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 use MediaWiki\MediaWikiServices;
  24
  25 /** @deprecated use class constant instead */
  26 define( 'MW_DIFF_VERSION', '1.11a' );
  27
  28 /**
  29  * @todo document
  30  * @ingroup DifferenceEngine
  31  */
  32 class DifferenceEngine extends ContextSource {
  33         /**
  34          * Constant to indicate diff cache compatibility.
  35          * Bump this when changing the diff formatting in a way that
  36          * fixes important bugs or such to force cached diff views to
  37          * clear.
  38          */
  39         const DIFF_VERSION = MW_DIFF_VERSION;
  40
  41         /** @var int */
  42         public $mOldid;
  43
  44         /** @var int */
  45         public $mNewid;
  46
  47         private $mOldTags;
  48         private $mNewTags;
  49
  50         /** @var Content */
  51         public $mOldContent;
  52
  53         /** @var Content */
  54         public $mNewContent;
  55
  56         /** @var Language */
  57         protected $mDiffLang;
  58
  59         /** @var Title */
  60         public $mOldPage;
  61
  62         /** @var Title */
  63         public $mNewPage;
  64
  65         /** @var Revision */
  66         public $mOldRev;
  67
  68         /** @var Revision */
  69         public $mNewRev;
  70
  71         /** @var bool Have the revisions IDs been loaded */
  72         private $mRevisionsIdsLoaded = false;
  73
  74         /** @var bool Have the revisions been loaded */
  75         public $mRevisionsLoaded = false;
  76
  77         /** @var int How many text blobs have been loaded, 0, 1 or 2? */
  78         public $mTextLoaded = 0;
  79
  80         /** @var bool Was the diff fetched from cache? */
  81         public $mCacheHit = false;
  82
  83         /**
  84          * Set this to true to add debug info to the HTML output.
  85          * Warning: this may cause RSS readers to spuriously mark articles as "new"
  86          * (T22601)
  87          */
  88         public $enableDebugComment = false;
  89
  90         /** @var bool If true, line X is not displayed when X is 1, for example
  91          *    to increase readability and conserve space with many small diffs.
  92          */
  93         protected $mReducedLineNumbers = false;
  94
  95         /** @var string Link to action=markpatrolled */
  96         protected $mMarkPatrolledLink = null;
  97
  98         /** @var bool Show rev_deleted content if allowed */
  99         protected $unhide = false;
 100
 101         /** @var bool Refresh the diff cache */
 102         protected $mRefreshCache = false;
 103
 104         /**#@-*/
 105
 106         /**
 107          * Constructor
 108          * @param IContextSource $context Context to use, anything else will be ignored
 109          * @param int $old Old ID we want to show and diff with.
 110          * @param string|int $new Either revision ID or 'prev' or 'next'. Default: 0.
 111          * @param int $rcid Deprecated, no longer used!
 112          * @param bool $refreshCache If set, refreshes the diff cache
 113          * @param bool $unhide If set, allow viewing deleted revs
 114          */
 115         public function __construct( $context = null, $old = 0, $new = 0, $rcid = 0,
 116                 $refreshCache = false, $unhide = false
 117         ) {
 118                 if ( $context instanceof IContextSource ) {
 119                         $this->setContext( $context );
 120                 }
 121
 122                 wfDebug( "DifferenceEngine old '$old' new '$new' rcid '$rcid'\n" );
 123
 124                 $this->mOldid = $old;
 125                 $this->mNewid = $new;
 126                 $this->mRefreshCache = $refreshCache;
 127                 $this->unhide = $unhide;
 128         }
 129
 130         /**
 131          * @param bool $value
 132          */
 133         public function setReducedLineNumbers( $value = true ) {
 134                 $this->mReducedLineNumbers = $value;
 135         }
 136
 137         /**
 138          * @return Language
 139          */
 140         public function getDiffLang() {
 141                 if ( $this->mDiffLang === null ) {
 142                         # Default language in which the diff text is written.
 143                         $this->mDiffLang = $this->getTitle()->getPageLanguage();
 144                 }
 145
 146                 return $this->mDiffLang;
 147         }
 148
 149         /**
 150          * @return bool
 151          */
 152         public function wasCacheHit() {
 153                 return $this->mCacheHit;
 154         }
 155
 156         /**
 157          * @return int
 158          */
 159         public function getOldid() {
 160                 $this->loadRevisionIds();
 161
 162                 return $this->mOldid;
 163         }
 164
 165         /**
 166          * @return bool|int
 167          */
 168         public function getNewid() {
 169                 $this->loadRevisionIds();
 170
 171                 return $this->mNewid;
 172         }
 173
 174         /**
 175          * Look up a special:Undelete link to the given deleted revision id,
 176          * as a workaround for being unable to load deleted diffs in currently.
 177          *
 178          * @param int $id Revision ID
 179          *
 180          * @return string|bool Link HTML or false
 181          */
 182         public function deletedLink( $id ) {
 183                 if ( $this->getUser()->isAllowed( 'deletedhistory' ) ) {
 184                         $dbr = wfGetDB( DB_REPLICA );
 185                         $row = $dbr->selectRow( 'archive', '*',
 186                                 [ 'ar_rev_id' => $id ],
 187                                 __METHOD__ );
 188                         if ( $row ) {
 189                                 $rev = Revision::newFromArchiveRow( $row );
 190                                 $title = Title::makeTitleSafe( $row->ar_namespace, $row->ar_title );
 191
 192                                 return SpecialPage::getTitleFor( 'Undelete' )->getFullURL( [
 193                                         'target' => $title->getPrefixedText(),
 194                                         'timestamp' => $rev->getTimestamp()
 195                                 ] );
 196                         }
 197                 }
 198
 199                 return false;
 200         }
 201
 202         /**
 203          * Build a wikitext link toward a deleted revision, if viewable.
 204          *
 205          * @param int $id Revision ID
 206          *
 207          * @return string Wikitext fragment
 208          */
 209         public function deletedIdMarker( $id ) {
 210                 $link = $this->deletedLink( $id );
 211                 if ( $link ) {
 212                         return "[$link $id]";
 213                 } else {
 214                         return (string)$id;
 215                 }
 216         }
 217
 218         private function showMissingRevision() {
 219                 $out = $this->getOutput();
 220
 221                 $missing = [];
 222                 if ( $this->mOldRev === null ||
 223                         ( $this->mOldRev && $this->mOldContent === null )
 224                 ) {
 225                         $missing[] = $this->deletedIdMarker( $this->mOldid );
 226                 }
 227                 if ( $this->mNewRev === null ||
 228                         ( $this->mNewRev && $this->mNewContent === null )
 229                 ) {
 230                         $missing[] = $this->deletedIdMarker( $this->mNewid );
 231                 }
 232
 233                 $out->setPageTitle( $this->msg( 'errorpagetitle' ) );
 234                 $msg = $this->msg( 'difference-missing-revision' )
 235                         ->params( $this->getLanguage()->listToText( $missing ) )
 236                         ->numParams( count( $missing ) )
 237                         ->parseAsBlock();
 238                 $out->addHTML( $msg );
 239         }
 240
 241         public function showDiffPage( $diffOnly = false ) {
 242                 # Allow frames except in certain special cases
 243                 $out = $this->getOutput();
 244                 $out->allowClickjacking();
 245                 $out->setRobotPolicy( 'noindex,nofollow' );
 246
 247                 // Allow extensions to add any extra output here
 248                 Hooks::run( 'DifferenceEngineShowDiffPage', [ $out ] );
 249
 250                 if ( !$this->loadRevisionData() ) {
 251                         if ( Hooks::run( 'DifferenceEngineShowDiffPageMaybeShowMissingRevision', [ $this ] ) ) {
 252                                 $this->showMissingRevision();
 253                         }
 254                         return;
 255                 }
 256
 257                 $user = $this->getUser();
 258                 $permErrors = $this->mNewPage->getUserPermissionsErrors( 'read', $user );
 259                 if ( $this->mOldPage ) { # mOldPage might not be set, see below.
