var _veUiMWCategoryInputWidgetPopulateLookupMenu = ve.ui.MWCategoryInputWidget.prototype.populateLookupMenu;

ve.ui.MWCategoryInputWidget.prototype.populateLookupMenu = function () {
    this.allowSuggestionsWhenEmpty = true;
    _veUiMWCategoryInputWidgetPopulateLookupMenu.call(this);
};

ve.ui.MWCategoryInputWidget.prototype.isekaiGetCategoryItemFromData = function (data, indent) {
    indent = indent || 0;
    var items = [];
    data.forEach(function (cInfo) {
        var item;
        var indentText = ' '.repeat(indent * 2);
        if (cInfo.isSection) {
            item = new OO.ui.MenuSectionOptionWidget({
                data: cInfo.category,
                label: indentText + cInfo.label
            });
        } else {
            item = new OO.ui.MenuOptionWidget({
                data: cInfo.category,
                label: indentText + cInfo.label,
            })
        }
        items.push(item);

        if (Array.isArray(cInfo.children)) {
            items = items.concat(this.isekaiGetCategoryItemFromData(cInfo.children, indent + 1));
        }
    }.bind(this));
    return items;
};

ve.ui.MWCategoryInputWidget.prototype.getLookupMenuItems = function () {
    deferred = $.Deferred();

    if (this.value === '') {
        if (this.cachedMainCategories) {
            return deferred.resolve(this.cachedMainCategories);
        }

        var mcUrl = mw.config.get('wgIsekaiMainCategoriesIndexUrl');
        var itemWidgets = [];

        // Section header
        itemWidgets.push(
            new OO.ui.MenuSectionOptionWidget({
                data: 'mainCategories',
                label: ve.msg('isekai-ve-dialog-meta-categories-input-maincategorieslabel')
            })
        );

        return $.ajax({
            url: mcUrl,
            type: 'GET',
            dataType: 'json',
        }).then(function (data) {
            var categoryItems = this.isekaiGetCategoryItemFromData(data);
            itemWidgets = itemWidgets.concat(categoryItems);
            this.cachedMainCategories = itemWidgets;
            return deferred.resolve(itemWidgets);
        }.bind(this));
    } else {
        return this.getRequestData().then(function (data) {
            return this.getLookupMenuOptionsFromData(data);
        }.bind(this));
    }
};