namespace ASC.Notify.Cron;

[Serializable]
public class CronExpression : ICloneable, IDeserializationCallback
{
    protected const int Second = 0;
    protected const int Minute = 1;
    protected const int Hour = 2;
    protected const int DayOfMonth = 3;
    protected const int Month = 4;
    protected const int DayOfWeek = 5;
    protected const int Year = 6;
    protected const int AllSpecInt = 99;
    protected const int NoSpecInt = 98;
    protected const int AllSpec = AllSpecInt;
    protected const int NoSpec = NoSpecInt;

    private static readonly Hashtable _monthMap = new Hashtable(20);
    private static readonly Hashtable _dayMap = new Hashtable(60);
    [NonSerialized] protected bool CalendardayOfMonth;
    [NonSerialized] protected bool CalendardayOfWeek;

    [NonSerialized] protected TreeSet DaysOfMonth;

    [NonSerialized] protected TreeSet DaysOfWeek;
    [NonSerialized] protected bool ExpressionParsed;
    [NonSerialized] protected TreeSet Hours;

    [NonSerialized] protected bool LastdayOfMonth;
    [NonSerialized] protected bool LastdayOfWeek;
    [NonSerialized] protected TreeSet Minutes;
    [NonSerialized] protected TreeSet Months;

    [NonSerialized] protected bool NearestWeekday;
    [NonSerialized] protected int NthdayOfWeek;
    [NonSerialized] protected TreeSet Seconds;
    private TimeZoneInfo _timeZone;
    [NonSerialized] protected TreeSet Years;

    static CronExpression()
    {
        _monthMap.Add("JAN", 0);
        _monthMap.Add("FEB", 1);
        _monthMap.Add("MAR", 2);
        _monthMap.Add("APR", 3);
        _monthMap.Add("MAY", 4);
        _monthMap.Add("JUN", 5);
        _monthMap.Add("JUL", 6);
        _monthMap.Add("AUG", 7);
        _monthMap.Add("SEP", 8);
        _monthMap.Add("OCT", 9);
        _monthMap.Add("NOV", 10);
        _monthMap.Add("DEC", 11);
        _dayMap.Add("SUN", 1);
        _dayMap.Add("MON", 2);
        _dayMap.Add("TUE", 3);
        _dayMap.Add("WED", 4);
        _dayMap.Add("THU", 5);
        _dayMap.Add("FRI", 6);
        _dayMap.Add("SAT", 7);
    }

    public CronExpression(string cronExpression)
    {
        if (cronExpression == null)
        {
            throw new ArgumentException("cronExpression cannot be null");
        }
        CronExpressionString = cronExpression.ToUpper(CultureInfo.InvariantCulture);
        BuildExpression(cronExpression);
    }

    public virtual TimeZoneInfo TimeZone
    {
        set { _timeZone = value; }
        get
        {
            if (_timeZone == null)
            {
                _timeZone = TimeZoneInfo.Utc;
            }

            return _timeZone;
        }
    }

    public string CronExpressionString { get; }

    public TimeSpan? Period()
    {
        var date = new DateTime(2014, 1, 1);
        DateTime.SpecifyKind(date, DateTimeKind.Utc);
        var after = GetTimeAfter(date);
        if (!after.HasValue)
        {
            return null;
        }

        return after.Value.Subtract(date);
    }

    #region ICloneable Members

    public object Clone()
    {
        CronExpression copy;
        try
        {
            copy = new CronExpression(CronExpressionString)
            {
                TimeZone = TimeZone
            };
        }
        catch (FormatException)
        {
            throw new Exception("Not Cloneable.");
        }

        return copy;
    }

    #endregion

    #region IDeserializationCallback Members

    public void OnDeserialization(object sender)
    {
        BuildExpression(CronExpressionString);
    }

    #endregion

    public virtual bool IsSatisfiedBy(DateTime dateUtc)
    {
        var test =
            new DateTime(dateUtc.Year, dateUtc.Month, dateUtc.Day, dateUtc.Hour, dateUtc.Minute, dateUtc.Second).
                AddSeconds(-1);
        var timeAfter = GetTimeAfter(test);
        if (timeAfter.HasValue && timeAfter.Value.Equals(dateUtc))
        {
            return true;
        }
        else
        {
            return false;
        }
    }

    public virtual DateTime? GetNextValidTimeAfter(DateTime date)
    {
        return GetTimeAfter(date);
    }

    public virtual DateTime? GetNextInvalidTimeAfter(DateTime date)
    {
        long difference = 1000;

        var lastDate =
            new DateTime(date.Year, date.Month, date.Day, date.Hour, date.Minute, date.Second).AddSeconds(-1);

        while (difference == 1000)
        {
            var newDate = GetTimeAfter(lastDate).Value;
            difference = (long)(newDate - lastDate).TotalMilliseconds;
            if (difference == 1000)
            {
                lastDate = newDate;
            }
        }

