CGI wrapper around Sass, written in Ruby

nph-sass.cgi

#!/usr/bin/env ruby

# This is a simple CGI wrapper around Sass. 
#
# Copy it into a directory on your site with CGI enabled. When invoked, the 
# script will search its directory and parent directories for a YAML file named
# "config/sass.yml" in order to load configuration information.
#
# If you set the environment variable "sass_generate_output_file" to 
# "true" the concatenation will be cached to disk. Use it in conjunction with 
# URL rewriting to cache your Sass output on the first request.
#
# Assuming a site layout like this:
#
#     mysite/
#       config/
#         sass.yml
#       css/
#         mysite.css
#         ...
#       public/
#         index.html
#         nph-sass.cgi (this file)
#       vendor/
#         sass/
#           mysite.scss
#           reset.scss
#
# mysite/config/sass.yml might look like this:
#
#     :source_path: vendor/sass/ecom.scss
#     :output_file: htdocs/css/ecom.css
#     :load_path:
#       - vendor/sass
#     :style: expanded
#     :syntax: scss
#
# The <link> tag in mysite/public/index.html could look like this:
#
#     <link rel="stylesheet" type="text/css" href="sass.css" />
#
# And you might have the following Apache configuration:
#
#     <VirtualHost ...>
#       ServerName mysite.example.org
#       DocumentRoot "/path/to/mysite/public"
#
#       <Directory "/path/to/mysite/public">
#         Options +ExecCGI +FollowSymLinks
#         AddHandler cgi-script .cgi
#         
#         RewriteEngine on
#         RewriteCond /sass.css !-f
#         RewriteRule ^sass\.css /nph-sass.cgi [P,L]
#       </Directory>
#     </VirtualHost>
#
# All requests to /sass.css will transparently proxy /nph-sass.cgi if
# mysite/public/sass.css does not exist. In production, you can add
#
#     SetEnv sass_generate_output_file true
#
# to your Apache configuration and mysites/public/sass.css will be cached
# on the first request to /sass.css.

require "yaml"
require "fileutils"

def respond_with(options = {})
  options = { :code => 200, :content => "", :type => "text/plain" }.merge(options)
  print "HTTP/1.0 #{options[:code]}\r\n"
  print "Content-Type: #{options[:type]}\r\n"
  print "Content-Length: #{options[:content].length}\r\n"
  print "\r\n#{options[:content]}"
  $stdout.flush
  exit!
end

def search_upwards_for(filename)
  pwd = original_pwd = Dir.pwd
  loop do
    return File.expand_path(filename) if File.file?(filename)
    Dir.chdir("..")
    respond_with(:code => 500, :content => "couldn't find "+filename) if Dir.pwd == pwd
    pwd = Dir.pwd
  end
ensure
  Dir.chdir(original_pwd)
end

def generate_output_file?
  (ENV["REDIRECT_sass_generate_output_file"] || ENV["sass_generate_output_file"]) =~ /true/i
end

configuration_file = search_upwards_for("config/sass.yml")
sass_root          = File.dirname(File.dirname(configuration_file))
configuration      = YAML.load(IO.read(configuration_file))

begin
  if File.directory?(sass_dir = File.join(sass_root, "vendor/gems/sass/lib"))
    $:.unshift sass_dir
  elsif File.directory?(sass_dir = File.join(sass_root, "vendor/sass/lib"))
    $:.unshift sass_dir
  else
    require "rubygems"
  end
  
  require "sass"
  
rescue Exception => e
  respond_with(:code => 500, :content => "couldn't find sass: #{e}")
end

begin
  sass_path = File.join(sass_root, configuration[:source_path])
  output_path = File.join(sass_root, configuration[:output_file])
  load_paths = configuration[:load_path].map  { |p| File.join(sass_root, p) }

  tmpl = IO.read(sass_path)
  engine = Sass::Engine.new(tmpl,
    :load_paths => load_paths,
    :style      => configuration[:style],
    :syntax     => :scss
  )
  css_text = engine.render

  if generate_output_file?
    out_file = File.new(output_path, "w+")
    out_file.write(css_text)
  end

  respond_with(:content => css_text, :type => "text/css")
  
rescue Exception => e
  respond_with(:code => 500, :content => "couldn't generate css: #{e}")
end