YouTube RSS Feed (hacky fork)

Adds an RSS feed button to YouTube channels next to the subscribe button

// ==UserScript==
// @name        YouTube RSS Feed (hacky fork)
// @namespace   https://greasyfork.org/en/users/4612-gdorn
// @author      Doodles (original) with hacky fixes by George Dorn
// @version     21
// @description Adds an RSS feed button to YouTube channels next to the subscribe button
// @icon        http://i.imgur.com/Ty5HNbT.png
// @icon64      http://i.imgur.com/1FfVvNr.png
// @match       *://www.youtube.com/*
// @match       *://youtube.com/*
// @grant       none
// @run-at      document-end
// @require     https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js
// @license MIT
// ==/UserScript==

this.$ = this.jQuery = jQuery.noConflict(true);

window.safejQuery = this.$;

window.getRSS = function () {

    "use strict";
    addRssFeedSupport(true);
    document.body.addEventListener("yt-navigate-finish", function (event) {
        addRssFeedSupport(false);
    });

}

function addRssFeedSupport(firstLoad) {
    if (isPlaylistPage()) {
        waitForElement("owner-container", function () {
            let playlistFeedLink = getPlaylistFeed(getPlatlistId());
            addRssLink(playlistFeedLink);
            addRssButtonPlaylist(playlistFeedLink);
        }, 330);
    } else if (isVideoPage()) {
        waitForElement("upload-info", function () {
            let channelFeedLink = getChannelFeed(getChannelIdFromPage());
            removeRssLink();
            addRssLink(channelFeedLink);
            addRssButton(channelFeedLink);
        }, 330);
    } else if (isChannelPage()) {
        waitForElement("subscribe-button", function () {
            let channelId = getChannelIdFromPage();
            if (channelId === null && firstLoad) {
                removeRssLink();
                addRefreshButton();
            } else {
                let channelFeedLink = getChannelFeed(channelId);
                removeRssLink();
                addRssLink(channelFeedLink);
                addRssButton(channelFeedLink);
            }
        }, 330);
    }
}

function isPlaylistPage() {
    return document.URL.indexOf("/playlist?list=") !== -1;
}

function isVideoPage() {
    return document.URL.indexOf("/watch") !== -1 && document.URL.indexOf("v=") !== -1;
}

function isChannelPage() {
    return $("#channel-header").length > 0;
}

function getPlatlistId() {
    let playlistId = document.URL.split("list=")[1].split("&")[0];
    if (!playlistId.startsWith("PL")) {
        playlistId = "PL" + playlistId;
    }
    return playlistId;
}

function getChannelIdFromPage() {

    let channelId = null;

    channelId = ytInitialPlayerResponse['videoDetails']['channelId'];
    if (channelId) {
        return channelId;
    }

    // try URL
    channelId = getChannelIdFromUrl(document.URL);
    if (channelId) {
        return channelId;
    }

    // try meta tags that are channel URLs
    let metaChannelUrlTags = [
        'og:url',
        'al:ios:url',
        'al:android:url',
        'al:web:url',
        'twitter:url',
        'twitter:app:url:iphone',
        'twitter:app:url:ipad'
    ];
    for (let i = 0; i < metaChannelUrlTags.length; i++) {
        let metaPropertyValue = getMetaTagValue(metaChannelUrlTags[i]);
        channelId = metaPropertyValue ? getChannelIdFromUrl(metaPropertyValue) : null;
        if (channelId) {
            return channelId;
        }
    }

    // try meta tags that are channel IDs
    let metaChannelIdTags = [
        'channelId'
    ];
    for (let i = 0; i < metaChannelIdTags.length; i++) {
        channelId = getMetaTagValue(metaChannelIdTags[i]);
        if (channelId) {
            return channelId;
        }
    }

    // try upload info box on video page
    let uploadInfoLink = $("#upload-info a[href*='/channel/']:first");
    if (uploadInfoLink.length) {
        let uploadInfoLinkHref = uploadInfoLink.attr("href");
        channelId = uploadInfoLinkHref ? getChannelIdFromUrl(uploadInfoLinkHref) : null;
        if (channelId) {
            return channelId;
        }
    }

