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         const ERROR_NONE = 'stashed';
  37         const ERROR_PARSE = 'error_parse';
  38         const ERROR_CACHE = 'error_cache';
  39         const ERROR_UNCACHEABLE = 'uncacheable';
  40
  41         public function execute() {
  42                 global $wgMemc;
  43
  44                 $user = $this->getUser();
  45                 $params = $this->extractRequestParams();
  46
  47                 $page = $this->getTitleOrPageId( $params );
  48                 $title = $page->getTitle();
  49
  50                 if ( !ContentHandler::getForModelID( $params['contentmodel'] )
  51                         ->isSupportedFormat( $params['contentformat'] )
  52                 ) {
  53                         $this->dieUsage( "Unsupported content model/format", 'badmodelformat' );
  54                 }
  55
  56                 // Trim and fix newlines so the key SHA1's match (see RequestContext::getText())
  57                 $text = rtrim( str_replace( "\r\n", "\n", $params['text'] ) );
  58                 $textContent = ContentHandler::makeContent(
  59                         $text, $title, $params['contentmodel'], $params['contentformat'] );
  60
  61                 $page = WikiPage::factory( $title );
  62                 if ( $page->exists() ) {
  63                         // Page exists: get the merged content with the proposed change
  64                         $baseRev = Revision::newFromPageId( $page->getId(), $params['baserevid'] );
  65                         if ( !$baseRev ) {
  66                                 $this->dieUsage( "No revision ID {$params['baserevid']}", 'missingrev' );
  67                         }
  68                         $currentRev = $page->getRevision();
  69                         if ( !$currentRev ) {
  70                                 $this->dieUsage( "No current revision of page ID {$page->getId()}", 'missingrev' );
  71                         }
  72                         // Merge in the new version of the section to get the proposed version
  73                         $editContent = $page->replaceSectionAtRev(
  74                                 $params['section'],
  75                                 $textContent,
  76                                 $params['sectiontitle'],
  77                                 $baseRev->getId()
  78                         );
  79                         if ( !$editContent ) {
  80                                 $this->dieUsage( "Could not merge updated section.", 'replacefailed' );
  81                         }
  82                         if ( $currentRev->getId() == $baseRev->getId() ) {
  83                                 // Base revision was still the latest; nothing to merge
  84                                 $content = $editContent;
  85                         } else {
  86                                 // Merge the edit into the current version
  87                                 $baseContent = $baseRev->getContent();
  88                                 $currentContent = $currentRev->getContent();
  89                                 if ( !$baseContent || !$currentContent ) {
  90                                         $this->dieUsage( "Missing content for page ID {$page->getId()}", 'missingrev' );
  91                                 }
  92                                 $handler = ContentHandler::getForModelID( $baseContent->getModel() );
  93                                 $content = $handler->merge3( $baseContent, $editContent, $currentContent );
  94                         }
  95                 } else {
  96                         // New pages: use the user-provided content model
  97                         $content = $textContent;
  98                 }
  99
 100                 if ( !$content ) { // merge3() failed
 101                         $this->getResult()->addValue( null,
 102                                 $this->getModuleName(), array( 'status' => 'editconflict' ) );
 103                         return;
 104                 }
 105
 106                 // The user will abort the AJAX request by pressing "save", so ignore that
 107                 ignore_user_abort( true );
 108
 109                 // Get a key based on the source text, format, and user preferences
 110                 $key = self::getStashKey( $title, $content, $user );
 111                 // De-duplicate requests on the same key
 112                 if ( $user->pingLimiter( 'stashedit' ) ) {
 113                         $status = 'ratelimited';
 114                 } elseif ( $wgMemc->lock( $key, 0, 30 ) ) {
 115                         /** @noinspection PhpUnusedLocalVariableInspection */
 116                         $unlocker = new ScopedCallback( function() use ( $key ) {
 117                                 global $wgMemc;
 118                                 $wgMemc->unlock( $key );
 119                         } );
 120                         $status = self::parseAndStash( $page, $content, $user );
 121                 } else {
 122                         $status = 'busy';
 123                 }
 124
 125                 $this->getResult()->addValue( null, $this->getModuleName(), array( 'status' => $status ) );
 126         }
 127
 128         /**
 129          * @param WikiPage $page
 130          * @param Content $content
 131          * @param User $user
 132          * @return integer ApiStashEdit::ERROR_* constant
 133          * @since 1.25
 134          */
 135         public static function parseAndStash( WikiPage $page, Content $content, User $user ) {
 136                 global $wgMemc;
 137
