Super Ichi by LuxAlgo - Help with Variables

Hi guys,

Trying to replicate the Tradingview indicator Superichi by LuxAlgo. This is my first complicated indicator. I am having trouble with the variables in the public double, i dont know how to declare the variable 'upper'  and 'lower' to look back at itself at an index - 1. my issues start at line 95. It isnt finished so please point out any addition errors improvements.

Thanks

using System;
using cAlgo.API;
using cAlgo.API.Indicators;

namespace cAlgo.Indicators
{
    [Indicator(IsOverlay = true, AccessRights = AccessRights.None)]
    public class AtrChannels : Indicator
    {
        private AverageTrueRange atr;
        private MovingAverage ma;

        [Parameter()]
        public DataSeries Source { get; set; }

        [Parameter("tenkan period", DefaultValue = 9)]
        public int tenkan_period { get; set; }

        [Parameter("tenkan_mult", DefaultValue = 2)]
        public int tenkan_mult { get; set; }

        [Parameter("kijun_period", DefaultValue = 26)]
        public int kijun_period { get; set; }

        [Parameter("kijun_mult", DefaultValue = 4)]
        public int kijun_mult { get; set; }

        [Parameter("spanB period", DefaultValue = 52)]
        public int spanB_period { get; set; }

        [Parameter("spanB_mult", DefaultValue = 6)]
        public int spanB_mult { get; set; }

        [Parameter(DefaultValue = MovingAverageType.Weighted)]
        public MovingAverageType MAType { get; set; }

        [Output("TenkanSen", Color = Colors.Red)]
        public IndicatorDataSeries tenkan { get; set; }
        [Output("Kijunsen", Color = Colors.Blue)]
        public IndicatorDataSeries kijun { get; set; }

        [Output("SenkouSpanB", Color = Colors.Red, LineStyle = LineStyle.Lines)]
        public IndicatorDataSeries senkouB { get; set; }
        [Output("SenkouSpanA", Color = Colors.Green, LineStyle = LineStyle.Lines)]
        public IndicatorDataSeries senkouA { get; set; }
        public AverageTrueRange atr_trial { get; set; }

        protected override void Initialize()
        {

            int atrperiods = tenkan_period;

            atr_trial = Indicators.AverageTrueRange(atrperiods, MovingAverageType.Simple);
            //atrtenkan = Indicators.AverageTrueRange(tenkan_period, MovingAverageType.Simple);
            //atrkijun = Indicators.AverageTrueRange(kijun_period, MovingAverageType.Simple);
            //atrspanB = Indicators.AverageTrueRange(spanB_period, MovingAverageType.Simple);

        }

        public override void Calculate(int index)
        {

            //Tenkan[index] = _avgtenkan(index);

            tenkan[index] = _avgtenkan(index, tenkan_period, tenkan_mult);
            kijun[index] = _avgtenkan(index, kijun_period, kijun_mult);
            senkouB[index] = _avgtenkan(index, spanB_period, spanB_mult);
            senkouA[index] = (kijun[index] + tenkan[index]) / 2;

        }

        public double _avgtenkan(int index, int periods, double multiplier)
        {

            int atrperiods = periods;
            //double upper = uppers;

            //double _atr = atrtenkan.Result.Last[index] * tenkan_mult;
            double _atr = atr_trial.Result[index] * multiplier;
            double up = (Bars.HighPrices[index] + Bars.LowPrices[index]) / 2 + _atr;
            double dn = (Bars.HighPrices[index] + Bars.LowPrices[index]) / 2 - _atr;
            var upper;
            var lower;
            var os;
            var spt;
            var _min;
            var _max;

            var upper1 = Math.Min(up, upper[index - 1]);

            if (Bars.ClosePrices[index - 1] < upper[index - 1])
            {
                upper = Math.Min(up, upper[index - 1]);

            }
            else
            {
                upper[index] = up;
            }

            if (Bars.ClosePrices[index + 1] > lower[index - 1])
                lower[index] = Math.Max(up, upper[index - 1]);
            else
            {
                lower[index] = dn;
            }

            if (Bars.ClosePrices[index] > upper[index])
            {
                os[index] = 1;
            }
            else if (Bars.ClosePrices[index] < lower[index])
            {
                os[index] = 0;
            }
            else
            { os[index] = os[index - 1]; }

            if (os[index] == 1)
            {
                spt = lower[index];
            }
            else
            {
                spt = upper[index];
            }

            //def _max = if src crosses spt then Max(src, _max[index - 1]) else if os == 1 then Max(src, _max[index - 1]) else spt;

            if (((Bars.ClosePrices[index - 1] > spt[index - 1] && Bars.ClosePrices[index] < spt[index]) || (Bars.ClosePrices[index - 1] < spt[index - 1] && Bars.ClosePrices[index] > spt[index])))
            {
                _max = Math.Max(Bars.ClosePrices[index], _max[index - 1]);
            }
            else if (os[index] == 1)
            {
                _max = Math.Max(Bars.ClosePrices[index], _max[index - 1]);
            }
            else
            {
                _max = spt[index];
            }

            //def _min = if src crosses spt then Min(src, _min[index - 1]) else if os == 0 then Min(src, _min[index - 1]) else spt;

            if (((Bars.ClosePrices[index - 1] > spt[index - 1] && Bars.ClosePrices[index] < spt[index]) || (Bars.ClosePrices[index - 1] < spt[index - 1] && Bars.ClosePrices[index] > spt[index])))
            {
                _min = Math.Min(Bars.ClosePrices[index], _min[index - 1]);
            }
            else if (os[index] == 0)
            {
                _min = Math.Min(Bars.ClosePrices[index], _min[index - 1]);
            }
            else
            {
                _min = spt[index];
            }

            return (_max + _min) / 2;

        }
    }
}