# -*- coding: utf-8 -*-
"""
Copyright Sylvain Bouveret, Yann Chevaleyre and François Durand
sylvain.bouveret@imag.fr, yann.chevaleyre@dauphine.fr, fradurand@gmail.com
This file is part of Whalrus.
Whalrus is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
Whalrus is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with Whalrus. If not, see <http://www.gnu.org/licenses/>.
"""
from pyparsing import ParseException
from whalrus.converters_ballot.converter_ballot import ConverterBallot
from whalrus.ballots.ballot import Ballot
from whalrus.ballots.ballot_one_name import BallotOneName
from whalrus.ballots.ballot_order import BallotOrder
from whalrus.ballots.ballot_levels import BallotLevels
from whalrus.ballots.ballot_plurality import BallotPlurality
from whalrus.ballots.ballot_veto import BallotVeto
from whalrus.priorities.priority import Priority
# noinspection PyUnresolvedReferences
[docs]class ConverterBallotGeneral(ConverterBallot):
"""
General ballot converter.
This is a default general converter. It tries to infer the type of input and converts it to an object of the
relevant subclass of :class:`Ballot`.
Parameters
----------
plurality_priority : Priority
Option passed to :meth:`BallotPlurality.restrict` when restricting the ballot if, once converted, it is a
:class:`BallotPlurality`.
veto_priority : Priority
Option passed to :meth:`BallotVeto.restrict` when restricting the ballot if, once converted, if is a
:class:`BallotVeto`.
one_name_priority : Priority
Option passed to :meth:`BallotOneName.restrict` when restricting the ballot if, once converted, it is a
:class:`BallotOneName` (but not a :class:`BallotPlurality` or :class:`BallotVeto`).
Examples
--------
Typical usage:
>>> converter = ConverterBallotGeneral()
>>> converter({'a': 10, 'b': 7, 'c': 0})
BallotLevels({'a': 10, 'b': 7, 'c': 0}, candidates={'a', 'b', 'c'}, scale=Scale())
>>> converter([{'a', 'b'}, {'c'}])
BallotOrder([{'a', 'b'}, 'c'], candidates={'a', 'b', 'c'})
>>> converter('a ~ b > c')
BallotOrder([{'a', 'b'}, 'c'], candidates={'a', 'b', 'c'})
>>> converter('Alice')
BallotOneName('Alice', candidates={'Alice'})
It is also possible to "restrict" the set of candidates on-the-fly:
>>> converter = ConverterBallotGeneral()
>>> converter('a ~ b > c', candidates={'b', 'c'})
BallotOrder(['b', 'c'], candidates={'b', 'c'})
>>> converter({'a': 10, 'b': 7, 'c': 0}, candidates={'b', 'c'})
BallotLevels({'b': 7, 'c': 0}, candidates={'b', 'c'}, scale=Scale())
Cf. :meth:`Ballot.restrict` for more information.
Use options for the restrictions:
>>> converter = ConverterBallotGeneral(one_name_priority=Priority.ASCENDING,
... plurality_priority=Priority.ASCENDING,
... veto_priority=Priority.ASCENDING)
>>> converter(BallotOneName('a', candidates={'a', 'b', 'c'}), candidates={'b', 'c'})
BallotOneName('b', candidates={'b', 'c'})
>>> converter(BallotPlurality('a', candidates={'a', 'b', 'c'}), candidates={'b', 'c'})
BallotPlurality('b', candidates={'b', 'c'})
>>> converter(BallotVeto('a', candidates={'a', 'b', 'c'}), candidates={'b', 'c'})
BallotVeto('c', candidates={'b', 'c'})
"""
def __init__(self,
plurality_priority: Priority = Priority.UNAMBIGUOUS,
veto_priority: Priority=Priority.UNAMBIGUOUS,
one_name_priority: Priority=Priority.UNAMBIGUOUS):
self.plurality_priority = plurality_priority
self.veto_priority = veto_priority
self.one_name_priority = one_name_priority
def __call__(self, x: object, candidates: set=None) -> Ballot:
# If it is a ballot, deal with the restriction to the candidates.
if isinstance(x, Ballot):
if candidates is None:
return x
if isinstance(x, BallotOrder):
return x.restrict(candidates)
if isinstance(x, BallotPlurality):
return x.restrict(candidates=candidates, priority=self.plurality_priority)
if isinstance(x, BallotVeto):
return x.restrict(candidates=candidates, priority=self.veto_priority)
if isinstance(x, BallotOneName):
return x.restrict(candidates=candidates, priority=self.one_name_priority)
raise NotImplementedError('Unable to restrict the candidates for ballot of class %s.' % x.__class__)
# If it is not a ballot, convert to ballot and call the method again.
if isinstance(x, dict):
return self(BallotLevels(x), candidates)
try:
ballot_order = BallotOrder(x)
if len(ballot_order) == 1:
return self(BallotOneName(x), candidates)
else:
return self(ballot_order, candidates)
except (TypeError, ParseException):
pass
return self(BallotOneName(x), candidates)