includes/diff/DifferenceEngine.php

   1 <?php
   2 /**
   3  * User interface for the difference engine
   4  *
   5  * @file
   6  * @ingroup DifferenceEngine
   7  */
   8
   9 /**
  10  * Constant to indicate diff cache compatibility.
  11  * Bump this when changing the diff formatting in a way that
  12  * fixes important bugs or such to force cached diff views to
  13  * clear.
  14  */
  15 define( 'MW_DIFF_VERSION', '1.11a' );
  16
  17 /**
  18  * @todo document
  19  * @ingroup DifferenceEngine
  20  */
  21 class DifferenceEngine extends ContextSource {
  22         /**#@+
  23          * @private
  24          */
  25         var $mOldid, $mNewid;
  26         var $mOldtext, $mNewtext;
  27         protected $mDiffLang;
  28
  29         /**
  30          * @var Title
  31          */
  32         var $mOldPage, $mNewPage;
  33         var $mRcidMarkPatrolled;
  34
  35         /**
  36          * @var Revision
  37          */
  38         var $mOldRev, $mNewRev;
  39         private $mRevisionsIdsLoaded = false; // Have the revisions IDs been loaded
  40         var $mRevisionsLoaded = false; // Have the revisions been loaded
  41         var $mTextLoaded = 0; // How many text blobs have been loaded, 0, 1 or 2?
  42         var $mCacheHit = false; // Was the diff fetched from cache?
  43
  44         /**
  45          * Set this to true to add debug info to the HTML output.
  46          * Warning: this may cause RSS readers to spuriously mark articles as "new"
  47          * (bug 20601)
  48          */
  49         var $enableDebugComment = false;
  50
  51         // If true, line X is not displayed when X is 1, for example to increase
  52         // readability and conserve space with many small diffs.
  53         protected $mReducedLineNumbers = false;
  54
  55         // Link to action=markpatrolled
  56         protected $mMarkPatrolledLink = null;
  57
  58         protected $unhide = false; # show rev_deleted content if allowed
  59         /**#@-*/
  60
  61         /**
  62          * Constructor
  63          * @param $context IContextSource context to use, anything else will be ignored
  64          * @param $old Integer old ID we want to show and diff with.
  65          * @param $new String either 'prev' or 'next'.
  66          * @param $rcid Integer ??? FIXME (default 0)
  67          * @param $refreshCache boolean If set, refreshes the diff cache
  68          * @param $unhide boolean If set, allow viewing deleted revs
  69          */
  70         function __construct( $context = null, $old = 0, $new = 0, $rcid = 0,
  71                 $refreshCache = false, $unhide = false )
  72         {
  73                 if ( $context instanceof IContextSource ) {
  74                         $this->setContext( $context );
  75                 }
  76
  77                 wfDebug( "DifferenceEngine old '$old' new '$new' rcid '$rcid'\n" );
  78
  79                 $this->mOldid = $old;
  80                 $this->mNewid = $new;
  81                 $this->mRcidMarkPatrolled = intval( $rcid );  # force it to be an integer
  82                 $this->mRefreshCache = $refreshCache;
  83                 $this->unhide = $unhide;
  84         }
  85
  86         /**
  87          * @param $value bool
  88          */
  89         function setReducedLineNumbers( $value = true ) {
  90                 $this->mReducedLineNumbers = $value;
  91         }
  92
  93         /**
  94          * @return Language
  95          */
  96         function getDiffLang() {
  97                 if ( $this->mDiffLang === null ) {
  98                         # Default language in which the diff text is written.
  99                         $this->mDiffLang = $this->getTitle()->getPageLanguage();
 100                 }
 101                 return $this->mDiffLang;
 102         }
 103
 104         /**
 105          * @return bool
 106          */
 107         function wasCacheHit() {
 108                 return $this->mCacheHit;
 109         }
 110
 111         /**
 112          * @return int
 113          */
 114         function getOldid() {
 115                 $this->loadRevisionIds();
 116                 return $this->mOldid;
 117         }
 118
 119         /**
 120          * @return Bool|int
 121          */
 122         function getNewid() {
 123                 $this->loadRevisionIds();
 124                 return $this->mNewid;
 125         }
 126
 127         /**
 128          * Look up a special:Undelete link to the given deleted revision id,
 129          * as a workaround for being unable to load deleted diffs in currently.
 130          *
 131          * @param int $id revision ID
 132          * @return mixed URL or false
 133          */
 134         function deletedLink( $id ) {
 135                 if ( $this->getUser()->isAllowed( 'deletedhistory' ) ) {
 136                         $dbr = wfGetDB( DB_SLAVE );
 137                         $row = $dbr->selectRow('archive', '*',
 138                                 array( 'ar_rev_id' => $id ),
 139                                 __METHOD__ );
 140                         if ( $row ) {
 141                                 $rev = Revision::newFromArchiveRow( $row );
 142                                 $title = Title::makeTitleSafe( $row->ar_namespace, $row->ar_title );
 143                                 return SpecialPage::getTitleFor( 'Undelete' )->getFullURL( array(
 144                                         'target' => $title->getPrefixedText(),
 145                                         'timestamp' => $rev->getTimestamp()
 146                                 ));
 147                         }
 148                 }
 149                 return false;
 150         }
 151
 152         /**
 153          * Build a wikitext link toward a deleted revision, if viewable.
 154          *
 155          * @param int $id revision ID
 156          * @return string wikitext fragment
 157          */
 158         function deletedIdMarker( $id ) {
 159                 $link = $this->deletedLink( $id );
 160                 if ( $link ) {
 161                         return "[$link $id]";
 162                 } else {
 163                         return $id;
 164                 }
 165         }
 166
 167         function showDiffPage( $diffOnly = false ) {
 168                 wfProfileIn( __METHOD__ );
 169
 170                 # Allow frames except in certain special cases
 171                 $out = $this->getOutput();
 172                 $out->allowClickjacking();
 173                 $out->setRobotPolicy( 'noindex,nofollow' );
 174
 175                 if ( !$this->loadRevisionData() ) {
 176                         // Sounds like a deleted revision... Let's see what we can do.
