class LocalStream

abstract class LocalStream implements StreamWrapperInterface {
    
    /**
     * Stream context resource.
     *
     * @var resource
     */
    public $context;
    
    /**
     * A generic resource handle.
     *
     * @var resource
     */
    public $handle = NULL;
    
    /**
     * Instance URI (stream).
     *
     * A stream is referenced as "scheme://target".
     *
     * @var string
     */
    protected $uri;
    
    /**
     * {@inheritdoc}
     */
    public static function getType() {
        return StreamWrapperInterface::NORMAL;
    }
    
    /**
     * Gets the path that the wrapper is responsible for.
     *
     * @return string
     *   String specifying the path.
     */
    public abstract function getDirectoryPath();
    
    /**
     * {@inheritdoc}
     */
    public function setUri($uri) {
        $this->uri = $uri;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getUri() {
        return $this->uri;
    }
    
    /**
     * Returns the local writable target of the resource within the stream.
     *
     * This function should be used in place of calls to realpath() or similar
     * functions when attempting to determine the location of a file. While
     * functions like realpath() may return the location of a read-only file, this
     * method may return a URI or path suitable for writing that is completely
     * separate from the URI used for reading.
     *
     * @param string $uri
     *   Optional URI.
     *
     * @return string|bool
     *   Returns a string representing a location suitable for writing of a file,
     *   or FALSE if unable to write to the file such as with read-only streams.
     */
    protected function getTarget($uri = NULL) {
        if (!isset($uri)) {
            $uri = $this->uri;
        }
        [
            ,
            $target,
        ] = explode('://', $uri, 2);
        // Remove erroneous leading or trailing, forward-slashes and backslashes.
        return trim($target, '\\/');
    }
    
    /**
     * {@inheritdoc}
     */
    public function realpath() {
        return $this->getLocalPath();
    }
    
    /**
     * Returns the canonical absolute path of the URI, if possible.
     *
     * @param string $uri
     *   (optional) The stream wrapper URI to be converted to a canonical
     *   absolute path. This may point to a directory or another type of file.
     *
     * @return string|bool
     *   If $uri is not set, returns the canonical absolute path of the URI
     *   previously set by the
     *   Drupal\Core\StreamWrapper\StreamWrapperInterface::setUri() function.
     *   If $uri is set and valid for this class, returns its canonical absolute
     *   path, as determined by the realpath() function. If $uri is set but not
     *   valid, returns FALSE.
     */
    protected function getLocalPath($uri = NULL) {
        if (!isset($uri)) {
            $uri = $this->uri;
        }
        $path = $this->getDirectoryPath() . '/' . $this->getTarget($uri);
        // In PHPUnit tests, the base path for local streams may be a virtual
        // filesystem stream wrapper URI, in which case this local stream acts like
        // a proxy. realpath() is not supported by vfsStream, because a virtual
        // file system does not have a real filepath.
        if (strpos($path, 'vfs://') === 0) {
            return $path;
        }
        $realpath = realpath($path);
        if (!$realpath) {
            // This file does not yet exist.
            $realpath = realpath(dirname($path)) . '/' . \Drupal::service('file_system')->basename($path);
        }
        $directory = realpath($this->getDirectoryPath());
        if (!$realpath || !$directory || strpos($realpath, $directory) !== 0) {
            return FALSE;
        }
        return $realpath;
    }
    
    /**
     * {@inheritdoc}
     */
    public function stream_open($uri, $mode, $options, &$opened_path) {
        $this->uri = $uri;
        $path = $this->getLocalPath();
        if ($path === FALSE) {
            if ($options & STREAM_REPORT_ERRORS) {
                trigger_error('stream_open() filename cannot be empty', E_USER_WARNING);
            }
            return FALSE;
        }
        $this->handle = $options & STREAM_REPORT_ERRORS ? fopen($path, $mode) : @fopen($path, $mode);
        if ((bool) $this->handle && $options & STREAM_USE_PATH) {
            $opened_path = $path;
        }
        return (bool) $this->handle;
    }
    
    /**
     * {@inheritdoc}
     */
    public function stream_lock($operation) {
        if (in_array($operation, [
            LOCK_SH,
            LOCK_EX,
            LOCK_UN,
            LOCK_NB,
        ])) {
            return flock($this->handle, $operation);
        }
        return TRUE;
    }
    
    /**
     * {@inheritdoc}
     */
    public function stream_read($count) {
        return fread($this->handle, $count);
    }
    
    /**
     * {@inheritdoc}
     */
    public function stream_write($data) {
        return fwrite($this->handle, $data);
    }
    
    /**
     * {@inheritdoc}
     */
    public function stream_eof() {
        return feof($this->handle);
    }
    
    /**
     * {@inheritdoc}
     */
    public function stream_seek($offset, $whence = SEEK_SET) {
        // fseek returns 0 on success and -1 on a failure.
        // stream_seek   1 on success and  0 on a failure.
        return !fseek($this->handle, $offset, $whence);
    }
    
    /**
     * {@inheritdoc}
     */
    public function stream_flush() {
        return fflush($this->handle);
    }
    
    /**
     * {@inheritdoc}
     */
    public function stream_tell() {
        return ftell($this->handle);
    }
    
