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/>.

/**

 * Lazy loaded list of items.

 *

 * @module     core_message/message_drawer_lazy_load_list

 * @copyright  2018 Ryan Wyllie <ryan@moodle.com>

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

 */

define(

[

    'jquery',

    'core/custom_interaction_events',

    'core/pending',

],

function(

    $,

    CustomEvents,

    PendingPromise,

) {

    var SELECTORS = {

        ROOT: '[data-region="lazy-load-list"]',

        LOADING_ICON_CONTAINER: '[data-region="loading-icon-container"]',

        CONTENT_CONTAINER: '[data-region="content-container"]',

        EMPTY_MESSAGE: '[data-region="empty-message-container"]',

        PLACEHOLDER: '[data-region="placeholder-container"]'

    };

    /**

     * Flag element as loading.

     *

     * @param {Object} root The section container element.

     */

    var startLoading = function(root) {

        root.attr('data-loading', true);

    };

    /**

     * Flag element as not loading.

     *

     * @param {Object} root The section container element.

     */

    var stopLoading = function(root) {

        root.attr('data-loading', false);

    };

    /**

     * Check if the element is loading.

     *

     * @param {Object} root The section container element.

     * @return {Bool}

     */

    var isLoading = function(root) {

        return root.attr('data-loading') === 'true';

    };

    /**

     * Get user id

     *

     * @param  {Object} root The section container element.

     * @return {Number} Logged in user id.

     */

    var getUserId = function(root) {

        return root.attr('data-user-id');

    };

    /**

     * Get the section content container element.

     *

     * @param  {Object} root The section container element.

     * @return {Object} The section content container element.

     */

    var getContentContainer = function(root) {

        return root.find(SELECTORS.CONTENT_CONTAINER);

    };

    /**

     * Get the root element.

     *

     * @param  {Object} containerElement The container element to search in.

     * @return {Object} The list root element.

     */

    var getRoot = function(containerElement) {

        return containerElement.find(SELECTORS.ROOT);

    };

    /**

     * Show the loading icon.

     *

     * @param {Object} root The section container element.

     */

    var showLoadingIcon = function(root) {

        root.find(SELECTORS.LOADING_ICON_CONTAINER).removeClass('hidden');

    };

    /**

     * Hide the loading icon.

     *

     * @param {Object} root The section container element.

     */

    var hideLoadingIcon = function(root) {

        root.find(SELECTORS.LOADING_ICON_CONTAINER).addClass('hidden');

    };

    /**

     * Show the empty message.

     *

     * @param {Object} root The section container element.

     */

    var showEmptyMessage = function(root) {

        root.find(SELECTORS.EMPTY_MESSAGE).removeClass('hidden');

    };

    /**

     * Hide the empty message.

     *

     * @param {Object} root The section container element.

     */

    var hideEmptyMessage = function(root) {

        root.find(SELECTORS.EMPTY_MESSAGE).addClass('hidden');

    };

    /**

     * Show the placeholder element.

     *

     * @param {Object} root The section container element.

     */

    var showPlaceholder = function(root) {

        root.find(SELECTORS.PLACEHOLDER).removeClass('hidden');

    };

    /**

     * Hide the placeholder element.

     *

     * @param {Object} root The section container element.

     */

    var hidePlaceholder = function(root) {

        root.find(SELECTORS.PLACEHOLDER).addClass('hidden');

    };

    /**

     * Show the section content container.

     *

     * @param {Object} root The section container element.

     */

    var showContent = function(root) {

        getContentContainer(root).removeClass('hidden');

    };

    /**

     * Hide the section content container.

     *

     * @param {Object} root The section container element.

     */

    var hideContent = function(root) {

        getContentContainer(root).addClass('hidden');

    };

    /**

     * If the section has loaded all content.

     *

     * @param {Object} root The section container element.

