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 CableTermination, 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', '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
    )

    objects = RestrictedQuerySet.as_manager()

    csv_headers = [
        'name', 'slug', 'asn', 'account', 'portal_url', 'noc_contact', 'admin_contact', 'comments',
    ]
    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])

    def to_csv(self):
        return (
            self.name,
            self.slug,
            self.asn,
            self.account,
            self.portal_url,
            self.noc_contact,
            self.admin_contact,
            self.comments,
        )


#
# Provider networks
#

@extras_features('custom_fields', 'custom_links', 'export_templates', '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
    )

    csv_headers = [
        'provider', 'name', 'description', 'comments',
    ]

    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])

    def to_csv(self):
        return (
            self.provider.name,
            self.name,
            self.description,
            self.comments,
        )


@extras_features('custom_fields', 'custom_links', 'export_templates', '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()

    csv_headers = ['name', 'slug', 'description']

    class Meta:
        ordering = ['name']

    def __str__(self):
        return self.name

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

    def to_csv(self):
        return (
            self.name,
            self.slug,
            self.description,
        )


@extras_features('custom_fields', 'custom_links', 'export_templates', '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
    )

    # 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()

    csv_headers = [
        'cid', 'provider', 'type', 'status', 'tenant', 'install_date', 'commit_rate', 'description', 'comments',
    ]
    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 to_csv(self):
        return (
            self.cid,
            self.provider.name,
            self.type.name,
            self.get_status_display(),
            self.tenant.name if self.tenant else None,
            self.install_date,
            self.commit_rate,
            self.description,
            self.comments,
        )

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


@extras_features('webhooks')
class CircuitTermination(ChangeLoggedModel, CableTermination):
    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