{#
Archive Sidebar Widget

Displays a navigable list of years/months with post counts.
Uses query indexes for O(1) lookups.

Usage:
{% include 'partials/archive-sidebar.html' %}

Optional variables:
- section_filter: Only show archives for a specific section (e.g., 'blog')
- show_months: Show month breakdown (default: false)
- title: Widget title (default: "Archives")

Example:
{% include 'partials/archive-sidebar.html' with section_filter='blog', show_months=true %}
#}

{% set
    title = title ?? 'Archives',
    show_months = show_months ?? false
%}

<aside class="archive-sidebar-widget">
  <h3>{{ title }}</h3>

  {# Get all years from the date_range index #}
  {% set all_years = site.indexes.date_range.keys()
  | select('match', '^\\d{4}$')
  | sort(reverse=true)
  | list %}

  {% if all_years %}
  <nav class="archive-nav" aria-label="Browse by date">
    <ul class="archive-year-list">
      {% for year in all_years %}
      {# O(1) lookup for year #}
      {% set year_posts = site.indexes.date_range.get(year) | resolve_pages %}

      {# Filter by section if specified #}
      {% if section_filter %}
      {% set year_posts = year_posts | selectattr('_section.name', 'equalto', section_filter) | list %}
      {% end %}

      {% if year_posts %}
      <li class="archive-year-item">
        {% if show_months %}
        {# Expandable year with months #}
        <details class="year-details">
          <summary class="year-summary">
            <span class="year-label">{{ year }}</span>
            <span class="year-count">({{ year_posts | length }})</span>
          </summary>

          <ul class="archive-month-list">
            {% for month_num in 1..12 %}
            {% set month_key = year ~ '-' ~ '%02d' | format(month_num) %}
            {% set month_posts = site.indexes.date_range.get(month_key) | resolve_pages %}

            {# Filter by section if specified #}
            {% if section_filter %}
            {% set month_posts = month_posts | selectattr('_section.name', 'equalto', section_filter) | list %}
            {% end %}

            {% if month_posts %}
            <li class="archive-month-item">
              <a href="{{ ('/archive/' ~ year ~ '/' ~ '%02d' | format(month_num) ~ '/') | absolute_url }}">
                <span class="month-label">
                  {{ [
                  'Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun',
                  'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'
                  ][month_num - 1] }}
                </span>
                <span class="month-count">({{ month_posts | length }})</span>
              </a>
            </li>
            {% end %}
            {% end %}
          </ul>
        </details>
        {% else %}
        {# Simple year link #}
        <a href="{{ ('/archive/' ~ year ~ '/') | absolute_url }}" class="year-link">
          <span class="year-label">{{ year }}</span>
          <span class="year-count">({{ year_posts | length }})</span>
        </a>
        {% end %}
      </li>
      {% end %}
      {% end %}
    </ul>
  </nav>

  {# Optional: Show total post count #}
  {# Portable pattern: accumulate counts then sum #}
  <div class="archive-total">
    {% set post_counts = [] %}
    {% for y in site.indexes.date_range.keys() | select('match', '^\\d{4}$') %}
    {% set _ = post_counts.append(site.indexes.date_range.get(y) | length) %}
    {% end %}
    <p class="total-text">
      <strong>{{ post_counts | sum }}</strong> total posts
    </p>
  </div>
  {% else %}
  <p class="no-archives">No archives available.</p>
  {% end %}
</aside>