includes/api/ApiStashEdit.php

   1 <?php
   2 /**
   3  * This program is free software; you can redistribute it and/or modify
   4  * it under the terms of the GNU General Public License as published by
   5  * the Free Software Foundation; either version 2 of the License, or
   6  * (at your option) any later version.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  11  * GNU General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License along
  14  * with this program; if not, write to the Free Software Foundation, Inc.,
  15  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  16  * http://www.gnu.org/copyleft/gpl.html
  17  *
  18  * @file
  19  * @author Aaron Schulz
  20  */
  21
  22 /**
  23  * Prepare and edit in shared cache so that it can be reused on edit
  24  *
  25  * This endpoint can be called via AJAX as the user focuses on the edit
  26  * summary box. By the time of submission, the parse may have already
  27  * finished, and can be immediately used on page save. Certain parser
  28  * functions like {{REVISIONID}} or {{CURRENTTIME}} may cause the cache
  29  * to not be used on edit. Template and files used are check for changes
  30  * since the output was generated. The cache TTL is also kept low for sanity.
  31  *
  32  * @ingroup API
  33  * @since 1.25
  34  */
  35 class ApiStashEdit extends ApiBase {
  36         public function execute() {
  37                 global $wgMemc;
  38
  39                 $user = $this->getUser();
  40                 $params = $this->extractRequestParams();
  41
  42                 $page = $this->getTitleOrPageId( $params );
  43                 $title = $page->getTitle();
  44
  45                 if ( !ContentHandler::getForModelID( $params['contentmodel'] )
  46                         ->isSupportedFormat( $params['contentformat'] )
  47                 ) {
  48                         $this->dieUsage( "Unsupported content model/format", 'badmodelformat' );
  49                 }
  50
  51                 // Trim and fix newlines so the key SHA1's match (see RequestContext::getText())
  52                 $text = rtrim( str_replace( "\r\n", "\n", $params['text'] ) );
  53                 $textContent = ContentHandler::makeContent(
  54                         $text, $title, $params['contentmodel'], $params['contentformat'] );
  55
  56                 $page = WikiPage::factory( $title );
  57                 if ( $page->exists() ) {
  58                         // Page exists: get the merged content with the proposed change
  59                         $baseRev = Revision::newFromPageId( $page->getId(), $params['baserevid'] );
  60                         if ( !$baseRev ) {
  61                                 $this->dieUsage( "No revision ID {$params['baserevid']}", 'missingrev' );
  62                         }
  63                         $currentRev = $page->getRevision();
  64                         if ( !$currentRev ) {
  65                                 $this->dieUsage( "No current revision of page ID {$page->getId()}", 'missingrev' );
  66                         }
  67                         // Merge in the new version of the section to get the proposed version
  68                         $editContent = $page->replaceSectionAtRev(
  69                                 $params['section'],
  70                                 $textContent,
  71                                 $params['sectiontitle'],
  72                                 $baseRev->getId()
  73                         );
  74                         if ( !$editContent ) {
  75                                 $this->dieUsage( "Could not merge updated section.", 'replacefailed' );
  76                         }
  77                         if ( $currentRev->getId() == $baseRev->getId() ) {
  78                                 // Base revision was still the latest; nothing to merge
  79                                 $content = $editContent;
  80                         } else {
  81                                 // Merge the edit into the current version
  82                                 $baseContent = $baseRev->getContent();
  83                                 $currentContent = $currentRev->getContent();
  84                                 if ( !$baseContent || !$currentContent ) {
  85                                         $this->dieUsage( "Missing content for page ID {$page->getId()}", 'missingrev' );
  86                                 }
  87                                 $handler = ContentHandler::getForModelID( $baseContent->getModel() );
  88                                 $content = $handler->merge3( $baseContent, $editContent, $currentContent );
  89                         }
  90                 } else {
  91                         // New pages: use the user-provided content model
  92                         $content = $textContent;
  93                 }
  94
  95                 if ( !$content ) { // merge3() failed
  96                         $this->getResult()->addValue( null,
  97                                 $this->getModuleName(), array( 'status' => 'editconflict' ) );
  98                         return;
  99                 }
 100
 101                 // The user will abort the AJAX request by pressing "save", so ignore that
 102                 ignore_user_abort( true );
 103
 104                 // Get a key based on the source text, format, and user preferences
 105                 $key = self::getStashKey( $title, $content, $user );
 106                 // De-duplicate requests on the same key
 107                 if ( $user->pingLimiter( 'stashedit' ) ) {
 108                         $editInfo = false;
 109                         $status = 'ratelimited';
 110                 } elseif ( $wgMemc->lock( $key, 0, 30 ) ) {
 111                         $format = $content->getDefaultFormat();
 112                         $editInfo = $page->prepareContentForEdit( $content, null, $user, $format, false );
