<?php
/**
 * EGroupware API: VFS - stream wrapper
 *
 * @link http://www.egroupware.org
 * @license http://opensource.org/licenses/gpl-license.php GPL - GNU General Public License
 * @package api
 * @subpackage vfs
 * @author Ralf Becker <RalfBecker-AT-outdoor-training.de>
 * @copyright (c) 2008-20 by Ralf Becker <RalfBecker-AT-outdoor-training.de>
 */

namespace EGroupware\Api\Vfs;

use EGroupware\Api\Vfs;
use EGroupware\Api;

/**
 * VFS - stream wrapper
 *
 * The new vfs stream wrapper uses a kind of fstab to mount different filesystems / stream wrapper types
 * together for eGW's virtual file system.
 *
 * @link http://www.php.net/manual/en/function.stream-wrapper-register.php
 */
class StreamWrapper extends Base implements StreamWrapperIface
{
	use UserContextTrait {
		check_access as parent_check_access;
	}

	const PREFIX = 'vfs://default';

	/**
	 * Should unreadable entries in a not writable directory be hidden, default yes
	 */
	const HIDE_UNREADABLES = true;

	/**
	 * Maximum depth of symlinks, if exceeded url_stat will return false
	 *
	 * Used to prevent infinit recursion by circular links
	 */
	const MAX_SYMLINK_DEPTH = 10;

	/**
	 * stream / ressouce this class is opened for by stream_open
	 *
	 * @var resource
	 */
	private $opened_stream;
	/**
	 * Mode of opened stream, eg. "r" or "w"
	 *
	 * @var string
	 */
	private $opened_stream_mode;
	/**
	 * Path of opened stream
	 *
	 * @var string
	 */
	private $opened_stream_path;
	/**
	 * URL of opened stream
	 *
	 * @var string
	 */
	private $opened_stream_url;
	/**
	 * Opened stream is a new file, false for existing files
	 *
	 * @var boolean
	 */
	private $opened_stream_is_new;
	/**
	 * directory-resource this class is opened for by dir_open
	 *
	 * @var resource
	 */
	private $opened_dir;
	/**
	 * URL of the opened dir, used to build the complete URL of files in the dir
	 *
	 * @var string
	 */
	private $opened_dir_url;

	/**
	 * Options for the opened directory
	 * (backup, etc.)
	 */
	protected $dir_url_params = array();

	/**
	 * Flag if opened dir is writable, in which case we return un-readable entries too
	 *
	 * @var boolean
	 */
	private $opened_dir_writable;
	/**
	 * Extra dirs from our fstab in the current opened dir
	 *
	 * @var array
	 */
	private $extra_dirs;
	/**
	 * Pointer in the extra dirs
	 *
	 * @var int
	 */
	private $extra_dir_ptr;

	/**
	 * The stream_wrapper interface checks is_{readable|writable|executable} against the webservers uid,
	 * which is wrong in case of our vfs, as we use the current users id and memberships
	 *
	 * @param string $path path
	 * @param int $check mode to check: one or more or'ed together of: 4 = Vfs::READABLE,
	 * 	2 = Vfs::WRITABLE, 1 = Vfs::EXECUTABLE
	 * @param array|boolean $stat =null stat array or false, to not query it again
	 * @return boolean
	 */
	function check_access($path, $check, $stat=null)
	{
		$ret = self::_call_on_backend('check_access', [$path, $check, $stat], "null", 0, true);
		if (!isset($ret))
		{
			$ret = $this->parent_check_access($path, $check, $stat);
		}
		return $ret;
	}

	/**
	 * Resolve the given path according to our fstab AND symlinks
	 *
	 * @param string $_path
	 * @param boolean $file_exists =true true if file needs to exists, false if not
	 * @param boolean $resolve_last_symlink =true
	 * @param array|boolean &$stat=null on return: stat of existing file or false for non-existing files
	 * @return string|boolean false if the url cant be resolved, should not happen if fstab has a root entry
	 */
	function resolve_url_symlinks($_path,$file_exists=true,$resolve_last_symlink=true,&$stat=null)
	{
		$path = self::get_path($_path);

		if (!($stat = $this->url_stat($path,$resolve_last_symlink?0:STREAM_URL_STAT_LINK)) && !$file_exists)
		{
			$url = null;
			$stat = self::check_symlink_components($path,0,$url);
			if (self::LOG_LEVEL > 1) $log = " (check_symlink_components('$path',0,'$url') = $stat)";
		}
		else
		{
			$url = $stat['url'];
		}
		// if the url resolves to a symlink to the vfs, resolve this vfs:// url direct
		if ($url && Vfs::parse_url($url,PHP_URL_SCHEME) == self::SCHEME)
		{
			$user = Vfs::parse_url($url,PHP_URL_USER);
			$url = self::resolve_url(Vfs::parse_url($url,PHP_URL_PATH));
			if (!empty($user) && empty(parse_url($url, PHP_URL_USER)))
			{
				$url = str_replace('://', '://'.$user.'@', $url);
			}
		}
		if (self::LOG_LEVEL > 1) error_log(__METHOD__."($path,file_exists=$file_exists,resolve_last_symlink=$resolve_last_symlink) = '$url'$log");
		return $url;
	}

