from collections import namedtuple
from onioningestor.onion import Onion

class Source(object):
    """Base class for all Source plugins.
    Note: This is an abstract class. You must override ``__init__`` and ``run``
    in child classes. You should not override ``process_element``. When adding
    additional methods to child classes, consider prefixing the method name
    with an underscore to denote a ``_private_method``.
    """
    def __init__(self, *args, **kwargs):
        """Override this constructor in child classes.
        The first argument must always be ``name``.
        Other argumentss should be url, auth, etc, whatever is needed to set
        up the object.
        """
        self.onion = Onion

    def set_onionQueue(self, queue):
        self.onionQueue = queue

    def run(self):
        """Run and return ``(saved_state, list(Artifact))``.
        Override this method in child classes.
        The method signature and return values must remain consistent.
        The method should attempt to pick up where we left off using
        ``saved_state``, if supported. If ``saved_state`` is ``None``, you can
        assume this is a first run. If state is maintained by the remote
        resource (e.g. as it is with SQS), ``saved_state`` should always be
        ``None``.
        """
        raise NotImplementedError()