<?php
/**
 * Changelog handling functions
 *
 * @license    GPL 2 (http://www.gnu.org/licenses/gpl.html)
 * @author     Andreas Gohr <andi@splitbrain.org>
 */

/**
 * parses a changelog line into it's components
 *
 * @author Ben Coburn <btcoburn@silicodon.net>
 */
function parseChangelogLine($line) {
  $tmp = explode("\t", $line);
    if ($tmp!==false && count($tmp)>1) {
      $info = array();
      $info['date']  = (int)$tmp[0]; // unix timestamp
      $info['ip']    = $tmp[1]; // IPv4 address (127.0.0.1)
      $info['type']  = $tmp[2]; // log line type
      $info['id']    = $tmp[3]; // page id
      $info['user']  = $tmp[4]; // user name
      $info['sum']   = $tmp[5]; // edit summary (or action reason)
      $info['extra'] = rtrim($tmp[6], "\n"); // extra data (varies by line type)
      return $info;
  } else { return false; }
}

/**
 * Add's an entry to the changelog and saves the metadata for the page
 *
 * @author Andreas Gohr <andi@splitbrain.org>
 * @author Esther Brunner <wikidesign@gmail.com>
 * @author Ben Coburn <btcoburn@silicodon.net>
 */
function addLogEntry($date, $id, $type='E', $summary='', $extra=''){
  global $conf, $INFO;

  $id = cleanid($id);
  $file = wikiFN($id);
  $created = @filectime($file);
  $minor = ($type==='e');
  $wasRemoved = ($type==='D');

  if(!$date) $date = time(); //use current time if none supplied
  $remote = $_SERVER['REMOTE_ADDR'];
  $user   = $_SERVER['REMOTE_USER'];

  $strip = array("\t", "\n");
  $logline = array(
    'date'  => $date,
    'ip'    => $remote,
    'type'  => str_replace($strip, '', $type),
    'id'    => $id,
    'user'  => $user,
    'sum'   => str_replace($strip, '', $summary),
    'extra' => str_replace($strip, '', $extra)
  );

  // update metadata
  if (!$wasRemoved) {
    $meta = array();
    if (!$INFO['exists']){ // newly created
      $meta['date']['created'] = $created;
      if ($user) $meta['creator'] = $INFO['userinfo']['name'];
    } elseif (!$minor) {   // non-minor modification
      $meta['date']['modified'] = $date;
      if ($user) $meta['contributor'][$user] = $INFO['userinfo']['name'];
    }
    $meta['last_change'] = $logline;
    p_set_metadata($id, $meta, true);
  }

  // add changelog lines
  $logline = implode("\t", $logline)."\n";
  io_saveFile(metaFN($id,'.changes'),$logline,true); //page changelog
  io_saveFile($conf['changelog'],$logline,true); //global changelog cache
}

/**
 * returns an array of recently changed files using the
 * changelog
 *
 * The following constants can be used to control which changes are
 * included. Add them together as needed.
 *
 * RECENTS_SKIP_DELETED   - don't include deleted pages
 * RECENTS_SKIP_MINORS    - don't include minor changes
 * RECENTS_SKIP_SUBSPACES - don't include subspaces
 *
 * @param int    $first   number of first entry returned (for paginating
 * @param int    $num     return $num entries
 * @param string $ns      restrict to given namespace
 * @param bool   $flags   see above
 *
 * @author Ben Coburn <btcoburn@silicodon.net>
 */
function getRecents($first,$num,$ns='',$flags=0){
  global $conf;
  $recent = array();
  $count  = 0;

  if(!$num)
    return $recent;

  // read all recent changes. (kept short)
  $lines = file($conf['changelog']);


