simple dsl for restful_acl

  def self.role_perms(role_name)
    if role_name == :anybody
      "return true"
    else
      "user.acts_as_if? '#{role_name}'"
    end
  end


  def self.access_func(method_name, info)

    self_clause = ""
    evaluator = ""

    info.each_pair do |key,value|
      case key
        when :owner
          if value.nil? || value === true
            assoc_id = "user_id"
          else
            assoc_id = value
          end
          self_clause = "return true if user and user.id == #{assoc_id}"
        else
          evaluator = role_perms(key)
      end
    end

    class_eval %{
    def #{method_name}(user, parent = nil)
      #{self_clause}
      #{evaluator}
    end
    }
  end


  def self.convert_to_role_hash(*role_names)
    role_hash = {}
    if role_names.last.is_a? Hash
      role_hash = role_names.pop
    end

    role_names.each do |role|
      role_hash[role] = true
    end
    role_hash
  end

  def self.update_by (*role_names)
    role_hash = convert_to_role_hash(*role_names)
    access_func(:is_updatable_by, role_hash)
  end

  def self.delete_by (*role_names)
    role_hash = convert_to_role_hash(*role_names)
    access_func(:is_deletable_by, role_hash)
  end

  def self.read_by (role_name)
    evaluator = role_perms(role_name)

    class_eval %{
    def is_readable_by(user, parent = nil)
      #{evaluator}
    end
    def self.is_indexable_by(user, parent = nil)
      #{evaluator}
    end
    }
  end

  def self.create_by (role_name)
    evaluator = role_perms(role_name)

    class_eval %{
    def self.is_creatable_by(user, object = nil)
      #{evaluator}
    end
    }
  end