from gcloudorm import model as ndb

class DatastoreManager(object):
    def __init__(self, model):
        assert isinstnace(model, ndb.Model)
        self._model = model

    def update(self, id, data):
        # update or replace
        obj = self._model.get_by_id(id)
        if not obj:
            return self.replace(id, data)

        return self.patch(obj, data)

    def patch(self, obj, data):
        for attr in data:
            setattr(obj, attr, data[attr])

        return obj

    def replace(self, id, data):
        obj = self._model(id=id)
        return self.patch(obj, data)

    def remove(self, id):
        obj = self._model(id=id)
        obj.delete()

class SyncMixin(models.Model):

    sync_manager = None

    last_sync = models.DateTimeField(null=True, blank=True, editable=False)

    class Meta:
        abstract = True

    def to_datastore_id(self):
        return self.pk

    def to_datastore_dict(self):
        raise NotImplementedError()

    def save(self, *args, **kwargs):
        assert isinstance(self.sync_manager, DatastoreManager)

        obj = self.sync_manager.replace(
            id=self.to_datastore_id(),
            self.to_datastore_dict()
        )
        obj.put()
        self.last_sync = datetime.utcnow()
        return super(SyncMixin, self).save(*args, **kwargs)

    def delete(self):
        assert isinstance(self.sync_manager, DatastoreManager)

        self.sync_manager.remove(self.to_datastore_id())
        super(SyncMixin, self).delete()

class Publisher(SyncMixin):
    name = models.CharField(max_length=255)

    query_settings = JSONField(null=True, blank=True, default=Publisher.DEFAULT_QUERY_SETTINGS)

    sync_manager = DatastoreManager(ad.models.Publisher)

    def to_datastore_dict(self):
        return {
            "setting": {
                "query_setting": self.query_settings,
                "limit": self.limit
            },
            "name": self.name,
            "publisher_id": self.pk
        }