import decimal
from functools import cached_property

import yaml
from django.contrib.contenttypes.fields import GenericForeignKey, GenericRelation
from django.contrib.contenttypes.models import ContentType
from django.core.exceptions import ValidationError
from django.core.files.storage import default_storage
from django.core.validators import MaxValueValidator, MinValueValidator
from django.db import models
from django.db.models import F, ProtectedError, prefetch_related_objects
from django.db.models.functions import Lower
from django.db.models.signals import post_save
from django.urls import reverse
from django.utils.safestring import mark_safe
from django.utils.translation import gettext_lazy as _

from dcim.choices import *
from dcim.constants import *
from dcim.fields import MACAddressField
from dcim.utils import create_port_mappings, update_interface_bridges
from extras.models import ConfigContextModel, CustomField
from extras.querysets import ConfigContextModelQuerySet
from netbox.choices import ColorChoices
from netbox.config import ConfigItem
from netbox.models import NestedGroupModel, OrganizationalModel, PrimaryModel
from netbox.models.features import ContactsMixin, ImageAttachmentsMixin
from netbox.models.mixins import WeightMixin
from utilities.exceptions import AbortRequest
from utilities.fields import ColorField, CounterCacheField
from utilities.prefetch import get_prefetchable_fields
from utilities.tracking import TrackingModelMixin

from .device_components import *
from .mixins import RenderConfigMixin
from .modules import Module

__all__ = (
    'Device',
    'DeviceRole',
    'DeviceType',
    'MACAddress',
    'Manufacturer',
    'Platform',
    'VirtualChassis',
    'VirtualDeviceContext',
)


#
# Device Types
#

class Manufacturer(ContactsMixin, OrganizationalModel):
    """
    A Manufacturer represents a company which produces hardware devices; for example, Juniper or Dell.
    """
    class Meta:
        ordering = ('name',)
        verbose_name = _('manufacturer')
        verbose_name_plural = _('manufacturers')


class DeviceType(ImageAttachmentsMixin, PrimaryModel, WeightMixin):
    """
    A DeviceType represents a particular make (Manufacturer) and model of device. It specifies rack height and depth, as
    well as high-level functional role(s).

    Each DeviceType can have an arbitrary number of component templates assigned to it, which define console, power, and
    interface objects. For example, a Juniper EX4300-48T DeviceType would have:

      * 1 ConsolePortTemplate
      * 2 PowerPortTemplates
      * 48 InterfaceTemplates

    When a new Device of this type is created, the appropriate console, power, and interface objects (as defined by the
    DeviceType) are automatically created as well.
    """
    manufacturer = models.ForeignKey(
        to='dcim.Manufacturer',
        on_delete=models.PROTECT,
        related_name='device_types'
    )
    model = models.CharField(
        verbose_name=_('model'),
        max_length=100
    )
    slug = models.SlugField(
        verbose_name=_('slug'),
        max_length=100
    )
    default_platform = models.ForeignKey(
        to='dcim.Platform',
        on_delete=models.SET_NULL,
        related_name='+',
        blank=True,
        null=True,
        verbose_name=_('default platform')
    )
    part_number = models.CharField(
        verbose_name=_('part number'),
        max_length=50,
        blank=True,
        help_text=_('Discrete part number (optional)')
    )
    u_height = models.DecimalField(
        max_digits=4,
        decimal_places=1,
        default=1.0,
        verbose_name=_('height (U)')
    )
    exclude_from_utilization = models.BooleanField(
        default=False,
        verbose_name=_('exclude from utilization'),
        help_text=_('Devices of this type are excluded when calculating rack utilization.')
    )
    is_full_depth = models.BooleanField(
        default=True,
        verbose_name=_('is full depth'),
        help_text=_('Device consumes both front and rear rack faces.')
    )
    subdevice_role = models.CharField(
        max_length=50,
        choices=SubdeviceRoleChoices,
        blank=True,
        null=True,
        verbose_name=_('parent/child status'),
        help_text=_('Parent devices house child devices in device bays. Leave blank '
                    'if this device type is neither a parent nor a child.')
    )
    airflow = models.CharField(
        verbose_name=_('airflow'),
        max_length=50,
        choices=DeviceAirflowChoices,
        blank=True,
        null=True
    )
    front_image = models.ImageField(
        upload_to='devicetype-images',
        blank=True
    )
    rear_image = models.ImageField(
        upload_to='devicetype-images',
        blank=True
    )

    # Counter fields
    console_port_template_count = CounterCacheField(
        to_model='dcim.ConsolePortTemplate',
        to_field='device_type'
    )
    console_server_port_template_count = CounterCacheField(
        to_model='dcim.ConsoleServerPortTemplate',
        to_field='device_type'
    )
    power_port_template_count = CounterCacheField(
        to_model='dcim.PowerPortTemplate',
        to_field='device_type'
    )
    power_outlet_template_count = CounterCacheField(
        to_model='dcim.PowerOutletTemplate',
        to_field='device_type'
    )
    interface_template_count = CounterCacheField(
        to_model='dcim.InterfaceTemplate',
        to_field='device_type'
    )
    front_port_template_count = CounterCacheField(
        to_model='dcim.FrontPortTemplate',
        to_field='device_type'
    )
    rear_port_template_count = CounterCacheField(
        to_model='dcim.RearPortTemplate',
        to_field='device_type'
    )
    device_bay_template_count = CounterCacheField(
        to_model='dcim.DeviceBayTemplate',
        to_field='device_type'
    )
    module_bay_template_count = CounterCacheField(
        to_model='dcim.ModuleBayTemplate',
        to_field='device_type'
    )
    inventory_item_template_count = CounterCacheField(
        to_model='dcim.InventoryItemTemplate',
        to_field='device_type'
    )
    device_count = CounterCacheField(
        to_model='dcim.Device',
        to_field='device_type'
    )

