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         function __construct( $context = null, $old = 0, $new = 0, $rcid = 0,
 109                 $refreshCache = false, $unhide = false ) {
 110                 if ( $context instanceof IContextSource ) {
 111                         $this->setContext( $context );
 112                 }
 113
 114                 wfDebug( "DifferenceEngine old '$old' new '$new' rcid '$rcid'\n" );
 115
 116                 $this->mOldid = $old;
 117                 $this->mNewid = $new;
 118                 $this->mRefreshCache = $refreshCache;
 119                 $this->unhide = $unhide;
 120         }
 121
 122         /**
 123          * @param bool $value
 124          */
 125         function setReducedLineNumbers( $value = true ) {
 126                 $this->mReducedLineNumbers = $value;
 127         }
 128
 129         /**
 130          * @return Language
 131          */
 132         function getDiffLang() {
 133                 if ( $this->mDiffLang === null ) {
 134                         # Default language in which the diff text is written.
 135                         $this->mDiffLang = $this->getTitle()->getPageLanguage();
 136                 }
 137
 138                 return $this->mDiffLang;
 139         }
 140
 141         /**
 142          * @return bool
 143          */
 144         function wasCacheHit() {
 145                 return $this->mCacheHit;
 146         }
 147
 148         /**
 149          * @return int
 150          */
 151         function getOldid() {
 152                 $this->loadRevisionIds();
 153
 154                 return $this->mOldid;
 155         }
 156
 157         /**
 158          * @return bool|int
 159          */
 160         function getNewid() {
 161                 $this->loadRevisionIds();
 162
 163                 return $this->mNewid;
 164         }
 165
 166         /**
 167          * Look up a special:Undelete link to the given deleted revision id,
 168          * as a workaround for being unable to load deleted diffs in currently.
 169          *
 170          * @param int $id Revision ID
 171          *
 172          * @return mixed URL or false
 173          */
 174         function deletedLink( $id ) {
 175                 if ( $this->getUser()->isAllowed( 'deletedhistory' ) ) {
 176                         $dbr = wfGetDB( DB_SLAVE );
 177                         $row = $dbr->selectRow( 'archive', '*',
 178                                 array( 'ar_rev_id' => $id ),
 179                                 __METHOD__ );
 180                         if ( $row ) {
 181                                 $rev = Revision::newFromArchiveRow( $row );
 182                                 $title = Title::makeTitleSafe( $row->ar_namespace, $row->ar_title );
 183
 184                                 return SpecialPage::getTitleFor( 'Undelete' )->getFullURL( array(
 185                                         'target' => $title->getPrefixedText(),
 186                                         'timestamp' => $rev->getTimestamp()
 187                                 ) );
 188                         }
 189                 }
 190
 191                 return false;
 192         }
 193
 194         /**
 195          * Build a wikitext link toward a deleted revision, if viewable.
 196          *
 197          * @param int $id Revision ID
 198          *
 199          * @return string Wikitext fragment
 200          */
 201         function deletedIdMarker( $id ) {
 202                 $link = $this->deletedLink( $id );
 203                 if ( $link ) {
 204                         return "[$link $id]";
 205                 } else {
 206                         return $id;
 207                 }
 208         }
 209
 210         private function showMissingRevision() {
 211                 $out = $this->getOutput();
 212
 213                 $missing = array();
 214                 if ( $this->mOldRev === null ||
 215                         ( $this->mOldRev && $this->mOldContent === null )
 216                 ) {
 217                         $missing[] = $this->deletedIdMarker( $this->mOldid );
 218                 }
 219                 if ( $this->mNewRev === null ||
 220                         ( $this->mNewRev && $this->mNewContent === null )
 221                 ) {
 222                         $missing[] = $this->deletedIdMarker( $this->mNewid );
 223                 }
 224
 225                 $out->setPageTitle( $this->msg( 'errorpagetitle' ) );
 226                 $out->addWikiMsg( 'difference-missing-revision',
 227                         $this->getLanguage()->listToText( $missing ), count( $missing ) );
 228         }
 229
 230         function showDiffPage( $diffOnly = false ) {
 231                 wfProfileIn( __METHOD__ );
 232
 233                 # Allow frames except in certain special cases
 234                 $out = $this->getOutput();
 235                 $out->allowClickjacking();
 236                 $out->setRobotPolicy( 'noindex,nofollow' );
 237
 238                 if ( !$this->loadRevisionData() ) {
 239                         $this->showMissingRevision();
 240                         wfProfileOut( __METHOD__ );
 241
 242                         return;
 243                 }
 244
 245                 $user = $this->getUser();
 246                 $permErrors = $this->mNewPage->getUserPermissionsErrors( 'read', $user );
 247                 if ( $this->mOldPage ) { # mOldPage might not be set, see below.
 248                         $permErrors = wfMergeErrorArrays( $permErrors,
 249                                 $this->mOldPage->getUserPermissionsErrors( 'read', $user ) );
 250                 }
 251                 if ( count( $permErrors ) ) {
 252                         wfProfileOut( __METHOD__ );
 253                         throw new PermissionsError( 'read', $permErrors );
 254                 }
 255
 256                 $rollback = '';
 257
 258                 $query = array();
 259                 # Carry over 'diffonly' param via navigation links
 260                 if ( $diffOnly != $user->getBoolOption( 'diffonly' ) ) {
 261                         $query['diffonly'] = $diffOnly;
 262                 }
 263                 # Cascade unhide param in links for easy deletion browsing
 264                 if ( $this->unhide ) {
 265                         $query['unhide'] = 1;
 266                 }
 267
 268                 # Check if one of the revisions is deleted/suppressed
 269                 $deleted = $suppressed = false;
 270                 $allowed = $this->mNewRev->userCan( Revision::DELETED_TEXT, $user );
 271
 272                 $revisionTools = array();
 273
 274                 # mOldRev is false if the difference engine is called with a "vague" query for
 275                 # a diff between a version V and its previous version V' AND the version V
 276                 # is the first version of that article. In that case, V' does not exist.
