// ==UserScript==
// @name         coursera中英双字幕+调节字幕大小
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  使coursera视频可以开启中英双字幕并调整字幕大小
// @author       wzj423
// @include      *://www.coursera.org/*
// @match        https://www.coursera.org/*
// @grant        none
// @downloadURL none
// ==/UserScript==

(function() {
    'use strict';

    //if you want to change the subtitles of other languages or add more subtitles,change the language tag of subtitles in line 41:'["en", "zh-CN"]'
    /*
    核心代码如下：
    var myvideo = document.getElementsByTagName('video')[0];
    for (var i = 0; i < myvideo.textTracks.length; i++) {
        ["en", "zh-CN"].indexOf(myvideo.textTracks[i].language) > -1 ? myvideo.textTracks[i].mode = "showing" : myvideo.textTracks[i].mode = "hidden";
    }
    不使用脚本或脚本失效时，只需在控制台执行以上代码，就能开启双字幕，但是每次切换视频都要重新执行一遍
    来源：https://hieast.github.io/2017/11/21/coursera-enable-bilingual-subtitle/

    主要来自@zhhsh的脚本 https://greasyfork.org/zh-CN/scripts/382357
    修好了不能显示(被页面自动刷新掉)的bug
    增加了字幕增大/缩小的功能(每次10%)
    */

    //双字幕按钮
    var dualSubtitlesBtn = document.createElement("a");
    dualSubtitlesBtn.innerHTML='双字幕';
    dualSubtitlesBtn.classList.add('nav-link');
    dualSubtitlesBtn.classList.add('dim');
    dualSubtitlesBtn.classList.add('body-1-text');
    dualSubtitlesBtn.setAttribute('aria-label','双字幕');
    dualSubtitlesBtn.href='javascript:void(0);';
    dualSubtitlesBtn.addEventListener('click',function(){
        myvideo = document.getElementsByTagName('video')[0];//每次都刷新video对象，避免“视频已经播放下一个，video还是上一个视频”的情况
        for (var i = 0; i < myvideo.textTracks.length; i++) {//显示中英双字幕
            ["en", "zh-CN"].indexOf(myvideo.textTracks[i].language) > -1 ? myvideo.textTracks[i].mode = "showing" : myvideo.textTracks[i].mode = "hidden";
        }
    });

    //关闭字幕按钮，因为使用双字幕后，原来的‘关闭字幕’功能会有异常，所以添加新的‘关闭字幕按钮’
    var closeSubtitlesBtn = document.createElement("a");
    closeSubtitlesBtn.innerHTML='无字幕';
    closeSubtitlesBtn.classList.add('nav-link');
    closeSubtitlesBtn.classList.add('dim');
    closeSubtitlesBtn.classList.add('body-1-text');
    closeSubtitlesBtn.setAttribute('aria-label','无字幕');
    closeSubtitlesBtn.href='javascript:void(0);';
    closeSubtitlesBtn.addEventListener('click',function(){
        myvideo = document.getElementsByTagName('video')[0];//每次都刷新video对象，避免“视频已经播放下一个，video还是上一个视频”的情况
        for (var i = 0; i < myvideo.textTracks.length; i++) {//关闭所有字幕
            myvideo.textTracks[i].mode = "hidden";
        }
    });

    var currentSubtitleSize=100;//当前字母大小(百分比)
    //增大字幕按钮
    var expandSubtitleSizeBtn = document.createElement("a");
    expandSubtitleSizeBtn.innerHTML='大字幕';
    expandSubtitleSizeBtn.classList.add('nav-link');
    expandSubtitleSizeBtn.classList.add('dim');
    expandSubtitleSizeBtn.classList.add('body-1-text');
    expandSubtitleSizeBtn.setAttribute('aria-label','大字幕');
    expandSubtitleSizeBtn.setAttribute("name","expandSubtitleSizeBtn");//加上名字,用做后期判断
    expandSubtitleSizeBtn.href='javascript:void(0);';
    expandSubtitleSizeBtn.addEventListener('click',function(){
        currentSubtitleSize=currentSubtitleSize+10;
        var css = 'video::-webkit-media-text-track-display {font-size: '+currentSubtitleSize+'%;}',
        head = document.head || document.getElementsByTagName('head')[0],
        style = document.createElement('style');

        style.type = 'text/css';
        if (style.styleSheet){
            style.styleSheet.cssText = css;
        } else {
            style.appendChild(document.createTextNode(css));
        }
        head.appendChild(style);
    });
    //缩小字幕按钮
    var reduceSubtitleSizeBtn = document.createElement("a");
    reduceSubtitleSizeBtn.innerHTML='小字幕';
    reduceSubtitleSizeBtn.classList.add('nav-link');
    reduceSubtitleSizeBtn.classList.add('dim');
    reduceSubtitleSizeBtn.classList.add('body-1-text');
    reduceSubtitleSizeBtn.setAttribute('aria-label','小字幕');
    reduceSubtitleSizeBtn.href='javascript:void(0);';
    reduceSubtitleSizeBtn.addEventListener('click',function(){
        currentSubtitleSize=currentSubtitleSize-10;
        if(currentSubtitleSize<=0) currentSubtitleSize=10;
        var css = 'video::-webkit-media-text-track-display {font-size: '+currentSubtitleSize+'%;}',
        head = document.head || document.getElementsByTagName('head')[0],
        style = document.createElement('style');

        style.type = 'text/css';
        if (style.styleSheet){
            style.styleSheet.cssText = css;
        } else {
            style.appendChild(document.createTextNode(css));
        }
        head.appendChild(style);
    });
    //分隔符
    var seperatorBar = document.createElement('div');
    seperatorBar.classList.add('divider');

    var mycon;
    var testBtn;
    var myvideo;

    var iterateTimes = 0;
    (function init(){
        //alert("Begin initing!");
        ++iterateTimes;
        mycon = document.getElementsByClassName('rc-PreviousAndNextItem')[0];
        myvideo = document.getElementsByTagName('video')[0];

        if(iterateTimes!=1) {
            testBtn = document.getElementsByName('expandSubtitleSizeBtn')[0];
            if(testBtn) return;//如果标记的按钮没了就说明页面自动刷新掉了,要再来一次;否则退出
        }

        if(mycon&&myvideo){//等mycon和myvideo都存在的时候执行
            //console.log("To Init!");
            mycon.prepend(seperatorBar);
            mycon.prepend(dualSubtitlesBtn);
            mycon.prepend(seperatorBar.cloneNode());
            mycon.prepend(closeSubtitlesBtn);
            mycon.prepend(seperatorBar);
            mycon.prepend(expandSubtitleSizeBtn);
            mycon.prepend(seperatorBar);
            mycon.prepend(reduceSubtitleSizeBtn);

            //console.log("Test!");
            setTimeout(init,1200);//递归检查
        }else{
            if(iterateTimes<15){//限制计时器的重复执行次数，避免那些本来就没有视频的coursera页面无限setTimeout...，也可以修改触发脚本的url的规则@include，不会
                setTimeout(init, 1000);
            }
        }
    })();

})();