 113                         $status = 'error'; // default
 114                         $unlocker = new ScopedCallback( function() use ( $key ) {
 115                                 global $wgMemc;
 116                                 $wgMemc->unlock( $key );
 117                         } );
 118                 } else {
 119                         $editInfo = false;
 120                         $status = 'busy';
 121                 }
 122
 123                 if ( $editInfo && $editInfo->output ) {
 124                         list( $stashInfo, $ttl ) = self::buildStashValue(
 125                                 $editInfo->pstContent, $editInfo->output, $editInfo->timestamp
 126                         );
 127                         if ( $stashInfo ) {
 128                                 $ok = $wgMemc->set( $key, $stashInfo, $ttl );
 129                                 if ( $ok ) {
 130                                         $status = 'stashed';
 131                                         wfDebugLog( 'StashEdit', "Cached parser output for key '$key'." );
 132                                 } else {
 133                                         $status = 'error';
 134                                         wfDebugLog( 'StashEdit', "Failed to cache parser output for key '$key'." );
 135                                 }
 136                         } else {
 137                                 $status = 'uncacheable';
 138                                 wfDebugLog( 'StashEdit', "Uncacheable parser output for key '$key'." );
 139                         }
 140                 }
 141
 142                 $this->getResult()->addValue( null, $this->getModuleName(), array( 'status' => $status ) );
 143         }
 144
 145         /**
 146          * Attempt to cache PST content and corresponding parser output in passing
 147          *
 148          * This method can be called when the output was already generated for other
 149          * reasons. Parsing should not be done just to call this method, however.
 150          * $pstOpts must be that of the user doing the edit preview. If $pOpts does
 151          * not match the options of WikiPage::makeParserOptions( 'canonical' ), this
 152          * will do nothing. Provided the values are cacheable, they will be stored
 153          * in memcached so that final edit submission might make use of them.
 154          *
 155          * @param Article|WikiPage $page Page title
 156          * @param Content $content Proposed page content
 157          * @param Content $pstContent The result of preSaveTransform() on $content
 158          * @param ParserOutput $pOut The result of getParserOutput() on $pstContent
 159          * @param ParserOptions $pstOpts Options for $pstContent (MUST be for prospective author)
 160          * @param ParserOptions $pOpts Options for $pOut
 161          * @param string $timestamp TS_MW timestamp of parser output generation
 162          * @return bool Success
 163          */
 164         public static function stashEditFromPreview(
 165                 Page $page, Content $content, Content $pstContent, ParserOutput $pOut,
 166                 ParserOptions $pstOpts, ParserOptions $pOpts, $timestamp
 167         ) {
 168                 global $wgMemc;
 169
 170                 // getIsPreview() controls parser function behavior that references things
 171                 // like user/revision that don't exists yet. The user/text should already
 172                 // be set correctly by callers, just double check the preview flag.
 173                 if ( !$pOpts->getIsPreview() ) {
 174                         return false; // sanity
 175                 } elseif ( $pOpts->getIsSectionPreview() ) {
 176                         return false; // short-circuit (need the full content)
 177                 }
 178
 179                 // PST parser options are for the user (handles signatures, etc...)
 180                 $user = $pstOpts->getUser();
 181                 // Get a key based on the source text, format, and user preferences
 182                 $key = self::getStashKey( $page->getTitle(), $content, $user );
 183
 184                 // Parser output options must match cannonical options.
 185                 // Treat some options as matching that are different but don't matter.
 186                 $canonicalPOpts = $page->makeParserOptions( 'canonical' );
 187                 $canonicalPOpts->setIsPreview( true ); // force match
 188                 $canonicalPOpts->setTimestamp( $pOpts->getTimestamp() ); // force match
 189                 if ( !$pOpts->matches( $canonicalPOpts ) ) {
 190                         wfDebugLog( 'StashEdit', "Uncacheable preview output for key '$key' (options)." );
 191                         return false;
 192                 }
 193
 194                 // Build a value to cache with a proper TTL
 195                 list( $stashInfo, $ttl ) = self::buildStashValue( $pstContent, $pOut, $timestamp );
 196                 if ( !$stashInfo ) {
 197                         wfDebugLog( 'StashEdit', "Uncacheable parser output for key '$key' (rev/TTL)." );
 198                         return false;
 199                 }
 200
 201                 $ok = $wgMemc->set( $key, $stashInfo, $ttl );
 202                 if ( !$ok ) {
 203                         wfDebugLog( 'StashEdit', "Failed to cache preview parser output for key '$key'." );
 204                 } else {
 205                         wfDebugLog( 'StashEdit', "Cached preview output for key '$key'." );
 206                 }
 207
 208                 return $ok;
 209         }
 210
 211         /**
 212          * Check that a prepared edit is in cache and still up-to-date
 213          *
 214          * This method blocks if the prepared edit is already being rendered,
 215          * waiting until rendering finishes before doing final validity checks.