 277                 if ( $this->mOldRev === false ) {
 278                         $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 279                         $samePage = true;
 280                         $oldHeader = '';
 281                 } else {
 282                         wfRunHooks( 'DiffViewHeader', array( $this, $this->mOldRev, $this->mNewRev ) );
 283
 284                         if ( $this->mNewPage->equals( $this->mOldPage ) ) {
 285                                 $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 286                                 $samePage = true;
 287                         } else {
 288                                 $out->setPageTitle( $this->msg( 'difference-title-multipage',
 289                                         $this->mOldPage->getPrefixedText(), $this->mNewPage->getPrefixedText() ) );
 290                                 $out->addSubtitle( $this->msg( 'difference-multipage' ) );
 291                                 $samePage = false;
 292                         }
 293
 294                         if ( $samePage && $this->mNewPage->quickUserCan( 'edit', $user ) ) {
 295                                 if ( $this->mNewRev->isCurrent() && $this->mNewPage->userCan( 'rollback', $user ) ) {
 296                                         $rollbackLink = Linker::generateRollback( $this->mNewRev, $this->getContext() );
 297                                         if ( $rollbackLink ) {
 298                                                 $out->preventClickjacking();
 299                                                 $rollback = '&#160;&#160;&#160;' . $rollbackLink;
 300                                         }
 301                                 }
 302
 303                                 if ( !$this->mOldRev->isDeleted( Revision::DELETED_TEXT ) &&
 304                                         !$this->mNewRev->isDeleted( Revision::DELETED_TEXT )
 305                                 ) {
 306                                         $undoLink = Html::element( 'a', array(
 307                                                         'href' => $this->mNewPage->getLocalURL( array(
 308                                                                 'action' => 'edit',
 309                                                                 'undoafter' => $this->mOldid,
 310                                                                 'undo' => $this->mNewid
 311                                                         ) ),
 312                                                         'title' => Linker::titleAttrib( 'undo' )
 313                                                 ),
 314                                                 $this->msg( 'editundo' )->text()
 315                                         );
 316                                         $revisionTools[] = $undoLink;
 317                                 }
 318                         }
 319
 320                         # Make "previous revision link"
 321                         if ( $samePage && $this->mOldRev->getPrevious() ) {
 322                                 $prevlink = Linker::linkKnown(
 323                                         $this->mOldPage,
 324                                         $this->msg( 'previousdiff' )->escaped(),
 325                                         array( 'id' => 'differences-prevlink' ),
 326                                         array( 'diff' => 'prev', 'oldid' => $this->mOldid ) + $query
 327                                 );
 328                         } else {
 329                                 $prevlink = '&#160;';
 330                         }
 331
 332                         if ( $this->mOldRev->isMinor() ) {
 333                                 $oldminor = ChangesList::flag( 'minor' );
 334                         } else {
 335                                 $oldminor = '';
 336                         }
 337
 338                         $ldel = $this->revisionDeleteLink( $this->mOldRev );
 339                         $oldRevisionHeader = $this->getRevisionHeader( $this->mOldRev, 'complete' );
 340                         $oldChangeTags = ChangeTags::formatSummaryRow( $this->mOldTags, 'diff' );
 341
 342                         $oldHeader = '<div id="mw-diff-otitle1"><strong>' . $oldRevisionHeader . '</strong></div>' .
 343                                 '<div id="mw-diff-otitle2">' .
 344                                 Linker::revUserTools( $this->mOldRev, !$this->unhide ) . '</div>' .
 345                                 '<div id="mw-diff-otitle3">' . $oldminor .
 346                                 Linker::revComment( $this->mOldRev, !$diffOnly, !$this->unhide ) . $ldel . '</div>' .
 347                                 '<div id="mw-diff-otitle5">' . $oldChangeTags[0] . '</div>' .
 348                                 '<div id="mw-diff-otitle4">' . $prevlink . '</div>';
 349
 350                         if ( $this->mOldRev->isDeleted( Revision::DELETED_TEXT ) ) {
 351                                 $deleted = true; // old revisions text is hidden
 352                                 if ( $this->mOldRev->isDeleted( Revision::DELETED_RESTRICTED ) ) {
 353                                         $suppressed = true; // also suppressed
 354                                 }
 355                         }
 356
 357                         # Check if this user can see the revisions
 358                         if ( !$this->mOldRev->userCan( Revision::DELETED_TEXT, $user ) ) {
 359                                 $allowed = false;
 360                         }
 361                 }
 362
 363                 # Make "next revision link"
 364                 # Skip next link on the top revision
 365                 if ( $samePage && !$this->mNewRev->isCurrent() ) {
 366                         $nextlink = Linker::linkKnown(
 367                                 $this->mNewPage,
 368                                 $this->msg( 'nextdiff' )->escaped(),
 369                                 array( 'id' => 'differences-nextlink' ),
 370                                 array( 'diff' => 'next', 'oldid' => $this->mNewid ) + $query
 371                         );
 372                 } else {
 373                         $nextlink = '&#160;';
 374                 }
 375
 376                 if ( $this->mNewRev->isMinor() ) {
 377                         $newminor = ChangesList::flag( 'minor' );
 378                 } else {
 379                         $newminor = '';
 380                 }
 381
 382                 # Handle RevisionDelete links...
 383                 $rdel = $this->revisionDeleteLink( $this->mNewRev );
 384
 385                 # Allow extensions to define their own revision tools
 386                 wfRunHooks( 'DiffRevisionTools', array( $this->mNewRev, &$revisionTools, $this->mOldRev ) );
 387                 $formattedRevisionTools = array();
 388                 // Put each one in parentheses (poor man's button)
 389                 foreach ( $revisionTools as $tool ) {
 390                         $formattedRevisionTools[] = $this->msg( 'parentheses' )->rawParams( $tool )->escaped();
 391                 }
 392                 $newRevisionHeader = $this->getRevisionHeader( $this->mNewRev, 'complete' ) .
 393                         ' ' . implode( ' ', $formattedRevisionTools );
 394                 $newChangeTags = ChangeTags::formatSummaryRow( $this->mNewTags, 'diff' );
 395
 396                 $newHeader = '<div id="mw-diff-ntitle1"><strong>' . $newRevisionHeader . '</strong></div>' .
 397                         '<div id="mw-diff-ntitle2">' . Linker::revUserTools( $this->mNewRev, !$this->unhide ) .
 398                         " $rollback</div>" .
 399                         '<div id="mw-diff-ntitle3">' . $newminor .
 400                         Linker::revComment( $this->mNewRev, !$diffOnly, !$this->unhide ) . $rdel . '</div>' .
 401                         '<div id="mw-diff-ntitle5">' . $newChangeTags[0] . '</div>' .
