47colborne/cloud-sesame

module CloudSesame
    module Query
        module Node
            class Sort < Abstract

                attr_writer :attributes

                def attributes
                    @attributes ||= {}
                end

                def [](attribute)
                    attributes[attribute.to_sym]
                end

                def []=(attribute, order)
                    attributes[attribute.to_sym] = order
                end

                def compile
                    unless (compiled = serialize attributes).empty?
                        compiled
                    end
                end

                private

                def serialize(hash)
                    hash.each_with_object("") do |(k, v), o|
                        o << (o.empty? ? '' : ',') << serialize_field(k, v)
                    end
                end

                def serialize_field(name, value)
                    "#{ field_name(name) } #{ value }"
                end

                def field_name(key)
                    (name = alias_field(key)) ? name : key
                end

                def alias_field(key)
                    context[:fields] &&
                    context[:fields][key] &&
                    context[:fields][key][:as]
                end

            end
        end
    end
end