Indicator Calculation on closed bars only / ignore current bar

Hi,

A newbie in coding for cTrader here, so excuse me if this might be a stupid question.

I have this ZigZag indicator which like any indicator calculates and updates the outputs up to and including the current(which is not closed) bar. I want this indicator to ignore the current bar in its calculations and only to take into account up to and including the last closed bar. And yes I played with "index" variable and changed it to "index-1" and whatnot but it messed up the whole indicator. 
Any help, tricks, hints and workarounds would be much appreciated. 

using System;
using cAlgo.API;
using cAlgo.API.Internals;


namespace cAlgo.Indicators
{
    [Indicator(IsOverlay = true, TimeZone = TimeZones.UTC, AccessRights = AccessRights.None)]
    public class MyZigZag : Indicator
    {

        [Parameter(DefaultValue = 20)]
        public int Depth { get; set; }

        [Parameter(DefaultValue = 5)]
        public int Deviation { get; set; }
        
        [Parameter(DefaultValue = 3)]
        public int BackStep { get; set; }

        [Output("MyZigZag", LineColor ="#FFFF0000")]
        public IndicatorDataSeries Result { get; set; }

        #region Private fields
        
        private double _lastLow;
        private double _lastHigh;
        private double _low;
        private double _high;
        private int _lastHighIndex;
        private int _lastLowIndex;
        private int _type;
        private double _point;
        private double _currentLow;
        private double _currentHigh;

        private IndicatorDataSeries _highZigZags; 
        private IndicatorDataSeries _lowZigZags;
        
        #endregion

        protected override void Initialize()
        {
            _highZigZags = CreateDataSeries();
            _lowZigZags = CreateDataSeries();
            _point = Symbol.TickSize;
        }

        public override void Calculate(int index)
        {
           
            if (index < Depth)
            {
                Result[index] = 0;
                _highZigZags[index] = 0;
                _lowZigZags[index] = 0;
                return;
            }

            _currentLow = Functions.Minimum(Bars.LowPrices, Depth);            
            if (Math.Abs(_currentLow - _lastLow) < double.Epsilon)
                _currentLow = 0.0;
            else
            {
                _lastLow = _currentLow;
                
                if ((Bars.LowPrices[index] - _currentLow) > (Deviation * _point))
                    _currentLow = 0.0;
                else
                {
                    for (int i = 1; i <= BackStep; i++)
                    {
                        if (Math.Abs(_lowZigZags[index - i]) > double.Epsilon 
                            && _lowZigZags[index - i] > _currentLow)
                            _lowZigZags[index - i] = 0.0;
                    }
                }
            }
            if (Math.Abs(Bars.LowPrices[index] - _currentLow) < double.Epsilon)
                _lowZigZags[index] = _currentLow;
            else
                _lowZigZags[index] = 0.0;

            _currentHigh = Bars.HighPrices.Maximum(Depth);

            if (Math.Abs(_currentHigh - _lastHigh) < double.Epsilon)
                _currentHigh = 0.0;
            else
            {
                _lastHigh = _currentHigh;

                if ((_currentHigh - Bars.HighPrices[index] ) > (Deviation * _point))
                    _currentHigh = 0.0;
                else
                {
                    for (int i = 1; i <= BackStep; i++)
                    {
                        if (Math.Abs(_highZigZags[index - i]) > double.Epsilon && _highZigZags[index - i] < _currentHigh)
                            _highZigZags[index - i] = 0.0;
                    }
                }
            }

            if (Math.Abs(Bars.HighPrices[index] - _currentHigh) < double.Epsilon)
                _highZigZags[index] = _currentHigh;
            else
                _highZigZags[index] = 0.0;


            switch(_type)
            {
                case 0:
                    if(Math.Abs(_low - 0) < double.Epsilon && Math.Abs(_high - 0) < double.Epsilon)
                    {
                        if(Math.Abs(_highZigZags[index]) > double.Epsilon)
                        {
                            _high = Bars.HighPrices[index];
                            _lastHighIndex = index;
                            _type = -1;
                            Result[index] = _high;
                        }
                        if(Math.Abs(_lowZigZags[index]) > double.Epsilon)
                        {
                            _low = Bars.LowPrices[index];
                            _lastLowIndex = index;
                            _type = 1;
                            Result[index] = _low;
                        }
                    }
                    break;
                case 1:
                    if (Math.Abs(_lowZigZags[index]) > double.Epsilon && _lowZigZags[index] < _low && Math.Abs(_highZigZags[index] - 0.0) < double.Epsilon)
                    {
                        Result[_lastLowIndex] = double.NaN;
                        _lastLowIndex = index;
                        _low = _lowZigZags[index];
                        Result[index] = _low;
                    }
                    if (Math.Abs(_highZigZags[index] - 0.0) > double.Epsilon && Math.Abs(_lowZigZags[index] - 0.0) < double.Epsilon)
                    {
                        _high = _highZigZags[index];
                        _lastHighIndex = index;
                        Result[index] = _high;
                        _type = -1;
                    }
                    break;
                case -1:
                    if (Math.Abs(_highZigZags[index]) > double.Epsilon && _highZigZags[index] > _high && Math.Abs(_lowZigZags[index] - 0.0) < double.Epsilon)
                    {
                        Result[_lastHighIndex] = double.NaN;
                        _lastHighIndex = index;
                        _high = _highZigZags[index];
                        Result[index] = _high;
                    }
                    if (Math.Abs(_lowZigZags[index]) > double.Epsilon && Math.Abs(_highZigZags[index]) <= double.Epsilon)
                    {
                        _low = _lowZigZags[index];
                        _lastLowIndex = index;
                        Result[index] = _low;
                        _type = 1;
                    }
                    break;
                default: return;
            }
            
        }
    }
}