using System;

namespace Science.Mathematics.VectorCalculus
{
    public class IteratedPartialDerivative
    {
        private Function.ToLastType<double[],double> dela;
        private Function.ToLastType<double[],double> delb;
        private Function.ToLastType<double[], double> delc;
        private Function.ToLastType<double[], double> del;
        private int howMany;
        public IteratedPartialDerivative(Function.ToLastType<double[], double> func, double[] at, 
            int howManyUpto4)
        {
            howMany = howManyUpto4;
            dela = func;
            this.at = at;
        }
        public void Compute()
        {
            switch(howMany)
            {
                case 2:
                {
                    del = new Function.ToLastType<double[], double>(FirstDerivative);
                    PartialDerivative obj = new PartialDerivative(del, at);
                    obj.WithRespectTo = comps;
                    obj.Compute();
                    result = obj.Result;
                    break;
                }
                case 3:
                {
                    del = new Function.ToLastType<double[], double>(SecondDerivative);
                    PartialDerivative obj = new PartialDerivative(del, at);
                    obj.WithRespectTo = compt;
                    obj.Compute();
                    result = obj.Result;
                    break;
                }
                case 4:
                {
                    del = new Function.ToLastType<double[], double>(ThirdDerivative);
                    PartialDerivative obj = new PartialDerivative(del, at);
                    obj.WithRespectTo = compfo;
                    obj.Compute();
                    result = obj.Result;
                    break;
                }
            }
        }
        private double FirstDerivative(double[] x)
        {
            PartialDerivative obj = new PartialDerivative(dela, x);
            obj.WithRespectTo = compf;
            obj.Compute();
            return obj.Result;
        }
        private double SecondDerivative(double[] x)
        {
            delb = new Function.ToLastType<double[], double>(FirstDerivative);
            PartialDerivative obj = new PartialDerivative(delb, x);
            obj.WithRespectTo = comps;
            obj.Compute();
            return obj.Result;
        }
        private double ThirdDerivative(double[] x)
        {
            delc = new Function.ToLastType<double[], double>(SecondDerivative);
            PartialDerivative obj = new PartialDerivative(delc, x);
            obj.WithRespectTo = compt;
            obj.Compute();
            return obj.Result;
        }
        
        private double[] at;
        public double[] At
        {
            set { at = value; }
        }
        private double result;
        public double Result
        {
            get { return result; }
        }  		
        private int compf;
        public int WithRespectToFirst
        {
            get { return compf; }
            set { compf = value; }
        }
        private int comps;
        public int WithRespectToSecond
        {
            get { return comps; }
            set { comps = value; }
        }
        private int compt;
        public int WithRespectToThird
        {
            get { return compt; }
            set { compt = value; }
        }
        private int compfo;
        public int WithRespectToFourth
        {
            get { return compfo; }
            set { compfo = value; }
        }
    }
}