AdventOfCode-js-2019/12/Moon.js

const Vector3 = require("./Vector3");

module.exports = class Moon {
    /**
     * @param {Vector3} position The starting position of the moon
     */
    constructor(position) {
        /**
         * The position of the moon in space
         */
        this.position = position;
        /**
         * The position of the moon at the time of creation
         *
         * This is a silly trick to get a clean copy of the Vector, but it works.
         *
         * @private
         */
        this._initialPosition = position.negate().negate();
        /**
         * The current velocity of the moon
         */
        this.velocity = new Vector3(0, 0, 0);
    }

    /**
     * Check whether or not the moon has returned to its initial position
     *
     * @returns {bool} True if the current position is the same as the initial position and if the velocity is zero
     */
    hasReachedInitialState() {
        return (
            this._initialPosition.x == this.position.x
            && this._initialPosition.y == this.position.y
            && this._initialPosition.z == this.position.z
        ) && (
            this.velocity.x == 0
            && this.velocity.y == 0
            && this.velocity.z == 0
        );
    }
};