main.py

""" Generation core.

mixer.main
~~~~~~~~~~

The module implements objects generation.

:copyright: 2013 by Kirill Klenov.
:license: BSD, see LICENSE for more details.

"""
from __future__ import absolute_import, unicode_literals

import warnings
from types import GeneratorType

import logging
import traceback
from collections import defaultdict
from contextlib import contextmanager
from copy import deepcopy
from functools import partial
from types import FunctionType, MethodType, BuiltinFunctionType

from . import mix_types as t, _compat as _
from .factory import GenFactory
from ._faker import faker


SKIP_VALUE = object()

LOGLEVEL = logging.WARN
LOGGER = logging.getLogger('mixer')
if not LOGGER.handlers and not LOGGER.root.handlers:
    LOGGER.addHandler(logging.StreamHandler())


class TypeMixerMeta(type):

    """ Cache typemixers by scheme. """

    mixers = dict()

    def __call__(cls, cls_type, mixer=None, factory=None, fake=True):
        backup = cls_type
        try:
            cls_type = cls.__load_cls(cls_type)
            assert cls_type
        except (AttributeError, AssertionError, LookupError):
            raise ValueError('Invalid scheme: %s' % backup)

        key = (mixer, cls_type, fake, factory)
        if key not in cls.mixers:
            cls.mixers[key] = super(TypeMixerMeta, cls).__call__(
                cls_type, mixer=mixer, factory=factory, fake=fake)

        return cls.mixers[key]

    @staticmethod
    def __load_cls(cls_type):
        if isinstance(cls_type, _.string_types):
            mod, cls_type = cls_type.rsplit('.', 1)
            mod = _.import_module(mod)
            cls_type = getattr(mod, cls_type)
        return cls_type


class TypeMixer(_.with_metaclass(TypeMixerMeta)):

    """ Generate objects by scheme. """

    factory = GenFactory

    FAKE = property(lambda s: Mixer.FAKE)
    MIX = property(lambda s: Mixer.MIX)
    RANDOM = property(lambda s: Mixer.RANDOM)
    SELECT = property(lambda s: Mixer.SELECT)
    SKIP = property(lambda s: Mixer.SKIP)

    def __init__(self, cls, mixer=None, factory=None, fake=True):
        self.middlewares = []
        self.__factory = factory or self.factory
        self.__fake = fake
        self.__gen_values = defaultdict(set)
        self.__fabrics = dict()
        self.__mixer = mixer
        self.__scheme = cls
        self.__fields = _.OrderedDict(self.__load_fields())

    def __repr__(self):
        return "<TypeMixer {0}>".format(self.__scheme)

    def blend(self, **values):
        """ Generate object.

        :param **values: Predefined fields
        :return value: a generated value

        """
        defaults = deepcopy(self.__fields)

        # Prepare relations
        for key, params in values.items():
            if '__' in key:
                name, value = key.split('__', 1)
                if name not in defaults:
                    defaults[name] = t.Field(None, name)
                defaults[name].params.update({value: params})
                continue
            defaults[key] = params

        values = dict(
            value.gen_value(self, name, value)
            if isinstance(value, t.ServiceValue)
            else self.get_value(name, value)
            for name, value in defaults.items()
        )

        # Parse MIX and SKIP values
        candidates = list(
            (name, value & values if isinstance(value, t.Mix) else value)
            for name, value in values.items()
            if value is not SKIP_VALUE
        )

        values = list()
        postprocess_values = list()
        for name, value in candidates:
            if isinstance(value, t._Deffered):
                postprocess_values.append((name, value))
            else:
                values.append((name, value))

        target = self.populate_target(values)

        # Run registered middlewares
        for middleware in self.middlewares:
            target = middleware(target)

        target = self.postprocess(target, postprocess_values)

        LOGGER.info('Blended: %s [%s]', target, self.__scheme) # noqa
        return target

    def postprocess(self, target, postprocess_values):
        """ Run the code after a generation. """
        if self.__mixer:
            target = self.__mixer.postprocess(target)

        for name, deffered in postprocess_values:
            setattr(target, name, deffered.value)

        return target

    def populate_target(self, values):
        """ Populate a target by values. """
        target = self.__scheme()
        for name, value in values:
            setattr(target, name, value)
        return target

    def get_value(self, name, value):
        """ Prepare value for field with name.

