YUI.add('moodle-mod_assign-history', function (Y) {
    // Define a function that will run in the context of a
    // Node instance:
    var CSS = {
            LINK: 'mod-assign-history-link',
            OPEN: 'mod-assign-history-link-open',
            CLOSED: 'mod-assign-history-link-closed',
            PANEL: 'mod-assign-history-panel'
        },
        COUNT = 0,
        TOGGLE = function() {
            var id = this.get('for'),
                panel = Y.one('#' + id);
            if (this.hasClass(CSS.OPEN)) {
                this.removeClass(CSS.OPEN);
                this.addClass(CSS.CLOSED);
                this.setStyle('overflow', 'hidden');
                panel.hide();
            } else {
                this.removeClass(CSS.CLOSED);
                this.addClass(CSS.OPEN);
                panel.show();
            }
        },
        HISTORY = function() {
            var link = null,
                panel = null,
                wrapper = null,
                container = this;

            // Loop through all the children of this container and turn
            // every odd node to a link to open/close the following panel.
            this.get('children').each(function () {
                if (link) {
                    COUNT++;
                    // First convert the link to an anchor.
                    wrapper = Y.Node.create('<a/>');
                    panel = this;
                    container.insertBefore(wrapper, link);
                    link.remove(false);
                    wrapper.appendChild(link);

                    // Add a for attribute to the link to link to the id of the panel.
                    if (!panel.get('id')) {
                        panel.set('id', CSS.PANEL + COUNT);
                    }
                    wrapper.set('for', panel.get('id'));
                    // Add an aria attribute for the live region.
                    panel.set('aria-live', 'polite');

                    wrapper.addClass(CSS.LINK);
                    wrapper.addClass(CSS.CLOSED);
                    panel.addClass(CSS.PANEL);
                    panel.hide();
                    link = null;
                } else {
                    link = this;
                }
            });

            // Setup event listeners.
            this.delegate('click', TOGGLE, '.' + CSS.LINK);
        };

    // Use addMethod to add history to the Node prototype:
    Y.Node.addMethod("history", HISTORY);

    // Extend this functionality to NodeLists.
    Y.NodeList.importMethod(Y.Node.prototype, "history");
}, '@VERSION@', { requires: ['node', 'transition'] });