Source code for services.users.followers

from apps.users.models import User
from services.notifications.notification import NotificationService
from services.users.exceptions import AlreadyFollowingUserException, NotFollowingUserException




class FollowersService:
    """
    Service class for managing followers for a user.

    This class contains methods to handle following and unfollowing operations for a user.
    It ensures that the operations are valid and raises exceptions if they are not.

    Attributes:
        _user (User): The user who is performing the follow or unfollow operation.
    """

    notification_service = NotificationService



    def __init__(self, user: User):
        self._user = user


    def _validate_follow(self, following_user: User) -> None:
        """
        Validate if the follow operation is permissible.
        """
        if self._user.following.filter(pk=following_user.pk).exists():
            raise AlreadyFollowingUserException



    def follow(self, following_user: User) -> None:
        """
        Follow a user.

        This method adds the given following_user to the user's following list after validating
        the operation using _validate_follow.

        Args:
            following_user (User): The user to follow.
        """
        self._validate_follow(following_user)
        self._user.following.add(following_user)
        self.notification_service.send_follow_notification(sender=self._user, receiver=following_user)


    def _validate_unfollow(self, following_user: User) -> None:
        """
        Validate if the unfollow operation is permissible.
        """
        if not self._user.following.filter(pk=following_user.pk).exists():
            raise NotFollowingUserException



    def unfollow(self, following_user: User):
        """
        Unfollow a user.

        This method removes the given following_user from the user's following list after
        validating the operation using _validate_unfollow.

        Args:
            following_user (User): The user to unfollow.
        """
        self._validate_unfollow(following_user)
        self._user.following.remove(following_user)