robots_dot_txt.rb

module RobotsDotTxt

  def generate_robots
    rules = YAML::parse( File.open( "#{Rails.root}/config/robots.yml" ) ).transform
    rules = rules[Rails.env]
    robots = "# Generated by Robots Dot Txt gem\n"
    rules.each do |rule_name, rule_values|
      robots += "# #{rule_name}\n"
      ["userAgent", "allow", "disallow"].each do |ua|
        v = rule_values.delete(ua)
        next if v == nil and ua == "disallow"
        robots += create_robots_value(ua, v)
      end
      
      rule_values.each do |k, v| 
        robots += create_robots_value(k, v)
      end
    end  
    robots
  end
  
  protected
  
  def create_robots_value(key, values)
    line = ""
    values = values.to_a
    values.each do |value|
      line += key.underscore.capitalize.sub('_','-') + ": " + path_value(value) + "\n"
    end
    line
  end
  
  def path_value(v)
    v = v.to_s
    v = "*" if v == nil?
    v =~ /.*_path$/ ? eval(v) : v
  end
  
end

Object.send :include, RobotsDotTxt