    /**
     * {@inheritdoc}
     */
    public function stream_stat() {
        return fstat($this->handle);
    }
    
    /**
     * {@inheritdoc}
     */
    public function stream_close() {
        return fclose($this->handle);
    }
    
    /**
     * {@inheritdoc}
     */
    public function stream_cast($cast_as) {
        return $this->handle ? $this->handle : FALSE;
    }
    
    /**
     * {@inheritdoc}
     */
    public function stream_metadata($uri, $option, $value) {
        $target = $this->getLocalPath($uri);
        $return = FALSE;
        switch ($option) {
            case STREAM_META_TOUCH:
                if (!empty($value)) {
                    $return = touch($target, $value[0], $value[1]);
                }
                else {
                    $return = touch($target);
                }
                break;
            case STREAM_META_OWNER_NAME:
            case STREAM_META_OWNER:
                $return = chown($target, $value);
                break;
            case STREAM_META_GROUP_NAME:
            case STREAM_META_GROUP:
                $return = chgrp($target, $value);
                break;
            case STREAM_META_ACCESS:
                $return = chmod($target, $value);
                break;
        }
        if ($return) {
            // For convenience clear the file status cache of the underlying file,
            // since metadata operations are often followed by file status checks.
            clearstatcache(TRUE, $target);
        }
        return $return;
    }
    
    /**
     * {@inheritdoc}
     *
     * Since Windows systems do not allow it and it is not needed for most use
     * cases anyway, this method is not supported on local files and will trigger
     * an error and return false. If needed, custom subclasses can provide
     * OS-specific implementations for advanced use cases.
     */
    public function stream_set_option($option, $arg1, $arg2) {
        trigger_error('stream_set_option() not supported for local file based stream wrappers', E_USER_WARNING);
        return FALSE;
    }
    
    /**
     * {@inheritdoc}
     */
    public function stream_truncate($new_size) {
        return ftruncate($this->handle, $new_size);
    }
    
    /**
     * {@inheritdoc}
     */
    public function unlink($uri) {
        $this->uri = $uri;
        return $this->getFileSystem()
            ->unlink($this->getLocalPath());
    }
    
    /**
     * {@inheritdoc}
     */
    public function rename($from_uri, $to_uri) {
        return rename($this->getLocalPath($from_uri), $this->getLocalPath($to_uri));
    }
    
    /**
     * {@inheritdoc}
     */
    public function dirname($uri = NULL) {
        [
            $scheme,
        ] = explode('://', $uri, 2);
        $target = $this->getTarget($uri);
        $dirname = dirname($target);
        if ($dirname == '.') {
            $dirname = '';
        }
        return $scheme . '://' . $dirname;
    }
    
    /**
     * {@inheritdoc}
     */
    public function mkdir($uri, $mode, $options) {
        $this->uri = $uri;
        $recursive = (bool) ($options & STREAM_MKDIR_RECURSIVE);
        if ($recursive) {
            // $this->getLocalPath() fails if $uri has multiple levels of directories
            // that do not yet exist.
            $localpath = $this->getDirectoryPath() . '/' . $this->getTarget($uri);
        }
        else {
            $localpath = $this->getLocalPath($uri);
        }
        
        /** @var \Drupal\Core\File\FileSystemInterface $file_system */
        $file_system = \Drupal::service('file_system');
        if ($options & STREAM_REPORT_ERRORS) {
            return $file_system->mkdir($localpath, $mode, $recursive);
        }
        else {
            return @$file_system->mkdir($localpath, $mode, $recursive);
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function rmdir($uri, $options) {
        $this->uri = $uri;
        
        /** @var \Drupal\Core\File\FileSystemInterface $file_system */
        $file_system = \Drupal::service('file_system');
        if ($options & STREAM_REPORT_ERRORS) {
            return $file_system->rmdir($this->getLocalPath());
        }
        else {
            return @$file_system->rmdir($this->getLocalPath());
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function url_stat($uri, $flags) {
        $this->uri = $uri;
        $path = $this->getLocalPath();
        // Suppress warnings if requested or if the file or directory does not
        // exist. This is consistent with PHP's plain filesystem stream wrapper.
        if ($flags & STREAM_URL_STAT_QUIET || !file_exists($path)) {
            return @stat($path);
        }
        else {
            return stat($path);
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function dir_opendir($uri, $options) {
        $this->uri = $uri;
        $this->handle = opendir($this->getLocalPath());
        return (bool) $this->handle;
    }
    
    /**
     * {@inheritdoc}
     */
    public function dir_readdir() {
        return readdir($this->handle);
    }
    
    /**
     * {@inheritdoc}
     */
    public function dir_rewinddir() {
        rewinddir($this->handle);
        // We do not really have a way to signal a failure as rewinddir() does not
        // have a return value and there is no way to read a directory handler
        // without advancing to the next file.
        return TRUE;
    }
    
    /**
     * {@inheritdoc}
     */
    public function dir_closedir() {
        closedir($this->handle);
        // We do not really have a way to signal a failure as closedir() does not
        // have a return value.
        return TRUE;
    }
    
    /**
     * Returns file system service.
     *
     * @return \Drupal\Core\File\FileSystemInterface
     *   The file system service.
     */
    private function getFileSystem() {
        return \Drupal::service('file_system');
    }

}