 402                         '<div id="mw-diff-ntitle4">' . $nextlink . $this->markPatrolledLink() . '</div>';
 403
 404                 if ( $this->mNewRev->isDeleted( Revision::DELETED_TEXT ) ) {
 405                         $deleted = true; // new revisions text is hidden
 406                         if ( $this->mNewRev->isDeleted( Revision::DELETED_RESTRICTED ) ) {
 407                                 $suppressed = true; // also suppressed
 408                         }
 409                 }
 410
 411                 # If the diff cannot be shown due to a deleted revision, then output
 412                 # the diff header and links to unhide (if available)...
 413                 if ( $deleted && ( !$this->unhide || !$allowed ) ) {
 414                         $this->showDiffStyle();
 415                         $multi = $this->getMultiNotice();
 416                         $out->addHTML( $this->addHeader( '', $oldHeader, $newHeader, $multi ) );
 417                         if ( !$allowed ) {
 418                                 $msg = $suppressed ? 'rev-suppressed-no-diff' : 'rev-deleted-no-diff';
 419                                 # Give explanation for why revision is not visible
 420                                 $out->wrapWikiMsg( "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 421                                         array( $msg ) );
 422                         } else {
 423                                 # Give explanation and add a link to view the diff...
 424                                 $query = $this->getRequest()->appendQueryValue( 'unhide', '1', true );
 425                                 $link = $this->getTitle()->getFullURL( $query );
 426                                 $msg = $suppressed ? 'rev-suppressed-unhide-diff' : 'rev-deleted-unhide-diff';
 427                                 $out->wrapWikiMsg(
 428                                         "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 429                                         array( $msg, $link )
 430                                 );
 431                         }
 432                 # Otherwise, output a regular diff...
 433                 } else {
 434                         # Add deletion notice if the user is viewing deleted content
 435                         $notice = '';
 436                         if ( $deleted ) {
 437                                 $msg = $suppressed ? 'rev-suppressed-diff-view' : 'rev-deleted-diff-view';
 438                                 $notice = "<div id='mw-$msg' class='mw-warning plainlinks'>\n" .
 439                                         $this->msg( $msg )->parse() .
 440                                         "</div>\n";
 441                         }
 442                         $this->showDiff( $oldHeader, $newHeader, $notice );
 443                         if ( !$diffOnly ) {
 444                                 $this->renderNewRevision();
 445                         }
 446                 }
 447                 wfProfileOut( __METHOD__ );
 448         }
 449
 450         /**
 451          * Get a link to mark the change as patrolled, or '' if there's either no
 452          * revision to patrol or the user is not allowed to to it.
 453          * Side effect: When the patrol link is build, this method will call
 454          * OutputPage::preventClickjacking() and load mediawiki.page.patrol.ajax.
 455          *
 456          * @return string
 457          */
 458         protected function markPatrolledLink() {
 459                 global $wgUseRCPatrol, $wgEnableAPI, $wgEnableWriteAPI;
 460                 $user = $this->getUser();
 461
 462                 if ( $this->mMarkPatrolledLink === null ) {
 463                         // Prepare a change patrol link, if applicable
 464                         if (
 465                                 // Is patrolling enabled and the user allowed to?
 466                                 $wgUseRCPatrol && $this->mNewPage->quickUserCan( 'patrol', $user ) &&
 467                                 // Only do this if the revision isn't more than 6 hours older
 468                                 // than the Max RC age (6h because the RC might not be cleaned out regularly)
 469                                 RecentChange::isInRCLifespan( $this->mNewRev->getTimestamp(), 21600 )
 470                         ) {
 471                                 // Look for an unpatrolled change corresponding to this diff
 472
 473                                 $db = wfGetDB( DB_SLAVE );
 474                                 $change = RecentChange::newFromConds(
 475                                         array(
 476                                                 'rc_timestamp' => $db->timestamp( $this->mNewRev->getTimestamp() ),
 477                                                 'rc_this_oldid' => $this->mNewid,
 478                                                 'rc_patrolled' => 0
 479                                         ),
 480                                         __METHOD__,
 481                                         array( 'USE INDEX' => 'rc_timestamp' )
 482                                 );
 483
 484                                 if ( $change && $change->getPerformer()->getName() !== $user->getName() ) {
 485                                         $rcid = $change->getAttribute( 'rc_id' );
 486                                 } else {
 487                                         // None found or the page has been created by the current user.
 488                                         // If the user could patrol this it already would be patrolled
 489                                         $rcid = 0;
 490                                 }
 491                                 // Build the link
 492                                 if ( $rcid ) {
 493                                         $this->getOutput()->preventClickjacking();
 494                                         if ( $wgEnableAPI && $wgEnableWriteAPI
 495                                                 && $user->isAllowed( 'writeapi' )
 496                                         ) {
 497                                                 $this->getOutput()->addModules( 'mediawiki.page.patrol.ajax' );
 498                                         }
 499
 500                                         $token = $user->getEditToken( $rcid );
 501                                         $this->mMarkPatrolledLink = ' <span class="patrollink">[' . Linker::linkKnown(
 502                                                 $this->mNewPage,
 503                                                 $this->msg( 'markaspatrolleddiff' )->escaped(),
 504                                                 array(),
 505                                                 array(
 506                                                         'action' => 'markpatrolled',
 507                                                         'rcid' => $rcid,
 508                                                         'token' => $token,
 509                                                 )
 510                                         ) . ']</span>';
 511                                 } else {
 512                                         $this->mMarkPatrolledLink = '';
 513                                 }
 514                         } else {
 515                                 $this->mMarkPatrolledLink = '';
 516                         }
 517                 }
 518
 519                 return $this->mMarkPatrolledLink;
 520         }
 521
 522         /**
 523          * @param Revision $rev
 524          *
 525          * @return string
 526          */
 527         protected function revisionDeleteLink( $rev ) {
 528                 $link = Linker::getRevDeleteLink( $this->getUser(), $rev, $rev->getTitle() );
 529                 if ( $link !== '' ) {
 530                         $link = '&#160;&#160;&#160;' . $link . ' ';
 531                 }
 532
 533                 return $link;
 534         }
 535
 536         /**
 537          * Show the new revision of the page.
 538          */
 539         function renderNewRevision() {
 540                 wfProfileIn( __METHOD__ );
 541                 $out = $this->getOutput();
 542                 $revHeader = $this->getRevisionHeader( $this->mNewRev );
 543                 # Add "current version as of X" title
 544                 $out->addHTML( "<hr class='diff-hr' />
 545                 <h2 class='diff-currentversion-title'>{$revHeader}</h2>\n" );
 546                 # Page content may be handled by a hooked call instead...
