articles/01_rubic/libcube/cubes/cube3x3.py

"""
Classic cube 3x3
"""
import enum
import collections

from . import _env
from . import _common

# environment API
State = collections.namedtuple("State", field_names=['corner_pos', 'side_pos', 'corner_ort', 'side_ort'])

# rendered state -- list of colors of every side
RenderedState = collections.namedtuple("RenderedState", field_names=['top', 'front', 'left', 'right', 'back', 'bottom'])

# initial (solved state)
initial_state = State(corner_pos=tuple(range(8)), side_pos=tuple(range(12)), corner_ort=tuple([0]*8), side_ort=tuple([0]*12))


def is_initial(state):
    """
    Checks that this state is initial state
    :param state: State instance
    :return: True if state match initial, False otherwise
    """
    return state.corner_pos == initial_state.corner_pos and \
           state.side_pos == initial_state.side_pos and \
           state.corner_ort == initial_state.corner_ort and \
           state.side_ort == initial_state.side_ort


# available actions. Capital actions denote clockwise rotation
class Action(enum.Enum):
    R = 0
    L = 1
    T = 2
    D = 3
    F = 4
    B = 5
    r = 6
    l = 7
    t = 8
    d = 9
    f = 10
    b = 11


_inverse_action = {
    Action.R: Action.r,
    Action.r: Action.R,
    Action.L: Action.l,
    Action.l: Action.L,
    Action.T: Action.t,
    Action.t: Action.T,
    Action.D: Action.d,
    Action.d: Action.D,
    Action.F: Action.f,
    Action.f: Action.F,
    Action.B: Action.b,
    Action.b: Action.B
}


def inverse_action(action):
    assert isinstance(action, Action)
    return _inverse_action[action]


def _flip(side_ort, sides):
    return [
        o if idx not in sides else 1-o
        for idx, o in enumerate(side_ort)
    ]


_transform_map = {
    Action.R: [
        ((1, 2), (2, 6), (6, 5), (5, 1)),           # corner map
        ((1, 6), (6, 9), (9, 5), (5, 1)),           # side map
        ((1, 2), (2, 1), (5, 1), (6, 2)),           # corner rotate
        ()                                          # side flip
    ],
    Action.L: [
        ((3, 0), (7, 3), (0, 4), (4, 7)),
        ((7, 3), (3, 4), (11, 7), (4, 11)),
        ((0, 1), (3, 2), (4, 2), (7, 1)),
        ()
    ],
    Action.T: [
        ((0, 3), (1, 0), (2, 1), (3, 2)),
        ((0, 3), (1, 0), (2, 1), (3, 2)),
        (),
        ()
    ],
    Action.D: [
        ((4, 5), (5,  6), (6, 7), (7, 4)),
        ((8, 9), (9, 10), (10, 11), (11, 8)),
        (),
        ()
    ],
    Action.F: [
        ((0, 1), (1, 5), (5, 4), (4, 0)),
        ((0, 5), (4, 0), (5, 8), (8, 4)),
        ((0, 2), (1, 1), (4, 1), (5, 2)),
        (0, 4, 5, 8)
    ],
    Action.B: [
        ((2, 3), (3, 7), (7, 6), (6, 2)),
        ((2, 7), (6, 2), (7, 10), (10, 6)),
        ((2, 2), (3, 1), (6, 1), (7, 2)),
        (2, 6, 7, 10)
    ]
}


def transform(state, action):
    assert isinstance(state, State)
    assert isinstance(action, Action)
    global _transform_map

    is_inv = action not in _transform_map
    if is_inv:
        action = inverse_action(action)
    c_map, s_map, c_rot, s_flp = _transform_map[action]
    corner_pos = _common._permute(state.corner_pos, c_map, is_inv)
    corner_ort = _common._permute(state.corner_ort, c_map, is_inv)
    corner_ort = _common._rotate(corner_ort, c_rot)
    side_pos = _common._permute(state.side_pos, s_map, is_inv)
    side_ort = state.side_ort
    if s_flp:
        side_ort = _common._permute(side_ort, s_map, is_inv)
        side_ort = _flip(side_ort, s_flp)
    return State(corner_pos=tuple(corner_pos), corner_ort=tuple(corner_ort),
                 side_pos=tuple(side_pos), side_ort=tuple(side_ort))