  // handle lines
  for($i = count($lines)-1; $i >= 0; $i--){
    $rec = _handleRecent($lines[$i], $ns, $flags);
    if($rec !== false) {
      if(--$first >= 0) continue; // skip first entries
      $recent[] = $rec;
      $count++;
      // break when we have enough entries
      if($count >= $num){ break; }
    }
  }

  return $recent;
}

/**
 * Internal function used by getRecents
 *
 * don't call directly
 *
 * @see getRecents()
 * @author Andreas Gohr <andi@splitbrain.org>
 * @author Ben Coburn <btcoburn@silicodon.net>
 */
function _handleRecent($line,$ns,$flags){
  static $seen  = array();         //caches seen pages and skip them
  if(empty($line)) return false;   //skip empty lines

  // split the line into parts
  $recent = parseChangelogLine($line);
  if ($recent===false) { return false; }

  // skip seen ones
  if(isset($seen[$recent['id']])) return false;

  // skip minors
  if($recent['type']==='e' && ($flags & RECENTS_SKIP_MINORS)) return false;

  // remember in seen to skip additional sights
  $seen[$recent['id']] = 1;

  // check if it's a hidden page
  if(isHiddenPage($recent['id'])) return false;

  // filter namespace
  if (($ns) && (strpos($recent['id'],$ns.':') !== 0)) return false;

  // exclude subnamespaces
  if (($flags & RECENTS_SKIP_SUBSPACES) && (getNS($recent['id']) != $ns)) return false;

  // check ACL
  if (auth_quickaclcheck($recent['id']) < AUTH_READ) return false;

  // check existance
  if((!@file_exists(wikiFN($recent['id']))) && ($flags & RECENTS_SKIP_DELETED)) return false;

  return $recent;
}

/**
 * Get the changelog information for a specific page id
 * and revision (timestamp). Adjacent changelog lines
 * are optimistically parsed and cached to speed up
 * consecutive calls to getRevisionInfo. For large
 * changelog files, only the chunk containing the
 * requested changelog line is read.
 *
 * @author Ben Coburn <btcoburn@silicodon.net>
 */
function getRevisionInfo($id, $rev, $chunk_size=8192) {
  global $cache_revinfo;
  $cache =& $cache_revinfo;
  if (!isset($cache[$id])) { $cache[$id] = array(); }
  $rev = max($rev, 0);

  // check if it's already in the memory cache
  if (isset($cache[$id]) && isset($cache[$id][$rev])) {
    return $cache[$id][$rev];
  }

  $file = metaFN($id, '.changes');
  if (!@file_exists($file)) { return false; }
  if (filesize($file)<$chunk_size || $chunk_size==0) {
    // read whole file
    $lines = file($file);
    if ($lines===false) { return false; }
  } else {
    // read by chunk
    $fp = fopen($file, 'rb'); // "file pointer"
    if ($fp===false) { return false; }
    $head = 0;
    fseek($fp, 0, SEEK_END);
    $tail = ftell($fp);
    $finger = 0;
    $finger_rev = 0;

    // find chunk
    while ($tail-$head>$chunk_size) {
      $finger = $head+floor(($tail-$head)/2.0);
      fseek($fp, $finger);
      fgets($fp); // slip the finger forward to a new line
      $finger = ftell($fp);
      $tmp = fgets($fp); // then read at that location
      $tmp = parseChangelogLine($tmp);
      $finger_rev = $tmp['date'];
      if ($finger==$head || $finger==$tail) { break; }
      if ($finger_rev>$rev) {
        $tail = $finger;
      } else {
        $head = $finger;
      }
    }

    if ($tail-$head<1) {
      // cound not find chunk, assume requested rev is missing
      fclose($fp);
      return false;
    }

    // read chunk
    $chunk = '';
    $chunk_size = max($tail-$head, 0); // found chunk size
    $got = 0;
    fseek($fp, $head);
    while ($got<$chunk_size && !feof($fp)) {
      $tmp = fread($fp, max($chunk_size-$got, 0));
      if ($tmp===false) { break; } //error state
      $got += strlen($tmp);
      $chunk .= $tmp;
    }
    $lines = explode("\n", $chunk);
    array_pop($lines); // remove trailing newline
    fclose($fp);
  }

