using System;
using System.Collections.Generic;
using TSLab.Script;
using TSLab.Script.Handlers;
using TSLab.Script.Helpers;


namespace RSquared_
{
    public class RSquared : IDouble2DoubleHandler
    {
        [HandlerParameter(true, "9", Min = "5", Max = "100", Step = "1")]
        public int RSQPeriod { get; set; }    
        
        public IList<double> Execute(IList<double> source)
        {
            var P = source;
        	var rsq1 = new double[P.Count];
            
            for(int i = 0; i < P.Count; i++)
            {
            	if(i<RSQPeriod)
            		rsq1[i]=0;
            	else
            	{
            		double x, y, div;
   					double Ex=0.0, Ey=0.0, Exy=0.0, Ex2=0.0, Ey2=0.0;
   					double Ex22, Ey22;
   					double r;
   					int ind;
   					
   					ind=1;
   					for(int j = i-1; j>=i-RSQPeriod ; j--)
   					{
   						x = ind;   // x axis value
   						y = P[j];  // y axis value
      					Ex  += x;
					    Ey  += y;
					    Exy += x*y;
					    Ex2 += Math.Pow(x,2);
					    Ey2 += Math.Pow(y,2);
					    ind++;
   					}
   					Ex22=Math.Pow(Ex,2);
   					Ey22=Math.Pow(Ey,2);
   					//slope = (per*Exy-Ex*Ey) / (per*Ex2-Ex22);  // slope of regression line
   					//b = (Ey-slope*Ex)/per;
   					div = Math.Sqrt((RSQPeriod*Ex2-Ex22)*(RSQPeriod*Ey2-Ey22));
   					if(div==0)
   						rsq1[i]=0;
   					else
   					{
   						r = (RSQPeriod*Exy-Ex*Ey) / div;	
   						rsq1[i]=Math.Pow(r,2);
   					}
            	}
            }
            return rsq1;
        }
    }
}