{% comment %}
SPDX-License-Identifier: GPL-3.0-or-later
SPDX-FileCopyrightText: 2026 Valentin Gagarin <valentin@gagarin.work>

Render a nested sitemap rooted at a given URL prefix.  Hierarchy is
derived from URL structure: a page is a direct child of prefix P iff
its URL starts with P, is not P itself, and contains no further path
segments below P.
{% endcomment %}

{%- assign default_root = "/" -%}
{% comment %}
`prefix` is the URL of the section to list children of.  It must end with "/",
which we assume if it is constructed by a directory and contains an index file.
{% endcomment %}
{%- assign prefix = include.prefix | default: default_root -%}
{%- capture inner -%}
  {%- assign candidates = site.html_pages
        | where_exp: "p", "p.url contains prefix"
        | where_exp: "p", "p.url != prefix" -%}
  {%- if prefix == default_root -%}
    {%- assign list_with_root_page = site.html_pages | where: "url", prefix -%}
    {%- assign candidates = list_with_root_page | concat: candidates -%}
  {%- endif -%}
  {%- comment %}
  Ordered pages first, ascending.  The rest after, in URL order, so output is deterministic.
  {%- endcomment %}
  {%- assign ordered = candidates | where_exp: "p", "p.nav_order" | sort: "nav_order" -%}
  {%- assign unordered = candidates | where_exp: "p", "p.nav_order == nil" | sort: "url" -%}
  {%- assign sorted = ordered | concat: unordered -%}
  {%- for p in sorted -%}
    {%- comment %}
    `assign` is page-global.  A recursive include below may have overwritten `prefix`.
    {%- endcomment %}
    {%- assign prefix = include.prefix | default: default_root -%}
    {%- assign url_start = p.url | slice: 0, prefix.size -%}
    {%- if url_start == prefix -%}
    {%- assign suffix = p.url | slice: prefix.size, p.url.size -%}
    {%- assign without_slashes = suffix | replace: "/", "" -%}
    {%- assign slashes = suffix.size | minus: without_slashes.size -%}
    {%- assign is_index = false -%}
    {%- if p.name == "index.adoc" or p.name == "index.html" -%}{%- assign is_index = true -%}{%- endif -%}
    {%- assign is_page = false -%}
    {%- if is_index == false and slashes == 0 -%}{%- assign is_page = true -%}{%- endif -%}
    {%- if is_index and suffix == "" -%}{%- assign is_page = true -%}{%- endif -%}
    {%- assign is_section = false -%}
    {%- if is_index and slashes == 1 -%}{%- assign is_section = true -%}{%- endif -%}
    {%- if is_page or is_section %}
    <li>
      <a href="{{ p.url | relative_url }}">{{ p.title }}</a>
      {%- if is_section -%}
        {%- include sitemap.html prefix=p.url -%}
      {%- endif -%}
    </li>
    {%- endif -%}
    {%- endif -%}
  {%- endfor -%}
{%- endcapture -%}
{%- assign trimmed = inner | strip -%}
{%- if trimmed != "" %}
<ul>{{ inner }}
</ul>
{%- endif -%}