 260                         $permErrors = wfMergeErrorArrays( $permErrors,
 261                                 $this->mOldPage->getUserPermissionsErrors( 'read', $user ) );
 262                 }
 263                 if ( count( $permErrors ) ) {
 264                         throw new PermissionsError( 'read', $permErrors );
 265                 }
 266
 267                 $rollback = '';
 268
 269                 $query = [];
 270                 # Carry over 'diffonly' param via navigation links
 271                 if ( $diffOnly != $user->getBoolOption( 'diffonly' ) ) {
 272                         $query['diffonly'] = $diffOnly;
 273                 }
 274                 # Cascade unhide param in links for easy deletion browsing
 275                 if ( $this->unhide ) {
 276                         $query['unhide'] = 1;
 277                 }
 278
 279                 # Check if one of the revisions is deleted/suppressed
 280                 $deleted = $suppressed = false;
 281                 $allowed = $this->mNewRev->userCan( Revision::DELETED_TEXT, $user );
 282
 283                 $revisionTools = [];
 284
 285                 # mOldRev is false if the difference engine is called with a "vague" query for
 286                 # a diff between a version V and its previous version V' AND the version V
 287                 # is the first version of that article. In that case, V' does not exist.
 288                 if ( $this->mOldRev === false ) {
 289                         $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 290                         $samePage = true;
 291                         $oldHeader = '';
 292                         // Allow extensions to change the $oldHeader variable
 293                         Hooks::run( 'DifferenceEngineOldHeaderNoOldRev', [ &$oldHeader ] );
 294                 } else {
 295                         Hooks::run( 'DiffViewHeader', [ $this, $this->mOldRev, $this->mNewRev ] );
 296
 297                         if ( $this->mNewPage->equals( $this->mOldPage ) ) {
 298                                 $out->setPageTitle( $this->msg( 'difference-title', $this->mNewPage->getPrefixedText() ) );
 299                                 $samePage = true;
 300                         } else {
 301                                 $out->setPageTitle( $this->msg( 'difference-title-multipage',
 302                                         $this->mOldPage->getPrefixedText(), $this->mNewPage->getPrefixedText() ) );
 303                                 $out->addSubtitle( $this->msg( 'difference-multipage' ) );
 304                                 $samePage = false;
 305                         }
 306
 307                         if ( $samePage && $this->mNewPage->quickUserCan( 'edit', $user ) ) {
 308                                 if ( $this->mNewRev->isCurrent() && $this->mNewPage->userCan( 'rollback', $user ) ) {
 309                                         $rollbackLink = Linker::generateRollback( $this->mNewRev, $this->getContext() );
 310                                         if ( $rollbackLink ) {
 311                                                 $out->preventClickjacking();
 312                                                 $rollback = '&#160;&#160;&#160;' . $rollbackLink;
 313                                         }
 314                                 }
 315
 316                                 if ( !$this->mOldRev->isDeleted( Revision::DELETED_TEXT ) &&
 317                                         !$this->mNewRev->isDeleted( Revision::DELETED_TEXT )
 318                                 ) {
 319                                         $undoLink = Html::element( 'a', [
 320                                                         'href' => $this->mNewPage->getLocalURL( [
 321                                                                 'action' => 'edit',
 322                                                                 'undoafter' => $this->mOldid,
 323                                                                 'undo' => $this->mNewid
 324                                                         ] ),
 325                                                         'title' => Linker::titleAttrib( 'undo' ),
 326                                                 ],
 327                                                 $this->msg( 'editundo' )->text()
 328                                         );
 329                                         $revisionTools['mw-diff-undo'] = $undoLink;
 330                                 }
 331                         }
 332
 333                         # Make "previous revision link"
 334                         if ( $samePage && $this->mOldRev->getPrevious() ) {
 335                                 $prevlink = Linker::linkKnown(
 336                                         $this->mOldPage,
 337                                         $this->msg( 'previousdiff' )->escaped(),
 338                                         [ 'id' => 'differences-prevlink' ],
 339                                         [ 'diff' => 'prev', 'oldid' => $this->mOldid ] + $query
 340                                 );
 341                         } else {
 342                                 $prevlink = '&#160;';
 343                         }
 344
 345                         if ( $this->mOldRev->isMinor() ) {
 346                                 $oldminor = ChangesList::flag( 'minor' );
 347                         } else {
 348                                 $oldminor = '';
 349                         }
 350
 351                         $ldel = $this->revisionDeleteLink( $this->mOldRev );
 352                         $oldRevisionHeader = $this->getRevisionHeader( $this->mOldRev, 'complete' );
 353                         $oldChangeTags = ChangeTags::formatSummaryRow( $this->mOldTags, 'diff', $this->getContext() );
 354
 355                         $oldHeader = '<div id="mw-diff-otitle1"><strong>' . $oldRevisionHeader . '</strong></div>' .
 356                                 '<div id="mw-diff-otitle2">' .
 357                                 Linker::revUserTools( $this->mOldRev, !$this->unhide ) . '</div>' .
 358                                 '<div id="mw-diff-otitle3">' . $oldminor .
 359                                 Linker::revComment( $this->mOldRev, !$diffOnly, !$this->unhide ) . $ldel . '</div>' .
 360                                 '<div id="mw-diff-otitle5">' . $oldChangeTags[0] . '</div>' .
 361                                 '<div id="mw-diff-otitle4">' . $prevlink . '</div>';
 362
 363                         // Allow extensions to change the $oldHeader variable
 364                         Hooks::run( 'DifferenceEngineOldHeader', [ $this, &$oldHeader, $prevlink, $oldminor,
 365                                 $diffOnly, $ldel, $this->unhide ] );
 366
 367                         if ( $this->mOldRev->isDeleted( Revision::DELETED_TEXT ) ) {
 368                                 $deleted = true; // old revisions text is hidden
 369                                 if ( $this->mOldRev->isDeleted( Revision::DELETED_RESTRICTED ) ) {
 370                                         $suppressed = true; // also suppressed
 371                                 }
 372                         }
 373
 374                         # Check if this user can see the revisions
 375                         if ( !$this->mOldRev->userCan( Revision::DELETED_TEXT, $user ) ) {
 376                                 $allowed = false;
 377                         }
 378                 }
 379
 380                 # Make "next revision link"
 381                 # Skip next link on the top revision
 382                 if ( $samePage && !$this->mNewRev->isCurrent() ) {
 383                         $nextlink = Linker::linkKnown(
 384                                 $this->mNewPage,
 385                                 $this->msg( 'nextdiff' )->escaped(),
 386                                 [ 'id' => 'differences-nextlink' ],
 387                                 [ 'diff' => 'next', 'oldid' => $this->mNewid ] + $query
 388                         );
 389                 } else {
 390                         $nextlink = '&#160;';
 391                 }
 392
 393                 if ( $this->mNewRev->isMinor() ) {
 394                         $newminor = ChangesList::flag( 'minor' );
 395                 } else {
 396                         $newminor = '';
 397                 }
 398
 399                 # Handle RevisionDelete links...
