{% set fallback_language = config.extra.sopran_language_switcher.fallback_language | d('ja') %}
{% set current_url = page.url if page and page.url else '' %}
{% set current_language = 'en' if current_url.startswith('en/') else fallback_language %}
{% set mirror_url = current_url[3:] if current_language == 'en' else 'en/' ~ current_url %}
{% set ja_url = mirror_url if current_language == 'en' else current_url %}
{% set en_url = current_url if current_language == 'en' else mirror_url %}

<nav
  class="md-header__option sopran-language-switcher"
  aria-label="{{ config.extra.sopran_language_switcher.label | d('Lang: 日本語/English') }}"
  data-label="{{ config.extra.sopran_language_switcher.label | d('Lang: 日本語/English') }}"
  data-fallback-language="{{ fallback_language }}"
>
  <span class="sopran-language-switcher__prefix">Lang</span>
  <span class="sopran-language-switcher__toggle" role="group" aria-label="Language">
    {% for alt in config.extra.alternate %}
      {% set target_url = ja_url if alt.lang == 'ja' else en_url %}
      <a
        href="{{ target_url | url }}"
        hreflang="{{ alt.lang }}"
        lang="{{ alt.lang }}"
        class="sopran-language-switcher__link{% if alt.lang == current_language %} sopran-language-switcher__link--active{% endif %}"
        {% if alt.lang == current_language %}aria-current="page"{% endif %}
      >{{ alt.name }}</a>
    {% endfor %}
  </span>
</nav>