clock.h

void update_clock_hands(AddressableLight &it, ESPTime time,
                        Color clock_ring_colors[], int offset) {
  static boolean initialized;
  int num_leds = it.size();

  if (initialized == false) {
    std::fill_n(clock_ring_colors, it.size(), Color::BLACK);
    initialized = true;
  }

  if (!time.is_valid()) {
    return;
  }

  // calculate led indices
  int second_idx = (int)(time.second * (it.size() / 60.0));
  int minute_idx = (int)(time.minute * (it.size() / 60.0));
  // this idx would "jump" in big steps
  int hour_idx = (int)((time.hour % 12) * (it.size() / 12.0));
  // this moves one led at a time
  int hour_inc_min_idx =
      hour_idx + (int)(((float)time.minute / 12.0) * (it.size() / 60.0));

  // the hour hand may be bigger than one led, so we use an array for that
  std::vector<int> hour_idx_vector;
  if (id(wide_hour_hand_enabled)) {
    hour_idx_vector.push_back((hour_inc_min_idx - 1 + it.size()) % (it.size()));
    hour_idx_vector.push_back(hour_inc_min_idx);
    hour_idx_vector.push_back((hour_inc_min_idx + 1) % it.size());
  } else {
    hour_idx_vector.push_back(hour_inc_min_idx);
  }

  // fade out old colors
  for (int i = 0; i < it.size(); i++) {
    Color old_color = clock_ring_colors[i];
    int percentage = 2;
    int red = old_color.red;
    int red_sub = std::max(1, (int)((red / 100.0) * percentage));
    int green = old_color.green;
    int green_sub = std::max(1, (int)((green / 100.0) * percentage));
    int blue = old_color.blue;
    int blue_sub = std::max(1, (int)((blue / 100.0) * percentage));
    if (red <= red_sub) {
      red = 0;
    } else {
      red -= red_sub;
    }
    if (green <= green_sub) {
      green = 0;
    } else {
      green -= green_sub;
    }
    if (blue <= blue_sub) {
      blue = 0;
    } else {
      blue -= blue_sub;
    }
    Color new_color = Color(red, green, blue, 0);
    clock_ring_colors[i] = new_color;
  }

  int indicator_brightness = id(clock_brightness) / 3;
  Color indicator_color =
      Color(indicator_brightness, indicator_brightness, indicator_brightness);

  // set base colors
  Color hour_color = Color(0, 0, id(clock_brightness));
  Color minute_color = Color(0, id(clock_brightness), 0);
  Color second_color = Color(id(clock_brightness), 0, 0);
  if (!id(clock_seconds_enabled)) {
    second_color = Color::BLACK;
  }

  // merge colors if they overlap
  // if minute idx inside hour idx range
  if (std::find(std::begin(hour_idx_vector), std::end(hour_idx_vector),
                minute_idx) != std::end(hour_idx_vector)) {
    minute_color += hour_color;
  }

  if (second_idx == minute_idx) {
    minute_color += second_color;
    second_color = minute_color;
  } else if (std::find(std::begin(hour_idx_vector), std::end(hour_idx_vector),
                       second_idx) != std::end(hour_idx_vector)) {
    second_color += hour_color;
  }

  // === set colors from bottom to top
  // indicators
  if (id(clock_indicators_enabled)) {
    for (int i = 0; i < it.size(); i += (int)((float)it.size() / 12)) {
      clock_ring_colors[i] = indicator_color;
    }
  }

  // hours
  for (int i = 0; i < hour_idx_vector.size(); i++) {
    clock_ring_colors[hour_idx_vector[i]] = hour_color;
  }
  // minutes
  clock_ring_colors[minute_idx] = minute_color;
  // seconds
  if (id(clock_seconds_enabled)) {
    clock_ring_colors[second_idx] = second_color;
  }

  // apply colors to light
  for (int i = 0; i < it.size(); i++) {
    int x = (i + offset) % it.size();
    it[x] = clock_ring_colors[i];
  }
}