public class Lamp {

    public static String draw(int unit, String lamp, int numberOfLamps) {

        StringBuilder lamps = initialiseTemplate(numberOfLamps);

        for (int i = 0; i<unit; i++) {
            lamps.replace(i, i + 1, lamp);
        }

        return lamps.toString();
    }

    private static StringBuilder initialiseTemplate(int numberOfLamps) {
        StringBuilder lamps = new StringBuilder();

        for (int i=0; i<numberOfLamps; i++) {
            lamps.append(LampsConsts.LAMP_OFF);
        }

        return lamps;
    }

    public static String drawTopMinutes(int unit, int numberOfLamps) {

        StringBuilder lamps = initialiseTemplate(numberOfLamps);

        for (int i=0; i<unit; i++) {
            turnOnLamp(lamps, i);
        }

        return lamps.toString();
    }

    private static void turnOnLamp(StringBuilder lamp, int positionInLampTemplate) {
        String lampType = isLampPositionRed(positionInLampTemplate) ? LampsConsts.RED_LAMP_ON : LampsConsts.YELLOW_LAMP_ON;

        turnOnLamp(lamp, positionInLampTemplate, lampType);
    }

    private static boolean isLampPositionRed(int positionInLampTemplate) {
        return 0 == (positionInLampTemplate + 1) % 3;
    }

    private static void turnOnLamp(StringBuilder lamp, int positionInLampTemplate, String lampType) {
        lamp.replace(positionInLampTemplate, positionInLampTemplate + 1, lampType);
    }
}