web/_includes/related-posts.html

<!--
  Recommend the other 3 posts according to the tags and categories of the current post,
  if the number is not enough, use the other latest posts to supplement.
-->

<!-- The total size of related posts -->
{% assign TOTAL_SIZE = 3 %}

<!-- An random integer that bigger than 0 -->
{% assign TAG_SCORE = 1 %}

<!-- Equals to TAG_SCORE / {max_categories_hierarchy} -->
{% assign CATEGORY_SCORE = 0.5 %}

{% assign SEPARATOR = ':' %}

{% assign score_list = '' | split: '' %}
{% assign last_index = site.posts.size | minus: 1 %}

{% for i in (0..last_index) %}
  {% assign post = site.posts[i] %}

  {% if post.url == page.url %}
    {% continue %}
  {% endif %}

  {% assign score = 0 %}

  {% for tag in post.tags %}
    {% if page.tags contains tag %}
      {% assign score = score | plus: TAG_SCORE %}
    {% endif %}
  {% endfor %}

  {% for category in post.categories %}
    {% if page.categories contains category %}
      {% assign score = score | plus: CATEGORY_SCORE %}
    {% endif %}
  {% endfor %}

  {% if score > 0 %}
    {% capture score_item %}{{ score }}{{ SEPARATOR }}{{ i }}{% endcapture %}
    {% assign score_list = score_list | push: score_item %}
  {% endif %}
{% endfor %}

{% assign index_list = '' | split: '' %}

{% if score_list.size > 0 %}
  {% assign score_list = score_list | sort | reverse %}
  {% for entry in score_list limit: TOTAL_SIZE %}
    {% assign index = entry | split: SEPARATOR | last %}
    {% assign index_list = index_list | push: index %}
  {% endfor %}
{% endif %}

<!-- Fill with the other newlest posts -->
{% assign less = TOTAL_SIZE | minus: index_list.size %}

{% if less > 0 %}
  {% for i in (0..last_index) %}
    {% assign post = site.posts[i] %}
    {% if post.url != page.url %}
      {% capture cur_index %}{{ i }}{% endcapture %}
      {% unless index_list contains cur_index %}
        {% assign index_list = index_list | push: cur_index %}
        {% assign less = less | minus: 1 %}
        {% if less <= 0 %}
          {% break %}
        {% endif %}
      {% endunless %}
    {% endif %}
  {% endfor %}
{% endif %}

{% if index_list.size > 0 %}
  <div id="related-posts" class="mb-2 mb-sm-4">
    <h3
      class="pt-2 mb-4 ml-1"
      data-toc-skip
    >
      {{ site.data.locales[include.lang].post.relate_posts }}
    </h3>
    <div class="card-deck mb-4">
      {% for entry in index_list %}
        {% assign index = entry | plus: 0 %}
        {% assign post = site.posts[index] %}
        <a href="{{ post.url | relative_url }}" class="card post-preview">
          <div class="card-body">
            {% include datetime.html date=post.date class="small" lang=include.lang %}
            <h3 class="pt-0 mt-2 mb-3" data-toc-skip>{{ post.title }}</h3>
            <div class="text-muted small">
              <p>
                {% include no-linenos.html content=post.content %}
                {{ content | markdownify | strip_html | truncate: 200 | escape }}
              </p>
            </div>
          </div>
        </a>
      {% endfor %}
    </div>
    <!-- .card-deck -->
  </div>
  <!-- #related-posts -->
{% endif %}