Source code for narrenschiff.common

# Copyright 2021 Petar Nikolovski

# 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


# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# 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:['shred', self.path]) except Exception: self._placebo_delete(passes=3) os.remove(self.path)
def _placebo_delete(self, passes=1): """ Overwrite file before deletaion. 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.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('ya?ml$', filename, re.I)) def is_jinja(filename): return bool('j(inja)?2$', filename, re.I))