 138                 $format = $content->getDefaultFormat();
 139                 $editInfo = $page->prepareContentForEdit( $content, null, $user, $format, false );
 140
 141                 if ( $editInfo && $editInfo->output ) {
 142                         $key = self::getStashKey( $page->getTitle(), $content, $user );
 143
 144                         list( $stashInfo, $ttl ) = self::buildStashValue(
 145                                 $editInfo->pstContent, $editInfo->output, $editInfo->timestamp
 146                         );
 147
 148                         if ( $stashInfo ) {
 149                                 $ok = $wgMemc->set( $key, $stashInfo, $ttl );
 150                                 if ( $ok ) {
 151                                         wfDebugLog( 'StashEdit', "Cached parser output for key '$key'." );
 152                                         return self::ERROR_NONE;
 153                                 } else {
 154                                         wfDebugLog( 'StashEdit', "Failed to cache parser output for key '$key'." );
 155                                         return self::ERROR_CACHE;
 156                                 }
 157                         } else {
 158                                 wfDebugLog( 'StashEdit', "Uncacheable parser output for key '$key'." );
 159                                 return self::ERROR_UNCACHEABLE;
 160                         }
 161                 }
 162
 163                 return self::ERROR_PARSE;
 164         }
 165
 166         /**
 167          * Attempt to cache PST content and corresponding parser output in passing
 168          *
 169          * This method can be called when the output was already generated for other
 170          * reasons. Parsing should not be done just to call this method, however.
 171          * $pstOpts must be that of the user doing the edit preview. If $pOpts does
 172          * not match the options of WikiPage::makeParserOptions( 'canonical' ), this
 173          * will do nothing. Provided the values are cacheable, they will be stored
 174          * in memcached so that final edit submission might make use of them.
 175          *
 176          * @param Article|WikiPage $page Page title
 177          * @param Content $content Proposed page content
 178          * @param Content $pstContent The result of preSaveTransform() on $content
 179          * @param ParserOutput $pOut The result of getParserOutput() on $pstContent
 180          * @param ParserOptions $pstOpts Options for $pstContent (MUST be for prospective author)
 181          * @param ParserOptions $pOpts Options for $pOut
 182          * @param string $timestamp TS_MW timestamp of parser output generation
 183          * @return bool Success
 184          */
 185         public static function stashEditFromPreview(
 186                 Page $page, Content $content, Content $pstContent, ParserOutput $pOut,
 187                 ParserOptions $pstOpts, ParserOptions $pOpts, $timestamp
 188         ) {
 189                 global $wgMemc;
 190
 191                 // getIsPreview() controls parser function behavior that references things
 192                 // like user/revision that don't exists yet. The user/text should already
 193                 // be set correctly by callers, just double check the preview flag.
 194                 if ( !$pOpts->getIsPreview() ) {
 195                         return false; // sanity
 196                 } elseif ( $pOpts->getIsSectionPreview() ) {
 197                         return false; // short-circuit (need the full content)
 198                 }
 199
 200                 // PST parser options are for the user (handles signatures, etc...)
 201                 $user = $pstOpts->getUser();
 202                 // Get a key based on the source text, format, and user preferences
 203                 $key = self::getStashKey( $page->getTitle(), $content, $user );
 204
 205                 // Parser output options must match cannonical options.
 206                 // Treat some options as matching that are different but don't matter.
 207                 $canonicalPOpts = $page->makeParserOptions( 'canonical' );
 208                 $canonicalPOpts->setIsPreview( true ); // force match
 209                 $canonicalPOpts->setTimestamp( $pOpts->getTimestamp() ); // force match
 210                 if ( !$pOpts->matches( $canonicalPOpts ) ) {
 211                         wfDebugLog( 'StashEdit', "Uncacheable preview output for key '$key' (options)." );
 212                         return false;
 213                 }
 214
 215                 // Build a value to cache with a proper TTL
 216                 list( $stashInfo, $ttl ) = self::buildStashValue( $pstContent, $pOut, $timestamp );
 217                 if ( !$stashInfo ) {
 218                         wfDebugLog( 'StashEdit', "Uncacheable parser output for key '$key' (rev/TTL)." );
 219                         return false;
 220                 }
 221
 222                 $ok = $wgMemc->set( $key, $stashInfo, $ttl );
 223                 if ( !$ok ) {
 224                         wfDebugLog( 'StashEdit', "Failed to cache preview parser output for key '$key'." );
 225                 } else {
 226                         wfDebugLog( 'StashEdit', "Cached preview output for key '$key'." );
 227                 }
 228
 229                 return $ok;
 230         }
 231
 232         /**
 233          * Check that a prepared edit is in cache and still up-to-date
 234          *
 235          * This method blocks if the prepared edit is already being rendered,
 236          * waiting until rendering finishes before doing final validity checks.
