namespace QuanTAlib;
using System;

/* <summary>
BIAS: Rate of change between the source and a moving average.
    Bias is a statistical term which means a systematic deviation from the actual value.

BIAS = (close - SMA) / SMA
       = (close / SMA) - 1

Sources:
	https://en.wikipedia.org/wiki/Bias_of_an_estimator

</summary> */

public class BIAS_Series : TSeries {
	protected readonly int _period;
	protected readonly bool _NaN;
	protected readonly TSeries _data;
	private readonly SMA_Series _sma;

	//core constructors
	public BIAS_Series(int period, bool useNaN) {
		_period = period;
		_NaN = useNaN;
		Name = $"BIAS({period})";
		_sma = new(period, false);	
	}
	public BIAS_Series(TSeries source, int period, bool useNaN) : this(period, useNaN) {
		_data = source;
		Name = Name.Substring(0, Name.IndexOf(")")) + $", {(string.IsNullOrEmpty(_data.Name) ? "data" : _data.Name)})";
		_data.Pub += Sub;
		Add(_data);
	}
	public BIAS_Series() : this(period: 0, useNaN: false) { }
	public BIAS_Series(int period) : this(period: period, useNaN: false) { }
	public BIAS_Series(TBars source) : this(source.Close, 0, false) { }
	public BIAS_Series(TBars source, int period) : this(source.Close, period, false) { }
	public BIAS_Series(TBars source, int period, bool useNaN) : this(source.Close, period, useNaN) { }
	public BIAS_Series(TSeries source) : this(source, 0, false) { }
	public BIAS_Series(TSeries source, int period) : this(source: source, period: period, useNaN: false) { }

	//////////////////
	// core Add() algo
	public override (DateTime t, double v) Add((DateTime t, double v) TValue, bool update = false) {
		var _s = _sma.Add(TValue,update);
		double _bias = (TValue.v / ((_s.v!=0)?_s.v:1)) - 1;

		var res = (TValue.t, Count < _period - 1 && _NaN ? double.NaN : _bias);
		return base.Add(res, update);
	}

	public override (DateTime t, double v) Add(TSeries data) {
		if (data == null) { return (DateTime.Today, Double.NaN); }
		foreach (var item in data) { Add(item, false); }
		return _data.Last;
	}
	public (DateTime t, double v) Add(bool update) {
		return this.Add(TValue: _data.Last, update: update);
	}
	public (DateTime t, double v) Add() {
		return Add(TValue: _data.Last, update: false);
	}
	private new void Sub(object source, TSeriesEventArgs e) {
		Add(TValue: _data.Last, update: e.update);
	}

	//reset calculation
	public override void Reset() {
		_sma.Reset();
	}
}