Tampermokey script for displaying music policy information for music videos on YouTube

yt-music-policy-display.tampermonkey.js

// ==UserScript==
// @name         YouTube music policy display
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  Show music policy info for music videos
// @author       siliconbrain
// @match        https://www.youtube.com/*
// @grant        none
// ==/UserScript==

function ajax(url, success, error) {
    var xhr = new XMLHttpRequest();
    xhr.onreadystatechange = function() {
        if (this.readyState == 4) {
            if (this.status >= 200 && this.status < 300) {
                if (success) success(this.responseText);
            } else {
                if (error) error(this.status, this.responseText);
            }
        }
    };
    xhr.open('GET', url, true);
    xhr.send();
    return xhr;
}

function getMusicPolicyInfoElement() {
    var id = 'musicPolicyInfo';
    var musicPolicyInfoElement = document.querySelector('#' + id);
    if (!musicPolicyInfoElement) {
        musicPolicyInfoElement = document.createElement('div');
        musicPolicyInfoElement.id = 'musicPolicyInfo';
        musicPolicyInfoElement.innerHTML = 'Determining availability...';
        document.querySelector('#watch-headline-title').append(musicPolicyInfoElement);
    }
    return musicPolicyInfoElement;
}

function videoTitleToQuery(title) {
    return title
        .replace(/\bft\b/gi, 'feat')
        .replace(/[\[\(](audio|lyric|music|official|video|\s)+[\]\)]/gi, '')
        .replace(/[^\w\d\u00C0-\u017F]/g, ' ');
}

function getWords(str) {
    return str
        .replace(/[^\w\d\u00C0-\u017F]/g, ' ')
        .trim()
        .replace(/ (?= )/g, '')
        .split(' ');
}

function symmetricDifference(setA, setB) {
    var all = setA.concat(setB);
    return all.reduce((set, val) => (setA.indexOf(val) >= 0 && setB.indexOf(val) >= 0) ? set : set.concat([val]), []);
}

function bestMatch(query, tracks) {
    if (tracks.length == 1) return tracks[0];

    var queryWords = getWords(query).map(w => w.toLowerCase());
    var tracksWords = tracks.map(track => getWords(track.artist).concat(getWords(track.title)).map(w => w.toLowerCase()));
    var diffs = tracksWords.map(trackWords => symmetricDifference(queryWords, trackWords));
    var ranks = diffs.map(d => d.length);
    var best = ranks.reduce((cur, val, idx) => val < cur.val ? {idx: idx, val: val} : cur, {idx: 0, val: Infinity});
    console.log('bestMatch', queryWords, tracksWords, diffs, best);
    return tracks[best.idx];
}

function loadMusicPolicy(player) {
    if (player.getCurrentVideoConfig().args.vmap.match(/ytpwatch.music/) || document.querySelector('meta[itemprop="genre"][content="Music"]')) {
        var q = videoTitleToQuery(player.getVideoData().title);
        console.info('Music policy query string:', q);
        ajax(`https://www.youtube.com/audioswap_ajax?action_get_tracks=1&s=ad_supported_music&q=${encodeURI(q)}`, function(resp) {
            var musicPolicyInfoElement = getMusicPolicyInfoElement();
            resp = JSON.parse(resp);
            var tracks = resp.tracks;
            console.info('Music policy query results:', tracks);
            if (tracks.length > 0) {
                var track = bestMatch(q, tracks);
                var trackName = `${track.title} by ${track.artist}`;
                ajax(`https://www.youtube.com/audioswap_ajax?action_get_track_details=1&asset_id=${track.asset_id}&isrc=${track.isrc}`, function(resp) {
                    resp = JSON.parse(resp);
                    if (resp.is_available) {
                        if (resp.sr_policy.restrictions) {
                            musicPolicyInfoElement.innerHTML = `© ${trackName} is blocked in ${resp.sr_policy.restrictions.blocked_terr_names.length} countries.`;
                        } else {
                            musicPolicyInfoElement.innerHTML = `✓ ${trackName} is viewable worldwide.`;
                        }
                    } else {
                        musicPolicyInfoElement.innerHTML = `✗ ${trackName} is not available for playback.`;
                    }
                    if (tracks.length > 1) musicPolicyInfoElement.innerHTML += ` (best of ${tracks.length} results)`;
                });
            } else {
                musicPolicyInfoElement.innerHTML = `⚠ Track info not found.`;
            }
        });
    }
}

function addPlayerEventListener(player, event, name, handler) {
    window[name] = handler;
    player.addEventListener(event, name);
}

(function() {
    'use strict';

    var player = yt.player.getPlayerByElement('player-api');

    addPlayerEventListener(player, 'onReady', 'playerReadyHandlerForMusicPolicy', function() {
        var lastVideoId = player.getVideoData().video_id;
        addPlayerEventListener(player, 'onStateChange', 'playerStateChangeHandlerForMusicPolicy', function(state) {
            var videoId = player.getVideoData().video_id;
            if (state == 1 && lastVideoId != videoId) {
                lastVideoId = videoId;
                loadMusicPolicy(player);
            }
        });
        if (lastVideoId) loadMusicPolicy(player);
    });

    //window.THE_PLAYER = player;  // for debugging
})();