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/>.

/**

 * Prefetch module to help lazily load content for use on the current page.

 *

 * @module     core/prefetch

 * @copyright  2020 Andrew Nicols <andrew@nicols.co.uk>

 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 *

 * @example <caption>Pre-fetching a set of strings to use later</caption>

 *

 * import prefetch from 'core/prefetch';

 *

 * // A single string prefetch.

 * prefetch.prefetchString('error', 'cannotfindteacher');

 *

 * // Prefetch multiple strings in the same component.

 * prefetch.prefetchStrings('core', [

 *     'yes',

 *     'no',

 * ]);

 *

 * // Use the strings.

 * import {getString, getStrings} from 'core/str';

 * getString('cannotfindteacher', 'error')

 * .then(str => {

 *     window.console.log(str); // Cannot find teacher

 * })

 * .catch();

 * getStrings([

 *     {

 *         key: 'cannotfindteacher',

 *         component: 'error',

 *     },

 *     {

 *         key: 'yes',

 *         component: 'core',

 *     },

 *     {

 *         key: 'no',

 *         component: 'core',

 *     },

 * ])

 * .then((cannotFindTeacher, yes, no) => {

 *     window.console.log(cannotFindTeacher); // Cannot find teacher

 *     window.console.log(yes); // Yes

 *     window.console.log(no); // No

 * })

 * .catch();

 */

import Config from 'core/config';

// Keep track of whether the initial prefetch has occurred.

let initialPrefetchComplete = false;

// Prefetch templates.

let templateList = [];

// Prefetch strings.

let stringList = {};

let prefetchTimer;

/**

 * Fetch all queued items in the queue.

 *

 * Should only be called via processQueue.

 * @private

 */

const fetchQueue = () => {

    // Prefetch templates.

    if (templateList) {

        const templatesToLoad = templateList.slice();

        templateList = [];

        import('core/templates')

        .then(Templates => Templates.prefetchTemplates(templatesToLoad))

        .catch();

    }

    // Prefetch strings.

    const mappedStringsToFetch = stringList;

    stringList = {};

    const stringsToFetch = [];

    Object.keys(mappedStringsToFetch).forEach(component => {

        stringsToFetch.push(...mappedStringsToFetch[component].map(key => {

            return {component, key};

        }));

    });

    if (stringsToFetch) {

        import('core/str')

        .then(Str => Str.get_strings(stringsToFetch))

        .catch();

    }

};

/**

 * Process the prefetch queues as required.

 *

 * The initial call will queue the first fetch after a delay.

 * Subsequent fetches are immediate.

 *

 * @private

 */

const processQueue = () => {

    if (prefetchTimer) {

        // There is a live prefetch timer. The initial prefetch has been scheduled but is not complete.

        return;

    }

    // The initial prefetch has compelted. Just queue as normal.

    if (initialPrefetchComplete) {

        fetchQueue();

        return;

    }

    // Queue the initial prefetch in a short while.

    prefetchTimer = setTimeout(() => {

        initialPrefetchComplete = true;

        prefetchTimer = null;

        // Ensure that the icon system is loaded.

        // This can be quite slow and delay UI interactions if it is loaded on demand.

        import(Config.iconsystemmodule)

        .then(IconSystem => {

            const iconSystem = new IconSystem();

            prefetchTemplate(iconSystem.getTemplateName());

            return iconSystem;

        })

        .then(iconSystem => {

            fetchQueue();

            iconSystem.init();

            return;

        })

        .catch();

    }, 500);

};

/**

 * Add a set of templates to the prefetch queue.

 *

 * @param {Array} templatesNames A list of the template names to fetch

 * @static

 */

const prefetchTemplates = templatesNames => {

    templateList = templateList.concat(templatesNames);

    processQueue();

};

/**

 * Add a single template to the prefetch queue.

 *

 * @param {String} templateName The template names to fetch

 * @static

 */

const prefetchTemplate = templateName => {

    prefetchTemplates([templateName]);

};

/**

 * Add a set of strings from the same component to the prefetch queue.

 *

 * @param {String} component The component that all of the strings belongs to

 * @param {String[]} keys An array of string identifiers.

 * @static

 */

const prefetchStrings = (component, keys) => {

    if (!stringList[component]) {

        stringList[component] = [];

    }

    stringList[component] = stringList[component].concat(keys);

    processQueue();

};

/**

 * Add a single string to the prefetch queue.

 *

 * @param {String} component The component that the string belongs to

 * @param {String} key The string identifier

 * @static

 */

const prefetchString = (component, key) => {

    if (!stringList[component]) {

        stringList[component] = [];

    }

    stringList[component].push(key);

    processQueue();

};

// Prefetch some commonly-used templates.

prefetchTemplates([].concat(

    ['core/loading'],

    ['core/modal'],

    ['core/modal_backdrop'],

));

// And some commonly used strings.

prefetchStrings('core', [

    'cancel',

    'closebuttontitle',

    'loading',

    'savechanges',

]);

prefetchStrings('core_form', [

    'showless',

    'showmore',

]);

export default {

    prefetchTemplate,

    prefetchTemplates,

    prefetchString,

    prefetchStrings,

};