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 // Deprecated, use class constant instead
  25 define( 'MW_DIFF_VERSION', '1.11a' );
  26
  27 /**
  28  * @todo document
  29  * @ingroup DifferenceEngine
  30  */
  31 class DifferenceEngine extends ContextSource {
  32         /**
  33          * Constant to indicate diff cache compatibility.
  34          * Bump this when changing the diff formatting in a way that
  35          * fixes important bugs or such to force cached diff views to
  36          * clear.
  37          */
  38         const DIFF_VERSION = MW_DIFF_VERSION;
  39
  40         /** @var int */
  41         public $mOldid;
  42
  43         /** @var int */
  44         public $mNewid;
  45
  46         private $mOldTags;
  47         private $mNewTags;
  48
  49         /** @var Content */
  50         public $mOldContent;
  51
  52         /** @var Content */
  53         public $mNewContent;
  54
  55         /** @var Language */
  56         protected $mDiffLang;
  57
  58         /** @var Title */
  59         public $mOldPage;
  60
  61         /** @var Title */
  62         public $mNewPage;
  63
  64         /** @var Revision */
  65         public $mOldRev;
  66
  67         /** @var Revision */
  68         public $mNewRev;
  69
  70         /** @var bool Have the revisions IDs been loaded */
  71         private $mRevisionsIdsLoaded = false;
  72
  73         /** @var bool Have the revisions been loaded */
  74         public $mRevisionsLoaded = false;
  75
  76         /** @var int How many text blobs have been loaded, 0, 1 or 2? */
  77         public $mTextLoaded = 0;
  78
  79         /** @var bool Was the diff fetched from cache? */
  80         public $mCacheHit = false;
  81
  82         /**
  83          * Set this to true to add debug info to the HTML output.
  84          * Warning: this may cause RSS readers to spuriously mark articles as "new"
  85          * (bug 20601)
  86          */
  87         public $enableDebugComment = false;
  88
  89         /** @var bool If true, line X is not displayed when X is 1, for example
  90          *    to increase readability and conserve space with many small diffs.
  91          */
  92         protected $mReducedLineNumbers = false;
  93
  94         /** @var string Link to action=markpatrolled */
  95         protected $mMarkPatrolledLink = null;
  96
  97         /** @var bool Show rev_deleted content if allowed */
  98         protected $unhide = false;
  99
 100         /** @var bool Refresh the diff cache */
 101         protected $mRefreshCache = false;
 102
 103         /**#@-*/
 104
 105         /**
 106          * Constructor
 107          * @param IContextSource $context Context to use, anything else will be ignored
 108          * @param int $old Old ID we want to show and diff with.
 109          * @param string|int $new Either revision ID or 'prev' or 'next'. Default: 0.
 110          * @param int $rcid Deprecated, no longer used!
 111          * @param bool $refreshCache If set, refreshes the diff cache
 112          * @param bool $unhide If set, allow viewing deleted revs
 113          */
 114         public function __construct( $context = null, $old = 0, $new = 0, $rcid = 0,
 115                 $refreshCache = false, $unhide = false
 116         ) {
 117                 if ( $context instanceof IContextSource ) {
 118                         $this->setContext( $context );
 119                 }
 120
 121                 wfDebug( "DifferenceEngine old '$old' new '$new' rcid '$rcid'\n" );
 122
 123                 $this->mOldid = $old;
 124                 $this->mNewid = $new;
 125                 $this->mRefreshCache = $refreshCache;
 126                 $this->unhide = $unhide;
 127         }
 128
 129         /**
 130          * @param bool $value
 131          */
 132         public function setReducedLineNumbers( $value = true ) {
 133                 $this->mReducedLineNumbers = $value;
 134         }
 135
 136         /**
 137          * @return Language
 138          */
 139         public function getDiffLang() {
 140                 if ( $this->mDiffLang === null ) {
 141                         # Default language in which the diff text is written.
 142                         $this->mDiffLang = $this->getTitle()->getPageLanguage();
 143                 }
 144
 145                 return $this->mDiffLang;
 146         }
 147
 148         /**
 149          * @return bool
 150          */
 151         public function wasCacheHit() {
 152                 return $this->mCacheHit;
 153         }
 154
 155         /**
 156          * @return int
 157          */
 158         public function getOldid() {
 159                 $this->loadRevisionIds();
 160
 161                 return $this->mOldid;
 162         }
 163
 164         /**
 165          * @return bool|int
 166          */
 167         public function getNewid() {
 168                 $this->loadRevisionIds();
 169
 170                 return $this->mNewid;
 171         }
 172
 173         /**
 174          * Look up a special:Undelete link to the given deleted revision id,
 175          * as a workaround for being unable to load deleted diffs in currently.
 176          *
 177          * @param int $id Revision ID
 178          *
 179          * @return mixed URL or false
 180          */
 181         public function deletedLink( $id ) {
 182                 if ( $this->getUser()->isAllowed( 'deletedhistory' ) ) {
 183                         $dbr = wfGetDB( DB_SLAVE );
 184                         $row = $dbr->selectRow( 'archive', '*',
 185                                 [ 'ar_rev_id' => $id ],
 186                                 __METHOD__ );
 187                         if ( $row ) {
 188                                 $rev = Revision::newFromArchiveRow( $row );
 189                                 $title = Title::makeTitleSafe( $row->ar_namespace, $row->ar_title );
 190
 191                                 return SpecialPage::getTitleFor( 'Undelete' )->getFullURL( [
 192                                         'target' => $title->getPrefixedText(),
 193                                         'timestamp' => $rev->getTimestamp()
 194                                 ] );
 195                         }
 196                 }
 197
 198                 return false;
 199         }
 200
 201         /**
 202          * Build a wikitext link toward a deleted revision, if viewable.
 203          *
 204          * @param int $id Revision ID
 205          *
 206          * @return string Wikitext fragment
 207          */
 208         public function deletedIdMarker( $id ) {
 209                 $link = $this->deletedLink( $id );
 210                 if ( $link ) {
 211                         return "[$link $id]";
 212                 } else {
 213                         return $id;
 214                 }
 215         }
 216
 217         private function showMissingRevision() {
 218                 $out = $this->getOutput();
 219
 220                 $missing = [];
 221                 if ( $this->mOldRev === null ||
 222                         ( $this->mOldRev && $this->mOldContent === null )
 223                 ) {
 224                         $missing[] = $this->deletedIdMarker( $this->mOldid );
 225                 }
 226                 if ( $this->mNewRev === null ||
 227                         ( $this->mNewRev && $this->mNewContent === null )
 228                 ) {
 229                         $missing[] = $this->deletedIdMarker( $this->mNewid );
 230                 }
 231
 232                 $out->setPageTitle( $this->msg( 'errorpagetitle' ) );
 233                 $msg = $this->msg( 'difference-missing-revision' )
 234                         ->params( $this->getLanguage()->listToText( $missing ) )
 235                         ->numParams( count( $missing ) )
 236                         ->parseAsBlock();
 237                 $out->addHTML( $msg );
 238         }
 239
 240         public function showDiffPage( $diffOnly = false ) {
 241
 242                 # Allow frames except in certain special cases
 243                 $out = $this->getOutput();
 244                 $out->allowClickjacking();
 245                 $out->setRobotPolicy( 'noindex,nofollow' );
 246
 247                 if ( !$this->loadRevisionData() ) {
 248                         $this->showMissingRevision();
 249
 250                         return;
 251                 }
 252
 253                 $user = $this->getUser();
 254                 $permErrors = $this->mNewPage->getUserPermissionsErrors( 'read', $user );
 255                 if ( $this->mOldPage ) { # mOldPage might not be set, see below.
