from __future__ import unicode_literals

import os
import stat
import sys
import tempfile
from os.path import abspath, dirname, isabs, join, normcase, normpath, sep

from django.core.exceptions import SuspiciousFileOperation
from django.utils import six
from django.utils.encoding import force_text

try:
    WindowsError = WindowsError
except NameError:
    class WindowsError(Exception):
        pass

if six.PY2:
    fs_encoding = sys.getfilesystemencoding() or sys.getdefaultencoding()


# Under Python 2, define our own abspath function that can handle joining
# unicode paths to a current working directory that has non-ASCII characters
# in it.  This isn't necessary on Windows since the Windows version of abspath
# handles this correctly. It also handles drive letters differently than the
# pure Python implementation, so it's best not to replace it.
if six.PY3 or os.name == 'nt':
    abspathu = abspath
else:
    def abspathu(path):
        """
        Version of os.path.abspath that uses the unicode representation
        of the current working directory, thus avoiding a UnicodeDecodeError
        in join when the cwd has non-ASCII characters.
        """
        if not isabs(path):
            path = join(os.getcwdu(), path)
        return normpath(path)


def upath(path):
    """
    Always return a unicode path.
    """
    if six.PY2 and not isinstance(path, six.text_type):
        return path.decode(fs_encoding)
    return path


def npath(path):
    """
    Always return a native path, that is unicode on Python 3 and bytestring on
    Python 2.
    """
    if six.PY2 and not isinstance(path, bytes):
        return path.encode(fs_encoding)
    return path


def safe_join(base, *paths):
    """
    Joins one or more path components to the base path component intelligently.
    Returns a normalized, absolute version of the final path.

    The final path must be located inside of the base path component (otherwise
    a ValueError is raised).
    """
    base = force_text(base)
    paths = [force_text(p) for p in paths]
    final_path = abspathu(join(base, *paths))
    base_path = abspathu(base)
    # Ensure final_path starts with base_path (using normcase to ensure we
    # don't false-negative on case insensitive operating systems like Windows),
    # further, one of the following conditions must be true:
    #  a) The next character is the path separator (to prevent conditions like
    #     safe_join("/dir", "/../d"))
    #  b) The final path must be the same as the base path.
    #  c) The base path must be the most root path (meaning either "/" or "C:\\")
    if (not normcase(final_path).startswith(normcase(base_path + sep)) and
            normcase(final_path) != normcase(base_path) and
            dirname(normcase(base_path)) != normcase(base_path)):
        raise SuspiciousFileOperation(
            'The joined path ({}) is located outside of the base path '
            'component ({})'.format(final_path, base_path))
    return final_path


def rmtree_errorhandler(func, path, exc_info):
    """
    On Windows, some files are read-only (e.g. in in .svn dirs), so when
    rmtree() tries to remove them, an exception is thrown.
    We catch that here, remove the read-only attribute, and hopefully
    continue without problems.
    """
    exctype, value = exc_info[:2]
    # looking for a windows error
    if exctype is not WindowsError or 'Access is denied' not in str(value):
        raise
    # file type should currently be read only
    if ((os.stat(path).st_mode & stat.S_IREAD) != stat.S_IREAD):
        raise
    # convert to read/write
    os.chmod(path, stat.S_IWRITE)
    # use the original function to repeat the operation
    func(path)


def symlinks_supported():
    """
    A function to check if creating symlinks are supported in the
    host platform and/or if they are allowed to be created (e.g.
    on Windows it requires admin permissions).
    """
    tmpdir = tempfile.mkdtemp()
    original_path = os.path.join(tmpdir, 'original')
    symlink_path = os.path.join(tmpdir, 'symlink')
    os.makedirs(original_path)
    try:
        os.symlink(original_path, symlink_path)
        supported = True
    except (OSError, NotImplementedError, AttributeError):
        supported = False
    else:
        os.remove(symlink_path)
    finally:
        os.rmdir(original_path)
        os.rmdir(tmpdir)
        return supported