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   1  <?php
   2  
   3  namespace dokuwiki\ChangeLog;
   4  
   5  use dokuwiki\Logger;
   6  
   7  /**
   8   * ChangeLog Prototype; methods for handling changelog
   9   */
  10  abstract class ChangeLog
  11  {
  12      use ChangeLogTrait;
  13  
  14      /** @var string */
  15      protected $id;
  16      /** @var false|int */
  17      protected $currentRevision;
  18      /** @var array */
  19      protected $cache = [];
  20  
  21      /**
  22       * Constructor
  23       *
  24       * @param string $id page id
  25       * @param int $chunk_size maximum block size read from file
  26       */
  27      public function __construct($id, $chunk_size = 8192)
  28      {
  29          global $cache_revinfo;
  30  
  31          $this->cache =& $cache_revinfo;
  32          if (!isset($this->cache[$id])) {
  33              $this->cache[$id] = [];
  34          }
  35  
  36          $this->id = $id;
  37          $this->setChunkSize($chunk_size);
  38      }
  39  
  40      /**
  41       * Returns path to current page/media
  42       *
  43       * @param string|int $rev empty string or revision timestamp
  44       * @return string path to file
  45       */
  46      abstract protected function getFilename($rev = '');
  47  
  48      /**
  49       * Check whether given revision is the current page
  50       *
  51       * @param int $rev timestamp of current page
  52       * @return bool true if $rev is current revision, otherwise false
  53       */
  54      public function isCurrentRevision($rev)
  55      {
  56          return $rev == $this->currentRevision();
  57      }
  58  
  59      /**
  60       * Checks if the revision is last revision
  61       *
  62       * @param int $rev revision timestamp
  63       * @return bool true if $rev is last revision, otherwise false
  64       */
  65      public function isLastRevision($rev = null)
  66      {
  67          return $rev === $this->lastRevision();
  68      }
  69  
  70      /**
  71       * Return the current revision identifier
  72       *
  73       * The "current" revision means current version of the page or media file. It is either
  74       * identical with or newer than the "last" revision, that depends on whether the file
  75       * has modified, created or deleted outside of DokuWiki.
  76       * The value of identifier can be determined by timestamp as far as the file exists,
  77       * otherwise it must be assigned larger than any other revisions to keep them sortable.
  78       *
  79       * @return int|false revision timestamp
  80       */
  81      public function currentRevision()
  82      {
  83          if (!isset($this->currentRevision)) {
  84              // set ChangeLog::currentRevision property
  85              $this->getCurrentRevisionInfo();
  86          }
  87          return $this->currentRevision;
  88      }
  89  
  90      /**
  91       * Return the last revision identifier, date value of the last entry of the changelog
  92       *
  93       * @return int|false revision timestamp
  94       */
  95      public function lastRevision()
  96      {
  97          $revs = $this->getRevisions(-1, 1);
  98          return empty($revs) ? false : $revs[0];
  99      }
 100  
 101      /**
 102       * Save revision info to the cache pool
 103       *
 104       * @param array $info Revision info structure
 105       * @return bool
 106       */
 107      protected function cacheRevisionInfo($info)
 108      {
 109          if (!is_array($info)) return false;
 110          //$this->cache[$this->id][$info['date']] ??= $info; // since php 7.4
 111          $this->cache[$this->id][$info['date']] ??= $info;
 112          return true;
 113      }
 114  
 115      /**
 116       * Get the changelog information for a specific revision (timestamp)
 117       *
 118       * Adjacent changelog lines are optimistically parsed and cached to speed up
 119       * consecutive calls to getRevisionInfo. For large changelog files, only the chunk
 120       * containing the requested changelog line is read.
