from _weakref import CallableProxyType
from typing import (  # noqa: I100, I201
    TYPE_CHECKING,
    Any,
    AsyncGenerator,
    Generic,
    MutableSequence,
    Optional,
    Sequence,
    TypeVar,
    Union,
    cast,
)

import ormar  # noqa: I100, I202
from ormar.exceptions import ModelPersistenceError, NoMatch, QueryDefinitionError

if TYPE_CHECKING:  # pragma no cover
    from ormar import OrderAction, RelationType
    from ormar.models import Model, T
    from ormar.queryset import QuerySet
    from ormar.relations import Relation
else:
    T = TypeVar("T", bound="Model")


class QuerysetProxy(Generic[T]):
    """
    Exposes QuerySet methods on relations, but also handles creating and removing
    of through Models for m2m relations.
    """

    if TYPE_CHECKING:  # pragma no cover
        relation: "Relation"

    def __init__(
        self,
        relation: "Relation",
        to: type["T"],
        type_: "RelationType",
        qryset: Optional["QuerySet[T]"] = None,
    ) -> None:
        self.relation: "Relation" = relation
        self._queryset: Optional["QuerySet[T]"] = qryset
        self.type_: "RelationType" = type_
        self._owner: Union[CallableProxyType, "Model"] = self.relation.manager.owner
        self.related_field_name = self._owner.ormar_config.model_fields[
            self.relation.field_name
        ].get_related_name()
        self.to: type[T] = to
        self.related_field = to.ormar_config.model_fields[self.related_field_name]
        self.owner_pk_value = self._owner.pk
        self.through_model_name = (
            self.related_field.through.get_name()
            if self.type_ == ormar.RelationType.MULTIPLE
            else ""
        )

    @property
    def queryset(self) -> "QuerySet[T]":
        """
        Returns queryset if it's set, AttributeError otherwise.
        :return: QuerySet
        :rtype: QuerySet
        """
        if not self._queryset:
            raise AttributeError
        return self._queryset

    @queryset.setter
    def queryset(self, value: "QuerySet") -> None:
        """
        set's the queryset. Initialized in RelationProxy.
        :param value: QuerySet
        :type value: QuerySet
        """
        self._queryset = value

    def _assign_child_to_parent(self, child: Optional["T"]) -> None:
        """
        Registers child in parents RelationManager.

        :param child: child to register on parent side.
        :type child: Model
        """
        if child:
            owner = self._owner
            rel_name = self.relation.field_name
            setattr(owner, rel_name, child)

    def _register_related(self, child: Union["T", Sequence[Optional["T"]]]) -> None:
        """
        Registers child/ children in parents RelationManager.

        :param child: child or list of children models to register.
        :type child: Union[Model,list[Model]]
        """
        if isinstance(child, list):
            for subchild in child:
                self._assign_child_to_parent(subchild)
        else:
            assert isinstance(child, ormar.Model)
            child = cast("T", child)
            self._assign_child_to_parent(child)

    def _clean_items_on_load(self) -> None:
        """
        Cleans the current list of the related models.
        """
        if isinstance(self.relation.related_models, MutableSequence):
            for item in self.relation.related_models[:]:
                self.relation.remove(item)

    async def create_through_instance(self, child: "T", **kwargs: Any) -> None:
        """
        Crete a through model instance in the database for m2m relations.

        :param kwargs: dict of additional keyword arguments for through instance
        :type kwargs: Any
        :param child: child model instance
        :type child: Model
        """
        model_cls = self.relation.through
        owner_column = self.related_field.default_target_field_name()  # type: ignore
        child_column = self.related_field.default_source_field_name()  # type: ignore
        rel_kwargs = {owner_column: self._owner.pk, child_column: child.pk}
        final_kwargs = {**rel_kwargs, **kwargs}
        if child.pk is None:
            raise ModelPersistenceError(
                f"You cannot save {child.get_name()} "
                f"model without primary key set! \n"
                f"Save the child model first."
            )
        await model_cls(**final_kwargs).save()

    async def update_through_instance(self, child: "T", **kwargs: Any) -> None:
        """
        Updates a through model instance in the database for m2m relations.

