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