rails_sinatra.rb

require "active_support/core_ext"
require "action_controller/new_base/http"
require "rack/router"

module Rails
  class Sinatra < ActionController::Http
    include AbstractController::Renderer
    include AbstractController::Callbacks
    include AbstractController::Helpers
    
    extlib_inheritable_accessor :router
    
    class << self
      def _routes()                    @_routes ||= []                    end
      def get(uri,    opts={}, &block) route(:get,    uri, opts, &block)  end
      def post(uri,   opts={}, &block) route(:post,   uri, opts, &block)  end
      def put(uri,    opts={}, &block) route(:put,    uri, opts, &block)  end
      def delete(uri, opts={}, &block) route(:delete, uri, opts, &block)  end
      
      def route(method, uri, opts, &block)
        method      = method.to_s.downcase
        action_name = "[#{method}] #{uri}"
        _routes << { :method => method, :uri => uri, :options => opts }
        define_method(uri, &block)
      end
      
      def set(config, value)
        self._view_paths = ActionView::Base.process_view_paths(value) if config == :views
      end
      
      def to_app(fallback = nil)
        self.router = Rack::Router.new(fallback) do |r|
          _routes.each { |route|
            r.map route[:uri], route[:method], (route[:options] || {}).merge(:to => action(route[:uri]))
          }
        end
      end
    end
    
    module Helpers
      def url(*args)         controller.class.router.url(*args) end
      def link_to(text, url) %[<a href="#{url}">#{text}</a>]    end
    end
    
    helper Helpers
    
    def halt(msg)
      throw :halt, msg
    end
    
    def render(name, options = {})
      options[:_template_name] = name
      super(options)
    end
    
    def render_to_body(options = {})
      options[:_prefix] = ""
      super
    end
    
    def process_action(*)
      retval = catch(:halt) { super }
      self.response_body ||= retval
      self.headers["Content-Type"] ||= "text/html"
      self.status ||= 200
    end
  end
end

the_app.rb

class MyApp < Rails::Sinatra
  set :views, File.dirname(__FILE__)
  
  get "/hello", :name => :hello do
    render :greetings
  end
  
  get "/world" do
    @name = "Carl"
    render :awesome
  end
end

class MyOtherApp < Rails::Sinatra
  before_filter do
    halt "EJECTED!"
  end
  
  get "/goodbye" do
    "Nope"
  end
end

run Rack::Router.new { |r|
  r.map "/",      :to => MyApp.to_app
  r.map "/other", :to => MyOtherApp.to_app
}