EPPlus/FormulaParsing/Excel/Functions/DateTime/Workdays/HolidayWeekdays.cs

using System;
using System.Collections.Generic;
using System.Linq;
using OfficeOpenXml.Utils;

namespace OfficeOpenXml.FormulaParsing.Excel.Functions.DateTime.Workdays;

public class HolidayWeekdays {
  private readonly List<DayOfWeek> _holidayDays = new();

  public HolidayWeekdays()
      : this(DayOfWeek.Saturday, DayOfWeek.Sunday) {}

  public int NumberOfWorkdaysPerWeek => 7 - _holidayDays.Count;

  public HolidayWeekdays(params DayOfWeek[] holidayDays) {
    foreach (var dayOfWeek in holidayDays) {
      _holidayDays.Add(dayOfWeek);
    }
  }

  public bool IsHolidayWeekday(System.DateTime dateTime) {
    return _holidayDays.Contains(dateTime.DayOfWeek);
  }

  public System.DateTime AdjustResultWithHolidays(
      System.DateTime resultDate,
      IEnumerable<FunctionArgument> arguments) {
    if (arguments.Count() == 2) {
      return resultDate;
    }
    var holidays = arguments.ElementAt(2).Value as IEnumerable<FunctionArgument>;
    if (holidays != null) {
      foreach (var arg in holidays) {
        if (ConvertUtil.IsNumeric(arg.Value)) {
          var dateSerial = ConvertUtil.GetValueDouble(arg.Value);
          var holidayDate = System.DateTime.FromOADate(dateSerial);
          if (!IsHolidayWeekday(holidayDate)) {
            resultDate = resultDate.AddDays(1);
          }
        }
      }
    } else {
      var range = arguments.ElementAt(2).Value as ExcelDataProvider.IRangeInfo;
      if (range != null) {
        foreach (var cell in range) {
          if (ConvertUtil.IsNumeric(cell.Value)) {
            var dateSerial = ConvertUtil.GetValueDouble(cell.Value);
            var holidayDate = System.DateTime.FromOADate(dateSerial);
            if (!IsHolidayWeekday(holidayDate)) {
              resultDate = resultDate.AddDays(1);
            }
          }
        }
      }
    }
    return resultDate;
  }

  public System.DateTime GetNextWorkday(
      System.DateTime date,
      WorkdayCalculationDirection direction = WorkdayCalculationDirection.Forward) {
    var changeParam = (int)direction;
    var tmpDate = date.AddDays(changeParam);
    while (IsHolidayWeekday(tmpDate)) {
      tmpDate = tmpDate.AddDays(changeParam);
    }
    return tmpDate;
  }
}