from collections import OrderedDict

import six

from django.utils.functional import SimpleLazyObject
from graphene import Field
from graphene.relay import Connection, Node
from graphene.types.objecttype import ObjectType, ObjectTypeOptions
from graphene.types.utils import yank_fields_from_attrs

from .converter import convert_django_field_with_choices
from .registry import Registry, get_global_registry
from .utils import (DJANGO_FILTER_INSTALLED, get_model_fields,
                    is_valid_django_model)


def construct_fields(model, registry, only_fields, exclude_fields):
    _model_fields = get_model_fields(model)

    fields = OrderedDict()
    for name, field in _model_fields:
        is_not_in_only = only_fields and name not in only_fields
        # is_already_created = name in options.fields
        is_excluded = name in exclude_fields # or is_already_created
        # https://docs.djangoproject.com/en/1.10/ref/models/fields/#django.db.models.ForeignKey.related_query_name
        is_no_backref = str(name).endswith('+')
        if is_not_in_only or is_excluded or is_no_backref:
            # We skip this field if we specify only_fields and is not
            # in there. Or when we exclude this field in exclude_fields.
            # Or when there is no back reference.
            continue
        converted = convert_django_field_with_choices(field, registry)
        fields[name] = converted

    return fields


class DjangoObjectTypeOptions(ObjectTypeOptions):
    model = None  # type: Model
    registry = None  # type: Registry
    connection = None  # type: Type[Connection]

    filter_fields = ()


class DjangoObjectType(ObjectType):
    @classmethod
    def __init_subclass_with_meta__(cls, model=None, registry=None, skip_registry=False,
        only_fields=(), exclude_fields=(), filter_fields=None, connection=None, use_connection=None, interfaces=(), **options):
        assert is_valid_django_model(model), (
            'You need to pass a valid Django Model in {}.Meta, received "{}".'
        ).format(cls.__name__, model)

        if not registry:
            registry = get_global_registry()

        assert isinstance(registry, Registry), (
            'The attribute registry in {} needs to be an instance of '
            'Registry, received "{}".'
        ).format(cls.__name__, registry)

        if not DJANGO_FILTER_INSTALLED and filter_fields:
            raise Exception("Can only set filter_fields if Django-Filter is installed")

        django_fields = yank_fields_from_attrs(
            construct_fields(model, registry, only_fields, exclude_fields),
            _as=Field,
        )

        if use_connection is None and interfaces:
            use_connection = any((issubclass(interface, Node) for interface in interfaces))

        if use_connection and not connection:
            # We create the connection automatically
            connection = Connection.create_type('{}Connection'.format(cls.__name__), node=cls)

        if connection is not None:
            assert issubclass(connection, Connection), "The connection must be a Connection. Received {}".format(connection.__name__)

        _meta = DjangoObjectTypeOptions(cls)
        _meta.model = model
        _meta.registry = registry
        _meta.filter_fields = filter_fields
        _meta.fields = django_fields
        _meta.connection = connection

        super(DjangoObjectType, cls).__init_subclass_with_meta__(_meta=_meta, interfaces=interfaces, **options)
            
        if not skip_registry:
            registry.register(cls)

    def resolve_id(self):
        return self.pk

    @classmethod
    def is_type_of(cls, root, context, info):
        if isinstance(root, SimpleLazyObject):
            root._setup()
            root = root._wrapped
        if isinstance(root, cls):
            return True
        if not is_valid_django_model(type(root)):
            raise Exception((
                'Received incompatible instance "{}".'
            ).format(root))
        model = root._meta.model
        return model == cls._meta.model

    @classmethod
    def get_node(cls, id, context, info):
        try:
            return cls._meta.model.objects.get(pk=id)
        except cls._meta.model.DoesNotExist:
            return None