// ==UserScript==
// @name         canTvas
// @namespace    https://gist.github.com/lulzsun/f8eff07e74b40126866d83a17d0fb256
// @downloadURL  https://gist.github.com/lulzsun/f8eff07e74b40126866d83a17d0fb256/raw/canTvas.user.js
// @version      0.2
// @description  Prevents the logging of specific canvas lms quiz events.
// @author       lulzsun
// @match        http*://*.instructure.com/*
// @match        http*://*.canvas.*.edu/*
// @icon         https://www.google.com/s2/favicons?sz=64&domain=canvaslms.com
// @grant        none
// ==/UserScript==

(function() {
    'use strict';
    
    window.cantvas = true;
    var oldXHROpen = window.XMLHttpRequest.prototype.open;
    var oldXHRSend = window.XMLHttpRequest.prototype.send;
    window.XMLHttpRequest.prototype.open = function (method, url) {
        this._url = url;
        var args = arguments;
        return oldXHROpen.apply(this, args);
    };

    window.XMLHttpRequest.prototype.send = function (body) {
        var url = this._url;
        var args = arguments;

        // testing for quiz events
        var regexMatches = new RegExp("*/api/v1/courses/*/quizzes/*/submissions/*/events".replace(/\*/g, "[^ ]*"));

        if (regexMatches.test(url) && window.cantvas === true) {
            if (body !== undefined) {
                var parsedBody = JSON.parse(body);
                var i = parsedBody["quiz_submission_events"].length;
                var prevents = 0;
                while (i--) {
                    var element = parsedBody["quiz_submission_events"][i];
                    if (element["event_type"] === "page_focused" || element["event_type"] === "page_blurred") {
                        parsedBody["quiz_submission_events"].splice(i, 1);
                        prevents++;
                    }
                }
                if (prevents > 0) console.warn(`[canTvas] '${prevents}' event(s) were prevented.`);
                args[0] = JSON.stringify(parsedBody["quiz_submission_events"]);
                console.log('on send body:', parsedBody["quiz_submission_events"]);
                if (parsedBody["quiz_submission_events"].length <= 0)
                    return;
            }
        }
        return oldXHRSend.apply(this, args);
    };

    console.warn(`[canTvas] Userscript loaded successfully.`);
})();