    // give up
    return null;
}

function getChannelIdFromUrl(url) {
    if (url && url.indexOf("youtube.com/channel/") !== -1) {
        return url.split("youtube.com/channel/")[1].split("/")[0].split("?")[0];
    } else {
        return null;
    }
}

function getMetaTagValue(metaPropertyKey) {
    // <meta property="og:url" content="https://www.youtube.com/channel/UCC8VtutLDSrreNEZj8CU01A">
    // <meta name="twitter:url" content="https://www.youtube.com/channel/UCC8VtutLDSrreNEZj8CU01A">
    // <meta itemprop="channelId" content="UCC8VtutLDSrreNEZj8CU01A">

    console.log("Trying to get metatagvalue for", metaPropertyKey);

    let nameAttributes = ['property', 'name', 'itemprop'];
    let metaProperty = null;
    for (let i = 0; i < nameAttributes.length; i++) {
        metaProperty = $("meta[" + nameAttributes[i] + "='" + metaPropertyKey + "']");
        console.log("Looking in:", metaProperty);
        if (metaProperty.length === 1) {
            break;
        }
        metaProperty = null;
    }

    if (metaProperty !== null) {
        let value = metaProperty.attr("content");
        if (value) {
            return value;
        }
    }
    return null;
}

function getChannelFeed(channelId) {
    return "https://www.youtube.com/feeds/videos.xml?channel_id=" + channelId;
}

function getPlaylistFeed(playlistId) {
    return "https://www.youtube.com/feeds/videos.xml?playlist_id=" + playlistId;
}

function addRssLink(link) {
    $("head").append('<link rel="alternate" type="application/rss+xml" title="RSS" href="' +
                     link + '" />');
}

function removeRssLink() {
    if ($("link[type='application/rss+xml']").length > 0) {
        $("link[type='application/rss+xml']").remove();
    }
}

function waitForElement(elementId, callbackFunction, intervalLength = 330) {
    var waitCount = 15000 / intervalLength; // wait 15 seconds maximum
    var wait = setInterval(function () {
        waitCount--;
        if ($("#" + elementId).length > 0) {
            callbackFunction();
            clearInterval(wait);
        } else if (waitCount <= 0) {
            console.log("YouTube RSS Feed UserScript - wait for element \"#" + elementId +
                        "\" failed! Time limit (15 seconds) exceeded.");
            clearInterval(wait);
        }
    }, intervalLength);
}

function addRssButton(link) {
    if ($("#rssSubButton").length > 0) {
        $("#rssSubButton").remove();
    }
    $("#subscribe-button")
        .css({
        "display": "flex",
        "flex-flow": "nowrap",
        "height": "37px"
    })
        .prepend(makeRssButton(link));
}

function addRssButtonPlaylist(link) {
    if ($("#rssSubButton").length === 0) {
        $("#owner-container > #button")
            .css({
            "display": "flex",
            "flex-flow": "nowrap",
            "height": "37px"
        })
            .prepend(makeRssButton(link));
    }
}

function makeRssButton(link) {
    return $("<a>RSS</a>")
        .attr("id", "rssSubButton")
        .attr("target", "_blank")
        .attr("href", rssLinkToData(link))
        .attr("download", "feed.rss")
        .css({
        "background-color": "#fd9b12",
        "border-radius": "3px",
        "padding": "10px 16px",
        "color": "#ffffff",
        "font-size": "14px",
        "text-decoration": "none",
        "text-transform": "uppercase",
        "margin-right": "5px"
    });
}

function rssLinkToData(link) {
    return link;
    return "data:application/atom+xml,<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
        "<feed xmlns=\"http://www.w3.org/2005/Atom\">" +
        "<title type=\"text\">YouTube RSS Button</title>" +
        "<link rel=\"self\" href=\"" + link + "\" type=\"application/atom+xml\" />" +
        "</feed>";
}

function addRefreshButton() {
    let refreshButton = $("<a>Refresh</a>")
    .attr("id", "rssSubButton")
    .attr("href", "#")
    .css({
        "background-color": "#fd9b12",
        "border-radius": "3px",
        "padding": "10px 16px",
        "color": "#ffffff",
        "font-size": "14px",
        "text-decoration": "none",
        "text-transform": "uppercase",
        "margin-right": "5px"
    });
    $(refreshButton).click(function (e) {
        e.preventDefault();
        let r = confirm("Due to how YouTube load pages, there isn't a reliable way to get channel" +
                        " IDs from channel pages if you've navigated to them from another YouTube page." +
                        " The solution is to reload the page.\n\nWould you like to reload the page?");
        if (r === true) {
            window.location.reload();
        }
    });
    if ($("#rssSubButton").length > 0) {
        $("#rssSubButton").remove();
    }
    $("#subscribe-button")
        .css({
        "display": "flex",
        "flex-flow": "nowrap",
        "height": "37px"
    })
        .prepend(refreshButton);
}

$(window.getRSS());