# Copyright 2021 The Narrenschiff Authors
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
# http://www.apache.org/licenses/LICENSE-2.0
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import os
import re
import subprocess
from contextlib import suppress
[docs]class AmbiguousConfiguration(Exception):
"""Give warning that something is wrong with configuration."""
pass
[docs]class Singleton(type):
"""
Define the Singleton.
"""
def __init__(cls, name, bases, attrs, **kwargs):
super().__init__(name, bases, attrs)
cls._instance = None
def __call__(cls, *args, **kwargs):
if cls._instance is None:
cls._instance = super().__call__(*args, **kwargs)
return cls._instance
[docs]class DeleteFile:
"""Delete file from the file system, ideally in secure manner."""
def __init__(self, path):
"""
Make an instance of :class:`narrenschiff.common.DeleteFile` class.
:param path: Absolute path to the file that needs to be deleted
:type path: ``str``
:return: Void
:rtype: ``None``
"""
self.path = path
[docs] def delete(self):
"""Delete the file."""
try:
subprocess.run(['shred', self.path])
except Exception:
self._placebo_delete(passes=3)
os.remove(self.path)
def _placebo_delete(self, passes=1):
"""
Overwrite file before deletion. This is executed in case the OS
does not have the ``shred`` command line utility. This may not work for
modern systems that use journaling file systems, copy-on-write file
systems, wear leveling, or similar.
:param passes: Number of times file will be overwritten
:type passes: ``int``
:return: Void
:rtype: ``None``
"""
length = os.path.getsize(self.path)
with open(self.path, 'wb') as f:
for _ in range(passes):
f.seek(0)
f.write(os.urandom(length))
os.fsync(f)
[docs]def get_chest_file_path(location):
"""
Check if there are duplicate chest files, and return paths if there are
not.
:param location: Relative path to course project directory
:type location: ``str``
:return: Absolute path to chest file
:rtype: ``str``
:raises: :class:`narrenschiff.common.AmbiguousConfiguration`
"""
paths = ['chest.yaml', 'chest.yml']
cwd = os.getcwd()
candidate = []
for path in paths:
chest_file = os.path.join(cwd, location, path)
if os.path.exists(chest_file):
candidate.append(chest_file)
candidate_length = len(candidate)
if candidate_length > 1:
raise AmbiguousConfiguration('Only one chest file can exist')
if candidate_length == 0:
raise AmbiguousConfiguration('Chest file does not exist')
return candidate[0]
[docs]def flatten(lst):
"""
Flatten list.
:param lst: A list to be flattened
:type lst: ``list``
:return: Flattened list
:rtype: ``list``
"""
flattened = []
for element in lst:
if isinstance(element, str):
flattened.append(element)
else:
with suppress(TypeError):
flattened.extend(element)
return flattened
def is_yaml(filename):
return bool(re.search(r'ya?ml$', filename, re.I))
def is_jinja(filename):
return bool(re.search(r'j(inja)?2$', filename, re.I))