import tempfile


class Storage(object):

  """Storage is organized as follow:
  $ROOT/images/<image_id>/json
  $ROOT/images/<image_id>/layer
  $ROOT/repositories/<namespace>/<repository_name>/<tag_name>
  """

  # Useful if we want to change those locations later without rewriting
  # the code which uses Storage
  repositories = 'repositories'
  images = 'images'
  shared_images = 'sharedimages'
  # Set the IO buffer to 64kB
  buffer_size = 64 * 1024

  @staticmethod
  def temp_store_handler():
    tmpf = tempfile.TemporaryFile()
  
    def fn(buf):
      try:
        tmpf.write(buf)
      except IOError:
        pass
  
    return tmpf, fn

  def image_path(self, namespace, repository, image_id, storage_uuid):
    if storage_uuid:
      return '{0}/{1}/'.format(self.shared_images, storage_uuid)
    else:
      return '{0}/{1}/{2}/{3}/'.format(self.images, namespace, repository,
                                       image_id)

  def image_json_path(self, namespace, repository, image_id, storage_uuid):
    base_path = self.image_path(namespace, repository, image_id, storage_uuid)
    return '{0}/json'.format(base_path)

  def image_mark_path(self, namespace, repository, image_id, storage_uuid):
    base_path = self.image_path(namespace, repository, image_id, storage_uuid)
    return '{0}/_inprogress'.format(base_path)

  def image_checksum_path(self, namespace, repository, image_id, storage_uuid):
    base_path = self.image_path(namespace, repository, image_id, storage_uuid)
    return '{0}/_checksum'.format(base_path)

  def image_layer_path(self, namespace, repository, image_id, storage_uuid):
    base_path = self.image_path(namespace, repository, image_id, storage_uuid)
    return '{0}/layer'.format(base_path)

  def image_ancestry_path(self, namespace, repository, image_id, storage_uuid):
    base_path = self.image_path(namespace, repository, image_id, storage_uuid)
    return '{0}/ancestry'.format(base_path)

  def image_file_trie_path(self, namespace, repository, image_id,
                           storage_uuid):
    base_path = self.image_path(namespace, repository, image_id, storage_uuid)
    return '{0}/files.trie'.format(base_path)

  def image_file_diffs_path(self, namespace, repository, image_id,
                            storage_uuid):
    base_path = self.image_path(namespace, repository, image_id, storage_uuid)
    return '{0}/diffs.json'.format(base_path)

  def get_direct_download_url(self, path, expires_in=60):
    return None

  def get_content(self, path):
    raise NotImplementedError

  def put_content(self, path, content):
    raise NotImplementedError

  def stream_read(self, path):
    raise NotImplementedError

  def stream_read_file(self, path):
    raise NotImplementedError

  def stream_write(self, path, fp):
    raise NotImplementedError

  def list_directory(self, path=None):
    raise NotImplementedError

  def exists(self, path):
    raise NotImplementedError

  def remove(self, path):
    raise NotImplementedError

  def get_size(self, path):
    raise NotImplementedError