 216          *
 217          * The cache is rejected if template or file changes are detected.
 218          * Note that foreign template or file transclusions are not checked.
 219          *
 220          * The result is a map (pstContent,output,timestamp) with fields
 221          * extracted directly from WikiPage::prepareContentForEdit().
 222          *
 223          * @param Title $title
 224          * @param Content $content
 225          * @param User $user User to get parser options from
 226          * @return stdClass|bool Returns false on cache miss
 227          */
 228         public static function checkCache( Title $title, Content $content, User $user ) {
 229                 global $wgMemc;
 230
 231                 $key = self::getStashKey( $title, $content, $user );
 232                 $editInfo = $wgMemc->get( $key );
 233                 if ( !is_object( $editInfo ) ) {
 234                         $start = microtime( true );
 235                         // We ignore user aborts and keep parsing. Block on any prior parsing
 236                         // so as to use it's results and make use of the time spent parsing.
 237                         if ( $wgMemc->lock( $key, 30, 30 ) ) {
 238                                 $editInfo = $wgMemc->get( $key );
 239                                 $wgMemc->unlock( $key );
 240                         }
 241                         $sec = microtime( true ) - $start;
 242                         if ( $sec > .01 ) {
 243                                 wfDebugLog( 'StashEdit', "Waited $sec seconds on '$key'." );
 244                         }
 245                 }
 246
 247                 if ( !is_object( $editInfo ) || !$editInfo->output ) {
 248                         wfDebugLog( 'StashEdit', "No cache value for key '$key'." );
 249                         return false;
 250                 }
 251
 252                 $time = wfTimestamp( TS_UNIX, $editInfo->output->getTimestamp() );
 253                 if ( ( time() - $time ) <= 3 ) {
 254                         wfDebugLog( 'StashEdit', "Timestamp-based cache hit for key '$key'." );
 255                         return $editInfo; // assume nothing changed
 256                 }
 257
 258                 $dbr = wfGetDB( DB_SLAVE );
 259                 // Check that no templates used in the output changed...
 260                 $cWhr = array(); // conditions to find changes/creations
 261                 $dWhr = array(); // conditions to find deletions
 262                 foreach ( $editInfo->output->getTemplateIds() as $ns => $stuff ) {
 263                         foreach ( $stuff as $dbkey => $revId ) {
 264                                 $cWhr[] = array( 'page_namespace' => $ns, 'page_title' => $dbkey,
 265                                         'page_latest != ' . intval( $revId ) );
 266                                 $dWhr[] = array( 'page_namespace' => $ns, 'page_title' => $dbkey );
 267                         }
 268                 }
 269                 $change = $dbr->selectField( 'page', '1', $dbr->makeList( $cWhr, LIST_OR ), __METHOD__ );
 270                 $n = $dbr->selectField( 'page', 'COUNT(*)', $dbr->makeList( $dWhr, LIST_OR ), __METHOD__ );
 271                 if ( $change || $n != count( $dWhr ) ) {
 272                         wfDebugLog( 'StashEdit', "Stale cache for key '$key'; template changed." );
 273                         return false;
 274                 }
 275
 276                 // Check that no files used in the output changed...
