Proyectos de Subversion Moodle

// 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);