     * @return {Bool}

     */

    var hasLoadedAll = function(root) {

        return root.attr('data-loaded-all') == 'true';

    };

    /**

     * If the section has loaded all content.

     *

     * @param {Object} root The section container element.

     * @param {Bool} value If all items have been loaded.

     */

    var setLoadedAll = function(root, value) {

        root.attr('data-loaded-all', value);

    };

    /**

     * If the section can load more items.

     *

     * @param {Object} root The section container element.

     * @return {Bool}

     */

    var canLoadMore = function(root) {

        return !hasLoadedAll(root) && !isLoading(root);

    };

    /**

     * Load all items in this container from callback and render them.

     *

     * @param {Object} root The section container element.

     * @param {Function} loadCallback The callback to load items.

     * @param {Function} renderCallback The callback to render the results.

     * @return {Object} jQuery promise

     */

    var loadAndRender = function(root, loadCallback, renderCallback) {

        var userId = getUserId(root);

        startLoading(root);

        return loadCallback(root, userId)

            .then(function(items) {

                if (items.length > 0) {

                    var contentContainer = getContentContainer(root);

                    return renderCallback(contentContainer, items, userId)

                        .then(function() {

                            return items;

                        });

                } else {

                    return items;

                }

            })

            .then(function(items) {

                stopLoading(root);

                root.attr('data-seen', true);

                if (!items.length) {

                    setLoadedAll(root, true);

                }

                return items;

            })

            .catch(function() {

                stopLoading(root);

                root.attr('data-seen', true);

                return;

            });

    };

    /**

     * First load of this section.

     *

     * @param {Object} root The section container element.

     * @param {Function} loadCallback The callback to load items.

     * @param {Function} renderCallback The callback to render the results.

     * @return {Object} promise

     */

    var initialLoadAndRender = function(root, loadCallback, renderCallback) {

        const pendingPromise = new PendingPromise('initialLoadAndRender');

        getContentContainer(root).empty();

        showPlaceholder(root);

        hideContent(root);

        return loadAndRender(root, loadCallback, renderCallback)

            .then(function(items) {

                hidePlaceholder(root);

                if (!items.length) {

                    showEmptyMessage(root);

                } else {

                    showContent(root);

                }

                return;

            })

            .catch(function() {

                hidePlaceholder(root);

                showContent(root);

                return;

            })

            .then(() => {

                pendingPromise.resolve();

                return;

            });

    };

    /**

     * Listen to, and handle events in this section.

     *

     * @param {Object} root The section container element.

     * @param {Function} loadCallback The callback to load items.

     * @param {Function} renderCallback The callback to render the results.

     */

    var registerEventListeners = function(root, loadCallback, renderCallback) {

        CustomEvents.define(root, [

            CustomEvents.events.scrollBottom

        ]);

        root.on(CustomEvents.events.scrollBottom, function() {

            if (canLoadMore(root)) {

                showLoadingIcon(root);

                loadAndRender(root, loadCallback, renderCallback)

                    .then(function() {

                        return hideLoadingIcon(root);

                    })

                    .catch(function() {

                        return hideLoadingIcon(root);

                    });

            }

        });

    };

    /**

     * Setup the section.

     *

     * @param {Object} root The section container element.

     * @param {Function} loadCallback The callback to load items.

     * @param {Function} renderCallback The callback to render the results.

     */

    var show = function(root, loadCallback, renderCallback) {

        root = $(root);

        if (!root.attr('data-init')) {

            registerEventListeners(root, loadCallback, renderCallback);

            initialLoadAndRender(root, loadCallback, renderCallback);

            root.attr('data-init', true);

        }

    };

    return {

        show: show,

        getContentContainer: getContentContainer,

        getRoot: getRoot,

        setLoadedAll: setLoadedAll,

        showEmptyMessage: showEmptyMessage,

        hideEmptyMessage: hideEmptyMessage,

        showContent: showContent,

        hideContent: hideContent

    };

});