#!/usr/bin/env python3.6

#pylint: disable=line-too-long

#

#  Copyright (2019).  Fermi Research Alliance, LLC.

#  Initial Author: Pat Riehecky <riehecky@fnal.gov>

#

'''

    Connect to the MQTT server and convert messages into dbus signals.

'''

## Uncomment these for python2 support

#from __future__ import unicode_literals

#from __future__ import absolute_import

#from __future__ import print_function

import datetime

import logging

import json

import os.path

import sys

import random

import textwrap

DBUS_INTERFACE = 'org.centos.git.mqtt'

try:

    import paho.mqtt.client

except ImportError:  # pragma: no cover

    print("Please install paho.mqtt.client - rpm: python-paho-mqtt", file=sys.stderr)

    raise

try:

    from pydbus import SystemBus, SessionBus

    from pydbus.generic import signal

except ImportError:  # pragma: no cover

    print("Please install pydbus - rpm: python-pydbus", file=sys.stderr)

    raise

try:

    from gi.repository.GLib import MainLoop

except ImportError:  # pragma: no cover

    print("Please install pygobject - rpm: python-gobject", file=sys.stderr)

    raise

try:

    from argparse import ArgumentParser

except ImportError:  # pragma: no cover

    print("Please install argparse - rpm: python-argparse", file=sys.stderr)

    raise

##########################################

def setup_args():

    '''

        Setup the argparse object.

        Make sure all fields have defaults so we could use this as an object

    '''

    ca_cert = str(os.path.expanduser('~/')) + '.centos-server-ca.cert'

    user_pubkey = str(os.path.expanduser('~/')) + '.centos.cert'

    user_privkey = str(os.path.expanduser('~/')) + '.centos.cert'

    # use a psudo random number for keepalive to help spread out the load

    #  some time between 1m 30s and 2m 10s

    keep_alive = random.randint(90, 130)

    parser = ArgumentParser(description=textwrap.dedent(__doc__))

    parser.add_argument('--debug',action='store_true',

                        help='Print out all debugging actions',

                        default=False)

    parser.add_argument('--client-connection-name', metavar='<UNIQUESTRING>',

                        help='Use this specific name when connecting. Default is a psudo-random string.',

                        default='', type=str)

    parser.add_argument('--mqtt-server', metavar='<HOSTNAME>',

                        help='Connect to this MQTT server',

                        default='mqtt.git.centos.org', type=str)

    parser.add_argument('--mqtt-port', metavar='<PORTNUMBER>',

                        help='Connect to MQTT server on this port',

                        default='8883', type=int)

    parser.add_argument('--mqtt-source-ip', metavar='<SOURCE_IP>',

                        help='Connect to MQTT server from this address. Default is any.',

                        default='', type=str)

    parser.add_argument('--mqtt-topic', metavar='<TOPIC_ID>',

                        action='append', nargs='+', type=str,

                        help='Which MQTT topic should we watch. You may set multiple times.')

    parser.add_argument('--mqtt-keepalive', metavar='<SECONDS>',

                        help='Seconds between MQTT keepalive packets.',

                        default=keep_alive, type=int)

    parser.add_argument('--mqtt-no-ssl', action='store_false', dest='mqtt_ssl',

                        help='Should MQTT use SSL? Default is to use SSL (and the SSL port).')

    parser.add_argument('--mqtt-server-ca', metavar='<ABSOLUTE_PATH>',

                        help='Use this CA cert to validate the MQTT Server.',

                        default=ca_cert, type=str)

    parser.add_argument('--mqtt-client-cert', metavar='<ABSOLUTE_PATH>',

                        help='Use this public key to identify yourself.',

                        default=user_pubkey, type=str)

    parser.add_argument('--mqtt-client-key', metavar='<ABSOLUTE_PATH>',

                        help='The private key that matches with --mqtt-client-cert .',

                        default=user_privkey, type=str)

    parser.add_argument('--dbus-use-system-bus',action='store_true',

                        help='Should we use the global SystemBus or the user SessionBus. The SystemBus requires settings in /etc/dbus-1/system.d/myservice.conf',

                        default=False)

    parser.add_argument('--dbus-config',action='store_true',

                        help='Just output the SystemBus permissions file and exit',

                        default=False)

    return parser

##########################################

class BusMessage(object):

    """

    Server_XML definition.

    """

    dbus = """

    <node>

        <interface name="{}">

            <signal name="message">

                <arg type='s'/>

            </signal>

        </interface>

    </node>

    """.format(DBUS_INTERFACE)

    # Function does all the work already

    message = signal()

def DbusPermissionsConf(interface_name):

    '''

        For the SystemBus you need permission to create endpoints

    '''

    import getpass

    whoami = getpass.getuser()

    xml = '''

          "-//freedesktop//DTD D-BUS Bus Configuration 1.0//EN"

          "http://www.freedesktop.org/standards/dbus/1.0/busconfig.dtd">

<busconfig>

    <policy user="root">

        <allow own="{interface_name}" />

        <allow send_interface="{interface_name}/" />

    </policy>

    <policy user="{whoami}">

        <allow own="{interface_name}" />

        <allow send_interface="{interface_name}" send_destination="{interface_name}.message" />

    </policy>

    <policy context="default">

        <allow receive_interface="{interface_name}" />

        <allow receive_sender="{interface_name}.message" />

    </policy>

</busconfig>

'''

    return xml.format(interface_name=interface_name, whoami=whoami)

##########################################

def on_mqtt_message(client, userdata, message):

