{% comment %}
Map grabs the tutorials sections, giving us an array of arrays. Join, flattens all
the items to a comma delimited string. Split turns it into an array again.
{% endcomment %}
{% assign tutorials = site.data.tutorials | map: 'tutorials' | join: ',' | split: ',' %}

{% comment %}
Because this is built for every page, lets find where we are in the ordered
document list by comparing url strings. Then if there's something previous or
next, lets build a link to it.
{% endcomment %}

{% for tutorial in tutorials %}
  {% assign tutorial_url = tutorial | prepend:"/tutorials/" | append:"/" %}
  {% if tutorial_url == page.url %}
    <div class="section-nav">
      <div class="left align-right">
          {% if forloop.first %}
            <span class="prev disabled">Back</span>
          {% else %}
            {% assign previous = forloop.index0 | minus: 1 %}
            {% assign previous_page = tutorials[previous] | prepend:"/tutorials/" | append:"/" %}
            <a href="{{ previous_page }}" class="prev">Back</a>
          {% endif %}
      </div>
      <div class="right align-left">
          {% if forloop.last %}
            <span class="next disabled">Next</span>
          {% else %}
            {% assign next = forloop.index0 | plus: 1 %}
            {% assign next_page = tutorials[next] | prepend:"/tutorials/" | append:"/" %}
            <a href="{{ next_page }}" class="next">Next</a>
          {% endif %}
      </div>
    </div>
    <div class="clear"></div>
    {% break %}
  {% endif %}
{% endfor %}