/* globals jspdf UPNG */

// ==UserScript==
// @name         Rain Classroom PDF Direct Download
// @name:zh-CN   雨课堂课件PDF下载工具
// @namespace    https://www.pizyds.com/
// @version      1.1.0
// @description  Automatic generation of direct download PDF on Rain Classroom
// @description:zh-CN 在雨课堂页面自动生成PDF版本课件提供下载
// @author       PillarsZhang
// @homepage     https://www.pizyds.com/rain-classroom-pdf-direct-download
// @license      MIT
// @match        https://*.yuketang.cn/*
// @icon         https://www.yuketang.cn/static/images/favicon.ico
// @require      https://cdnjs.cloudflare.com/ajax/libs/jspdf/2.3.1/jspdf.umd.min.js
// @require      https://cdnjs.cloudflare.com/ajax/libs/pako/2.0.3/pako.min.js
// @require      https://cdnjs.cloudflare.com/ajax/libs/upng-js/2.1.0/UPNG.min.js
// @resource     pizyds_iconfont_css https://at.alicdn.com/t/font_2448118_l5d66dc50k9.css
// @grant        GM_getResourceText
// @grant        GM_addStyle
// @downloadURL none
// ==/UserScript==

(function() {
    'use strict';
    console.log("雨课堂课件PDF下载工具：已载入");

    //对自动添加客观题答案到PPT页面的配置
    var ans_config = {
        enabled: true,
        right: 30,
        up: 25,
        fontSize: 40,
        fontColor: "#000000"
    };

    //jsPDF用于PDF生成，UPNG、pako用于PNG的反交错和压缩
    const {jsPDF} = jspdf;

    //下载的图标，感谢iconfont
    const pizyds_iconfont_css = GM_getResourceText("pizyds_iconfont_css");
    GM_addStyle(pizyds_iconfont_css);

    //实时查找PPT窗口
    setInterval(()=>{
        var el_dialog = find_basePPTDialog();
        check_url && el_dialog && add_button_download(el_dialog);
    },200);

    //更改为内部校验链接，因为大量ajax页面跳转的存在
    function check_url(){
        return /https:\/\/.*\.yuketang\.cn\/v2\/web\/student.*/.test(window.location.href)
    }

    //按钮触发PDF生成逻辑
    function download_process(el_dialog){
        var url_slides = get_url_slides(el_dialog);
        if (url_slides.length > 0){
            refreshProcessStatus("处理图片...");
            console.groupCollapsed("雨课堂课件PDF下载工具：处理图片...");
            image_process(url_slides)
                .then(img_list => {
                console.groupEnd();
                refreshProcessStatus("生成PDF...");
                var ppt_name = document.getElementsByClassName("ppt_name")[0].innerText;
                var filename = ppt_name + ".pdf";
                var answer_list = ans_config.enabled ? get_answers(url_slides): [];
                pdf_process(img_list, filename, answer_list);
                refreshProcessStatus("下载课件");
            })
        } else{
            alert("雨课堂课件PDF下载工具：没有提取到图片");
        }
    }

    //第一步-借助UPNG，进行图片下载与反交错、压缩处理
    function image_process(url_slides){
        var promiseList = new Array(url_slides.length);
        var finished_num = 0;
        var count_finished_num = (index) => {
            var processStatus = `${++finished_num}/${url_slides.length}`;
            refreshProcessStatus(`处理图片(${processStatus})`);
            console.log(`雨课堂课件PDF下载工具：${processStatus} - 第${index+1}页 - ${url_slides[index]}`);
        }
        for (let i = 0; i < url_slides.length; i++){
            promiseList[i] = fetch(url_slides[i]).then(response => {
                return response.arrayBuffer();
            }).then(arrayBuffer_origin => {
                var img = UPNG.decode(arrayBuffer_origin);
                var rgba = UPNG.toRGBA8(img);
                var arrayBuffer_compress = UPNG.encode(rgba, img.width, img.height, 0);
                count_finished_num(i);
                return {unit8: new Uint8Array(arrayBuffer_compress), width: img.width, height: img.height};
            }).catch(err => {
                console.error(err);
                alert("雨课堂课件PDF下载工具：图像处理出错");
            });
        }
        return Promise.all(promiseList);
    }

    //第二步-借助jsPDF，进行PDF的生成
    function pdf_process(img_list, filename, answer_list){
        console.groupCollapsed("雨课堂课件PDF下载工具：生成PDF...");
        var doc = new jsPDF({
            orientation: "landscape",
            unit: "px",
            format: [img_list[0].width, img_list[0].height],
            hotfixes: ["px_scaling"]
        });
        var addPPT = (index) => {
            console.log(`雨课堂课件PDF下载工具：第 ${index+1} 页 - PPT`);
            doc.addImage(img_list[index].unit8, 'PNG', 0, 0, img_list[index].width, img_list[index].height);
            let answer_item = answer_list.find(obj => obj.index == index);
            if (answer_item && answer_item.ans != "") {
                let answer_img = text2img(answer_item.ans, ans_config.fontSize, ans_config.fontColor);
                console.log(`雨课堂课件PDF下载工具：第 ${index+1} 页 - 答案 - ${answer_item.ans}`);
                doc.addImage(answer_img.data, 'PNG', img_list[index].width - answer_img.width - ans_config.right,
                             ans_config.up, answer_img.width, answer_img.height);
            };
        };
        addPPT(0);
        for (let i = 1; i < img_list.length; i++){
            doc.addPage([img_list[i].width, img_list[i].height], "landscape");
            addPPT(i);
        }
        console.groupEnd();
        doc.save(filename);
        console.log(`雨课堂课件PDF下载工具：完成下载`);
        console.log(`雨课堂课件PDF下载工具：https://www.pizyds.com/rain-classroom-pdf-direct-download/`);
    }