    clone_fields = (
        'manufacturer', 'default_platform', 'u_height', 'is_full_depth', 'subdevice_role', 'airflow', 'weight',
        'weight_unit',
    )
    prerequisite_models = (
        'dcim.Manufacturer',
    )

    class Meta:
        ordering = ['manufacturer', 'model']
        constraints = (
            models.UniqueConstraint(
                fields=('manufacturer', 'model'),
                name='%(app_label)s_%(class)s_unique_manufacturer_model'
            ),
            models.UniqueConstraint(
                fields=('manufacturer', 'slug'),
                name='%(app_label)s_%(class)s_unique_manufacturer_slug'
            ),
        )
        verbose_name = _('device type')
        verbose_name_plural = _('device types')

    def __str__(self):
        return self.model

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

        # Save a copy of u_height for validation in clean()
        self._original_u_height = self.__dict__.get('u_height')

        # Save references to the original front/rear images
        self._original_front_image = self.__dict__.get('front_image')
        self._original_rear_image = self.__dict__.get('rear_image')

    @property
    def full_name(self):
        return f"{self.manufacturer} {self.model}"

    def to_yaml(self):
        data = {
            'manufacturer': self.manufacturer.name,
            'model': self.model,
            'slug': self.slug,
            'description': self.description,
            'default_platform': self.default_platform.name if self.default_platform else None,
            'part_number': self.part_number,
            'u_height': float(self.u_height),
            'is_full_depth': self.is_full_depth,
            'subdevice_role': self.subdevice_role,
            'airflow': self.airflow,
            'weight': float(self.weight) if self.weight is not None else None,
            'weight_unit': self.weight_unit,
            'comments': self.comments,
        }

        # Component templates
        if self.consoleporttemplates.exists():
            data['console-ports'] = [
                c.to_yaml() for c in self.consoleporttemplates.all()
            ]
        if self.consoleserverporttemplates.exists():
            data['console-server-ports'] = [
                c.to_yaml() for c in self.consoleserverporttemplates.all()
            ]
        if self.powerporttemplates.exists():
            data['power-ports'] = [
                c.to_yaml() for c in self.powerporttemplates.all()
            ]
        if self.poweroutlettemplates.exists():
            data['power-outlets'] = [
                c.to_yaml() for c in self.poweroutlettemplates.all()
            ]
        if self.interfacetemplates.exists():
            data['interfaces'] = [
                c.to_yaml() for c in self.interfacetemplates.all()
            ]
        if self.frontporttemplates.exists():
            data['front-ports'] = [
                c.to_yaml() for c in self.frontporttemplates.all()
            ]
        if self.rearporttemplates.exists():
            data['rear-ports'] = [
                c.to_yaml() for c in self.rearporttemplates.all()
            ]

        # Port mappings
        port_mapping_data = [
            c.to_yaml() for c in self.port_mappings.all()
        ]

        if port_mapping_data:
            data['port-mappings'] = port_mapping_data

        if self.modulebaytemplates.exists():
            data['module-bays'] = [
                c.to_yaml() for c in self.modulebaytemplates.all()
            ]
        if self.devicebaytemplates.exists():
            data['device-bays'] = [
                c.to_yaml() for c in self.devicebaytemplates.all()
            ]

        return yaml.dump(dict(data), sort_keys=False)

    def clean(self):
        super().clean()

        # U height must be divisible by 0.5
        if decimal.Decimal(self.u_height) % decimal.Decimal(0.5):
            raise ValidationError({
                'u_height': _("U height must be in increments of 0.5 rack units.")
            })

        # If editing an existing DeviceType to have a larger u_height, first validate that *all* instances of it have
        # room to expand within their racks. This validation will impose a very high performance penalty when there are
        # many instances to check, but increasing the u_height of a DeviceType should be a very rare occurrence.
        if not self._state.adding and self.u_height > self._original_u_height:
            for d in Device.objects.filter(device_type=self, position__isnull=False):
                face_required = None if self.is_full_depth else d.face
                u_available = d.rack.get_available_units(
                    u_height=self.u_height,
                    rack_face=face_required,
                    exclude=[d.pk]
                )
                if d.position not in u_available:
                    raise ValidationError({
                        'u_height': _(
                            "Device {device} in rack {rack} does not have sufficient space to accommodate a "
                            "height of {height}U"
                        ).format(device=d, rack=d.rack, height=self.u_height)
                    })

        # If modifying the height of an existing DeviceType to 0U, check for any instances assigned to a rack position.
        elif not self._state.adding and self._original_u_height > 0 and self.u_height == 0:
            racked_instance_count = Device.objects.filter(
                device_type=self,
                position__isnull=False
            ).count()
            if racked_instance_count:
                url = f"{reverse('dcim:device_list')}?manufactuer_id={self.manufacturer_id}&device_type_id={self.pk}"
                raise ValidationError({
                    'u_height': mark_safe(_(
                        'Unable to set 0U height: Found <a href="{url}">{racked_instance_count} instances</a> already '
                        'mounted within racks.'
                    ).format(url=url, racked_instance_count=racked_instance_count))
                })

        if (
                self.subdevice_role != SubdeviceRoleChoices.ROLE_PARENT
        ) and self.pk and self.devicebaytemplates.count():
            raise ValidationError({
                'subdevice_role': _("Must delete all device bay templates associated with this device before "
                                  "declassifying it as a parent device.")
            })

        if self.u_height and self.subdevice_role == SubdeviceRoleChoices.ROLE_CHILD:
            raise ValidationError({
                'u_height': _("Child device types must be 0U.")
            })

    def save(self, *args, **kwargs):
        ret = super().save(*args, **kwargs)