        return lastDate.AddSeconds(1);
    }

    public override string ToString()
    {
        return CronExpressionString;
    }

    public static bool IsValidExpression(string cronExpression)
    {
        try
        {
            new CronExpression(cronExpression);
        }
        catch (FormatException)
        {
            return false;
        }

        return true;
    }

    protected void BuildExpression(string expression)
    {
        ExpressionParsed = true;
        try
        {
            if (Seconds == null)
            {
                Seconds = new TreeSet();
            }
            if (Minutes == null)
            {
                Minutes = new TreeSet();
            }
            if (Hours == null)
            {
                Hours = new TreeSet();
            }
            if (DaysOfMonth == null)
            {
                DaysOfMonth = new TreeSet();
            }
            if (Months == null)
            {
                Months = new TreeSet();
            }
            if (DaysOfWeek == null)
            {
                DaysOfWeek = new TreeSet();
            }
            if (Years == null)
            {
                Years = new TreeSet();
            }
            var exprOn = Second;


#if NET_20
                string[] exprsTok = expression.Trim().Split(new char[] { ' ', '\t', '\r', '\n' }, StringSplitOptions.RemoveEmptyEntries);
#else
            var exprsTok = expression.Trim().Split(new[] { ' ', '\t', '\r', '\n' });
#endif
            foreach (var exprTok in exprsTok)
            {
                var expr = exprTok.Trim();
                if (expr.Length == 0)
                {
                    continue;
                }
                if (exprOn > Year)
                {
                    break;
                }

                if (exprOn == DayOfMonth && expr.IndexOf('L') != -1 && expr.Length > 1 && expr.IndexOf(',') >= 0)
                {
                    throw new FormatException(
                        "Support for specifying 'L' and 'LW' with other days of the month is not implemented");
                }

                if (exprOn == DayOfWeek && expr.IndexOf('L') != -1 && expr.Length > 1 && expr.IndexOf(',') >= 0)
                {
                    throw new FormatException(
                        "Support for specifying 'L' with other days of the week is not implemented");
                }
                var vTok = expr.Split(',');
                foreach (var v in vTok)
                {
                    StoreExpressionVals(0, v, exprOn);
                }
                exprOn++;
            }
            if (exprOn <= DayOfWeek)
            {
                throw new FormatException("Unexpected end of expression.");
            }
            if (exprOn <= Year)
            {
                StoreExpressionVals(0, "*", Year);
            }
            var dow = GetSet(DayOfWeek);
            var dom = GetSet(DayOfMonth);

            var dayOfMSpec = !dom.Contains(NoSpec);
            var dayOfWSpec = !dow.Contains(NoSpec);
            if (dayOfMSpec && !dayOfWSpec)
            {
            }
            else if (dayOfWSpec && !dayOfMSpec)
            {
            }
            else
            {
                throw new FormatException(
                    "Support for specifying both a day-of-week AND a day-of-month parameter is not implemented.");
            }
        }
        catch (FormatException)
        {
            throw;
        }
        catch (Exception e)
        {
            throw new FormatException(string.Format(CultureInfo.InvariantCulture,
                                                    "Illegal cron expression format ({0})", e));
        }
    }

    protected virtual int StoreExpressionVals(int pos, string s, int type)
    {
        var incr = 0;
        var i = SkipWhiteSpace(pos, s);
        if (i >= s.Length)
        {
            return i;
        }
        var c = s[i];
        if ((c >= 'A') && (c <= 'Z') && (!s.Equals("L")) && (!s.Equals("LW")))
        {
            var sub = s.Substring(i, 3);
            int sval;
            var eval = -1;
            if (type == Month)
            {
                sval = GetMonthNumber(sub) + 1;
                if (sval <= 0)
                {
                    throw new FormatException($"Invalid Month value: '{sub}'");
                }
                if (s.Length > i + 3)
                {
                    c = s[i + 3];
                    if (c == '-')
                    {
                        i += 4;
                        sub = s.Substring(i, 3);
                        eval = GetMonthNumber(sub) + 1;
                        if (eval <= 0)
                        {
                            throw new FormatException($"Invalid Month value: '{sub}'");
                        }
                    }
                }
            }
            else if (type == DayOfWeek)
            {
                sval = GetDayOfWeekNumber(sub);
                if (sval < 0)
                {
                    throw new FormatException($"Invalid Day-of-Week value: '{sub}'");
                }
                if (s.Length > i + 3)
                {
                    c = s[i + 3];
                    if (c == '-')
                    {
                        i += 4;
                        sub = s.Substring(i, 3);
                        eval = GetDayOfWeekNumber(sub);
                        if (eval < 0)
                        {
                            throw new FormatException($"Invalid Day-of-Week value: '{sub}'");
                        }
                    }
                    else if (c == '#')
                    {
                        try
                        {
                            i += 4;
                            NthdayOfWeek = Convert.ToInt32(s.Substring(i), CultureInfo.InvariantCulture);
                            if (NthdayOfWeek < 1 || NthdayOfWeek > 5)
                            {
                                throw new Exception();
                            }
                        }
                        catch (Exception)
                        {
                            throw new FormatException(
                                "A numeric value between 1 and 5 must follow the '#' option");
                        }
                    }
                    else if (c == 'L')
                    {
                        LastdayOfWeek = true;
                        i++;
                    }
                }
            }
            else
            {
                throw new FormatException($"Illegal characters for this position: '{sub}'");
            }
            if (eval != -1)
            {
                incr = 1;
            }
            AddToSet(sval, eval, incr, type);

