(function () {
  "use strict";

  var BODYTYPES = ["DAYS", "MONTHS", "YEARS"];

  /** @typedef {Object.<string, Function[]>} Handlers */
  /** @typedef {function(String, Function): null} AddHandler */
  /** @typedef {("DAYS"|"MONTHS"|"YEARS")} BodyType */
  /** @typedef {string|number} StringNum */
  /** @typedef {Object.<string, StringNum>} StringNumObj */

  /**
   * The local state
   * @typedef {Object} InstanceState
   * @property {Date} value
   * @property {Number} year
   * @property {Number} month
   * @property {Number} day
   * @property {Number} time
   * @property {Number} hours
   * @property {Number} minutes
   * @property {Number} seconds
   * @property {BodyType} bodyType
   * @property {Boolean} visible
   * @property {Number} cancelBlur
   */

  /** 
   * @typedef {Object} Config
   * @property {String} dateFormat
   * @property {String} timeFormat
   * @property {Boolean} showDate
   * @property {Boolean} showTime
   * @property {Boolean} showSeconds
   * @property {Number} paddingX
   * @property {Number} paddingY
   * @property {BodyType} defaultView
   * @property {"TOP"|"BOTTOM"} direction
   * @property {Array} months
   * @property {Array} monthsShort
   * @property {Array} weekdaysShort
   * @property {Array} timeDescr
  */

  /**
   * @class
   * @param {HTMLElement} elem 
   * @param {Config} config 
   */
  function DTS(elem, config) {
      var config = config || {};

      /** @type {Config} */
      var defaultConfig = {
          defaultView: BODYTYPES[0],
          dateFormat: "yyyy-mm-dd",
          timeFormat: "HH:MM:SS",
          showDate: true,
          showTime: false,
          showSeconds: true,
          paddingX: 5,
          paddingY: 5,
          direction: 'TOP',
          months: [
              "January", "February", "March", "April", "May", "June",
              "July", "August", "September", "October", "November", "December"
          ],
          monthsShort: [
              "Jan", "Feb", "Mar", "Apr", "May", "Jun",
              "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
          ], 
          weekdaysShort: [
              "Su", "Mo", "Tu", "We", "Th", "Fr", "Sa"
          ],
          timeDescr: [
              "HH:", "MM:", "SS:"
          ]
      }

      if (!elem) {
          throw TypeError("input element or selector required for contructor");
      }
      if (Object.getPrototypeOf(elem) === String.prototype) {
          var _elem = document.querySelectorAll(elem);
          if (!_elem[0]){
              throw Error('"' + elem + '" not found.');
          }
          elem = _elem[0];
      }
      this.config = setDefaults(config, defaultConfig);
      this.dateFormat = this.config.dateFormat;
      this.timeFormat = this.config.timeFormat;
      this.dateFormatRegEx = new RegExp("yyyy|yy|mm|dd", "gi");
      this.timeFormatRegEx = new RegExp("hh|mm|ss|a", "gi");
      this.inputElem = elem;
      this.dtbox = null;
      this.setup();
  }
  DTS.prototype.setup = function () {
      var handler = this.inputElemHandler.bind(this);
      this.inputElem.addEventListener("focus", handler, false)
      this.inputElem.addEventListener("blur", handler, false);
  }
  DTS.prototype.inputElemHandler = function (e) {
      if (e.type == "focus") {
          if (!this.dtbox) {
              this.dtbox = new DTBox(e.target, this);
          }
          this.dtbox.visible = true;
      } else if (e.type == "blur" && this.dtbox && this.dtbox.visible) {
          var self = this;
          setTimeout(function () {
              if (self.dtbox.cancelBlur > 0) {
                  self.dtbox.cancelBlur -= 1;
               } else {
                  self.dtbox.visible = false;
                  self.inputElem.blur();
               }
          }, 100);
      }
  }
  /**
   * @class
   * @param {HTMLElement} elem 
   * @param {DTS} settings 
   */
  function DTBox(elem, settings) {
      /** @type {DTBox} */
      var self = this;

      /** @type {Handlers} */
      var handlers = {};

      /** @type {InstanceState} */
      var localState = {};

