Function bfsNextStep

bfsNextStep(
    matrix: Cell[][],
    isWalkable: IsWalkable,
    from: Coord,
    to: Coord,
): Direction | null

First step of a shortest walk from from to to. Returns null when the target is the start cell or no walk exists. Greedy axis steps are not used: beside a long wall they step toward the target and then reverse.

Parameters

matrix: Cell[][]
Board the walk is planned on.
isWalkable: IsWalkable
Which cells may be entered. Also blocks cells the caller wants skipped.
from: Coord
Start coordinate.
to: Coord
Target coordinate.

Returns Direction | null

The first direction, or null.

Example: Straight corridor

import { bfsNextStep, walkableUnlessTypes } from "@tamb/gamegrid/npc";

const matrix = [
  [{ type: "wall" }, { type: "wall" }, { type: "wall" }],
  [{ type: "wall" }, { type: "floor" }, { type: "floor" }],
  [{ type: "wall" }, { type: "wall" }, { type: "wall" }],
];
const isWalkable = walkableUnlessTypes(["wall"]);
const toward = bfsNextStep(matrix, isWalkable, [1, 1], [2, 1]);
// "right"

Example: Around a wall

import { bfsNextStep, walkableUnlessTypes } from "@tamb/gamegrid/npc";

const matrix = [
  [{ type: "floor" }, { type: "floor" }, { type: "floor" }, { type: "wall" }, { type: "floor" }],
  [{ type: "floor" }, { type: "wall" }, { type: "wall" }, { type: "wall" }, { type: "floor" }],
  [{ type: "floor" }, { type: "floor" }, { type: "floor" }, { type: "floor" }, { type: "floor" }],
];
const isWalkable = walkableUnlessTypes(["wall"]);
const toward = bfsNextStep(matrix, isWalkable, [0, 0], [4, 0]);
// "down". The cells to the right dead-end, so the first step goes around.