 256                         $permErrors = wfMergeErrorArrays( $permErrors,
 257                                 $this->mOldPage->getUserPermissionsErrors( 'read', $user ) );
 258                 }
 259                 if ( count( $permErrors ) ) {
 260                         throw new PermissionsError( 'read', $permErrors );
 261                 }
 262
 263                 $rollback = '';
 264
 265                 $query = [];
 266                 # Carry over 'diffonly' param via navigation links
 267                 if ( $diffOnly != $user->getBoolOption( 'diffonly' ) ) {
 268                         $query['diffonly'] = $diffOnly;
 269                 }
 270                 # Cascade unhide param in links for easy deletion browsing
 271                 if ( $this->unhide ) {
 272                         $query['unhide'] = 1;
 273                 }
 274
 275                 # Check if one of the revisions is deleted/suppressed
 276                 $deleted = $suppressed = false;
 277                 $allowed = $this->mNewRev->userCan( Revision::DELETED_TEXT, $user );
 278
 279                 $revisionTools = [];
 280
 281                 # mOldRev is false if the difference engine is called with a "vague" query for
 282                 # a diff between a version V and its previous version V' AND the version V
 283                 # is the first version of that article. In that case, V' does not exist.
 284                 if ( $this->mOldRev === false ) {
 285                         $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 286                         $samePage = true;
 287                         $oldHeader = '';
 288                 } else {
 289                         Hooks::run( 'DiffViewHeader', [ $this, $this->mOldRev, $this->mNewRev ] );
 290
 291                         if ( $this->mNewPage->equals( $this->mOldPage ) ) {
 292                                 $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 293                                 $samePage = true;
 294                         } else {
 295                                 $out->setPageTitle( $this->msg( 'difference-title-multipage',
 296                                         $this->mOldPage->getPrefixedText(), $this->mNewPage->getPrefixedText() ) );
 297                                 $out->addSubtitle( $this->msg( 'difference-multipage' ) );
 298                                 $samePage = false;
 299                         }
 300
 301                         if ( $samePage && $this->mNewPage->quickUserCan( 'edit', $user ) ) {
 302                                 if ( $this->mNewRev->isCurrent() && $this->mNewPage->userCan( 'rollback', $user ) ) {
 303                                         $rollbackLink = Linker::generateRollback( $this->mNewRev, $this->getContext() );
 304                                         if ( $rollbackLink ) {
 305                                                 $out->preventClickjacking();
 306                                                 $rollback = '&#160;&#160;&#160;' . $rollbackLink;
 307                                         }
 308                                 }
 309
 310                                 if ( !$this->mOldRev->isDeleted( Revision::DELETED_TEXT ) &&
 311                                         !$this->mNewRev->isDeleted( Revision::DELETED_TEXT )
 312                                 ) {
 313                                         $undoLink = Html::element( 'a', [
 314                                                         'href' => $this->mNewPage->getLocalURL( [
 315                                                                 'action' => 'edit',
 316                                                                 'undoafter' => $this->mOldid,
 317                                                                 'undo' => $this->mNewid
 318                                                         ] ),
 319                                                         'title' => Linker::titleAttrib( 'undo' ),
 320                                                 ],
 321                                                 $this->msg( 'editundo' )->text()
 322                                         );
 323                                         $revisionTools['mw-diff-undo'] = $undoLink;
 324                                 }
 325                         }
 326
 327                         # Make "previous revision link"
 328                         if ( $samePage && $this->mOldRev->getPrevious() ) {
 329                                 $prevlink = Linker::linkKnown(
 330                                         $this->mOldPage,
 331                                         $this->msg( 'previousdiff' )->escaped(),
 332                                         [ 'id' => 'differences-prevlink' ],
 333                                         [ 'diff' => 'prev', 'oldid' => $this->mOldid ] + $query
 334                                 );
 335                         } else {
 336                                 $prevlink = '&#160;';
 337                         }
 338
 339                         if ( $this->mOldRev->isMinor() ) {
 340                                 $oldminor = ChangesList::flag( 'minor' );
 341                         } else {
 342                                 $oldminor = '';
 343                         }
 344
 345                         $ldel = $this->revisionDeleteLink( $this->mOldRev );
 346                         $oldRevisionHeader = $this->getRevisionHeader( $this->mOldRev, 'complete' );
 347                         $oldChangeTags = ChangeTags::formatSummaryRow( $this->mOldTags, 'diff', $this->getContext() );
 348
 349                         $oldHeader = '<div id="mw-diff-otitle1"><strong>' . $oldRevisionHeader . '</strong></div>' .
 350                                 '<div id="mw-diff-otitle2">' .
 351                                 Linker::revUserTools( $this->mOldRev, !$this->unhide ) . '</div>' .
 352                                 '<div id="mw-diff-otitle3">' . $oldminor .
 353                                 Linker::revComment( $this->mOldRev, !$diffOnly, !$this->unhide ) . $ldel . '</div>' .
 354                                 '<div id="mw-diff-otitle5">' . $oldChangeTags[0] . '</div>' .
 355                                 '<div id="mw-diff-otitle4">' . $prevlink . '</div>';
 356
 357                         if ( $this->mOldRev->isDeleted( Revision::DELETED_TEXT ) ) {
 358                                 $deleted = true; // old revisions text is hidden
 359                                 if ( $this->mOldRev->isDeleted( Revision::DELETED_RESTRICTED ) ) {
 360                                         $suppressed = true; // also suppressed
 361                                 }
 362                         }
 363
 364                         # Check if this user can see the revisions
 365                         if ( !$this->mOldRev->userCan( Revision::DELETED_TEXT, $user ) ) {
 366                                 $allowed = false;
 367                         }
 368                 }
 369
 370                 # Make "next revision link"
 371                 # Skip next link on the top revision
 372                 if ( $samePage && !$this->mNewRev->isCurrent() ) {
 373                         $nextlink = Linker::linkKnown(
 374                                 $this->mNewPage,
 375                                 $this->msg( 'nextdiff' )->escaped(),
 376                                 [ 'id' => 'differences-nextlink' ],
 377                                 [ 'diff' => 'next', 'oldid' => $this->mNewid ] + $query
 378                         );
 379                 } else {
 380                         $nextlink = '&#160;';
 381                 }
 382
 383                 if ( $this->mNewRev->isMinor() ) {
 384                         $newminor = ChangesList::flag( 'minor' );
 385                 } else {
 386                         $newminor = '';
 387                 }
 388
 389                 # Handle RevisionDelete links...