            return i + 3;
        }
        if (c == '?')
        {
            i++;
            if ((i + 1) < s.Length
                && s[i] != ' ' && s[i + 1] != '\t')
            {
                throw new FormatException("Illegal character after '?': "
                                          + s[i]);
            }
            if (type != DayOfWeek && type != DayOfMonth)
            {
                throw new FormatException(
                    "'?' can only be specified for Day-of-Month or Day-of-Week.");
            }
            if (type == DayOfWeek && !LastdayOfMonth)
            {
                var val = (int)DaysOfMonth[^1];
                if (val == NoSpecInt)
                {
                    throw new FormatException(
                        "'?' can only be specified for Day-of-Month -OR- Day-of-Week.");
                }
            }
            AddToSet(NoSpecInt, -1, 0, type);

            return i;
        }
        if (c == '*' || c == '/')
        {
            if (c == '*' && (i + 1) >= s.Length)
            {
                AddToSet(AllSpecInt, -1, incr, type);

                return i + 1;
            }
            else if (c == '/'
                     && ((i + 1) >= s.Length || s[i + 1] == ' ' || s[i + 1] == '\t'))
            {
                throw new FormatException("'/' must be followed by an integer.");
            }
            else if (c == '*')
            {
                i++;
            }
            c = s[i];
            if (c == '/')
            {
                i++;
                if (i >= s.Length)
                {
                    throw new FormatException("Unexpected end of string.");
                }
                incr = GetNumericValue(s, i);
                i++;
                if (incr > 10)
                {
                    i++;
                }
                if (incr > 59 && (type == Second || type == Minute))
                {
                    throw new FormatException(
                        string.Format(CultureInfo.InvariantCulture, "Increment > 60 : {0}", incr));
                }
                else if (incr > 23 && (type == Hour))
                {
                    throw new FormatException(
                        string.Format(CultureInfo.InvariantCulture, "Increment > 24 : {0}", incr));
                }
                else if (incr > 31 && (type == DayOfMonth))
                {
                    throw new FormatException(
                        string.Format(CultureInfo.InvariantCulture, "Increment > 31 : {0}", incr));
                }
                else if (incr > 7 && (type == DayOfWeek))
                {
                    throw new FormatException(
                        string.Format(CultureInfo.InvariantCulture, "Increment > 7 : {0}", incr));
                }
                else if (incr > 12 && (type == Month))
                {
                    throw new FormatException(string.Format(CultureInfo.InvariantCulture, "Increment > 12 : {0}",
                                                            incr));
                }
            }
            else
            {
                incr = 1;
            }
            AddToSet(AllSpecInt, -1, incr, type);

            return i;
        }
        else if (c == 'L')
        {
            i++;
            if (type == DayOfMonth)
            {
                LastdayOfMonth = true;
            }
            if (type == DayOfWeek)
            {
                AddToSet(7, 7, 0, type);
            }
            if (type == DayOfMonth && s.Length > i)
            {
                c = s[i];
                if (c == 'W')
                {
                    NearestWeekday = true;
                    i++;
                }
            }

            return i;
        }
        else if (c >= '0' && c <= '9')
        {
            var val = Convert.ToInt32(c.ToString(), CultureInfo.InvariantCulture);
            i++;
            if (i >= s.Length)
            {
                AddToSet(val, -1, -1, type);
            }
            else
            {
                c = s[i];
                if (c >= '0' && c <= '9')
                {
                    var vs = GetValue(val, s, i);
                    val = vs.TheValue;
                    i = vs.Pos;
                }
                i = CheckNext(i, s, val, type);

                return i;
            }
        }
        else
        {
            throw new FormatException(string.Format(CultureInfo.InvariantCulture, "Unexpected character: {0}", c));
        }

        return i;
    }

    protected virtual int CheckNext(int pos, string s, int val, int type)
    {
        var end = -1;
        var i = pos;
        if (i >= s.Length)
        {
            AddToSet(val, end, -1, type);

            return i;
        }
        var c = s[pos];
        if (c == 'L')
        {
            if (type == DayOfWeek)
            {
                LastdayOfWeek = true;
            }
            else
            {
                throw new FormatException(string.Format(CultureInfo.InvariantCulture,
                                                        "'L' option is not valid here. (pos={0})", i));
            }
            var data = GetSet(type);
            data.Add(val);
            i++;

