# ======================================================================
#  zbeacon - LAN discovery and presence
#
#  Copyright (c) the Contributors as noted in the AUTHORS file.
#  This file is part of CZMQ, the high-level C binding for 0MQ:
#  http://czmq.zeromq.org.
#
#  This Source Code Form is subject to the terms of the Mozilla Public
#  License, v. 2.0. If a copy of the MPL was not distributed with this
#  file, You can obtain one at http://mozilla.org/MPL/2.0/.

"""
    The zbeacon class implements a peer-to-peer discovery service for local
    networks. A beacon can broadcast and/or capture service announcements
    using UDP messages on the local area network. This implementation uses
    IPv4 UDP broadcasts. You can define the format of your outgoing beacons,
    and set a filter that validates incoming beacons. Beacons are sent and
    received asynchronously in the background.

    This class replaces zbeacon_v2, and is meant for applications that use
    the CZMQ v3 API (meaning, zsock).
"""

import logging
import ipaddress
import socket
import zmq
import struct
import time
from sys import platform
from .zactor import ZActor
from . import zhelper
from .zhelper import u

logger = logging.getLogger(__name__)

INTERVAL_DFLT = 1.0
BEACON_MAX = 255      # Max size of beacon data
MULTICAST_GRP = '225.25.25.25'


class ZBeacon(object):

    def __init__(self, ctx, pipe, *args, **kwargs):
        self.ctx = ctx                #  ZMQ context
        self.pipe = pipe              #  Actor command pipe
        self.udpsock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
                                      #  UDP socket for send/recv
        self.port_nbr = 0             #  UDP port number we work on
        self.interval = INTERVAL_DFLT #  Beacon broadcast interval
        self.ping_at = 0              #  Next broadcast time
        self.transmit = None          #  Beacon transmit data
        self.filter = b""             #  Beacon filter data

        self.terminated = False       #  Did caller ask us to quit?
        self.verbose = False          #  Verbose logging enabled?
        self.hostname = ""            #  Saved host name

        self.address = None
        self.network_address = None
        self.broadcast_address = None
        self.interface_name = None
        self.run()

    def __del__(self):
        if self.udpsock:
            self.udpsock.close()

    def prepare_udp(self):
        self._prepare_socket()
        try:
            self.udpsock.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
            self.udpsock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)

            #  On some platforms we have to ask to reuse the port
            try:
                self.udpsock.setsockopt(socket.SOL_SOCKET,
                                        socket.SO_REUSEPORT, 1)

            except AttributeError:
                pass

            if self.broadcast_address.is_multicast:
                # TTL
                self.udpsock.setsockopt(socket.IPPROTO_IP,
                                        socket.IP_MULTICAST_TTL, 2)

                # TODO: This should only be used if we do not have inproc method!
                self.udpsock.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_LOOP, 1)

                # Usually, the system administrator specifies the
                # default interface multicast datagrams should be
                # sent from. The programmer can override this and
                # choose a concrete outgoing interface for a given
                # socket with this option.
                #
                # this results in the loopback address?
                # host = socket.gethostbyname(socket.gethostname())
                # self.udpsock.setsockopt(socket.SOL_IP, socket.IP_MULTICAST_IF, socket.inet_aton(host))
                # You need to tell the kernel which multicast groups
                # you are interested in. If no process is interested
                # in a group, packets destined to it that arrive to
                # the host are discarded.
                # You can always fill this last member with the
                # wildcard address (INADDR_ANY) and then the kernel
                # will deal with the task of choosing the interface.
                #
                # Maximum memberships: /proc/sys/net/ipv4/igmp_max_memberships
                # self.udpsock.setsockopt(socket.SOL_IP, socket.IP_ADD_MEMBERSHIP,
                #       socket.inet_aton("225.25.25.25") + socket.inet_aton(host))
                self.udpsock.bind(("", self.port_nbr))

                group = socket.inet_aton("{0}".format(self.broadcast_address))
                mreq = struct.pack('4sl', group, socket.INADDR_ANY)

                self.udpsock.setsockopt(socket.SOL_IP,
                                        socket.IP_ADD_MEMBERSHIP, mreq)

            else:
                # Platform specifics
                if platform.startswith("linux"):
                    # on linux we bind to the broadcast address and send to
                    # the broadcast address
                    self.udpsock.bind((str(self.broadcast_address),
                                       self.port_nbr))
                else:
                    self.udpsock.bind(("", self.port_nbr))

                logger.debug("Set up a broadcast beacon to {0}:{1}".format(self.broadcast_address, self.port_nbr))
        except socket.error:
            logger.exception("Initializing of {0} raised an exception".format(self.__class__.__name__))

    def _prepare_socket(self):
        netinf = zhelper.get_ifaddrs()

        logger.debug("Available interfaces: {0}".format(netinf))

        for iface in netinf:
            # Loop over the interfaces and their settings to try to find the broadcast address.
            # ipv4 only currently and needs a valid broadcast address
            for name, data in iface.items():
                logger.debug("Checking out interface {0}.".format(name))
                # For some reason the data we need lives in the "2" section of the interface.
                data_2 = data.get(2)

                if not data_2:
                    logger.debug("No data_2 found for interface {0}.".format(name))
                    continue