 390                 $rdel = $this->revisionDeleteLink( $this->mNewRev );
 391
 392                 # Allow extensions to define their own revision tools
 393                 Hooks::run( 'DiffRevisionTools',
 394                         [ $this->mNewRev, &$revisionTools, $this->mOldRev, $user ] );
 395                 $formattedRevisionTools = [];
 396                 // Put each one in parentheses (poor man's button)
 397                 foreach ( $revisionTools as $key => $tool ) {
 398                         $toolClass = is_string( $key ) ? $key : 'mw-diff-tool';
 399                         $element = Html::rawElement(
 400                                 'span',
 401                                 [ 'class' => $toolClass ],
 402                                 $this->msg( 'parentheses' )->rawParams( $tool )->escaped()
 403                         );
 404                         $formattedRevisionTools[] = $element;
 405                 }
 406                 $newRevisionHeader = $this->getRevisionHeader( $this->mNewRev, 'complete' ) .
 407                         ' ' . implode( ' ', $formattedRevisionTools );
 408                 $newChangeTags = ChangeTags::formatSummaryRow( $this->mNewTags, 'diff', $this->getContext() );
 409
 410                 $newHeader = '<div id="mw-diff-ntitle1"><strong>' . $newRevisionHeader . '</strong></div>' .
 411                         '<div id="mw-diff-ntitle2">' . Linker::revUserTools( $this->mNewRev, !$this->unhide ) .
 412                         " $rollback</div>" .
 413                         '<div id="mw-diff-ntitle3">' . $newminor .
 414                         Linker::revComment( $this->mNewRev, !$diffOnly, !$this->unhide ) . $rdel . '</div>' .
 415                         '<div id="mw-diff-ntitle5">' . $newChangeTags[0] . '</div>' .
 416                         '<div id="mw-diff-ntitle4">' . $nextlink . $this->markPatrolledLink() . '</div>';
 417
 418                 if ( $this->mNewRev->isDeleted( Revision::DELETED_TEXT ) ) {
 419                         $deleted = true; // new revisions text is hidden
 420                         if ( $this->mNewRev->isDeleted( Revision::DELETED_RESTRICTED ) ) {
 421                                 $suppressed = true; // also suppressed
 422                         }
 423                 }
 424
 425                 # If the diff cannot be shown due to a deleted revision, then output
 426                 # the diff header and links to unhide (if available)...
 427                 if ( $deleted && ( !$this->unhide || !$allowed ) ) {
 428                         $this->showDiffStyle();
 429                         $multi = $this->getMultiNotice();
 430                         $out->addHTML( $this->addHeader( '', $oldHeader, $newHeader, $multi ) );
 431                         if ( !$allowed ) {
 432                                 $msg = $suppressed ? 'rev-suppressed-no-diff' : 'rev-deleted-no-diff';
 433                                 # Give explanation for why revision is not visible
 434                                 $out->wrapWikiMsg( "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 435                                         [ $msg ] );
 436                         } else {
 437                                 # Give explanation and add a link to view the diff...
 438                                 $query = $this->getRequest()->appendQueryValue( 'unhide', '1' );
 439                                 $link = $this->getTitle()->getFullURL( $query );
 440                                 $msg = $suppressed ? 'rev-suppressed-unhide-diff' : 'rev-deleted-unhide-diff';
 441                                 $out->wrapWikiMsg(
 442                                         "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 443                                         [ $msg, $link ]
 444                                 );
 445                         }
 446                 # Otherwise, output a regular diff...
 447                 } else {
 448                         # Add deletion notice if the user is viewing deleted content
 449                         $notice = '';
 450                         if ( $deleted ) {
 451                                 $msg = $suppressed ? 'rev-suppressed-diff-view' : 'rev-deleted-diff-view';
 452                                 $notice = "<div id='mw-$msg' class='mw-warning plainlinks'>\n" .
 453                                         $this->msg( $msg )->parse() .
 454                                         "</div>\n";
 455                         }
 456                         $this->showDiff( $oldHeader, $newHeader, $notice );
 457                         if ( !$diffOnly ) {
 458                                 $this->renderNewRevision();
 459                         }
 460                 }
 461         }
 462
 463         /**
 464          * Build a link to mark a change as patrolled.
 465          *
 466          * Returns empty string if there's either no revision to patrol or the user is not allowed to.
 467          * Side effect: When the patrol link is build, this method will call
 468          * OutputPage::preventClickjacking() and load mediawiki.page.patrol.ajax.
 469          *
 470          * @return string HTML or empty string
 471          */
 472         protected function markPatrolledLink() {
 473                 if ( $this->mMarkPatrolledLink === null ) {
 474                         $linkInfo = $this->getMarkPatrolledLinkInfo();
 475                         // If false, there is no patrol link needed/allowed
 476                         if ( !$linkInfo ) {
 477                                 $this->mMarkPatrolledLink = '';
 478                         } else {
 479                                 $this->mMarkPatrolledLink = ' <span class="patrollink" data-mw="interface">[' .
 480                                         Linker::linkKnown(
 481                                                 $this->mNewPage,
 482                                                 $this->msg( 'markaspatrolleddiff' )->escaped(),
 483                                                 [],
 484                                                 [
 485                                                         'action' => 'markpatrolled',
 486                                                         'rcid' => $linkInfo['rcid'],
 487                                                         'token' => $linkInfo['token'],
 488                                                 ]
 489                                         ) . ']</span>';
 490                         }
 491                 }
 492                 return $this->mMarkPatrolledLink;
 493         }
 494
 495         /**
 496          * Returns an array of meta data needed to build a "mark as patrolled" link and
 497          * adds the mediawiki.page.patrol.ajax to the output.
 498          *
 499          * @return array|false An array of meta data for a patrol link (rcid & token)
 500          *  or false if no link is needed
 501          */
 502         protected function getMarkPatrolledLinkInfo() {
 503                 global $wgUseRCPatrol, $wgEnableAPI, $wgEnableWriteAPI;
 504
 505                 $user = $this->getUser();
 506
 507                 // Prepare a change patrol link, if applicable
 508                 if (
 509                         // Is patrolling enabled and the user allowed to?
 510                         $wgUseRCPatrol && $this->mNewPage->quickUserCan( 'patrol', $user ) &&
 511                         // Only do this if the revision isn't more than 6 hours older
 512                         // than the Max RC age (6h because the RC might not be cleaned out regularly)
 513                         RecentChange::isInRCLifespan( $this->mNewRev->getTimestamp(), 21600 )
 514                 ) {
 515                         // Look for an unpatrolled change corresponding to this diff
 516                         $db = wfGetDB( DB_SLAVE );
 517                         $change = RecentChange::newFromConds(
 518                                 [
 519                                         'rc_timestamp' => $db->timestamp( $this->mNewRev->getTimestamp() ),
 520                                         'rc_this_oldid' => $this->mNewid,
 521                                         'rc_patrolled' => 0
 522                                 ],
 523                                 __METHOD__
 524                         );
 525
 526                         if ( $change && !$change->getPerformer()->equals( $user ) ) {
 527                                 $rcid = $change->getAttribute( 'rc_id' );
 528                         } else {
 529                                 // None found or the page has been created by the current user.