        :return : (name, value) or None

        """
        if isinstance(value, GeneratorType):
            return self.get_value(name, next(value))

        if isinstance(value, (FunctionType, MethodType, BuiltinFunctionType)):
            return self.get_value(name, value())

        return name, value

    def gen_field(self, field):
        """ Generate value by field.

        :param field: Instance of :class:`Field`

        :return : None or (name, value) for later usage

        """
        default = self.get_default(field)

        if default is not SKIP_VALUE:
            return self.get_value(field.name, default)

        if not self.is_required(field):
            return field.name, SKIP_VALUE

        unique = self.is_unique(field)
        return self.gen_value(field.name, field, unique=unique)

    def gen_random(self, field_name, random):
        """ Generate a random value for field with `field_name`.

        :param field_name: Name of field for generation.
        :param random: Instance of :class:`~mixer.main.Random`.

        :return : None or (name, value) for later use

        """
        if not random.scheme:
            random = deepcopy(self.__fields.get(field_name))

        elif not isinstance(random.scheme, type):
            return self.get_value(field_name, faker.random_element(random.choices))

        return self.gen_value(field_name, random, fake=False)

    gen_select = gen_random

    def gen_fake(self, field_name, fake):
        """ Generate a fake value for field with `field_name`.

        :param field_name: Name of field for generation.
        :param fake: Instance of :class:`~mixer.main.Fake`.

        :return : None or (name, value) for later use

        """
        if not fake.scheme:
            fake = deepcopy(self.__fields.get(field_name))

        return self.gen_value(field_name, fake, fake=True)

    def gen_value(self, field_name, field, fake=None, unique=False):
        """ Generate values from basic types.

        :return : (name, value) for later use

        """
        fake = self.__fake if fake is None else fake
        if not field:
            field = t.Field(getattr(self.__scheme, field_name, None), field_name)

        fab = self.get_fabric(field, field_name, fake=fake)

        try:
            value = fab()
        except ValueError:
            value = None
        except Exception as exc:
            LOGGER.exception(exc)
            raise ValueError("Generation for %s (%s) has been stopped. Exception: %s" % (
                field_name, self.__scheme.__name__, exc))

        if unique and value is not SKIP_VALUE:
            counter = 0
            try:
                while value in self.__gen_values[field_name]:
                    value = fab()
                    counter += 1
                    if counter > 100:
                        raise RuntimeError("Cannot generate a unique value for %s" % field_name)
                self.__gen_values[field_name].add(value)
            except TypeError:
                pass

        return self.get_value(field_name, value)

    def get_fabric(self, field, field_name=None, fake=None):
        """ Get an objects fabric for field and cache it.

        :param field: Field for looking a fabric
        :param field_name: Name of field for generation
        :param fake: Generate fake data instead of random data.

        :return function:

        """
        if fake is None:
            fake = self.__fake

        if field.params:
            return self.make_fabric(field.scheme, field_name, fake, kwargs=field.params)

        key = (field.scheme, field_name, fake)

        if key not in self.__fabrics:
            self.__fabrics[key] = self.make_fabric(field.scheme, field_name, fake)

        return self.__fabrics[key]

    def make_fabric(self, scheme, field_name=None, fake=None, kwargs=None): # noqa
        """ Make a fabric for scheme.

        :param field_class: Class for looking a fabric
        :param scheme: Scheme for generation
        :param fake: Generate fake data instead of random data.

        :return function:

        """
        kwargs = {} if kwargs is None else kwargs

        fab = self.__factory.get_fabric(scheme, field_name, fake)
        if not fab:
            return partial(type(self)(scheme, mixer=self.__mixer, fake=self.__fake,
                                      factory=self.__factory).blend, **kwargs)

        if kwargs:
            return partial(fab, **kwargs)

        return fab

    def register(self, field_name, func, fake=None):
        """ Register function as fabric for the field.