                address_str = data_2.get("addr")
                netmask_str = data_2.get("netmask")

                if not address_str or not netmask_str:
                    logger.debug("Address or netmask not found for interface {0}.".format(name))
                    continue

                if isinstance(address_str, bytes):
                    address_str = address_str.decode("utf8")

                if isinstance(netmask_str, bytes):
                    netmask_str = netmask_str.decode("utf8")

                interface_string = "{0}/{1}".format(address_str, netmask_str)

                interface = ipaddress.ip_interface(u(interface_string))

                if interface.is_loopback:
                    logger.debug("Interface {0} is a loopback device.".format(name))
                    continue

                if interface.is_link_local:
                    logger.debug("Interface {0} is a link-local device.".format(name))
                    continue

                self.address = interface.ip
                self.network_address = interface.network.network_address
                self.broadcast_address = interface.network.broadcast_address
                self.interface_name = name

            if self.address:
                break

        logger.debug("Finished scanning interfaces.")

        if not self.address:
            self.network_address = ipaddress.IPv4Address(u('127.0.0.1'))
            self.broadcast_address = ipaddress.IPv4Address(u(MULTICAST_GRP))
            self.interface_name = 'loopback'
            self.address = u('127.0.0.1')

        logger.debug("Address: {0}".format(self.address))
        logger.debug("Network: {0}".format(self.network_address))
        logger.debug("Broadcast: {0}".format(self.broadcast_address))
        logger.debug("Interface name: {0}".format(self.interface_name))

    def configure(self, port_nbr):
        self.port_nbr = port_nbr
        self.prepare_udp()
        self.pipe.send_unicode(str(self.address))

    def handle_pipe(self):
        #  Get just the commands off the pipe
        request = self.pipe.recv_multipart()
        command = request.pop(0).decode('UTF-8')
        if not command:
            return -1                  #  Interrupted

        if self.verbose:
            logger.debug("zbeacon: API command={0}".format(command))

        if command == "VERBOSE":
            self.verbose = True
        elif command == "CONFIGURE":
            port = struct.unpack('I', request.pop(0))[0]
            self.configure(port)
        elif command == "PUBLISH":
            self.transmit = request.pop(0)
            if self.interval == 0:
                self.interval = INTERVAL_DFLT
            # Start broadcasting immediately
            self.ping_at = time.time()
        elif command == "SILENCE":
            self.transmit = None
        elif command == "SUBSCRIBE":
            self.filter = request.pop(0)
        elif command == "UNSUBSCRIBE":
            self.filter = None
        elif command == "$TERM":
            self.terminated = True
        else:
            logger.error("zbeacon: - invalid command: {0}".format(command))

    def handle_udp(self):
        try:
            frame, addr = self.udpsock.recvfrom(BEACON_MAX)

        except Exception as e:
            logger.exception("Exception while receiving: {0}".format(e))
            return

        peername = addr[0]

        #  If filter is set, check that beacon matches it
        is_valid = False
        if self.filter is not None:
            if len(self.filter) <= len(frame):
                match_data = frame[:len(self.filter)]
                if (match_data == self.filter):
                    is_valid = True

        #  If valid, discard our own broadcasts, which UDP echoes to us
        if is_valid and self.transmit:
            if frame == self.transmit:
                is_valid = False

        #  If still a valid beacon, send on to the API
        if is_valid:
            self.pipe.send_unicode(peername, zmq.SNDMORE)
            self.pipe.send(frame)

    def send_beacon(self):
        try:
            self.udpsock.sendto(self.transmit, (str(self.broadcast_address),
                                                self.port_nbr))
        except OSError:
            logger.debug("Network seems gone, exiting zbeacon")
            self.terminated = True

    def run(self):
        # Signal actor successfully initialized
        self.pipe.signal()

        self.poller = zmq.Poller()
        self.poller.register(self.pipe, zmq.POLLIN)
        self.poller.register(self.udpsock, zmq.POLLIN)

        while not self.terminated:
            timeout = 1
            if self.transmit:
                timeout = self.ping_at - time.time()
                if timeout < 0:
                    timeout = 0
            # Poll on API pipe and on UDP socket
            items = dict(self.poller.poll(timeout * 1000))
            if self.pipe in items and items[self.pipe] == zmq.POLLIN:
                self.handle_pipe()
            if self.udpsock.fileno() in items and items[self.udpsock.fileno()] == zmq.POLLIN:
                self.handle_udp()

            if self.transmit and time.time() >= self.ping_at:
                self.send_beacon()
                self.ping_at = time.time() + self.interval

            if self.terminated:
                break


if __name__ == '__main__':
    import zmq
    import struct
    import time
    speaker = ZActor(zmq.Context(), ZBeacon)
    speaker.send_unicode("VERBOSE")
    speaker.send_unicode("CONFIGURE", zmq.SNDMORE)
    speaker.send(struct.pack("I", 9999))
    speaker.send_unicode("PUBLISH", zmq.SNDMORE)
    import uuid
    transmit = struct.pack('cccb16sH', b'Z', b'R', b'E',
                           1, uuid.uuid4().bytes,
                           socket.htons(1300))
    speaker.send(transmit)
    speaker.destroy()