 177                         $t = $this->getTitle()->getPrefixedText();
 178                         $d = $this->msg( 'missingarticle-diff',
 179                                 $this->deletedIdMarker( $this->mOldid ),
 180                                 $this->deletedIdMarker( $this->mNewid ) )->escaped();
 181                         $out->setPageTitle( $this->msg( 'errorpagetitle' ) );
 182                         $out->addWikiMsg( 'missing-article', "<nowiki>$t</nowiki>", "<span class='plainlinks'>$d</span>" );
 183                         wfProfileOut( __METHOD__ );
 184                         return;
 185                 }
 186
 187                 $user = $this->getUser();
 188                 $permErrors = $this->mNewPage->getUserPermissionsErrors( 'read', $user );
 189                 if ( $this->mOldPage ) { # mOldPage might not be set, see below.
 190                         $permErrors = wfMergeErrorArrays( $permErrors,
 191                                 $this->mOldPage->getUserPermissionsErrors( 'read', $user ) );
 192                 }
 193                 if ( count( $permErrors ) ) {
 194                         wfProfileOut( __METHOD__ );
 195                         throw new PermissionsError( 'read', $permErrors );
 196                 }
 197
 198                 # If external diffs are enabled both globally and for the user,
 199                 # we'll use the application/x-external-editor interface to call
 200                 # an external diff tool like kompare, kdiff3, etc.
 201                 if ( ExternalEdit::useExternalEngine( $this->getContext(), 'diff' ) ) {
 202                         $urls = array(
 203                                 'File' => array( 'Extension' => 'wiki', 'URL' =>
 204                                         # This should be mOldPage, but it may not be set, see below.
 205                                         $this->mNewPage->getCanonicalURL( array(
 206                                                 'action' => 'raw', 'oldid' => $this->mOldid ) )
 207                                 ),
 208                                 'File2' => array( 'Extension' => 'wiki', 'URL' =>
 209                                         $this->mNewPage->getCanonicalURL( array(
 210                                                 'action' => 'raw', 'oldid' => $this->mNewid ) )
 211                                 ),
 212                         );
 213
 214                         $externalEditor = new ExternalEdit( $this->getContext(), $urls );
 215                         $externalEditor->execute();
 216
 217                         wfProfileOut( __METHOD__ );
 218                         return;
 219                 }
 220
 221                 $rollback = '';
 222                 $undoLink = '';
 223
 224                 $query = array();
 225                 # Carry over 'diffonly' param via navigation links
 226                 if ( $diffOnly != $user->getBoolOption( 'diffonly' ) ) {
 227                         $query['diffonly'] = $diffOnly;
 228                 }
 229                 # Cascade unhide param in links for easy deletion browsing
 230                 if ( $this->unhide ) {
 231                         $query['unhide'] = 1;
 232                 }
 233
 234                 # Check if one of the revisions is deleted/suppressed
 235                 $deleted = $suppressed = false;
 236                 $allowed = $this->mNewRev->userCan( Revision::DELETED_TEXT, $user );
 237
 238                 # mOldRev is false if the difference engine is called with a "vague" query for
 239                 # a diff between a version V and its previous version V' AND the version V
 240                 # is the first version of that article. In that case, V' does not exist.
 241                 if ( $this->mOldRev === false ) {
 242                         $out->setPageTitle( $this->mNewPage->getPrefixedText() );
 243                         $out->addSubtitle( $this->msg( 'difference' ) );
 244                         $samePage = true;
 245                         $oldHeader = '';
 246                 } else {
 247                         wfRunHooks( 'DiffViewHeader', array( $this, $this->mOldRev, $this->mNewRev ) );
 248
 249                         $sk = $this->getSkin();
 250                         if ( method_exists( $sk, 'suppressQuickbar' ) ) {
 251                                 $sk->suppressQuickbar();
 252                         }
 253
 254                         if ( $this->mNewPage->equals( $this->mOldPage ) ) {
 255                                 $out->setPageTitle( $this->mNewPage->getPrefixedText() );
 256                                 $out->addSubtitle( $this->msg( 'difference' ) );
 257                                 $samePage = true;
 258                         } else {
 259                                 $out->setPageTitle( $this->mOldPage->getPrefixedText() . ', ' . $this->mNewPage->getPrefixedText() );
 260                                 $out->addSubtitle( $this->msg( 'difference-multipage' ) );
 261                                 $samePage = false;
 262                         }
 263
 264                         if ( $samePage && $this->mNewPage->userCan( 'edit', $user ) ) {
 265                                 if ( $this->mNewRev->isCurrent() && $this->mNewPage->userCan( 'rollback', $user ) ) {
 266                                         $out->preventClickjacking();
 267                                         $rollback = '&#160;&#160;&#160;' . Linker::generateRollback( $this->mNewRev );
 268                                 }
 269                                 if ( !$this->mOldRev->isDeleted( Revision::DELETED_TEXT ) && !$this->mNewRev->isDeleted( Revision::DELETED_TEXT ) ) {
 270                                         $undoLink = ' ' . $this->msg( 'parentheses' )->rawParams(
 271                                                 Html::element( 'a', array(
 272                                                         'href' => $this->mNewPage->getLocalUrl( array(
 273                                                                 'action' => 'edit',
 274                                                                 'undoafter' => $this->mOldid,
 275                                                                 'undo' => $this->mNewid ) ),
 276                                                         'title' => Linker::titleAttrib( 'undo' )
 277                                                 ),
 278                                                 $this->msg( 'editundo' )->text()
 279                                         ) )->escaped();
 280                                 }
 281                         }
 282
 283                         # Make "previous revision link"
 284                         if ( $samePage && $this->mOldRev->getPrevious() ) {
 285                                 $prevlink = Linker::linkKnown(
 286                                         $this->mOldPage,
 287                                         $this->msg( 'previousdiff' )->escaped(),
 288                                         array( 'id' => 'differences-prevlink' ),
 289                                         array( 'diff' => 'prev', 'oldid' => $this->mOldid ) + $query
 290                                 );
 291                         } else {
 292                                 $prevlink = '&#160;';
 293                         }
 294
 295                         if ( $this->mOldRev->isMinor() ) {
 296                                 $oldminor = ChangesList::flag( 'minor' );
 297                         } else {
 298                                 $oldminor = '';
 299                         }
 300
 301                         $ldel = $this->revisionDeleteLink( $this->mOldRev );
 302                         $oldRevisionHeader = $this->getRevisionHeader( $this->mOldRev, 'complete' );
 303
 304                         $oldHeader = '<div id="mw-diff-otitle1"><strong>' . $oldRevisionHeader . '</strong></div>' .
