Trying to modify this ctrader indicator

Hi all,

I have this ctrader indicator which alerts me on Telegram when a candle changes colour/direction. I use it on Renko and range charts.
The problem is it sometimes triggers multiple times while the candle is forming, I only want it to trigger once when the candle has closed and a new candle begins.
I can't work out how to modify it to achieve this.
If anyone can help, much appreciated :-)

using cAlgo.API;
using cAlgo.API.Alert;
using cAlgo.API.Alert.Enums;
using cAlgo.API.Alert.Models;
namespace cAlgo
{
[Indicator(IsOverlay = true, TimeZone = TimeZones.UTC, AccessRights = AccessRights.FullAccess)]
public class BarColorChangeAlert : Indicator
{
#region Fields
private int _lastAlertBarIndex;
#endregion Fields
#region Parameters
[Parameter("Type", DefaultValue = AlertType.Popup, Group = "Alert")]
public AlertType AlertType { get; set; }
[Parameter("Show Window", DefaultValue = false, Group = "Alert")]
public bool ShowWindow { get; set; }
#endregion Parameters
#region Overridden methods
protected override void Initialize()
{
_lastAlertBarIndex = Bars.ClosePrices.Count - 1;
if (ShowWindow)
{
Notifications.ShowPopup();
}
}
public override void Calculate(int index)
{
if (Bars.ClosePrices[index] > Bars.OpenPrices[index] && Bars.ClosePrices[index - 1] < Bars.OpenPrices[index - 1])
{
TriggerAlert(index, "Bullish");
}
else if (Bars.ClosePrices[index] < Bars.OpenPrices[index] && Bars.ClosePrices[index - 1] > Bars.OpenPrices[index - 1])
{
TriggerAlert(index, "Bearish");
}
}
#endregion Overridden methods
#region Other methods
private void TriggerAlert(int index, string type)
{
if (index == _lastAlertBarIndex || !IsLastBar || AlertType == AlertType.None)
{
return;
}
_lastAlertBarIndex = index;
var alertModel = new AlertModel
{
TimeFrame = TimeFrame.ToString(),
Price = Bars.ClosePrices[index],
Symbol = Symbol.Name,
TriggeredBy = "Bar Color Change",
Time = Server.Time,
Type = type
};
if (AlertType == AlertType.Popup)
{
Notifications.ShowPopup(alertModel);
}
else if (AlertType == AlertType.Triggers)
{
Notifications.TriggerAlert(alertModel);
}
}
#endregion Other methods
}
}