#!/usr/bin/env python
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import collections
import io
import logging
import threading

try:
    import Queue
except ImportError:
    import queue as Queue

import message
import sniffer_transport


class Sniffer:

    """ Class representing the Sniffing node, whose main task is listening and logging message exchange performed by other nodes. """

    logger = logging.getLogger("sniffer.Sniffer")

    RECV_BUFFER_SIZE = 4096

    def __init__(self, nodeid, message_factory):
        """
        Args:
            nodeid (int): Node identifier
            message_factory (MessageFactory): Class producing messages from data bytes.
        """

        self.nodeid = nodeid
        self._message_factory = message_factory

        # Create transport
        transport_factory = sniffer_transport.SnifferTransportFactory()
        self._transport = transport_factory.create_transport(nodeid)

        self._thread = None
        self._thread_alive = threading.Event()
        self._thread_alive.clear()

        self._buckets = collections.defaultdict(Queue.Queue)

    def __del__(self):
        del self._transport

    def _sniffer_main_loop(self):
        """ Sniffer main loop. """

        self.logger.debug("Sniffer started.")

        while self._thread_alive.is_set():
            data, nodeid = self._transport.recv(self.RECV_BUFFER_SIZE)

            # Ignore any exceptions
            try:
                msg = self._message_factory.create(io.BytesIO(data))

                if msg is not None:
                    self.logger.debug("Received message: {}".format(msg))
                    self._buckets[nodeid].put(msg)

            except Exception as e:
                # Just print the exception to the console
                print("EXCEPTION: %s" % e)
                pass

        self.logger.debug("Sniffer stopped.")

    def start(self):
        """ Start sniffing. """

        self._thread = threading.Thread(target=self._sniffer_main_loop)
        self._thread.daemon = True

        self._transport.open()

        self._thread_alive.set()
        self._thread.start()

    def stop(self):
        """ Stop sniffing. """

        self._thread_alive.clear()

        self._transport.close()
        
        self._thread.join()
        self._thread = None

    def get_messages_sent_by(self, nodeid):
        """ Get sniffed messages.

        Note! This method flushes the message queue so calling this method again will return only the newly logged messages.

        Args:
            nodeid (int): node id

        Returns:
            MessagesSet: a set with received messages.
        """
        bucket = self._buckets[nodeid]
        messages = []

        while not bucket.empty():
            messages.append(bucket.get_nowait())

        return message.MessagesSet(messages)