 305                                 '<div id="mw-diff-otitle2">' .
 306                                         Linker::revUserTools( $this->mOldRev, !$this->unhide ) . '</div>' .
 307                                 '<div id="mw-diff-otitle3">' . $oldminor .
 308                                         Linker::revComment( $this->mOldRev, !$diffOnly, !$this->unhide ) . $ldel . '</div>' .
 309                                 '<div id="mw-diff-otitle4">' . $prevlink . '</div>';
 310
 311                         if ( $this->mOldRev->isDeleted( Revision::DELETED_TEXT ) ) {
 312                                 $deleted = true; // old revisions text is hidden
 313                                 if ( $this->mOldRev->isDeleted( Revision::DELETED_RESTRICTED ) ) {
 314                                         $suppressed = true; // also suppressed
 315                                 }
 316                         }
 317
 318                         # Check if this user can see the revisions
 319                         if ( !$this->mOldRev->userCan( Revision::DELETED_TEXT, $user ) ) {
 320                                 $allowed = false;
 321                         }
 322                 }
 323
 324                 # Make "next revision link"
 325                 # Skip next link on the top revision
 326                 if ( $samePage && !$this->mNewRev->isCurrent() ) {
 327                         $nextlink = Linker::linkKnown(
 328                                 $this->mNewPage,
 329                                 $this->msg( 'nextdiff' )->escaped(),
 330                                 array( 'id' => 'differences-nextlink' ),
 331                                 array( 'diff' => 'next', 'oldid' => $this->mNewid ) + $query
 332                         );
 333                 } else {
 334                         $nextlink = '&#160;';
 335                 }
 336
 337                 if ( $this->mNewRev->isMinor() ) {
 338                         $newminor = ChangesList::flag( 'minor' );
 339                 } else {
 340                         $newminor = '';
 341                 }
 342
 343                 # Handle RevisionDelete links...
 344                 $rdel = $this->revisionDeleteLink( $this->mNewRev );
 345                 $newRevisionHeader = $this->getRevisionHeader( $this->mNewRev, 'complete' ) . $undoLink;
 346
 347                 $newHeader = '<div id="mw-diff-ntitle1"><strong>' . $newRevisionHeader . '</strong></div>' .
 348                         '<div id="mw-diff-ntitle2">' . Linker::revUserTools( $this->mNewRev, !$this->unhide ) .
 349                                 " $rollback</div>" .
 350                         '<div id="mw-diff-ntitle3">' . $newminor .
 351                                 Linker::revComment( $this->mNewRev, !$diffOnly, !$this->unhide ) . $rdel . '</div>' .
 352                         '<div id="mw-diff-ntitle4">' . $nextlink . $this->markPatrolledLink() . '</div>';
 353
 354                 if ( $this->mNewRev->isDeleted( Revision::DELETED_TEXT ) ) {
 355                         $deleted = true; // new revisions text is hidden
 356                         if ( $this->mNewRev->isDeleted( Revision::DELETED_RESTRICTED ) )
 357                                 $suppressed = true; // also suppressed
 358                 }
 359
 360                 # If the diff cannot be shown due to a deleted revision, then output
 361                 # the diff header and links to unhide (if available)...
 362                 if ( $deleted && ( !$this->unhide || !$allowed ) ) {
 363                         $this->showDiffStyle();
 364                         $multi = $this->getMultiNotice();
 365                         $out->addHTML( $this->addHeader( '', $oldHeader, $newHeader, $multi ) );
 366                         if ( !$allowed ) {
 367                                 $msg = $suppressed ? 'rev-suppressed-no-diff' : 'rev-deleted-no-diff';
 368                                 # Give explanation for why revision is not visible
 369                                 $out->wrapWikiMsg( "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n",
 370                                         array( $msg ) );
 371                         } else {
 372                                 # Give explanation and add a link to view the diff...
 373                                 $link = $this->getTitle()->getFullUrl( $this->getRequest()->appendQueryValue( 'unhide', '1', true ) );
 374                                 $msg = $suppressed ? 'rev-suppressed-unhide-diff' : 'rev-deleted-unhide-diff';
 375                                 $out->wrapWikiMsg( "<div id='mw-$msg' class='mw-warning plainlinks'>\n$1\n</div>\n", array( $msg, $link ) );
 376                         }
 377                 # Otherwise, output a regular diff...
 378                 } else {
 379                         # Add deletion notice if the user is viewing deleted content
 380                         $notice = '';
 381                         if ( $deleted ) {
 382                                 $msg = $suppressed ? 'rev-suppressed-diff-view' : 'rev-deleted-diff-view';
 383                                 $notice = "<div id='mw-$msg' class='mw-warning plainlinks'>\n" . $this->msg( $msg )->parse() . "</div>\n";
 384                         }
 385                         $this->showDiff( $oldHeader, $newHeader, $notice );
 386                         if ( !$diffOnly ) {
 387                                 $this->renderNewRevision();
 388                         }
 389                 }
 390                 wfProfileOut( __METHOD__ );
 391         }
 392
 393         /**
 394          * Get a link to mark the change as patrolled, or '' if there's either no
 395          * revision to patrol or the user is not allowed to to it.
 396          * Side effect: this method will call OutputPage::preventClickjacking()
 397          * when a link is builded.