    //按钮文本刷新
    function refreshProcessStatus(processStatus){
        var el_download = document.getElementsByClassName("pizyds_download")[0];
        el_download.innerHTML = `<i class="iconfont icon-pizyds-rain-down-xiazai"></i> ${processStatus}`;
    }

    //查找PPT窗口
    function find_basePPTDialog(){
        var el_dialogs = document.getElementsByClassName("basePPTDialog");
        if (el_dialogs.length == 1){
            return el_dialogs[0];
        } else{
            return false;
        }
    }

    //客观题答案
    function get_answers(url_slides){
        var el_problem = document.getElementById("problem");
        var answer_list = [];
        if (el_problem){
            var el_exercises_info = el_problem.getElementsByClassName("exercises_info");
            for (let i = 0; i < el_exercises_info.length; i++){
                let el_url = el_exercises_info[i].querySelector(".img_box>img");
                let el_ans = el_exercises_info[i].querySelector(".answer_info>.correct_answer");
                var answer_item = { url: el_url ? el_url.src : "", ans: el_ans ? el_ans.innerText : "", index: -1 };
                answer_item.index = url_slides.indexOf(answer_item.url);
                answer_list.push(answer_item);
            }
        }
        console.groupCollapsed(`雨课堂课件PDF下载工具：提取到 ${answer_list.length} 项答案`);
        console.table(answer_list);
        console.groupEnd();
        return answer_list;
    }

    //对添加客观题答案到PPT的开关
    function switch_answer(processStatus){
        var el_switchAnswer = document.getElementsByClassName("pizyds_switchAnswer")[0];
        if (ans_config.enabled){
            el_switchAnswer.innerHTML = "<del>[ 答案 ]</del>";
            ans_config.enabled = false;
        } else{
            el_switchAnswer.innerHTML = "[ 答案 ]";
            ans_config.enabled = true;
        }
    }

    //PPT图片链接提取
    function get_url_slides(el_dialog){
        try{
            var el_swiper = el_dialog.getElementsByClassName("pptSwiper")[0];
            var el_slides = el_swiper.getElementsByClassName("swiper-slide");
            var url_slides = new Array(el_slides.length);
            for (let i = 0; i < el_slides.length; i++){
                url_slides[i] = el_slides[i].getElementsByTagName("img")[0].src;
            }
            console.groupCollapsed(`雨课堂课件PDF下载工具：提取到 ${url_slides.length} 页 PPT`);
            console.table(url_slides);
            console.groupEnd();
            return url_slides;
        } catch(err){
            return new Array();
        }
    }

    //按钮注入
    function add_button_download(el_dialog){
        var el_header = el_dialog.getElementsByClassName("layout_header")[0];
        if (el_header.getElementsByClassName("pizyds_download").length == 0){
            var el_download = create_node_from_html(`<span class="print pizyds_download" style="right:160px" title="点击下载PPT">
              <i class="iconfont icon-pizyds-rain-down-xiazai"></i> 下载课件</span>`);
            el_download.onclick = () => download_process(el_dialog);
            el_header.appendChild(el_download);

            var el_switchAnswer = create_node_from_html(`<span class="print pizyds_switchAnswer" style="right:110px" title="点击切换是否添加客观题答案到PPT">[ 答案 ]</span>`);
            el_switchAnswer.onclick = () => switch_answer();
            el_header.appendChild(el_switchAnswer);
            console.log("雨课堂课件PDF下载工具：按钮注入成功");
            return true;
        } else{
            return false;
            console.log("雨课堂课件PDF下载工具：按钮注入失败");
        }
    }

    //HTML字符串转节点
    function create_node_from_html(html){
        let tempNode = document.createElement('div');
        tempNode.innerHTML = html;
        return tempNode.firstChild;
    }

    //修改自：http://www.jsfun.cn/#textBecomeImg
    //js使用canvas将文字转换成图像数据base64
    function text2img(text, fontsize, fontcolor){
        var canvas = document.createElement('canvas');
        canvas.height = parseInt(fontsize * 1.2);
        var ctx = canvas.getContext('2d');

        ctx.clearRect(0, 0, canvas.width, canvas.height);
        ctx.fillStyle = fontcolor;
        ctx.font = fontsize + "px Arial";

        ctx.textBaseline = 'middle';
        ctx.fillText(text, 0, fontsize/2);

        canvas.width = ctx.measureText(text).width;
        ctx.fillStyle = fontcolor;
        ctx.font = fontsize + "px Arial";
        ctx.textBaseline = 'middle';
        ctx.fillText(text, 0, fontsize/2);

        var dataUrl = canvas.toDataURL('image/png');
        return {data: dataUrl, width: canvas.width, height: canvas.height};
    }
})();