        :param kwargs: dict of additional keyword arguments for through instance
        :type kwargs: Any
        :param child: child model instance
        :type child: Model
        """
        model_cls = self.relation.through
        owner_column = self.related_field.default_target_field_name()  # type: ignore
        child_column = self.related_field.default_source_field_name()  # type: ignore
        rel_kwargs = {owner_column: self._owner.pk, child_column: child.pk}
        through_model = await model_cls.objects.get(**rel_kwargs)
        await through_model.update(**kwargs)

    async def upsert_through_instance(self, child: "T", **kwargs: Any) -> None:
        """
        Updates a through model instance in the database for m2m relations if
        it already exists, else creates one.

        :param kwargs: dict of additional keyword arguments for through instance
        :type kwargs: Any
        :param child: child model instance
        :type child: Model
        """
        try:
            await self.update_through_instance(child=child, **kwargs)
        except NoMatch:
            await self.create_through_instance(child=child, **kwargs)

    async def delete_through_instance(self, child: "T") -> None:
        """
        Removes through model instance from the database for m2m relations.

        :param child: child model instance
        :type child: Model
        """
        queryset = ormar.QuerySet(model_cls=self.relation.through)  # type: ignore
        owner_column = self.related_field.default_target_field_name()  # type: ignore
        child_column = self.related_field.default_source_field_name()  # type: ignore
        kwargs = {owner_column: self._owner, child_column: child}
        link_instance = await queryset.filter(**kwargs).get()  # type: ignore
        await link_instance.delete()

    async def exists(self) -> bool:
        """
        Returns a bool value to confirm if there are rows matching the given criteria
        (applied with `filter` and `exclude` if set).

        Actual call delegated to QuerySet.

        :return: result of the check
        :rtype: bool
        """
        return await self.queryset.exists()

    async def count(self, distinct: bool = True) -> int:
        """
        Returns number of rows matching the given criteria
        (applied with `filter` and `exclude` if set before).
        If `distinct` is `True` (the default), this will return
        the number of primary rows selected. If `False`,
        the count will be the total number of rows returned
        (including extra rows for `one-to-many` or `many-to-many`
        left `select_related` table joins).
        `False` is the legacy (buggy) behavior for workflows that depend on it.

        Actual call delegated to QuerySet.

        :param distinct: flag if the primary table rows should be distinct or not
        :return: number of rows
        :rtype: int
        """
        return await self.queryset.count(distinct=distinct)

    async def max(self, columns: Union[str, list[str]]) -> Any:  # noqa: A003
        """
        Returns max value of columns for rows matching the given criteria
        (applied with `filter` and `exclude` if set before).

        :return: max value of column(s)
        :rtype: Any
        """
        return await self.queryset.max(columns=columns)

    async def min(self, columns: Union[str, list[str]]) -> Any:  # noqa: A003
        """
        Returns min value of columns for rows matching the given criteria
        (applied with `filter` and `exclude` if set before).

        :return: min value of column(s)
        :rtype: Any
        """
        return await self.queryset.min(columns=columns)

    async def sum(self, columns: Union[str, list[str]]) -> Any:  # noqa: A003
        """
        Returns sum value of columns for rows matching the given criteria
        (applied with `filter` and `exclude` if set before).

        :return: sum value of columns
        :rtype: int
        """
        return await self.queryset.sum(columns=columns)

    async def avg(self, columns: Union[str, list[str]]) -> Any:
        """
        Returns avg value of columns for rows matching the given criteria
        (applied with `filter` and `exclude` if set before).

        :return: avg value of columns
        :rtype: Union[int, float, list]
        """
        return await self.queryset.avg(columns=columns)

    async def clear(self, keep_reversed: bool = True) -> int:
        """
        Removes all related models from given relation.

