import pika
import sys


connection = pika.BlockingConnection(pika.ConnectionParameters(
    'localhost', credentials=pika.PlainCredentials('guest','guest')))

channel = connection.channel()

channel.queue_declare(queue='request')
channel.queue_bind(queue='request', exchange='amq.topic')

def factorial(n):
    if n == 0:
        return 1
    else :
        return n * factorial (n -1)


def on_request(ch, method, props, body):
    n = int(body)

    print (" [.] factorial(%s)")  % (n,)
    response = factorial(n)

    #Publish message after processing response | Client is subscribed to this queue.
    ch.basic_publish(exchange='',
                     routing_key='mqtt-subscription-client123qos1',
                     properties=pika.BasicProperties(correlation_id = \
                                                     props.correlation_id),
                     body=str(response))
    ch.basic_ack(delivery_tag = method.delivery_tag)

channel.basic_qos(prefetch_count=1)
channel.basic_consume(on_request, queue='request')

print (" Awaiting RPC requests")
channel.start_consuming()