generate a diff, no caching
 814          *
 815          * @param string $otext Old text, must be already segmented
 816          * @param string $ntext New text, must be already segmented
 817          *
 818          * @return bool|string
 819          * @deprecated since 1.21, use generateContentDiffBody() instead!
 820          */
 821         public function generateDiffBody( $otext, $ntext ) {
 822                 ContentHandler::deprecated( __METHOD__, "1.21" );
 823
 824                 return $this->generateTextDiffBody( $otext, $ntext );
 825         }
 826
 827         /**
 828          * Generate a diff, no caching
 829          *
 830          * @todo move this to TextDifferenceEngine, make DifferenceEngine abstract. At some point.
 831          *
 832          * @param string $otext Old text, must be already segmented
 833          * @param string $ntext New text, must be already segmented
 834          *
 835          * @return bool|string
 836          */
 837         public function generateTextDiffBody( $otext, $ntext ) {
 838                 global $wgExternalDiffEngine, $wgContLang;
 839
 840                 wfProfileIn( __METHOD__ );
 841
 842                 $otext = str_replace( "\r\n", "\n", $otext );
 843                 $ntext = str_replace( "\r\n", "\n", $ntext );
 844
 845                 if ( $wgExternalDiffEngine == 'wikidiff' && function_exists( 'wikidiff_do_diff' ) ) {
 846                         # For historical reasons, external diff engine expects
 847                         # input text to be HTML-escaped already
 848                         $otext = htmlspecialchars( $wgContLang->segmentForDiff( $otext ) );
 849                         $ntext = htmlspecialchars( $wgContLang->segmentForDiff( $ntext ) );
 850                         wfProfileOut( __METHOD__ );
 851
 852                         return $wgContLang->unsegmentForDiff( wikidiff_do_diff( $otext, $ntext, 2 ) ) .
 853                         $this->debug( 'wikidiff1' );
 854                 }
 855
 856                 if ( $wgExternalDiffEngine == 'wikidiff2' && function_exists( 'wikidiff2_do_diff' ) ) {
 857                         # Better external diff engine, the 2 may some day be dropped
 858                         # This one does the escaping and segmenting itself
 859                         wfProfileIn( 'wikidiff2_do_diff' );
 860                         $text = wikidiff2_do_diff( $otext, $ntext, 2 );
 861                         $text .= $this->debug( 'wikidiff2' );
 862                         wfProfileOut( 'wikidiff2_do_diff' );
 863                         wfProfileOut( __METHOD__ );
 864
 865                         return $text;
 866                 }
 867                 if ( $wgExternalDiffEngine != 'wikidiff3' && $wgExternalDiffEngine !== false ) {
 868                         # Diff via the shell
 869                         $tmpDir = wfTempDir();
 870                         $tempName1 = tempnam( $tmpDir, 'diff_' );
 871                         $tempName2 = tempnam( $tmpDir, 'diff_' );
 872
 873                         $tempFile1 = fopen( $tempName1, "w" );
 874                         if ( !$tempFile1 ) {
 875                                 wfProfileOut( __METHOD__ );
 876
 877                                 return false;
 878                         }
 879                         $tempFile2 = fopen( $tempName2, "w" );
 880                         if ( !$tempFile2 ) {
 881                                 wfProfileOut( __METHOD__ );
 882
 883                                 return false;
 884                         }
 885                         fwrite( $tempFile1, $otext );
 886                         fwrite( $tempFile2, $ntext );
 887                         fclose( $tempFile1 );
 888                         fclose( $tempFile2 );
 889                         $cmd = wfEscapeShellArg( $wgExternalDiffEngine, $tempName1, $tempName2 );
 890                         wfProfileIn( __METHOD__ . "-shellexec" );
 891                         $difftext = wfShellExec( $cmd );
 892                         $difftext .= $this->debug( "external $wgExternalDiffEngine" );
 893                         wfProfileOut( __METHOD__ . "-shellexec" );
 894                         unlink( $tempName1 );
 895                         unlink( $tempName2 );
 896                         wfProfileOut( __METHOD__ );
 897
 898                         return $difftext;
 899                 }
 900
 901                 # Native PHP diff
 902                 $ota = explode( "\n", $wgContLang->segmentForDiff( $otext ) );
 903                 $nta = explode( "\n", $wgContLang->segmentForDiff( $ntext ) );
 904                 $diffs = new Diff( $ota, $nta );
 905                 $formatter = new TableDiffFormatter();
 906                 $difftext = $wgContLang->unsegmentForDiff( $formatter->format( $diffs ) ) .