 398          *
 399          * @return String
 400          */
 401         protected function markPatrolledLink() {
 402                 global $wgUseRCPatrol;
 403
 404                 if ( $this->mMarkPatrolledLink === null ) {
 405                         // Prepare a change patrol link, if applicable
 406                         if ( $wgUseRCPatrol && $this->mNewPage->userCan( 'patrol', $this->getUser() ) ) {
 407                                 // If we've been given an explicit change identifier, use it; saves time
 408                                 if ( $this->mRcidMarkPatrolled ) {
 409                                         $rcid = $this->mRcidMarkPatrolled;
 410                                         $rc = RecentChange::newFromId( $rcid );
 411                                         // Already patrolled?
 412                                         $rcid = is_object( $rc ) && !$rc->getAttribute( 'rc_patrolled' ) ? $rcid : 0;
 413                                 } else {
 414                                         // Look for an unpatrolled change corresponding to this diff
 415                                         $db = wfGetDB( DB_SLAVE );
 416                                         $change = RecentChange::newFromConds(
 417                                                 array(
 418                                                 // Redundant user,timestamp condition so we can use the existing index
 419                                                         'rc_user_text'  => $this->mNewRev->getRawUserText(),
 420                                                         'rc_timestamp'  => $db->timestamp( $this->mNewRev->getTimestamp() ),
 421                                                         'rc_this_oldid' => $this->mNewid,
 422                                                         'rc_last_oldid' => $this->mOldid,
 423                                                         'rc_patrolled'  => 0
 424                                                 ),
 425                                                 __METHOD__
 426                                         );
 427                                         if ( $change instanceof RecentChange ) {
 428                                                 $rcid = $change->mAttribs['rc_id'];
 429                                                 $this->mRcidMarkPatrolled = $rcid;
 430                                         } else {
 431                                                 // None found
 432                                                 $rcid = 0;
 433                                         }
 434                                 }
 435                                 // Build the link
 436                                 if ( $rcid ) {
 437                                         $this->getOutput()->preventClickjacking();
 438                                         $token = $this->getUser()->getEditToken( $rcid );
 439                                         $this->mMarkPatrolledLink = ' <span class="patrollink">[' . Linker::linkKnown(
 440                                                 $this->mNewPage,
 441                                                 $this->msg( 'markaspatrolleddiff' )->escaped(),
 442                                                 array(),
 443                                                 array(
 444                                                         'action' => 'markpatrolled',
 445                                                         'rcid' => $rcid,
 446                                                         'token' => $token,
 447                                                 )
 448                                         ) . ']</span>';
 449                                 } else {
 450                                         $this->mMarkPatrolledLink = '';
 451                                 }
 452                         } else {
 453                                 $this->mMarkPatrolledLink = '';
 454                         }
 455                 }
 456
 457                 return $this->mMarkPatrolledLink;
 458         }
 459
 460         /**
 461          * @param $rev Revision
 462          * @return String
 463          */
 464         protected function revisionDeleteLink( $rev ) {
 465                 $link = '';
 466                 $user = $this->getUser();
 467                 $canHide = $user->isAllowed( 'deleterevision' );
 468                 // Show del/undel link if:
 469                 // (a) the user can delete revisions, or
 470                 // (b) the user can view deleted revision *and* this one is deleted
 471                 if ( $canHide || ( $rev->getVisibility() && $user->isAllowed( 'deletedhistory' ) ) ) {
 472                         if ( !$rev->userCan( Revision::DELETED_RESTRICTED, $user ) ) {
 473                                 $link = Linker::revDeleteLinkDisabled( $canHide ); // revision was hidden from sysops
 474                         } else {
 475                                 $query = array(
 476                                         'type'   => 'revision',
 477                                         'target' => $rev->getTitle()->getPrefixedDBkey(),
 478                                         'ids'    => $rev->getId()
 479                                 );
 480                                 $link = Linker::revDeleteLink( $query,
 481                                         $rev->isDeleted( Revision::DELETED_RESTRICTED ), $canHide );
 482                         }
 483                         $link = '&#160;&#160;&#160;' . $link . ' ';
 484                 }
 485                 return $link;
 486         }
 487
 488         /**
 489          * Show the new revision of the page.
 490          */
 491         function renderNewRevision() {
 492                 wfProfileIn( __METHOD__ );
 493                 $out = $this->getOutput();
 494                 $revHeader = $this->getRevisionHeader( $this->mNewRev );
 495                 # Add "current version as of X" title
 496                 $out->addHTML( "<hr class='diff-hr' />
 497                 <h2 class='diff-currentversion-title'>{$revHeader}</h2>\n" );
 498                 # Page content may be handled by a hooked call instead...
 499                 if ( wfRunHooks( 'ArticleContentOnDiff', array( $this, $out ) ) ) {
 500                         $this->loadNewText();
 501                         $out->setRevisionId( $this->mNewid );
 502                         $out->setArticleFlag( true );
 503
 504                         if ( $this->mNewPage->isCssJsSubpage() || $this->mNewPage->isCssOrJsPage() ) {
 505                                 // Stolen from Article::view --AG 2007-10-11
 506                                 // Give hooks a chance to customise the output
 507                                 // @TODO: standardize this crap into one function
 508                                 if ( wfRunHooks( 'ShowRawCssJs', array( $this->mNewtext, $this->mNewPage, $out ) ) ) {
 509                                         // Wrap the whole lot in a <pre> and don't parse
 510                                         $m = array();
 511                                         preg_match( '!\.(css|js)$!u', $this->mNewPage->getText(), $m );
 512                                         $out->addHTML( "<pre class=\"mw-code mw-{$m[1]}\" dir=\"ltr\">\n" );
 513                                         $out->addHTML( htmlspecialchars( $this->mNewtext ) );
 514                                         $out->addHTML( "\n</pre>\n" );
 515                                 }
 516                         } elseif ( !wfRunHooks( 'ArticleViewCustom', array( $this->mNewtext, $this->mNewPage, $out ) ) ) {
 517                                 // Handled by extension
 518                         } else {
 519                                 # Use the current version parser cache if applicable
 520                                 $wikiPage = WikiPage::factory( $this->mNewPage );
 521                                 $useParserCache = $wikiPage->isParserCacheUsed( $this->getUser(), $this->mNewid );
 522
 523                                 $parserOptions = ParserOptions::newFromContext( $this->getContext() );
 524                                 $parserOptions->enableLimitReport();
 525                                 $parserOptions->setTidy( true );
 526
 527                                 if ( !$this->mNewRev->isCurrent() ) {
 528                                         $parserOptions->setEditSection( false );
 529                                 }
 530
 531                                 $parserOutput = false;
 532                                 if ( $useParserCache ) {
 533                                         $parserOutput = ParserCache::singleton()->get( $wikiPage, $parserOptions );
 534                                 }
 535
 536                                 if( $parserOutput ) {
 537                                         $out->addParserOutput( $parserOutput );
 538                                 } else {
 539                                         $out->addWikiTextTidy( $this->mNewtext );
 540                                 }
 541                         }
 542                 }
 543                 # Add redundant patrol link on bottom...