            return i;
        }
        if (c == 'W')
        {
            if (type == DayOfMonth)
            {
                NearestWeekday = true;
            }
            else
            {
                throw new FormatException(string.Format(CultureInfo.InvariantCulture,
                                                        "'W' option is not valid here. (pos={0})", i));
            }
            var data = GetSet(type);
            data.Add(val);
            i++;

            return i;
        }
        if (c == '#')
        {
            if (type != DayOfWeek)
            {
                throw new FormatException(
                    string.Format(CultureInfo.InvariantCulture, "'#' option is not valid here. (pos={0})", i));
            }
            i++;
            try
            {
                NthdayOfWeek = Convert.ToInt32(s.Substring(i), CultureInfo.InvariantCulture);
                if (NthdayOfWeek < 1 || NthdayOfWeek > 5)
                {
                    throw new Exception();
                }
            }
            catch (Exception)
            {
                throw new FormatException(
                    "A numeric value between 1 and 5 must follow the '#' option");
            }
            var data = GetSet(type);
            data.Add(val);
            i++;

            return i;
        }
        if (c == 'C')
        {
            if (type == DayOfWeek)
            {
                CalendardayOfWeek = true;
            }
            else if (type == DayOfMonth)
            {
                CalendardayOfMonth = true;
            }
            else
            {
                throw new FormatException(string.Format(CultureInfo.InvariantCulture,
                                                        "'C' option is not valid here. (pos={0})", i));
            }
            var data = GetSet(type);
            data.Add(val);
            i++;

            return i;
        }
        if (c == '-')
        {
            i++;
            c = s[i];
            var v = Convert.ToInt32(c.ToString(), CultureInfo.InvariantCulture);
            end = v;
            i++;
            if (i >= s.Length)
            {
                AddToSet(val, end, 1, type);

                return i;
            }
            c = s[i];
            if (c >= '0' && c <= '9')
            {
                var vs = GetValue(v, s, i);
                var v1 = vs.TheValue;
                end = v1;
                i = vs.Pos;
            }
            if (i < s.Length && (s[i] == '/'))
            {
                i++;
                c = s[i];
                var v2 = Convert.ToInt32(c.ToString(), CultureInfo.InvariantCulture);
                i++;
                if (i >= s.Length)
                {
                    AddToSet(val, end, v2, type);

                    return i;
                }
                c = s[i];
                if (c >= '0' && c <= '9')
                {
                    var vs = GetValue(v2, s, i);
                    var v3 = vs.TheValue;
                    AddToSet(val, end, v3, type);
                    i = vs.Pos;

                    return i;
                }
                else
                {
                    AddToSet(val, end, v2, type);

                    return i;
                }
            }
            else
            {
                AddToSet(val, end, 1, type);

                return i;
            }
        }
        if (c == '/')
        {
            i++;
            c = s[i];
            var v2 = Convert.ToInt32(c.ToString(), CultureInfo.InvariantCulture);
            i++;
            if (i >= s.Length)
            {
                AddToSet(val, end, v2, type);

                return i;
            }
            c = s[i];
            if (c >= '0' && c <= '9')
            {
                var vs = GetValue(v2, s, i);
                var v3 = vs.TheValue;
                AddToSet(val, end, v3, type);
                i = vs.Pos;

                return i;
            }
            else
            {
                throw new FormatException(string.Format(CultureInfo.InvariantCulture,
                                                        "Unexpected character '{0}' after '/'", c));
            }
        }

        AddToSet(val, end, 0, type);
        i++;

        return i;
    }

    public virtual string GetExpressionSummary()
    {
        var buf = new StringBuilder();
        buf.Append("seconds: ");
        buf.Append(GetExpressionSetSummary(Seconds));
        buf.Append('\n');
        buf.Append("minutes: ");
        buf.Append(GetExpressionSetSummary(Minutes));
        buf.Append('\n');
        buf.Append("hours: ");
        buf.Append(GetExpressionSetSummary(Hours));
        buf.Append('\n');
        buf.Append("daysOfMonth: ");
        buf.Append(GetExpressionSetSummary(DaysOfMonth));
        buf.Append('\n');
        buf.Append("months: ");
        buf.Append(GetExpressionSetSummary(Months));
        buf.Append('\n');
        buf.Append("daysOfWeek: ");
        buf.Append(GetExpressionSetSummary(DaysOfWeek));
        buf.Append('\n');
        buf.Append("lastdayOfWeek: ");
        buf.Append(LastdayOfWeek);
        buf.Append('\n');
        buf.Append("nearestWeekday: ");
        buf.Append(NearestWeekday);
        buf.Append('\n');
        buf.Append("NthDayOfWeek: ");
        buf.Append(NthdayOfWeek);
        buf.Append('\n');
        buf.Append("lastdayOfMonth: ");
        buf.Append(LastdayOfMonth);
        buf.Append('\n');
        buf.Append("calendardayOfWeek: ");
        buf.Append(CalendardayOfWeek);
        buf.Append('\n');
        buf.Append("calendardayOfMonth: ");
        buf.Append(CalendardayOfMonth);
        buf.Append('\n');
        buf.Append("years: ");
        buf.Append(GetExpressionSetSummary(Years));
        buf.Append('\n');