 907                         wfProfileOut( __METHOD__ );
 908
 909                 return $difftext;
 910         }
 911
 912         /**
 913          * Generate a debug comment indicating diff generating time,
 914          * server node, and generator backend.
 915          *
 916          * @param string $generator : What diff engine was used
 917          *
 918          * @return string
 919          */
 920         protected function debug( $generator = "internal" ) {
 921                 global $wgShowHostnames;
 922                 if ( !$this->enableDebugComment ) {
 923                         return '';
 924                 }
 925                 $data = array( $generator );
 926                 if ( $wgShowHostnames ) {
 927                         $data[] = wfHostname();
 928                 }
 929                 $data[] = wfTimestamp( TS_DB );
 930
 931                 return "<!-- diff generator: " .
 932                         implode( " ", array_map( "htmlspecialchars", $data ) ) .
 933                         " -->\n";
 934         }
 935
 936         /**
 937          * Replace line numbers with the text in the user's language
 938          *
 939          * @param string $text
 940          *
 941          * @return mixed
 942          */
 943         public function localiseLineNumbers( $text ) {
 944                 return preg_replace_callback(
 945                         '/<!--LINE (\d+)-->/',
 946                         array( &$this, 'localiseLineNumbersCb' ),
 947                         $text
 948                 );
 949         }
 950
 951         public function localiseLineNumbersCb( $matches ) {
 952                 if ( $matches[1] === '1' && $this->mReducedLineNumbers ) {
 953                         return '';
 954                 }
 955
 956                 return $this->msg( 'lineno' )->numParams( $matches[1] )->escaped();
 957         }
 958
 959         /**
 960          * If there are revisions between the ones being compared, return a note saying so.
 961          *
 962          * @return string
 963          */
 964         public function getMultiNotice() {
 965                 if ( !is_object( $this->mOldRev ) || !is_object( $this->mNewRev ) ) {
 966                         return '';
 967                 } elseif ( !$this->mOldPage->equals( $this->mNewPage ) ) {
 968                         // Comparing two different pages? Count would be meaningless.
 969                         return '';
 970                 }
 971
 972                 if ( $this->mOldRev->getTimestamp() > $this->mNewRev->getTimestamp() ) {
 973                         $oldRev = $this->mNewRev; // flip
 974                         $newRev = $this->mOldRev; // flip
 975                 } else { // normal case
 976                         $oldRev = $this->mOldRev;
 977                         $newRev = $this->mNewRev;
 978                 }
 979
 980                 // Sanity: don't show the notice if too many rows must be scanned
 981                 // @todo show some special message for that case
 982                 $nEdits = $this->mNewPage->countRevisionsBetween( $oldRev, $newRev, 1000 );
 983                 if ( $nEdits > 0 && $nEdits <= 1000 ) {
 984                         $limit = 100; // use diff-multi-manyusers if too many users
 985                         $users = $this->mNewPage->getAuthorsBetween( $oldRev, $newRev, $limit );
 986                         $numUsers = count( $users );
 987
 988                         if ( $numUsers == 1 && $users[0] == $newRev->getRawUserText() ) {
 989                                 $numUsers = 0; // special case to say "by the same user" instead of "by one other user"
 990                         }
 991
 992                         return self::intermediateEditsMsg( $nEdits, $numUsers, $limit );
 993                 }
 994
 995                 return ''; // nothing
 996         }
 997
 998         /**
 999          * Get a notice about how many intermediate edits and users there are
1000          *
1001          * @param int $numEdits
1002          * @param int $numUsers
1003          * @param int $limit
1004          *
1005          * @return string
1006          */
1007         public static function intermediateEditsMsg( $numEdits, $numUsers, $limit ) {
1008                 if ( $numUsers === 0 ) {
1009                         $msg = 'diff-multi-sameuser';
1010                 } elseif ( $numUsers > $limit ) {
1011                         $msg = 'diff-multi-manyusers';
1012                         $numUsers = $limit;
1013                 } else {
1014                         $msg = 'diff-multi-otherusers';
1015                 }
1016
1017                 return wfMessage( $msg )->numParams( $numEdits, $numUsers )->parse();
1018         }
1019
1020         /**
1021          * Get a header for a specified revision.