 530                                 // If the user could patrol this it already would be patrolled
 531                                 $rcid = 0;
 532                         }
 533                         // Build the link
 534                         if ( $rcid ) {
 535                                 $this->getOutput()->preventClickjacking();
 536                                 if ( $wgEnableAPI && $wgEnableWriteAPI
 537                                         && $user->isAllowed( 'writeapi' )
 538                                 ) {
 539                                         $this->getOutput()->addModules( 'mediawiki.page.patrol.ajax' );
 540                                 }
 541
 542                                 $token = $user->getEditToken( $rcid );
 543                                 return [
 544                                         'rcid' => $rcid,
 545                                         'token' => $token,
 546                                 ];
 547                         }
 548                 }
 549
 550                 // No mark as patrolled link applicable
 551                 return false;
 552         }
 553
 554         /**
 555          * @param Revision $rev
 556          *
 557          * @return string
 558          */
 559         protected function revisionDeleteLink( $rev ) {
 560                 $link = Linker::getRevDeleteLink( $this->getUser(), $rev, $rev->getTitle() );
 561                 if ( $link !== '' ) {
 562                         $link = '&#160;&#160;&#160;' . $link . ' ';
 563                 }
 564
 565                 return $link;
 566         }
 567
 568         /**
 569          * Show the new revision of the page.
 570          */
 571         public function renderNewRevision() {
 572                 $out = $this->getOutput();
 573                 $revHeader = $this->getRevisionHeader( $this->mNewRev );
 574                 # Add "current version as of X" title
 575                 $out->addHTML( "<hr class='diff-hr' id='mw-oldid' />
 576                 <h2 class='diff-currentversion-title'>{$revHeader}</h2>\n" );
 577                 # Page content may be handled by a hooked call instead...
 578                 # @codingStandardsIgnoreStart Ignoring long lines.
 579                 if ( Hooks::run( 'ArticleContentOnDiff', [ $this, $out ] ) ) {
 580                         $this->loadNewText();
 581                         $out->setRevisionId( $this->mNewid );
 582                         $out->setRevisionTimestamp( $this->mNewRev->getTimestamp() );
 583                         $out->setArticleFlag( true );
 584
 585                         // NOTE: only needed for B/C: custom rendering of JS/CSS via hook
 586                         if ( $this->mNewPage->isCssJsSubpage() || $this->mNewPage->isCssOrJsPage() ) {
 587                                 // This needs to be synchronised with Article::showCssOrJsPage(), which sucks
 588                                 // Give hooks a chance to customise the output
 589                                 // @todo standardize this crap into one function
 590                                 if ( ContentHandler::runLegacyHooks( 'ShowRawCssJs', [ $this->mNewContent, $this->mNewPage, $out ] ) ) {
 591                                         // NOTE: deprecated hook, B/C only
 592                                         // use the content object's own rendering
 593                                         $cnt = $this->mNewRev->getContent();
 594                                         $po = $cnt ? $cnt->getParserOutput( $this->mNewRev->getTitle(), $this->mNewRev->getId() ) : null;
 595                                         if ( $po ) {
 596                                                 $out->addParserOutputContent( $po );
 597                                         }
 598                                 }
 599                         } elseif ( !Hooks::run( 'ArticleContentViewCustom', [ $this->mNewContent, $this->mNewPage, $out ] ) ) {
 600                                 // Handled by extension
 601                         } elseif ( !ContentHandler::runLegacyHooks( 'ArticleViewCustom', [ $this->mNewContent, $this->mNewPage, $out ] ) ) {
 602                                 // NOTE: deprecated hook, B/C only
 603                                 // Handled by extension
 604                         } else {
 605                                 // Normal page
 606                                 if ( $this->getTitle()->equals( $this->mNewPage ) ) {
 607                                         // If the Title stored in the context is the same as the one
 608                                         // of the new revision, we can use its associated WikiPage
 609                                         // object.
 610                                         $wikiPage = $this->getWikiPage();
 611                                 } else {
 612                                         // Otherwise we need to create our own WikiPage object
 613                                         $wikiPage = WikiPage::factory( $this->mNewPage );
 614                                 }
 615
 616                                 $parserOutput = $this->getParserOutput( $wikiPage, $this->mNewRev );
 617
 618                                 # WikiPage::getParserOutput() should not return false, but just in case
 619                                 if ( $parserOutput ) {
 620                                         $out->addParserOutput( $parserOutput );
 621                                 }
 622                         }
 623                 }
 624                 # @codingStandardsIgnoreEnd
 625
 626                 # Add redundant patrol link on bottom...
 627                 $out->addHTML( $this->markPatrolledLink() );
 628
 629         }
 630
 631         protected function getParserOutput( WikiPage $page, Revision $rev ) {
 632                 $parserOptions = $page->makeParserOptions( $this->getContext() );
 633
 634                 if ( !$rev->isCurrent() || !$rev->getTitle()->quickUserCan( 'edit', $this->getUser() ) ) {
 635                         $parserOptions->setEditSection( false );
 636                 }
 637
 638                 $parserOutput = $page->getParserOutput( $parserOptions, $rev->getId() );
 639
 640                 return $parserOutput;
 641         }
 642
 643         /**
 644          * Get the diff text, send it to the OutputPage object
 645          * Returns false if the diff could not be generated, otherwise returns true
 646          *
 647          * @param string|bool $otitle Header for old text or false
 648          * @param string|bool $ntitle Header for new text or false
 649          * @param string $notice HTML between diff header and body
 650          *
 651          * @return bool
 652          */
 653         public function showDiff( $otitle, $ntitle, $notice = '' ) {
 654                 $diff = $this->getDiff( $otitle, $ntitle, $notice );
 655                 if ( $diff === false ) {
 656                         $this->showMissingRevision();
 657
 658                         return false;
 659                 } else {
 660                         $this->showDiffStyle();
 661                         $this->getOutput()->addHTML( $diff );
 662
 663                         return true;
 664                 }
 665         }
 666
 667         /**
 668          * Add style sheets and supporting JS for diff display.
 669          */
 670         public function showDiffStyle() {
 671                 $this->getOutput()->addModuleStyles( 'mediawiki.action.history.diff' );
 672         }
 673
 674         /**
 675          * Get complete diff table, including header
 676          *
 677          * @param string|bool $otitle Header for old text or false
 678          * @param string|bool $ntitle Header for new text or false
 679          * @param string $notice HTML between diff header and body
 680          *
 681          * @return mixed
 682          */
 683         public function getDiff( $otitle, $ntitle, $notice = '' ) {
 684                 $body = $this->getDiffBody();
 685                 if ( $body === false ) {
 686                         return false;
 687                 }
 688
 689                 $multi = $this->getMultiNotice();
 690                 // Display a message when the diff is empty
 691                 if ( $body === '' ) {
 692                         $notice .= '<div class="mw-diff-empty">' .
