src/engine/liberty.js


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import { board } from "../board.js"
import { Vector2 } from "../engine/vector2.js"

const SURROUNDING = [
    new Vector2(-1, 0),
    new Vector2(0, 1),
    new Vector2(0, -1),
    new Vector2(1, 0),
]

export function hasLiberties({
    position,
    team
}) {
    return Array.from(SURROUNDING)
	.map(v => Vector2.sum(v, position))
	.filter(z => 0 <= z.x && z.x < board.size &&
	    0 <= z.y && z.y < board.size
	)
	.some(z => board.stones[z.x][z.y] == undefined ?
	    true :
	    board.stones[z.x][z.y].team == team
	)
}