 400                 $rdel = $this->revisionDeleteLink( $this->mNewRev );
 401
 402                 # Allow extensions to define their own revision tools
 403                 Hooks::run( 'DiffRevisionTools',
 404                         [ $this->mNewRev, &$revisionTools, $this->mOldRev, $user ] );
 405                 $formattedRevisionTools = [];
 406                 // Put each one in parentheses (poor man's button)
 407                 foreach ( $revisionTools as $key => $tool ) {
 408                         $toolClass = is_string( $key ) ? $key : 'mw-diff-tool';
 409                         $element = Html::rawElement(
 410                                 'span',
 411                                 [ 'class' => $toolClass ],
 412                                 $this->msg( 'parentheses' )->rawParams( $tool )->escaped()
 413                         );
 414                         $formattedRevisionTools[] = $element;
 415                 }
 416                 $newRevisionHeader = $this->getRevisionHeader( $this->mNewRev, 'complete' ) .
 417                         ' ' . implode( ' ', $formattedRevisionTools );
 418                 $newChangeTags = ChangeTags::formatSummaryRow( $this->mNewTags, 'diff', $this->getContext() );
 419
 420                 $newHeader = '<div id="mw-diff-ntitle1"><strong>' . $newRevisionHeader . '</strong></div>' .
 421                         '<div id="mw-diff-ntitle2">' . Linker::revUserTools( $this->mNewRev, !$this->unhide ) .
 422                         " $rollback</div>" .
 423                         '<div id="mw-diff-ntitle3">' . $newminor .
 424                         Linker::revComment( $this->mNewRev, !$diffOnly, !$this->unhide ) . $rdel . '</div>' .
 425                         '<div id="mw-diff-ntitle5">' . $newChangeTags[0] . '</div>' .
 426                         '<div id="mw-diff-ntitle4">' . $nextlink . $this->markPatrolledLink() . '</div>';
 427
 428                 // Allow extensions to change the $newHeader variable
 429                 Hooks::run( 'DifferenceEngineNewHeader', [ $this, &$newHeader, $formattedRevisionTools,
 430                         $nextlink, $rollback, $newminor, $diffOnly, $rdel, $this->unhide ] );
 431
 432                 if ( $this->mNewRev->isDeleted( Revision::DELETED_TEXT ) ) {
 433                         $deleted = true; // new revisions text is hidden
 434                         if ( $this->mNewRev->isDeleted( Revision::DELETED_RESTRICTED ) ) {
 435                                 $suppressed = true; // also suppressed
 436                         }
 437                 }
 438
 439                 # If the diff cannot be shown due to a deleted revision, then output
 440                 # the diff header and links to unhide (if available)...
 441                 if ( $deleted && ( !$this->unhide || !$allowed ) ) {
 442                         $this->showDiffStyle();
 443                         $multi = $this->getMultiNotice();
 444                         $out->addHTML( $this->addHeader( '', $oldHeader, $newHeader, $multi ) );
 445                         if ( !$allowed ) {
 446                                 $msg = $suppressed ? 'rev-suppressed-no-diff' : 'rev-deleted-no-diff';
 447                                 # Give explanation for why revision is not visible
 448                                 $out->wrapWikiMsg( "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 449                                         [ $msg ] );
 450                         } else {
 451                                 # Give explanation and add a link to view the diff...
 452                                 $query = $this->getRequest()->appendQueryValue( 'unhide', '1' );
 453                                 $link = $this->getTitle()->getFullURL( $query );
 454                                 $msg = $suppressed ? 'rev-suppressed-unhide-diff' : 'rev-deleted-unhide-diff';
 455                                 $out->wrapWikiMsg(
 456                                         "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 457                                         [ $msg, $link ]
 458                                 );
 459                         }
 460                 # Otherwise, output a regular diff...
 461                 } else {
 462                         # Add deletion notice if the user is viewing deleted content
 463                         $notice = '';
 464                         if ( $deleted ) {
 465                                 $msg = $suppressed ? 'rev-suppressed-diff-view' : 'rev-deleted-diff-view';
 466                                 $notice = "<div id='mw-$msg' class='mw-warning plainlinks'>\n" .
 467                                         $this->msg( $msg )->parse() .
 468                                         "</div>\n";
 469                         }
 470                         $this->showDiff( $oldHeader, $newHeader, $notice );
 471                         if ( !$diffOnly ) {
 472                                 $this->renderNewRevision();
 473                         }
 474                 }
 475         }
 476
 477         /**
 478          * Build a link to mark a change as patrolled.
 479          *
 480          * Returns empty string if there's either no revision to patrol or the user is not allowed to.
 481          * Side effect: When the patrol link is build, this method will call
 482          * OutputPage::preventClickjacking() and load mediawiki.page.patrol.ajax.
 483          *
 484          * @return string HTML or empty string
 485          */
 486         public function markPatrolledLink() {
 487                 if ( $this->mMarkPatrolledLink === null ) {
 488                         $linkInfo = $this->getMarkPatrolledLinkInfo();
 489                         // If false, there is no patrol link needed/allowed
 490                         if ( !$linkInfo ) {
 491                                 $this->mMarkPatrolledLink = '';
 492                         } else {
 493                                 $this->mMarkPatrolledLink = ' <span class="patrollink" data-mw="interface">[' .
 494                                         Linker::linkKnown(
 495                                                 $this->mNewPage,
 496                                                 $this->msg( 'markaspatrolleddiff' )->escaped(),
 497                                                 [],
 498                                                 [
 499                                                         'action' => 'markpatrolled',
 500                                                         'rcid' => $linkInfo['rcid'],
 501                                                 ]
 502                                         ) . ']</span>';
 503                                 // Allow extensions to change the markpatrolled link
 504                                 Hooks::run( 'DifferenceEngineMarkPatrolledLink', [ $this,
 505                                         &$this->mMarkPatrolledLink, $linkInfo['rcid'] ] );
 506                         }
 507                 }
 508                 return $this->mMarkPatrolledLink;
 509         }
 510
 511         /**
 512          * Returns an array of meta data needed to build a "mark as patrolled" link and
 513          * adds the mediawiki.page.patrol.ajax to the output.