 693                                 $this->msg( 'diff-empty' )->parse() .
 694                                 "</div>\n";
 695                 }
 696
 697                 return $this->addHeader( $body, $otitle, $ntitle, $multi, $notice );
 698         }
 699
 700         /**
 701          * Get the diff table body, without header
 702          *
 703          * @return mixed (string/false)
 704          */
 705         public function getDiffBody() {
 706                 $this->mCacheHit = true;
 707                 // Check if the diff should be hidden from this user
 708                 if ( !$this->loadRevisionData() ) {
 709                         return false;
 710                 } elseif ( $this->mOldRev &&
 711                         !$this->mOldRev->userCan( Revision::DELETED_TEXT, $this->getUser() )
 712                 ) {
 713                         return false;
 714                 } elseif ( $this->mNewRev &&
 715                         !$this->mNewRev->userCan( Revision::DELETED_TEXT, $this->getUser() )
 716                 ) {
 717                         return false;
 718                 }
 719                 // Short-circuit
 720                 if ( $this->mOldRev === false || ( $this->mOldRev && $this->mNewRev
 721                         && $this->mOldRev->getId() == $this->mNewRev->getId() )
 722                 ) {
 723                         return '';
 724                 }
 725                 // Cacheable?
 726                 $key = false;
 727                 $cache = ObjectCache::getMainWANInstance();
 728                 if ( $this->mOldid && $this->mNewid ) {
 729                         $key = $this->getDiffBodyCacheKey();
 730
 731                         // Try cache
 732                         if ( !$this->mRefreshCache ) {
 733                                 $difftext = $cache->get( $key );
 734                                 if ( $difftext ) {
 735                                         wfIncrStats( 'diff_cache.hit' );
 736                                         $difftext = $this->localiseLineNumbers( $difftext );
 737                                         $difftext .= "\n<!-- diff cache key $key -->\n";
 738
 739                                         return $difftext;
 740                                 }
 741                         } // don't try to load but save the result
 742                 }
 743                 $this->mCacheHit = false;
 744
 745                 // Loadtext is permission safe, this just clears out the diff
 746                 if ( !$this->loadText() ) {
 747                         return false;
 748                 }
 749
 750                 $difftext = $this->generateContentDiffBody( $this->mOldContent, $this->mNewContent );
 751
 752                 // Save to cache for 7 days
 753                 if ( !Hooks::run( 'AbortDiffCache', [ &$this ] ) ) {
 754                         wfIncrStats( 'diff_cache.uncacheable' );
 755                 } elseif ( $key !== false && $difftext !== false ) {
 756                         wfIncrStats( 'diff_cache.miss' );
 757                         $cache->set( $key, $difftext, 7 * 86400 );
 758                 } else {
 759                         wfIncrStats( 'diff_cache.uncacheable' );
 760                 }
 761                 // Replace line numbers with the text in the user's language
 762                 if ( $difftext !== false ) {
 763                         $difftext = $this->localiseLineNumbers( $difftext );
 764                 }
 765
 766                 return $difftext;
 767         }
 768
 769         /**
 770          * Returns the cache key for diff body text or content.
 771          *
 772          * @since 1.23
 773          *
 774          * @throws MWException
 775          * @return string
 776          */
 777         protected function getDiffBodyCacheKey() {
 778                 if ( !$this->mOldid || !$this->mNewid ) {
 779                         throw new MWException( 'mOldid and mNewid must be set to get diff cache key.' );
 780                 }
 781
 782                 return wfMemcKey( 'diff', 'version', self::DIFF_VERSION,
 783                         'oldid', $this->mOldid, 'newid', $this->mNewid );
 784         }
 785
 786         /**
 787          * Generate a diff, no caching.
 788          *
 789          * This implementation uses generateTextDiffBody() to generate a diff based on the default
 790          * serialization of the given Content objects. This will fail if $old or $new are not
 791          * instances of TextContent.
 792          *
 793          * Subclasses may override this to provide a different rendering for the diff,
 794          * perhaps taking advantage of the content's native form. This is required for all content
 795          * models that are not text based.
 796          *
 797          * @since 1.21
 798          *
 799          * @param Content $old Old content
 800          * @param Content $new New content
 801          *
 802          * @throws MWException If old or new content is not an instance of TextContent.
 803          * @return bool|string
 804          */
 805         public function generateContentDiffBody( Content $old, Content $new ) {
 806                 if ( !( $old instanceof TextContent ) ) {
 807                         throw new MWException( "Diff not implemented for " . get_class( $old ) . "; " .
 808                                 "override generateContentDiffBody to fix this." );
 809                 }
 810
 811                 if ( !( $new instanceof TextContent ) ) {
 812                         throw new MWException( "Diff not implemented for " . get_class( $new ) . "; "
 813                                 . "override generateContentDiffBody to fix this." );
 814                 }
 815
 816                 $otext = $old->serialize();
 817                 $ntext = $new->serialize();
 818
 819                 return $this->generateTextDiffBody( $otext, $ntext );
 820         }
 821
 822         /**
 823          * Generate a diff, no caching
 824          *
 825          * @param string $otext Old text, must be already segmented
 826          * @param string $ntext New text, must be already segmented
 827          *
 828          * @return bool|string
 829          * @deprecated since 1.21, use generateContentDiffBody() instead!
 830          */
 831         public function generateDiffBody( $otext, $ntext ) {
 832                 ContentHandler::deprecated( __METHOD__, "1.21" );
 833
 834                 return $this->generateTextDiffBody( $otext, $ntext );
 835         }
 836
 837         /**
 838          * Generate a diff, no caching
 839          *
 840          * @todo move this to TextDifferenceEngine, make DifferenceEngine abstract. At some point.
