from typing import Any, Dict, List, Optional

from django.db.models import Model
from rest_framework.serializers import Serializer

from .collection import CollectionElement


class BaseAccessPermissions:
    """
    Base access permissions container.

    Every app which has autoupdate models has to create classes subclassing
    from this base class for every autoupdate root model.
    """

    def check_permissions(self, user: Optional[CollectionElement]) -> bool:
        """
        Returns True if the user has read access to model instances.
        """
        return False

    def get_serializer_class(self, user: CollectionElement = None) -> Serializer:
        """
        Returns different serializer classes according to users permissions.

        This should return the serializer for full data access if user is
        None. See get_full_data().
        """
        raise NotImplementedError(
            "You have to add the method 'get_serializer_class' to your "
            "access permissions class.".format(self))

    def get_full_data(self, instance: Model) -> Dict[str, Any]:
        """
        Returns all possible serialized data for the given instance.
        """
        return self.get_serializer_class(user=None)(instance).data

    def get_restricted_data(
            self, full_data: List[Dict[str, Any]],
            user: Optional[CollectionElement]) -> List[Dict[str, Any]]:
        """
        Returns the restricted serialized data for the instance prepared
        for the user.

        The argument full_data has to be a list of full_data dicts as they are
        created with CollectionElement.get_full_data(). The type of the return
        is the same. Returns an empty list if the user has no read access.
        Returns reduced data if the user has limited access.
        Default: Returns full data if the user has read access to model instances.

        Hint: You should override this method if your get_serializer_class()
        method returns different serializers for different users or if you
        have access restrictions in your view or viewset in methods like
        retrieve() or list().
        """
        return full_data if self.check_permissions(user) else []