/*
 *
 * Membrane
 *
 */
//import gjt.MAssert;
import java.lang.Math;

public class Membrane {
	private final int Max_Elem=100;
	private double[] ProbCross;
	private double Vm;
	private int NumElements=0;

	public Membrane(){
		Vm=0.0;
		ProbCross = new double[Max_Elem];
	}

	public Membrane(int NumElements, double[] PCross, double Vm){
		this.Vm=Vm;
		//MAssert.notFalse(NumElements > 0 && NumElements <= Max_Elem);
		ProbCross = new double[Max_Elem];
		for (int i=0; i<NumElements; i++){
			ProbCross[i]=PCross[i];
			this.NumElements++;
		}
	}

	public void SetElementProb(int Number, double PCross){
		//MAssert.notFalse( PCross >= 0.0 && PCross <=1.0 );
		//MAssert.notFalse( Number >=0 && Number < NumElements);
		ProbCross[Number]=PCross;
	}

	public void SetVoltage(double Vm){
		this.Vm=Vm;
	}

	public double GetVoltage(){
		return Vm;
	}

	public double ElementProb(int Number){
		//MAssert.notFalse( Number >=0 && Number < NumElements);
		return ProbCross[Number];
	}


	public void addElement(double PCross){
		//MAssert.notFalse( PCross >= 0.0 && PCross <=1.0 );
		ProbCross[NumElements]=PCross;
		NumElements++;
	}

	public boolean Permeate(int Number, int Charge, boolean FromInside){
		//MAssert.notFalse( Number >= 0 && Number < NumElements);
		if (Vm==0.0 || Charge==0) return ( Math.random() <= ProbCross[Number] );
		double K,eK,Prob;
		K=Charge*Vm/25;
		eK=Math.exp(K);

		if (FromInside){
			Prob=ProbCross[Number]*K*eK/(eK-1.0);
		}else{
			Prob=ProbCross[Number]*K/(eK-1.0);	
		}
		if (Prob>1.0) Prob=1.0;
		return ( Math.random() <= Prob );
	}



}