# This file is part of dnmgmt, a number resource management system
# Licensed under GNU General Public License v3 or later
# Written by Sebastian Lohff (seba@someserver.de)

from django.db import models
from django.urls import reverse

from whoisdb.models import MntdObject, WhoisObject, Contact, InetNum

import ipaddress

# generally allow domains for .dn to be created
# allow owners of a subnet to create reverse dns record?


class Nameserver(MntdObject):
    handleSuffix = "NS"
    # dns name
    # ip address, if glue
    #    ipv4/ipv6 address?
    handle = None
    name = models.CharField(max_length=256)
    glueIPv4 = models.GenericIPAddressField(protocol='IPv4', blank=True, null=True)
    glueIPv6 = models.GenericIPAddressField(protocol='IPv6', blank=True, null=True)

    admin_c = models.ManyToManyField(Contact)

    def getPK(self):
        return self.pk

    def get_absolute_url(self):
        return reverse("domains:nameserver-show", args=(self.pk,))

    def __str__(self):
        return self.name

    def getAppName(self):
        return "domains"

    def getNoDeleteReasons(self):
        # nameservers can always be deleted
        return []


class Domain(MntdObject):
    handle = None
    handleSuffix = "DOM"
    name = models.CharField(max_length=67, unique=True, db_index=True)

    nameservers = models.ManyToManyField(Nameserver, blank=True)
    admin_c = models.ManyToManyField(Contact)

    ds_records = models.TextField(blank=True, verbose_name='DS Records',
                                  help_text='DS Records in the format of [id] [crypto-algo] [hash-algo] [hash]')

    def getPK(self):
        return self.name

    def getZone(self):
        return self.name

    def get_absolute_url(self):
        return reverse("domains:domain-show", args=(self.name,))

    def __str__(self):
        return self.name

    def getAppName(self):
        return "domains"

    def getNoDeleteReasons(self):
        reasons = []

        nameservers = Nameserver.objects.filter(name__endswith="." + self.name)
        for ns in nameservers:
            # FIXME: check if the nameserver has a glue record.... and also if it is maintained by us
            reasons.append("Nameserver %s depends on this domain" % ns.name)

        return reasons

    @classmethod
    def fixName(clazz, name):
        if not name.endswith("."):
            name += "."
        return name.lower()


class ReverseZone(WhoisObject):
    handle = None

    parentNet = models.ForeignKey(InetNum)
    address = models.GenericIPAddressField(db_index=True)
    netmask = models.PositiveIntegerField()

    nameservers = models.ManyToManyField(Nameserver)

    def getPK(self):
        return self.pk

    def prefix(self):
        """ Helper function, mainly used in templates """
        return "%s/%s" % (self.address, self.netmask)

    def getNetwork(self):
        return ipaddress.ip_network(self.prefix())

    def getZone(self):
        net = self.parentNet.getNetwork()
        if net.version == 4:
            # does not work with python3.4
            ## for these we delegate the full domain
            #if 0 < net.prefixlen < 32 and net.prefixlen % 8 == 0:
            #    zoneParts = net.reverse_pointer.split(".")

            #    return ".".join(zoneParts[1:])
            #else:
            #    # return RFC2317 compliant zone
            #    return net.reverse_pointer
            parts = list(reversed(str(net.network_address).split(".")))
            domain = ".".join(parts[4 - net.prefixlen // 8:]) + ".in-addr.arpa."
            if net.prefixlen % 8 == 0:
                # clean cut!
                return domain
            else:
                # RFC2317 compliant!
                rfc2317Domain = "%s/%s.%s" % (parts[4 - net.prefixlen // 8 - 1], net.prefixlen, domain)
                return rfc2317Domain
        else:
            ## does not work with python3.4
            ## ipv6
            ## thefuck ipaddress lib... _the_ _fuck_
            #zoneParts = net.reverse_pointer.split(".")[-2 - net.prefixlen // 4:]
            #return ".".join(zoneParts)

            parts = list(reversed(net.exploded.split("/")[0].replace(":", "")))[32 - net.prefixlen // 4:]
            return ".".join(parts) + ".ip6.arpa."

    def get_absolute_url(self):
        return reverse("domains:reversezone-show", args=(self.pk,))

    def getAppName(self):
        return "domains"

    def __str__(self):
        return "%s @ %s" % (self.prefix(), self.parentNet)

    def getNoDeleteReasons(self):
        return []

    def canEdit(self, user):
        if self.parentNet:
            return self.parentNet.canEdit(user)
        else:
            return False