parse-html-list.rb

require 'nokogiri'

unordered_list = <<~END
<ul>
  <li>
    First item
  </li>
  <li>
    Second item
    <ul>
      <li>
        Second item's first item
        <ul>
          <li>
            Second item's first item's first item
          </li>
          <li>
            Second item's first item's second item
          </li>
        </ul>
      </li>
    </ul>
  </li>
</ul>
END

def parse_html_list_item(li, indents)
  first_text_child = li.children.select{|c| c.text? }[0].text.strip
  ul = li.at_css('ul')
  if ul
    '  ' * indents + "• #{first_text_child}\n" + parse_html_list(ul, indents + 1)
  else
    '  ' * indents + "• #{first_text_child}\n"
  end
end

def parse_html_list(ul, indents)
  text = ''
  ul.children.select{|l| l.name == 'li' }.each do |li|
    text += parse_html_list_item(li, indents)
  end
  text
end

def parse_html(content)
  all = Nokogiri::HTML(content)
  ul = all.css('ul')[0]
  parse_html_list(ul, 0) if ul
end

puts parse_html(unordered_list)