	/**
	 * This method is called immediately after your stream object is created.
	 *
	 * @param string $path URL that was passed to fopen() and that this object is expected to retrieve
	 * @param string $mode mode used to open the file, as detailed for fopen()
	 * @param int $options additional flags set by the streams API (or'ed together):
	 * - STREAM_USE_PATH      If path is relative, search for the resource using the include_path.
	 * - STREAM_REPORT_ERRORS If this flag is set, you are responsible for raising errors using trigger_error() during opening of the stream.
	 *                        If this flag is not set, you should not raise any errors.
	 * @param string $opened_path full path of the file/resource, if the open was successfull and STREAM_USE_PATH was set
	 * @return boolean true if the ressource was opened successful, otherwise false
	 */
	function stream_open ( $path, $mode, $options, &$opened_path )
	{
		unset($options,$opened_path);	// not used but required by function signature
		$this->opened_stream = null;

		$stat = null;
		if (!($url = $this->resolve_url_symlinks($path,$mode[0]=='r',true,$stat)))
		{
			return false;
		}
		if (str_replace('b', '', $mode) != 'r' && self::url_is_readonly($url))
		{
			return false;
		}
		$this->check_set_context($url);

		if (!($this->opened_stream = $this->context ?
			fopen($url, $mode, false, $this->context) : fopen($url, $mode, false)))
		{
			return false;
		}
		$this->opened_stream_mode = $mode;
		$this->opened_stream_path = $path[0] == '/' ? $path : Vfs::parse_url($path, PHP_URL_PATH);
		$this->opened_stream_url = $url;
		$this->opened_stream_is_new = !$stat;

		// are we requested to treat the opened file as new file (only for files opened NOT for reading)
		if ($mode[0] != 'r' && !$this->opened_stream_is_new && $this->context &&
			($opts = stream_context_get_options($this->context)) &&
			!empty($opts['options'][self::SCHEME]['treat_as_new']))
		{
			$this->opened_stream_is_new = true;
			//error_log(__METHOD__."($path,$mode,...) stat=$stat, context=".array2string($opts)." --> ".array2string($this->opened_stream_is_new));
		}
		return true;
	}

	/**
	 * This method is called when the stream is closed, using fclose().
	 *
	 * You must release any resources that were locked or allocated by the stream.
	 *
	 * VFS calls either "vfs_read", "vfs_added" or "vfs_modified" hook
	 */
	function stream_close ( )
	{
		$ret = fclose($this->opened_stream);
		// clear PHP's stat cache, it contains wrong size of just closed file,
		// causing eg. notifications to be ignored, because of previous size 0, when using WebDAV
		clearstatcache(false);

		if (!class_exists('setup_process', false))
		{
			Api\Hooks::process(array(
				'location' => str_replace('b','',$this->opened_stream_mode) == 'r' ? 'vfs_read' :
					($this->opened_stream_is_new ? 'vfs_added' : 'vfs_modified'),
				'path' => $this->opened_stream_path,
				'mode' => $this->opened_stream_mode,
				'url'  => $this->opened_stream_url,
			),'',true);
		}
		$this->opened_stream = $this->opened_stream_mode = $this->opened_stream_path = $this->opened_stream_url = $this->opened_stream_is_new = null;

		return $ret;
	}

	/**
	 * This method is called in response to fread() and fgets() calls on the stream.
	 *
	 * You must return up-to count bytes of data from the current read/write position as a string.
	 * If there are less than count bytes available, return as many as are available.
	 * If no more data is available, return either FALSE or an empty string.
	 * You must also update the read/write position of the stream by the number of bytes that were successfully read.
	 *
	 * @param int $count
	 * @return string/false up to count bytes read or false on EOF
	 */
	function stream_read ( $count )
	{
		return fread($this->opened_stream,$count);
	}

	/**
	 * This method is called in response to fwrite() calls on the stream.
	 *
	 * You should store data into the underlying storage used by your stream.
	 * If there is not enough room, try to store as many bytes as possible.
	 * You should return the number of bytes that were successfully stored in the stream, or 0 if none could be stored.
	 * You must also update the read/write position of the stream by the number of bytes that were successfully written.
	 *
	 * @param string $data
	 * @return integer
	 */
	function stream_write ( $data )
	{
		return fwrite($this->opened_stream,$data);
	}

 	/**
 	 * This method is called in response to feof() calls on the stream.
 	 *
 	 * Important: PHP 5.0 introduced a bug that wasn't fixed until 5.1: the return value has to be the oposite!
 	 *
 	 * if(version_compare(PHP_VERSION,'5.0','>=') && version_compare(PHP_VERSION,'5.1','<'))
  	 * {
 	 * 		$eof = !$eof;
 	 * }
  	 *
 	 * @return boolean true if the read/write position is at the end of the stream and no more data availible, false otherwise
 	 */
	function stream_eof ( )
	{
		return feof($this->opened_stream);
	}

