using System;
using System.Collections.Generic;
using System.Linq;
using Kreta.BusinessLogic.Classes;
using Kreta.Ellenorzo.Domain.VN.Ertekeles;

namespace Kreta.Ellenorzo.BL.VN.Logic
{
    public static class AtlagLogic
    {
        public static decimal? GetSubListAtlag(List<ErtekelesListResponse> ertekelesek)
            => (decimal?)ertekelesek.WeightedAverage(x => x.SzamErtek.Value, x => x.SulySzazalekErteke.Value, 2); // TODO ne legyen nullable

        public static decimal GetSimpleAtlag(IEnumerable<decimal> ertekelesek)
            => Math.Round(ertekelesek.Average(), 2);

        public static (decimal? SulyozottOsztalyzatOsszege, decimal? SulyozottOsztalyzatSzama, decimal? SulyozottAtlag) GetAtlagTuple(List<ErtekelesListResponse> ertekelesek)
            => GetSubListAtlagTuple(ErtekelesLogic.ListAtlagbaSzamitoErtekelesek(ertekelesek).ToList());

        public static (decimal? SulyozottOsztalyzatOsszege, decimal? SulyozottOsztalyzatSzama, decimal? SulyozottAtlag) GetSubListAtlagTuple(List<ErtekelesListResponse> atlagbaSzamitoErtekelesek)
        => ((decimal? SulyozottOsztalyzatOsszege, decimal? SulyozottOsztalyzatSzama, decimal? SulyozottAtlag))atlagbaSzamitoErtekelesek.WeightedAverageTuple(x => x.SzamErtek.Value, x => x.SulySzazalekErteke.Value, 2);

        private static (double? weightedValueSum, double? weightSum, double? weightAverage) WeightedAverageTuple<T>(this IEnumerable<T> recordEnumeration, Func<T, double> value, Func<T, double> weight, int? round = null)
        {
            if (!recordEnumeration.Any())
            {
                return (null, null, null);
            }

            var weightedValueSum = recordEnumeration.Sum(x => value(x) * weight(x));
            var weightSum = recordEnumeration.Sum(weight);
            var weightAverage = round.HasValue && round > 0 ? Math.Round(weightedValueSum / weightSum, round.Value) : weightedValueSum / weightSum;

            return (weightedValueSum, weightSum, weightAverage);
        }

    }
}