 121       *
 122       * @param int $rev revision timestamp
 123       * @param bool $retrieveCurrentRevInfo allows to skip for getting other revision info in the
 124       *                                     getCurrentRevisionInfo() where $currentRevision is not yet determined
 125       * @return bool|array false or array with entries:
 126       *      - date:  unix timestamp
 127       *      - ip:    IPv4 address (127.0.0.1)
 128       *      - type:  log line type
 129       *      - id:    page id
 130       *      - user:  user name
 131       *      - sum:   edit summary (or action reason)
 132       *      - extra: extra data (varies by line type)
 133       *      - sizechange: change of filesize
 134       *
 135       * @author Ben Coburn <btcoburn@silicodon.net>
 136       * @author Kate Arzamastseva <pshns@ukr.net>
 137       */
 138      public function getRevisionInfo($rev, $retrieveCurrentRevInfo = true)
 139      {
 140          $rev = max(0, $rev);
 141          if (!$rev) return false;
 142  
 143          //ensure the external edits are cached as well
 144          if (!isset($this->currentRevision) && $retrieveCurrentRevInfo) {
 145              $this->getCurrentRevisionInfo();
 146          }
 147  
 148          // check if it's already in the memory cache
 149          if (isset($this->cache[$this->id]) && isset($this->cache[$this->id][$rev])) {
 150              return $this->cache[$this->id][$rev];
 151          }
 152  
 153          //read lines from changelog
 154          [$fp, $lines] = $this->readloglines($rev);
 155          if ($fp) {
 156              fclose($fp);
 157          }
 158          if (empty($lines)) return false;
 159  
 160          // parse and cache changelog lines
 161          foreach ($lines as $value) {
 162              $info = static::parseLogLine($value);
 163              $this->cacheRevisionInfo($info);
 164          }
 165          if (!isset($this->cache[$this->id][$rev])) {
 166              return false;
 167          }
 168          return $this->cache[$this->id][$rev];
 169      }
 170  
 171      /**
 172       * Return a list of page revisions numbers
 173       *
 174       * Does not guarantee that the revision exists in the attic,
 175       * only that a line with the date exists in the changelog.
 176       * By default the current revision is skipped.
 177       *
 178       * The current revision is automatically skipped when the page exists.
 179       * See $INFO['meta']['last_change'] for the current revision.
 180       * A negative $first let read the current revision too.
 181       *
 182       * For efficiency, the log lines are parsed and cached for later
 183       * calls to getRevisionInfo. Large changelog files are read
 184       * backwards in chunks until the requested number of changelog
 185       * lines are received.
 186       *
 187       * @param int $first skip the first n changelog lines
 188       * @param int $num number of revisions to return
 189       * @return array with the revision timestamps
 190       *
 191       * @author Ben Coburn <btcoburn@silicodon.net>
 192       * @author Kate Arzamastseva <pshns@ukr.net>
 193       */
 194      public function getRevisions($first, $num)
 195      {
 196          $revs = [];
 197          $lines = [];
 198          $count = 0;
 199  
 200          $logfile = $this->getChangelogFilename();
 201          if (!file_exists($logfile)) return $revs;
 202  
 203          $num = max($num, 0);
 204          if ($num == 0) {
 205              return $revs;
 206          }
 207  
 208          if ($first < 0) {
 209              $first = 0;
 210          } else {
 211              $fileLastMod = $this->getFilename();
 212              if (file_exists($fileLastMod) && $this->isLastRevision(filemtime($fileLastMod))) {
 213                  // skip last revision if the page exists
 214                  $first = max($first + 1, 0);
 215              }
 216          }
 217  
 218          if (filesize($logfile) < $this->chunk_size || $this->chunk_size == 0) {
 219              // read whole file
 220              $lines = file($logfile);
 221              if ($lines === false) {
 222                  return $revs;
 223              }
 224          } else {
 225              // read chunks backwards
 226              $fp = fopen($logfile, 'rb'); // "file pointer"
 227              if ($fp === false) {
 228                  return $revs;
 229              }
 230              fseek($fp, 0, SEEK_END);
 231              $tail = ftell($fp);
 232  
 233              // chunk backwards
 234              $finger = max($tail - $this->chunk_size, 0);
 235              while ($count < $num + $first) {
 236                  $nl = $this->getNewlinepointer($fp, $finger);
 237  
 238                  // was the chunk big enough? if not, take another bite
 239                  if ($nl > 0 && $tail <= $nl) {
 240                      $finger = max($finger - $this->chunk_size, 0);
 241                      continue;
 242                  } else {
 243                      $finger = $nl;