	/**
	 * This method is called in response to ftell() calls on the stream.
	 *
	 * @return integer current read/write position of the stream
	 */
 	function stream_tell ( )
 	{
 		return ftell($this->opened_stream);
 	}

 	/**
 	 * This method is called in response to fseek() calls on the stream.
 	 *
 	 * You should update the read/write position of the stream according to offset and whence.
 	 * See fseek() for more information about these parameters.
 	 *
 	 * @param integer $offset
 	 * @param integer $whence	SEEK_SET - 0 - Set position equal to offset bytes
 	 * 							SEEK_CUR - 1 - Set position to current location plus offset.
 	 * 							SEEK_END - 2 - Set position to end-of-file plus offset. (To move to a position before the end-of-file, you need to pass a negative value in offset.)
 	 * @return boolean TRUE if the position was updated, FALSE otherwise.
 	 */
	function stream_seek ( $offset, $whence )
	{
		return !fseek($this->opened_stream,$offset,$whence);	// fseek returns 0 on success and -1 on failure
	}

	/**
	 * This method is called in response to fflush() calls on the stream.
	 *
	 * If you have cached data in your stream but not yet stored it into the underlying storage, you should do so now.
	 *
	 * @return boolean TRUE if the cached data was successfully stored (or if there was no data to store), or FALSE if the data could not be stored.
	 */
	function stream_flush ( )
	{
		return fflush($this->opened_stream);
	}

	/**
	 * This method is called in response to fstat() calls on the stream.
	 *
	 * If you plan to use your wrapper in a require_once you need to define stream_stat().
	 * If you plan to allow any other tests like is_file()/is_dir(), you have to define url_stat().
	 * stream_stat() must define the size of the file, or it will never be included.
	 * url_stat() must define mode, or is_file()/is_dir()/is_executable(), and any of those functions affected by clearstatcache() simply won't work.
	 * It's not documented, but directories must be a mode like 040777 (octal), and files a mode like 0100666.
	 * If you wish the file to be executable, use 7s instead of 6s.
	 * The last 3 digits are exactly the same thing as what you pass to chmod.
	 * 040000 defines a directory, and 0100000 defines a file.
	 *
	 * @return array containing the same values as appropriate for the stream.
	 */
	function stream_stat ( )
	{
		return fstat($this->opened_stream);
	}

	/**
	 * StreamWrapper method (PHP 5.4+) for touch, chmod, chown and chgrp
	 *
	 * @param string $path
	 * @param int $option STREAM_META_(TOUCH|ACCESS|((OWNER|GROUP)(_NAME)?))
	 * @param array|int|string $value
	 * - STREAM_META_TOUCH array($time, $atime)
	 * - STREAM_META_ACCESS int
	 * - STREAM_(OWNER|GROUP) int
	 * - STREAM_(OWNER|GROUP)_NAME string
	 * @return boolean true on success, false on failure
	 */
	function stream_metadata($path, $option, $value)
	{
		if (!($url = $this->resolve_url_symlinks($path, $option != STREAM_META_TOUCH, false)))	// true,false file need to exist, but do not resolve last component
		{
			return false;
		}
		if (self::url_is_readonly($url))
		{
			return false;
		}
		if (self::LOG_LEVEL > 1) error_log(__METHOD__."('$path', $option, ".array2string($value).") url=$url");

		switch($option)
		{
			case STREAM_META_TOUCH:
				return touch($url, $value[0]);	// atime is not supported

			case STREAM_META_ACCESS:
				return chmod($url, $value);

			case STREAM_META_OWNER_NAME:
				if (($value = $GLOBALS['egw']->accounts->name2id($value, 'account_lid', 'u')) === false)
					return false;
				// fall through
			case STREAM_META_OWNER:
				return chown($url, $value);

			case STREAM_META_GROUP_NAME:
				if (($value = $GLOBALS['egw']->accounts->name2id($value, 'account_lid', 'g')) === false)
					return false;
				// fall through
			case STREAM_META_GROUP:
				return chgrp($url, $value);
		}
		return false;
	}

	/**
	 * This method is called in response to unlink() calls on URL paths associated with the wrapper.
	 *
	 * It should attempt to delete the item specified by path.
	 * In order for the appropriate error message to be returned, do not define this method if your wrapper does not support unlinking!
	 *
	 * @param string $path
	 * @return boolean TRUE on success or FALSE on failure
	 */
	function unlink ( $path )
	{
		if (!($url = $this->resolve_url_symlinks($path,true,false)))	// true,false file need to exist, but do not resolve last component
		{
			return false;
		}
		if (self::url_is_readonly($url))
		{
			return false;
		}
		// set user-context
		$this->check_set_context($url);
		$stat = $this->url_stat($path, STREAM_URL_STAT_LINK);

		self::symlinkCache_remove($path);
		$ok = unlink($url, $this->context);

