using System;

namespace Science.Physics.GeneralPhysics
{
	/// <summary>
	/// PotentialEnergy U related with work W as
	/// W = - Delta U = U_{i} - U_{f}.
	/// </summary>
	public class PotentialEnergy : Scalar
	{
		private void SetDim()
		{
			this.DimensionMass = 1;
			this.DimensionLength = 2;
			this.DimensionTime = -2;
		}
		public PotentialEnergy()
		{
			SetDim();			
		}
		public PotentialEnergy(ElectricCharge q0, ElectricPotential V)
		{
			SetDim();			
			this.Magnitude = q0.C*V.V;
		}
		public PotentialEnergy(Capacitance C, ElectricPotentialDifference V)
		{
			SetDim();			
			this.Magnitude = 0.5*C.F*V.V*V.V;
		}
		public PotentialEnergy(Capacitance C, ElectricCharge Q)
		{
			SetDim();			
			this.Magnitude = 0.5/C.F*Q.C*Q.C;
		}
		private double[] x = new double[3];
		public void At(Position r)
		{
			this.Set(r);
		}
		public double J
		{
			get{return this.Magnitude;}
			set{this.Magnitude=value;}
		}
		public double Difference(Position from, Position to)
		{
			this.Set(from);
			double Ui = this.Magnitude;
			this.Set(to);
			double Uf = this.Magnitude;
			return Uf - Ui;
		}

		private Force force;
		private double Ui = 0.0, Uf;
		public PotentialEnergy(Force f,	Position referencePosition,PotentialEnergy referenceValue)
		{
			SetDim();
			force = f;
			x[0] = referencePosition.X;
			x[1] = referencePosition.Y;
			x[2] = referencePosition.Z;
			Ui = referenceValue.Magnitude;
		}		
		private double[] xx = new Double[3];
		public double ValueAt(Position r)
		{
			xx[0] = r.X;
			xx[1] = r.Y;
			xx[2] = r.Z;
            Line.Parameterization fun = new Line.Parameterization(rvst);
			Line p = new Line();
            p.ParameterToPosition = fun;
			p.ParameterStartValue = 0.0;
			p.ParameterEndValue = 1.0;
			Work w = new Work(force,p);
			Uf = -w.J + Ui;			
			return Uf;
		}
		private Position rvst(double t)
		{
			double[] r = new double[3];
			for(int i = 0; i < 3; i++) r[i] = (xx[i] - x[i])*t+x[i];
            Position p = new Position();
            p.X = r[0];
            p.Y = r[1];
            p.Z = r[2];
            return p;
		}
        public override string ToString()
        {
            return base.ToString() + "(J)";
        }
	}
}