generateid.js

/**
 * @fileOverview Generate an Id
 */
const _ = require('lodash');
const Hashids = require('hashids');
const hashids = new Hashids(
    '',
    null,
    'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_-',
);

const SEQUENCE_BITS = 12;
const CUSTOM_EPOCH = 1514725199000n;
const maxSequence = Math.pow(2, SEQUENCE_BITS) - 1;

let currentTimestamp = BigInt(new Date().getTime()) - CUSTOM_EPOCH;
let lastTimestamp = currentTimestamp;
let sequence = 0;

/**
 * Create a nodeId buffer
 *
 * Read in the mac addresses into a buffer
 *
 * @type {(function(): Buffer) & MemoizedFunction}
 */
const createNodeId = _.memoize(() => {
    const interfaces = _.compact(
        _.flatMap(
            require('os').networkInterfaces(),
            (value) => {
                return _.map(value, (ifaceData) => {
                    const mac = _.get(
                        ifaceData,
                        'mac',
                        '000000000000'
                    ).replace(/:/gm, '');

                    if (mac === '000000000000') {
                        return null;
                    }

                    return BigInt(`0x${mac}`);
                });
            }
        )
    );

    return _.reduce(
        interfaces,
        (result, value) => {
             result = result + value;
             return result;
        },
        BigInt('0x0')
    );
});

/**
 * (-.-) zzZZ
 *
 * @return {Promise<undefined>}
 */
const sleep = () => {
    return new Promise((resolve) => setTimeout(resolve, 1000));
};

const nodeId = createNodeId();

/**
 * Generates an id
 *
 * @return {Promise<*>}
 */
module.exports = async () => {
    sequence = (currentTimestamp === lastTimestamp)
        ? (sequence + 1) & maxSequence
        : 0;

    // Sequence Exhausted, wait till next millisecond.
    if (sequence === 0) {
        await sleep();
        currentTimestamp = BigInt(new Date().getTime()) - CUSTOM_EPOCH;
    }

    lastTimestamp = currentTimestamp;
    const idParts = currentTimestamp + nodeId + BigInt(`0x${sequence}`);
    return hashids.encodeHex(idParts);
};