from collections import namedtuple

class ShapeFilter(namedtuple("ShapeFilter", ['group', 'categories', 'mask'])):
    """
    Pymunk has two primary means of ignoring collisions: groups and 
    category masks.

    Groups are used to ignore collisions between parts on a complex object. A 
    ragdoll is a good example. When jointing an arm onto the torso, you'll 
    want them to allow them to overlap. Groups allow you to do exactly that. 
    Shapes that have the same group don't generate collisions. So by placing 
    all of the shapes in a ragdoll in the same group, you'll prevent it from 
    colliding against other parts of itself. Category masks allow you to mark 
    which categories an object belongs to and which categories it collides 
    with.

    For example, a game has four collision categories: player (0), enemy (1), 
    player bullet (2), and enemy bullet (3). Neither players nor enemies 
    should not collide with their own bullets, and bullets should not collide 
    with other bullets. However, players collide with enemy bullets, and 
    enemies collide with player bullets.

    ============= =============== ====================
    Object        Object Category Category Mask
    ============= =============== ====================
    Player        0b00001 (1)     0b11000 (4, 5)       
    Enemy         0b00010 (2)     0b01110 (2, 3, 4)
    Player Bullet 0b00100 (3)     0b10001 (1, 5)
    Enemy Bullet  0b01000 (4)     0b10010 (2, 5)
    Walls         0b10000 (5)     0b01111 (1, 2, 3, 4)
    ============= =============== ====================
    
    Note that in the table the categories and masks are written as binary 
    values to clearly show the logic. To save space only 5 digits are used. The 
    default type of categories and mask in ShapeFilter is an unsigned int, 
    with a resolution of 32 bits. That means that the you have 32 bits to use, 
    in binary notation that is `0b00000000000000000000000000000000` to 
    `0b11111111111111111111111111111111` which can be written in hex as 
    `0x00000000` to 0xFFFFFFFF`.

    Everything in this example collides with walls. Additionally, 
    the enemies collide with each other.

    By default, objects exist in every category and collide with every category.

    Objects can fall into multiple categories. For instance, you might have a 
    category for a red team, and have a red player bullet. In the above 
    example, each object only has one category. 

    The default type of categories and mask in ShapeFilter is unsigned int 
    which has a resolution of 32 bits on most systems. 

    There is one last way of filtering collisions using collision handlers. 
    See the section on callbacks for more information. Collision handlers can 
    be more flexible, but can be slower. Fast collision filtering rejects 
    collisions before running the expensive collision detection code, so 
    using groups or category masks is preferred.

    Example of how category and mask can be used to filter out player from 
    enemy object:

    >>> import pymunk
    >>> s = pymunk.Space()
    >>> player_b = pymunk.Body(1,1)
    >>> player_c = pymunk.Circle(player_b, 10)
    >>> s.add(player_b, player_c)
    >>> player_c.filter = pymunk.ShapeFilter(categories=0b1)
    >>> hit = s.point_query_nearest((0,0), 0, pymunk.ShapeFilter())
    >>> hit != None
    True
    >>> filter = pymunk.ShapeFilter(mask=pymunk.ShapeFilter.ALL_MASKS ^ 0b1)
    >>> hit = s.point_query_nearest((0,0), 0, filter)
    >>> hit == None
    True
    >>> enemy_b = pymunk.Body(1,1)
    >>> enemy_c = pymunk.Circle(enemy_b, 10)
    >>> s.add(enemy_b, enemy_c)
    >>> hit = s.point_query_nearest((0,0), 0, filter)
    >>> hit != None
    True

    """
    __slots__ = ()    

    ALL_CATEGORIES = 0xffffffff

    ALL_MASKS = 0xffffffff

    def __new__(cls, group = 0, categories = 0xffffffff, mask = 0xffffffff):
        self = super(ShapeFilter, cls).__new__(cls, group, categories, mask)
        return self