 544                 $out->addHTML( $this->markPatrolledLink() );
 545
 546                 wfProfileOut( __METHOD__ );
 547         }
 548
 549         /**
 550          * Get the diff text, send it to the OutputPage object
 551          * Returns false if the diff could not be generated, otherwise returns true
 552          *
 553          * @return bool
 554          */
 555         function showDiff( $otitle, $ntitle, $notice = '' ) {
 556                 $diff = $this->getDiff( $otitle, $ntitle, $notice );
 557                 if ( $diff === false ) {
 558                         $this->getOutput()->addWikiMsg( 'missing-article', "<nowiki>(fixme, bug)</nowiki>", '' );
 559                         return false;
 560                 } else {
 561                         $this->showDiffStyle();
 562                         $this->getOutput()->addHTML( $diff );
 563                         return true;
 564                 }
 565         }
 566
 567         /**
 568          * Add style sheets and supporting JS for diff display.
 569          */
 570         function showDiffStyle() {
 571                 $this->getOutput()->addModuleStyles( 'mediawiki.action.history.diff' );
 572         }
 573
 574         /**
 575          * Get complete diff table, including header
 576          *
 577          * @param $otitle Title: old title
 578          * @param $ntitle Title: new title
 579          * @param $notice String: HTML between diff header and body
 580          * @return mixed
 581          */
 582         function getDiff( $otitle, $ntitle, $notice = '' ) {
 583                 $body = $this->getDiffBody();
 584                 if ( $body === false ) {
 585                         return false;
 586                 } else {
 587                         $multi = $this->getMultiNotice();
 588                         return $this->addHeader( $body, $otitle, $ntitle, $multi, $notice );
 589                 }
 590         }
 591
 592         /**
 593          * Get the diff table body, without header
 594          *
 595          * @return mixed (string/false)
 596          */
 597         public function getDiffBody() {
 598                 global $wgMemc;
 599                 wfProfileIn( __METHOD__ );
 600                 $this->mCacheHit = true;
 601                 // Check if the diff should be hidden from this user
 602                 if ( !$this->loadRevisionData() ) {
 603                         wfProfileOut( __METHOD__ );
 604                         return false;
 605                 } elseif ( $this->mOldRev && !$this->mOldRev->userCan( Revision::DELETED_TEXT, $this->getUser() ) ) {
 606                         wfProfileOut( __METHOD__ );
 607                         return false;
 608                 } elseif ( $this->mNewRev && !$this->mNewRev->userCan( Revision::DELETED_TEXT, $this->getUser() ) ) {
 609                         wfProfileOut( __METHOD__ );
 610                         return false;
 611                 }
 612                 // Short-circuit
 613                 // If mOldRev is false, it means that the
 614                 if ( $this->mOldRev === false || ( $this->mOldRev && $this->mNewRev
 615                         && $this->mOldRev->getID() == $this->mNewRev->getID() ) )
 616                 {
 617                         wfProfileOut( __METHOD__ );
 618                         return '';
 619                 }
 620                 // Cacheable?
 621                 $key = false;
 622                 if ( $this->mOldid && $this->mNewid ) {
 623                         $key = wfMemcKey( 'diff', 'version', MW_DIFF_VERSION,
 624                                 'oldid', $this->mOldid, 'newid', $this->mNewid );
 625                         // Try cache
 626                         if ( !$this->mRefreshCache ) {
 627                                 $difftext = $wgMemc->get( $key );
 628                                 if ( $difftext ) {
 629                                         wfIncrStats( 'diff_cache_hit' );
 630                                         $difftext = $this->localiseLineNumbers( $difftext );
 631                                         $difftext .= "\n<!-- diff cache key $key -->\n";
 632                                         wfProfileOut( __METHOD__ );
 633                                         return $difftext;
 634                                 }
 635                         } // don't try to load but save the result
 636                 }
 637                 $this->mCacheHit = false;
 638
 639                 // Loadtext is permission safe, this just clears out the diff
 640                 if ( !$this->loadText() ) {
 641                         wfProfileOut( __METHOD__ );
 642                         return false;
 643                 }
 644
 645                 $difftext = $this->generateDiffBody( $this->mOldtext, $this->mNewtext );
 646
 647                 // Save to cache for 7 days
 648                 if ( !wfRunHooks( 'AbortDiffCache', array( &$this ) ) ) {
 649                         wfIncrStats( 'diff_uncacheable' );
 650                 } elseif ( $key !== false && $difftext !== false ) {
 651                         wfIncrStats( 'diff_cache_miss' );
 652                         $wgMemc->set( $key, $difftext, 7 * 86400 );
 653                 } else {
 654                         wfIncrStats( 'diff_uncacheable' );
 655                 }
 656                 // Replace line numbers with the text in the user's language
 657                 if ( $difftext !== false ) {
 658                         $difftext = $this->localiseLineNumbers( $difftext );
 659                 }
 660                 wfProfileOut( __METHOD__ );
 661                 return $difftext;
 662         }
 663
 664         /**
 665          * Make sure the proper modules are loaded before we try to
 666          * make the diff
 667          */
 668         private function initDiffEngines() {
 669                 global $wgExternalDiffEngine;
 670                 if ( $wgExternalDiffEngine == 'wikidiff' && !function_exists( 'wikidiff_do_diff' ) ) {
 671                         wfProfileIn( __METHOD__ . '-php_wikidiff.so' );
 672                         wfDl( 'php_wikidiff' );
 673                         wfProfileOut( __METHOD__ . '-php_wikidiff.so' );
