130 lines
3.6 KiB
Python
130 lines
3.6 KiB
Python
"""question.py
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Contains our Question class, which knows how to ask a question, then
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run abitrary code.
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----------------------------------------------------------------------
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Copyright 2019 Canonical Ltd
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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"""
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from typing import Tuple
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class InvalidQuestion(Exception):
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"""Exception to raies in the case where a Question subclass has not
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been properly implemented.
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"""
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class InvalidAnswer(Exception):
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"""Exception to raise in the case where the user has specified an
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invalid answer.
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"""
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class AnswerNotImplemented(Exception):
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"""Exception to raise in the case where a 'yes' or 'no' routine has
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not been overriden in the subclass, as required.
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"""
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class Question():
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"""
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Ask the user a question, and then run code as appropriate.
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Contains a support for always defaulting to yes.
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TODO: Add support for finding answers in a config.yaml.
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"""
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_valid_types = [
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'binary', # Yes or No, and variants thereof
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'string', # Accept (and sanitize) any string
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'auto' # Don't actually ask a question -- just execute self.yes(True)
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]
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_question = '(required)'
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_type = 'auto' # can be binary, string or auto
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_invalid_prompt = 'Please answer Yes or No.'
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_retries = 3
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_input_func = input
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def __init__(self):
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if self._type not in ['binary', 'string', 'auto']:
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raise InvalidQuestion(
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'Invalid type {} specified'.format(self._type))
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def _validate(self, answer: bytes) -> Tuple[str, bool]:
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"""Validate an answer.
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:param anwser: raw input from the user.
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Returns the answer, and whether or not the answer was valid.
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"""
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if self._type == 'auto':
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return True, True
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answer = answer.decode('utf8')
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if self._type == 'string':
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# TODO Santize this!
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return answer, True
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# self._type is binary
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if answer.lower() in ['y', 'yes']:
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return True, True
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if answer.lower() in ['n', 'no']:
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return False, True
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return answer, False
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def yes(self, answer: str) -> None:
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"""Routine to run if the user answers 'yes' or with a value."""
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raise AnswerNotImplemented('You must override this method.')
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def no(self, answer: str) -> None:
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"""Routine to run if the user answers 'no'"""
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raise AnswerNotImplemented('You must override this method.')
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def ask(self) -> None:
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"""
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Ask the user a question.
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Run self.yes or self.no as appropriate. Raise an error if the
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user cannot specify a valid answer after self._retries tries.
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"""
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prompt = self._question
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for i in range(0, self._retries):
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awr, valid = self._validate(
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self._type == 'auto' or self._input_func(prompt))
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if valid:
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if awr:
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return self.yes(awr)
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return self.no(awr)
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prompt = '{} is not valid. {}'.format(awr, self._invalid_prompt)
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raise InvalidAnswer('Too many invalid answers.')
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