 244                  }
 245  
 246                  // read chunk
 247                  $chunk = '';
 248                  $read_size = max($tail - $finger, 0); // found chunk size
 249                  $got = 0;
 250                  while ($got < $read_size && !feof($fp)) {
 251                      $tmp = @fread($fp, max(min($this->chunk_size, $read_size - $got), 0));
 252                      if ($tmp === false) {
 253                          break;
 254                      } //error state
 255                      $got += strlen($tmp);
 256                      $chunk .= $tmp;
 257                  }
 258                  $tmp = explode("\n", $chunk);
 259                  array_pop($tmp); // remove trailing newline
 260  
 261                  // combine with previous chunk
 262                  $count += count($tmp);
 263                  $lines = [...$tmp, ...$lines];
 264  
 265                  // next chunk
 266                  if ($finger == 0) {
 267                      break;
 268                  } else { // already read all the lines
 269                      $tail = $finger;
 270                      $finger = max($tail - $this->chunk_size, 0);
 271                  }
 272              }
 273              fclose($fp);
 274          }
 275  
 276          // skip parsing extra lines
 277          $num = max(min(count($lines) - $first, $num), 0);
 278          if ($first > 0 && $num > 0) {
 279              $lines = array_slice($lines, max(count($lines) - $first - $num, 0), $num);
 280          } elseif ($first > 0 && $num == 0) {
 281              $lines = array_slice($lines, 0, max(count($lines) - $first, 0));
 282          } elseif ($first == 0 && $num > 0) {
 283              $lines = array_slice($lines, max(count($lines) - $num, 0));
 284          }
 285  
 286          // handle lines in reverse order
 287          for ($i = count($lines) - 1; $i >= 0; $i--) {
 288              $info = static::parseLogLine($lines[$i]);
 289              if ($this->cacheRevisionInfo($info)) {
 290                  $revs[] = $info['date'];
 291              }
 292          }
 293  
 294          return $revs;
 295      }
 296  
 297      /**
 298       * Get the nth revision left or right-hand side  for a specific page id and revision (timestamp)
 299       *
 300       * For large changelog files, only the chunk containing the
 301       * reference revision $rev is read and sometimes a next chunk.
 302       *
 303       * Adjacent changelog lines are optimistically parsed and cached to speed up
 304       * consecutive calls to getRevisionInfo.
 305       *
 306       * @param int $rev revision timestamp used as start date
 307       *    (doesn't need to be exact revision number)
 308       * @param int $direction give position of returned revision with respect to $rev;
 309            positive=next, negative=prev
 310       * @return bool|int
 311       *      timestamp of the requested revision
 312       *      otherwise false
 313       */
 314      public function getRelativeRevision($rev, $direction)
 315      {
 316          $rev = max($rev, 0);
 317          $direction = (int)$direction;
 318  
 319          //no direction given or last rev, so no follow-up
 320          if (!$direction || ($direction > 0 && $this->isCurrentRevision($rev))) {
 321              return false;
 322          }
 323  
 324          //get lines from changelog
 325          [$fp, $lines, $head, $tail, $eof] = $this->readloglines($rev);
 326          if (empty($lines)) return false;
 327  
 328          // look for revisions later/earlier than $rev, when founded count till the wanted revision is reached
 329          // also parse and cache changelog lines for getRevisionInfo().
 330          $revCounter = 0;
 331          $relativeRev = false;
 332          $checkOtherChunk = true; //always runs once
 333          while (!$relativeRev && $checkOtherChunk) {
 334              $info = [];
 335              //parse in normal or reverse order
 336              $count = count($lines);
 337              if ($direction > 0) {
 338                  $start = 0;
 339                  $step = 1;
 340              } else {
 341                  $start = $count - 1;
 342                  $step = -1;
 343              }
 344              for ($i = $start; $i >= 0 && $i < $count; $i += $step) {
 345                  $info = static::parseLogLine($lines[$i]);
 346                  if ($this->cacheRevisionInfo($info)) {
 347                      //look for revs older/earlier then reference $rev and select $direction-th one
 348                      if (($direction > 0 && $info['date'] > $rev) || ($direction < 0 && $info['date'] < $rev)) {
 349                          $revCounter++;
 350                          if ($revCounter == abs($direction)) {
 351                              $relativeRev = $info['date'];
 352                          }
 353                      }
 354                  }
 355              }
 356  
 357              //true when $rev is found, but not the wanted follow-up.
