from functools import partial

from django.db.models.query import QuerySet

from promise import Promise
from neomodel import NodeSet

from graphene.types import Field, List
from graphene.types.scalars import Boolean, Int
from graphene.relay import ConnectionField, PageInfo
from graphql_relay.connection.arrayconnection import connection_from_list_slice

from .settings import graphene_settings
from .utils import maybe_queryset, is_parent_set


class DjangoListField(Field):
    def __init__(self, _type, *args, **kwargs):
        super(DjangoListField, self).__init__(List(_type), *args, **kwargs)

    @property
    def model(self):
        return self.type.of_type._meta.node._meta.model

    @staticmethod
    def list_resolver(resolver, root, info, **args):
        return maybe_queryset(resolver(root, info, **args))

    def get_resolver(self, parent_resolver):
        return partial(self.list_resolver, parent_resolver)


class DjangoConnectionField(ConnectionField):
    def __init__(self, *args, **kwargs):
        self.on = "nodes"
        self.max_limit = kwargs.pop(
            "max_limit", graphene_settings.RELAY_CONNECTION_MAX_LIMIT
        )
        self.enforce_first_or_last = kwargs.pop(
            "enforce_first_or_last",
            graphene_settings.RELAY_CONNECTION_ENFORCE_FIRST_OR_LAST,
        )
        kwargs.setdefault('know_parent', Boolean(default_value=False,
                                                 description='Know parent type in nodes?'
                                                 ' \n Default = <False>'))
        kwargs['first'] = Int(default_value=100)
        super(DjangoConnectionField, self).__init__(*args, **kwargs)

    @property
    def type(self):
        from .types import DjangoObjectType

        _type = super(ConnectionField, self).type
        assert issubclass(
            _type, DjangoObjectType
        ), "DjangoConnectionField only accepts DjangoObjectType types"
        assert _type._meta.connection, "The type {} doesn't have a connection".format(
            _type.__name__
        )
        return _type._meta.connection

    @property
    def node_type(self):
        return self.type._meta.node

    @property
    def model(self):
        return self.node_type._meta.model

    def get_manager(self):
        if self.on:
            return getattr(self.model, self.on)
        else:
            return self.model._default_manager

    @classmethod
    def merge_querysets(cls, default_queryset, queryset):
        if default_queryset.query.distinct and not queryset.query.distinct:
            queryset = queryset.distinct()
        elif queryset.query.distinct and not default_queryset.query.distinct:
            default_queryset = default_queryset.distinct()
        return queryset & default_queryset

    @classmethod
    def resolve_connection(cls, connection, default_manager, args, iterable):
        if iterable is None:
            iterable = default_manager
        iterable = maybe_queryset(iterable)
        _len = len(iterable)
        connection = connection_from_list_slice(
            iterable,
            args,
            slice_start=0,
            list_length=_len,
            list_slice_length=_len,
            connection_type=connection,
            edge_type=connection.Edge,
            pageinfo_type=PageInfo,
        )
        connection.iterable = iterable
        connection.length = _len
        return connection

    @classmethod
    def connection_resolver_original(
        cls,
        resolver,
        connection,
        default_manager,
        max_limit,
        enforce_first_or_last,
        root,
        info,
        **args
    ):
        first = args.get("first")
        last = args.get("last")

        if enforce_first_or_last:
            assert first or last, (
                "You must provide a `first` or `last` value to properly paginate the `{}` connection."
            ).format(info.field_name)

        if max_limit:
            if first:
                assert first <= max_limit, (
                    "Requesting {} records on the `{}` connection exceeds the `first` limit of {} records."
                ).format(first, info.field_name, max_limit)
                args["first"] = min(first, max_limit)

            if last:
                assert last <= max_limit, (
                    "Requesting {} records on the `{}` connection exceeds the `last` limit of {} records."
                ).format(last, info.field_name, max_limit)
                args["last"] = min(last, max_limit)

        iterable = resolver(root, info, **args)
        on_resolve = partial(cls.resolve_connection, connection, default_manager, args)

        if Promise.is_thenable(iterable):
            return Promise.resolve(iterable).then(on_resolve)

        return on_resolve(iterable)

    @classmethod
    def connection_resolver(
        cls,
        resolver,
        connection,
        default_manager,
        max_limit,
        enforce_first_or_last,
        root,
        info,
        **args
    ):
        _parent = is_parent_set(info)

        if not _parent:
            _parent = args.get('know_parent', False)

        def new_resolver(root, info, **kwargs):
            qs = resolver(root, info, **kwargs)
            if qs is None:
                qs = default_manager.filter()
            if _parent and root is not None:
                instances = []
                for instance in qs:
                    setattr(instance, '_parent', root)
                    instances.append(instance)
                return instances
            return qs

        return cls.connection_resolver_original(
            new_resolver,
            connection,
            default_manager,
            max_limit,
            enforce_first_or_last,
            root,
            info,
            **args)

    def get_resolver(self, parent_resolver):
        return partial(
            self.connection_resolver,
            parent_resolver,
            self.type,
            self.get_manager(),
            self.max_limit,
            self.enforce_first_or_last,
        )