(() => {
    const defaultConfig = "{\"outer\":\"v-collapse\",\"listenTo\":\"body\",\"itemSelector\":\"v-collapse-item\",\"headSelector\":\"v-collapse-head\",\"contentSelector\":\"v-collapse-content\"}";

    window.VCollapse = class VCollapse {
        constructor(options = {}) {
            this.options = Object.assign(options, JSON.parse(defaultConfig));
            this.initListener();
        }

        initListener() {
            const self = this,
                opt = self.options;
            $(opt.listenTo).addDelegatedEventListener('click', opt.headSelector, (e, el) => {
                self.toggleItem(el, false);
            });
            this.resize();
            window.addEventListener('resize', this.resize.bind(this));
        }

        toggleItem(el, forceClose, noClose) {
            if (!el._maxHeight) {
                this.resize();
            }
            if (!noClose && el.find(this.options.outer).hasAttribute('accordion')) {
                this.closeAll(el);
            }
            let parent = el.find(this.options.itemSelector),
                cont = $(this.options.contentSelector, parent),
                cl = parent.classList;
            if (cl.contains('open') || forceClose) {
                cont.style.maxHeight = '0px';
                cl.remove('open');
            } else {
                cont.style.maxHeight = parent._maxHeight + 'px';
                cl.add('open');
            }
        }

        closeAll(el) {
            const self = this,
                opt = self.options,
                items = $$(opt.headSelector, el.find(opt.outer));
            VUtils.forEach(items, e => {
                if (e !== el) {
                    self.toggleItem(e, true, true);
                }
            })
        }

        calcHeight(el) {
            let children = $(this.options.contentSelector, el).children,
                height = 0;
            VUtils.forEach(children, e => {
                height += e.offsetHeight;
            })
            el._maxHeight = height;
        }

        resize() {
            const self = this,
                opt = self.options,
                items = $$(opt.itemSelector, $(opt.listenTo));
            VUtils.forEach(items, e => {
                self.calcHeight(e);
                if (e.classList.contains('open')) {
                    $(opt.contentSelector, e).style.maxHeight = parent._maxHeight + 'px';
                }
            })
        }
    }
    new VCollapse();
})();