    ''' What should I do if I get a message? '''

    logging.debug('Message received topic:%s payload:%s', message.topic, message.payload.decode("utf-8"))

    # Or you can customize this to fit your needs

    signal = {message.topic: json.loads(message.payload.decode("utf-8"))}

    userdata['emit'].message(json.dumps((signal)))

    logging.debug('Sending signal: %s', json.dumps(signal))

def on_mqtt_disconnect(client, userdata, rc):

    ''' If you get a connection error, print it out '''

    if rc:

        logging.error('Disconnected with error ErrCode:%s', rc)

        logging.error('ErrCode:%s might be - %s', rc, paho.mqtt.client.error_string(rc))

        logging.error('ErrCode:%s might be - %s', rc, paho.mqtt.client.connack_string(rc))

        raise SystemExit

    logging.error('Disconnected from MQTT Server')

def on_mqtt_connect(client, userdata, flags, rc):

    ''' Automatically subscribe to all topics '''

    logging.debug('Connected with status code : %s', rc)

    for topic in userdata['topics']:

        client.subscribe(topic)

        logging.info('Subscribing to topic %s', topic)

        signal = {'mqtt.setup': 'Subscribing to topic {} at {}'.format(topic, datetime.datetime.now())}

        userdata['emit'].message(json.dumps(signal))

##########################################

##########################################

if __name__ == '__main__':

    PARSER = setup_args()

    ARGS = PARSER.parse_args()

    if ARGS.dbus_config:

        print(DbusPermissionsConf(DBUS_INTERFACE))

        raise SystemExit

    MYLOGGER = logging.getLogger()

    if ARGS.debug:

        MYLOGGER.setLevel(logging.DEBUG)

    else:

        MYLOGGER.setLevel(logging.WARNING)

    handler = logging.StreamHandler(sys.stderr)

    handler.setLevel(logging.DEBUG)

    formatter = logging.Formatter('%(asctime)s - %(levelname)s - %(message)s')

    handler.setFormatter(formatter)

    MYLOGGER.addHandler(handler)

    PROGRAM_NAME = os.path.basename(sys.argv[0])

    MYLOGGER.debug('Running:%s args:%s', PROGRAM_NAME, sys.argv[1:])

    if ARGS.client_connection_name:

        MYLOGGER.info('Attempting to connect as %s to %s:%s', ARGS.client_connection_name, ARGS.mqtt_server, ARGS.mqtt_port)

    else:

        MYLOGGER.info('Attempting to connect with random name to %s:%s', ARGS.mqtt_server, ARGS.mqtt_port)

    CLIENT = paho.mqtt.client.Client(client_id=ARGS.client_connection_name, clean_session=True)

    if ARGS.mqtt_ssl:

        ARGS.mqtt_server_ca = os.path.expanduser(ARGS.mqtt_server_ca)

        if not os.path.exists(ARGS.mqtt_server_ca):

            raise ValueError('No such file %s', ARGS.mqtt_server_ca)

        ARGS.mqtt_client_cert = os.path.expanduser(ARGS.mqtt_client_cert)

        if not os.path.exists(ARGS.mqtt_client_cert):

            raise ValueError('No such file %s', ARGS.mqtt_client_cert)

        ARGS.mqtt_client_key = os.path.expanduser(ARGS.mqtt_client_key)

        if not os.path.exists(ARGS.mqtt_client_key):

            raise ValueError('No such file %s', ARGS.mqtt_client_key)

        MYLOGGER.info('SSL enabled CA=%s PUBKEY=%s PRIVKEY=%s', ARGS.mqtt_server_ca, ARGS.mqtt_client_cert, ARGS.mqtt_client_key)

        CLIENT.tls_set(ca_certs=ARGS.mqtt_server_ca, certfile=ARGS.mqtt_client_cert, keyfile=ARGS.mqtt_client_key)

    try:

        CLIENT.enable_logger(logger=MYLOGGER)

    except AttributeError:

        # Added in 1.2.x of mqtt library

        pass

    CLIENT.on_connect = on_mqtt_connect

    CLIENT.on_message = on_mqtt_message

    CLIENT.on_disconnect = on_mqtt_disconnect

    CLIENT.connect_async(host=ARGS.mqtt_server, port=ARGS.mqtt_port, keepalive=ARGS.mqtt_keepalive, bind_address=ARGS.mqtt_source_ip)

    DBUS_MESSAGE = BusMessage()

    if not ARGS.mqtt_topic:

        ARGS.mqtt_topic = ['git.centos.org/#',]

    CLIENT.user_data_set({'topics': ARGS.mqtt_topic, 'emit': DBUS_MESSAGE})

    # loop_start will run in background async

    CLIENT.loop_start()

    if ARGS.dbus_use_system_bus:

        BUS = SystemBus()

    else:

        BUS = SessionBus()

    if ARGS.dbus_use_system_bus:

        MYLOGGER.debug('Publishing to system bus %s', DBUS_INTERFACE)

    else:

        MYLOGGER.debug('Publishing to session bus %s', DBUS_INTERFACE)

    BUS.publish(DBUS_INTERFACE, DBUS_MESSAGE)

    # loop forever, until CTRL+C, or something goes wrong

    try:

        MainLoop().run()

    except KeyboardInterrupt:

        CLIENT.disconnect()

        logging.debug('Got CTRL+C, exiting cleanly')

        raise SystemExit

    except:

        CLIENT.disconnect()

        raise

    finally:

        CLIENT.disconnect()