 237          *
 238          * The cache is rejected if template or file changes are detected.
 239          * Note that foreign template or file transclusions are not checked.
 240          *
 241          * The result is a map (pstContent,output,timestamp) with fields
 242          * extracted directly from WikiPage::prepareContentForEdit().
 243          *
 244          * @param Title $title
 245          * @param Content $content
 246          * @param User $user User to get parser options from
 247          * @return stdClass|bool Returns false on cache miss
 248          */
 249         public static function checkCache( Title $title, Content $content, User $user ) {
 250                 global $wgMemc;
 251
 252                 $key = self::getStashKey( $title, $content, $user );
 253                 $editInfo = $wgMemc->get( $key );
 254                 if ( !is_object( $editInfo ) ) {
 255                         $start = microtime( true );
 256                         // We ignore user aborts and keep parsing. Block on any prior parsing
 257                         // so as to use it's results and make use of the time spent parsing.
 258                         if ( $wgMemc->lock( $key, 30, 30 ) ) {
 259                                 $editInfo = $wgMemc->get( $key );
 260                                 $wgMemc->unlock( $key );
 261                         }
 262                         $sec = microtime( true ) - $start;
 263                         if ( $sec > .01 ) {
 264                                 wfDebugLog( 'StashEdit', "Waited $sec seconds on '$key'." );
 265                         }
 266                 }
 267
 268                 if ( !is_object( $editInfo ) || !$editInfo->output ) {
 269                         wfDebugLog( 'StashEdit', "No cache value for key '$key'." );
 270                         return false;
 271                 }
 272
 273                 $time = wfTimestamp( TS_UNIX, $editInfo->output->getTimestamp() );
 274                 if ( ( time() - $time ) <= 3 ) {
 275                         wfDebugLog( 'StashEdit', "Timestamp-based cache hit for key '$key'." );
 276                         return $editInfo; // assume nothing changed
 277                 }
 278
 279                 $dbr = wfGetDB( DB_SLAVE );
 280
 281                 $templates = array(); // conditions to find changes/creations
 282                 $templateUses = 0; // expected existing templates
 283                 foreach ( $editInfo->output->getTemplateIds() as $ns => $stuff ) {
 284                         foreach ( $stuff as $dbkey => $revId ) {
 285                                 $templates[(string)$ns][$dbkey] = (int)$revId;
 286                                 ++$templateUses;
 287                         }
 288                 }
 289                 // Check that no templates used in the output changed...
 290                 if ( count( $templates ) ) {
 291                         $res = $dbr->select(
 292                                 'page',
 293                                 array( 'ns' => 'page_namespace', 'dbk' => 'page_title', 'page_latest' ),
 294                                 $dbr->makeWhereFrom2d( $templates, 'page_namespace', 'page_title' ),
 295                                 __METHOD__
 296                         );
 297                         $changed = false;
 298                         foreach ( $res as $row ) {
 299                                 $changed = $changed || ( $row->page_latest != $templates[$row->ns][$row->dbk] );
 300                         }
 301
 302                         if ( $changed || $res->numRows() != $templateUses ) {
 303                                 wfDebugLog( 'StashEdit', "Stale cache for key '$key'; template changed." );
 304                                 return false;
 305                         }
 306                 }
 307
 308                 $files = array(); // conditions to find changes/creations
 309                 foreach ( $editInfo->output->getFileSearchOptions() as $name => $options ) {
 310                         $files[$name] = (string)$options['sha1'];
 311                 }
 312                 // Check that no files used in the output changed...