        # Delete any previously uploaded image files that are no longer in use
        if self._original_front_image and self.front_image != self._original_front_image:
            default_storage.delete(self._original_front_image)
        if self._original_rear_image and self.rear_image != self._original_rear_image:
            default_storage.delete(self._original_rear_image)

        return ret

    def delete(self, *args, **kwargs):
        super().delete(*args, **kwargs)

        # Delete any uploaded image files
        if self.front_image:
            self.front_image.delete(save=False)
        if self.rear_image:
            self.rear_image.delete(save=False)

    @property
    def is_parent_device(self):
        return self.subdevice_role == SubdeviceRoleChoices.ROLE_PARENT

    @property
    def is_child_device(self):
        return self.subdevice_role == SubdeviceRoleChoices.ROLE_CHILD


#
# Devices
#

class DeviceRole(NestedGroupModel):
    """
    Devices are organized by functional role; for example, "Core Switch" or "File Server". Each DeviceRole is assigned a
    color to be used when displaying rack elevations. The vm_role field determines whether the role is applicable to
    virtual machines as well.
    """
    color = ColorField(
        verbose_name=_('color'),
        default=ColorChoices.COLOR_GREY
    )
    vm_role = models.BooleanField(
        default=True,
        verbose_name=_('VM role'),
        help_text=_('Virtual machines may be assigned to this role')
    )
    config_template = models.ForeignKey(
        to='extras.ConfigTemplate',
        on_delete=models.PROTECT,
        related_name='device_roles',
        blank=True,
        null=True
    )

    clone_fields = ('parent', 'description')

    class Meta:
        ordering = ('name',)
        # Empty tuple triggers Django migration detection for MPTT indexes
        # (see #21016, django-mptt/django-mptt#682)
        indexes = ()
        constraints = (
            models.UniqueConstraint(
                fields=('parent', 'name'),
                name='%(app_label)s_%(class)s_parent_name'
            ),
            models.UniqueConstraint(
                fields=('name',),
                name='%(app_label)s_%(class)s_name',
                condition=Q(parent__isnull=True),
                violation_error_message=_("A top-level device role with this name already exists.")
            ),
            models.UniqueConstraint(
                fields=('parent', 'slug'),
                name='%(app_label)s_%(class)s_parent_slug'
            ),
            models.UniqueConstraint(
                fields=('slug',),
                name='%(app_label)s_%(class)s_slug',
                condition=Q(parent__isnull=True),
                violation_error_message=_("A top-level device role with this slug already exists.")
            ),
        )
        verbose_name = _('device role')
        verbose_name_plural = _('device roles')


class Platform(NestedGroupModel):
    """
    Platform refers to the software or firmware running on a Device. For example, "Cisco IOS-XR" or "Juniper Junos". A
    Platform may optionally be associated with a particular Manufacturer.
    """
    manufacturer = models.ForeignKey(
        to='dcim.Manufacturer',
        on_delete=models.PROTECT,
        related_name='platforms',
        blank=True,
        null=True,
        help_text=_('Optionally limit this platform to devices of a certain manufacturer')
    )
    config_template = models.ForeignKey(
        to='extras.ConfigTemplate',
        on_delete=models.PROTECT,
        related_name='platforms',
        blank=True,
        null=True
    )

    clone_fields = ('parent', 'description')

    class Meta:
        ordering = ('name',)
        # Empty tuple triggers Django migration detection for MPTT indexes
        # (see #21016, django-mptt/django-mptt#682)
        indexes = ()
        verbose_name = _('platform')
        verbose_name_plural = _('platforms')
        constraints = (
            models.UniqueConstraint(
                fields=('manufacturer', 'name'),
                name='%(app_label)s_%(class)s_manufacturer_name',
            ),
            models.UniqueConstraint(
                fields=('name',),
                name='%(app_label)s_%(class)s_name',
                condition=Q(manufacturer__isnull=True),
                violation_error_message=_("Platform name must be unique.")
            ),
            models.UniqueConstraint(
                fields=('manufacturer', 'slug'),
                name='%(app_label)s_%(class)s_manufacturer_slug',
            ),
            models.UniqueConstraint(
                fields=('slug',),
                name='%(app_label)s_%(class)s_slug',
                condition=Q(manufacturer__isnull=True),
                violation_error_message=_("Platform slug must be unique.")
            ),
        )


class Device(
    ContactsMixin,
    ImageAttachmentsMixin,
    RenderConfigMixin,
    ConfigContextModel,
    TrackingModelMixin,
    PrimaryModel
):
    """
    A Device represents a piece of physical hardware mounted within a Rack. Each Device is assigned a DeviceType,
    DeviceRole, and (optionally) a Platform. Device names are not required, however if one is set it must be unique.

    Each Device must be assigned to a site, and optionally to a rack within that site. Associating a device with a
    particular rack face or unit is optional (for example, vertically mounted PDUs do not consume rack units).