1022          *
1023          * @param Revision $rev
1024          * @param string $complete 'complete' to get the header wrapped depending
1025          *        the visibility of the revision and a link to edit the page.
1026          *
1027          * @return string HTML fragment
1028          */
1029         protected function getRevisionHeader( Revision $rev, $complete = '' ) {
1030                 $lang = $this->getLanguage();
1031                 $user = $this->getUser();
1032                 $revtimestamp = $rev->getTimestamp();
1033                 $timestamp = $lang->userTimeAndDate( $revtimestamp, $user );
1034                 $dateofrev = $lang->userDate( $revtimestamp, $user );
1035                 $timeofrev = $lang->userTime( $revtimestamp, $user );
1036
1037                 $header = $this->msg(
1038                         $rev->isCurrent() ? 'currentrev-asof' : 'revisionasof',
1039                         $timestamp,
1040                         $dateofrev,
1041                         $timeofrev
1042                 )->escaped();
1043
1044                 if ( $complete !== 'complete' ) {
1045                         return $header;
1046                 }
1047
1048                 $title = $rev->getTitle();
1049
1050                 $header = Linker::linkKnown( $title, $header, array(),
1051                         array( 'oldid' => $rev->getID() ) );
1052
1053                 if ( $rev->userCan( Revision::DELETED_TEXT, $user ) ) {
1054                         $editQuery = array( 'action' => 'edit' );
1055                         if ( !$rev->isCurrent() ) {
1056                                 $editQuery['oldid'] = $rev->getID();
1057                         }
1058
1059                         $key = $title->quickUserCan( 'edit', $user ) ? 'editold' : 'viewsourceold';
1060                         $msg = $this->msg( $key )->escaped();
1061                         $editLink = $this->msg( 'parentheses' )->rawParams(
1062                                 Linker::linkKnown( $title, $msg, array( ), $editQuery ) )->plain();
1063                         $header .= ' ' . Html::rawElement(
1064                                 'span',
1065                                 array( 'class' => 'mw-diff-edit' ),
1066                                 $editLink
1067                         );
1068                         if ( $rev->isDeleted( Revision::DELETED_TEXT ) ) {
1069                                 $header = Html::rawElement(
1070                                         'span',
1071                                         array( 'class' => 'history-deleted' ),
1072                                         $header
1073                                 );
1074                         }
1075                 } else {
1076                         $header = Html::rawElement( 'span', array( 'class' => 'history-deleted' ), $header );
1077                 }
1078
1079                 return $header;
1080         }
1081
1082         /**
1083          * Add the header to a diff body
1084          *
1085          * @param string $diff Diff body
1086          * @param string $otitle Old revision header
1087          * @param string $ntitle New revision header
1088          * @param string $multi Notice telling user that there are intermediate
1089          *   revisions between the ones being compared
1090          * @param string $notice Other notices, e.g. that user is viewing deleted content
1091          *
1092          * @return string
1093          */
1094         public function addHeader( $diff, $otitle, $ntitle, $multi = '', $notice = '' ) {
1095                 // shared.css sets diff in interface language/dir, but the actual content
1096                 // is often in a different language, mostly the page content language/dir
1097                 $tableClass = 'diff diff-contentalign-' . htmlspecialchars( $this->getDiffLang()->alignStart() );
1098                 $header = "<table class='$tableClass'>";
1099
1100                 if ( !$diff && !$otitle ) {
1101                         $header .= "
1102                         <tr style='vertical-align: top;'>
1103                         <td class='diff-ntitle'>{$ntitle}</td>
1104                         </tr>";
1105                         $multiColspan = 1;
1106                 } else {
1107                         if ( $diff ) { // Safari/Chrome show broken output if cols not used
1108                                 $header .= "
1109                                 <col class='diff-marker' />
1110                                 <col class='diff-content' />
1111                                 <col class='diff-marker' />
1112                                 <col class='diff-content' />";
1113                                 $colspan = 2;
1114                                 $multiColspan = 4;
1115                         } else {
1116                                 $colspan = 1;
1117                                 $multiColspan = 2;
1118                         }
1119                         if ( $otitle || $ntitle ) {
1120                                 $header .= "
1121                                 <tr style='vertical-align: top;'>
1122                                 <td colspan='$colspan' class='diff-otitle'>{$otitle}</td>
1123                                 <td colspan='$colspan' class='diff-ntitle'>{$ntitle}</td>
1124                                 </tr>";
1125                         }
1126                 }
1127
1128                 if ( $multi != '' ) {
1129                         $header .= "<tr><td colspan='{$multiColspan}' style='text-align: center;' " .
