{%- comment -%}
  Include as: {%- include components/children_nav.html -%}
  Depends on: page, site, nav_breadcrumbs.
  Results in: HTML for the children-navigation component.
  Includes: components/nav/sorted.html, toc_heading_custom.html.
  Overwrites:
    nav_ancestor_links, nav_top_node_titles, nav_child_candidates, nav_children,
    nav_child, nav_child_ok, nav_child_ancestor, nav_sorted.
{%- endcomment -%}

{%- comment -%}
  Whether a page has any children is checked efficiently by inspecting the cached
  site_nav. If the page has no children, nav_children is set to an empty array;
  otherwise nav_children is left unset.
{%- endcomment -%}

{%- if page.has_children == false -%}
  {%- assign nav_children = "" | split: "" -%}
{%- else -%}

  {%- assign nav_children = nil -%}

  {%- capture nav_list_link -%}
  <a href="{{ page.url | relative_url }}" class="nav-list-link">
  {%- endcapture -%}

  {%- capture site_nav -%}
  {%- include_cached components/site_nav.html all=true -%}
  {%- endcapture -%}

  {%- capture nav_list_simple -%}
  <ul class="nav-list">
  {%- endcapture -%}

  {%- assign nav_child_start = site_nav
        | split: nav_list_link | last
        | split: "</a>" | slice: 1 | first -%}

  {%- assign nav_child_test = nav_child_start 
        | remove_first: nav_list_simple | prepend: nav_list_simple -%}
    
  {%- if nav_child_start != nav_child_test -%}
    {%- assign nav_children = "" | split: "" -%}
  {%- endif -%}

{%- endif -%}

{%- unless nav_children -%}

  {%- comment -%}
    The layout is assumed to include components/breadcrumbs.html before this file,
    otherwise it needs to be included here.
  {%- endcomment -%}

  {%- assign nav_ancestors = "" | split: "" -%}
  {%- for nav_link in nav_breadcrumbs -%}
    {%- assign nav_title = nav_link | split: ">" | slice: 1 | first | append: ">" | remove: "</a>" -%}
    {%- assign nav_ancestors = nav_ancestors | push: nav_title -%}
  {%- endfor -%}

  {%- assign nav_parenthood = site[page.collection] | default: site.html_pages
    | where_exp: "item", "item.title != nil" | group_by: "parent" -%}

  {%- assign nav_top_nodes = nav_parenthood
      | where_exp: "item", "item.name == ''" | map: "items" | first -%}

  {% assign nav_top_node_titles = nav_top_nodes | map: "title" -%}

  {%- include components/nav/children.html node=page ancestors=nav_ancestors all=true -%}

{%- endunless -%}

{%- if nav_children.size >= 1 -%}

  {%- if page.child_nav_order == 'desc' or page.child_nav_order == 'reversed' -%}
    {%- assign nav_children = nav_children | reverse -%}
  {%- endif -%}

<hr>
{% include toc_heading_custom.html %}
<ul>
  {% for nav_child in nav_children %}
  <li>
    <a href="{{ nav_child.url | relative_url }}">{{ nav_child.title }}</a>{% if nav_child.summary %} - {{ nav_child.summary }}{% endif %}
  </li>
  {% endfor %}
</ul>

{%- endif -%}