      /**
       * @param {String} key 
       * @param {*} default_val 
       */
      function getterSetter(key, default_val) {
          return {
              get: function () {
                  var val = localState[key];
                  return val === undefined ? default_val : val;
              },
              set: function (val) {
                  var prevState = self.state;
                  var _handlers = handlers[key] || [];
                  localState[key] = val;
                  for (var i = 0; i < _handlers.length; i++) {
                      _handlers[i].bind(self)(localState, prevState);
                  }
              },
          };
      };

      /** @type {AddHandler} */
      function addHandler(key, handlerFn) {
          if (!key || !handlerFn) {
              return false;
          }
          if (!handlers[key]) {
              handlers[key] = [];
          }
          handlers[key].push(handlerFn);
      }

      Object.defineProperties(this, {
          visible: getterSetter("visible", false),
          bodyType: getterSetter("bodyType", settings.config.defaultView),
          value: getterSetter("value"),
          year: getterSetter("year", 0),
          month: getterSetter("month", 0),
          day: getterSetter("day", 0),
          hours: getterSetter("hours", 0),
          minutes: getterSetter("minutes", 0),
          seconds: getterSetter("seconds", 0),
          cancelBlur: getterSetter("cancelBlur", 0),
          addHandler: {value: addHandler},
          month_long: {
              get: function () {
                  return self.settings.config.months[self.month];
              },
          },
          month_short: {
              get: function () {
                  return self.settings.config.monthsShort[self.month]
              },
          },
          state: {
              get: function () {
                  return Object.assign({}, localState);
              },
          },
          time: {
              get: function() {
                  var hours = self.hours * 60 * 60 * 1000;
                  var minutes = self.minutes * 60 * 1000;
                  var seconds = self.seconds * 1000;
                  return  hours + minutes + seconds;
              }
          },
      });
      this.el = {};
      this.settings = settings;
      this.elem = elem;
      this.setup();
  }
  DTBox.prototype.setup = function () {
      Object.defineProperties(this.el, {
          wrapper: { value: null, configurable: true },
          header: { value: null, configurable: true },
          body: { value: null, configurable: true },
          footer: { value: null, configurable: true }
      });
      this.setupWrapper();
      if (this.settings.config.showDate) {
          this.setupHeader();
          this.setupBody();
      }
      if (this.settings.config.showTime) {
          this.setupFooter();
      }

      var self = this;
      this.addHandler("visible", function (state, prevState) {
          if (state.visible && !prevState.visible){
              document.body.appendChild(this.el.wrapper);

              var parts = self.elem.value.split(/\s*,\s*/);
              var startDate = undefined;
              var startTime = 0;
              if (self.settings.config.showDate) {
                  startDate = parseDate(parts[0], self.settings);
              }
              if (self.settings.config.showTime) {
                  startTime = parseTime(parts[parts.length-1], self.settings);
                  startTime = startTime || 0;
              }
              if (!(startDate && startDate.getTime())) {
                  startDate = new Date();
                  startDate = new Date(
                      startDate.getFullYear(),
                      startDate.getMonth(),
                      startDate.getDate()
                  );
              }
              var value = new Date(startDate.getTime() + startTime);
              self.value = value;
              self.year = value.getFullYear();
              self.month = value.getMonth();
              self.day = value.getDate();
              self.hours = value.getHours();
              self.minutes = value.getMinutes();
              self.seconds = value.getSeconds();

              if (self.settings.config.showDate) {
                  self.setHeaderContent();
                  self.setBodyContent();
              }
              if (self.settings.config.showTime) {
                  self.setFooterContent();
              }
          } else if (!state.visible && prevState.visible) {
              document.body.removeChild(this.el.wrapper);
          }
      });
  }
  DTBox.prototype.setupWrapper = function () {
      if (!this.el.wrapper) {
          var el = document.createElement("div");
          el.classList.add("date-selector-wrapper");
          Object.defineProperty(this.el, "wrapper", { value: el });
      }
      var self = this;
      var htmlRoot = document.getElementsByTagName('html')[0];
      function setPosition(e){
          var minTopSpace = 300;
          var box = getOffset(self.elem);
          var config = self.settings.config;
          var paddingY = config.paddingY || 5;
          var paddingX = config.paddingX || 5;
          var top = box.top + self.elem.offsetHeight + paddingY;
          var left = box.left + paddingX;
          var bottom = htmlRoot.clientHeight - box.top + paddingY;

          self.el.wrapper.style.left = `${left}px`;
          if (box.top > minTopSpace && config.direction != 'BOTTOM') {
              self.el.wrapper.style.bottom = `${bottom}px`;
              self.el.wrapper.style.top = '';
          } else {
              self.el.wrapper.style.top = `${top}px`;
              self.el.wrapper.style.bottom = ''; 
          }
      }

