Question

I have a Rails site, where the content is written in markdown. I wish to display a snippet of each, with a ‘Read more..’ link.

How do I go about this? Simple truncating the raw text will not work, for example..

>> 'This is an [example](http://example.com)'[0..25] => 'This is an [example](http:' 

Ideally I want to allow the author to (optionally) insert a marker to specify what to use as the ‘snippet’, if not it would take 250 words, and append ‘…’ – for example..

This article is an example of something or other.  This segment will be used as the snippet on the index page.  ^^^^^^^^^^^^^^^  This text will be visible once clicking the 'Read more..' link 

The marker could be thought of like an EOF marker (which can be ignored when displaying the full document)

I am using maruku for the Markdown processing (RedCloth is very biased towards Textile, BlueCloth is extremely buggy, and I wanted a native-Ruby parser which ruled out peg-markdown and RDiscount)

Alternatively (since the Markdown is translated to HTML anyway) truncating the HTML correctly would be an option – although it would be preferable to not markdown() the entire document, just to get the first few lines.

So, the options I can think of are (in order of preference)..

• Add a ‘truncate’ option to the maruku parser, which will only parse the first x words, or till the ‘excerpt’ marker.
• Write/find a parser-agnostic Markdown truncate’r
• Write/find an intelligent HTML truncating function

Answer 1

• Write/find an intelligent HTML truncating function

The following from http://mikeburnscoder.wordpress.com/2006/11/11/truncating-html-in-ruby/, with some modifications will correctly truncate HTML, and easily allow appending a string before the closing tags.

>> puts '<p><b><a href=\'hi\'>Something</a></p>'.truncate_html(5, at_end = '...') => <p><b><a href='hi'>Someth...</a></b></p> 

The modified code:

require 'rexml/parsers/pullparser'  class String   def truncate_html(len = 30, at_end = nil)     p = REXML::Parsers::PullParser.new(self)     tags = []     new_len = len     results = ''     while p.has_next? && new_len > 0       p_e = p.pull       case p_e.event_type       when :start_element         tags.push p_e[0]         results << '<#{tags.last}#{attrs_to_s(p_e[1])}>'       when :end_element         results << '</#{tags.pop}>'       when :text         results << p_e[0][0..new_len]         new_len -= p_e[0].length       else         results << '<!-- #{p_e.inspect} -->'       end     end     if at_end       results << '...'     end     tags.reverse.each do |tag|       results << '</#{tag}>'     end     results   end    private    def attrs_to_s(attrs)     if attrs.empty?       ''     else       ' ' + attrs.to_a.map { |attr| %{#{attr[0]}='#{attr[1]}'} }.join(' ')     end   end end