Some Userscript to play soundcloud tracks in stream in reverse order

soundcloud-stream-revers.js

// ==UserScript==
// @name         SoundCloud Stream Player
// @namespace    https://stefafafan.hatenablog.com/
// @version      0.1
// @description  play songs from the stream, in oldest to newest order.
// @author       stefafafan
// @match        https://soundcloud.com/stream
// @grant        none
// ==/UserScript==

window.onload = function () {
    main();
}

// 指定した要素を最後まで再生してくれる関数
// 再生中の曲のURLと状態はlocalStorageに保存する
function playElement(element) {
    let playControls = document.getElementsByClassName('playControls__timeline')[0];
    let button = element.getElementsByClassName('sc-button-play')[0];
    button.click();

    let link = element.getElementsByClassName('soundTitle__title')[0].href;
    localStorage.setItem('nowPlaying', link);
    localStorage.setItem('playState', 'playing');

    let timer = setInterval(() => {
        let timePassed = playControls.getElementsByClassName('playbackTimeline__timePassed')[0].children[1].innerText;
        let timeDuration = playControls.getElementsByClassName('playbackTimeline__duration')[0].children[1].innerText;
        let timePassedInt = parseInt(timePassed.replace(':', ''));
        let timeDurationInt = parseInt(timeDuration.replace(':', ''));
        let songEnd = timePassedInt + 1 >= timeDurationInt;
        if (songEnd) {
            button.click();
            localStorage.setItem('playState', 'done');
            clearInterval(timer);
        }
    }, 500);
};

function main() {

    // playStateを初期化
    localStorage.setItem('playState', 'stopped');

    // 前回再生した曲が上位5要素の中にあるかどうかを探し出す
    // ない場合は最後の要素を使う
    let nowPlaying = localStorage.getItem('nowPlaying');
    let topFiveElements = document.getElementsByClassName('soundList__item');
    let indexFound = 5; // デフォルトでは最後の曲からスタート
    for (let i = 0; i < 5; i++) {
        let currentElement = topFiveElements[i];
        let link = currentElement.getElementsByClassName('soundTitle__title')[0].href;
        if (nowPlaying == link) {
            indexFound = i;
            break;
        }
    }

    // 0番目の要素が最後に再生した曲の場合はとりあえずリロードする
    // ある場合は見つけたindexの直前の要素から逆順に再生していく
    if (indexFound != 0) {
        let j = indexFound - 1;
        let timer = setInterval(() => {
            if (j < 0) {
                // j が0以下ということはStreamの最初の曲までやってきたので、再生状態を確認して、再生中でなければtimerストップしてリロード
                let playState = localStorage.getItem('playState');
                if (playState != 'playing') {
                    clearInterval(timer);
                    setTimeout(() => {
                        location.reload();
                    }, 5000);
                }
            } else {
                let currentElement = topFiveElements[j];
                let link = currentElement.getElementsByClassName('soundTitle__title')[0].href;

                let nowPlaying = localStorage.getItem('nowPlaying');
                let playState = localStorage.getItem('playState');

                if (link != nowPlaying && playState != 'playing') {
                    playElement(currentElement);
                    j--;
                }
            }
        }, 500);
    } else {
        setTimeout(() => {
            location.reload();
        }, 60000);
    }
}