from collections import OrderedDict

from django.core.validators import ValidationError
from django.db import models
from django.urls import reverse

from extras.querysets import ConfigContextQuerySet
from extras.utils import extras_features
from netbox.models import ChangeLoggedModel
from utilities.utils import deepmerge


__all__ = (
    'ConfigContext',
    'ConfigContextModel',
)


#
# Config contexts
#

@extras_features('webhooks')
class ConfigContext(ChangeLoggedModel):
    """
    A ConfigContext represents a set of arbitrary data available to any Device or VirtualMachine matching its assigned
    qualifiers (region, site, etc.). For example, the data stored in a ConfigContext assigned to site A and tenant B
    will be available to a Device in site A assigned to tenant B. Data is stored in JSON format.
    """
    name = models.CharField(
        max_length=100,
        unique=True
    )
    weight = models.PositiveSmallIntegerField(
        default=1000
    )
    description = models.CharField(
        max_length=200,
        blank=True
    )
    is_active = models.BooleanField(
        default=True,
    )
    regions = models.ManyToManyField(
        to='dcim.Region',
        related_name='+',
        blank=True
    )
    site_groups = models.ManyToManyField(
        to='dcim.SiteGroup',
        related_name='+',
        blank=True
    )
    sites = models.ManyToManyField(
        to='dcim.Site',
        related_name='+',
        blank=True
    )
    device_types = models.ManyToManyField(
        to='dcim.DeviceType',
        related_name='+',
        blank=True
    )
    roles = models.ManyToManyField(
        to='dcim.DeviceRole',
        related_name='+',
        blank=True
    )
    platforms = models.ManyToManyField(
        to='dcim.Platform',
        related_name='+',
        blank=True
    )
    cluster_groups = models.ManyToManyField(
        to='virtualization.ClusterGroup',
        related_name='+',
        blank=True
    )
    clusters = models.ManyToManyField(
        to='virtualization.Cluster',
        related_name='+',
        blank=True
    )
    tenant_groups = models.ManyToManyField(
        to='tenancy.TenantGroup',
        related_name='+',
        blank=True
    )
    tenants = models.ManyToManyField(
        to='tenancy.Tenant',
        related_name='+',
        blank=True
    )
    tags = models.ManyToManyField(
        to='extras.Tag',
        related_name='+',
        blank=True
    )
    data = models.JSONField()

    objects = ConfigContextQuerySet.as_manager()

    class Meta:
        ordering = ['weight', 'name']

    def __str__(self):
        return self.name

    def get_absolute_url(self):
        return reverse('extras:configcontext', kwargs={'pk': self.pk})

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

        # Verify that JSON data is provided as an object
        if type(self.data) is not dict:
            raise ValidationError(
                {'data': 'JSON data must be in object form. Example: {"foo": 123}'}
            )


class ConfigContextModel(models.Model):
    """
    A model which includes local configuration context data. This local data will override any inherited data from
    ConfigContexts.
    """
    local_context_data = models.JSONField(
        blank=True,
        null=True,
    )

    class Meta:
        abstract = True

    def get_config_context(self):
        """
        Return the rendered configuration context for a device or VM.
        """

        # Compile all config data, overwriting lower-weight values with higher-weight values where a collision occurs
        data = OrderedDict()

        if not hasattr(self, 'config_context_data'):
            # The annotation is not available, so we fall back to manually querying for the config context objects
            config_context_data = ConfigContext.objects.get_for_object(self, aggregate_data=True)
        else:
            # The attribute may exist, but the annotated value could be None if there is no config context data
            config_context_data = self.config_context_data or []

        for context in config_context_data:
            data = deepmerge(data, context)

        # If the object has local config context data defined, merge it last
        if self.local_context_data:
            data = deepmerge(data, self.local_context_data)

        return data

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

        # Verify that JSON data is provided as an object
        if self.local_context_data and type(self.local_context_data) is not dict:
            raise ValidationError(
                {'local_context_data': 'JSON data must be in object form. Example: {"foo": 123}'}
            )