{#
    Reusable meta-tags macro for listing pages.

    Renders the standard set of Open Graph and SEO ``<meta>`` tags used on
    pages that list posts (tag pages, category pages, archive pages, etc.).
    Centralising the markup here means that a single edit to this file
    changes the meta tags for every listing page at once.

    Parameters:
        title (str): The page title used in ``og:title`` and
            ``twitter:title``.  The caller is responsible for constructing
            a meaningful title (e.g. ``"Tag: python - My Blog"``).

    Context variables used (passed via ``with context``):
        site_description (str): Site description used for ``description``,
            ``og:description``, and ``twitter:description``.
        site_keywords (list[str]): Keywords used for the ``keywords`` tag.
        site_url (str): Base URL of the site, used for ``og:url`` and
            constructing absolute image URLs.
        site_title (str): Site name used for ``og:site_name``.
        canonical_url (str): Canonical URL of the page used for ``og:url``.
        has_platform_icons (bool): Whether platform icons have been
            generated, used as the preferred source for ``og:image``.
        site_logo (str): URL of the site logo, used as a fallback source
            for ``og:image`` when no platform icons are present.
#}
{% macro listing_meta_tags(title) %}
{% if has_platform_icons %}
{% set og_image = site_url ~ '/icons/android-chrome-512x512.png' %}
{% elif site_logo %}
{% if site_logo.startswith('http://') or site_logo.startswith('https://') %}
{% set og_image = site_logo %}
{% elif site_logo.startswith('/') %}
{% set og_image = site_url ~ site_logo %}
{% else %}
{% set og_image = site_url ~ '/' ~ site_logo %}
{% endif %}
{% else %}
{% set og_image = '' %}
{% endif %}
<meta property="og:title" content="{{ title }}">
<meta property="og:type" content="website">
{% if canonical_url %}
<meta property="og:url" content="{{ canonical_url }}">
{% endif %}
<meta property="og:site_name" content="{{ site_title }}">
{% if site_description %}
<meta name="description" content="{{ site_description }}">
<meta property="og:description" content="{{ site_description }}">
{% endif %}
{% if og_image %}
<meta property="og:image" content="{{ og_image }}">
{% endif %}
{% if site_keywords %}
<meta name="keywords" content="{{ site_keywords|join(', ') }}">
{% endif %}
<meta name="twitter:card" content="{{ 'summary_large_image' if og_image else 'summary' }}">
<meta name="twitter:title" content="{{ title }}">
{% if site_description %}
<meta name="twitter:description" content="{{ site_description }}">
{% endif %}
{% if og_image %}
<meta name="twitter:image" content="{{ og_image }}">
{% endif %}
{% endmacro %}