from collections import Counter
from django import template

register = template.Library()


@register.inclusion_tag('counter_table.html')
def counter_table(counter, column_title=None):
    """
    Render a given instance of collections.Counter into a 2 column html table.

    Optionally accepts `column_title` keyword argument which sets the table
    key column header.

    Usage:

    {% counter_table event_counter column_title='event type' %}

    The above will render the a table from the `event_counter` variable
    with the first (key) column set to "event type".
    """
    assert isinstance(counter, Counter), (
        "first argument to counter_table must be an instance "
        "of collections.Counter"
    )

    return dict(most_common=counter.most_common(),
                total_count=len(list(counter.elements())),
                column_title=column_title)