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