 514          *
 515          * @return array|false An array of meta data for a patrol link (rcid only)
 516          *  or false if no link is needed
 517          */
 518         protected function getMarkPatrolledLinkInfo() {
 519                 global $wgUseRCPatrol, $wgEnableAPI, $wgEnableWriteAPI;
 520
 521                 $user = $this->getUser();
 522
 523                 // Prepare a change patrol link, if applicable
 524                 if (
 525                         // Is patrolling enabled and the user allowed to?
 526                         $wgUseRCPatrol && $this->mNewPage->quickUserCan( 'patrol', $user ) &&
 527                         // Only do this if the revision isn't more than 6 hours older
 528                         // than the Max RC age (6h because the RC might not be cleaned out regularly)
 529                         RecentChange::isInRCLifespan( $this->mNewRev->getTimestamp(), 21600 )
 530                 ) {
 531                         // Look for an unpatrolled change corresponding to this diff
 532                         $db = wfGetDB( DB_REPLICA );
 533                         $change = RecentChange::newFromConds(
 534                                 [
 535                                         'rc_timestamp' => $db->timestamp( $this->mNewRev->getTimestamp() ),
 536                                         'rc_this_oldid' => $this->mNewid,
 537                                         'rc_patrolled' => 0
 538                                 ],
 539                                 __METHOD__
 540                         );
 541
 542                         if ( $change && !$change->getPerformer()->equals( $user ) ) {
 543                                 $rcid = $change->getAttribute( 'rc_id' );
 544                         } else {
 545                                 // None found or the page has been created by the current user.
 546                                 // If the user could patrol this it already would be patrolled
 547                                 $rcid = 0;
 548                         }
 549
 550                         // Allow extensions to possibly change the rcid here
 551                         // For example the rcid might be set to zero due to the user
 552                         // being the same as the performer of the change but an extension
 553                         // might still want to show it under certain conditions
 554                         Hooks::run( 'DifferenceEngineMarkPatrolledRCID', [ &$rcid, $this, $change, $user ] );
 555
 556                         // Build the link
 557                         if ( $rcid ) {
 558                                 $this->getOutput()->preventClickjacking();
 559                                 if ( $wgEnableAPI && $wgEnableWriteAPI
 560                                         && $user->isAllowed( 'writeapi' )
 561                                 ) {
 562                                         $this->getOutput()->addModules( 'mediawiki.page.patrol.ajax' );
 563                                 }
 564
 565                                 return [
 566                                         'rcid' => $rcid,
 567                                 ];
 568                         }
 569                 }
 570
 571                 // No mark as patrolled link applicable
 572                 return false;
 573         }
 574
 575         /**
 576          * @param Revision $rev
 577          *
 578          * @return string
 579          */
 580         protected function revisionDeleteLink( $rev ) {
 581                 $link = Linker::getRevDeleteLink( $this->getUser(), $rev, $rev->getTitle() );
 582                 if ( $link !== '' ) {
 583                         $link = '&#160;&#160;&#160;' . $link . ' ';
 584                 }
 585
 586                 return $link;
 587         }
 588
 589         /**
 590          * Show the new revision of the page.
 591          */
 592         public function renderNewRevision() {
 593                 $out = $this->getOutput();
 594                 $revHeader = $this->getRevisionHeader( $this->mNewRev );
 595                 # Add "current version as of X" title
 596                 $out->addHTML( "<hr class='diff-hr' id='mw-oldid' />
 597                 <h2 class='diff-currentversion-title'>{$revHeader}</h2>\n" );
 598                 # Page content may be handled by a hooked call instead...
 599                 # @codingStandardsIgnoreStart Ignoring long lines.
 600                 if ( Hooks::run( 'ArticleContentOnDiff', [ $this, $out ] ) ) {
 601                         $this->loadNewText();
 602                         $out->setRevisionId( $this->mNewid );
 603                         $out->setRevisionTimestamp( $this->mNewRev->getTimestamp() );
 604                         $out->setArticleFlag( true );
 605
 606                         if ( !Hooks::run( 'ArticleContentViewCustom', [ $this->mNewContent, $this->mNewPage, $out ] ) ) {
 607                                 // Handled by extension
 608                         } else {
 609                                 // Normal page
 610                                 if ( $this->getTitle()->equals( $this->mNewPage ) ) {
 611                                         // If the Title stored in the context is the same as the one
 612                                         // of the new revision, we can use its associated WikiPage
 613                                         // object.
 614                                         $wikiPage = $this->getWikiPage();
 615                                 } else {
 616                                         // Otherwise we need to create our own WikiPage object
 617                                         $wikiPage = WikiPage::factory( $this->mNewPage );
 618                                 }
 619
 620                                 $parserOutput = $this->getParserOutput( $wikiPage, $this->mNewRev );
 621
 622                                 # WikiPage::getParserOutput() should not return false, but just in case
 623                                 if ( $parserOutput ) {
 624                                         // Allow extensions to change parser output here
 625                                         if ( Hooks::run( 'DifferenceEngineRenderRevisionAddParserOutput', [ $this, $out, $parserOutput, $wikiPage ] ) ) {
 626                                                 $out->addParserOutput( $parserOutput );
 627                                         }
 628                                 }
 629                         }
 630                 }
 631                 # @codingStandardsIgnoreEnd
 632
 633                 // Allow extensions to optionally not show the final patrolled link
 634                 if ( Hooks::run( 'DifferenceEngineRenderRevisionShowFinalPatrolLink' ) ) {
 635                         # Add redundant patrol link on bottom...
 636                         $out->addHTML( $this->markPatrolledLink() );
 637                 }
 638         }
 639
 640         protected function getParserOutput( WikiPage $page, Revision $rev ) {
 641                 $parserOptions = $page->makeParserOptions( $this->getContext() );
 642
 643                 if ( !$rev->isCurrent() || !$rev->getTitle()->quickUserCan( 'edit', $this->getUser() ) ) {
 644                         $parserOptions->setEditSection( false );
 645                 }
 646
 647                 $parserOutput = $page->getParserOutput( $parserOptions, $rev->getId() );
 648
 649                 return $parserOutput;
 650         }
 651
 652         /**
 653          * Get the diff text, send it to the OutputPage object
 654          * Returns false if the diff could not be generated, otherwise returns true
 655          *
 656          * @param string|bool $otitle Header for old text or false
 657          * @param string|bool $ntitle Header for new text or false
 658          * @param string $notice HTML between diff header and body
 659          *
 660          * @return bool
 661          */
 662         public function showDiff( $otitle, $ntitle, $notice = '' ) {
 663                 // Allow extensions to affect the output here
 664                 Hooks::run( 'DifferenceEngineShowDiff', [ $this ] );
 665
 666                 $diff = $this->getDiff( $otitle, $ntitle, $notice );
 667                 if ( $diff === false ) {
 668                         $this->showMissingRevision();
 669
 670                         return false;
 671                 } else {
 672                         $this->showDiffStyle();
 673                         $this->getOutput()->addHTML( $diff );
 674
 675                         return true;
 676                 }
 677         }
 678
 679         /**
 680          * Add style sheets for diff display.
