Gym-MiniGrid/gym_minigrid/envs/obstructedmaze.py

from gym_minigrid.minigrid import COLOR_NAMES, DIR_TO_VEC, Ball, Box, Key, MissionSpace
from gym_minigrid.roomgrid import RoomGrid


class ObstructedMazeEnv(RoomGrid):

    """
    ### Description

    The agent has to pick up a box which is placed in a corner of a 3x3 maze.
    The doors are locked, the keys are hidden in boxes and doors are obstructed
    by balls. This environment can be solved without relying on language.

    ### Mission Space

    "pick up the {COLOR_NAMES[0]} ball"

    ### Action Space

    | Num | Name         | Action                    |
    |-----|--------------|---------------------------|
    | 0   | left         | Turn left                 |
    | 1   | right        | Turn right                |
    | 2   | forward      | Move forward              |
    | 3   | pickup       | Pick up an object         |
    | 4   | drop         | Unused                    |
    | 5   | toggle       | Toggle/activate an object |
    | 6   | done         | Unused                    |

    ### Observation Encoding

    - Each tile is encoded as a 3 dimensional tuple:
        `(OBJECT_IDX, COLOR_IDX, STATE)`
    - `OBJECT_TO_IDX` and `COLOR_TO_IDX` mapping can be found in
        [gym_minigrid/minigrid.py](gym_minigrid/minigrid.py)
    - `STATE` refers to the door state with 0=open, 1=closed and 2=locked

    ### Rewards

    A reward of '1' is given for success, and '0' for failure.

    ### Termination

    The episode ends if any one of the following conditions is met:

    1. The agent picks up the blue ball.
    2. Timeout (see `max_steps`).

    ### Registered Configurations

    "NDl" are the number of doors locked.
    "h" if the key is hidden in a box.
    "b" if the door is obstructed by a ball.
    "Q" number of quarters that will have doors and keys out of the 9 that the
    map already has.
    "Full" 3x3 maze with "h" and "b" options.

    - `MiniGrid-ObstructedMaze-1Dl-v0`
    - `MiniGrid-ObstructedMaze-1Dlh-v0`
    - `MiniGrid-ObstructedMaze-1Dlhb-v0`
    - `MiniGrid-ObstructedMaze-2Dl-v0`
    - `MiniGrid-ObstructedMaze-2Dlh-v0`
    - `MiniGrid-ObstructedMaze-2Dlhb-v0`
    - `MiniGrid-ObstructedMaze-1Q-v0`
    - `MiniGrid-ObstructedMaze-2Q-v0`
    - `MiniGrid-ObstructedMaze-Full-v0`

    """

    def __init__(self, num_rows, num_cols, num_rooms_visited, **kwargs):
        room_size = 6
        max_steps = 4 * num_rooms_visited * room_size**2

        mission_space = MissionSpace(
            mission_func=lambda: f"pick up the {COLOR_NAMES[0]} ball",
        )
        super().__init__(
            mission_space=mission_space,
            room_size=room_size,
            num_rows=num_rows,
            num_cols=num_cols,
            max_steps=max_steps,
            **kwargs,
        )
        self.obj = Ball()  # initialize the obj attribute, that will be changed later on

    def _gen_grid(self, width, height):
        super()._gen_grid(width, height)

        # Define all possible colors for doors
        self.door_colors = self._rand_subset(COLOR_NAMES, len(COLOR_NAMES))
        # Define the color of the ball to pick up
        self.ball_to_find_color = COLOR_NAMES[0]
        # Define the color of the balls that obstruct doors
        self.blocking_ball_color = COLOR_NAMES[1]
        # Define the color of boxes in which keys are hidden
        self.box_color = COLOR_NAMES[2]

        self.mission = "pick up the %s ball" % self.ball_to_find_color

    def step(self, action):
        obs, reward, terminated, truncated, info = super().step(action)

        if action == self.actions.pickup:
            if self.carrying and self.carrying == self.obj:
                reward = self._reward()
                terminated = True

