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"""

@author: Gordeev Andrey <gordeev.and.and@gmail.com>

*TL;DR

Provides recombination business logic by chaining together using boolean logic.

"""

from abc import abstractmethod

class Specification:

def and_specification(self, candidate):

raise NotImplementedError()

def or_specification(self, candidate):

raise NotImplementedError()

def not_specification(self):

raise NotImplementedError()

@abstractmethod

def is_satisfied_by(self, candidate):

pass

class CompositeSpecification(Specification):

@abstractmethod

def is_satisfied_by(self, candidate):

pass

def and_specification(self, candidate):

return AndSpecification(self, candidate)

def or_specification(self, candidate):

return OrSpecification(self, candidate)

def not_specification(self):

return NotSpecification(self)

class AndSpecification(CompositeSpecification):

_one = Specification()

_other = Specification()

def __init__(self, one, other):

self._one = one

self._other = other

def is_satisfied_by(self, candidate):

return bool(

self._one.is_satisfied_by(candidate)

and self._other.is_satisfied_by(candidate)

)

class OrSpecification(CompositeSpecification):

_one = Specification()

_other = Specification()

def __init__(self, one, other):

self._one = one

self._other = other

def is_satisfied_by(self, candidate):

return bool(

self._one.is_satisfied_by(candidate)

or self._other.is_satisfied_by(candidate)

)

class NotSpecification(CompositeSpecification):

_wrapped = Specification()

def __init__(self, wrapped):

self._wrapped = wrapped

def is_satisfied_by(self, candidate):

return bool(not self._wrapped.is_satisfied_by(candidate))

class User:

def __init__(self, super_user=False):

self.super_user = super_user

class UserSpecification(CompositeSpecification):

def is_satisfied_by(self, candidate):

return isinstance(candidate, User)

class SuperUserSpecification(CompositeSpecification):

def is_satisfied_by(self, candidate):

return getattr(candidate, "super_user", False)

def main():

"""

>>> andrey = User()

>>> ivan = User(super_user=True)

>>> vasiliy = 'not User instance'

>>> root_specification = UserSpecification().and_specification(SuperUserSpecification())

# Is specification satisfied by <name>

>>> root_specification.is_satisfied_by(andrey), 'andrey'

(False, 'andrey')

>>> root_specification.is_satisfied_by(ivan), 'ivan'

(True, 'ivan')

>>> root_specification.is_satisfied_by(vasiliy), 'vasiliy'

(False, 'vasiliy')

"""

if __name__ == "__main__":

import doctest

doctest.testmod()