        Removes all through models for m2m relation.

        For reverse FK relations keep_reversed flag marks if the reversed models
        should be kept or deleted from the database too (False means that models
        will be deleted, and not only removed from relation).

        :param keep_reversed: flag if reverse models in reverse FK should be deleted
        or not, keep_reversed=False deletes them from database.
        :type keep_reversed: bool
        :return: number of deleted models
        :rtype: int
        """
        if self.type_ == ormar.RelationType.MULTIPLE:
            queryset = ormar.QuerySet(model_cls=self.relation.through)  # type: ignore
            owner_column = self._owner.get_name()
        else:
            queryset = ormar.QuerySet(model_cls=self.relation.to)  # type: ignore
            owner_column = self.related_field_name
        kwargs = {owner_column: self._owner}
        self._clean_items_on_load()
        if keep_reversed and self.type_ == ormar.RelationType.REVERSE:
            update_kwrgs = {f"{owner_column}": None}
            return await queryset.filter(_exclude=False, **kwargs).update(
                each=False, **update_kwrgs
            )
        return await queryset.delete(**kwargs)  # type: ignore

    async def values(
        self,
        fields: Union[list, str, set, dict, None] = None,
        exclude_through: bool = False,
    ) -> list:
        """
        Return a list of dictionaries with column values in order of the fields
        passed or all fields from queried models.

        To filter for given row use filter/exclude methods before values,
        to limit number of rows use limit/offset or paginate before values.

        Note that it always return a list even for one row from database.

        :param exclude_through: flag if through models should be excluded
        :type exclude_through: bool
        :param fields: field name or list of field names to extract from db
        :type fields:  Union[list, str, set, dict]
        """
        return await self.queryset.values(
            fields=fields, exclude_through=exclude_through
        )

    async def values_list(
        self,
        fields: Union[list, str, set, dict, None] = None,
        flatten: bool = False,
        exclude_through: bool = False,
    ) -> list:
        """
        Return a list of tuples with column values in order of the fields passed or
        all fields from queried models.

        When one field is passed you can flatten the list of tuples into list of values
        of that single field.

        To filter for given row use filter/exclude methods before values,
        to limit number of rows use limit/offset or paginate before values.

        Note that it always return a list even for one row from database.

        :param exclude_through: flag if through models should be excluded
        :type exclude_through: bool
        :param fields: field name or list of field names to extract from db
        :type fields: Union[str, list[str]]
        :param flatten: when one field is passed you can flatten the list of tuples
        :type flatten: bool
        """
        return await self.queryset.values(
            fields=fields,
            exclude_through=exclude_through,
            _as_dict=False,
            _flatten=flatten,
        )

    async def first(self, *args: Any, **kwargs: Any) -> "T":
        """
        Gets the first row from the db ordered by primary key column ascending.

        Actual call delegated to QuerySet.

        Passing args and/or kwargs is a shortcut and equals to calling
        `filter(*args, **kwargs).first()`.

        List of related models is cleared before the call.

        :param kwargs:
        :type kwargs:
        :return:
        :rtype: _asyncio.Future
        """
        first = await self.queryset.first(*args, **kwargs)
        self._clean_items_on_load()
        self._register_related(first)
        return first

    async def get_or_none(self, *args: Any, **kwargs: Any) -> Optional["T"]:
        """
        Gets the first row from the db meeting the criteria set by kwargs.

        If no criteria set it will return the last row in db sorted by pk.

        Passing args and/or kwargs is a shortcut and equals to calling
        `filter(*args, **kwargs).get_or_none()`.

        If not match is found None will be returned.

        :param kwargs: fields names and proper value types
        :type kwargs: Any
        :return: returned model
        :rtype: Model
        """
        try:
            get = await self.queryset.get(*args, **kwargs)
        except ormar.NoMatch:
            return None

        self._clean_items_on_load()
        self._register_related(get)
        return get

    async def get(self, *args: Any, **kwargs: Any) -> "T":
        """
        Gets the first row from the db meeting the criteria set by kwargs.

