Jekyll include for generating random strings

random

{% capture random %}
{% comment %}This include generates a random string.
Save it to _includes. Then use {% include random %} 
to get an 8-character string of numbers and letters.

Optionally:

* Specify the length of string you want. E.g. 
  {% include random length=16 %} or
  {% include random length="16" %}
* Specify a character type as any of "numbers", "letters",
  vowels", "consonants", "symbols" or "characters". E.g.
  {% include random type="numbers" %} or 
  {% include random type="numbers, symbols" %}
* If you use "characters", you define which ones. E.g.
  {% include random type="characters" characters="foobar" %} or
  {% include random type="characters" characters="a,b,c,1,2,3" %}

Because we capture and return the random string without <p>
or newlines, this can be used inline in markdown.{% endcomment %}

{% comment %}Set the length of the string.{% endcomment %}
{% if include.length %}
    {% assign length = include.length %}
{% else %}
    {% assign length = 8 %}
{% endif %}

{% comment %}Create arrays of possible characters.
We avoid symbols that might clash with markdown syntax, 
such as $, since $$ triggers MathJax script tags.
Users can define their own characters, too.{% endcomment %}
{% assign numbers = "1,2,3,4,5,6,7,8,9,0" | split: "," %}
{% assign vowels = "a,e,i,o,u" | split: "," %}
{% assign consonants = "b,c,d,f,g,h,j,k,l,m,n,p,q,r,s,t,v,w,x,y,z" | split: "," %}
{% assign symbols = "~,!,@,#,%,&,(,)" | split: "," %}
{% assign characters = include.characters | remove: " " | remove: "," | split: "" %}

{% comment %}And combine vowels and consonants into one 'letters' array.{% endcomment %}
{% assign letters = vowels %}
{% for consonant in consonants %}
    {% assign letters = letters | push: consonant %}
{% endfor %}

{% comment %}Add array names to the array of default types.{% endcomment %}
{% assign default-types = "numbers,vowels,consonants,letters,characters" | split: "," %}

{% comment %}If any types were defined in the include tag,
use only those. Otherwise use all possible types.{% endcomment %}
{% if include.type %}
    {% assign types = include.type | remove: " " | split: "," %}
{% else %}
    {% assign types = default-types %}
{% endif %}

{% comment %}Create an array from the first type,
then add the values of any other types.{% endcomment %}
{% for type in types %}
    {% if forloop.first == true %}
        {% assign chars = [type] %}
    {% endif %}
    {% if forloop.first == false %}
        {% for char in [type] %}
            {% assign chars = chars | push: char %}
        {% endfor %}
    {% endif %}
{% endfor %}

{% comment %}Remove duplicates from the chars array. E.g.
if we have both letters and vowels or consonants.{% endcomment %}
{% assign chars = chars | uniq %}

{% comment %}Create a random string by sampling that array
as often as the string-length limit.{% endcomment %}
{% for char in (1..length) %}
{{ chars | sample }}
{% endfor %}

{% endcapture %}{{ random | remove: '<p>' | remove: '</p>' | strip_newlines }}