// ==UserScript==
// @name                YouTube Music Opus Codec
// @icon                https://www.youtube.com/img/favicon_48.png
// @author              ElectroKnight22
// @namespace           electroknight22_youtube_music_opus_codec_namespace
// @version             1.0.0
// @match               *://music.youtube.com/*
// @grant               none
// @license             MIT
// @description         Reloads songs on YouTube Music using the regular YouTube video backend to force playback with the Opus audio codec, since desktop YouTube Music seems to be unable to play in Opus codec always defaults to AAC. This also bypasses YouTube Music's quality restriction for non-premium users.
// @downloadURL none
// ==/UserScript==

/*jshint esversion: 11 */

(function () {
    "use strict";

    let moviePlayer = null;
    let musicPlayer = null;
    let videoElement = null;
    let currentTime = 0;

    function handleSongLoad() {
        try {
            const videoId = moviePlayer.getVideoData().video_id;
            moviePlayer.loadVideoById({
                videoId: videoId,
                startSeconds: currentTime
            });
        } catch (error) {
            console.error("Failed to handle song load. Error: ", error);
        }
    }

    // currently no additional behaviour other than to load the song
    // may change in the future
    function handleMusicPlayerModeChange() {
        try {
            handleSongLoad();
        } catch (error) {
            console.error("Failed to handle music player mode change. Error: ", error);
        }
    }

    function observeSongTitleChange() {
        try {
            const titleElement = document.querySelector('.title.ytmusic-player-bar');
            if (!titleElement) throw new Error("Title element not found.");
            let currentTitle = titleElement.textContent.trim();
            handleSongLoad();
            const observer = new MutationObserver(() => {
                const newTitle = titleElement.textContent.trim();
                if (newTitle && newTitle !== currentTitle) {
                    currentTitle = newTitle;
                    currentTime = 0;
                    handleSongLoad();
                }
            });

            observer.observe(titleElement, {
                childList: true,
                subtree: true,
            });
        } catch (error) {
            throw new Error("Failed to handle song title change. Error: " + error);
        }
    }

    // playback mode can be in "OMV_PREFERRED" for video and '"ATV_PREFERRED" for audio only
    function observeMusicPlayerModeChange() {
        try {
            if (!musicPlayer) throw new Error("Music player not found.");
            const observer = new MutationObserver(() => {
                handleMusicPlayerModeChange();
            });
            observer.observe(musicPlayer, {
                attributes: true,
                attributeFilter: ['playback-mode']
            });
        } catch (error) {
            throw new Error("Failed to handle music player mode change. Error: " + error);
        }
    }

    function initialize() {
        try {
            moviePlayer = document.querySelector('#movie_player');
            musicPlayer = document.querySelector('ytmusic-player');
            videoElement = musicPlayer.querySelector('video');
            musicPlayer.addEventListener('timeupdate', () => {
                currentTime = videoElement?.currentTime ?? 0;
            }, true);
            observeSongTitleChange();
            observeMusicPlayerModeChange();
        } catch (error) {
            console.error(`Error when initializing script: ${error}. Aborting script.`);
        }
    }

    window.addEventListener('pageshow', initialize, { once: true });
})();