        If no criteria set it will return the last row in db sorted by pk.

        Passing args and/or kwargs is a shortcut and equals to calling
        `filter(*args, **kwargs).get()`.

        Actual call delegated to QuerySet.

        List of related models is cleared before the call.

        :raises NoMatch: if no rows are returned
        :raises MultipleMatches: if more than 1 row is returned.
        :param kwargs: fields names and proper value types
        :type kwargs: Any
        :return: returned model
        :rtype: Model
        """
        get = await self.queryset.get(*args, **kwargs)
        self._clean_items_on_load()
        self._register_related(get)
        return get

    async def all(self, *args: Any, **kwargs: Any) -> list["T"]:  # noqa: A003
        """
        Returns all rows from a database for given model for set filter options.

        Passing args and/or kwargs is a shortcut and equals to calling
        `filter(*args, **kwargs).all()`.

        If there are no rows meeting the criteria an empty list is returned.

        Actual call delegated to QuerySet.

        List of related models is cleared before the call.

        :param kwargs: fields names and proper value types
        :type kwargs: Any
        :return: list of returned models
        :rtype: list[Model]
        """
        all_items = await self.queryset.all(*args, **kwargs)
        self._clean_items_on_load()
        self._register_related(all_items)
        return all_items

    async def iterate(  # noqa: A003
        self,
        *args: Any,
        **kwargs: Any,
    ) -> AsyncGenerator["T", None]:
        """
        Return async iterable generator for all rows from a database for given model.

        Passing args and/or kwargs is a shortcut and equals to calling
        `filter(*args, **kwargs).iterate()`.

        If there are no rows meeting the criteria an empty async generator is returned.

        :param kwargs: fields names and proper value types
        :type kwargs: Any
        :return: asynchronous iterable generator of returned models
        :rtype: AsyncGenerator[Model]
        """

        async for item in self.queryset.iterate(*args, **kwargs):
            yield item

    async def create(self, **kwargs: Any) -> "T":
        """
        Creates the model instance, saves it in a database and returns the updates model
        (with pk populated if not passed and autoincrement is set).

        The allowed kwargs are `Model` fields names and proper value types.

        For m2m relation the through model is created automatically.

        Actual call delegated to QuerySet.

        :param kwargs: fields names and proper value types
        :type kwargs: Any
        :return: created model
        :rtype: Model
        """
        through_kwargs = kwargs.pop(self.through_model_name, {})
        if self.type_ == ormar.RelationType.REVERSE:
            kwargs[self.related_field_name] = self._owner
        created = await self.queryset.create(**kwargs)
        self._register_related(created)
        if self.type_ == ormar.RelationType.MULTIPLE:
            await self.create_through_instance(created, **through_kwargs)
        return created

    async def update(self, each: bool = False, **kwargs: Any) -> int:
        """
        Updates the model table after applying the filters from kwargs.

        You have to either pass a filter to narrow down a query or explicitly pass
        each=True flag to affect whole table.

        :param each: flag if whole table should be affected if no filter is passed
        :type each: bool
        :param kwargs: fields names and proper value types
        :type kwargs: Any
        :return: number of updated rows
        :rtype: int
        """
        # queryset proxy always have one filter for pk of parent model
        if (
            not each
            and (len(self.queryset.filter_clauses) + len(self.queryset.exclude_clauses))
            == 1
        ):
            raise QueryDefinitionError(
                "You cannot update without filtering the queryset first. "
                "If you want to update all rows use update(each=True, **kwargs)"
            )

        through_kwargs = kwargs.pop(self.through_model_name, {})
        children = await self.queryset.all()
        for child in children:
            await child.update(**kwargs)  # type: ignore
            if self.type_ == ormar.RelationType.MULTIPLE and through_kwargs:
                await self.update_through_instance(
                    child=child,
                    **through_kwargs,  # type: ignore
                )
        return len(children)

    async def get_or_create(
        self,
        _defaults: Optional[dict[str, Any]] = None,
        *args: Any,
        **kwargs: Any,
    ) -> tuple["T", bool]:
        """
        Combination of create and get methods.

