{{/* Series Navigation — top-of-article banner for multi-part essays.
     Activates when frontmatter contains:
       series:
         name: 系列名
         slug: ignite-and-settle
         order: N
         total: M
     Renders a compact card with: eyebrow, series title, "N / M" badge,
     and an inline ordered list of all parts (current highlighted).
     Looks across the same language only; uses series.slug to group.
*/}}
{{- $page := . }}
{{- $series := $page.Params.series }}
{{- if and $series $series.slug }}
  {{- $slug := $series.slug }}
  {{- $isZh := eq $page.Lang "zh" }}
  {{/* Collect siblings: pages in the same language whose series.slug matches */}}
  {{- $siblings := slice }}
  {{- range where (where site.RegularPages "Lang" $page.Lang) "Params.series.slug" $slug }}
    {{- $siblings = $siblings | append . }}
  {{- end }}
  {{/* Sort by series.order ascending */}}
  {{- $ordered := sort $siblings "Params.series.order" "asc" }}
  {{- $order := $series.order | default 0 }}
  {{- $total := $series.total | default (len $ordered) }}
  {{- $eyebrow := cond $isZh "系列长文" "Series" }}
  {{- $partLabel := cond $isZh (printf "第 %d 篇 / 共 %d 篇" $order $total) (printf "Part %d of %d" $order $total) }}

  <aside class="series-nav" role="complementary" aria-label="{{ $eyebrow }}: {{ $series.name }}">
    <div class="series-nav__head">
      <span class="series-nav__eyebrow">
        <svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" aria-hidden="true">
          <path d="M4 19.5A2.5 2.5 0 0 1 6.5 17H20"/>
          <path d="M6.5 2H20v20H6.5A2.5 2.5 0 0 1 4 19.5v-15A2.5 2.5 0 0 1 6.5 2z"/>
        </svg>
        <span>{{ $eyebrow }}</span>
      </span>
      <span class="series-nav__name">{{ $series.name }}</span>
      <span class="series-nav__badge">{{ $partLabel }}</span>
    </div>
    {{- if $ordered }}
    <ol class="series-nav__list">
      {{- range $i, $sib := $ordered }}
        {{- $sibOrder := $sib.Params.series.order | default (add $i 1) }}
        {{- $isCurrent := eq $sib.RelPermalink $page.RelPermalink }}
        <li class="series-nav__item{{ if $isCurrent }} series-nav__item--current{{ end }}">
          <span class="series-nav__num">{{ $sibOrder }}</span>
          {{- if $isCurrent }}
          <span class="series-nav__title" aria-current="page">{{ $sib.Title }}</span>
          {{- else }}
          <a class="series-nav__title" href="{{ $sib.RelPermalink }}">{{ $sib.Title }}</a>
          {{- end }}
        </li>
      {{- end }}
    </ol>
    {{- end }}
  </aside>
{{- end }}