    When a new Device is created, console/power/interface/device bay components are created along with it as dictated
    by the component templates assigned to its DeviceType. Components can also be added, modified, or deleted after the
    creation of a Device.
    """
    device_type = models.ForeignKey(
        to='dcim.DeviceType',
        on_delete=models.PROTECT,
        related_name='instances'
    )
    role = models.ForeignKey(
        to='dcim.DeviceRole',
        on_delete=models.PROTECT,
        related_name='devices',
        help_text=_("The function this device serves")
    )
    tenant = models.ForeignKey(
        to='tenancy.Tenant',
        on_delete=models.PROTECT,
        related_name='devices',
        blank=True,
        null=True
    )
    platform = models.ForeignKey(
        to='dcim.Platform',
        on_delete=models.SET_NULL,
        related_name='devices',
        blank=True,
        null=True
    )
    name = models.CharField(
        verbose_name=_('name'),
        max_length=64,
        blank=True,
        null=True,
        db_collation="natural_sort"
    )
    serial = models.CharField(
        max_length=50,
        blank=True,
        verbose_name=_('serial number'),
        help_text=_("Chassis serial number, assigned by the manufacturer")
    )
    asset_tag = models.CharField(
        max_length=50,
        blank=True,
        null=True,
        unique=True,
        verbose_name=_('asset tag'),
        help_text=_('A unique tag used to identify this device')
    )
    site = models.ForeignKey(
        to='dcim.Site',
        on_delete=models.PROTECT,
        related_name='devices'
    )
    location = models.ForeignKey(
        to='dcim.Location',
        on_delete=models.PROTECT,
        related_name='devices',
        blank=True,
        null=True
    )
    rack = models.ForeignKey(
        to='dcim.Rack',
        on_delete=models.PROTECT,
        related_name='devices',
        blank=True,
        null=True
    )
    position = models.DecimalField(
        max_digits=4,
        decimal_places=1,
        blank=True,
        null=True,
        validators=[MinValueValidator(1), MaxValueValidator(RACK_U_HEIGHT_MAX + 0.5)],
        verbose_name=_('position (U)'),
        help_text=_('The lowest-numbered unit occupied by the device')
    )
    face = models.CharField(
        max_length=50,
        blank=True,
        null=True,
        choices=DeviceFaceChoices,
        verbose_name=_('rack face')
    )
    status = models.CharField(
        verbose_name=_('status'),
        max_length=50,
        choices=DeviceStatusChoices,
        default=DeviceStatusChoices.STATUS_ACTIVE
    )
    airflow = models.CharField(
        verbose_name=_('airflow'),
        max_length=50,
        choices=DeviceAirflowChoices,
        blank=True,
        null=True
    )
    primary_ip4 = models.OneToOneField(
        to='ipam.IPAddress',
        on_delete=models.SET_NULL,
        related_name='+',
        blank=True,
        null=True,
        verbose_name=_('primary IPv4')
    )
    primary_ip6 = models.OneToOneField(
        to='ipam.IPAddress',
        on_delete=models.SET_NULL,
        related_name='+',
        blank=True,
        null=True,
        verbose_name=_('primary IPv6')
    )
    oob_ip = models.OneToOneField(
        to='ipam.IPAddress',
        on_delete=models.SET_NULL,
        related_name='+',
        blank=True,
        null=True,
        verbose_name=_('out-of-band IP')
    )
    cluster = models.ForeignKey(
        to='virtualization.Cluster',
        on_delete=models.SET_NULL,
        related_name='devices',
        blank=True,
        null=True
    )
    virtual_chassis = models.ForeignKey(
        to='VirtualChassis',
        on_delete=models.SET_NULL,
        related_name='members',
        blank=True,
        null=True
    )
    vc_position = models.PositiveIntegerField(
        verbose_name=_('VC position'),
        blank=True,
        null=True,
        help_text=_('Virtual chassis position')
    )
    vc_priority = models.PositiveSmallIntegerField(
        verbose_name=_('VC priority'),
        blank=True,
        null=True,
        validators=[MaxValueValidator(255)],
        help_text=_('Virtual chassis master election priority')
    )
    latitude = models.DecimalField(
        verbose_name=_('latitude'),
        max_digits=8,
        decimal_places=6,
        blank=True,
        null=True,
        validators=[
            MinValueValidator(decimal.Decimal('-90.0')),
            MaxValueValidator(decimal.Decimal('90.0'))
        ],
        help_text=_("GPS coordinate in decimal format (xx.yyyyyy)")
    )
    longitude = models.DecimalField(
        verbose_name=_('longitude'),
        max_digits=9,
        decimal_places=6,
        blank=True,
        null=True,
        validators=[
            MinValueValidator(decimal.Decimal('-180.0')),
            MaxValueValidator(decimal.Decimal('180.0'))
        ],
        help_text=_("GPS coordinate in decimal format (xx.yyyyyy)")
    )
    services = GenericRelation(
        to='ipam.Service',
        content_type_field='parent_object_type',
        object_id_field='parent_object_id',
        related_query_name='device',
    )

