class ChromeFileSystem extends ChromeApi {
 static final JsObject _fileSystem = chrome['fileSystem'];

 ChromeFileSystem._();

 bool get available => _fileSystem != null;

 /**
  * Get the display path of an Entry object. The display path is based on the
  * full path of the file or directory on the local file system, but may be
  * made more readable for display purposes.
  */
 Future<String> getDisplayPath(Entry entry) {
   if (_fileSystem == null) _throwNotAvailable();

   var completer = new ChromeCompleter<String>.oneArg();
   _fileSystem.callMethod('getDisplayPath', [jsify(entry), completer.callback]);
   return completer.future;
 }

 /**
  * Get a writable Entry from another Entry. This call will fail with a runtime
  * error if the application does not have the 'write' permission under
  * 'fileSystem'. If entry is a DirectoryEntry, this call will fail if the
  * application does not have the 'directory' permission under 'fileSystem'.
  */
 Future<Entry> getWritableEntry(Entry entry) {
   if (_fileSystem == null) _throwNotAvailable();

   var completer = new ChromeCompleter<Entry>.oneArg(_createEntry);
   _fileSystem.callMethod('getWritableEntry', [jsify(entry), completer.callback]);
   return completer.future;
 }

 /**
  * Gets whether this Entry is writable or not.
  */
 Future<bool> isWritableEntry(Entry entry) {
   if (_fileSystem == null) _throwNotAvailable();

   var completer = new ChromeCompleter<bool>.oneArg();
   _fileSystem.callMethod('isWritableEntry', [jsify(entry), completer.callback]);
   return completer.future;
 }

 /**
  * Ask the user to choose a file or directory.
  * 
  * Returns:
  * [entry] null
  * [fileEntries] null
  */
 Future<ChooseEntryResult> chooseEntry([ChooseEntryOptions options]) {
   if (_fileSystem == null) _throwNotAvailable();

   var completer = new ChromeCompleter<ChooseEntryResult>.twoArgs(ChooseEntryResult._create);
   _fileSystem.callMethod('chooseEntry', [jsify(options), completer.callback]);
   return completer.future;
 }

 /**
  * Returns the file entry with the given id if it can be restored. This call
  * will fail with a runtime error otherwise. This method is new in Chrome 31.
  */
 Future<Entry> restoreEntry(String id) {
   if (_fileSystem == null) _throwNotAvailable();

   var completer = new ChromeCompleter<Entry>.oneArg(_createEntry);
   _fileSystem.callMethod('restoreEntry', [id, completer.callback]);
   return completer.future;
 }

 /**
  * Returns whether the app has permission to restore the entry with the given
  * id. This method is new in Chrome 31.
  */
 Future<bool> isRestorable(String id) {
   if (_fileSystem == null) _throwNotAvailable();

   var completer = new ChromeCompleter<bool>.oneArg();
   _fileSystem.callMethod('isRestorable', [id, completer.callback]);
   return completer.future;
 }

 /**
  * Returns an id that can be passed to restoreEntry to regain access to a
  * given file entry. Only the 500 most recently used entries are retained,
  * where calls to retainEntry and restoreEntry count as use. If the app has
  * the 'retainEntries' permission under 'fileSystem', entries are retained
  * indefinitely. Otherwise, entries are retained only while the app is running
  * and across restarts. This method is new in Chrome 31.
  */
 String retainEntry(Entry entry) {
   if (_fileSystem == null) _throwNotAvailable();

   return _fileSystem.callMethod('retainEntry', [jsify(entry)]);
 }

 void _throwNotAvailable() {
   throw new UnsupportedError("'chrome.fileSystem' is not available");
 }
}