yet another rack router

config.ru

require 'router'

use Rack::Static, :urls => ['/css', '/js'], :root => "static"

run Router.new

default.rb

# /controllers/default.rb
module Controllers
  class Default
    def self.default env
      [200, {'content-type' => 'text/html'}, "default text"]
    end
  end
end

router.rb

require 'yaml'

# Instantiating the Router class does a couple things:
# 1. read route definition file, and generate case/when logic
# 2. define a "call" function (called by Rack) that calls the appropriate controller.action pair
#
# Routes are defined as "<path pattern> <controller name> <action name>"
#
# Example routes.yml
# # pattern     Controller    action
# - /user/\d+   User          note
# - /users      User          index
# - /           Default       default
#
# Controllers are assumed to be wrapped in a "Controllers" module
# Actions are assumed to be static, and accept the env object
#
# For example,
# module Controllers
#   class Foo
#     def static.default env
#       [200, {'content-type' => 'text/html'}, "foo"]
#     end
#   end
# end

require 'yaml'
require './controllers.rb'

class Router
  def initialize
    whens = ''
    YAML.load_file('routes.yml').each do |route|
      pattern, controller, action = route.split /\s+/
      whens += <<-EOS
        when %r{#{pattern}}
          controller = Controllers::#{controller}.new env
          controller.#{action}
          controller.response
      EOS
    end
    Router.class_eval <<-EOS
      def call env
        case env['REQUEST_PATH']
          #{whens}
        end
      end
    EOS
  end
end

routes.yml

# pattern     Controller    action
- /user/\d+   User          find
- /user       User          default
- /           Default       default

user.rb

# /controllers/user.rb
module Controllers
  class User
    def self.default env
      [200, {'content-type' => 'text/html'}, "User#default"]
    end
    def self.find env
      [200, {'content-type' => 'text/html'}, "User#find"]
    end
  end
end