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// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle. If not, see <http://www.gnu.org/licenses/>.
function NewHttpReq() {
var httpReq = false;
if (typeof XMLHttpRequest != 'undefined') {
httpReq = new XMLHttpRequest();
} else {
try {
httpReq = new ActiveXObject("Msxml2.XMLHTTP.4.0");
} catch (e) {
try {
httpReq = new ActiveXObject("Msxml2.XMLHTTP");
} catch (ee) {
try {
httpReq = new ActiveXObject("Microsoft.XMLHTTP");
} catch (eee) {
httpReq = false;
}
}
}
}
return httpReq;
}
/**
*
* @param {XMLHttpRequest} httpReq
* @param {string} url
* @param {string} param
* @param {boolean} allowBeaconAPI Should the BeaconAPI be used if required? Defaults to true
* If True, and we can use the Beacon API and are should use the beacon API then we will.
* If False, we will not use the Beacon API, even if we expect a synchronous XHR request to fail.
* @returns {string|boolean|*}
* @constructor
*/
function DoRequest(httpReq, url, param, allowBeaconAPI) {
// Default allowBeaconAPI to true. This argument was added to the function late.
if (typeof allowBeaconAPI === 'undefined') {
allowBeaconAPI = true;
}
/**
* Returns true if we are able to use the Beacon API in this browser.
* @returns boolean
*/
var canUseBeaconAPI = function() {
return (allowBeaconAPI && navigator && navigator.sendBeacon && FormData);
};
/**
* Returns true if we should use the Beacon API.
* We don't use the Beacon API unless we have to as it stiffles our ability to return data on the request.
* @returns {boolean}
*/
var useBeaconAPI = function() {
if (typeof window.mod_scorm_useBeaconAPI === 'undefined' || window.mod_scorm_useBeaconAPI === false) {
// Last ditch effort, the SCORM package may have introduced its own listeners before our listeners.
// This is OLD API, window.event is not reliable and is not recommended API.
// https://developer.mozilla.org/en-US/docs/Web/API/Window/event
if (window.event && ['beforeunload', 'unload', 'pagehide'].indexOf(window.event.type)) {
window.mod_scorm_useBeaconAPI = true;
}
}
return (window.mod_scorm_useBeaconAPI && canUseBeaconAPI());
};
/**
* Uses the Beacon API to communicate this request to the server.
* This function always returns a successful result, because we don't get the actual result, the page doesn't wait for it.
* @param {string} url
* @param {string} param
* @returns {string}
*/
var useSendBeacon = function(url, param) {
// Ok, old API alert, the param is a URI encoded string. We need to split it and convert it to a supported format.
// I've chosen FormData and FormData.append as they are compatible with our supported browsers:
// - https://developer.mozilla.org/en-US/docs/Web/API/FormData/FormData
// - https://developer.mozilla.org/en-US/docs/Web/API/FormData/append
var vars = param.split('&'),
i = 0,
pair,
key,
value,
formData = new FormData();
for (i = 0; i < vars.length; i++) {
pair = vars[i].split('=');
key = decodeURIComponent(pair[0]);
value = decodeURIComponent(pair[1]);
formData.append(key, value);
}
// We'll also inform it that we are unloading, potentially useful in the future.
formData.append('unloading', '1');
// We're going to add a token to the URL that will identify this request as going to the beacon API.
// In the future this would allow our server side scripts to respond differently when the beacon API
// is being used, as the response will be discarded.
if (url.indexOf('?') === -1) {
// First param
url += '?api=beacon';
} else {
url += '&api=beacon';
}
// The results is true or false, we don't get the response from the server. Make it look like it was a success.
var outcome = navigator.sendBeacon(url, formData);
if (!outcome) {
if (console && console.log) {
console.log('mod_scorm: Failed to queue navigator.sendBeacon request');
}
return "false\n101";
}
// This is what a success looks like when it comes back from the server.
return "true\n0";
};
// If we are unloading, and we can use sendBeacon then do that, Chrome does not permit synchronous XHR requests on unload.
