# Copyright 2019 The Fuchsia Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.


class FvmImage(object):
  """Represents an FVM (Fuchsia Volume Manager) image."""

  def __init__(self, api, path, fvm_tool):
    """
    Args:
      api (recipe_api.RecipeApi): A recipe API.
      path (Path): The path to the image.
      fvm_tool (Path): The path to the `fvm` tool.
    """
    self._api = api
    self._path = path
    self._tool = fvm_tool
    self._size = None

  @property
  def required_size(self):
    """The size in bytes that the paved image would require.

    Only supported for sparse images.
    """
    if not self._size:
      basename = self._api.path.basename(self._path)
      self._size = self._api.file.filesizes('%s size' % basename,
                                            [self._path])[0]
    return self._size

  def extend(self, factor):
    """Extends the size of the image by a scaling factor.

    This operation is only valid for non-sparse images.

    Args:
      factor (int or float): A factor by which to scale the size of the image.
    """
    assert factor > 1, 'scaling factor must be greater than one'
    new_size = int(self.required_size * factor)
    size_result = self._api.step(
        '%s extend' % self._api.path.basename(self._path),
        [self._tool, self._path, 'extend', '--length', new_size])
    self._size = new_size
    return size_result