 313                 if ( count( $files ) ) {
 314                         $res = $dbr->select(
 315                                 'image',
 316                                 array( 'name' => 'img_name', 'img_sha1' ),
 317                                 array( 'img_name' => array_keys( $files ) ),
 318                                 __METHOD__
 319                         );
 320                         $changed = false;
 321                         foreach ( $res as $row ) {
 322                                 $changed = $changed || ( $row->img_sha1 != $files[$row->name] );
 323                         }
 324
 325                         if ( $changed || $res->numRows() != count( $files ) ) {
 326                                 wfDebugLog( 'StashEdit', "Stale cache for key '$key'; file changed." );
 327                                 return false;
 328                         }
 329                 }
 330
 331                 wfDebugLog( 'StashEdit', "Cache hit for key '$key'." );
 332
 333                 return $editInfo;
 334         }
 335
 336         /**
 337          * Get the temporary prepared edit stash key for a user
 338          *
 339          * This key can be used for caching prepared edits provided:
 340          *   - a) The $user was used for PST options
 341          *   - b) The parser output was made from the PST using cannonical matching options
 342          *
 343          * @param Title $title
 344          * @param Content $content
 345          * @param User $user User to get parser options from
 346          * @return string
 347          */
 348         protected static function getStashKey( Title $title, Content $content, User $user ) {
 349                 $hash = sha1( implode( ':', array(
 350                         $content->getModel(),
 351                         $content->getDefaultFormat(),
 352                         sha1( $content->serialize( $content->getDefaultFormat() ) ),
 353                         $user->getId() ?: md5( $user->getName() ), // account for user parser options
 354                         $user->getId() ? $user->getDBTouched() : '-' // handle preference change races
 355                 ) ) );
 356
 357                 return wfMemcKey( 'prepared-edit', md5( $title->getPrefixedDBkey() ), $hash );
 358         }
 359
 360         /**
 361          * Build a value to store in memcached based on the PST content and parser output
 362          *
 363          * This makes a simple version of WikiPage::prepareContentForEdit() as stash info
 364          *
 365          * @param Content $pstContent
 366          * @param ParserOutput $parserOutput
 367          * @param string $timestamp TS_MW
 368          * @return array (stash info array, TTL in seconds) or (null, 0)
 369          */
 370         protected static function buildStashValue(
 371                 Content $pstContent, ParserOutput $parserOutput, $timestamp
 372         ) {
 373                 // If an item is renewed, mind the cache TTL determined by config and parser functions
 374                 $since = time() - wfTimestamp( TS_UNIX, $parserOutput->getTimestamp() );
 375                 $ttl = min( $parserOutput->getCacheExpiry() - $since, 5 * 60 );
 376
 377                 if ( $ttl > 0 && !$parserOutput->getFlag( 'vary-revision' ) ) {
 378                         // Only store what is actually needed
 379                         $stashInfo = (object)array(
 380                                 'pstContent' => $pstContent,
 381                                 'output'     => $parserOutput,
 382                                 'timestamp'  => $timestamp
 383                         );
 384                         return array( $stashInfo, $ttl );
 385                 }
 386
 387                 return array( null, 0 );
 388         }
 389
 390         public function getAllowedParams() {
 391                 return array(
 392                         'title' => array(
 393                                 ApiBase::PARAM_TYPE => 'string',
 394                                 ApiBase::PARAM_REQUIRED => true
 395                         ),
 396                         'section' => array(
 397                                 ApiBase::PARAM_TYPE => 'string',
 398                         ),
 399                         'sectiontitle' => array(
 400                                 ApiBase::PARAM_TYPE => 'string'
 401                         ),
 402                         'text' => array(
 403                                 ApiBase::PARAM_TYPE => 'text',
 404                                 ApiBase::PARAM_REQUIRED => true
 405                         ),
 406                         'contentmodel' => array(
 407                                 ApiBase::PARAM_TYPE => ContentHandler::getContentModels(),
 408                                 ApiBase::PARAM_REQUIRED => true
 409                         ),
 410                         'contentformat' => array(
 411                                 ApiBase::PARAM_TYPE => ContentHandler::getAllContentFormats(),
 412                                 ApiBase::PARAM_REQUIRED => true
 413                         ),
 414                         'baserevid' => array(
 415                                 ApiBase::PARAM_TYPE => 'integer',
 416                                 ApiBase::PARAM_REQUIRED => true
 417                         )
 418                 );
 419         }
 420
 421         function needsToken() {
 422                 return 'csrf';
 423         }
 424
 425         function mustBePosted() {
 426                 return true;
 427         }
 428
 429         function isInternal() {
 430                 return true;
 431         }
 432 }