/*************************************************************************************************
  Required Notice: Copyright (C) EPPlus Software AB. 
  This software is licensed under PolyForm Noncommercial License 1.0.0 
  and may only be used for noncommercial purposes 
  https://polyformproject.org/licenses/noncommercial/1.0.0/

  A commercial license to use this software can be purchased at https://epplussoftware.com
 *************************************************************************************************
  Date               Author                       Change
 *************************************************************************************************
  12/10/2020         EPPlus Software AB       EPPlus 5.5
 *************************************************************************************************/
using OfficeOpenXml.FormulaParsing.Excel.Functions.Metadata;
using OfficeOpenXml.FormulaParsing.FormulaExpressions;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace OfficeOpenXml.FormulaParsing.Excel.Functions.MathFunctions
{
    [FunctionMetadata(
        Category = ExcelFunctionCategory.MathAndTrig,
        EPPlusVersion = "5.5",
        Description = "Returns the ratio of the factorial of a sum of values to the product of factorials.")]
    internal class Multinomial : ExcelFunction
    {
        public override int ArgumentMinLength => 1;
        public override CompileResult Execute(IList<FunctionArgument> arguments, ParsingContext context)
        {
            var numbers = ArgsToDoubleEnumerable(arguments, context, out ExcelErrorValue e1);
            if (e1 != null) return CompileResult.GetErrorResult(e1.Type);
            var part1 = 0d;
            var part2 = 1d;
            foreach(var number in numbers)
            {
                part1 += number;
                part2 *= MathHelper.Factorial(number);
            }
            var result = MathHelper.Factorial(part1) / part2;
            return CreateResult(result, DataType.Decimal);
        }
    }
}
