"""RabbitMQ helpers"""
import pika
from flask import Flask, json
from pika.adapters.blocking_connection import BlockingChannel


class RabbitMQ:
    host: str
    connection: pika.BlockingConnection
    channel: BlockingChannel

    def __init__(self, app: Flask = None):
        if app is not None:
            self.init_app(app)

    def init_app(self, app: Flask):
        self.host = app.config.get('RABBITMQ_HOST', 'localhost')

    def _ensure_connection(self):
        if self.channel is None:
            self.connection = pika.BlockingConnection(
                pika.ConnectionParameters(host=self.host))
            self.channel = self.connection.channel()

    def ensure_queue_exists(self, queue_name: str):
        """Ensures the queue exists on the default exchange

        :param queue_name: the name of the queue
        """
        self._ensure_connection()
        self.channel.queue_declare(queue=queue_name, durable=True)

    def queue_publish(self, queue_name: str, message):
        self._ensure_connection()
        self.ensure_queue_exists(queue_name)

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

    def ensure_exchange_exists(self, name: str) -> None:
        """Ensures exchange exists

        :param name: the name of the exchange
        """
        self._ensure_connection()
        self.channel.exchange_declare(exchange=name, exchange_type='topic', durable=True)

    def exchange_publish(self, exchange_name: str, topic: str, message):
        """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)
        """
        self._ensure_connection()
        self.ensure_exchange_exists(exchange_name)

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