import uuid
import ipaddress

from django.db import models
from django.contrib.auth import get_user_model
from django.core.validators import MinValueValidator, MaxValueValidator
from django.core.exceptions import FieldError, ValidationError

from uncloud_pay.models import Order

class WireGuardVPNPool(models.Model):
    """
    Network address pools from which VPNs can be created
    """

    class Meta:
        constraints = [
            models.UniqueConstraint(fields=['wg_name', 'vpn_server_hostname' ],
                                    name='unique_interface_name_per_host')
            ]


    # Linux interface naming is restricing to max 15 characters
    wg_name = models.CharField(max_length=15)

    network = models.GenericIPAddressField(unique=True)
    network_mask = models.IntegerField(validators=[MinValueValidator(0),
                                                   MaxValueValidator(128)])

    subnetwork_mask = models.IntegerField(validators=[
        MinValueValidator(0),
        MaxValueValidator(128)
    ])

    vpn_server_hostname = models.CharField(max_length=256)
    wireguard_private_key = models.CharField(max_length=48)
    wireguard_public_key = models.CharField(max_length=48)

    @property
    def max_pool_index(self):
        """
        Return the highest possible network / last network id
        """

        bits = self.subnetwork_mask - self.network_mask

        return (2**bits)-1

    @property
    def ip_network(self):
        return ipaddress.ip_network(f"{self.network}/{self.network_mask}")

    def __str__(self):
        return f"{self.ip_network} (subnets: /{self.subnetwork_mask})"

    @property
    def wireguard_config(self):
        wireguard_config = [ f"[Interface]\nListenPort = 51820\nPrivateKey = {self.wireguard_private_key}\n" ]

        peers = []

        for vpn in self.wireguardvpn_set.all():
            public_key = vpn.wireguard_public_key
            peer_network = f"{vpn.address}/{self.subnetwork_mask}"
            owner = vpn.owner

            peers.append(f"# Owner: {owner}\n[Peer]\nPublicKey = {public_key}\nAllowedIPs = {peer_network}\n\n")

        wireguard_config.extend(peers)

        return "\n".join(wireguard_config)


class WireGuardVPN(models.Model):
    """
    Created VPNNetworks
    """
    owner = models.ForeignKey(get_user_model(),
            on_delete=models.CASCADE)
    vpnpool = models.ForeignKey(WireGuardVPNPool,
                                 on_delete=models.CASCADE)

    pool_index = models.IntegerField(unique=True)

    wireguard_public_key = models.CharField(max_length=48, unique=True)

    class Meta:
        constraints = [
            models.UniqueConstraint(fields=['vpnpool', 'wireguard_public_key'],
                                    name='wg_key_unique_per_pool')
        ]


    @property
    def network_mask(self):
        return self.vpnpool.subnetwork_mask

    @property
    def vpn_server(self):
        return self.vpnpool.vpn_server_hostname

    @property
    def vpn_server_public_key(self):
        return self.vpnpool.wireguard_public_key

    @property
    def address(self):
        """
        Locate the correct subnet in the supernet

        First get the network itself

        """

        net = self.vpnpool.ip_network
        subnet = net[(2**(128-self.vpnpool.subnetwork_mask)) * self.pool_index]

        return str(subnet)

    def __str__(self):
        return f"{self.address} ({self.pool_index})"


class WireGuardVPNFreeLeases(models.Model):
    """
    Previously used VPNNetworks
    """
    vpnpool = models.ForeignKey(WireGuardVPNPool,
                                 on_delete=models.CASCADE)

    pool_index = models.IntegerField(unique=True)

################################################################################

class MACAdress(models.Model):
    default_prefix = 0x420000000000


class ReverseDNSEntry(models.Model):
    """
    A reverse DNS entry
    """
    owner = models.ForeignKey(get_user_model(),
            on_delete=models.CASCADE)

    ip_address = models.GenericIPAddressField(null=False, unique=True)

    name = models.CharField(max_length=253, null=False)

    @property
    def reverse_pointer(self):
        return ipaddress.ip_address(self.ip_address).reverse_pointer

    def implement(self):
        """
        The implement function implements the change
        """

        # Get all DNS entries (?) / update this DNS entry
        # convert to DNS name
        #
        pass


    def save(self, *args, **kwargs):
        # Product.objects.filter(config__parameters__contains='reverse_dns_network')
        # FIXME: check if order is still active / not replaced

        allowed = False
        product = None

        for order in Order.objects.filter(config__parameters__reverse_dns_network__isnull=False,
                             owner=self.owner):
            network = order.config['parameters']['reverse_dns_network']

            net = ipaddress.ip_network(network)
            addr = ipaddress.ip_address(self.ip_address)

            if addr in net:
                allowed = True
                product = order.product
                break


        if not allowed:
            raise ValidationError(f"User {self.owner} does not have the right to create reverse DNS entry for {self.ip_address}")

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


    def __str__(self):
        return f"{self.ip_address} - {self.name}"