from django.contrib.contenttypes.fields import GenericRelation
from django.core.exceptions import ValidationError
from django.db import models
from django.urls import reverse

from dcim.fields import ASNField
from dcim.models import LinkTermination, PathEndpoint
from extras.models import ObjectChange
from extras.utils import extras_features
from netbox.models import BigIDModel, ChangeLoggedModel, OrganizationalModel, PrimaryModel
from utilities.querysets import RestrictedQuerySet
from .choices import *


__all__ = (
    'Circuit',
    'CircuitTermination',
    'CircuitType',
    'ProviderNetwork',
    'Provider',
)


@extras_features('custom_fields', 'custom_links', 'export_templates', 'tags', 'webhooks')
class Provider(PrimaryModel):
    """
    Each Circuit belongs to a Provider. This is usually a telecommunications company or similar organization. This model
    stores information pertinent to the user's relationship with the Provider.
    """
    name = models.CharField(
        max_length=100,
        unique=True
    )
    slug = models.SlugField(
        max_length=100,
        unique=True
    )
    asn = ASNField(
        blank=True,
        null=True,
        verbose_name='ASN',
        help_text='32-bit autonomous system number'
    )
    account = models.CharField(
        max_length=30,
        blank=True,
        verbose_name='Account number'
    )
    portal_url = models.URLField(
        blank=True,
        verbose_name='Portal URL'
    )
    noc_contact = models.TextField(
        blank=True,
        verbose_name='NOC contact'
    )
    admin_contact = models.TextField(
        blank=True,
        verbose_name='Admin contact'
    )
    comments = models.TextField(
        blank=True
    )

    # Generic relations
    contacts = GenericRelation(
        to='tenancy.ContactAssignment'
    )

    objects = RestrictedQuerySet.as_manager()

    clone_fields = [
        'asn', 'account', 'portal_url', 'noc_contact', 'admin_contact',
    ]

    class Meta:
        ordering = ['name']

    def __str__(self):
        return self.name

    def get_absolute_url(self):
        return reverse('circuits:provider', args=[self.pk])


#
# Provider networks
#

@extras_features('custom_fields', 'custom_links', 'export_templates', 'tags', 'webhooks')
class ProviderNetwork(PrimaryModel):
    """
    This represents a provider network which exists outside of NetBox, the details of which are unknown or
    unimportant to the user.
    """
    name = models.CharField(
        max_length=100
    )
    provider = models.ForeignKey(
        to='circuits.Provider',
        on_delete=models.PROTECT,
        related_name='networks'
    )
    description = models.CharField(
        max_length=200,
        blank=True
    )
    comments = models.TextField(
        blank=True
    )

    objects = RestrictedQuerySet.as_manager()

    class Meta:
        ordering = ('provider', 'name')
        constraints = (
            models.UniqueConstraint(
                fields=('provider', 'name'),
                name='circuits_providernetwork_provider_name'
            ),
        )
        unique_together = ('provider', 'name')

    def __str__(self):
        return self.name

    def get_absolute_url(self):
        return reverse('circuits:providernetwork', args=[self.pk])


@extras_features('custom_fields', 'custom_links', 'export_templates', 'tags', 'webhooks')
class CircuitType(OrganizationalModel):
    """
    Circuits can be organized by their functional role. For example, a user might wish to define CircuitTypes named
    "Long Haul," "Metro," or "Out-of-Band".
    """
    name = models.CharField(
        max_length=100,
        unique=True
    )
    slug = models.SlugField(
        max_length=100,
        unique=True
    )
    description = models.CharField(
        max_length=200,
        blank=True,
    )

    objects = RestrictedQuerySet.as_manager()

    class Meta:
        ordering = ['name']

    def __str__(self):
        return self.name

    def get_absolute_url(self):
        return reverse('circuits:circuittype', args=[self.pk])


