blob: f5c7afa9f5951e58b709d5be914d3fd3680b7847 [file] [log] [blame] [edit]
# Copyright 2016 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
"""User input handlers."""
class InputError(Exception):
"""An error with a user provided input."""
class _InputHandler(object):
"""An input handler base class."""
def get_choices_supplements(self):
"""Returns a pair of supplement strings representing input choices.
@return: A pair consisting of a detailed representation of available
choices, and a corresponding concise descriptor of available
input choices with optional default.
"""
input_choices, default = self._get_input_choices_and_default()
if input_choices:
input_choices = '[%s]' % input_choices
if default is not None:
input_choices += ' (default: %s)' % default
return self._get_choices_details(), input_choices
def _get_input_choices_and_default(self):
"""Returns an input choices descriptor and a default (if any)."""
raise NotImplementedError
def _get_choices_details(self):
"""Returns a detailed description (string) of input choices."""
raise NotImplementedError
def process(self, input_str):
"""Returns the result of processing the user input.
@param input_str: The user input.
@return: The result of processing the input.
@raise InputError: Provided input is invalid.
"""
raise NotImplementedError
class PauseInputHandler(_InputHandler):
"""A quiet input handler that just returns on any input."""
# Interface overrides.
#
def _get_input_choices_and_default(self):
return None, None
def _get_choices_details(self):
return None
def process(self, input_str):
pass
class YesNoInputHandler(_InputHandler):
"A yes/no input handler with optional default."""
def __init__(self, default=None):
"""Initializes the input handler.
@param default: The Boolean value to return by default.
"""
self._default = default
self._input_choices = '%s/%s' % ('Y' if default is True else 'y',
'N' if default is False else 'n')
# Interface overrides.
#
def _get_input_choices_and_default(self):
# We highlight the default by uppercasing the corresponding choice
# directly, so no need to return a default separately.
return self._input_choices, None
def _get_choices_details(self):
return None
def process(self, input_str):
input_str = input_str.lower().strip()
if input_str == 'y':
return True
if input_str == 'n':
return False
if not input_str and self._default is not None:
return self._default
raise InputError
class MultipleChoiceInputHandler(_InputHandler):
"""A multiple choice input handler with optional default."""
def __init__(self, choices, default=None):
"""Initializes the input handler.
@param choices: An iterable of input choices.
@param default: Index of default choice (integer).
"""
max_idx = len(choices)
if not (default is None or default in range(1, max_idx + 1)):
raise ValueError('Default choice is not a valid index')
self._choices = choices
self._idx_range = '1-%d' % max_idx if max_idx > 1 else str(max_idx)
self._default = None if default is None else str(default)
# Interface overrides.
#
def _get_input_choices_and_default(self):
return self._idx_range, self._default
def _get_choices_details(self):
return '\n'.join(['%d) %s' % (idx, choice)
for idx, choice in enumerate(self._choices, 1)])
def process(self, input_str):
"""Returns the index (zero-based) and value of the chosen option."""
input_str = input_str or self._default
if input_str:
try:
input_idx = int(input_str) - 1
if input_idx in range(len(self._choices)):
return input_idx, self._choices[input_idx]
except ValueError:
pass
raise InputError