    # Counter fields
    console_port_count = CounterCacheField(
        to_model='dcim.ConsolePort',
        to_field='device'
    )
    console_server_port_count = CounterCacheField(
        to_model='dcim.ConsoleServerPort',
        to_field='device'
    )
    power_port_count = CounterCacheField(
        to_model='dcim.PowerPort',
        to_field='device'
    )
    power_outlet_count = CounterCacheField(
        to_model='dcim.PowerOutlet',
        to_field='device'
    )
    interface_count = CounterCacheField(
        to_model='dcim.Interface',
        to_field='device'
    )
    front_port_count = CounterCacheField(
        to_model='dcim.FrontPort',
        to_field='device'
    )
    rear_port_count = CounterCacheField(
        to_model='dcim.RearPort',
        to_field='device'
    )
    device_bay_count = CounterCacheField(
        to_model='dcim.DeviceBay',
        to_field='device'
    )
    module_bay_count = CounterCacheField(
        to_model='dcim.ModuleBay',
        to_field='device'
    )
    inventory_item_count = CounterCacheField(
        to_model='dcim.InventoryItem',
        to_field='device'
    )

    objects = ConfigContextModelQuerySet.as_manager()

    clone_fields = (
        'device_type', 'role', 'tenant', 'platform', 'site', 'location', 'rack', 'face', 'status', 'airflow',
        'cluster', 'virtual_chassis',
    )
    prerequisite_models = (
        'dcim.Site',
        'dcim.DeviceRole',
        'dcim.DeviceType',
    )

    class Meta:
        ordering = ('name', 'pk')  # Name may be null
        indexes = (
            models.Index(fields=('name', 'id')),  # Default ordering
        )
        constraints = (
            models.UniqueConstraint(
                Lower('name'), 'site', 'tenant',
                name='%(app_label)s_%(class)s_unique_name_site_tenant'
            ),
            models.UniqueConstraint(
                Lower('name'), 'site',
                name='%(app_label)s_%(class)s_unique_name_site',
                condition=Q(tenant__isnull=True),
                violation_error_message=_("Device name must be unique per site.")
            ),
            models.UniqueConstraint(
                fields=('rack', 'position', 'face'),
                name='%(app_label)s_%(class)s_unique_rack_position_face'
            ),
            models.UniqueConstraint(
                fields=('virtual_chassis', 'vc_position'),
                name='%(app_label)s_%(class)s_unique_virtual_chassis_vc_position'
            ),
        )
        verbose_name = _('device')
        verbose_name_plural = _('devices')
        permissions = [
            ('render_config', 'Render configuration'),
        ]

    def __str__(self):
        if self.label and self.asset_tag:
            return f'{self.label} ({self.asset_tag})'
        if self.label:
            return self.label
        if self.device_type and self.asset_tag:
            return f'{self.device_type.manufacturer} {self.device_type.model} ({self.asset_tag})'
        if self.device_type:
            return f'{self.device_type.manufacturer} {self.device_type.model} ({self.pk})'
        return super().__str__()

    def clean(self):
        super().clean()

        # Validate site/location/rack combination
        if self.rack and self.site != self.rack.site:
            raise ValidationError({
                'rack': _("Rack {rack} does not belong to site {site}.").format(rack=self.rack, site=self.site),
            })
        if self.location and self.site != self.location.site:
            raise ValidationError({
                'location': _(
                    "Location {location} does not belong to site {site}."
                ).format(location=self.location, site=self.site)
            })
        if self.rack and self.location and self.rack.location != self.location:
            raise ValidationError({
                'rack': _(
                    "Rack {rack} does not belong to location {location}."
                ).format(rack=self.rack, location=self.location)
            })

        if self.rack is None:
            if self.face:
                raise ValidationError({
                    'face': _("Cannot select a rack face without assigning a rack."),
                })
            if self.position:
                raise ValidationError({
                    'position': _("Cannot select a rack position without assigning a rack."),
                })

        # Validate rack position and face
        if self.position and self.position % decimal.Decimal(0.5):
            raise ValidationError({
                'position': _("Position must be in increments of 0.5 rack units.")
            })
        if self.position and not self.face:
            raise ValidationError({
                'face': _("Must specify rack face when defining rack position."),
            })

        # Prevent 0U devices from being assigned to a specific position
        if hasattr(self, 'device_type'):
            if self.position and self.device_type.u_height == 0:
                raise ValidationError({
                    'position': _(
                        "A 0U device type ({device_type}) cannot be assigned to a rack position."
                    ).format(device_type=self.device_type)
                })

        if self.rack:

            try:
                # Child devices cannot be assigned to a rack face/unit
                if self.device_type.is_child_device and self.face:
                    raise ValidationError({
                        'face': _(
                            "Child device types cannot be assigned to a rack face. This is an attribute of the parent "
                            "device."
                        )
                    })
                if self.device_type.is_child_device and self.position:
                    raise ValidationError({
                        'position': _(
                            "Child device types cannot be assigned to a rack position. This is an attribute of the "
                            "parent device."
                        )
                    })

                # Validate rack space
                rack_face = self.face if not self.device_type.is_full_depth else None
                exclude_list = [self.pk] if self.pk else []
                available_units = self.rack.get_available_units(
                    u_height=self.device_type.u_height, rack_face=rack_face, exclude=exclude_list
                )
                if self.position and self.position not in available_units:
                    raise ValidationError({
                        'position': _(
                            "U{position} is already occupied or does not have sufficient space to accommodate this "
                            "device type: {device_type} ({u_height}U)"
                        ).format(
                            position=self.position, device_type=self.device_type, u_height=self.device_type.u_height
                        )
                    })

