class ApplicationController < ActionController::Base
  class ActionHandler < Module
    # Get the controller, and call methods on that.
    # In other words, all rails controller macros
    # are accessible for methods defined inside
    # this module.
    # Awsuuum!
    def method_missing(meth, *args, &blk)
      controller_class = Module.nesting[1]
      controller_class.send meth, *args, &blk
    end
  end

  def self.handle( action, &action_module_block )
    action_module =
    if block_given?
      # as a block to this method
      ActionHandler.new &action_module_block
    else
      # it's defined in it's own module
      instance_eval action.to_s.camelize
    end

    # Set up the controller action so rails will call it.
    # Dynamically include the relevant module to handle the call.
    # Assume that module implements "handle"
    define_method action do
      singleton_class.include action_module
      handle
    end

    def handle
      raise NotImplementedError, "You didn't implement 'handle' for #{params[:action]}"
    end
  end
end

class ProjectsController < ApplicationController
  # warning: ruby-2.1 syntax
  helper_method def project
    @project ||= Project[params[:id]]
  end

  # handle GET /projects/:id/owner
  handle :owner do
    helper_method def projects_for( owner )
      # this makes no sense in this limited context
      # just take my word that it does Useful Stuff
      grinder.filter[:persons__id] = owner.pk
      grinder.transform projects
    end

    # you can even redefine this if you like
    helper_method def owner
      @owner ||= project.owner
    end

    helper_method def owners
      @owners ||= roller.dataset.grind filter
    end

    private

    # this does all the normal rails action method stuff
    def handle
      filter.extract!{|k,v| k == :year || k == :budget_gte}
    end

    def grinder
      @grinder ||= Grinder.new filter
    end
  end
end