"""A mixin that implements generic methods."""

import datetime


class FlowBaseMixin:
    """A mixin that adds generic methods to a flow class."""

    def workflow_id(self, initial_context):
        """Generate workflow id.

        Args:
            initial_context (dict): The initial context for the flow.
        Returns:
            str: A unique identifier for a workflow being executed
                In the forms of '<self.flow_name>-YYYY-MM-DD', where
                YYYY-MM-DD is the context date or, if none passed the
                current date.

        """
        if 'context_date' not in initial_context:
            date = datetime.datetime.today().strftime('%Y-%m-%d')
        else:
            date = initial_context['context_date']

        return '{flow_name}-{date}'.format(
            flow_name=self.name,
            date=date)

    @staticmethod
    def generate_feed_name(feed_name):
        """Generate workflow name.

        Args:
            feed_name (str): Name of the feed the work flow is processing,
                must be lower case and have spaces replaced with underscores.
        Returns:
            str: SWF name in the format of 'swf_<feed_name>'.

        """
        assert feed_name.islower() and ' ' not in feed_name, (
            'feed name must be lower case with no spaces')

        return 'swf_{feed_name}'.format(feed_name=feed_name)