            except DeviceType.DoesNotExist:
                pass

        # Validate primary & OOB IP addresses
        vc_interfaces = self.vc_interfaces(if_master=False)
        if self.primary_ip4:
            if self.primary_ip4.family != 4:
                raise ValidationError({
                    'primary_ip4': _("{ip} is not an IPv4 address.").format(ip=self.primary_ip4)
                })
            if self.primary_ip4.assigned_object in vc_interfaces:
                pass
            elif (
                    self.primary_ip4.nat_inside is not None and
                    self.primary_ip4.nat_inside.assigned_object in vc_interfaces
            ):
                pass
            else:
                raise ValidationError({
                    'primary_ip4': _(
                        "The specified IP address ({ip}) is not assigned to this device."
                    ).format(ip=self.primary_ip4)
                })
        if self.primary_ip6:
            if self.primary_ip6.family != 6:
                raise ValidationError({
                    'primary_ip6': _("{ip} is not an IPv6 address.").format(ip=self.primary_ip6)
                })
            if self.primary_ip6.assigned_object in vc_interfaces:
                pass
            elif (
                    self.primary_ip6.nat_inside is not None and
                    self.primary_ip6.nat_inside.assigned_object in vc_interfaces
            ):
                pass
            else:
                raise ValidationError({
                    'primary_ip6': _(
                        "The specified IP address ({ip}) is not assigned to this device."
                    ).format(ip=self.primary_ip6)
                })
        if self.oob_ip:
            if self.oob_ip.assigned_object in vc_interfaces:
                pass
            elif self.oob_ip.nat_inside is not None and self.oob_ip.nat_inside.assigned_object in vc_interfaces:
                pass
            else:
                raise ValidationError({
                    'oob_ip': f"The specified IP address ({self.oob_ip}) is not assigned to this device."
                })

        # Validate manufacturer/platform
        if hasattr(self, 'device_type') and self.platform:
            if self.platform.manufacturer and self.platform.manufacturer != self.device_type.manufacturer:
                raise ValidationError({
                    'platform': _(
                        "The assigned platform is limited to {platform_manufacturer} device types, but this device's "
                        "type belongs to {devicetype_manufacturer}."
                    ).format(
                        platform_manufacturer=self.platform.manufacturer,
                        devicetype_manufacturer=self.device_type.manufacturer
                    )
                })

        # A Device can only be assigned to a Cluster in the same Site (or no Site)
        if self.cluster and self.cluster._site is not None and self.cluster._site != self.site:
            raise ValidationError({
                'cluster': _("The assigned cluster belongs to a different site ({site})").format(
                    site=self.cluster._site
                )
            })

        if self.cluster and self.cluster._location is not None and self.cluster._location != self.location:
            raise ValidationError({
                'cluster': _("The assigned cluster belongs to a different location ({location})").format(
                    location=self.cluster._location
                )
            })

        # Validate virtual chassis assignment
        if self.virtual_chassis and self.vc_position is None:
            raise ValidationError({
                'vc_position': _("A device assigned to a virtual chassis must have its position defined.")
            })

        if hasattr(self, 'vc_master_for') and self.vc_master_for and self.vc_master_for != self.virtual_chassis:
            raise ValidationError({
                'virtual_chassis': _(
                    'Device cannot be removed from virtual chassis {virtual_chassis} because it is currently '
                    'designated as its master.'
                ).format(virtual_chassis=self.vc_master_for)
            })

    def _check_duplicate_component_names(self, components):
        """
        Check for duplicate component names after resolving {vc_position} placeholders.
        Raises AbortRequest if duplicates are found.
        """
        names = [c.name for c in components]
        duplicates = {n for n in names if names.count(n) > 1}
        if duplicates:
            raise AbortRequest(
                _("Component name conflict after resolving {{vc_position}}: {names}").format(
                    names=', '.join(duplicates)
                )
            )

    def _instantiate_components(self, queryset, bulk_create=True):
        """
        Instantiate components for the device from the specified component templates.

        Args:
            bulk_create: If True, bulk_create() will be called to create all components in a single query
                         (default). Otherwise, save() will be called on each instance individually.
        """
        model = queryset.model.component_model

        if bulk_create:
            components = [obj.instantiate(device=self) for obj in queryset]
            if not components:
                return

            # Check for duplicate names after resolution {vc_position}
            self._check_duplicate_component_names(components)

            # Set default values for any applicable custom fields
            if cf_defaults := CustomField.objects.get_defaults_for_model(model):
                for component in components:
                    component.custom_field_data = cf_defaults
            # Set denormalized references
            for component in components:
                component._site = self.site
                component._location = self.location
                component._rack = self.rack
            components = model.objects.bulk_create(components)
            # Prefetch related objects to minimize queries needed during post_save
            prefetch_fields = get_prefetchable_fields(model)
            prefetch_related_objects(components, *prefetch_fields)
            # Manually send the post_save signal for each of the newly created components
            for component in components:
                post_save.send(
                    sender=model,
                    instance=component,
                    created=True,
                    raw=False,
                    using='default',
                    update_fields=None
                )
        else:
            components = [obj.instantiate(device=self) for obj in queryset]
            if not components:
                return

            # Check for duplicate names after resolution {vc_position}
            self._check_duplicate_component_names(components)

            for component in components:
                # Set default values for any applicable custom fields
                if cf_defaults := CustomField.objects.get_defaults_for_model(model):
                    component.custom_field_data = cf_defaults
                component.save()

    def save(self, *args, **kwargs):
        is_new = not bool(self.pk)

        # Inherit airflow attribute from DeviceType if not set
        if is_new and not self.airflow:
            self.airflow = self.device_type.airflow

        # Inherit default_platform from DeviceType if not set
        if is_new and not self.platform:
            self.platform = self.device_type.default_platform

        # Inherit location from Rack if not set
        if self.rack and self.rack.location:
            self.location = self.rack.location

        super().save(*args, **kwargs)