        return buf.ToString();
    }

    protected virtual string GetExpressionSetSummary(ISet data)
    {
        if (data.Contains(NoSpec))
        {
            return "?";
        }
        if (data.Contains(AllSpec))
        {
            return "*";
        }
        var buf = new StringBuilder();
        var first = true;
        foreach (int iVal in data)
        {
            var val = iVal.ToString(CultureInfo.InvariantCulture);
            if (!first)
            {
                buf.Append(',');
            }
            buf.Append(val);
            first = false;
        }

        return buf.ToString();
    }

    protected virtual int SkipWhiteSpace(int i, string s)
    {
        for (; i < s.Length && (s[i] == ' ' || s[i] == '\t'); i++)
        {

        }

        return i;
    }

    protected virtual int FindNextWhiteSpace(int i, string s)
    {
        for (; i < s.Length && (s[i] != ' ' || s[i] != '\t'); i++)
        {

        }

        return i;
    }

    protected virtual void AddToSet(int val, int end, int incr, int type)
    {
        var data = GetSet(type);
        if (type == Second || type == Minute)
        {
            if ((val < 0 || val > 59 || end > 59) && (val != AllSpecInt))
            {
                throw new FormatException(
                    "Minute and Second values must be between 0 and 59");
            }
        }
        else if (type == Hour)
        {
            if ((val < 0 || val > 23 || end > 23) && (val != AllSpecInt))
            {
                throw new FormatException(
                    "Hour values must be between 0 and 23");
            }
        }
        else if (type == DayOfMonth)
        {
            if ((val < 1 || val > 31 || end > 31) && (val != AllSpecInt)
                && (val != NoSpecInt))
            {
                throw new FormatException(
                    "Day of month values must be between 1 and 31");
            }
        }
        else if (type == Month)
        {
            if ((val < 1 || val > 12 || end > 12) && (val != AllSpecInt))
            {
                throw new FormatException(
                    "Month values must be between 1 and 12");
            }
        }
        else if (type == DayOfWeek)
        {
            if ((val == 0 || val > 7 || end > 7) && (val != AllSpecInt)
                && (val != NoSpecInt))
            {
                throw new FormatException(
                    "Day-of-Week values must be between 1 and 7");
            }
        }
        if ((incr == 0 || incr == -1) && val != AllSpecInt)
        {
            if (val != -1)
            {
                data.Add(val);
            }
            else
            {
                data.Add(NoSpec);
            }

            return;
        }
        var startAt = val;
        var stopAt = end;
        if (val == AllSpecInt && incr <= 0)
        {
            incr = 1;
            data.Add(AllSpec);
        }
        if (type == Second || type == Minute)
        {
            if (stopAt == -1)
            {
                stopAt = 59;
            }
            if (startAt == -1 || startAt == AllSpecInt)
            {
                startAt = 0;
            }
        }
        else if (type == Hour)
        {
            if (stopAt == -1)
            {
                stopAt = 23;
            }
            if (startAt == -1 || startAt == AllSpecInt)
            {
                startAt = 0;
            }
        }
        else if (type == DayOfMonth)
        {
            if (stopAt == -1)
            {
                stopAt = 31;
            }
            if (startAt == -1 || startAt == AllSpecInt)
            {
                startAt = 1;
            }
        }
        else if (type == Month)
        {
            if (stopAt == -1)
            {
                stopAt = 12;
            }
            if (startAt == -1 || startAt == AllSpecInt)
            {
                startAt = 1;
            }
        }
        else if (type == DayOfWeek)
        {
            if (stopAt == -1)
            {
                stopAt = 7;
            }
            if (startAt == -1 || startAt == AllSpecInt)
            {
                startAt = 1;
            }
        }
        else if (type == Year)
        {
            if (stopAt == -1)
            {
                stopAt = 2099;
            }
            if (startAt == -1 || startAt == AllSpecInt)
            {
                startAt = 1970;
            }
        }

        var max = -1;
        if (stopAt < startAt)
        {
            max = type switch
            {
                Second => 60,
                Minute => 60,
                Hour => 24,
                Month => 12,
                DayOfWeek => 7,
                DayOfMonth => 31,
                Year => throw new ArgumentException("Start year must be less than stop year"),
                _ => throw new ArgumentException("Unexpected type encountered"),
            };
            stopAt += max;
        }
        for (var i = startAt; i <= stopAt; i += incr)
        {
            if (max == -1)
            {
                data.Add(i);
            }
            else
            {
                var i2 = i % max;

