(function() {
  'use strict';

  window.utils = window.utils || {};

  var JS_INITIALIZED_CLASS = 'js-show-hide-initialized';
  var LOCAL_STORAGE_SHOW_HIDE = 'SHOW_HIDE';
  var SHOW_HIDE_TOGGLE_CLASS = 'js-show-hide__toggle';
  var SHOW_HIDE_COLLAPSED_CLASS = 'js-show-hide--collapsed';
  var SHOW_HIDE_TARGET_CLASS = 'js-show-hide__target';

  /**
   * div
   *   div.js-show-hide__toggle
   *     toggle here
   *   div
   *     content here
   */
  window.utils.showHide = function(wrapper, options) {

    options = options || {};

    function addEventHandler(el) {
      el.addEventListener('click', function elClickListener() {
        var newState = el.parentElement.classList.toggle(SHOW_HIDE_COLLAPSED_CLASS);
        updateLSState(el.dataset.shIndex || null, newState);
      });
    }

    function updateLSState(index, state) {
      if (!index) {
        return false;
      }
      var lsData = getLocalStorageData();
      lsData[index] = state;
      window.localStorage.setItem(LOCAL_STORAGE_SHOW_HIDE, JSON.stringify(lsData));
    }

    function collapsedStateInLocalStorage(index) {
      var lsState = getLocalStorageData();
      return lsState[index];
    }

    function getLocalStorageData() {
      return JSON.parse(window.localStorage.getItem(LOCAL_STORAGE_SHOW_HIDE)) || {};
    }

    Array
      .from(wrapper.querySelectorAll('.' + SHOW_HIDE_TOGGLE_CLASS))
      .forEach(function(el) {
        if (el.classList.contains(JS_INITIALIZED_CLASS)) {
          return false;
        }

        var index = el.dataset.shIndex || null;
        var isCollapsed = el.dataset.collapsed === 'true';
        var lsCollapsedState = collapsedStateInLocalStorage(index);
        if (typeof lsCollapsedState !== 'undefined') {
          isCollapsed = lsCollapsedState;
        }
        el.parentElement.classList.toggle(SHOW_HIDE_COLLAPSED_CLASS, isCollapsed);

        Array.from(el.parentElement.children).forEach(function(el) {
          if (!el.classList.contains('' + SHOW_HIDE_TOGGLE_CLASS)) {
            el.classList.add(SHOW_HIDE_TARGET_CLASS);
          }
        });
        el.classList.add(JS_INITIALIZED_CLASS);
        addEventHandler(el);
    });

    return {
      scope: wrapper,
      destroy: function() {},
    };
  };
})();