		// call "vfs_unlink" hook only after successful unlink, with data from (not longer possible) stat call
		if ($ok && !class_exists('setup_process', false))
		{
			Api\Hooks::process(array(
				'location' => 'vfs_unlink',
				'path' => $path[0] == '/' ? $path : Vfs::parse_url($path, PHP_URL_PATH),
				'url'  => $url,
				'stat' => $stat,
			),'',true);
		}
		return $ok;
	}

	/**
	 * This method is called in response to rename() calls on URL paths associated with the wrapper.
	 *
	 * It should attempt to rename the item specified by path_from to the specification given by path_to.
	 * In order for the appropriate error message to be returned, do not define this method if your wrapper does not support renaming.
	 *
	 * The regular filesystem stream-wrapper returns an error, if $url_from and $url_to are not either both files or both dirs!
	 *
	 * @param string $path_from
	 * @param string $path_to
	 * @return boolean TRUE on success or FALSE on failure
	 * @throws Exception\ProtectedDirectory if trying to delete a protected directory, see Vfs::isProtected()
	 */
	function rename ( $path_from, $path_to )
	{
		if (Vfs::isProtectedDir($path_from))
		{
			throw new Exception\ProtectedDirectory("Renaming protected directory '$path_from' rejected!");
		}
		if (!($url_from = $this->resolve_url_symlinks($path_from,true,false)) ||
			!($url_to = $this->resolve_url_symlinks($path_to,false)))
		{
			return false;
		}
		// refuse to modify readonly target (eg. readonly share)
		if (self::url_is_readonly($url_to))
		{
			return false;
		}
		// set user-context
		$this->check_set_context($url_from);

		// if file is moved from one filesystem / wrapper to an other --> copy it (rename fails cross wrappers)
		if (Vfs::parse_url($url_from,PHP_URL_SCHEME) == Vfs::parse_url($url_to,PHP_URL_SCHEME))
		{
			self::symlinkCache_remove($path_from);
			$ret = rename($url_from, $url_to, $this->context);
		}
		elseif (($from = fopen($url_from,'r', false, $this->context)) && ($to = fopen($url_to,'w')))
		{
			$ret = stream_copy_to_stream($from,$to) !== false;
			fclose($from);
			fclose($to);
			if ($ret) $this->unlink($path_from);
		}
		else
		{
			$ret = false;
		}
		if (self::LOG_LEVEL > 1 || self::LOG_LEVEL && !$ret)
		{
			error_log(__METHOD__."('$path_from','$path_to') url_from='$url_from', url_to='$url_to' returning ".array2string($ret));
		}
		// call "vfs_rename" hook
		if ($ret && !class_exists('setup_process', false))
		{
			Api\Hooks::process(array(
				'location' => 'vfs_rename',
				'from' => $path_from[0] == '/' ? $path_from : Vfs::parse_url($path_from, PHP_URL_PATH),
				'to' => $path_to[0] == '/' ? $path_to : Vfs::parse_url($path_to, PHP_URL_PATH),
				'url_from' => $url_from,
				'url_to' => $url_to,
			),'',true);
		}
		return $ret;
	}

	/**
	 * This method is called in response to mkdir() calls on URL paths associated with the wrapper.
	 *
	 * Not all wrappers, eg. smb(client) support recursive directory creation.
	 * Therefore we handle that here instead of passing the options to underlaying wrapper.
	 *
	 * @param string $path
	 * @param int $mode
	 * @param int $options Posible values include STREAM_REPORT_ERRORS and STREAM_MKDIR_RECURSIVE
	 * @return boolean TRUE on success or FALSE on failure
	 */
	function mkdir ( $path, $mode, $options )
	{
		if (!($url = $this->resolve_url_symlinks($path,false)))	// false = directory does not need to exists
		{
			return false;
		}
		// refuse to modify readonly target (eg. readonly share)
		if (self::url_is_readonly($url))
		{
			return false;
		}
		// set user context
		if (Vfs::parse_url($url, PHP_URL_USER))
		{
			$this->check_set_context($url);
		}
		// check if recursive option is set and needed
		if (($options & STREAM_MKDIR_RECURSIVE) &&
			($parent_url = Vfs::dirname($url)) &&
			!($this->url_stat($parent_url, STREAM_URL_STAT_QUIET)) &&
			Vfs::parse_url($parent_url, PHP_URL_PATH) !== '/')
		{
			if (!self::mkdir(Vfs::dirname($path), $mode, $options)) return false;
		}
		// unset it now, as it was handled above
		if (strpos($url, 'smb://') === 0)
		{
			$options = 0;	// smbclient php extension treats every bit as recursive
		}
		else
		{
			$options &= ~STREAM_MKDIR_RECURSIVE;
		}

