icssify/src/find-cycle-sets.js

"use strict";

const findCycle = require("find-cycle/directed");

module.exports = function findCycleSets(nodes) {
	let queue = nodes.slice();
	let cycleSets = [];
	let innocentNodes = [];
	let lastQueueLength = queue.length; 

	while (queue.length > 0) {
		let queueSet = new Set(queue);

		let cycle = findCycle(queue, (node) => {
			return node.children.filter((child) => {
				// We want to prevent findCycle from discovering and traversing any nodes that are not in our "conflict set"; otherwise a second pass will fail, because it will rediscover already-handled nodes (that have been removed from the queue) indirectly, and endlessly loop on discovering that cycle.
				return queueSet.has(child);
			});
		});
		
		if (cycle != null) {
			cycleSets.push(cycle);
			queue = queue.filter((node) => !cycle.includes(node));

			if (queue.length === lastQueueLength) {
				throw new Error(`Failed to reduce queue length; this is a bug, please report it!`);
			} else {
				lastQueueLength = queue.length;
			}
		} else {
			innocentNodes = queue;
			break;
		}
	}

	return {
		cycleSets: cycleSets,
		innocentNodes: innocentNodes
	};
};