index.js

const config = require("./config.json"),
Discord = require("discord.js"),
Parser = require("rss-parser"),
parser = new Parser(),
Youtube = require("simple-youtube-api"),
youtube = new Youtube(config.youtubeKey);

const startAt = Date.now();
const lastVideos = {};

const client = new Discord.Client();
client.login(config.token).catch(console.log);

client.on("ready", () => {
    console.log(`[!] Ready to listen ${config.youtubers.length} youtubers!`);
    check();
    setInterval(check, 20*1000);
});

/**
 * Format a date to a readable string
 * @param {Date} date The date to format 
 */
function formatDate(date) {
    let monthNames = [ "January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December" ];
    let day = date.getDate(), month = date.getMonth(), year = date.getFullYear();
    return `${day} ${monthNames[parseInt(month, 10)]} ${year}`;
}

/**
 * Call a rss url to get the last video of a youtuber
 * @param {string} youtubeChannelName The name of the youtube channel
 * @param {string} rssURL The rss url to call to get the videos of the youtuber
 * @returns The last video of the youtuber
 */
async function getLastVideo(youtubeChannelName, rssURL){
    console.log(`[${youtubeChannelName}]  | Getting videos...`);
    let content = await parser.parseURL(rssURL);
    console.log(`[${youtubeChannelName}]  | ${content.items.length} videos found`);
    let tLastVideos = content.items.sort((a, b) => {
        let aPubDate = new Date(a.pubDate || 0).getTime();
        let bPubDate = new Date(b.pubDate || 0).getTime();
        return bPubDate - aPubDate;
    });
    console.log(`[${youtubeChannelName}]  | The last video is "${tLastVideos[0] ? tLastVideos[0].title : "err"}"`);
    return tLastVideos[0];
}

/**
 * Check if there is a new video from the youtube channel
 * @param {string} youtubeChannelName The name of the youtube channel to check
 * @param {string} rssURL The rss url to call to get the videos of the youtuber
 * @returns The video || null
 */
async function checkVideos(youtubeChannelName, rssURL){
    console.log(`[${youtubeChannelName}] | Get the last video..`);
    let lastVideo = await getLastVideo(youtubeChannelName, rssURL);
    // If there isn't any video in the youtube channel, return
    if(!lastVideo) return console.log("[ERR] | No video found for "+lastVideo);
    // If the date of the last uploaded video is older than the date of the bot starts, return 
    if(new Date(lastVideo.pubDate).getTime() < startAt) return console.log(`[${youtubeChannelName}] | Last video was uploaded before the bot starts`);
    let lastSavedVideo = lastVideos[youtubeChannelName];
    // If the last video is the same as the last saved, return
    if(lastSavedVideo && (lastSavedVideo.id === lastVideo.id)) return console.log(`[${youtubeChannelName}] | Last video is the same as the last saved`);
    return lastVideo;
}

/**
 * Get the youtube channel id from an url
 * @param {string} url The URL of the youtube channel
 * @returns The channel ID || null
 */
function getYoutubeChannelIdFromURL(url) {
    let id = null;
    url = url.replace(/(>|<)/gi, "").split(/(\/channel\/|\/user\/)/);
    if(url[2]) {
      id = url[2].split(/[^0-9a-z_-]/i)[0];
    }
    return id;
}

/**
 * Get infos for a youtube channel
 * @param {string} name The name of the youtube channel or an url
 * @returns The channel info || null
 */
async function getYoutubeChannelInfos(name){
    console.log(`[${name.length >= 10 ? name.slice(0, 10)+"..." : name}] | Resolving channel infos...`);
    let channel = null;
    /* Try to search by ID */
    let id = getYoutubeChannelIdFromURL(name);
    if(id){
        channel = await youtube.getChannelByID(id);
    }
    if(!channel){
        /* Try to search by name */
        let channels = await youtube.searchChannels(name);
        if(channels.length > 0){
            channel = channels[0];
        }
    }
    console.log(`[${name.length >= 10 ? name.slice(0, 10)+"..." : name}] | Title of the resolved channel: ${channel.raw ? channel.raw.snippet.title : "err"}`);
    return channel;
}

/**
 * Check for new videos
 */
async function check(){
    console.log("Checking...");
    config.youtubers.forEach(async (youtuber) => {
        console.log(`[${youtuber.length >= 10 ? youtuber.slice(0, 10)+"..." : youtuber}] | Start checking...`);
        let channelInfos = await getYoutubeChannelInfos(youtuber);
        if(!channelInfos) return console.log("[ERR] | Invalid youtuber provided: "+youtuber);
        let video = await checkVideos(channelInfos.raw.snippet.title, "https://www.youtube.com/feeds/videos.xml?channel_id="+channelInfos.id);
        if(!video) return console.log(`[${channelInfos.raw.snippet.title}] | No notification`);
        let channel = client.channels.cache.get(config.channel);
        if(!channel) return console.log("[ERR] | Channel not found");
        channel.send({ content: 
            config.message
            .replace("{videoURL}", video.link)
            .replace("{videoAuthorName}", video.author)
            .replace("{videoTitle}", video.title)
            .replace("{videoPubDate}", formatDate(new Date(video.pubDate)))
        });
        console.log("Notification sent !");
        lastVideos[channelInfos.raw.snippet.title] = video;
    });
}