		$ret = mkdir($url, $mode, $options, $this->context);

		// call "vfs_mkdir" hook
		if ($ret && !class_exists('setup_process', false))
		{
			Api\Hooks::process(array(
				'location' => 'vfs_mkdir',
				'path' => $path[0] == '/' ? $path : Vfs::parse_url($path, PHP_URL_PATH),
				'url' => $url,
			),'',true);
		}
		return $ret;
	}

	/**
	 * This method is called in response to rmdir() calls on URL paths associated with the wrapper.
	 *
	 * It should attempt to remove the directory specified by path.
	 * In order for the appropriate error message to be returned, do not define this method if your wrapper does not support removing directories.
	 *
	 * @param string $path
	 * @param int $options Possible values include STREAM_REPORT_ERRORS.
	 * @return boolean TRUE on success or FALSE on failure.
	 * @throws Exception\ProtectedDirectory if trying to delete a protected directory, see Vfs::isProtected()
	 */
	function rmdir ( $path, $options )
	{
		if (Vfs::isProtectedDir($path))
		{
			throw new Exception\ProtectedDirectory("Deleting protected directory '$path' rejected!");
		}
		unset($options);	// not uses but required by function signature
		if (!($url = $this->resolve_url_symlinks($path)))
		{
			return false;
		}
		if (self::url_is_readonly($url))
		{
			return false;
		}
		$stat = $this->url_stat($path, STREAM_URL_STAT_LINK);

		// set user context
		if (Vfs::parse_url($url, PHP_URL_USER))
		{
			$this->check_set_context($url);
		}
		self::symlinkCache_remove($path);
		$ok = rmdir($url, $this->context);
		clearstatcache();	// otherwise next stat call still returns it

		// call "vfs_rmdir" hook, only after successful rmdir
		if ($ok && !class_exists('setup_process', false))
		{
			Api\Hooks::process(array(
				'location' => 'vfs_rmdir',
				'path' => $path[0] == '/' ? $path : Vfs::parse_url($path, PHP_URL_PATH),
				'url' => $url,
				'stat' => $stat,
			),'',true);
		}
		return $ok;
	}

	/**
	 * This method is called immediately when your stream object is created for examining directory contents with opendir().
	 *
	 * @param string $path URL that was passed to opendir() and that this object is expected to explore.
	 * @return booelan
	 */
	function dir_opendir ( $path, $options )
	{
		$this->opened_dir = $this->extra_dirs = null;
		$this->dir_url_params = array();
		$this->extra_dir_ptr = 0;

		if (!($this->opened_dir_url = $this->resolve_url_symlinks($path)))
		{
			if (self::LOG_LEVEL > 0) error_log(__METHOD__."( $path,$options) resolve_url_symlinks() failed!");
			return false;
		}
		// need to set user-context from resolved url
		$this->check_set_context($this->opened_dir_url);

		if (!($this->opened_dir = $this->context ?
			opendir($this->opened_dir_url, $this->context) : opendir($this->opened_dir_url)))
		{
			if (self::LOG_LEVEL > 0) error_log(__METHOD__."( $path,$options) opendir($this->opened_dir_url) failed!");
			return false;
		}
		$this->opened_dir_writable = $this->check_access($this->opened_dir_url,Vfs::WRITABLE);
		// check our fstab if we need to add some of the mountpoints
		$basepath = Vfs::parse_url($path,PHP_URL_PATH);
		foreach(array_keys(self::$fstab) as $mounted)
		{
			if (((Vfs::dirname($mounted) == $basepath || Vfs::dirname($mounted).'/' == $basepath) && $mounted != '/') &&
				// only return children readable by the user, if dir is not writable
				(!self::HIDE_UNREADABLES || $this->opened_dir_writable ||
					$this->check_access($mounted,Vfs::READABLE)))
			{
				$this->extra_dirs[] = Vfs::basename($mounted);
			}
		}


		if (self::LOG_LEVEL > 1) error_log(__METHOD__."( $path,$options): opendir($this->opened_dir_url)=$this->opened_dir, extra_dirs=".array2string($this->extra_dirs).', '.function_backtrace());
		return true;
	}

