/*************************************************************************************************
  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
 *************************************************************************************************
  22/10/2022         EPPlus Software AB           EPPlus v6
 *************************************************************************************************/
using OfficeOpenXml.FormulaParsing.Excel.Functions.Helpers;
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.Statistical
{
    [FunctionMetadata(
            Category = ExcelFunctionCategory.Statistical,
            EPPlusVersion = "6.0",
            IntroducedInExcelVersion = "2010",
            Description = "Calculates the inverse of the left-tailed probability of the Chi-Square Distribution.")]
    internal class ChisqInv : ExcelFunction
    {
        public override string NamespacePrefix => "_xlfn.";
        public override int ArgumentMinLength => 2;
        public override CompileResult Execute(IList<FunctionArgument> arguments, ParsingContext context)
        {
            var n = ArgToDecimal(arguments, 0, out ExcelErrorValue e1);
            if (e1 != null) return CompileResult.GetErrorResult(e1.Type);

            var degreesOfFreedom = ArgToInt(arguments, 1, out ExcelErrorValue e2);
            if (e2 != null) return CompileResult.GetErrorResult(e2.Type);
            if (n < 0d || degreesOfFreedom < 1 || degreesOfFreedom > System.Math.Pow(10, 10))
            {
                return CreateResult(eErrorType.Num);
            }
            var result = 2d * GammaPinvHelper.gammapinv(n, (double)degreesOfFreedom/2d);
            return CreateResult(result, DataType.Decimal);
        }
    }
}
