Serve a directory of files AND parse them if they're not HTML!

simple_server.ru

# from your working directory, just run `rackup /path/to/simple_server.ru`

require 'tilt'
require 'sass'

run lambda{ |env|
  path = ENV['PWD'] + env['REQUEST_PATH']
  path += 'index' if path =~ %r[/$]
  path.gsub! /\?(.+)$/, ''
  params = $1
  params = Rack::Utils.parse_nested_query(params) if params.is_a? String
  params ||= {}

  file = nil
  potential_files = [path, Dir.glob("#{path}.*"), Dir.glob("#{path}/index.*")].flatten

  potential_files.each do |potential_file|
    if file.nil? and File.exists? potential_file
      file = potential_file
    end
  end
  
  if file
    status = 200
    output = Tilt.new(file).render(Struct.new(:params), params: params)
    
    extension = File.extname(file)[1 .. -1]
    content_type = case extension
    when 'html', 'haml', 'erb'
      'text/html'
    when 'css', 'sass'
      'text/css'
    else
      'text/plain'
    end
    
  else
    status = 404
    output = 'Not found'
    content_type = 'text/plain'
  end

  [status, {'Content-Type' => content_type}, [output]]
}