 358              $checkOtherChunk = $fp
 359                  && ($info['date'] == $rev || ($revCounter > 0 && !$relativeRev))
 360                  && (!($tail == $eof && $direction > 0) && !($head == 0 && $direction < 0));
 361  
 362              if ($checkOtherChunk) {
 363                  [$lines, $head, $tail] = $this->readAdjacentChunk($fp, $head, $tail, $direction);
 364  
 365                  if (empty($lines)) break;
 366              }
 367          }
 368          if ($fp) {
 369              fclose($fp);
 370          }
 371  
 372          return $relativeRev;
 373      }
 374  
 375      /**
 376       * Returns revisions around rev1 and rev2
 377       * When available it returns $max entries for each revision
 378       *
 379       * @param int $rev1 oldest revision timestamp
 380       * @param int $rev2 newest revision timestamp (0 looks up last revision)
 381       * @param int $max maximum number of revisions returned
 382       * @return array with two arrays with revisions surrounding rev1 respectively rev2
 383       */
 384      public function getRevisionsAround($rev1, $rev2, $max = 50)
 385      {
 386          $max = (int) (abs($max) / 2) * 2 + 1;
 387          $rev1 = max($rev1, 0);
 388          $rev2 = max($rev2, 0);
 389  
 390          if ($rev2) {
 391              if ($rev2 < $rev1) {
 392                  $rev = $rev2;
 393                  $rev2 = $rev1;
 394                  $rev1 = $rev;
 395              }
 396          } else {
 397              //empty right side means a removed page. Look up last revision.
 398              $rev2 = $this->currentRevision();
 399          }
 400          //collect revisions around rev2
 401          [$revs2, $allRevs, $fp, $lines, $head, $tail] = $this->retrieveRevisionsAround($rev2, $max);
 402  
 403          if (empty($revs2)) return [[], []];
 404  
 405          //collect revisions around rev1
 406          $index = array_search($rev1, $allRevs);
 407          if ($index === false) {
 408              //no overlapping revisions
 409              [$revs1, , , , , ] = $this->retrieveRevisionsAround($rev1, $max);
 410              if (empty($revs1)) $revs1 = [];
 411          } else {
 412              //revisions overlaps, reuse revisions around rev2
 413              $lastRev = array_pop($allRevs); //keep last entry that could be external edit
 414              $revs1 = $allRevs;
 415              while ($head > 0) {
 416                  for ($i = count($lines) - 1; $i >= 0; $i--) {
 417                      $info = static::parseLogLine($lines[$i]);
 418                      if ($this->cacheRevisionInfo($info)) {
 419                          $revs1[] = $info['date'];
 420                          $index++;
 421  
 422                          if ($index > (int) ($max / 2)) break 2;
 423                      }
 424                  }
 425  
 426                  [$lines, $head, $tail] = $this->readAdjacentChunk($fp, $head, $tail, -1);
 427              }
 428              sort($revs1);
 429              $revs1[] = $lastRev; //push back last entry
 430  
 431              //return wanted selection
 432              $revs1 = array_slice($revs1, max($index - (int) ($max / 2), 0), $max);
 433          }
 434  
 435          return [array_reverse($revs1), array_reverse($revs2)];
 436      }
 437  
 438      /**
 439       * Return an existing revision for a specific date which is
 440       * the current one or younger or equal then the date
 441       *
 442       * @param number $date_at timestamp
 443       * @return string revision ('' for current)
 444       */
 445      public function getLastRevisionAt($date_at)
 446      {
 447          $fileLastMod = $this->getFilename();
 448          //requested date_at(timestamp) younger or equal then modified_time($this->id) => load current
 449          if (file_exists($fileLastMod) && $date_at >= @filemtime($fileLastMod)) {
 450              return '';
 451          } elseif ($rev = $this->getRelativeRevision($date_at + 1, -1)) {
 452              //+1 to get also the requested date revision
 453              return $rev;
 454          } else {
 455              return false;
 456          }
 457      }
 458  
 459      /**
 460       * Collect the $max revisions near to the timestamp $rev
 461       *
 462       * Ideally, half of retrieved timestamps are older than $rev, another half are newer.
 463       * The returned array $requestedRevs may not contain the reference timestamp $rev
 464       * when it does not match any revision value recorded in changelog.
 465       *
 466       * @param int $rev revision timestamp
 467       * @param int $max maximum number of revisions to be returned
 468       * @return bool|array
 469       *     return array with entries:
 470       *       - $requestedRevs: array of with $max revision timestamps
 471       *       - $revs: all parsed revision timestamps
 472       *       - $fp: file pointer only defined for chuck reading, needs closing.
