local fmts = {
	["zł"] = "%.2f %s",
	l = "%.2f %s",
	km = "%.1f %s",
}


local function fmt (value, unit)
	return (fmts[unit] or "%.1f"):format(value, unit)
end


local last_milage = 0


local function relative (kilometres)
	return last_milage + kilometres
end


local function fill (id, date, time, milage, fuel, cost, volume)
	if last_milage > milage then
		error "new milage may not be less than the previous"
	end
	last_milage = milage
	print(id, date, time, fmt(last_milage, "km"), fuel, fmt(cost, "zł"), fmt(volume, "l"))
end


return {fill=fill, relative=relative}