index.js

const fs = require('fs');
const RSSparser = require('rss-parser');
const request = require('request-promise-native');
const parser = new RSSparser();

const {log, err, avatar} = require('./util');
const {config, comics} = require('./config/config');

const last = require('./config/last.json');

let lastFlag = false;

const poll = () => {
    comics.forEach((comic, i) => {
        setTimeout(comic => {
            log(comic, 'Polling')

            if(comic.info.feed) {
                parser.parseURL(comic.info.feed)
                .then(feed => check(comic, feed.items[0]))
                .catch(err(comic))
            } else {
                comic.getItem()
                .then(item => check(comic, item))
                .catch(err(comic))
            }
        }, config.delay*i*1000, comic)
    })

    setTimeout(() => {
        if(lastFlag) {
            lastFlag = false;
            log(null, "Flushing last known comic data to disk")

            fs.writeFile(`${__dirname}/config/last.json`, JSON.stringify(last), 'utf8', e => {
                e ? err()(e) : log(null, "Last known comic data saved")
            })
        } else {
            log(null, "No new last known comic data to flush")
        }
    }, config.delay*comics.length*1000)
}

const check = async function(comic, item) {
    const pubDate = new Date(item.pubDate)

    if(!last[comic.info.id] || pubDate > new Date(last[comic.info.id])) {
        log(comic, `New comic published at ${pubDate.toJSON()}`)

        const parsed = await comic.parse(item)
        const avatar_url = await avatar(comic.info.image)

        const data = {
            'username': comic.info.name,
            avatar_url,
            'embeds': [{
                'title': parsed.title,
                'description': parsed.desc,
                'url': parsed.url,
                'timestamp': pubDate.toJSON(),
                'footer': {'text': parsed.footer},
                'image': {'url': parsed.image},
                'thumbnail': {'url': parsed.thumbnail}
            }]
        }

        log(comic, `Posting new comic, ${parsed.title}`)

        await request({url: config.webhook, method: 'POST', json: data})
        log(comic,`Posted ${parsed.title}`)
        last[comic.info.id] = pubDate
        lastFlag = true
    } else {
        log(comic, 'No new comic')
    }
}

if((config.delay * comics.length) > (config.interval / 1.5))
    throw new Error("Interval is too short for configured delay and comic amount")

poll()
setInterval(poll, config.interval*1000)