      function handler(e) {
          self.cancelBlur += 1;
          setTimeout(function(){
              self.elem.focus();
          }, 50);
      }
      setPosition();
      this.setPosition = setPosition;
      this.el.wrapper.addEventListener("mousedown", handler, false);
      this.el.wrapper.addEventListener("touchstart", handler, false);
      window.addEventListener('resize', this.setPosition);
  }
  DTBox.prototype.setupHeader = function () {
      if (!this.el.header) {
          var row = document.createElement("div");
          var classes = ["cal-nav-prev", "cal-nav-current", "cal-nav-next"];
          row.classList.add("cal-header");
          for (var i = 0; i < 3; i++) {
              var cell = document.createElement("div");
              cell.classList.add("cal-nav", classes[i]);
              cell.onclick = this.onHeaderChange.bind(this);
              row.appendChild(cell);
          }
          row.children[0].innerHTML = "&lt;";
          row.children[2].innerHTML = "&gt;";
          Object.defineProperty(this.el, "header", { value: row });
          tryAppendChild(row, this.el.wrapper);
      }
      this.setHeaderContent();
  }
  DTBox.prototype.setHeaderContent = function () {
      var content = this.year;
      if ("DAYS" == this.bodyType) {
          content = this.month_long + " " + content;
      } else if ("YEARS" == this.bodyType) {
          var start = this.year + 10 - (this.year % 10);
          content = start - 10 + "-" + (start - 1);
      }
      this.el.header.children[1].innerText = content;
  }
  DTBox.prototype.setupBody = function () {
      if (!this.el.body) {
          var el = document.createElement("div");
          el.classList.add("cal-body");
          Object.defineProperty(this.el, "body", { value: el });
          tryAppendChild(el, this.el.wrapper);
      }
      var toAppend = null;
      function makeGrid(rows, cols, className, firstRowClass, clickHandler) {
          var grid = document.createElement("div");
          grid.classList.add(className);
          for (var i = 1; i < rows + 1; i++) {
              var row = document.createElement("div");
              row.classList.add("cal-row", "cal-row-" + i);
              if (i == 1 && firstRowClass) {
                  row.classList.add(firstRowClass);
              }
              for (var j = 1; j < cols + 1; j++) {
                  var col = document.createElement("div");
                  col.classList.add("cal-cell", "cal-col-" + j);
                  col.onclick = clickHandler;
                  row.appendChild(col);
              }
              grid.appendChild(row);
          }
          return grid;
      }
      if ("DAYS" == this.bodyType) {
          toAppend = this.el.body.calDays;
          if (!toAppend) {
              toAppend = makeGrid(7, 7, "cal-days", "cal-day-names", this.onDateSelected.bind(this));
              for (var i = 0; i < 7; i++) {
                  var cell = toAppend.children[0].children[i];
                  cell.innerText = this.settings.config.weekdaysShort[i];
                  cell.onclick = null;
              }
              this.el.body.calDays = toAppend;
          }
      } else if ("MONTHS" == this.bodyType) {
          toAppend = this.el.body.calMonths;
          if (!toAppend) {
              toAppend = makeGrid(3, 4, "cal-months", null, this.onMonthSelected.bind(this));
              for (var i = 0; i < 3; i++) {
                  for (var j = 0; j < 4; j++) {
                      var monthShort = this.settings.config.monthsShort[4 * i + j];
                      toAppend.children[i].children[j].innerText = monthShort;
                  }
              }
              this.el.body.calMonths = toAppend;
          }
      } else if ("YEARS" == this.bodyType) {
          toAppend = this.el.body.calYears;
          if (!toAppend) {
              toAppend = makeGrid(3, 4, "cal-years", null, this.onYearSelected.bind(this));
              this.el.body.calYears = toAppend;
          }
      }
      empty(this.el.body);
      tryAppendChild(toAppend, this.el.body);
      this.setBodyContent();
  }
  DTBox.prototype.setBodyContent = function () {
      var grid = this.el.body.children[0];
      var classes = ["cal-cell-prev", "cal-cell-next", "cal-value"];
      if ("DAYS" == this.bodyType) {
          var oneDayMilliSecs = 24 * 60 * 60 * 1000;
          var start = new Date(this.year, this.month, 1);
          var adjusted = new Date(start.getTime() - oneDayMilliSecs * start.getDay());

