from django.contrib.postgres.fields import ArrayField
from django.core.exceptions import ValidationError
from django.core.validators import MaxValueValidator, MinValueValidator
from django.db import models
from django.urls import reverse
from taggit.managers import TaggableManager

from extras.models import TaggedItem
from extras.utils import extras_features
from ipam.choices import *
from ipam.constants import *
from netbox.models import PrimaryModel
from utilities.querysets import RestrictedQuerySet
from utilities.utils import array_to_string


__all__ = (
    'Service',
)


@extras_features('custom_fields', 'custom_links', 'export_templates', 'webhooks')
class Service(PrimaryModel):
    """
    A Service represents a layer-four service (e.g. HTTP or SSH) running on a Device or VirtualMachine. A Service may
    optionally be tied to one or more specific IPAddresses belonging to its parent.
    """
    device = models.ForeignKey(
        to='dcim.Device',
        on_delete=models.CASCADE,
        related_name='services',
        verbose_name='device',
        null=True,
        blank=True
    )
    virtual_machine = models.ForeignKey(
        to='virtualization.VirtualMachine',
        on_delete=models.CASCADE,
        related_name='services',
        null=True,
        blank=True
    )
    name = models.CharField(
        max_length=100
    )
    protocol = models.CharField(
        max_length=50,
        choices=ServiceProtocolChoices
    )
    ports = ArrayField(
        base_field=models.PositiveIntegerField(
            validators=[
                MinValueValidator(SERVICE_PORT_MIN),
                MaxValueValidator(SERVICE_PORT_MAX)
            ]
        ),
        verbose_name='Port numbers'
    )
    ipaddresses = models.ManyToManyField(
        to='ipam.IPAddress',
        related_name='services',
        blank=True,
        verbose_name='IP addresses'
    )
    description = models.CharField(
        max_length=200,
        blank=True
    )
    tags = TaggableManager(through=TaggedItem)

    objects = RestrictedQuerySet.as_manager()

    csv_headers = ['device', 'virtual_machine', 'name', 'protocol', 'ports', 'description']

    class Meta:
        ordering = ('protocol', 'ports', 'pk')  # (protocol, port) may be non-unique

    def __str__(self):
        return f'{self.name} ({self.get_protocol_display()}/{self.port_list})'

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

    @property
    def parent(self):
        return self.device or self.virtual_machine

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

        # A Service must belong to a Device *or* to a VirtualMachine
        if self.device and self.virtual_machine:
            raise ValidationError("A service cannot be associated with both a device and a virtual machine.")
        if not self.device and not self.virtual_machine:
            raise ValidationError("A service must be associated with either a device or a virtual machine.")

    def to_csv(self):
        return (
            self.device.name if self.device else None,
            self.virtual_machine.name if self.virtual_machine else None,
            self.name,
            self.get_protocol_display(),
            self.ports,
            self.description,
        )

    @property
    def port_list(self):
        return array_to_string(self.ports)