QuanTAlib/lib/trends/butter/Butter.Quantower.cs

using System.Drawing;
using System.Runtime.CompilerServices;
using TradingPlatform.BusinessLayer;

namespace QuanTAlib;

[SkipLocalsInit]
public class ButterIndicator : Indicator, IWatchlistIndicator
{
    [InputParameter("Period", sortIndex: 1, 2, 2000, 1, 0)]
    public int Period { get; set; } = 14;

    [IndicatorExtensions.DataSourceInput]
    public SourceType Source { get; set; } = SourceType.Close;

    [InputParameter("Show cold values", sortIndex: 21)]
    public bool ShowColdValues { get; set; } = true;

    private Butter? _ma;
    protected LineSeries? _series;
    protected string? SourceName;
    private Func<IHistoryItem, double>? _priceSelector;

    public static int MinHistoryDepths => 0;
    int IWatchlistIndicator.MinHistoryDepths => MinHistoryDepths;

    public override string ShortName => $"BUTTER {Period}:{SourceName}";
    public override string SourceCodeLink => "https://github.com/mihakralj/QuanTAlib/blob/main/lib/trends/butter/Butter.Quantower.cs";

    public ButterIndicator()
    {
        OnBackGround = true;
        SeparateWindow = false;
        SourceName = Source.ToString();
        Name = "BUTTER - Butterworth Filter";
        Description = "A 2nd-order low-pass filter with maximally flat frequency response in the passband.";
        _series = new(name: $"BUTTER {Period}", color: IndicatorExtensions.Averages, width: 2, style: LineStyle.Solid);
        AddLineSeries(_series);
    }

    protected override void OnInit()
    {
        _ma = new Butter(Period);
        SourceName = Source.ToString();
        _priceSelector = Source.GetPriceSelector();
        base.OnInit();
    }

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    protected override void OnUpdate(UpdateArgs args)
    {
        var item = HistoricalData[Count - 1, SeekOriginHistory.Begin];
        
        TValue result = _ma!.Update(new TValue(item.TimeLeft.Ticks, _priceSelector!(item)), isNew: args.IsNewBar());

        _series!.SetValue(result.Value, _ma.IsHot, ShowColdValues);
    }
}