        return obs, reward, terminated, truncated, info

    def add_door(
        self,
        i,
        j,
        door_idx=0,
        color=None,
        locked=False,
        key_in_box=False,
        blocked=False,
    ):
        """
        Add a door. If the door must be locked, it also adds the key.
        If the key must be hidden, it is put in a box. If the door must
        be obstructed, it adds a ball in front of the door.
        """

        door, door_pos = super().add_door(i, j, door_idx, color, locked=locked)

        if blocked:
            vec = DIR_TO_VEC[door_idx]
            blocking_ball = Ball(self.blocking_ball_color) if blocked else None
            self.grid.set(door_pos[0] - vec[0], door_pos[1] - vec[1], blocking_ball)

        if locked:
            obj = Key(door.color)
            if key_in_box:
                box = Box(self.box_color)
                box.contains = obj
                obj = box
            self.place_in_room(i, j, obj)

        return door, door_pos


class ObstructedMaze_1Dlhb(ObstructedMazeEnv):
    """
    A blue ball is hidden in a 2x1 maze. A locked door separates
    rooms. Doors are obstructed by a ball and keys are hidden in boxes.
    """

    def __init__(self, key_in_box=True, blocked=True, **kwargs):
        self.key_in_box = key_in_box
        self.blocked = blocked

        super().__init__(num_rows=1, num_cols=2, num_rooms_visited=2, **kwargs)

    def _gen_grid(self, width, height):
        super()._gen_grid(width, height)

        self.add_door(
            0,
            0,
            door_idx=0,
            color=self.door_colors[0],
            locked=True,
            key_in_box=self.key_in_box,
            blocked=self.blocked,
        )

        self.obj, _ = self.add_object(1, 0, "ball", color=self.ball_to_find_color)
        self.place_agent(0, 0)


class ObstructedMaze_Full(ObstructedMazeEnv):
    """
    A blue ball is hidden in one of the 4 corners of a 3x3 maze. Doors
    are locked, doors are obstructed by a ball and keys are hidden in
    boxes.
    """

    def __init__(
        self,
        agent_room=(1, 1),
        key_in_box=True,
        blocked=True,
        num_quarters=4,
        num_rooms_visited=25,
        **kwargs,
    ):
        self.agent_room = agent_room
        self.key_in_box = key_in_box
        self.blocked = blocked
        self.num_quarters = num_quarters

        super().__init__(
            num_rows=3, num_cols=3, num_rooms_visited=num_rooms_visited, **kwargs
        )

    def _gen_grid(self, width, height):
        super()._gen_grid(width, height)

        middle_room = (1, 1)
        # Define positions of "side rooms" i.e. rooms that are neither
        # corners nor the center.
        side_rooms = [(2, 1), (1, 2), (0, 1), (1, 0)][: self.num_quarters]
        for i in range(len(side_rooms)):
            side_room = side_rooms[i]

            # Add a door between the center room and the side room
            self.add_door(
                *middle_room, door_idx=i, color=self.door_colors[i], locked=False
            )

            for k in [-1, 1]:
                # Add a door to each side of the side room
                self.add_door(
                    *side_room,
                    locked=True,
                    door_idx=(i + k) % 4,
                    color=self.door_colors[(i + k) % len(self.door_colors)],
                    key_in_box=self.key_in_box,
                    blocked=self.blocked,
                )

        corners = [(2, 0), (2, 2), (0, 2), (0, 0)][: self.num_quarters]
        ball_room = self._rand_elem(corners)

        self.obj, _ = self.add_object(
            ball_room[0], ball_room[1], "ball", color=self.ball_to_find_color
        )
        self.place_agent(*self.agent_room)


class ObstructedMaze_2Dl(ObstructedMaze_Full):
    def __init__(self, **kwargs):
        super().__init__((2, 1), False, False, 1, 4, **kwargs)


class ObstructedMaze_2Dlh(ObstructedMaze_Full):
    def __init__(self, **kwargs):
        super().__init__((2, 1), True, False, 1, 4, **kwargs)


class ObstructedMaze_2Dlhb(ObstructedMaze_Full):
    def __init__(self, **kwargs):
        super().__init__((2, 1), True, True, 1, 4, **kwargs)