          grid.children[6].style.display = "";
          for (var i = 1; i < 7; i++) {
              for (var j = 0; j < 7; j++) {
                  var cell = grid.children[i].children[j];
                  var month = adjusted.getMonth();
                  var date = adjusted.getDate();
                  
                  cell.innerText = date;
                  cell.classList.remove(classes[0], classes[1], classes[2]);
                  if (month != this.month) {
                      if (i == 6 && j == 0) {
                          grid.children[6].style.display = "none";
                          break;
                      }
                      cell.classList.add(month < this.month ? classes[0] : classes[1]);
                  } else if (isEqualDate(adjusted, this.value)){
                      cell.classList.add(classes[2]);
                  }
                  adjusted = new Date(adjusted.getTime() + oneDayMilliSecs);
              }
          }
      } else if ("YEARS" == this.bodyType) {
          var year = this.year - (this.year % 10) - 1;
          for (i = 0; i < 3; i++) {
              for (j = 0; j < 4; j++) {
                  grid.children[i].children[j].innerText = year;
                  year += 1;
              }
          }
          grid.children[0].children[0].classList.add(classes[0]);
          grid.children[2].children[3].classList.add(classes[1]);
      }
  }

  /** @param {Event} e */
  DTBox.prototype.onTimeChange = function(e) {
      e.stopPropagation();
      if (e.type == 'mousedown') {
          this.cancelBlur += 1;
          return;
      }
      if (e.type == 'mouseup') {
          var self = this;
          setTimeout(function(){
              self.elem.focus();
          }, 50);
          return;
      }
      
      var el = e.target;
      this[el.name] = parseInt(el.value) || 0;
      this.setupFooter();
      this.setInputValue();
  }

  DTBox.prototype.setupFooter = function() {
      if (!this.el.footer) {
          var footer = document.createElement("div");
          var handler = this.onTimeChange.bind(this);
          var self = this;
          
          function makeRow(label, name, range, changeHandler) {
              var row = document.createElement("div");
              row.classList.add('cal-time');

              var labelCol = row.appendChild(document.createElement("div"));
              labelCol.classList.add('cal-time-label');
              labelCol.innerText = label;

              var valueCol = row.appendChild(document.createElement("div"));
              valueCol.classList.add('cal-time-value');
              valueCol.innerText = '00';

              var inputCol = row.appendChild(document.createElement("div"));
              var slider = inputCol.appendChild(document.createElement("input"));
              Object.assign(slider, {step:1, min:0, max:range, name:name, type:'range'});
              Object.defineProperty(footer, name, {value: slider});
              inputCol.classList.add('cal-time-slider');
              slider.onchange = changeHandler;
              slider.oninput = changeHandler;
              slider.onmousedown = changeHandler;
              slider.onmouseup = changeHandler;
              self[name] = self[name] || parseInt(slider.value) || 0;
              footer.appendChild(row)
          }
          makeRow(this.settings.config.timeDescr[0], 'hours', 23, handler);
          makeRow(this.settings.config.timeDescr[1], 'minutes', 59, handler);
          if (this.settings.config.showSeconds) {
              makeRow(this.settings.config.timeDescr[2], 'seconds', 59, handler);
          }

          footer.classList.add("cal-footer");
          Object.defineProperty(this.el, "footer", { value: footer });
          tryAppendChild(footer, this.el.wrapper);
      }
      this.setFooterContent();
  }

  DTBox.prototype.setFooterContent = function() {
      if (this.el.footer) {
          var footer = this.el.footer;
          footer.hours.value = this.hours;
          footer.children[0].children[1].innerText = padded(this.hours, 2);
          footer.minutes.value = this.minutes;
          footer.children[1].children[1].innerText = padded(this.minutes, 2);
          if (this.settings.config.showSeconds) {
              footer.seconds.value = this.seconds;
              footer.children[2].children[1].innerText = padded(this.seconds, 2);
          }
      }
  }

  DTBox.prototype.setInputValue = function() {
      var date = new Date(this.year, this.month, this.day);
      var strings = [];
      if (this.settings.config.showDate) {
          strings.push(renderDate(date, this.settings));
      }
      if (this.settings.config.showTime) {
          var joined = new Date(date.getTime() + this.time);
          strings.push(renderTime(joined, this.settings));
      }
      this.elem.value = strings.join(', ');
  }

