weekly release 4.0dev
[moodle.git] / mod / scorm / request.js
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1// This file is part of Moodle - http://moodle.org/
2//
3// Moodle is free software: you can redistribute it and/or modify
4// it under the terms of the GNU General Public License as published by
5// the Free Software Foundation, either version 3 of the License, or
6// (at your option) any later version.
7//
8// Moodle is distributed in the hope that it will be useful,
9// but WITHOUT ANY WARRANTY; without even the implied warranty of
10// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11// GNU General Public License for more details.
12//
13// You should have received a copy of the GNU General Public License
14// along with Moodle. If not, see <http://www.gnu.org/licenses/>.
15
2a0407b7 16function NewHttpReq() {
17 var httpReq = false;
15d2f0ca 18 if (typeof XMLHttpRequest != 'undefined') {
2a0407b7 19 httpReq = new XMLHttpRequest();
20 } else {
21 try {
5e5b6b7f 22 httpReq = new ActiveXObject("Msxml2.XMLHTTP.4.0");
2a0407b7 23 } catch (e) {
5e5b6b7f 24 try {
25 httpReq = new ActiveXObject("Msxml2.XMLHTTP");
26 } catch (ee) {
27 try {
28 httpReq = new ActiveXObject("Microsoft.XMLHTTP");
29 } catch (eee) {
30 httpReq = false;
31 }
32 }
33 }
2a0407b7 34 }
35 return httpReq;
36}
37
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38/**
39 *
40 * @param {XMLHttpRequest} httpReq
41 * @param {string} url
42 * @param {string} param
43 * @param {boolean} allowBeaconAPI Should the BeaconAPI be used if required? Defaults to true
44 * If True, and we can use the Beacon API and are should use the beacon API then we will.
45 * If False, we will not use the Beacon API, even if we expect a synchronous XHR request to fail.
46 * @returns {string|boolean|*}
47 * @constructor
48 */
49function DoRequest(httpReq, url, param, allowBeaconAPI) {
9633a423 50
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51 // Default allowBeaconAPI to true. This argument was added to the function late.
52 if (typeof allowBeaconAPI === 'undefined') {
53 allowBeaconAPI = true;
54 }
55
56 /**
57 * Returns true if we are able to use the Beacon API in this browser.
58 * @returns boolean
59 */
60 var canUseBeaconAPI = function() {
61 return (allowBeaconAPI && navigator && navigator.sendBeacon && FormData);
62 };
63
64 /**
65 * Returns true if we should use the Beacon API.
66 * We don't use the Beacon API unless we have to as it stiffles our ability to return data on the request.
67 * @returns {boolean}
68 */
69 var useBeaconAPI = function() {
70 if (typeof window.mod_scorm_useBeaconAPI === 'undefined' || window.mod_scorm_useBeaconAPI === false) {
71 // Last ditch effort, the SCORM package may have introduced its own listeners before our listeners.
72 // This is OLD API, window.event is not reliable and is not recommended API.
73 // https://developer.mozilla.org/en-US/docs/Web/API/Window/event
74 if (window.event && ['beforeunload', 'unload', 'pagehide'].indexOf(window.event.type)) {
75 window.mod_scorm_useBeaconAPI = true;
76 }
77 }
78 return (window.mod_scorm_useBeaconAPI && canUseBeaconAPI());
79 };
80
81 /**
82 * Uses the Beacon API to communicate this request to the server.
83 * This function always returns a successful result, because we don't get the actual result, the page doesn't wait for it.
84 * @param {string} url
85 * @param {string} param
86 * @returns {string}
87 */
88 var useSendBeacon = function(url, param) {
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89 // Ok, old API alert, the param is a URI encoded string. We need to split it and convert it to a supported format.
90 // I've chosen FormData and FormData.append as they are compatible with our supported browsers:
91 // - https://developer.mozilla.org/en-US/docs/Web/API/FormData/FormData
92 // - https://developer.mozilla.org/en-US/docs/Web/API/FormData/append
93
94 var vars = param.split('&'),
95 i = 0,
96 pair,
97 key,
98 value,
99 formData = new FormData();
100 for (i = 0; i < vars.length; i++) {
101 pair = vars[i].split('=');
102 key = decodeURIComponent(pair[0]);
103 value = decodeURIComponent(pair[1]);
104 formData.append(key, value);
105 }
106 // We'll also inform it that we are unloading, potentially useful in the future.
107 formData.append('unloading', '1');
108
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109 // We're going to add a token to the URL that will identify this request as going to the beacon API.
110 // In the future this would allow our server side scripts to respond differently when the beacon API
111 // is being used, as the response will be discarded.
112 if (url.indexOf('?') === -1) {
113 // First param
114 url += '?api=beacon';
115 } else {
116 url += '&api=beacon';
117 }
118
841d8559 119 // The results is true or false, we don't get the response from the server. Make it look like it was a success.