 473       *       - $lines: non-parsed changelog lines before the parsed revisions
 474       *       - $head: position of first read changelog line
 475       *       - $lastTail: position of end of last read changelog line
 476       *     otherwise false
 477       */
 478      protected function retrieveRevisionsAround($rev, $max)
 479      {
 480          $revs = [];
 481          $afterCount = 0;
 482          $beforeCount = 0;
 483  
 484          //get lines from changelog
 485          [$fp, $lines, $startHead, $startTail, $eof] = $this->readloglines($rev);
 486          if (empty($lines)) return false;
 487  
 488          //parse changelog lines in chunk, and read forward more chunks until $max/2 is reached
 489          $head = $startHead;
 490          $tail = $startTail;
 491          while (count($lines) > 0) {
 492              foreach ($lines as $line) {
 493                  $info = static::parseLogLine($line);
 494                  if ($this->cacheRevisionInfo($info)) {
 495                      $revs[] = $info['date'];
 496                      if ($info['date'] >= $rev) {
 497                          //count revs after reference $rev
 498                          $afterCount++;
 499                          if ($afterCount == 1) $beforeCount = count($revs);
 500                      }
 501                      //enough revs after reference $rev?
 502                      if ($afterCount > (int) ($max / 2)) break 2;
 503                  }
 504              }
 505              //retrieve next chunk
 506              [$lines, $head, $tail] = $this->readAdjacentChunk($fp, $head, $tail, 1);
 507          }
 508          $lastTail = $tail;
 509  
 510          // add a possible revision of external edit, create or deletion
 511          if (
 512              $lastTail == $eof && $afterCount <= (int) ($max / 2) &&
 513              count($revs) && !$this->isCurrentRevision($revs[count($revs) - 1])
 514          ) {
 515              $revs[] = $this->currentRevision;
 516              $afterCount++;
 517          }
 518  
 519          if ($afterCount == 0) {
 520              //given timestamp $rev is newer than the most recent line in chunk
 521              return false; //FIXME: or proceed to collect older revisions?
 522          }
 523  
 524          //read more chunks backward until $max/2 is reached and total number of revs is equal to $max
 525          $lines = [];
 526          $i = 0;
 527          $head = $startHead;
 528          $tail = $startTail;
 529          while ($head > 0) {
 530              [$lines, $head, $tail] = $this->readAdjacentChunk($fp, $head, $tail, -1);
 531  
 532              for ($i = count($lines) - 1; $i >= 0; $i--) {
 533                  $info = static::parseLogLine($lines[$i]);
 534                  if ($this->cacheRevisionInfo($info)) {
 535                      $revs[] = $info['date'];
 536                      $beforeCount++;
 537                      //enough revs before reference $rev?
 538                      if ($beforeCount > max((int) ($max / 2), $max - $afterCount)) break 2;
 539                  }
 540              }
 541          }
 542          //keep only non-parsed lines
 543          $lines = array_slice($lines, 0, $i);
 544  
 545          sort($revs);
 546  
 547          //trunk desired selection
 548          $requestedRevs = array_slice($revs, -$max, $max);
 549  
 550          return [$requestedRevs, $revs, $fp, $lines, $head, $lastTail];
 551      }
 552  
 553      /**
 554       * Get the current revision information, considering external edit, create or deletion
 555       *
 556       * When the file has not modified since its last revision, the information of the last
 557       * change that had already recorded in the changelog is returned as current change info.
 558       * Otherwise, the change information since the last revision caused outside DokuWiki
 559       * should be returned, which is referred as "external revision".
 560       *
 561       * The change date of the file can be determined by timestamp as far as the file exists,
 562       * however this is not possible when the file has already deleted outside of DokuWiki.
 563       * In such case we assign 1 sec before current time() for the external deletion.
 564       * As a result, the value of current revision identifier may change each time because:
 565       *   1) the file has again modified outside of DokuWiki, or
 566       *   2) the value is essentially volatile for deleted but once existed files.