 681          */
 682         public function showDiffStyle() {
 683                 $this->getOutput()->addModuleStyles( 'mediawiki.diff.styles' );
 684         }
 685
 686         /**
 687          * Get complete diff table, including header
 688          *
 689          * @param string|bool $otitle Header for old text or false
 690          * @param string|bool $ntitle Header for new text or false
 691          * @param string $notice HTML between diff header and body
 692          *
 693          * @return mixed
 694          */
 695         public function getDiff( $otitle, $ntitle, $notice = '' ) {
 696                 $body = $this->getDiffBody();
 697                 if ( $body === false ) {
 698                         return false;
 699                 }
 700
 701                 $multi = $this->getMultiNotice();
 702                 // Display a message when the diff is empty
 703                 if ( $body === '' ) {
 704                         $notice .= '<div class="mw-diff-empty">' .
 705                                 $this->msg( 'diff-empty' )->parse() .
 706                                 "</div>\n";
 707                 }
 708
 709                 return $this->addHeader( $body, $otitle, $ntitle, $multi, $notice );
 710         }
 711
 712         /**
 713          * Get the diff table body, without header
 714          *
 715          * @return mixed (string/false)
 716          */
 717         public function getDiffBody() {
 718                 $this->mCacheHit = true;
 719                 // Check if the diff should be hidden from this user
 720                 if ( !$this->loadRevisionData() ) {
 721                         return false;
 722                 } elseif ( $this->mOldRev &&
 723                         !$this->mOldRev->userCan( Revision::DELETED_TEXT, $this->getUser() )
 724                 ) {
 725                         return false;
 726                 } elseif ( $this->mNewRev &&
 727                         !$this->mNewRev->userCan( Revision::DELETED_TEXT, $this->getUser() )
 728                 ) {
 729                         return false;
 730                 }
 731                 // Short-circuit
 732                 if ( $this->mOldRev === false || ( $this->mOldRev && $this->mNewRev
 733                         && $this->mOldRev->getId() == $this->mNewRev->getId() )
 734                 ) {
 735                         if ( Hooks::run( 'DifferenceEngineShowEmptyOldContent', [ $this ] ) ) {
 736                                 return '';
 737                         }
 738                 }
 739                 // Cacheable?
 740                 $key = false;
 741                 $cache = ObjectCache::getMainWANInstance();
 742                 if ( $this->mOldid && $this->mNewid ) {
 743                         $key = $this->getDiffBodyCacheKey();
 744
 745                         // Try cache
 746                         if ( !$this->mRefreshCache ) {
 747                                 $difftext = $cache->get( $key );
 748                                 if ( $difftext ) {
 749                                         wfIncrStats( 'diff_cache.hit' );
 750                                         $difftext = $this->localiseLineNumbers( $difftext );
 751                                         $difftext .= "\n<!-- diff cache key $key -->\n";
 752
 753                                         return $difftext;
 754                                 }
 755                         } // don't try to load but save the result
 756                 }
 757                 $this->mCacheHit = false;
 758
 759                 // Loadtext is permission safe, this just clears out the diff
 760                 if ( !$this->loadText() ) {
 761                         return false;
 762                 }
 763
 764                 $difftext = $this->generateContentDiffBody( $this->mOldContent, $this->mNewContent );
 765
 766                 // Avoid PHP 7.1 warning from passing $this by reference
 767                 $diffEngine = $this;
 768
 769                 // Save to cache for 7 days
 770                 if ( !Hooks::run( 'AbortDiffCache', [ &$diffEngine ] ) ) {
 771                         wfIncrStats( 'diff_cache.uncacheable' );
 772                 } elseif ( $key !== false && $difftext !== false ) {
 773                         wfIncrStats( 'diff_cache.miss' );
 774                         $cache->set( $key, $difftext, 7 * 86400 );
 775                 } else {
 776                         wfIncrStats( 'diff_cache.uncacheable' );
 777                 }
 778                 // Replace line numbers with the text in the user's language
 779                 if ( $difftext !== false ) {
 780                         $difftext = $this->localiseLineNumbers( $difftext );
 781                 }
 782
 783                 return $difftext;
 784         }
 785
 786         /**
 787          * Returns the cache key for diff body text or content.
 788          *
 789          * @since 1.23
 790          *
 791          * @throws MWException
 792          * @return string
 793          */
 794         protected function getDiffBodyCacheKey() {
 795                 if ( !$this->mOldid || !$this->mNewid ) {
 796                         throw new MWException( 'mOldid and mNewid must be set to get diff cache key.' );
 797                 }
 798
 799                 return wfMemcKey( 'diff', 'version', self::DIFF_VERSION,
 800                         'oldid', $this->mOldid, 'newid', $this->mNewid );
 801         }
 802
 803         /**
 804          * Generate a diff, no caching.
 805          *
 806          * This implementation uses generateTextDiffBody() to generate a diff based on the default
 807          * serialization of the given Content objects. This will fail if $old or $new are not
 808          * instances of TextContent.
 809          *
 810          * Subclasses may override this to provide a different rendering for the diff,
 811          * perhaps taking advantage of the content's native form. This is required for all content
 812          * models that are not text based.
 813          *
 814          * @since 1.21
 815          *
 816          * @param Content $old Old content
 817          * @param Content $new New content
 818          *
 819          * @throws MWException If old or new content is not an instance of TextContent.
 820          * @return bool|string
 821          */
 822         public function generateContentDiffBody( Content $old, Content $new ) {
 823                 if ( !( $old instanceof TextContent ) ) {
 824                         throw new MWException( "Diff not implemented for " . get_class( $old ) . "; " .
 825                                 "override generateContentDiffBody to fix this." );
 826                 }
 827
 828                 if ( !( $new instanceof TextContent ) ) {
 829                         throw new MWException( "Diff not implemented for " . get_class( $new ) . "; "
 830                                 . "override generateContentDiffBody to fix this." );
 831                 }
 832
 833                 $otext = $old->serialize();
 834                 $ntext = $new->serialize();
 835
 836                 return $this->generateTextDiffBody( $otext, $ntext );
 837         }
 838
 839         /**
 840          * Generate a diff, no caching
 841          *
 842          * @todo move this to TextDifferenceEngine, make DifferenceEngine abstract. At some point.
