{% load i18n brickwork_components %}
{% comment %}
Docs table of contents (icvoss/django-brickwork#627): the labelled
"On this page" landmark over a consumer-authored heading outline. Reuses the
existing .bw-docs-toc / __title / __list / __sub chrome in shell.css; this
file is the first-class composition, not a parallel treatment.

Preferred call: {% bw_toc items=... active=... %} (validates shape, matches
active by href or bare id). Also {% include %}able with the same context
keys when the caller already trusts its items list.

Required context:
  items: sequence of {label, href} mappings; optional children=[{label, href}]
         one level deep (rendered as .bw-docs-toc__sub siblings, matching the
         article archetype's flat outline). Empty or absent items render
         nothing (no empty landmark).
Optional:
  active: href or bare id of the current location; matching link gets
        aria-current="location". Omit for no current marker.
  heading: title text (default translated "On this page").
  heading_id: id pairing the title with aria-labelledby (default
        "bw-toc-heading").

States: with items (normal) and empty (renders nothing). Active is a marker
  on one link, not a visual state of the nav.
Accessibility: a single <nav> landmark labelled by the visible title;
  aria-current="location" on the active link (in-page location, not a new
  page). Covered by axe against toc-<theme>.html and by tests/test_toc.py.
Responsive: no breakpoint of its own; inherits .bw-docs-toc's prose max
  measure from shell.css.
{% endcomment %}
{% if items %}
{% translate "On this page" as bw_toc_default_heading %}
{% with toc_heading=heading|default:bw_toc_default_heading toc_heading_id=heading_id|default:"bw-toc-heading" %}
<nav class="bw-docs-toc" aria-labelledby="{{ toc_heading_id }}">
  <p class="bw-docs-toc__title" id="{{ toc_heading_id }}">{{ toc_heading }}</p>
  <ol class="bw-docs-toc__list">
    {% for item in items %}
      <li>
        <a {% bw_attr "href" item.href %}{% if item.is_active or active and active == item.href %} aria-current="location"{% endif %}>{{ item.label }}</a>
      </li>
      {% for child in item.children %}
      <li class="bw-docs-toc__sub">
        <a {% bw_attr "href" child.href %}{% if child.is_active or active and active == child.href %} aria-current="location"{% endif %}>{{ child.label }}</a>
      </li>
      {% endfor %}
    {% endfor %}
  </ol>
</nav>
{% endwith %}
{% endif %}