// ==UserScript==
// @name    超星学习通课件PDF下载
// @namespace    https://greasyfork.org/zh-CN/users/41700
// @version      0.1
// @description  抓取图片链接下载PDF
// @author       QHS
// @require  http://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js
// @match        *://*.chaoxing.com/*
// @grant        none
// @downloadURL https://update.greasyfork.icu/scripts/397137/%E8%B6%85%E6%98%9F%E5%AD%A6%E4%B9%A0%E9%80%9A%E8%AF%BE%E4%BB%B6PDF%E4%B8%8B%E8%BD%BD.user.js
// @updateURL https://update.greasyfork.icu/scripts/397137/%E8%B6%85%E6%98%9F%E5%AD%A6%E4%B9%A0%E9%80%9A%E8%AF%BE%E4%BB%B6PDF%E4%B8%8B%E8%BD%BD.meta.js
// ==/UserScript==\\\
/*--- waitForKeyElements():  A utility function, for Greasemonkey scripts,
    that detects and handles AJAXed content.

    Usage example:

        waitForKeyElements (
            "div.comments"
            , commentCallbackFunction
        );

        //--- Page-specific function to do what we want when the node is found.
        function commentCallbackFunction (jNode) {
            jNode.text ("This comment changed by waitForKeyElements().");
        }

    IMPORTANT: This function requires your script to have loaded jQuery.
*/
function waitForKeyElements (
    selectorTxt,    /* Required: The jQuery selector string that
                        specifies the desired element(s).
                    */
    actionFunction, /* Required: The code to run when elements are
                        found. It is passed a jNode to the matched
                        element.
                    */
    bWaitOnce,      /* Optional: If false, will continue to scan for
                        new elements even after the first match is
                        found.
                    */
    iframeSelector  /* Optional: If set, identifies the iframe to
                        search.
                    */
) {
    var targetNodes, btargetsFound;

    if (typeof iframeSelector == "undefined")
        targetNodes     = $(selectorTxt);
    else
        targetNodes     = $(iframeSelector).contents ()
                                           .find (selectorTxt);

    if (targetNodes  &&  targetNodes.length > 0) {
        btargetsFound   = true;
        /*--- Found target node(s).  Go through each and act if they
            are new.
        */
        targetNodes.each ( function () {
            var jThis        = $(this);
            var alreadyFound = jThis.data ('alreadyFound')  ||  false;

            if (!alreadyFound) {
                //--- Call the payload function.
                var cancelFound     = actionFunction (jThis);
                if (cancelFound)
                    btargetsFound   = false;
                else
                    jThis.data ('alreadyFound', true);
            }
        } );
    }
    else {
        btargetsFound   = false;
    }

    //--- Get the timer-control variable for this selector.
    var controlObj      = waitForKeyElements.controlObj  ||  {};
    var controlKey      = selectorTxt.replace (/[^\w]/g, "_");
    var timeControl     = controlObj [controlKey];

    //--- Now set or clear the timer as appropriate.
    if (btargetsFound  &&  bWaitOnce  &&  timeControl) {
        //--- The only condition where we need to clear the timer.
        clearInterval (timeControl);
        delete controlObj [controlKey]
    }
    else {
        //--- Set a timer, if needed.
        if ( ! timeControl) {
            timeControl = setInterval ( function () {
                    waitForKeyElements (    selectorTxt,
                                            actionFunction,
                                            bWaitOnce,
                                            iframeSelector
                                        );
                },
                300
            );
            controlObj [controlKey] = timeControl;
        }
    }
    waitForKeyElements.controlObj   = controlObj;
}

waitForKeyElements("#iframe", addPdfIcon);

function addPdfIcon() {
    var iframes = document.querySelectorAll("iframe")[0].contentWindow.document.querySelectorAll("iframe");
    var imageIframe = iframes[iframes.length - 1];
    var hash = imageIframe.getAttribute("objectid");
    var xmlHttp = new XMLHttpRequest();
    xmlHttp.open("GET", "https://mooc1-2.chaoxing.com/ananas/status/" + hash, true);
    xmlHttp.send(null);
    xmlHttp.onreadystatechange = function() {
        if (xmlHttp.readyState == 4 && xmlHttp.status == 200) {
            var json = JSON.parse(xmlHttp.responseText);
            var pdf = json.pdf;
            console.log(pdf);
            document.querySelector(".tabs .lists").children[0].innerHTML += "<li id=\"tit4\" onclick=\" window.open('" + pdf + "');\" class=\"current01\">下载PDF</li>";
        }
    };
}