# -*- coding: utf-8 -*-
from __future__ import unicode_literals

from itertools import chain
import types

from django.apps import apps

from . import Error, register


@register('models')
def check_all_models(app_configs=None, **kwargs):
    errors = [model.check(**kwargs)
        for model in apps.get_models()
        if app_configs is None or model._meta.app_config in app_configs]
    return list(chain(*errors))


@register('models', 'signals')
def check_model_signals(app_configs=None, **kwargs):
    """Ensure lazily referenced model signals senders are installed."""
    from django.db import models
    errors = []

    for name in dir(models.signals):
        obj = getattr(models.signals, name)
        if isinstance(obj, models.signals.ModelSignal):
            for reference, receivers in obj.unresolved_references.items():
                for receiver, _, _ in receivers:
                    # The receiver is either a function or an instance of class
                    # defining a `__call__` method.
                    if isinstance(receiver, types.FunctionType):
                        description = "The '%s' function" % receiver.__name__
                    else:
                        description = "An instance of the '%s' class" % receiver.__class__.__name__
                    errors.append(
                        Error(
                            "%s was connected to the '%s' signal "
                            "with a lazy reference to the '%s' sender, "
                            "which has not been installed." % (
                                description, name, '.'.join(reference)
                            ),
                            obj=receiver.__module__,
                            hint=None,
                            id='signals.E001'
                        )
                    )
    return errors