#!/usr/bin/python

# Copyright (c) 2010 The Chromium Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

"""Utilities for PyAuto."""

import logging
import os
import shutil
import tempfile


class ExistingPathReplacer(object):
  """Facilitates backing up a given path (file or dir)..

  Often you want to manipulate a directory or file for testing but don't want to
  meddle with the existing contents.  This class lets you make a backup, and
  reinstate the backup when done.  A backup is made in an adjacent directory,
  so you need to make sure you have write permissions to the parent directory.

  Works seemlessly in cases where the requested path already exists, or not.

  Automatically reinstates the backed up path (if any) when object is deleted.
  """
  _path = ''
  _backup_dir = None  # dir to which existing content is backed up
  _backup_basename = ''

  def __init__(self, path, path_type='dir'):
    """Initialize the object, making backups if necessary.

    Args:
      path: the requested path to file or directory
      path_type: path type. Options: 'file', 'dir'. Default: 'dir'
    """
    assert path_type in ('file', 'dir'), 'Invalid path_type: %s' % path_type
    self._path_type = path_type
    self._path = path
    if os.path.exists(self._path):
      if 'dir' == self._path_type:
        assert os.path.isdir(self._path), '%s is not a directory' % self._path
      else:
        assert os.path.isfile(self._path), '%s is not a file' % self._path
      # take a backup
      self._backup_basename = os.path.basename(self._path)
      self._backup_dir = tempfile.mkdtemp(dir=os.path.dirname(self._path),
                                          prefix='bkp-' + self._backup_basename)
      logging.info('Backing up %s in %s' % (self._path, self._backup_dir))
      shutil.move(self._path,
                  os.path.join(self._backup_dir, self._backup_basename))
    self._CreateRequestedPath()

  def __del__(self):
    """Cleanup. Reinstate backup."""
    self._CleanupRequestedPath()
    if self._backup_dir:  # Reinstate, if backed up.
      from_path = os.path.join(self._backup_dir, self._backup_basename)
      logging.info('Reinstating backup from %s to %s' % (from_path, self._path))
      shutil.move(from_path, self._path)
    self._RemoveBackupDir()

  def _CreateRequestedPath(self):
    # Create intermediate dirs if needed.
    if not os.path.exists(os.path.dirname(self._path)):
      os.makedirs(os.path.dirname(self._path))
    if 'dir' == self._path_type:
      os.mkdir(self._path)
    else:
      open(self._path, 'w').close()

  def _CleanupRequestedPath(self):
    if os.path.exists(self._path):
      if os.path.isdir(self._path):
        shutil.rmtree(self._path, ignore_errors=True)
      else:
        os.remove(self._path)

  def _RemoveBackupDir(self):
    if self._backup_dir and os.path.isdir(self._backup_dir):
      shutil.rmtree(self._backup_dir, ignore_errors=True)


def RemovePath(path):
  """Remove the given path (file or dir)."""
  if os.path.isdir(path):
    shutil.rmtree(path, ignore_errors=True)
    return
  try:
    os.remove(path)
  except OSError:
    pass