from django.contrib.contenttypes.fields import GenericForeignKey, GenericRelation
from django.contrib.contenttypes.models import ContentType
from django.contrib.postgres.fields import ArrayField, IntegerRangeField
from django.core.exceptions import ValidationError
from django.core.validators import MaxValueValidator, MinValueValidator
from django.db import models
from django.db.backends.postgresql.psycopg_any import NumericRange
from django.utils.translation import gettext_lazy as _

from dcim.models import Interface, Site, SiteGroup
from ipam.choices import *
from ipam.constants import *
from ipam.querysets import VLANGroupQuerySet, VLANQuerySet
from netbox.models import NetBoxModel, OrganizationalModel, PrimaryModel
from utilities.data import (
    check_ranges_overlap,
    get_inclusive_integer_range_bounds,
    normalize_integer_range,
    ranges_to_string,
    ranges_to_string_list,
)
from virtualization.models import VMInterface

__all__ = (
    'VLAN',
    'VLANGroup',
    'VLANTranslationPolicy',
    'VLANTranslationRule',
)


def default_vid_ranges():
    return [NumericRange(VLAN_VID_MIN, VLAN_VID_MAX + 1)]


class VLANGroup(OrganizationalModel):
    """
    A VLAN group is an arbitrary collection of VLANs within which VLAN IDs and names must be unique. Each group must
     define one or more ranges of valid VLAN IDs, and may be assigned a specific scope.
    """
    name = models.CharField(
        verbose_name=_('name'),
        max_length=100,
        db_collation="natural_sort"
    )
    slug = models.SlugField(
        verbose_name=_('slug'),
        max_length=100
    )
    scope_type = models.ForeignKey(
        to='contenttypes.ContentType',
        on_delete=models.CASCADE,
        blank=True,
        null=True
    )
    scope_id = models.PositiveBigIntegerField(
        blank=True,
        null=True
    )
    scope = GenericForeignKey(
        ct_field='scope_type',
        fk_field='scope_id'
    )
    # Normalized to canonical '[)' bounds on save() to match PostgreSQL storage.
    vid_ranges = ArrayField(
        IntegerRangeField(),
        verbose_name=_('VLAN ID ranges'),
        default=default_vid_ranges
    )
    total_vlan_ids = models.PositiveBigIntegerField(
        default=VLAN_VID_MAX - VLAN_VID_MIN + 1,
    )
    tenant = models.ForeignKey(
        to='tenancy.Tenant',
        on_delete=models.PROTECT,
        related_name='vlan_groups',
        blank=True,
        null=True
    )

    objects = VLANGroupQuerySet.as_manager()

    class Meta:
        ordering = ('name', 'pk')  # Name may be non-unique
        indexes = (
            models.Index(fields=('name', 'id')),  # Default ordering
            models.Index(fields=('scope_type', 'scope_id')),
        )
        constraints = (
            models.UniqueConstraint(
                fields=('scope_type', 'scope_id', 'name'),
                name='%(app_label)s_%(class)s_unique_scope_name'
            ),
            models.UniqueConstraint(
                fields=('scope_type', 'scope_id', 'slug'),
                name='%(app_label)s_%(class)s_unique_scope_slug'
            ),
        )
        verbose_name = _('VLAN group')
        verbose_name_plural = _('VLAN groups')

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

        # Validate scope assignment
        if self.scope_type and not self.scope_id:
            raise ValidationError(_("Cannot set scope_type without scope_id."))
        if self.scope_id and not self.scope_type:
            raise ValidationError(_("Cannot set scope_id without scope_type."))

        # Validate VID ranges
        for vid_range in self.vid_ranges:
            lower_vid, upper_vid = get_inclusive_integer_range_bounds(vid_range)
            if lower_vid < VLAN_VID_MIN:
                raise ValidationError({
                    'vid_ranges': _("Starting VLAN ID in range ({value}) cannot be less than {minimum}").format(
                        value=lower_vid, minimum=VLAN_VID_MIN
                    )
                })
            if upper_vid > VLAN_VID_MAX:
                raise ValidationError({
                    'vid_ranges': _("Ending VLAN ID in range ({value}) cannot exceed {maximum}").format(
                        value=upper_vid, maximum=VLAN_VID_MAX
                    )
                })
            if lower_vid > upper_vid:
                raise ValidationError({
                    'vid_ranges': _(
                        "Ending VLAN ID in range must be greater than or equal to the starting VLAN ID ({range})"
                    ).format(range=f'{lower_vid}-{upper_vid}')
                })

        # Check for overlapping VID ranges
        if self.vid_ranges and check_ranges_overlap(self.vid_ranges):
            raise ValidationError({'vid_ranges': _("Ranges cannot overlap.")})

    def save(self, *args, **kwargs):
        # Canonicalize vid_ranges on the instance so callers (e.g. Custom Scripts)
        # see the same value in memory that PostgreSQL stores.
        self.total_vlan_ids = 0
        vid_ranges = []
        for vid_range in self.vid_ranges:
            vid_range = normalize_integer_range(vid_range)
            vid_ranges.append(vid_range)
            self.total_vlan_ids += vid_range.upper - vid_range.lower
        self.vid_ranges = vid_ranges

        update_fields = kwargs.get('update_fields')
        if update_fields is not None and 'vid_ranges' in update_fields:
            # total_vlan_ids is a denormalized cache of vid_ranges; persist them together.
            kwargs['update_fields'] = list(set(update_fields) | {'total_vlan_ids'})