        Tries to get a row meeting the criteria for kwargs
        and if `NoMatch` exception is raised
        it creates a new one with given kwargs and _defaults.

        :param kwargs: fields names and proper value types
        :type kwargs: Any
        :param _defaults: default values for creating object
        :type _defaults: Optional[dict[str, Any]]
        :return: model instance and a boolean
        :rtype: tuple("T", bool)
        """
        try:
            return await self.get(*args, **kwargs), False
        except NoMatch:
            _defaults = _defaults or {}
            return await self.create(**{**kwargs, **_defaults}), True

    async def update_or_create(self, **kwargs: Any) -> "T":
        """
        Updates the model, or in case there is no match in database creates a new one.

        Actual call delegated to QuerySet.

        :param kwargs: fields names and proper value types
        :type kwargs: Any
        :return: updated or created model
        :rtype: Model
        """
        pk_name = self.queryset.model_config.pkname
        if "pk" in kwargs:
            kwargs[pk_name] = kwargs.pop("pk")
        if pk_name not in kwargs or kwargs.get(pk_name) is None:
            return await self.create(**kwargs)
        model = await self.queryset.get(pk=kwargs[pk_name])
        return await model.update(**kwargs)

    def filter(  # noqa: A003, A001
        self, *args: Any, **kwargs: Any
    ) -> "QuerysetProxy[T]":
        """
        Allows you to filter by any `Model` attribute/field
        as well as to fetch instances, with a filter across an FK relationship.

        You can use special filter suffix to change the filter operands:

        *  exact - like `album__name__exact='Malibu'` (exact match)
        *  iexact - like `album__name__iexact='malibu'` (exact match case insensitive)
        *  contains - like `album__name__contains='Mal'` (sql like)
        *  icontains - like `album__name__icontains='mal'` (sql like case insensitive)
        *  in - like `album__name__in=['Malibu', 'Barclay']` (sql in)
        *  isnull - like `album__name__isnull=True` (sql is null)
           (isnotnull `album__name__isnull=False` (sql is not null))
        *  gt - like `position__gt=3` (sql >)
        *  gte - like `position__gte=3` (sql >=)
        *  lt - like `position__lt=3` (sql <)
        *  lte - like `position__lte=3` (sql <=)
        *  startswith - like `album__name__startswith='Mal'` (exact start match)
        *  istartswith - like `album__name__istartswith='mal'` (case insensitive)
        *  endswith - like `album__name__endswith='ibu'` (exact end match)
        *  iendswith - like `album__name__iendswith='IBU'` (case insensitive)

        Actual call delegated to QuerySet.

        :param kwargs: fields names and proper value types
        :type kwargs: Any
        :return: filtered QuerysetProxy
        :rtype: QuerysetProxy
        """
        queryset = self.queryset.filter(*args, **kwargs)
        return self.__class__(
            relation=self.relation, type_=self.type_, to=self.to, qryset=queryset
        )

    def exclude(self, *args: Any, **kwargs: Any) -> "QuerysetProxy[T]":  # noqa: A003, A001
        """
        Works exactly the same as filter and all modifiers (suffixes) are the same,
        but returns a *not* condition.

        So if you use `filter(name='John')` which is `where name = 'John'` in SQL,
        the `exclude(name='John')` equals to `where name <> 'John'`

        Note that all conditions are joined so if you pass multiple values it
        becomes a union of conditions.

        `exclude(name='John', age>=35)` will become
        `where not (name='John' and age>=35)`

        Actual call delegated to QuerySet.