 843          *
 844          * @param string $otext Old text, must be already segmented
 845          * @param string $ntext New text, must be already segmented
 846          *
 847          * @return bool|string
 848          */
 849         public function generateTextDiffBody( $otext, $ntext ) {
 850                 $diff = function () use ( $otext, $ntext ) {
 851                         $time = microtime( true );
 852
 853                         $result = $this->textDiff( $otext, $ntext );
 854
 855                         $time = intval( ( microtime( true ) - $time ) * 1000 );
 856                         MediaWikiServices::getInstance()->getStatsdDataFactory()->timing( 'diff_time', $time );
 857                         // Log requests slower than 99th percentile
 858                         if ( $time > 100 && $this->mOldPage && $this->mNewPage ) {
 859                                 wfDebugLog( 'diff',
 860                                         "$time ms diff: {$this->mOldid} -> {$this->mNewid} {$this->mNewPage}" );
 861                         }
 862
 863                         return $result;
 864                 };
 865
 866                 /**
 867                  * @param Status $status
 868                  * @throws FatalError
 869                  */
 870                 $error = function ( $status ) {
 871                         throw new FatalError( $status->getWikiText() );
 872                 };
 873
 874                 // Use PoolCounter if the diff looks like it can be expensive
 875                 if ( strlen( $otext ) + strlen( $ntext ) > 20000 ) {
 876                         $work = new PoolCounterWorkViaCallback( 'diff',
 877                                 md5( $otext ) . md5( $ntext ),
 878                                 [ 'doWork' => $diff, 'error' => $error ]
 879                         );
 880                         return $work->execute();
 881                 }
 882
 883                 return $diff();
 884         }
 885
 886         /**
 887          * Generates diff, to be wrapped internally in a logging/instrumentation
 888          *
 889          * @param string $otext Old text, must be already segmented
 890          * @param string $ntext New text, must be already segmented
 891          * @return bool|string
 892          */
 893         protected function textDiff( $otext, $ntext ) {
 894                 global $wgExternalDiffEngine, $wgContLang;
 895
 896                 $otext = str_replace( "\r\n", "\n", $otext );
 897                 $ntext = str_replace( "\r\n", "\n", $ntext );
 898
 899                 if ( $wgExternalDiffEngine == 'wikidiff' || $wgExternalDiffEngine == 'wikidiff3' ) {
 900                         wfDeprecated( "\$wgExternalDiffEngine = '{$wgExternalDiffEngine}'", '1.27' );
 901                         $wgExternalDiffEngine = false;
 902                 } elseif ( $wgExternalDiffEngine == 'wikidiff2' ) {
 903                         // Same as above, but with no deprecation warnings
 904                         $wgExternalDiffEngine = false;
 905                 } elseif ( !is_string( $wgExternalDiffEngine ) && $wgExternalDiffEngine !== false ) {
 906                         // And prevent people from shooting themselves in the foot...
 907                         wfWarn( '$wgExternalDiffEngine is set to a non-string value, forcing it to false' );
 908                         $wgExternalDiffEngine = false;
 909                 }
 910
 911                 if ( function_exists( 'wikidiff2_do_diff' ) && $wgExternalDiffEngine === false ) {
 912                         # Better external diff engine, the 2 may some day be dropped
 913                         # This one does the escaping and segmenting itself
 914                         $text = wikidiff2_do_diff( $otext, $ntext, 2 );
 915                         $text .= $this->debug( 'wikidiff2' );
 916
 917                         return $text;
 918                 } elseif ( $wgExternalDiffEngine !== false && is_executable( $wgExternalDiffEngine ) ) {
 919                         # Diff via the shell
 920                         $tmpDir = wfTempDir();
 921                         $tempName1 = tempnam( $tmpDir, 'diff_' );
 922                         $tempName2 = tempnam( $tmpDir, 'diff_' );
 923
 924                         $tempFile1 = fopen( $tempName1, "w" );
 925                         if ( !$tempFile1 ) {
 926                                 return false;
 927                         }
 928                         $tempFile2 = fopen( $tempName2, "w" );
 929                         if ( !$tempFile2 ) {
 930                                 return false;
 931                         }
 932                         fwrite( $tempFile1, $otext );
 933                         fwrite( $tempFile2, $ntext );
 934                         fclose( $tempFile1 );
 935                         fclose( $tempFile2 );
 936                         $cmd = wfEscapeShellArg( $wgExternalDiffEngine, $tempName1, $tempName2 );
 937                         $difftext = wfShellExec( $cmd );
 938                         $difftext .= $this->debug( "external $wgExternalDiffEngine" );
 939                         unlink( $tempName1 );
 940                         unlink( $tempName2 );
 941
 942                         return $difftext;
 943                 }
 944
 945                 # Native PHP diff
 946                 $ota = explode( "\n", $wgContLang->segmentForDiff( $otext ) );
 947                 $nta = explode( "\n", $wgContLang->segmentForDiff( $ntext ) );
 948                 $diffs = new Diff( $ota, $nta );
 949                 $formatter = new TableDiffFormatter();
 950                 $difftext = $wgContLang->unsegmentForDiff( $formatter->format( $diffs ) );
 951
 952                 return $difftext;
 953         }
 954
 955         /**
 956          * Generate a debug comment indicating diff generating time,
 957          * server node, and generator backend.
 958          *
 959          * @param string $generator : What diff engine was used
 960          *
 961          * @return string
 962          */
 963         protected function debug( $generator = "internal" ) {
 964                 global $wgShowHostnames;
 965                 if ( !$this->enableDebugComment ) {
 966                         return '';
 967                 }
 968                 $data = [ $generator ];
 969                 if ( $wgShowHostnames ) {
 970                         $data[] = wfHostname();
 971                 }
 972                 $data[] = wfTimestamp( TS_DB );
 973
 974                 return "<!-- diff generator: " .
 975                         implode( " ", array_map( "htmlspecialchars", $data ) ) .
 976                         " -->\n";
 977         }
 978
 979         /**
 980          * Replace line numbers with the text in the user's language
 981          *
 982          * @param string $text
 983          *
 984          * @return mixed
 985          */
 986         public function localiseLineNumbers( $text ) {
 987                 return preg_replace_callback(
 988                         '/<!--LINE (\d+)-->/',
 989                         [ $this, 'localiseLineNumbersCb' ],
 990                         $text
 991                 );
 992         }
 993
 994         public function localiseLineNumbersCb( $matches ) {
 995                 if ( $matches[1] === '1' && $this->mReducedLineNumbers ) {
 996                         return '';
 997                 }
 998
 999                 return $this->msg( 'lineno' )->numParams( $matches[1] )->escaped();
1000         }
1001
1002         /**
1003          * If there are revisions between the ones being compared, return a note saying so.
1004          *
1005          * @return string
1006          */
1007         public function getMultiNotice() {
1008                 if ( !is_object( $this->mOldRev ) || !is_object( $this->mNewRev ) ) {
1009                         return '';
1010                 } elseif ( !$this->mOldPage->equals( $this->mNewPage ) ) {
1011                         // Comparing two different pages? Count would be meaningless.