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

    def get_available_vids(self):
        """
        Return all available VLANs within this group.
        """
        available_vlans = set()
        for vlan_range in self.vid_ranges:
            lower_vid, upper_vid = get_inclusive_integer_range_bounds(vlan_range)
            available_vlans.update(range(lower_vid, upper_vid + 1))
        available_vlans -= set(VLAN.objects.filter(group=self).values_list('vid', flat=True))

        return sorted(available_vlans)

    def get_next_available_vid(self):
        """
        Return the first available VLAN ID (1-4094) in the group.
        """
        available_vids = self.get_available_vids()
        if available_vids:
            return available_vids[0]
        return None

    def get_child_vlans(self):
        """
        Return all VLANs within this group.
        """
        return VLAN.objects.filter(group=self).order_by('vid')

    @property
    def vid_ranges_items(self):
        """
        Property that converts VID ranges to a list of string representations.
        """
        return ranges_to_string_list(self.vid_ranges)

    @property
    def vid_ranges_list(self):
        """
        Property that converts VID ranges into a string representation.
        """
        return ranges_to_string(self.vid_ranges)


class VLAN(PrimaryModel):
    """
    A VLAN is a distinct layer two forwarding domain identified by a 12-bit integer (1-4094). Each VLAN must be assigned
    to a Site, however VLAN IDs need not be unique within a Site. A VLAN may optionally be assigned to a VLANGroup,
    within which all VLAN IDs and names but be unique.

    Like Prefixes, each VLAN is assigned an operational status and optionally a user-defined Role. A VLAN can have zero
    or more Prefixes assigned to it.
    """
    site = models.ForeignKey(
        to='dcim.Site',
        on_delete=models.PROTECT,
        related_name='vlans',
        blank=True,
        null=True,
        help_text=_("The specific site to which this VLAN is assigned (if any)")
    )
    group = models.ForeignKey(
        to='ipam.VLANGroup',
        on_delete=models.PROTECT,
        related_name='vlans',
        blank=True,
        null=True,
        help_text=_("VLAN group (optional)")
    )
    vid = models.PositiveSmallIntegerField(
        verbose_name=_('VLAN ID'),
        validators=(
            MinValueValidator(VLAN_VID_MIN),
            MaxValueValidator(VLAN_VID_MAX)
        ),
        help_text=_("Numeric VLAN ID (1-4094)")
    )
    name = models.CharField(
        verbose_name=_('name'),
        max_length=64
    )
    tenant = models.ForeignKey(
        to='tenancy.Tenant',
        on_delete=models.PROTECT,
        related_name='vlans',
        blank=True,
        null=True
    )
    status = models.CharField(
        verbose_name=_('status'),
        max_length=50,
        choices=VLANStatusChoices,
        default=VLANStatusChoices.STATUS_ACTIVE,
        help_text=_("Operational status of this VLAN")
    )
    role = models.ForeignKey(
        to='ipam.Role',
        on_delete=models.SET_NULL,
        related_name='vlans',
        blank=True,
        null=True,
        help_text=_("The primary function of this VLAN")
    )
    qinq_svlan = models.ForeignKey(
        to='self',
        on_delete=models.PROTECT,
        related_name='qinq_cvlans',
        blank=True,
        null=True
    )
    qinq_role = models.CharField(
        verbose_name=_('Q-in-Q role'),
        max_length=50,
        choices=VLANQinQRoleChoices,
        blank=True,
        null=True,
        help_text=_("Customer/service VLAN designation (for Q-in-Q/IEEE 802.1ad)")
    )
    l2vpn_terminations = GenericRelation(
        to='vpn.L2VPNTermination',
        content_type_field='assigned_object_type',
        object_id_field='assigned_object_id',
        related_query_name='vlan'
    )

    objects = VLANQuerySet.as_manager()

    clone_fields = [
        'site', 'group', 'tenant', 'status', 'role', 'description', 'qinq_role', 'qinq_svlan',
    ]

    class Meta:
        ordering = ('site', 'group', 'vid', 'pk')  # (site, group, vid) may be non-unique
        indexes = (
            models.Index(fields=('site', 'group', 'vid', 'id')),  # Default ordering
        )
        constraints = (
            models.UniqueConstraint(
                fields=('group', 'vid'),
                name='%(app_label)s_%(class)s_unique_group_vid'
            ),
            models.UniqueConstraint(
                fields=('group', 'name'),
                name='%(app_label)s_%(class)s_unique_group_name'
            ),
            models.UniqueConstraint(
                fields=('qinq_svlan', 'vid'),
                name='%(app_label)s_%(class)s_unique_qinq_svlan_vid'
            ),
            models.UniqueConstraint(
                fields=('qinq_svlan', 'name'),
                name='%(app_label)s_%(class)s_unique_qinq_svlan_name'
            ),
        )
        verbose_name = _('VLAN')
        verbose_name_plural = _('VLANs')

    def __str__(self):
        return f'{self.name} ({self.vid})'