  // parse and cache changelog lines
  foreach ($lines as $value) {
    $tmp = parseChangelogLine($value);
    if ($tmp!==false) {
      $cache[$id][$tmp['date']] = $tmp;
    }
  }
  if (!isset($cache[$id][$rev])) { return false; }
  return $cache[$id][$rev];
}

/**
 * Return a list of page revisions numbers
 * Does not guarantee that the revision exists in the attic,
 * only that a line with the date exists in the changelog.
 * By default the current revision is skipped.
 *
 * id:    the page of interest
 * first: skip the first n changelog lines
 * num:   number of revisions to return
 *
 * The current revision is automatically skipped when the page exists.
 * See $INFO['meta']['last_change'] for the current revision.
 *
 * For efficiency, the log lines are parsed and cached for later
 * calls to getRevisionInfo. Large changelog files are read
 * backwards in chunks untill the requested number of changelog
 * lines are recieved.
 *
 * @author Ben Coburn <btcoburn@silicodon.net>
 */
function getRevisions($id, $first, $num, $chunk_size=8192) {
  global $cache_revinfo;
  $cache =& $cache_revinfo;
  if (!isset($cache[$id])) { $cache[$id] = array(); }

  $revs = array();
  $lines = array();
  $count  = 0;
  $file = metaFN($id, '.changes');
  $num = max($num, 0);
  $chunk_size = max($chunk_size, 0);
  if ($first<0) { $first = 0; }
  else if (@file_exists(wikiFN($id))) {
     // skip current revision if the page exists
    $first = max($first+1, 0);
  }

  if (!@file_exists($file)) { return $revs; }
  if (filesize($file)<$chunk_size || $chunk_size==0) {
    // read whole file
    $lines = file($file);
    if ($lines===false) { return $revs; }
  } else {
    // read chunks backwards
    $fp = fopen($file, 'rb'); // "file pointer"
    if ($fp===false) { return $revs; }
    fseek($fp, 0, SEEK_END);
    $tail = ftell($fp);

    // chunk backwards
    $finger = max($tail-$chunk_size, 0);
    while ($count<$num+$first) {
      fseek($fp, $finger);
      if ($finger>0) {
        fgets($fp); // slip the finger forward to a new line
        $finger = ftell($fp);
      }

      // read chunk
      if ($tail<=$finger) { break; }
      $chunk = '';
      $read_size = max($tail-$finger, 0); // found chunk size
      $got = 0;
      while ($got<$read_size && !feof($fp)) {
        $tmp = fread($fp, max($read_size-$got, 0));
        if ($tmp===false) { break; } //error state
        $got += strlen($tmp);
        $chunk .= $tmp;
      }
      $tmp = explode("\n", $chunk);
      array_pop($tmp); // remove trailing newline

      // combine with previous chunk
      $count += count($tmp);
      $lines = array_merge($tmp, $lines);

      // next chunk
      if ($finger==0) { break; } // already read all the lines
      else {
        $tail = $finger;
        $finger = max($tail-$chunk_size, 0);
      }
    }
    fclose($fp);
  }

  // skip parsing extra lines
  $num = max(min(count($lines)-$first, $num), 0);
  if      ($first>0 && $num>0)  { $lines = array_slice($lines, max(count($lines)-$first-$num, 0), $num); }
  else if ($first>0 && $num==0) { $lines = array_slice($lines, 0, max(count($lines)-$first, 0)); }
  else if ($first==0 && $num>0) { $lines = array_slice($lines, max(count($lines)-$num, 0)); }

  // handle lines in reverse order
  for ($i = count($lines)-1; $i >= 0; $i--) {
    $tmp = parseChangelogLine($lines[$i]);
    if ($tmp!==false) {
      $cache[$id][$tmp['date']] = $tmp;
      $revs[] = $tmp['date'];
    }
  }

  return $revs;
}