# Copyright 2013 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.

import posixpath


# TODO(kalman): Write a Path class and use that everywhere rather than a
# utility class.


def IsDirectory(path):
  '''Returns whether |path| should be considered a directory.
  '''
  # This assertion is sprinkled throughout the code base.
  AssertIsValid(path)
  return path in ('', '.', '..') or path.endswith('/') or path.endswith('/..')


def IsValid(path):
  '''Returns whether |path| is a valid path for the purposes of the docserver.
  Paths may not start with /, must be posix paths, and for sanity shouldn't
  repeat the path separator //.
  '''
  return not path.startswith('/') and not '\\' in path and not '//' in path


def AssertIsValid(path):
  assert IsValid(path), 'Path "%s" is invalid' % path


def Join(*paths):
  assert all(IsValid(path) for path in paths), paths
  return posixpath.join(*paths)


def SplitParent(path):
  '''Returns the parent directory and base name of |path| in a tuple.
  Any trailing slash of |path| is preserved, such that the parent of
  '/hello/world/' is '/hello' and the base is 'world/'.
  '''
  parent, base = posixpath.split(path.rstrip('/'))
  if path.endswith('/'):
    base += '/'
  return parent, base


def Split(path):
  '''Returns a list of the directories and filename in a path. 'p1/p2/p3'
  will return ['p1/', 'p2/', 'p3'].
  '''
  AssertIsValid(path)
  names = [name + '/' for name in path.rstrip('/').split('/')]
  if names and not path.endswith('/'):
    names[-1] = names[-1][:-1]
  return names


def ToDirectory(path):
  '''Returns a string representing |path| as a directory, that is,
  IsDirectory(result) is True (and does not fail assertions). If |path| is
  already a directory then this is a no-op.
  '''
  return path if IsDirectory(path) else (path + '/')


def AssertIsDirectory(path):
  assert IsDirectory(path), '"%s" is not a directory' % path


def AssertIsFile(path):
  assert not IsDirectory(path), '"%s" is not a file' % path

def Segment(path):
  '''Yields a tuple (url, file) for directory split pairs.
  For example, if we split the path 'foo/bar/baz', it will yield:
  ('', 'foo/bar/baz'), ('foo', "bar/baz'), ('foo/bar', 'baz'),
  ('foo/bar/baz', '')
  '''
  AssertIsValid(path)

  last_path = ''
  yield (last_path, path)

  for segment in (segment for segment in path.split('/') if segment != ''):
    last_path = posixpath.join(last_path, segment)
    rel_path = posixpath.relpath(path, last_path)

    # Don't let relpath say the filename is '.'
    if rel_path == '.':
      rel_path = ''
    else:
      last_path = ToDirectory(last_path)

    yield (last_path, rel_path)