 277                 $cWhr = array(); // conditions to find changes/creations
 278                 $dWhr = array(); // conditions to find deletions
 279                 foreach ( $editInfo->output->getFileSearchOptions() as $name => $options ) {
 280                         $cWhr[] = array( 'img_name' => $dbkey,
 281                                 'img_sha1 != ' . $dbr->addQuotes( strval( $options['sha1'] ) ) );
 282                         $dWhr[] = array( 'img_name' => $dbkey );
 283                 }
 284                 $change = $dbr->selectField( 'image', '1', $dbr->makeList( $cWhr, LIST_OR ), __METHOD__ );
 285                 $n = $dbr->selectField( 'image', 'COUNT(*)', $dbr->makeList( $dWhr, LIST_OR ), __METHOD__ );
 286                 if ( $change || $n != count( $dWhr ) ) {
 287                         wfDebugLog( 'StashEdit', "Stale cache for key '$key'; file changed." );
 288                         return false;
 289                 }
 290
 291                 wfDebugLog( 'StashEdit', "Cache hit for key '$key'." );
 292
 293                 return $editInfo;
 294         }
 295
 296         /**
 297          * Get the temporary prepared edit stash key for a user
 298          *
 299          * This key can be used for caching prepared edits provided:
 300          *   - a) The $user was used for PST options
 301          *   - b) The parser output was made from the PST using cannonical matching options
 302          *
 303          * @param Title $title
 304          * @param Content $content
 305          * @param User $user User to get parser options from
 306          * @return string
 307          */
 308         protected static function getStashKey( Title $title, Content $content, User $user ) {
 309                 $hash = sha1( implode( ':', array(
 310                         $content->getModel(),
 311                         $content->getDefaultFormat(),
 312                         sha1( $content->serialize( $content->getDefaultFormat() ) ),
 313                         $user->getId() ?: md5( $user->getName() ), // account for user parser options
 314                         $user->getId() ? $user->getTouched() : '-' // handle preference change races
 315                 ) ) );
 316
 317                 return wfMemcKey( 'prepared-edit', md5( $title->getPrefixedDBkey() ), $hash );
 318         }
 319
 320         /**
 321          * Build a value to store in memcached based on the PST content and parser output
 322          *
 323          * This makes a simple version of WikiPage::prepareContentForEdit() as stash info
 324          *
 325          * @param Content $pstContent
 326          * @param ParserOutput $parserOutput
 327          * @param string $timestamp TS_MW
 328          * @return array (stash info array, TTL in seconds) or (null, 0)
 329          */
 330         protected static function buildStashValue(
 331                 Content $pstContent, ParserOutput $parserOutput, $timestamp
 332         ) {
 333                 // If an item is renewed, mind the cache TTL determined by config and parser functions
 334                 $since = time() - wfTimestamp( TS_UNIX, $parserOutput->getTimestamp() );
 335                 $ttl = min( $parserOutput->getCacheExpiry() - $since, 5 * 60 );
 336
 337                 // Note: ParserOutput with that contains secondary data update callbacks can not be
 338                 // stashed, since the callbacks are not serializable (see ParserOutput::__sleep).
 339                 $hasCustomDataUpdates = $parserOutput->hasCustomDataUpdates();
 340
 341                 if ( $ttl > 0 && !$parserOutput->getFlag( 'vary-revision' ) && !$hasCustomDataUpdates ) {
 342                         // Only store what is actually needed
 343                         $stashInfo = (object)array(
 344                                 'pstContent' => $pstContent,
 345                                 'output'     => $parserOutput,
 346                                 'timestamp'  => $timestamp
 347                         );
 348                         return array( $stashInfo, $ttl );
 349                 }
 350
 351                 return array( null, 0 );
 352         }
 353
 354         public function getAllowedParams() {
 355                 return array(
 356                         'title' => array(
 357                                 ApiBase::PARAM_TYPE => 'string',
 358                                 ApiBase::PARAM_REQUIRED => true
 359                         ),
 360                         'section' => array(
 361                                 ApiBase::PARAM_TYPE => 'string',
 362                         ),
 363                         'sectiontitle' => array(
 364                                 ApiBase::PARAM_TYPE => 'string'
 365                         ),
 366                         'text' => array(
 367                                 ApiBase::PARAM_TYPE => 'string',
 368                                 ApiBase::PARAM_REQUIRED => true
 369                         ),
 370                         'contentmodel' => array(
 371                                 ApiBase::PARAM_TYPE => ContentHandler::getContentModels(),
 372                                 ApiBase::PARAM_REQUIRED => true
 373                         ),
 374                         'contentformat' => array(
 375                                 ApiBase::PARAM_TYPE => ContentHandler::getAllContentFormats(),
 376                                 ApiBase::PARAM_REQUIRED => true
 377                         ),
 378                         'baserevid' => array(
 379                                 ApiBase::PARAM_TYPE => 'integer',
 380                                 ApiBase::PARAM_REQUIRED => true
 381                         )
 382                 );
 383         }
 384
 385         function needsToken() {
 386                 return 'csrf';
 387         }
 388
 389         function mustBePosted() {
 390                 return true;
 391         }
 392
 393         function isInternal() {
 394                 return true;
 395         }
 396 }