 674                 }
 675                 elseif ( $wgExternalDiffEngine == 'wikidiff2' && !function_exists( 'wikidiff2_do_diff' ) ) {
 676                         wfProfileIn( __METHOD__ . '-php_wikidiff2.so' );
 677                         wfDl( 'wikidiff2' );
 678                         wfProfileOut( __METHOD__ . '-php_wikidiff2.so' );
 679                 }
 680         }
 681
 682         /**
 683          * Generate a diff, no caching
 684          *
 685          * @param $otext String: old text, must be already segmented
 686          * @param $ntext String: new text, must be already segmented
 687          */
 688         function generateDiffBody( $otext, $ntext ) {
 689                 global $wgExternalDiffEngine, $wgContLang;
 690
 691                 wfProfileIn( __METHOD__ );
 692
 693                 $otext = str_replace( "\r\n", "\n", $otext );
 694                 $ntext = str_replace( "\r\n", "\n", $ntext );
 695
 696                 $this->initDiffEngines();
 697
 698                 if ( $wgExternalDiffEngine == 'wikidiff' && function_exists( 'wikidiff_do_diff' ) ) {
 699                         # For historical reasons, external diff engine expects
 700                         # input text to be HTML-escaped already
 701                         $otext = htmlspecialchars ( $wgContLang->segmentForDiff( $otext ) );
 702                         $ntext = htmlspecialchars ( $wgContLang->segmentForDiff( $ntext ) );
 703                         wfProfileOut( __METHOD__ );
 704                         return $wgContLang->unsegmentForDiff( wikidiff_do_diff( $otext, $ntext, 2 ) ) .
 705                         $this->debug( 'wikidiff1' );
 706                 }
 707
 708                 if ( $wgExternalDiffEngine == 'wikidiff2' && function_exists( 'wikidiff2_do_diff' ) ) {
 709                         # Better external diff engine, the 2 may some day be dropped
 710                         # This one does the escaping and segmenting itself
 711                         wfProfileIn( 'wikidiff2_do_diff' );
 712                         $text = wikidiff2_do_diff( $otext, $ntext, 2 );
 713                         $text .= $this->debug( 'wikidiff2' );
 714                         wfProfileOut( 'wikidiff2_do_diff' );
 715                         wfProfileOut( __METHOD__ );
 716                         return $text;
 717                 }
 718                 if ( $wgExternalDiffEngine != 'wikidiff3' && $wgExternalDiffEngine !== false ) {
 719                         # Diff via the shell
 720                         global $wgTmpDirectory;
 721                         $tempName1 = tempnam( $wgTmpDirectory, 'diff_' );
 722                         $tempName2 = tempnam( $wgTmpDirectory, 'diff_' );
 723
 724                         $tempFile1 = fopen( $tempName1, "w" );
 725                         if ( !$tempFile1 ) {
 726                                 wfProfileOut( __METHOD__ );
 727                                 return false;
 728                         }
 729                         $tempFile2 = fopen( $tempName2, "w" );
 730                         if ( !$tempFile2 ) {
 731                                 wfProfileOut( __METHOD__ );
 732                                 return false;
 733                         }
 734                         fwrite( $tempFile1, $otext );
 735                         fwrite( $tempFile2, $ntext );
 736                         fclose( $tempFile1 );
 737                         fclose( $tempFile2 );
 738                         $cmd = wfEscapeShellArg( $wgExternalDiffEngine, $tempName1, $tempName2 );
 739                         wfProfileIn( __METHOD__ . "-shellexec" );
 740                         $difftext = wfShellExec( $cmd );
 741                         $difftext .= $this->debug( "external $wgExternalDiffEngine" );
 742                         wfProfileOut( __METHOD__ . "-shellexec" );
 743                         unlink( $tempName1 );
 744                         unlink( $tempName2 );
 745                         wfProfileOut( __METHOD__ );
 746                         return $difftext;
 747                 }
 748
 749                 # Native PHP diff
 750                 $ota = explode( "\n", $wgContLang->segmentForDiff( $otext ) );
 751                 $nta = explode( "\n", $wgContLang->segmentForDiff( $ntext ) );
 752                 $diffs = new Diff( $ota, $nta );
 753                 $formatter = new TableDiffFormatter();
 754                 $difftext = $wgContLang->unsegmentForDiff( $formatter->format( $diffs ) ) .
 755                 wfProfileOut( __METHOD__ );
 756                 return $difftext;
 757         }
 758
 759         /**
 760          * Generate a debug comment indicating diff generating time,
 761          * server node, and generator backend.
 762          */
 763         protected function debug( $generator = "internal" ) {
 764                 global $wgShowHostnames;
 765                 if ( !$this->enableDebugComment ) {
 766                         return '';
 767                 }
 768                 $data = array( $generator );
 769                 if ( $wgShowHostnames ) {
 770                         $data[] = wfHostname();
 771                 }
 772                 $data[] = wfTimestamp( TS_DB );
 773                 return "<!-- diff generator: " .
 774                 implode( " ",
 775                 array_map(
 776                                         "htmlspecialchars",
 777                 $data ) ) .
 778                         " -->\n";
 779         }
 780
 781         /**
 782          * Replace line numbers with the text in the user's language
 783          */
 784         function localiseLineNumbers( $text ) {
 785                 return preg_replace_callback( '/<!--LINE (\d+)-->/',
 786                 array( &$this, 'localiseLineNumbersCb' ), $text );
 787         }
 788
 789         function localiseLineNumbersCb( $matches ) {
 790                 if ( $matches[1] === '1' && $this->mReducedLineNumbers ) return '';
 791                 return $this->msg( 'lineno' )->numParams( $matches[1] )->escaped();
 792         }
 793
 794
 795         /**
 796          * If there are revisions between the ones being compared, return a note saying so.