# make initial state of rendered side
def _init_side(color):
    return [color if idx == 4 else None for idx in range(9)]


# create initial sides in the right order
def _init_sides():
    return [
        _init_side('W'),    # top
        _init_side('G'),    # left
        _init_side('O'),    # back
        _init_side('R'),    # front
        _init_side('B'),    # right
        _init_side('Y')     # bottom
    ]


# corner cubelets colors (clockwise from main label). Order of cubelets are first top,
# in counter-clockwise, started from front left
corner_colors = (
    ('W', 'R', 'G'), ('W', 'B', 'R'), ('W', 'O', 'B'), ('W', 'G', 'O'),
    ('Y', 'G', 'R'), ('Y', 'R', 'B'), ('Y', 'B', 'O'), ('Y', 'O', 'G')
)

side_colors = (
    ('W', 'R'), ('W', 'B'), ('W', 'O'), ('W', 'G'),
    ('R', 'G'), ('R', 'B'), ('O', 'B'), ('O', 'G'),
    ('Y', 'R'), ('Y', 'B'), ('Y', 'O'), ('Y', 'G')
)


# map every 3-side cubelet to their projection on sides
# sides are indexed in the order of _init_sides() function result
corner_maps = (
    # top layer
    ((0, 6), (3, 0), (1, 2)),
    ((0, 8), (4, 0), (3, 2)),
    ((0, 2), (2, 0), (4, 2)),
    ((0, 0), (1, 0), (2, 2)),
    # bottom layer
    ((5, 0), (1, 8), (3, 6)),
    ((5, 2), (3, 8), (4, 6)),
    ((5, 8), (4, 8), (2, 6)),
    ((5, 6), (2, 8), (1, 6))
)

# map every 2-side cubelet to their projection on sides
side_maps = (
    # top layer
    ((0, 7), (3, 1)),
    ((0, 5), (4, 1)),
    ((0, 1), (2, 1)),
    ((0, 3), (1, 1)),
    # middle layer
    ((3, 3), (1, 5)),
    ((3, 5), (4, 3)),
    ((2, 3), (4, 5)),
    ((2, 5), (1, 3)),
    # bottom layer
    ((5, 1), (3, 7)),
    ((5, 5), (4, 7)),
    ((5, 7), (2, 7)),
    ((5, 3), (1, 7))
)


# render state into human readable form
def render(state):
    assert isinstance(state, State)
    global corner_colors, corner_maps, side_colors, side_maps

    sides = _init_sides()

    for corner, orient, maps in zip(state.corner_pos, state.corner_ort, corner_maps):
        cols = corner_colors[corner]
        cols = _common._map_orient(cols, orient)
        for (arr_idx, index), col in zip(maps, cols):
            sides[arr_idx][index] = col

    for side, orient, maps in zip(state.side_pos, state.side_ort, side_maps):
        cols = side_colors[side]
        cols = cols if orient == 0 else (cols[1], cols[0])
        for (arr_idx, index), col in zip(maps, cols):
            sides[arr_idx][index] = col

    return RenderedState(top=sides[0], left=sides[1], back=sides[2], front=sides[3],
                         right=sides[4], bottom=sides[5])


# shape of encoded cube state
encoded_shape = (20, 24)


def encode_inplace(target, state):
    """
    Encode cude into existig zeroed numpy array
    Follows encoding described in paper https://arxiv.org/abs/1805.07470
    :param target: numpy array
    :param state: state to be encoded
    """
    assert isinstance(state, State)

    # handle corner cubelets: find their permuted position
    for corner_idx in range(8):
        perm_pos = state.corner_pos.index(corner_idx)
        corn_ort = state.corner_ort[perm_pos]
        target[corner_idx, perm_pos * 3 + corn_ort] = 1

    # handle side cubelets
    for side_idx in range(12):
        perm_pos = state.side_pos.index(side_idx)
        side_ort = state.side_ort[perm_pos]
        target[8 + side_idx, perm_pos * 2 + side_ort] = 1


# register env
_env.register(_env.CubeEnv(name="cube3x3", state_type=State, initial_state=initial_state,
                           is_goal_pred=is_initial, action_enum=Action,
                           transform_func=transform, inverse_action_func=inverse_action,
                           render_func=render, encoded_shape=encoded_shape, encode_func=encode_inplace))