netbox-community-netbox/netbox/utilities/utils.py

from django.db.models import Count, ManyToOneRel, OuterRef, Subquery
from django.db.models.functions import Coalesce
from django.utils import timezone
from django.utils.timezone import localtime

from .string import title


def dynamic_import(name):
    """
    Dynamically import a class from an absolute path string
    """
    components = name.split('.')
    mod = __import__(components[0])
    for comp in components[1:]:
        mod = getattr(mod, comp)
    return mod


def count_related(model, field):
    """
    Return a Subquery suitable for annotating a child object count.
    """
    subquery = Subquery(
        model.objects.filter(
            **{field: OuterRef('pk')}
        ).order_by().values(
            field
        ).annotate(
            c=Count('*')
        ).values('c')
    )

    return Coalesce(subquery, 0)


def dict_to_filter_params(d, prefix=''):
    """
    Translate a dictionary of attributes to a nested set of parameters suitable for QuerySet filtering. For example:

        {
            "name": "Foo",
            "rack": {
                "facility_id": "R101"
            }
        }

    Becomes:

        {
            "name": "Foo",
            "rack__facility_id": "R101"
        }

    And can be employed as filter parameters:

        Device.objects.filter(**dict_to_filter(attrs_dict))
    """
    params = {}
    for key, val in d.items():
        k = prefix + key
        if isinstance(val, dict):
            params.update(dict_to_filter_params(val, k + '__'))
        else:
            params[k] = val
    return params


def content_type_name(ct, include_app=True):
    """
    Return a human-friendly ContentType name (e.g. "DCIM > Site").
    """
    try:
        meta = ct.model_class()._meta
        app_label = title(meta.app_config.verbose_name)
        model_name = title(meta.verbose_name)
        if include_app:
            return f'{app_label} > {model_name}'
        return model_name
    except AttributeError:
        # Model no longer exists
        return f'{ct.app_label} > {ct.model}'


def content_type_identifier(ct):
    """
    Return a "raw" ContentType identifier string suitable for bulk import/export (e.g. "dcim.site").
    """
    return f'{ct.app_label}.{ct.model}'


def local_now():
    """
    Return the current date & time in the system timezone.
    """
    return localtime(timezone.now())


def get_related_models(model, ordered=True):
    """
    Return a list of all models which have a ForeignKey to the given model and the name of the field. For example,
    `get_related_models(Tenant)` will return all models which have a ForeignKey relationship to Tenant.
    """
    related_models = [
        (field.related_model, field.remote_field.name)
        for field in model._meta.related_objects
        if type(field) is ManyToOneRel
    ]

    if ordered:
        return sorted(related_models, key=lambda x: x[0]._meta.verbose_name.lower())

    return related_models