NSoft.NFramework.TimePeriods.Calendars.DateAdd.CalculateEnd C# (CSharp) Method

        protected DateTime? CalculateEnd(DateTime start, TimeSpan offset, SeekDirection seekDirection, SeekBoundaryMode seekBoundaryMode,
                                         out TimeSpan? remaining) {
            if(IsDebugEnabled)
                log.Debug("기준시각으로부터 오프셋만큼 떨어진 시각을 구합니다... " +
                          @"start=[{0}], offset=[{1}], seekDirection=[{2}], seekBoundaryMode=[{3}]",
                          start, offset, seekDirection, seekBoundaryMode);

            Guard.Assert(offset >= TimeSpan.Zero, "offset 값은 항상 0 이상이어야 합니다. offset=[{0}]", offset);

            remaining = offset;

            // search periods
            ITimePeriodCollection searchPeriods = new TimePeriodCollection(IncludePeriods);
            if(searchPeriods.Count == 0)
                searchPeriods.Add(TimeRange.Anytime);

            // available periods
            ITimePeriodCollection availablePeriods = new TimePeriodCollection();
            if(ExcludePeriods.Count == 0) {
                availablePeriods.AddAll(searchPeriods);
            }
            else {
                // 예외 기간을 제외합니다.
                //
                var gapCalculator = new TimeGapCalculator<TimeRange>();

                var query
                    = searchPeriods
#if !SILVERLIGHT
                        .AsParallel()
                        .AsOrdered()
#endif
                        .SelectMany(searchPeriod =>
                                    ExcludePeriods.HasOverlapPeriods(searchPeriod)
                                        ? gapCalculator.GetGaps(ExcludePeriods, searchPeriod) // 예외 기간과 검색 기간에서 겹치지 않는 기간을 계산하여, 추려냅니다.
                                        : new TimePeriodCollection { searchPeriod } // 예외 기간과 겹쳐진 부분이 없다면, 기간 전체를 추가합니다.
                        );

                availablePeriods.AddAll(query);
            }

            // 유효한 Period가 없다면 중단합니다.
            if(availablePeriods.Count == 0)
                return null;

            // 기간중에 중복되는 부분의 없도록 유효한 기간을 결합합니다.
            if(availablePeriods.Count > 1) {
                var periodCombiner = new TimePeriodCombiner<TimeRange>();
                availablePeriods = periodCombiner.CombinePeriods(availablePeriods);
            }

            // 첫 시작 기간을 찾습니다.
            //
            DateTime seekMoment;
            var startPeriod = (seekDirection == SeekDirection.Forward)
                                  ? FindNextPeriod(start, availablePeriods, out seekMoment)
                                  : FindPreviousPeriod(start, availablePeriods, out seekMoment);

            // 첫 시작 기간이 없다면 중단합니다.
            if(startPeriod == null)
                return null;

            // 오프셋 값이 0 이라면, 바로 다음 값이므로 seekMoment를 반환합니다.
            if(offset == TimeSpan.Zero)
                return seekMoment;

            if(seekDirection == SeekDirection.Forward) {
                for(var i = availablePeriods.IndexOf(startPeriod); i < availablePeriods.Count; i++) {
                    var gap = availablePeriods[i];
                    var gapRemaining = gap.End - seekMoment;

                    if(IsDebugEnabled)
                        log.Debug("Seek Forward... gap=[{0}], gapRemaining=[{1}], remaining=[{2}], seekMoment=[{3}]", gap, gapRemaining,
                                  remaining, seekMoment);

                    var isTargetPeriod = (seekBoundaryMode == SeekBoundaryMode.Fill)
                                             ? gapRemaining >= remaining
                                             : gapRemaining > remaining;

                    if(isTargetPeriod) {
                        var end = seekMoment + remaining.Value;
                        remaining = null;
                        return end;
                    }

                    remaining = remaining - gapRemaining;

                    if(i == availablePeriods.Count - 1)
                        return null;

                    seekMoment = availablePeriods[i + 1].Start; // next period
                }
            }
            else {
                for(var i = availablePeriods.IndexOf(startPeriod); i >= 0; i--) {
                    var gap = availablePeriods[i];
                    var gapRemaining = seekMoment - gap.Start;

                    if(IsDebugEnabled)
                        log.Debug("Seek Backward... gap=[{0}], gapRemaining=[{1}], remaining=[{2}], seekMoment=[{3}]", gap, gapRemaining,
                                  remaining, seekMoment);

                    var isTargetPeriod = (seekBoundaryMode == SeekBoundaryMode.Fill)
                                             ? gapRemaining >= remaining
                                             : gapRemaining > remaining;

                    if(isTargetPeriod) {
                        var end = seekMoment - remaining.Value;
                        remaining = null;
                        return end;
                    }
                    remaining = remaining - gapRemaining;

                    if(i == 0)
                        return null;

                    seekMoment = availablePeriods[i - 1].End; // previous period
                }
            }
            return null;
        }