        :param field_name: Name of field for generation
        :param func: Function for data generation
        :param fake: Generate fake data instead of random data.

        ::

            class Scheme:
                id = str

            def func():
                return 'ID'

            mixer = TypeMixer(Scheme)
            mixer.register('id', func)

            test = mixer.blend()
            test.id == 'id'

        """
        if fake is None:
            fake = self.__fake

        field = self.__fields.get(field_name)
        if not field:
            return False

        key = (field.scheme, field_name, fake)
        self.__fabrics[key] = func

        if not isinstance(func, (FunctionType, MethodType)):
            self.__fabrics[key] = lambda: func

    @staticmethod
    def is_unique(field):
        """ Return True is field's value should be a unique.

        :return bool:

        """
        return False

    @staticmethod
    def is_required(field):
        """ Return True is field's value should be defined.

        :return bool:

        """
        return True

    @staticmethod
    def get_default(field):
        """ Return a default value for the field if it exists.

        :return value:

        """
        return SKIP_VALUE

    @staticmethod
    def guard(*args, **kwargs):
        """ Look in storage.

        :returns: False

        """
        return False

    def reload(self, obj):
        """ Reload the object from storage. """
        return deepcopy(obj)

    def __load_fields(self):
        """ Return scheme's fields. """
        for fname in dir(self.__scheme):
            if fname.startswith('_'):
                continue
            prop = getattr(self.__scheme, fname)
            yield fname, t.Field(prop, fname)


class ProxyMixer:

    """ A Mixer's proxy. Using for generate more than one object.

    ::

        mixer.cycle(5).blend(somemodel)

    """

    def __init__(self, mixer, count=5, guards=None):
        self.count = count
        self.mixer = mixer
        self.guards = guards

    def blend(self, scheme, **values):
        """ Call :meth:`Mixer.blend` a few times. And stack results to list.

        :returns: A list of generated objects.

        """
        result = []

        if self.guards:
            return self.mixer._guard(scheme, self.guards, **values) # noqa

        for _ in range(self.count):
            result.append(
                self.mixer.blend(scheme, **values)
            )
        return result

    def __getattr__(self, name):
        raise AttributeError('Use "cycle" only for "blend"')


# Support depricated attributes
class _MetaMixer(type):

    FAKE = property(lambda cls: t.Fake())
    MIX = property(lambda cls: t.Mix())
    RANDOM = property(lambda cls: t.Random())
    SELECT = property(lambda cls: t.Select())
    SKIP = property(lambda cls: SKIP_VALUE)


class Mixer(_.with_metaclass(_MetaMixer)):

    """ This class is using for integration to an application.

    :param fake: (True) Generate fake data instead of random data.
    :param factory: (:class:`~mixer.main.GenFactory`) Fabric's factory

    ::

        class SomeScheme:
            score = int
            name = str

        mixer = Mixer()
        instance = mixer.blend(SomeScheme)
        print instance.name  # Some like: 'Mike Douglass'

        mixer = Mixer(fake=False)
        instance = mixer.blend(SomeScheme)
        print instance.name  # Some like: 'AKJfdjh3'

    """

    # generator's controller class
    type_mixer_cls = TypeMixer

    def __init__(self, fake=True, factory=None, loglevel=LOGLEVEL,
                 silence=False, locale=faker.locale, **params):
        """Initialize the Mixer instance.

        :param fake: (True) Generate fake data instead of random data.
        :param loglevel: ('WARN') Set level for logging
        :param silence: (False) Don't raise any errors if creation was falsed
        :param factory: (:class:`~mixer.main.GenFactory`) A class for
                          generation values for types

        """
        self.params = params
        self.faker = faker
        self.__init_params__(fake=fake, loglevel=loglevel, silence=silence, locale=locale)
        self.__factory = factory or self.type_mixer_cls.factory

    def __getattr__(self, name):
        if name in ['f', 'g', 'fake', 'random', 'mix', 'select']:
            warnings.warn('"mixer.%s" is depricated, use "mixer.%s" instead.'
