window.price_sum_field_calculator = (count_fields_sel='.count.field', sum_field_sel='#sum_field') ->
	fields    = document.querySelectorAll count_fields_sel
	sum_field = document.querySelector sum_field_sel

	change_f = (e) ->
		sum = 0

		for el in fields
			price = el.getAttribute 'data-price'
			sf = el.getAttribute 'for'
			s = 1 * el.value * price
			sfe = document.querySelector "##{sf}"
			sfe.textContent = (if 0==s then '' else s)  if sfe
			sum += s

		sum_field.textContent = sum 

	for el in fields
		el.addEventListener 'change', change_f
		el.addEventListener 'input', change_f
	change_f()