	/**
	 * This method is called in response to stat() calls on the URL paths associated with the wrapper.
	 *
	 * It should return as many elements in common with the system function as possible.
	 * Unknown or unavailable values should be set to a rational value (usually 0).
	 *
	 * If you plan to use your wrapper in a require_once you need to define stream_stat().
	 * If you plan to allow any other tests like is_file()/is_dir(), you have to define url_stat().
	 * stream_stat() must define the size of the file, or it will never be included.
	 * url_stat() must define mode, or is_file()/is_dir()/is_executable(), and any of those functions affected by clearstatcache() simply won't work.
	 * It's not documented, but directories must be a mode like 040777 (octal), and files a mode like 0100666.
	 * If you wish the file to be executable, use 7s instead of 6s.
	 * The last 3 digits are exactly the same thing as what you pass to chmod.
	 * 040000 defines a directory, and 0100000 defines a file.
	 *
	 * @param string $path
	 * @param int $flags holds additional flags set by the streams API. It can hold one or more of the following values OR'd together:
	 * - STREAM_URL_STAT_LINK	For resources with the ability to link to other resource (such as an HTTP Location: forward,
	 *                          or a filesystem symlink). This flag specified that only information about the link itself should be returned,
	 *                          not the resource pointed to by the link.
	 *                          This flag is set in response to calls to lstat(), is_link(), or filetype().
	 * - STREAM_URL_STAT_QUIET	If this flag is set, your wrapper should not raise any errors. If this flag is not set,
	 *                          you are responsible for reporting errors using the trigger_error() function during stating of the path.
	 *                          stat triggers it's own warning anyway, so it makes no sense to trigger one by our stream-wrapper!
	 * @param boolean $try_create_home =false should a user home-directory be created automatic, if it does not exist
	 * @param boolean $check_symlink_components =true check if path contains symlinks in path components other then the last one
	 * @return array
	 */
	function url_stat ( $path, $flags, $try_create_home=false, $check_symlink_components=true, $check_symlink_depth=self::MAX_SYMLINK_DEPTH, $try_reconnect=true )
	{
		// we have no context, but $path is a URL with a valid user --> set it
		$this->check_set_context($path);

		if (!($url = static::resolve_url($path, !($flags & STREAM_URL_STAT_LINK), $check_symlink_components, true, false, $mount_point)))
		{
			if (self::LOG_LEVEL > 0) error_log(__METHOD__."('$path',$flags) can NOT resolve path!");
			return false;
		}

		// we need to make sure the mount-point is readable eg. if something is mounted into an other users home-directory
		if (!isset($mount_point)) Vfs::mount_url($url, $mount_point);	// resolve_url only returns mount-point for pathes or vfs urls
		if (!($mount_point === '/' || Vfs::dirname($mount_point) === '/') &&	// they all are public readable
			($class = self::scheme2class(Vfs::parse_url($url, PHP_URL_SCHEME))) &&
			!is_a($class, Vfs\Sqlfs\StreamWrapper::class) &&	// decendents of SqlFS stream-wrapper always check traversal right to /
			!$this->check_access(Vfs::dirname($mount_point), Vfs::READABLE))
		{
			return false;	// mount-point is not reachable
		}

		if (empty(parse_url($url, PHP_URL_USER)))
		{
			$url = str_replace('://', '://'.Api\Accounts::id2name($this->context ? stream_context_get_options($this->context)[self::SCHEME]['user'] : Vfs::$user).'@', $url);
		}

		try {
			if ($flags & STREAM_URL_STAT_LINK)
			{
				$stat = @lstat($url);	// suppressed the stat failed warnings
			}
			else
			{
				$stat = @stat($url);	// suppressed the stat failed warnings