 841          *
 842          * @param string $otext Old text, must be already segmented
 843          * @param string $ntext New text, must be already segmented
 844          *
 845          * @return bool|string
 846          */
 847         public function generateTextDiffBody( $otext, $ntext ) {
 848                 $diff = function() use ( $otext, $ntext ) {
 849                         $time = microtime( true );
 850
 851                         $result = $this->textDiff( $otext, $ntext );
 852
 853                         $time = intval( ( microtime( true ) - $time ) * 1000 );
 854                         $this->getStats()->timing( 'diff_time', $time );
 855                         // Log requests slower than 99th percentile
 856                         if ( $time > 100 && $this->mOldPage && $this->mNewPage ) {
 857                                 wfDebugLog( 'diff',
 858                                         "$time ms diff: {$this->mOldid} -> {$this->mNewid} {$this->mNewPage}" );
 859                         }
 860
 861                         return $result;
 862                 };
 863
 864                 $error = function( $status ) {
 865                         throw new FatalError( $status->getWikiText() );
 866                 };
 867
 868                 // Use PoolCounter if the diff looks like it can be expensive
 869                 if ( strlen( $otext ) + strlen( $ntext ) > 20000 ) {
 870                         $work = new PoolCounterWorkViaCallback( 'diff',
 871                                 md5( $otext ) . md5( $ntext ),
 872                                 [ 'doWork' => $diff, 'error' => $error ]
 873                         );
 874                         return $work->execute();
 875                 }
 876
 877                 return $diff();
 878         }
 879
 880         /**
 881          * Generates diff, to be wrapped internally in a logging/instrumentation
 882          *
 883          * @param string $otext Old text, must be already segmented
 884          * @param string $ntext New text, must be already segmented
 885          * @return bool|string
 886          */
 887         protected function textDiff( $otext, $ntext ) {
 888                 global $wgExternalDiffEngine, $wgContLang;
 889
 890                 $otext = str_replace( "\r\n", "\n", $otext );
 891                 $ntext = str_replace( "\r\n", "\n", $ntext );
 892
 893                 if ( $wgExternalDiffEngine == 'wikidiff' || $wgExternalDiffEngine == 'wikidiff3' ) {
 894                         wfDeprecated( "\$wgExternalDiffEngine = '{$wgExternalDiffEngine}'", '1.27' );
 895                         $wgExternalDiffEngine = false;
 896                 } elseif ( $wgExternalDiffEngine == 'wikidiff2' ) {
 897                         // Same as above, but with no deprecation warnings
 898                         $wgExternalDiffEngine = false;
 899                 } elseif ( !is_string( $wgExternalDiffEngine ) && $wgExternalDiffEngine !== false ) {
 900                         // And prevent people from shooting themselves in the foot...
 901                         wfWarn( '$wgExternalDiffEngine is set to a non-string value, forcing it to false' );
 902                         $wgExternalDiffEngine = false;
 903                 }
 904
 905                 if ( function_exists( 'wikidiff2_do_diff' ) && $wgExternalDiffEngine === false ) {
 906                         # Better external diff engine, the 2 may some day be dropped
 907                         # This one does the escaping and segmenting itself
 908                         $text = wikidiff2_do_diff( $otext, $ntext, 2 );
 909                         $text .= $this->debug( 'wikidiff2' );
 910
 911                         return $text;
 912                 } elseif ( $wgExternalDiffEngine !== false && is_executable( $wgExternalDiffEngine ) ) {
 913                         # Diff via the shell
 914                         $tmpDir = wfTempDir();
 915                         $tempName1 = tempnam( $tmpDir, 'diff_' );
 916                         $tempName2 = tempnam( $tmpDir, 'diff_' );
 917
 918                         $tempFile1 = fopen( $tempName1, "w" );
 919                         if ( !$tempFile1 ) {
 920                                 return false;
 921                         }
 922                         $tempFile2 = fopen( $tempName2, "w" );
 923                         if ( !$tempFile2 ) {
 924                                 return false;
 925                         }
 926                         fwrite( $tempFile1, $otext );
 927                         fwrite( $tempFile2, $ntext );
 928                         fclose( $tempFile1 );
 929                         fclose( $tempFile2 );
 930                         $cmd = wfEscapeShellArg( $wgExternalDiffEngine, $tempName1, $tempName2 );
 931                         $difftext = wfShellExec( $cmd );
 932                         $difftext .= $this->debug( "external $wgExternalDiffEngine" );
 933                         unlink( $tempName1 );
 934                         unlink( $tempName2 );
 935
 936                         return $difftext;
 937                 }
 938
 939                 # Native PHP diff
 940                 $ota = explode( "\n", $wgContLang->segmentForDiff( $otext ) );
 941                 $nta = explode( "\n", $wgContLang->segmentForDiff( $ntext ) );
 942                 $diffs = new Diff( $ota, $nta );
 943                 $formatter = new TableDiffFormatter();
 944                 $difftext = $wgContLang->unsegmentForDiff( $formatter->format( $diffs ) );
 945
 946                 return $difftext;
 947         }
 948
 949         /**
 950          * Generate a debug comment indicating diff generating time,
 951          * server node, and generator backend.
 952          *
 953          * @param string $generator : What diff engine was used
 954          *
 955          * @return string
 956          */
 957         protected function debug( $generator = "internal" ) {
 958                 global $wgShowHostnames;
 959                 if ( !$this->enableDebugComment ) {
 960                         return '';
 961                 }
 962                 $data = [ $generator ];
 963                 if ( $wgShowHostnames ) {
 964                         $data[] = wfHostname();
 965                 }
 966                 $data[] = wfTimestamp( TS_DB );
 967
 968                 return "<!-- diff generator: " .
 969                         implode( " ", array_map( "htmlspecialchars", $data ) ) .
 970                         " -->\n";
 971         }
 972
 973         /**
 974          * Replace line numbers with the text in the user's language
 975          *
 976          * @param string $text
 977          *
 978          * @return mixed
 979          */
 980         public function localiseLineNumbers( $text ) {
 981                 return preg_replace_callback(
 982                         '/<!--LINE (\d+)-->/',
 983                         [ &$this, 'localiseLineNumbersCb' ],
 984                         $text
 985                 );
 986         }
 987
 988         public function localiseLineNumbersCb( $matches ) {
 989                 if ( $matches[1] === '1' && $this->mReducedLineNumbers ) {
 990                         return '';
 991                 }
 992
 993                 return $this->msg( 'lineno' )->numParams( $matches[1] )->escaped();
 994         }
 995
 996         /**
 997          * If there are revisions between the ones being compared, return a note saying so.
 998          *
 999          * @return string
1000          */
1001         public function getMultiNotice() {
1002                 if ( !is_object( $this->mOldRev ) || !is_object( $this->mNewRev ) ) {
1003                         return '';
1004                 } elseif ( !$this->mOldPage->equals( $this->mNewPage ) ) {
1005                         // Comparing two different pages? Count would be meaningless.
