Advent of Code 2019 day 6 solution (both parts)

methods.js

const {read} = require("../util/read")

class SpaceJunk {
	constructor(name) {
		this.name = name
		/** @type {SpaceJunk} */
		this.parent = null
		this.children = []
	}

	setParent(parent) {
		this.parent = parent
		this.parent.children.push(this)
	}

	countOrbiting() {
		if (this.parent) return this.parent.countOrbiting()+1
		else return 0
	}

	/**
	 * @returns {SpaceJunk[]}
	 */
	enumerateParents() {
		if (this.parent) return [this.parent].concat(this.parent.enumerateParents())
		else return []
	}

	/**
	 * @param {SpaceJunk} base
	 * @param {SpaceJunk} alter
	 */
	static findClosestSharedNode(base, alter) {
		const baseTree = base.enumerateParents()
		const alterTree = alter.enumerateParents()
		const join = alterTree.find(junk => baseTree.includes(junk))
		return baseTree.indexOf(join) + alterTree.indexOf(join)
	}
}

class Universe {
	constructor() {
		/** @type {Map<string, SpaceJunk>} */
		this.nodes = new Map()
	}

	get(name) {
		return this.nodes.get(name)
	}

	getOrCreateNode(name) {
		if (this.nodes.has(name)) {
			return this.nodes.get(name)
		} else {
			const newNode = new SpaceJunk(name)
			this.nodes.set(name, newNode)
			return newNode
		}
	}

	countAllOrbits() {
		return [...this.nodes.values()].reduce((a, c) => a + (c.countOrbiting()), 0)
	}
}

function loadUniverse(file) {
	const lines = read(file).asLines()
	const universe = new Universe()
	lines.forEach(line => {
		const [orbited, orbiter] = line.split(")").map(name => universe.getOrCreateNode(name))
		orbiter.setParent(orbited)
	})
	return universe
}

function countAllOrbiting(file) {
	const universe = loadUniverse(file)
	return universe.countAllOrbits()
}

function countTransfers(file) {
	const universe = loadUniverse(file)
	//console.log(universe.get("YOU").enumerateParents())
	return SpaceJunk.findClosestSharedNode(universe.get("SAN"), universe.get("YOU"))
}

module.exports.countAllOrbiting = countAllOrbiting
module.exports.countTransfers = countTransfers