        # If this is a new Device, instantiate all the related components per the DeviceType definition
        if is_new:
            self._instantiate_components(self.device_type.consoleporttemplates.all())
            self._instantiate_components(self.device_type.consoleserverporttemplates.all())
            self._instantiate_components(self.device_type.powerporttemplates.all())
            self._instantiate_components(self.device_type.poweroutlettemplates.all())
            self._instantiate_components(self.device_type.interfacetemplates.all())
            self._instantiate_components(self.device_type.rearporttemplates.all())
            self._instantiate_components(self.device_type.frontporttemplates.all())
            # Replicate any front/rear port mappings from the DeviceType
            create_port_mappings(self, self.device_type)
            # Disable bulk_create to accommodate MPTT
            self._instantiate_components(self.device_type.modulebaytemplates.all(), bulk_create=False)
            self._instantiate_components(self.device_type.devicebaytemplates.all())
            # Disable bulk_create to accommodate MPTT
            self._instantiate_components(self.device_type.inventoryitemtemplates.all(), bulk_create=False)
            # Interface bridges have to be set after interface instantiation
            update_interface_bridges(self, self.device_type.interfacetemplates.all())

        # Update Site and Rack assignment for any child Devices
        devices = Device.objects.filter(parent_bay__device=self)
        for device in devices:
            device.site = self.site
            device.rack = self.rack
            device.location = self.location
            device.save()

    @property
    def label(self):
        """
        Return the device name if set; otherwise return a generated name if available.
        """
        if self.name:
            return self.name
        if self.virtual_chassis:
            return f'{self.virtual_chassis.name}:{self.vc_position}'
        return None

    @property
    def identifier(self):
        """
        Return the device name if set; otherwise return the Device's primary key as {pk}
        """
        return self.label or '{{{}}}'.format(self.pk)

    @property
    def primary_ip(self):
        if ConfigItem('PREFER_IPV4')() and self.primary_ip4:
            return self.primary_ip4
        if self.primary_ip6:
            return self.primary_ip6
        if self.primary_ip4:
            return self.primary_ip4
        return None

    @property
    def interfaces_count(self):
        return self.vc_interfaces().count()

    def get_vc_master(self):
        """
        If this Device is a VirtualChassis member, return the VC master. Otherwise, return None.
        """
        return self.virtual_chassis.master if self.virtual_chassis else None

    def vc_interfaces(self, if_master=True):
        """
        Return a QuerySet matching all Interfaces assigned to this Device or, if this Device is a VC master, to another
        Device belonging to the same VirtualChassis.

        :param if_master: If True, return VC member interfaces only if this Device is the VC master.
        """
        filter = Q(device=self) if self.pk else Q()
        if self.virtual_chassis and (self.virtual_chassis.master == self or not if_master):
            filter |= Q(device__virtual_chassis=self.virtual_chassis, mgmt_only=False)
        return Interface.objects.filter(filter)

    def get_cables(self, pk_list=False):
        """
        Return a QuerySet or PK list matching all Cables connected to a component of this Device.
        """
        from .cables import Cable
        cable_pks = []
        for component_model in [
            ConsolePort, ConsoleServerPort, PowerPort, PowerOutlet, Interface, FrontPort, RearPort
        ]:
            cable_pks += component_model.objects.filter(
                device=self, cable__isnull=False
            ).values_list('cable', flat=True)
        if pk_list:
            return cable_pks
        return Cable.objects.filter(pk__in=cable_pks)

    def get_children(self):
        """
        Return the set of child Devices installed in DeviceBays within this Device.
        """
        return Device.objects.filter(parent_bay__device=self.pk)

    def get_status_color(self):
        return DeviceStatusChoices.colors.get(self.status)

    @cached_property
    def total_weight(self):
        total_weight = sum(
            module.module_type._abs_weight
            for module in Module.objects.filter(device=self)
            .exclude(module_type___abs_weight__isnull=True)
            .prefetch_related('module_type')
        )
        if self.device_type._abs_weight:
            total_weight += self.device_type._abs_weight
        return round(total_weight / 1000, 2)


#
# Virtual chassis
#

class VirtualChassis(PrimaryModel):
    """
    A collection of Devices which operate with a shared control plane (e.g. a switch stack).
    """
    master = models.OneToOneField(
        to='Device',
        on_delete=models.PROTECT,
        related_name='vc_master_for',
        blank=True,
        null=True
    )
    name = models.CharField(
        verbose_name=_('name'),
        max_length=64,
        db_collation="natural_sort"
    )
    domain = models.CharField(
        verbose_name=_('domain'),
        max_length=30,
        blank=True
    )

    # Counter fields
    member_count = CounterCacheField(
        to_model='dcim.Device',
        to_field='virtual_chassis'
    )

    class Meta:
        ordering = ['name']
        indexes = (
            models.Index(fields=('name',)),  # Default ordering
        )
        verbose_name = _('virtual chassis')
        verbose_name_plural = _('virtual chassis')

    def __str__(self):
        return self.name

    def clean(self):
        super().clean()

        # Verify that the selected master device has been assigned to this VirtualChassis. (Skip when creating a new
        # VirtualChassis.)
        if not self._state.adding and self.master and self.master not in self.members.all():
            raise ValidationError({
                'master': _("The selected master ({master}) is not assigned to this virtual chassis.").format(
                    master=self.master
                )
            })

    def delete(self, *args, **kwargs):
        # Check for LAG interfaces split across member chassis
        interfaces = Interface.objects.filter(
            device__in=self.members.all(),
            lag__isnull=False
        ).exclude(
            lag__device=F('device')
        )
        if interfaces:
            raise ProtectedError(
                _(
                    "Unable to delete virtual chassis {virtual_chassis}. One or more member interfaces form a "
                    "cross-chassis LAG."
                ).format(virtual_chassis=self),
                set(interfaces),
            )