				if ($stat && ($stat['mode'] & self::MODE_LINK) === self::MODE_LINK)
				{
					if (!$check_symlink_depth)
					{
						if (self::LOG_LEVEL > 0) error_log(__METHOD__."('$path',$flags) maximum symlink depth exceeded, might be a circular symlink!");
						$stat = false;
					}
					elseif (($lpath = Vfs::readlink($url)))
					{
						if ($lpath[0] != '/')	// concat relative path
						{
							$lpath = Vfs::concat(Vfs::parse_url($path,PHP_URL_PATH),'../'.$lpath);
						}
						$u_query = parse_url($url,PHP_URL_QUERY);
						$url = Vfs::PREFIX.$lpath;
						if (self::LOG_LEVEL > 1) error_log(__METHOD__."($path,$flags) symlif (substr($path,-1) == '/' && $path != '/') $path = substr($path,0,-1);	// remove trailing slash eg. added by WebDAVink found and resolved to $url");
						// try reading the stat of the link
						if (($stat = $this->url_stat($lpath, STREAM_URL_STAT_QUIET, false, true, $check_symlink_depth-1)))
						{
							$stat_query = parse_url($stat['url'], PHP_URL_QUERY);
							if($u_query || $stat_query)
							{
								$stat_url = parse_url($stat['url']);
								parse_str($stat_query,$stat_query);
								parse_str($u_query, $u_query);
								$stat_query = http_build_query(array_merge($stat_query, $u_query));
								$stat['url'] = $stat_url['scheme'].'://'.$stat_url['host'].$stat_url['path'].'?'.$stat_query;
							}
							if(isset($stat['url'])) $url = $stat['url'];	// if stat returns an url use that, as there might be more links ...
							self::symlinkCache_add($path,$url);
						}
					}
				}
			}
		}
		catch (Api\Db\Exception $e) {
			// some long running operations, eg. merge-print, run into situation that DB closes our separate sqlfs connection
			// we try now to reconnect Vfs\Sqlfs\StreamWrapper once
			// it's done here in vfs_stream_wrapper as situation can happen in sqlfs, links, stylite.links or stylite.versioning
			if ($try_reconnect)
			{
				// reconnect to db
				Vfs\Sqlfs\StreamWrapper::reconnect();
				return $this->url_stat($path, $flags, $try_create_home, $check_symlink_components, $check_symlink_depth, false);
			}
			// if numer of tries is exceeded, re-throw exception
			throw $e;
		}
		// check if a failed url_stat was for a home dir, in that case silently create it
		if (!$stat && $try_create_home && Vfs::dirname(Vfs::parse_url($path,PHP_URL_PATH)) == '/home' &&
			($id = $GLOBALS['egw']->accounts->name2id(Vfs::basename($path))) &&
			$GLOBALS['egw']->accounts->id2name($id) == Vfs::basename($path))	// make sure path has the right case!
		{
			$hook_data = array(
				'location' => $GLOBALS['egw']->accounts->get_type($id) == 'g' ? 'addgroup' : 'addaccount',
				'account_id' => $id,
				'account_lid' => Vfs::basename($path),
				'account_name' => Vfs::basename($path),
			);
			call_user_func(array(__NAMESPACE__.'\\Hooks',$hook_data['location']),$hook_data);
			unset($hook_data);
			$stat = $this->url_stat($path,$flags,false);
		}
		$query = parse_url($url, PHP_URL_QUERY);
		if (!$stat && $check_symlink_components)	// check if there's a symlink somewhere inbetween the path
		{
			$stat = self::check_symlink_components($path,$flags,$url);
			if ($stat && isset($stat['url']) && !$query) self::symlinkCache_add($path,$stat['url']);
		}
		elseif(is_array($stat) && !isset($stat['url']))
		{
			$stat['url'] = $url;
		}
		if ($stat && ($stat['mode'] & 0222) && self::url_is_readonly($stat['url']))
		{
			$stat['mode'] &= ~0222;
		}
		if ($stat && $stat['url'] && $query && strpos($stat['url'],'?'.$query) === false)
		{
			$stat['url'] .= '?'.$query;
		}

		if (self::LOG_LEVEL > 1) error_log(__METHOD__."('$path',$flags,try_create_home=$try_create_home,check_symlink_components=$check_symlink_components) returning ".array2string($stat));

		return $stat;

		/* Todo: if we hide non readables, we should return false on url_stat for consitency (if dir is not writabel)
		// Problem: this does NOT stop (calles itself infinit recursive)!
		if (self::HIDE_UNREADABLES && !Vfs::check_access($path,Vfs::READABLE,$stat) &&
			!Vfs::check_access(Vfs::dirname($path,Vfs::WRITABLE)))
		{
			return false;
		}
		return $stat;*/
	}

	/**
	 * Check if extendes ACL (stored in eGW's ACL table) grants access
	 *
	 * The extended ACL is inherited, so it's valid for all subdirs and the included files!
	 * The used algorithm break on the first match. It could be used, to disallow further access.
	 *
	 * @param string $path path to check
	 * @param int $check mode to check: one or more or'ed together of: 4 = read, 2 = write, 1 = executable
	 * @return boolean
	 */
	function check_extended_acl($path, $check)
	{
		if (!($url = self::resolve_url($path)))
		{
			if (self::LOG_LEVEL > 0) error_log(__METHOD__."('$path', $check) can NOT resolve path: ".function_backtrace(1));
			return false;
		}
		// check backend for extended acls (only if path given)
		return self::_call_on_backend('check_extended_acl', [$url, $check], true, 0, true);	// true = fail silent if backend does not support
	}

	/**
	 * Check if the current use has owner rights for the given path or stat
	 *
	 * We define all eGW admins the owner of the group directories!
	 *
	 * @param string $path
	 * @param array $stat =null stat for path, default queried by this function
	 * @return boolean
	 */
	function has_owner_rights($path,array $stat=null)
	{
		if (!$stat)
		{
			$stat = $this->url_stat($path,0);
		}
		return $stat['uid'] == $this->user ||	// (current) user is the owner
			Vfs::$is_root ||					// class runs with root rights
			!$stat['uid'] && $stat['gid'] && Vfs::$is_admin;	// group directory and user is an eGW admin
	}

	/**
	 * Check if path (which fails the stat call) contains symlinks in path-components other then the last one
	 *
	 * @param string $path
	 * @param int $flags =0 see url_stat
	 * @param string &$url=null already resolved path
	 * @return array|boolean stat array or false if not found
	 */
	private function check_symlink_components($path,$flags=0,&$url=null)
	{
		if (is_null($url) && !($url = self::resolve_url($path)))
		{
			if (self::LOG_LEVEL > 0) error_log(__METHOD__."('$path',$flags,'$url') can NOT resolve path: ".function_backtrace(1));
			return false;
		}
		if (self::LOG_LEVEL > 1) error_log(__METHOD__."('$path',$flags,'$url'): ".function_backtrace(1));