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120 var outcome = navigator.sendBeacon(url, formData);
121 if (!outcome) {
122 if (console && console.log) {
123 console.log('mod_scorm: Failed to queue navigator.sendBeacon request');
124 }
125 return "false\n101";
126 }
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127 // This is what a success looks like when it comes back from the server.
128 return "true\n0";
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129 };
130
131 // If we are unloading, and we can use sendBeacon then do that, Chrome does not permit synchronous XHR requests on unload.
132 if (useBeaconAPI()) {
133 return useSendBeacon(url, param);
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134 }
135
2a0407b7 136 // httpReq.open (Method("get","post"), URL(string), Asyncronous(true,false))
aedbddfd 137 //popupwin(url+"\n"+param);
9633a423 138 httpReq.open("POST", url,false);
139 httpReq.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
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140 try {
141 httpReq.send(param);
142 } catch (e) {
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143 if (console && console.log) {
144 // This may be frivolous as during a shutdown the console log will most likely be lost. But it may help someone.
145 var message = 'XHR request from mod_scorm::DoRequest failed';
146 if (canUseBeaconAPI()) {
147 message += '; attempting to use Beacon API.';
148 }
149 console.log(message);
150 }
151 // 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
152 // we will attempt to send the request one more time using the Beacon API. This will result in a successful result regardless
153 // of the actual outcome.
154 if (canUseBeaconAPI()) {
155 return useSendBeacon(url, param);
156 }
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157 return false;
158 }
1daed920 159 if (httpReq.status == 200) {
aedbddfd 160 //popupwin(url+"\n"+param+"\n"+httpReq.responseText);
9633a423 161 return httpReq.responseText;
1daed920 162 } else {
9633a423 163 return httpReq.status;
1daed920 164 }
a5463b34 165}
166
aedbddfd 167function popupwin(content) {
15d2f0ca 168 var op = window.open();
a5463b34 169 op.document.open('text/plain');
170 op.document.write(content);
171 op.document.close();
aedbddfd 172}
841d8559 173
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174/**
175 * Global variable to track whether we should use the Beacon API instead of synchronous XHR.
176 * This gets set to true in situations where we expect synchronoush XHR requests to fail.
177 */
178window.mod_scorm_useBeaconAPI = false;
179
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180/**
181 * We wire up a small marker for the unload events triggered when the user is navigating away or closing the tab.
182 * This is done because Chrome does not allow synchronous XHR requests on the following unload events:
183 * - beforeunload
184 * - unload
185 * - pagehide
186 * - visibilitychange
187 */
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188function mod_scorm_monitorForBeaconRequirement(target) {
189
190 if (typeof target.mod_scorm_monitoring_for_beacon_requirement !== 'undefined') {
191 // We're already observing unload events on this target.
192 console.log('mod_scorm: unload event handlers already attached');
193 return;
194 }
195 target.mod_scorm_monitoring_for_beacon_requirement = true;
196
197 // The navigator.sendBeacon API is available in all browsers EXCEPT Internet Explorer (IE)
198 // Internet explorer should never get past this check.
199 if (!navigator || !navigator.sendBeacon) {
200 // We can't use the BeaconAPI. There is no point in proceeding to observe unload events.
201 // This is done after adding the flag to target, and establishing the window variable.
202 return;
203 }
204
205 /**
206 * Turns on the use of the Beacon API.
207 */
208 var toggleOn = function() {
209 window.mod_scorm_useBeaconAPI = true;
841d8559 210 };
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211
212 /**
213 * Turns off the use of the Beacon API.
214 */
215 var toggleOff = function() {
216 window.mod_scorm_useBeaconAPI = false;
217 };
218
219 /**
220 * Observes an event.
221 * Required because this patch will be backported.
222 * @param {string} on
223 * @param {CallableFunction} callback
224 */
225 var observe = function(on, callback) {
226 if (!target.addEventListener) {
227 console.log('Unable to attach page dismissal event listeners');
228 return null;
229 }
230 return target.addEventListener(on, callback);
231 };
232
233 // Listen to the three events known to represent an unload operation.
234 observe('beforeunload', toggleOn);
235 observe('unload', toggleOn);
236 observe('pagehide', toggleOn);
237
238 // Listen to the event fired when navigating to a page and ensure we toggle useBeaconAPI off.
239 // This shouldn't be needed (page should be uncached) but just in case!
240 observe('pageshow', toggleOff);
241
242 // Finally listen to the visibility change event, and respond to it.
243 // This unfortunately is not ideal, but is required as a SCORM package may also be listening to this and
244 // trying to save content when the user hides the page. As this can occur as part of the page dismissal lifecycle
245 // we also need to ensure we use the Beacon API here.
246 observe('visibilitychange', function() {
247 // Visible means synchronous XHR permitted, use XHR.
248 // Hidden means synchronous XHR not permitted, use Beacon API.
249 if (document.visibilityState === 'visible' || document.visibilityState === 'prerender') {
250 toggleOff();
251 } else if (document.visibilityState === 'hidden') {
252 toggleOn();
253 }
254 });
255}
256// Begin monitoring on the main window immediately.
257mod_scorm_monitorForBeaconRequirement(window);