 797          * @return string
 798          */
 799         function getMultiNotice() {
 800                 if ( !is_object( $this->mOldRev ) || !is_object( $this->mNewRev ) ) {
 801                         return '';
 802                 } elseif ( !$this->mOldPage->equals( $this->mNewPage ) ) {
 803                         // Comparing two different pages? Count would be meaningless.
 804                         return '';
 805                 }
 806
 807                 if ( $this->mOldRev->getTimestamp() > $this->mNewRev->getTimestamp() ) {
 808                         $oldRev = $this->mNewRev; // flip
 809                         $newRev = $this->mOldRev; // flip
 810                 } else { // normal case
 811                         $oldRev = $this->mOldRev;
 812                         $newRev = $this->mNewRev;
 813                 }
 814
 815                 $nEdits = $this->mNewPage->countRevisionsBetween( $oldRev, $newRev );
 816                 if ( $nEdits > 0 ) {
 817                         $limit = 100; // use diff-multi-manyusers if too many users
 818                         $numUsers = $this->mNewPage->countAuthorsBetween( $oldRev, $newRev, $limit );
 819                         return self::intermediateEditsMsg( $nEdits, $numUsers, $limit );
 820                 }
 821                 return ''; // nothing
 822         }
 823
 824         /**
 825          * Get a notice about how many intermediate edits and users there are
 826          * @param $numEdits int
 827          * @param $numUsers int
 828          * @param $limit int
 829          * @return string
 830          */
 831         public static function intermediateEditsMsg( $numEdits, $numUsers, $limit ) {
 832                 if ( $numUsers > $limit ) {
 833                         $msg = 'diff-multi-manyusers';
 834                         $numUsers = $limit;
 835                 } else {
 836                         $msg = 'diff-multi';
 837                 }
 838                 return wfMessage( $msg )->numParams( $numEdits, $numUsers )->parse();
 839         }
 840
 841         /**
 842          * Get a header for a specified revision.
 843          *
 844          * @param $rev Revision
 845          * @param $complete String: 'complete' to get the header wrapped depending
 846          *        the visibility of the revision and a link to edit the page.
 847          * @return String HTML fragment
 848          */
 849         private function getRevisionHeader( Revision $rev, $complete = '' ) {
 850                 $lang = $this->getLang();
 851                 $user = $this->getUser();
 852                 $revtimestamp = $rev->getTimestamp();
 853                 $timestamp = $lang->userTimeAndDate( $revtimestamp, $user );
 854                 $dateofrev = $lang->userDate( $revtimestamp, $user );
 855                 $timeofrev = $lang->userTime( $revtimestamp, $user );
 856
 857                 $header = $this->msg(
 858                         $rev->isCurrent() ? 'currentrev-asof' : 'revisionasof',
 859                         $timestamp,
 860                         $dateofrev,
 861                         $timeofrev
 862                 )->escaped();
 863
 864                 if ( $complete !== 'complete' ) {
 865                         return $header;
 866                 }
 867
 868                 $title = $rev->getTitle();
 869
 870                 $header = Linker::linkKnown( $title, $header, array(),
 871                         array( 'oldid' => $rev->getID() ) );
 872
 873                 if ( $rev->userCan( Revision::DELETED_TEXT, $user ) ) {
 874                         $editQuery = array( 'action' => 'edit' );
 875                         if ( !$rev->isCurrent() ) {
 876                                 $editQuery['oldid'] = $rev->getID();
 877                         }
 878
 879                         $msg = $this->msg( $title->userCan( 'edit', $user ) ? 'editold' : 'viewsourceold' )->escaped();
 880                         $header .= ' (' . Linker::linkKnown( $title, $msg, array(), $editQuery ) . ')';
 881                         if ( $rev->isDeleted( Revision::DELETED_TEXT ) ) {
 882                                 $header = Html::rawElement( 'span', array( 'class' => 'history-deleted' ), $header );
 883                         }
 884                 } else {
 885                         $header = Html::rawElement( 'span', array( 'class' => 'history-deleted' ), $header );
 886                 }
 887
 888                 return $header;
 889         }
 890
 891         /**
 892          * Add the header to a diff body
 893          *
 894          * @return string
 895          */
 896         function addHeader( $diff, $otitle, $ntitle, $multi = '', $notice = '' ) {
 897                 // shared.css sets diff in interface language/dir, but the actual content
 898                 // is often in a different language, mostly the page content language/dir
 899                 $tableClass = 'diff diff-contentalign-' . htmlspecialchars( $this->getDiffLang()->alignStart() );
 900                 $header = "<table class='$tableClass'>";
 901
 902                 if ( !$diff && !$otitle ) {
 903                         $header .= "
 904                         <tr valign='top'>
 905                         <td class='diff-ntitle'>{$ntitle}</td>
 906                         </tr>";
 907                         $multiColspan = 1;
 908                 } else {
 909                         if ( $diff ) { // Safari/Chrome show broken output if cols not used
 910                                 $header .= "
 911                                 <col class='diff-marker' />
 912                                 <col class='diff-content' />
 913                                 <col class='diff-marker' />
 914                                 <col class='diff-content' />";
 915                                 $colspan = 2;
 916                                 $multiColspan = 4;
 917                         } else {
 918                                 $colspan = 1;
 919                                 $multiColspan = 2;
 920                         }
 921                         $header .= "
 922                         <tr valign='top'>
 923                         <td colspan='$colspan' class='diff-otitle'>{$otitle}</td>
 924                         <td colspan='$colspan' class='diff-ntitle'>{$ntitle}</td>
 925                         </tr>";
 926                 }
 927
 928                 if ( $multi != '' ) {
 929                         $header .= "<tr><td colspan='{$multiColspan}' align='center' class='diff-multi'>{$multi}</td></tr>";
 930                 }
 931                 if ( $notice != '' ) {
 932                         $header .= "<tr><td colspan='{$multiColspan}' align='center'>{$notice}</td></tr>";
 933                 }
 934
 935                 return $header . $diff . "</table>";
 936         }
 937
 938         /**
 939          * Use specified text instead of loading from the database
 940          */
 941         function setText( $oldText, $newText ) {
 942                 $this->mOldtext = $oldText;
 943                 $this->mNewtext = $newText;
 944                 $this->mTextLoaded = 2;
 945                 $this->mRevisionsLoaded = true;
 946         }
 947
 948         /**
 949          * Set the language in which the diff text is written
 950          * (Defaults to page content language).
