public static Trigger asTrigger (Action action)
      {
        switch ( action )
          {
            case LEFT_CLICK_AIR :
              return LEFT_CLICK_AIR;
            case LEFT_CLICK_BLOCK :
              return LEFT_CLICK_BLOCK;
            case RIGHT_CLICK_AIR :
              return RIGHT_CLICK_AIR;
            case RIGHT_CLICK_BLOCK :
              return RIGHT_CLICK_BLOCK;
            default :
              return null;
          }
      }