  DTBox.prototype.onDateSelected = function (e) {
      var row = e.target.parentNode;
      var date = parseInt(e.target.innerText);
      if (!(row.nextSibling && row.nextSibling.nextSibling) && date < 8) {
          this.month += 1;
      } else if (!(row.previousSibling && row.previousSibling.previousSibling) && date > 7) {
          this.month -= 1;
      }
      this.day = parseInt(e.target.innerText);
      this.value = new Date(this.year, this.month, this.day);
      this.setInputValue();
      this.setHeaderContent();
      this.setBodyContent();
  }

  /** @param {Event} e */
  DTBox.prototype.onMonthSelected = function (e) {
      var col = 0;
      var row = 2;
      var cell = e.target;
      if (cell.parentNode.nextSibling){
          row = cell.parentNode.previousSibling ? 1: 0;
      }
      if (cell.previousSibling) {
          col = 3;
          if (cell.nextSibling) {
              col = cell.previousSibling.previousSibling ? 2 : 1;
          }
      }
      this.month = 4 * row + col;
      this.bodyType = "DAYS";
      this.setHeaderContent();
      this.setupBody();
  }

  /** @param {Event} e */
  DTBox.prototype.onYearSelected = function (e) {
      this.year = parseInt(e.target.innerText);
      this.bodyType = "MONTHS";
      this.setHeaderContent();
      this.setupBody();
  }

  /** @param {Event} e */
  DTBox.prototype.onHeaderChange = function (e) {
      var cell = e.target;
      if (cell.previousSibling && cell.nextSibling) {
          var idx = BODYTYPES.indexOf(this.bodyType);
          if (idx < 0 || !BODYTYPES[idx + 1]) {
              return;
          }
          this.bodyType = BODYTYPES[idx + 1];
          this.setupBody();
      } else {
          var sign = cell.previousSibling ? 1 : -1;
          switch (this.bodyType) {
              case "DAYS":
                  this.month += sign * 1;
                  break;
              case "MONTHS":
                  this.year += sign * 1;
                  break;
              case "YEARS":
                  this.year += sign * 10;
          }
          if (this.month > 11 || this.month < 0) {
              this.year += Math.floor(this.month / 11);
              this.month = this.month > 11 ? 0 : 11;
          }
      }
      this.setHeaderContent();
      this.setBodyContent();
  }


  /**
   * @param {HTMLElement} elem 
   * @returns {{left:number, top:number}}
   */
  function getOffset(elem) {
      var box = elem.getBoundingClientRect();
      var left = window.pageXOffset !== undefined ? window.pageXOffset : 
          (document.documentElement || document.body.parentNode || document.body).scrollLeft;
      var top = window.pageYOffset !== undefined ? window.pageYOffset : 
          (document.documentElement || document.body.parentNode || document.body).scrollTop;
      return { left: box.left + left, top: box.top + top };
  }
  function empty(e) {
      for (; e.children.length; ) e.removeChild(e.children[0]);
  }
  function tryAppendChild(newChild, refNode) {
      try {
          refNode.appendChild(newChild);
          return newChild;
      } catch (e) {
          console.trace(e);
      }
  }

  /** @class */
  function hookFuncs() {
      /** @type {Handlers} */
      this._funcs = {};
  }
  /**
   * @param {string} key 
   * @param {Function} func 
   */
  hookFuncs.prototype.add = function(key, func){
      if (!this._funcs[key]){
          this._funcs[key] = [];
      }
      this._funcs[key].push(func)
  }
  /**
   * @param {String} key 
   * @returns {Function[]} handlers
   */
  hookFuncs.prototype.get = function(key){
      return this._funcs[key] ? this._funcs[key] : [];
  }

  /**
   * @param {Array.<string>} arr 
   * @param {String} string 
   * @returns {Array.<string>} sorted string
   */
  function sortByStringIndex(arr, string) {
      return arr.sort(function(a, b){
          var h = string.indexOf(a);
          var l = string.indexOf(b);
          var rank = 0;
          if (h < l) {
              rank = -1;
          } else if (l < h) {
              rank = 1;
          } else if (a.length > b.length) {
              rank = -1;
          } else if (b.length > a.length) {
              rank = 1;
          }
          return rank;
      });
  }

