class Router
  Route = Struct.new(:pattern, :block)

  class RouteSet
    def on(pattern, &block)
      Router.routes.push Route.new(pattern, block)
    end
  end

  @routes = []

  def self.routes
    @routes
  end

  def self.define(&block)
    route_set = RouteSet.new
    route_set.instance_eval(&block)
  end

  def self.run(path)
    params = {}

    matched_route = routes.find do |route|
      matched = path.match /\A#{route.pattern}\z/i
      params = matched.named_captures if matched
      !!matched
    end

    matched_route.block.call(params) if matched_route
  end
end

Router.define do
  on 'patterm' do
    # do something, return response
  end
end