if (useBeaconAPI()) {
return useSendBeacon(url, param);
}
// httpReq.open (Method("get","post"), URL(string), Asyncronous(true,false))
//popupwin(url+"\n"+param);
httpReq.open("POST", url,false);
httpReq.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
try {
httpReq.send(param);
} catch (e) {
if (console && console.log) {
// This may be frivolous as during a shutdown the console log will most likely be lost. But it may help someone.
var message = 'XHR request from mod_scorm::DoRequest failed';
if (canUseBeaconAPI()) {
message += '; attempting to use Beacon API.';
}
console.log(message);
}
// The HTTP request failed. We don't know why, but as a last ditch effort, in case we are unloading and haven't detected it
// we will attempt to send the request one more time using the Beacon API. This will result in a successful result regardless
// of the actual outcome.
if (canUseBeaconAPI()) {
return useSendBeacon(url, param);
}
return false;
}
if (httpReq.status == 200) {
//popupwin(url+"\n"+param+"\n"+httpReq.responseText);
return httpReq.responseText;
} else {
return httpReq.status;
}
}
function popupwin(content) {
var op = window.open();
op.document.open('text/plain');
op.document.write(content);
op.document.close();
}
/**
* Global variable to track whether we should use the Beacon API instead of synchronous XHR.
* This gets set to true in situations where we expect synchronoush XHR requests to fail.
*/
window.mod_scorm_useBeaconAPI = false;
/**
* We wire up a small marker for the unload events triggered when the user is navigating away or closing the tab.
* This is done because Chrome does not allow synchronous XHR requests on the following unload events:
* - beforeunload
* - unload
* - pagehide
* - visibilitychange
*/
function mod_scorm_monitorForBeaconRequirement(target) {
if (typeof target.mod_scorm_monitoring_for_beacon_requirement !== 'undefined') {
// We're already observing unload events on this target.
console.log('mod_scorm: unload event handlers already attached');
return;
}
target.mod_scorm_monitoring_for_beacon_requirement = true;
// The navigator.sendBeacon API is available in all browsers EXCEPT Internet Explorer (IE)
// Internet explorer should never get past this check.
if (!navigator || !navigator.sendBeacon) {
// We can't use the BeaconAPI. There is no point in proceeding to observe unload events.
// This is done after adding the flag to target, and establishing the window variable.
return;
}
/**
* Turns on the use of the Beacon API.
*/
var toggleOn = function() {
window.mod_scorm_useBeaconAPI = true;
};
/**
* Turns off the use of the Beacon API.
*/
var toggleOff = function() {
window.mod_scorm_useBeaconAPI = false;
};
/**
* Observes an event.
* Required because this patch will be backported.
* @param {string} on
* @param {CallableFunction} callback
*/
var observe = function(on, callback) {
if (!target.addEventListener) {
console.log('Unable to attach page dismissal event listeners');
return null;
}
return target.addEventListener(on, callback);
};
// Listen to the three events known to represent an unload operation.
observe('beforeunload', toggleOn);
observe('unload', toggleOn);
observe('pagehide', toggleOn);
// Listen to the event fired when navigating to a page and ensure we toggle useBeaconAPI off.
// This shouldn't be needed (page should be uncached) but just in case!
observe('pageshow', toggleOff);
// Finally listen to the visibility change event, and respond to it.
// This unfortunately is not ideal, but is required as a SCORM package may also be listening to this and
// trying to save content when the user hides the page. As this can occur as part of the page dismissal lifecycle
// we also need to ensure we use the Beacon API here.
observe('visibilitychange', function() {
// Visible means synchronous XHR permitted, use XHR.
// Hidden means synchronous XHR not permitted, use Beacon API.
if (document.visibilityState === 'visible' || document.visibilityState === 'prerender') {
toggleOff();
} else if (document.visibilityState === 'hidden') {
toggleOn();
}
});
}
// Begin monitoring on the main window immediately.
mod_scorm_monitorForBeaconRequirement(window);