        # Clear vc_position and vc_priority on member devices BEFORE calling super().delete()
        # This must be done here because on_delete=SET_NULL executes before pre_delete signal
        for device in self.members.all():
            device.vc_position = None
            device.vc_priority = None
            device.save()

        return super().delete(*args, **kwargs)


class VirtualDeviceContext(PrimaryModel):
    device = models.ForeignKey(
        to='Device',
        on_delete=models.PROTECT,
        related_name='vdcs',
        blank=True,
        null=True
    )
    name = models.CharField(
        verbose_name=_('name'),
        max_length=64,
        db_collation="natural_sort"
    )
    status = models.CharField(
        verbose_name=_('status'),
        max_length=50,
        choices=VirtualDeviceContextStatusChoices,
    )
    identifier = models.PositiveSmallIntegerField(
        verbose_name=_('identifier'),
        help_text=_('Numeric identifier unique to the parent device'),
        blank=True,
        null=True,
    )
    primary_ip4 = models.OneToOneField(
        to='ipam.IPAddress',
        on_delete=models.SET_NULL,
        related_name='+',
        blank=True,
        null=True,
        verbose_name=_('primary IPv4')
    )
    primary_ip6 = models.OneToOneField(
        to='ipam.IPAddress',
        on_delete=models.SET_NULL,
        related_name='+',
        blank=True,
        null=True,
        verbose_name=_('primary IPv6')
    )
    tenant = models.ForeignKey(
        to='tenancy.Tenant',
        on_delete=models.PROTECT,
        related_name='vdcs',
        blank=True,
        null=True
    )
    comments = models.TextField(
        verbose_name=_('comments'),
        blank=True
    )

    class Meta:
        ordering = ['name']
        constraints = (
            models.UniqueConstraint(
                fields=('device', 'identifier',),
                name='%(app_label)s_%(class)s_device_identifier'
            ),
            models.UniqueConstraint(
                fields=('device', 'name',),
                name='%(app_label)s_%(class)s_device_name'
            ),
        )
        indexes = (
            models.Index(fields=('name',)),  # Default ordering
        )
        verbose_name = _('virtual device context')
        verbose_name_plural = _('virtual device contexts')

    def __str__(self):
        return self.name

    def get_status_color(self):
        return VirtualDeviceContextStatusChoices.colors.get(self.status)

    @property
    def primary_ip(self):
        if ConfigItem('PREFER_IPV4')() and self.primary_ip4:
            return self.primary_ip4
        if self.primary_ip6:
            return self.primary_ip6
        if self.primary_ip4:
            return self.primary_ip4
        return None

    def clean(self):
        super().clean()

        # Validate primary IPv4/v6 assignment
        for primary_ip, family in ((self.primary_ip4, 4), (self.primary_ip6, 6)):
            if not primary_ip:
                continue
            if primary_ip.family != family:
                raise ValidationError({
                    f'primary_ip{family}': _(
                        "{ip} is not an IPv{family} address."
                    ).format(family=family, ip=primary_ip)
                })
            device_interfaces = self.device.vc_interfaces(if_master=False)
            if primary_ip.assigned_object not in device_interfaces:
                raise ValidationError({
                    f'primary_ip{family}': _('Primary IP address must belong to an interface on the assigned device.')
                })


#
# Addressing
#

class MACAddress(PrimaryModel):
    mac_address = MACAddressField(
        verbose_name=_('MAC address')
    )
    assigned_object_type = models.ForeignKey(
        to='contenttypes.ContentType',
        on_delete=models.PROTECT,
        related_name='+',
        blank=True,
        null=True
    )
    assigned_object_id = models.PositiveBigIntegerField(
        blank=True,
        null=True
    )
    assigned_object = GenericForeignKey(
        ct_field='assigned_object_type',
        fk_field='assigned_object_id'
    )

    class Meta:
        ordering = ('mac_address', 'pk')
        indexes = (
            models.Index(fields=('mac_address', 'id')),  # Default ordering
            models.Index(fields=('assigned_object_type', 'assigned_object_id')),
        )
        verbose_name = _('MAC address')
        verbose_name_plural = _('MAC addresses')

    def __str__(self):
        return str(self.mac_address)

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

        # Denote the original assigned object (if any) for validation in clean()
        self._original_assigned_object_id = self.__dict__.get('assigned_object_id')
        self._original_assigned_object_type_id = self.__dict__.get('assigned_object_type_id')

    @cached_property
    def is_primary(self):
        if self.assigned_object and hasattr(self.assigned_object, 'primary_mac_address'):
            if self.assigned_object.primary_mac_address and self.assigned_object.primary_mac_address.pk == self.pk:
                return True
        return False

    def clean(self, *args, **kwargs):
        super().clean()
        if self._original_assigned_object_id and self._original_assigned_object_type_id:
            assigned_object = self.assigned_object
            ct = ContentType.objects.get_for_id(self._original_assigned_object_type_id)
            original_assigned_object = ct.get_object_for_this_type(pk=self._original_assigned_object_id)

            if (
                original_assigned_object.primary_mac_address
                and original_assigned_object.primary_mac_address.pk == self.pk
            ):
                if not assigned_object:
                    raise ValidationError(
                        _("Cannot unassign MAC Address while it is designated as the primary MAC for an object")
                    )
                if original_assigned_object != assigned_object:
                    raise ValidationError(
                        _("Cannot reassign MAC Address while it is designated as the primary MAC for an object")
                    )