 567       *
 568       * @return bool|array false when page had never existed or array with entries:
 569       *      - date:  revision identifier (timestamp or last revision +1)
 570       *      - ip:    IPv4 address (127.0.0.1)
 571       *      - type:  log line type
 572       *      - id:    id of page or media
 573       *      - user:  user name
 574       *      - sum:   edit summary (or action reason)
 575       *      - extra: extra data (varies by line type)
 576       *      - sizechange: change of filesize
 577       *      - timestamp: unix timestamp or false (key set only for external edit occurred)
 578       *
 579       * @author  Satoshi Sahara <sahara.satoshi@gmail.com>
 580       */
 581      public function getCurrentRevisionInfo()
 582      {
 583          global $lang;
 584  
 585          if (isset($this->currentRevision)) return $this->getRevisionInfo($this->currentRevision);
 586  
 587          // get revision id from the item file timestamp and changelog
 588          $fileLastMod = $this->getFilename();
 589          $fileRev = @filemtime($fileLastMod); // false when the file not exist
 590          $lastRev = $this->lastRevision();    // false when no changelog
 591  
 592          if (!$fileRev && !$lastRev) {                // has never existed
 593              $this->currentRevision = false;
 594              return false;
 595          } elseif ($fileRev === $lastRev) {           // not external edit
 596              $this->currentRevision = $lastRev;
 597              return $this->getRevisionInfo($lastRev);
 598          }
 599  
 600          if (!$fileRev && $lastRev) {                 // item file does not exist
 601              // check consistency against changelog
 602              $revInfo = $this->getRevisionInfo($lastRev, false);
 603              if ($revInfo['type'] == DOKU_CHANGE_TYPE_DELETE) {
 604                  $this->currentRevision = $lastRev;
 605                  return $revInfo;
 606              }
 607  
 608              // externally deleted, set revision date as late as possible
 609              $revInfo = [
 610                  'date' => max($lastRev + 1, time() - 1), // 1 sec before now or new page save
 611                  'ip'   => '127.0.0.1',
 612                  'type' => DOKU_CHANGE_TYPE_DELETE,
 613                  'id'   => $this->id,
 614                  'user' => '',
 615                  'sum'  => $lang['deleted'] . ' - ' . $lang['external_edit'] . ' (' . $lang['unknowndate'] . ')',
 616                  'extra' => '',
 617                  'sizechange' => -io_getSizeFile($this->getFilename($lastRev)),
 618                  'timestamp' => false,
 619              ];
 620          } else {                                     // item file exists, with timestamp $fileRev
 621              // here, file timestamp $fileRev is different with last revision timestamp $lastRev in changelog
 622              $isJustCreated = $lastRev === false || (
 623                      $fileRev > $lastRev &&
 624                      $this->getRevisionInfo($lastRev, false)['type'] == DOKU_CHANGE_TYPE_DELETE
 625              );
 626              $filesize_new = filesize($this->getFilename());
 627              $filesize_old = $isJustCreated ? 0 : io_getSizeFile($this->getFilename($lastRev));
 628              $sizechange = $filesize_new - $filesize_old;
 629  
 630              if ($isJustCreated) {
 631                  $timestamp = $fileRev;
 632                  $sum = $lang['created'] . ' - ' . $lang['external_edit'];
 633              } elseif ($fileRev > $lastRev) {
 634                  $timestamp = $fileRev;
 635                  $sum = $lang['external_edit'];
 636              } else {
 637                  // $fileRev is older than $lastRev, that is erroneous/incorrect occurrence.
 638                  $msg = "Warning: current file modification time is older than last revision date";
 639                  $details = 'File revision: ' . $fileRev . ' ' . dformat($fileRev, "%Y-%m-%d %H:%M:%S") . "\n"
 640                            . 'Last revision: ' . $lastRev . ' ' . dformat($lastRev, "%Y-%m-%d %H:%M:%S");
 641                  Logger::error($msg, $details, $this->getFilename());
 642                  $timestamp = false;
 643                  $sum = $lang['external_edit'] . ' (' . $lang['unknowndate'] . ')';
 644              }
 645  
 646              // externally created or edited
 647              $revInfo = [
 648                  'date' => $timestamp ?: $lastRev + 1,
 649                  'ip'   => '127.0.0.1',
 650                  'type' => $isJustCreated ? DOKU_CHANGE_TYPE_CREATE : DOKU_CHANGE_TYPE_EDIT,
 651                  'id'   => $this->id,
 652                  'user' => '',
 653                  'sum'  => $sum,
 654                  'extra' => '',
 655                  'sizechange' => $sizechange,
 656                  'timestamp' => $timestamp,
 657              ];
 658          }
 659  
 660          // cache current revision information of external edition
 661          $this->currentRevision = $revInfo['date'];
 662          $this->cache[$this->id][$this->currentRevision] = $revInfo;
 663          return $this->getRevisionInfo($this->currentRevision);
 664      }
 665  
 666      /**
 667       * Mechanism to trace no-actual external current revision
 668       * @param int $rev
 669       */
 670      public function traceCurrentRevision($rev)
 671      {
 672          if ($rev > $this->lastRevision()) {
 673              $rev = $this->currentRevision();
 674          }
 675          return $rev;
 676      }
 677  }