1130                                 "class='diff-multi'>{$multi}</td></tr>";
1131                 }
1132                 if ( $notice != '' ) {
1133                         $header .= "<tr><td colspan='{$multiColspan}' style='text-align: center;'>{$notice}</td></tr>";
1134                 }
1135
1136                 return $header . $diff . "</table>";
1137         }
1138
1139         /**
1140          * Use specified text instead of loading from the database
1141          * @deprecated since 1.21, use setContent() instead.
1142          */
1143         public function setText( $oldText, $newText ) {
1144                 ContentHandler::deprecated( __METHOD__, "1.21" );
1145
1146                 $oldContent = ContentHandler::makeContent( $oldText, $this->getTitle() );
1147                 $newContent = ContentHandler::makeContent( $newText, $this->getTitle() );
1148
1149                 $this->setContent( $oldContent, $newContent );
1150         }
1151
1152         /**
1153          * Use specified text instead of loading from the database
1154          * @param Content $oldContent
1155          * @param Content $newContent
1156          * @since 1.21
1157          */
1158         public function setContent( Content $oldContent, Content $newContent ) {
1159                 $this->mOldContent = $oldContent;
1160                 $this->mNewContent = $newContent;
1161
1162                 $this->mTextLoaded = 2;
1163                 $this->mRevisionsLoaded = true;
1164         }
1165
1166         /**
1167          * Set the language in which the diff text is written
1168          * (Defaults to page content language).
1169          * @param Language|string $lang
1170          * @since 1.19
1171          */
1172         public function setTextLanguage( $lang ) {
1173                 $this->mDiffLang = wfGetLangObj( $lang );
1174         }
1175
1176         /**
1177          * Maps a revision pair definition as accepted by DifferenceEngine constructor
1178          * to a pair of actual integers representing revision ids.
1179          *
1180          * @param int $old Revision id, e.g. from URL parameter 'oldid'
1181          * @param int|string $new Revision id or strings 'next' or 'prev', e.g. from URL parameter 'diff'
1182          *
1183          * @return int[] List of two revision ids, older first, later second.
1184          *     Zero signifies invalid argument passed.
1185          *     false signifies that there is no previous/next revision ($old is the oldest/newest one).
1186          */
1187         public function mapDiffPrevNext( $old, $new ) {
1188                 if ( $new === 'prev' ) {
1189                         // Show diff between revision $old and the previous one. Get previous one from DB.
1190                         $newid = intval( $old );
1191                         $oldid = $this->getTitle()->getPreviousRevisionID( $newid );
1192                 } elseif ( $new === 'next' ) {
1193                         // Show diff between revision $old and the next one. Get next one from DB.
1194                         $oldid = intval( $old );
1195                         $newid = $this->getTitle()->getNextRevisionID( $oldid );
1196                 } else {
1197                         $oldid = intval( $old );
1198                         $newid = intval( $new );
1199                 }
1200
1201                 return array( $oldid, $newid );
1202         }
1203
1204         /**
1205          * Load revision IDs
1206          */
1207         private function loadRevisionIds() {
1208                 if ( $this->mRevisionsIdsLoaded ) {
1209                         return;
1210                 }
1211
1212                 $this->mRevisionsIdsLoaded = true;
1213
1214                 $old = $this->mOldid;
1215                 $new = $this->mNewid;
1216
1217                 list( $this->mOldid, $this->mNewid ) = self::mapDiffPrevNext( $old, $new );
1218                 if ( $new === 'next' && $this->mNewid === false ) {
1219                         # if no result, NewId points to the newest old revision. The only newer
1220                         # revision is cur, which is "0".
1221                         $this->mNewid = 0;
1222                 }
1223
1224                 wfRunHooks(
1225                         'NewDifferenceEngine',
1226                         array( $this->getTitle(), &$this->mOldid, &$this->mNewid, $old, $new )
1227                 );
1228         }
1229
1230         /**
1231          * Load revision metadata for the specified articles. If newid is 0, then compare
1232          * the old article in oldid to the current article; if oldid is 0, then
1233          * compare the current article to the immediately previous one (ignoring the
1234          * value of newid).