 547                 # @codingStandardsIgnoreStart Ignoring long lines.
 548                 if ( wfRunHooks( 'ArticleContentOnDiff', array( $this, $out ) ) ) {
 549                         $this->loadNewText();
 550                         $out->setRevisionId( $this->mNewid );
 551                         $out->setRevisionTimestamp( $this->mNewRev->getTimestamp() );
 552                         $out->setArticleFlag( true );
 553
 554                         // NOTE: only needed for B/C: custom rendering of JS/CSS via hook
 555                         if ( $this->mNewPage->isCssJsSubpage() || $this->mNewPage->isCssOrJsPage() ) {
 556                                 // Stolen from Article::view --AG 2007-10-11
 557                                 // Give hooks a chance to customise the output
 558                                 // @todo standardize this crap into one function
 559                                 if ( ContentHandler::runLegacyHooks( 'ShowRawCssJs', array( $this->mNewContent, $this->mNewPage, $out ) ) ) {
 560                                         // NOTE: deprecated hook, B/C only
 561                                         // use the content object's own rendering
 562                                         $cnt = $this->mNewRev->getContent();
 563                                         $po = $cnt ? $cnt->getParserOutput( $this->mNewRev->getTitle(), $this->mNewRev->getId() ) : null;
 564                                         $txt = $po ? $po->getText() : '';
 565                                         $out->addHTML( $txt );
 566                                 }
 567                         } elseif ( !wfRunHooks( 'ArticleContentViewCustom', array( $this->mNewContent, $this->mNewPage, $out ) ) ) {
 568                                 // Handled by extension
 569                         } elseif ( !ContentHandler::runLegacyHooks( 'ArticleViewCustom', array( $this->mNewContent, $this->mNewPage, $out ) ) ) {
 570                                 // NOTE: deprecated hook, B/C only
 571                                 // Handled by extension
 572                         } else {
 573                                 // Normal page
 574                                 if ( $this->getTitle()->equals( $this->mNewPage ) ) {
 575                                         // If the Title stored in the context is the same as the one
 576                                         // of the new revision, we can use its associated WikiPage
 577                                         // object.
 578                                         $wikiPage = $this->getWikiPage();
 579                                 } else {
 580                                         // Otherwise we need to create our own WikiPage object
 581                                         $wikiPage = WikiPage::factory( $this->mNewPage );
 582                                 }
 583
 584                                 $parserOutput = $this->getParserOutput( $wikiPage, $this->mNewRev );
 585
 586                                 # WikiPage::getParserOutput() should not return false, but just in case
 587                                 if ( $parserOutput ) {
 588                                         $out->addParserOutput( $parserOutput );
 589                                 }
 590                         }
 591                 }
 592                 # @codingStandardsIgnoreEnd
 593
 594                 # Add redundant patrol link on bottom...
 595                 $out->addHTML( $this->markPatrolledLink() );
 596
 597                 wfProfileOut( __METHOD__ );
 598         }
 599
 600         protected function getParserOutput( WikiPage $page, Revision $rev ) {
 601                 $parserOptions = $page->makeParserOptions( $this->getContext() );
 602
 603                 if ( !$rev->isCurrent() || !$rev->getTitle()->quickUserCan( "edit" ) ) {
 604                         $parserOptions->setEditSection( false );
 605                 }
 606
 607                 $parserOutput = $page->getParserOutput( $parserOptions, $rev->getId() );
 608
 609                 return $parserOutput;
 610         }
 611
 612         /**
 613          * Get the diff text, send it to the OutputPage object
 614          * Returns false if the diff could not be generated, otherwise returns true
 615          *
 616          * @param string|bool $otitle Header for old text or false
 617          * @param string|bool $ntitle Header for new text or false
 618          * @param string $notice HTML between diff header and body
 619          *
 620          * @return bool
 621          */
 622         function showDiff( $otitle, $ntitle, $notice = '' ) {
 623                 $diff = $this->getDiff( $otitle, $ntitle, $notice );
 624                 if ( $diff === false ) {
 625                         $this->showMissingRevision();
 626
 627                         return false;
 628                 } else {
 629                         $this->showDiffStyle();
 630                         $this->getOutput()->addHTML( $diff );
 631
 632                         return true;
 633                 }
 634         }
 635
 636         /**
 637          * Add style sheets and supporting JS for diff display.
 638          */
 639         function showDiffStyle() {
 640                 $this->getOutput()->addModuleStyles( 'mediawiki.action.history.diff' );
 641         }
 642
 643         /**
 644          * Get complete diff table, including header
 645          *
 646          * @param string|bool $otitle Header for old text or false
 647          * @param string|bool $ntitle Header for new text or false
 648          * @param string $notice HTML between diff header and body
 649          *
 650          * @return mixed
 651          */
 652         function getDiff( $otitle, $ntitle, $notice = '' ) {
 653                 $body = $this->getDiffBody();
 654                 if ( $body === false ) {
 655                         return false;
 656                 }
 657
 658                 $multi = $this->getMultiNotice();
 659                 // Display a message when the diff is empty
 660                 if ( $body === '' ) {
 661                         $notice .= '<div class="mw-diff-empty">' .
 662                                 $this->msg( 'diff-empty' )->parse() .
 663                                 "</div>\n";
 664                 }
 665
 666                 return $this->addHeader( $body, $otitle, $ntitle, $multi, $notice );
 667         }
 668
 669         /**
 670          * Get the diff table body, without header
 671          *
 672          * @return mixed (string/false)
 673          */
 674         public function getDiffBody() {
 675                 global $wgMemc;
 676                 wfProfileIn( __METHOD__ );
 677                 $this->mCacheHit = true;
 678                 // Check if the diff should be hidden from this user
 679                 if ( !$this->loadRevisionData() ) {
 680                         wfProfileOut( __METHOD__ );
 681
 682                         return false;
 683                 } elseif ( $this->mOldRev &&
 684                         !$this->mOldRev->userCan( Revision::DELETED_TEXT, $this->getUser() )
 685                 ) {
 686                         wfProfileOut( __METHOD__ );
 687
 688                         return false;
 689                 } elseif ( $this->mNewRev &&
 690                         !$this->mNewRev->userCan( Revision::DELETED_TEXT, $this->getUser() )
 691                 ) {
 692                         wfProfileOut( __METHOD__ );
 693
 694                         return false;
 695                 }
 696                 // Short-circuit
 697                 if ( $this->mOldRev === false || ( $this->mOldRev && $this->mNewRev
 698                         && $this->mOldRev->getID() == $this->mNewRev->getID() )
 699                 ) {
 700                         wfProfileOut( __METHOD__ );
 701
 702                         return '';
 703                 }
 704                 // Cacheable?
