### Binder Models

# Standard Imports
import socket
import urllib2

# 3rd Party
from BeautifulSoup import BeautifulStoneSoup as BS
import dns.exception
import dns.query
import dns.tsig
import dns.zone

# App Imports
from binder import exceptions
from django.db import models

TSIG_ALGORITHMS = (('hmac-md5', 'MD5'),
                   ('hmac-sha1', 'SHA1'),
                   ('hmac-sha256', 'SHA256'),
                   ('hmac-sha384', 'SHA384'),
                   ('hmac-sha512', 'SHA512'))

class Key(models.Model):
    """ Store and reference TSIG keys.

    TODO: Should/Can we encrypt these DNS keys in the DB?
    """
    name = models.CharField(max_length=255)
    data = models.CharField(max_length=255)
    algorithm = models.CharField(max_length=255, choices=TSIG_ALGORITHMS)

    def __unicode__(self):
        return self.name

    def create_keyring(self):
        if self.name is None:
            return None

        try:
            keyring = dns.tsigkeyring.from_text({
                    self.name : self.data
                    })
        except binascii.Error, err:
            raise exceptions.KeyringException("Incorrect key data. Verify key: %s. Reason: %s" % (key_name, err))

        return keyring


class BindServer(models.Model):
    """ Store DNS servers and attributes for referencing their
        statistics ports. Also reference FK for TSIG transfer keys,
        if required.
    """
    hostname = models.CharField(max_length=255)
    statistics_port = models.IntegerField()
    default_transfer_key = models.ForeignKey(Key, null=True, blank=True)

    def __unicode__(self):
        return self.hostname

    def list_zones(self):
        """ List the DNS zones and attributes.

        TODO: Parse these XML more intelligently. Grab the view name. Any other data available?

        Returns:
          List of Dicts { String view_name,
                          String zone_name,
                          String zone_class,
                          String zone_serial }
        """
        zone_req  = urllib2.Request("http://%s:%s" % (self.hostname, self.statistics_port))
        try:
            http_request = urllib2.urlopen(zone_req)
        except urllib2.URLError, err:
            raise exceptions.ZoneException(err)

        return_array = []
        xmloutput = http_request.read()
        mysoup = BS(xmloutput)
        views = mysoup.findAll("view")
        for view in views:
            view_name = view.find("name").string
            for zone in view.findAll("zone"):
                zone_name, zone_class = zone.find("name").string.split("/")
                zone_serial = zone.find("serial").string
                if zone_class == "IN":
                    return_array.append({"view_name" : view_name,
                                         "zone_name" : zone_name,
                                         "zone_class" : zone_class,
                                         "zone_serial" : zone_serial })

        return return_array

    def list_zone_records(self, zone_name):
        """ List all records in a specific zone.

        TODO: Print out current_record in the loop and see if we can parse this more programatically,
              rather than just splitting on space. What is the difference between class and type?
        Arguments:
          String zone_name: Name of the zone

        Returns:
          List of Dicts { String rr_name, String rr_ttl, String rr_class, String rr_type, String rr_data }
        """

        try:
            transfer_key = Key.objects.get(name=self.default_transfer_key)
            keyring = transfer_key.create_keyring()
        except Key.DoesNotExist:
            keyring = None

        try:
            zone = dns.zone.from_xfr(dns.query.xfr(self.hostname, zone_name, keyring=keyring))
        except dns.tsig.PeerBadKey:
            # The incorrect TSIG key was selected for transfers.
            raise exceptions.TransferException("Unable to list zone records because of a TSIG key mismatch.")
        except socket.error, err:
            # Thrown when the DNS server does not respond for a zone transfer (XFR).
            raise exceptions.TransferException("DNS server did not respond for transfer. Reason: %s" % err)
        except dns.exception.FormError:
            # When the DNS message is malformed.
            # * Can happen if a TSIG key is required but a default_transfer_key is not specified.
            raise exceptions.TransferException("Unable to perform AXFR to list zone records. Did you forget to specify a default transfer key?")

        names = zone.nodes.keys()
        names.sort()
        record_array = []
        for current_name in names:
            current_record = zone[current_name].to_text(current_name)
            for split_record in current_record.split("\n"):
                current_record = split_record.split(" ")
                rr_dict = {}
                rr_dict["rr_name"] = current_record[0]
                rr_dict["rr_ttl"] = current_record[1]
                rr_dict["rr_class"] = current_record[2]
                rr_dict["rr_type"] = current_record[3]
                rr_dict["rr_data"] = current_record[4]

                record_array.append(rr_dict)

        return record_array