from django import template
from django.utils.safestring import SafeString, mark_safe

@register.simple_tag
def list_punctuation(loop, conjunction: str = "or") -> SafeString:
    # return commas between items if > 2, and the appropriate conjunction
    num_items = loop["counter"] + loop["revcounter"] - 1
    if loop["revcounter0"] > 1:
        # if >2 remaining, add commas
        return mark_safe(", ")
    elif loop["revcounter0"] == 1:
        return mark_safe(f"{',' if num_items >= 3 else ''} {conjunction} ")
    return mark_safe("")


# unit tests

import pytest
from django.template import Context, Template

@pytest.mark.parametrize(
    "input, conj, expected",
    [
        (["a"], "", "a"),
        (["a", "b"], "", "a or b"),
        (["a", "b"], "'and'", "a and b"),
        (["a", "b", "c"], "", "a, b, or c"),
        (["a", "b", "c"], "'and'", "a, b, and c"),
    ],
)
def test_list_punctuation(input, conj, expected):
    template_to_render = "{% load bs4 %}{% for item in items %}{{item}}{% list_punctuation forloop ZZZ %}{% endfor %}"
    rendered_template = Template(template_to_render.replace("ZZZ", conj)).render(
        Context({"items": input})
    )
    assert rendered_template.strip() == expected