        :param kwargs: fields names and proper value types
        :type kwargs: Any
        :return: filtered QuerysetProxy
        :rtype: QuerysetProxy
        """
        queryset = self.queryset.exclude(*args, **kwargs)
        return self.__class__(
            relation=self.relation, type_=self.type_, to=self.to, qryset=queryset
        )

    def select_all(self, follow: bool = False) -> "QuerysetProxy[T]":
        """
        By default adds only directly related models.

        If follow=True is set it adds also related models of related models.

        To not get stuck in an infinite loop as related models also keep a relation
        to parent model visited models set is kept.

        That way already visited models that are nested are loaded, but the load do not
        follow them inside. So Model A -> Model B -> Model C -> Model A -> Model X
        will load second Model A but will never follow into Model X.
        Nested relations of those kind need to be loaded manually.

        :param follow: flag to trigger deep save -
        by default only directly related models are saved
        with follow=True also related models of related models are saved
        :type follow: bool
        :return: reloaded Model
        :rtype: Model
        """
        queryset = self.queryset.select_all(follow=follow)
        return self.__class__(
            relation=self.relation, type_=self.type_, to=self.to, qryset=queryset
        )

    def select_related(self, related: Union[list, str]) -> "QuerysetProxy[T]":
        """
        Allows to prefetch related models during the same query.

        **With `select_related` always only one query is run against the database**,
        meaning that one (sometimes complicated) join is generated and later nested
        models are processed in python.

        To fetch related model use `ForeignKey` names.

        To chain related `Models` relation use double underscores between names.

        Actual call delegated to QuerySet.

        :param related: list of relation field names, can be linked by '__' to nest
        :type related: Union[list, str]
        :return: QuerysetProxy
        :rtype: QuerysetProxy
        """
        queryset = self.queryset.select_related(related)
        return self.__class__(
            relation=self.relation, type_=self.type_, to=self.to, qryset=queryset
        )

    def prefetch_related(self, related: Union[list, str]) -> "QuerysetProxy[T]":
        """
        Allows to prefetch related models during query - but opposite to
        `select_related` each subsequent model is fetched in a separate database query.

        **With `prefetch_related` always one query per Model is run against the
        database**, meaning that you will have multiple queries executed one
        after another.

        To fetch related model use `ForeignKey` names.

        To chain related `Models` relation use double underscores between names.

        Actual call delegated to QuerySet.

        :param related: list of relation field names, can be linked by '__' to nest
        :type related: Union[list, str]
        :return: QuerysetProxy
        :rtype: QuerysetProxy
        """
        queryset = self.queryset.prefetch_related(related)
        return self.__class__(
            relation=self.relation, type_=self.type_, to=self.to, qryset=queryset
        )

    def paginate(self, page: int, page_size: int = 20) -> "QuerysetProxy[T]":
        """
        You can paginate the result which is a combination of offset and limit clauses.
        Limit is set to page size and offset is set to (page-1) * page_size.

        Actual call delegated to QuerySet.

        :param page_size: numbers of items per page
        :type page_size: int
        :param page: page number
        :type page: int
        :return: QuerySet
        :rtype: QuerySet
        """
        queryset = self.queryset.paginate(page=page, page_size=page_size)
        return self.__class__(
            relation=self.relation, type_=self.type_, to=self.to, qryset=queryset
        )

    def limit(self, limit_count: int) -> "QuerysetProxy[T]":
        """
        You can limit the results to desired number of parent models.

        Actual call delegated to QuerySet.

        :param limit_count: number of models to limit
        :type limit_count: int
        :return: QuerysetProxy
        :rtype: QuerysetProxy
        """
        queryset = self.queryset.limit(limit_count)
        return self.__class__(
            relation=self.relation, type_=self.type_, to=self.to, qryset=queryset
        )

    def offset(self, offset: int) -> "QuerysetProxy[T]":
        """
        You can also offset the results by desired number of main models.

        Actual call delegated to QuerySet.

