@EventHandler(priority = EventPriority.NORMAL)
  public void togglePlayerStacker(PlayerInteractEvent event) {
    // Do nothing if player is not right clicking.
    Action action = event.getAction();
    if (action != RIGHT_CLICK_AIR && action != RIGHT_CLICK_BLOCK) return;

    // Do nothing if player does not have permission.
    Player player = event.getPlayer();
    if (!Perm.PLAYERSTACKER.has(player)) return;

    // Do nothing if player is not clicking the player hider item.
    if (!player.getItemInHand().equals(plugin.getSettings().getPlayerStackerItemDisabled())
        && !player.getItemInHand().equals(plugin.getSettings().getPlayerStackerItemEnabled()))
      return;

    // Do nothing if user is null.
    User user = plugin.getUser(player.getUniqueId());
    if (user == null) return;

    // Toggle users stacking option.
    user.setStacking(!user.isStacking());

    // Update players inventory with the newer player hider item.
    if (plugin.getSettings().getPlayerStackerSlot() >= 0) {
      ItemStack reverse =
          player.getItemInHand().equals(plugin.getSettings().getPlayerStackerItemEnabled())
              ? plugin.getSettings().getPlayerStackerItemDisabled()
              : plugin.getSettings().getPlayerStackerItemEnabled();
      player.getInventory().setItem(plugin.getSettings().getPlayerStackerSlot(), reverse);
      player.updateInventory();
    }

    // Play a clicking sound.
    player.playSound(player.getLocation(), Sound.CLICK, 2.0F, 1.0F);
  }