1012                         return '';
1013                 }
1014
1015                 if ( $this->mOldRev->getTimestamp() > $this->mNewRev->getTimestamp() ) {
1016                         $oldRev = $this->mNewRev; // flip
1017                         $newRev = $this->mOldRev; // flip
1018                 } else { // normal case
1019                         $oldRev = $this->mOldRev;
1020                         $newRev = $this->mNewRev;
1021                 }
1022
1023                 // Sanity: don't show the notice if too many rows must be scanned
1024                 // @todo show some special message for that case
1025                 $nEdits = $this->mNewPage->countRevisionsBetween( $oldRev, $newRev, 1000 );
1026                 if ( $nEdits > 0 && $nEdits <= 1000 ) {
1027                         $limit = 100; // use diff-multi-manyusers if too many users
1028                         $users = $this->mNewPage->getAuthorsBetween( $oldRev, $newRev, $limit );
1029                         $numUsers = count( $users );
1030
1031                         if ( $numUsers == 1 && $users[0] == $newRev->getUserText( Revision::RAW ) ) {
1032                                 $numUsers = 0; // special case to say "by the same user" instead of "by one other user"
1033                         }
1034
1035                         return self::intermediateEditsMsg( $nEdits, $numUsers, $limit );
1036                 }
1037
1038                 return ''; // nothing
1039         }
1040
1041         /**
1042          * Get a notice about how many intermediate edits and users there are
1043          *
1044          * @param int $numEdits
1045          * @param int $numUsers
1046          * @param int $limit
1047          *
1048          * @return string
1049          */
1050         public static function intermediateEditsMsg( $numEdits, $numUsers, $limit ) {
1051                 if ( $numUsers === 0 ) {
1052                         $msg = 'diff-multi-sameuser';
1053                 } elseif ( $numUsers > $limit ) {
1054                         $msg = 'diff-multi-manyusers';
1055                         $numUsers = $limit;
1056                 } else {
1057                         $msg = 'diff-multi-otherusers';
1058                 }
1059
1060                 return wfMessage( $msg )->numParams( $numEdits, $numUsers )->parse();
1061         }
1062
1063         /**
1064          * Get a header for a specified revision.
1065          *
1066          * @param Revision $rev
1067          * @param string $complete 'complete' to get the header wrapped depending
1068          *        the visibility of the revision and a link to edit the page.
1069          *
1070          * @return string HTML fragment
1071          */
1072         public function getRevisionHeader( Revision $rev, $complete = '' ) {
1073                 $lang = $this->getLanguage();
1074                 $user = $this->getUser();
1075                 $revtimestamp = $rev->getTimestamp();
1076                 $timestamp = $lang->userTimeAndDate( $revtimestamp, $user );
1077                 $dateofrev = $lang->userDate( $revtimestamp, $user );
1078                 $timeofrev = $lang->userTime( $revtimestamp, $user );
1079
1080                 $header = $this->msg(
1081                         $rev->isCurrent() ? 'currentrev-asof' : 'revisionasof',
1082                         $timestamp,
1083                         $dateofrev,
1084                         $timeofrev
1085                 )->escaped();
1086
1087                 if ( $complete !== 'complete' ) {
1088                         return $header;
1089                 }
1090
1091                 $title = $rev->getTitle();
1092
1093                 $header = Linker::linkKnown( $title, $header, [],
1094                         [ 'oldid' => $rev->getId() ] );
1095
1096                 if ( $rev->userCan( Revision::DELETED_TEXT, $user ) ) {
1097                         $editQuery = [ 'action' => 'edit' ];
1098                         if ( !$rev->isCurrent() ) {
1099                                 $editQuery['oldid'] = $rev->getId();
1100                         }
1101
1102                         $key = $title->quickUserCan( 'edit', $user ) ? 'editold' : 'viewsourceold';
1103                         $msg = $this->msg( $key )->escaped();
1104                         $editLink = $this->msg( 'parentheses' )->rawParams(
1105                                 Linker::linkKnown( $title, $msg, [], $editQuery ) )->escaped();
1106                         $header .= ' ' . Html::rawElement(
1107                                 'span',
1108                                 [ 'class' => 'mw-diff-edit' ],
1109                                 $editLink
1110                         );
1111                         if ( $rev->isDeleted( Revision::DELETED_TEXT ) ) {
1112                                 $header = Html::rawElement(
1113                                         'span',
1114                                         [ 'class' => 'history-deleted' ],
1115                                         $header
1116                                 );
1117                         }
1118                 } else {
1119                         $header = Html::rawElement( 'span', [ 'class' => 'history-deleted' ], $header );
1120                 }
1121
1122                 return $header;
1123         }
1124
1125         /**
1126          * Add the header to a diff body
1127          *
1128          * @param string $diff Diff body
1129          * @param string $otitle Old revision header
1130          * @param string $ntitle New revision header
1131          * @param string $multi Notice telling user that there are intermediate
1132          *   revisions between the ones being compared
1133          * @param string $notice Other notices, e.g. that user is viewing deleted content
1134          *
1135          * @return string
1136          */
1137         public function addHeader( $diff, $otitle, $ntitle, $multi = '', $notice = '' ) {
1138                 // shared.css sets diff in interface language/dir, but the actual content
1139                 // is often in a different language, mostly the page content language/dir
1140                 $header = Html::openElement( 'table', [
1141                         'class' => [ 'diff', 'diff-contentalign-' . $this->getDiffLang()->alignStart() ],
1142                         'data-mw' => 'interface',
1143                 ] );
1144                 $userLang = htmlspecialchars( $this->getLanguage()->getHtmlCode() );
1145
1146                 if ( !$diff && !$otitle ) {
1147                         $header .= "
1148                         <tr style='vertical-align: top;' lang='{$userLang}'>
1149                         <td class='diff-ntitle'>{$ntitle}</td>
1150                         </tr>";
1151                         $multiColspan = 1;
1152                 } else {
1153                         if ( $diff ) { // Safari/Chrome show broken output if cols not used
1154                                 $header .= "
1155                                 <col class='diff-marker' />
1156                                 <col class='diff-content' />
1157                                 <col class='diff-marker' />
1158                                 <col class='diff-content' />";
1159                                 $colspan = 2;
1160                                 $multiColspan = 4;
1161                         } else {
1162                                 $colspan = 1;
1163                                 $multiColspan = 2;
1164                         }
1165                         if ( $otitle || $ntitle ) {
1166                                 $header .= "
1167                                 <tr style='vertical-align: top;' lang='{$userLang}'>
1168                                 <td colspan='$colspan' class='diff-otitle'>{$otitle}</td>
1169                                 <td colspan='$colspan' class='diff-ntitle'>{$ntitle}</td>
1170                                 </tr>";
1171                         }
1172                 }
1173
1174                 if ( $multi != '' ) {
1175                         $header .= "<tr><td colspan='{$multiColspan}' style='text-align: center;' " .
1176                                 "class='diff-multi' lang='{$userLang}'>{$multi}</td></tr>";
1177                 }
1178                 if ( $notice != '' ) {
1179                         $header .= "<tr><td colspan='{$multiColspan}' style='text-align: center;' " .
1180                                 "lang='{$userLang}'>{$notice}</td></tr>";
1181                 }
1182
1183                 return $header . $diff . "</table>";
1184         }
1185
1186         /**
1187          * Use specified text instead of loading from the database
1188          * @param Content $oldContent
1189          * @param Content $newContent
1190          * @since 1.21
1191          */
1192         public function setContent( Content $oldContent, Content $newContent ) {
1193                 $this->mOldContent = $oldContent;
1194                 $this->mNewContent = $newContent;
1195
1196                 $this->mTextLoaded = 2;
1197                 $this->mRevisionsLoaded = true;
1198         }
1199
1200         /**
1201          * Set the language in which the diff text is written
1202          * (Defaults to page content language).
1203          * @param Language|string $lang
1204          * @since 1.19
1205          */
1206         public function setTextLanguage( $lang ) {
1207                 $this->mDiffLang = wfGetLangObj( $lang );
1208         }
1209
1210         /**
1211          * Maps a revision pair definition as accepted by DifferenceEngine constructor
1212          * to a pair of actual integers representing revision ids.
