"use strict";

// Inverts an object of arrays, eg. {a: [x, y], b: [x, z]} becomes {x: [a, b], y: [a], z: [b]}
// TODO: See if this can be replaced with an off-the-shelf module with equivalent semantics, something transpose-y maybe?

module.exports = function invertMapping(mapping) {
	let newObject = {};

	for (let [ key, values ] of Object.entries(mapping)) {
		for (let value of values) {
			if (newObject[value] == null) {
				newObject[value] = [];
			}

			newObject[value].push(key);
		}
	}

	return newObject;
};