@extras_features('custom_fields', 'custom_links', 'export_templates', 'tags', 'webhooks')
class Circuit(PrimaryModel):
    """
    A communications circuit connects two points. Each Circuit belongs to a Provider; Providers may have multiple
    circuits. Each circuit is also assigned a CircuitType and a Site.  Circuit port speed and commit rate are measured
    in Kbps.
    """
    cid = models.CharField(
        max_length=100,
        verbose_name='Circuit ID'
    )
    provider = models.ForeignKey(
        to='circuits.Provider',
        on_delete=models.PROTECT,
        related_name='circuits'
    )
    type = models.ForeignKey(
        to='CircuitType',
        on_delete=models.PROTECT,
        related_name='circuits'
    )
    status = models.CharField(
        max_length=50,
        choices=CircuitStatusChoices,
        default=CircuitStatusChoices.STATUS_ACTIVE
    )
    tenant = models.ForeignKey(
        to='tenancy.Tenant',
        on_delete=models.PROTECT,
        related_name='circuits',
        blank=True,
        null=True
    )
    install_date = models.DateField(
        blank=True,
        null=True,
        verbose_name='Date installed'
    )
    commit_rate = models.PositiveIntegerField(
        blank=True,
        null=True,
        verbose_name='Commit rate (Kbps)')
    description = models.CharField(
        max_length=200,
        blank=True
    )
    comments = models.TextField(
        blank=True
    )

    # Generic relations
    contacts = GenericRelation(
        to='tenancy.ContactAssignment'
    )
    images = GenericRelation(
        to='extras.ImageAttachment'
    )

    # Cache associated CircuitTerminations
    termination_a = models.ForeignKey(
        to='circuits.CircuitTermination',
        on_delete=models.SET_NULL,
        related_name='+',
        editable=False,
        blank=True,
        null=True
    )
    termination_z = models.ForeignKey(
        to='circuits.CircuitTermination',
        on_delete=models.SET_NULL,
        related_name='+',
        editable=False,
        blank=True,
        null=True
    )

    objects = RestrictedQuerySet.as_manager()

    clone_fields = [
        'provider', 'type', 'status', 'tenant', 'install_date', 'commit_rate', 'description',
    ]

    class Meta:
        ordering = ['provider', 'cid']
        unique_together = ['provider', 'cid']

    def __str__(self):
        return self.cid

    def get_absolute_url(self):
        return reverse('circuits:circuit', args=[self.pk])

    def get_status_class(self):
        return CircuitStatusChoices.CSS_CLASSES.get(self.status)


@extras_features('webhooks')
class CircuitTermination(ChangeLoggedModel, LinkTermination):
    circuit = models.ForeignKey(
        to='circuits.Circuit',
        on_delete=models.CASCADE,
        related_name='terminations'
    )
    term_side = models.CharField(
        max_length=1,
        choices=CircuitTerminationSideChoices,
        verbose_name='Termination'
    )
    site = models.ForeignKey(
        to='dcim.Site',
        on_delete=models.PROTECT,
        related_name='circuit_terminations',
        blank=True,
        null=True
    )
    provider_network = models.ForeignKey(
        to=ProviderNetwork,
        on_delete=models.PROTECT,
        related_name='circuit_terminations',
        blank=True,
        null=True
    )
    port_speed = models.PositiveIntegerField(
        verbose_name='Port speed (Kbps)',
        blank=True,
        null=True
    )
    upstream_speed = models.PositiveIntegerField(
        blank=True,
        null=True,
        verbose_name='Upstream speed (Kbps)',
        help_text='Upstream speed, if different from port speed'
    )
    xconnect_id = models.CharField(
        max_length=50,
        blank=True,
        verbose_name='Cross-connect ID'
    )
    pp_info = models.CharField(
        max_length=100,
        blank=True,
        verbose_name='Patch panel/port(s)'
    )
    description = models.CharField(
        max_length=200,
        blank=True
    )

    objects = RestrictedQuerySet.as_manager()

    class Meta:
        ordering = ['circuit', 'term_side']
        unique_together = ['circuit', 'term_side']

    def __str__(self):
        return f'Termination {self.term_side}: {self.site or self.provider_network}'

    def get_absolute_url(self):
        if self.site:
            return self.site.get_absolute_url()
        return self.provider_network.get_absolute_url()

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

        # Must define either site *or* provider network
        if self.site is None and self.provider_network is None:
            raise ValidationError("A circuit termination must attach to either a site or a provider network.")
        if self.site and self.provider_network:
            raise ValidationError("A circuit termination cannot attach to both a site and a provider network.")

    def to_objectchange(self, action):
        # Annotate the parent Circuit
        try:
            circuit = self.circuit
        except Circuit.DoesNotExist:
            # Parent circuit has been deleted
            circuit = None
        return super().to_objectchange(action, related_object=circuit)

    @property
    def parent_object(self):
        return self.circuit

    def get_peer_termination(self):
        peer_side = 'Z' if self.term_side == 'A' else 'A'
        try:
            return CircuitTermination.objects.prefetch_related('site').get(
                circuit=self.circuit,
                term_side=peer_side
            )
        except CircuitTermination.DoesNotExist:
            return None