import md5
from logger import Logger

class IllegalEventException(Exception):
    def __init__(self, msg):
        self.msg = msg


class Event(object):
    @classmethod
    def setParams(cls, entries, msgTimeCorridor, dnsq):
        cls.entries = entries
        cls.msgTimeCorridor = msgTimeCorridor
        cls.dnsq = dnsq

    def __init__(self, address, data, receiveTime):
        self.address = address
        self.data = data
        self.receiveTime = receiveTime

    def prepare(self):
        self.port = self.address[1]
        self.address = self.address[0]
        parts = self.data.split(' ')
        if len(parts) != 3:
            raise IllegalEventException("data format error 1")
        (self.dynid, self.msgTime, self.checksum) = self.data.split(' ')
        try:
            self.msgTime = int(self.msgTime)
        except ValueError, e:
            raise IllegalEventException("data format error 2")
        self.prepared = True

    def process(self):
        if not self.prepared:
            self.prepare()

        if not Event.entries.has_key(self.dynid):
            raise IllegalEventException("unknown dynid in event %s" % str(self))
        entry = Event.entries[self.dynid]

        if self.msgTime + Event.msgTimeCorridor < self.receiveTime:
            raise IllegalEventException("event too old %s" % str(self))
        if self.msgTime - Event.msgTimeCorridor > self.receiveTime:
            raise IllegalEventException("event too young %s" % str(self))


        if entry.lastEventTime >= self.msgTime:
            raise IllegalEventException("timing sequence failure in event, possibly replay %s" % str(self))

        di = "%s %s %d" % (self.dynid, entry.sharedSecret, self.msgTime)
        d = md5.new(di).hexdigest()
        Logger.debug("%s, received: %s, calculated: %s" % (di, self.checksum, d))
        if d != self.checksum:
            raise IllegalEventException("wrong checksum for event %s" % str(self))

	entry.lastEventTime = self.msgTime
	entry.address = self.address
	Logger.debug("Set in DNS: %s -> %s" % (entry.name, entry.address))
	try:
	    Event.dnsq.put_nowait(entry)
	except Queue.Full, e:
	    Logger.log("Dns Queue overrun, drop event for %s" % str(entry))

    def __str__(self):
        if not self.prepared:
            self.prepare()
        return "%s from %s:%d" % (self.data, self.address, self.port)