(function () {
  var Diller = window.Diller = window.Diller || {};

  function toDate(unknown) {
    if (!unknown) {
      return undefined;
    } else if (moment.isMoment(unknown)) {
      return unknown;
    } else if (typeof unknown === 'string') {
      unknown = unknown.trim();

      if (unknown == '') {
        return moment();
      }

      return moment(unknown, 'YYYY-MM-DDTHH:mm.sssZ');
    } else if (typeof unknown === 'string' || moment.isDate(unknown)) {
      return moment(unknown);
    } else {
      return undefined;
    }
  }

  Diller.Interval = function (from, to, level) {
    // console.log('Diller.Interval, from', from && from.toISOString(), 'to', to && to.toISOString(), 'level', level);
    var f = moment.isMoment(from) && from || moment(from),
      t = moment.isMoment(to) && to || moment(to);

    f = f.isValid() ? f : moment();
    t = t.isValid() ? t : moment();

    if (f && t && f.isAfter(t)) {
      var tmp = f;
      f = t;
      t = tmp;
    }

    var diffMs = t.diff(f);
    var diffMinutes = diffMs / (1000 * 60);
    var diffHours = diffMinutes / 60;

    var l = level;

    if (!l) {
      if (diffMinutes < 100) {
        l = 'minute';
      } else if (diffHours < 100) {
        l = 'hour';
      } else {
        l = 'day';
      }
    }

    function getFrom() {
      return f;
    }

    function getTo() {
      return t;
    }

    function getLevel() {
      return l;
    }

    /** @lends Diller.Interval.prototype */
    return {
      getFrom: getFrom,
      getTo: getTo,
      getLevel: getLevel
    };
  };

  Diller.Interval.hours = function (hours) {
    var to = moment();
    var from = moment(to).subtract(hours, 'hours');

    return new Diller.Interval(from, to);
  };

  Diller.Interval.days = function (days) {
    var to = moment();
    var from = moment(to).subtract(hours, 'days');
    return new Diller.Interval(from, to);
  };

  Diller.Interval.months = function (months) {
    var to = moment();
    var from = moment(to).subtract(months, 'months');
    return new Diller.Interval(from, to);
  };
})();