1006                         return '';
1007                 }
1008
1009                 if ( $this->mOldRev->getTimestamp() > $this->mNewRev->getTimestamp() ) {
1010                         $oldRev = $this->mNewRev; // flip
1011                         $newRev = $this->mOldRev; // flip
1012                 } else { // normal case
1013                         $oldRev = $this->mOldRev;
1014                         $newRev = $this->mNewRev;
1015                 }
1016
1017                 // Sanity: don't show the notice if too many rows must be scanned
1018                 // @todo show some special message for that case
1019                 $nEdits = $this->mNewPage->countRevisionsBetween( $oldRev, $newRev, 1000 );
1020                 if ( $nEdits > 0 && $nEdits <= 1000 ) {
1021                         $limit = 100; // use diff-multi-manyusers if too many users
1022                         $users = $this->mNewPage->getAuthorsBetween( $oldRev, $newRev, $limit );
1023                         $numUsers = count( $users );
1024
1025                         if ( $numUsers == 1 && $users[0] == $newRev->getUserText( Revision::RAW ) ) {
1026                                 $numUsers = 0; // special case to say "by the same user" instead of "by one other user"
1027                         }
1028
1029                         return self::intermediateEditsMsg( $nEdits, $numUsers, $limit );
1030                 }
1031
1032                 return ''; // nothing
1033         }
1034
1035         /**
1036          * Get a notice about how many intermediate edits and users there are
1037          *
1038          * @param int $numEdits
1039          * @param int $numUsers
1040          * @param int $limit
1041          *
1042          * @return string
1043          */
1044         public static function intermediateEditsMsg( $numEdits, $numUsers, $limit ) {
1045                 if ( $numUsers === 0 ) {
1046                         $msg = 'diff-multi-sameuser';
1047                 } elseif ( $numUsers > $limit ) {
1048                         $msg = 'diff-multi-manyusers';
1049                         $numUsers = $limit;
1050                 } else {
1051                         $msg = 'diff-multi-otherusers';
1052                 }
1053
1054                 return wfMessage( $msg )->numParams( $numEdits, $numUsers )->parse();
1055         }
1056
1057         /**
1058          * Get a header for a specified revision.
1059          *
1060          * @param Revision $rev
1061          * @param string $complete 'complete' to get the header wrapped depending
1062          *        the visibility of the revision and a link to edit the page.
1063          *
1064          * @return string HTML fragment
1065          */
1066         protected function getRevisionHeader( Revision $rev, $complete = '' ) {
1067                 $lang = $this->getLanguage();
1068                 $user = $this->getUser();
1069                 $revtimestamp = $rev->getTimestamp();
1070                 $timestamp = $lang->userTimeAndDate( $revtimestamp, $user );
1071                 $dateofrev = $lang->userDate( $revtimestamp, $user );
1072                 $timeofrev = $lang->userTime( $revtimestamp, $user );
1073
1074                 $header = $this->msg(
1075                         $rev->isCurrent() ? 'currentrev-asof' : 'revisionasof',
1076                         $timestamp,
1077                         $dateofrev,
1078                         $timeofrev
1079                 )->escaped();
1080
1081                 if ( $complete !== 'complete' ) {
1082                         return $header;
1083                 }
1084
1085                 $title = $rev->getTitle();
1086
1087                 $header = Linker::linkKnown( $title, $header, [],
1088                         [ 'oldid' => $rev->getId() ] );
1089
1090                 if ( $rev->userCan( Revision::DELETED_TEXT, $user ) ) {
1091                         $editQuery = [ 'action' => 'edit' ];
1092                         if ( !$rev->isCurrent() ) {
1093                                 $editQuery['oldid'] = $rev->getId();
1094                         }
1095
1096                         $key = $title->quickUserCan( 'edit', $user ) ? 'editold' : 'viewsourceold';
1097                         $msg = $this->msg( $key )->escaped();
1098                         $editLink = $this->msg( 'parentheses' )->rawParams(
1099                                 Linker::linkKnown( $title, $msg, [], $editQuery ) )->escaped();
1100                         $header .= ' ' . Html::rawElement(
1101                                 'span',
1102                                 [ 'class' => 'mw-diff-edit' ],
1103                                 $editLink
1104                         );
1105                         if ( $rev->isDeleted( Revision::DELETED_TEXT ) ) {
1106                                 $header = Html::rawElement(
1107                                         'span',
1108                                         [ 'class' => 'history-deleted' ],
1109                                         $header
1110                                 );
1111                         }
1112                 } else {
1113                         $header = Html::rawElement( 'span', [ 'class' => 'history-deleted' ], $header );
1114                 }
1115
1116                 return $header;
1117         }
1118
1119         /**
1120          * Add the header to a diff body
1121          *
1122          * @param string $diff Diff body
1123          * @param string $otitle Old revision header
1124          * @param string $ntitle New revision header
1125          * @param string $multi Notice telling user that there are intermediate
1126          *   revisions between the ones being compared
1127          * @param string $notice Other notices, e.g. that user is viewing deleted content
1128          *
1129          * @return string
1130          */
1131         public function addHeader( $diff, $otitle, $ntitle, $multi = '', $notice = '' ) {
1132                 // shared.css sets diff in interface language/dir, but the actual content
1133                 // is often in a different language, mostly the page content language/dir
1134                 $header = Html::openElement( 'table', [
1135                         'class' => [ 'diff', 'diff-contentalign-' . $this->getDiffLang()->alignStart() ],
1136                         'data-mw' => 'interface',
1137                 ] );
1138                 $userLang = htmlspecialchars( $this->getLanguage()->getHtmlCode() );
1139
1140                 if ( !$diff && !$otitle ) {
1141                         $header .= "
1142                         <tr style='vertical-align: top;' lang='{$userLang}'>
1143                         <td class='diff-ntitle'>{$ntitle}</td>
1144                         </tr>";
1145                         $multiColspan = 1;
1146                 } else {
1147                         if ( $diff ) { // Safari/Chrome show broken output if cols not used
1148                                 $header .= "
1149                                 <col class='diff-marker' />
1150                                 <col class='diff-content' />
1151                                 <col class='diff-marker' />
1152                                 <col class='diff-content' />";
1153                                 $colspan = 2;
1154                                 $multiColspan = 4;
1155                         } else {
1156                                 $colspan = 1;
1157                                 $multiColspan = 2;
1158                         }
1159                         if ( $otitle || $ntitle ) {
1160                                 $header .= "
1161                                 <tr style='vertical-align: top;' lang='{$userLang}'>
1162                                 <td colspan='$colspan' class='diff-otitle'>{$otitle}</td>
1163                                 <td colspan='$colspan' class='diff-ntitle'>{$ntitle}</td>
1164                                 </tr>";
1165                         }
1166                 }
1167
1168                 if ( $multi != '' ) {
1169                         $header .= "<tr><td colspan='{$multiColspan}' style='text-align: center;' " .
1170                                 "class='diff-multi' lang='{$userLang}'>{$multi}</td></tr>";
1171                 }
1172                 if ( $notice != '' ) {
1173                         $header .= "<tr><td colspan='{$multiColspan}' style='text-align: center;' " .
1174                                 "lang='{$userLang}'>{$notice}</td></tr>";
1175                 }
1176
1177                 return $header . $diff . "</table>";
1178         }
1179
1180         /**
1181          * Use specified text instead of loading from the database
1182          * @param Content $oldContent
1183          * @param Content $newContent
1184          * @since 1.21
1185          */
1186         public function setContent( Content $oldContent, Content $newContent ) {
1187                 $this->mOldContent = $oldContent;
1188                 $this->mNewContent = $newContent;
1189
1190                 $this->mTextLoaded = 2;
1191                 $this->mRevisionsLoaded = true;
1192         }
1193
1194         /**
1195          * Set the language in which the diff text is written
1196          * (Defaults to page content language).