                if (i2 == 0 && (type == Month || type == DayOfWeek || type == DayOfMonth))
                {
                    i2 = max;
                }
                data.Add(i2);
            }
        }
    }

    protected virtual TreeSet GetSet(int type)
    {
        return type switch
        {
            Second => Seconds,
            Minute => Minutes,
            Hour => Hours,
            DayOfMonth => DaysOfMonth,
            Month => Months,
            DayOfWeek => DaysOfWeek,
            Year => Years,
            _ => null,
        };
    }

    protected virtual ValueSet GetValue(int v, string s, int i)
    {
        var c = s[i];
        var sb = new StringBuilder();
        sb.Append(v.ToString(CultureInfo.InvariantCulture));
        while (c >= '0' && c <= '9')
        {
            sb.Append(c);
            i++;
            if (i >= s.Length)
            {
                break;
            }
            c = s[i];
        }
        var val = new ValueSet();
        if (i < s.Length)
        {
            val.Pos = i;
        }
        else
        {
            val.Pos = i + 1;
        }
        val.TheValue = Convert.ToInt32(sb.ToString(), CultureInfo.InvariantCulture);

        return val;
    }

    protected virtual int GetNumericValue(string s, int i)
    {
        var endOfVal = FindNextWhiteSpace(i, s);
        var val = s[i..endOfVal];

        return Convert.ToInt32(val, CultureInfo.InvariantCulture);
    }

    protected virtual int GetMonthNumber(string s)
    {
        if (_monthMap.ContainsKey(s))
        {
            return (int)_monthMap[s];
        }
        else
        {
            return -1;
        }
    }

    protected virtual int GetDayOfWeekNumber(string s)
    {
        if (_dayMap.ContainsKey(s))
        {
            return (int)_dayMap[s];
        }
        else
        {
            return -1;
        }
    }

    protected virtual DateTime? GetTime(int sc, int mn, int hr, int dayofmn, int mon)
    {
        try
        {
            if (sc == -1)
            {
                sc = 0;
            }
            if (mn == -1)
            {
                mn = 0;
            }
            if (hr == -1)
            {
                hr = 0;
            }
            if (dayofmn == -1)
            {
                dayofmn = 0;
            }
            if (mon == -1)
            {
                mon = 0;
            }

            return new DateTime(DateTime.UtcNow.Year, mon, dayofmn, hr, mn, sc);
        }
        catch (Exception)
        {
            return null;
        }
    }

    public virtual DateTime? GetTimeAfter(DateTime afterTimeUtc)
    {
        if (afterTimeUtc == DateTime.MaxValue)
            return null;

        afterTimeUtc = afterTimeUtc.AddSeconds(1);

        var d = CreateDateTimeWithoutMillis(afterTimeUtc);

        d = TimeZoneInfo.ConvertTimeFromUtc(d, TimeZone);
        var gotOne = false;

        while (!gotOne)
        {
            ISortedSet st;
            int t;
            var sec = d.Second;

            st = Seconds.TailSet(sec);
            if (st != null && st.Count != 0)
            {
                sec = (int)st.First();
            }
            else
            {
                sec = (int)Seconds.First();
                d = d.AddMinutes(1);
            }
            d = new DateTime(d.Year, d.Month, d.Day, d.Hour, d.Minute, sec, d.Millisecond);
            var min = d.Minute;
            var hr = d.Hour;
            t = -1;

            st = Minutes.TailSet(min);
            if (st != null && st.Count != 0)
            {
                t = min;
                min = (int)st.First();
            }
            else
            {
                min = (int)Minutes.First();
                hr++;
            }
            if (min != t)
            {
                d = new DateTime(d.Year, d.Month, d.Day, d.Hour, min, 0, d.Millisecond);
                d = SetCalendarHour(d, hr);

                continue;
            }
            d = new DateTime(d.Year, d.Month, d.Day, d.Hour, min, d.Second, d.Millisecond);
            hr = d.Hour;
            var day = d.Day;
            t = -1;

            st = Hours.TailSet(hr);
            if (st != null && st.Count != 0)
            {
                t = hr;
                hr = (int)st.First();
            }
            else
            {
                hr = (int)Hours.First();
                day++;
            }
            if (hr != t)
            {
                var daysInMonth = DateTime.DaysInMonth(d.Year, d.Month);
                if (day > daysInMonth)
                {
                    d =
                        new DateTime(d.Year, d.Month, daysInMonth, d.Hour, 0, 0, d.Millisecond).AddDays(day -
                                                                                                        daysInMonth);
                }
                else
                {
                    d = new DateTime(d.Year, d.Month, day, d.Hour, 0, 0, d.Millisecond);
                }
                d = SetCalendarHour(d, hr);

                continue;
            }
            d = new DateTime(d.Year, d.Month, d.Day, hr, d.Minute, d.Second, d.Millisecond);
            day = d.Day;
            var mon = d.Month;
            t = -1;
            var tmon = mon;

