using System;

namespace Science.Physics.GeneralPhysics
{
	/// <summary>
	/// CenterOfMass
	/// </summary>
	public class CenterOfMass : Vector
	{
		private void SetDim()
		{
			this.DimensionMass = 1;
			this.DimensionLength = 0;
			this.DimensionTime = 0;
		}
		public CenterOfMass()
		{
	    	SetDim();
		}
		public CenterOfMass(Mass[] m, Position[] r)
		{
        	SetDim();
			double sumOfMass = 0.0;
			foreach(Mass mass in m) sumOfMass += mass.kg;
			double x = 0.0, y = 0.0, z = 0.0;
			for(int i = 0; i < m.Length; i++)
			{
				x += m[i].kg*r[i].X;
				y += m[i].kg*r[i].Y;
				z += m[i].kg*r[i].Z;
			}
			this.X = x/sumOfMass; 
			this.Y = y/sumOfMass;
			this.Z = z/sumOfMass;
		}
		private Scalar.FunctionOfPosition fp;
		public CenterOfMass(Density rho, Volume v)
		{
			SetDim();
			fp = rho.ScalarFunctionOfPosition;

            Scalar.FunctionOfPosition ff = new Scalar.FunctionOfPosition(Rho);
            Scalar s = new Scalar(ff);
            Scalar res = VectorCalculus.VolumeIntegral(s, v);
         	double mass = res.Magnitude;

            Scalar.FunctionOfPosition fx = new Scalar.FunctionOfPosition(Xrho);
            Scalar sx = new Scalar(fx);
            Scalar resx = VectorCalculus.VolumeIntegral(sx, v);
         	this.X = resx.Magnitude/mass;
            this.StandardDeviationOfX = resx.StandardDeviation / mass;

            Scalar.FunctionOfPosition fy = new Scalar.FunctionOfPosition(Yrho);
            Scalar sy = new Scalar(fy);
            Scalar resy = VectorCalculus.VolumeIntegral(sy, v);
            this.Y = resy.Magnitude / mass;
            this.StandardDeviationOfY = resy.StandardDeviation / mass;

            Scalar.FunctionOfPosition fz = new Scalar.FunctionOfPosition(Zrho);
            Scalar sz = new Scalar(fz);
            Scalar resz = VectorCalculus.VolumeIntegral(sz, v);
            this.Z = resz.Magnitude / mass;
            this.StandardDeviationOfZ = resz.StandardDeviation / mass;
		}
		private Scalar Rho(Position r)
		{
         	return fp(r);
		}
		private Scalar Xrho(Position r)
		{
			return r.X*fp(r);
		}
		private Scalar Yrho(Position r)
		{
			return r.Y*fp(r);
		}
		private Scalar Zrho(Position r)
		{
			return r.Z*fp(r);
		}
        public override string ToString()
        {
            return base.ToString() + "(m)";
        }
	}
}