 705                 $key = false;
 706                 if ( $this->mOldid && $this->mNewid ) {
 707                         $key = $this->getDiffBodyCacheKey();
 708
 709                         // Try cache
 710                         if ( !$this->mRefreshCache ) {
 711                                 $difftext = $wgMemc->get( $key );
 712                                 if ( $difftext ) {
 713                                         wfIncrStats( 'diff_cache_hit' );
 714                                         $difftext = $this->localiseLineNumbers( $difftext );
 715                                         $difftext .= "\n<!-- diff cache key $key -->\n";
 716                                         wfProfileOut( __METHOD__ );
 717
 718                                         return $difftext;
 719                                 }
 720                         } // don't try to load but save the result
 721                 }
 722                 $this->mCacheHit = false;
 723
 724                 // Loadtext is permission safe, this just clears out the diff
 725                 if ( !$this->loadText() ) {
 726                         wfProfileOut( __METHOD__ );
 727
 728                         return false;
 729                 }
 730
 731                 $difftext = $this->generateContentDiffBody( $this->mOldContent, $this->mNewContent );
 732
 733                 // Save to cache for 7 days
 734                 if ( !wfRunHooks( 'AbortDiffCache', array( &$this ) ) ) {
 735                         wfIncrStats( 'diff_uncacheable' );
 736                 } elseif ( $key !== false && $difftext !== false ) {
 737                         wfIncrStats( 'diff_cache_miss' );
 738                         $wgMemc->set( $key, $difftext, 7 * 86400 );
 739                 } else {
 740                         wfIncrStats( 'diff_uncacheable' );
 741                 }
 742                 // Replace line numbers with the text in the user's language
 743                 if ( $difftext !== false ) {
 744                         $difftext = $this->localiseLineNumbers( $difftext );
 745                 }
 746                 wfProfileOut( __METHOD__ );
 747
 748                 return $difftext;
 749         }
 750
 751         /**
 752          * Returns the cache key for diff body text or content.
 753          *
 754          * @since 1.23
 755          *
 756          * @throws MWException
 757          * @return string
 758          */
 759         protected function getDiffBodyCacheKey() {
 760                 if ( !$this->mOldid || !$this->mNewid ) {
 761                         throw new MWException( 'mOldid and mNewid must be set to get diff cache key.' );
 762                 }
 763
 764                 return wfMemcKey( 'diff', 'version', MW_DIFF_VERSION,
 765                         'oldid', $this->mOldid, 'newid', $this->mNewid );
 766         }
 767
 768         /**
 769          * Generate a diff, no caching.
 770          *
 771          * This implementation uses generateTextDiffBody() to generate a diff based on the default
 772          * serialization of the given Content objects. This will fail if $old or $new are not
 773          * instances of TextContent.
 774          *
 775          * Subclasses may override this to provide a different rendering for the diff,
 776          * perhaps taking advantage of the content's native form. This is required for all content
 777          * models that are not text based.
 778          *
 779          * @since 1.21
 780          *
 781          * @param Content $old Old content
 782          * @param Content $new New content
 783          *
 784          * @throws MWException If old or new content is not an instance of TextContent.
 785          * @return bool|string
 786          */
 787         function generateContentDiffBody( Content $old, Content $new ) {
 788                 if ( !( $old instanceof TextContent ) ) {
 789                         throw new MWException( "Diff not implemented for " . get_class( $old ) . "; " .
 790                                 "override generateContentDiffBody to fix this." );
 791                 }
 792
 793                 if ( !( $new instanceof TextContent ) ) {
 794                         throw new MWException( "Diff not implemented for " . get_class( $new ) . "; "
 795                                 . "override generateContentDiffBody to fix this." );
 796                 }
 797
 798                 $otext = $old->serialize();
 799                 $ntext = $new->serialize();
 800
 801                 return $this->generateTextDiffBody( $otext, $ntext );
 802         }
 803
 804         /**
 805          * Generate a diff, no caching
 806          *
 807          * @param string $otext Old text, must be already segmented
 808          * @param string $ntext New text, must be already segmented
 809          *
 810          * @return bool|string
 811          * @deprecated since 1.21, use generateContentDiffBody() instead!
 812          */
 813         function generateDiffBody( $otext, $ntext ) {
 814                 ContentHandler::deprecated( __METHOD__, "1.21" );
 815
 816                 return $this->generateTextDiffBody( $otext, $ntext );
 817         }
 818
 819         /**
 820          * Generate a diff, no caching
 821          *
 822          * @todo move this to TextDifferenceEngine, make DifferenceEngine abstract. At some point.
 823          *
 824          * @param string $otext old text, must be already segmented
 825          * @param string $ntext new text, must be already segmented
 826          *
 827          * @return bool|string
 828          */
 829         function generateTextDiffBody( $otext, $ntext ) {
 830                 global $wgExternalDiffEngine, $wgContLang;
 831
 832                 wfProfileIn( __METHOD__ );
 833
 834                 $otext = str_replace( "\r\n", "\n", $otext );
 835                 $ntext = str_replace( "\r\n", "\n", $ntext );
 836
 837                 if ( $wgExternalDiffEngine == 'wikidiff' && function_exists( 'wikidiff_do_diff' ) ) {
 838                         # For historical reasons, external diff engine expects
 839                         # input text to be HTML-escaped already
 840                         $otext = htmlspecialchars( $wgContLang->segmentForDiff( $otext ) );
 841                         $ntext = htmlspecialchars( $wgContLang->segmentForDiff( $ntext ) );
 842                         wfProfileOut( __METHOD__ );
 843
 844                         return $wgContLang->unsegmentForDiff( wikidiff_do_diff( $otext, $ntext, 2 ) ) .