            var dayOfMSpec = !DaysOfMonth.Contains(NoSpec);
            var dayOfWSpec = !DaysOfWeek.Contains(NoSpec);
            if (dayOfMSpec && !dayOfWSpec)
            {
                st = DaysOfMonth.TailSet(day);
                if (LastdayOfMonth)
                {
                    if (!NearestWeekday)
                    {
                        t = day;
                        day = GetLastDayOfMonth(mon, d.Year);
                    }
                    else
                    {
                        t = day;
                        day = GetLastDayOfMonth(mon, d.Year);
                        var tcal = new DateTime(d.Year, mon, day, 0, 0, 0);
                        var ldom = GetLastDayOfMonth(mon, d.Year);
                        var dow = tcal.DayOfWeek;
                        if (dow == System.DayOfWeek.Saturday && day == 1)
                        {
                            day += 2;
                        }
                        else if (dow == System.DayOfWeek.Saturday)
                        {
                            day -= 1;
                        }
                        else if (dow == System.DayOfWeek.Sunday && day == ldom)
                        {
                            day -= 2;
                        }
                        else if (dow == System.DayOfWeek.Sunday)
                        {
                            day += 1;
                        }
                        var nTime = new DateTime(tcal.Year, mon, day, hr, min, sec, d.Millisecond);
                        if (nTime.ToUniversalTime() < afterTimeUtc)
                        {
                            day = 1;
                            mon++;
                        }
                    }
                }
                else if (NearestWeekday)
                {
                    t = day;
                    day = (int)DaysOfMonth.First();
                    var tcal = new DateTime(d.Year, mon, day, 0, 0, 0);
                    var ldom = GetLastDayOfMonth(mon, d.Year);
                    var dow = tcal.DayOfWeek;
                    if (dow == System.DayOfWeek.Saturday && day == 1)
                    {
                        day += 2;
                    }
                    else if (dow == System.DayOfWeek.Saturday)
                    {
                        day -= 1;
                    }
                    else if (dow == System.DayOfWeek.Sunday && day == ldom)
                    {
                        day -= 2;
                    }
                    else if (dow == System.DayOfWeek.Sunday)
                    {
                        day += 1;
                    }
                    tcal = new DateTime(tcal.Year, mon, day, hr, min, sec);
                    if (tcal.ToUniversalTime() < afterTimeUtc)
                    {
                        day = (int)DaysOfMonth.First();
                        mon++;
                    }
                }
                else if (st != null && st.Count != 0)
                {
                    t = day;
                    day = (int)st.First();

                    var lastDay = GetLastDayOfMonth(mon, d.Year);
                    if (day > lastDay)
                    {
                        day = (int)DaysOfMonth.First();
                        mon++;
                    }
                }
                else
                {
                    day = (int)DaysOfMonth.First();
                    mon++;
                }
                if (day != t || mon != tmon)
                {
                    if (mon > 12)
                    {
                        d = new DateTime(d.Year, 12, day, 0, 0, 0).AddMonths(mon - 12);
                    }
                    else
                    {
                        var lDay = DateTime.DaysInMonth(d.Year, mon);
                        if (day <= lDay)
                        {
                            d = new DateTime(d.Year, mon, day, 0, 0, 0);
                        }
                        else
                        {
                            d = new DateTime(d.Year, mon, lDay, 0, 0, 0).AddDays(day - lDay);
                        }
                    }

                    continue;
                }
            }
            else if (dayOfWSpec && !dayOfMSpec)
            {
                if (LastdayOfWeek)
                {
                    var dow = (int)DaysOfWeek.First();

                    var cDow = (int)d.DayOfWeek;
                    var daysToAdd = 0;
                    if (cDow < dow)
                    {
                        daysToAdd = dow - cDow;
                    }
                    if (cDow > dow)
                    {
                        daysToAdd = dow + (7 - cDow);
                    }
                    var lDay = GetLastDayOfMonth(mon, d.Year);
                    if (day + daysToAdd > lDay)
                    {
                        if (mon == 12)
                        {
                            if (d.Year == DateTime.MaxValue.Year)
                            {
                                return null;
                            }

                            d = new DateTime(d.Year, mon - 11, 1, 0, 0, 0).AddYears(1);
                        }
                        else
                        {
                            d = new DateTime(d.Year, mon + 1, 1, 0, 0, 0);
                        }

                        continue;
                    }

                    while ((day + daysToAdd + 7) <= lDay)
                    {
                        daysToAdd += 7;
                    }
                    day += daysToAdd;
                    if (daysToAdd > 0)
                    {
                        d = new DateTime(d.Year, mon, day, 0, 0, 0);

