AppsheetEpplus/FormulaParsing/Excel/Functions/DateTime/Workdays/AdditionalHolidayDays.cs

using System.Collections.Generic;
using System.Linq;

namespace AppsheetEpplus;

public class AdditionalHolidayDays {
  private readonly FunctionArgument _holidayArg;
  private readonly List<System.DateTime> _holidayDates = new();

  public AdditionalHolidayDays(FunctionArgument holidayArg) {
    _holidayArg = holidayArg;
    Initialize();
  }

  public IEnumerable<System.DateTime> AdditionalDates => _holidayDates;

  private void Initialize() {
    var holidays = _holidayArg.Value as IEnumerable<FunctionArgument>;
    if (holidays != null) {
      foreach (var holidayDate in from arg in holidays
          where ConvertUtil.IsNumeric(arg.Value)
          select ConvertUtil.GetValueDouble(arg.Value) into dateSerial
          select System.DateTime.FromOADate(dateSerial)) {
        _holidayDates.Add(holidayDate);
      }
    }
    var range = _holidayArg.Value as ExcelDataProvider.IRangeInfo;
    if (range != null) {
      foreach (var holidayDate in from cell in range
          where ConvertUtil.IsNumeric(cell.Value)
          select ConvertUtil.GetValueDouble(cell.Value) into dateSerial
          select System.DateTime.FromOADate(dateSerial)) {
        _holidayDates.Add(holidayDate);
      }
    }
    if (ConvertUtil.IsNumeric(_holidayArg.Value)) {
      _holidayDates.Add(System.DateTime.FromOADate(ConvertUtil.GetValueDouble(_holidayArg.Value)));
    }
  }
}