  /**
   * Remove keys from array that are not in format
   * @param {string[]} keys 
   * @param {string} format 
   * @returns {string[]} new filtered array
   */
  function filterFormatKeys(keys, format) {
      var out = [];
      var formatIdx = 0;
      for (var i = 0; i<keys.length; i++) {
          var key = keys[i];
          if (format.slice(formatIdx).indexOf(key) > -1) {
              formatIdx += key.length;
              out.push(key);
          }
      }
      return out;
  }

  /**
   * @template {StringNumObj} FormatObj
   * @param {string} value 
   * @param {string} format 
   * @param {FormatObj} formatObj 
   * @param {function(Object.<string, hookFuncs>): null} setHooks 
   * @returns {FormatObj} formatObj
   */
  function parseData(value, format, formatObj, setHooks) {
      var hooks = {
          canSkip: new hookFuncs(),
          updateValue: new hookFuncs(),
      }
      var keys = sortByStringIndex(Object.keys(formatObj), format);
      var filterdKeys = filterFormatKeys(keys, format);
      var vstart = 0; // value start
      if (setHooks) {
          setHooks(hooks);
      }

      for (var i = 0; i < keys.length; i++) {
          var key = keys[i];
          var fstart = format.indexOf(key);
          var _vstart = vstart; // next value start
          var val = null;
          var canSkip = false;
          var funcs = hooks.canSkip.get(key);

          vstart = vstart || fstart;

          for (var j = 0; j < funcs.length; j++) {
              if (funcs[j](formatObj)){
                  canSkip = true;
                  break;
              }
          }
          if (fstart > -1 && !canSkip) {
              var sep = null;
              var stop = vstart + key.length;
              var fnext = -1;
              var nextKeyIdx = i + 1;
              _vstart += key.length; // set next value start if current key is found

              // get next format token used to determine separator
              while (fnext == -1 && nextKeyIdx < keys.length){
                  var nextKey = keys[nextKeyIdx];
                  nextKeyIdx += 1;
                  if (filterdKeys.indexOf(nextKey) === -1) {
                      continue;
                  }
                  fnext = nextKey ? format.indexOf(nextKey) : -1; // next format start
              }
              if (fnext > -1){
                  sep = format.slice(stop, fnext);
                  if (sep) {
                      var _stop = value.slice(vstart).indexOf(sep);
                      if (_stop && _stop > -1){
                          stop = _stop + vstart;
                          _vstart = stop + sep.length;
                      }
                  }
              }
              val = parseInt(value.slice(vstart, stop));

              var funcs = hooks.updateValue.get(key);
              for (var k = 0; k < funcs.length; k++) {
                  val = funcs[k](val, formatObj, vstart, stop);
              }
          }
          formatObj[key] = { index: vstart, value: val };
          vstart = _vstart; // set next value start
      }
      return formatObj;
  }

  /**
   * @param {String} value 
   * @param {DTS} settings 
   * @returns {Date} date object
   */
  function parseDate(value, settings) {
      /** @type {{yyyy:number=, yy:number=, mm:number=, dd:number=}} */
      var formatObj = {yyyy:null, yy:null, mm:null, dd:null};
      var format = ((settings.dateFormat) || '').toLowerCase();
      if (!format) {
          throw new TypeError('dateFormat not found (' + settings.dateFormat + ')');
      }
      var formatObj = parseData(value, format, formatObj, function(hooks){
          hooks.canSkip.add("yy", function(data){
              return data["yyyy"].value;
          });
          hooks.updateValue.add("yy", function(val){
              return 100 * Math.floor(new Date().getFullYear() / 100) + val;
          });
      });
      var year = formatObj["yyyy"].value || formatObj["yy"].value;
      var month = formatObj["mm"].value - 1;
      var date = formatObj["dd"].value;
      var result = new Date(year, month, date);
      return result;
  }

  /**
   * @param {String} value 
   * @param {DTS} settings 
   * @returns {Number} time in milliseconds <= (24 * 60 * 60 * 1000) - 1
   */
  function parseTime(value, settings) {
      var format = ((settings.timeFormat) || '').toLowerCase();
      if (!format) {
          throw new TypeError('timeFormat not found (' + settings.timeFormat + ')');
      }