		$rel_path = null;
		while (($rel_path = Vfs::basename($url).(isset($rel_path) ? '/'.$rel_path : '')) &&
		       ($url = Vfs::dirname($url)))
		{
			if (($stat = $this->url_stat($url, 0, false, false)))
			{
				if (is_link($url) && ($lpath = Vfs::readlink($url)))
				{
					if (self::LOG_LEVEL > 1) $log = "rel_path='$rel_path', url='$url': lpath='$lpath'";

					if ($lpath[0] != '/')
					{
						$lpath = Vfs::concat(Vfs::parse_url($url,PHP_URL_PATH),'../'.$lpath);
					}
					//self::symlinkCache_add($path,Vfs::PREFIX.$lpath);
					$url = Vfs::PREFIX.Vfs::concat($lpath,$rel_path);
					if (self::LOG_LEVEL > 1) error_log("$log --> lpath='$lpath', url='$url'");
					return $this->url_stat($url,$flags);
				}
				$url = Vfs::concat($url,$rel_path);
				if (self::LOG_LEVEL > 1) error_log(__METHOD__."('$path',$flags,'$url') returning null");
				return null;
			}
		}
		if (self::LOG_LEVEL > 1) error_log(__METHOD__."('$path',$flags,'$url') returning false");
		return false;	// $path does not exist
	}

	/**
	 * This method is called in response to readdir().
	 *
	 * It should return a string representing the next filename in the location opened by dir_opendir().
	 *
	 * Unless other filesystem, we only return files readable by the user, if the dir is not writable for him.
	 * This is done to hide files and dirs not accessible by the user (eg. other peoples home-dirs in /home).
	 *
	 * @return string
	 */
	function dir_readdir ( )
	{
		if ($this->extra_dirs && count($this->extra_dirs) > $this->extra_dir_ptr)
		{
			$file = $this->extra_dirs[$this->extra_dir_ptr++];
		}
		else
		{
			 // only return children readable by the user, if dir is not writable
			do {
				$file = readdir($this->opened_dir);
			}
			while($file !== false &&
				(is_array($this->extra_dirs) && in_array($file,$this->extra_dirs) || // do NOT return extra_dirs twice
				self::HIDE_UNREADABLES && !$this->opened_dir_writable &&
				!$this->check_access(Vfs::concat($this->opened_dir_url,$file),Vfs::READABLE)));
		}
		if (self::LOG_LEVEL > 1) error_log(__METHOD__."( $this->opened_dir ) = '$file'");
		return $file;
	}

	/**
	 * This method is called in response to rewinddir().
	 *
	 * It should reset the output generated by dir_readdir(). i.e.:
	 * The next call to dir_readdir() should return the first entry in the location returned by dir_opendir().
	 *
	 * @return boolean
	 */
	function dir_rewinddir ( )
	{
		$this->extra_dir_ptr = 0;

		return rewinddir($this->opened_dir);
	}

	/**
	 * This method is called in response to closedir().
	 *
	 * You should release any resources which were locked or allocated during the opening and use of the directory stream.
	 *
	 * @return boolean
	 */
	function dir_closedir ( )
	{
		$ret = closedir($this->opened_dir);

		$this->opened_dir = $this->extra_dirs = null;

		return $ret;
	}

	/**
	 * Init our static properties and register this wrapper
	 *
	 * Must be called when Vfs::$user is changed!
	 */
	static function init_static()
	{
		if (in_array(self::SCHEME, stream_get_wrappers())) {
			stream_wrapper_unregister(self::SCHEME);
		}
		stream_wrapper_register(self::SCHEME,__CLASS__);

		if (($fstab = $GLOBALS['egw_info']['server']['vfs_fstab']) && is_array($fstab) && count($fstab))
		{
			self::$fstab = $fstab;
		}

		// get the user Vfs is currently using, might be different from $GLOBALS['egw_info']['user']['account_id']
		if (!isset(Vfs::$user))
		{
			Vfs::init_static();
		}
		if (Vfs::$user != $GLOBALS['egw_info']['user']['account_id'])
		{
			$prefs = new Api\Preferences(Vfs::$user);
			$vfs_fstab = $prefs->data['common']['vfs_fstab'] ?? [];
		}
		else
		{
			$vfs_fstab = $GLOBALS['egw_info']['user']['preferences']['common']['vfs_fstab'] ?? [];
		}
		if (!empty($vfs_fstab) && is_array($vfs_fstab))
		{
			self::$fstab += $vfs_fstab;
		}

		// set default context for our schema ('vfs') with current user
		if (!($context = stream_context_get_options(stream_context_get_default())) || empty($context[self::SCHEME]['user']) ||
			$context[self::SCHEME]['user'] !== (int)Vfs::$user)
		{
			$context[self::SCHEME]['user'] = (int)Vfs::$user;
			stream_context_set_default($context);
		}
	}
}

StreamWrapper::init_static();