import traceback
from .message import Message


class Worker(object):
    """
    A "worker" process that continually looks for available messages to run
    and runs their consumers.
    """

    def __init__(self, channel_backend, callback=None):
        self.channel_backend = channel_backend
        self.callback = callback

    def run(self):
        """
        Tries to continually dispatch messages to consumers.
        """
        channels = self.channel_backend.registry.all_channel_names()
        while True:
            channel, content = self.channel_backend.receive_many_blocking(channels)
            message = Message(
                content=content,
                channel=channel,
                channel_backend=self.channel_backend,
                reply_channel=content.get("reply_channel", None),
            )
            # Handle the message
            consumer = self.channel_backend.registry.consumer_for_channel(channel)
            if self.callback:
                self.callback(channel, message)
            try:
                consumer(message)
            except:
                traceback.print_exc()