                        continue;
                    }
                }
                else if (NthdayOfWeek != 0)
                {
                    var dow = (int)DaysOfWeek.First();

                    var cDow = (int)d.DayOfWeek;
                    var daysToAdd = 0;
                    if (cDow < dow)
                    {
                        daysToAdd = dow - cDow;
                    }
                    else if (cDow > dow)
                    {
                        daysToAdd = dow + (7 - cDow);
                    }
                    var dayShifted = false;
                    if (daysToAdd > 0)
                    {
                        dayShifted = true;
                    }
                    day += daysToAdd;
                    var weekOfMonth = day / 7;
                    if (day % 7 > 0)
                    {
                        weekOfMonth++;
                    }
                    daysToAdd = (NthdayOfWeek - weekOfMonth) * 7;
                    day += daysToAdd;
                    if (daysToAdd < 0 || day > GetLastDayOfMonth(mon, d.Year))
                    {
                        if (mon == 12)
                        {
                            if (d.Year == DateTime.MaxValue.Year)
                            {
                                return null;
                            }

                            d = new DateTime(d.Year, mon - 11, 1, 0, 0, 0).AddYears(1);
                        }
                        else
                        {
                            d = new DateTime(d.Year, mon + 1, 1, 0, 0, 0);
                        }

                        continue;
                    }
                    else if (daysToAdd > 0 || dayShifted)
                    {
                        d = new DateTime(d.Year, mon, day, 0, 0, 0);

                        continue;
                    }
                }
                else
                {
                    var cDow = ((int)d.DayOfWeek) + 1;
                    var dow = (int)DaysOfWeek.First();

                    st = DaysOfWeek.TailSet(cDow);
                    if (st != null && st.Count > 0)
                    {
                        dow = (int)st.First();
                    }
                    var daysToAdd = 0;
                    if (cDow < dow)
                    {
                        daysToAdd = dow - cDow;
                    }
                    if (cDow > dow)
                    {
                        daysToAdd = dow + (7 - cDow);
                    }
                    var lDay = GetLastDayOfMonth(mon, d.Year);
                    if (day + daysToAdd > lDay)
                    {
                        if (mon == 12)
                        {
                            if (d.Year == DateTime.MaxValue.Year)
                            {
                                return null;
                            }

                            d = new DateTime(d.Year, mon - 11, 1, 0, 0, 0).AddYears(1);
                        }
                        else
                        {
                            d = new DateTime(d.Year, mon + 1, 1, 0, 0, 0);
                        }

                        continue;
                    }
                    else if (daysToAdd > 0)
                    {
                        d = new DateTime(d.Year, mon, day + daysToAdd, 0, 0, 0);

                        continue;
                    }
                }
            }
            else
            {
                throw new Exception(
                    "Support for specifying both a day-of-week AND a day-of-month parameter is not implemented.");
            }
            d = new DateTime(d.Year, d.Month, day, d.Hour, d.Minute, d.Second);
            mon = d.Month;
            var year = d.Year;
            t = -1;

            if (year > 2099)
            {
                return null;
            }

            st = Months.TailSet(mon);
            if (st != null && st.Count != 0)
            {
                t = mon;
                mon = (int)st.First();
            }
            else
            {
                mon = (int)Months.First();
                year++;
            }
            if (mon != t)
            {
                d = new DateTime(year, mon, 1, 0, 0, 0);

                continue;
            }
            d = new DateTime(d.Year, mon, d.Day, d.Hour, d.Minute, d.Second);
            year = d.Year;
            st = Years.TailSet(year);
            if (st != null && st.Count != 0)
            {
                t = year;
                year = (int)st.First();
            }
            else
            {
                return null;
            }
            if (year != t)
            {
                d = new DateTime(year, 1, 1, 0, 0, 0);

                continue;
            }
            d = new DateTime(year, d.Month, d.Day, d.Hour, d.Minute, d.Second);
            gotOne = true;
        }

        return TimeZoneInfo.ConvertTimeToUtc(d, TimeZone);
    }

    protected static DateTime CreateDateTimeWithoutMillis(DateTime time)
    {
        return new DateTime(time.Year, time.Month, time.Day, time.Hour, time.Minute, time.Second);
    }

    protected static DateTime SetCalendarHour(DateTime date, int hour)
    {
        var hourToSet = hour;
        if (hourToSet == 24)
        {
            hourToSet = 0;
        }
        var d =
            new DateTime(date.Year, date.Month, date.Day, hourToSet, date.Minute, date.Second, date.Millisecond);
        if (hour == 24)
        {
            d = d.AddDays(1);
        }

        return d;
    }

    public virtual DateTime? GetTimeBefore(DateTime? endTime)
    {
        return null;
    }

    public virtual DateTime? GetFinalFireTime()
    {
        return null;
    }

    protected virtual bool IsLeapYear(int year)
    {
        return DateTime.IsLeapYear(year);
    }

    protected virtual int GetLastDayOfMonth(int monthNum, int year)
    {
        return DateTime.DaysInMonth(year, monthNum);
    }
}

public class ValueSet
{
    public int Pos { get; set; }
    public int TheValue { get; set; }
}