FPbase/backend/favit/managers.py at c8a97a3f474940e80c777d4392758da92c4fd520 · tlambert03/FPbase · GitHub

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from django.apps import apps
from django.contrib.contenttypes.models import ContentType
from django.db import models


def _get_content_type_and_obj(obj, model=None):
    if isinstance(model, str):
        model = apps.get_model(*model.split("."))

    if isinstance(obj, int):
        obj = model.objects.get(pk=obj)

    return ContentType.objects.get_for_model(type(obj)), obj


class FavoriteManager(models.Manager):
    """
    A Manager for Favorite objects
    """

    from django import VERSION

    if VERSION > (1, 8):

        def get_query_set(self):
            return self.get_queryset()

    def for_user(self, user, model=None):
        """
        Returns a Favorite objects queryset for a given user.

        If a model params is provided, it returns only the
        favorited objects of that model class

        Usage:

            Favorite.objects.for_user(user)
            Favorite.objects.for_user(user, model=Song)
            Favorite.objects.for_user(user, model="music.song")
        """

        qs = self.get_query_set().filter(user=user)

        if model:
            if isinstance(model, str):
                model = apps.get_model(*model.split("."))

            content_type = ContentType.objects.get_for_model(model)
            qs = qs.filter(target_content_type=content_type)

        return qs.order_by("-timestamp")

    def for_model(self, model):
        """
        Returns a Favorite objects queryset for a given model.
        `model` may be a django model class or an string representing
        a model in module-notation, ie: "auth.User"

        Usage:

            Favorite.objects.for_model(Song)
            Favorite.objects.for_model("music.Song")
        """

        # if model is an app_label.model string make it a Model class
        if isinstance(model, str):
            model = apps.get_model(*model.split("."))

        content_type = ContentType.objects.get_for_model(model)

        qs = self.get_query_set().filter(target_content_type=content_type)

        return qs.order_by("-timestamp")

    def for_object(self, obj, model=None):
        """
        Returns a Favorite objects queryset for a given object

        Usage:
            Favorite.objects.for_object(1, "music.Song")
            Favorite.objects.for_object(1, Song)

        or given a music app with a Song model:

            song = Song.objects.get(pk=1)
            Favorite.objects.for_object(song)
        """

        content_type, obj = _get_content_type_and_obj(obj, model)

        qs = self.get_query_set().filter(target_content_type=content_type, target_object_id=obj.pk)

        return qs.order_by("-timestamp")

    def get_favorite(self, user, obj, model=None):
        """
        Returns a Favorite instance if the `user` has favorited
        the given object `obj`. Otherwise returns None

        Usage:
            Favorite.objects.get_favorite(user, 1, "music.Song")
            Favorite.objects.get_favorite(user, 1, Song)

        or given a music app with a Song model:

            song = Song.objects.get(pk=1)
            Favorite.objects.get_favorite(user, song)
        """
        try:
            content_type, obj = _get_content_type_and_obj(obj, model)
        except AttributeError:
            return None

        try:
            return self.get_query_set().get(
                user=user, target_content_type=content_type, target_object_id=obj.id
            )
        except self.model.DoesNotExist:
            return None

    def create(self, user, obj, model=None):
        """
        Creates and returns a new Favorite obj for the given user and obj
        """

        content_type, content_object = _get_content_type_and_obj(obj, model)
        fav = super().create(
            user=user,
            target_content_type=content_type,
            target_object_id=content_object.pk,
            target=content_object,
        )

        return fav

    def get_or_create(self, user, obj, model=None):
        """
        Gets or creates a Favorite for the given user and obj.
        Returns tuple (favorite, created) where created is a boolean.

        This method is atomic and safe from race conditions.
        """
        content_type, content_object = _get_content_type_and_obj(obj, model)
        fav, created = super().get_or_create(
            user=user,
            target_content_type=content_type,
            target_object_id=content_object.pk,
            defaults={"target": content_object},
        )
        return fav, created