 845                         $this->debug( 'wikidiff1' );
 846                 }
 847
 848                 if ( $wgExternalDiffEngine == 'wikidiff2' && function_exists( 'wikidiff2_do_diff' ) ) {
 849                         # Better external diff engine, the 2 may some day be dropped
 850                         # This one does the escaping and segmenting itself
 851                         wfProfileIn( 'wikidiff2_do_diff' );
 852                         $text = wikidiff2_do_diff( $otext, $ntext, 2 );
 853                         $text .= $this->debug( 'wikidiff2' );
 854                         wfProfileOut( 'wikidiff2_do_diff' );
 855                         wfProfileOut( __METHOD__ );
 856
 857                         return $text;
 858                 }
 859                 if ( $wgExternalDiffEngine != 'wikidiff3' && $wgExternalDiffEngine !== false ) {
 860                         # Diff via the shell
 861                         $tmpDir = wfTempDir();
 862                         $tempName1 = tempnam( $tmpDir, 'diff_' );
 863                         $tempName2 = tempnam( $tmpDir, 'diff_' );
 864
 865                         $tempFile1 = fopen( $tempName1, "w" );
 866                         if ( !$tempFile1 ) {
 867                                 wfProfileOut( __METHOD__ );
 868
 869                                 return false;
 870                         }
 871                         $tempFile2 = fopen( $tempName2, "w" );
 872                         if ( !$tempFile2 ) {
 873                                 wfProfileOut( __METHOD__ );
 874
 875                                 return false;
 876                         }
 877                         fwrite( $tempFile1, $otext );
 878                         fwrite( $tempFile2, $ntext );
 879                         fclose( $tempFile1 );
 880                         fclose( $tempFile2 );
 881                         $cmd = wfEscapeShellArg( $wgExternalDiffEngine, $tempName1, $tempName2 );
 882                         wfProfileIn( __METHOD__ . "-shellexec" );
 883                         $difftext = wfShellExec( $cmd );
 884                         $difftext .= $this->debug( "external $wgExternalDiffEngine" );
 885                         wfProfileOut( __METHOD__ . "-shellexec" );
 886                         unlink( $tempName1 );
 887                         unlink( $tempName2 );
 888                         wfProfileOut( __METHOD__ );
 889
 890                         return $difftext;
 891                 }
 892
 893                 # Native PHP diff
 894                 $ota = explode( "\n", $wgContLang->segmentForDiff( $otext ) );
 895                 $nta = explode( "\n", $wgContLang->segmentForDiff( $ntext ) );
 896                 $diffs = new Diff( $ota, $nta );
 897                 $formatter = new TableDiffFormatter();
 898                 $difftext = $wgContLang->unsegmentForDiff( $formatter->format( $diffs ) ) .
 899                         wfProfileOut( __METHOD__ );
 900
 901                 return $difftext;
 902         }
 903
 904         /**
 905          * Generate a debug comment indicating diff generating time,
 906          * server node, and generator backend.
 907          *
 908          * @param string $generator : What diff engine was used
 909          *
 910          * @return string
 911          */
 912         protected function debug( $generator = "internal" ) {
 913                 global $wgShowHostnames;
 914                 if ( !$this->enableDebugComment ) {
 915                         return '';
 916                 }
 917                 $data = array( $generator );
 918                 if ( $wgShowHostnames ) {
 919                         $data[] = wfHostname();
 920                 }
 921                 $data[] = wfTimestamp( TS_DB );
 922
 923                 return "<!-- diff generator: " .
 924                         implode( " ", array_map( "htmlspecialchars", $data ) ) .
 925                         " -->\n";
 926         }
 927
 928         /**
 929          * Replace line numbers with the text in the user's language
 930          *
 931          * @param string $text
 932          *
 933          * @return mixed
 934          */
 935         function localiseLineNumbers( $text ) {
 936                 return preg_replace_callback(
 937                         '/<!--LINE (\d+)-->/',
 938                         array( &$this, 'localiseLineNumbersCb' ),
 939                         $text
 940                 );
 941         }
 942
 943         function localiseLineNumbersCb( $matches ) {
 944                 if ( $matches[1] === '1' && $this->mReducedLineNumbers ) {
 945                         return '';
 946                 }
 947
 948                 return $this->msg( 'lineno' )->numParams( $matches[1] )->escaped();
 949         }
 950
 951         /**
 952          * If there are revisions between the ones being compared, return a note saying so.
 953          *
 954          * @return string
 955          */
 956         function getMultiNotice() {
 957                 if ( !is_object( $this->mOldRev ) || !is_object( $this->mNewRev ) ) {
 958                         return '';
 959                 } elseif ( !$this->mOldPage->equals( $this->mNewPage ) ) {
 960                         // Comparing two different pages? Count would be meaningless.
 961                         return '';
 962                 }
 963
 964                 if ( $this->mOldRev->getTimestamp() > $this->mNewRev->getTimestamp() ) {
 965                         $oldRev = $this->mNewRev; // flip
 966                         $newRev = $this->mOldRev; // flip
 967                 } else { // normal case
 968                         $oldRev = $this->mOldRev;
 969                         $newRev = $this->mNewRev;
 970                 }
 971
 972                 $nEdits = $this->mNewPage->countRevisionsBetween( $oldRev, $newRev );
 973                 if ( $nEdits > 0 ) {
 974                         $limit = 100; // use diff-multi-manyusers if too many users
 975                         $users = $this->mNewPage->getAuthorsBetween( $oldRev, $newRev, $limit );
 976                         $numUsers = count( $users );
 977
 978                         if ( $numUsers == 1 && $users[0] == $newRev->getRawUserText() ) {
 979                                 $numUsers = 0; // special case to say "by the same user" instead of "by one other user"
 980                         }
 981
 982                         return self::intermediateEditsMsg( $nEdits, $numUsers, $limit );
 983                 }
 984
 985                 return ''; // nothing
 986         }
 987
 988         /**
 989          * Get a notice about how many intermediate edits and users there are
 990          *
 991          * @param int $numEdits
 992          * @param int $numUsers
 993          * @param int $limit
 994          *
 995          * @return string
 996          */
 997         public static function intermediateEditsMsg( $numEdits, $numUsers, $limit ) {
 998                 if ( $numUsers === 0 ) {
 999                         $msg = 'diff-multi-sameuser';
1000                 } elseif ( $numUsers > $limit ) {
1001                         $msg = 'diff-multi-manyusers';
1002                         $numUsers = $limit;
1003                 } else {
1004                         $msg = 'diff-multi-otherusers';
1005                 }
1006
1007                 return wfMessage( $msg )->numParams( $numEdits, $numUsers )->parse();
1008         }
1009
1010         /**
1011          * Get a header for a specified revision.