1235          *
1236          * If oldid is false, leave the corresponding revision object set
1237          * to false. This is impossible via ordinary user input, and is provided for
1238          * API convenience.
1239          *
1240          * @return bool
1241          */
1242         public function loadRevisionData() {
1243                 if ( $this->mRevisionsLoaded ) {
1244                         return true;
1245                 }
1246
1247                 // Whether it succeeds or fails, we don't want to try again
1248                 $this->mRevisionsLoaded = true;
1249
1250                 $this->loadRevisionIds();
1251
1252                 // Load the new revision object
1253                 if ( $this->mNewid ) {
1254                         $this->mNewRev = Revision::newFromId( $this->mNewid );
1255                 } else {
1256                         $this->mNewRev = Revision::newFromTitle(
1257                                 $this->getTitle(),
1258                                 false,
1259                                 Revision::READ_NORMAL
1260                         );
1261                 }
1262
1263                 if ( !$this->mNewRev instanceof Revision ) {
1264                         return false;
1265                 }
1266
1267                 // Update the new revision ID in case it was 0 (makes life easier doing UI stuff)
1268                 $this->mNewid = $this->mNewRev->getId();
1269                 $this->mNewPage = $this->mNewRev->getTitle();
1270
1271                 // Load the old revision object
1272                 $this->mOldRev = false;
1273                 if ( $this->mOldid ) {
1274                         $this->mOldRev = Revision::newFromId( $this->mOldid );
1275                 } elseif ( $this->mOldid === 0 ) {
1276                         $rev = $this->mNewRev->getPrevious();
1277                         if ( $rev ) {
1278                                 $this->mOldid = $rev->getId();
1279                                 $this->mOldRev = $rev;
1280                         } else {
1281                                 // No previous revision; mark to show as first-version only.
1282                                 $this->mOldid = false;
1283                                 $this->mOldRev = false;
1284                         }
1285                 } /* elseif ( $this->mOldid === false ) leave mOldRev false; */
1286
1287                 if ( is_null( $this->mOldRev ) ) {
1288                         return false;
1289                 }
1290
1291                 if ( $this->mOldRev ) {
1292                         $this->mOldPage = $this->mOldRev->getTitle();
1293                 }
1294
1295                 // Load tags information for both revisions
1296                 $dbr = wfGetDB( DB_SLAVE );
1297                 if ( $this->mOldid !== false ) {
1298                         $this->mOldTags = $dbr->selectField(
1299                                 'tag_summary',
1300                                 'ts_tags',
1301                                 array( 'ts_rev_id' => $this->mOldid ),
1302                                 __METHOD__
1303                         );
1304                 } else {
1305                         $this->mOldTags = false;
1306                 }
1307                 $this->mNewTags = $dbr->selectField(
1308                         'tag_summary',
1309                         'ts_tags',
1310                         array( 'ts_rev_id' => $this->mNewid ),
1311                         __METHOD__
1312                 );
1313
1314                 return true;
1315         }
1316
1317         /**
1318          * Load the text of the revisions, as well as revision data.
1319          *
1320          * @return bool
1321          */
1322         public function loadText() {
1323                 if ( $this->mTextLoaded == 2 ) {
1324                         return true;
1325                 }
1326
1327                 // Whether it succeeds or fails, we don't want to try again
1328                 $this->mTextLoaded = 2;
1329
1330                 if ( !$this->loadRevisionData() ) {
1331                         return false;
1332                 }
1333
1334                 if ( $this->mOldRev ) {
1335                         $this->mOldContent = $this->mOldRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1336                         if ( $this->mOldContent === null ) {
1337                                 return false;
1338                         }
1339                 }
1340
1341                 if ( $this->mNewRev ) {
1342                         $this->mNewContent = $this->mNewRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1343                         if ( $this->mNewContent === null ) {
1344                                 return false;
1345                         }
1346                 }
1347
1348                 return true;
1349         }
1350
1351         /**
1352          * Load the text of the new revision, not the old one
1353          *
1354          * @return bool
1355          */
1356         public function loadNewText() {
1357                 if ( $this->mTextLoaded >= 1 ) {
1358                         return true;
1359                 }
1360
1361                 $this->mTextLoaded = 1;
1362
1363                 if ( !$this->loadRevisionData() ) {
1364                         return false;
1365                 }
1366
1367                 $this->mNewContent = $this->mNewRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1368
1369                 return true;
1370         }
1371
1372 }