 951          * @since 1.19
 952          */
 953         function setTextLanguage( $lang ) {
 954                 $this->mDiffLang = wfGetLangObj( $lang );
 955         }
 956
 957         /**
 958          * Load revision IDs
 959          */
 960         private function loadRevisionIds() {
 961                 if ( $this->mRevisionsIdsLoaded ) {
 962                         return;
 963                 }
 964
 965                 $this->mRevisionsIdsLoaded = true;
 966
 967                 $old = $this->mOldid;
 968                 $new = $this->mNewid;
 969
 970                 if ( $new === 'prev' ) {
 971                         # Show diff between revision $old and the previous one.
 972                         # Get previous one from DB.
 973                         $this->mNewid = intval( $old );
 974                         $this->mOldid = $this->getTitle()->getPreviousRevisionID( $this->mNewid );
 975                 } elseif ( $new === 'next' ) {
 976                         # Show diff between revision $old and the next one.
 977                         # Get next one from DB.
 978                         $this->mOldid = intval( $old );
 979                         $this->mNewid = $this->getTitle()->getNextRevisionID( $this->mOldid );
 980                         if ( $this->mNewid === false ) {
 981                                 # if no result, NewId points to the newest old revision. The only newer
 982                                 # revision is cur, which is "0".
 983                                 $this->mNewid = 0;
 984                         }
 985                 } else {
 986                         $this->mOldid = intval( $old );
 987                         $this->mNewid = intval( $new );
 988                         wfRunHooks( 'NewDifferenceEngine', array( $this->getTitle(), &$this->mOldid, &$this->mNewid, $old, $new ) );
 989                 }
 990         }
 991
 992         /**
 993          * Load revision metadata for the specified articles. If newid is 0, then compare
 994          * the old article in oldid to the current article; if oldid is 0, then
 995          * compare the current article to the immediately previous one (ignoring the
 996          * value of newid).
 997          *
 998          * If oldid is false, leave the corresponding revision object set
 999          * to false. This is impossible via ordinary user input, and is provided for
1000          * API convenience.
1001          *
1002          * @return bool
1003          */
1004         function loadRevisionData() {
1005                 if ( $this->mRevisionsLoaded ) {
1006                         return true;
1007                 }
1008
1009                 // Whether it succeeds or fails, we don't want to try again
1010                 $this->mRevisionsLoaded = true;
1011
1012                 $this->loadRevisionIds();
1013
1014                 // Load the new revision object
1015                 $this->mNewRev = $this->mNewid
1016                         ? Revision::newFromId( $this->mNewid )
1017                         : Revision::newFromTitle( $this->getTitle() );
1018
1019                 if ( !$this->mNewRev instanceof Revision ) {
1020                         return false;
1021                 }
1022
1023                 // Update the new revision ID in case it was 0 (makes life easier doing UI stuff)
1024                 $this->mNewid = $this->mNewRev->getId();
1025                 $this->mNewPage = $this->mNewRev->getTitle();
1026
1027                 // Load the old revision object
1028                 $this->mOldRev = false;
1029                 if ( $this->mOldid ) {
1030                         $this->mOldRev = Revision::newFromId( $this->mOldid );
1031                 } elseif ( $this->mOldid === 0 ) {
1032                         $rev = $this->mNewRev->getPrevious();
1033                         if ( $rev ) {
1034                                 $this->mOldid = $rev->getId();
1035                                 $this->mOldRev = $rev;
1036                         } else {
1037                                 // No previous revision; mark to show as first-version only.
1038                                 $this->mOldid = false;
1039                                 $this->mOldRev = false;
1040                         }
1041                 } /* elseif ( $this->mOldid === false ) leave mOldRev false; */
1042
1043                 if ( is_null( $this->mOldRev ) ) {
1044                         return false;
1045                 }
1046
1047                 if ( $this->mOldRev ) {
1048                         $this->mOldPage = $this->mOldRev->getTitle();
1049                 }
1050
1051                 return true;
1052         }
1053
1054         /**
1055          * Load the text of the revisions, as well as revision data.
1056          *
1057          * @return bool
1058          */
1059         function loadText() {
1060                 if ( $this->mTextLoaded == 2 ) {
1061                         return true;
1062                 } else {
1063                         // Whether it succeeds or fails, we don't want to try again
1064                         $this->mTextLoaded = 2;
1065                 }
1066
1067                 if ( !$this->loadRevisionData() ) {
1068                         return false;
1069                 }
1070                 if ( $this->mOldRev ) {
1071                         $this->mOldtext = $this->mOldRev->getText( Revision::FOR_THIS_USER );
1072                         if ( $this->mOldtext === false ) {
1073                                 return false;
1074                         }
1075                 }
1076                 if ( $this->mNewRev ) {
1077                         $this->mNewtext = $this->mNewRev->getText( Revision::FOR_THIS_USER );
1078                         if ( $this->mNewtext === false ) {
1079                                 return false;
1080                         }
1081                 }
1082                 return true;
1083         }
1084
1085         /**
1086          * Load the text of the new revision, not the old one
1087          *
1088          * @return bool
1089          */
1090         function loadNewText() {
1091                 if ( $this->mTextLoaded >= 1 ) {
1092                         return true;
1093                 } else {
1094                         $this->mTextLoaded = 1;
1095                 }
1096                 if ( !$this->loadRevisionData() ) {
1097                         return false;
1098                 }
1099                 $this->mNewtext = $this->mNewRev->getText( Revision::FOR_THIS_USER );
1100                 return true;
1101         }
1102 }