                          % (name, name.upper()), stacklevel=2)
            name = name.upper()
            return getattr(self, name)
        raise AttributeError("Attribute %s not found." % name)

    @property
    def SKIP(self, *args, **kwargs):
        """ Do not generate a field.

        ::
            # Don't generate field 'somefield'
            mixer.blend(SomeScheme, somefield=mixer.skip)

        :returns: SKIP_VALUE

        """
        return SKIP_VALUE

    @property
    def FAKE(self, *args, **kwargs):
        """ Force generation of fake values. See :class:`~mixer.main.Fake`.

        :returns: Fake object

        """
        return self.__class__.FAKE

    @property
    def RANDOM(self, *args, **kwargs):
        """ Force generation of random values. See :class:`~mixer.main.Random`.

        :returns: Random object

        """
        return self.__class__.RANDOM

    @property
    def SELECT(self, *args, **kwargs):
        """ Select data from a storage. See :class:`~mixer.main.Select`.

        :returns: Select object

        """
        return self.__class__.SELECT

    @property
    def MIX(self, *args, **kwargs):
        """ Point to mixed object from future. See :class:`~mixer.main.Mix`.

        :returns: Mix object

        """
        return self.__class__.MIX

    def __init_params__(self, locale=None, **params):
        self.params.update(params)
        if locale:
            faker.locale = locale
            self.params['locale'] = faker.locale
        LOGGER.setLevel(self.params.get('loglevel'))

    def __repr__(self):
        return "<Mixer [{0}]>".format(
            'fake' if self.params.get('fake') else 'rand')

    def blend(self, scheme, **values):
        """Generate instance of `scheme`.

        :param scheme: Scheme class for generation or string with class path.
        :param values: Keyword params with predefined values
        :return value: A generated instance

        ::

            mixer = Mixer()

            mixer.blend(SomeScheme, active=True)
            print scheme.active  # True

            mixer.blend('module.SomeScheme', active=True)
            print scheme.active  # True

        """
        type_mixer = self.get_typemixer(scheme)
        try:
            return type_mixer.blend(**values)
        except Exception as e:
            if self.params.get('silence'):
                return None
            if e.args:
                e.args = ('Mixer (%s): %s' % (scheme, e.args[0]),) + e.args[1:]
            LOGGER.error(traceback.format_exc())
            raise

    def get_typemixer(self, scheme):
        """ Return a cached typemixer instance.

        :return TypeMixer:

        """
        return self.type_mixer_cls(
            scheme, mixer=self,
            fake=self.params.get('fake'), factory=self.__factory)

    @staticmethod
    def postprocess(target):
        """ Run the code after generation.

        :return target:

        """
        return target

    @staticmethod # noqa
    def sequence(*args):
        """ Create a sequence for predefined values.

        It makes a infinity loop with given function where does increment the
        counter on each iteration.

        :param args: If method get more one arguments, them make generator
                      from arguments (loop on arguments). If that get one
                      argument and this equal a function, method makes
                      a generator from them. If argument is equal string it
                      should be using as format string.

                      By default function is equal 'lambda x: x'.

        :returns: A generator

        Mixer can uses a generators.
        ::

            gen = (name for name in ['test0', 'test1', 'test2'])
            for counter in range(3):
                mixer.blend(Scheme, name=gen)

        Mixer.sequence is a helper for create generators more easy.