1213          *
1214          * @param int $old Revision id, e.g. from URL parameter 'oldid'
1215          * @param int|string $new Revision id or strings 'next' or 'prev', e.g. from URL parameter 'diff'
1216          *
1217          * @return int[] List of two revision ids, older first, later second.
1218          *     Zero signifies invalid argument passed.
1219          *     false signifies that there is no previous/next revision ($old is the oldest/newest one).
1220          */
1221         public function mapDiffPrevNext( $old, $new ) {
1222                 if ( $new === 'prev' ) {
1223                         // Show diff between revision $old and the previous one. Get previous one from DB.
1224                         $newid = intval( $old );
1225                         $oldid = $this->getTitle()->getPreviousRevisionID( $newid );
1226                 } elseif ( $new === 'next' ) {
1227                         // Show diff between revision $old and the next one. Get next one from DB.
1228                         $oldid = intval( $old );
1229                         $newid = $this->getTitle()->getNextRevisionID( $oldid );
1230                 } else {
1231                         $oldid = intval( $old );
1232                         $newid = intval( $new );
1233                 }
1234
1235                 return [ $oldid, $newid ];
1236         }
1237
1238         /**
1239          * Load revision IDs
1240          */
1241         private function loadRevisionIds() {
1242                 if ( $this->mRevisionsIdsLoaded ) {
1243                         return;
1244                 }
1245
1246                 $this->mRevisionsIdsLoaded = true;
1247
1248                 $old = $this->mOldid;
1249                 $new = $this->mNewid;
1250
1251                 list( $this->mOldid, $this->mNewid ) = self::mapDiffPrevNext( $old, $new );
1252                 if ( $new === 'next' && $this->mNewid === false ) {
1253                         # if no result, NewId points to the newest old revision. The only newer
1254                         # revision is cur, which is "0".
1255                         $this->mNewid = 0;
1256                 }
1257
1258                 Hooks::run(
1259                         'NewDifferenceEngine',
1260                         [ $this->getTitle(), &$this->mOldid, &$this->mNewid, $old, $new ]
1261                 );
1262         }
1263
1264         /**
1265          * Load revision metadata for the specified articles. If newid is 0, then compare
1266          * the old article in oldid to the current article; if oldid is 0, then
1267          * compare the current article to the immediately previous one (ignoring the
1268          * value of newid).
1269          *
1270          * If oldid is false, leave the corresponding revision object set
1271          * to false. This is impossible via ordinary user input, and is provided for
1272          * API convenience.
1273          *
1274          * @return bool
1275          */
1276         public function loadRevisionData() {
1277                 if ( $this->mRevisionsLoaded ) {
1278                         return true;
1279                 }
1280
1281                 // Whether it succeeds or fails, we don't want to try again
1282                 $this->mRevisionsLoaded = true;
1283
1284                 $this->loadRevisionIds();
1285
1286                 // Load the new revision object
1287                 if ( $this->mNewid ) {
1288                         $this->mNewRev = Revision::newFromId( $this->mNewid );
1289                 } else {
1290                         $this->mNewRev = Revision::newFromTitle(
1291                                 $this->getTitle(),
1292                                 false,
1293                                 Revision::READ_NORMAL
1294                         );
1295                 }
1296
1297                 if ( !$this->mNewRev instanceof Revision ) {
1298                         return false;
1299                 }
1300
1301                 // Update the new revision ID in case it was 0 (makes life easier doing UI stuff)
1302                 $this->mNewid = $this->mNewRev->getId();
1303                 $this->mNewPage = $this->mNewRev->getTitle();
1304
1305                 // Load the old revision object
1306                 $this->mOldRev = false;
1307                 if ( $this->mOldid ) {
1308                         $this->mOldRev = Revision::newFromId( $this->mOldid );
1309                 } elseif ( $this->mOldid === 0 ) {
1310                         $rev = $this->mNewRev->getPrevious();
1311                         if ( $rev ) {
1312                                 $this->mOldid = $rev->getId();
1313                                 $this->mOldRev = $rev;
1314                         } else {
1315                                 // No previous revision; mark to show as first-version only.
1316                                 $this->mOldid = false;
1317                                 $this->mOldRev = false;
1318                         }
1319                 } /* elseif ( $this->mOldid === false ) leave mOldRev false; */
1320
1321                 if ( is_null( $this->mOldRev ) ) {
1322                         return false;
1323                 }
1324
1325                 if ( $this->mOldRev ) {
1326                         $this->mOldPage = $this->mOldRev->getTitle();
1327                 }
1328
1329                 // Load tags information for both revisions
1330                 $dbr = wfGetDB( DB_REPLICA );
1331                 if ( $this->mOldid !== false ) {
1332                         $this->mOldTags = $dbr->selectField(
1333                                 'tag_summary',
1334                                 'ts_tags',
1335                                 [ 'ts_rev_id' => $this->mOldid ],
1336                                 __METHOD__
1337                         );
1338                 } else {
1339                         $this->mOldTags = false;
1340                 }
1341                 $this->mNewTags = $dbr->selectField(
1342                         'tag_summary',
1343                         'ts_tags',
1344                         [ 'ts_rev_id' => $this->mNewid ],
1345                         __METHOD__
1346                 );
1347
1348                 return true;
1349         }
1350
1351         /**
1352          * Load the text of the revisions, as well as revision data.
1353          *
1354          * @return bool
1355          */
1356         public function loadText() {
1357                 if ( $this->mTextLoaded == 2 ) {
1358                         return true;
1359                 }
1360
1361                 // Whether it succeeds or fails, we don't want to try again
1362                 $this->mTextLoaded = 2;
1363
1364                 if ( !$this->loadRevisionData() ) {
1365                         return false;
1366                 }
1367
1368                 if ( $this->mOldRev ) {
1369                         $this->mOldContent = $this->mOldRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1370                         if ( $this->mOldContent === null ) {
1371                                 return false;
1372                         }
1373                 }
1374
1375                 if ( $this->mNewRev ) {
1376                         $this->mNewContent = $this->mNewRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1377                         Hooks::run( 'DifferenceEngineLoadTextAfterNewContentIsLoaded', [ $this ] );
1378                         if ( $this->mNewContent === null ) {
1379                                 return false;
1380                         }
1381                 }
1382
1383                 return true;
1384         }
1385
1386         /**
1387          * Load the text of the new revision, not the old one
1388          *
1389          * @return bool
1390          */
1391         public function loadNewText() {
1392                 if ( $this->mTextLoaded >= 1 ) {
1393                         return true;
1394                 }
1395
1396                 $this->mTextLoaded = 1;
1397
1398                 if ( !$this->loadRevisionData() ) {
1399                         return false;
1400                 }
1401
1402                 $this->mNewContent = $this->mNewRev->getContent( Revision::FOR_THIS_USER, $this->getUser() );
1403
1404                 Hooks::run( 'DifferenceEngineAfterLoadNewText', [ $this ] );
1405
1406                 return true;
1407         }
1408
1409 }