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

        # Validate VLAN group (if assigned)
        if self.group and self.site and self.group.scope_type == ContentType.objects.get_for_model(Site):
            if self.site != self.group.scope:
                raise ValidationError(
                    _(
                        "VLAN is assigned to group {group} (scope: {scope}); cannot also assign to site {site}."
                    ).format(group=self.group, scope=self.group.scope, site=self.site)
                )
        if self.group and self.site and self.group.scope_type == ContentType.objects.get_for_model(SiteGroup):
            if self.site not in self.group.scope.sites.all():
                raise ValidationError(
                    _(
                        "The assigned site {site} is not a member of the assigned group {group} (scope: {scope})."
                    ).format(group=self.group, scope=self.group.scope, site=self.site)
                )

        # Check that the VLAN ID is permitted in the assigned group (if any)
        if self.group and self.vid is not None:
            if not any([self.vid in r for r in self.group.vid_ranges]):
                raise ValidationError({
                    'vid': _(
                        "VID must be in ranges {ranges} for VLANs in group {group}"
                    ).format(ranges=ranges_to_string(self.group.vid_ranges), group=self.group)
                })

        # Only Q-in-Q customer VLANs may be assigned to a service VLAN
        if self.qinq_svlan and self.qinq_role != VLANQinQRoleChoices.ROLE_CUSTOMER:
            raise ValidationError({
                'qinq_svlan': _("Only Q-in-Q customer VLANs maybe assigned to a service VLAN.")
            })

        # A Q-in-Q customer VLAN must be assigned to a service VLAN
        if self.qinq_role == VLANQinQRoleChoices.ROLE_CUSTOMER and not self.qinq_svlan:
            raise ValidationError({
                'qinq_role': _("A Q-in-Q customer VLAN must be assigned to a service VLAN.")
            })

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

    def get_qinq_role_color(self):
        return VLANQinQRoleChoices.colors.get(self.qinq_role)

    def get_interfaces(self):
        # Return all device interfaces assigned to this VLAN
        return Interface.objects.filter(
            Q(untagged_vlan_id=self.pk) |
            Q(tagged_vlans=self.pk)
        ).distinct()

    def get_vminterfaces(self):
        # Return all VM interfaces assigned to this VLAN
        return VMInterface.objects.filter(
            Q(untagged_vlan_id=self.pk) |
            Q(tagged_vlans=self.pk)
        ).distinct()

    @property
    def l2vpn_termination(self):
        return self.l2vpn_terminations.first()


class VLANTranslationPolicy(PrimaryModel):
    name = models.CharField(
        verbose_name=_('name'),
        max_length=100,
        unique=True,
    )

    class Meta:
        verbose_name = _('VLAN translation policy')
        verbose_name_plural = _('VLAN translation policies')
        ordering = ('name',)

    def __str__(self):
        return self.name


class VLANTranslationRule(NetBoxModel):
    policy = models.ForeignKey(
        to=VLANTranslationPolicy,
        related_name='rules',
        on_delete=models.CASCADE,
    )
    description = models.CharField(
        verbose_name=_('description'),
        max_length=200,
        blank=True
    )
    local_vid = models.PositiveSmallIntegerField(
        verbose_name=_('Local VLAN ID'),
        validators=(
            MinValueValidator(VLAN_VID_MIN),
            MaxValueValidator(VLAN_VID_MAX)
        ),
        help_text=_("Numeric VLAN ID (1-4094)")
    )
    remote_vid = models.PositiveSmallIntegerField(
        verbose_name=_('Remote VLAN ID'),
        validators=(
            MinValueValidator(VLAN_VID_MIN),
            MaxValueValidator(VLAN_VID_MAX)
        ),
        help_text=_("Numeric VLAN ID (1-4094)")
    )
    prerequisite_models = (
        'ipam.VLANTranslationPolicy',
    )

    clone_fields = ['policy']

    class Meta:
        verbose_name = _('VLAN translation rule')
        ordering = ('policy', 'local_vid',)
        constraints = (
            models.UniqueConstraint(
                fields=('policy', 'local_vid'),
                name='%(app_label)s_%(class)s_unique_policy_local_vid'
            ),
            models.UniqueConstraint(
                fields=('policy', 'remote_vid'),
                name='%(app_label)s_%(class)s_unique_policy_remote_vid'
            ),
        )

    def __str__(self):
        return f'{self.local_vid} -> {self.remote_vid} ({self.policy})'

    def to_objectchange(self, action):
        objectchange = super().to_objectchange(action)
        objectchange.related_object = self.policy
        return objectchange