        Generate values from sequence:
        ::

            for _ in range(3):
                mixer.blend(Scheme, name=mixer.sequence('john', 'mike'))


        Make a generator from function:
        ::

            for counter in range(3):
                mixer.blend(Scheme, name=mixer.sequence(
                    lambda c: 'test%s' % c
                ))


        Short format is a python formating string
        ::

            for counter in range(3):
                mixer.blend(Scheme, name=mixer.sequence('test{0}'))

        """
        if len(args) > 1:
            def gen():
                while True:
                    for o in args:
                        yield o
            return gen()

        func = args and args[0] or None
        if isinstance(func, _.string_types):
            func = func.format

        elif func is None:
            func = lambda x: x

        def gen2():
            counter = 0
            while True:
                yield func(counter)
                counter += 1
        return gen2()

    def cycle(self, count=5):
        """ Generate a few objects. The syntastic sugar for cycles.

        :param count: List of objects or integer.
        :returns: ProxyMixer

        ::

            users = mixer.cycle(5).blend('somemodule.User')

            profiles = mixer.cycle(5).blend(
                'somemodule.Profile', user=(user for user in users)

            apples = mixer.cycle(10).blend(
                Apple, title=mixer.sequence('apple_{0}')

        """
        return ProxyMixer(self, count)

    def middleware(self, scheme):
        """ Middleware decorator.

        You could add the middleware layers to generation process: ::

            from mixer.backend.django import mixer

            # Register middleware to model
            @mixer.middleware('auth.user')
            def encrypt_password(user):
                user.set_password('test')
                return user


        You can add several middlewares.
        Each middleware should get one argument (generated value) and return
        them.

        """
        type_mixer = self.type_mixer_cls(
            scheme, mixer=self, fake=self.params.get('fake'),
            factory=self.__factory)

        def wrapper(middleware):
            type_mixer.middlewares.append(middleware)
            return middleware

        return wrapper

    def unregister_middleware(self, scheme, middleware):
        """Remove middleware from scheme
        """
        type_mixer = self.type_mixer_cls(
            scheme, mixer=self, fake=self.params.get('fake'),
            factory=self.__factory)
        type_mixer.middlewares.remove(middleware)

    def register(self, scheme, **params):
        """ Manualy register a function as value's generator for class.field.

        :param scheme: Scheme for generation (class or class path)
        :param params: Kwargs with generator's definitions (field_name=field_generator)

        ::

            class Scheme:
                id = str
                title = str

            def func():
                return 'ID'

            mixer.register(
                Scheme,
                id=func,
                title='Always same',
            )

            test = mixer.blend(Scheme)
            test.id == 'ID'
            test.title == 'Always same'

        """
        fake = self.params.get('fake')
        type_mixer = self.type_mixer_cls(
            scheme, mixer=self, fake=fake, factory=self.__factory)

        for field_name, func in params.items():
            type_mixer.register(field_name, func, fake=fake)

            # Double register for RANDOM
            if fake:
                type_mixer.register(field_name, func, fake=False)

    @contextmanager
    def ctx(self, **params):
        """ Redifine params for current mixer as context.

        ::

            with mixer.ctx(commit=False):
                hole = mixer.blend(Hole)
                self.assertTrue(hole)
                self.assertFalse(Hole.objects.count())

        """
        _params = dict((k, v) for k, v in self.params.items() if k in params)
        _params['locale'] = self.faker.locale

        try:
            self.__init_params__(**params)
            yield self
        finally:
            self.__init_params__(**_params)

    def reload(self, *objs):
        """ Reload the objects from storage. """
        results = []
        for obj in objs:
            scheme = type(obj)
            tm = self.get_typemixer(scheme)
            results.append(tm.reload(obj))

        return results if len(results) > 1 else results[0]

    def guard(self, *args, **kwargs):
        """ Abstract method. In some backends used for prevent object creation.

        :returns: A Proxy to mixer

        """
        return ProxyMixer(self, count=1, guards=(args, kwargs))

    def _guard(self, scheme, guards, **values):
        type_mixer = self.get_typemixer(scheme)
        args, kwargs = guards
        seek = type_mixer.guard(*args, **kwargs)
        if seek:
            LOGGER.info('Finded: %s [%s]', seek, type(seek)) # noqa
            return seek

        return self.blend(scheme, **values)


# Default mixer
mixer = Mixer()

# pylama:ignore=E1120