      /** @type {{hh:number=, mm:number=, ss:number=, a:string=}} */
      var formatObj = {hh:null, mm:null, ss:null, a:null};
      var formatObj = parseData(value, format, formatObj, function(hooks){
          hooks.updateValue.add("a", function(val, data, start, stop){
              return value.slice(start, start + 2);
          });
      });
      var hours = formatObj["hh"].value;
      var minutes = formatObj["mm"].value;
      var seconds = formatObj["ss"].value;
      var am_pm = formatObj["a"].value;
      var am_pm_lower = am_pm ? am_pm.toLowerCase() : am_pm;
      if (am_pm && ["am", "pm"].indexOf(am_pm_lower) > -1){
          if (am_pm_lower == 'am' && hours == 12){
              hours = 0;
          } else if (am_pm_lower == 'pm') {
              hours += 12;
          }
      }
      var time = hours * 60 * 60 * 1000 + minutes * 60 * 1000 + seconds * 1000;
      return time;
  }

  /**
   * @param {Date} value 
   * @param {DTS} settings 
   * @returns {String} date string
   */
  function renderDate(value, settings) {
      var format = settings.dateFormat.toLowerCase();
      var date = value.getDate();
      var month = value.getMonth() + 1;
      var year = value.getFullYear();
      var yearShort = year % 100;
      var formatObj = {
          dd: date < 10 ? "0" + date : date,
          mm: month < 10 ? "0" + month : month,
          yyyy: year,
          yy: yearShort < 10 ? "0" + yearShort : yearShort
      };
      var str = format.replace(settings.dateFormatRegEx, function (found) {
          return formatObj[found];
      });
      return str;
  }

  /**
   * @param {Date} value 
   * @param {DTS} settings 
   * @returns {String} date string
   */
  function renderTime(value, settings) {
      var Format = settings.timeFormat;
      var format = Format.toLowerCase();
      var hours = value.getHours();
      var minutes = value.getMinutes();
      var seconds = value.getSeconds();
      var am_pm = null;
      var hh_am_pm = null;
      if (format.indexOf('a') > -1) {
          am_pm = hours >= 12 ? 'pm' : 'am';
          am_pm = Format.indexOf('A') > -1 ? am_pm.toUpperCase() : am_pm;
          hh_am_pm = hours == 0 ? '12' : (hours > 12 ? hours%12 : hours);
      }
      var formatObj = {
          hh: am_pm ? hh_am_pm : (hours < 10 ? "0" + hours : hours),
          mm: minutes < 10 ? "0" + minutes : minutes,
          ss: seconds < 10 ? "0" + seconds : seconds,
          a: am_pm,
      };
      var str = format.replace(settings.timeFormatRegEx, function (found) {
          return formatObj[found];
      });
      return str;
  }

  /**
   * checks if two dates are equal
   * @param {Date} date1 
   * @param {Date} date2 
   * @returns {Boolean} true or false
   */
  function isEqualDate(date1, date2) {
      if (!(date1 && date2)) return false;
      return (date1.getFullYear() == date2.getFullYear() && 
              date1.getMonth() == date2.getMonth() && 
              date1.getDate() == date2.getDate());
  }

  /**
   * @param {Number} val 
   * @param {Number} pad 
   * @param {*} default_val 
   * @returns {String} padded string
   */
  function padded(val, pad, default_val) {
      var default_val = default_val || 0;
      var valStr = '' + (parseInt(val) || default_val);
      var diff = Math.max(pad, valStr.length) - valStr.length;
      return ('' + default_val).repeat(diff) + valStr;
  }

  /**
   * @template X
   * @template Y
   * @param {X} obj 
   * @param {Y} objDefaults 
   * @returns {X|Y} merged object
   */
  function setDefaults(obj, objDefaults) {
      var keys = Object.keys(objDefaults);
      for (var i=0; i<keys.length; i++) {
          var key = keys[i];
          if (!Object.prototype.hasOwnProperty.call(obj, key)) {
              obj[key] = objDefaults[key];
          }
      }
      return obj;
  }


  window.dtsel = Object.create({},{
      DTS: { value: DTS },
      DTObj: { value: DTBox },
      fn: {
          value: Object.defineProperties({}, {
              empty: { value: empty },
              appendAfter: {
                  value: function (newElem, refNode) {
                      refNode.parentNode.insertBefore(newElem, refNode.nextSibling);
                  },
              },
              getOffset: { value: getOffset },
              parseDate: { value: parseDate },
              renderDate: { value: renderDate },
              parseTime: {value: parseTime},
              renderTime: {value: renderTime},
              setDefaults: {value: setDefaults},
          }),
      },
  });
})();