1197          * @param Language|string $lang
1198          * @since 1.19
1199          */
1200         public function setTextLanguage( $lang ) {
1201                 $this->mDiffLang = wfGetLangObj( $lang );
1202         }
1203
1204         /**
1205          * Maps a revision pair definition as accepted by DifferenceEngine constructor
1206          * to a pair of actual integers representing revision ids.
1207          *
1208          * @param int $old Revision id, e.g. from URL parameter 'oldid'
1209          * @param int|string $new Revision id or strings 'next' or 'prev', e.g. from URL parameter 'diff'
1210          *
1211          * @return int[] List of two revision ids, older first, later second.
1212          *     Zero signifies invalid argument passed.
1213          *     false signifies that there is no previous/next revision ($old is the oldest/newest one).
1214          */
1215         public function mapDiffPrevNext( $old, $new ) {
1216                 if ( $new === 'prev' ) {
1217                         // Show diff between revision $old and the previous one. Get previous one from DB.
1218                         $newid = intval( $old );
1219                         $oldid = $this->getTitle()->getPreviousRevisionID( $newid );
1220                 } elseif ( $new === 'next' ) {
1221                         // Show diff between revision $old and the next one. Get next one from DB.
1222                         $oldid = intval( $old );
1223                         $newid = $this->getTitle()->getNextRevisionID( $oldid );
1224                 } else {
1225                         $oldid = intval( $old );
1226                         $newid = intval( $new );
1227                 }
1228
1229                 return [ $oldid, $newid ];
1230         }
1231
1232         /**
1233          * Load revision IDs
1234          */
1235         private function loadRevisionIds() {
1236                 if ( $this->mRevisionsIdsLoaded ) {
1237                         return;
1238                 }
1239
1240                 $this->mRevisionsIdsLoaded = true;
1241
1242                 $old = $this->mOldid;
1243                 $new = $this->mNewid;
1244
1245                 list( $this->mOldid, $this->mNewid ) = self::mapDiffPrevNext( $old, $new );
1246                 if ( $new === 'next' && $this->mNewid === false ) {
1247                         # if no result, NewId points to the newest old revision. The only newer
1248                         # revision is cur, which is "0".
1249                         $this->mNewid = 0;
1250                 }
1251
1252                 Hooks::run(
1253                         'NewDifferenceEngine',
1254                         [ $this->getTitle(), &$this->mOldid, &$this->mNewid, $old, $new ]
1255                 );
1256         }
1257
1258         /**
1259          * Load revision metadata for the specified articles. If newid is 0, then compare
1260          * the old article in oldid to the current article; if oldid is 0, then
1261          * compare the current article to the immediately previous one (ignoring the
1262          * value of newid).
1263          *
1264          * If oldid is false, leave the corresponding revision object set
1265          * to false. This is impossible via ordinary user input, and is provided for
1266          * API convenience.
1267          *
1268          * @return bool
1269          */
1270         public function loadRevisionData() {
1271                 if ( $this->mRevisionsLoaded ) {
1272                         return true;
1273                 }
1274
1275                 // Whether it succeeds or fails, we don't want to try again
1276                 $this->mRevisionsLoaded = true;
1277
1278                 $this->loadRevisionIds();
1279
1280                 // Load the new revision object
1281                 if ( $this->mNewid ) {
1282                         $this->mNewRev = Revision::newFromId( $this->mNewid );
1283                 } else {
1284                         $this->mNewRev = Revision::newFromTitle(
1285                                 $this->getTitle(),
1286                                 false,
1287                                 Revision::READ_NORMAL
1288                         );
1289                 }
1290
1291                 if ( !$this->mNewRev instanceof Revision ) {
1292                         return false;
1293                 }
1294
1295                 // Update the new revision ID in case it was 0 (makes life easier doing UI stuff)
1296                 $this->mNewid = $this->mNewRev->getId();
1297                 $this->mNewPage = $this->mNewRev->getTitle();
1298
1299                 // Load the old revision object
1300                 $this->mOldRev = false;
1301                 if ( $this->mOldid ) {
1302                         $this->mOldRev = Revision::newFromId( $this->mOldid );
1303                 } elseif ( $this->mOldid === 0 ) {
1304                         $rev = $this->mNewRev->getPrevious();
1305                         if ( $rev ) {
1306                                 $this->mOldid = $rev->getId();
1307                                 $this->mOldRev = $rev;
1308                         } else {
1309                                 // No previous revision; mark to show as first-version only.
1310                                 $this->mOldid = false;
1311                                 $this->mOldRev = false;
1312                         }
1313                 } /* elseif ( $this->mOldid === false ) leave mOldRev false; */
1314
1315                 if ( is_null( $this->mOldRev ) ) {
1316                         return false;
1317                 }
1318
1319                 if ( $this->mOldRev ) {
1320                         $this->mOldPage = $this->mOldRev->getTitle();
1321                 }
1322
1323                 // Load tags information for both revisions
1324                 $dbr = wfGetDB( DB_SLAVE );
1325                 if ( $this->mOldid !== false ) {
1326                         $this->mOldTags = $dbr->selectField(
1327                                 'tag_summary',
1328                                 'ts_tags',
1329                                 [ 'ts_rev_id' => $this->mOldid ],
1330                                 __METHOD__
1331                         );
1332                 } else {
1333                         $this->mOldTags = false;
1334                 }
1335                 $this->mNewTags = $dbr->selectField(
1336                         'tag_summary',
1337                         'ts_tags',
1338                         [ 'ts_rev_id' => $this->mNewid ],
1339                         __METHOD__
1340                 );
1341
1342                 return true;
1343         }
1344
1345         /**
1346          * Load the text of the revisions, as well as revision data.
1347          *
1348          * @return bool
1349          */
1350         public function loadText() {
1351                 if ( $this->mTextLoaded == 2 ) {
1352                         return true;
1353                 }
1354
1355                 // Whether it succeeds or fails, we don't want to try again
1356                 $this->mTextLoaded = 2;
1357
1358                 if ( !$this->loadRevisionData() ) {
1359                         return false;
1360                 }
1361
1362                 if ( $this->mOldRev ) {
1363                         $this->mOldContent = $this->mOldRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1364                         if ( $this->mOldContent === null ) {
1365                                 return false;
1366                         }
1367                 }
1368
1369                 if ( $this->mNewRev ) {
1370                         $this->mNewContent = $this->mNewRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1371                         if ( $this->mNewContent === null ) {
1372                                 return false;
1373                         }
1374                 }
1375
1376                 return true;
1377         }
1378
1379         /**
1380          * Load the text of the new revision, not the old one
1381          *
1382          * @return bool
1383          */
1384         public function loadNewText() {
1385                 if ( $this->mTextLoaded >= 1 ) {
1386                         return true;
1387                 }
1388
1389                 $this->mTextLoaded = 1;
1390
1391                 if ( !$this->loadRevisionData() ) {
1392                         return false;
1393                 }
1394
1395                 $this->mNewContent = $this->mNewRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1396
1397                 return true;
1398         }
1399
1400 }