        :param offset: numbers of models to offset
        :type offset: int
        :return: QuerysetProxy
        :rtype: QuerysetProxy
        """
        queryset = self.queryset.offset(offset)
        return self.__class__(
            relation=self.relation, type_=self.type_, to=self.to, qryset=queryset
        )

    def fields(self, columns: Union[list, str, set, dict]) -> "QuerysetProxy[T]":
        """
        With `fields()` you can select subset of model columns to limit the data load.

        Note that `fields()` and `exclude_fields()` works both for main models
        (on normal queries like `get`, `all` etc.)
        as well as `select_related` and `prefetch_related`
        models (with nested notation).

        You can select specified fields by passing a `str, list[str], set[str] or
        dict` with nested definition.

        To include related models use notation
        `{related_name}__{column}[__{optional_next} etc.]`.

        `fields()` can be called several times, building up the columns to select.

        If you include related models into `select_related()` call but you won't specify
        columns for those models in fields - implies a list of all fields for
        those nested models.

        Mandatory fields cannot be excluded as it will raise `ValidationError`,
         to exclude a field it has to be nullable.

        Pk column cannot be excluded - it's always auto added even if
        not explicitly included.

        You can also pass fields to include as dictionary or set.

        To mark a field as included in a dictionary use it's name as key
        and ellipsis as value.

        To traverse nested models use nested dictionaries.

        To include fields at last level instead of nested dictionary a set can be used.

        To include whole nested model specify model related field name and ellipsis.

        Actual call delegated to QuerySet.

        :param columns: columns to include
        :type columns: Union[list, str, set, dict]
        :return: QuerysetProxy
        :rtype: QuerysetProxy
        """
        queryset = self.queryset.fields(columns)
        return self.__class__(
            relation=self.relation, type_=self.type_, to=self.to, qryset=queryset
        )

    def exclude_fields(
        self, columns: Union[list, str, set, dict]
    ) -> "QuerysetProxy[T]":
        """
        With `exclude_fields()` you can select subset of model columns that will
        be excluded to limit the data load.

        It's the opposite of `fields()` method so check documentation above
        to see what options are available.

        Especially check above how you can pass also nested dictionaries
        and sets as a mask to exclude fields from whole hierarchy.

        Note that `fields()` and `exclude_fields()` works both for main models
        (on normal queries like `get`, `all` etc.)
        as well as `select_related` and `prefetch_related` models
        (with nested notation).

        Mandatory fields cannot be excluded as it will raise `ValidationError`,
        to exclude a field it has to be nullable.

        Pk column cannot be excluded - it's always auto added even
        if explicitly excluded.

        Actual call delegated to QuerySet.

        :param columns: columns to exclude
        :type columns: Union[list, str, set, dict]
        :return: QuerysetProxy
        :rtype: QuerysetProxy
        """
        queryset = self.queryset.exclude_fields(columns=columns)
        return self.__class__(
            relation=self.relation, type_=self.type_, to=self.to, qryset=queryset
        )

    def order_by(self, columns: Union[list, str, "OrderAction"]) -> "QuerysetProxy[T]":
        """
        With `order_by()` you can order the results from database based on your
        choice of fields.

        You can provide a string with field name or list of strings with fields names.

        Ordering in sql will be applied in order of names you provide in order_by.

        By default if you do not provide ordering `ormar` explicitly orders by
        all primary keys

        If you are sorting by nested models that causes that the result rows are
        unsorted by the main model `ormar` will combine those children rows into
        one main model.

        The main model will never duplicate in the result

        To order by main model field just provide a field name

        To sort on nested models separate field names with dunder '__'.

        You can sort this way across all relation types -> `ForeignKey`,
        reverse virtual FK and `ManyToMany` fields.

        To sort in descending order provide a hyphen in front of the field name

        Actual call delegated to QuerySet.

        :param columns: columns by which models should be sorted
        :type columns: Union[list, str]
        :return: QuerysetProxy
        :rtype: QuerysetProxy
        """
        queryset = self.queryset.order_by(columns)
        return self.__class__(
            relation=self.relation, type_=self.type_, to=self.to, qryset=queryset
        )
