import dns
import dns.query
import dns.update
import dns.rdataclass
import dns.rdatatype
import dns.rdtypes.IN.A
import dns.tsigkeyring
import dns.rcode 
import threading
from logger import Logger

class LocalDnsHandlerException(Exception):
    def __init__(self, msg):
	Exception.__init__(self, msg)

class DnsHandler(threading.Thread):
    def __init__(self, msgQueue, tsigKey, nsAddress, ttl):
        threading.Thread.__init__(self)
        self.msgQueue = msgQueue
        self.nsAddress = nsAddress
        self.ttl = ttl
        self.keyring = dns.tsigkeyring.from_text(tsigKey)
	self.setDaemon(True)


    def run(self):
        while(True):
            msg = self.msgQueue.get()
            
	    if msg.address != msg.addressInDns:
		try:
		    self.deleteARR(msg.dynid, msg.name, msg.zone)
		    self.insertARR(msg.dynid, msg.name, msg.zone, msg.address)
		    Logger.log("Update: %s, %s.%s, %s -> %s" % 
			       (msg.dynid, msg.name, msg.zone, msg.addressInDns, msg.address))
		    msg.addressInDns = msg.address
		except Exception, e:
		    Logger.log("Failure for %s when updating DNS: %s" % (str(msg), str(e)))
                
                    
    def insertARR(self, dynid, name, zone, address):
        # send A-RR insertion for ip to DNS server
        rr = dns.rdtypes.IN.A.A(dns.rdataclass.IN, dns.rdatatype.A, address)
        u = dns.update.Update(zone, keyring=self.keyring)
        u.add(name, self.ttl, rr)
        r = dns.query.tcp(u, self.nsAddress)

	rc = r.rcode()
        if rc != 0:
	    raise LocalDnsHandlerException("failure when inserting: %d, %s" % (rc, dns.rcode.to_text(rc)))


    def deleteARR(self, dynid, name, zone):
        # send A-RR deletion for ip to DNS server
        u = dns.update.Update(zone, keyring=self.keyring)
        u.delete(name)
        r = dns.query.tcp(u, self.nsAddress)

	rc = r.rcode()
        if rc != 0:
	    raise LocalDnsHandlerException("failure when deleting: %d, %s" % (rc, dns.rcode.to_text(rc)))