# -*- coding: utf-8 -*-
"""
 werkzeug.filesystem
 ~~~~~~~~~~~~~~~~~~~

 Various utilities for the local filesystem.

 :copyright: 2007 Pallets
 :license: BSD-3-Clause
"""
import codecs
import sys
import warnings

# We do not trust traditional unixes.
has_likely_buggy_unicode_filesystem = (
 sys.platform.startswith("linux") or "bsd" in sys.platform
)


def _is_ascii_encoding(encoding):
 """Given an encoding this figures out if the encoding is actually ASCII (which
 is something we don't actually want in most cases). This is necessary
 because ASCII comes under many names such as ANSI_X3.4-1968.
 """
 if encoding is None:
 return False
 try:
 return codecs.lookup(encoding).name == "ascii"
 except LookupError:
 return False


class BrokenFilesystemWarning(RuntimeWarning, UnicodeWarning):
 """The warning used by Werkzeug to signal a broken filesystem. Will only be
 used once per runtime."""


_warned_about_filesystem_encoding = False


def get_filesystem_encoding():
 """Returns the filesystem encoding that should be used. Note that this is
 different from the Python understanding of the filesystem encoding which
 might be deeply flawed. Do not use this value against Python's unicode APIs
 because it might be different. See :ref:`filesystem-encoding` for the exact
 behavior.

 The concept of a filesystem encoding in generally is not something you
 should rely on. As such if you ever need to use this function except for
 writing wrapper code reconsider.
 """
 global _warned_about_filesystem_encoding
 rv = sys.getfilesystemencoding()
 if has_likely_buggy_unicode_filesystem and not rv or _is_ascii_encoding(rv):
 if not _warned_about_filesystem_encoding:
 warnings.warn(
 "Detected a misconfigured UNIX filesystem: Will use"
 " UTF-8 as filesystem encoding instead of {0!r}".format(rv),
 BrokenFilesystemWarning,
 )
 _warned_about_filesystem_encoding = True
 return "utf-8"
 return rv