1012          *
1013          * @param Revision $rev
1014          * @param string $complete 'complete' to get the header wrapped depending
1015          *        the visibility of the revision and a link to edit the page.
1016          *
1017          * @return string HTML fragment
1018          */
1019         protected function getRevisionHeader( Revision $rev, $complete = '' ) {
1020                 $lang = $this->getLanguage();
1021                 $user = $this->getUser();
1022                 $revtimestamp = $rev->getTimestamp();
1023                 $timestamp = $lang->userTimeAndDate( $revtimestamp, $user );
1024                 $dateofrev = $lang->userDate( $revtimestamp, $user );
1025                 $timeofrev = $lang->userTime( $revtimestamp, $user );
1026
1027                 $header = $this->msg(
1028                         $rev->isCurrent() ? 'currentrev-asof' : 'revisionasof',
1029                         $timestamp,
1030                         $dateofrev,
1031                         $timeofrev
1032                 )->escaped();
1033
1034                 if ( $complete !== 'complete' ) {
1035                         return $header;
1036                 }
1037
1038                 $title = $rev->getTitle();
1039
1040                 $header = Linker::linkKnown( $title, $header, array(),
1041                         array( 'oldid' => $rev->getID() ) );
1042
1043                 if ( $rev->userCan( Revision::DELETED_TEXT, $user ) ) {
1044                         $editQuery = array( 'action' => 'edit' );
1045                         if ( !$rev->isCurrent() ) {
1046                                 $editQuery['oldid'] = $rev->getID();
1047                         }
1048
1049                         $key = $title->quickUserCan( 'edit', $user ) ? 'editold' : 'viewsourceold';
1050                         $msg = $this->msg( $key )->escaped();
1051                         $header .= ' ' . $this->msg( 'parentheses' )->rawParams(
1052                                 Linker::linkKnown( $title, $msg, array(), $editQuery ) )->plain();
1053                         if ( $rev->isDeleted( Revision::DELETED_TEXT ) ) {
1054                                 $header = Html::rawElement(
1055                                         'span',
1056                                         array( 'class' => 'history-deleted' ),
1057                                         $header
1058                                 );
1059                         }
1060                 } else {
1061                         $header = Html::rawElement( 'span', array( 'class' => 'history-deleted' ), $header );
1062                 }
1063
1064                 return $header;
1065         }
1066
1067         /**
1068          * Add the header to a diff body
1069          *
1070          * @param string $diff Diff body
1071          * @param string $otitle Old revision header
1072          * @param string $ntitle New revision header
1073          * @param string $multi Notice telling user that there are intermediate
1074          *   revisions between the ones being compared
1075          * @param string $notice Other notices, e.g. that user is viewing deleted content
1076          *
1077          * @return string
1078          */
1079         function addHeader( $diff, $otitle, $ntitle, $multi = '', $notice = '' ) {
1080                 // shared.css sets diff in interface language/dir, but the actual content
1081                 // is often in a different language, mostly the page content language/dir
1082                 $tableClass = 'diff diff-contentalign-' . htmlspecialchars( $this->getDiffLang()->alignStart() );
1083                 $header = "<table class='$tableClass'>";
1084
1085                 if ( !$diff && !$otitle ) {
1086                         $header .= "
1087                         <tr style='vertical-align: top;'>
1088                         <td class='diff-ntitle'>{$ntitle}</td>
1089                         </tr>";
1090                         $multiColspan = 1;
1091                 } else {
1092                         if ( $diff ) { // Safari/Chrome show broken output if cols not used
1093                                 $header .= "
1094                                 <col class='diff-marker' />
1095                                 <col class='diff-content' />
1096                                 <col class='diff-marker' />
1097                                 <col class='diff-content' />";
1098                                 $colspan = 2;
1099                                 $multiColspan = 4;
1100                         } else {
1101                                 $colspan = 1;
1102                                 $multiColspan = 2;
1103                         }
1104                         if ( $otitle || $ntitle ) {
1105                                 $header .= "
1106                                 <tr style='vertical-align: top;'>
1107                                 <td colspan='$colspan' class='diff-otitle'>{$otitle}</td>
1108                                 <td colspan='$colspan' class='diff-ntitle'>{$ntitle}</td>
1109                                 </tr>";
1110                         }
1111                 }
1112
1113                 if ( $multi != '' ) {
1114                         $header .= "<tr><td colspan='{$multiColspan}' style='text-align: center;' " .
1115                                 "class='diff-multi'>{$multi}</td></tr>";
1116                 }
1117                 if ( $notice != '' ) {
1118                         $header .= "<tr><td colspan='{$multiColspan}' style='text-align: center;'>{$notice}</td></tr>";
1119                 }
1120
1121                 return $header . $diff . "</table>";
1122         }
1123
1124         /**
1125          * Use specified text instead of loading from the database
1126          * @deprecated since 1.21, use setContent() instead.
1127          */
1128         function setText( $oldText, $newText ) {
1129                 ContentHandler::deprecated( __METHOD__, "1.21" );
1130
1131                 $oldContent = ContentHandler::makeContent( $oldText, $this->getTitle() );
1132                 $newContent = ContentHandler::makeContent( $newText, $this->getTitle() );
1133
1134                 $this->setContent( $oldContent, $newContent );
1135         }
1136
1137         /**
1138          * Use specified text instead of loading from the database
1139          * @since 1.21
1140          */
1141         function setContent( Content $oldContent, Content $newContent ) {
1142                 $this->mOldContent = $oldContent;
1143                 $this->mNewContent = $newContent;
1144
1145                 $this->mTextLoaded = 2;
1146                 $this->mRevisionsLoaded = true;
1147         }
1148
1149         /**
1150          * Set the language in which the diff text is written
1151          * (Defaults to page content language).
1152          * @since 1.19
1153          */
1154         function setTextLanguage( $lang ) {
1155                 $this->mDiffLang = wfGetLangObj( $lang );
1156         }
1157
1158         /**
1159          * Maps a revision pair definition as accepted by DifferenceEngine constructor
1160          * to a pair of actual integers representing revision ids.
1161          *
1162          * @param int $old Revision id, e.g. from URL parameter 'oldid'
1163          * @param int|string $new Revision id or strings 'next' or 'prev', e.g. from URL parameter 'diff'
1164          *
1165          * @return int[] List of two revision ids, older first, later second.
