import json

from pika.adapters.blocking_connection import BlockingChannel

from .extension import with_pika_channel


@with_pika_channel
def ensure_exchange_exists(name: str, channel: BlockingChannel = None) -> None:
    """Ensures exchange exists

    :param name: the name of the exchange
    :param channel: a pika channel, if none specified a new one will be created
    """
    channel.exchange_declare(exchange=name, exchange_type='topic')


@with_pika_channel
def exchange_publish(exchange_name: str, topic: str, message, channel: BlockingChannel = None):
    """Publishes a message to a

    :param exchange_name: the name of the exchange
    :param topic: the topic to publish to
    :param message: the message to publish (will be turned into a json)
    :param channel: a pika channel, if none specified a new one will be created
    """
    ensure_exchange_exists(exchange_name, channel=channel)

    body = json.dumps(message)
    body_bytes = body.encode('utf-8')
    channel.basic_publish(exchange=exchange_name, routing_key=topic, body=body_bytes)