# (c) Nelen & Schuurmans

from datetime import datetime
from datetime import timezone
from typing import Optional
from typing import Type
from typing import TypeVar

from .exceptions import BadRequest
from .value_object import ValueObject

__all__ = ["RootEntity", "now"]


def now():
    # this function is there so that we can mock it in tests
    return datetime.now(timezone.utc)


T = TypeVar("T", bound="RootEntity")


class RootEntity(ValueObject):
    id: Optional[int] = None
    created_at: datetime
    updated_at: datetime

    @classmethod
    def create(cls: Type[T], **values) -> T:
        values.setdefault("created_at", now())
        values.setdefault("updated_at", values["created_at"])
        return super(RootEntity, cls).create(**values)

    def update(self: T, **values) -> T:
        if "id" in values and self.id is not None and values["id"] != self.id:
            raise BadRequest("Cannot change the id of an entity")
        values.setdefault("updated_at", now())
        return super().update(**values)

    def __hash__(self):
        assert self.id is not None
        return hash(self.__class__) + hash(self.id)