1166          *     Zero signifies invalid argument passed.
1167          *     false signifies that there is no previous/next revision ($old is the oldest/newest one).
1168          */
1169         public function mapDiffPrevNext( $old, $new ) {
1170                 if ( $new === 'prev' ) {
1171                         // Show diff between revision $old and the previous one. Get previous one from DB.
1172                         $newid = intval( $old );
1173                         $oldid = $this->getTitle()->getPreviousRevisionID( $newid );
1174                 } elseif ( $new === 'next' ) {
1175                         // Show diff between revision $old and the next one. Get next one from DB.
1176                         $oldid = intval( $old );
1177                         $newid = $this->getTitle()->getNextRevisionID( $oldid );
1178                 } else {
1179                         $oldid = intval( $old );
1180                         $newid = intval( $new );
1181                 }
1182
1183                 return array( $oldid, $newid );
1184         }
1185
1186         /**
1187          * Load revision IDs
1188          */
1189         private function loadRevisionIds() {
1190                 if ( $this->mRevisionsIdsLoaded ) {
1191                         return;
1192                 }
1193
1194                 $this->mRevisionsIdsLoaded = true;
1195
1196                 $old = $this->mOldid;
1197                 $new = $this->mNewid;
1198
1199                 list( $this->mOldid, $this->mNewid ) = self::mapDiffPrevNext( $old, $new );
1200                 if ( $new === 'next' && $this->mNewid === false ) {
1201                         # if no result, NewId points to the newest old revision. The only newer
1202                         # revision is cur, which is "0".
1203                         $this->mNewid = 0;
1204                 }
1205
1206                 wfRunHooks(
1207                         'NewDifferenceEngine',
1208                         array( $this->getTitle(), &$this->mOldid, &$this->mNewid, $old, $new )
1209                 );
1210         }
1211
1212         /**
1213          * Load revision metadata for the specified articles. If newid is 0, then compare
1214          * the old article in oldid to the current article; if oldid is 0, then
1215          * compare the current article to the immediately previous one (ignoring the
1216          * value of newid).
1217          *
1218          * If oldid is false, leave the corresponding revision object set
1219          * to false. This is impossible via ordinary user input, and is provided for
1220          * API convenience.
1221          *
1222          * @return bool
1223          */
1224         function loadRevisionData() {
1225                 if ( $this->mRevisionsLoaded ) {
1226                         return true;
1227                 }
1228
1229                 // Whether it succeeds or fails, we don't want to try again
1230                 $this->mRevisionsLoaded = true;
1231
1232                 $this->loadRevisionIds();
1233
1234                 // Load the new revision object
1235                 if ( $this->mNewid ) {
1236                         $this->mNewRev = Revision::newFromId( $this->mNewid );
1237                 } else {
1238                         $this->mNewRev = Revision::newFromTitle(
1239                                 $this->getTitle(),
1240                                 false,
1241                                 Revision::READ_NORMAL
1242                         );
1243                 }
1244
1245                 if ( !$this->mNewRev instanceof Revision ) {
1246                         return false;
1247                 }
1248
1249                 // Update the new revision ID in case it was 0 (makes life easier doing UI stuff)
1250                 $this->mNewid = $this->mNewRev->getId();
1251                 $this->mNewPage = $this->mNewRev->getTitle();
1252
1253                 // Load the old revision object
1254                 $this->mOldRev = false;
1255                 if ( $this->mOldid ) {
1256                         $this->mOldRev = Revision::newFromId( $this->mOldid );
1257                 } elseif ( $this->mOldid === 0 ) {
1258                         $rev = $this->mNewRev->getPrevious();
1259                         if ( $rev ) {
1260                                 $this->mOldid = $rev->getId();
1261                                 $this->mOldRev = $rev;
1262                         } else {
1263                                 // No previous revision; mark to show as first-version only.
1264                                 $this->mOldid = false;
1265                                 $this->mOldRev = false;
1266                         }
1267                 } /* elseif ( $this->mOldid === false ) leave mOldRev false; */
1268
1269                 if ( is_null( $this->mOldRev ) ) {
1270                         return false;
1271                 }
1272
1273                 if ( $this->mOldRev ) {
1274                         $this->mOldPage = $this->mOldRev->getTitle();
1275                 }
1276
1277                 // Load tags information for both revisions
1278                 $dbr = wfGetDB( DB_SLAVE );
1279                 if ( $this->mOldid !== false ) {
1280                         $this->mOldTags = $dbr->selectField(
1281                                 'tag_summary',
1282                                 'ts_tags',
1283                                 array( 'ts_rev_id' => $this->mOldid ),
1284                                 __METHOD__
1285                         );
1286                 } else {
1287                         $this->mOldTags = false;
1288                 }
1289                 $this->mNewTags = $dbr->selectField(
1290                         'tag_summary',
1291                         'ts_tags',
1292                         array( 'ts_rev_id' => $this->mNewid ),
1293                         __METHOD__
1294                 );
1295
1296                 return true;
1297         }
1298
1299         /**
1300          * Load the text of the revisions, as well as revision data.
1301          *
1302          * @return bool
1303          */
1304         function loadText() {
1305                 if ( $this->mTextLoaded == 2 ) {
1306                         return true;
1307                 }
1308
1309                 // Whether it succeeds or fails, we don't want to try again
1310                 $this->mTextLoaded = 2;
1311
1312                 if ( !$this->loadRevisionData() ) {
1313                         return false;
1314                 }
1315
1316                 if ( $this->mOldRev ) {
1317                         $this->mOldContent = $this->mOldRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1318                         if ( $this->mOldContent === null ) {
1319                                 return false;
1320                         }
1321                 }
1322
1323                 if ( $this->mNewRev ) {
1324                         $this->mNewContent = $this->mNewRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1325                         if ( $this->mNewContent === null ) {
1326                                 return false;
1327                         }
1328                 }
1329
1330                 return true;
1331         }
1332
1333         /**
1334          * Load the text of the new revision, not the old one
1335          *
1336          * @return bool
1337          */
1338         function loadNewText() {
1339                 if ( $this->mTextLoaded >= 1 ) {
1340                         return true;
1341                 }
1342
1343                 $this->mTextLoaded = 1;
1344
1345                 if ( !$this->loadRevisionData() ) {
1346                         return false;
1347                 }
1348
1349                 $this->mNewContent = $this->mNewRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1350
1351                 return true;
1352         }
1353
1354 }